Channel Estimation for FDD Massive MIMO OFDM Systems

摘要

For frequency-division duplexing (FDD) massive multiple-input multiple-output (MIMO) systems, it is challenging for the base station (BS) to acquire downlink channel state information (CSI) since the number of channel parameters is proportional to the number of BS antennas. To reduce the downlink training and the uplink feedback overhead for orthogonal frequency-division multiplexing (OFDM)-based FDD massive MIMO systems, we propose an effective and practical downlink channel estimation approach that does not require statistical information of the channels. In the proposed method, we parameterize the wideband MIMO channel by a limited number of distinct paths, each characterized by path delay, path angle and path gain. Based on this parametric channel model, we first estimate the reciprocal channel properties, i.e., the number of paths, path delays and path angles at the BS in uplink, and then estimate the non-reciprocal channel properties, i.e., the path gains at the user-side in downlink. A compressive sensing (CS)-based algorithm is proposed to obtain the estimates of the path number and the path delays, and based on these estimates, a low- complexity algorithm is presented to estimate the path angles. Simulation results demonstrate that the proposed method can provide reliable channel estimation for FDD massive MIMO OFDM systems.