Reverse channel

In 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 internet access (e.g. ASTRA2Connect).

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 television system for the forward channel and a dial-up modem and telephone line for the return channel.

Even when the return and forward channels use the same medium, their differences often dictate the use of very different data modulation and coding techniques. For example, in a star radio network, only the central hub transmits on the forward link, so multiple access contention is a consideration only on the return link.

The "forward/return" terminology is also used for spacecraft command and telemetry links. Because the return link carries telemetry, often including imagery, it is often orders of magnitude faster than the forward link that transmits only a 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 with conventional bent pipe spacecraft transponders requires 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 terminal, and another uplink/downlink pair are used for the return link from the user terminal to the central hub.

See also

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.