Technology Glossary . TELECOMS TECHNOLOGY GLOSSARY 3G Third Generation 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. AMPS 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. ATM 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. Bluetooth 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. Broadband 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. Bypass 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. CDMA 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 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). Circuit-switching 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. D-AMPS 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. xDSL x 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. EDGE 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. Ethernet 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. FDMA Frequency Division Multiple Access See AMPS, Cellular Radio Frame Relay 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. FWA 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. GPRS 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. GSM 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. HSCSD 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. HTML Hypertext Markup Language Page description language used by designers of web pages to create information content for the World Wide Web. Markers such as

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. IN 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. IP See TCP/IP IP Telephony 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. ISDN 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. ISP 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. 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. Internet Telephony See IP Telephony LAN 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. LEO See MSS 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. Modem 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. NMT 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. Narrowband 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. PDC 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. Packet Switching 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. Router 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. SDH 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. TACS 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. TCP/IP 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. TDMA 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. Telco Telecommunications operator or carrier Third Generation See 3G VoIP See IP Telephony VPN 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. WAP 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. WCDMA 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. WDM 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. WLL Wireless Local Loop See FWA. Wideband 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. XML 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 TELECOM Secretariat at +41 22 730 6161 (phone) or +41 22 730 6444 (fax), or see the Telecom web site at www.itu.int/TELECOM. 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.