Space-time adaptive detection in turbo-coded DS-CDMA wireless systems over Rayleigh fast-fading channels

This paper investigates the performance improvement due to channel coding in a direct sequence code division multiple-access (DS-CDMA) system that employs space-time adaptive minimum mean-square-error (MMSE) interference suppression. A synchronous DS-CDMA transmission is assumed, and we focused on the performance gain attain through error control coding when used with binary phase-shift keyed (BPSK) modulation. It is shown that the use of adaptive antenna array at the receiver side, assists in attenuating multiuser interference and at the same time speeds-up the convergence rate of the adaptive receiver. Both the least-mean square (LMS) and the recursive-least-square (RLS) adaptive receiver algorithms are considered. Also, a performance comparison between turbo codes and soft-decision convolutional codes (SD-CC) in the space-time system is provided. It is found that the use of antenna arrays at the receiver side helps to bring the adaptive receiver´s performance close to its multiuser counterpart. Both analyses and simulations show that the turbo-coded system outperforms the convolutionally coded one with a coding gain of approximately 1.7 dB.