Downlink Channel Estimation Based on Multipath Separation in an FDD MIMO System

Abstract

Although TDD has been mainly considered for massive MIMO systems, many traditional systems have been operating in FDD, and FDD may generally be more effective for delay-sensitive applications. In this paper, we present downlink channel acquisition with a few pilot symbols. At a base station (BS), we estimate delays and angles-of-arrival (AOAs) of multipath components using a compressed sensing technique. The BS transmits pilot symbols from a single antenna or two, and user equipment (UE) feeds back the downlink channels to the BS. Using the delays, AOAs, and the downlink channels fed back from the UE, we estimate all the remaining downlink channels. It is shown that the proposed method reveals excellent downlink channel estimation performance.