Adaptive MMSE channel estimation algorithms for MIMO systems

In this paper, two adaptive linear minimum mean-square error (MMSE) channel estimation algorithms for multiple-input multiple-output (MIMO) wireless communication systems are proposed. An adaptive recursive MMSE channel estimation algorithm is devised that computes the channel auto-correlation statistics and the noise variance required by the linear MMSE channel estimator without any prior knowledge. A low-complexity stochastic gradient-based MMSE channel estimation algorithm is also proposed for tracking time-varying MIMO channels. Simulation results show comparisons between the proposed algorithms, the linear least squares (LS) and the linear MMSE channel estimators, revealing that the proposed methods approach the performance of the linear MMSE estimator.