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Sometimes things need some explaining.
AND NEW NETWORKS IN TELECOMMUNICATIONS
Contents
Asymmetric Digital Subscriber Line (ADSL) ADSL2 ADSL2+ Asynchronous Transfer Mode (ATM) Bluetooth Cellular Digital Subscriber Line Lite (DSL Lite) Extended-rate Single-pair High-speed DSL (ESHDSL) Fixed Radio Access (FRA) Frame Relay General Packet Radio System (GPRS) High speed Digital Subscriber Line (HDSL) Integrated Services Digital Network (ISDN) Internet Internet Protocol (IP) Networks Intranet IP Multimedia Subsystem Local Area Network (LAN) Mesh systems Metropolitan Area Network (MAN) Multipoint Video Distribution Systems (MVDS) Next Generation Access Next Generation Networks (NGN) Optical fibre Personal Communications Networks (PCN) Power Line Telecommunications (PLT) SuperJANET Synchronous Digital Hierarchy (SDH) Ultra Wide Band (UWB) Universal Mobile Telecommunications Systems (UMTS) Very high speed Digital Subscriber Line (VDSL) Wave Division Multiplexing (WDM) Wide Area Network (WAN) Wi-Fi WiMAX Wireless Application Protocol (WAP) World Wide Web (WWW) x Digital Subscriber Line (xDSL) ZigBee
Asymmetric Digital Subscriber Line (ADSL)
Asymmetric Digital Subscriber Line – or, as it is known in the United States, Asymmetric Digital Subscriber Loop - is a digital transmission technique for enhancing the information-carrying capacity of traditional copper pair cables in the local access network. Since the bandwidth of the return channel is less than that of the outgoing channel, the technique is described as asymmetric. It was originally conceived as suitable for video on demand services by delivering video signals to the customer's premises with a low-capacity return channel for customer selection or ordering purposes. However, ADSL has become the principal means of delivering broadband telecommunications services to domestic premises - originally at 512 kilobits a second, but now (especially throught local loop unbundling) up to 8 Megabits a second.
See: ADSL2, ADSL2+, DSL Lite, HDSL, VDSL, xDSL
ADSL2
ADSL services typically operate at a maximum speed of 1.5 megabits per second (Mbps), supporting e-mail, Web access, Voice over Internet Protocol (VoIP) and some multimedia applications. ADSL2 is an enhanced version delivering speeds of up to 12 Mbps.
ADSL2+
ADSL2+ reached consent at the International Telecommunications Union (ITU) in January 2003, joining the ADSL2 standards family. While the first two members of the ADSL2 standards family specify a downstream frequency band up to 1.1 MHz and 552 kHz respectively, ADSL2+ specifies a downstream frequency up to 2.2 MHz. The result is a significant increase in data rates on shorter phone lines, doubling the downstream bandwidth and increasing the downstream data rate to as much as 24 Mbps. Although the technological standard behind ADSL2+ was agreed some time ago, its introduction in the UK has been hampered by the fact that it interferes with another technology called Very high speed Digital Subscriber Line (VDSL). Other countries that have implemented ADSL2+ have been forced to ban VDSL. In Britain, however, a technological solution has now been found to allow both technologies to be used.
See: ADSL, DSL Lite, HDSL, VDSL, xDSL
Asynchronous Transfer Mode (ATM)
This is a digital transmission technique which uses packet switching technology. These packets are of a uniform, short fixed length and are called cells, so that ATM is sometimes called Cell Relay. Each packet contains 48 bytes of the information to be transported and 5 bytes of control information - called the header - that allows the network's switches to route the packets very quickly to their destinations where the packets are recombined in the correct order. With ATM, the same circuit can be used to carry data from many different sources simultaneously which dramatically increases the capacity of existing systems. Even more importantly, compared to earlier transmission speeds of 10 million bits a second, ATM delivers streams of information at very high speeds - currently up to 155 million bits a second - which makes it possible to send video as easily as voice. It is this technology which is used by the SuperJANET (Joint Academic Network). Eventually ATM is expected to push transmission speeds up to as much as 622 million bits a second.
