研究者詳細 - 山里　敬也

論文 - 山里　敬也

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逐次型干渉除去法を用いたCDMA Unslotted ALOHA方式の特性評価査読有り

田所幸浩, 岡田啓, 山里敬也, 片山正昭, 小川明

電子情報通信学会論文誌頁： - 2003年1月

記述言語：日本語掲載種別：研究論文（学術雑誌）

CDMA Unslotted ALOHA方式では多元接続干渉が発生し，特性劣化の大きな要因となっている．さらにこの方式では受信信号電力の不均一となる状況がしばしば発生し，多元接続干渉の影響の増大を引き起こす．現在多元接続干渉を抑制する方法として干渉除去技術がある．しかしこの手法は主に信号が時間的に連続して送受信されているシステムを扱っており，特性評価もビット誤り率によるものであった．パケット通信システムでは各ビットの伝送の成否ではなく各パケットの伝送の成否がシステム特性の鍵を握る．そこで本研究では，CDMA Unslotted ALOHA方式に干渉除去技術の１つである逐次型干渉除去法を用いたシステムを提案し，スループット特性を解析的に求め，特性評価を行なう．また一般的に受信信号電力の不均一な状況下での特性は，受信信号電力の均一な場合の特性よりも劣化することが知られている. しかし提案方式では，受信信号電力の不均一な状況下において，受信信号電力の均一な場合より特性が良くなることを示す．

Soft-Decision Decoding of Low-Density Parity-Check Codes for Hard-Detected Optical Communication Signals 査読有り

C. Zheng, T. Yamazato, H. Okada, M. Katayama, and A. Ogawa

電子情報通信学会英文論文誌頁： - 2003年1月

記述言語：英語掲載種別：研究論文（学術雑誌）

A soft-decision decoding scheme of low-density parity-check codes (LDPC) is proposed for hard-detected signals of optical fiber communication (OFC) systems. Based on the error detection, the proposed scheme converts the received hard-decision into soft reliability for the input of the LDPC decoder, and soft-decision decoding is performed. Simulation results under OFC channels are shown and superior performance is obtained by using the proposed decoding scheme of the LDPC codes.

Medium Access Control Protocol Based on Estimation ofMultimedia Traffic with an Adaptive Algorithm in CDMA PacketCommunications 査読有り

Y. Hirayama, H. Okada, T. Yamazato, and M. Katayama

電子情報通信学会英文論文誌頁： - 2002年12月

画像隠蔽技術を即時型並列復号方式に適応した場合における画質復元能力に関する検討査読有り

本庄勝，山里敬也，岡田啓，片山正昭，小川明

電子情報通信学会論文誌頁： - 2002年12月

記述言語：日本語掲載種別：研究論文（学術雑誌）

動画像のリアルタイム性を維持しつつ, かつ劣悪な通信環境でも画像の劣化を抑えることができる方法に即時型動画像並列復号方式(以下, RT-PVD)がある. RT-PVDは, 誤り訂正符号の復号処理遅延を減らすために動画像符号化のフレーム間符号化の復号原理に着眼した復号方式で出力画像と参照画像を別々に復号して参照画像の画質を保持し, 動画像全体の画質を向上させている. 本稿では, このRT-PVD に画像隠蔽技術を適用することで, 更に特性改善をはかる. 本来, 画像隠蔽は劣化したブロックが完全に補間されない限り, 2次的な誤り伝搬を引き起こす要因となる. しかしRT-PVD では, 出力画像の画像隠蔽において画像品質の高い参照画像を補間に利用することができるので誤り伝搬を発生させることなく実現できる. またRT-PVDでは, 発生する劣化ブロックがランダムに発生することから, その補間されたブロックも人間の目には気づきにくく, 主観評価では画質特性の大きな向上が期待できる.

