An analysis and model for Automatic Dependent Surveillance Broadcast (ADS-B) continuity

The surveillance function of air traffic management is critical to aviation safety. It determines the identity of an aircraft, its state and intent to support air traffic controllers in ensuring that aircraft comply with the specified separation minima. The conventional surveillance system in use for many years is the radio detection and ranging (radar) system, with the more recent ones being wide area multi-lateration based on distance measurement equipment, and Automatic Dependent Surveillance System Broadcast (ADS-B) exploiting the navigation and communications functions of Air Traffic Management to disseminate aircraft state vector and other relevant data to air traffic controllers and other suitably equipped aircraft. The differences between these systems lie in their performance measured in terms of accuracy, integrity, continuity, availability, reliability, adaptability and scalability to the operational environment. The ADS-B system was proposed by the International Civil Aviation Organization, to address the limitations of the radar system, which include unavailability of coverage in remote, oceanic and lower altitude areas, limited services in extreme weather conditions, obsolescence of spare parts, inability to accommodate increasing air traffic and incapability to support future enhanced airborne and ground surveillance applications. However, to date research on the characterization of ADS-B system performance is lacking. This work analyzes ADS-B continuity using real-time data collected from ADS-B ground stations in the London Terminal Maneuvering Area. ADS-B continuity is measured as the rate (in seconds) at which periodic ADS-B messages are received at the ground stations. The results reveal that there is a deterministic pattern in the update rate, with 80% of the messages broadcast within the required 2 s. The factors that influence continuity are identified using statistical methods and incorporated in a mathematical model relating the factors to ADS-B continuity. This model is recommended to the relevant stakeholders including Air Navigation Service Providers and regulators to evaluate and monitor the system performance.