Abstract: The problem of optimal training design for channel estimation in MIMO-OFDM systems is investigated. The optimality condition and training structure based on minimizing the channel estimation MSE is analyzed, and a new training sequence is presented. This sequence combines the optimal structures of frequency division multiplexing, time division multiplexing and code division multiplexing, and retains the orthogonality in the time domain, frequency domain and space domain, thus decreasing the effect of the multiple antennas interference and reducing the channel estimation complexity effectively. With a flexible structure, it can be transformed according to channel environment, system parameters, system performance, etc.

Key words: MIMO-OFDM, training sequence, time division multiplexing, frequency division multiplexing, code division multiplexing