Satoshi OHZAHATA
| Department of Informatics | Professor |
| Cluster II (Emerging Multi-interdisciplinary Engineering) | Professor |
| Fundamental Program for Advanced Engineering (Evening Course) | Professor |
| Meta-Networking Research Center | Professor |
- Profile:
Mobile Internet
Wireless Internet
Ad hoc network
Overlay network
Researcher Information
Research Keyword
Career
- Apr. 2016 - Mar. 2023
The University of Electro-Communications, Graduate School of Informatics and Engineering Department of Informatics, Associate Professor - Apr. 2009 - Mar. 2016
The University of Electro-Communications, Graduate School of Information Systems Department of Information Network Systems, Associate Professor, Japan - 01 Apr. 2007 - 31 Mar. 2009
東京農工大学大学院共生科学技術研究院, 助教 - 01 Apr. 2003 - 31 Mar. 2007
東京農工大学 工学部 情報コミュニケーション工学科, 助手
Educational Background
Member History
- Jun. 2021 - May 2023
通信ソサイエティ 研専運営会議 総務幹事, 電子情報通信学会, Society - 01 Jun. 2018 - 31 May 2020
編集副委員長, 電子情報通信学会 英文論文誌B - 01 Jun. 2014 - 31 May 2018
編集委員, 電子情報通信学会 英文論文誌B - 01 Apr. 2015 - 31 Mar. 2017
教科科目第一委員会委員, 独立行政法人大学入試センター - Jun. 2012 - May 2014
通信ソサイエティ 会員事業企画幹事, IEICE, Society - Jun. 2010 - May 2012
通信ソサイエティ アドホックネットワーク研究専門委員会 幹事, IEICE, Society
Research Activity Information
Award
Paper
- Auto Annotation using Object Tracking with Multiple in-vehicle Cameras for Federated Learning
Yuuki Nakahama; Satoshi Ohzahata; Ryo Yamamoto
2024 International Conference on Artificial Intelligence in Information and Communication (ICAIIC), IEEE, 19 Feb. 2024
International conference proceedings - Deep Learning-Based No-Reference Video Streaming QoE Estimation Using WebRTC Statistics
Keisuke Sakakibara; Satoshi Ohzahata; Ryo Yamamoto
2024 International Conference on Artificial Intelligence in Information and Communication (ICAIIC), IEEE, 19 Feb. 2024
International conference proceedings - Detecting Zero-day Attack with Federated Learning using Autonomously Extracted Anomalies in IoT
Takahiro Ohtani; Ryo Yamamoto; Satoshi Ohzahata
CCNC 2024, Jan. 2024, Peer-reviwed
International conference proceedings - Accelerating Feedback Control for QoE Fairness in Adaptive Video Streaming over ICN
Rei Nakagawa; Satoshi Ohzahata; Ryo Yamamoto
CCNC 2024, Jan. 2024, Peer-reviwed
International conference proceedings - VORTEX: Network-Driven Opportunistic Routing for Ad Hoc Networks
Ryo Yamamoto; Taku Yamazaki; Satoshi Ohzahata
Sensors, MDPI AG, 23, 6, 2893-2893, 07 Mar. 2023, Peer-reviwed, The potential of ad hoc networks, which enable flexible and dynamic network establishment only by mobile terminals equipped with wireless communication devices, has recently attracted attention for the coming IoT era. Although the nature of ad hoc networks shows the advantages of their autonomous and distributed network management, a manifestation of drawbacks owing to the nature of wireless communication and the mobility of terminals are inevitable. Many routing protocols have already been proposed to address the issues by adapting to nature and achieving a certain level of improvement. However, the routing protocols still suffer from difficulties in information collection for routing and adaptive route management during communication. Moreover, there is another issue that end pair-based routing procedures prevent other end pairs from reusing the routing information effectively. To address the drawbacks of conventional routing protocols, this paper proposes VORTEX, a novel routing protocol that employs an opportunistic routing strategy using hierarchization. One of the characteristic features of VORTEX is its network-driven opportunistic forwarding, in which packets travel toward destination terminals using hierarchy as a guide without conventional route discovery procedures. Moreover, another characteristic feature of VORTEX is that the hierarchical structure also contributes to adapting to communication environment changes in an autonomous manner. In other words, VORTEX enables flexible network-wide information-based routing only with the locally collected information. The simulation results show that the proposed VORTEX could provide better service quality and reliability with improved efficiency compared to the conventional routing protocols. Furthermore, the most significant contribution is not only in the communication performance but also VORTEX omits route discovery or route maintenance from routing protocols, and formed networks themselves have a function to deliver packets toward destination terminals.
Scientific journal - A Visual-Identification Based Forwarding Strategy for Vehicular Named Data Networking
Minh NGO; Satoshi OHZAHATA; Ryo YAMAMOTO; Toshihiko KATO
IEICE Transactions on Information and Systems, Institute of Electronics, Information and Communications Engineers (IEICE), E106.D, 2, 204-217, 01 Feb. 2023, Peer-reviwed
Scientific journal - VNE-HAGBE: A Hybrid Approach to Improve VNR Request Acceptance Rate for Wireless Virtual Network Embedding
Raihaanjun Kushiyama; Ryo Yamamoto; Satoshi Ohzahata
2022 23rd Asia-Pacific Network Operations and Management Symposium (APNOMS), IEEE, 28 Sep. 2022, Peer-reviwed
International conference proceedings - A Link State Routing Method for CCN with Blockchain
Shuichi Tokunaga; Satoshi Ohzahata; Ryo Yamamoto
ASON 2021, 7 pages, 27 Nov. 2021, Peer-reviwed
International conference proceedings, English - A novel visual-identification based forwarding strategy for Vehicular Named Data Networking
Minh Ngo; Satoshi Ohzahata; Ryo Yamamoto; Toshihiko Kato
EAI MONAMI 2021, 6 pages, 27 Oct. 2021, Peer-reviwed
International conference proceedings, English - Mitigating Congestion with Explicit Cache Placement Notification for Adaptive Video Streaming over ICN
Rei NAKAGAWA; Satoshi OHZAHATA; Ryo YAMAMOTO; Toshihiko KATO
IEICE ED, E104.D, 9, 1406-1419, 01 Sep. 2021, Peer-reviwed
Scientific journal, English - A Congestion-Aware Adaptive Streaming over ICN combined with Explicit Congestion Notification for QoE Improvement
R. Nakagawa; S. Ohzahata; R. Yamamoto; T. Kato
IEICE ED, E104.D, 2, 264-274, 2021, Peer-reviwed
Scientific journal, English - A Content Registration Method for CCN Routers with Blockchain
S. Tokunaga; R. Nakagawa; S. Ohzahata; R. Yamamoto; T. Kato
Proc. of IEEE ICCE-TW, 2 pages, Sep. 2020, Peer-reviwed
International conference proceedings, English - A Container-based Content Delivery Method for Edge Cloud over Wide Area Network
K. Nakanishi; F. Suzuki; S. Ohzahata; R. Yamamoto; T. Kato
Proc. of International Conference on Information Networking (ICOIN) 2020, 568-573, Jan. 2020, Peer-reviwed
International conference proceedings, English - モバイル環境における通信品質指標を用いた機械学習によるWeb転送遅延判定方式
小林 史弥; 川口 銀河; 岡本 淳; 大坐畠 智; 小川 秀貴; 高橋 玲
電子情報通信学会 和文論文誌B, J103-B, 6, 210-222, 2020, Peer-reviwed
Scientific journal, Japanese - A congestion avoidance for adaptive streaming over ICN using bitrate feedback from in-network nodes
Rei Nakagawa; Satoshi Ohzahata; Ryo Yamamoto; Toshihiko Kato
ASON 2019, **-**, Nov. 2019, Peer-reviwed
International conference proceedings, English - Performance Evaluation of MANET Based on Named Data Networking Using Hybrid Routing Mechanism
Quang Minh Ngo; Ryo Yamamoto; Satoshi Ohzahata; Toshihiko Kato
Journal of Communications, 14, 9, 819-825, Sep. 2019, Peer-reviwed
Scientific journal, English - Proposal and Performance Evaluation of Hybrid Routing Mechanism for NDN Ad Hoc Networks Combining Proactive and Reactive Approaches
Quang Minh Ngo; Ryo Yamamoto; Satoshi Ohzahata; Toshihiko Kato
IEICE Transactions on Information and Systems, E102-D, 9, 1784-1796, Sep. 2019, Peer-reviwed
Scientific journal, English - Applying SMOTE for a Sequential Classifiers Combination Method to Improve the Performance of Intrusion Detection System
Sornxayya Phetlasy; Satoshi Ohzahata; Celimuge Wu; Toshihito Kato
IEEE CyberSciTech 2019, **-**, Aug. 2019, Peer-reviwed
International conference proceedings, English - EXPERIMENTAL ANALYSIS OF MPTCP CONGESTION CONTROL ALGORITHMS; LIA, OLIA AND BALIA
Toshihiko Kato; Adhikari Diwakar; Ryo Yamamoto; Satoshi Ohzahata; Nobuo Suzuki
Proceedings of the International Conferences Big Data Analytics, Data Mining and Computational Intelligence 2019; and Theory and Practice in Modern Computing 2019, IADIS Press, 16 Jul. 2019
International conference proceedings - An Efficient Dynamic Bandwidth Reservation Method in Content-Centric Network
Fumiya Suzuki; Satoshi Ohzahata; Ryo Yamamoto; Toshihiko Kato
IEEE International Conference on Consumer Electronics -Taiwan (ICCE-TW) 2019, 2 pages, May 2019, Peer-reviwed
International conference proceedings, English - Opportunistic Routing for Heterogeneous IoT Networks
Fumiya Suzuki; Satoshi Ohzahata; Ryo Yamamoto; Toshihiko Kato
IEEE International Conference on Consumer Electronics -Taiwan (ICCE-TW) 2019, 2 pages, May 2019, Peer-reviwed
International conference proceedings, English - Analysis of Performance Degradation of TCP Reno over WLAN Caused by Access Point Scanning
Toshihiko Kato; Sota Tasaki; Ryo Yamamoto; Satoshi Ohzahata
World Conference on Information Systems and Technologies (WorldCIST’19), 385-395, Apr. 2019, Peer-reviwed
International conference proceedings, English - Estimating TCP Congestion Control Algorithms from Passively Collected Packet Traces using Recurrent Neural Network
Naoki Ohzeki; Ryo Yamamoto; Satoshi Ohzahata; Toshihiko Kato
Proceedings of the 16th International Joint Conference on e-Business and Telecommunications, SCITEPRESS - Science and Technology Publications, 2019
International conference proceedings - Impacts of System Clock Granularity on Performance of NDN Rate-based Congestion Control
Toshihiko Kato; Kazuki Osada; Ryo Yamamoto; Satoshi Ohzahata
International Journal On Advances in Telecommunications, 11, 3&4, 135-143, Jan. 2019, Peer-reviwed
Scientific journal, English - 輻輳ウィンドウとその増加分に着目したパッシブなTCP輻輳制御アルゴリズムの推定方法
加藤聰彦; 小田 淳; Xiaofan Ya; 山本 嶺; 大坐畠智
情報処理学会 論文誌, 60, 2, 479-490, 2019, Peer-reviwed
Scientific journal, Japanese - A Sequential Classifiers Combination Method to Reduce False Negative for Intrusion Detection System
Sornxayya Phetlasy; Satoshi Ohzahata; Celimuge Wu; Toshihito Kato
IEICE Transactions on Information and Systems, 102, 5, 888-897, 2019, Peer-reviwed
Scientific journal, English - A Traffic Distribution System Among Multiple Terminals Using MPTCP in Multihomed Network Environment
R. Asakura; R. Horigome; N. Yamai; N. Kitagawa; S. Ohzahata
IEEE 43rd Annual Computer Software and Applications Conference (COMPSAC) 2019 workshop SRS, 900-903, 2019, Peer-reviwed
International conference proceedings, English - Performance Evaluation of TCP Spurious Timeout Detection Methods Under Delay Spike and Packet Loss Emulating LTE Handover
Toshihiko Kato; Masahito Moriyama; Ryo Yamamoto; Satoshi Ohzahata
IADIS International Journal on Computer Science and Information Systems, 13, 2, 16-29, Dec. 2018, Peer-reviwed
Scientific journal, English - How to Implement NDN MANET over ndnSIM Simulator
Toshihiko Kato; Ngo Quang Minh; Ryo Yamamoto; Satoshi Ohzahata
IEEE 4th International Conference on Computer and Communications 2018, 451-456, Dec. 2018, Peer-reviwed
International conference proceedings, English - IEEE802.11ac無線LANのMU-MIMOダウンリンク伝送における動的フレームアグリゲーションサイズ選択によるスループット改善手法
森山友和; 山本 嶺; 大坐畠 智; 加藤聰彦
電子情報通信学会 和文論文誌B, 電子情報通信学会, J101-B, No.7, 558-569, 01 Jul. 2018, Peer-reviwed
Scientific journal, Japanese - Adaptive geo-fencing with local storage architecture on ad hoc networks
Ryo Yamamoto; Satoshi Ohzahata; Toshihiko Kato
International Conference on Electronics, Information and Communication, ICEIC 2018, Institute of Electrical and Electronics Engineers Inc., 2018-, 1-4, 02 Apr. 2018, Peer-reviwed, Recently, the growth of communication services and technology make networks essential for our daily life, and mobile user terminals such as a smartphone becomes a major communication tool to access the Internet for obtaining information. Moreover, local information services with geo-fencing can provide adaptive information provisioning to users entering specific pre-defined area according to the user location. However, these services are still trapped in the conventional client/server-oriented services, which generally has lower adaptability to the immediate information dissemination such as traffic information on VANET. As concerns this, this paper proposes a novel information localization method for geo-fencing data dissemination with ad hoc communication.
International conference proceedings, English - Proposal and Study on Implementation of Data Eavesdropping Protection Method over Multipath TCP Communication Using Data Scrambling and Path Dispersion
Toshihiko Kato; Shihan Cheng; Ryo Yamamoto; Satoshi Ohzahata; Nobuo Suzuki
International Journal On Advances in Security, 11, 1&2, 118-126, 2018, Peer-reviwed
Scientific journal, English - Proposal and Performance Analysis of Hybrid NDN Based Ad Hoc Routing Combining Proactive and Reactive Mechanisms
Ngo Quang Minh; Ryo Yamamoto; Satoshi Ohzahata; Toshihiko Kato
International Journal On Advances in Networks and Services, 11, 1&2, 1-10, 2018, Peer-reviwed
Scientific journal, English - Experimental Analysis and Resolution Proposal on Performance Degradation of TCP over IEEE 802.11n Wireless LAN Caused by Access Point Scanning
Toshihiko Kato; Kento Kobayashi; Sota Tasaki; Masataka Nomoto; Ryo Yamamoto; Satoshi Ohzahata
International Journal On Advances in Telecommunications, 11, 1&2, 10-19, 2018, Peer-reviwed
Scientific journal, English - How insufficient send socket buffer affects MPTCP performance over paths with different delay
Toshihiko Kato; Adhikari Diwakar; Ryo Yamamoto; Satoshi Ohzahata; Nobuo Suzuki
Advances in Intelligent Systems and Computing, Springer Verlag, 746, 614-624, 2018, Peer-reviwed, Recently, the multipath transport protocol such as Multipath TCP becomes increasingly important. It allows more than one TCP connections via different paths to compose one Multipath TCP communication. However, it has some problems when those paths have different delay. Especially, the limited buffer space at either sender or receiver may degrade the throughput due to head-of-line blocking. Our previous paper pointed out that insufficient send socket buffer and receive socket buffer provide different situations of performance degradation, and that insufficient send socket buffer gives poorer throughput. This paper extends the performance analysis of our previous paper in the conditions with various combinations of send socket buffer size and transmission delay. It gives more detailed analysis using Multipath TCP level sequence number and congestion window size, and suggests the reasons for performance degradation.
International conference proceedings, English - A Study on How Coarse-grained Clock System Influences NDN Rate-based Congestion Control
Toshihiko Kato; Kazuki Osada; Ryo Yamamoto; Satoshi Ohzahata
Proceedings of The Seventeenth International Conference on Networks (ICN 2018), 35-40, 2018, Peer-reviwed
International conference proceedings, English - Experimental Analysis of Spurious Timeout Detection Methods with LTE Handover Emulation
Toshihiko Kato; Masahito Moriyama; Ryo Yamamoto; Satoshi Ohzahata
Proceedings of 7th International Conference on Theory and Practice in Modern Computing (TPMC 2018), 104-112, 2018, Peer-reviwed
International conference proceedings, English - Applying Lomb Periodogram to Round-trip Time Estimation from Unidirectional Packet Traces with Different TCP Congestion Controls
Toshihiko Kato; Xiaofan Yan; Ryo Yamamoto; Satoshi Ohzahata
Proceedings of The Thirteenth International Conference on Internet Monitoring and Protection (ICIMP 2018), 1-6, 2018, Peer-reviwed
International conference proceedings, English - TCP Congestion Control over IEEE 802.11 Wireless LANs Based on K-means Clustering Focusing on Congestion Window Size and Round-trip Time
Tomokazu Moriyama; Ryo Yamamoto; Satoshi Ohzahata; Toshihiko Kato
Proceedings of 9th International Conference on Data Communication Networking (DCNET 2018), 25-32, 2018, Peer-reviwed
International conference proceedings, English - An Adaptive BandwidthReservation Method for a Content-Centric Network
Tomoharu Endo; Atsuko Yokotani; Satoshi Ohzahata; Ryo Yamamoto; Toshihiko Kato
Proc. of IEEE COMPSAC 2018 Workshop IWFIT, 6-pages, 2018, Peer-reviwed
International conference proceedings, English - Implementation of Eavesdropping Protection Method over MPTCP Using Data Scrambling and Path Dispersion
Toshihiko Kato; Shihan Cheng; Ryo Yamamoto; Satoshi Ohzahata; Nobuo Suzuki
Proceedings of The Twelfth International Conference on Emerging Security Information, Systems and Technologies (SECURWARE 2018), 108-113, 2018, Peer-reviwed
International conference proceedings, English - Identification of TCP Congestion Control Algorithms from Unidirectional Packet Traces
Toshihiko Kato; Xiaofan Yan; Ryo Yamamoto; Satoshi Ohzahata
Proceedings of 2nd International Conference on Communication and Network Technology (ICCNT 2018), 1-6, 2018, Peer-reviwed
International conference proceedings, English - Alternating Primary Subflow in MPTCP by External Program without Kernel Modification
R. Horigome; N. Yamai; N. Kitagawa; S. Ohzahata
Proc. of SRS 2018 in IEEE 42nd Annual Computer Software and Applications Conference (COMPSAC 2018), 962-965, 2018, Peer-reviwed
International conference proceedings, English - Throughput Improvement of MPTCP by Selective Bicasting with Cross-Layer Control in Wireless Environment
M. Fukuyama; N. Yamai; S. Ohzahata; N. Kitagawa
Proc. of ADMNET 2018 in IEEE 42nd Annual Computer Software and Applications Conference (COMPSAC 2018), 204-209, 2018, Peer-reviwed
International conference proceedings, English - Performance Evaluation of MultiPath TCP Congestion Control
Toshihiko Kato; Adhikari Diwakar; Ryo Yamamoto; Satoshi Ohzahata; Nobuo Suzuki
Proc. of WorldCIST'18, 19-24, 2018, Peer-reviwed
International conference proceedings, English - Resolving Bufferbloat in TCP Communication over IEEE 802.11n WLAN by Reducing MAC Retransmission Limit at Low Data Rate
Masataka Nomoto; Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
Proc. ICN 2017, 69-74, 01 Apr. 2017, Peer-reviwed
International conference proceedings, English - Resolving Bufferbloat in TCP Communication over IEEE 802.11n WLAN by Reducing MAC Retransmission Limit at Low Data Rate
Masataka Nomoto; Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
Proc. ICN 2017, 69-74, 01 Apr. 2017, Peer-reviwed
International conference proceedings, English - IEEE 802.11n無線LANのアップロードTCP通信におけるBufferbloat問題に対するアクセスポイントでの対応方式
野元 祐孝; 策力木格; 大坐畠智; 加藤 聰彦
情報処理学会論文誌, 情報処理学会論文誌, 58, 2, 427-438, 01 Feb. 2017, Peer-reviwed, IEEE 802.11n無線アクセスポイントを経由するTCP通信では，低いMACレベルデータレートが使用される場合に，往復遅延が増加するBufferbloat問題が発生し，同じキューを共通する他の通信の遅延時間が増加し，ユーザレベルの品質の悪化となる．この対処として，アクティブキュー管理方式，筆者らが先に示した無線LANの最大再送回数を制限する方法，遅延増加時にTCP通信を停止する方法などが提案されている．しかしこれらはすべて，データの送信側に実装する必要がある．このため，端末からアクセスポイントへのアップロード転送においては，端末のすべてにこのような方式を導入しなければならない．そこで本稿では，データの受信側であるアクセスポイントにおいて，低いMACレベルデータレートで無線LANフレームの最大再送回数を制限したと同様な効果を与えることにより，TCPの輻輳ウィンドウを減少させ，Bufferbloat問題に対応する方法を提案する．パソコンを用いたアクセスポイントに提案方式を実装することにより，Bufferbloat問題に対応していない端末で，低いMACレベルデータレートでの往復遅延を減少させられること，さらにBufferbloat問題に対する方法を実装している端末においてもTCP通信のスループットを悪化させることがないことを明らかにした．IEEE 802.11n wireless LANs provides a Bufferbloat problem such that the round-tirp delay increases in TCP communications when the MAC level data is low such as 6.5Mbps. This problem degrades user level quality of service for communications sharing the transmission queue with the TCP communications. In order to resolve this problem, several schemes are proposed such as a scheme based on active queue management, our previous scheme reducing the retry-out limit at low data rate, and a scheme stopping sending TCP level data when the queue contains more than a specific number of packes. However, those schemes need to be implemented at the sender side. In this paper, we propose a new scheme resolving a Bufferbloat problem in the upload TCP communications by providing an effect at a receiving side access point similar to reducing the retry-out limit when the MAC level data rate is low. This decreases the congestion window size in the sending side and can reduce the delay. This paper also shows the results of the performance evaluation by implementing the proposed method in a PC based access point. According to the results, the proposed method decreases the round-trip time in the low MAC data rate and does not reduce the TCP throughput. It does not give any influences on the TCP thoughput for the terminals supporting the conventional schemes for Bufferbroat problems.
Scientific journal, Japanese - Inferring partial orders of nodes for hierarchical network layout
Hsiang-Yun Wu; Shigeo Takahashi; Hiroko Nakamura Miyamura; Satoshi Ohzahata; Akihiro Nakao
IS and T International Symposium on Electronic Imaging Science and Technology, Society for Imaging Science and Technology, 60, 6, 118-130, 2017, Peer-reviwed, Extracting hierarchical structures from networks provides us with an effective means of visualizing them, especially when they contain complicated node connectivities such as those in traffic and distributed networks. Although many techniques have been developed for such purposes, they often deterministically break unwanted cycles that may arise from inconsistencies in the network hierarchies, and thus never seek the best compromise among possible partial orders of nodes inherent in the cycle. This article presents an algorithm for inferring such partial orders by optimizing the network hierarchies along flow paths that are given as input. Our idea is to extract network hierarchies from round-trip paths as well as one-way ones by deriving reasonably consistent multi-layered structures even from possibly inconsistent flow data over the networks. This problem is formulated as mixed-integer programming where we incorporate additional constraints into fundamental layout criteria according to the type and/or expected use of the network. For better visual readability of the network layout, the nodes in individual layers are clustered and reordered for minimizing edge crossings, which is followed by fine adjustment of intervals between neighboring nodes. We study several network examples to demonstrate the feasibility of the proposed approach including course dependency charts, railway networks, and peer-to-peer (P2P) networks.
International conference proceedings, English - A Hierarchical Opportunistic Routing with Moderate Clustering for Ad Hoc Networks
Ryo Yamamoto; Satoshi Ohzahata; Toshihiko Kato
IEICE TRANSACTIONS ON COMMUNICATIONS, IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG, E100B, 1, 54-66, Jan. 2017, Peer-reviwed, The self-organizing nature of ad hoc networks is a good aspect in that terminals are not dependent on any infrastructure, that is, networks can be formed with decentralized and autonomous manner according to communication demand. However, this characteristic might affect the performance in terms of stability, reliability and so forth. Moreover, ad hoc networks face a scalability problem, which arise when the number of terminals in a network increases or a physical network domain expands, due to the network capacity limitation caused by the decentralized and the autonomous manner. Regarding this problem, some hierarchical and cluster-based routings have been proposed to effectively manage the networks. In this paper, we apply the concept of hierarchical routing and clustering to opportunistic routing, which can forward packets without using any pre-established path to achieve a path diversity gain with greater reachability. The simulation results show that the proposed method can achieve 110'o higher reliability with a reasonable end-to-end delay in dense environments and 30010 higher in large-scale networks.
Scientific journal, English - A TDMA/DCF Hybrid QoS Scheme for Ad Hoc Networks
Jing Lin; Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
IEICE TRANSACTIONS ON COMMUNICATIONS, IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG, E100B, 1, 42-53, Jan. 2017, Peer-reviwed, We propose a QoS scheme for ad hoc networks by combining TDMA and IEEE 802.11 DCF, and present performance evaluation results of the scheme. In the proposed scheme, the channel time is composed of two different periods, specifically TDMA period and DCF period. The TDMA period provides contention free transmission opportunities for QoS flows, and the DCF period provides contention-based access for best effort or low priority flows. We evaluate the proposed scheme for various numbers of TCP flows and different CBR data rates with QualNet simulator. Simulation results show that the protocol is able to provide an efficient solution for QoS control in ad hoc networks.
Scientific journal, English - A Routing Protocol Proposal for NDN Based Ad Hoc Networks Combining Proactive and Reactive Routing Mechanisms
Ngo Quang Minh; Ryo Yamamoto; Satoshi Ohzahata; Toshihiko Kato
The Thirteenth Advanced International Conference on Telecommunications (AICT 2017), 80-86, 2017, Peer-reviwed
International conference proceedings, English - A QoS Aware Ad Hoc Multicast by Combining TDMA and IEEE 802.11 DCF, International Conferences Computer Graphics
Jing Lin; Ryo Yamamoto; Satoshi Ohzahata; Toshihiko Kato
Visualization, Computer Vision and Image Processing 2017 and Big Data Analysis, Data Mining and Computational Intelligence 2017, 204-211, 2017, Peer-reviwed
International conference proceedings, English - Frame Aggregation Size Determination for IEEE 802.11ac WLAN Considering Channel Utilization and Transfer Delay
Tomokazu Moriyama; Ryo Yamamoto; Satoshi Ohzahata; Toshihiko Kato
14th International Conference on Wireless Networks and Mobile Systems (WINSYS 2017), 89-94, 2017, Peer-reviwed
International conference proceedings, English - Protecting Eavesdropping over Multipath TCP Communication Based on Not-Every-Not-Any Protection
Toshihiko Kato; Shilan Cheng; Ryo Yamamoto; Satoshi Ohzahata; Nobuo Suzuki
The Eleventh International Conference on Emerging Security Information, Systems and Technologies (SECURWARE 2017), 87-92, 2017, Peer-reviwed
International conference proceedings, English - A Solution for Bufferbloat Problem in Upload TCP Communication over IEEE 802.11n WLAN Only by Modifying Access Point
Masataka Nomoto; Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
The Sixth International Conference on Communications, Computation, Networks and Technologies (INNOV 2017), 8-13, 2017, Peer-reviwed
International conference proceedings, English - Increasing the Number of Connectable ONUs with Subcarrier Digital Modulation Passive Optical Network
Atsuko Yokotani; Satoshi Ohzahata; Hiromi Ueda
Proc.of APCC 2017, 6 pages, 2017, Peer-reviwed
International conference proceedings, English - Experimental Analysis on How Access Point Scanning Impacts on TCP Throughput over IEEE802.11n Wireless LAN
Kento Kobayashi; Yoshiki Hashimoto; Ryo Yamamoto; Satoshi Ohzahata; Toshihiko Kato
Twelfth International Conference on Wireless and Mobile Communications (ICWMC 2016), 115-120, Nov. 2016, Peer-reviwed
International conference proceedings, English - Microscopic Approach for Experimental Analysis of Multipath TCP Troughput under Insufficient Send/Receive Socket Buffers
Toshihiko Kato; Masaaki Tenjin; Ryo Yamamoto; Satoshi Ohzahata; Hiroyuki Shinbo
15th International Conference WWW/Internet 2016 (ICWI 2016), 191-199, Oct. 2016, Peer-reviwed
International conference proceedings, English - Combining two sequential algorithms for classification of intrusion detection system dataset
Phetlasy Sornxayya; Satoshi Ohzahata; Celimuge Wu; Toshihiko Kato
IWSEC 2016, reviewed by abstract only, Sep. 2016, Peer-reviwed
International conference proceedings, English - Performance Anomaly in Download TCP Flows Over IEEE 802.11n Wireless LAN
Yoshiki Hashimoto; Masataka Nomoto; Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
Proc. The Fifth International Conference on Communications, Computation, Networks and Technologies, 13-18, Aug. 2016, Peer-reviwed
International conference proceedings, English - IBGP Solution by Combining Route Reflection And Shared Tree Based Multicast
Toshihiko Kato; Yao Koffi; Hubert Wilfried; Celimuge Wu; Satoshi Ohzahata
Proc. 5th International Conference on Theory and Practice in Modern Computing, 203-210, Jul. 2016, Peer-reviwed
International conference proceedings, English - A Study on How to Characterize TCP Congestion Control Algorithms from Unidirectional Packet Traces
Toshihiko Kato; Leelianou Yongxialee; Ryo Yamamoto; Satoshi Ohzahata
The Eleventh International Conference on Internet Monitoring and Protection, 23-28, 22 May 2016, Peer-reviwed
International conference proceedings, English - How to Utilize Inter-flow Network Coding in VANETs: A Backbone Based Approach
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
IEEE Transactions on Intelligent Transportation Systems, IEEE, 17, 8, 2223-2237, 05 Feb. 2016, Peer-reviwed
Scientific journal, English - A Practical and Efficient Overhearing Strategy for Reliable Content Distribution over a Single Hop Ad Hoc Network
Hiroaki Yokose; Koji Nitta; Satoshi Ohzahata; Toshihiko Kato
IPSJ, IPSJ, 24, 2, 292-301, 01 Feb. 2016, Peer-reviwed, Nowadays, wireless LAN is equipped in most portable devices and widely deployed, and then we can communicate over wireless link with low cost. However, when the same content is simultaneously downloaded by several terminals with unicast in a wireless LAN, the bandwidth must be divided among the terminals and the download speed is reduced. With using the broadcast nature of wireless media, pseudo multicasting methods, which overhear the unicast flow to realize multicast like communication, have been proposed. In the pseudo multicasting methods, since parts of the content is obtained by overhearing the TCP/UDP flows of a specific content going to other terminals in a wireless LAN, and the server need not send the content for each client repeatedly. These methods enable to realize multicasting with a practical way. However, redundant unicast traffic is still generated because the receivers do not obtain contents via overhearing in an efficient way. Based on the pseudo multicasting, we propose an efficient, flexible and reliable content distribution method over single hop wireless ad hoc network in this paper. In the proposed method a content is divided into pieces and the server distributes it according to the download status of each receivers at the application level. To accelerate downloading, we propose a method for selecting the piece and the terminal for transmission taking the effect of network coding for efficient overhearing. We developed a testbed and confirmed that the proposed scheduling accelerates the download speed even when the communication speed of each terminal is different.
