SABRE: Swarm-Based Aerial Beamforming Radios: Experimentation and Emulation

• Published in: IEEE transactions on wireless communications Vol. 21; no. 9; pp. 7460 - 7475
• Main Authors: Mohanti, Subhramoy, Bocanegra, Carlos, Sanchez, Sara Garcia, Alemdar, Kubra, Chowdhury, Kaushik Roy
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-09-2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; Array signal processing; Autonomous aerial vehicles; Beamforming; Channel estimation; coordinated beamforming; distributed aerial beamforming; Experimentation; Hovering; IEEE 80211be; multi-transmitter coordination; Polynomials; Radio transmitters; Receivers; Resource allocation; Signal to noise ratio; Synchronism; Synchronization; Transmitters; Unamanned aerial vehicle; Unmanned aerial vehicles; WiFi 7
• ISSN: 1536-1276; 1558-2248
• DOI: 10.1109/TWC.2022.3158866

We propose a novel distributed beamforming framework for UAVs, called SABRE, wherein airborne transmitters synchronize their operations for data communication with target receivers. SABRE chooses the best-suited subset of transmitters that maximizes user-defined QoS, considering relative distances from receivers, traffic characteristics, cumulative SNR desired at the receiver, and individual SNR estimated for each link. This paper makes three main contributions: (i) It shows how to achieve distributed beamforming in challenging, aerial hovering conditions by accurately synchronizing start-times and eliminating relative clock offsets. (ii) It proposes an algorithm with polynomial complexity that groups transmitters and chooses the receiver, maximizing the number of satisfied receivers in each round. (iii) It experimentally validates the concept of aerial beamforming in a testbed composed of four DJI-M100 UAVs in realistic outdoor environments. We follow this up with at-scale emulation involving beamforming with multiple candidate UAV transmitters in Colosseum, the world's largest RF emulator. SABRE keeps the overall network frame error rate below 10% with a probability of 0.95 and manifests a 40% improvement in meeting user QoS thresholds over classical resource allocation methods. From a community viewpoint, the beamforming code, UAV interfacing designs, and the Colosseum container will be released publicly, allowing further independent investigations.