Probability of bit error for DS/SSMA systems with MPSK signaling and complex signature sequences

The authors consider a direct-sequence spread-spectrum multiple-access (DS/SSMA) communication system with M-ary phase-shift keyed (MPSK) signaling. Users in the system use complex signature sequences. A bounding technique is used to obtain arbitrarily tight upper and lower bounds on the probability of bit error. Numerical results are presented for Frank-Zadoff-Chu (FZC) and near-optimal four-phase complex sequences, as well as binary Gold sequences, for binary phase shift keying, (BPSK), 4-PSK, and 8-PSK. Results show that complex sequences can yield better performance than binary sequences in MPSK signaling. Using complex sequences, the number of signature sequences with good correlation properties is greatly enlarged.<>