On the performance of two-way relaying with multiple-antenna relay stations

This paper considers the two-hop relaying case where two nodes S1 and S2 in a wireless network can communicate with each other via an intermediate relay station (RS). Assuming that an RS can only receive and transmit on orthogonal channel resources, the required resources in one-way amplify-and-forward relaying are doubled compared to a direct communication between two nodes. Recently, two-way relaying has been introduced as a promising protocol in order to compensate for this drawback. In this paper, the two-way relaying protocol is extended to the case of nodes and RSs with multiple antennas where both nodes S1 and S2 have the same number of antennas and the number of antennas at the RS is at least twice as much. This multiple input multiple output (MIMO) two-way relaying protocol only requires channel state information (CSI) at the RS which reduces the CSI signaling overhead in the two-way relay network compared to previous work. Comparing with other relaying protocols, the performance gain in terms of sum rate of the proposed MIMO two-way relaying protocol is verified. It is shown that the sum rate may be further increased for the case of different channel qualities on the two channels to the RS.