Telecommunications link

In telecommunications a link is a communication channel that connects two or more devices. This link may be an actual physical link or it may be a logical link that uses one or more physical links or shares a physical link with other telecommunications links.

A telecommunications link is generally one of several types of information transmission paths such as those provided by communication satellites, terrestrial radio communications infrastructure and computer networks to connect two or more points.

The term link is widely used in computer networking to refer to the communications facilities that connect nodes of a network.[1][a] When the link is a logical link the type of physical link should always be specified (e.g., data link, uplink, downlink, fiber optic link, point-to-point link, etc.)

Types

Point-to-point

A point-to-point link is a dedicated link that connects exactly two communication facilities (e.g., two nodes of a network, an intercom station at an entryway with a single internal intercom station, a radio path between two points, etc.).

Broadcast

Broadcast links connect two or more nodes and support broadcast transmission, where one node can transmit so that all other nodes can receive the same transmission. Ethernet is an example.

Multipoint

Also known as a multidrop link, a multipoint link is a link that connects two or more nodes. Also known as general topology networks, these include ATM and Frame Relay links, as well as X.25 networks when used as links for a network layer protocol like IP.

Unlike broadcast links, there is no mechanism to efficiently send a single message to all other nodes without copying and retransmitting the message.

Point-to-multipoint

A point-to-multipoint link (or simply a multipoint) is a specific type of multipoint link which consists of a central connection endpoint (CE) that is connected to multiple peripheral CEs. Any transmission of data that originates from the central CE is received by all of the peripheral CEs while any transmission of data that originates from any of the peripheral CEs is only received by the central CE.

Private and public — accessibility and ownership

Links are often referred to by terms which refer to the ownership and / or accessibility of the link.

  • A private link is a link that is either owned by a specific entity or a link that is only accessible by a specific entity.
  • A public link is a link that uses the public switched telephone network or other public utility or entity to provide the link and which may also be accessible by anyone.

Direction

Uplink y Downlink
Feeder links, here: uplink / downlink

Uplink

Downlink

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).[2]

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

Notes

  1. ^ Sometimes the communications facilities that provide the communications channel that constitutes a link are also included in the definition of link.

References

  1. ^ ATIS committee PRQC. "network topology". ATIS Telecom Glossary 2007. Alliance for Telecommunications Industry Solutions. Retrieved 2008-10-10.
  2. ^ Basics of C & Ku Band Scatmag.com
Atlantic Telegraph Company

The Atlantic Telegraph Company was a company formed on 6 November 1856 to undertake and exploit a commercial telegraph cable across the Atlantic ocean, the first such telecommunications link.

Automated ECG interpretation

Automated ECG interpretation is the use of artificial intelligence and pattern recognition software and knowledge bases to carry out automatically the interpretation, test reporting, and computer-aided diagnosis of electrocardiogram tracings obtained usually from a patient.

Construction collaboration technology

Construction collaboration technology refers to software applications used to enable effective sharing of project-related information between geographically dispersed members of a construction project team, often through use of a web-based software as a service platform.

Delta-DOR

Delta-Differential One-Way Ranging (or Delta-DOR, Δ-DOR for short) is an interplanetary radio-tracking and navigation technique.

End instrument

In telecommunications an end instrument is a piece of equipment connected to the wires at the end of a telecommunications link. In telephony, this is usually a telephone connected by a local loop. End instruments that relate to data terminal equipment include printers, computers, barcode readers, automated teller machines (ATMs) and the console ports of routers.

Ground station

For stations controlling unmanned aerial vehicles (UAVs), see Ground control station.A ground station, earth station, or earth terminal is a terrestrial radio station designed for extraplanetary telecommunication with spacecraft (constituting part of the ground segment of the spacecraft system), or reception of radio waves from astronomical radio sources. Ground stations may be located either on the surface of the Earth, or in its atmosphere. Earth stations communicate with spacecraft by transmitting and receiving radio waves in the super high frequency or extremely high frequency bands (e.g., microwaves). When a ground station successfully transmits radio waves to a spacecraft (or vice versa), it establishes a telecommunications link. A principal telecommunications device of the ground station is the parabolic antenna.

Ground stations may have either a fixed or itinerant position. Article 1 § III of the ITU Radio Regulations describes various types of stationary and mobile ground stations, and their interrelationships.Specialized satellite earth stations are used to telecommunicate with satellites—chiefly communications satellites. Other ground stations communicate with manned space stations or unmanned space probes. A ground station that primarily receives telemetry data, or that follows a satellite not in geostationary orbit, is called a tracking station.

When a satellite is within a ground station's line of sight, the station is said to have a view of the satellite (see pass). It is possible for a satellite to communicate with more than one ground station at a time. A pair of ground stations are said to have a satellite in mutual view when the stations share simultaneous, unobstructed, line-of-sight contact with the satellite.

High-altitude platform station

High-altitude platform station or High-Altitude Pseudo-Satellite (short: HAPS) or High-Altitude Platform (short: HAP or HAPs[plural]) is – according to Article 1.66A of the International Telecommunication Union´s (ITU) ITU Radio Regulations (RR) – defined as "a station on an object at an altitude of 20 to 50 km and at a specified, nominal, fixed point relative to the Earth".

Each station shall be classified by the service in which it operates permanently or temporarily.

