Energy Efficiency Analysis of Intelligent Reflecting Surface System with Hardware Impairments

TL;DR

This paper analyzes the energy efficiency of intelligent reflecting surface (IRS) systems considering hardware impairments, deriving optimal beamforming, asymptotic capacity, and bounds, showing IRS can achieve high efficiency with moderate hardware quality.

Contribution

It introduces a comprehensive energy efficiency analysis of IRS systems accounting for hardware impairments, including optimal beamforming and capacity bounds.

Findings

IRS can achieve high spectral and energy efficiency with moderate antennas.

Hardware impairments significantly affect system performance.

Optimal beamforming enhances energy efficiency in practical IRS systems.

Abstract

Recently, as explosive growth of mobile data traffic, the performance of wireless communication systems requires to be enhanced significantly in future. Intelligent reflecting surface (IRS) can be used as a promising way to improve the energy efficiency of wireless communications with less complexity and hardware cost. Most existing studies consider the cases with ideal hardware, however, both physical transceiver and IRS suffer from non-negligible hardware impairments which may greatly degrade the system performance. In this paper, by taking hardware impairments into consideration, we focus on the energy efficiency analysis of IRS system. Our first contribution is to derive the optimal receive combining and transmit beamforming vectors. After that, we characterize the asymptotic channel capacity. With the derived asymptotic channel capacity and the power consumption model, the analytical upper and lower bounds of energy efficiency are provided. Our results show that an IRS system can achieve both high spectral efficiency and high energy efficiency with moderate number of antennas. This observation is encouraging for that there is no need to cost a lot on expensive high-quality antennas, which corresponds to the requirements of new communication paradigms.