Energy Efficiency Analysis of IRS-aided Wireless Communication Systems Under Statistical QoS Constraints: An Information-Theoretic Perspective

TL;DR

This paper analyzes the energy efficiency of IRS-assisted wireless systems under statistical QoS constraints, revealing how IRS deployment and channel conditions impact energy and spectral efficiency tradeoffs in low-SNR regimes.

Contribution

It provides an information-theoretic analysis of energy efficiency under QoS constraints, deriving minimum bit energy and characterizing spectral efficiency tradeoffs with IRS deployment.

Findings

Energy efficiency can approach unconstrained systems at low SNR.

Large IRS elements significantly reduce energy consumption in low-power regimes.

Sparse multipath fading improves effective capacity without increasing minimum bit energy.

Abstract

This paper investigates the information-theoretic energy efficiency of intelligent reflecting surface (IRS)-aided wireless communication systems, taking into account the statistical quality-of-service (QoS) constraints on delay violation probabilities. Specifically, effective capacity is adopted to capture the maximum constant arrival rate that can be supported by a time-varying service process while fulfilling these statistical QoS requirements. We derive the minimum bit energy required for the IRS-aided wireless communication system under QoS constraints and analyze the spectral efficiency and energy efficiency tradeoff at low but nonzero signal-to-noise ratio (SNR) levels by also characterizing the wideband slope values. Our analysis demonstrates that the energy efficiency for the considered system under statistical QoS constraints can approach that for a system without QoS limitations in the low-SNR regime. Additionally, deploying a sufficiently large number of practical IRS reflecting elements can substantially reduce energy consumption required to achieve desired spectral efficiency performance in the low-power regime, even with limited bit-resolution phase shifters. Besides, we reveal that compared with the results applied to the low-power regime, higher effective capacity performance can be achieved in scenarios with sparse multipath fading while achieving the same minimum bit energy in the wideband regime.