Kojima Toshiharu
| Department of Computer and Network Engineering | Associate Professor |
| Cluster II (Emerging Multi-interdisciplinary Engineering) | Associate Professor |
| Center for Space Science and Radio Engineering | Associate Professor |
Researcher Information
Degree
Field Of Study
Career
- Apr. 2007
電気通信大学, 准教授 - Oct. 2002 - Mar. 2007
電気通信大学, 助教授 - Apr. 2001 - Oct. 2002
大阪大学, 非常勤講師 - Apr. 2002 - Sep. 2002
三菱電機株式会社, 専任 - Mar. 1998 - Mar. 2002
三菱電機株式会社, チームリーダー - Sep. 1997 - Mar. 1998
三菱電機株式会社, 主事専門企画職 - Mar. 1996 - Sep. 1997
三菱電機株式会社, 主事 - Mar. 1991 - Mar. 1996
三菱電機株式会社, 一級主員 - Mar. 1988 - Mar. 1991
三菱電機株式会社, 二級主員 - Apr. 1987 - Mar. 1988
三菱電機株式会社, 技術研修生 - Jul. 1984 - Mar. 1986
南極地域観測隊, 観測隊員（宙空系） - Jul. 1984 - Mar. 1986
電気通信大学, 助手
Educational Background
- Mar. 1998
Osaka University, Graduate School, Division of Engineering, 通信工学専攻 - Mar. 1987
The University of Electro-Communications, Graduate School, Division of Electro Communications, 応用電子工学専攻 - Mar. 1983
The University of Electro-Communications, Faculty of Electro Communications, 応用電子工学科 - Apr. 1976 - Mar. 1979
神奈川県立川崎北高等学校
Research Activity Information
Award
Paper
- Selected Mapping Without Side Information for PAPR Reduction in Modified Walsh-Hadamard Code Division Multiplexing
Daihi Maruyama; Toshiharu Kojima
Proc. of 2024 International Conference on Advanced Technologies for Communications (ATC'24), 227-231, Oct. 2024, Peer-reviwed
International conference proceedings - Joint CFO and STO Estimation for Modified Walsh-Hadamard Code Division Multiplexing
Masaki Kitagawa; Toshiharu Kojima
Proc. of 2024 International Conference on Advanced Technologies for Communications (ATC'24), 358-362, Oct. 2024, Peer-reviwed
International conference proceedings - A Study on Modified Walsh-Hadamard Code Division Multiplexing with Enhanced Anti-Periodic-Blockage Capability
Toshiharu Kojima; Shinya Sotome
Proc. of 2024 International Conference on Advanced Technologies for Communications (ATC'24), 445-450, Oct. 2024, Peer-reviwed
International conference proceedings - A Channel Estimation Method for Modified Walsh-Hadamard Code Division Multiplexing in Helicopter Satellite Communications and Its Application to Initial Acquisition
Yuto Yoshinaka; Toshiharu Kojima
Proc. of 2023 International Conference on Advanced Technologies for Communications (ATC'23), 435-439, Oct. 2023, Peer-reviwed
International conference proceedings - An Accurate and Wide-Range AFC for Modified Walsh-Hadamard Code Division Multiplexing
Toshiharu Kojima; Koki Iwabuchi
Proc. of 2023 International Conference on Advanced Technologies for Communications (ATC'23), 207-211, Oct. 2023, Peer-reviwed
International conference proceedings - An Initial Acquisition Scheme with Reduced Complexity for Modified Walsh-Hadamard Code Division Multiplexing
Toshiharu Kojima; Yuto Yoshinaka
Proc. of 2022 International Conference on Advanced Technologies for Communications (ATC'22), 386-390, Oct. 2022, Peer-reviwed
International conference proceedings, English - Data-Aided Channel Estimation for Time Diversity in Helicopter Satellite Communications
Toshiharu Kojima; Riki Azuma
Proc. of 2022 International Conference on Advanced Technologies for Communications (ATC'22), 391-394, Oct. 2022, Peer-reviwed
International conference proceedings, English - A Novel ZF and MMSE Receiver for Modified Walsh-Hadamard Code Division Multiplexing in Helicopter Satellite Communications
Toshiharu Kojima; Tsubasa Yamada
Proc. of 2021 International Conference on Advanced Technologies for Communications (ATC'21), 18-21, Oct. 2021, Peer-reviwed
International conference proceedings, English - A Spectral Analysis Based Channel Estimation Method for Time Diversity Combining in Helicopter Satellite Communications
Toshiharu Kojima; Seiya Yako
Proc. of 2021 International Conference on Advanced Technologies for Communications (ATC'21), 152-155, Oct. 2021, Peer-reviwed
International conference proceedings, English - ヘリコプター衛星通信における統計的手法に基づく回線遮断率推定法の検討
蔡雅史; 小島年春
電子情報通信学会技術研究報告, SAT2020, 39, 54-57, Feb. 2021
Symposium, Japanese - An Initial Acquisition Scheme Combined with Carrier Recovery for Modified Walsh-Hadamard Code Division Multiplexing
Toshiharu Kojima; Yota Yamamura
Proc. of 2020 International Conference on Advanced Technologies for Communications (ATC'20), 74-78, Oct. 2020, Peer-reviwed
International conference proceedings, English - An Improved AFC Scheme for Modified Walsh-Hadamard Code Division Multiplexing
Anna Himeno; Toshiharu Kojima
Proc. of 2020 International Conference on Advanced Technologies for Communications (ATC'20), 79-83, Oct. 2020, Peer-reviwed
International conference proceedings, English - Inter-Code Interference Reduction in Walsh-Hadamard Code Division Multiplexing for Helicopter Satellite Communications
Genta Muto; Toshiharu Kojima
Proc. of 2019 International Conference on Advanced Technologies for Communications (ATC'19), 19-22, Oct. 2019, Peer-reviwed
International conference proceedings, English - A Chip Timing Recovery Scheme for Walsh-Hadamard Code Division Multiplexing
Yuta Kato; Toshiharu Kojima
Proc. of 2019 3rd International Conference on Recent Advances in Signal Processing, Telecommunications & Computing (SigTelCom), 1-4, Mar. 2019, Peer-reviwed
International conference proceedings, English - A Low Inter-Code Interference Walsh-Hadamard Code Division Multiplexing for Helicopter Satellite Communications
Toshiharu Kojima; Genta Muto
Proc. of 2018 International Conference on Advanced Technologies for Communications (ATC'18), 1-4, Oct. 2018, Peer-reviwed
