Performance Analysis of RIS-Assisted mmWave Communications under Rectangular Blockages

Abstract

While millimeter wave (mmWave) communications offer vast bandwidth, their coverage is highly susceptible to blockages. Reconfigurable intelligent surface (RIS) have emerged as a promising solution to enhance mmWave connectivity. In this study, we analyze the coverage probability of RIS-assisted mmWave communications, which for the first time incorporates rectangular blockages, a two-step association strategy, and a far-field path loss model for RIS. Specifically, utilizing tools from stochastic geometry, we establish the system model, which includes the base station (BS), the blockage, the RIS, and the user distribution models. Subsequently, we define the association criterion and derive the conditional coverage probabilities for three distinct scenarios: line of sight (LOS) association, non-line-of-sight (NLOS) association, and RIS-assisted association. Finally, we combine the three cases to obtain the exact expressions for the coverage probability. Simulation results validate the theoretical analysis, showing that RIS provides up to 25% coverage gain and exhibits deployment-specific behavior under realistic blockage and interference. Notably, the benefits of RIS are most pronounced in heavily obstructed environments. Furthermore, as RIS deployment density and surface size increase, the optimal signal to interference plus noise ratio (SINR) threshold for maximizing area spectral efficiency (ASE) scales upward, shifting the network's peak performance toward higher operating regimes.