Joint data detection and channel estimation for MIMO-OFDM systems via EM algorithm and sphere decoding

We consider joint data detection and channel estimation for Multiple-input Multiple-output Orthogonal Frequency Division Multiplexing systems. The Expectation Maximization algorithm is employed to capture the dynamics of a time-varying fading channel and also to recover the channel input. This is done iteratively: channel estimates are updated in the E-step, whilst the Sphere Decoding algorithm is used in the M-step to realize data recovery. Initial channel estimates are obtained through the use of a small number of pilot symbols. We show by simulation that the performance of the proposed algorithm can approach coherent detection with reasonable computational complexity.