Performance of multi-code CDMA systems with concatenated coding and iterative decoding in multipath Rayleigh fading channels

Multi-code CDMA (MC-CDMA) is proposed as an alternative multiple access scheme which provides the flexibility, high data rates, and bandwidth-on-demand features necessary in next-generation wireless integrated services networks. In a conventional MC-CDMA configuration (e.g., in IS-95B) a user can transmit information in multiples (M times) of a basic data rate by using M orthogonal supplemental DS-CDMA channels. In this paper, motivated by the remarkable performance of turbo codes with large interleaving lengths in AWGN channels, we investigate the performance of a MC-CDMA system employing different concatenated encoding schemes combined with iterative decoding. Furthermore, we examine the frame error rate performance of the various schemes by considering CRC codewords in each of the M frames corresponding to each data block. We show that coding and interleaving at the block level improves the block error rate (BlER) performance, especially when turbo schemes are used, while the extra CRC overhead is beneficial mainly when convolutional codes are used.