Cooperative beamforming with link‐adaptive regenerative relays

This paper examines a new beamforming method, and detector for a multi‐relay system is proposed, in which the signals from relays, and direct link are combined to achieve optimal performance. Relays employ link‐adaptive regeneration relaying method to scale their decoded symbols before retransmitting them in order to alleviate the error propagation. The scaling is adapted with the signal‐to‐noise ratio of the source‐relay, and the intended relay‐destination links. In the proposed beamforming scheme, two‐bit quantized phase information of the channel gain between the relay, and destination is used to retransmit decoded symbols at relays. It is analytically shown that the proposed method achieves full diversity order. Numerical results show a close match between simulation, and analytical derivations.