Analysis of the voice communication capacity for a free-route sectorless airspace

Air traffic demand around the world is forecasted to increase, and will therefore put additional strain on the air traffic management system currently used. In the sectorless airspace concept, air traffic controllers are no longer tied to sectors of airspace, but to specific flights. Each controller will maintain radio contact with several aircraft and guide them from the entry to the exit of the airspace. This is a move away from the current geographical attachment of one sector to one controller. For this concept to work, each controller will have a unique voice communication frequency, and this frequency has to propagate to the extreme ends of the airspace. Furthermore, a free-route sectorless airspace has the capacity to support many more aircraft than the current system. Consequently, the number of controllers and indirectly, the number of voice communication frequencies required, will increase as well. This paper presents several restrictions on VHF frequency usage and discusses the problem with regards to the VHF frequencies allocation arising from the implementation of a sectorless airspace. It also provides a preliminary analysis of the VHF voice communication capacity through a simple mathematical formulation. Using a simple concentric buffer zone in which the repeated use of the same frequency is prohibited, the current voice communication infrastructure is estimated to only support up to 5% or 18% of the maximum capacity of a sectorless airspace. Finally, several possible solutions such as adaptations to the VHF system, digital radio, and satellite systems are briefly reviewed.