Device-to-device Cooperation in Massive MIMO Systems with Cascaded Precoding

TL;DR

This paper explores user cooperation in massive MIMO systems with cascaded precoding, proposing a decoding codebook scheme that enhances capacity without requiring channel state information, leveraging device-to-device links.

Contribution

It introduces a decoding codebook-based user cooperation scheme that reduces information sharing and bandwidth needs in massive MIMO systems with cascaded precoding.

Findings

User cooperation improves system capacity.

The proposed scheme operates without channel state information.

Bandwidth requirements for cooperation are analyzed.

Abstract

This paper investigates user cooperation in massive multiple-input multiple-output (MIMO) systems with cascaded precoding. The high-dimensional physical channel in massive MIMO systems can be converted into a low-dimensional effective channel through the inner precoder to reduce the overhead of channel estimation and feedback. The inner precoder depends on the spatial covariance matrix of the channels, and thus the same precoder can be used for different users as long as they have the same spatial covariance matrix. Spatial covariance matrix is determined by the surrounding environment of user terminals. Therefore, the users that are close to each other will share the same spatial covariance matrix. In this situation, it is possible to achieve user cooperation by sharing receiver information through some dedicated link, such as device-to-device communications. To reduce the amount of information that needs to be shared, we propose a decoding codebook based scheme, which can achieve user cooperation without the need of channel state information. Moreover, we also investigate the amount of bandwidth required to achieve efficient user cooperation. Simulation results show that user cooperation can improve the capacity compared to the non-cooperation scheme.