Automatic Dependant Surveillance-Broadcast (ADS-B) is a terrestrial aeronautical monitoring system, broadcasting (twice per second) position, altitude, velocity, aircraft ID, and other related avionics information. This information enables accurate position determination and monitoring of aircraft and the safe airspace separation of aircraft by air traffic control management. The system is presently in use, as well as being implemented in a number of countries. ICAO has developed Standards and Recommended Practices (SARP) for the ADS-B system (ICAO Annex 10).ADS-B transmissions centred on 1090 MHz use pulse-position modulation in a ±1.3 MHz bandwidth. ICAO SARPs define the 3 dB signal bandwidth to be ±2.3 MHz (including a maximum ±1 MHz allowable carrier tolerance) therefore the band 1087.7-1092.3 MHz fully corresponds with the ICAO defined ADS-B signal. The ICAO standardized ADS-B signal broadcasts in accordance with the aeronautical mobile (route) service (AM(R)S) allocation. ADS-B signals are currently received by other aircraft and terrestrial stations on the ground within line-of-sight. In oceanic, Polar regions, remote areas or other areas where deployment of ground based surveillance systems is not feasible, ADS-B signals are currently not being utilized to track aircraft. In these situations, procedural airspace separation standards of approximately 80 nautical miles are used when air traffic management does not have availability of ADS-B data. This level of separation distance is a less than optimal means of airspace use and altitude availability.