Scientific journal, English - Experimental Analysis on Performance Anomaly for Download Data Transfer at IEEE 802.11n Wireless LAN
Yoshiki Hashimoto; Masataka Nomoto; Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
Proc. of ICN 2016, 22-27, 01 Feb. 2016, Peer-reviwed
International conference proceedings, English - Comparing TCP Congestion Control Algorithms Based on Passively Collected Packet Traces
Toshihiko Kato; Atsushi Oda; Celimuge Wu; Satoshi Ohzahata
Proc. of ICSNC 2015, 135-141, 01 Feb. 2016, Peer-reviwed
International conference proceedings, English - Reinforcement learning-based parameter tuning for a broadcast protocol in VANETs
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Tsutomu Yoshinaga; Yoshihiko Kato
IEICE Technical Report, 115, 408,CQ2015-105, 73-78, Jan. 2016
English - Piece Distribution Scheduling for Streaming Content Delivery with Pseudo-Multicast over Wireless LAN
Akihiro Kanayama; Satoshi Ohzahata; Toshihiko Kato
2016 13TH IEEE ANNUAL CONSUMER COMMUNICATIONS & NETWORKING CONFERENCE (CCNC), IEEE, 2 pages, 2016, Peer-reviwed
International conference proceedings, English - Improving the Tor Traffic Distribution with Circuit Switching Method
Timothy Girry Kale; Satoshi Ohzahata; Celimuge Wu; Toshihiko Kato
2016 IEEE 17TH INTERNATIONAL CONFERENCE ON HIGH PERFORMANCE SWITCHING AND ROUTING (HPSR), IEEE, 106-107, 2016, Peer-reviwed, The Tor network has its user grown by thousands every year. The increasing number of users around the world makes Tor become one of the widely used privacy networks today. However, as the number of Tor user increases, the performance of Tor degrades badly due to traffic is not fairly distributed. As a result, the Tor network does not provide a better quality of communication for all its users. To improve these problems, we proposed a simple method of dynamic circuit switching on the Tor application level to distribute the bulk and light traffic on Tor. We calculated the fairness indexes of transferred bulk and light traffic to observe any improvement and, compared our method with the default entry onion router algorithm. Our experimental results show the proposed method improves the distribution of traffic and achieves fairness of throughputs for all Tor users.
International conference proceedings, English - Evaluating Tor Modified Switching Algorithm in the Emulation Environment
Timothy Girry Kale; Satoshi Ohzahata; Celimuge Wu; Toshihiko Kato
2016 22ND ASIA-PACIFIC CONFERENCE ON COMMUNICATIONS (APCC), IEEE, 510-516, 2016, Peer-reviwed, The Tor network is an open network that helps its users to defend against adversaries who performed traffic analysis and threatens the personal privacy and confidential security. Tor protects its users by preventing the sites they visit from revealing their physical location. As the number of Tor user increases, the performance of Tor degrades badly due to Tor's scheduler is not fairly distributing the traffic in Tor. In this paper, we highlight the problems in Tor performance due to scheduling design of Tor, which degrades the web and bulk traffic performances that multiplexes on a single TCP connection. To solve these problems, this paper emphasis on applying a simple method of active circuit switching on Tor application level, in order to distribute the bulk and web traffics on different TCP connections when congestion is detected in the Tor network. We evaluate our modified switching algorithm with the other default schedulers in Tor, such as vanilla Tor and priority EWMA scheduler in a shadow wide deployment network emulator. The experimental results show that our switching technique considerably offers stable improvement of traffic performance for all the web and bulk traffics.
International conference proceedings, English - Suppressing Selfish Transmissions with Extending NAV Period and Resetting CW of Access Point in Wireless LAN
Takashi Sasagawa; Satoshi Ohzahata; Toshihiko Kato
2016 IEEE TRUSTCOM/BIGDATASE/ISPA, IEEE, 1910-1916, 2016, Peer-reviwed, In case that a selfish terminal generates a large amount of traffic with high priority control of IEEE 802.11e, an access point (AP) and terminals in the AP cannot get transmission opportunities because of the media access control technique. In our previous work, we proposed traffic suppression method for the selfish terminal by cooperative controls between AP and terminals with considering the fairness of upstream traffic and down stream traffic. In the method, a Fake period is added to the Network Allocation Vector (NAV) and a dynamic contention window (CW) control of AP suppress excessive transmission of the selfish terminal at the initiative of AP. However, the previous method cannot completely suppress traffic of the selfish terminal because the current backoff of AP cannot be adjusted until next its transmission success. In this paper, AP retrieves its transmission opportunities from the selfish terminal with resetting its current backoff when AP receives a frame from the selfish terminal. In addition, the transmission opportunity of downlink communication is ensured with an improved control of the fake period. Effectiveness of the proposed method is evaluated in computer simulation.
International conference proceedings, English - A Hierarchical Opportunistic Routing with Stability Information for Mobile Ad Hoc Networks
Ryo Yamamoto; Satoshi Ohzahata; Toshihiko Kato
PROCEEDINGS OF THE 2016 INTERNATIONAL CONFERENCE ON ADVANCED TECHNOLOGIES FOR COMMUNICATIONS (ATC), IEEE, 43-47, 2016, Peer-reviwed, In ad hoc networks, terminals form a network with decentralized and self-organizing manners. Although this can surely extend its potentials, it also suffers from unstable and unreliable communication environments. As concerns this, a broadcast-based routing protocol called opportunistic routing (OR) has been proposed. ORs do not establish any specific route from a source terminal to a destination terminal unlike conventional unicast routing protocols. This characteristic contributes to obtain path diversity and improves end-to-end reliability with multiple forwarding paths. However, the metrics to select appropriate forwarders to a destination terminal greatly affect its performance and grasp of comprehensive terminal status still remains as an issue to be discussed. In this paper, we propose a hierarchical opportunistic routing with stability information of terminals to enable more efficient and reliable forwarding in ad hoc networks to address the issue. The performance evaluation shows that the proposed method has better performance than the conventional protocols.
International conference proceedings, English - Improving Consistency of Parallel Emulation for Multi-hop Wireless Ad-hoc Network
Yusuke Yamazaki; Timothy Girry Kale; Satoshi Ohzahata; Toshihiko Kato
2016 FOURTH INTERNATIONAL SYMPOSIUM ON COMPUTING AND NETWORKING (CANDAR), IEEE, 338-342, 2016, Peer-reviwed, When parallel and distribution processing is used for wireless network emulation, the results are different in case that each of the receiver nodes independently run the events without synchronizing among these events. In our previous study for the parallel wireless network emulation, we proposed a synchronizing method to get the same result of collision event among the terminals that receive the same frame over the wireless network. The frame has a seed of the random number to be used for an event execution at the receiver terminals within one hop. In addition, the information needed for the event execution is also previously shared among the receivers in order to get the same result. However, the effectiveness of our previous work is limited to one-hop wireless communication. In this paper, we extend our previous method to multi-hop wireless network environment with considering a hidden terminal and sharing parameters needed for the event execution. Our proposed method is evaluated with comparing our previous work and the original extendable mobile ad-hoc network emulator (EMANE).
International conference proceedings, English - Toward Practical and Intelligent Routing in Vehicular Ad Hoc Networks
Celimuge Wu; Yusheng Ji; Fuqiang Liu; Satoshi Ohzahata; Toshihiko Kato
IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 64, 12, 5503-5519, Dec. 2015, Peer-reviwed, Apart from vehicle mobility, data rate (bit rate) and multihop data transmission efficiency (including route length) have a significant impact on the performance of a routing protocol for vehicular ad hoc networks (VANETs). Existing routing protocols do not seriously address all these issues and are not evaluated for a real VANET environment. Therefore, it is difficult for these protocols to attain a high performance and to work properly under various scenarios. In this paper, we first discuss the challenges of routing in VANETs based on the data acquired from real-world experiments and then propose a routing protocol that is able to learn the best transmission parameters by interacting with the environment. The protocol takes into account multiple metrics, specifically data transmission rate, vehicle movement, and route length. We use both real-world experiments and computer simulations to evaluate the proposed protocol.
Scientific journal, English - Adaptive Multi-hop Broadcasting Considering Packet Payload Size
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
IEICE Technical Report, 115, 327,CQ2015-83, 43-48, Nov. 2015
English - Efficient Broadcasting in VANETs Using Dynamic Backbone and Network Coding
Celimuge Wu; Xianfu Chen; Yusheng Ji; Satoshi Ohzahata; Toshihiko Kato
IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 14, 11, 6057-6071, Nov. 2015, Peer-reviwed, Multihop data dissemination in vehicular ad hoc networks (VANETs) is very important for the realization of collision avoidance systems and many other interesting applications. However, designing an efficient data dissemination protocol for VANETs has been a challenging issue due to vehicle movements, limited wireless resources, and the lossy characteristics of wireless communication. In this paper, we propose a protocol that can provide a lightweight and reliable solution for data dissemination in VANETs. The protocol employs dynamically generated backbone vehicles to disseminate broadcast packets to reduce the MAC-layer contention time at each node while maintaining a high packet dissemination ratio by taking into account vehicle movement dynamics and the link quality between vehicles for the backbone selection. The protocol also uses network coding to reduce the protocol overhead and to improve the packet reception probability as compared with conventional approaches. We use theoretical analysis and computer simulations to show the advantage of the proposed protocol over other existing alternatives.
Scientific journal, English - Reducing congestion in the tor network with circuit switching
Kale Timothy Girry; Satoshi Ohzahata; Celimuge Wu; Toshihiko Kato
Journal of Information Processing, Information Processing Society of Japan, 23, 5, 589-602, 15 Sep. 2015, Peer-reviwed, The Tor network is a distributed circuit-switching overlay network, which provides anonymous communication by using voluntarily running onion routers around the world. Tor is vulnerable to network congestion and performance problems because circuit traffics with different rates are competing to transfer their data through a single TCP connection. A large fraction of available network capacity is consumed by the bulk users’ traffic, resulting in increasing delays for the light interactive users. The unfair distribution between the circuit traffics of bulk and light users are contributing to bottleneck in the Tor routers. This problem increases the end-to-end latency and reduces the quality of communication in Tor, which discourages many users from using and joining the network. As a result, the degradation of Tor performance does not only affect the users’ experience, but also degrade the anonymity of Tor. In this work, we discovered that the current Tor design encountered problems from several performance and deployment issues relating to lower network capacity. To improve the problems in Tor, we applied the circuit switching method and addressed the short-comings of limited network capacity, by connecting the congested OR to higher bandwidth ORs. The proposed method is evaluated on our setup testbed environment and partly in the live Tor network. The experimental results showed that TCP socket buffers and Tor network capacity are better utilized and the overall end-to-end latency is reduced.
Scientific journal, English - An Intelligent Broadcast Protocol for VANETs Based on Transfer Learning
Celimuge Wu; Xianfu Chen; Yusheng Ji; Satoshi Ohzahata; Toshihiko Kato
in Proceedings of IEEE VTC 2015 Spring, 2015, Jun. 2015, Peer-reviwed
International conference proceedings, English - Joint Fuzzy Relays and Network-Coding-Based Forwarding for Multihop Broadcasting in VANETs
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
IEEE TRANSACTIONS ON INTELLIGENT TRANSPORTATION SYSTEMS, IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 16, 3, 1415-1427, Jun. 2015, Peer-reviwed, In vehicular ad hoc networks (VANETs), due to the limited radio propagation range of wireless devices, many safety applications require a multihop broadcast protocol to disseminate traffic warning information. However, providing an efficient multihop forwarding of broadcast messages has been a challenging problem due to vehicle movement, limited wireless resources, and unstable signal strength. In this paper we propose a broadcast protocol that can provide a low message overhead and a high packet dissemination ratio. The proposed scheme uses a fuzzy logic algorithm to choose the next hop relay nodes and uses network coding to improve the packet dissemination ratio without increasing the message overhead. By using the fuzzy logic algorithm, the protocol can choose the best relay node by taking intervehicle distance, vehicle velocity, and link quality into account. Network coding is used to improve the packet reception ratio by utilizing the broadcast nature of wireless channels. We show the effectiveness of the proposed scheme by using both theoretical analysis and computer simulations.
Scientific journal, English - Inter-vehicle Communications: Research Challenges & Opportunities
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
Technical Report of IEICE, 115, 42, IN2015-6, 27-32, May 2015, Invited
Symposium, English - A Routing Protocol for VANETs with Adaptive Frame Aggregation and Packet Size Awareness
Celimuge Wu; Yusheng Ji; Satoshi Ohzahata; Toshihiko Kato
ICC 2015, IEEE, 6565-6570, May 2015, Peer-reviwed
International conference proceedings, English - Combining Sequential Minimal Optimization and Naïve Bayes Algorithms for Accurate Data Classification
Sornxayya Phetlasy; Satoshi Ohzahata; Celimuge Wu; Toshihiko Kato
Proc. of ICT-ISPC 2015, 4 pages, May 2015, Peer-reviwed
International conference proceedings, English - Design of EV Common Service Platform,
Jing WEI; Jinglin LI; Zhihan LIU; Celimuge WU; Satoshi OHZAHATA; Toshihiko KATO
ICT-ISPC 2015, 4 pages, May 2015, Peer-reviwed
International conference proceedings, English - 並列処理を用いたネットワークエミュレーションにおける無線1ホップ隣接端末間の因果関係改善方式
新田幸司; 大坐畠 智; 加藤聰彦
電子情報通信学会 和文論文誌Ｂ, J98-B, 2, 141-152, 01 Feb. 2015, Peer-reviwed
Scientific journal, Japanese - Future Channel Utilization-Aware Routing for Cognitive Radio Ad Hoc Networks
Celimuge Wu; Juan Xu; Yusheng Ji; Satoshi Ohzahata; Toshihiko Kato
IEICE TRANSACTIONS ON COMMUNICATIONS, IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG, E98B, 1, 107-115, Jan. 2015, Peer-reviwed, Cognitive radio ad hoc networks can be used to solve the problems of limited available spectrum and inefficient spectrum usage by adaptively changing their transmission parameters. Routing protocol design has a significant impact on the network performance. However, an efficient protocol that takes account of primary user flows and the long-term channel assignment issue in route selection is still missing. In this paper, we propose AODV-cog, a cognitive routing protocol for CSMA/CA ad hoc networks based on AODV. AODV-cog chooses a route by considering the effect on the primary users, available channel bandwidth and link reliability. AODV-cog also takes account of future channel utilization which is an important but underexplored issue. AODV-cog switches channels for secondary user flows when network congestion occurs. We use theoretical analysis and computer simulations to show the advantage of AODV-cog over existing alternatives.
Scientific journal, English - A Routing Protocol for VANETs with Adaptive Frame Aggregation and Packet Size Awareness
Celimuge Wu; Yusheng Ji; Satoshi Ohzahata; Toshihiko Kato
2015 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE, 6565-6570, 2015, Peer-reviwed, Existing multi-hop routing protocols for vehicular ad hoc networks (VANETs) do not consider the packet payload size and some important MAC layer issues for the route selection. In this paper, we first solve the performance anomaly problem by providing the same transmission time for different nodes which have different channel qualities using an adaptive frame aggregation mechanism. Next, we propose a packet size-aware routing protocol where a communication route is determined by taking into account the payload size of data packets. We consider multiple metrics for the route selection specifically vehicle mobility, frame aggregation efficiency, and link quality. The proposed protocol is evaluated using real-world experiments as well as computer simulations.
International conference proceedings, English - Performance Evaluation of Time Slot Based QoS Aware Ad Hoc Network Scheme for CBR and TCP Flows
Jing Lin; Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
2015 17TH ASIA-PACIFIC NETWORK OPERATIONS AND MANAGEMENT SYMPOSIUM APNOMS, IEEE, 139-144, 2015, Peer-reviwed, We propose a QoS supporting ad hoc network scheme which employs a hybrid approach utilizing both TDMA and 802.11 DCF and present performance evaluation results of the scheme. In the scheme, TDMA period provides contention free transmissions for QoS flows, and DCF period is used to provide contention-based access for best effort or low priority flows. We evaluate the proposed scheme for various numbers of TCP flows and different CBR data rates with QualNet simulator. Simulation results show that the protocol is able to provide an efficient solution for QoS control in ad hoc networks by combing TDMA and 802.11 DCF.
International conference proceedings, English - Evaluation of Dynamic Circuit Switching to Reduce Congestion in Tor
Timothy Girry Kale; Satoshi Ohzahata; Celimuge Wu; Toshihiko Kato
25TH INTERNATIONAL TELECOMMUNICATION NETWORKS AND APPLICATIONS CONFERENCE (ITNAC 2015), IEEE, 326-331, 2015, Peer-reviwed, The Tor network is a widespread overlay anonymous network that is used by millions of users today. Tor focuses on improving the privacy of its users by routing their traffics through a series of onion routers that are located around the world. Since Tor operations mainly depend on volunteers who donated onion routers in the network, there are variances of capacities amongst different onion routers, which degrade the performances of Tor. In an effort to reduce the congestion problems in Tor, first we implemented control metrics to detect congestion on the entry OR. Second, we performed dynamic estimation of circuit congestion to select the best path in Tor. Third, we addressed the unfair distribution of bandwidth between the bulk and light traffics in Tor. We distributed the light and bulk traffics in Tor by having almost the same throughputs compared to default Tor multiplexing circuit approach. We use RTTs, circuit congestion and OR capacities as the main metrics to select the path. From our experimental analysis, we showed that our circuit switching method is effective to reduce the congestion problems in Tor.
International conference proceedings, English - Can DTN Improve the Performance of Vehicle-to-roadside Communication?
Celimuge Wu; Yusheng Ji; Satoshi Ohzahata; Toshihiko Kato
2015 IEEE 26TH ANNUAL INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR, AND MOBILE RADIO COMMUNICATIONS (PIMRC), IEEE, 1934-1939, 2015, Peer-reviwed, We propose a routing protocol for drive-thru Internet access in delay tolerant vehicular networks. The contribution of this paper is two-folds. First, we propose a new approach which utilizes the concept of delay tolerant network (DTN) to supplement the conventional communication approach. Second, we propose an algorithm to schedule DTN transmissions in order to maximize the system throughput. The proposed protocol is able to attain higher TCP throughput than the conventional approach by providing more efficient wireless resource utilization. We use theoretical analysis and computer simulations to evaluate the proposed protocol.
International conference proceedings, English - Packet Size-Aware Broadcasting in VANETs With Fuzzy Logic and RL-Based Parameter Adaptation
Celimuge Wu; Xianfu Chen; Yusheng Ji; Fuqiang Liu; Satoshi Ohzahata; Tsutomu Yoshinaga; Toshihiko Kato
IEEE ACCESS, IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 3, 2481-2491, 2015, Peer-reviwed, Most existing multi-hop broadcast protocols for vehicular ad hoc networks do not consider the problem of how to adapt transmission parameters according to the network environment. Besides the propagation environment that determines the channel bit error rate, packet payload size has a significant effect on the packet loss rate. In this paper, we first discuss the effect of packet size on the packet reception ratio, and then propose a broadcast protocol that is able to specify the best relay node by taking into account the data payload size. The proposed protocol employs a fuzzy logic-based algorithm to jointly consider multiple metrics (link quality, inter-vehicle distance, and vehicle mobility) and uses a redundancy transmission approach to ensure high reliability. Since the fuzzy membership functions are tuned by using reinforcement learning, the protocol can adapt to various network scenarios. We use both real-world experiments and computer simulations to evaluate the proposed protocol.
Scientific journal, English - Sequential Combination of Two Classifier Algorithms for Binary Classification to Improve the Accuracy
Sornxayya Phetlasy; Satoshi Ohzahata; Celimuge Wu; Toshihiko Kato
PROCEEDINGS OF 2015 THIRD INTERNATIONAL SYMPOSIUM ON COMPUTING AND NETWORKING (CANDAR), IEEE, 576-580, 2015, Peer-reviwed, Binary classification is a process of classifying the elements of a data set into two groups on the basis of a classification rule. It is useful and widely applied in many fields: Information Technology, Business, Medical Diagnosis, Finance, and so on. The problems of the previous works do not specify clearly which classifier utilizes to minimize which type of false, False Positive (FP) or False Negative (FN), because they are tradeoffs. In this study, we propose a hybrid method for data classification with two different classifier algorithms. The first classifier responds to reduce FN, and the second classifier is in charge of reducing FP. Our experiments utilize the data set of breast cancer, Wisconsin Breast Cancer (WBC) which is popular data set among the researchers for breast cancer diagnosis. The results show that the proposed method improves accuracy.
International conference proceedings, English - A Packet Size-aware Multi-hop Broadcast Protocol for VANETs Based on Adaptive Redundancy
Celimuge Wu; Xianfu Chen; Yusheng Ji; Satoshi Ohzahata; Toshihiko Kato
The 24th International Conference on Computer Communications and Networks (ICCCN), 134-139, 2015, Peer-reviwed
International conference proceedings, English - A Distributed Dynamic Channel Assignment and Routing Framework for Cognitive Sensor Systems
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
IEICE TRANSACTIONS ON INFORMATION AND SYSTEMS, IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG, E97D, 10, 2613-2622, Oct. 2014, Peer-reviwed, With the increase of the number of wireless sensing or metering devices, the collection of sensing data using wireless communication becomes an important part of a smart grid system. Cognitive radio technology can be used to facilitate the deployment of smart grid systems. In this paper, we propose a data collection and dissemination framework for cognitive radio smart grid systems to fully utilize wireless resources while maintaining a reliably connected and efficient topology for each channel. In the proposed framework, each sensor node selects a channel considering the primary user (PU) channel utilization and network connectivity. In this way, the data collection and dissemination can be performed with a high reliability and short delay while avoiding a harmful effect on primary users. We use computer simulations to evaluate the proposed framework.
Scientific journal, English - Coded packets over lossy links: A redundancy-based mechanism for reliable and fast data collection in sensor networks
Celimuge Wu; Yusheng Ji; Juan Xu; Satoshi Ohzahata; Toshihiko Kato
COMPUTER NETWORKS, ELSEVIER SCIENCE BV, 70, 9, 179-191, Sep. 2014, Peer-reviwed, In wireless sensor networks (WSNs), many applications require a high degree of reliability with low delay. Due to the lossy nature of wireless channels, achieving reliable communication can be very challenging. The most commonly adopted approach for achieving reliability is the acknowledgment based retransmission mechanism; however, this approach is inefficient in terms of end-to-end delay especially when there are a large number of hops from a sensor to the sink node. In this paper, we propose a redundancy-based approach that achieves high reliability and low end-to-end delay. The proposed protocol employs a network coding-based approach to improve packet redundancy when a link is unreliable or there is a strict end-to-end delay requirement. The protocol adaptively changes the redundancy level according to the application requirements and link loss rate. The protocol can be implemented easily because modification of the application layer at the source node and destination node is the only mandatory requirement. We implement the proposed mechanism on a real testbed which consists of IRIS motes, and evaluate the performance of the proposed mechanism using real-world experiments, network simulations and theoretical analysis. (C) 2014 Elsevier B.V. All rights reserved.
Scientific journal, English - A Multi-hop Broadcast Protocol for VANETs Utilizing Backbone-based Forwarding and Network Coding
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
IEICE Technical Report, 114, 160, 75-80, Jul. 2014
Symposium, English - Inter-flow Network Coding for Unicast Routing Protocols in Vehicular Ad Hoc Networks
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
IEICE Technical Report, 114, 110, 1-6, Jun. 2014
Symposium, English - 無線LAN におけるアクセスポイントと端末の協調による送信機会確保のためのメディアアクセス制御
熊谷雄太; 大坐畠 智; 加藤聰彦
電子情報通信学会 和文論文誌Ｂ, 電子情報通信学会, J97-B, 2, 110-119, Feb. 2014, Peer-reviwed
Scientific journal, Japanese - Analyzing the Drawbacks of Node-Based Delays in Tor
Timothy Girry Kale; Satoshi Ohzahata; Celimuge Wu; Toshihiko Kato
Proc. of IEEE CQR, 6 pages, 01 Jan. 2014, Peer-reviwed
International conference proceedings, English - TCP Performance Problem on Timeout Retransmission Triggered by Bursty Packet Losses
Weikai Wang; Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
Proc. of International Conference on Theory and Practice in Modern Computing, 141-148, 01 Jan. 2014, Peer-reviwed
International conference proceedings, English - Providing Fast Broadcasting by Reserving Time Slots for Multi-hop Distance in VANETs
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
2014 INTERNATIONAL WIRELESS COMMUNICATIONS AND MOBILE COMPUTING CONFERENCE (IWCMC), IEEE, 213-218, 2014, Peer-reviwed, In vehicular ad hoc networks (VANETs), multi-hop broadcast protocols arc required for many applications including driver assistance systems. However, providing a low end-to-end latency has been very challenging. In this paper, we propose a protocol which can provide a fast channel access for broadcast traffic flows in %AMA's. The protocol introduces new control messages to reserve time slots fill- the li)rwarder nodes and eliminate the hidden terminal problem. By providing a contention-free multihop forwarding scheme based on reliably generated forwarding backbone, the protocol can provide low end-to-end delay and high packet dissemination ratio. The theoretical analysis and simulation results demonstrate the advantage of the proposed protocol over other existing alternatives.
International conference proceedings, English - Toward a Totally Distributed Flat Location Service for Vehicular Ad Hoc Networks
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
2014 IEEE 79TH VEHICULAR TECHNOLOGY CONFERENCE (VTC-SPRING), IEEE, 6 pages, 2014, Peer-reviwed, Many routing protocols in vehicular ad hoc networks (VANETs) utilize location information to find a route to the destination. However, tracking the location information of other nodes is very challenging in highly dynamic VANETs. We propose a location service which can provide location information with low overhead and low delay. The location service periodically disseminates the location of each vehicle to 3-hop distance for every second with very low overhead. By eliminating location errors by taking account of the velocity of a vehicle, the proposed protocol can provide accurate position information. The location service also provides a lightweight location query mechanism for longer distance destination nodes. We show the effectiveness of the protocol by using theoretical analysis and computer simulations.
International conference proceedings, English - Joint MAC and Network Layer Control for VANET Broadcast Communications Considering End-to-end Latency
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
2014 IEEE 28TH INTERNATIONAL CONFERENCE ON ADVANCED INFORMATION NETWORKING AND APPLICATIONS (AINA), IEEE, 689-696, 2014, Peer-reviwed, In vehicular ad hoc networks (VANETs), multi-hop broadcast communications are required for many applications including driver assistance systems. However, providing a low end-to-end latency has been very challenging. In this paper, we propose a joint MAC network layer multi-hop broadcast protocol. For the network layer, the proposed protocol reduces the number of sender nodes by using common forwarder nodes for different traffic flows. At the MAC layer, the proposed protocol uses a Q-Learning algorithm to adjust the contention window size. By interacting with the environment, the protocol can find the best contention window size to transmit data packets and therefore can provide a high packet dissemination ratio and low end-to-end delay for various scenarios. The simulation results demonstrate the advantage of the proposed protocol over other existing alternatives.