See: SuperJANET
Bluetooth
This is a wireless communications system based on the IEE standard 802.15.1 and utilising the 2.4 GHz band. It is named after King Harald Blaatand (Bluetooth) and it is a radio frequency networking system that enables a host of electronic devices to connect to and communicate with various networks including the Internet. Such devices can include domestic equipment like heating, lighting and ventilation systems and personal equipment like handheld and notebook computers, mobile telephone and personal stereo. Combining Bluetooth and Ultra Wide Band wireless technologies in a common standard is being investigated by the Bluetooth Special Interest Group. Combining Ultra Wide Band with Bluetooth would satisfy increasing demand for higher data rates, such as needed between a digital camera and a PC.
See: ZigBee, Ultra Wide Band
Cellular
This is a radio technology used for first generation mobile services. The country is sub-divided into small cells each with its own low power radio transmitter. No two adjacent cells use the same transmission frequency and, in this way, radio frequencies can be re-used, dramatically increasing the capacity of the network compared to previous mobile systems. As the mobile passes from one cell to an adjoining one transmitting on a different frequency, it is automatically switched by a computer with a speed so rapid that it is undetectable by the user. In Britain, cellular systems operate at around 900 MHz. The original analogue networks were based on the Total Access Communications System (TACS) standard, while the more recent digital networks are based on the Global Systems Mobile (GSM) standard. Two companies were licensed to operate analogue networks and five companies have won licences to operate digital networks.
See: General Packet Radio System, Personal Communications Networks, Universal Mobile Telecommunications Systems
Digital Subscriber Line Lite (DSL Lite)
This operates in accordance with the same principle as Asymmetric Digital Subscriber Line (ADSL) – that is, faster speed than conventional telephony but over existing telephone lines – but at lower speeds than ADSL. Downstream speeds are between 64 kilobits – 1.5 megabits a second, while upstream speeds are between 32 kilobits – 512 megabits a second. Although speeds are slower than for ADSL, installation costs are lower too.
See: ADSL, HDSL, VDSL, xDSL.
Extended-rate Single-pair High-speed DSL (ESHDSL)
This is a version of Digital Subscriber Line (DSL) technology used mainly for corporate broadband applications and providing up to 5Mb/s in both directions.
Fixed Radio Access (FRA)
This is a radio technique to provide local access between a local telephone exchange and a local telephone customer. It is the technology that was used by Ionica to provide a competitive local telephony service to that of BT before the company colapsed. The frequency used was between 3,425 - 3,490 MHz. Each base station could service up to 2,000 users and was linked to the nearest Ionica exchange. Each customer had a 30 cm-diameter radio transceiver unit, containing an antenna and electronics, mounted on the roof. A thin cable connected the roof equipment to an internal double telephone socket into which the customer's existing telephone equipment was plugged. Power was provided by the household mains with a rechargeable battery backup. Each residential unit supported the equivalent of two exchange lines providing voice quality equivalent to conventional wireline technology.
Frame Relay
Like Asynchronous Transfer Mode (ATM), this is a digital transmission technique which uses packet switching technology to provide fast data transmission. However, Frame Relay uses a variable length unit of data called a frame and it does not have the speed of ATM technology. Public frame relay services are much more prominent in the USA than Europe (with the notable exception of Finland) and such services have been used in the Asia-Pacific region.
See: Asynchronous Transfer Mode
General Packet Radio System (GPRS)
Like Wireless Application Protocol (WAP), this is a technology for permitting mobile telephones and other devices to access the Internet, but it is a packet-based system which enhances the capacity of existing digital mobile networks (cellular and PCN) through making better use of the network’s bandwidth by creating packets of network time that can be accessed exclusively by any one user. GPRS has data rates of 144 kilobits a second – much slower than the 2 megabits a second offered by the new 3G networks, but roughly three times faster than the normal data rate of a fixed line between a computer and the Internet. Heavy demand could create delays in access times, a problem not be faced by 3G systems which operate on their own dedicated networks.
