Iterative decoding of serially concatenated space-time codes in WCDMA systems

In this paper, concatenated space-time codes applying iterative decoding topologies are investigated in wideband code division multiple access (WCDMA) communication systems. The coding operations are based on the concatenation of a convolutional encoder, an interleaver, and a space-time code employing multiple-transmitter/multiple-receiver diversity. As the decoding algorithm, an iterative (turbo) process is used, where a priori probability is exchanged between the symbol-by-symbol space-time decoder and the bit-by-bit convolutional decoder. Through the iterative decoding process and the optimum parameter selection operations a considerable improvement in the error rate performance is obtained. The simulation results for the multi-user forward link WCDMA system show that in a flat Rayleigh fading channel environment the serially concatenated interleaved space-time coding systems perform significant levels of error correction, and additionally, for the applied system configurations, it was observed that the nonrecursive space-time code outperforms the recursive spacetime code.