A new joint symbol detection and channel estimation algorithm was proposed for MIMO-OFDM systems over the time-varying fading channel based on the variational Bayes expectation maximization algorithm and Turbo principle.The channel estimation error covariance matrix was considered in the soft-input soft-output detector which circumvented the undesirable exhaustive search via list sphere decoder（LSD）.In addition

a novel Kalman forward-backward channel estimator was derived based on the posterior distributions of the transmitted symbols which were obtained from the space-time detection.Simulation results show that the proposed algorithm has more robust performance than the conven-tional EM algorithm and decision-directed technique in the time varying multipath channel.