Asymptotic Max-Min SINR Analysis of Reconfigurable Intelligent Surface Assisted MISO Systems

• Published in: IEEE transactions on wireless communications Vol. 19; no. 12; pp. 7748 - 7764
• Main Authors: Nadeem, Qurrat-Ul-Ain, Kammoun, Abla, Chaaban, Anas, Debbah, Merouane, Alouini, Mohamed-Slim
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.12.2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Antenna arrays; Antennas; asymptotic analysis; Asymptotic properties; Downlink; Electromagnetic radiation; Interference; Line of sight; MIMO communication; MISO (control systems); MISO communication; multiple-input single-output (MISO) system; Noise propagation; Optimization; projected gradient ascent; random matrix theory (RMT); Reconfigurable intelligent surface (RIS); Reconfigurable intelligent surfaces; Signal to noise ratio; Wave propagation; Wireless communication
• ISSN: 1536-1276; 1558-2248
• DOI: 10.1109/TWC.2020.2986438

This work focuses on the downlink of a single-cell multi-user system in which a base station (BS) equipped with <inline-formula> <tex-math notation="LaTeX">M </tex-math></inline-formula> antennas communicates with <inline-formula> <tex-math notation="LaTeX">K </tex-math></inline-formula> single-antenna users through a reconfigurable intelligent surface (RIS) installed in the line-of-sight (LoS) of the BS. RIS is envisioned to offer unprecedented spectral efficiency gains by utilizing <inline-formula> <tex-math notation="LaTeX">N </tex-math></inline-formula> passive reflecting elements that induce phase shifts on the impinging electromagnetic waves to smartly reconfigure the signal propagation environment. We study the minimum signal-to-interference-plus-noise ratio (SINR) achieved by the optimal linear precoder (OLP), that maximizes the minimum SINR subject to a given power constraint for any given RIS phase matrix, for the cases where the LoS channel matrix between the BS and the RIS is of rank-one and of full-rank. In the former scenario, the minimum SINR achieved by the RIS-assisted link is bounded by a quantity that goes to zero with <inline-formula> <tex-math notation="LaTeX">K </tex-math></inline-formula>. For the high-rank scenario, we develop accurate deterministic approximations for the parameters of the asymptotically OLP, which are then utilized to optimize the RIS phase matrix. Simulation results show that RISs can outperform half-duplex relays with a small number of passive reflecting elements while large RISs are needed to outperform full-duplex relays.