Time Division Multiple Access (TDMA)

Definition of Time Division Multiple Access (TDMA) in The Network Encyclopedia.

What is TDMA (Time Division Multiple Access)?

Time Division Multiple Access or TDMAis a cellular phone technology based on time-division multiplexing (TDM) techniques.

How It Works

Time Division Multiple Access (TDMA) is an analog cellular phone technology that evolved from the Advanced Mobile Phone Service (AMPS), which was developed in 1979. TDMA takes a cellular communication channel (frequency band) and slices it into a series of time segments, as in this example:

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Each cellular user is assigned the time slices with a given number and transmits information only for the duration of his or her time segments using the TDMA scheme. This means that voice communication must be buffered and transmitted as short bursts. The time segments are so small and the slicing frequency is so high that the user perceives a continuous communication channel. TDMA allows more communication sessions to be crammed onto a single cellular channel.

TDMA is used by both the 800-MHz frequency band of Digital Advanced Mobile Phone Service (D-AMPS) and the 1900-MHz frequency band of Personal Communications Services (PCS) technologies.

The first version of TDMA was developed in 1991 and was known as the IS-54 standard (developed by the EIA/TIA). It divided each 30-KHz channel into three multiplexed subchannels. A revised version using digital control channels was developed in 1994 and is known as the IS-136 standard or, more popularly, D-AMPS. Another cellular phone technology that is based on TDMA is the Global System for Mobile Communications (GSM), which multiplexes eight subchannels into a single 200-KHz channel.

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