Amplify and forward relay network optimization with imperfect CSI

In this paper, we consider a wireless communication with a single source node, single destination node and L number of amplify and forward (AF) relay nodes. With rayleigh channel, the communication between source node and destination node is established through relay nodes. The channel coefficient and their estimate are related by two error models namely, stochastic error model and channel time variation model. Beamforming is made at the relay nodes to increase the strength of the desired signals and coverage range of the nodes. Our proposed scheme is to optimize the beamforming and equalization coefficients by minimizing the conditional expectation of mean square error between the transmitted and received signals respectively. Here, optimization is made with imperfect channel state information. Simulation result on comparing with that of without beamforming relay strategy result in lower bit error rate. It also shows that the proposed method results with lower BER when the CSI contains time delay and estimation error.