International conference proceedings, English - A MAC Protocol for Delay-sensitive VANET Applications With Self-learning Contention Scheme
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
2014 IEEE 11TH CONSUMER COMMUNICATIONS AND NETWORKING CONFERENCE (CCNC), IEEE, 729-734, 2014, Peer-reviwed, Packet delivery ratio and end-to-end delay are the two most important metrics for vehicular ad hoc network applications. In this paper, we propose a MAC layer protocol which can provide a high packet delivery ratio, low end-to-end delay, and high fairness for various scenarios. The proposed protocol uses a Q-Learning algorithm to adjust the contention window size in order to provide an efficient channel access scheme for various network situations. The simulation results demonstrate the advantage of the proposed protocol over other alternatives.
International conference proceedings, English - A Circuit Switching Method for Improving Congestion of Tor Network
Kale Timothy Girry; Satoshi Ohzahata; Celimuge Wu; Toshihiko Kato
2014 NINTH INTERNATIONAL CONFERENCE ON BROADBAND AND WIRELESS COMPUTING, COMMUNICATION AND APPLICATIONS (BWCCA), IEEE, 416-421, 2014, Peer-reviwed, The Tor Network is a low-latency anonymity and censorship resistance network, which relaying traffics through series of onion routers (OR) before being forwarded to the destination. Tor is vulnerable to network congestion and performance problems, due to bulk and light traffics arc competing to transfer data on a single TCP connection. A large fraction of the available network capacity is consumed by bulk users' traffic, resulting in higher buffer occupancy and delays for interactive light users. To address the problems, we propose a method of switching the bulk traffic that contributes to increasing delays to another path, which built preemptively at the beginning. This approach allows the light interactive circuits to utilize the bandwidth resources well and, easily writes their cells from the circuit queue to the output buffer and outgoing TCP socket. Our approach of switching bulk circuits in the overloaded ORs comes to effect if the Tor output queues increases beyond the threshold value, and when sending TCP socket is congested and un-writable. Our goal is to reduce the congestion in the ORs and improve the throughput from the incoming traffic (upstream), and outgoing traffic (downstream). Through measurements and evaluation conducted in the live Tor network, we observed that the throughput of the light interactive traffic is improved. The light circuit traffics are no longer forced to wait behind the bulk traffic when transfer their data to the outgoing TCP socket.
International conference proceedings, English - Performance Analysis of a Content Distribution Method using Pseudo-Multicast with File Piecing for Wireless Multi-hop Environment
Kazuaki Nishizaka; Satoshi Ohzahata; Toshihiko Kato
2014 SECOND INTERNATIONAL SYMPOSIUM ON COMPUTING AND NETWORKING (CANDAR), IEEE, 192-197, 2014, Peer-reviwed, Nowadays, wireless LAN is included in many portable devices and is widely deployed, which has correspondingly increased the potential to distribute documents electronically. However, a wireless network shares bandwidth with multiple terminals under media access control, so the bandwidth is not used efficiently when the same content is simultaneously transferred to each terminal with unicast. Therefore, we have proposed a method for content distribution in wireless networks that achieves faster downloads by combining file piecing and pseudo-multicast, allowing multiple terminals to overhear packets of the same content. Applying this method to a multi-hop wireless network should improve content distribution efficiency by collecting the frames from different hops. However, the overheard frames have to be adequately provisioned against losses and disordered delivery order due to different hops. To handle these problems, we have improved the byte stream management method in the overhearing node to efficiently obtain the required pieces. The proposed method is evaluated in a testbed.
International conference proceedings, English - 熊谷雄太, 大坐畠 智, 加藤聰彦
無線LAN におけるアクセスポイントと端末の協調による送信機会確保のためのメディアアクセス制御
電子情報通信学会 和文論文誌Ｂ, J97-B, 2, 110-119, 2014, Peer-reviwed
Scientific journal, Japanese - Multi-hop Broadcasting in VANETs Integrating Intra-flow and Inter-flow Network Coding
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
2014 IEEE 80TH VEHICULAR TECHNOLOGY CONFERENCE (VTC FALL), IEEE, 1091-1096, 2014, Peer-reviwed, Multi-hop data dissemination in vehicular ad hoc networks (VANETs) is very important for the realization of collision avoidance systems and other many interesting applications. However, designing an efficient data dissemination protocol in VANETs has been a challenging issue due to vehicle movements, limited wireless resources and lossy characteristics of wireless communication. In this paper, we propose a protocol which employs intra-flow and inter-flow network coding to reduce the protocol overhead as compared to traditional protocols. The protocol also can improve the packet reception probability at the receiver nodes by using the network coding. Therefore, the protocol can provide a lightweight and reliable solution for data dissemination in VANETs. We use theoretical analysis and computer simulations to show the advantage of the proposed protocol over other existing alternatives.
International conference proceedings, English - A QoS Supporting Ad Hoc Network Protocol Combing Admission Based TDMA and 802.11 DCF
Jing Lin; Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
2014 16th Asia-Pacific Network Operations and Management Symposium (APNOMS), IEEE, 4pages, 2014, Peer-reviwed, We propose a QoS supporting ad hoc network protocol which employs a hybrid approach utilizing both TDMA and 802.11 DCF. TDMA period provides contention free transmissions for QoS flows, and DCF period is used to provide contention-based access for best effort or low priority flows. TDMA time slots are assigned on admission basis in a distributed manner by utilizing network routing information and considering current assignment situation. In DCF period, frames are transmitted not to disturb the TDMA period. By combing TDMA and 802.11 DCF, the proposed ad hoc network is able to provide an efficient solution for QoS control in ad hoc networks. We use QualNet simulator to evaluate the proposed scheme.
International conference proceedings, English - Multi-hop Broadcasting in WAVE Multi-channel Vehicular Networks: Single Transceiver Case
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
2014 IEEE 17TH INTERNATIONAL CONFERENCE ON INTELLIGENT TRANSPORTATION SYSTEMS (ITSC), IEEE, 1091-1096, 2014, Peer-reviwed, Multi-hop data dissemination in vehicular ad hoc networks (VANETs) has been very challenging due to the vehicle movement, various vehicle densities and the lossy characteristics of a wireless channel. The problem of how to provide an efficient broadcasting of time-critical broadcast messages under multi-channel operation of IEEE WAVE standard has not been discussed sufficiently. In this paper, we discuss the multi-hop broadcast problem in multi-channel environment defined by IEEE WAVE, and propose a multi-hop broadcast protocol which conducts efficient channel utilization with single transceiver. We use computer simulations to show the advantage of the proposed protocol over other existing alternatives.
International conference proceedings, English - Resolving bufferbloat problem in 802.11n WLAN by weakening MAC loss recovery for TCP stream
Masataka Nomoto; Toshihiko Kato; Celimuge Wu; Satoshi Ohzahata
Proceedings of the IASTED International Conference on Parallel and Distributed Computing and Networks, PDCN 2014, Acta Press, 293-300, 2014, Peer-reviwed, IEEE 802.11n wireless LANs provide high-speed data transfer. If the radio condition degrades, however, the transfer rate will be reduced significantly and there may be some problems in the data transfer. In order to clarify this problem, we have evaluated the TCP performance over IEEE 802.11n LAN by changing the distance between the access point and a terminal. As a result, a severe increase of round trip time has been measured in the case of low data rate. This is a sort of bufferbloat problem, which is being actively studied in recent years. The detailed analysis of this experiment is our first contribution. We have inferred that one of the reasons for this increased delay is the powerful retransmission function of 802.11n. So, we propose, as the second contribution, a method to improve TCP delay performance by reducing this retransmission capability and by generating TCP segment loss intentionally. This paper describes the performance evaluations for our proposal in comparison with CoDel, which is an active queue management approach, and with the native 802.11n.
International conference proceedings, English - Experimental Analysis of TCP Behaviors against Bursty Packet Losses Caused by Transmission Interruption
Weikai Wang; Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
ICN 2014, 136-141, 2014, Peer-reviwed
International conference proceedings, English - Inferring TCP Congestion Control Algorithms by Correlating Congestion Window Sizes and their Differences
Toshihiko Kato; Atsushi Oda; Shun Ayukawa; Celimuge Wu; Satoshi Ohzahata
ICSNC 2014, 42-47, 2014, Peer-reviwed
International conference proceedings, English - Making Inter-flow Network Coding Possible for Unicast Routing in VANETs
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
2014 INTERNATIONAL CONFERENCE ON CONNECTED VEHICLES AND EXPO (ICCVE), IEEE, 829-835, 2014, Peer-reviwed, Designing an efficient unicast routing protocol for vehicular ad hoc networks has been a challenging issue due to the vehicle movement, limited wireless resources and lossy feature of wireless channel. We propose a protocol which utilizes inter-flow network coding to route data messages. The proposed protocol uses common backbone vehicles for different traffic flows. A reliability connected backbone is selected by considering vehicle movement dynamics and link quality between vehicles. By using inter-flow network coding at the backbone vehicles, the protocol can reduce the number of generated packets by 25% in most cases as compared to the traditional routing approach. As a result, the proposed protocol can provide a high packet delivery ratio, low overhead and low delay. We show the effectiveness of the protocol using theoretical analysis and computer simulations.
International conference proceedings, English - Practical Solution for Broadcasting in VANETs using Neighbor Information
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
IEICE Transactions on Communications, E96-B, 11, 2856-2864, Nov. 2013, Peer-reviwed
Scientific journal, English - A VANET Routing Protocol Considering MAC Efficiency
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
IEICE Technical Report, 113, Nov. 2013
Symposium, English - Flexible, Portable, and Practicable Solution for Routing in VANETs: A Fuzzy Constraint Q-Learning Approach
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 62, 9, 4251-4263, Nov. 2013, Peer-reviwed, Vehicular ad hoc networks (VANETs) have been attracting interest for their potential uses in driving assistance, traffic monitoring, and entertainment systems. However, due to vehicle movement, limited wireless resources, and the lossy characteristics of a wireless channel, providing a reliable multi-hop communication in VANETs is particularly challenging. In this paper, we propose PFQ-AODV, which is a portable VANET routing protocol that learns the optimal route by employing a fuzzy constraint Q-learning algorithm based on ad hoc on-demand distance vector (AODV) routing. The protocol uses fuzzy logic to evaluate whether a wireless link is good or not by considering multiple metrics, which are, specifically, the available bandwidth, link quality, and relative vehicle movement. Based on an evaluation of each wireless link, the proposed protocol learns the best route using the route request (RREQ) messages and hello messages. The protocol can infer vehicle movement based on neighbor information when position information is unavailable. PFQ-AODV is also independent of lower layers. Therefore, PFQ-AODV provides a flexible, portable, and practicable solution for routing in VANETs. We show the effectiveness of the proposed protocol by using both computer simulations and real-world experiments.
Scientific journal, English - Improving VANET unicast routing protocols by using cooperative relays and network coding
Celimuge Wu; Satoshi Ohzahata; Yusheng Ji; Toshihiko Kato
IEICE Technical Report, 113, Oct. 2013
Symposium, English - Can We Generate Efficient Routes by Using Only Beacons? Backbone Routing in VANETs
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
2013 IEEE 24TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR, AND MOBILE RADIO COMMUNICATIONS (PIMRC), IEEE, 2929-2934, 2013, Peer-reviwed, Point-to-point data delivery in Vehicular Ad hoc NETworks (VANETs) has been a challenging issue due to the vehicle movement, limited wireless resources and lossy feature of wireless channel. In VANETs, due to the frequent topology changes, traditional ad hoc routing protocols incur a high overhead for the route maintenance. In this paper, we propose a new approach to route data messages in VANETs. The proposed protocol uses dynamically generated backbone vehicles to forward data messages. The protocol generates the backbone by using only hello messages. The protocol selects the backbone vehicles by considering vehicle movement dynamics and link quality between vehicles. As a result, the selected backbone vehicles generate a reliably connected network. By using packet forwarding with the backbone nodes, the proposed protocol can reduce the message overhead and MAC layer contention time at each node while maintaining a high packet delivery ratio. We show the effectiveness of the proposed protocol with both theoretical analysis and computer simulations.
International conference proceedings, English - Network Coding Assisted Cooperative Relay Scheme for Sender-oriented Broadcast in VANETs
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
2013 IEEE WIRELESS COMMUNICATIONS AND NETWORKING CONFERENCE (WCNC), IEEE, 1369-1374, 2013, Peer-reviwed, In vehicular ad hoc networks (VANETs), a multi-hop broadcast protocol is required to disseminate traffic warning information. Reducing broadcast message overhead while maintaining a high dissemination ratio is a very challenging task. In this paper, we study how to improve the performance of sender-oriented broadcast protocols using network coding. We propose a scheme which uses network coding to improve the packet dissemination ratio without increasing the message overhead. In the proposed scheme, the source node specifies two relay nodes. With cooperation between two relay nodes, the proposed scheme significantly increases the packet reception ratio by utilizing the broadcast nature of wireless channel. We show the effectiveness of the proposed scheme by using both theoretical analysis and computer simulations.
International conference proceedings, English - A reliable and flexible data gathering protocol for battery limited wireless sensor networks
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
International Journal of Communication Networks and Distributed Systems, 11, 2, 139-156, 2013, Peer-reviwed, In this paper, we consider a wireless sensor network (WSN) for a clinical purpose. However, due to the fading in wireless communications and limited battery power of electronic devices, providing an efficient and reliable communication is extremely challenging. As a solution, we propose fuzzy one-phase pull (FOPP), a fuzzy logic-based one-phase pull protocol. The protocol considers signal strength, route length and residual energy in the route selection. The protocol employs a fuzzy logic to consider these metrics jointly. Since the parameters and the rules used in the fuzzy logic are reconfigurable, the proposed protocol can be used in any scenarios by simple parameter tuning. We also propose two mechanisms (timeout retransmission mechanism and double-path mechanism) to further improve the reliability of the protocol. We use computer simulations to evaluate the performance of the proposed protocol. Copyright © 2013 Inderscience Enterprises Ltd.
Scientific journal, English - Practical Solution for Broadcasting in VANETs using Neighbor Information
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
IEICE Transaction on Communication, J97-B, 2, 110-119, 2013, Peer-reviwed
Scientific journal, English - Data Dissemination with Dynamic Backbone Selection in Vehicular Ad Hoc Networks
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
2013 IEEE 78TH VEHICULAR TECHNOLOGY CONFERENCE (VTC FALL), IEEE, 6 pages, 2013, Peer-reviwed, Efficient data dissemination in Vehicular Ad hoc NETworks (VANETs) has been a challenging issue due to vehicle movements, limited wireless resources and lossy characteristics of wireless communication. In this paper, we use dynamically generated backbone vehicles to disseminate information. The proposed protocol selects the backbone vehicles by considering vehicle movement dynamics and link quality between vehicles. The proposed approach can significantly reduce the MAC layer contention time at each node while maintaining a high packet dissemination ratio. We show the effectiveness of the proposed protocol by using theoretical analysis and computer simulations.
International conference proceedings, English - A Loss-tolerant Scheme for Unicast Routing in VANETs using Network Coding
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
2013 9TH INTERNATIONAL WIRELESS COMMUNICATIONS AND MOBILE COMPUTING CONFERENCE (IWCMC), IEEE, 1058-1063, 2013, Peer-reviwed, In vehicular ad hoc networks (VANETs), designing an efficient routing protocol is particularly challenging due to the vehicle movement and lossy wireless channel. A packet can be lost at a forwarder node even when a proper node is selected as the forwarder. In this paper, we propose a loss-tolerant scheme for unicast routing protocols in VANETs. The proposed scheme uses multiple forwarder nodes to improve the packet reception ratio at the forwarders. The scheme uses network coding to reduce the number of required transmissions, resulting in a significant improvement of end-to-end packet delivery ratio without increasing the message overhead. We show the effectiveness of the proposed scheme by using both theoretical analysis and computer simulations.
International conference proceedings, English - Joint MAC network layer broadcast protocol for vehicular ad hoc networks
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
2013 IEEE International Conference on Communications Workshops, ICC 2013, 495-499, 2013, Peer-reviwed, Packet dissemination ratio and end-to-end delay are the two most important metrics for multi-hop broadcast protocols in vehicular ad hoc networks (VANETs). In this paper, we propose a joint MAC network layer broadcast protocol. The proposed protocol uses selected relay nodes to forward packets. A reliable communication is conducted between the sender node and each relay node by using MAC layer acknowledgments. The protocol can provide a low delay and high packet dissemination ratio by reducing the packet loss detection delay and providing retransmissions at the MAC layer. We show the effectiveness of the proposed protocol by using both theoretical analysis and computer simulations. © 2013 IEEE.
International conference proceedings, English - OPTIMIZATION OF AREA SPLITTING TO MINIMIZE OSPF LSA EXCHANGE
Toshihiko Kato; Tsukasa Miyamae; Celimuge Wu; Satoshi Ohzahata
The IADIS Theory and Practice in Modern Computing 2013 (TPMC 2013) Conference, *, 2013, Peer-reviwed
International conference proceedings, English - Can We Generate Efficient Routes by Using Only Beacons? Backbone Routing in VANETs,
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
Proc. of PIMRC 2013, 2944-2949, 2013, Peer-reviwed
International conference proceedings, English - An Improvement of OLSR Using Fuzzy Logic Based MPR selection
Narangerei Dashbyamba; Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
2013 15TH ASIA-PACIFIC NETWORK OPERATIONS AND MANAGEMENT SYMPOSIUM (APNOMS), IEEE, 6 pages, 2013, Peer-reviwed, Optimized Link State Routing Protocol (OLSR) is a well-known proactive routing protocol for mobile ad hoc networks. OLSR reduces the number of control messages by using MPRs to forward topology control messages as compared with typical proactive protocols. Since OLSR does not consider the node mobility and signal strength condition for the MPR (MultiPoint Relays) selection, OLSR cannot work well in a highly mobile and lossy network. In this paper, we propose a protocol which improves OLSR by taking into account the node mobility and signal strength in the selection of MPRs. We use network simulations to evaluate the proposed protocol's performance.
International conference proceedings, English - Effectiveness of Performance Flag Selection for Enhancing Tor Circuits
Kale Timothy Girry; Satoshi Ohzahata; Celimuge Wu; Toshihiko Kato
2013 15TH ASIA-PACIFIC NETWORK OPERATIONS AND MANAGEMENT SYMPOSIUM (APNOMS), IEEE, 3 pages, 2013, Peer-reviwed, Tor is an open network that defends against network surveillance, preserving personal freedom and privacy on the Internet. The barrier to a more widespread use of Tor is a variety of performance problems. We focused on enhancing Tor circuits by selecting the relays on the basis of assigned performance flags, which are known as a guard, fast and stable flags. We observed that these simple strategies can improve the selection method for relays with high bandwidth and TCP advertised window sizes. In this work, we regard bandwidth as the key factor in Tor design and path selection. We determine a better method of circuit selection based on actively measuring RTTs, TCP throughput and the TCP advertised window sizes of the relays.
International conference proceedings, English - An efficient overhearing strategy for content distribution in wireless LAN
Hiroaki Yokose; Satoshi Ohzahata; Toshihiko Kato
Asian Internet Engineeering Conference, AINTEC 2013, Association for Computing Machinery, 33-40, 2013, Peer-reviwed, When the same content is simultaneously downloaded by several terminals with unicast in a wireless LAN, the band- width must be divided among the terminals and download speed is reduced. With using broadcast nature of wireless media, we propose an efficient method that can achieve reli- able content distribution by using overheard TCP flows of a specific content going to other terminals in a wireless LAN. In the proposed method a content is divided into pieces and the server distributes them according to the download status of the receivers in application level. To accelerate down- loading, we propose a method for selecting the piece and the terminal for transmission taking the effect of network coding for efficient overhearing. We developed a testbed and con- firmed that the proposed scheduling accelerates the down- load speed even where the communication speed of each ter- minal is different. Copyright © 2013 ACM.
International conference proceedings, English - A routing protocol for cognitive radio ad hoc networks giving consideration to future channel assignment
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
Proceedings - 2013 1st International Symposium on Computing and Networking, CANDAR 2013, 227-232, 2013, Peer-reviwed, Cognitive radio technology can be used to solve the problems of limited available spectrum and inefficient spectrum usage by adaptively changing transmission parameters. By utilizing CR technology for dynamic and distributed multi-hop networks, cognitive radio ad hoc networks can efficiently utilize free wireless resources. However, the routing protocols for cognitive radio CSMA/CA ad hoc networks have not been discussed seriously. An efficient protocol considering primary user flows and channel assignment incurred network connectivity issue in the route selection is still missing. In this paper, we propose AODV-cog, a cognitive routing protocol for CSMA/CA ad hoc networks based on AODV. AODV-cog chooses a route by considering the effect on the primary users, available channel bandwidth and link reliability. AODV-cog also takes in account of future channel utilization which is important but overlooked by existing works. AODV-cog switches channels for secondary user flows when network congestion is occurred. We use computer simulations to show the advantage of AODV-cog over existing alternatives. © 2013 IEEE.
International conference proceedings, English - Routing in VANETs: A Fuzzy Constraint Q-Learning Approach
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
Proc. of GLOBECOM 2012, 231-218, Dec. 2012, Peer-reviwed
International conference proceedings, English - An Efficient Contents Distribution Method Using Overhearing and File Piecing in Wireless LAN
Hiroaki Yokose; Satoshi Ohzahata; Toshihiko Kato
Proc. of APSITT 2012, 6 pages, Nov. 2012, Peer-reviwed
International conference proceedings, English - Winnyネットワークにおける検索クエリの遮断によるファイル流通制御方式
中澤 大暁; 吉田 雅裕; 大坐畠 智; 中尾 彰宏; 川島 幸之助
電子情報通信学会 和文論文誌Ｂ, The Institute of Electronics, Information and Communication Engineers, 95-B, 5, 636-648, May 2012, Peer-reviwed, 近年,P2P方式を用いたファイル共有やVoIP,広告配信,データ通信などが世界中で広く使われている.しかしながら,ファイル共有システムでは情報流出や著作権侵害ファイルの流通の問題が発生している.そこで本研究では,ネットワーク上にファイル検索リンクを多数もつ制御ピアを配置することで,ファイルの検索効率を適切に変化させ,制御対象ファイルの流通を制御する方式を提案する.提案方式では,ネットワーク構造やピア特性に着目した制御により,ファイル共有システムでファイル検索に利用される"検索クエリ"をブロックすることで,制御対象フアイルの位置情報を含む"キー"の検索効率を低下させる.そして,実際のWinnyネットワーク上で提案方式の有用性を評価した.評価実験では,検索クエリの帰還率や検索成功率,"キー"の拡散度合いを測定した.その結果,検索ネットワーク全体の70%以上のピアを制御範囲とすることで,検索ネットワーク上の"キー"を減少させ,検索成功率を1%以下にすることができた.
Scientific journal, Japanese - VANET Broadcast Protocol Based on Fuzzy Logic and Lightweight Retransmission Mechanism
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
IEICE TRANSACTIONS ON COMMUNICATIONS, IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG, E95B, 2, 415-425, Feb. 2012, Peer-reviwed, Vehicular ad hoc networks have been attracting the interest of both academic and industrial communities on account of their potential role in Intelligent Transportation Systems (ITS). However, due to vehicle movement and fading in wireless communications, providing a reliable and efficient multi-hop broadcast service in vehicular ad hoc networks is still an open research topic. In this paper, we propose FUZZBR (FUZZy BRoadcast), a fuzzy logic based multi-hop broadcast protocol for information dissemination in vehicular ad hoc networks. FUZZBR has low message overhead since it uses only a subset of neighbor nodes to relay data messages. In the relay node selection. FUZZBR jointly considers multiple metrics of inter-vehicle distance, node mobility and signal strength by employing the fuzzy logic. FUZZBR also uses a lightweight retransmission mechanism to retransmit a packet when a relay fails. We use computer simulations to evaluate the performance of FUZZBR.
Scientific journal, English - Routing in VANETs: A Fuzzy Constraint Q-Learning Approach
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
2012 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), IEEE, 195-200, 2012, Peer-reviwed, Vehicular ad hoc networks (VANETs) can be used for the purpose of driving assistance, environment monitoring and entertainment. However, due to the vehicle movement, limited wireless resources and lossy feature of wireless channel, providing a reliable multi-hop communication in VANETs is particularly challenging. In this paper, we propose a VANET routing protocol which learns the optimal route by employing a fuzzy constraint Q-Learning algorithm. The protocol uses a fuzzy logic to evaluate a wireless link is whether good or not by considering multiple metrics of signal strength, available bandwidth and relative vehicle movement. Based on the evaluation of each wireless link, the proposed protocol learns the best route using the route request messages and hello messages. Upon reception of a route request message, each node maintains an evaluation value for each possible next hop node. In this way, the protocol can choose the best route, which is difficult to acquire in a typical reactive routing protocol. We show the effectiveness of the proposed protocol by using computer simulations.
International conference proceedings, English - A low latency path diversity mechanism for sender-oriented broadcast protocols in VANETs
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
Elsevier Journal of Ad Hoc Networks, 11, 7, 2059-2068, 2012, Peer-reviwed
Scientific journal, English - An adaptive redundancy-based mechanism for fast and reliable data collection in WSNs
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
2012 IEEE 8TH INTERNATIONAL CONFERENCE ON DISTRIBUTED COMPUTING IN SENSOR SYSTEMS (DCOSS), IEEE, 347-352, 2012, Peer-reviwed, Wireless sensor networks (WSNs) can be used for a variety of applications. For many applications, a high reliability and low delay are required. Due to lossy feature of wireless channel, providing a reliable communication is very challenging. The most frequently used approach for providing the reliability is to use the acknowledgement based retransmission mechanism which increases the end-to-end delay especially when the number of hops from a sensor to the sink node is large. In this paper, we propose a redundancy-based approach to provide a high reliability while maintaining a low end-to-end delay. The proposed mechanism uses a redundant transmission when a link is unreliable or the end-to-end delay requirement is strict. We implement the proposed mechanism on a wireless sensor network which consists of IRIS motes, and evaluate the performance of the proposed mechanism.
International conference proceedings, English - Dynamic channel assignment and routing for cognitive sensor networks
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
Proceedings of the International Symposium on Wireless Communication Systems, 86-90, 2012, Peer-reviwed, With the increase of the number of wireless sensing or metering devices, the collection of sensing data using wireless communication becomes an important part of many applications. Cognitive radio technology can be used to facilitate the deployment of a bandwidth efficient sensor system. In this paper, we propose a data collection and dissemination framework for cognitive radio sensor systems to fully utilize wireless resources while maintaining a reliably connected and efficient topology for each channel. In the proposed framework, each sensor node selects a channel considering primary user channel utilization and network connectivity. In this way, the data collection and dissemination can be performed with a high reliability and short delay while avoiding a harmful effect on primary users. We use computer simulations to evaluate the proposed framework. © 2012 IEEE.
International conference proceedings, English - How to Broadcast Efficiently in Vehicular Ad Hoc Networks Without GPS
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
2012 IEEE VEHICULAR NETWORKING CONFERENCE (VNC), IEEE, 258-264, 2012, Peer-reviwed, In vehicular ad hoc networks (VANETs), a multi-hop broadcast protocol is required to disseminate traffic warning information to multiple receivers. Reducing broadcast message overhead is important because it could directly affect the packet collision probability and MAC layer contention time at each node. There have been some broadcast protocols for VANETs. However, many of them assume the availability of the global positioning system. In this paper, we propose a broadcast protocol which does not require position information. The protocol uses two-hop neighbor information to select relay nodes which are used to forward a packet. The proposed protocol also uses a joint redundancy and opportunistic transmission approach to recover a packet loss. We show the effectiveness of the proposed protocol by evaluating in a real vehicular ad hoc network.
International conference proceedings, English - A Broadcast Path Diversity Mechanism for Delay Sensitive VANET Safety Applications
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
Proc. of IEEE Vehicular Networking Conference, 292-297, Nov. 2011, Peer-reviwed
International conference proceedings, English - Shareネットワークに対するコンテンツポイズニングを用いたファイル流通制御方式
吉田 雅裕; 大坐畠 智; 川島 幸之助; 中尾 彰宏
電子情報通信学会 和文論文誌Ｂ, The Institute of Electronics, Information and Communication Engineers, 94, 5, 686-697, May 2011, Peer-reviwed, P2Pファイル共有ネットワークは世界中で非常に多くのユーザに利用されている.しかし,現在のP2Pファイル共有ネットワークにはファイル流通制御機能が実装されていないため,著作権侵害ファイルやマルウェアなどの流通が大きな社会問題となっている.これらの問題を解決するために,コンテンツポイズニングを用いたファイル流通制御方式が提案されている.コンテンツポイズニングとは,一つのファイルを複数のブロックに分割して転送するP2Pファイル共有ネットワークに対して,ファイル転送中に偽装ブロックを混ぜて転送することで,ダウンロードしたファイルを不完全なものにして破損させる方式である.しかしながら,コンテンツポイズニングの従来の適用方式には,制御によってP2Pトラヒックが著しく増加してしまうなど,四つの解決すべき課題が存在する.そこで本論文では,これら四つの課題を解決したコンテンツポイズニングの改良方式を提案する.そして,10万台以上のアクティブピアによって構成される実際のShareネットワーク上で提案方式の有効性を評価した.評価実験の結果,提案方式をShareネットワークに適用した場合は,Shareピアが特定のファイルを入手できる確率が,適用しない場合と比較して5%まで低下することを確認した.また,提案方式はP2Pトラヒックの増加を,従来方式と比較して4%まで抑えられることを示した.
