Network Communications Evolution’s Effects on Air Traffic Systems – Nuisance or National Risk

The evolution of telecommunications transport networks from synchronous to asynchronous communications is mass-market commercial service driven, where operational affordability and efficiencies for telecommunications network providers are realized. However, while delivering advancements in capabilities and services, the product quality has suffered for consumers, sacrificing phone voice call quality for the flexibility, mobility and functionality of smart phone devices, as evidenced by the change in advertisements from "a pin drop" to "can you hear me now" [1]. In aviation and other safety centric industries, accurate and precise network timing are critical for applications reliant on integrated communications. These applications require consistent guaranteed data delivery measured using a network timing capability that is absent in asynchronous networks, which introduces packet delay variation (i.e., jitter), packet loss, and inconsistent latency characteristics in the performance of these systems. Approximately 90% of applications supporting air traffic navigation require the network timing capability inherent in synchronous communications networks but the slow migration of these applications to use native asynchronous communications has been outpaced by the telecommunications industry sunsetting of the underlying synchronous services and equipment. There are mature hardware based technologies (e.g., tunneling) dedicated to migrate data from systems reliant on synchronous networks, unaltered, for transport over asynchronous packet switched networks. Aided by existing network protocols (e.g., QoS, Sync Ethernet, Frequency based PTP, SD-WAN, Segment routing, and Traffic Engineering), these hardware-based technologies have been successful in providing communications for a subset of these systems that require guaranteed data delivery but lab vs real-world experience migrating these applications have delivered mixed results due to the end-application sensitivity to network performance variability.An alternative to terrestrial asynchronous networks for successful communications of native synchronous or sensitive asynchronous/IP applications leverage the proliferation and acceptance of newer fixed wireless last mile network transport technologies such as 5G and Low Earth Orbit Satellite (LEO), offering even greater performance variance compared to terrestrial asynchronous networks. While 5G testing in under optimal conditions has shown promise, field testing has been less successful due to the inconsistency in real-world network performance. The LEO constellations are not yet mature to perform adequate testing but the expectation is to perform this evaluation in the near future as the constellation coverage gaps are closed.With such varying degrees of success when transporting native synchronous or sensitive asynchronous/IP applications over modern asynchronous networks, there are two basic approaches for addressing the effects of the network communications evolution away from synchronous technologies. First, migrate the existing applications to IP-based asynchronous networks, optimizing the network for last mile transport. Second, upgrade the applications and system architecture to reduce inherent dependency on predictable network performance simply not available with asynchronous network technologies. Either approach requires characterizing the real-world network performance dependencies of precision time-sensitive applications to determine the viability of the modern telecommunication transport technologies, and migrate those synchronous applications without impacting operational usability and safety. Ultimately, application modernization is the best solution for asynchronous transport communications (i.e., native packet/IP transport) with prioritization based on business/operational need, ability for intermediate migration strategies, and time and budget constraints.Is the impending sunsetting of synchronous technologies just a nuisance that can be overcome with personnel and budget investments, or is there an impending risk to the safety of critical systems such as air traffic navigations systems? In this paper, we explore technologies and techniques that can be used to overcome the effect of emerging communications technologies on air traffic navigation systems that rely on integrated communications for air-navigation services.