On the Deployment of Reconfigurable Intelligent Surfaces in the Presence of Blockages

TL;DR

This paper investigates how joint blockages affect RIS-assisted wireless coverage and proposes optimal RIS placement strategies using stochastic geometry to enhance downlink performance in blockage-prone environments.

Contribution

It introduces a stochastic geometry-based framework to optimize RIS placement considering joint blockages, improving coverage in mm-wave/THz networks.

Findings

RISs near cell edges improve coverage

Street intersection RIS deployment enhances coverage

Intersection-mounted RISs outperform BS-coupled RISs near intersections

Abstract

Wireless communications aided by reconfigurable intelligent surfaces (RISs) is a promising way to improve the coverage for cellular users. The controlled reflection of signals from RISs is especially useful in mm-wave/THz networks when the direct link between a cellular user and its serving base station (BS) is weak or unavailable due to blockages. However, the joint blockage of the user-RIS and the user-BS links may significantly degrade the performance of RIS-aided transmissions. This paper aims to study the impact of joint blockages on downlink performance. When RIS locations are coupled with BS locations, using tools from stochastic geometry, we obtain an optimal placement of RISs to either minimize the joint blockage probability of the user-RIS and the user-BS links or maximize the downlink coverage probability. The results show that installing RISs near the cell edge of BSs usually provides optimal coverage. Moreover, deploying RISs on street intersections improves the coverage probability. For users associated with BSs that are deployed sufficiently close to intersections, the intersection-mounted RISs offer a better coverage performance as compared to BS-coupled RISs.