Efficient Phase Control Determination by Codebook without CSI for Standalone IRS Realization

Abstract

Intelligent Reflecting Surfaces (IRS) have attracted attention in recent years as devices that can improve communication quality by controlling the propagation environment that was originally given to them, and their use in future communications is highly anticipated. This study focuses on Standalone-IRS (SA- IRS), a device that can autonomously estimate and control its environment. SA-IRS is independent of existing communication systems and has the ability to collect the necessary information to exert control by itself. Therefore, it does not need to be connected to other devices for control, and is expected to be used as a low- installation-cost device for improving the propagation environment for small-scale communications, such as in factories using local 5G. Basically, the control of IRSs requires Channel State Information (CSI) to understand the propagation environment. However, because an IRS is a passive device that cannot transmit or receive information, CSI estimated from the difference of transmitted and received signals is not available for SA-IRS. This motivated us to propose an SA-IRS codebook that links IRS control to user location information to control IRS without CSI. In addition, because of the overhead involved in calculating the linked IRS control, which is an element of the SA-IRS codebook, we propose an efficient SA-IRS codebook construction method. The objective of this research is to efficiently control SA-IRS, which is an IRS with low installation cost, and to ensure high communication quality by using the above-mentioned proposed method. Simulations are also conducted to evaluate the effectiveness of the proposed method.