Time-division multiple access
Introduction


[thumbnail\|350px\|TDMA frame structure showing a data stream divided into frames and those frames divided into time slots](/wiki/Image:Tdma-frame-structure.png "Tdma-frame-structure.png")

**Time\-division multiple access** (**TDMA**) is a [channel access method](/wiki/Channel_access_method "Channel access method") for [shared\-medium networks](/wiki/Shared-medium_network "Shared-medium network"). It allows several users to share the same [frequency channel](/wiki/Frequency_channel "Frequency channel") by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium (e.g. radio frequency channel) while using only a part of its [channel capacity](/wiki/Channel_capacity "Channel capacity"). **Dynamic TDMA** is a TDMA variant that dynamically reserves a variable number of time slots in each frame to variable bit\-rate data streams, based on the traffic demand of each data stream.

TDMA is used in the digital [2G](/wiki/2G "2G") [cellular systems](/wiki/Cellular_communication_networks "Cellular communication networks") such as [Global System for Mobile Communications](/wiki/Global_System_for_Mobile_Communications "Global System for Mobile Communications") (GSM), [IS\-136](/wiki/IS-136 "IS-136"), [Personal Digital Cellular](/wiki/Personal_Digital_Cellular "Personal Digital Cellular") (PDC) and [iDEN](/wiki/IDEN "IDEN"), and in the [Digital Enhanced Cordless Telecommunications](/wiki/Digital_Enhanced_Cordless_Telecommunications "Digital Enhanced Cordless Telecommunications") (DECT) standard for [portable phones](/wiki/Portable_phone "Portable phone"). TDMA was first used in [satellite communication](/wiki/Satellite_communication "Satellite communication") systems by [Western Union](/wiki/Western_Union "Western Union") in its [Westar 3](/wiki/Westar_3 "Westar 3") communications satellite in 1979\. It is now used extensively in satellite communications, [combat\-net radio](/wiki/Combat-net_radio "Combat-net radio") systems, and [passive optical network](/wiki/Passive_optical_network "Passive optical network") (PON) networks for upstream traffic from premises to the operator.

TDMA is a type of [time\-division multiplexing](/wiki/Time-division_multiplexing "Time-division multiplexing") (TDM), with the special point that instead of having one [transmitter](/wiki/Transmitter "Transmitter") connected to one [receiver](/wiki/Receiver_%28radio%29 "Receiver (radio)"), there are multiple transmitters. In the case of the *[uplink](/wiki/Uplink "Uplink")* from a [mobile phone](/wiki/Mobile_phone "Mobile phone") to a [base station](/wiki/Base_station "Base station") this becomes particularly difficult because the mobile phone can move around and vary the *timing advance* required to make its transmission match the gap in transmission from its peers.


Can TDMA be used in wired networks?