Telecommunications link

Last updated

In a telecommunications network, a link is a communication channel that connects two or more devices for the purpose of data transmission. The link may be a dedicated physical link or a virtual circuit that uses one or more physical links or shares a physical link with other telecommunications links.

Contents

A telecommunications link is generally based on 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]

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

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. Classic 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. All of the peripheral CEs receive any transmission of data that originates from the central CE while any transmission of data that originates from any of the peripheral CEs is only received by the central CE.

Private and public

Links are often referred to by terms that refer to the ownership or accessibility of the link.

Direction

Feeder links, here: uplink / downlink Uplink y Downlink.jpg
Feeder links, here: uplink / downlink

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]

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.

Related Research Articles

<span class="mw-page-title-main">Time-division multiple access</span> Channel access method for networks using a shared communications medium

Time-division multiple access (TDMA) is a channel access method for shared-medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium while using only a part of its channel capacity. Dynamic TDMA is a TDMA variant that dynamically reserves a variable number of time slots in each frame to variable bit-rate data streams, based on the traffic demand of each data stream.

<span class="mw-page-title-main">Wireless network</span> Computer network not fully connected by cables

A wireless network is a computer network that uses wireless data connections between network nodes. Wireless networking allows homes, telecommunications networks and business installations to avoid the costly process of introducing cables into a building, or as a connection between various equipment locations. Admin telecommunications networks are generally implemented and administered using radio communication. This implementation takes place at the physical level (layer) of the OSI model network structure.

<span class="mw-page-title-main">Network topology</span> Arrangement of a communication network

Network topology is the arrangement of the elements of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, including command and control radio networks, industrial fieldbusses and computer networks.

The Ku band is the portion of the electromagnetic spectrum in the microwave range of frequencies from 12 to 18 gigahertz (GHz). The symbol is short for "K-under", because it is the lower part of the original NATO K band, which was split into three bands because of the presence of the atmospheric water vapor resonance peak at 22.24 GHz, (1.35 cm) which made the center unusable for long range transmission. In radar applications, it ranges from 12 to 18 GHz according to the formal definition of radar frequency band nomenclature in IEEE Standard 521–2002.

In telecommunications and computer networks, a channel access method or multiple access method allows more than two terminals connected to the same transmission medium to transmit over it and to share its capacity. Examples of shared physical media are wireless networks, bus networks, ring networks and point-to-point links operating in half-duplex mode.

<span class="mw-page-title-main">Communication channel</span> Physical or logical connection used for transmission of information

A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for information transfer of, for example, a digital bit stream, from one or several senders to one or several receivers. A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second.

<span class="mw-page-title-main">Ultra high frequency</span> Electromagnetic spectrum 300–3000 MHz

Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter. Radio waves with frequencies above the UHF band fall into the super-high frequency (SHF) or microwave frequency range. Lower frequency signals fall into the VHF or lower bands. UHF radio waves propagate mainly by line of sight; they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception. They are used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, satellite phones, and numerous other applications.

<span class="mw-page-title-main">Wireless</span> Transfer of information or power that does not require the use of physical wires

Wireless communication is the transfer of information (telecommunication) between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most common wireless technologies use radio waves. With radio waves, intended distances can be short, such as a few meters for Bluetooth or as far as millions of kilometers for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of applications of radio wireless technology include GPS units, garage door openers, wireless computer mouse, keyboards and headsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones. Somewhat less common methods of achieving wireless communications involve other electromagnetic phenomena, such as light and magnetic or electric fields, or the use of sound.

In telecommunications, a point-to-point connection refers to a communications connection between two communication endpoints or nodes. An example is a telephone call, in which one telephone is connected with one other, and what is said by one caller can only be heard by the other. This is contrasted with a point-to-multipoint or broadcast connection, in which many nodes can receive information transmitted by one node. Other examples of point-to-point communications links are leased lines and microwave radio relay.

