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ADSL (Asymmetrical Digital Subscriber Line) - an xDSL technology used for the high-speed transmission of data. This technology transforms a telephone line consisting of a twisted pair of copper wires (local loop) into a high-speed, always-on, internet connection capable of simultaneously carrying voice and data. It is termed 'asymmetric' because data moves in one direction faster than in the other i.e. data is transmitted faster from the local telephone exchange to the broadband user or subscriber (download), than from the end-user premises to the exchange (upload).

 

ADSL works by reserving part of the bandwidth for voice traffic and another part for data. Splitters located at each end of the line eliminate the parts of the signal that are not needed.

 

ADSL is capable of supporting download rates of up to 10Mbps over telephone lines in good condition at line distances of up to 3.4 miles (5.4 kilometres), though the standard products available in the UK market today have a rate of 0.5, 1 or 2Mbps. The bandwidth of an ADSL line is divided as follows:

 

 

Bandwidth deteriorates rapidly with line length; which means that broadband-users located beyond 3.8 miles (6 kilometres) from their local telephone exchange are restricted to 1Mbps or less.

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ADSL 2 - an evolution of the ADSL technology, which allows a higher rate of data transmission. It can provide download speeds of up to 12Mbps over a single copper pair up to 1 mile (1.6 kilometres) from the telephone exchange, or 24Mbps up to 1 mile (1.6 kilometres) using 2 copper pairs bonded together.

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ADSL 2+ (Extended bandwidth ADSL) – an evolution of the ADSL 2 technology which allows a higher rate of data transmission. It can provide download connection speeds of 26Mbps within 0.6 miles (1 kilometre) of the telephone exchange, falling to around 12.5Mbps at a range of 1.1 miles (1.8 kilometres). The higher bandwidth allows users to access multiple high bandwidth applications, including broadband television, concurrently. Bandwidth deteriorates rapidly with line distance beyond 1.6 miles (2.5 kilometres) from the exchange, and at a range of 2.8 miles (4.5 kilometres) it does not offer any speed advantage over ADSL. ADSL 2+ uses a signal of 2.2MHz.

 

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Backbone - the part of a network that handles the major traffic. It employs the highest - speed transmission paths in the network and may also run the longest distances. Smaller networks are attached to the backbone.

 

A backbone can span a geographic area of any size from a single building to an entire campus, or even an entire country.

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Backhaul - the transmission links between cell sites and the system operator's switching centre. In general, transmitting data from remote locations over the network "backbone" to a point from which it can be distributed over the network.

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Bandwidth – the capacity of a telephone line. It determines the amount of data (in bits) that can be transmitted over a line per second.

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Broadband - a term generally used for an always-on, high-bandwidth network connection using one of a variety of technologies. Broadband refers to telecommunication in which a wide band of frequencies is used to transmit data. The wide band allows data to be sent on many different frequencies within the band concurrently, allowing a greater amount of data to be sent in a given amount of time.

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Broadband over Powerline (BPL) - a technology that allows data to be transmitted over utility power lines. BPL works by modulating high-frequency radio waves with the digital signals from the internet. The radio waves are then fed into the utility grid at certain points, travelling along the power lines and passing through the utility transformers to subscriber's homes and businesses. A subscriber installs a modem that plugs into an ordinary power socket to receive broadband services.

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Cable – the cable broadband technology uses the same hybrid fibre and coaxial cable network that carry cable TV signals. The term hybrid signifies that fibre is used to carry signals from a serving location to a suburb whilst a coaxial cable is used to carry the TV and broadband signals from the suburb to the end users premises. Download rates of up to 50Mbps are possible through cable broadband with 10Mbps services expected to be made available in 2005. Meanwhile 150 kbps to 4Mbps services are offered by UK cable operators today.

 

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Dial-up (Narrowband) – this refers to the use of a telephone line and a modem to access an internet service. A narrowband modem supports a maximum download rate of 56kbps, and a maximum upload rate of 33.6kbps.

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Download - an end-user receiving data from the main public telecommunications network (e.g. getting a webpage from the internet), the reverse process of upload.

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DSLAM (Digital Subscriber Line Access Multiplexer)– a piece of equipment installed in a telephone exchange, that transforms a telephone line into an xDSL broadband connection.

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Ethernet - the IEEE's 802.3 standard for local area networking (LAN), which allows computers to communicate with each other over a wired network. Ethernet usually uses a coaxial ot twisted pair cable, although fibre and wireless versions are also available.

 

There are four main types of Ethernet:

 

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Fibre – an optical fibre line consists of an extremely thin glass cylinder core surrounded by a concentric layer of glass sheath. Data is transmitted along fibre lines in the form of modulated pulses of light. Potentially the bandwidth that can be passed through fibre can be as high as 2.5Gbps.

 

Fibre has traditionally been used by public telecoms operators in their core telecoms networks and sold as 'dedicated leased lines' to corporate and public sector customers for use in their private wide area networks.

 

There are a variety of different forms of fibre broadband (FTTx) including Fibre to the Curb (FTTC), Fibre to the Building (FTTB) and Fibre to the Home (FTTH).

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Fibrespeed - a term used to describe symmetrical broadband services with rates of 10Mbps and over.

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First Generation Broadband - a term used to describe broadband services with asymmetric download speeds of 512kbps to 2Mbps and upload speeds of 256kbps to 512kbps.

