Communication, Navigation and Surveillance are three main functions (domains) which constitute the foundation of Air Traffic Management (ATM) infrastructure.
The following provide further details about relevant domains of CNS:
(a) Communication:- Communication is the exchange of voice and data information between the pilot and air traffic controllers or flight information centres.
(b) Navigation:- Navigation Element Of CNS/ATM Systems Is meant To provide Accurate, Reliable And Seamless Position Determination Capability to aircrafts.
(c) Surveillance:- The surveillance systems can be divided into two main types:- Dependent surveillance and Independent surveillance. In dependent surveillance systems, aircraft position is determined on board and then transmitted to ATC. The current voice position reporting is a dependent surveillance systems in which the position of the aircraft is determined from on-board navigation equipment and then conveyed by the pilot to ATC. Independent surveillance is a system which measures aircraft position from the ground. Current surveillance is either based on voice position reporting or based on radar (primary surveillance radar (PSR) or secondary surveillance radar (SSR)) which measures range and azimuth of aircraft from the ground station.