Offset invariance in maximum-likelihood decoding for a class of partial response channels

In this letter we show that for a class of partial response channels with discrete-time pulse response of the form (1-D)P(D) whose output samples are corrupted by independent samples of additive white Gaussian noise with mean m, a maximum likelihood sequence detector designed for the case of m=0 is also the maximum likelihood sequence detector for an arbitrary value of m. The studied class of partial response channels is widely used for the characterization of digital magnetic recording channels where the DC offset is frequently an issue.