International conference proceedings, English - An Accurate Time Diversity Combining with a Novel Channel Estimation for Helicopter Satellite Communications
Daijiro Sato; Toshiharu Kojima
Proc. of 2018 International Conference on Advanced Technologies for Communications (ATC'18), 89-93, Oct. 2018, Peer-reviwed
International conference proceedings, English - LDPC符号を用いた附加情報不要のSLM法におけるスクランブル系列推定の演算量低減に関する検討
島田宙輝; 小島年春
電子情報通信学会技術研究報告, CS2017, 101, 81-86, Mar. 2018
Symposium, Japanese - キャリア周波数オフセットによるWH符号のコード間干渉に基づくWHCDM用AFC方式
金丸雄紀; 小島年春
電子情報通信学会技術研究報告, SAT2017, 58, 13-18, Feb. 2018
Symposium, Japanese - 多重分離後の信号エネルギー分布の非対称性に基づくWHCDM用初期捕捉方式の簡単化
長嶋優貴; 小島年春
電子情報通信学会技術研究報告, SAT2017, 59, 19-24, Feb. 2018
Symposium, Japanese - A Channel Estimation Scheme for Helicopter Satellite Communications Based on Pseudo Bit Error Rate
Shunpei Kutsukake; Toshiharu Kojima
Proc. of the 2017 International Symposium on Electrical and Electronics Engineering (ISEE 2017), 269-273, Nov. 2017, Peer-reviwed
International conference proceedings, English - A Study on Code Synchronization for Time Diversity in Helicopter Satellite Communications
Ryosuke Ito; Toshiharu Kojima
Proc. of 2017 International Conference on Advanced Technologies for Communications (ATC'17), 103-107, Oct. 2017, Peer-reviwed
International conference proceedings, English - An Initial Acquisition Scheme for Walsh-Hadamard Code Division Multiplexing
Toshiharu Kojima; Yuki Nagashima
PROCEEDINGS OF THE 2016 INTERNATIONAL CONFERENCE ON ADVANCED TECHNOLOGIES FOR COMMUNICATIONS (ATC), IEEE, 397-400, 2016, Peer-reviwed, This paper addresses the problem of initial acquisition in code division multiplexing employing Walsh-Hadamard code (WHCDM). Unlike pseudo-noise codes used in direct-sequence spread spectrum communications, Walsh-Hadamard code has many side lobes in its autocorrelation function. Well-known initial acquisition schemes for direct-sequence spread spectrum communications, therefore, cannot be applied to WHCDM. In order to solve this problem, we propose an initial acquisition scheme for WHCDM with a novel approach. It detects the symbol timing on the basis of not the autocorrelation function of Walsh-Hadamard code but the energy variance of the signal after demultiplexing. The results of computer simulation confirm that the proposed scheme provides rapid acquisition.
International conference proceedings, English - An Improved Time Diversity Combining for Helicopter Satellite Communications
Toshiharu Kojima; Yurii Takanashi
2015 INTERNATIONAL CONFERENCE ON ADVANCED TECHNOLOGIES FOR COMMUNICATIONS (ATC), IEEE, 6-9, 2015, Peer-reviwed, Periodic blockage of the received signal due to rotor blades is one of the most important problems in helicopter satellite communications. Time diversity is a promising method in order to overcome the periodic blockage. In this paper, a novel time diversity combining scheme is proposed. It performs maximal ratio combining on the basis of the channel blockage information estimated with a pseudo bit error rate. The performance of the proposed scheme is evaluated by the computer simulation. The results show that the proposed scheme remarkably improves the bit error rate performance of the conventional one employing equal gain combining.
International conference proceedings, English - Performance of Walsh-Hadamard Code Division Multiplexing in Helicopter Satellite Communications
Toshiharu Kojima; Shuri Fujiwara
2015 INTERNATIONAL CONFERENCE ON ADVANCED TECHNOLOGIES FOR COMMUNICATIONS (ATC), IEEE, 662-665, 2015, Peer-reviwed, One of the most important problems in helicopter satellite communications is the periodic blockage of the received signal caused by rotor blades. Code division multiplexing (CDM) has an implicit time diversity effect overcoming the periodic blockage. Performance of CDM employing Walsh-Hadamard code (WHCDM) under the periodic blockage environment is investigated in this paper. First, we show that a simple WHCDM scheme has the implicit time diversity effect by computer simulation. Next, a WHCDM scheme combined with explicit time diversity is proposed. The proposed scheme improves the bit error rate performance of the conventional time diversity scheme in high speed data transmission.
International conference proceedings, English - Hybrid Walsh-Hadamard Code Division Multiplexing for Helicopter Satellite Communications
Ayako Suzuki; Toshiharu Kojima
2014 INTERNATIONAL CONFERENCE ON ADVANCED TECHNOLOGIES FOR COMMUNICATIONS (ATC), IEEE, 1-4, 2014, Peer-reviwed, In helicopter satellite communications, periodic channel blockage due to rotor blades and Doppler shift caused by helicopter maneuvers are major issues. Code division multiplexing employing Walsh-Hadamard code (WHCDM) is a promising solution for the periodic blockage. However, automatic frequency control (AFC) removing Doppler shift limits the multiplexing factor of WHCDM to less than its maximum value because of its frequency discrimination performance. This limitation reduces the spectral efficiency in the conventional WHCDM. In this paper, we propose a novel WHCDM achieving the maximum spectral efficiency with the multiplexing factor of its maximum value minus one. In the proposed WHCDM, one Walsh-Hadamard code selected by information data is excluded from the transmitted signal. Results of computer simulation show that the bit error rate performance of the proposed WHCDM is slightly better than that of the conventional one in the higher E-b/N-0 region.
