An analytical framework for Reconfigurable Intelligent Surfaces placement in a mobile user environment

Abstract

The primary role of a reconfigurable intelligent surface (RIS) is to restore the propagation path between the access point (AP) and the user equipment (UE) in a non-line-of-sight communication link. Depending on the RIS placement with respect to the AP and UE positions, different power levels can reach the UE, thus affecting the quality of the communication. Particularly when the UE moves freely, the RIS position that maximizes the received signal will depend strongly on the UE location. In this context, we use an analytical model to assess the decisions that have to be made concerning the positioning of the RIS, which are determined by the interplay of three crucial quantities, namely (a) the available AP gain, (b) the available positions for the AP and RIS placement, and (c) the minimum desired power levels at the UE. The impact of the AP antenna gain tunability on the RIS placement selection is assessed and illustrated in D-band indoor scenarios.