An LMMSE receiver scheme for amplify-and-forward relay systems with imperfect channel state information

In realistic cases, imperfect channel state information (CSI) occur either due to an imperfect channel estimation algorithm or due to fast changing channel. In this paper, we investigate the effect of channel estimation error on the linear minimum mean square error (LMMSE) receiver in amplify-and-forward (AF) relay systems. We derive the mathematical forms of the LMMSE receiver in the presence of channel estimation error and introduce a novel receiver structure for AF relay systems, which consider the channel estimation error as a part of the total equivalent noise power on the LMMSE receiver. In order to illustrate the performance gains brought by the proposed receive scheme, received data mean square error (MSE) in the situations of channel estimation error considered and non-considered are compared. At the end of this paper, simulation results of bit error rate (BER) performance are presented to validate our theoretical analysis.