IP: The Way Out

ATC turns to dynamic routing for enterprise-wide voice communications

Voice communication control systems (VCCS) serve as a nexus for various air traffic control resources, among them very high frequency (VHF), ultra high frequency (UHF), and high frequency (HF) radios, as well as weather information displays and traffic-flow management systems. Typically, these elements are integrated on a ‘local’ level—at an individual airport or flight control centre, for example.

The drawback to this approach is that it creates a silo of communications capabilities, integrated only within the single location. The system operates independently of other VCCS systems within a country or region, and often uses different equipment providing varying capabilities. This poses significant drawbacks in an increasingly interconnected digital world.

How to solve this challenge going forward? Air traffic control organisations are looking to the application of Internet protocol (IP)- based systems to provide effective voice control and data communications capabilities across the total enterprise. This includes the US Federal Aviation Administration as well as the European agencies, which are seeking to modernise their VCCS with platforms that deliver new technology and capabilities across the voice enterprise.

Technology Evolution: Analogue, Digital (TDM), and Dynamic Routing (IP)

The path to IP is the result of continued technology evolution. Like every other industry, the field of air traffic control communications has advanced over the years in the physical hardware used and the signal format quality as well as in environmental factors.

Hardware has evolved from very large, noisy, heat-producing equipment with mechanical relays and vacuum tubes to much smaller, uniform-sized chassis and surface mount components. These produce very little noise and a fraction of the heat of legacy equipment, while also using much less power and providing greatly enhanced reliability.

The transition from analogue to digital signal processing eliminated the problems of extraneous noise and interference from external electrical fields, while increasing the quality of voice or data. Equally important, digital signals also offered the ability to transmit information over longer distances without the degradation inherent in analogue circuits.

For years, time division multiplexing (TDM) was the standard method of transmission for digital signals. TDM is a direct signal connection that links two points over cable or radio. It requires that both points share the exact timing, data transmission protocols, and data speeds—and often requires the same type of equipment at both ends. Because TDM provides a direct connection between two end-points or devices, there is minimal signal processing, which enables TDM to have lower latency than other modern transmission technologies.

This direct connection is both a benefit and a drawback to TDM. While it speeds signal transmission, the bandwidth of the transmission path can be used only for the communications between the two devices involved. No dynamic recovery is possible apart from providing a parallel, dedicated path.

Dynamic data routing was to be the next step in the evolution of communications. While there are many protocols that use dynamic routing, the most prevalent and commonly used is Internet protocol (IP). This has become the name commonly used to refer to all routed data networks—whether or not the actual protocol used is in fact IP.