PAGE CONTENTS
Objectives
The goal of this activity is to explore the use of aerial mobile platforms in the search of unauthorized transmitters, and in exploring the potential benefits it can give to the spectrum management efforts. The aim of the airborne platform is to aid the geolocation procedure in its final stages or also called the last mile geolocation. The first stage geolocation of the unauthorized transmitter is done with the use of the satellites, mainly by cross correlation algorithms using one, two, or three satellites. The accuracy of this first stage is greatly affected by the number of satellites available, as well as by other factors such as satellite ephemeris. The result from the first stage geolocation is presented as an area, usually in the form of an ellipse, described by the latitude and longitude of its central point, the major and minor axis lengths, and the angle relative to North. The size of the initial search area is dependent on the initial technique used, and based on the feedback from satellite operators is usually below 10km. However, in the cases when a single satellite is used for geolocation this area can be even larger, up to 50km.
Challenges
Geolocating interference presents several challenges, including the large size of the search area, which complicates the identification of the interferer’s exact location. Additionally, the assumption that the interferer’s antenna is directional rather than omnidirectional limits the signal detectability and affects the search algorithm. Regulatory restrictions also pose a significant challenge, as flight operations must adhere to Visual Line of Sight (VLOS) rather than Beyond Visual Line of Sight (BVLOS), limiting the range and flexibility of the airborne platform used for geolocation.
System Architecture
The drone-based geolocation system is composed of two main hardware parts, the Aerial Mobile Platform for measurements and the Ground Processing Module. The software running the system is also divided into two main parts, the control software which is part of the onboard control of the drone and payload and the mission and control software running on the ground processing module allowing the user to operate the system.
Plan
The Project Phases needed to advance the technology from its current status to the point where a prototype is ready at Technology Readiness Level (TRL) 5 is presented:
- Requirement Specification
- State or the art analysis and Solution Design
- Technology development and prototype integration
- Final test and validation
Current Status
The proposed drone-based geolocation solution tackles unauthorised signal interference in satellite communications while adhering to regulatory constraints like Visual Line of Sight (VLOS).
Using Angle of Arrival (AOA) measurements and geometry-based position estimation, the drone localises interference sources with directional antennas after coarse geolocation via satellite data. The system achieves 100-metre accuracy when the drone is within 1 km of the target.
A recursive search approach refines accuracy as the drone moves closer with each AOA measurement. Due to the interferer’s directional antenna aimed at a satellite and VLOS altitude limits, the drone cannot align with the antenna’s boresight beyond 1 km, detecting signals from side lobes. With typical VSAT EIRPs and RF payload sensitivity, detection is possible within 5-10 km, depending on the carrier frequency. Larger search areas are divided into sub-areas for scanning until a signal is detected, triggering the search algorithm. Using a single drone for both direction finding and geolocation ensures flexibility and scalability, while an interference-aware algorithm enhances accuracy in detecting and localising directional antenna sources like VSATs.
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