Coverage and Rate Performance Analysis of Multi-RIS-Assisted Dual-Hop mmWave Networks

2025-08-31

AI Summary

To address severe path loss, frequent blockage, and strong interference induced by high-density reconfigurable intelligent surface (RIS) deployment in millimeter-wave (mmWave) communications, this paper investigates a dual-hop mmWave system assisted by multiple RISs under Nakagami-𝑚 fading. Leveraging stochastic geometry, we model interference and connectivity in dense-RIS scenarios. We propose a dynamic RIS–user association mechanism coupled with a distributed multi-RIS joint phase-shift optimization strategy, integrated with maximum-ratio transmission beamforming to construct efficient reflective paths. Compared with static association and independent phase control, the proposed approach significantly improves the signal-to-interference-plus-noise ratio (SINR) coverage probability and end-to-end achievable rate. It effectively mitigates blockage and interference under high-RIS-density deployments, thereby enhancing system robustness and spectral efficiency.

Technology Category

• Intelligent Robots: Multi-Robot Systems
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Distributed Search

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Applied ML and AI for Web-based mobile applications
• Security and Privacy: Large-scale security measurements
• Search and Retrieval-Augmented AI: Retrieval-Augmented Generation (RAG) and multi-modal RAG

Abstract

Millimeter-wave (mmWave) communication, which operates at high frequencies, has gained extensive research interest due to its significantly wide spectrum and short wavelengths. However, mmWave communication suffers from the notable drawbacks as follows: i) The mmWave signals are sensitive to the blockage, which is caused by the weak diffraction ability of mmWave propagation; ii) Even though the introduction of reconfigurable intelligent surfaces (RISs) can overcome the performance degradation caused by serve path loss, the location of users and RISs as well as their densities incur a significant impact on the coverage and rate performance; iii) When the RISs' density is very high, i.e., the network becomes extremely dense, a user sees several line-of-sight RISs and thus experiences significant interference, which degrades the system performance. Motivated by the challenges above, we first analyze distributed multi-RISaided mmWave communication system over Nakagami-m fading from the stochastic geometry perspective. To be specific, we analyze the end-to-end (E2E) signal-to-interference-plus-noiseratio (SINR) coverage and rate performance of the system. To improve the system performance in terms of the E2E SINR coverage probability and rate, we study the optimization of the phase-shifting control of the distributed RISs and optimize the E2E SINR coverage particularly when deploying a large number of reflecting elements in RISs. To facilitate the study, we optimize the dynamic association criterion between the RIS and destination. Furthermore, we optimize the multi-RIS-user association based on the physical distances between the RISs and destination by exploiting the maximum-ratio transmission.

Problem

• Analyzing coverage and rate in multi-RIS-assisted mmWave networks
• Optimizing phase-shifting control to improve SINR performance
• Enhancing RIS-user association based on distance criteria

Innovation

• Multi-RIS phase-shifting optimization for mmWave
• Dynamic RIS-user association using distance criteria
• Maximum-ratio transmission for interference mitigation