Hybrid Beamforming for Reconfigurable Intelligent Surface based Multi-User Communications: Achievable Rates With Limited Discrete Phase Shifts

By Boya Di, Hongliang Zhang, Lingyang Song, Yonghui Li, Zhu Han, H. Vincent Poor. IEEE Journal on Selected Areas in Communications, 2019

496 citations recorded by the source corpus.

Reconfigurable intelligent surfaces (RISs) have drawn considerable attention from the research community recently. RISs create favorable propagation conditions by controlling the phase shifts of reflected waves at the surface, thereby enhancing wireless transmissions. In this paper, we study a downlink multi-user system where the transmission from a multi-antenna base station (BS) to various users is achieved by an RIS reflecting the incident signals of the BS towards the users. Unlike most existing works, we consider the practical case where only a limited number of discrete phase shifts can be realized by a finite-sized RIS. A hybrid beamforming scheme is proposed and the sum-rate maximization problem is formulated. Specifically, continuous digital beamforming and discrete RIS-based analog beamforming are performed at the BS and the RIS, respectively, and an iterative algorithm is designed to solve this problem. Both theoretical analysis and numerical validations show that the RIS-based system can achieve good sum-rate performance by setting a reasonable size of the RIS and a small number of discrete phase shifts.

Subfields: Aerospace Engineering, Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/2a23b3010cad847e3b114f2622c740b35b0c1e3d

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Citations in the corpus

Reconfigurable Intelligent Surfaces Assisted Communications With Limited Phase Shifts: How Many Phase Shifts Are Enough? (2019, unknown): “The parameters are selected according to 3GPP standard [5] and existing works [2], [3].”
Smart Radio Environments Empowered by Reconfigurable Intelligent Surfaces: How it Works, State of Research, and Road Ahead (2020, background): “In [191], the authors consider a downlink multi-user MISO”
Smart Radio Environments Empowered by Reconfigurable Intelligent Surfaces: How It Works, State of Research, and The Road Ahead (2020, unknown): “In [192], the authors consider a downlink multi-user MISO system, in which an RIS is used to help a base station communicate with the downlink users.”
Reconfigurable Intelligent Surface (RIS) Assisted Wireless Coverage Extension: RIS Orientation and Location Optimization (2020, methodology): “In [7], a multi-user network assisted by an RIS was investigated, where the digital beamformer and the RIS configuration are jointly optimized to maximize the sum rate.”
Intelligent Reflecting Surface-Aided Wireless Communications: A Tutorial (2020, background): “achieving both high spectral and energy efficiencies [20], [77], [179]–[183].”
An Overview of Signal Processing Techniques for RIS/IRS-Aided Wireless Systems (2021, unknown): “2) Optimization Techniques for Discrete Phase Shifts Due to hardware limitations, it is challenging to implement continuous-valued phase shifts in practice [135], [136].”
A Joint Precoding Framework for Wideband Reconfigurable Intelligent Surface-Aided Cell-Free Network (2020, background): “For instance, the RIS-aided millimeter-wave (mmWave) system was considered in [18] and [27], where the authors discussed the signal-to-noise ratio (SNR) maximization problem and the joint hybrid precoding design, respectively.”