Scientific journal, Japanese - An experimental study of peer behavior in a pure P2P network
Satoshi Ohzahata; Konosuke Kawashima
JOURNAL OF SYSTEMS AND SOFTWARE, ELSEVIER SCIENCE INC, 84, 1, 21-28, Jan. 2011, Peer-reviwed, Dynamic peer behavior in P2P networks has a large impact on the performance of the network because each peer acts simultaneously as a server and a client in an overlay network. However, peer behavior in pure P2P networks is not well known because there is no management system and the network size is large. We have proposed a measurement method to collect information efficiently, and a method of analyzing the peer behavior with or without file uploading for pure P2P file sharing networks. These methods have been applied to Winny, which is the most popular P2P file sharing application in Japan. The analysis results show that the network is composed of about 30% of peers observed in 24 h, and 50% of peers contribute to the network as file uploaders. Selfish peers, which leave the network after downloading, are observed especially in the morning. The file uploading peers and the peers joining after midnight remain in the network for a long period. We also give mathematical fitting for the distribution of the peer lifetime and the frequency of joining the network. These results show that the distribution of lifetime does not have a heavy tail, and the behavior of peers joining the network is not a Poisson process. (C) 2010 Elsevier Inc. All rights reserved.
Scientific journal, English - Adaptive view-dependent tree graph visualization
Hiroko Nakamura Miyamura; Satoshi Ohzahata; Yuji Shinano; Ryuhei Miyashiro
Proceedings of the 2011 8th International Joint Conference on Computer Science and Software Engineering, JCSSE 2011, 187-192, 2011, Peer-reviwed, This paper proposes an adaptive visualization technique for representing a large-scale hierarchical dataset within a limited display space. A hierarchical dataset has nodes and links that reveal the parent-child relationship between the nodes. These nodes and links are described using graphics primitives. When the number of these primitives is large, it is difficult to recognize the structure of the hierarchical data because several primitives overlap within a display space. In order To overcome this difficulty, we propose an adaptive visualization technique for hierarchical datasets. The proposed technique selects an appropriate graph style according to the nodal density in each area. © 2011 IEEE.
International conference proceedings, English - Fuzzy One-phase Pull Diffusion for WSNs in Fading Channel
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
2011 INTERNATIONAL CONFERENCE ON DISTRIBUTED COMPUTING IN SENSOR SYSTEMS AND WORKSHOPS (DCOSS), IEEE, 1-6, 2011, Peer-reviwed, Using wireless sensor networks (WSNs) for a clinical purpose has many potential advantages. However, due to fading feature of wireless channel, providing an efficient and reliable communication is very challenging. In this paper, we propose FUZZ-OPP (FUZZy One-Phase Pull), a fuzzy logic based one-phase pull protocol. The protocol considers signals strength, internode distance and residual energy in the route selection. The protocol employs a fuzzy logic to consider these metrics jointly. Since the parameters and the rules used in the fuzzy logic are all reconfigurable, the proposed protocol can be used in any scenario by simple parameter tuning. We use computer simulations to evaluate the performance of the proposed protocol.
International conference proceedings, English - Learning route from beaconing and interest dissemination in vehicular sensor networks
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
Proceedings of 2011 6th International Conference on Telecommunication Systems, Services, and Applications, TSSA 2011, 49-54, 2011, Peer-reviwed, Vehicular sensor networks can be used to collect information for the purpose of driving assistance, environment monitoring and entertainment. However, due to the vehicle movement and lossy feature of wireless channel, providing a reliable multi-hop communication between a sensor node and a sink node is particularly challenging. In this paper, we propose a protocol which learns the optimal route in the exchange of hello messages and interest messages. The proposed protocol uses a fuzzy logic to evaluate a direct wireless link and uses a Q-learning algorithm to learn the best route from a multi-hop perspective. We use computer simulations to show the effectiveness of the proposed protocol. © 2011 IEEE.
International conference proceedings, English - A broadcast path diversity mechanism for delay sensitive VANET safety applications
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
IEEE Vehicular Networking Conference, VNC, 171-176, 2011, Peer-reviwed, Reliable multi-hop broadcast protocols for vehicular ad hoc networks have been widely discussed recently. However, most of them use acknowledgement based retransmissions to provide reliability. The retransmission method incurs delays when a packet loss cannot be detected on time. Acknowledgement messages also increase the MAC layer contention time at each node. In this paper, we propose a mechanism to use path diversity to provide the reliability. In the proposed mechanism, a message is disseminated by two different paths. By cooperation of these two paths, broadcast messages can be disseminated with a short delay and a high reliability compared with acknowledgement based retransmission approach. The proposed mechanism does not use any explicit acknowledgement message. We evaluate the proposed mechanism using both theoretical analysis and computer simulations. © 2011 IEEE.
International conference proceedings, English - OFA: Opportunistic forwarding and acknowledgement for vehicular ad hoc networks
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
IB2COM 2011 - 6th International Conference on Broadband Communications and Biomedical Applications, Program, 213-218, 2011, Peer-reviwed, In vehicular ad hoc networks (VANETs), providing a multi-hop communication is challenging due to the vehicle movement and lossy feature of wireless channel. Opportunistic routing provides an alternative solution with its utilization of the broadcast nature of wireless communication and the diversity of packet reception. However, most of opportunistic routing protocols specify the forwarding nodes at the sender side and therefore the opportunism cannot be fully utilized. Moreover, existing opportunistic routing protocols cannot provide a high reliability because of the lack of efficient packet reception check mechanism. In this paper, we propose OFA, an opportunistic forwarding and acknowledgement protocol for vehicular ad hoc networks. OFA performs both data forwarding and acknowledgement by taking advantage of multiuser diversity and route opportunism. In OFA, the forwarder node selection occurs at receiver nodes. An intermediate node is selected opportunistically to acknowledge the sender on the behalf the forwarder node when the forwarder node cannot communicate with the sender node directly. The proposed protocol can fully utilize the path diversity and also can provide hop-by-hop reliability. © 2011 IEEE.
International conference proceedings, English - A Method for Controlling Search in a Pure P2P File Sharing Network
Hiroaki Nakazawa; Masahiro Yoshida; Satoshi Ohzahata; Akihiro Nakao; Konosuke Kawashima
Proc. of 8th Asia-Pacific Symposium on Information and Telecommunication Technologies (APSITT 2010), 6 pages, Jun. 2010, Peer-reviwed
International conference proceedings, English - Controlling File Distribution in The Share Network Through Content Poisoning
Masahiro Yoshida; Satoshi Ohzahata; Akihiro Nakao; Konosuke Kawashima
Proc. of AINA 2010, 1004-1011, Apr. 2010, Peer-reviwed
International conference proceedings, English - TCP window control for QoS improvement based on channel occupancy information over wireless LAN
Keiya Ijiri; Satoshi Ohzahata; Konosuke Kawashima
IEEE International Conference on Industrial Informatics (INDIN), 1016-1021, 2010, Peer-reviwed, TCP has been a congestion control method in the Internet. However, since TCP is not able to directly measure the network status from the end nodes, the TCP window control gradually increases the congestion window size until congestion occurs. This control gets network bandwidth aggressively and affects communication of all stations (STAs) which belong to the same access point of IEEE 802.11 standards. Especially, the communication quality for real-time applications such as video streaming becomes worse. To improve this problem, we have proposed a TCP window control method with adjusting the congestion window size for available bandwidth of the access point. TCP window size is adequately controlled by measuring the channel occupancy of each STA. The channel status information is passed to the TCP window control function via a cross layer control mechanism. We have developed a testbed and shown the effectiveness of our method by empirical evaluations. © 2010 IEEE.
International conference proceedings, English - A TCP Congestion Control Method for Real-Time Communication Based on Channel Occupancy of a Wireless LAN
Toshiyuki Hirai; Satoshi Ohzahata; Konosuke Kawashima
2010 16TH ASIA-PACIFIC CONFERENCE ON COMMUNICATIONS (APCC 2010), IEEE, 153-158, 2010, Peer-reviwed, The demand for real-time communication over wireless LANs is increasing. In the infrastructure mode of IEEE 802.11, wireless terminals, or stations (STAs), share one access point (AP). Since TCP congestion control increases the congestion window size until packet loss occurs, TCP communication takes excessive bandwidth from other communications. Then, TCP communication affect the communication quality of the other STAs which share the same AP. Especially, the communication quality for real-time applications such as video streaming becomes worse. In order to solve this problem, our method estimates the channel occupancy of the wireless LAN and adjusts TCP window size so as not to affect the other communications. When an STA simultaneously makes a real-time UDP communication and a background TCP communication, the proposed method controls the window size without taking bandwidth from the UDP communication. We have evaluated the proposed method by computer simulation experiments and show that the proposed method makes it possible to improve the communication quality of the real- time UDP communication.
International conference proceedings, English - An Analysis of the P2P Traffic Characteristics on File Transfers Between Prefectures and Between Autonomous Systems in the Winny Network
Takashi Koizumi; Masahiro Yoshida; Satoshi Ohzahata; Konosuke Kawashima
2010 16TH ASIA-PACIFIC CONFERENCE ON COMMUNICATIONS (APCC 2010), IEEE, 147-152, 2010, Peer-reviwed, Peer-to-peer (P2P) file-sharing applications are now widely used. The traffic generated by the P2P applications occupies a significant proportion of Internet traffic, and has an enormous impact on the backbone networks. Since these peers communicate by constructing virtual overlay routes, which are constructed independently from the IP networks topology, the characteristics of P2P traffic between regional networks such as those in prefectures and Autonomous Systems (ASs) have become an important issue. Consequently, it is necessary to understand the actual status of the characteristics of traffic matrices in order to construct and manage future networks. In this paper, we measured and analyzed the file transfer characteristics, such as traffic matrices, between prefectures and between ASs, by identifying file transfers between peers in Winny network, one of the most popular P2P applications in Japan. The results reveal that Winny increases traffic between prefectures and ASs, because file transfers in Winny network does not take account of locality.
International conference proceedings, English - Fuzzy logic based multi-hop broadcast for high-density vehicular ad hoc networks
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
2010 IEEE Vehicular Networking Conference, VNC 2010, 17-24, 2010, Peer-reviwed, Vehicular ad hoc networks have been attracting the interest of both academic and industrial communities on account of their potential role in Intelligent Transportation Systems (ITS). In vehicular ad hoc networks, vehicles are usually located quite densely within the range of radio transmission. In this paper, we propose a fuzzy logic based multi-hop broadcast protocol for information dissemination in high-density vehicular ad hoc networks. The proposed protocol exhibits low message overheads by means of using only a subset of neighbor nodes to relay messages. In the relay node selection, the proposed protocol jointly considers multiple metrics of inter-vehicle distance, node mobility and signal strength by employing the fuzzy logic. We use computer simulations to evaluate the performance of the proposed protocol. © 2010 IEEE.
International conference proceedings, English - Winnyネットワークに対するインデックスポイズニングを用いたファイル流通制御方式
吉田 雅裕; 大坐畠 智; 中尾 彰宏; 川島 幸之助
情報処理学会論文誌, 50, 9, 2008-2023, Sep. 2009, Peer-reviwed
Scientific journal, Japanese - Controlling File Distribution in Winny Network Through Index Poisoning
Masahiro Yoshida; Satoshi Ohzahata; Akihiro Nakao; Konosuke Kawashima
ICOIN: 2009 INTERNATIONAL CONFERENCE ON INFORMATION NETWORKING, IEEE, 210-+, 2009, Peer-reviwed, Peer-to-Peer (P2P) file sharing networks have witnessed dramatic increase in popularity for the past few years. In order to meet the demand of users, most P2P file sharing networks have been primarily focusing on improving transmission efficiency and network scalability. However, these networks do not usually have management mechanisms for distributing files in general. Consequently, copyright infringements in P2P file sharing networks have become prevalent. In order to prevent illegal file distribution, several anti-P2P companies have controlled the file distribution by index poisoning. Although index poisoning aims to obfuscate uses by diffusing a lot of dummy metadata in P2P networks, its effects have not been well studied yet. In this paper, we apply index poisoning to a Winny network, one of the most popular P2P file sharing networks in Japan, to control the file distribution. Our evaluation includes index poisoning in a live Winny network composed of over 100,000 active peers. The result shows that our proposed method can decrease the number of query hits to less than 0.004% compared to the case without our control, and that index poisoning is effective to control a small number of files. However, the result also shows that the index poisoning could cause a serious damage on a Winny network, when many files are under our control simultaneously.
International conference proceedings, English - A Traffic Control Method with Channel Occupancy Information from MAC Layer in IEEE 802.11
Hiroshi Nakashima; Satoshi Ohzahata; Konosuke Kawashima
ICOIN: 2009 INTERNATIONAL CONFERENCE ON INFORMATION NETWORKING, IEEE, 220-224, 2009, Peer-reviwed, Wireless LAN has recently come into wide use because of its easy installation and low operating cost. Consequently, real-time applications, such as voice and video streaming, have seen increasing use in wireless environments. IEEE 802.11e was prepared as a standard for wireless LAN to improve the quality of service (QoS) for real-time applications; however, it cannot offer the required QoS when there is excessive traffic. This is because the controls in IEEE 802.11e only schedule traffic in the MAC layer for the generated traffic in the upper layer, and do not control the volume of traffic generation itself. To solve this problem, we propose an autonomous method to control traffic generation in the application layer by using wireless channel occupancy information in the MAC layer. In the proposed method, the wireless channel occupancy is estimated from the network allocation vector (NAV) in the CSMA/CA control, and then traffic generation is managed adequately with cross-layer controls. We implemented and evaluated the proposed method in a testbed, demonstrating that the QoS is improved against the conventional IEEE 802.11 control.
International conference proceedings, English - A Measurement Study on Peer Behaviors for a Pure P2P Network
Satoshi Ohzahata; Konosuke Kawashima
2009 INTERNATIONAL CONFERENCE ON ADVANCED INFORMATION NETWORKING AND APPLICATIONS, IEEE, 241-248, 2009, Peer-reviwed, Dynamic peer behavior in P2P networks has a large impact on the performance because the peer acts simultaneously as the server and client of an overlay network. However peer behavior in pure P2P networks is not well known because there is no management system and the size is large. We have proposed a measurement method to efficiently collect information of an entire network for Winny, which is the most popular P2P file sharing application in Japan. Especially, we analyze behaviors of the peer with/without files and identify long life peers in the network. The analysis results show that the network is composed of about 30 % of observed peers in 24 hours, and 50 % of peers contribute to the network as the files uploaders. Selfish peers, which leave the network after downloading, are observed especially in the morning. The file uploading peers and the joining peers after the midnight live long period in the network.
International conference proceedings, English - Adjusting TCP Window Flow Control based on Channel Occupancy Information of IEEE 802.11 Systems
Kengo Mikoshiba; Satoshi Ohzahata; Konosuke Kawashima
2009 IEEE 20TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, IEEE, 1522-1526, 2009, Peer-reviwed, TCP has been used as the main method of congestion control in the Internet. In the TCP window control, the window size is gradually increased until congestion occurs. This method of control acquires network bandwidth aggressively and affects other stations which communicate via the same access point using IEEE 802.11 standards. To improve this problem, we propose a congestion window control method which involves adjusting the window size without affecting the communication of the other stations. The congestion window size is adequately controlled by measuring the channel occupancy of each station. The channel occupancy is estimated by measuring the Network Allocation Vector (NAV) in each station. The channel status information is passed to the TCP congestion control function via a cross-layer control mechanism. Then, the TCP congestion window and advertised window are adjusted to take account of the channel occupancy. We have developed a testbed and shown the effectiveness of our method by empirical evaluations.
International conference proceedings, English - Fair Bandwidth Assignment to Each Terminal by Adjusting Contention Window Size in Access Point
Toshihiro Yoshioka; Satoshi Ohzahata; Konosuke Kawashima
2009 IEEE 20TH INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR AND MOBILE RADIO COMMUNICATIONS, IEEE, 762-766, 2009, Peer-reviwed, Recently, wireless LANs have been used widely because they are flexible and easy to install. However, there are unfairness problems in wireless LANs, in that a small number of stations (STAs) may obtain a large throughput while other STAs hardly get any bandwidth. One of the unfairness problems occurs between upstream and downstream flows because the access point (AP) and each STA have the same transmission opportunity under CSMA/CA control. In addition, the bandwidth in the wireless network is not shared fairly among STAs. To improve these problems, we proposed a simple method combining the Deficit Round-Robin (DRR) queuing method in the MAC layer and a dynamic contention window control in the MAC layer in the AP. By cross-layer controls, the proposed method can be realized without using information from the TCP/UDP transport protocol. We evaluated the proposed method by computer simulation experiments, and show that the proposed method gives perstation fairness in throughput under multiple TCP/UDP flow communication.
International conference proceedings, English - クライアント／サーバ関係に着目したピュアP2Pアプリケーショントラヒック特定方式と評価
大坐畠 智; 川島 幸之助
情報処理学会論文誌, 49, 2, 988-998, Feb. 2008, Peer-reviwed
Scientific journal, Japanese - A Study on Traffic Characteristics Evaluation for a Pure P2P Application
Satoshi Ohzahata; Konosuke Kawashima
Proc. the 2nd International Workshop on Modeling, Simulation , and Optimization of Peer-to-Peer Environments (MSOP2P), 483-490, Feb. 2008, Peer-reviwed
International conference proceedings, English - A Performance Evaluation of Wireless Ad Hoc Network based on the Forward Interference Avoidance Concept
Alain Solheid; Yukihiro, Kamiha; Satoshi Ohzahata; Konosuke Kawashima
Proc. the 10th International Symposium on Wireless Personal Multimedia Communications (WPMC'07), 5, Dec. 2007, Peer-reviwed
International conference proceedings, English - A Cross-Layer Retransmission Control for Improving TCP Performance in Wireless LAN
Satoshi Ohzahata; Shigetomo Kimura; Yoshihiko Ebihara; Konosuke Kawashima
IEICE Transactions on Communications, The Institute of Electronics, Information and Communication Engineers, E90-B, 8, 2070-2080, Aug. 2007, Peer-reviwed, In this paper we propose a cross-layer retransmission control for TCP communication over a wireless link. With our proposed control, a retransmission delay for lost packet is reduced, packet losses in the wireless link are eliminated and all packets are delivered in the correct order. No change is required to TCP itself or to the sender. Our proposed method is implemented in a queue between the media access control (MAC) layer and logical link layer in a base station, and is designed to assist local retransmission control in the MAC layer. Computer simulations show that our proposed method can maximally use the bandwidth of the wireless link under high bit error rates conditions with conventional TCP control. The fairness problem of TCP communication between connections with different bit error rates in a wireless link is also improved, and MAC level fairness is also controllable.
Scientific journal, English - Basic Throughput Evaluation of Wireless Network Employing User Guidance to Hotspot by Advertising through Ad Hoc Network
Satoshi Ohzahata; Konosuke Kawashima
Proc. of The 17th Internationa Teletraffic Congress Specialist Seminar, 2, May 2006, Peer-reviwed
International conference proceedings, English - A traffic identification method and evaluations for a pure P2P application
S Ohzahata; Y Hagiwara; M Terada; K Kawashima
PASSIVE AND ACTIVE NETWORK MEASUREMENT, PROCEEDINGS, SPRINGER-VERLAG BERLIN, 3431, 55-68, 2005, Peer-reviwed, Pure P2P applications are widely used nowadays as a file sharing system. In the overlay networks, music and video files are the main items exchanged, and it is known that the traffic volume is much larger than that of classical client/server applications. However, the current status of the P2P application traffic is not well known because of their anonymous communication architectures. In particular, in cases where the application does not use the default service port, and the communication route and the shared file are also encrypted, the identification traffic has not been feasible. To solve this problem, we have developed an identification method for pure Peer-to-Peer communication applications, especially for traffic for Winny, the most popular Peer-to-Peer application in Japan, by using server/client relationships among the peers. We will give some evaluation results for our proposed identification method.
Scientific journal, English - A pure P2P network size estimation method using network measurements and computer simulation experiments
S Ohzahata; K Kawashima
Performance Challenges for Efficient Next Generation Networks, Vols 6A-6C, BEIJING UNIV POSTS TELECOMMUNICAT PRESS, 6A-6C, 69-78, 2005, Peer-reviwed, In this paper we estimate the size of the Winny network (one of the most popular pure P2P file sharing applications in Japan) using a combination of network measurements and computer simulation experiments. For the measurement analysis, we use an improved maxk-recapture method to estimate the number of newly active Winny peers per unit time. We estimate the number of active peers in the Winny network by applying the actual measurement results to computer simulation experiments. The simulation results reveal that the Winny network had about 200,000 active Winny peers in October 2004.
International conference proceedings, English - Evaluation of a Queue Management Method for TCP Communications over Multi-hop Wireless Links
Satoshi Ohzahata; Konosuke Kawashima
Proc. The Fifth European Wireless Conference Mobile and Wireless Systems beyond 3G (European Wireless 2004), 298-304, Feb. 2004, Peer-reviwed
International conference proceedings, English - A queue management method for improving TCP performance in wireless environments
S Ohzahata; S Kimura; Y Ebihara; K Kawashima
2004 IEEE WIRELESS COMMUNICATIONS AND NETWORKING CONFERENCE, VOLS 1-4, IEEE, 2, 1069-1074, 2004, Peer-reviwed, In this paper we propose a queue management method for improving TCP performance over a wireless link. With our proposed control method. packet loss in the wireless link- is completely eliminated and all packets are delivered in the correct order. No change is required to TCP itself or to the servers. Our proposed method is implemented between the media access control (MAC) layer and logical link layer in a base station, and is designed to help the local retransmission control in the MAC layer. Computer-simulation experiments show that (our proposed method can maximumly use the bandwidth of the wireless link at high bit error rate conditions under conventional TCP controls. The fairness problem of TCP communication between connections with different bit error rate in wireless link is also improved.
International conference proceedings, English - Adaptive Handoff Algorithm for Efficient Network Resource Utilization in Mobile Internet Environments
Satoshi Ohzahata; Shigetomo Kimura; Yoshihiko Ebihara
World Scienific Journal of Interconnection Networks, 4, 3, 361-375, Sep. 2003, Peer-reviwed
Scientific journal, English - Adaptive handoff algorithm for efficient network resource utilization
S Ohzahata; S Kimura; Y Ebihara
AINA 2003: 17TH INTERNATIONAL CONFERENCE ON ADVANCED INFORMATION NETWORKING AND APPLICATIONS, IEEE COMPUTER SOC, 743-748, 2003, Peer-reviwed, In this paper we propose an adaptive handoff algorithm based on the "threshold-with-hysteresis." In general, such handoff algorithms are proposed to improve the handoff decision for a specific user Our algorithm aims to provide effective network utilization for all users. To realize the handoff decision based on the mobile nodes, the agent advertisements include information of the congestion status at the base station in the algorithm. For implementing the algorithm to Mobile IP we also propose the system architecture with a QoS mechanism. The simulation experiment shows that our proposed algorithm improves the average handoff blocking rate than the previous method in spite of low overhead of our expansion.
International conference proceedings, English - A Fast Authentication Method for Secure and Seamless Handoff
Satoshi Ohzahata; Shigetomo Kimura; Yoshihiko Ebihara
Proc. 16th International Conference on Information Networking, 243-252, Jan. 2002, Peer-reviwed
International conference proceedings, English - A proposal of seamless handoff method for cellular Internet environments
S Ohzahata; S Kimura; Y Ebihara
IEICE TRANSACTIONS ON COMMUNICATIONS, IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG, E84B, 4, 752-759, Apr. 2001, Peer-reviwed, Mobile IP can provide macro mobility for a mobile node (RIN) instead of the original IP communication. Since the orignal Mobile IP does not consider micro mobility, it can riot avoid handoff latency. The latency causes packets loss or large variations of the delivery times. To prevent it, several methods are proposed to improve the orignal Mobile IP handoff method. In our previous work, we proposed the fast registration method which enabled an RIN to have two communication routes from the home agent (HA), and realized lower latency in the handoff procedures by the doublecasting on the two communication routes. But, the simulation results also show that the proposed method still has large overhead. This paper presents a seamless handoff method, which improves the fast registration method. In the method, the RIN can know the first and second suitable base stations for the communications through information from the R IAC media. The control helps for seamless handoff in case that the RIN must frequently change its current base station (BS). The computer simulations for Constant Bit Rate (CBR) over real-time transport protocol (RTP) how shows that the proposed method provides no handoff latency with low overhead even if the R IN must occur frequent handoffs in a second.
