Concatenated codes for Class IV partial response channels

We present the design and analysis of parallel and serial concatenated code s with iterative decoding for Class IV partial response (PR4) signaling. Co de rates of the form K-0/(K-0 + 1), for K-0 = 4, 8, 16, 32, and 64, are con sidered. We show that the 1/(1 + D-2) (Tomlinson) precoder, first proposed by Wolf and Ungerboeck for trellis coded PR4 channels, is effective for bot h parallel and serial concatenations, but the error-rate "floor" is relativ ely high for the serial case. This leads to new interleaver and precoder de signs for serial concatenations, the latter involving an examination of the conditional distance enumerator of each precoded PR4 channel. The new prec oders substantially reduce the floors of the serial concatenated codes, but degrade the performance of the parallel concatenated codes. For a bit-erro r rate of 10(-5), the best parallel and serial concatenated codes come with in 1.7 dB of a lower bound on the capacity limit for PR4 signaling on an ad ditive white Gaussian noise channel.