An approach to transitioning FAA air/ground communications to a digital system

The current VHF air-to-ground communication system used by the Federal Aviation Administration (FAA) for air traffic control (ATC) is projected to reach the limit of its capacity in high traffic density areas within five to ten years. Regardless of the specific architecture of a replacement system, there will be a significant period of time during which the FAA must operate both the old and new systems. The single most important factor that lends urgency to the design, development, and installation of a new system is the dwindling availability of radio frequencies on which to operate both systems. The authors discuss a proposed replacement system that will use digital modulation and multiple channel per frequency access techniques, that will employ full-duplex frequency assignments to dramatically increase frequency reuse, and that will make possible several features that will deliver direct operational benefits to users. They compare the proposed system to current and planned terrestrial cellular systems and present an analysis of the advantages offered by full duplex operation. An analysis is also presented that shows why channel splitting is not a viable long-term solution to the impending shortage of frequencies in the ATC band