Scientific journal, English - Soft Handoff Method for Wireless Cellular Real-Time Communications in Mobile IP
Satoshi Ohzahata; Shigetomo Kimura; Yoshihiko Ebihara
Proc. 14th International Conference on Information Networking, 4C-2.1-2.6, Jan. 2000, Peer-reviwed
International conference proceedings, English
MISC
- Communication Resources Allocation in Multi-Channel In-Car Wireless Networks
高谷空飛; 山本嶺; 大坐畠智; 細川元気; 國立忠秀
2022, 電子情報通信学会技術研究報告(Web), 121, 421(CQ2021 100-138), 2432-6380, 202202223940786722 - Poster Presentation : A Bandwidth Reservation Method According to User Request in Content Centric Network
遠藤 朝陽; 大坐畠 智; 山本 嶺; 加藤 聰彦
電子情報通信学会, 26 Oct. 2017, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 117, 262, 43-46, Japanese, 0913-5685, 40021373558, AA11546431 - A cache control method considering bandwidth reservation content in CCN
李 智輝; 大坐畠 智; 山本 嶺; 加藤 聰彦
電子情報通信学会, 07 Sep. 2017, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 117, 204, 85-90, Japanese, 0913-5685, 40021342062, AA11546431 - A Hybrid Approach for Named Data Networking Based Ad Hoc Routing (ネットワークシステム)
Minh Ngo Quang; Yamamoto Ryo; Ohzahata Satoshi; Kato Toshihiko
電子情報通信学会, 07 Sep. 2017, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 117, 204, 97-102, English, 0913-5685, 40021342073, AA11546431 - Improvement of Confidentiality over Multipath TCP Using Data Scrambling and Path Dispersion
程 詩涵; 山本 嶺; 大坐畠 智; 加藤 聰彦; 鈴木 信雄
電子情報通信学会, 28 Aug. 2017, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 117, 185, 105-111, Japanese, 0913-5685, 40021316324, AN1054106X - Frame Aggregation Size Selection for Improving IEEE 802.11ac MU-MIMO Downlink Throughput
森山 友和; 山本 嶺; 大坐畠 智; 加藤 聰彦
電子情報通信学会, 28 Aug. 2017, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 117, 185, 87-92, Japanese, 0913-5685, 40021316256, AN1054106X - プロセス間通信と端末間通信の把握による踏み台追跡 (ライフインテリジェンスとオフィス情報システム)
今田 寛; 大坐畠 智; 加藤 聰彦
電子情報通信学会, 11 May 2017, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 117, 24, 29-36, Japanese, 0913-5685, 40021214561 - A fast and secure payment confirmation method in Bitcoin
中西 建登; 大坐畠 智; 加藤 聰彦
電子情報通信学会, 20 Apr. 2017, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 117, 3, 13-18, Japanese, 0913-5685, 40021187260, AA11546431 - Performance Evaluation of MPTCP under Different Transmission Delay and Insufficient Send/Receive Socket Buffer
天真 正晶; 山本 嶺; 大坐畠 智; 加藤 聰彦; 鈴木 信雄
電子情報通信学会, 06 Mar. 2017, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 116, 497, 61-66, Japanese, 0913-5685, 40021161171, AN1054106X - An Evaluation of Resource Management Method of CCN for Serving QoS
趙 ハン; 大坐畠 智; 加藤 聰彦
電子情報通信学会, 02 Mar. 2017, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 116, 484, 1-6, Japanese, 0913-5685, 40021158399, AA11546431 - An Efficient Pseudo-Multicast Method for Streaming Content Delivery with Cached Network Coding Pieces
井上 裕太; 大坐畠 智; 加藤 聰彦
電子情報通信学会, 02 Mar. 2017, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 116, 484, 293-296, Japanese, 0913-5685, 40021159297, AA11546431 - Experimental analysis on impacts to TCP throughput of power save mode in IEEE 802.11n wireless LAN
小林 健人; 橋本 善季; 野元 祐孝; 山本 嶺; 大坐畠 智; 加藤 聰彦
電子情報通信学会, 24 May 2016, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 116, 62, 39-44, Japanese, 0913-5685, 40020849857, AN1054106X - Evaluation of Improving Cause-and-effect Relationships among Multi-hop Wireless Ad-hoc Network for Parallel Network Emulation
山崎 佑典; 大坐畠 智; 加藤 聰彦
電子情報通信学会, 19 May 2016, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 116, 45, 13-18, Japanese, 0913-5685, 40020848757, AN10013072 - B-7-13 Optimizing P2P Network Hierarchies for Visual Analytics
Wu Hsiang-Yun; Takahashi Shigeo; Miyamura Hiroko N.; Ohzahata Satoshi; Nakao Akihiro
The Institute of Electronics, Information and Communication Engineers, 01 Mar. 2016, Proceedings of the IEICE General Conference, 2016, 2, 146-146, Japanese, 110010038027, AN10471452 - B-7-14 Network Graph Layout with a Hierarchical Optimization Technique
Nakamura Miyamura Hiroko; Wu Hsiang-Yun; Takahashi Shigeo; Ohzahata Satoshi; Nakao Aihiro
The Institute of Electronics, Information and Communication Engineers, 01 Mar. 2016, Proceedings of the IEICE General Conference, 2016, 2, 147-147, Japanese, 110010038028, AN10471452 - BS-3-13 Analyzing the Traffic Correlation-Based Attacks on Tor(BS-3. Advanced Networking Technologies for Innovative Information Networks)
Kale Timothy Girry; Ohzahata Satoshi; Wu Celimuge; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 01 Mar. 2016, Proceedings of the IEICE General Conference, 2016, 2, "S-36"-"S-37", English, 110010038480, AN10471452 - B-11-18 Impacts of power saving mode of 802.11n WLAN to TCP small queues
Kobayashi Kento; Hashimoto Yoshiki; Nomoto Masataka; Yamamoto Ryo; Ohzahata Satoshi; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 01 Mar. 2016, Proceedings of the IEICE General Conference, 2016, 2, 398-398, Japanese, 110010038279, AN10471452 - B-11-15 Inferring TCP Congestion Control Algorithm Using One Way Packet Logs
Yongxialee Leelianou; Yamamoto Ryo; Ohzahata Satoshi; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 01 Mar. 2016, Proceedings of the IEICE General Conference, 2016, 2, 395-395, Japanese, 110010038276, AN10471452 - Suppressing Selfish Transmission with Extending NAV and Resetting CW in Consideration of Fairness of Upstream/Downstream for Wireless LAN
笹川 隆; 大坐畠 智; 加藤 聰彦
電子情報通信学会, 21 Jan. 2016, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 115, 404, 7-12, Japanese, 0913-5685, 40020737544, AA11546431 - Performance comparison between a hybrid DCF/TDMA QoS scheme and the pure TDMA approach (コミュニケーションクオリティ)
Lin Jing; WU Celimuge; OHZAHATA Satoshi
電子情報通信学会, 21 Jan. 2016, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 115, 408, 13-18, English, 0913-5685, 40020737141, AN1054106X - Improving Traffic Load Distribution for Tor Network (情報ネットワーク)
Kale Timothy Girry; Ohzahata Satoshi; Wu Celimuge
電子情報通信学会, 15 Oct. 2015, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 115, 252, 29-34, English, 0913-5685, 40020651042, AN10013072 - Improving Cause-and-effect Relationships of Parallel Emulation for Multi-hop Wireless Ad-hoc Network
山崎 佑典; 大坐畠 智; 加藤 聰彦
電子情報通信学会, 15 Oct. 2015, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 115, 251, 73-78, Japanese, 0913-5685, 40020650518, AA11546431 - Reducing Congestion in the Tor Network with Circuit Switching
Kale Timothy Girry; Satoshi Ohzahata; Celimuge Wu; Toshihiko Kato
The Tor network is a distributed circuit-switching overlay network, which provides anonymous communication by using voluntarily running onion routers around the world. Tor is vulnerable to network congestion and performance problems because circuit traffics with different rates are competing to transfer their data through a single TCP connection. A large fraction of available network capacity is consumed by the bulk users' traffic, resulting in increasing delays for the light interactive users. The unfair distribution between the circuit traffics of bulk and light users are contributing to bottleneck in the Tor routers. This problem increases the end-to-end latency and reduces the quality of communication in Tor, which discourages many users from using and joining the network. As a result, the degradation of Tor performance does not only affect the users' experience, but also degrade the anonymity of Tor. In this work, we discovered that the current Tor design encountered problems from several performance and deployment issues relating to lower network capacity. To improve the problems in Tor, we applied the circuit switching method and addressed the short-comings of limited network capacity, by connecting the congested OR to higher bandwidth ORs. The proposed method is evaluated on our setup testbed environment and partly in the live Tor network. The experimental results showed that TCP socket buffers and Tor network capacity are better utilized and the overall end-to-end latency is reduced.\n------------------------------This is a preprint of an article intended for publication Journal ofInformation Processing(JIP). This preprint should not be cited. Thisarticle should be cited as: Journal of Information Processing Vol.23(2015) No.5 (online)DOI http://dx.doi.org/10.2197/ipsjjip.23.589------------------------------The Tor network is a distributed circuit-switching overlay network, which provides anonymous communication by using voluntarily running onion routers around the world. Tor is vulnerable to network congestion and performance problems because circuit traffics with different rates are competing to transfer their data through a single TCP connection. A large fraction of available network capacity is consumed by the bulk users' traffic, resulting in increasing delays for the light interactive users. The unfair distribution between the circuit traffics of bulk and light users are contributing to bottleneck in the Tor routers. This problem increases the end-to-end latency and reduces the quality of communication in Tor, which discourages many users from using and joining the network. As a result, the degradation of Tor performance does not only affect the users' experience, but also degrade the anonymity of Tor. In this work, we discovered that the current Tor design encountered problems from several performance and deployment issues relating to lower network capacity. To improve the problems in Tor, we applied the circuit switching method and addressed the short-comings of limited network capacity, by connecting the congested OR to higher bandwidth ORs. The proposed method is evaluated on our setup testbed environment and partly in the live Tor network. The experimental results showed that TCP socket buffers and Tor network capacity are better utilized and the overall end-to-end latency is reduced.\n------------------------------This is a preprint of an article intended for publication Journal ofInformation Processing(JIP). This preprint should not be cited. Thisarticle should be cited as: Journal of Information Processing Vol.23(2015) No.5 (online)DOI http://dx.doi.org/10.2197/ipsjjip.23.589------------------------------, 15 Sep. 2015, 情報処理学会論文誌, 56, 9, English, 1882-7764, 170000130711, AN00116647 - Suppressing Selfish Transmission with Extending NAV Period and Resetting CW size for Wireless LAN
笹川 隆; 大坐畠 智; 加藤 聰彦
電子情報通信学会, 03 Sep. 2015, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 115, 210, 45-50, Japanese, 0913-5685, 40020617324, AN10013072 - Improving bufferbloat problem of TCP communication by MAC transmission limitation at IEEE 802.11n access point
野元 祐孝; 策力木格; 大坐畠 智
電子情報通信学会, 01 Sep. 2015, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 115, 206, 113-118, Japanese, 0913-5685, 40020617271, AN1054106X - BS-6-18 Improving Tor Performance with Dynamic Circuit Switching(BS-6.Network and service Design, Control and Management)
Kale Timothy Girry; Ohzahata Satoshi; Wu Celimuge; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 25 Aug. 2015, Proceedings of the Society Conference of IEICE, 2015, 2, "S-50"-"S-51", English, 110009984256, AN10489017 - BS-3-5 A scheduling method considering cached pieces for the content distribution system using overhearing
Ogasawara Masaru; Ohzahata Satoshi; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 25 Aug. 2015, Proceedings of the Society Conference of IEICE, 2015, 2, "S-5", Japanese, 110009984231, AN10489017 - B-18-6 Providing collision-free access for QoS flows in ad hoc networks
Lin Jing; Wu Celimuge; Ohzahata Satoshi; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 25 Aug. 2015, Proceedings of the Society Conference of IEICE, 2015, 2, 340-340, English, 110009984188, AN10489017 - An Efficient Time Slot Allocation Scheme for QoS flows in Ad Hoc Networks (スマートファシリティ研究会・スマートグリッド、スマートシティ/スマートコミュニティに関する技術動向)
Lin Jing; Wu Celimuge; Ohzahata Satoshi
電気学会, 18 Jun. 2015, 電気学会研究会資料. SMF = The papers of Technical Meeting on Smart Facilities, IEE Japan, 2015, 6, 31-36, English, 40020650898, AA1267322X - An Efficient Time Slot Allocation Scheme for QoS flows in Ad Hoc Networks (情報ネットワーク)
Lin Jing; Wu Celimuge; Ohzahata Satoshi
電子情報通信学会, 18 Jun. 2015, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 115, 95, 43-48, English, 0913-5685, 40020523163, AN10013072 - Inter-vehicle Communications : Research Challenges & Opportunities (無線通信システム) -- (特集セッション 将来無線通信に適した無線アクセス及びネットワーク技術)
WU Celimuge; OHZAHATA Satoshi; JI Yusheng
電子情報通信学会, 21 May 2015, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 115, 43, 21-26, English, 0913-5685, 40020491821, AN10060822 - A NAV Period Control and CW Control of an AP for Keeping Transmission Opportunity from Selfish Terminal in Wireless LAN
笹川 隆; 大坐畠 智; 加藤 聰彦
電子情報通信学会, 14 May 2015, 電子情報通信学会技術研究報告 = IEICE technical report : 信学技報, 115, 26, 95-97, Japanese, 0913-5685, 40020492140 - Implementation of a Bandwidth Control Method for Content-Centric Network
KUWAYAMA Tomoya; OHZAHATA Satoshi; KATO Toshihiko
Recently, CCN (Content-Centric Network) that reduces redundant traffic using caches on network nodes attracts much attention. CCN is desighed veiwpoint of "does not care where source of content is," but clients expect a certain level of QoS during content retrieval. It's necessary to guarantee communication quality in order to solve the problem. In this research, we propose a network resource reservation method for CCN with QoS. The proposed method implement control packet to reserve network resource or to release bandwidth by expanding Interest/Data packet, and CCN router reserve network resource by prefix of content ID., The Institute of Electronics, Information and Communication Engineers, 02 Mar. 2015, IEICE technical report, 114, 477, 535-539, Japanese, 0913-5685, 110010018721, AA11546431 - BS-3-7 Improving Tor Network Throughput by the Circuit Switching(BS-3. Advanced Technologies in the Design, Management and Control for Future Innovative Communication Network)
Girry Kale Timothy; Ohzahata Satoshi; Wu Celimuge; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 24 Feb. 2015, Proceedings of the IEICE General Conference, 2015, 2, "S-22"-"S-23", English, 110009928708, AN10471452 - B-11-19 Multihop Ad-hoc Networking for Smart Garage : Experiment and Results
An Ruijian; Wu Celimuge; Yu Dong; Ji Yusheng; Ohzahata Satoshi; Kato Toshihiko
In this paper, we introduce a communication system for Smart Garage. The system connects the intelligent vehicles to the local server with multi-hop ad-hoc communication. The throughput of the ad-hoc communication is evaluated by the real-world experiments conducted both in the indoor environment and in the SUPER GT 2014 contests., The Institute of Electronics, Information and Communication Engineers, 24 Feb. 2015, Proceedings of the IEICE General Conference, 2015, 2, 436-436, English, 110009928632, AN10471452 - Common Service Platform for Electric Vehicles
WEI Jing; LI Jinglin; LIU Zhihan; WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
We propose a common service platform for electric vehicles (EVs). The platform is supposed to make use of information of EVs, EVs users, traffic flow, map and charging network to provide common service such as GIS service, resource management service, billing service, and open API service for EVs users, charging service operators and service developers. We divide the platform into three layers, which are resource layer, capability layer and service layer. Resource layer is to store data, and provide data access interface to capability layer. Capability layer encapsulates some common function, and provides the function to service layer. Meanwhile, capability layer will authorize and authenticate the invoking services. Service layer provides common service for platform users. Service developers can use open API of capability layer to organize new customized service. We describe our demo implementation of the proposed platform framework., The Institute of Electronics, Information and Communication Engineers, 22 Jan. 2015, Technical report of IEICE. CQ, 114, 404, 1-6, English, 0913-5685, 110010002156, AN1054106X - Consideration on iOS TCP Performance Problem at Busty Packet Losses
Wang Weikai; WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
Recently, packet losses can be caused by transmission interruptions such as handoffs in the mobile networks and protection switching in the transport networks. These packet losses are bursty because the transmission interruptions continue for tens of miliseconds through several seconds. Previously, we performed the experimental analysis for various TCP versions running on Linux and MAC OS, and found that, although TCPs in Linux recover from bursty losses quickly, TCP in OS X shows an intermittent data transfer during the timeout retransmission invoked by bursty losses, which takes several seconds for retransmitting all of the lost packets. In this paper, we give detailed results of experimental analysis. Based on this analysis, we clarify the reason for the intermittent data transfer in MAC OS X by taking account of newly introduced TCP procedures, such as F-RTO and Early Retransmit., The Institute of Electronics, Information and Communication Engineers, 22 Jan. 2015, Technical report of IEICE. CQ, 114, 404, 19-24, English, 0913-5685, 110010002159, AN1054106X - A Routing Protocol for Drive-thru Internet Access in Delay Tolerant Vehicular Ad Hoc Networks
OHYA Yoshimasa; WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
We propose a routing protocol for drive-thru Internet access in delay tolerant vehicular networks. The contribution of this paper is two-folds. First, we propose a new approach which utilizes the concept of delay tolerant network (DTN) to supplement the conventional communication approach. Second, we propose an algorithm to schedule DTN transmissions in order to maximize the system throughput. The proposed protocol is able to attain higher TCP throughput than the conventional approach by providing more efficient wireless resource utilization. We use computer simulations to evaluate the proposed protocol., The Institute of Electronics, Information and Communication Engineers, 22 Jan. 2015, Technical report of IEICE. CQ, 114, 404, 85-89, English, 0913-5685, 110010002171, AN1054106X - Performance Evaluation of Qos Supporting Ad Hoc Scheme Combining TDMA and 802.11 DCF
Lin Jing; WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
We present performance evaluation results of a QoS supporting ad hoc network protocol which employs a hybrid approach utilizing both TDMA and 802.11 DCF. In the protocol, TDMA period provides contention free transmissions for QoS flows, and DCF period is used to provide contention-based access for best effort or low priority flows. TDMA time slots are assigned on admission basis in a distributed manner by utilizing network routing information and considering current assignment situation. In DCF period, frames are transmitted without disturbing the TDMA period. We evaluate the protocol for various numbers of best effort flows with QualNet simulator. Simulation results show that the protocol is able to provide an efficient solution for QoS control in ad hoc networks by combing TDMA and 802.11 DCF., The Institute of Electronics, Information and Communication Engineers, 22 Jan. 2015, Technical report of IEICE. CQ, 114, 404, 35-40, English, 0913-5685, 110010002162, AN1054106X - Poster Session : A Network Resource Management Method for Content-Centric Network with QoS
KUWAYAMA Tomoya; OHZAHATA Satoshi; KATO Toshihiko
Recently, CCN (Content-Centric Network) that reduces redundant traffic using caches on network nodes attracts much attention. CCN is desighed veiwpoint of "does not care where source of content is," but clients expect a certain level of QoS during content retrieval. It's necessary to guarantee communication quality in order to solve the problem. In this research, we propose a network resource management method for CCN with QoS. In the proposed method, End-to-End resource reservation is not needed by utilizing the content caches., The Institute of Electronics, Information and Communication Engineers, 16 Oct. 2014, IEICE technical report, 114, 252, 55-58, Japanese, 0913-5685, 110009958939, AA11546431 - A Design of Circuit Switching Method for Reducing Congestion in the Tor Network
Girry Kale Timothy; Ohzahata Satoshi; Wu Celimuge; Kato Toshihiko
The Tor network is a distributed circuit-switching overlay network, and consists of voluntarily run onion routers around the world. Tor is vulnerable to network congestion and performance problems, due to circuit traffics with different rates are competing to transfer their data on a single TCP connection. A large fraction of available network capacity is consumed by the bulk users' traffic, resulting in increasing delays for the light interactive users. The unfair distribution of circuit traffic makes a bottleneck in Tor output buffer. We apply the circuit switching method and make the OR to construct a multiple TCP connections to improve the traffic flow rate and reduce the congestion in the Tor network. This approach increase the OR capacity and fairly distributing the multiple traffics that are competing to send data. The proposed method was evaluated on our setup ORs that are online in the Tor network. The experimental results show that TCP socket buffers and Tor network capacity are utilized and circuit congestion is reduced., The Institute of Electronics, Information and Communication Engineers, 16 Oct. 2014, IEICE technical report, 114, 252, 87-92, English, 0913-5685, 110009958945, AA11546431 - Piece Distribution Scheduling for Streaming with Pseudo-Multicast in Wireless LAN
KANAYAMA Akihiro; OHZAHATA Satoshi; KATO Toshihiko
In a Wireless LAN environment, the waiting time of downloading streaming contents through unicast becomes longer because the bandwidth is shared among the users. Then, Pseudo-Multicast with content piecing is promising because of the flexibility. Applying Pseudo-Multicast to streaming delivery, scheduling of piece and terminal to send is important. Therefore we studied and proposed effective scheduling methods through experiments of testbed., The Institute of Electronics, Information and Communication Engineers, 11 Sep. 2014, IEICE technical report, 114, 206, 97-102, Japanese, 0913-5685, 110009945616, AA11546431 - Characterization of TCP Congestion Control Algorithm by Estimating Congestion Window : Increase Relation and Decrease Parameter
Oda Atsushi; Wu Celimuge; Ohzahata Satoshi; Kato Toshihiko
Recently, according to the diversification of network environments, a lot of TCP congestion control mechanisms have been introduced. Since the congestion control algorithms affect the performance of the Internet, it is important to analyze which algorithms are used widely. This paper proposes a passive scheme to characterize individual congestion control algorithms by (1) estimating congestion window at round-trip time intervals, (2) correlating window sizes and their increases, and (3) identifying the discrete coefficient of congestion window. Our scheme aims at dealing with many of recent proposed congestion control algorithms including TCP Vegas, TCP Veno, Cubic TCP and TCP Illinois., The Institute of Electronics, Information and Communication Engineers, 11 Sep. 2014, Technical report of IEICE. CQ, 114, 209, 171-176, Japanese, 0913-5685, 110009950367, AN1054106X - B-11-10 A Multi-hop Broadcast Protocol for WAVE Multi-channel Single-radio Vehicular Networks
Wu Celimuge; Ohzahata Satoshi; Ji Yusheng; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 09 Sep. 2014, Proceedings of the Society Conference of IEICE, 2014, 2, 241-241, English, 110009883573, AN10489017 - BS-6-19 Measuring output buffer utilization for Interactive Users in Tor(BS-6.Network and service Design, Control and Management)
KALE Timothy Girry; OHZAHATA Satoshi; CELIMUGE Wu; KATO Toshihiko
The Institute of Electronics, Information and Communication Engineers, 09 Sep. 2014, Proceedings of the Society Conference of IEICE, 2014, 2, "S-72"-"S-73", English, 110009883792, AN10489017 - Performance Analysis of a Content Distribution Method using File Piecing and Overhearing for Wireless Multi-hop Network
NISHIZAKA Kazuaki; OHZAHATA Satoshi; KATO Toshihiko
In wireless LAN, since the bandwidth is shared with terminals, the throughput is reduced when the same content is downloaded by plural terminals. Therefore, we have proposed a method for content distribution in wireless LAN which achieve faster downloads by combining file piecing and pseudo-multicast which is overhearing packets of the same content for other terminals. When applying this method in the wireless multi-hop network, improvement of the piece distrubution efficiency by collecting the frames from the different hops. However, in the multi-hop situation, the overheared frames have to be delt adequently for packet loss and disorder deliverly because that the overhearing terminals extract the pieces by matching the sequence number of TCP segments. To handle the problems, we improve a byte steam management method in the overhearing node to get peaces from the overhearing efficiently. The proposed method is evaluated in testbed., The Institute of Electronics, Information and Communication Engineers, 29 Jul. 2014, IEICE technical report. MoNA, Mobile network and applications, 114, 160, 57-62, Japanese, 0913-5685, 110009945830, AA12618946 - A Study on QoS Support in Ad Hoc Networks Using TDMA and 802.11 DCF
Lin Jing; WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
We propose a QoS supporting ad hoc network protocol, which employs a hybrid approach utilizing both TDMA and 802.11 DCF. TDMA period provides contention free transmissions for QoS flows, and DCF period is used to provide contention-based access for best effort or low priority flows. TDMA time slots are assigned on admission basis in a distributed manner by utilizing network routing information and considering current assignment situation. In DCF period, frames are transmitted not to disturb the TDMA period. By combing TDMA and 802.11 DCF, the proposed ad hoc network is able to provide an efficient solution for QoS control in ad hoc networks. We use QualNet simulator to evaluate the proposed scheme., The Institute of Electronics, Information and Communication Engineers, 10 Jul. 2014, Technical report of IEICE. CQ, 114, 131, 25-30, English, 0913-5685, 110009942500, AN1054106X - Improving cause-and-effect relationships among single-hop neighbors of wireless network in distributed emulation
NITTA Koji; OHZAHATA Satoshi; KATO Toshihiko
In distributed emulator, emulation processes are divided into Logical Processes (LPs), and each LP can be processed in parallel. To obtain the same result as performing emulation with sequential processing, synchronization is needed among LPs. In wireless LAN emulation, the both of the MAC-Layer retransmission times and the collision events cannot be synchronized among terminals (LPs), contradiction occur among LPs. In this paper, we propose a method to correct a cause-and-effect relationship among terminals for the collision and the retransmission times in MAC, and implement the proposed method in EMANE. We evaluate the proposed method and discuss its scalability., The Institute of Electronics, Information and Communication Engineers, 29 May 2014, IEICE technical report. ASN, Ambient intelligence and sensor networks, 114, 65, 7-12, Japanese, 0913-5685, 110009902436, AA12618979 - Improving cause-and-effect relationships among single-hop neighbors of wireless ad-hoc network in distributed emulation
新田 幸司; 大坐畠 智; 加藤 聰彦
In emulation environment, packets have to be delivered from sender to receiver in real-time. For a scalable emulation, distributed and parallel emulators have been developed. In distributed emulator EMANE, emulation is divided into Logical Processes(LPs), and each LP can process in parallel. To obtain the same result as performing emulation with sequential processing synchronization is needed among LPs. In WLAN emulation with EMANE, the both of the MAC-Layer retransmission times and the collision events cannot be synchronized among terminals (LPs), contradiction occur among LPs. In this paper, we propose a method to correct a cause-and-effect relationship among terminals for the collision and the retransmission times in MAC. We evaluate the proposed method and constructed environments scalability in the emulation., The Institute of Electronics, Information and Communication Engineers, 14 Mar. 2014, IEICE technical report. MoNA, Mobile network and applications, 113, 495, 125-130, Japanese, 0913-5685, 110009861145, AA12618946 - Improving cause-and-effect relationships among single-hop neighbors of wireless ad-hoc network in distributed emulation
Koji Nitta; Satoshi Ohzahata; Toshihiko Kato
In emulation environment, packets have to be delivered from sender to receiver in real-time. For a scalable emulation, distributed and parallel emulators have been developed. In distributed emulator EMANE, emulation is divided into Logical Processes(LPs), and each LP can process in parallel. To obtain the same result as performing emulation with sequential processing synchronization is needed among LPs. In WLAN emulation with EMANE, the both of the MAC-Layer retransmission times and the collision events cannot be synchronized among terminals (LPs), contradiction occur among LPs. In this paper, we propose a method to correct a cause-and-effect relationship among terminals for the collision and the retransmission times in MAC. We evaluate the proposed method and constructed environments scalability in the emulation., Information Processing Society of Japan (IPSJ), 07 Mar. 2014, 研究報告ユビキタスコンピューティングシステム（UBI）, 2014, 30, 1-6, Japanese, 0919-6072, 110009676792, AA11838947 - Improving cause-and-effect relationships among single-hop neighbors of wireless ad-hoc network in distributed emulation
Koji Nitta; Satoshi Ohzahata; Toshihiko Kato
In emulation environment, packets have to be delivered from sender to receiver in real-time. For a scalable emulation, distributed and parallel emulators have been developed. In distributed emulator EMANE, emulation is divided into Logical Processes(LPs), and each LP can process in parallel. To obtain the same result as performing emulation with sequential processing synchronization is needed among LPs. In WLAN emulation with EMANE, the both of the MAC-Layer retransmission times and the collision events cannot be synchronized among terminals (LPs), contradiction occur among LPs. In this paper, we propose a method to correct a cause-and-effect relationship among terminals for the collision and the retransmission times in MAC. We evaluate the proposed method and constructed environments scalability in the emulation., Information Processing Society of Japan (IPSJ), 07 Mar. 2014, IPSJ SIG technical reports, 2014, 30, 1-6, Japanese, 0919-6072, 110009676739, AA11851388 - A NAV Period Control and CW Control of an Access Point for Keeping Transmission Opportunity and Achieving Fairness in Wireless LAN
HAYAMI Ryunosuke; OHZAHATA Satoshi; KATO Toshihiko
In this paper, we propose a dynamic NAV control method to suppress excessive traffic of EDCA terminal that generates TCP or UDP traffic with small contention window size in case that EDCA terminals and DCF terminals coexists in the same AR In the propose method, two kind of the fake period are prepared to increase the downstream traffic of AP. We also adapt appropriate size of CW_for AP to ensure opportunity of downstream transmission with reducing collision between an upload frame and a download frame. We evaluate performance of the proposed method by simulation experiments, and show that the proposed methods achieves fairness between upstream and downstream of the proposed terminals., The Institute of Electronics, Information and Communication Engineers, 06 Mar. 2014, IEICE technical report, 113, 472, 561-566, Japanese, 0913-5685, 110009861557, AA11546431 - B-18-36 Extending Content Delivery Method of Overhearing for Wireless Multi-hop Network
Nishizaka Kazuaki; Ohzahata Satoshi; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 04 Mar. 2014, Proceedings of the IEICE General Conference, 2014, 2, 604-604, Japanese, 110009849941, AN10471452 - BS-1-15 Towards Improving Congestion Control in Tor(BS-1. Future Network Technologies for Advanced Information and Communications Society)
Girry Kale Timothy; Ohzahata Satoshi; Wu Celimuge; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 04 Mar. 2014, Proceedings of the IEICE General Conference, 2014, 2, "S-29", English, 110009850012, AN10471452 - B-7-63 A Stabilization Method of Streaming Distribution in Wireless LAN with Overhearing
Kanayama Akihiro; Ohzahata Satoshi; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 04 Mar. 2014, Proceedings of the IEICE General Conference, 2014, 2, 238-238, Japanese, 110009850243, AN10471452 - B-11-18 A Cross Layer Approach for Multi-hop Broadcasting in VANETs with Reserved Time Slots
Wu Celimuge; Ohzahata Satoshi; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 04 Mar. 2014, Proceedings of the IEICE General Conference, 2014, 2, 466-466, English, 110009850368, AN10471452 - Behavior Analysis of Different TCP Implementations under Burst Error Environment
Wang Weikai; KATO Toshihiko; WU Celimuge; OHZAHATA Satoshi