See : Cellular, Personal Communications Networks, Universal Mobile Telecommunications Systems, Wireless Application Protocol
High speed Digital Subscriber Line (HDSL)
This is a digital transmission technique used by public telecommunications operators to provide advanced services to business premises using the copper access cable. Unlike Asymmetric Digital Subscriber Line (ADSL), it provides the same bit rate in each direction, operating at up to 2 megabits a second. Therefore it can be used for Web/email hosting as well as fast Internet access and other applications.
See: ADSL, DSL Lite, VDSL, xDSL
Integrated Services Digital Network (ISDN)
This technology uses special lines and special switches for the simultaneous transmission of voice and data on the same wire in common digital form. Each channel within an ISDN line carries 64,000 bits a second and an ISDN line can have up to 30 channels which adds up to a maximum transfer rate of just under 2 megabits a second. Therefore ISDN is a medium-band technology that can sustain routine videoconferencing but not full-quality video. Whereas ISDN started as a business service, in Europe it was increasingly used in the residential market as home computer users sought faster access to the Internet, but it has now been overtaken by braodband technologiers such as ADSL.
Internet
The Internet evolved out of an American government network of military computers into a much wider grouping of American government and academic networks into today's global network of networks. In most countries, it uses lines leased from local telephone companies for the transmission of data using packet-switching techniques. Therefore no single organisation owns the Internet and no-one controls it. A major use of the Internet is for the sending of electronic mail (e-mail). However, the most high-profile part of the Internet is the World Wide Web. This is the commercial graphic side of the network and uses words and pictures. Although the Internet has grown up as a network for the transmission of data, it is now being used for the carriage of voice. Since when one is using the Internet one is only paying for the cost of a local telephone call, the ability of the Internet to carry international telephone calls is exciting the interest of telephone users and telephone companies.
See: Internet Protocol Networks, Intranet, Voice over Internet Protocol, World Wide Web
Internet Protocol (IP) Networks
New networks are being built which are able to exploit the cost advantages of the Internet, which is based largely on its use of packet switching, without the congestion and quality problems currently experienced by provision of telephony over the Internet. These new networks will use the Internet Protocol (IP) which will enable them to carry voice as well as data with quality comparable to current telephony networks. While some quality, standards and interconnection issues remain to be resolved, many believe that that these IP networks will provide a greater competitive threat than the Internet to operators of traditional telephony networks using circuit swiching. Indeed incumbent operators are likely to have to respond by building IP networks of their own. BT is building an IP network called the 21st Century Network (21CN).
See: Internet
Intranet
An Intranet is a closed-access variation of the Internet used for corporate applications. Whereas achieving a corporate presence on the Internet is easily done using the web server and software of an Internet Service Provider (ISP), running an Intranet application requires a hardware platform, web server software, and a high-speed leased line to a service provider.
See: Internet
IP Multimedia Subsystem (IMS)
IMS is a network architecture that was originally defined for 3G mobile networks by the 3rd Generation Partnership Project (3GPP) and it is based on the standard Session Initiation Protocol (SIP) signalling language. It has since been extended to wireline networks by the European Telecommunications Standards Institute (ETSI) through its initiative on Telecoms & Internet Converged Services & Protocols for Advanced Networks (TISPAN). It is becoming increasingly clear that IMS will be the core technology platform for next generation networks and services in telecommunications and, since it is access independent and extremely flexible because of its layed structure, it enables rapid design and deployment of new applications and services.
See: Next Generation Networks
Local Area Network (LAN)
This is a data communications network designed to provide facilities for users within a particular office or group of buildings and typically operates at a data rate of 2 megabits a second or more. A LAN is owned by the organisation using it and does not necessarily use public service facilities.
See: Metropolitan Area Network, Wide Area Network
Mesh systems
Wireless systems for industry such as Wi-Fi have mostly used cellular phone-style radio links, using point-to-point or point-to-multipoint transmission, but such traditional wireless formats have limitations in industrial applications, including rigid structure, meticulous planning requirements, and dropped signals. In contrast, wireless mesh networks are multi-hop systems in which devices assist each other in transmitting packets through the network, especially in adverse conditions. One can locate ad hoc networks into place with minimal preparation and they provide a reliable, flexible system that can be extended to hundreds of devices over a wide geographical area. What mesh networks have in common is that, instead of the current hub-and-spoke model of wireless communications with every device connecting to an overburdened central antenna, any time mesh-enabled devices are in close proximity to each other, they automatically create a wireless mesh network. On such systems, data can 'hop' up to 2 Km from rooftop to rooftop.
