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UAV-Assisted Wireless Communications: An Experimental Analysis of A2G and G2A Channels

Kamran Shafafi, Eduardo Nuno Almeida, André Coelho, Helder Fontes, Manuel Ricardo, Rui Campos

TL;DR

This work addresses the gap in heading-aware UAV channel modeling by conducting open-environment experiments to characterize Air-to-Ground and Ground-to-Air channels as a function of distance (50–500 m) and UAV heading. It combines RSSI measurements and TCP throughput, with a detailed analysis of the antenna ERP patterns and the impact of UAV body obstruction on link performance, using a 2x2 MIMO Wi-Fi payload and LTE backhaul. The results show that heading and antenna orientation create nonuniform radiation patterns, yet MIMO signal combining can recover single-stream performance, and UAV relaying can substantially improve Internet throughput when direct LoS paths are blocked. These findings offer practical guidance for designing UAV-based on-demand connectivity and highlight the need to optimize antenna systems and rate adaptation in dynamic aerial networks.

Abstract

Unmanned Aerial Vehicles (UAVs) offer promising potential as communications node carriers, providing on-demand wireless connectivity to users. While existing literature presents various wireless channel models, it often overlooks the impact of UAV heading. This paper provides an experimental characterization of the Air-to-Ground (A2G) and Ground-to-Air (G2A) wireless channels in an open environment with no obstacles nor interference, considering the distance and the UAV heading. We analyze the received signal strength indicator and the TCP throughput between a ground user and a UAV, covering distances between 50~m and 500~m, and considering different UAV headings. Additionally, we characterize the antenna's radiation pattern based on UAV headings. The paper provides valuable perspectives on the capabilities of UAVs in offering on-demand and dynamic wireless connectivity, as well as highlights the significance of considering UAV heading and antenna configurations in real-world scenarios.

UAV-Assisted Wireless Communications: An Experimental Analysis of A2G and G2A Channels

TL;DR

This work addresses the gap in heading-aware UAV channel modeling by conducting open-environment experiments to characterize Air-to-Ground and Ground-to-Air channels as a function of distance (50–500 m) and UAV heading. It combines RSSI measurements and TCP throughput, with a detailed analysis of the antenna ERP patterns and the impact of UAV body obstruction on link performance, using a 2x2 MIMO Wi-Fi payload and LTE backhaul. The results show that heading and antenna orientation create nonuniform radiation patterns, yet MIMO signal combining can recover single-stream performance, and UAV relaying can substantially improve Internet throughput when direct LoS paths are blocked. These findings offer practical guidance for designing UAV-based on-demand connectivity and highlight the need to optimize antenna systems and rate adaptation in dynamic aerial networks.

Abstract

Unmanned Aerial Vehicles (UAVs) offer promising potential as communications node carriers, providing on-demand wireless connectivity to users. While existing literature presents various wireless channel models, it often overlooks the impact of UAV heading. This paper provides an experimental characterization of the Air-to-Ground (A2G) and Ground-to-Air (G2A) wireless channels in an open environment with no obstacles nor interference, considering the distance and the UAV heading. We analyze the received signal strength indicator and the TCP throughput between a ground user and a UAV, covering distances between 50~m and 500~m, and considering different UAV headings. Additionally, we characterize the antenna's radiation pattern based on UAV headings. The paper provides valuable perspectives on the capabilities of UAVs in offering on-demand and dynamic wireless connectivity, as well as highlights the significance of considering UAV heading and antenna configurations in real-world scenarios.
Paper Structure (12 sections, 8 figures)

This paper contains 12 sections, 8 figures.

Table of Contents

  1. Introduction
  2. Related Work
  3. System Setup
  4. Field Trial
  5. Scenario A
  6. Scenario B
  7. Scenario C
  8. Experimental Results
  9. Scenario A: RSSI and Throughput vs. UAV Heading
  10. RSSI and Throughput vs. Distance
  11. Scenario C: Internet Throughput vs LoS
  12. Conclusions

Figures (8)

  • Figure 1: ATLAS site, showing the hangar and runway near which the experimental measurements were performed.
  • Figure 2: Communications payload installed in the ALPHA 800 UAV.
  • Figure 3: Scenario A -- Measured RSSI of the packets received at both UAV antennas, depending on the relative heading between the UAV and the UE at a Euclidean distance of 206 m, compared to Friis with an isotropic antenna.
  • Figure 4: Scenario A -- Measured RSSI of the antenna system (sum of both antennas), and downlink TCP throughput at the UE, depending on the relative heading between the UAV and the UE.
  • Figure 5: Scenario A -- Resulting expected coverage (in meters) for an RSSI of -85 dBm (link still stable but with low throughput) and -75 dBm (link with still good performance for multiple video streams) cut-offs.
  • ...and 3 more figures