Beamforming with quantized feedback to increase diversity of relay channels

In this paper, beamforming schemes that maximize diversity of the relay systems for amplify and forward (AF) and decode and forward (DF) methods are presented. For fading relay channels, these schemes are simulated with the relays having partial (quantized) information of the relay-destination channel, and compared to complete information case. Under utilized quantization process, phases and amplitudes of the channel fading coefficients are fed back to the relays in different number of bits. Phase information of the channel coefficients appear to be more crucial for both AF and DF methods. While the beamforming scheme for AF results in roughly full diversity order, the scheme for DF cannot achieve full diversity order because of its dependence to the decoding errors made at the relays.