Reconfigurable Intelligent Surfaces: Potentials, Applications, and Challenges for 6G Wireless Networks

• Published in: IEEE wireless communications 2021-12, Vol.28 (6), p.184-191
• Main Authors: Basharat, Sarah, Hassan, Syed Ali, Pervaiz, Haris, Mahmood, Aamir, Ding, Zhiguo, Gidlund, Mikael
• Format: Article
• Language: English
• Subjects: 6G mobile communication; Channel estimation; Channel state information; Communication technologies; Cost effectiveness; Cost-effective technology; Costs; Energy efficiency; Future research directions; Hardware; Imperfect channel state information; Impinging signals; Interference cancellation; Interlocking signals; NOMA; Nonorthogonal multiple access; Numerical results; Optimization; Propagation channels; Receivers; Reconfigurable intelligent surfaces; Reconfiguration; Reflecting elements; Signal receivers; Wireless networks
• ISSN: 1536-1284; 1558-0687; 1558-0687
• DOI: 10.1109/MWC.011.2100016

Reconfigurable intelligent surfaces (RISs), with the potential to realize smart radio environments, have emerged as an energy-efficient and a cost-effective technology to support the services and demands foreseen for coming decades. By leveraging a large number of low-cost passive reflecting elements, RISs introduce a phase-shift in the impinging signal to create a favorable propagation channel between the transmitter and the receiver. In this article, we provide a tutorial overview of RISs for sixth-generation (6G) wireless networks. Specifically, we present a comprehensive discussion on performance gains that can be achieved by integrating RISs with emerging communication technologies. We address the practical implementation of RIS-assisted networks and expose the crucial challenges, including the RIS reconfiguration, deployment and size optimization, and channel estimation. Furthermore, we explore the integration of RIS and non-orthogonal multiple access (NOMA) under imperfect channel state information (CSI). Our numerical results illustrate the importance of better channel estimation in RIS-assisted networks and indicate the various factors that impact the size of RIS. Finally, we present promising future research directions for realizing RIS-assisted networks in 6G communication.