Quantize-and-Forward Schemes for the Orthogonal Multiple-Access Relay Channel

Abstract

The multiple-access relay channel with two sources, a single relay, and one destination is considered. Under the assumption of noisy source–relay links causing the relay to be unable to decode without error, we propose a framework for designing one- and two-dimensional quantizers for quantizing the soft information at the relay. These quantizers are mutualinformation preserving. Simulation results show a) that mutualinformation preserving quantization schemes outperform techniques in which the soft information is forwarded in an analog fashion to the destination, b) that two-dimensional quantization outperforms one-dimensional quantization for source–relay links of different quality, and c) that diversity order of two can be gained in block Rayleigh fading channels by having the relay adaptively select a two-dimensional quantizer from a fixed set of quantizers shared with the destination, depending on the channel state on the source–relay links