SDR-Based ADS-B with Dual-Frequency for UAS: A Universal Design

The use of Unmanned Arial Systems (UAS) in both civil and military applications has greatly increased over the last few years. At the same time, issues related to the safety of air traffic operation arise when considering UAS insertion into non-segregated airspace. Thus, surveillance plays a key role in monitoring and controlling air traffic, enabling UASs and manned aircrafts to insure themselves against collision. Automatic Dependent Surveillance-Broadcast (ADS-B) has been proposed as a potential solution. It empowers aircraft to automatically broadcast their locations and intents to provide enhanced situational awareness. However, the use of two different ADS-B frequencies (1090MHz or 978MHz)restricts communication between different types of aircraft mainly relating to their routine flight altitude. Aircraft with ADS-B capability is either through 978 MHz Universal Access Transceivers (UAT) on general aviation below 18,000 ft or 1090 MHz Extended Squitter (1090ES) transponders above on commercial flight. In view of the manoeuvrability of UAS with a wide flight range, it will bring safety hazards and risks related to surveillance systems, if a single-frequency ADSBis adopted in a traditional way. Motivated by this, this paper proposes a novel Software-Defined Radio (SDR)-basedADS-B with dual-frequency for UAS that is called SAS. It exploits the SDR technology that uses software running on a generic hardware platform to perform signal processing. The SAS can thus integrate the dual-datalink hardware devices into a single generic device, which improves flexibility and connectivity of surveillance for general use. We performed simulation studies with SDR-based BeeCube and also built its prototype implementation to verify its performance.