TY - JOUR
T1 - Hybrid Beamforming for Reconfigurable Intelligent Surface based Multi-User Communications
T2 - Achievable Rates with Limited Discrete Phase Shifts
AU - Di, Boya
AU - Zhang, Hongliang
AU - Song, Lingyang
AU - Li, Yonghui
AU - Han, Zhu
AU - Poor, H. Vincent
N1 - Funding Information:
Manuscript received October 1, 2019; revised January 15, 2020; accepted February 17, 2020. Date of publication June 8, 2020; date of current version August 20, 2020. This work was supported in part by the National Natural Science Foundation of China under Grant 61625101, Grant 61829101, Grant 61941101, in part by the U.S. Air Force Office of Scientific Research under MURI Grant 18RT0073, and in part by the U.S. National Science Foundation under Grant EARS-1839818, Grant CNS1717454, Grant CNS-1731424, Grant CNS-1702850, Grant CNS-1646607, and Grant CCF-1908308. The work of Yonghui Li was supported by ARC under Grant DP190101988. (Corresponding author: Lingyang Song.) Boya Di is with the Department of Electronics Engineering, Peking University, Beijing 100871, China, and also with the Department of Computing, Imperial College London, London SW7 2AZ, U.K. (e-mail: diboya92@gmail.com).
Publisher Copyright:
© 1983-2012 IEEE.
PY - 2020/8
Y1 - 2020/8
N2 - 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.
AB - 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.
KW - Reconfigurable intelligent surface
KW - hybrid beamforming
KW - limited discrete phase shifts
KW - multi-user communications
KW - non-convex optimization
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U2 - 10.1109/JSAC.2020.3000813
DO - 10.1109/JSAC.2020.3000813
M3 - Article
AN - SCOPUS:85086710793
SN - 0733-8716
VL - 38
SP - 1809
EP - 1822
JO - IEEE Journal on Selected Areas in Communications
JF - IEEE Journal on Selected Areas in Communications
IS - 8
M1 - 9110889
ER -