If you have been asking about the actual technology regarding ADS-B.
The excellent presentation below by Eurocontrol (ADS_B for Dummies) describes the transmission in detail:
http://www.ans.dhmi.gov.tr/TR/Sistem/Dok/ADS-B%20for%20Dummies-1090ES%20v04.pdfAlso, see the brief description below:
Automatic Dependent Surveillance-Broadcast (also called ADS-B) is a system by which aircraft constantly broadcast their current position and altitude, category of aircraft, airspeed, identification, and whether the aircraft is turning, climbing or descending over a dedicated radio datalink. This functionality is known as "ADS-B out" and is the basic level of ADS-B functionality.
The current ADS-B system was developed in the 1990s though its lineage dates back to the 1960s. It relies on data from the Global Positioning System, or any navigation system that provides an equivalent or better service. The maximum range of the system is line-of-sight, typically less than 200 nautical miles (370 km).
The ADS-B transmissions are received by air traffic control stations, and all other ADS-B equipped aircraft within reception range. Reception by aircraft of ADS-B data is known as "ADS-B in".
The initial use of ADS-B is expected to be by air traffic control and for surveillance purposes and for enhancing pilot situational awareness. ADS-B is lower cost than conventional radar and permits higher quality surveillance of airborne and surface movements. ADS-B is effective in remote areas or in mountainous terrain where there is no radar coverage, or where radar coverage is limited. The outback of Australia is one such area where ADS-B will provide surveillance where previously none existed. ADS-B also enhances surveillance on the airport surface, so it can also be used to monitor traffic on the taxiways and runways of an airport.
ADS-B equipped aircraft may also have a display unit in the cockpit picturing surrounding air traffic from ADS-B data (ADS-B in) and TIS-B (Traffic Information Service-Broadcast) data derived from air traffic radar. Both Pilots and air traffic controllers will then be able to "see" the positions of air traffic in the vicinity of the aircraft, and this may be used to provide an ASAS (Airborne Separation Assurance System).
Airborne Collision Avoidance Systems may in the future also make use of "ADS-B in", supplementing the existing TCAS collision avoidance system by what is called 'hybrid surveillance'.
Airbus and Boeing are expected to include ADS-B out (i.e. the transmitter of information) as standard on all new-build aircraft.