Metropolitan Area Network (MAN)
This is a data communications network designed to cover a particular city which makes it larger than a Local Area Network (LAN) but smaller than a Wide Area Network (WAN). A British example of a MAN is the London Metropolitan Area Network which links the databases of the capital's academic institutions. It is an extension of the SuperJANET national academic network. However, compared to SuperJANET which operates at 10 megabits a second at most sites, the London MAN operates at data transfer rates of 155 megabits a second - that is, more than 15 times faster.
See: Local Area Network, Wide Area Network, WiMax
Multipoint Video Distribution Systems (MVDS)
Multipoint Video Distribution Systems (MVDS) - or, as they are known in the United States, Multichannel Multipoint Distribution Service (MMDS) - are a means of delivering multi-channel television to a particular locality by microwave - what is sometimes called 'wireless cable'. Currently there are some four million subscribers worldwide with around 750,000 in the USA.
Optical fibre
This technology involves the generation of light signals by miniature lasers the size of a grain of sand which then travel along glass fibres as fine as a strand of human hair to be received by tiny diodes. The main advantage of optical fibre over traditional copper cable is the enormously greater capacity or bandwidth. However, there are many other advantages: optical fibres are smaller, lighter, far more reliable, are not affected by electrical interference, and do not cause interference with other equipment, while optical fibre systems can carry signals far greater distances without the need for the signal to be boosted. The cost of fibre - which is basically silica or sand - is falling rapidly, but currently the cost of opto-electronic components - which convert electrical signals into light signals at one end and light signals back into electrical signals at the other - remains high. Therefore, most fibre is used in the backhaul network, but fibre will increasingly be pushed closer to the customer as fibre to the cabinet (FTTCab), fibre to the curb (FTTC), fibre to the building (FTTB) or fibre to the home (FTTH).
See: Wave Division Multiplexing
Next Generation Access
Ofcom’s Phase Two consultation document as part of its strategic review of telcommunications devoted six pages to the subject of regulating next generation access networks. The document defined them simply as "those that go beyond the capabiities of the existing copper, cable and wireless public networks that exist today", that is networks that "will allow the delivery of much higher bandwidths to consumers and in consequence the delivery of much richer services". Typically next generation access would involve fibre in ther local loop.
See: Next Generation Networks
Next Generation Networks (NGNs)
There is no agreed definition of Next Generation Networks but, at the heart of the concept, there is the integration of existing separate voice and data networks into a much simpler and more flexible network using packing switching and IP protocols. This will enable voice, text and visual messages to be carried on the same network and for each type of message to be responded to in any of these formats on that network. This is sometimes characterised as a move from the existing model of a smart network and dumb terminals to a new model of a dumb network and smart terminals. In fact, the NGN will be far from dumb, but it is true that, compared to the existing PSTN, there will be much more intelligence in terminals. A major example of such a NGN is BT's 21st Century Network (21CN).
See: Next Generation Access
Personal Communications Networks (PCN)
Personal Communications Networks (PCN) - or, as they are known in the United States, Personal Communications Services (PCS) - are second generation mobile networks similar to cellular networks but operating at a higher part of the radio frequency spectrum. They use smaller cells than the original cellular systems because higher frequencies travel less distance. At such frequencies, the radio signal is more attenuated which means that handsets must be closer to cell base stations. On the other hand, since the handset is closer to the base station, smaller batteries can be used which allow the handsets themselves to be significantly smaller. In Britain, PCN systems operate between 1.7-2.3 GHz.
