Zero Forcing Uplink Detection through Large-Scale RIS: System Performance and Phase Shift Design

TL;DR

This paper analytically evaluates the performance of a large-scale RIS-assisted MIMO system using zero-forcing detection, providing closed-form outage expressions and an efficient phase shift design adaptable to different CSI conditions.

Contribution

It introduces a novel phase shift design method for LRIS that scales linearly with passive elements and antennas, applicable to both instantaneous and statistical CSI scenarios.

Findings

Closed-form outage probability expressions derived for various configurations.

The proposed phase shift design improves system performance with linear complexity.

Insights on the impact of fading, CSI accuracy, and array size on system reliability.

Abstract

A multiple-input multiple-output wireless communication system is analytically studied, which operates with the aid of a large-scale reconfigurable intelligent surface (LRIS). LRIS is equipped with multiple passive elements with discrete phase adjustment capabilities, and independent Rician fading conditions are assumed for both the transmitter-to-LRIS and LRIS-to-receiver links. A direct transceiver link is also considered which is modeled by Rayleigh fading distribution. The system performance is analytically studied when the linear yet efficient zero-forcing detection is implemented at the receiver. In particular, the outage performance is derived in closed-form expression for different system configuration setups with regards to the available channel state information (CSI) at the receiver. In fact, the case of both perfect and imperfect CSI is analyzed. Also, an efficient phase shift design approach at LRIS is introduced, which is linear on the number of passive elements and receive antennas. The proposed phase shift design can be applied on two different modes of operation; namely, when the system strives to adapt either on the instantaneous or statistical CSI. Finally, some impactful engineering insights are provided, such as how the channel fading conditions, CSI, discrete phase shift resolution, and volume of antenna/LRIS element arrays impact on the overall system performance.