Iterative receiver for Qc-LDPC coded underwater acoustic communication systems

Quasi Cyclic-Low Density Parity Check (QC-LDPC) codes are easy to construct and provide the considerable coding gain, which is suitable for underwater acoustic communication (UWAC). Single-carrier (SC) transmission with frequency-domain equalization (FDE) is today recognized as an attractive alternative to orthogonal frequency-division multiplexing (OFDM) for communication application with the inter-symbol interference (ISI) caused by multi-path propagation, especially in shallow water channel. In this paper, the turbo theory is applied on the QC-LDPC codes and minimum mean square error (MMSE) decision feedback equalizer (DFE) to design iterative data processing for underwater acoustic communication system. In the proposed iterative structure, the MMSE based FD-DFE and QC-LDPC decoder exchange soft information through an iterative manner so that the performance of underwater acoustic communication system can be improved greatly. Based on sound speed profiles (SSP) measured in the lake and finite-element ray tracking method, the shallow water channel is constructed to verify the validity of the proposed system structure.