Enhanced-rate Iterative Beamformers for Active IRS-assisted Wireless Communications

TL;DR

This paper introduces three novel iterative beamforming methods for active IRS-assisted wireless networks, significantly improving achievable rates over existing passive IRS and other beamforming techniques.

Contribution

It proposes three enhanced-rate iterative beamforming algorithms, including Max-SSNR-RR, GMRR, and Max-SNR-FP, for active IRS to boost wireless communication rates.

Findings

All three methods outperform passive IRS and existing beamforming techniques.

Max-SNR-FP achieves the highest rate among the proposed methods.

Simulation results confirm substantial rate enhancements with the new algorithms.

Abstract

Compared to passive intelligent reflecting surface (IRS), active IRS is viewed as a more efficient promising technique to combat the double-fading impact in IRS-aided wireless network. In this paper, in order to boost the achievable rate of user in such a wireless network, three enhanced-rate iterative beamforming methods are proposed by designing the amplifying factors and the corresponding phases at active IRS. The first method, maximizing the simplified signal-to-noise ratio (Max-SSNR) is designed by omitting the cross-term in the definition of rate. Using the Rayleigh-Ritz (RR) theorem, Max-SSNR-RR is proposed to iteratively optimize the norm of beamforming vector and its associated normalized vector. In addition, generalized maximum ratio reflection (GMRR) is presented with a closed-form expression, which is motivated by the maximum ratio combining. To further improve rate, maximizing SNR (Max-SNR) is designed by fractional programming (FP), which is called Max-SNR-FP. Simulation results show that the proposed three methods make an obvious rate enhancement over Max-reflecting signal-to-noise ratio (Max-RSNR), maximum ratio reflection (MRR), selective ratio reflecting (SRR), equal gain reflection (EGR) and passive IRS, and are in increasing order of rate performance as follows: Max-SSNR-RR, GMRR, and Max-SNR-FP.