International conference proceedings, English - An Improved Quantization Scheme for Lattice-Reduction Aided MIMO Detection Based on Gram-Schmidt Orthogonalization
Wei Hou; Tadashi Fujino; Toshiharu Kojima
IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES, IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG, E96A, 12, 2405-2414, Dec. 2013, Peer-reviwed, Lattice-reduction (LR) technique has been adopted to improve the performance and reduce the complexity in MIMO data detection. This paper presents an improved quantization scheme for LR aided MIMO detection based on Gram-Schmidt orthogonalization. For the LR aided detection, the quantization step applies the simple rounding operation, which often leads to the quantization errors. Meanwhile, these errors may result in the detection errors. Hence the purpose of the proposed detection is to further solve the problem of degrading the performance due to the quantization errors in the signal estimation. In this paper, the proposed quantization scheme decreases the quantization errors using a simple tree search with a threshold function. Through the analysis and the simulation results, we observe that the proposed detection can achieve the nearly optimal performance with very low complexity, and require a little additional complexity compared to the conventional LR-MMSE detection in the high E-b/N-0 region. Furthermore, this quantization error reduction scheme is also efficient even for the high modulation order.
Scientific journal, English - Low complexity MIMO detection using OSIC with conditional list generation
Wei Hou; Tadashi Fujino; Toshiharu Kojima
IEICE Communications Express (ComEX), The Institute of Electronics, Information and Communication Engineers, 2, 10, 447-452, Oct. 2013, Peer-reviwed, This paper proposes a low complexity MIMO detection using ordering SIC (OSIC) with conditional list generation. Combined with lattice-reduction (LR) technique, OSIC further gains the BER performance compared to SIC, since the more reliable signal is prior to being detected. However OSIC based on LR (LR-OSIC) has inferior performance to the maximum likelihood (ML) detection in large size MIMO systems. In this paper, we investigate the mean square error in LR domain to evaluate the condition of the channel. The proposed detection applies the conditional list detection to update the estimate of the LR-OSIC. The simulation results exhibited that the proposed detection achieved near-ML performance in the 8×8 MIMO and required almost same complexity of the LR-OSIC in the high Eb/N0 region.
Scientific journal, English - Quantization Error Reduction for MIMO Detection Based on Orthogonal Lattices
Wei Hou; Tadashi Fujino; Toshiharu Kojima
IEICE Communications Express, The Institute of Electronics, Information and Communication Engineers, 2, 2, 42-48, Feb. 2013, Peer-reviwed, Lattice-reduction is an effective technique to improve the performance of MIMO data detection. This paper presents a quantization error reduction scheme for MIMO detection based on orthogonal lattices. The motivation of the proposed detection is to solve the problem of degrading the performance due to the rounding quantization error in the signal estimate stage. The simulation results exhibit that the proposed detection can achieve the near-ML performance with a little additional complexity in the high Eb/N0 region. In addition, this quantization error reduction scheme is efficient even for the high modulation order.
Scientific journal, English - Efficient Quantization Scheme for Lattice-Reduction Aided MIMO Detection
Wei Hou; Tadashi Fujino; Toshiharu Kojima
2013 INTERNATIONAL CONFERENCE ON ADVANCED TECHNOLOGIES FOR COMMUNICATIONS (ATC), IEEE, 275-279, 2013, Peer-reviwed, In this paper, we present an efficient quantization scheme for lattice-reduction (LR) aided (LRA) MIMO detection using Gram-Schmidt orthogonalization. For the LRA detection, the quantization step applies the simple rounding operation, which often leads to the quantization errors. Meanwhile, these errors may result in the detection errors. Hence, the motivation of the proposed detection is to further solve the problem of degrading the performance due to the quantization errors in the signal estimation. In this paper, the proposed quantization scheme decreases the quantization errors using a simple tree search with a threshold function. Through the analysis and the simulation results, the proposed detection can achieve the near-ML performance with only a little additional complexity.
International conference proceedings, English - A Novel AFC Scheme for Walsh-Hadamard Code Division Multiplexing
Toshiharu Kojima; Ayako Suzuki
2013 INTERNATIONAL CONFERENCE ON ADVANCED TECHNOLOGIES FOR COMMUNICATIONS (ATC), IEEE, 271-274, 2013, Peer-reviwed, In this paper, we propose a novel automatic frequency control (AFC) scheme for code division multiplexing (CDM) system employing Walsh code. The proposed AFC scheme discriminates the frequency shift of the received signal by detecting the signal energy after Walsh-Hadamard transform (WHT). The configuration of the proposed AFC scheme is analogous with that of delay locked loop (DLL) for direct-sequence spread-spectrum (DS-SS) communications. The initial acquisition performance of the proposed AFC scheme is evaluated by computer simulation. It is confirmed that the proposed AFC scheme achieves fast acquisition when the multiplexing factor is less than WHT order.
International conference proceedings, English - MIMO System and Its Detection for Wireless Communication
Wei Hou; Tadashi Fujino; Toshiharu Kojima
Proc. of Int. WCEIT 2012, 1, Aug. 2012, Peer-reviwed
International conference proceedings, English - Adaptive Tree Search Detection with Variable Path Expansion Based on Gram-Schmidt Orthogonalization in MIMO Systems
Wei Hou; Tadashi Fujino; Toshiharu Kojima
Journal of Selected Areas in Telecommunications, 2012, July Edition, Jul. 2012, Peer-reviwed
Scientific journal, English - A Fast Acquisition AFC for Helicopter Satellite Communications
Toshiharu Kojima; Shingo Yasue
2012 INTERNATIONAL CONFERENCE ON ADVANCED TECHNOLOGIES FOR COMMUNICATIONS (ATC 2012), IEEE, 106-109, 2012, Peer-reviwed, In helicopter satellite communications, removal of time-varying Doppler shift due to helicopter maneuver is one of the most important issues. The conventional automatic frequency control (AFC) scheme for helicopter satellite communications removes Doppler shift exactly. However, its acquisition time is extremely long. This is caused by a delay element in the feed-back loop. In this paper, we propose a novel AFC scheme for helicopter satellite communications to reduce the acquisition time. The proposed AFC scheme consists of a feed-back loop and a feed-forward loop. This configuration excludes the delay element from the feed-back loop. Results of computer simulation show that the proposed AFC scheme significantly reduces its acquisition time.
