Intelligent reflecting surfaces (IRS) have been considered a novel technology for 6G wireless communications. They allow to have a reliable transmission in scenarios where the LOS communication is not available (e.g, in case of blockage) [1]. They also allow to perform Integrated sensing and communication [2].

A very important scenario in which the IRS can be useful is the Multi-user one, where a BS is communicating with multiple UEs. In this case the IRS can be used in order to perform channel estimation or to improve the communication quality by increasing the Beamforming quality [3-4-5].

The task of the student is to make a literature review based on this case scenarios, in order to give an overview on the pros and cons of those technologies. The student can focus either on the channel estimation side or the beamforming one.

[1] He, Jiguang, et al. "Adaptive beamforming design for mmWave RIS-aided joint localization and communication." 2020 IEEE Wireless Communications and Networking Conference Workshops (WCNCW). IEEE, 2020.

[2] Muhr, F., Zaniboni, L., Dehkordi, S. K., Pedraza, F., & Caire, G. (2023, May). Beam Alignment with an Intelligent Reflecting Surface for Integrated Sensing and Communication. In 2023 IEEE International Conference on Communications Workshops (ICC Workshops) (pp. 679-684). IEEE.   [3] Wei, Li, et al. "Channel estimation for RIS-empowered multi-user MISO wireless communications." IEEE Transactions on Communications 69.6 (2021): 4144-4157.   [4] Verde, Francesco, Donatella Darsena, and Vincenzo Galdi. "Rapidly time-varying reconfigurable intelligent surfaces for downlink multiuser transmissions." IEEE Transactions on Communications (2024).   [5] Rafieifar, Anahid, et al. "Secure beamforming in multi-user multi-IRS millimeter wave systems." IEEE Transactions on Wireless Communications (2023).