Robust Successive Compute-and-Forward Over Multiuser Multirelay Networks

This paper develops efficient compute-and-forward (CMF) schemes in multiuser multirelay networks. To solve the rank failure problem in CMF setups and to achieve full diversity of the network, we introduce two novel CMF methods, namely, extended CMF and successive CMF. The former, having low complexity, is based on recovering multiple equations at relays. The latter utilizes successive interference cancelation (SIC) to enhance system performance compared with the state-of-the-art schemes. Both methods can be utilized in a network with different number of users, relays, and relay antennas, with negligible feedback channels or signaling overhead. We derive new concise formulations and explicit framework for the successive CMF method, as well as an approach to reduce its computational complexity. Our theoretical analysis and computer simulations demonstrate the superior performance of our proposed CMF methods over the conventional schemes. Furthermore, based on our simulation results, the successive CMF method yields additional signal-to-noise ratio (SNR) gains and shows considerable robustness against channel estimation error (CEE), compared with the extended CMF method.