International conference proceedings, English - Adaptive candidate selection scheme in QRM-MLD algorithm for MIMO detection
Wei Hou; Tadashi Fujino; Toshiharu Kojima
International Conference on Wireless and Mobile Computing, Networking and Communications, 502-506, 2012, This paper proposes an adaptive candidate selection scheme in the QRM-MLD algorithm for MIMO detection. The QRM-MLD is a near-ML detection algorithm which can achieve a tradeoff between the BER performance and the computational complexity in the MIMO systems. In this paper, we adopt an adaptive candidate selection scheme into the QRM-MLD. First, similarly to the conventional QRM-MLD, the proposed detection applies a fixed number of the survived branches to achieve a near-ML performance. Next, in order to evaluate the reliability of the survived branches in each detection layer, we introduce a ratio function of the path metric to the smallest path metric among the survived branches. The survived branch with lower reliability has less children nodes as the candidates in the next detection layer, which can avoid a large amount of the path metric evaluations and sorting. Hence, the complexity of the proposed detection should be low. Numerical results exhibit that the proposed scheme achieves the near-ML performance with lower complexity compared to the conventional QRM-MLD. © 2012 IEEE.
International conference proceedings, English - A novel SLM PAPR reduction of OFDM signals without side information
Toshiharu Kojima; Shohei Iwamoto; Yuki Shida; Tadashi Fujino
2010 IEEE International Symposium on Signal Processing and Information Technology, ISSPIT 2010, 321-325, 2011, Peer-reviwed, Selected mapping (SLM) is a well-known technique to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM). SLM generally requires the side information for each OFDM symbol, which leads to decrease the transmitting efficiency. In addition, false side information detection degrades the bit error rate (BER) performance significantly. In this paper, we propose a novel SLM scheme without any side information by devising a phase rotation and simple scrambler detection in the receiver. Computer simulation results show that the proposed scheme achieves excellent performances in terms of both PAPR reduction and BER. © 2011 IEEE.
International conference proceedings, English - A study of SLM PAPR reduction of OFDM signals without side information
Toshiharu Kojima; Yuki Shida; Tadashi Fujino
Proceedings - 2010 International Conference on Advanced Technologies for Communications, ATC 2010, 168-171, 2010, Peer-reviwed, Selected mapping (SLM) is a well-known technique to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM). SLM generally requires the side information for each OFDM symbol, which leads to decrease the transmitting efficiency. In addition, false side information detection degrades the bit error rate performance significantly. In this paper, we propose a novel SLM scheme without any side information by devising a phase rotation and simple scrambler detection in the receiver. Computer simulation results show that the proposed scheme achieves excellent performances in terms of both PAPR reduction and BER. ©2010 IEEE.
International conference proceedings, English - A novel AFC scheme with time diversity combining for helicopter satellite communications
Toshiharu Kojima; Batmunkh Batbaatar; Chuluunsukh Batzorig; Tadashi Fujino
ATC 2009 - Proceedings of the 2009 International Conference on Advanced Technologies for Communications, 304-307, 2009, Peer-reviwed, In helicopter satellite communications, the periodic blockage of received signal and the carrier frequency fluctuation are the most important problems. In this paper, we propose a novel automatic frequency controller (AFC) scheme with time diversity combining. The proposed AFC generates the frequency error signal based on the time diversity combined signal. The signal-to-noise power ratio (SNR) of the frequency error signal is therefore prevented from falling to zero even in the condition of signal blockage. The proposed AFC thus tracks and removes the carrier frequency fluctuation due to Doppler shift more exactly than the conventional one. Results of computer simulation show that the proposed AFC improves the SNR of the frequency error signal significantly. It is meant that the proposed AFC also improves both of the acquisition characteristics and jitter performance even in the severe environments of the helicopter satellite communications. ©2009 IEEE.
International conference proceedings, English - Pre-Detection Time Diversity Combining with Accurate AFC for Helicopter Satellite Communications
Toshiharu Kojima; Chuluunsukh Batzorig; Tadashi Fujino
2008 INTERNATIONAL CONFERENCE ON ADVANCED TECHNOLOGIES FOR COMMUNICATIONS, PROCEEDINGS, IEEE, 309-312, 2008, Peer-reviwed, In helicopter satellite communications, the periodic blockage of the received signal and the carrier frequency fluctuation are the most important problems. In this paper, we propose a novel pre-detection time diversity combining scheme with accurate automatic frequency controller (AFC) for helicopter satellite communications. In the proposed scheme, a novel AFC tracks and removes the carrier frequency fluctuation due to Doppler shift exactly, and the in-phase combining or the time, diversity signal is performed before the coherent detection. Results; of computer simulation show that the proposed scheme improves the BER performance of the previous post-detection combining scheme.
International conference proceedings, English - タイミングオフセット多重化SS方式の初期捕そく方式に関する一検討
小島年春; 大久保政二; 久保博嗣; 村上圭司
電子情報通信学会論文誌B, The Institute of Electronics, Information and Communication Engineers, J86-B, 10, 2245-2248, Oct. 2003, Peer-reviwed, 本論文では,タイミングオフセット多重化スペクトル拡散(SS)方式における符号同期の初期捕そくを容易にするため,符号周期内に複数の相関ピークを有する多重化信号のマッチドフィルタ出力に整合する新たなマルチドフィルタを設けた初期捕そく方式を提案する.
Scientific journal, Japanese - A novel demodulation scheme for PSK-FM command signal based on DS/SS technique
Toshiharu Kojima; Takehiko Sagara; Futaba Ejima; Keishi Murakami
Proceedings of 21st AIAA International Communications Satellite Systems Conference, 1, Apr. 2003, Peer-reviwed
International conference proceedings, English - A Novel Accurate AFC scheme for Helicopter Satellite Communications Combined with Time Diversity
小島年春; 打木達也; 大久保政二; 谷口順
電子情報通信学会論文誌 B, The Institute of Electronics, Information and Communication Engineers, J85-B, 10, 1728-1737, Oct. 2002, Peer-reviwed, ヘリコプタ衛星通信では,回転翼による回線の周期的瞬断や機体の加速度運動に伴うドップラーシフトの変化によるキャリヤ周波数の変動が問題となる.筆者らは以前,前者を克服する手法として,時間ダイバーシチを利用したキャリヤスリップ補償方式を提案した.今回,後者を克服する手法として時間ダイバーシチAFC方式を提案する.本方式は,時間ダイバーシチにより複数回送出される同一データを変調した信号の位相を比較して周波数誤差を推定し,2次ループにより周波数の時間変動を追跡するPLLタイプのAFCである.計算機シミュレーションの結果,時間ダイバーシチAFC方式は,低受信CN比で回転翼による回線の周期的瞬断が生じるヘリコプタ衛星通信特有の環境において,キャリヤ周波数の時間変動に極めて高い精度で同期することを確認した.また,キャリヤスリップ補償を適用した同期検波との組合せにより,キャリヤ再生が完全の理想的な場合とほぼ同一の良好なビット誤り率特性が得られ,時間ダイバーシチ技術に立脚したキャリヤスリップ補償方式と時間ダイバーシチAFC方式の組合せが,ヘリコプタ衛星通信を実現するための有効な技術であることを確認した.
