Concatenated coding and iterative SOVA decoding with PR4 signaling

We modify the iterative soft-output Viterbi algorithm (SOVA) for partial response (PR) channels and examine its performance for parallel and serial concatenated codes on a preceded Class IV partial response (PR4) channel. We present a SOVA that differs slightly from what appears in the literature and compare the performance of the two versions. Code rates of the form k(0)/k(0)+1 (k(0) = 4, 8, and 64) are considered. Our simulations indicate that the loss at P(b) = 10(-5) suffered by the SOVA, relative to the APP algorithm, is at most 1.2 dB for parallel concatenations and at most 1.6 dB for serial concatenations.