An iterative synchronization scheme for multi-user MIMO systems

In multi-user multi-input multi-output (MIMO) systems, multiple timing and frequency offsets may occur in the procedure of synchronization. Conventional MIMO synchronization methods deal with timing and frequency offsets separately. In fact, these methods can not achieve the best performances because the unknown parameters will interfere with each other. In this paper, we propose a joint timing-frequency offsets and channel estimation method in multi-user MIMO systems. Based on a maximum-likelihood (ML) estimation model, an iterative space-alternating generalized expectation-maximization (SAGE) estimator is adopted to solve the multi-dimensional extreme-value problem. Simulations show that the performances of the proposed scheme are better than the conventional method.