A Simple Algebraic Channel Estimation Method for FDD Massive MIMO Systems

Downlink (DL) channel estimation from nonorthogonal training is a problem of importance in frequency division duplex based massive MIMO systems. In this paper, we propose a novel channel estimation framework to address this problem. Specifically, a structural training sequence that imposes a tensor structure on the received signal is proposed. We show that with such a training sequence, the multipath parameters of DL channels can be provably identified even when the number of paths largely exceeds the number of receive antennas - under very small training overhead. Moreover, the proposed approach does not involve any hard optimization but very lightweight algebraic operations. Simulation results are carried out to showcase the effectiveness of the proposed algorithm.