Multi-Hop Collaborative Relay Beamforming

In this paper, we consider a three-hop multi-relay network with one transmitter, one receiver and two clusters of relay nodes. With the aid of perfect channel state information (CSI), two different design approaches are devised. In the first approach, we aim to maximize the received signal to noise ratio (SNR) under different transmit power constraint at the relay nodes by performing optimization on the beamforming vectors of the two clusters jointly, whilst in the second design, the total transmit power of the relay nodes is minimized under the QoS constraint at the receiver. It is shown that, in both approaches, upon the coefficients of either one cluster being determined, the other one could be optimized, and therefore the overall optimization problem can be resorted to an efficient iteration process. Simulation results show that our proposed approaches outperform the existing solutions for improved energy efficiency and increased receiving SNR.