On the Performance of Independently Designed LDPC Codes for the Relay Channel

A decode-and-forward LDPC-based coding and decoding scheme is proposed and applied to the BAWGN single-relay channel. The source broadcasts information to both the relay and the destination. The relay is able to simultaneously receive and transmit. Both the relay and the destination apply successive iterative decoding using belief propagation. In the proposed scheme, the LDPC code used by the source and the LDPC code used by the relay are designed independently of each outer: optimality properties of this approach are established via information-theoretic upper and lower bounds. Asymptotic analysis shows that the performance of the proposed scheme can be as close as 0.02 dB away from the theoretical limit for any decode-and-forward scheme, and simulation results show that its performance for a block code of length 2¹⁴ can be within 0.55 dB away from the same limit with a corresponding bit error probability of ~10^-6