Relay Techniques for MIMO Wireless Networks with Multiple Source and Destination Pairs

: A multiple-input multiple-output (MIMO) relay network comprises source, relay, and destination nodes, each of which is equipped with multiple antennas. In a previous work, we proposed a MIMO relay scheme for a relay network with a single source and destination pair in which each of the multiple relay nodes performs QR decompositions of the backward and forward channel matrices in conjunction with phase control (QR-P-QR). In this paper, we extend this scheme to a MIMO relay network employing multiple source and destination pairs. Towards this goal, we use a group nulling approach to decompose a multiple S-D MIMO relay channel into parallel independent S-D MIMO relay channels, and then apply the QR-P-QR scheme to each of the decomposed MIMO relay links. We analytically show the logarithmic capacity scaling of the proposed relay scheme. Numerical examples confirm that the proposed relay scheme offers higher capacity than existing relay schemes.