Equation based LDPC decoder for intersymbol interference channels

The application of LDPC codes to intersymbol interference (ISI) channels requires efficient soft decoding methods for the ISI channel as well as the outer LDPC code. We introduce a fully pipelined turbo equalization architecture that combines soft decoders for the channel and the LDPC code. This equation based LDPC decoder uses a signed sum product (SSP) decoding algorithm, and stores soft information for each equation, in contrast to each edge in conventional LDPC decoders. The memory size of the LDPC decoder is greatly reduced, and the delay of the LDPC decoder is absorbed by the delay of the soft channel detector.