Optimal training sequence for wireless MIMO channel estimation

The capability to increase the channel capacity of wireless systems without increasing the transmit power depends on the accuracy of channel estimation at the receiver. In this paper, the problem of designing training signals is investigated for correlated and uncorrelated multi-input multioutput (MIMO) channels. For this, the optimum channel estimation is briefly addressed in the sense of mean square error. Then the optimum training signal is designed for correlated and uncorrelated channels by maximizing the mutual information (carried by training signal) between the channel and the received sequence during the training. Simulations show that employing the optimal training provides improvement as compared with employing the orthogonal training. This improvement is more significant at low SNR and for correlated channels. However, this performance gap between the optimum training and orthogonal training is negligible in a high SNR scenario or for uncorrelated channels.