What is AMPS
AMPS is an acronym for ‘Advance Mobile Phone Service’. It was the first cellular based mobile phone service that was developed in the 1970’s by AT&T Bell Laboratories and was first deployed in the Chicago region in U.S.A in 1982 by Ameritech. The main features of this service are mentioned below:-
It was allocated a band of 50 MHz by FCC in the 900 MHz frequency range. More precisely the system used 824-849 MHz range for the reverse link i.e. radio communication from the users to the base towers and it used 869-894 MHz range for the forward link i.e. radio communication from the base towers to the users. It used a seven cell frequency re-use pattern for the deployment of its services. The whole frequency range was divided among the seven cells that repeated themselves over the whole coverage area, just like a unit cell repeats itself over the range of a crystal lattice. Frequency modulation was used for the radio transmission of voice, and the system employed frequency division multiple access (FDMA) scheme. Each voice channel consisted of 30 KHz bandwidth and there were a total of 832 voice channels used. Separate voice channels were used for the reverse and the forward link along the lines of frequency division duplexing (FDD). The system used circuit switching with every pair of voice channels dedicated only to an individual user during the whole time of the conversation. Besides the voice channels, forward and reverse control channels were used for functions such as setting up and termination of calls. The system capacity was limited because of the limited bandwidth and also because of adjacent and co-channel interference due to the use of cellular architecture.
AMPS is very much known as the first generation of mobile phone systems. It was a great leap in terms of both technology and system architecture at the time over the existent traditional radio systems. In Europe a similar system known as ETACS was deployed, based very much on the AMPS architecture but with a few technical differences.
The importance of AMPS and ETACS can be known from the fact that the widely used CDMA and GSM systems today are only an extension of these first generation systems. In fact these second generation technologies continue to use the cellular architecture and bandwidth specifications of AMPS and ETACS without any considerable changes.