Modified MAP algorithm for extended turbo BCH codes and turbo equalisers

The maximum a-posteriori (MAP) algorithm is modified in order to incorporate the parity check bit of extended BCH codes into calculating the log likelihood ratio (LLR) of the coded bits. The algorithm is then used jointly with channel equalisation-in a scheme referred to as turbo equalisation-in order to mitigate the effects of intersymbol interference (ISI) introduced by dispersive channels. The performance of the extended BCH codes is evaluated and compared to that of conventional BCH codes. For example, the extended BCH(32,26) code was found to outperform the conventional BCH(31,26) code by approximately 0.5-1.0 dB at a bit error rate (BER) of 10/sup -5/ over dispersive Rayleigh-fading channels.