  |
 |
 |
 |
 . |
|||
TELECOMS TECHNOLOGY GLOSSARY3G The next generation of Cellular
Radio for mobile telephony. Due to come on stream from 2001 onwards, 3G will be the
first cellular radio technology designed from the outset to support wideband data
communications just as well as it supports voice communications. It will be the basis for
a wireless information society where access to information and information services such
as electronic commerce is available anytime, anyplace and anywhere to anybody. 3G’s
technical framework is being defined by the ITU with its International Mobile
Telecommunications 2000 (IMT-2000) programme. Advanced Mobile Phone System First Generation Cellular Radio standard developed in the USA. It is an analogue system which uses different frequency carriers to create communications channels in a technique known as Frequency Division Multiple Access (FDMA). AMPS is still widely used and forms the basis for a number of other cellular radio standards such as TACS and D-AMPS. Asynchronous Transfer Mode Broadband transmission technology which provides
the backbone of the world's telecommunications network. ATM breaks information flows into
small fixed-length cells of 53 bytes. Cells of any type of traffic – voice,
multimedia, data or video – can be interspersed with each other. ATM operates at
speeds of 25, 155 and 622 Mbps. A new technology designed to be embedded in electronic devices in order to provide wireless and seamless connections over short distances. The idea is to provide an easier to use alternative to the cable-based interfaces currently in use to link computers and computer peripherals. Other devices in which Bluetooth chips could be embedded include mobile telephones, personal digital assistants, headsets and wristwatches. A term applied to telecommunications systems
capable of simultaneously supporting multiple information formats at relatively high
speeds such as voice, high-speed data services and video services on demand. Overall
transmission speeds are typically hundreds to thousands of times faster than those of Narrowband systems. Usually refers to the practice of avoiding local telephone companies' long-distance access fees to local operators by routing traffic from private networks directly to the long-distance carrier – ie bypassing the local carrier. With the advent of Mobile Satellite Systems, bypass may also now refer to the bypassing of national carriers to establish international connections. Code Division Multiple Access Technology straddling second generation and third
generation (3G) mobile Cellular Radio
systems. Under CDMA, communications channels are created by assigning a special coding
scheme to information flows. CDMA-based second generation cellular radio systems are in
use in parts of Asia and North and South America. New variations of CDMA are likely to
provide the base for many third generation cellular systems. Cellular Radio is the technology that has made
wide scale mobile telephony possible – before cellular radio the problem with the
mobile phone as a concept was how to get large numbers of users to share small amounts of
radio spectrum. Cellular radio solved this problem by allowing the re-use of the same
radio frequencies by assigning them to cells which were far enough apart to prevent
noticeable interference. Frequency Division Multiple Access (FDMA) was
the basis for first generation cellular radio systems. Second generation cellular radio
systems - the current generation - use digital techniques such as TDMA
and CDMA to support high bit rate voice and limited data
communications. Third generation (3G) systems will support voice and
high bit rate data allowing mobile multimedia applications (see also Narrowband,
Wideband). Means of creating telecoms connections by setting up an end-to-end circuit. The circuit remains open for the duration of the communication and a fixed share of network resources is tied up with no one else able to make use of them until the connection is closed. The main advantage of circuit-switching is that it enables performance guarantees to be offered. See also Packet Switching. Digital Advanced Mobile Phone System TDMA-based second generation
cellular radio standard originated in North America. Sometimes D-AMPS is also referred to
as TDMA although it is not the only form of TDMA, with others including GSM
and PDC. D-AMPS is widely used throughout the Americas, and uses
