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1. Effect of Antenna Orientation on the Air-to-Air Channel in Arbitrary 3D Space

   https://doi.org/10.1109/WoWMoM51794.2021.00055  

   Matson, N. Cameron; Hashir, Syed Muhammad; Song, Sicheng; Rajan, Dinesh; Camp, Joseph (June 2021, 2021 IEEE 22nd International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM))

   null (Ed.)

   Unmanned Aerial Vehicles (UAVs) often lack the size, weight, and power to support large antenna arrays or a large number of radio chains. Despite such limitations, emerging applications that require the use of swarms, where UAVs form a pattern and coordinate towards a common goal, must have the capability to transmit in any direction in three-dimensional (3D) space from moment to moment. In this work, we design a measurement study to evaluate the role of antenna polarization diversity on UAV systems communicating in arbitrary 3D space. To do so, we construct flight patterns where one transmitting UAV is hovering at a high altitude (80 m) and a receiving UAV hovers at 114 different positions that span 3D space at a radial distance of approximately 20 m along equally-spaced elevation and azimuth angles. To understand the role of diverse antenna polarizations, both UAVs have a horizontally-mounted antenna and a vertically-mounted antenna-each attached to a dedicated radio chain-creating four wireless channels. With this measurement campaign, we seek to understand how to optimally select an antenna orientation and quantify the gains in such selections. 

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2. Deep Reinforcement Learning for Interference Management in UAV-Based 3D Networks: Potentials and Challenges

   https://doi.org/10.1109/MCOM.001.2200973  

   Vaezi, Mojtaba; Lin, Xingqin; Zhang, Hongliang; Saad, Walid; Poor, H Vincent (February 2024, IEEE Communications Magazine)

   Modern cellular networks are multi-cell and use universal frequency reuse to maximize spectral efficiency. This results in high inter-cell interference. This challenge is growing as cellular networks become three-dimensional with the adoption of unmanned aerial vehicles (UAVs). This is because the strength and number of interference links rapidly increase due to the line-of-sight channels in UAV communications. Existing interference management solutions require each transmitter to know the channel information of interfering signals, rendering them impractical due to excessive signaling overhead. In this article, we propose leveraging deep reinforcement learning for interference management to tackle this shortcoming. In particular, we show that interference can still be effectively mitigated even without knowing its channel information. We then discuss novel approaches to scale the algorithms with linear/sublinear complexity and decentralize them using multi-agent reinforcement learning. By harnessing interference, the proposed solutions enable the continued growth of civilian UAVs. 

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3. Interference Analysis and Mitigation for UAV Communications in Drone Corridors

   https://doi.org/10.1109/WPMC59531.2023.10338970  

   Ellis, Cameron; Zhang, Minglong; Marojevic, Vuk (November 2023, IEEE)

   Unmanned aerial vehicles (UAVs) have witnessed widespread adoption in the modern world, with their development set to continue into the future. As UAV technology and applications advance, it becomes imperative to understand their communication capabilities. UAVs experience distinct radio propagation conditions compared to ground-based radio nodes, necessitating a critical investigation into aerial radio node performance. This paper analyzes interference in UAV-to-UAV (U2U) communications within drone corridors and proposes an interference mitigation strategy utilizing millimeter wave (mmWave) beamforming. Employing a semi-persistent scheduling approach from the Third Generation Partnership Project (3GPP) sidelink communications for low altitude aerial nodes in drone corridors, the study primarily examines interference from drone clusters within designated air corridors. To assess U2U communication performance, a 3GPP standard-compliant cross-layer simulator is developed. Simulation results demonstrate that employing mmWave beamforming instead of isotropic transmission substantially reduces interference, leading to higher communications reliability and enabling more UAVs to occupy and communicate in the airspace. 

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4. A Container-based DoS Attack-Resilient Control Framework for Real-Time UAV Systems

   https://doi.org/10.23919/DATE.2019.8714888  

   Chen, Jiyang; Feng, Zhiwei; Wen, Jen-Yang; Liu, Bo; Sha, Lui (March 2019, IEEE Design, Automation & Test in Europe Conference & Exhibition)

   The Unmanned aerial vehicles (UAVs) sector is fast-expanding. Protection of real-time UAV applications against malicious attacks has become an urgent problem that needs to be solved. Denial-of-service (DoS) attack aims to exhaust system resources and cause important tasks to miss deadlines. DoS attack may be one of the common problems of UAV systems, due to its simple implementation. In this paper, we present a software framework that offers DoS attack-resilient control for real-time UAV systems using containers: Container Drone. The framework provides defense mechanisms for three critical system resources: CPU, memory, and communication channel. We restrict the attacker's access to the CPU core set and utilization. Memory bandwidth throttling limits the attacker's memory usage. By simulating sensors and drivers in the container, a security monitor constantly checks DoS attacks over communication channels. Upon the detection of a security rule violation, the framework switches to the safety controller to mitigate the attack. We implemented a prototype quadcopter with commercially off-the-shelf (COTS) hardware and open-source software. Our experimental results demonstrated the effectiveness of the proposed framework defending against various DoS attacks. 

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5. Trajectory and Power Optimization in sub-THz band for UAV Communications

   Alali, A.; Rawat, D.; Liu, C. (January 2022, Proceedings of the IEEE International Conference on Communications (ICC 2022))

   Vapor loss and molecular absorption make the transmission distance in sub-Terahertz bands a challenge, especially in mobile statues such as UAVs communication. The molecular absorption element is an essential part of the path loss in THz communication channel modeling that cannot be neglected. Along this direction, we investigated the UAV trajectories in sub-THz band. To maximize the secrecy rate of the UAVs communication, an optimization problem has been proposed to jointly optimize the trajectory and transmit power. To enhance the obtained average secrecy rate, MIMO communication and a cooperative UAV jammer strategy were used in this paper. Also, analysis and simulations results were presented to show the performance of UAV-ground communication at THz communications. Finally, Secrecy Outage Probability was obtained for each UAV trajectories in different flight periods to examine the performance of physical layer security added to the UAVground communication at sub-THz communication. 

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