An Iterative Detection/Decoding Algorithm of Correlated Sources for the LDPC-Based Relay Systems

An iterative detection/decoding algorithm of correlated sources for the LDPC-based relay systems is presented. The signal from the source-destination (S-D) link is formulated as a highly correlated counterpart from the relay-destination (R-D) link. A special XOR vector is defined using the correlated hard decision information blocks from two decoders and the extrinsic information exchanged between the two decoders is derived by the log-likelihood ratio (LLR) associated with the XOR vector. Such the decoding scheme is different from the traditional turbo-like detection/decoding algorithm, where the extrinsic information is computed by the side information and the soft decoder outputs. Simulations show that the presented algorithm has a slightly better performance than the traditional turbo-like algorithm (Taking the (255,175) EG-LDPC code as an example, it achieves about 0.1dB performance gains around BLER=10-4). Furthermore, the presented algorithm requires fewer computing operations per iteration and has faster convergence rate. For example, the average iteration of the presented algorithm is 33 at SNR=1.8dB, which is about twice faster than that of the turbo-like algorithm, when decoding the (961,721) QC-LDPC code. Therefore, the presented decoding algorithm of correlated sources provides an alternative decoding solution for the LDPC-based relay systems.