frequencies in the 800 MHz and 1900 MHz frequency bands. xDSLx Digital Subscriber Line Collective description for a range of Digital Subscriber Line technologies designed to provide high speed data links over ordinary copper telephone lines. Asynchronous DSL (ADSL), for example, is called asynchronous because the downstream (to the customer) speed is faster than the upstream (to the telco) speed. ADSL speeds are typically 1.5 – 6 Mbps downstream and 64 kbps upstream. Very high data rate DSL (VDSL) is similar to ADSL, but operates at 12 – 51 Mbps downstream and 1.6 – 2.3 Mbps upstream. Rate Adaptive DSL (RADSL) is also similar to ADSL but the transfer rate can be altered allowing it to work over poorer quality lines or over longer distances, albeit at lower speeds. High Bit Rate Digital Subscriber Line (HDSL) uses the same modulation as ISDN on a wider bandwidth and with more sophisticated processing. It operates at speeds of up to 2 Mbps at distances up to 4 km. Enhanced Data Rates for GSM Evolution An enhanced modulation technique designed to
increase network capacity and data rates on GSM networks. EDGE, due to
be introduced in 2000-2001, promises to provide a three-fold improvement to current data
rates without requiring new network infrastructure. Instead it is based on a major change
in the GSM standard to support 8-PSK (Phase Shift Keying) based signal modulation as well
as existing GSM modulation. The most widely-installed LAN technology. Standardised as IEEE 802.3, an Ethernet LAN uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol (originally developed to manage radio based data communications - hence the name Ethernet) running over a coaxial cable or twisted pair wires. The most commonly installed Ethernet systems are called 10BASE-T and provide transmission speeds up to 10 Mbps. Fast Ethernet, or 100BASE-T10, provides transmission speeds of up to 100 Mbps and is typically used for LAN backbone systems, supporting workstations with 10BASE-T cards. Gigabit Ethernet provides an even higher level of backbone support at 1 Gbps. Frequency Division Multiple Access See AMPS, Cellular Radio High speed transmission method, switching packets
of data through its network to their destination. Access to the network is via Frame Relay
Access Devices (FRADs) which translate the data (eg Ethernet, Token Ring) into frame relay
packets. The network sets up a virtual circuit which is a path to the destination. Frame
relay is more popular in the US than in Europe, but the main European carriers offer frame
relay service. Frame relay can operate at speeds of up to 45 Mbps, since it is a
lightweight system without error correction, relying on the integrity of the fibre optic
hardware. Fixed Wireless Access Term describing a general means of providing the last "mile" link to fixed telecommunications network subscribers through the use of radio technology. FWA is typically deployed in rural areas where the cost of cabled local loops can be particularly high and for projects where the rapid deployment of new telecommunications subscriber connections is particularly important. General Packet Radio Services Packet Switched
data radio technology for GSM networks. GPRS connections are always open giving mobile
terminal users the same kind of network availability they may be used to from corporate
networks. There are no set up and clear down times associated with data calls made via
GPRS. Terminals can therefore effectively become a part of the Internet. Global System for Mobile communications TDMA-based second generation mobile Cellular Radio technology, originated in Europe but now used in over 100 countries around the world. GSM supports voice, data and text messaging and allows roaming between different networks – which means that GSM users can take their phones with them to many parts of the world. GSM systems currently operate at 800 MHz, 900 MHz, 1800 MHz or 1900 MHz. High Speed Circuit Switched Data Dedicated Circuit
Switched data communications technology for GSM systems which
boosts GSM data speeds from the regular 9.6 kbps to 14.4 kbps in a single traffic channel
and, by using multiplexing techniques, up to 57.6 kbps. EDGE will
boost HSCSD rates even further. Hypertext Markup Language Page description language used by designers of web pages to create information content for the World Wide Web. Markers such as <P> define page layout features such as New Paragraph. Elements of the page can also be set using HTML to become hypertext links to information on the same page or other pages on the web. Intelligent Network A telephone network architecture where the
switching and service functions are separated. This adds great flexibility to the design
of telephone networks by allowing services to be added or changed without having to
redesign switching equipment. A certain portion of a dialled number can trigger a request
for a specific service which can then be dealt with by equipment other than the telephone