Currently, large amount of data are transferred through the Internet. TCP plays an important role in this data transfer for the reliable data delivery. On the other hand, recent transmission technologies and media access control technologies realize high quality of data transmission in both backbone transport networks and mobile telecommunication networks. Therefore, packet losses detected in TCP level are considered as an indication of network congestion. However, packet losses can be caused by transmission interruptions such as handoffs in the mobile networks and protection switching in the transport networks. These packet losses are bursty because the transmission interruptions continue for tens of mili seconds through several seconds. This paper describes the results of experimental analysis of various TCP versions, several TCP versions in the Linux, that in Mac OS, against bursty packet losses. The result for Mac OS has some problem in retransmitting contiguously lost packets. This paper shows a detailed packet level analysis of TCP behaviors and points out that the key is the retransmission invoked by TCP SACK option., The Institute of Electronics, Information and Communication Engineers, 24 Jan. 2014, Technical report of IEICE. CQ, 113, 405, 17-22, English, 0913-5685, 110009822172, AN1054106X - An Evaluation of Node-Based Delays in the Tor Network
Girry Kale Timothy; Ohzahata Satoshi; Wu Celimuge; Kato Toshihiko
The Tor Network is a low-latency anonymity and censorship resistance network, which relaying traffics through onion routers before being forwarded to the destination. The distribution of trust offered by Tor creates resilience in the face of compromise and censorship; however, there are performance and usability issues in the Tor network. In this paper, we analyze in more details the delay contributions from different components that cause delays in the Tor nodes. We measured the application packet that passes through all the relay nodes and closely compute the sources of latency. The experimental analysis shows that the delays occurring on relay nodes are caused by the heavy circuit queuing, TCP kernel memory exhaustion and TCP advertised window not able to accept more data. We present our experimental detail analysis and measurement results as a prerequisite for addressing the Tor's poor performance and usability., The Institute of Electronics, Information and Communication Engineers, 23 Jan. 2014, IEICE technical report. Information networks, 113, 389, 121-126, English, 0913-5685, 110009825115, AN10013072 - Improving optimistic unchoke for reducing cross-ISP traffic of BitTorrent
ETO Hisashi; OHZAHATA Satoshi; KATO Toshihiko
In BitTorrent, network consist of overlay network on IP network. Therefore, even if peer wants a piece that exists in the same AS, the peer may get the piece from the outside AS. This behavior causes redundant traffic, and becomes burden for ISPs. In the peer selection algorithm, each peer randomly selects a peer with the optimistic unchoke every thirty seconds from its peer list We improve the optimistic unchoke to reduces the cross-AS traffic in this paper. The proposed method uses original Tit-for-tat strategy to keep fairness between an uploader and a downloader, but we modify the optimistic unchoke to reduce the redundant traffic across ASes., The Institute of Electronics, Information and Communication Engineers, 23 Jan. 2014, IEICE technical report. Information networks, 113, 389, 127-132, Japanese, 0913-5685, 110009825116, AN10013072 - A NAV Period Control for Keeping Transmission Opportunity and Achieving Fairness in Wireless LAN
HAYAMI Ryunosuke; OHZAHATA Satoshi; KATO Toshihiko
In this paper, we propose a extended dynamic NAV control method to suppress excessive traffic of EDCA terminal with small contention window size in case that EDCA terminals and DCF terminals coexists in the same AP. In the propose method, two patterns of the fake period are prepared to increase the downstream traffic of AP. We also adapt small size of CW_for AP to ensure opportunity of downstream transmission with reducing collision between an upload frame and a download frame. We evaluate performance of the proposed method by simulation experiments, and show that the proposed methods achieves fairness between upstream and downstream of the proposed terminals., The Institute of Electronics, Information and Communication Engineers, 23 Jan. 2014, IEICE technical report. Information networks, 113, 389, 115-120, Japanese, 0913-5685, 110009825114, AN10013072 - The Effect of Node-Based Delays on Tor Performance
Girry Kale Timothy; Ohzahata Satoshi; Wu Celimuge; Kato Toshihiko
Tor is an anonymous network that provides privacy and anonymity to users all over the world, by relaying traffics through the three onion routers before being forwarded to the destination. In this paper, we show that Tor suffers from the performance issues, because bandwidth is limited to how much a user is willing to allocate for Tor's usage. This scenario frequently leads to increasing delays that are not tolerated by the average end-users. We discuss these delays in more detail and perform the comprehensive study to evaluate the relative contributions for delays in the node. We use a simple model to analyze the delay components that contribute to degrade the Tor performance, due to poor TCP congestion control and high traffic queuing in the buffers. We evaluate our proposed mathematical models and present our experimental results as a prerequisite for addressing the Tor's poor delay performance., The Institute of Electronics, Information and Communication Engineers, 17 Oct. 2013, IEICE technical report, 113, 244, 111-116, English, 0913-5685, 110009783040, AA11546431 - Improving VANET unicast routing protocols by using network coding and cooperative relays
WU Celimuge; OHZAHATA Satoshi; JI Yusheng; KATO Toshihiko
We present a scheme for VANET routing protocols. The scheme uses multiple forwarder nodes to forward data and uses network coding to reduce the number of required transmissions, resulting in a significant improvement in end-to-end packet delivery ratio with low message overhead. The scheme can be used with any VANET routing protocols by simple modification. The effectiveness of the scheme is evaluated by using both theoretical analysis and computer simulations., The Institute of Electronics, Information and Communication Engineers, 17 Oct. 2013, IEICE technical report. Information networks, 113, 245, 13-18, English, 0913-5685, 110009818863, AN10013072 - Peer cooperation for accelerating piece diffusion and localization in BitTorrent
ETO Hisashi; OHZAHATA Satoshi; KATO Toshihiko
In Bit Torrent, network consist of overlay network on IP network. Therefore, even if peer wants a piece that exists in the same AS, the peer may get the piece from the outside AS. This behavior causes redundant traffic, and becomes burden for ISPs. In the peer selection algorithm, each peer selects randomly select a peer with the optimistic unchoke every thirty seconds from its peer list. In this paper, we improve the optimistic unchoke to reduces the cross-AS traffic. The proposed method uses original Tit-for-tat strategy to keep fairness between an uploader and a downloader, but we modify the optimistic unchoke to reduce the redundant traffic across A Ses., The Institute of Electronics, Information and Communication Engineers, 10 Oct. 2013, IEICE technical report, 113, 244, 73-74, Japanese, 110009783031, AA11546431 - Improvement of TCP Delay Performance at Large Rate Change in IEEE 802.11n Wireless LANs
NOMOTO Masataka; KATO Toshihiko; WU Celimuge; OZAHATA Satoshi
IEEE 802.11n wireless LANs provide high-speed data transfer. If the radio condition becomes bad, however, the transfer rate will be reduced significantly and there will be some problems in the data transfer. So, we have evaluated the performance of IEEE 802.11n LAN by changing the distance between the access point and a station. As a result, a severe increase of round-trip time was measured in the case of low transfer rate. A reason for this increased round-trip delay will be powerful retransmission function of 802.11n. So, we propose a method to improve TCP delay performance by reducing this retransmission capability and by generating TCP segment loss intentionally., The Institute of Electronics, Information and Communication Engineers, 12 Sep. 2013, Technical report of IEICE. CQ, 113, 208, 75-80, Japanese, 0913-5685, 110009814864, AN1054106X - BS-7-10 A Backbone-based Multi-hop Broadcast Protocol for VANETs
Wu Celimuge; Ohzahata Satoshi; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 03 Sep. 2013, Proceedings of the Society Conference of IEICE, 2013, 2, "S-51"-"S-52", English, 110009730227, AN10489017 - BS-7-50 A Simple Modeling for Delay Analysis of the Tor Network
KALE Timothy Girry; OHZAHATA Satoshi; KATO Toshihiko
The Institute of Electronics, Information and Communication Engineers, 03 Sep. 2013, Proceedings of the Society Conference of IEICE, 2013, 2, "S-128"-"S-129", English, 110009730267, AN10489017 - Improving a cause-and-effect relationship in a distributed emulation environment for wireless ad-hoc network
NITTA Koji; OHZAHATA Satoshi; KATO Toshihiko
In this paper, we construct an emulation environment for wireless ad-hoc network with EMANE. In the emulation environment, since a collision of frame is not dealt in the distributed emulation, we propose a method to correct a cause-and-effect relationship for the collision and the retransmission times in MAC. We evaluate the proposed method in the emulation environment., The Institute of Electronics, Information and Communication Engineers, 18 Jul. 2013, IEICE technical report, 113, 129, 173-178, Japanese, 0913-5685, 110009777836, AA11546431 - A Fuzzy Inference Intelligent Routing Protocol for Vehicular Ad Hoc Networks
WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
Due to vehicle movement, limited wireless resources and lossy feature of wireless channels, providing a reliable multi-hop communication in VANETs is particularly challenging. We present a VANET routing protocol which learns the optimal route by employing a fuzzy constraint Q-Learning algorithm. The protocol uses fuzzy logic to evaluate a wireless link is whether good or not by considering multiple metrics of signal strength, available bandwidth and relative vehicle movement. Based on the evaluation of each wireless link, the protocol learns the best route using the route request messages and hello messages. The protocol can achieve high packet delivery ratio and low end-to-end delay. We show the effectiveness of the protocol by using computer simulations., The Institute of Electronics, Information and Communication Engineers, 17 Jul. 2013, IEICE technical report. ASN, Ambient intelligence and sensor networks, 113, 132, 201-206, English, 0913-5685, 110009778122, AA12618979 - An Implementation-friendly Broadcast Protocol for VANETs Utilizing Neighbor Information
WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
We present BR-NB (broadcast with neighbor information), a fuzzy logic based multi-hop broadcast protocol for VANETs. BR-NB achieves a low overhead by using only a subset of neighbor nodes to relay data packets. For the relay node selection, BR-NB takes account of the inter-vehicle distance, vehicle mobility and link quality by employing fuzzy logic. The expected coverage and vehicle mobility are inferred from the two-hop neighbor information which can be acquired from the hello message exchange. Since it is independent of lower layers and does not require GPS, BR-NB provides an implementation-friendly solution for broadcasting in VANETs. We use computer simulations and real-world experiments to evaluate the performance of BR-NB., The Institute of Electronics, Information and Communication Engineers, 11 Jul. 2013, Technical report of IEICE. CQ, 113, 123, 7-12, English, 0913-5685, 110009773226, AN1054106X - A Redundant Traffic Elimination Method with using Overhearing in Wireless LAN
YOKOSE Hiroaki; NITTA Koji; OHZAHATA Satoshi; KATO Toshihiko
In wireless LAN, since the bandwidth is shared with the terminals, the download speed is reduced even if the same content is downloaded. We have proposed a download acceleration method for content distribution by overhearing packets of the same content for other nodes in wireless LAN. Since parts of the content are obtained by the overhearing, the download time is reduced. In the method, the content is divided into pieces and the server distributes them. We show scheduling methods of pieces to send and destination with applying network coding, and evaluated these methods in testbed., The Institute of Electronics, Information and Communication Engineers, 16 May 2013, IEICE technical report. ASN, Ambient intelligence and sensor networks, 113, 38, 35-40, Japanese, 0913-5685, 110009771441, AA12618979 - A NAV Period Control for Suppressing Excessive Traffic from Terminals in Wireless LAN
Ryunosuke Hayami; Satoshi Ohzahata; Toshihiko Kato
There is a problem that DCF terminal transmits low rate when EDCA terminals and DCF terminals coexists in the same AP because EDCA terminal occupies the channel more than that of DCF terminals. In this paper, we propose a dynamic NAV control method that adds a fake period not to overlap the contention period with the EDCA terminals, and Backoff control is also considered to enhance in the fake scheme to improve the problem., Information Processing Society of Japan (IPSJ), 09 May 2013, 研究報告ユビキタスコンピューティングシステム（UBI）, 2013, 37, 1-2, Japanese, 0919-6072, 110009579753, AA11838947 - A Redundant Traffic Elimination Method with using Overhearing in Wireless LAN
Hiroaki Yokose; Koji Nitta; Satoshi Ohzahata; Toshihiko Kato
In wireless LAN, since the bandwidth is shared with the terminals, the download speed is reduced even if the same content is downloaded. We have proposed a download acceleration method for content distribution by overhearing packets of the same content for other nodes in wireless LAN. Since parts of the content are obtained by the overhearing, the download time is reduced. In the method, the content is divided into pieces and the server distributes them. We show scheduling methods of pieces to send and destination with applying network coding, and evaluated these methods in testbed., Information Processing Society of Japan (IPSJ), 09 May 2013, 研究報告ユビキタスコンピューティングシステム（UBI）, 2013, 7, 1-6, Japanese, 0919-6072, 110009579723, AA11838947 - A NAV Period Control for Suppressing Excessive Traffic from Terminals in Wireless LAN
HAYAMI Ryunosuke; OHZAHATA Satoshi; KATO Toshihiko
There is a problem that DCF terminal transmits low rate when EDCA terminals and DCF terminals coexists in the same AP because EDCA terminal occupies the channel more than that of DCF terminals. In this paper, we propose a dynamic NAV control method that adds a fake period not to overlap the contention period with the EDCA terminals, and Backoff control is also considered to enhance in the fake scheme to improve the problem., The Institute of Electronics, Information and Communication Engineers, 09 May 2013, IEICE technical report. ASN, Ambient intelligence and sensor networks, 113, 38, 149-150, Japanese, 110009771463, AA12618979 - Measuring Available Bandwidth for Path Selection of Tor Network
KALE Timothy Girry; OHZAHATA Satoshi; KATO Toshihiko
The Tor routing protocol aimed at providing anonymity for latency-sensitive applications such as web-browsing by routing traffic through a randomly-constructed circuit of intermediate relays. Previous studies showed that the barriers to widespread use of Tor are the unfairly load distribution and the low TCP throughput. We consider the available bandwidth metric as important for path selection to keep the TCP throughput and distribution of traffics across the Tor network. Then, we have studied the key attributes that degrade the Tor's performance, and introduced the adaptation measurement technique in Tor by applying the active network measurement. This measurement technique is useful to determine the available bandwidth on selected relays., The Institute of Electronics, Information and Communication Engineers, 18 Apr. 2013, IEICE technical report. Information networks, 113, 5, 49-54, English, 0913-5685, 110009768581, AN10013072 - A MAC protocol to improve QoS in VANETs using contention window adjustment
WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
Packet delivery ratio and end-to-end delay are the two most important QoS (Quality of Service) metrics. In this paper, we propose a MAC layer protocol which can provide a high packet delivery ratio and low end-to-end delay for various scenarios. The proposed protocol uses a Q-Learning algorithm to tune the contention window size in order to provide an efficient channel access scheme for various network situations. We show the effectiveness of the proposed protocol by using computer simulations., The Institute of Electronics, Information and Communication Engineers, 18 Apr. 2013, Technical report of IEICE. CQ, 113, 7, 65-70, English, 0913-5685, 110009769138, AN1054106X - A Dynamic NAV Period Control for High Priority Media Access Control in Wireless LAN
KUMAGAI Yuta; OHZAHATA Satoshi; KATO Toshihiko
A policy of QoS control in wireless LAN is important in case that a terminal of Voice category of IEEE 802.11e generates excessive traffic. In this paper, we propose a dynamic NAV control, Dynamic cwmin control for an access point(AP)and queuing method, even if the high priority terminals and the proposed terminals coexist. In the proposed method a fake period is added to conventional NAV period to control priority, and Dynamic CWmin control and adaptive queuing controls are added to AP. Then the proposed method archives fairness among terminals even when excessive uplink traffic is generated. We evaluate performance of the proposed method by simulation experiments, and show that the proposed methods serves controlled priority., The Institute of Electronics, Information and Communication Engineers, 14 Mar. 2013, Ad hoc networks IEICE technical report, 112, 494, 131-136, Japanese, 0913-5685, 110009712612, AA12214856 - Visualization of Overlay Network using Autonomous System Relationships
Nakamura Miyamura Hiroko; Hu Hsiang-Yun; Yoshida Masahiro; Ohzahata Satoshi; Nakao Akihiro; Takahashi Shigeo
This report presents a method for visualizing scale-free networks. Scale-free networks are said to be difficult to analyze and visualize, because distribution of the vertex degrees follow the power-law nature. Sasaki et al proposed scale-free network visualization technique that creates the hierarchical representation, referring to their vertex degrees. By using the AS relations data, we improve the method of Sasaki et al, and visualize the scale-free networks more clearly. We also applied the proposed method to overlay traffic data of BitTorrent in order to demonstrate the effective visualization of communication paths between a pair of peers over the scale-free network., The Institute of Electronics, Information and Communication Engineers, 07 Mar. 2013, IEICE technical report, 112, 463, 577-582, Japanese, 0913-5685, 110009712168, AA11546431 - Encouragement Talk : A Piece Scheduling Method for a Content Distribution Method using File Piecing and Overhearing in Wireless LAN
YOKOSE Hiroaki; OHZAHATA Satoshi; KATO Toshihiko
In wireless LAN, since the bandwidth is shared with the terminals, the download speed is reduced even if the same content is downloaded. We have proposed a download acceleration method for content distribution by overhearing packets of the same content for other nodes in wireless LAN. Since parts of the content are obtained by the overhearing, the download time is reduced. In the method, the content is divided into pieces and the server distributes them/We show scheduling methods of pieces to send and destination with applying network coding, and evaluated these methods in testbed., The Institute of Electronics, Information and Communication Engineers, 07 Mar. 2013, IEICE technical report, 112, 463, 25-30, Japanese, 0913-5685, 110009712073, AA11546431 - A Dynamic NAV Period Control for High Priority Media Access Control in Wireless LAN
熊谷 雄太; 大坐 畠智; 加藤 聰彦
無線 LAN 環境での通信の課題の一つとして QoS 制御をどのように行うかという問題がある．本稿では，IEEE 802.11e の Vo カテゴリーのような高優先制御で大量のトラヒックを生成する端末が混在した場合でも NAV の動的な変更，AP の CWmin の動的な変更，キューイング制御を組み合わせることで提案方式の端末の通信の QoS 確保を基地局主導で実現する制御方式を提案する．NAV に通信状況で動的に変更する値 (Fake 期間) を追加し，優先度の調整を行い従来の優先端末の過剰な通信を抑え，提案端末の通信量を増加させる．また，キューイングと動的 CW の変更を行うことで，下りトラヒックの割合を増加させ，端末間の公平性を達成する．提案方式の性能をコンピュータシミュレーションにより評価し，提案方式を用いることで既存の優先端末の通信量を抑え，提案方式の端末の通信量が向上していることを示す．A policy of QoS control in wireless LAN is important in case that a terminal of Voice category of IEEE 802.11e generates excessive traffic. In this paper, we propose a dynamic NAV control, Dynamic CWmin control for an access point(AP) and queuing method, even if the high priority terminals and the proposed terminals coexist. In the proposed method a fake period is added to conventional NAV period to control priority, and Dynamic CWmin control and adaptive queuing controls are added to AP. Then the proposed method archives fairness among terminals even when excessive uplink traffic is generated. We evaluate performance of the proposed method by simulation experiments, and show that the proposed methods serves controlled priority., 07 Mar. 2013, 研究報告ユビキタスコンピューティングシステム（UBI）, 2013, 21, 1-6, Japanese, 110009551481, AA11838947 - B-6-59 An Implementation-friendly Multi-hop Broadcast Protocol for VANETs
Wu Celimuge; Ohzahata Satoshi; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 05 Mar. 2013, Proceedings of the IEICE General Conference, 2013, 2, 59-59, English, 110009760983, AN10471452 - A Network Emulation Evaluation for a Redundant Traffic Elimination Method using File Piecing and Overhearing in Wireless LAN
NITTA Koji; YOKOSE Hiroaki; OHZAHATA Satoshi; KATO Toshihiko
In wireless LAN, since the bandwidth is shared with the terminals, the download speed is reduced even if the same content is downloaded We propose a download acceleration method for content distribution by overhearing packets of the same content for other nodes in wireless LAN Since parts of the content are obtained by the overhearing, the download time is reduced In the proposed method, the content is divided into pieces and the server distributes them with considering download status of the receivers The proposed method can accelerate the download speed even if terminals start downloading at different timing In this paper, we evaluate the proposed method in network emulator, and analyzed differences between testbed and emulator We also evaluate effects when the number of nodes is increased, The Institute of Electronics, Information and Communication Engineers, 24 Jan. 2013, Ad hoc networks IEICE technical report, 112, 405, 31-36, Japanese, 0913-5685, 110009727308, AA12214856 - Applying Network Coding to a Redundant Traffic Elimination Method using File Piecing and Overhearing in Wireless LAN
YOKOSE Hiroaki; OHZAHATA Satoshi; KATO Toshihiko
In wireless LAN, since the bandwidth is shared with the terminals, the download speed is reduced even if the same content is downloaded. We have proposed a download acceleration method for content distribution by overhearing packets of the same content for other nodes in wireless LAN. Since parts of the content are obtained by the overhearing, the download time is reduced. In the method, the content is divided into pieces and the server distributes them.We apply network coding for sending pieces in the method when terminals request different pieces to improve speed, and we evaluated the proposed method in testbed., The Institute of Electronics, Information and Communication Engineers, 13 Dec. 2012, IEICE technical report, 112, 350, 139-144, Japanese, 0913-5685, 110009666960, AA11546431 - A NAV Period Control for High Prioritized Channel Access in Wireless LAN
KUMAGAI Yuta; OHZAHATA Satoshi; KATO Toshihiko
There is a problem how to QoS control in wireless LAN. In this paper, we perpose a dynamic NAV control method, even if a high priority terminal (conventional IEEE802.11 Vo category) and DCF terminal are coexisted. In the proposed method a fake value is added to NAV period to control priority of the channel access. Under the proposed control, the conventional high priority terminal has to wait an additional time of the fake period than the proposed terminal to start t the carrier sense. However, the proposed terminal start the carrier sense earlier the conventional high priority terminal because the terminals under the proposed control know NAV includes the fake period. We evaluate performance of the proposed method by simulation experiments, and show that the proposed methods are given higher priority., The Institute of Electronics, Information and Communication Engineers, 14 Nov. 2012, IEICE technical report. Information networks, 112, 307, 63-68, Japanese, 0913-5685, 110009641655, AN10013072 - Improving OLSR for highly mobile and lossy networks
DASHBYAMBA Narangerel; WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
Optimized Link State Routing Protocol (OLSR) is a well-known proactive, routing protocol for mobile ad hoc networks. OLSR reduces the number of control messages by using MPRs to forward topology control messages as compared with typical proactive protocols. Since OLSR does not consider the node mobility and signal strength condition in the MPR selection, OLSR cannot work well in a highly mobile and lossy network. In this paper, we propose a protocol to improve OLSR by considering the node mobility and signal strength in the route selection. We use network simulator to evaluate the proposed protocol's performance., The Institute of Electronics, Information and Communication Engineers, 08 Nov. 2012, Technical report of IEICE. CQ, 112, 288, 47-52, English, 0913-5685, 110009642101, AN1054106X - An Evaluation of Piece Scheduling for a Redundant Traffic Elimination using File Piecing and Overhearing in Wireless LAN
YOKOSE Hiroaki; OHZAHATA Satoshi; KATO Toshihiko
In wireless LAN, since the bandwidth is shared with the terminals, the download speed is reduced even if the same content is downloaded. We propose a download acceleration method for content distribution by overhearing packets of the same content for other nodes in wireless LAN. Since parts of the content are obtained by the overhearing, the download time is reduced. In the proposed method, the content is divided into pieces and the server distributes them. We propose a piece scheduling to be fair download speed with considering download status of the receivers even if the receivers start download at different times or the receivers are under different communication conditions. We evaluated the scheduling of the proposed method., The Institute of Electronics, Information and Communication Engineers, 03 Oct. 2012, IEICE technical report. Information networks, 112, 230, 191-196, Japanese, 0913-5685, 110009636559, AN10013072 - Fuzzy logic based MPR selection for OLSR
DASHBYAMBA N.; WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
Optimized Link State Routing Protocol(OLSR) provides a low control overhead in high-density networks by using only MPRs to forward topology control messages. Since signal strength and mobility i \ssues are not considered in the MPR selection, OLSR fails to work properly in lossy or mobile wireless networks. In this paper, we propose a fuzzy logic based MPR selection algorithm to improve the performance of OLSR. The proposed protocol selects MPRs by considering inter-node distance, RSSI and node velocity. We use computer simulations to evaluate the proposed protocol., The Institute of Electronics, Information and Communication Engineers, 27 Sep. 2012, IEICE Technical Report, 112, 218, 83-88, English, 0913-5685, 110009666597, AN1054106X - BS-5-27 Eliminating Redundant Traffic with File Piecing and Overhearing for Contents Distribution over Wireless LAN(BS-5. Network and Service Design, Control and Management)
Yokose Hiroaki; Ohzahata Satoshi; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 28 Aug. 2012, Proceedings of the Society Conference of IEICE, 2012, 2, "S-78"-"S-79", English, 110009592120, AN10489017 - B-7-42 A Dynamic NAV Period Control Method for QoS Control in Wireless LAN
KUMAGAI Yuta; OHZAHATA Satoshi; KATO Toshihiko
The Institute of Electronics, Information and Communication Engineers, 28 Aug. 2012, Proceedings of the Society Conference of IEICE, 2012, 2, 121-121, Japanese, 110009591758, AN10489017 - B-6-18 A Redundant Transmission Mechanism for WSNs
Wu Celimuge; Ohzahata Satoshi; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 28 Aug. 2012, Proceedings of the Society Conference of IEICE, 2012, 2, 18-18, English, 110009591655, AN10489017 - An Evaluation of a Redundant Traffic Elimination Method for Wireless LAN using File Piecing and Overhearing under Different Transfer Rate Conditions
YOKOSE Hiroaki; OHZAHATA Satoshi; KATO Toshihiko
In wireless LAN, since the bandwidth is shared with the terminals, the download speed is reduced even if the same content is downloaded. We propose a download acceleration method for content distribution by overhearing packets of the same content for other nodes in wireless LAN. Since parts of the content are obtained by the overhearing, the download time is reduced. In the proposed method, the content is divided into pieces and the server distributes them with considering download status of the receivers. We evaluated the proposed method under the condition that terminals are communicating in different transfer rate., The Institute of Electronics, Information and Communication Engineers, 12 Jul. 2012, IEICE technical report, 112, 131, 1-6, Japanese, 0913-5685, 110009625782, AA11546431 - Fast and reliable data collection in WSNs with adaptive redundant transmission
WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
For many wireless sensor network (WSN) applications, high reliability and low delay are required. The acknowledgement based retransmission mechanism is the most frequently used approach for providing the reliability. However, the retransmission increases the end-to-end delay especially when the number of hops from a sensor to the sink node is large. In this paper, we propose a redundancy-based approach to provide high reliability and low end-to-end delay. Redundant transmissions are used when a link is unreliable or the end-to-end delay requirement is strict. We evaluate the proposed mechanism using a wireless sensor network which consists of IRIS motes., The Institute of Electronics, Information and Communication Engineers, 05 Jul. 2012, Technical report of IEICE. CQ, 112, 119, 95-100, English, 0913-5685, 110009626641, AN1054106X - A Method for Eliminating Redundant Traffic using Piece Dividing and Overhearing
横瀬 広明; 大坐畠 智; 加藤 聰彦
無線 LAN において同一のコンテンツを多数の端末が同時にダウンロードすると，同じ内容が各端末に宛ててそれぞれ送信されるため冗長であり，ダウンロードの速度も低下する．本稿では，他の端末あての無線フレームを互いにオーバヒアリングし，まだ所持していないコンテンツの一部分を入手することで冗長なトラヒックを削減し，ダウンロード速度を向上させる方式を提案する．コンテンツはピースに分割して管理し，コンテンツ配信サーバが各端末のピースのダウンロード状況をもとに送信宛先端末や送信ピースを決定する．実機を用いた実験を行い，提案方式が冗長トラヒックを削減しスループットを向上させること，ダウンロード開始のタイミングが端末ごとに異なる場合でも有効であることを示す．In wireless LAN, since the bandwidth is shared with the terminals, the download speed is reduced even if the same content is downloaded. We propose a download acceleration method for content distribution by overhearing packets of the same content for other nodes in wireless LAN. Since parts of the content are obtained by the overhearing, the download time is reduced. In the proposed method, the content is divided into pieces and the server distributes them with considering download status of the receivers. We developed a testbed and confirmed that the proposed method accelerates the download speed even if terminals start downloading at different timing., 14 May 2012, 研究報告モバイルコンピューティングとユビキタス通信（MBL）, 2012, 9, 1-6, Japanese, 170000070978, AA11851388 - A Method for Eliminating Redundant Traffic using Piece Dividing and Overhearing
YOKOSE Hiroaki; OHZAHATA Satoshi; KATO Toshihiko
In wireless LAN, since the bandwidth is shared with the terminals, the download speed is reduced even if the same content is downloaded. We propose a download acceleration method for content distribution by overhearing packets of the same content for other nodes in wireless LAN. Since parts of the content are obtained by the overhearing, the download time is reduced. In the proposed method, the content is divided into pieces and the server distributes them with considering download status of the receivers. We developed a testbed and confirmed that the proposed method accelerates the download speed even if terminals start downloading at different timing., The Institute of Electronics, Information and Communication Engineers, 14 May 2012, IEICE technical report, 112, 44, 45-50, Japanese, 0913-5685, 110009569087, AA1154676X - A VANET routing protocol with full utilization of opportunism
WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
