On the physical layer network coded LDPC codes for a multiple-access relaying system

In this paper we propose a novel network coded LDPC code design for a multiple-access relay channel (MARC). We first investigate the achievable rate region for the MARC. Then we propose a novel physical layer network coded (PNC) LDPC code structure, named PNC-LDPC code. Next, an iterative detection-and-decoding receiver is designed to deal with the multi-user interference at the destination. Based on the code structure and the iterative receiver, we optimize the degree distribution of the PNC-LDPC code to approach the system achievable rate by utilizing the extrinsic mutual information transfer (EXIT) chart. Simulations show that the performance of our PNC-LDPC code, with a code length of 10000, at the destination, is 1:5 dB away from the capacity.