See: Cellular, General Packet Radio System, Universal Mobile Telecommunications Systems
Power Line Telecommunications (PLT)
Power Line Telecommunications (PLT), Power Line Communications (PLC) and Broadband over Power Line (BPL) are all terms used to refer to the process of delivering high frequency broadband data over existing electricity supply cables, on a secondary use basis. PLT products are designed to provide broadband Internet access using the electricity distribution network as a transmission medium. In concept, PLT has some similarities with DSL in that it delivers high frequency broadband data using existing infrastructure cables on a secondary use basis. However, electricity supply cables are not designed, screened or balanced for high frequency use and even when buried below ground they can radiate significant leakage emissions. PLT leakage emissions occupy parts of the high frequency radio spectrum above 2 MHz and have the potential to interfere with the reception of radio communication services including short wave broadcasts. The PLT interference issue has proved to be contentious and remains under discussion both within Europe and elsewhere. Various radiated emission limits have been proposed, either for establishing network compliance or less rigidly, for the purposes of adjudication in cases of reported interference. It appears, however, that none of the proposed emission limits can currently satisfy the dual objective of protecting radio reception whilst, at the same time, allowing PLT to operate in a commercially viable manner.
SuperJANET
What was originally called the Joint Academic NETwork (JANET) was developed into the faster SuperJANET. It is a data network linking British universities and uses Asynchronous Transfer Mode (ATM) technology. At most sites, the operating speed is 10 megabits a second, but in some cases access is only 4 megabits a second or as much as 16 megabits a second. The body in charge of the network, UKERNA, is now planning SuperJANET 4 which will have links up to 2.5 Gbps.
See: Asynchronous Transfer Mode
Synchronous Digital Hierarchy (SDH)
This is the next stage in the evolution in the world's telecommunications networks, following on from the digital transmission network based on what is called plesiochronous digital hierarchy (PDH). SDH provides a more reliable and responsive transmission platform and SDH networks can self-heal, repairing themselves in the event of a fault, and can be remotely reconfigured to provide alternative routes. SDH is in extensive use in the core network.
Ultra Wide Band
This is a wireless communications system that can send huge amounts of data using tiny signals across a wide spectrum. It could replace USB cables on personal computers. The Federal Communications Commission (FCC) in the USA has licencised UWB which provides 500 megabits a second. So far, howver, it is not licensed by Ofcom in the UK and faces objections from fixed wireless operators.
Universal Mobile Telecommunications Systems (UMTS)
Cellular was the first generation of mobile telephony and Personal Communications Systems (PCS) the second. The third generation is Universal Mobile Telecommunications Services (UMTS). In the UK, five operators were awarded licences by auction in early 2000 which raised £22.5 billion for the Chancellor and subsequently several virtual operators have come along who use the networks of one of the five original operators. Like Wireless Application Protocol (WAP) and General Packet Radio Service (GPRS), UMTS permits mobile telephones to access the Internet but at extremely high speeds of up to 2 megabits a second. UMTS comprises the European component of the global family of third generation mobile systems known as IMT-2000 and operates at 2.1-2.3 GHz.
See : Cellular, General Packet Radio System, Personal Communications Networks, Wireless Application Protocol
Very high speed Digital Subscriber Line (VDSL)
Like Asymmetric Digital Subscriber Line (ADSL) and High speed Digital Subscriber Line (HDSL), this is a digital transmission technique intended to provide advanced services over existing copper cables. It will provide asymmetric data transfer at high rates but over shorter distances than for ADSL and HDSL. There might be downstream rates of 12 - 52 megabits a second and upstream rates at 1.6 – 2.3 megabits a second.
See: ADSL, DSL Lite, HDSL, xDSL
Voice over Internet Protocol (VoIP)
Ever since the Internet 'took off' as a data network - for sending e-mail and browsing web sites - companies have been exploring the option of putting voice traffic on to the Net or other networks deploying the same technical specifications. Since the Internet uses particular protocols (known as Transmission Control Protocol/Internet Protocol or TCP/IP), this development is called Voice over Internet Protocol (VoIP). So one could define VoIP as voice services over networks which use the Internet Protocol (IP) which might be the public Internet itself or public or private communications networks. Other similar terms sometimes used are Voice over Broadband (VoB) and new voice services.
