SOVA-based soft interference cancellation for multi-user FEC-coded DS-CDMA for 384 kbps transmission in WCDMA

This paper introduces a multi-user detection (MUD) algorithm applying iterative soft interference cancellation for a direct-sequence code-division multiple-access (DS-CDMA) system with forward error correction (FEC) coding. The proposed algorithm involves iterative decoding and soft interference cancellation that uses SOVA-based, FEC decoder decision feedback. The investigation of the iterative algorithm uses a full CDMA system model which involves three types of commonly used spreading sequences: Gold, Kasami, and extended S(2) sequences. Computer simulations are used to obtain the performance of the proposed algorithm with each of the spreading sequences. For an AWGN channel, the classical CDMA detector with no MUD supports 5 high-bit-rate users in 5 MHz WCDMA at a bit-error-rate of 10^-5 for the constraint length 7, rate-½ convolutionally-coded system. The iterative algorithm proposed doubles the number of users in the targeted application when SOVA is used for soft decision feedback. Perfect power control and chip and carrier synchronization, with no multipath fading, are assumed