<span class="mw-page-title-main">Point-to-multipoint communication</span> Communications method involving a one-to-many connection

In telecommunications, point-to-multipoint communication is communication which is accomplished via a distinct type of one-to-many connection, providing multiple paths from a single location to multiple locations.

<span class="mw-page-title-main">Cellular network</span> Communication network

A cellular network or mobile network is a telecommunications network where the link to and from end nodes is wireless and the network is distributed over land areas called cells, each served by at least one fixed-location transceiver. These base stations provide the cell with the network coverage which can be used for transmission of voice, data, and other types of content. A cell typically uses a different set of frequencies from neighboring cells, to avoid interference and provide guaranteed service quality within each cell.

A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow for simultaneous communication in both directions between two connected parties or to provide a reverse path for the monitoring and remote adjustment of equipment in the field. There are two types of duplex communication systems: full-duplex (FDX) and half-duplex (HDX).

In communications systems, the return channel 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 asymmetric digital subscriber line, cable modems, mobile broadband and satellite internet access.

<span class="mw-page-title-main">E-UTRA</span> 3GPP interface

E-UTRA is the air interface of 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) upgrade path for mobile networks. It is an acronym for Evolved UMTS Terrestrial Radio Access, also known as the Evolved Universal Terrestrial Radio Access in early drafts of the 3GPP LTE specification. E-UTRAN is the combination of E-UTRA, user equipment (UE), and a Node B.

In a hierarchical telecommunications network, the backhaul portion of the network comprises the intermediate links between the core network, or backbone network, and the small subnetworks at the edge of the network.

<span class="mw-page-title-main">High Speed Packet Access</span> Communications protocols

High Speed Packet Access (HSPA) is an amalgamation of two mobile protocols—High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA)—that extends and improves the performance of existing 3G mobile telecommunication networks using the WCDMA protocols. A further-improved 3GPP standard called Evolved High Speed Packet Access was released late in 2008, with subsequent worldwide adoption beginning in 2010. The newer standard allows bit rates to reach as high as 337 Mbit/s in the downlink and 34 Mbit/s in the uplink; however, these speeds are rarely achieved in practice.

DVB-RCS provides a method by which the DVB-S platform can become a bi-directional, asymmetric data path using wireless between broadcasters and customers. It is a specification for an interactive on-demand multimedia satellite communication system formulated in 1999 by the DVB consortium. Without this method, various degrees of interactivity can be offered, without implying any return channel back from the user to the service provider: Data Carrousel or Electronic Programs Guides (EPG) are examples of such enhanced TV services which make use of “local interactivity”, without any return path from customer to provider.

Multi-user MIMO (MU-MIMO) is a set of multiple-input and multiple-output (MIMO) technologies for multipath wireless communication, in which multiple users or terminals, each radioing over one or more antennas, communicate with one another. In contrast, single-user MIMO (SU-MIMO) involves a single multi-antenna-equipped user or terminal communicating with precisely one other similarly equipped node. Analogous to how OFDMA adds multiple-access capability to OFDM in the cellular-communications realm, MU-MIMO adds multiple-user capability to MIMO in the wireless realm.

In radio, cooperative multiple-input multiple-output is a technology that can effectively exploit the spatial domain of mobile fading channels to bring significant performance improvements to wireless communication systems. It is also called network MIMO, distributed MIMO, virtual MIMO, and virtual antenna arrays.

An amateur radio satellite is an artificial satellite built and used by amateur radio operators. It forms part of the Amateur-satellite service. These satellites use amateur radio frequency allocations to facilitate communication between amateur radio stations.

References

  1. ATIS committee PRQC. "network topology". ATIS Telecom Glossary 2007. Alliance for Telecommunications Industry Solutions. Archived from the original on 2018-08-03. Retrieved 2008-10-10.
  2. Basics of C & Ku Band Archived 2015-07-24 at the Wayback Machine Scatmag.com