Joint design of QC-LDPC codes for cascade-based multisource coded cooperation

Quasi-cyclic low-density-parity-check (QC-LDPC) codes are jointly designed for cascade-based multisource coded cooperation system. Firstly, QC-LDPC codes based on the base matrix and exponent matrix are introduced, and then two types of girth-4 cycles in QC-LDPC codes employed by the sources and relay are explicated. Secondly, we propose joint design method of QC-LDPC codes employed by the sources and relay, by which all girth-4 cycles including both Type-I and Type-II are canceled. Numerical simulations show that the jointly designed QC-LDPC coded cooperation well combines cooperation gain and channel coding gain, and outperforms the coded noncooperation under the same conditions. Furthermore, the bit error rate (BER) performance of the coded cooperation employing jointly designed QC-LDPC codes is better than those of random LDPC codes and separately designed QC-LDPC codes over AWGN channels.