Joint network-channel coding for the asymmetric multiple-access relay channel

In this paper we consider the time-division multiple-access relay channel (MARC). We propose a low-complexity compress-and-forward-based transmission scheme that consists of a scalar quantization of log-likelihood ratios (LLRs), followed by a suitably defined network code. This scheme is well suited also for asymmetric source-relay channel conditions. We use the information bottleneck method (IBM) for designing the LLR quantizers and we propose a modified IBM algorithm with more favorable numerical properties. Finally, we assess the performance of the proposed scheme in AWGN and fading channels using numerical simulations, including a comparison with existing transmission schemes.