PASTd-based CSI Tracking in Massive MIMO Systems

Abstract

conventional semi-blind channel estimation schemes for MU-MIMO systems are based on eigenvalue decomposition (EVD) or singular value decomposition (SVD). However, EVD- or SVD-based channel estimation would impose a high computational complexity when the base station is equipped with large number antennas. Those methods are not well suited for real-time processing, especially for Channel State Information (CSI) tracking in time-varying environments. In order to reduce the computational complexity, a PASTd-based (Projection Approximation Subspace Tracking with deflation) CSI tracking algorithm is proposed. The PASTd-based algorithm converges fast, has low computational complexity, and can operate with very small training overhead. Simulation results show that the proposed algorithm can effectively track the CS[ with mild Doppler spreads. Only one pilot symbol per user at the beginning of transmission session is needed to resolve the multiplicative factor ambiguity.