Scientific journal, Japanese - A frequency offset compensation scheme for the received signal under the influence of rician fading channels with a direct component shifted by doppler effect
Takashi Asahara; Toshiharu Kojima; Makoto Miyake
Electronics and Communications in Japan, Part I: Communications (English translation of Denshi Tsushin Gakkai Ronbunshi), 85, 12, 65-75, 2002, Peer-reviwed, A scheme that estimates and compensates for the frequency offset from the phase rotation of pilot symbols is proposed as a carrier frequency offset compensation scheme that periodically inserts pilot symbols in the transmitted signal. Since the frequency offset is estimated and compensated for at a frequency close to the direct path wave when a conventional scheme is applied in a Rician fading environment where the direct path wave is Doppler shifted, the Doppler spread appears to widen further, the estimation error of the fading distortion increases, and the error rate performance degrades. In this paper, we propose a frequency offset compensation scheme that estimates the center frequency of the Doppler spread and reduces the effects of the Doppler-shifted direct path wave by (1) calculating the signal power in the frequency domain by taking the discrete Fourier transform (DFT) of the pilot symbols and (2) smoothing the signal power in a frequency window. Computer simulations demonstrate the superior error rate performance of the proposed scheme compared to the conventional scheme and clearly show its effectiveness.
Scientific journal, English - Relationship between Adaptive Maximum-Likelihood Sequence Estimation and Multiple-Symbol Differential Detection and its Application to Wireless Communications
久保博嗣; 小島年春; 谷口順
電子情報通信学会論文誌 B, The Institute of Electronics, Information and Communication Engineers, J84-B, 11, 1909-1917, Nov. 2001, Peer-reviwed, 本論文では, 状態ごとに生き残りパスに従って伝送路特性を推定する適応形最ゆう系列推定(PSP-MLSE)と多重遅延検波(MDD)の関係に関して論じる.まず, PSP-MLSEとMDDの共通性について述べ, 符号間干渉メモリのないPSP-MLSEからMDDのパスメトリックを導出する.次に, 計算機シミュレーションにより, 両手法は、既知系列なく復調(ブラインド)動作が可能であり, 無線通信において問題となる高速フェージング環境に有効な復調方式であることを明らかにする.
Scientific journal, Japanese - A Frequency Offset Compensation Scheme for the Received Signal under the Influence of Rician Fading Channels with a Direct Component Shifted by Doppler Effect
浅原隆; 小島年春; 三宅真
電子情報通信学会論文誌 B, The Institute of Electronics, Information and Communication Engineers, J84-B, 7, 1265-1275, Jul. 2001, Peer-reviwed, 送信信号に周期的に挿入されたパイロットシンボルを用いるキャリヤ周波数オフセット補償方式として, パイロットシンボルの位相回転量から周波数オフセットを推定。補償する方式が提案されている。この従来方式を直接波がドップラーシフトしたライスフェージング環境に適用した場合, 直接波に近い周波数で周波数オフセットの推定・補償を行うため, ドップラー広がりが見掛け上更に広がり, フェージングひずみの推定誤差が増加し誤り率特性が劣化する。本論文では, (1)パイロットシンボルを用いた離散フーリエ変換(DFT)による周波数領域における信号電力の算出(2)周波数ウィンドウによる信号電力の平滑化, を行うことにより, ドップラー広がりの中心周波数を推定し, ドップラーシフトした直接波の影響を低減する周波数オフセット補償方式を提案する。そして, 計算機シミュレーションにより, 提案方式が従来方式よりも良好な誤り率特性を実現することを示し, その有効性を明らかにする。
Scientific journal, Japanese - Viterbi decoding with per-survivor processing of adaptive array antenna
T Uchiki; T Kojima; M Miyake
2000 IEEE 51ST VEHICULAR TECHNOLOGY CONFERENCE, PROCEEDINGS, VOLS 1-3, IEEE, 1295-1299, 2000, Peer-reviwed, Adaptive array technique is expected to reduce the multipath fading that causes degradation of bit error rate (BER)performance in the future broadband wireless systems. Some prior works proposed the joint schemes of the adaptive array and the equalizer technique, however few reports discuss the combination of a forward error correction scheme and the adaptive array. In this paper, we propose a novel combination scheme of Viterbi decoding and the adaptive array based on a per-survivor processing. In the proposed scheme, each state of the Viterbi decoder has array weights that are adaptively updated along with the surviving paths. The proposed scheme has a coding effect on the weight estimation without decoding delay and estimates the accurate weights. We evaluate the performance of the proposed scheme by computer simulation. Results of computer simulation show that the proposed scheme provides good tracking performance to the interference and good performance in terms of BER under the severe low wrier-to-interference power ratio (CIR) environments.
International conference proceedings, English - An improved pilot symbol assisted coherent detection scheme for Rician fading channels
T Asahara; T Kojima; M Miyake
IEICE TRANSACTIONS ON COMMUNICATIONS, IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG, E82B, 12, 2041-2048, Dec. 1999, Peer-reviwed, This paper proposes a coherent detection scheme that can reduce the estimation errors of the carrier phase due to Gaussian noise in communication systems where pilot symbol assisted modulation is employed to compensate for Rician fading distortion. This paper introduces two functions in addition to conventional fading estimation methods using Wiener interpolation, etc. The first is the weighted average function for reducing the estimation errors of the fading distortion detected by pilot symbols. The second is the moving average function for estimating the phase errors that are residual after being compensated for by the estimated fading distortion. This paper evaluates the bit error rate (BER) performance for the proposed method in both Rician fading channel and additive white Gaussian noise (AWGN) channel by computer simulation. Simulation results verify that the BER performance of the proposed method is superior to that of a conventional method in both Rician fading channel and AWGN channel. Simulation results also confirm that the degradation of the BER performance of the proposed method is only 0.1 dB in AWGN channel and only 0.3 dB in Rician fading channel compared with the theoretical curves even if ae reduce the number of computations by simplifying the calculation of interpolation coefficients optimized for Wiener interpolation.
