Performance Analysis of Wireless Network Aided by Discrete-Phase-Shifter IRS

TL;DR

This paper analyzes the performance degradation caused by discrete phase quantization in IRS-assisted wireless networks, deriving closed-form expressions for key metrics and showing that performance loss diminishes with more quantization bits.

Contribution

It provides the first comprehensive closed-form analysis of SNR, achievable rate, and BER loss due to phase quantization in IRS with both LoS and Rayleigh channels, including approximate formulas.

Findings

Performance loss decreases with more quantization bits.

Performance loss increases with more IRS phase shifter elements.

Quantization bits ≥ 3 result in negligible performance degradation.

Abstract

Discrete phase shifters of intelligent reflecting surface (IRS) generates phase quantization error (QE) and degrades the receive performance at the receiver. To make an analysis of the performance loss caused by IRS with phase QE, based on the law of large numbers, the closed-form expressions of signal-to-noise ratio (SNR) performance loss (PL), achievable rate (AR), and bit error rate (BER) are successively derived under line-of-sight (LoS) channels and Rayleigh channels. Moreover, based on the Taylor series expansion, the approximate simple closed form of PL of IRS with approximate QE is also given. The simulation results show that the performance losses of SNR and AR decrease as the number of quantization bits increase, while they gradually increase with the number of IRS phase shifter elements increase. Regardless of LoS channels or Rayleigh channels, when the number of quantization bits is larger than or equal to 3, the performance losses of SNR and AR are less than 0.23dB and 0.08bits/s/Hz, respectively, and the BER performance degradation is trivial. In particular, the performance loss difference between IRS with QE and IRS with approximate QE is negligible when the number of quantization bits is not less than 2.