User Selection Methods for Multiuser Two-Way Relay Communications Using Space Division Multiple Access

In this paper, we design a multiuser two-way relay system using space division multiple access (SDMA) communications and devise an optimal scheduling method that maximizes the sum rate while ensuring fairness among users. To reduce the computational load at the relays, we propose rate- and angle-based suboptimal scheduling methods. The numerical results illustrate tradeoff between complexity and the performance. Specifically, when the relay has two antennas, we verify that the rate- based method can provide significant computational savings at the cost of a rate reduction of less than 4% when compared with the optimal scheduling method.