Co-Cyclic Jacket Matrix Based Optimal Training Design and Placement for MIMO OFDM Channel Estimation

This paper deals with optimal training design and placement over multiple OFDM symbols for the least squares (LS) channel estimation in multiple-input multiple- output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. When the number of transmit antennas increases, more pilot tones are required and the transmission efficiency decreases. To solve this problem, the pilot sequences are distributed over multiple OFDM symbols. Motivated by the properties of co-cyclic Jacket matrices, we derive the optimal pilot sequences from co-cyclic Jacket matrices based on the minimum mean square error (MSE) of the LS channel estimation. Simulation results show that the derived optimal pilot sequences over one, two and four OFDM symbols have the same performance, and greatly outperform the orthogonal pilot sequences in slowly time-varying channels.