Iterative network/channel decoding for the noisy multiple-access relay channel (MARC)

In this paper, we study the three-node multiple-access relay channel under realistic operating conditions. More specifically, in our setup all wireless links are subjected to Rayleigh fading and Gaussian noise, and the relay node can be located at different distances from source and destination nodes. We assume that coded bits are fully-interleaved, so that the transmitted symbols are mutually independent. By exploiting factor graph representation, we propose a joint network/channel decoding algorithm, which takes into account decoding errors introduced by the relay node. The convergence of the proposed iterative decoding algorithm is studied through EXIT chart analysis. The proposed decoder is compared with a recently proposed algorithm, which employs the demodulate-and-forward protocol and works on coded bits, and it is shown that it provides better performance. More specifically, for a bit error rate (BER) equal to 1e-3, it is 1.5dB better when the relay is located near the destination and 2.0dB better when the relay is in between source and destination.