Joint Beamforming for Intelligent Reflecting Surface-Assisted Millimeter Wave Communications

Abstract

Millimeter wave (mmWave) communications are evolving as a promising technology to meet the ever increasing data rate requirements. However, high directivity and severe path loss make it vulnerable to blockages, which could be frequent in indoor or urban environments. To address this issue, intelligent reflecting surfaces (IRSs) are introduced to provide additional adjustable reflected paths. Most prior works assume that elements of IRSs have an infinite phase resolution, which is difficult to be realized in practical systems. In this paper, IRSs with low-resolution phase shifters are considered. We aim to maximize the receive signal power at the user by jointly optimizing discrete phase shifts of IRSs and the transmit beamforming vector at the base station for mmWave downlink systems. An analytical near-optimal solution is developed by exploiting some important characteristics of mmWave channels. Our theoretical analysis reveals that low-resolution phase shifters can still achieve a receive signal power that increases quadratically with the number of reflecting elements. Simulation results are provided to corroborate our analysis and show the effectiveness of the proposed solution.

IRS-Assisted Millimeter Wave Communications: Joint Power Allocation and Beamforming Design

“…In IRS-assisted systems with mmWave, in addition to sumrate optimization of multiple users addressed in our paper and [9], [23], many other problems have also been investigated in the literature, including information rate maximization of one user in [26]- [28], channel estimation in [29]- [31], and positioning in [32], [33].…”

mmWave Doubly-Massive-MIMO Communications Enhanced with an Intelligent Reflecting Surface

“…When N r increases from 8 to 36 and N t increases from 8 to 64, Fig. 5 plots analytical results based on (23) and Monte Carlo simulation results for different values of distances, namely, D 1 = 2, 25, 45 . It can be seen from this figure that when the IRS is close to the transmitter or the receiver, the system has better rate performance.…”

“…To date, there are a few works that investigate IRS-aided mmWave MIMO systems for both single-user and multi-user scenarios, and with one or multiple IRSs. These works were concerned with rate optimization [19]- [21], joint active and passive beamforming design [22], [23], joint power allocation and beamforming design [24], hybrid beamforming design [25], [26], and channel estimation [27].…”

High-Resolution Channel Estimation for Intelligent Reflecting Surface-Assisted MmWave Communications

“…Specifically, IRS, acting as a planar array, is composed of a large number of low-cost passive reflective elements, which can smartly steer the incident signals towards the dedicated directions via a software-controlled manner [6]. Most recently, IRS is also considered as an energy-efficient solution to combat the blockage of mmWave communications by creating the virtual light-of-sight (LOS) path [7]- [9]. Specifically, the authors in [7]- [9] investigated the joint beamforming issue and verified that the presence of IRS can improve the mmWave coverage obviously.…”

“…Most recently, IRS is also considered as an energy-efficient solution to combat the blockage of mmWave communications by creating the virtual light-of-sight (LOS) path [7]- [9]. Specifically, the authors in [7]- [9] investigated the joint beamforming issue and verified that the presence of IRS can improve the mmWave coverage obviously. However, most of these works are based on the assumption of perfect channel state information (CSI), while CSI acquirement is actually a very challenging task, especially for IRS-assisted mmWave communications.…”