Two-way relaying based two-hop two-user MIMO system

Two-way relaying is the one of the solutions to mitigate the loss in spectral efficiency due to the half-duplex transmission in the multi-hop communication. In this paper we propose a simple two-way relaying scheme for the two-hop two-user multiple input multiple output (MIMO) system. In this system, a base station and a relay station (RS), both equipped with two antennas, form a point-to-point MIMO channel while RS and two single-antenna mobile users form a point-to-multipoint multiuser MIMO channel. Based on the proposed scheme, we also propose optimal power allocation algorithm at RS. Through the numerical examples, we show that our proposed scheme achieves significant sum rate gain compared to the one-way relaying scheme and its performance gain increases as the distance between RS and both users becomes closer.