Analysis of Bit Error Probability of Direct-Sequence CDMA Multiuser Demodulators

Part of Advances in Neural Information Processing Systems 13 (NIPS 2000)

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Toshiyuki Tanaka


We analyze the bit error probability of multiuser demodulators for direct(cid:173) sequence binary phase-shift-keying (DSIBPSK) CDMA channel with ad(cid:173) ditive gaussian noise. The problem of multiuser demodulation is cast into the finite-temperature decoding problem, and replica analysis is ap(cid:173) plied to evaluate the performance of the resulting MPM (Marginal Pos(cid:173) terior Mode) demodulators, which include the optimal demodulator and the MAP demodulator as special cases. An approximate implementa(cid:173) tion of demodulators is proposed using analog-valued Hopfield model as a naive mean-field approximation to the MPM demodulators, and its performance is also evaluated by the replica analysis. Results of the per(cid:173) formance evaluation shows effectiveness of the optimal demodulator and the mean-field demodulator compared with the conventional one, espe(cid:173) cially in the cases of small information bit rate and low noise level.