A reduced-complexity sequence detector with soft outputs for partial-response channels

Data transmission in a binary partial-response channel is often accomplished using a concatenated code consisting of an inner modulation code and an outer error-correcting code (ECC). We consider two inner decoders for such a code, each consisting of a reduced-complexity sequence detector modified to provide an estimate of the reliability of each bit. These reliability values are then used by the outer decoder to achieve improved performance. Although one of these decoders is considerably simpler than the other, their performances were comparable in the cases we considered. Both achieve considerable improvement over a decoder that uses hard-decision decoding of the inner code