Efficient Feedback Mechanisms for FDD Massive MIMO under User-level Cooperation

TL;DR

This paper proposes a cooperative feedback scheme for FDD massive MIMO that leverages device-to-device communications for CSI exchange, improving interference mitigation and system performance under limited D2D capacity.

Contribution

It introduces an adaptive CSI exchange strategy using subspace projection and optimal bit partition, enhancing feedback efficiency in massive MIMO systems.

Findings

Cooperative precoder feedback outperforms traditional CSI feedback in interference mitigation.

Adaptive CSI exchange significantly improves system performance under rate-limited D2D links.

Numerical results confirm the effectiveness of the proposed scheme.

Abstract

Channel state information (CSI) feedback is a challenging issue in frequency division multiplexing (FDD) massive MIMO systems. This paper studies a cooperative feedback scheme, where the users first exchange their CSI with each other by exploiting device-to-device (D2D) communications, then compute the precoder by themselves, and feed back the precoder to the base station (BS). Analytical results are derived to show that the cooperative precoder feedback is more efficient than the CSI feedback in terms of interference mitigation. Under the constraint of limited D2D communication capacity, we develop an adaptive CSI exchange strategy based on signal subspace projection and optimal bit partition. Numerical results demonstrate that the proposed cooperative precoder feedback scheme with adaptive CSI exchange significantly outperforms the CSI feedback scheme, even when the CSI is exchanged via rate-limited D2D communications.