Coverage Analysis for Multi-Hop Communication in Intelligent-Surface-Assisted mmWave WLANs

Reconfigurable intelligent surfaces (RISs) are an emerging technology to improve coverage in millimeter-wave bands, by providing reflective links between access points and user devices when line-of-sight (LoS) links are blocked. To understand the limits of multi-RIS coverage performance in mmWave wireless local area networks (WLANs), we employ stochastic geometry to analyze connection probability with both single-RIS and multi-RIS links with a sparse obstacle distribution. The connection probability for single-RIS links and an upper bound on connection probability for multi-RIS links are derived under an approximation where independence of LoS statuses of different links is assumed. Numerical simulations validate the analytical results and provide a comparison between single-RIS and multi-RIS links. Results demonstrate that single-RIS links provide substantial coverage increases for relatively short-distance communications but are not as effective for longer distances. Meanwhile, two-RIS links can provide substantially increased coverage for longer-range communications, but do not exhibit a significant advantage compared with single-RIS links for short distances.