Performance tradeoff among concatenated codes and processing gain for high capacity DS/CDMA transmission in wireless communications

In this paper, we evaluate the use of a proposed forward error correction (FEC) scheme as well as concatenated coding in asynchronous DS/CDMA system over multipath Rayleigh fading channels. The FEC scheme combines selection diversity with low complexity concatenated codes which consist of a Reed-Solomon outer code and a convolutional inner code. Chernoff bounds and Union bounds for both coding schemes are derived, and the tightness of these bounds are confirmed by computer simulations. We analyze the BER performance and capacity tradeoffs between various system parameters under a fixed total bandwidth expansion and concatenated codes constraint requirements. In addition, the throughput performance for both systems is presented under fixed processing gain/signal-to-noise ratio constraints. It is shown that the proposed system drastically decreases the BER and increases the system capacity