Applying Relay Stations with Multiple Antennas in the One- and Two-Way Relay Channel

This paper considers the two-hop relaying case with bidirectional communication of two nodes 51 and 52 via an intermediate relay station (RS). The RS is equipped with multiple antennas and channel state information is available at the RS. Either the multiple antennas can be used to achieve spatial diversity by applying receive and transmit maximum ratio combining (MRC) at the RS in a one-way relaying approach where up- and downlink are transmitted on orthogonal channel resources, or they can be used to apply the recently introduced multiple input multiple output (MHVIO) two-way relaying. In MIMO two-way relaying, the number of required channel resources is reduced since up- and downlink are transmitted on the same channel resources. In this paper, it is investigated which approach provides a better average and outage performance, respectively. Concerning the average performance, MIMO two-way relaying always outperforms MRC one-way relaying. However, the outage performance in MIMO two-way relaying significantly depends on the choice of the linear filter at the RS. MIMO two-way relaying with a linear zero forcing filter provides a worse outage performance than MRC one-way relaying while MIMO two-way relaying with a linear minimum mean square error filter outperforms MRC one-way relaying.