A Study on Turbo Soft-Decision Decoding for Hard Detected Optical Communication Signals 査読有り

C. Zheng, T. Yamazato, H. Okada, M. Katayama, A. Ogawa

電子情報通信学会英文論文誌頁： - 2002年12月

記述言語：英語掲載種別：研究論文（学術雑誌）

We propose a method to realize soft-decision decoding for hard-detected signals. In this paper, a novel concept is introduced as ``error-detected reliability''. The method is very useful for optical fiber communications (OFC) as hard detection is the only detection method for the OFC systems. We demonstrate our proposed method using the turbo code in which soft information is required for decoding. As a result, the simulation shows slight difference in the range of moderate to high signal-to-noise ratio between the proposed decoding scheme and the conventional turbo decoding scheme. Moreover, the bit error rate of $10^{-11}$ can be achieved by serial concatenation of a Reed-Solomon code and a turbo code for Q-factor lower than $8.0$ dB with a bandwidth expansion ratio of $33.3\%$.

フェージング環境下における送信ダイバーシチ方式の誤り率特性の統計的性質に関する一検討

打田良介, 岡田啓, 山里敬也, 片山正昭

情報理論とその応用シンポジウム頁： - 2002年12月

記述言語：日本語

本稿では, 無線通信システムの信頼性保証のために, ビット誤り率(BER)の確率分布という観点からシステムの解析を行う. 送信アンテナ数Mの送信ダイバーシチを適用し, それぞれ独立なスローレイリーフェージングチャネルのもとで, 受信機での信号合成方法や送信アンテナ数がBERに及ぼす影響を明らかにする.

Medium access control protocol based on estimation of multimedia traffic with an adaptive algorithm in CDMA packet communications 査読有り

Hirayama Y, Okada H, Yamazato T, Katayama M

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES E85A 巻 ( 12 ) 頁： 2868 - 2876 2002年12月

Medium access control protocol based on estimation of multimedia traffic with an adaptive algorithm in CDMA packet communications 査読有り

Hirayama Y.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences E85-A 巻 ( 12 ) 頁： 2868 - 2876 2002年12月

Medium Access Control Protocol Based on Estimation of Multimedia Traffic with an Adaptive Algorithm in CDMA Packet Communications 査読有り

Y. Hirayama, H. Okada, T. Yamazato, M. Katayama

IEICE Transactions on Fundamentals E85-A 巻 ( 12 ) 頁： 2868-2876 - 2876 2002年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人電子情報通信学会

In this paper, we propose a medium access control (MAC) protocol for multimedia code division multiple access (CDMA) communications. In the proposed protocol, a base station (BS) estimates the instantaneous number of simultaneously transmitted packets in the future slots with exploiting a stochastic property of traffic. In order to carry out this estimation, we employ an adaptive algorithm. We evaluate the performance of the proposed protocol by comparing that with two different cases. One is no estimation case and the other is perfect estimation case. From these results, we clarify the advantage of the proposed MAC protocol.

CiNii Books

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Performance improvement of OFDM system with consideration on the characteristics of power-line noise 査読有り

Sugimoto K, Okada H, Yamazato T, Katayama M

IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES E85A 巻 ( 12 ) 頁： 2822 - 2829 2002年12月

Performance improvement of OFDM system with consideration on the characteristics of power-line noise 査読有り

Sugimoto K.

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences E85-A 巻 ( 12 ) 頁： 2822 - 2829 2002年12月

Performance Improvement of OFDM System with Consideration on the Characteristics of Power-Line Noise 査読有り

K. Sugimoto, H. Okada, T. Yamazato, M. Katayama

IEICE Transactions on Fundamentals E85-A 巻 ( 12 ) 頁： 2822-2829 - 2829 2002年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人電子情報通信学会

In narrow band power-line communication (PLC) systems, which use frequency band below a few hundred kHz, the noise on power-line is non-white and non-stationary. Under such environment, the performance of Orthogonal Frequency Division Multiplex (OFDM) modulation system is analyzed, and time and frequency dependence of bit error rate (BER) is clarified. In addition, the possibility of performance improvement with the symbol level repetition coding employing cyclo-stationary feature of power-line noise is presented.

CiNii Books

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画像隠蔽技術を即時型並列復号方式に適応した場合における画質復元能力に関する検討査読有り

本庄勝, 山里敬也, 岡田啓, 片山正昭, 小川明

電子情報通信学会論文誌 J85-A 巻 ( 12 ) 頁： 1463-1468 2002年12月

Calculation of Mobile Location using a Statistical Scatterer

N. J. Thomas, H. Okada, T. Yamazato, M. Katayama

電子情報通信学会技術研究報告 SST2002-34 巻頁： 45-50 2002年10月

記述言語：英語

A statistical technique to calculate the location of a signal source, e.g. a mobile phone, in a multipath, non--line of sight environment, is proposed. The technique relies on angular spread and relative time of arrival measurements of multipath signals received at a base station antenna array. The source location is estimated using an a priori known statistical model for the distribution of single bounce multipath scatterers around the signal source, and fitting the measured channel impulse response received at the base station to this model. Further improvement in location estimation accuracy is demonstrated using the Kalman filter, or time average filter on the time sequence of location estimates in a moving scenario.

