# Interference Avoidance Position Planning in Dual-hop and Multi-hop UAV Relay Networks

## TL;DR

This paper develops methods for optimal UAV positioning in dual-hop and multi-hop relay networks to maximize signal quality amid interference, introducing novel algorithms for placement and UAV number optimization.

## Contribution

It presents new algorithms for optimal UAV placement and number determination in interference-prone environments, including distributed methods with performance guarantees.

## Key findings

- Proposed placement algorithms improve SIR in simulated environments.
- Optimal UAV configurations depend on interference scenarios and network topology.
- Distributed algorithms achieve near-optimal performance with reduced coordination.

## Abstract

We consider unmanned aerial vehicle (UAV)-assisted wireless communication employing UAVs as relay nodes to increase the throughput between a pair of transmitter and receiver. We focus on developing effective methods to position the UAV(s) in the sky in the presence of interference in the environment, the existence of which makes the problem non-trivial and our methodology different from the current art. We study the optimal position planning, which aims to maximize the (average) signal-to-interference-ratio (SIR) of the system, in the presence of: i) one major source of interference, ii) stochastic interference. For each scenario, we first consider utilizing a single UAV in the dual-hop relay mode and determine its optimal position. Afterward, multiple UAVs in the multi-hop relay mode are considered, for which we investigate two novel problems concerned with determining the optimal number of required UAVs and developing an optimal fully distributed position alignment method. Subsequently, we propose a cost-effective method that simultaneously minimizes the number of UAVs and determines their optimal positions to guarantee a certain (average) SIR of the system. Alternatively, for a given number of UAVs, we develop a fully distributed placement algorithm along with its performance guarantee. Numerical simulations are provided to evaluate the performance of our proposed methods.