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

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…

• NS
  National Science Foundation

  Awards: CNS1717454, CNS-1731424, EARS-1839818, CNS-1646607, CNS-1702850, CCF-1908308
• NN
  National Natural Science Foundation of China

  Awards: 61829101, 61625101, 61941101
• AR
  Australian Research Council

  Award: DP190101988
• AF
  Air Force Office of Scientific Research

  Award: 18RT0073