# Analysis of Worst-Case Interference in Underlay Radar-Massive MIMO Spectrum Sharing Scenarios

## TL;DR

This paper models and analyzes the worst-case and average interference from massive MIMO base stations to radar systems in spectrum sharing scenarios, providing analytical bounds and insights into how deployment parameters affect interference levels.

## Contribution

It introduces a novel method to bound the worst-case elevation angles for interference analysis using Poisson-Voronoi cell geometry, and derives tight analytical bounds on average interference in spectrum sharing.

## Key findings

- Interference bounds are tight and analytically derived.
- Interference levels depend on deployment parameters like antenna heights and BS density.
- The gap between worst-case and average interference remains constant with the exclusion zone radius.

## Abstract

In this paper, we consider an underlay radar-massive MIMO spectrum sharing scenario in which massive MIMO base stations (BSs) are allowed to operate outside a circular exclusion zone centered at the radar. Modeling the locations of the massive MIMO BSs as a homogeneous Poisson point process (PPP), we derive an analytical expression for a tight upper bound on the average interference at the radar due to cellular transmissions. The technical novelty is in bounding the worst-case elevation angle for each massive MIMO BS for which we devise a novel construction based on the circumradius distribution of a typical Poisson-Voronoi (PV) cell. While these worst-case elevation angles are correlated for neighboring BSs due to the structure of the PV tessellation, it does not explicitly appear in our analysis because of our focus on the average interference. We also provide an estimate of the nominal average interference by approximating each cell as a circle with area equal to the average area of the typical cell. Using these results, we demonstrate that the gap between the two results remains approximately constant with respect to the exclusion zone radius. Our analysis reveals useful trends in average interference power, as a function of key deployment parameters such as radar/BS antenna heights, number of antenna elements per radar/BS, BS density, and exclusion zone radius.