Beamforming for Dual-Hop MIMO AF Relay Networks with Channel Estimation Error and Feedback Delay

This paper concerns the beamforming (BF) design for a dual-hop multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay network. Both a general antenna configuration and imperfect channel state information are taking into consideration, where multiple antennas are deployed at the source, relay, and destination, channel impairments exist at the source-relay and relay-destination hops. The BF scheme is optimized to maximize the received signal-to-noise ratio (SNR). In order to evaluate the performance of the relay network, asymptotic average symbol error rate (ASER) at high SNR is derived. Computer simulations are conducted to show the superiority of the designed BF scheme and the impacts of channel impairments and antenna configurations on the performance of the MIMO AF relay systems. It is shown that the diversity order of the relay network can be reduced to one due to the channel impairments.