A protocol based on D2D cooperation for FDD massive MIMO communications without instantaneous CSI feedback

Abstract

We propose a novel protocol for fast fading massive MIMO systems in Frequency Division Duplex (FDD) mode and, in general, non-reciprocal channels. Our approach relies on Device-to-Device (D2D) cooperation to avoid instantaneous channel state information (CSI) feedback, unaffordable in practical systems. This protocol assumes that clusters of user terminals (UT) cooperate to create virtual MIMO at a target UT via D2D cooperation. The base station (BS) has statistical knowledge of the downlink channel and it is aware of the cooperation but it is oblivious of the statistics of the D2D links and the transmitter is designed based on the downlink channel statistics solely. The performance of the proposed protocol is analyzed and compared to state-of-art schemes based on instantaneous CSI feedback.