switch itself. See TCP/IP Also known as Internet Telephony or Voice over IP (VoIP). Use of Internet Protocol (IP, see TCP/IP) to carry and route two-way voice communications. IP Telephony can support telephone to telephone links through suitable adapters but also voice communications from telephone to IP terminal (such as a PC with sound card) or from IP terminal to IP terminal. The technique promises drastically reduced costs to carriers and therefore prices to end users – but it still suffers problems with quality. Integrated Services Digital Network A fully digital telecommunications network access
method which works over copper wires. There are two types of ISDN, basic rate and primary
rate. Basic rate ISDN provides subscribers with two 64 kbps information channels and a
single 16 kbps control channel. Primary rate provides users with thirty 64 kbps
information channels and a 64 kbps control channel. Internet Service Provider Point of access to the Internet for small business and individual users. The ISP provides its customers with dial-up access to its router which relays traffic to web servers on the Internet. A world-wide network of computer networks in which
users at any one computer can, if they have permission, get information from any other
computer. The idea was conceived by the Advanced Research Projects Agency (ARPA) of the US
government in 1969 and was first known as Arpanet. Since then it has been demilitarised
and commercialised and augmented by a series of inventions and innovations, not least of
which is the web browser invented by a team led by Tim Berners-Lee in 1991 at CERN, the
European Laboratory for Particle Physics. This is the basis for the World Wide Web which
has been so successful that it is now often confused in popular conversation with the
Internet itself. See IP Telephony Local Area Network A LAN is a means of interconnecting computers at relatively high speed within a relatively small geographic area. Peer-to-peer LANs assign equal status to all the computers connected to them. A server-based LAN runs applications and stores data on a computer designated as the server with the other computers acting as workstations. A LAN may serve as few as a handful of users or as many as several thousand. See MSS Mobile-Satellite Service A satellite communications system designed
principally to support mobile terminals. Some MSS use Low Earth Orbit (LEO) satellite
systems for their infrastructure. Each LEO satellite has the advantage of being smaller
and cheaper to build and launch than geostationary satellites. And, because of their lower
heights, they can be accessed more easily by mobile handsets. They can also cover parts of
the world where it would otherwise be uneconomical to provide a telecommunications
infrastructure. MSS operators include Globalstar, Inmarsat, ICO and Iridium. MOdulator/DEModulator Device which converts the digital signals from a computer into the analogue tones which are compatible with all telephone networks, and back again. It effectively allows computers to use telephone networks for communication with other computers. The term ISDN modem which is in current usage is strictly speaking incorrect as the signal at both ends of an ISDN modem is in fact digital. The correct term should be ISDN terminal adapter. Nordic Mobile Telephone One of the earliest commercial Cellular Radio systems developed jointly by organisations in
the countries of Northern Europe, Denmark, Finland, Iceland, Norway and Sweden. It comes
in two variants – NMT450 – the original specification operating in the 450 MHz
band and particularly suited to covering wide areas with low usage densities – and
NMT900 – introduced in the late 1980s and designed to support handheld portable
devices in urban environments. A term applied to telecommunications facilities capable of carrying only voice, facsimile images, slow-scan video images and data transmissions at kilobit speeds. Narrowband facilities, unlike broadband facilities, cannot handle full-colour, full-motion video images or data transmissions at megabit speeds. The term is commonly applied to voice-grade analogue facilities and to digital facilities operating at speeds of less than 1.544 Mbps. Personal Digital Communications TDMA-based second generation Cellular Radio technology originated in, and mainly used in, Japan. PDC-based services operate in the 800 MHz and 1500 MHz frequency bands. Means of creating connections by breaking up the
information to be sent into packets of bytes, sending them along a network with other
information streams and reassembling the original information flow at the other end. The
main advantage of packet-switching is that it makes very efficient use of fixed capacity.
