Science Fair Project Encyclopedia
Advanced Mobile Phone System
This article is about AMPS, the North American mobile phone system standard; AMPS is also an initialism for the "All Media and Products Survey" published by the South African Advertising Research Foundation .
Advanced Mobile Phone System or AMPS is the analog mobile phone system standard, introduced in the Americas during the early 1980s. Though analog is no longer considered advanced at all, the relatively seamless cellular switching technology AMPS introduced was what made the original mobile radiotelephone practical, and was considered quite advanced at the time.
It was a first-generation technology, using FDMA which meant each cell site would transmit on different frequencies, allowing many cell sites to be built near each other. However it had the disadvantage that each site did not have much capacity for carrying calls. It also had a poor security system which allowed people to steal a phone's serial code to use for making illegal calls. It was later replaced by the newer Digital TDMA systems, such as Digital AMPS and GSM, which brought improved security as well as increased capacity.
For each market area, there were to be two licensee (networks). Each network is authorized to use 416 channels in the 800 MHz band. Each channel is composed of 2 frequencies . 416 of these are in the 824~849 MHz range for transmissions from mobile stations to the base stations, paired with 416 frequencies in the 869~894 MHz range for transmissions from base stations to the mobile stations. Each cell site will use a subset of these channels, and must use a different set than neighboring cells to avoid interference. This significantly reduces the number of channels available at each site in real-world systems. Each AMPS frequency is 30kHz wide.
The AMPS band was taken from the same 806~890 MHz frequency band which was originally UHF TV channels 70~83. This meant that these UHF channels could not be used for UHF TV transmission as these frequencies were to be used for AMPS transmission.
Introduction of digital TDMA
Later, many AMPS networks were partially converted to what became (incorrectly) known as TDMA, a digital, TDMA, based 2G standard used mainly by Cingular Wireless (who has purchased AT&T Wireless in October 2004) and U.S. Cellular. TDMA networks were backward compatiable with AMPS. The mis-use of the term TDMA (which is a type of channel sharing scheme) to refer to a particular access protocol has caused some confusion. The first version of the TDMA standard was known as IS-54 and was supplanted by IS-136.
Introduction of GSM and CDMA
AMPS and TDMA are now being phased out in favor of either CDMA and GSM which allow for higher capacity data transfers which open for gateway services over WAP and i-mode, Multimedia Messaging Services (MMS), and wireless Internet Access. The major difference between the two options is that many CDMA phones can fall-back on to AMPS networks if the phone can not get a CDMA signal but can get a AMPS signal. CDMA phones can not use TDMA, only AMPS. GSM phones, being designed by Europeans who had never intended that GSM be used in America, do not normally support this feature. However there are some phones capable of supporting AMPS, TDMA and GSM all in one phone. However AMPS/CDMA phones supports seamless handoffs between CDMA and AMPS/TDMA while GSM phones can not.
Analog system in Europe
Total Access Communication System or TACS is the European version of AMPS. ETACS was an extended version of TACS with more channels. TACS and ETACS are now obsolete in Europe, having been replaced by the more scalable and all-digital GSM system.
Companies using AMPS
- Telecom New Zealand - Telecom customers are in the process of migrating over to the new CDMA service. The old AMPS/D-AMPS system is due to be phased out in 2007. Since the establishment of the AMPS service in 1987 the network had always had the largest coverage of any network in New Zealand. However in recent times Digital GSM and CDMA coverage has matured enough to match or exceed AMPS coverage in many areas.
- Verizon Wireless - Although most Verizon customers use digital services, the backup AMPS network is the largest in the United States.
- Bell Mobility, Telus Mobility and Rogers Wireless all operate AMPS networks in Canada, though they have since been overlaid with digital services.
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