Editing Duplex (telecommunications) (section)

=== Time-division duplexing === <!--[[Time-division duplex]] and others link here-->
'''Time-division duplexing''' ('''TDD''') is the application of [[time-division multiplexing]] to separate outward and return signals. It emulates full-duplex communication over a half-duplex communication link.

Time-division duplexing is flexible in the case where there is [[asymmetry]] of the [[Telecommunications link|uplink]] and [[downlink]] data rates or utilization. As the amount of uplink data increases, more communication capacity can be dynamically allocated, and as the traffic load becomes lighter, capacity can be taken away. The same applies in the downlink direction. 

The ''transmit/receive transition gap'' (TTG) is the gap (time) between a downlink burst and the subsequent uplink burst. Similarly, the ''receive/transmit transition gap'' (RTG) is the gap between an uplink burst and the subsequent downlink burst.<ref>{{cite web |url=http://www.rfwireless-world.com/Terminology/TTG-gap-vs-RTG-gap-in-WiMAX-LTE.html |title=TTG vs RTG-What is TTG and RTG Gaps in WIMAX, LTE |access-date=2021-06-05}}</ref>

Examples of time-division duplexing systems include:
* [[UMTS-TDD]] for data communications on [[3G]] mobile networks
* [[LTE-TDD]] for data communications on [[4G]] mobile networks
* [[DECT]] wireless telephony
* Half-duplex [[packet switched]] networks based on [[carrier-sense multiple access]], for example, 2-wire or [[Ethernet hub|hubbed Ethernet]], [[Wireless local area network]]s and [[Bluetooth]], can be considered as time-division duplexing systems, albeit not TDMA with fixed frame-lengths.
* [[WiMAX]]
* [[PACTOR]]
* ISDN BRI [[U interface]], variants using the time-compression multiplex (TCM) line system
* [[G.fast]], a [[digital subscriber line]] (DSL) standard developed by the [[ITU-T]]