EM-based Channel Estimation for MIMO OFDM System

In this paper, a low complexity adaptive EM-based channel estimation algorithm is proposed for Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems in slow time-varying frequency selective environment. The proposed algorithm was an adaptive channel estimation technique based on an expectation maximization (EM) algorithm for space-time block coded (STBC) MIMO OFDM systems. Simulation results show that in slow fading environment there was no degradation in normalized mean square error (MSE) as we increased the number of users. Comparing the Recursive Least-Squares (RLS) algorithm, the proposed algorithm exploits the structure of Alamouti STBC codes to reduce computational complexity.