Significance of extreme reflection angles in RIS-assisted wireless networks

This study examines the importance of the extreme reflection angles in terms of the spectral efficiency in a Reconfigurable Intelligent Surfaces (RIS) - assisted wireless communication system. The investigation considers practical RIS unit cells with a non-ideal reflection response, which is typical, especially when the extreme angles of incidence, as well as reflection, are considered. A significant disparity was found in spectral efficiency when RIS is employed to reflect signals at extreme angles, with a notable 150 % - 200 % increase in the required number of unit cells to maintain the same spectral efficiency compared to scenarios with normal reflection angles. This observation underscores the importance of considering reflection angles in the design and optimization of RIS hardware. The results contribute valuable insights to the understanding of RIS behaviour in practical scenarios, paving the way for enhanced spectral efficiency and improved network performance.