- Return channel
communications systems that use star topologies, the return channel (also reverse channel, back channel or return link) is the transmission link from a user terminal to the central hub.
Return links are often, but not always, slower than the corresponding forward links. Examples where this is true include ADSL (where the "A" stands for "asymmetric"), cable modems, cellular Internet access facilities (e.g.
3G) and satellite internetaccess.
The return channel need not use the same medium as the main channel. For example, some "hybrid" Internet access services use a one-way
cable televisionsystem for the forward channel and a dial-up modemand telephone linefor the return channel.
Even when the return and forward channels use the same medium, their differencesoften dictate the use of very different data
modulationand codingtechniques. For example, in a star radio network,only the central hub transmits on the forward link, so multiple access contentionisa consideration only on the return link.
The "forward/return" terminology is also used for
spacecraftcommand and telemetrylinks. Because the return link carries telemetry, it is often orders of magnitude faster than the forward link that transmits onlya few predefined spacecraft commands.
"Return" and "forward" links are distinct from, and should not be confused with, uplinks and downlinks in satellite communication systems. For example, satellite Internet access withconventional
bent pipespacecraft transpondersrequires a total of two uplinks and two downlinks. One uplink and downlink pair are used for the forward link from the central ground hub through the satellite to the user termanal, and another uplink/downlink pair areused for the return link from the user terminal to the central hub.
Wikimedia Foundation. 2010.
См. также в других словарях:
DVB return channel — Dieser Artikel wurde wegen inhaltlicher Mängel auf der Qualitätssicherungsseite der Redaktion Film und Fernsehen unter Angabe von Verbesserungsvorschlägen eingetragen. Beteilige Dich an der Verbesserung dieses Artikels und entferne diesen… … Deutsch Wikipedia
Astra Return Channel System — Astra Return Channel System, ARCS … Universal-Lexikon
Return — may refer to:* Return (architecture), the receding edge of a flat face * Return (finance), the financial term for the profit or loss derived from an investment * Tax return, a form submitted to taxation authorities * Carriage return, a key on an… … Wikipedia
Channel (communications) — Old telephone wires are a challenging communications channel for modern digital communications. In telecommunications and computer networking, a communication channel, or channel, refers either to a physical transmission medium such as a wire, or … Wikipedia
Channel 5 (UK) programming — Channel 5 airs a wide variety of programming that coveres various genres and themes. Launched in 1997, the channel has always been seen to have less distinctive programming than their other terrestrial rivals at the BBC, ITV and Channel 4. The… … Wikipedia
Channel 5 (UK) — Channel 5 Channel 5 logo Launched 30 March 1997 (1997 03 30) Owned by Northern Shell … Wikipedia
Return of the Living Dead (film series) — Return of the Living Dead is a series of films that was produced between 1985 2005. The series came about as a dispute between John Russo and George A. Romero over how to handle sequels to their 1968 film, Night of the Living Dead . The two… … Wikipedia
Return to Halloweentown — DVD cover Distributed by Disney Channel … Wikipedia
Channel Airways — IATA CW ICAO Callsign Founded 1946 Cease … Wikipedia
Channel coordination — (or supply chain coordination) aims at improving supply chain performance by aligning the plans and the objectives of individual enterprises. It usually focuses on inventory management and ordering decisions in distributed inter company settings … Wikipedia