Designs of Training Signals for Spatially Correlated Multi-User MIMO-OFDM

Optimal training design and channel estimation for spatially correlated multi-user multi-input multi-output with orthogonal frequency-division multiplexing (MIMO-OFDM) systems is still an open research topic of great interest. This paper applies tractable semi-definite programming to obtain the optimal training signal for the general case of spatial channel correlations for multi-user MIMO-OFDM. The optimal solution in closed-form expression is also derived for a special case of transmit correlations. Analytical and simulation results demonstrate the excellent performance of the proposed designs and their performance advantage over the equi-powered training designs.