Joint Relay and User Selection for Two-hop Multi-relay Multi-user MIMO Systems

In this work, we investigate the joint relay and user selection problem in two different multi-relay multi-user MIMO transmission modes, namely, an existing competition mode and a proposed cooperation mode. Each user is served by a single relay in competition mode while multiple users are served by active relays cooperatively in cooperation mode. Due to the high computational complexity of the optimal exhaustive enumeration algorithm, we propose a suboptimal capacity-based best-fit algorithm, which achieves above 86% and 89% of the system capacity of the optimal algorithm in competition and cooperation mode, respectively, while the computational complexity is linear with the number of relays and users in the system. Our simulation results also show that the proposed cooperation transmission mode has a better system performance than competition mode when signal-to-noise ratio is high.