IS-136

IS-136

The latest generation of the digital standard TDMA technology. (Cingular)

IS-54 and IS-136 are second-generation (2G) mobile phone systems, known as Digital AMPS (D-AMPS). It is used throughout the Americas, particularly in the United States and Canada. D-AMPS is considered end-of-life, and existing networks are in the process of being replaced by GSM/GPRS and CDMA2000 technologies. Although most often referred to as TDMA, this is an incorrect reference to the protocols. IS-54 and IS-136 do, however, use Time Division Multiple Access as an air interface.

D-AMPS uses 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 and digitally compressing the voice data, yielding three times the call capacity in a single cell. A digital system also made calls more secure because analog scanners could not access digital signals. Calls were encrypted, although the algorithm used (CMEA) was later found to be weak. [1]