The disadvantage is that the quality of service of an information channel cannot be
guaranteed. See also Circuit Switching. A device, or in some cases software in a computer, that determines the next network point to which a packet should be forwarded on its way to its destination. Typically, a packet will travel through a number of network points with routers before arriving at its destination. Synchronous Digital Hierarchy Before SDH, networks were extremely rigid and
creating a new link between two points was time consuming. It could take months to set up
new services. In the late 1980s operators and suppliers standardized first on SONET and
then SDH standards for optical transmission. By using add/drop multiplexers new signals
can be added to or dropped from the network quickly and easily. The network can then be
monitored centrally, adding to both flexibility and reliability. When a fault does occur,
the traffic can be re-routed so quickly that the user does not even realise there was
anything wrong. Total Access Communications System A first generation Cellular Radio system which is a derivative of AMPS. Designed originally for the UK market but later adopted in many countries across the world including Hong Kong and Japan, TACS improved upon AMPS by offering features necessary to more densely populated markets. Transmission Control Protocol/Internet Protocol Collective name for the set of protocols on which
the Internet is based. TCP and IP are the best known of this set, but they are by no means
the only ones. TCP guarantees that every byte sent from one port arrives at the other in
the same order and without duplication or loss. IP assigns local IP addresses to physical
network addresses providing a structure which can be recognised by Routers.
Other members of the TCP/IP family include the Telnet protocol which allows a remote
terminal to log in to another host, the Domain Name System (DNS) which allows users to
refer to hosts by name rather than having to know their numeric IP addresses, the File
Transfer Protocol (FTP) which defines a mechanism for storing and retrieving files, and
HyperText Transfer Protocol (HTTP) which allows information to be transferred from host
computers to computers equipped with web browsers. Time Division Multiple Access TDMA is a general approach to creating second generation mobile Cellular Radio systems where communications channels are created by assigning time slots to information flows. TDMA is the base technology for the D-AMPS, GSM and PDC digital cellular radio systems. Telecommunications operator or carrier See 3G See IP Telephony Virtual Private Network Looks for all intents and purposes like a private network but is actually just access to a shared network. Careful management and guarantees of quality of service levels ensure that corporate customers get the privacy and facilities they want but at a lower cost. Wireless Access Protocol WAP is being jointly developed in the mainstream
of Internet standardisation activities, with the broad support of many vendors. It
provides the basis for a whole host of new wireless information applications by offering a
gateway between the Internet and mobile telephones. If an application can be put on the
Internet, it can be made available to mobile terminal users through WAP. Wideband Code Division Multiple Access An access mode proposed for the radio interface of 3G or third generation Cellular Radio systems. It divides available radio spectrum into highly efficient information carriers based on a special coding scheme. It is characterised by high capacity, small cell radius and spread spectrum radio transmission. Wave Division Multiplexing Means of getting more information down a fibre
optic cable by using different wavelengths of light – ie different colours within the
light frequency spectrum – to act as multiple carriers. Typical numbers of
wavelengths being used are 4, 8 and 16, although in the labs the laser has been split into
32 and even 100 channels. Theoretically WDM could allow all US data traffic to be carried
on just one fibre optic pair. Wireless Local Loop See FWA. Somewhere between Narrowband
and Broadband. While capable of supporting communications links
of up to megabit speeds and therefore moving images and very fast information downloads,
this may be done at the cost of overall bandwidth availability to other applications and
other users. EXtensible Mark-up Language New way of creating information content for the World Wide Web. A complement to HTML, XML not only describes the appearance of the elements of a web page but also the function. XML should allow advanced interactive applications in banking, e-commerce and many other areas to be created more easily and effectively, and should dramatically improve web access times, especially for business and home users.
For further information on Telecom
99 + Interactive 99, please contact the
The views expressed in these backgrounders are those of their authors and do not necessarily reflect the views of the International Telecommunication Union or its Members. These backgrounders are posted free of copyright and may be used in part or in full by anyone who so desires. |