See also

Jupiter Icy Moons Orbiter

The Jupiter Icy Moons Orbiter (JIMO) was a proposed NASA spacecraft designed to explore the icy moons of Jupiter. The main target was Europa, where an ocean of liquid water may harbor alien life. Ganymede and Callisto, which are now thought to have liquid, salty oceans beneath their icy surfaces, were also targets of interest for the probe.

Optical link

An optical link is a telecommunications link that consists of a single end-to-end optical circuit. A cable of optical fibers, possibly concatenated into a dark fiber link, is the simplest form of an optical link.

Other forms of optical link can include single-"colour" links over a wavelength division multiplex infrastructure, and/or links that use optical amplifiers to compensate for attenuation over long distances.

Other forms of optical links include free-space optical telecommunication links.

In the rail transport sector, optical links are used in two forms depending on whether the feeding station is a main station or not. Thus main stations are called 'long halls', and all remaining stations are said to be 'short halls'.

Repeater

In telecommunications, a repeater is an electronic device that receives a signal and retransmits it. Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction.

Some types of repeaters broadcast an identical signal, but alter its method of transmission, for example, on another frequency or baud rate.

There are several different types of repeaters; a telephone repeater is an amplifier in a telephone line, an optical repeater is an optoelectronic circuit that amplifies the light beam in an optical fiber cable; and a radio repeater is a radio receiver and transmitter that retransmits a radio signal.

A broadcast relay station is a repeater used in broadcast radio and television.

Royal Observer Corps

The Royal Observer Corps (ROC) was a civil defence organisation intended for the visual detection, identification, tracking and reporting of aircraft over Great Britain. It operated in the United Kingdom between 29 October 1925 and 31 December 1995, when the Corps' civilian volunteers were stood down (ROC headquarters staff at RAF Bentley Priory stood down on 31 March 1996). Composed mainly of civilian spare-time volunteers, ROC personnel wore a Royal Air Force (RAF) style uniform and latterly came under the administrative control of RAF Strike Command and the operational control of the Home Office. Civilian volunteers were trained and administered by a small cadre of professional full-time officers under the command of the Commandant Royal Observer Corps; latterly a serving RAF Air Commodore.

Sign language

Sign languages (also known as signed languages) are languages that use the visual-manual modality to convey meaning. Language is expressed via the manual signstream in combination with non-manual elements. Sign languages are full-fledged natural languages with their own grammar and lexicon. This means that sign languages are not universal and they are not mutually intelligible, although there are also striking similarities among sign languages.

Linguists consider both spoken and signed communication to be types of natural language, meaning that both emerged through an abstract, protracted aging process and evolved over time without meticulous planning. Sign language should not be confused with body language, a type of nonverbal communication.

Wherever communities of deaf people exist, sign languages have developed as handy means of communication and they form the core of local deaf cultures. Although signing is used primarily by the deaf and hard of hearing, it is also used by hearing individuals, such as those unable to physically speak, those who have trouble with spoken language due to a disability or condition (augmentative and alternative communication), or those with deaf family members, such as children of deaf adults.

It is unclear how many sign languages currently exist worldwide. Each country generally has its own, native sign language, and some have more than one. The 2013 edition of Ethnologue lists 137 sign languages. Some sign languages have obtained some form of legal recognition, while others have no status at all.Linguists distinguish natural sign languages from other systems that are precursors to them or derived from them, such as invented manual codes for spoken languages, home sign, "baby sign", and signs learned by non-human primates.

Svalbard Undersea Cable System

The Svalbard Undersea Cable System is a twin submarine communications cable which connects Svalbard to the mainland of Norway. The two optical fiber cable consist of two segments, from Harstad to Breivika in Andøy, and from Breivika to Hotellneset near Longyearbyen in Svalbard. The segments from Harstad to Breivika are 74 and 61 kilometers (46 and 38 mi) long, respectively, and the segments from Breivika to Hotellneset 1,375 and 1,339 kilometers (854 and 832 mi). Each consists of eight fiber pairs and there are twenty optical communications repeaters on each segment. Each segment has a speed of 10 gigabits per second (Gb/s), with a future potential capacity of 2,500 Gbit/s. The system is now the sole telecommunications link to the archipelago.

Planning of the cables started in 2002 by the Norwegian Space Centre (NSC), who wanted increased bandwidth to expand their business at Svalbard Satellite Station (SvalSat). At the time all telecommunications from Svalbard were relayed via communications satellite. Financing was secured through a deal with the National Aeronautics and Space Administration (NASA). The cable system was supplied by Tyco Communications and laying of the cable was carried out by Global Marine Systems in July and August 2003.

Terminal (telecommunication)

In the context of telecommunications, a terminal is a device which ends a telecommunications link and is the point at which a signal enters and/or leaves a network. Examples of equipment containing network terminations are telephones, fax machines, computer terminals and network devices, printers and workstations.

Trunkline

A trunkline may refer to any of the following:

A natural gas or oil line using pipeline transport

Trunkline LNG, a liquid natural gas plant in Lake Charles, Louisiana

Trunkline Pipeline, a pipeline that runs from Texas and Louisiana to Illinois and Indiana

A main telecommunications link such as a phone line directly connecting exchanges or switchboards at a considerable distance apart

A main transportation link such as:

A component of the Michigan State Trunkline Highway System

A main rail line

Uplink (disambiguation)

Uplink may refer to:

Uplink, a telecommunications link

Uplink (video game), a 2001 "hacking simulation" video game released by Introversion Software

Half-Life: Uplink, a 1998 demo version of the Half-Life video game

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