Scientific journal, English - Carrier slip compensating time diversity scheme for helicopter satellite communication systems
T Uchiki; T Kojima; M Miyake; T Fujino
IEICE TRANSACTIONS ON COMMUNICATIONS, IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG, E81B, 12, 2311-2317, Dec. 1998, Peer-reviwed, This paper proposes a novel signal transmission scheme for helicopter satellite communications. The proposed scheme is based on time diversity, and combined with a novel algorithm to suppress an influence of carrier phase slip. In the proposed scheme, carrier phase slip is detected in cross correlation processing of the received signal, and is effectively suppressed. The proposed scheme thus makes it possible to employ coherent phase shift keying modulation to achieve bit error rate performance superior to that of differential phase shift keying modulation even in the low carrier-to-noise power ratio environment.
Scientific journal, English - A Novel Pilot Symbol Assisted Coherent Detection Scheme for Rician Fading Channels
Takashi ASAHARA; Toshiharu KOJIMA; Makoto MIYAKE
The First International Symposium on Wireless Personal Multimedia Communications, 236-241, Nov. 1998, Peer-reviwed
International conference proceedings, English - Metric Weighted Diversity Combining Based on Multiple Differential Phase Detection and its Performance in Mobile Communication Environments
小島年春; 三宅真; 藤野忠; 森永規彦
電子情報通信学会論文誌 B-II, The Institute of Electronics, Information and Communication Engineers, J81-B-II, 9, 846-854, Sep. 1998, Peer-reviwed, 差動PSK信号をダイバーシチ受信する場合, 原理上は同期検波後最大比合成方式によりビット誤り率特性の理論下界を達成可能であるが, フェージング下で完全な搬送波再生を行うことは困難である.本論文では, 理論下界へのアプローチとして, さきに提案した多重位相遅延検波の信号処理をダイバーシチ受信に導入し, その有効性につき検討する.フェージングにより伝送路特性が変動する場合, 受信信号がコヒーレントである(すなわち, フェージングの時間相関が高い)とみなせる時間内に多シンボル遅延検波を完了する必要がある.従って, 多重位相遅延検波の信号処理は, 変動の緩慢なフェージング下で特に有効となり, 高速変動するフェージング下では有効性は低下するものと予想される.この観点に基づき, さまざまな速さのレイリーフェージング下でのビット誤り率特性を, 計算機シミュレーションにより検証した.その結果, (1)緩慢なフェージング下では理論下界に0.5dB差にまで迫る特性を示す, (2)高速変動するフェージング下でも場合により従来の遅延検波後最大比合成方式よりも良好な特性を示す, 等のことが判明し, ダイバーシチ受信に多重位相遅延検波の信号処理を導入することの有効性が確認された.
Scientific journal, Japanese - Carrier Slip Compensating Time Diversity Scheme for Helicopter Satellite Communication Systems
Tatsuya UCHIKI; Toshiharu KOJIMA; Makoto MIYAKE; Tadashi FUJINO
17th AIAA International Communications Satellite Systems Conference, 635-641, Feb. 1998, Peer-reviwed
International conference proceedings, English - Design of an Anti-Rician-Fading Modem for Mobile Satellite Communication Systems
Toshiharu KOJIMA; Fumio ISHIZU; Makoto MIYAKE; Keishi MURAKAMI; Tadashi FUJINO
International Mobile Satellite Con-ference 1995, 13-18, Jun. 1995, Peer-reviwed
International conference proceedings, English - Differential detection scheme for DPSK using phase sequence estimation
Toshiharu Kojima; Makoto Miyake; Tadashi Fujino
Electronics and Communications in Japan (Part I: Communications), 77, 12, 88-100, 1994, Peer-reviwed, Recently, the differential detection scheme has attracted considerable attention as a demodulated scheme for digital mobile communications because of its robustness in the frequency nonselective fading channel. A problem of the differential detection scheme is that its bit error rate (BER) performance in the additive white Gaussian noise (AWGN) channel is inferior to that of the coherent detection scheme. To solve this problem, many methods to improve BER performance of the differential detection in the AWGN channel have been proposed. However, those methods require complex signal processings. This paper proposes a novel differential detection scheme as a simpler improvement method which estimates the differential phase of the transmitted signal by a sequence estimation scheme using the Viterbi algorithm. The proposed scheme is simplified in a manner such that its signal processing is composed of only additions and subtractions on the phase information of the received signal. Results of computer simulation show that BER performance of the proposed scheme is close to that of the ideal coherent detection in the AWGN channel. In addition, the trellis diagram of the Viterbi algorithm can be reduced without performance degradation introducing the signal processing similar to the Scarece State Transition (SST) type Viterbi decoding. The proposed scheme also is useful in the case of the fast Rician fading channel and the slow Rayleigh fading channel. Copyright © 1994 Wiley Periodicals, Inc., A Wiley Company
Scientific journal, English - Differential Detection Scheme for DPSK Using Phase Sequence Estimation
小島年春; 三宅真; 藤野忠
電子情報通信学会論文誌 B-II, The Institute of Electronics, Information and Communication Engineers, J76-B-II, 10, 783-792, Oct. 1993, Peer-reviwed, 移動体通信のディジタル化の急速な進展に伴い,復調方式として遅延検波方式が注目されている.遅延検波方式は,周波数非選択性フェージング下での動作が安定である等の利点を有しているが,その一方で静特性が同期検波方式に劣るという問題も有している.この問題を解決するため,遅延検波の静特性を改善する手法が研究され,種々の提案が行われてきたが,これらの改善手法では複雑な信号処理が必要であった.本論文では,より単純な信号処理で従来の改善手法に匹敵する静特性を実現する手段として,ビタビアルゴリズムにより送信差動位相の系列推定を行う遅延検波方式を提案する.提案方式は受信信号の位相情報のみを扱うため,信号処理は加減算のみの単純なものとなる.計算機シミュレーションにより,提案方式は良好な静特性を実現することを確認した.また,SST型ビタビ復号法に対応した信号処理を導入することにより,ビット誤り率特性の劣化を招くことなくトレリスの状態を削減できることを明らかにした.更に,ライスフェージング通信路や緩慢なレイリーフェージング通信路においても提案方式が有効であることを確認した.
