Location based communication services for UAS in the NAS

Unmanned aerial systems (UAS) are soon to cloud our skies in all areas of the national airspace, uncontrolled as well as controlled. Allowing UAS operation in controlled airspace is the responsibility of the National Navigation Service Providers (ANSP), such as the Federal Aviation Administration (FAA). Being able to locate UAS and thus associate it with its respective ground control station(s) is a prerequisite for seamless integration into the National Airspace (NAS). This contribution describes the concept of using the GPS capability of the UAS to provide location-based services to the air traffic control systems, to automate the association with appropriate air traffic control (ATC) communications channels and data links. It is a common expectation now that UAS will soon operate not as individual devices, but as part of a highly networked UAS infrastructure. Small to large UASs will need to be properly addressable from the ANSP's ground control systems such as tower, TRACON, or en-route center. As defined in RTCA DO-320 all UAS pilot-in-control (PIC) are subject to the same regulations as pilots flying aircraft while physically residing on the aircraft, thus need to adhere to commands and directives by air traffic control personnel located in these facilities. Communications links to ATC facilities include data and voice links between air traffic control and the PIC in the UAS ground station. In addition, voice commands need to be broadcasted to all other users (i.e. aircraft, and other UAS - PIC) operating in the same ATC sector. When a UAS transitions the boundary of two sectors the corresponding responsibility changes from one controller to another residing within the same or different ATC facilities. The described Location Based Services (LBS) may be used to dynamically associate the communication service to its responsible ATC facility without PIC intervention. Current communications links between UAS ground control stations (GCS) and ATC are relayed via the UAS itself resulting in the need for a special transceiver on the UAS in addition to the control link transceiver. Especially in the case of small UAS (sUAS) this transceiver constitutes a significant reduction in maximum vehicle payload capacity. This paper proposes a solution that operates without the need for a retransmission transceiver on board the UAS. All communications links between UAS GCS and ATC utilize solely ground based communications assets, networks, and protocols. The LBS concept allows calls to automatically find their way to the correct ATC center, respectively the ATC controller in charge for the associated airspace block. Such a mapping between the user location and the service boundary can be implemented using a Location-to-Service Translation (LoST) system. The LoST system fetches the geographic data representing the boundaries of the airspace sector from its authoritative AIXM database and looks up the unique identifier of the responsible sector, and ATC center. This information is then used to identify the corresponding radio frequency, represented by its EUROCAE ED-137 based identifier, which in turn is used to establish the communications association/link between the PIC and the ATC controller using available Ground communication facilities. We further discuss the dynamic communications link establishment from the ATC controller to the UAS PIC using the LBS. In the UAS network we propose the LBS to be setup as a subscribe/notify service allowing the sharing of additional metadata ahead of a sector handoff. The paper ends with an outlook into the option of a make-before-break automatic link establishment, which may enhanced operational safety and security and could further reduce complexity in the UAS coordination effort for air traffic controllers in the NAS.