Performance Analysis of Active RIS-aided Systems in the Face of Imperfect CSI and Phase Shift Noise

TL;DR

This paper develops a comprehensive performance analysis of active RIS-assisted wireless systems considering practical impairments like imperfect CSI and phase noise, providing closed-form expressions for outage probability and capacity.

Contribution

It introduces a new LMMSE estimator for active RIS systems and derives analytical performance metrics accounting for realistic noise and estimation errors.

Findings

RIS amplifiers effectively increase transmit power.

Channel estimation errors degrade system performance.

Phase shift noise impacts capacity and outage probability.

Abstract

The linear minimal mean square error (LMMSE) estimator for active reconfigurable intelligent surface (RIS)-aided wireless systems is formulated. Furthermore, based on the moment-matching method, we employ the Gamma distribution to approximate the distribution of the instantaneous received signal-to-interference-plus-noise ratio (SINR), and then derive the closed-form outage probability and ergodic channel capacity in the presence of realistic channel estimation errors, the thermal noise of RIS amplifiers and the RIS phase shift noise. Our theoretical analysis and simulation results show that the introduction of RIS amplifiers is equivalent to increasing of the transmit power, and also present the performance degradation resulting from the channel estimation error and the RIS phase noise.