Advanced mobile phone system (AMPS) was a standard for analog cellular phone system developed by Bell Labs and officially introduced by AT&T in 1983.
It is an analog system based on the initial electromagnetic spectrum allocation for cellular service by the Federal Communications Commission.
It uses frequency division multiple access (FDMA) for multiple simultaneous conversations.
Frequency ranges within the 800 and 900 MHz are allocated for cellular telephones in AMPS. Half of the signal is used for sending signals and half is used for receiving signals.
It has a high bandwidth requirement particularly when the number of conversations is very high.
It was the first system to use hexagonal cells. So, the pioneers of AMPS had coined the term coined cellular.
The cells in AMPS are 10km to 20 km across.
Since, it was an analog technology, it suffered from noise and eavesdropping.