See; Internet
Wave Division Multiplexing (WDM)
This is a technology which doubles the bandwith of optical fibre by simultaneously sending separate light signals down the same optical fibre cable. By transmitting the signals as different colours, which have different light wavelengths, each signal acts as a unique ‘channel’, capable of carrying its own information stream. Using 40 wavelengths or channels, it is possible to put 1.3 million simultaneous telephone conversations down one fibre.
See: Optical Fibre
Wide Area Network (WAN)
This is a data communications network that spans long distances, typically from city to city and across countries, and generally uses a data rate of 1.544 megabits a second. The communications network on which the WAN is built is usually owned by a telephone company, but the host processors may be owned by multiple organisations.
See: Local Area Network, Metropolitan Area Network
Wi-Fi
This is a wireless communications system formally known as IEEE 802.11b. It is also known as "wireless Ethernet" or "Wi-Fi" (Wireless Fidelity). It operates in the 2.4 GHz band and, since this is low power, the spectrum is unlicensed. Wi-Fi is a means of providing wireless connectivity in an office or a home for computers (or other devices) within around 50-100 metres (150-300 feet) of a base station.
See: WiMax
WiMax
This is a wireless communications system based on a new standard called IEEE 802.16a which is supported by a group called the World Inter-operability for Microwave Access (WIMAX). WiMax is a wireless metropolitan area network (MAN) technology with a bandwidth of around 75 megabit a second across a distance of about 30 miles and operates mainly in the 2.4, 3.5 and 5.8GHz range. It is predicted to extend the reach of DSL and to support mobile broadband. In Britain, the 3.5GHz spectrum, owned by UK Broadband, currently only allows fixed wireless access and not the mobile version of WiMax, though Ofcom is reviewing this restriction. Intel will soon unveil its first WiMax products for fixed wireless broadband services and BT is expected to get production equipment before the end of 2005 and roll out services thereafter. It is not yet clear which part of the radio spectrum will be used for WiMax. Although Europe is settling towards 2.5GHz and 3.5GHz, these frequencies may not come up for auction by Ofcom until 2007. Although much hype has been written about future WiMax services, many obstacles remain that could impede take up of the technology. Therefore WiMax is not expected to be widely available in PCs until around 2008 and by this time 3G operators should have millions of customers and may well be offering WiFi/3G roaming. Further uncertainty is caused by the regulation of WiMax. Currently WiFi networks are not regulated; however, Ofcom is reviewing radio spectrum which could lead to the regulation of WiMax networks.
See: Wi-Fi, Metropolitan Area Network
Wireless Application Protocol (WAP)
This is a technology for permitting mobile telephones and other devices to access the Internet. However, it only permits the browsing of an abbreviated, almost entirely text-only version of the Internet. The system operates at a very slow speed of 9.6 kilobits a second.
See: General Packet Radio Service, Universal Mobile Telecommunications Services
World Wide Web (WWW)
This is the commercial graphical side of the Internet and uses words and pictures. It originated in 1990 with scientists at CERN (the European laboratory for particle physics in Switzerland) and it is now the most-used part of the Internet. Many Web pages are connected to other pages by hyperlinks. Such linking is achieved through the use of a special language called HyperText Markup Language (HMTL).
See: Internet
x Digital Subscriber Line (xDSL)
This is the collective term for the family of technologies designed to bring advanced digital services to customers using the copper cable in the local network.
See: ADSL, ADSL2, ADSL2+, DSL Lite, HDSL, VDSL
ZigBee
Like Wi-Fi, WiMax and UWB, this is a wireless communications system, but it is slower (250 kilobits a second) and has shorter range than the other systems which means that it requires less power (so batteries can last up to 10 years). It is designed for wireless controls and sensors in the home or office such as lights, switches, doors and appliances. It has the IEEE standard 802.15.4 and, like Wi-Fi and Bluetooth, it operates at 2.4 GHz.
See: Bluetooth, Wi-Fi, WiMax, Ultra Wide Band
ROGER DARLINGTON
Last modified 16 November 2005