Opportunistic routing can be a solution for data forwarding in vehicular ad hoc networks (VANETs). However, existing opportunistic protocols specify the forwarding nodes at the sender side and therefore the opportunism cannot be fully utilized. Most opportunistic routing protocols cannot provide a high reliability due to the lack of efficient packet reception check mechanism. In this paper, we present OFA, an opportunistic forwarding and acknowledgement protocol for VANETs. In OFA, the forwarder node selection occurs at receiver nodes. An intermediate node is selected opportunistically to acknowledge the sender on the behalf the forwarder node when the forwarder node cannot communicate with the sender node directly. OFA can fully utilize the path diversity and also can provide hop-by-hop reliability., The Institute of Electronics, Information and Communication Engineers, 12 Apr. 2012, Technical report of IEICE. CQ, 112, 10, 19-24, English, 110009564453, AN1054106X - A PU Aware Route Discovery Approach for Cognitive Ad Hoc Networks (アドホックネットワーク)
Wu Celimuge; Ohzahata Satoshi; Kato Toshihiko
電子情報通信学会, 12 Mar. 2012, 電子情報通信学会技術研究報告 : 信学技報, 111, 477, 147-152, English, 0913-5685, 40019224950 - B-6-14 A Primary User Aware Routing Protocol for Cognitive CSMA/CA Ad Hoc Networks
Nakato Tatsuaki; Wu Celimuge; Ohzahata Satoshi; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 06 Mar. 2012, Proceedings of the IEICE General Conference, 2012, 2, 14-14, English, 110009462487, AN10471452 - A PU Aware Route Discovery Approach for Cognitive Ad Hoc Networks
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
Cognitive ad hoc networks have been attracting interests in recent years. Designing an efficient routing protocol for cognitive ad hoc networks is important for full utilization of free wireless resources. A protocol considering primary user (PU) flows and channel assignment incurred network connectivity issue in the route selection is still missing. In this paper, we propose AODV-cog, a cognitive routing protocol for CSMA/CA ad hoc networks based on AODV. AODV-cog utilizes the availability of multiple channels by considering the effect on the primary users. AODV-cog chooses a route by considering available channel bandwidth and future channel utilization. AODV-cog switches channels for secondary user flows when network congestion is occurred. We use network simulations to show the advantage of AODV-cog over existing alternatives.Cognitive ad hoc networks have been attracting interests in recent years. Designing an efficient routing protocol for cognitive ad hoc networks is important for full utilization of free wireless resources. A protocol considering primary user (PU) flows and channel assignment incurred network connectivity issue in the route selection is still missing. In this paper, we propose AODV-cog, a cognitive routing protocol for CSMA/CA ad hoc networks based on AODV. AODV-cog utilizes the availability of multiple channels by considering the effect on the primary users. AODV-cog chooses a route by considering available channel bandwidth and future channel utilization. AODV-cog switches channels for secondary user flows when network congestion is occurred. We use network simulations to show the advantage of AODV-cog over existing alternatives., 05 Mar. 2012, 研究報告ユビキタスコンピューティングシステム（UBI）, 2012, 9, 1-6, English, 170000069867, AA11838947 - A PU Aware Route Discovery Approach for Cognitive Ad Hoc Networks
Celimuge Wu; Satoshi Ohzahata; Toshihiko Kato
Cognitive ad hoc networks have been attracting interests in recent years. Designing an efficient routing protocol for cognitive ad hoc networks is important for full utilization of free wireless resources. A protocol considering primary user (PU) flows and channel assignment incurred network connectivity issue in the route selection is still missing. In this paper, we propose AODV-cog, a cognitive routing protocol for CSMA/CA ad hoc networks based on AODV. AODV-cog utilizes the availability of multiple channels by considering the effect on the primary users. AODV-cog chooses a route by considering available channel bandwidth and future channel utilization. AODV-cog switches channels for secondary user flows when network congestion is occurred. We use network simulations to show the advantage of AODV-cog over existing alternatives.Cognitive ad hoc networks have been attracting interests in recent years. Designing an efficient routing protocol for cognitive ad hoc networks is important for full utilization of free wireless resources. A protocol considering primary user (PU) flows and channel assignment incurred network connectivity issue in the route selection is still missing. In this paper, we propose AODV-cog, a cognitive routing protocol for CSMA/CA ad hoc networks based on AODV. AODV-cog utilizes the availability of multiple channels by considering the effect on the primary users. AODV-cog chooses a route by considering available channel bandwidth and future channel utilization. AODV-cog switches channels for secondary user flows when network congestion is occurred. We use network simulations to show the advantage of AODV-cog over existing alternatives., 05 Mar. 2012, 研究報告モバイルコンピューティングとユビキタス通信（MBL）, 2012, 9, 1-6, English, 170000069825, AA11851388 - A Multilevel Graph Layout for Analysing Large-scale Network Datasets
MIYAMUYA NAKAMURA Hiroko; YOSHIDA Yoshihiro; OHZAHATA Satoshi; TAKAHASHI Shigeo; NAKAO Akihiro; KAWASHIMA Konosuke
We propose a multilevel graph layout technique for visualizing large scale file-sharing network datasets. Large-scale datasets are said to be difficult to analyze and visualize. However, with our technique, the datasets can be displayed in multistep. For instance the outline of network dataset is shown first, and when focused on a certain region, the detailed information is shown as well. By using this technique, users can observe a large scale dataset from the outline to the detail seamlessly, and therefore this is valuable for the structural analysis of network datasets., The Institute of Electronics, Information and Communication Engineers, 01 Mar. 2012, IEICE technical report, 111, 468, 243-248, Japanese, 0913-5685, 110009545036, AA11546431 - Visualizing Scale Free Networks for the Analysis of P2P Network Traffic Data
SASAKI Kai; WU Hsiang-Yun; YOSHIDA Yoshihiro; MIYAMURA NAKAMURA Hiroko; OHZAHATA Satoshi; NAKAO Akihiro; TAKAHASHI Shigeo
This report presents a method for visualizing scale-free networks including P2P networks as an typical example. Visualizing large-scale and complicated networks such as social networks has recently been very popular while conventional network visualization techniques cannot allow us to understand the topological structure of the scale-free networks. This is because the vertex degrees vary at an exponential rate in the scale-free network and thus special attention should be given when visualizing the network connectivity and analyzing the network traffic there. In this report, we employ the hierarchical representation of the scale-free network by referring to their vertex degrees, so that we can clearly visualize the topological structure of the network in 3D space and retrieve the traffic paths over the network. We also applied the proposed method to BitTorrent traffic data in order to demonstrate that we can effectively visualize communication paths between a pair of peers over the scale-free network., The Institute of Electronics, Information and Communication Engineers, 01 Mar. 2012, IEICE technical report, 111, 468, 249-254, Japanese, 0913-5685, 110009545037, AA11546431 - Detailed Analysis of iPad2 TCP Behaviours
WANG Weikai; WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
Nowadays, tablet device such as iPad2 is getting popular as a platform for portable wireless computing and is used in various communication scenarios, such as web browsing and e-mail transmissions. However, iPad2 is newly introduced in the market and it may possibly have some differences form the common notebook computers. So, we analyze the behaviors of iPad2 TCP communication, which works as a basis of various communication applications. In this analysis, we examine the TCP communication in various conditions by introducing transmission errors. We analyze the segment sequences in detail. This paper shows the evaluation results and points out some issues which iPad2 has in its TCP implementation., The Institute of Electronics, Information and Communication Engineers, 26 Jan. 2012, IEICE technical report. Information networks, 111, 409, 95-100, English, 0913-5685, 110009481034, AN10013072 - A High Speed Contents Distribution Method with Overhearing File Pieces in Wireless LAN
横瀬 広明; 大坐畠 智; 加藤 聰彦
電子情報通信学会, 19 Jan. 2012, 電子情報通信学会技術研究報告 : 信学技報, 111, 385, 89-94, Japanese, 0913-5685, 40019153409 - A TCP Window Control using Channel Occupancy for Improving Video Streaming Quality at Wireless LAN Terminal
HIRAI Toshiyuki; OHZAHATA Satoshi; WADA Naoya; KAWASHIMA Konosuke
In TCP communication, each terminal tries to obtain as much bandwidth as possible. This control causes the differences of transfer rates among terminals and disrupts the video stream service. In order to solve this problem, we propose a new TCP window size control method using the channel occupancy for a wireless network. Our method is intended to fairly share the bandwidth among the terminals. Each terminal controls the maximum TCP window size not to generate excessive traffic. We confirmed that the proposed method improves the quality of video communication by computer simulation experiments., The Institute of Electronics, Information and Communication Engineers, 15 Dec. 2011, IEICE technical report, 111, 344, 19-24, Japanese, 0913-5685, 110009466628, AA11546431 - Joint Retransmission and Relay Node Selection Scheme for Multi-hop Broadcast in VANETs
WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
Providing a reliable and efficient multi-hop broadcast in vehicular ad hoc networks (VANETs) is crucial for Intelligent Transportation Systems. In order to provide a high reliability, a retransmission mechanism is required because a packet can be lost depending on the wireless link status and vehicle movement. The retransmission can significantly increase the message overhead if the relay nodes are not selected properly. The solution involves a joint consideration of retransmission and relay node selection. In this paper, we present a broadcast scheme which provides a high reliability with a low overhead. The scheme uses a fuzzy logic based approach to select relay nodes and uses a lightweight retransmission mechanism to retransmit a packet when a relay fails. We use computer simulations to evaluate the performance of the scheme and show the simulation results., The Institute of Electronics, Information and Communication Engineers, 03 Nov. 2011, Technical report of IEICE. CQ, 111, 278, 79-84, English, 0913-5685, 110009465887, AN1054106X - A Study on TCP Performance of Android Tablet Devices
WU Celimuge; WANG Weikai; OHZAHATA Satoshi; KATO Toshihiko
Tablet devices are expected to account for a large portion of the Internet traffic in the near future due to their increasing shipments. As an open source platform, Android has been attracting interests from many communities. In this paper, we analyze the performance of TCP communication on Android tablet devices. We examine the TCP behaviors of Android tablet devices in various conditions by using a network emulator. We show the analysis results and point out possible improvements., The Institute of Electronics, Information and Communication Engineers, 01 Sep. 2011, IEICE technical report, 111, 202, 51-56, English, 0913-5685, 110008900628, AN1054106X - B-20-6 An Evaluation of Congestion Control of Wireless Mesh Network Connecting with Wired Network
NAKAYAMA Yosuke; OHZAHATA Satoshi; KATO Toshihiko
The Institute of Electronics, Information and Communication Engineers, 30 Aug. 2011, Proceedings of the Society Conference of IEICE, 2011, 2, 471-471, Japanese, 110008725298, AN10489017 - BS-6-40 A Lightweight Approach for Reliable Broadcast in VANETs(BS-6. Planning, Control and Management on Networks and Services)
Wu Celimuge; Ohzahata Satoshi; Kato Toshihiko
The Institute of Electronics, Information and Communication Engineers, 30 Aug. 2011, Proceedings of the Society Conference of IEICE, 2011, 2, "S-108"-"S-109", English, 110008725367, AN10489017 - Improvement of one-phase pull diffusion using fuzzy logic (アドホックネットワーク)
Wu Celimuge; Ohzahata Satoshi; Kato Toshihiko
電子情報通信学会, 15 Jul. 2011, 電子情報通信学会技術研究報告, 111, 139, 1-6, English, 0913-5685, 40018944969 - Performance analysis of iPad TCP communications
WANG Weikai; WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
Nowadays, a tablet terminal such as iPad is getting popular as a platform of the portable wireless computing and is used in various communication scenarios such as web accesses and e-mail transmissions. However, iPad is newly introduced in the market and it may possibly have some differences from the common wireless terminals such as notebook computers. So, we analyze the performance of iPad TCP communication, which works as a basis of various communication applications. In this analysis, we examine the TCP performance in various conditions by introducing propagation delays and transmission errors. We have analyzed the segment sequences in detail. This paper shows the evaluation results and points out some issues which iPad has in its TCP implementation., The Institute of Electronics, Information and Communication Engineers, 09 Jun. 2011, IEICE technical report, 111, 80, 85-90, English, 0913-5685, 110008746085, AN10013072 - Controls at an Access Point and Terminals for Video Streaming over Wireless LAN and its QoE Evaluation
KOYAMA Takayuki; IJIRI Keiya; OHZAHATA Satoshi; KAWASHIMA Konosuke
In wireless LAN, since an access point is shared by several terminals, there is a problem that communication quality of video streaming is affected by background traffic of TCP. Therefore, we propose priority control for improving quality of video streaming by setting EDCA (Enhanced Distributed Channel Access) parameters in an access point. In addition, we also propose a cross-layer control to adjust the bandwidth, and set TCP window size of TCP from wireless terminals according to the congestion status. In evaluation, we construct the testbed and the proposed method shows improvement of QoE for the video streaming., The Institute of Electronics, Information and Communication Engineers, 28 Feb. 2011, IEICE technical report, 110, 455, 63-68, Japanese, 0913-5685, 110008690055, AN1054106X - B-6-83 A Congestion Control Method with Queuing Time for Dynamic CW Control in Wireless Mesh Network
KOBAYASHI Hirokazui; OHZAHATA Satoshi; KATO Toshihiko
The Institute of Electronics, Information and Communication Engineers, 28 Feb. 2011, Proceedings of the IEICE General Conference, 2011, 2, 83-83, Japanese, 110008577005, AN10471452 - B-6-109 A Performance Evaluation of BitTorrent in IP Network Topologies
MISHINA Tomoyuki; OHZAHATA Satoshi; KATO Toshihiko
The Institute of Electronics, Information and Communication Engineers, 28 Feb. 2011, Proceedings of the IEICE General Conference, 2011, 2, 109-109, Japanese, 110008577031, AN10471452 - B-7-3 A QoS Control Scheme at Access Point for Video Streaming to Mobile Terminals
Koyama Takayuki; Ijiri Keiya; Ohzahata Satoshi; Kawashima Konosuke
携帯電話で、映像を利用する状況が急増している。無線LANを用いて携帯端末で映像を快適に視聴するためには、ビデオストリーミングによる下り帯域の利用を上りより優先させる必要がある。本稿では、携帯端末からアクセスポイント(AP)におけるIEEE 802.11c規格のEDCA (Enhanced Distributed Channel Access)パラメータを変更することにより、下りトラヒックを優先させる通信速度制御を実現する。, The Institute of Electronics, Information and Communication Engineers, 28 Feb. 2011, Proceedings of the IEICE General Conference, 2011, 2, 167-167, Japanese, 110008577089, AN10471452 - A Search Control for P2P Networks Focused on Peer Property and Network Structure
NAKAZAWA Hiroaki; YOSHIDA Masahiro; OHZAHATA Satoshi; NAKAO Akihiro; KAWASHIMA Konosuke
P2P systems have been used for file sharing, VoIP and video streaming services all over the world. In particular, P2P file sharing systems have various problems such as copyright infringement, personal information leakage. One of the reasons of these problems is that a pure P2P file sharing network does not have a management and control mechanism for file exchange. Our previous study has proposed a file search method by controlling file search network. In this method, the control peers set up a lot of search links to the peers. In this paper, we propose a search control method focused on peer property and network structure. We evaluated effects of our method by computer simulation using measured data set. The results show that the propose method improves the control efficiency., The Institute of Electronics, Information and Communication Engineers, 13 Jan. 2011, IEICE technical report, 110, 373, 49-54, Japanese, 0913-5685, 110008676230, AN10013072 - An Improvement of QoE for Video Streaming over Wireless LAN Using the Cross Layer Control between the MAC Layer and the TCP Layer
IJIRI Keiya; OHZAHATA Satoshi; KAWASHIMA Konosuke
In Wireless LAN's infrastructure mode, several terminals use the same AP (Access Point) to share wireless bandwidth. Terminals making TCP communications will get more and more bandwidth which results in difficulty for the terminals making video streaming to get enough bandwidth. In this paper, we propose a cross layer control algorithm which adjusts the TCP window size adequately by using wireless channel occupancy information. We show that the proposed control scheme improves quality of communication for video streaming by modulating bandwidth for TCP communications. The quality is evaluated by using QoE (Quality of Experience) assessment techniques based on the ITU-T J.247., The Institute of Electronics, Information and Communication Engineers, 09 Dec. 2010, IEICE technical report, 110, 339, 155-160, Japanese, 0913-5685, 110008675460, AA11546431 - A multi-hop broadcast protocol for driver assistance in high-density environments
WU Celimuge; OHZAHATA Satoshi; KATO Toshihiko
Recently, as a component of Intelligent Transportation Systems (ITS), vehicular ad hoc networks have been rapidly attracting interests for the driver assistance systems. In this paper, we propose a multi-hop broadcast protocol for information dissemination in high-density environments. The proposed protocol redues redundant broadcast messages by means of using only a subset of neighbor nodes to relay messages. In the relay node selection, the proposed protocol considers multiple metrics of inter-vehicle distance, node mobility and signal strength, and integrates them by introducing the fuzzy logic. The effectiveness of the proposed protocol is also evaluated by computer simulations., The Institute of Electronics, Information and Communication Engineers, 02 Sep. 2010, Technical report of IEICE. CQ, 110, 198, 37-42, Japanese, 0913-5685, 110008108069, AN1054106X - A multi-hop broadcast protocol for driver assistance in high-density environments
策力木格; 大坐畠 智; 加藤 聰彦
映像情報メディア学会, Sep. 2010, ITE technical report, 34, 35, 65-70, Japanese, 1342-6893, 40017339510, AN1059086X - Adaptive Visualization for Analyzing Large-Scale Network Datasets
MIYAMUYA NAKAMURA Hiroko; OHZAHATA Satoshi; NAKAO Akihiro; KAWASHIMA Konosuke
Traditional network visualization techniques have problem that not all data can be displayed at the same time because the file-sharing network data is too large-scale. Therefore, we propose a concept of adaptive network graph display, in which the graph style can be changed according to the details of user's observation. We construct a visualization system based on this concept. When observing data globally, the proposed system selectively displays information based on the clustering result, and when observing data locally, the system displays detailed information., The Institute of Electronics, Information and Communication Engineers, 26 Aug. 2010, IEICE technical report, 110, 190, 103-108, Japanese, 0913-5685, 110008107993, AA11546431 - A Cross Layer Control of TCP Window in Wireless LAN for QoS Improvement
IJIRI Keiya; OHZAHATA Satoshi; KAWASHIMA Konosuke
In wireless LAN environment, QoS (Quality of Service) for real-time communication service such as streaming distribution is deteriorated with simultaneously connected TCP communications. This is because that a termial which communicates by TCP increases its congestion window size until packet loss occurs in the network under the congestion control algorithm of TCP Reno. The terminal for TCP communication uses the bandwidth greedily even if there are some real-time communications being carried over the same wireless channel. In this paper, we propose a cross layer control algorithm which adjusts the window size adequately to guarantee QoS for real-time communication by using wireless channel occupancy information directly from TCP layer. Empirical evaluations show that our method improves QoS for real-time communication., The Institute of Electronics, Information and Communication Engineers, 01 Jul. 2010, IEICE technical report, 110, 118, 81-86, Japanese, 0913-5685, 110007890161, AN1054106X - A TCP Congestion Control Method at Wireless LAN Terminal for Improving Real-Time Communication Quality
HIRAI Toshiyuki; OHZAHATA Satoshi; KAWASHIMA Konosuke
TCP Reno is often used as congestion control algorithm of TCP. In the congestion control of TCP Reno, the window size is increased until congestion occurs, consequently, quality of the real-time communication may be decreased. To resolve this problem, we propose a TCP congestion control to improve quality of real-time communications with channel occupancy. The channel occupancy is calculated by analyzing the frame size and wireless link speed of IEEE 802.11. Then, the window size is adequately adjusted to the communication situation of wireless LAN. Computer simulation results show that our method improves quality of the real-time communication with TCP communication in the same terminal., The Institute of Electronics, Information and Communication Engineers, 08 Apr. 2010, IEICE technical report, 110, 4, 11-16, Japanese, 0913-5685, 110007863017, AA11546431 - A Network Visualization System with Interactive Operations for Important Nodes Discovery
NAKAMURA MIYAMURA Hiroko; OHZAHATA Satoshi; NAKAO Akihiro; KAWASHIMA Konosuke; SUZUKI Yoshio
電気学会, 08 Mar. 2010, 電気学会研究会資料. IIC, 産業計測制御研究会, 2010, 79, 27-32, Japanese, 10026070304, AN10074226 - A Topological Analysis and Evaluation for Peer-to-Peer File Sharing Network
HIRANO Makoto; YOSHIDA Masahiro; OHZAHATA Satoshi; KAWASHIMA Konosuke
08 Mar. 2010, 全国大会講演論文集, 72, 403-404, Japanese, 110008123238, AN00349328 - A TCP Congestion Control using Number of Active Wireless Users and Information of Wired Communication Delay
HIRAI Toshiyuki; OHZAHATA Satoshi; KAWASHIMA Konosuke
08 Mar. 2010, 全国大会講演論文集, 72, 355-356, Japanese, 110008123215, AN00349328 - TCP Window Control for QoS Improvement using the MAC Layer Information over Wireless LAN
IJIRI Keiya; OHZAHATA Satoshi; KAWASHIMA Konosuke
08 Mar. 2010, 全国大会講演論文集, 72, 353-354, Japanese, 110008123214, AN00349328 - Terminal Based Fair Bandwidth Assignment with Adjusting Contention Window Size of Access Point
YOSHIOKA Toshihiro; OHZAHATA Satoshi; KAWASHIMA Konosuke
Recently, wireless LANs have been used widely. However, there are unfairness problems in wireless LANs. One of which is that a small number of stations (STAs) may obtain a large throughput while other STAs hardly get any bandwidth. This unfairness problem occurs between an upstream flow and a downstream flow because access point(AP) and STAs have the same transmission opportunity by CSMA/CA control. To improve these problems, we proposed a simple method combining the Deficit Round-Robin (DRR) queuing method and a dynamic contention window control in the AP. Also, we estimated channel occupancy by NAV on RTS/CTS. However, in this paper, channel occupancy is estimated by communication that does not use RTS/CTS. The proposed method acheived fairness in throughput per-station which have multiple UDP and TCP flows by computer simulation experiments., The Institute of Electronics, Information and Communication Engineers, 25 Feb. 2010, IEICE technical report, 109, 449, 7-12, Japanese, 0913-5685, 110008000317, AN10013072 - A Dynamic Index Poisoning Method for A P2P File Sharing Network
YOSHIDA Masahiro; OHZAHATA Satoshi; NAKAO Akihiro; KAWASHIMA Konosuke
In recent years, the copyright infringements and malware propagation in P2P file sharing networks have become prevalent. Therefore, an index poisoning method has attracted much attention to prevent illegal file distribution. However, applying an index poisoning method on a large scale P2P file sharing networks is difficult because of the possible bad influence it might have on them. In this paper, we propose a low-load index poisoning method for file distribution control. Our proposed method calculates an appropriate count of dummy metadata to control file distribution sufficiently. And we dynamically control the count of dummy metadata with a PID controller. Finally, we apply the proposed method to the live Winny network and evaluate our method., The Institute of Electronics, Information and Communication Engineers, 25 Feb. 2010, IEICE technical report, 109, 448, 279-284, Japanese, 0913-5685, 110007867040, AA11546431 - A Network Visualization System Focusing on Important Nodes
NAKAMURA MIYAMUYA Hiroko; OHZAHATA Satoshi; NAKAO Akihiro; KAWASHIMA Konosuke; SUZUKI Yoshio
We propose a visualization system for file-sharing network data. The file-sharing networks have some problems, for example: the contents distribution of the copyright infringement files, an increase in the amount of traffic, and so on. To overcome these problems, techniques for observing the network state and controlling the file sharing are proposed. In addition, the proposed techniques realize effective control by giving retrieval control to the key nodes, which are important roles in the file-sharing network., The Institute of Electronics, Information and Communication Engineers, 25 Feb. 2010, IEICE technical report, 109, 448, 357-362, Japanese, 0913-5685, 110007867055, AA11546431 - A Method of Controlling Search Network in Winny Network
NAKAZAWA Hiroaki; YOSHIDA Masahiro; OHZAHATA Satoshi; NAKAO Akihiro; KAWASHIMA Konosuke
Problems such as copyright infringement, personal information leakage and large portion of traffic have occurred by P2P file sharing applications recently. One of the reasons of these problems is that a pure P2P network is an autonomous distributed system and does not have management and control mechanism, which makes difficult to control the file distribution and the traffic volume. As solution to control the illegal file distributon, we proposed a search control method, however, the previous proposed method has enough room for efficient control. In this paper, we propose an improved file search efficiency controlling method by using uncooperative peers. The basic idea is that the control peers distufb the file search by setting up a lot of search links to important peers in the search network. We evaluated our method in a live Winny network. The results show that the proposed method improves the control efficiency., The Institute of Electronics, Information and Communication Engineers, 07 Jan. 2010, IEICE technical report, 109, 362, 71-76, Japanese, 0913-5685, 110008000294, AN10013072 - A measurement and analysis of the file transfer traffic characteristics between prefectures and ASes in Winny network
KOIZUMI Takashi; YOSHIDA Masahiro; OHZAHATA Satoshi; KAWASHIMA Konosuke
In recent years, peer-to-peer file-sharing applications have occupied a significant portion of Internet traffic, and given enormous impact to backbones. In particular, traffic characteristics between prefectures and ASes of the P2P traffic have become more important problem. Consequently, we have to understand actual status of the traffic interchange characteristics to construct and manage the future networks. In this paper, we measured and analyzed the file transfer characteristics such as traffic matrices between prefectures and ASes by identifying the file transfer between peers with tracing the file key information in Winny network. The results reveal that Winny increases traffic between prefectures and ASes because file transfer in Winny network do not have locality., The Institute of Electronics, Information and Communication Engineers, 07 Jan. 2010, IEICE technical report, 109, 362, 77-82, Japanese, 0913-5685, 110008000295, AN10013072 - A Traffic Control Method using Uncooperative High-Degree Peers for Winny Network
UENO Masahiro; OHZAHATA Satoshi; KAWASHIMA Konosuke
From the early 2000s, traffic of P2P file sharing applications have been increasing dramatically, and become heavily traffic load for IP networks. Winny, one of the most popular P2P file sharing applications in Japan, has approximately 100,000 peers at anytime, then the traffic makes a large impact on Japanese ISPs. In this paper, we propose a file sharing efficiency control method using control peers for Winny. Our control peers are uncooperative for searching files by discarding queries and metadata with the high degrees. We evaluated effects of our method in several situations by computer simulation. From the results, we confirm decrease of the file search efficiency and transfer traffic., The Institute of Electronics, Information and Communication Engineers, 08 Oct. 2009, IEICE technical report, 109, 228, 115-120, Japanese, 0913-5685, 110007482244, AA11546431 - A Large Scale Network Visualization for Important Nodes Discovery
NAKAMURA MIYAMURA Hiroko; OHZAHATA Satoshi; NAKAO Akihiro; KAWASHIMA Konosuke; SUZUKI Yoshio
We propose a network visualization method for a large-scale file-sharing network dataset. The network dataset has nodes and links that represent the connection between two nodes. When the number of links is large, it is difficult to recognize the structure of the network data, because many links are crossed. In this context, for recognizing the structure and exploring the key nodes, we propose a link-less network visualization method using matrix based representation. In addition, we demonstrate the effectiveness of the proposed method by applying it to the file-sharing network log data., The Institute of Electronics, Information and Communication Engineers, 03 Sep. 2009, IEICE technical report, 109, 188, 85-90, Japanese, 0913-5685, 110007386602, AA11546431 - A Proposal and Evaluation of Content Poisoning Method for The Share Network
YOSHIDA Masahiro; OHZAHATA Satoshi; NAKAO Akihiro; KAWASHIMA Konosuke
In recent years, P2P file sharing networks have been widely used all over the world, and a lot of files are transferred among the users without using web servers. Especially, the Share network, one of the most popular P2P file sharing networks in Japan, has very strong anonymity. Then the live Share network is composed of over 100,000 active peers. However, the Share network does not have management mechanisms for the file distribution. Consequently, the copyright infringements and malware propagation in the Share network has become prevalent. In this paper, we propose a content poisoning method for file distribution control. Then, we apply the content poisoning method to the live Share network. The evaluation results show that the proposed content poisoning is effective in the Share network, however, it could also give a bad influence on the network., The Institute of Electronics, Information and Communication Engineers, 03 Sep. 2009, IEICE technical report, 109, 188, 91-96, Japanese, 0913-5685, 110007386603, AA11546431 - BS-10-22 Fair Bandwidth Assignment to Each Terminal in Wireless LAN Access Point
Yoshioka Toshihiro; Ohzahata satoshi; Kawashima Konosuke
The Institute of Electronics, Information and Communication Engineers, 01 Sep. 2009, Proceedings of the Society Conference of IEICE, 2009, 2, "S-107"-"S-108", English, 110007870417, AN10489017 - A Communication Quality Control Method for Video Communication by Channel Occupancy Information from IEEE 802.11 MAC Layer
NAKASHIMA Hiroshi; OHZAHATA Satoshi; KAWASHIMA Konosuke
Wireless LAN has been widely used recently. Consequently, real-time applications have been increasingly used in wireless environments. IEEE802.11e is prepared as the standard of wireless LAN to improve Quality of Service (QoS) for the real-time applications, however, it cannot offer required QoS for such applications when an application generates excessive traffic. This is because controls of IEEE802.11e only schedule traffic in MAC layer for the generated traffic in upper layer. To solve this problem, we propose an autonomous method to control traffic generation in application layer with using wireless channel occupancy information in MAC layer., The Institute of Electronics, Information and Communication Engineers, 09 Apr. 2009, IEICE technical report, 109, 3, 55-58, Japanese, 0913-5685, 110007225829, AA11546431 - A Proposal of File Search Control Method and its Evaluation in a Pure P2P Network
NAKAZAWA Hiroaki; YOSHIDA Masahiro; OHZAHATA Satoshi; KAWASHIMA Konosuke
