Digital air/ground communications for air traffic control

Present day communications for Air Traffic Control (ATC) uses analog single channel radios with conventional amplitude modulation (AM) in the Very High Frequency (VHF) band. The communications system which allows for air/ground controller exchanges serves approximately 5000 commercial aircraft and 200,000 general aviation aircraft. Over the past several decades the number of airborne users has increased steadily at a mean annual rate of 5%. The cumulative effects of increased traffic densities, finite frequency allocations, and the spectral inefficiencies of the existing equipment are being felt in various regions around the world. To overcome eventual saturation of the current system, the Federal Aviation Administration (FAA) in concert with RTCA and ICAO organizations is developing a communications system to increase capabilities and provide a graceful transition from the current system. The MITRE Corporation has developed a prototype system based on the physical layer parameters and protocols recently defined