Time-varying channel estimation for MIMO OFDM systems

Time-varying channel estimation methods for MIMO OFDM systems, based on pilot sequences, are investigated. In this paper, we assume that the channel varies in a linear fashion during a block period and express the channel impulse response (CIR) as a function of the middle impulse response and the slope of the channel variation. Hence, the channel estimation method proposed first estimates the middle CIR of the current OFDM symbol and then estimates the slope. The mean square error (MSE) part of the estimation is computed and the optimal pilot sequences which can reduce the MSE are given. The simulation results show that the proposed estimation method has good performance and the use of the optimal pilot sequences can enhance channel estimation.