Telecommunications link

Telecommunications link
"Uplink" redirects here. For other uses, see Uplink (disambiguation).

A telecommunications link is generally one of several types of information transmission paths such as those provided by communication satellites to connect two points on earth.

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Uplink

An uplink (UL or U/L) is the portion of a communications link used for the transmission of signals from an Earth terminal to a satellite or to an airborne platform. An uplink is the inverse of a downlink. An uplink or downlink is distinguished from reverse link or forward link (see below).

  • Pertaining to data transmission from a data station to the headend.
  • Pertaining to GSM and cellular networks, the radio uplink is the transmission path from the Mobile Station (Cell Phone) to a Base Station (Cell Site). Traffic and signalling flows within the BSS and NSS may also be identified as uplink and downlink.

This is similar to the general computer network concept of the upstream direction.

Downlink

A downlink (DL) is the link from a satellite to a ground station.

  • Pertaining to cellular networks, the radio downlink is the transmission path from a Base Transceiver Station (Cell Site) to the Mobile Station (Cell Phone). Traffic and signalling flows within the Base Station Subsystem (BSS) and Network and Switching Subsystem (NSS) may also be identified as uplink and downlink.

This is similar to the general computer network concept of the downstream direction.

Forward link

A forward link is the link from a fixed location (e.g., a base station) to a mobile user. If the link includes a communications relay satellite, the forward link will consist of both an uplink (base station to satellite) and a downlink (satellite to mobile user).

Reverse link

The reverse link (sometimes called a return channel) is the link from a mobile user to a fixed base station.

If the link includes a communications relay satellite, the reverse link will consist of both an uplink (mobile station to satellite) and a downlink (satellite to base station) which together constitute a half hop.

See also: Backhaul (telecommunications) and Return channel

Sources

See also


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