The LDACS1 Link Layer Design

Air transportation is an important factor for the economic growth of the European Union, however, the current system is already approaching its capacity limits and needs to be reformed to meet the demands of further sustainable development (Commission of the European Communities, 2001). These limitations stem mainly from the current European air traffic control system. Air traffic control within Europe is fragmented due to political frontiers into regions with different legal, operational, and regulative contexts. This fragmentation decreases the overall capacity of the European air traffic control system and, as the system is currently approaching its capacity limits, causes significant congestion of the airspace. According to the European Commission airspace congestion and the delays caused by it cost airlines between €1.3 and €1.9 billion a year (European Commission, 2011). For this reason, the European Commission agreed to adopt a set of measures on air traffic management to ensure the further growth and sustainable development of European air transportation. The key enabler of this transformation is the establishment of a Single European Sky1 (SES). The objective of the SES is to put an end to the fragmentation of the European airspace and to create an efficient and safe airspace without frontiers. This will be accomplished by merging national airspace regions into a single European Flight Information Region (FIR) within which air traffic services will be provided according to the same rules and procedures. In addition to the fragmentation of the airspace the second limiting factor for the growth of European air transportation lies within the legacy Air Traffic Control (ATC) concept. In the current ATC system, which has been developed during the first half of the twentieth century, aircraft fly on fixed airways and change course only over navigation waypoints (e.g. radio beacons). This causes non-optimal paths as aircraft cannot fly directly to their destination and results in a considerable waste of fuel and time2. In addition, it concentrates aircraft onto airways requiring ATC controllers to ascertain their safe separation. The tactical control of aircraft by ATC controllers generates a high demand of voice communication which is proportional to the amount of air traffic. As voice communication