Iterative interference cancellation and decoding for spread-signature CDMA systems

Spread-signature code-division multiple-access systems are designed to allow both time and frequency diversity to be exploited in multiuser wireless systems operating in fading environments. Computationally efficient multipass demodulation and decoding algorithms are developed for use in receivers with these systems. These algorithms efficiently suppress both intersymbol and interuser (multiple-access) interference to achieve a substantial diversity benefit and good near-far resistance characteristics. Moreover, it is shown that relatively few iterations are required for convergence to typical target bit-error rates. Several other aspects of the performance of the algorithms are also explored.