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FWA (Fixed Wireless Access) – a point-to-point radio wave or microwave link to the home or the office from a cell site or base station. Fixed wireless can be used for cellular backhaul, private WANs and for 'last mile' connectivity to buildings.

 

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Hotspot - an area in which an access point provides public wireless broadband network services to users through a wireless LAN, or Wi-Fi. Hotspots are often located in places with high footfall such as airports, hotels, coffee shops, libraries and convention centres.

 

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ISDN (Integrated Service Digital Network) - the digital transmission of data over a telephone line, using adapters at both ends of the transmission. ISDN services available in the UK typically provide download rates of up to 128kbps and upload rates of up to 16kbps. ISDN is only available to premises within 3.4 miles (5.5kilometres) of the local telephone exchange.

 

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LAN (Local Area Network) - a LAN is a group of computers and associated devices that share a common communications line or wireless link and, typically, share the resources of a single processor or server within a small geographic area.

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Last mile - a term used for any telecommunications technology that carries signals along the short distance between the main public telecommunications network and the home or business premise i.e. the infrastructure at the neighbourhood level, or local loop. The actual distance of the "last mile" can vary.

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Leased line - a permanent dedicated, direct connection leased by an end user from a telecommunications provider. Leased lines are often used by businesses to connect geographically distant offices.

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LLU (Local Loop Unbundling) – when an operator co-locates DSLAM equipment in the telephone exchange, in order to offer broadband to end users in competition to the incumbent.

 

The LLU operator determines the price and speed of the broadband connection offered over the unbundled telephone line.

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Local loop - the connection between an individual subscriber's telephone or data connection to the public telecommunication operator's central office or other local terminating point. It is sometimes referred to as the "last mile".

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Quadruple Play - the same as triple play but including the addition of a mobile telephony service

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Satellite – a broadband technology that uses a satellite located in geostationary orbit. Satellite broadband is available in two forms.

 

One way satellite, where dial-up is required to upload data (from the end user) and satellite is used to download data (to the end user).

 

Two way satellite, where satellite is used to both upload and download data (to and from the end user).

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SDSL(Symmetrical Digital Subscriber Line)– an xDSL broadband technology that works by using all of the bandwidth available over the twisted copper pair (local loop), to support the transmission of data at equal upload and download rates. SDSL does not reserve a part of the bandwidth for voice traffic and, as a result, does not support an analogue telephone line.

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Second generation broadband - a term used to describe asymmetrical services with download rates of between 2Mbps and 10Mbps and upload rates of between 512kbps and 1Mbps, as well as symmetrical services with download and upload rates of 2Mbps or above.

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Triple play - a term used to describe a bundled service offering voice, data and video services, usually for a price that is lower than the accumulative cost of the three individual services. The services will be delivered by one operator over a single converged network infrastructure

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Upload - transmitting data from the end-user to the main public telecommunications network (e.g. sending information to a website on the internet), the reverse process of download.

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VDSL (Very high speed Digital Subscriber Line) – a broadband technology that can provide download rates of up to 52Mbps and upload rates of up to 3Mbps over short local loops of up to 0.5 miles (0.8 kilometres). As VDSL can only transmit over a shorter distance, it requires service providers to deploy fibre optic cables in the local loop in order to get closer to the end user. VDSL can also be configured to operate in a symmetrical mode, delivering in excess of 10Mbps in each direction up to 0.9 Miles (1.4 kilometres).

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VoIP (Voice over Internet Protocol) – a broadband connection that allows users/subscribers to send and receive voice calls over the internet.

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VPN (Virtual Private Network) – a secure, encrypted connection between two points over the telecoms network, that allows private network traffic to travel over public networks without the need for a dedicated leased line. VPNs provide remote offices and telecommuters with secure access to a corporate LAN or WAN. Because VPN traffic is encrypted, it cannot be deciphered as it travels over the network.

 

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WAN (Wide Area Network) - a computer network that spans a relatively large geographical area. Typically, a WAN consists of two or more local-area networks (LANs) linked together. WANs can be used to share information across multiple sites. The world's largest WAN is the internet.

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Wi-Fi (Wireless Fidelity) – a form of short range (up to 0.1 kilometres) wireless networking, supporting download rates of up to 54Mbps. It allows the connection of two or more computers without the need for physical cabling between them. The most commonly used Wi-Fi standards are 802.11b and 802.11g. Wi-Fi is used in many community wireless networks and in the provision of wireless 'hotspots' set up in hotels, coffee shops, airports etc. Wi-Fi can also be used to create a wireless network in the home and office.

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Wi-Max – a wireless technology that provides high bandwidth broadband infrastructure over long distances (up to 31 miles or 50 kilometres). Wi-MAX can provide download rates of up to 70Mbps and can be used for wireless 'hotspots', cellular backhaul and even 'last mile' broadband solutions. Wi-Max can also be used for high-speed enterprise connectivity for business.

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Wireless – a term used to describe broadband technologies where data is transmitted by radio wave and microwaves, i.e. there are no physical links between the networked devices. There are a variety of different forms of wireless broadband including FWA, Wi-Fi and Wi-Max.

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Wireline - a term used to describe telecommunications systems, where a service is provided over some form of cabled or wired network, as opposed to a wireless or radio network

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xDSL (x Digital Subscriber Line) – a family of technologies that are used to transmit data. This technology transforms a telephone line consisting of a twisted pair of copper wires (local loop) into a high-speed always on connection. xDSL technologies include ADSL, SDSL, VDSL, and ADSL 2+.

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