Scientific journal, Japanese - A DS/SS RAKE receiver Using Weighted Averaging Technique with Forgetting Factor
浅原隆; 小島年春; 三宅真; 藤野忠
電子情報通信学会論文誌 B-II, The Institute of Electronics, Information and Communication Engineers, J76-B-II, 9, 777-780, Sep. 1993, Peer-reviwed, 忘却係数による加重平均法によってチャネルインパルスレスポンスを推定するRAKE方式を提案する.本方式は単純なハードウェアで構成可能であり,軟判定ビット数は4ビット程度まで削減可能で,従来方式より優れたビット誤り率特性を実現し得る.
Scientific journal, Japanese - A Study on Concatenated Coding Scheme with Variable Coding Gain
小島年春; 吉田英夫; 藤村明憲; 三宅真; 山岸篤弘; 藤野忠
電子情報通信学会論文誌 A, 電子情報通信学会基礎・境界ソサイエティ, J75-A, 8, 1240-1249, Aug. 1992, Peer-reviwed
Scientific journal, Japanese - PERFORMANCE OF SOFT DECISION DIGITAL MATCHED-FILTER IN DIRECT-SEQUENCE SPREAD-SPECTRUM COMMUNICATION-SYSTEMS
N KATAOKA; T KOJIMA; M MIYAKE; T FUJINO
IEICE TRANSACTIONS ON COMMUNICATIONS ELECTRONICS INFORMATION AND SYSTEMS, IEICE-INST ELECTRON INFO COMMUN ENG, 74, 5, 1115-1122, May 1991, Peer-reviwed, This paper considers the problem of realizing excellent performance of rapid acquisition in direct-sequence spread-spectrum communication systems. In this paper, we consider a scheme of digital matched filter (DMF) combined with soft decision function, which has potential capability of improving the characteristics of hard decision function by about 2 dB in the environment of additive white Gaussian noise (AWGN) channel and is capable of handling long PN codes by means of simple LSIs. Analysis is made on the performance in the environment of AWGN channel and results of experiments are provided. It is confirmed that the scheme provides attractive means for acquisition of direct-sequence spread-spectrum signals. Namely, soft decision DMF achieves rapid acquisition; the dwell time for soft decision DMF in the process of acquisition is half of that for hard decision DMF. In addition, it is shown that the correlator output signal produced by the acquisition circuit can also be used for the purpose of demodulation; excellent performance of bit error probability is experimentally observed.
Scientific journal, English - A Theoretical Approach to Digital Demodulation in Direct-Sequence Spread-Spectrum Commu-nication Systems
Toshiharu KOJIMA; Nobuhisa KATAOKA; Makoto MIYAKE; Tadashi FUJINO
1991 Global Satellite Communication Symposium, 383-388, May 1991, Peer-reviwed
International conference proceedings, English - Design And Performance Of Direct-sequence Spread-spectrum Modem Using Soft Decision Digital Matched Filter
Makoto Miyake; Toshiharu Kojima; Nobuhisa Kataoka; Tadashi Fujino
Proceedings of IEEE International Symposium on Spread Spectrum Techniques and Applications, 135-139, Sep. 1990, Peer-reviwed
International conference proceedings, English - A STUDY ON ACQUISITION OF DIRECT-SEQUENCE SPREAD-SPECTRUM SIGNALS USING SOFT DECISION DIGITAL MATCHED FILTERING
N KATAOKA; T KOJIMA; M MIYAKE; T FUJINO
COMMUNICATION SYSTEMS : TOWARDS GLOBAL INTEGRATION - SINGAPORE ICCS 90 : CONFERENCE PROCEEDINGS, VOLS 1 AND 2, ELSEVIER SCIENCE PUBL B V, 1064-1068, 1990, Peer-reviwed
International conference proceedings, English
MISC
- B-5-112 Low Complexity Approximate Matrix Inversion for Data Detection in Large-Scale MIMO
Fukui Kotoha; Kojima Toshiharu
The Institute of Electronics, Information and Communication Engineers, 24 Feb. 2015, Proceedings of the IEICE General Conference, 2015, 1, 467-467, Japanese, 110009927563, AN10471452 - B-5-16 Improved SIC Based on Lattice Reduction and Gram-SchmidtProcedure in MIMO Systems
Wei Hou; Tadashi Fujino; Toshiharu Kojima
The Institute of Electronics, Information and Communication Engineers, 05 Mar. 2013, Proceedings of the IEICE General Conference, 2013, 1, 426-426, Japanese, 110009733426, AN10471452 - SS復調方式のディジタル化に関する一検討
小島年春
1989, 信学技報, SSTA89-34, 10006931844, AN00245490
Lectures, oral presentations, etc.
