Maximizing Throughput with Routing Interference Avoidance in RIS-Assisted Relay Mesh Networks

TL;DR

This work tackles interference-aware routing in RIS-assisted THz relay mesh networks for indoor, cell-less deployments. It develops a geometry-based analytical model for beam footprints (conical from BS/RN and cylindrical from RIS), derives end-to-end SNR expressions, and characterizes interference via illuminated-element intersections. A three-step framework is proposed: candidate-path generation, interference-avoidance transmission scheduling, and MILP-based throughput maximization using a Throughput Controlling Coefficient $\lambda$. Results demonstrate that least-interference path selection can substantially improve throughput over shortest-path routing, highlighting the practical gains of interference-aware routing in RIS-enabled THz networks.

Abstract

In the modern landscape of wireless communications, multi-hop, high-bandwidth, indoor Terahertz (THz) wireless communications are gaining significant attention. These systems couple Reconfigurable Intelligent Surface (RIS) and relay devices within the emerging 6G network framework, offering promising solutions for creating cell-less, indoor, and on-demand mesh networks. RIS devices are especially attractive, constructed by an array of reflecting elements that can phase shifts, such that the reflecting signals can be focused, steered, and the power of the signal enhanced towards the destination. This paper presents an in-depth, analytical examination of how path allocation impacts interference within such networks. We develop the first model which analyzes interference based on the geometric parameters of beams (conic, cylindrical) as they interact with RIS, User Equipment (UE), and relay devices. We introduce a transmission scheduling heuristic designed to mitigate interference, alongside an efficient optimization method to maximize throughput. Our performance results elucidate the interference's effect on communication path quality and highlight effective path selection strategies with throughput maximization.

Figures (7)

• Figure 1: An example of interference on a RIS.
• Figure 2: Reference scenario for the analysis, where BS $b$ (Base Station), UE $u$ ((User Equipment)), RN $e$ (Relay Node), $\alpha$ (directivity angle), $be$ (transmitting node BS or RN), $eu$ (receiving node RN or UE), $R_{IRA}$ (radius of illuminated area), $d_{be-r_1}$ (distance from $be$ to the first RIS $r_1$ of any transmission), RIS (Reconfigurable Intelligent Surface).
• Figure 3: Analysis of beam shapes, where (a): left figure, (b): right figure.
• Figure 4: Interference analysis and channel capacity, where (a): left figure, (b): right figure
• Figure 5: THz relay mesh network as 3D area $(32,32,32)$.