Grant-in-Aid for Scientific Research (C).
|Research Institution||Saitama University|
YASHIMA Hiroyuki Saitama University Faculty of Engineering Department of Information and Computer Sciences, Associate Professor, 工学部, 助教授 (30230197)
|Project Fiscal Year
1997 – 1999
Completed(Fiscal Year 1999)
|Budget Amount *help
¥3,100,000 (Direct Cost : ¥3,100,000)
Fiscal Year 1999 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1998 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 1997 : ¥1,400,000 (Direct Cost : ¥1,400,000)
|Keywords||Optical Communication / Optical CDMA / error control code / PPM / convolutional code / Viterbi decoding / 光CDMA / 畳み込み符号 / Viterbi復号 / 光通信 / 誤り訂正符号 / 音声 / 多重通信|
1. Multibit Code for Optical CDMA
We have proposed a new class of code as signature sequences for optical Code Division Multiple Access (OCDMA) systems. OCDMA combined with F-ary Multibit/Sequence period has been investigated. We derive the performance of the proposed CDMA systems. It is shown that the proposed system achieves higher throughput, keeping advantage of the power efficiency and low bit error rate performances.
2. M-ary PPM with Multibit code
The multibit/Sequence period code has been applied in OCDMA with M-ary Pulse Position Modulation (PPM). In PPM signaling, interference from other users are reduced, which results in increase of simultaneous users. It is found that the proposed system achieves higher throughput, keeping advantage of low bit error rate.
3. OCDMA with Error Control Coding
We apply error control coding to improve the system performance of pulse position modulated OCDMA (PPM/OCDMA) systems and we investigate the performance of M-ary PPM/OCDMA systems with M-ary
convolutional coding. Dual-k code is used as the M-ary convolutional code and Optical Orthogonal Codes with the maximum cross correlation value of 1 and 2 are employed as the signature sequences. We derive an expression for the bit error probability of the new system and show that combining M-ary convolutional coding and M-ary PPM results in an improved error performance. Also it is shown that the number of simultaneous user can be significantly increased with the proposed system compared to the uncoded PPM/OCDMA system with the same bit error probability and with the same information bit rate. We also analyze the system with binary convolutional coding and a comparison with the proposed system is given.
4. OCDMA with Prime Code
We investigate the performance of prime code in OCDMA systems. The correlation properties of primecode to derive BER in OCDMA. The value of the crosscorrelation between prime codes and its probability density function are analyzed. Bit error rate (BER) are, then, derived for the case of the worst choice of codes and also for the case of random choice. Simulation results show that the results obtained in the analysis provides well approximated BER. BER for prime code is compared with that for optical orthogonal code (OOC). IT is shown that prime code provides better performance than the OOC.