Antenna Combining for Multi-Antenna Multi-Relay Channels

In this paper, the authors analyze the performance of multiple relay channels when multiple antennas are deployed only at relays. They apply two antenna diversity techniques at relays, namely Maximum Ratio Combining (MRC) on receive and Transmit Beamforming (TB). They show that for both decode-and-forward and amplify-and-forward relaying protocols, with K relays the network can be decomposed into K diversity channels each with a different channel gain, and that the signals can be effectively combined at the destination. They assume that the total number of antennas at all relays is fixed at N.