Stochastic Geometry based Interference Analysis of Multiuser mmWave Networks with RIS

TL;DR

This paper uses stochastic geometry to analyze interference in multiuser mmWave networks with RIS, showing that RIS-induced interference is small and that far field assumptions hold well in high-frequency large-array systems.

Contribution

It provides a novel stochastic geometry framework for interference estimation in RIS-assisted mmWave networks, including validation and analysis of near-field effects.

Findings

RIS interference levels are small compared to LOS interference

Far field assumptions are valid up to half the near field in large arrays

High frequency systems require large arrays for effective RIS use

Abstract

In this paper, we utilize tools from stochastic geometry to estimate the interference propagation via reconfigurable intelligent surface (RIS) in the millimeter wave (mmWave, 30-300 GHz) band and specifically on the D band (110-170 GHz). The RISs have been of great interest lately to maximize the channel gains in non-line-of-sight (NLOS) communication situations. We derive expressions for stochastic interference level in RIS powered systems and validate those with simulations. It will be shown that the interference levels via RIS link are rather small compared to the designed RIS link or the LOS interference as the random interference loses significant part of the RIS gain. We also analyse the validity of far field channel and antenna gains in the near field of a large array. It is shown that, while the high frequency systems require large arrays that push the far field far away from the antenna, the far field equations are very accurate up to about half way of the near field.