Beamforming and combining based on estimated channels in cooperative relay networks

In this paper, we study an amplify-and-forward (AF) based multiple-input multiple-output (MIMO) cooperative relay network in which beamforming is done by using estimated channels in a Rayleigh fading environment. A protocol for training of the source, relay and destination is described and methods of channel estimation are proposed. Simulation results show that the trained MIMO relay system based on beamforming outperforms the trained MIMO relay system without beamforming. It is also shown that the performance of the beamforming based MIMO relay system improves with increase in the number of receive antennas at the destination. We analyze the symbol error rate (SER) versus signal-to-noise ratio (SNR) performance of beamforming based AF relaying with perfect channel knowledge at the source, relay, and destination. An expression of the moment generating function (m.g.f.) of the received instantenous SNR at the destination is derived. By using this m.g.f., an exact expression for the SER of M-ary phase-shift keying is obtained.