In this paper, a cancellation technique using a reference signal which does not contain the components of the desired signal is proposed for optical synchronous M-ary FSK/CDMA. As spreading codes, the modified prime sequence codes which can increase the number of users are employed. Interference cancellation is done by using the correlation property of the modified prime sequence codes. A reference signal is constructed by using one of the modified prime sequence codes that do not have data components of the desired signal, and cancellation is performed by subtracting the reference signal from the received signal of the desired user. In the theoretical analysis, the Poisson effect in the input-output characteristic of the photodetector is considered, and the upper bound on the bit error rate (BER) is derived. The performance is compared to the optical synchronous M-ary PPM/CDMA system with an interference canceler in which a reference signal does not contain the data components of the desired signal. It is found that an optical synchronous M-ary FSK/CDMA system with an interference canceler has better BER performance than optical synchronous M-ary PPM/CDMA systems with an interference canceler under the condition of the same chip rate and number of symbols M, and achieves higher bit rate. Also, when the chip rate and bit rate are constant, it is found that optical synchronous M-ary FSK/CDMA system with an interference canceler can increase the number of simultaneous users.
|ジャーナル||Electronics and Communications in Japan, Part I: Communications (English translation of Denshi Tsushin Gakkai Ronbunshi)|
|出版ステータス||Published - 2000|
ASJC Scopus subject areas
- Computer Networks and Communications
- Electrical and Electronic Engineering