The problem such as copyright infringement, personal information leakage and increment of traffic have occurred by P2P file sharing application recently. In this paper, we propose a file search efficiency decrement by using uncooperative peers for the file search. The basic idea is that the control peers disturb the file search by setting up a lot of search links to the upstream peers. We evaluated our method by participation of the control peers in a live Wiiny network. As the results, we confirm decrement of the file search efficiency., The Institute of Electronics, Information and Communication Engineers, 09 Apr. 2009, IEICE technical report, 109, 3, 31-36, Japanese, 0913-5685, 110007225840, AA11546431 - Winny Network Topology Measurement using File Search Queries
PUTRA Pratama; YOSHIDA Masahiro; OHZAHATA Satoshi; NAKAO Akihiro; KAWASHIMA Konosuke
Network topology information in P2P network is useful for increasing network performances, and facilitate the generation of accurate model of topologies for simulation experiments. Unfortunately, the dynamic peer's joining and leaving behavior makes difficult to obtain the accurate network topology information. In this paper, we propose a method of measuring Winny network topolgy by using search queries, and we also evaluate the completeness of the snapshots from the measurement. The results show that completeness of measured link is lower compare to the completeness of measured node., The Institute of Electronics, Information and Communication Engineers, 09 Apr. 2009, IEICE technical report, 109, 3, 25-30, Japanese, 0913-5685, 110007225843, AA11546431 - BS-4-17 A Measurement Method for Capturing Winny Network Topology(BS-4. System, control and design technologies for emerging network)
Putra Pratama; Yoshida Masahiro; Ohzahata Satoshi; Nakao Akihiro; Kawashima Konosuke
The Institute of Electronics, Information and Communication Engineers, 04 Mar. 2009, Proceedings of the IEICE General Conference, 2009, 2, "S-33"-"S-34", English, 110007099429, AN10471452 - A TCP Flow Control Method using Advertised Window based on MAC Layer Information in IEEE 802.11
MIKOSHIBA Kengo; NAKASHIMA Hiroshi; OHZAHATA Satoshi; KAWASHIMA Konosuke
We propose a TCP window flow control method with channel occupancy information in IEEE 802.11 MAC layer to improve communication quality. In congestion control of TCP, the window size is increased until congestion occurs. But this control affects the communication quality of the other communications via the same access point. To resolve this problem, we propose an advertised window controlling method with channel occupancy information in the receiver. The channel occupancy is calculated by analyzing the network allocation vector in the MAC frame of the other terminals. Then, the congestion window size of the sender is adjusted not to affect communications for the other communications. Experimental evaluations show that our method works well under TCP communication from QoS viewpoint., The Institute of Electronics, Information and Communication Engineers, 24 Feb. 2009, IEICE technical report, 108, 458, 37-42, Japanese, 0913-5685, 110007324754, AN10013072 - A QoS Adjustment by using TCP Window Flow Control with MAC Layer Information in IEEE 802.11
MIKOSHIBA Kengo; NAKASHIMA Hiroshi; OHZAHATA Satoshi; KAWASHIMA Konosuke
We propose a method for improving communication quality by TCP window flow control with channel occupancy information in IEEE 802.11 MAC layer. In the congestion control of TCP, the window size is increased for the communication until congestion occurs. But this control affects the communication quality of the other terminals connected to the same access point. To resolve this problem, we propose to modify the congestion window size dynamitically with channel occupancy. The channel occupancy is calculated by analyzing the network allocation vector in the MAC frame from the other terminals. Then, the congestion window size is adjusted not to affect communications in the other terminals. Experimental evaluation shows that our method conducts TCP communication without affecting communication in the other terminals., The Institute of Electronics, Information and Communication Engineers, 04 Dec. 2008, IEICE technical report, 108, 342, 7-12, Japanese, 0913-5685, 110007114135, AN10013072 - A Proposal of Index Poisoning Method for Winny Network and Evaluation
YOSHIDA Masahiro; OHZAHATA Satoshi; NAKAO Akihiro; KAWASHIMA Konosuke
P2P file sharing applications have been widely used by millions of users all over the world. However, these applications do not usually have management mechanisms for distributing files in general. Consequently, copyright infringements in P2P file sharing networks have become prevalent. In order to prevent illegal file distribution, an index poisoning has attracted much attention recently. Although the index poisoning aims to obfuscate uses by diffusing a lot of dummy metadata in P2P networks, its effects have not been well studied yet. In this paper, we propose an index poisoning method for Winny network, one of the most popular P2P file sharing networks in Japan, and evaluate the effectiveness of our control over file distribution. The evaluation result show that index poisoning is effective in Winny network but it could also give a bad influence on the network., The Institute of Electronics, Information and Communication Engineers, 11 Sep. 2008, IEICE technical report, 108, 203, 93-98, English, 0913-5685, 110007004744, AA11546431 - M-024 An Enhanced TCP Window Flow Control with MAC Layer Information in Wireless LAN
Mikoshiba Kengo; Nakashima Hiroshi; Ohzahata Satoshi; Kawashima Konosuke
Forum on Information Technology, 20 Aug. 2008, 情報科学技術フォーラム講演論文集, 7, 4, 217-218, Japanese, 110007641671, AA1242354X - A proposal of poisoning method for file ID search in a P2P file sharing network
YOSHIDA Masahiro; OHZAHATA Satoshi; KAWASHIMA Konosuke
Some P2P file sharing networks do not control distribution files in their protocol. In these cases, the poisoning method is effective. The poisoning method complicates file download by diffusing controlled metadata or files in the network. When keywords are used for the file search, simple poisoning technique is effective. But Winny or Share, very popular P2P file sharing networks in Japan, resist poisoning by file ID search. In this report, we implement poisoning system for Winny network to improve the problem, and the results of evaluation experiment show effectiveness of poisoning methods of proposed file ID search., The Institute of Electronics, Information and Communication Engineers, 15 May 2008, IEICE technical report, 108, 31, 49-54, Japanese, 0913-5685, 110006861885, AA11546431 - An evaluation of a file distibution control method by the poisoning technology for the unstructured P2P file sharing network
YOSHIDA MASAHIRO; OHZAHATA SATOSHI; KAWASHIMA KONOSUKE
Some unstructured P2P file sharing applications do not have a file eliminate in their protocol. It is difficult to control a file distribution in such networks. In those case, the poisoning is effective. In this report, we implement poisoning system for Wirmy network, and the resulets of evaluation experiment show effectiveness of poisoning methods., Information Processing Society of Japan (IPSJ), 19 Mar. 2008, 情報処理学会研究報告システム評価（EVA）, 2008, 30, 31-36, Japanese, 0919-6072, 110006820510, AA11583959 - An adaptive routing method using channel load information for wireless ad-hoc network
YOSHIOKA Toshihiro; OHZAHATA Satoshi; KAWASHIMA Konosuke
13 Mar. 2008, 全国大会講演論文集, 70, 219-220, Japanese, 110006866714, AN00349328 - A wireless LAN bandwidth control by using MAC layer state information
NAKASHIMA Hiroshi; MIKOSHIBA Kengo; OHZAHATA Satoshi; KAWASHIMA Konosuke
13 Mar. 2008, 全国大会講演論文集, 70, 257-258, Japanese, 110006866732, AN00349328 - A File-Sharing Suppression Method for Pure P2P File-Sharing Network by Using COntrol Peers
YAMAZAKI Takayuki; OHZAHATA Satoshi; KAWASHIMA Konosuke
13 Mar. 2008, 全国大会講演論文集, 70, 429-430, Japanese, 110006866818, AN00349328 - A Study on file distribution control method by poisoning for a P2P file sharing network
YOSHIDA Masahiro; OHZAHATA Satoshi; KAWASHIMA Konosuke
13 Mar. 2008, 全国大会講演論文集, 70, 169-170, Japanese, 110006866689, AN00349328 - A Network Configuration Method for Pure P2P Streaming Media Distribution using Statistical Characteristic of Peer Lifetime
KURAKAKE Morihisa; OHZAHATA Satoshi; KAWASHIMA Konosuke
13 Mar. 2008, 全国大会講演論文集, 70, 571-572, Japanese, 110006864615, AN00349328 - A File Sharing Control Method for Pure P2P File Sharing Network by using Control Peers
YAMAZAKI Takayuki; OHZAHATA Satoshi; KAWASHIMA Konosuke
We proposed a file sharing control method for a pure P2P network, Winny. In our method, control peers join the overlay network and establish file search links to the file uploading peers. Since the all search links are controlled by the control peers, the meta file for file advertisement is not diffused over the file search network. Then, the other peers in the Winny network cannot find the desired file via file search network because the query hit is never returned. We develop a prototype system and give basic evaluations of our proposed method., The Institute of Electronics, Information and Communication Engineers, 13 Sep. 2007, IEICE technical report, 107, 222, 79-82, Japanese, 0913-5685, 110006420524, AN10013072 - BS-8-4 A Proposal of Pure P2P Network Topology Estimation Method by Active Measurement
Ohzahata Satoshi; Kawashima Konosuke
The Institute of Electronics, Information and Communication Engineers, 29 Aug. 2007, Proceedings of the Society Conference of IEICE, 2007, 2, "S-84"-"S-85", Japanese, 110006632455, AN10489017 - A Pure P2P Application Traffic Identification Method and Evaluations of Traffic Characteristics
OHZAHATA Satoshi; KAWASHIMA Konosuke
In P2P networks, it is mainly music and video files that are transferred, and it is known that the traffic volume is much larger than that of classical Client/Server applications. However, the nature of current P2P application traffic is not well known because of the anonymous communication architectures used. To solve this problem, we have developed an identification method for pure P2P application traffic, especially for Winny, the most popular pure P2P file sharing application in Japan. Our proposed method relies only on Client/Server relationships among the peers, without recourse to application header information. In addition to describing the method, we also give an evaluation of the characteristics of the identified traffic collected in an ISP., Information Processing Society of Japan (IPSJ), 22 Jun. 2007, 情報処理学会研究報告システム評価（EVA）, 2007, 63, 7-14, English, 0919-6072, 110006345299, AA11583959 - An Identification and Evaluation for a Pure P2P Application Traffic
OHZAHATA Satoshi; KAWASHIMA Konosuke
Pure Peer-to-peer (P2P) networks are widely used nowadays as a file sharing system because of their acalability and flexibility. However, the current the P2P application traffic is not well known because of their anonymous communication architectures. To solve this problem, we have developed and identification method for pure P2P application traffic, especially for Winny. Our proposed method only relies on Client/Server relationships among the peers without application header information. We give some evaluation results for our proposed identification method and characteristic of the identified traffic measured in ISP., The Institute of Electronics, Information and Communication Engineers, 12 Apr. 2007, IEICE technical report, 107, 6, 43-48, English, 0913-5685, 110006273332, AA11546431 - BS-8-8 A Traffic Identification Method with Client/Server Relationships
OHZAHATA Satoshi; KAWASHIMA Konosuke
The Institute of Electronics, Information and Communication Engineers, 07 Mar. 2007, Proceedings of the IEICE General Conference, 2007, 2, "S-77"-"S-78", Japanese, 110006464445, AN10471452 - A Control Method for Improving Communication Quality of Robot Wireless Ad Hoc Network
WANG Biao; OHZAHATA Satoshi; KAWASHIMA Kounosuke
Wireless ad hoc network constructed by robots will be useful to obtain information on the spots where people cannot access by some reasons. However, if we adopt wireless LAN for communication media, so-called "exposed terminal problem" and moreover obstacles on the wireless communication environment may cause the throughput decrease inevitably. This paper proposes a method to obtain good throughput between the spot to be monitored and the center. Robots are estimating the available bandwidth of wireless link by using information contained in the packets and move to appropriate location to realize a good communication route. We make an experimental network and evaluate the proposed method., Information Processing Society of Japan (IPSJ), 14 Nov. 2005, IPSJ SIG Notes, 2005, 111, 13-18, Japanese, 0919-6072, 110002973435, AN10116224 - Available Bandwidth Estimation Method during TCP Communication Employing IPID
OHZAHATA Satoshi; KAWASHIMA Konosuke
Investigating network status is impotant issue to evaluate communication quality and network design, and traffic has been measured for the evaluation. A passive measurement method for available bandwidth estimation over the comunication route is difficult by the cost, and an active measurement has been proposed by many studies. However, an active measurement has tradeoff between the number of probe packets and accuracy, because the probe traffic affects the other traffic. To solve the problem, we foucus on the fact that IPID value is sequentially assigned by the sender and deal the sequential packet as the packet train. By passive measurement of TCP communication, we can estimate available bandwidthe over the communicaiton route as if real active measurement., The Institute of Electronics, Information and Communication Engineers, 15 Sep. 2005, IEICE technical report, 105, 278, 95-98, Japanese, 0913-5685, 110003224405, AA11546431 - L-017 Evaluations of TCP Communication by Throughput Measurements
Suzuki Hideaki; Ohzahata Satoshi; Kawashima Konosuke
Forum on Information Technology, 22 Aug. 2005, 情報科学技術フォーラム一般講演論文集, 4, 4, 39-40, Japanese, 110007684479, AA11740605 - F-015 A Control Method for Robot Ad Hoc Network by using Communication Quality Information
Wang Biao; Ohzahata Satoshi; Kawashima Kounosuke
Forum on Information Technology, 22 Aug. 2005, 情報科学技術フォーラム一般講演論文集, 4, 2, 223-224, Japanese, 110007687847, AA11740605 - A Study on Pure P2P Network Size Estimation Method
HACHISUKA Daiki; OHZAHATA Satoshi; KAWASHIMA Konosuke
P2P applications rapidly increase their users with spreading of high performance personal computer connecting to broadband Internet. P2P applications have different architecture from the classical server-client based computing application. Winny is one of the most popular pure P2P file exchange application in Japan. In the Pure P2P architecture, there is no network administrator. This feature make difficult to administrate the users and no one knows the number of the users. This paper presents a size estimation method for Winny network with combination of measurement analysis and computer simulation experiments., The Institute of Electronics, Information and Communication Engineers, 14 Apr. 2005, IEICE technical report, 105, 12, 1-4, Japanese, 0913-5685, 110003203939, AA11546431 - B-7-81 A Proposal of a Guidance Architecture for Hot-spot Users by Employing an Ad-hoc Network
OHZAHATA Satoshi; KAWASHIMA Konosuke; KOBAYASHI Takehiko
The Institute of Electronics, Information and Communication Engineers, 07 Mar. 2005, Proceedings of the IEICE General Conference, 2005, 2, 235-235, Japanese, 110004694389, AN10471452 - A Recent Topic of Traffic Study on Wireless Local Area Networks
KAWASHIMA Konosuke; OHZAHATA Satoshi
Recently portable computers have been smaller, much more powerful and widely used. We can access to the Internet over cellular or hot-spot network by using these devices. Ubiquitous networking environments are preparing to realize advanced information society where anyone communicates with anyone, in anytime and in anywhere. In the near future, each device has many wireless interfaces and dynamically constructs cellular and ad-hoc networks. By integrating these networks, we will be able to flexibly access to the Internet. The wireless LAN will play a large role in the next generation wireless networks. We focus on the wireless network which is configured by the wireless LAN. First, we show our proposed queue management method for improving TCP performance over a wireless link, and the evaluations. Second, evaluations of the queue management over multi-hop wireless LAN networks are depicted. Next, we show traffic characteristics in the mobile backbone network with the wireless LAN, which is configured by the mobile ad-hoc network. Finally, we discuss the future orientation of the wireless LAN., The Institute of Electronics, Information and Communication Engineers, 10 Jun. 2004, IEICE technical report. Information networks, 104, 120, 43-48, Japanese, 0913-5685, 110003177603, AN10013072 - B-6-195 A Stable Network Configuration Method for Pure P2P Streaming Media Distribution
FUJISAKI Takaaki; OHZAHATA Satoshi; KAWASHIMA Konosuke
The Institute of Electronics, Information and Communication Engineers, 08 Mar. 2004, Proceedings of the IEICE General Conference, 2004, 2, 195-195, Japanese, 110003265159, AN10471452 - Evaluations of Communication Quality for Mobile Ad-Hoc Networks Constructed by Pedestrians
OHZAHATA Satoshi; KAWASHIMA Konosuke; KOBAYASHI Takehiko
We measure trace data of pedestrian mobility. With using the trace data, we simulate pedestrian mobility between them and evaluate communication quality for Ad-hoc routing protocols over the topology., The Institute of Electronics, Information and Communication Engineers, 27 Feb. 2004, Technical report of IEICE. RCS, 103, 682, 65-69, Japanese, 0913-5685, 110003304431, AN10060822 - A Network Reconfiguration Method for Pure P2P Streaming Media Distribution in Case of Peer Drop-out
FUJISAKI Takaaki; KAWASHIMA Konosuke; OHZAHATA Satoshi
We propose a network reconfiguration method in case of peer drop-out for Pure P2P streaming media distribution. In our method, each peer is correctly notified of addresses information of active peers in the network, and is classified into permanent or temporary one. We quantitatively show that these controls can reduce the network deviation and serve firmer network after the reconfiguration than the one of the before., The Institute of Electronics, Information and Communication Engineers, 12 Dec. 2003, 電子情報通信学会技術研究報告. PN, フォトニックネットワーク, 103, 508, 29-32, Japanese, 0913-5685, 110003223593, AA11864040 - Some Traffic Characteristics of Peer-to-Peer (P2P) Network
KAWASHIMA Konosuke; OHZAHATA Satoshi
Peer-to-peer (P2P) file-sharing software appeared for the last two or three years. A software named as Napster had been explosively used from the beginning of the appearance and caused the copyright problems on music file exchanges. At the same time, progress of digital technologies, density growth of LSI, and capacity expansion of optical fiber have been advancing. By virtue of the advancement of technologies, the speed of access channel has been becoming higher and higher, and always-on connection environments have been available with very cheap price. Such environments enable the broader use of P2P file-sharing. P2P traffic volume in the network is increasing enormously, and the portion of P2P traffic occupies over a half of the total traffic in many of networks. This paper surveys characteristics of P2P traffic based on many recent literatures. We focused on some measurements such as traffic ratio of the each application, file size, signaling traffic volume and throughput behavior. Although P2P technology is extremely excellent technology under sufficient large network resources environments, however we should control P2P traffic to maintain appropriate communication quality for the users. The traffic control technologies have important role in the future and we also slightly discuss them., The Institute of Electronics, Information and Communication Engineers, 04 Dec. 2003, IEICE technical report, 103, 492, 37-42, Japanese, 0913-5685, 110003177384, AN10013072 - Evaluation of a Queue Management Method for TCP Communications over Multi-hop Lossy Wireless Links
OHZAHATA Satoshi; KAWASHIMA Konosuke
In this paper we propose a queue management method for improving TCP performance over multi-hop wireless links. With our proposed control method, packet loss in the wireless link is completely eliminated and all packets are delivered in the correct order. No change is required to TCP itself or to the servers. Our proposed method is implemented between the media access control layer (MAC) and logical link layer in each node, and is designed to help the local retransmission control in the MAC layer. Computer simulation experiments show that our proposed method can communicate in high error wireless link conditions even when conventional methods cannot maintain communication. The fairness problem of TCP communication, between connections with different round trip times, is also improved., The Institute of Electronics, Information and Communication Engineers, 07 Nov. 2003, Technical report of IEICE. Multimedia and virtual environment, 103, 425, 71-76, English, 0913-5685, 110003270376, AN10476092 - A Proposal of Queue Management Method and Retransmission Mechanism for Wireless TCP Communications
Satoshi Ohzahata; Shigetomo Kimura; Yoshihiko Ebihara
This paper proposes a queue management method for improving TCP performance over a wireless link. The proposed method is implemented between the media access control (MAC) layer and the logical link (LL) layer in BS and designed to help the local retransmission control in the MAC layer. No change is required to TCP itself and servers. From the proposed control any packet loss in the wireless link is completely eliminated and all packets are delivered in the order. The proposed method keeps trying to consume the available bandwidth of the wireless link at high bit error rate conditions under the ordinal TCP controls.This paper proposes a queue management method for improving TCP performance over a wireless link. The proposed method is implemented between the media access control (MAC) layer and the logical link (LL) layer in BS, and designed to help the local retransmission control in the MAC layer. No change is required to TCP itself and servers. From the proposed control, any packet loss in the wireless link is completely eliminated and all packets are delivered in the order. The proposed method keeps trying to consume the available bandwidth of the wireless link at high bit error rate conditions under the ordinal TCP controls., 06 Mar. 2003, 情報処理学会研究報告モバイルコンピューティングとユビキタス通信（MBL）, 2003, 21, 111-118, Japanese, 170000039256, AA11851388
Books and other publications
- ゴールドスミス ワイヤレス通信工学
Andrea Goldsmith; 著; 小林岳彦; 訳; 岩切直彦; 大坐畠智; 幸谷智; 高橋賢; 森香津夫; 山嵜彰一郎
Japanese, Joint translation, 丸善, 2007 - A Traffic Identification Method and Evaluations for a Pure P2P Application
Satoshi Ohzahata; Yoichi Hagiwara; Matsuaki Terada; Konosuke Kawashima
English, Editor, Springer-Verlag, Mar. 2005 - A Fast Authentication Method for Secure and Seamless Handoff
Satoshi Ohzahata; Shigetomo Kimura; Yoshihiko Ebihara
English, Editor, Springer-Verlag, Sep. 2002
Courses
- ユビキタスネットワーク
The University of Electro-Communications - ユビキタスネットワーク
電気通信大学 - アカデミックリテラシー
The University of Electro-Communications - アカデミックリテラシー
電気通信大学 - Graduate Technical English
The University of Electro-Communications - 大学院技術英語
電気通信大学 - コンピュータネットワーク特論
The University of Electro-Communications - コンピュータネットワーク
The University of Electro-Communications - 暗号・情報セキュリティ
The University of Electro-Communications - 数値計算およびプログラミング演習
The University of Electro-Communications - コンピュータネットワーク特論
The University of Electro-Communications - コンピュータネットワーク特論
電気通信大学 - 暗号・情報セキュリティ
The University of Electro-Communications - 暗号・情報セキュリティ
電気通信大学 - コンピュータネットワーク
The University of Electro-Communications - コンピュータネットワーク
電気通信大学 - 数値計算およびプログラミング演習
The University of Electro-Communications - 数値計算およびプログラミング演習
電気通信大学 - ネットワークアーキテクチャ論2
The University of Electro-Communications - ネットワークアーキテクチャ論2
The University of Electro-Communications - Network Architecture 2
The University of Electro-Communications - ネットワークアーキテクチャ論2
電気通信大学
Research Themes
- ルータキャッシュを用いた優先度制御による超低遅延通信基盤
大坐畠 智
Principal investigator, 本研究では、コンピュータネットワークで用いられているルータのStore-and-Forward転送において輻輳時に起きるキュー遅延をなくすアーキ テクチャ、制御を明らかにする。ルータにキャッシュをすることができる情報指向ネットワーク（ICN）を用い、輻輳時には、ルータのインタ ーフェースからパケットをキャッシュに退避することで、常にキューにはパケットがたまらない状況にして遅延が起きないアーキテクチャを明 らかにする。さらに、通信（コンテンツ）に優先度をつけ、キューの待ち時間が全くないコンテンツと、キャッシュにコンテンツ一時退避され るコンテンツの間で優先制御を行う仕組みを明らかにする。
Apr. 2022 - Mar. 2026 - 通信品質を考慮したコンテンツセントリックネットワークのアーキテクチャ設計と構築
Ohzahata Satoshi
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for Scientific Research (C), We propose QoS architecture for video streaming over CCN. First, we propose a congestion-aware adaptive streaming over CCN combined with the explicit congestion notification (CAAS with ECN) to avoid QoE degradation. The simulation experiments show that the bitrate adjustment for all the clients improves QoE degradation and QoE fairness due to effective congestion avoidance. Next, we propose a content registration method for CCN routers with a blockchain technology to get content information in the architecture. We design and implement the content registration in CCN software platform Cefore and evaluated content information registration time., 18K11258
01 Apr. 2018 - 31 Mar. 2021 - Access Cloud: Fast and Fair Communication Using Multiple Wireless Networks
Yamai Nariyoshi
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Tokyo University of Agriculture and Technology, Grant-in-Aid for Scientific Research (C), In this research, we propose a network access method to realize high-speed and fair communication with multiple users in a multihomed network where each terminal can use multiple access points simultaneously. The proposed method introduces a VPN server on the network side to communicate with multiple terminals with MPTCP so that terminals can perform high-speed access while ensuring reliability and fairness by means of selective bicasting and route selection by VPN server. As a result, based on the communication status of each access point, the VPN server can alternate the communication path between each terminal and the VPN server using use an external program., 17K00118
01 Apr. 2017 - 31 Mar. 2020 - ブロックチェーンにおける安全で高速なトランザクション確定方式
（公財）大川情報通信基金, 研究助成
01 Apr. 2018 - 31 Mar. 2019 - Network-Driven Packet Transfer Method on Wireless Ad Hoc Networks
Yamamoto Ryo; OKAMURA Yasushi; KATO Toshihiko; OHZAHATA Satoshi; YAMAZAKI Taku; TANAKA Yoshiaki; MIYOSHI Takumi
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for Young Scientists (B), This research aims to improve the communication performance of wireless ad hoc networks, which consists of terminals equipped with wireless communication devices without the help of communication infrastructures such as base stations and access points. Wireless ad hoc networks generally take source terminal-driven communication control principle and it may face the difficulties in network state prehension and adaptive communication control. This research studied a novel network-driven communication control which does not require controls on source terminals to address the former issues. The performance evaluation confirms that the proposed method could achieve higher communication performance, such as reliability and efficiency., 15K15978
01 Apr. 2015 - 31 Mar. 2018 - 並列分散エミュレーション環境における通信ノード間のイベント同期改善方式
Ohzahata Satoshi
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for Scientific Research (C), Principal investigator, When parallel and distribution processing is used for wireless network emulation, the results are different in case that each of the receiver nodes independently run the events without synchronizing among these events. In the previous method, the frame has a seed of the random number to be used for an event execution at the receiver terminals within one hop because a frame is broadcasted in its transmission range. In addition, the information needed for the event execution is also previously shared among the receivers in order to get the same result with being generated by the random values. However, the effectiveness of our previous work is limited within one-hop wireless communication. In this study, we extend our previous method to multi-hop wireless network environment with considering a hidden terminal and sharing parameters needed for the synchronized event execution., 15K00117
01 Apr. 2015 - 31 Mar. 2018 - 無線LAN環境における効率の良いオンデマンドストリーミング配信に関する研究
（公財）電気通信普及財団, 研究助成
01 Apr. 2016 - 31 Mar. 2017 - コンテンツ指向ネットワークに対するドメインの概念の導入に関する研究
日揮・実吉奨学会研究助成金
01 Sep. 2014 - 31 Aug. 2015 - 無線LAN環境におけるオーバヒアリングを用いた高速ダウンロード方式
OHZAHATA Satoshi
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Electro-Communications, Grant-in-Aid for Young Scientists (B), In wireless LAN, since the bandwidth is shared with the terminals, the download speed is reduced even if the same content is downloaded. We have proposed a download acceleration method for content distribution by overhearing packets of the same content for other nodes in wireless LAN. Since parts of the content are obtained by the overhearing, the download time is reduced. In the method, the content is divided into pieces and the server distributes them. First, we show scheduling methods of pieces to send and destination with applying network coding, and evaluated these methods in testbed. Next, we evaluate scalability of the proposed method but we found that a distributed emulator has problems for modeling accuracy. We improve modeling of the emulator and evaluate scalability of the proposed method., 23700071
2011 - 2013 - 大規模分散環境を用いたP2Pネットワーク流通ファイル制御システムの研究
NAKAO Akihiro; KAWASHIMA Konosuke; OHZAHATA Satoshi; MIYAMURA Hiroko
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, The University of Tokyo, Grant-in-Aid for Scientific Research (B), The objective of this research is to develop the control methods for P2P file distribution and P2P traffic through poisoning where fake files and meta-information of the files are injected into the targeted P2P network and to examine the effectiveness of our proposed methods in the real internet network environment. For example, we conduct research on (1) the control method for distributed poisoning to restrict the dissemination of targeted files, (2) the localization of the P2P traffic and (3) the visualization of the effectiveness of our control against large-scale P2P file distribution networks., 21300020
2009 - 2012 - P2Pファイル共有ネットワークの測定と制御に関する研究
KAWASHIMA Konosuke; OHZAHATA Satoshi; NAKAO Akihiro
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Tokyo University of Agriculture and Technology, Grant-in-Aid for Scientific Research (B), We measured Winny network to model behavior of peers with/without a file, and modeled join/leave process of peers. To control file distribution in Winny network, we developed two file control methods and confirmed the effectiveness. The one is controlling the search network to control file search query. Another one is the index poisoning for the file search., 20300025
2008 - 2010 - 無線インターネットにおけるMAC層から得られる情報を用いたクロスレイヤ制御方式
OHZAHATA Satoshi
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Tokyo University of Agriculture and Technology, Grant-in-Aid for Young Scientists (B), A Channel occupancy is estimated from information of MAC layer. The information is used for the higher layer control via a cross layer control. The higher layer adjusts the traffic generation for the channel occupancy. The proposed methods are evaluated by computer simulation experiments and testbed., 20700057
2008 - 2009 - P2Pファイル共有トラヒックの特定法と測定・分析
KAWASHIMA Konosuke; OHZAHATA Satoshi
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Tokyo University of Agriculture and Technology, Grant-in-Aid for Scientific Research (C), (1) P2P Traffic Identification Method Peer-to-Peer (P2P) file sharing applications are widely used nowadays. In overlay networks, it is mainly music and video files that are transferred, and it is known that the traffic volume is much larger than that of classical Client/Server applications. However, the nature of current P2P application traffic is not well known because of the anonymous communication architectures used. To solve this problem, we have developed an identification method for pure P2P application traffic, especially for Winny, the most popular pure P2P file sharing application in Japan. Our method relies only on Client/Server relationships among the peers, without recourse to application header information. Our experiment shows that our identification of FN is 0.053-0.116 and FP is lower than 1/10000. (2) Characteristics Evaluation of P2P Traffic We applied our method to ISP traffic and gave an evaluation of the identified Winny traffic. The characteristics of the Winny flows are almost symmetric for the outgoing flows to the Internet and the incoming flows. A small number of peers are responsible for producing almost all the traffic volume. Small correlation is observed between uploading traffic and downloading traffic in one peer. This is because that there is not explicit incentive mechanism in Winny network., 18500047
2006 - 2007