The signal multiplexing technology used in the Advanced Mobile Phone Service (AMPS) analog version of cellular phone technology is FDMA. Frequency Division Multiple Access (FDMA) is one of three methods used for allocating channels to users over the shared wireless communications medium in cellular phone communication

FDMA is implemented at the media access control (MAC) layer of the data-link layer in the Open Systems Interconnection (OSI) reference model for networking protocol stacks. FDMA is based on the frequency-division multiplexing (FDM) technique used in wireless networking. In FDMA, the user is assigned a specific frequency band in the electromagnetic spectrum, and during a call that user is the only one who has the right to access the specific band. In the AMPS cellular phone system, these frequency bands are allocated from the electromagnetic spectrum