MIMO channel estimation in correlated fading environments

Pilot aided channel estimation is considered for wireless MIMO systems in the presence of fading correlation. Assuming a linear minimum mean squared error based channel estimator, we study statistical shaping of the training sequence via a matrix prefilter depending on the correlation properties of the channel. The new scheme is a general concept that can readily be applied to smart antenna multiple-input single-output systems. Furthermore, in a quasi-stationary environment with limited mobility, it requires only a long-term update interval of the prefilter, thus admitting its use in FDD systems with a low-rate feedback link for the correlation matrices. Simulation results of a MIMO system with maximum eigenmode transmission, including realistic channel estimation, demonstrate the effectiveness of the proposed scheme with a significant SNR gain.