Page "Advanced Mobile Phone System" Paragraph 2

AMPS is a first-generation cellular technology that uses separate frequencies, or " channels ", for each conversation ( see FDMA ).

It therefore required considerable bandwidth for a large number of users.

In general terms, AMPS was very similar to the older " 0G " Improved Mobile Telephone Service, but used considerably more computing power in order to select frequencies, hand off conversations to PSTN lines, and handle billing and call setup.