(Advanced Mobile Phone Service) The primary analog cellular mobile phone system deployed in North and South America and more than 35 other countries. It used FDMA transmission in the 800 Mhz band. The first AMPS system in the U.S. was deployed in Chicago in 1983. See N-AMPS, NMT and TACS.
The first smartphones used analog radio waves to communicate with the base stations that have since sprouted like weeds across the world, and the first such system to see widespread use in the US was the Advanced Mobile Phone System, or AMPS.