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Automatic Dependent Surveillance - Broadcast (ADS-B)
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According to the U.S. Federal Aviation Administration, "Automatic Dependent Surveillance-Broadcast (ADS-B) is FAA's satellite-based successor to radar. ADS-B makes use of GPS technology to determine and share precise aircraft location information, and streams additional flight information to the cockpits of properly equipped aircraft."
Position, speed, heading, and other flight data are determined by instruments on the aircraft, and broadcast once per second to a network of relatively simple ground stations, and directly to other aircraft.
In this case, the data are "dependent" on on-board instruments, as opposed to radar, which can determine the location of an aircraft independent of any signals transmitted by the plane. Some of the benefits of ADS-B include improved accuracy through the use of GPS, improved coverage since the system does not rely on relatively weak return radar echoes, and improved abilities to route planes directly to their destination, rather than relying on pre-determined routes between a sequence of established waypoints.
While the U.S. and other countries are building out networks of ground stations to receive ADS-B broadcasts, it will be many years before a large fraction of commercial and private aircraft are equipped with ADS-B transmiters. The U.S. hopes to have its ground station network completed by the end of 2013.
The term "ADS-B Out" refers to the broadcasts sent from the aircraft. "ADS-B In" refers to the ability of the aircraft to monitor ADS-B transmissions from other aircraft and from the ground, and display the information to the pilot. This information may include the positions of other planes, weather data, terrain data, and other information that can be encoded through ADS-B.
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Frequencies |
| Frequency | Bandwidth | Use | Service | Table |
| 978 MHz | - | ADS-B (optional frequency, U.S. only, below 18,000 ft) | Aeronautical Radionavigation | - |
| 1090 MHz | - | Primary worldwide ADS-B frequency | Aeronautical Radionavigation | - |
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Multiple Address System (MAS)
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According to the FCC, MAS is defined as "a point-to-multipoint or point-to-point radio communications system used for either one-way or two-way transmissions that operates in the 928/952/956 MHz, the 928/959 MHz or the 932/941 MHz bands" in accordance with section 101.147 of the FCC's rules. Specific rules for MAS are in Subpart O of Part 101.
Limited mobile operations are permitted under MAS, per 101.1307.
According to frequency coordinator Micronet, MAS are "point-to multipoint microwave systems that provide corporations and other institutions with the ability to support their dedicated operations."
Details of the MAS service were established in a 1999 FCC Report and Order (FCC 99-415), which took the following actions:
- Designate the 928/952/956 MHz bands exclusively for private internal services, licensed on a site-by-site basis.
- License the 928/959 MHz bands on a geographic area basis.
- License twenty of the forty paired channels in the 932/941 MHz bands on a geographic area basis.
- Reserve twenty of the forty channel pairs in the 932/941 MHz bands for public safety/Federal Government and private internal services, licensed on a first-come, first-served, site-by-site basis. Designate five of the twenty channels in the 932/941 MHz bands' set-aside exclusively for public safety/Federal Government services.
- Grandfather existing operations on the MAS bands and restrict expansion in the 928/959 MHz bands.
- Establish service areas based on the Federal Communications Commission's definition of Economic Areas (EAs) and on the U.S. Department of Commerce's definition of EAs.
- Establish construction/coverage requirements for EA licensees -- specifically, coverage to at least one-fifth of the population in their service areas or substantial service within five years of the license grant -- and a showing of substantial service within ten years of being licensed.
- Introduce flexibility to the MAS technical rules.
- Allow licensees to provide mobile and fixed operations on a co-primary basis for point-to-point and point-to-multipoint operations.
- Adopt a flexible approach for defining the regulatory status of MAS licensees by allowing the licensee to indicate its regulatory status.
- Lift the suspension on the acceptance of applications for the 928/952/956 MHz bands and the twenty channels in the 932/941 MHz bands designated for public safety/Federal Government and/or private internal services upon the release of this Report and Order.
- Adopt Part 1 competitive bidding rules for MAS spectrum.
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Frequency Bands |
| Band | Use | Service | Table |
| 928 - 929 MHz | Multiple Address System | Fixed | N |
| 932 - 932.5 MHz | Multiple Address System | Fixed | N |
| 941 - 941.5 MHz | Multiple Address System | Fixed | N |
| 952 - 960 MHz | Multiple Address System | Fixed | N |
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