Mismatched decoding of intersymbol interference using a parallel concatenated scheme

A turbo-type scheme that uses parallel concatenation and soft-output iterative detection is proposed for transmission over linear intersymbol interference channels. When the receiver has perfect knowledge of the channel, the scheme offers only marginal improvement in performance over optimum linear coded modulation with Viterbi or reduced search detection. However, the improvement is significantly higher when the detector is mismatched, i.e., if it uses an imperfect channel estimate. The delay is low since the block sizes are small, and the performance improvement is achieved with few iterations. The technique may be applied as a retransmission strategy in order to save power for systems that suffer from losses due to ISI and channel mismatch.