- 簡易な奇数次対称直交行列の導入によるMWHCDMの多重数拡張に関する検討
小島年春; 張卓一
Oral presentation, 電子情報通信学会コミュニケーションシステム研究会
Sep. 2024
05 Sep. 2024- 06 Sep. 2024 - MWHCDMにおける初期捕捉のためのキャリア周波数オフセット推定法に関する検討
北川正起; 小島年春
Oral presentation, 電子情報通信学会コミュニケーションシステム研究会
15 Mar. 2024
14 Mar. 2024- 15 Mar. 2024 - MWHCDMの耐周期的遮断能力の向上に関する検討
河野智大; 小島年春
2023年電子情報通信学会総合大会
Mar. 2023
Mar. 2023 Mar. 2023 - 帯域制限を行うMWHCDMシステムにおけるチップタイミング再生方式の改良に関する検討
田上隼斗; 小島年春
2023年電子情報通信学会総合大会
Mar. 2023
Mar. 2023 Mar. 2023 - ロールオフ波形整形を行うWHCDMの初期捕捉方式に関する一検討
小松央次郎; 小島年春
Oral presentation, Japanese, 電子情報通信学会ワイドバンドシステム研究会
Mar. 2022
Mar. 2022 Mar. 2022 - キャリア周波数オフセット耐性を改善したMWHCDM初期捕捉方式
山村洋太; 小島年春
Oral presentation, Japanese, 電子情報通信学会ワイドバンドシステム研究会
Mar. 2022
Mar. 2022 Mar. 2022 - 周期的遮断回線におけるMWHCDM信号の簡易な準最尤検出法
山田翼; 小島年春
Oral presentation, Japanese, 2022年電子情報通信学会総合大会
Mar. 2022
Mar. 2022 Mar. 2022 - ヘリコプター衛星通信におけるスペクトル解析に基づく遮断率推定法の特性改善に関する検討
八子聖也; 小島年春
Oral presentation, Japanese, 2022年電子情報通信学会総合大会
Mar. 2022
Mar. 2022 Mar. 2022 - ヘリコプター衛星通信用WHCDMにおける回線推定法の一検討
張海威; 小島年春
Oral presentation, Japanese, 2021年電子情報通信学会ソサイエティ大会, Domestic conference
Sep. 2021 - ヘリコプター衛星通信における統計的手法に基づく回線遮断率推定法の検討
蔡雅史; 小島年春
Oral presentation, Japanese, 電子情報通信学会衛星通信研究会
Feb. 2021 - LDPC符号を用いた附加情報不要のSLM法におけるスクランブル系列推定の演算量低減に関する検討
島田宙輝; 小島年春
Oral presentation, Japanese, 電子情報通信学会通信方式研究会
Mar. 2018 - キャリア周波数オフセットによるWH符号のコード間干渉に基づくWHCDM用AFC方式
金丸雄紀; 小島年春
Oral presentation, Japanese, 電子情報通信学会衛星通信研究会
Feb. 2018 - 多重分離後の信号エネルギー分布の非対称性に基づくWHCDM用初期捕捉方式の簡単化
長嶋優貴; 小島年春
Oral presentation, Japanese, 電子情報通信学会衛星通信研究会
Feb. 2018 - DSFBC-OFDMに適した附加情報不要なSLM法に関する検討
鈴木太一; 小島年春
Oral presentation, Japanese, 2015年電子情報通信学会総合大会
Mar. 2015 - LDPC符号を用いたOFDMシステムに適した附加情報不要のSLM法
長﨑啓志; 小島年春
Oral presentation, Japanese, 2015年電子情報通信学会総合大会
Mar. 2015 - 大規模MIMO信号検出法のための低複雑な近似逆行列計算法
福井言葉; 小島年春
Oral presentation, Japanese, 2015年電子情報通信学会総合大会
Mar. 2015 - ヘリコプタ衛星通信に適したWHCDMの一検討
鈴木あやこ; 小島年春
Oral presentation, Japanese, 2015年電子情報通信学会総合大会
Mar. 2015 - OFDMを用いるヘリコプタ衛星通信システムのBER特性改善
安江伸吾; 小島年春
Oral presentation, Japanese, 2014年電子情報通信学会総合大会
Mar. 2014 - 空間変調における周波数領域等化の検討
石本清太郎; 小島年春
Oral presentation, Japanese, 2014年電子情報通信学会総合大会
Mar. 2014 - Alamouti MIMO-OFDMのための附加情報不要のSLM法の計算量削減
何 超; 小島年春
Oral presentation, Japanese, 2014年電子情報通信学会総合大会
Mar. 2014 - ICT国際PBL(4):ディジタル信号処理
福井言葉; 船橋鴻志; 高橋謙三; 山尾 泰; 小島年春; 崎山一男
Oral presentation, Japanese, 2014年電子情報通信学会総合大会
Mar. 2014 - MIMO 環境での M Algorithm を用いた Lattice-Reduction による信号推定法
中田智重; 藤野 忠; 小島年春
Oral presentation, Japanese, 電子情報通信学会,2013年総合大会
Mar. 2013 - MIMOにおけるLRを用いたSphere-Detectionの演算量削減法
四ツ橋達彦; 小島年春; 藤野 忠
Oral presentation, Japanese, 電子情報通信学会,2013年総合大会
Mar. 2013 - MIMO環境におけるLattice-Reduction Aided Ordering SIC及びLISTを用いた送信信号推定法
森 直樹; 藤野 忠; 小島年春
Oral presentation, Japanese, 電子情報通信学会,2013年総合大会
Mar. 2013 - 直交符号並列伝送方式を用いたヘリコプタ衛星通信システム
ムンフエルデネ ビルグーントゥグス; 小島年春
Oral presentation, Japanese, 電子情報通信学会,2013年総合大会
Mar. 2013 - Improved SIC Based on Lattice Reduction and Gram-Schmidt Procedure in MIMO Systems
Wei Hou; Tadashi Fujino; Toshiharu Kojima
Oral presentation, English, 電子情報通信学会,2013年総合大会
Mar. 2013 - ヘリコプタ衛星通信へのLDPC符号の適用
岩本奨平; 小島年春
Oral presentation, Japanese, 電子情報通信学会,2012年総合大会
Mar. 2012 - ヘリコプタ衛星通信へのOFDMの適用
小島年春; 岩本奨平; 志田裕紀; 丁硯冬
Oral presentation, Japanese, 電子情報通信学会,2011年ソサイエティ大会
Sep. 2011 - ビタビ復号の尤度情報を用いる付加情報不要のSLM法
本田高太郎; 小島年春
Oral presentation, Japanese, 電子情報通信学会,2010ソサイエティ大会
Sep. 2010 - 付加情報を不要としたSLM法の一検討
小島年春; 志田裕紀; 藤野 忠
Oral presentation, Japanese, 電子情報通信学会,2010総合大会
Mar. 2010
Courses
- Information and Communication Engineering Laboratory A2
Present
The University of Electro-Communications - 集積回路設計特論
Present
電気通信大学 - Fundamentals of Circuits and Systems
Present
The University of Electro-Communications - Electronic Engineering Workshop
Present
The University of Electro-Communications - Information and Communication Engineering Laboratory B2
Present
The University of Electro-Communications - Logical Circuits
Present
The University of Electro-Communications - Electronics Circuits
Present
The University of Electro-Communications - Space Communication Technology (Lecture and Practice)
Present
The University of Electro-Communications - Advanced Radio Communication Systems
Present
The University of Electro-Communications
