Factor graph EM algorithm for joint channel tracking and MAP detection of MIMO-OFDMA in fading channels

Based on the expectation maximization (EM) algorithm, a joint channel tracking and maximal a posteriori symbol detection method is proposed for orthogonal frequency division multiple access systems employing multiple transmit and receive antennas (MIMO). Using the Forney-style factor graph (FFG), a forward-and-backward signal processing method is developed to recursively solve the EM problem for joint estimation and detection (JED) in MIMO fading channels. By proper message scheduling and passing over the FFG, simulations show that the proposed algorithm is effective for joint MIMO channel tracking and symbol detection in fast fading channels.