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On the Placement and Sustainability of Drone FSO Backhaul Relays

Salim Janji, Adam Samorzewski, Małgorzata Wasilewska, Adrian Kliks

TL;DR

The paper addresses the challenge of providing reliable FSO backhaul to urban small cells using UAV-mounted drone relay stations (DRSs) in the presence of tall buildings. It introduces a visibility-graph–based placement framework, augmented with a solar-powered energy harvesting and storage model, to ensure LOS connectivity across hops from a macro base station to a hotspot. A sunny-spot extension prioritizes solar locations by modifying the path cost to favor hops in sunlit areas, reducing recharge trips. In simulations of a Madrid urban scenario, the approach yields sunny paths across the day, reduces recharge trips by about 35%, and decreases the number of hops during daytime, thereby improving backhaul sustainability and practicality for urban UAV-based networks.

Abstract

We consider free-space optical (FSO) communication links for the backhaul connectivity of small cells (SCs) where a UAV with an FSO apparatus can serve as a backhaul relay node. We demonstrate how such drone relay stations (DRSs) can be deployed in a high-rise urban area in order to provide FSO line-of-sight (LOS) links that are unobstructed by buildings. Also, in our solution we consider the case where solar panels are mounted on DRSs such that placing the DRS in a sunny location is prioritized, and we show the gain in terms of number of required trips to recharge the UAV.

On the Placement and Sustainability of Drone FSO Backhaul Relays

TL;DR

The paper addresses the challenge of providing reliable FSO backhaul to urban small cells using UAV-mounted drone relay stations (DRSs) in the presence of tall buildings. It introduces a visibility-graph–based placement framework, augmented with a solar-powered energy harvesting and storage model, to ensure LOS connectivity across hops from a macro base station to a hotspot. A sunny-spot extension prioritizes solar locations by modifying the path cost to favor hops in sunlit areas, reducing recharge trips. In simulations of a Madrid urban scenario, the approach yields sunny paths across the day, reduces recharge trips by about 35%, and decreases the number of hops during daytime, thereby improving backhaul sustainability and practicality for urban UAV-based networks.

Abstract

We consider free-space optical (FSO) communication links for the backhaul connectivity of small cells (SCs) where a UAV with an FSO apparatus can serve as a backhaul relay node. We demonstrate how such drone relay stations (DRSs) can be deployed in a high-rise urban area in order to provide FSO line-of-sight (LOS) links that are unobstructed by buildings. Also, in our solution we consider the case where solar panels are mounted on DRSs such that placing the DRS in a sunny location is prioritized, and we show the gain in terms of number of required trips to recharge the UAV.
Paper Structure (16 sections, 5 equations, 4 figures, 1 table)

This paper contains 16 sections, 5 equations, 4 figures, 1 table.

Table of Contents

  1. Introduction and Related Work
  2. System Model
  3. Environment Description
  4. Power Consumption Model
  5. Energy Harvesting Model
  6. Energy Storage System
  7. FSO Backhaul Shortest Path
  8. Problem Formulation
  9. Proposed DRS Placement Algorithm
  10. Proposed Solar Powered DRS Placement
  11. Sunny Points Search
  12. DRS Placement in Sunny Spots Algorithm
  13. Simulation and Results
  14. Placement of DRSs
  15. Sustainability
  16. ...and 1 more sections

Figures (4)

  • Figure 1: High-rise buildings with MBS and hotspot destination.
  • Figure 2: Test points grid for finding sunny spots for $C_T=4$.
  • Figure 3: DRSs placements at different hours of the day.
  • Figure 4: Required number of DRS trips back and forth to the charging location.