Joint receiver-and-collaborative beamforming for the multi-user relay network in the uplink

In this paper, the problem of receiver-and-collaborative beamforming is considered for a network which consists of K single-antenna transmitters, R single-antenna relay nodes, and a destination base station equipped with N antennas. For such network, we propose two different design approaches. In the first approach, we jointly design the two beamformers aiming to minimize the total transmit power of the relay nodes, while maintaining the quality of service (QoS) at a predefined level. We apply the genetic algorithm (GA) to obtain the receiver equalizer and relay weight. In the second approach, we design the beamformer by maximizing the smallest SINR_k at the receiver subject to the total relay power constraint. The GA is used iteratively to optimize the relay weight and equalizer matrix at the relay nodes and the receiver equalizer. Simulation results demonstrate that significant performance improvements are achieved by our proposed schemes as compared with the existing solutions.