Spread Sequence for Multicarrier CDMA under the Effect of Nonlinear Amplifier 査読有り

M. Harada, T. Yamazato, H. Okada, and M. Katayama

International Symposium on Information Theory and Its Applications (ISITA) ISITA2002 巻頁： - 2002年10月

Decoding of low-density parity-check codes for hard-detected optical fiber communication signals 査読有り

C. Zheng, T. Yamazato, H. Okada, M. Katayama, and A. Ogawa

International Symposium on Information Theory and Its Applications (ISITA) ISITA2002 巻頁： - 2002年10月

記述言語：英語

A soft-decision decoding scheme of low-density parity-check codes (LDPC) is proposed for hard-detected signals of optical fiber communication (OFC) systems. The scheme converts the received hard-decision into soft reliability for the input of the LDPC decoder, and soft-decision decoding is performed. Simulation results under OFC channels are shown and superior performance is obtained by using the proposed decoding scheme of the LDPC codes.

An access control protocol based on estimation of multimedia traffic with an adaptive algorithm in CDMA packet network 査読有り

Y. Hirayama, H. Okada, T. Yamazato, M. Katayama

IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) PIMRC2002 巻頁： 619-623 2002年9月

記述言語：英語

In multimedia wireless communications, various types of traffic are handled. Generally, each of these traffic has a different stochastic property. An access control protocol for multimedia wireless communications, therefore, are required to adopt a stochastic property of multimedia traffic. Conventional access control protocols, however, do not consider such characteristics of multimedia traffic. In this paper, we propose an access control protocol for multimedia CDMA packet communications. The proposed protocol controls the data packet transmissions based on the estimation of the instantaneous number of simultaneously transmitted voice and video packets. This estimation exploits the stochastic property of multimedia traffic. To carry out such estimation, we employ an adaptive algorithm as an estimation method. We evaluate the performance of the proposed protocol by comparing it with the performance in the case where a stochastic property of traffic is not considered.

Effect of Interleaving and FEC on the Throughput of CDMA Unslotted ALOHA System with Adaptive Multiuser Receiver 査読有り

H. Okada, T. Yamazato, M. Katayama

IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) PIMRC2002 巻 ( 2 ) 頁： 941-945 2002年9月

記述言語：英語

A CDMA unslotted ALOHA system is a connectionless-type of CDMA packet communication system. In this system, a user station can transmit a packet asynchronously and randomly, and so the packet birth/death event is one of the most important problems for multiuser detection. We have proposed the CDMA unslotted ALOHA system using an adaptive filter receiver based on minimum mean square error criterion in [8], and shown the improvement in the throughput performance even considering the effect of birth/death event. The ensemble-averaged squared error, however, increases at the point of packet birth. In this paper, we employ interleaving and forward error correction (FEC) coding techniques to mitigate the momentary increase in ensemble-averaged squared error. The use of FEC, however, causes the increase in MAI due to redundancy bits of FEC. Moreover, signal power is reduced under the condition that the energy of an information bit is the same. In such cases, whether an adaptive filter can operate effectively or not interests us. We evaluate the system performance and show that the improvement in throughput is achieved with interleaving and FEC techniques.

A Proposal of OFDM Synchronization Scheme with Subtraction Operation 査読有り

T. Shibata, N. Itoh, M. Fujimoto, N. Suzuki, A. Ogawa, T. Yamazato, M. Harada

7th International-OFDM Workshop 2002 頁： 237-240 2002年9月

BER Performance of Asynchronous Multicarrier-CDMA System and Asynchronous DS-CDMA System in Frequency Selective Fading 査読有り

H. Takeuchi, T. Yamazato, H. Okada, and M. Katayama

7th International-OFDM Workshop 2002 頁： 26-30 2002年9月

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