Paper Highlight: Optimising Drone Paths for Better Communication Coverage

Title: UAV Trajectory Optimization Based on Predicted User Locations

Authors: Lester Ho, Sobia Jangsher

Link: https://ieeexplore.ieee.org/document/10570825

What is this paper about?

With every passing year, Unmanned Aerial Vehicles (UAVs), also commonly known as drones, are becoming increasingly common as platforms for carrying out mapping and surveying tasks, as used by commercial, law enforcement, and emergency organisations. While remotely controlled aircraft have been in use for decades among the leading militaries, innovations in electronic motors, battery technology, and miniaturised processing capabilities have increased the capabilities of these devices, while significantly reducing the cost-of-entry. As a result, drones today have become easily accessible tools, that are used in a wide array of applications, from photography to performing deliveries.

One application in which drones have significant potential is in the area of telecommunications, in particular radio communications. Typically, a radio link between a transmitter and receiver on the ground suffers from blockage due to obstacles such as terrain, buildings and vegetation. This limits the distances in which the radio signal can travel. However, the radio link between a transmitter on the ground and a drone flying high in the sky experiences little to none of this blockage, resulting in very large increases in radio range. This means that drones can be used to carry radio relays to extend the useful range of radio communications significantly, as illustrated in Fig.1. A single drone flying at high altitudes can potentially extend the radio communications range by over 50X, as shown in Fig. 2.

In field measurements, we were able to increase the range of a handheld radio from 2km to 100km using a drone relay, an increase of 50 times. This capability to provide long-range radio communications is particularly valuable to organisations that operate in remote areas with unreliable or unavailable infrastructure, such as search and rescue teams, or organisations performing humanitarian or peacekeeping missions.

Fig. 1: Overview of a drone used as a radio relay (left), and an illustration of the radio coverage provided by a drone in challenging, mountainous terrain.

Fig 2. Drone radio relay coverage map calculations using 160MHz radio models calibrated with field measurements, for drone flying at 2000m with a 20W radio (left). The coverage of a 20m radio tower is shown (right) as a baseline comparison

Two key requirements for these use cases are a high availability and reliability of the radio links between the users and the base, there any extended breaks in communications can result in loss of life. The optimization of the position of the drone relays to provide this radio link reliability is therefore an important factor to consider. This is very challenging as the drone has to consider the movement of all the users on the ground, along with the effects of the terrain that can block the radio signals.

What have you discovered?

We developed the UAV Trajectory Optimization based on Predicted User Locations (UTO-PUL) algorithm, which is a smart system that helps drones, acting as communication relays, find the best paths to keep people connected, even in areas with rough terrain like mountains. Here’s how it works in simple terms:

1. Predicting User Movement: It predicts where people will move in the near future, so the drones can get ready to adjust their positions ahead of time.
2. Grouping People: The system groups people who are close to each other and assigns a drone to serve each group, ensuring no one is left out.
3. Finding the Best Path: It calculates the best route for each drone to move while staying connected to people and avoiding obstacles like hills or forests.
4. Smart Scoring: The algorithm checks different possible spots for the drones and picks the ones that provide the strongest and most reliable signals.

By planning ahead and moving strategically, this system ensures that people stay connected, even when they’re in remote or difficult-to-reach places. It reduces the chances of someone losing their signal by up to 85%. It also boosts the signal strength, making it up to 10 times stronger compared to other methods. This means fewer dropped connections and clearer communication, even in tough places like mountains or forests.

Fig. 3 illustrates the proposed UTO-PUL technique that calculates not just where the relay drone needs to be, but the best path it should take to get to its destination to guarantee radio coverage to users. The further forward the prediction of the user is, the better the result, although there is a point where looking too far forward stops making a difference.

So what?

Radio relay drones can quickly provide wide-area communication during emergencies, like search and rescue, disaster response, peacekeeping or humanitarian missions. Reliable communication is crucial in these situations because even a brief loss of connection could be life-threatening. This paper introduces a new system that predicts where people will move and plans the drone’s flight path to ensure uninterrupted, reliable communication for those who need it most. The UTO-PUL algorithm can also be used to smartly guide drones in improving coverage for cellular networks like 5G or future 6G, ensuring better connectivity over larger areas.

CONNECT is the world leading Science Foundation Ireland Research Centre for Future Networks and Communications. CONNECT is funded under the Science Foundation Ireland Research Centres Programme and is co-funded under the European Regional Development Fund. We engage with over 35 companies including large multinationals, SMEs and start-ups. CONNECT brings together world-class expertise from ten Irish academic institutes to create a one-stop-shop for telecommunications research, development and innovation.