Digital AMPS

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Digital AMPS" – news · newspapers · books · scholar · JSTOR (April 2011) (Learn how and when to remove this message)

Part of a series on the
Wireless network technologies
Analog
0G 1G (1.5G)
Digital
2G (2.5G, 2.75G, 2.9G) 3G (3.5G, 3.75G, 3.9G/3.95G) 4G (4G/4.5G, 4.5G, 4.9G) 5G (5.5G) 6G
Mobile telecommunications
v t e

Digital AMPS (D-AMPS), most often referred to as TDMA, is a second-generation (2G) cellular phone system that was once prevalent throughout the Americas, particularly in the United States and Canada since the first commercial network was deployed in 1993.^[1] Former large D-AMPS networks included those of AT&T and Rogers Wireless. The name TDMA is based on the abbreviation for time-division multiple access, a common multiple access technique which is used in most 2G standards, including GSM. D-AMPS competed against GSM and systems based on code-division multiple access (CDMA). It is now considered end-of-life, as existing networks have shut and been replaced by GSM/GPRS or CDMA2000 technologies. The last carrier to operate a D-AMPS network was U.S. Cellular, who terminated it on February 10, 2009.^[2]

The technical names for D-AMPS are IS-54 and its successor IS-136.^[3][4] IS-54 was the first mobile communication system which had provision for security, and the first to employ time-division multiple access (TDMA) technology.^[5] IS-136 added a number of features to the original IS-54 specification, including text messaging (SMS), circuit switched data (CSD), and an improved compression protocol. SMS and CSD were both available as part of the GSM protocol, and IS-136 implemented them in a nearly identical fashion.

D-AMPS was a further development of the North American 1G mobile system Advanced Mobile Phone System (AMPS) and used existing AMPS channels and allows for smooth transition between digital and analog systems in the same area. Capacity was increased over the preceding analog design by dividing each 30 kHz channel pair into three time slots (hence time division) and digitally compressing the voice data, yielding three times the call capacity in a single cell. A digital system also made calls more secure in the beginning, as analogue scanners could not access digital signals. Calls were encrypted, using CMEA, which was later found to be weak.^[6]