Training-based estimation of spatially correlated channels in AF MIMO multi-relay systems using LMMSE criterion
Jae‐Mo Kang, Jae‐Hwan Lee, Hyung-Myung Kim · International Conference on Telecommunications · 2015
This paper considers a training-based channel estimation problem for two-hop AF relay systems in the presence of spatial fading correlation, where the system consists of one source, one destination and multiple relays and each node is equipped with multiple antennas. We first derive an estimator of overall cascade channel based on the LMMSE criterion. To further enhance the estimation accuracy, the source training signal, relay precoding matrices and relay amplification parameters are then optimized to minimize the MSE of the LMMSE channel estimator under training power constraint and relay power constraints. We obtain optimal structures of the MSE-minimizing training signal and relay precoding matrices. Also, an iterative scheme and a closed-form suboptimal scheme for training and relay power allocation are presented. Simulation result shows that the proposed schemes considerably outperform the conventional schemes in terms of the estimation MSE, and the closed-form suboptimal training scheme provides comparable performance to that of the iterative one.