Title: Design of LDPC Code for Cooperative Diversity Systems
Authors: Chuxiang Li, Guosen Yue, Mohammad Ali Khojastepour, Xiaodong Wang, Mohammad Madihian (Poster I, 10)

ABSTRACT

In this study, we treat the low-density parity-check (LDPC) code design for cooperative relay channels. The capacity of relay channels has been analyzed in current literature. How to approach such capacity with the aid of good codes is, however, a challenging problem. An efficient structure is proposed in the existing work to decouple the factor graph (FG) of B-block transmission into successive partial FGs, each of which corresponds to a two-block transmission, and then, the code design is performed over the partial FG. Based on this efficient structure, we develop the approaches to find the optimum code ensemble. In particular, we formulate the destination operations as the equivalent virtual multiple-antenna channels, and the relay operations approximately as the binary symmetric channel. Moreover, we develop the sub-optimal detector with significantly reduced complexity via Gaussian approximation to fast estimate the extrinsic mutual information of the detector output at the destination. Based on the above approximations and schemes, we can quickly analyze the performance of the LDPC-coded relay system using the extrinsic mutual information transfer (EXIT) technique. Differential evolution is employed to search for the optimum code ensemble. Extensive simulations are carried out to show the results of the optimum code design.