Glossary of Terms relevant to Mobile Communications
Flying Boat Mobile Communications
Version: November 2004
This glossary aims to de-mystify mobile communications and the adjacent areas of telecommunications and data communications. This latest version contains around 900 cross-referenced terms but it still isn't comprehensive, as you will see under the entry for glossary
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HOW IT WORKS
Find a term which relates to your area of interest using the index on the left of this page or just look below for those pesky non-alphabet terms such as 3G. Follow the cross-linked entries to related terms. Pursue your thread of enquiry to learn about a whole subject area.
If you have any remaining or more detailed questions, contact Flying Boat Mobile Communications by emailing the Glossary editor at glossary@flying-boat.co.uk. The Glossary is under continuous review so comments, suggestions, objections and even simple abuse are all welcome. You can also find other glossaries under glossary below
- 1G
- The First Generation of mobile telecommunications, as distinct from 2G, the Second Generation and 3G, the Third Generation. Systems include AMPS, TACS, and NMT. A 4G is also envisaged.
- 2G
- The Second Generation of mobile telecommunications, as distinct from 1G, the First Generation and 3G, the Third Generation. Systems include GSM, PDC, cdmaOne IS-95, and TDMA IS-136. A 4G is also envisaged.
- 3G
- The Third Generation of mobile telecommunications, as distinct from the First Generation, 1G, and the Second Generation, 2G. Two groups are standardising Third Generation systems, 3GPP (Third Generation Partnership Project) and 3GPP2. The requirements for 3G were specified by the ITU as IMT-2000. All forms of 3G offer substantial increases in data rates and can support services like music, video and multimedia. 3G systems may be rivalled by even higher bandwidth systems such as Wi-Fi (using 802.11 standards) and Hiperlan especially where 3G spectrum allocation has been made expensive. Sometimes called 4G.
- 3GPP
- 3rd Generation Partnership Project standardising mobile communications based on an evolved GSM core network architecture, UMTS, and EDGE or UTRA radio access. Owner of the 3GPP specifications.
- 3GPP2
- 3rd Generation Partnership Project for IS-41 (North American core network technology) and radio access via UTRA or cdma2000.
- 4G
- The Fourth Generation of mobile telecommunications. Originally conceived as broadband wireless through MAN technologies like BRAN, Hiperlan & MESA, the fourth generation may now arrive in practice through Wi-Fi and the 802.11 series of standards and is thus arriving before 3G in some places. 4G as currently envisaged will not attain the coverage of 3G, or of satellite systems, both LEO and GEO.
- 802.11
- Physical and MAC layer standard for Wireless LAN defined by IEEE. Several variants - IEEE 802.11b also known as Wi-Fi, higher speed standards include 802.11a 54 Mbps in 5 GHz band and 802.11g 54 Mbps in 2 GHz band . Other 802.11X series standards work addresses topics such as -802.11 standards continue to multiply.
- 802.11a
- A 802.11 wireless LAN standard, later and higher-speed than 802.11b / Wi-Fi. 802.11a shares most physical layer characteristics with ETSI Hiperlan. 802.11a uses a 5 GHz radio band and delivers up to 54 Mbps using OFDM (Orthogonal Frequency Division Multiplexing).
- 802.11b
- The most widely available variant of IEEE 802.11 wireless LAN standards - also known as Wi-Fi, see WECA (Wireless Internet Compatibility Alliance). Official range up to 100m so an informal MAN is possible if security and access control issues can be resolved. 802.11b uses 2.4 GHz radio and delivers up to 11 Mbps using direct sequence spread spectrum modulation (similar to CDMA as used in IS-95 and UMTS). Typically a 80211.b LAN can use one of 14 channels but if all are occupied then no new service is possible. 802.11b operates "license free" so occupying a channel constitutes ownership.
- 802.11g
- An enhancement of IEEE 802.11b to provide similar speeds to 802.11a using OFDM (Orthogonal Frequency Division Multiplexing) in the same band as 802.11b. The number of 802.11 and 802.X standards continues to multiply.
- 802.11i
- new (as of 3Q03) IEEE standard to enhance the current 802.11 MAC to provide improvements in WLAN security and provide better network access control. 802.11i provides encryption protocols to replace WEP and allowing for stronger AES encryption. WPA (Wi-Fi Protected Access) will be extended to include 802.11i when it becomes stable.
- 802.15
- A set of IEEE 802.X standards for Wireless PAN (Personal Area Network) including 802.15.1 - 1Mbit/second Bluetooth co-operative work, 802.15.2 - Recommended Practice for Coexistence in Unlicensed Bands, 802.15.3 - 20+ Mb/s High Rate Wireless PAN for Multimedia and Digital Imaging, 802.15.4 - 200 kb/s for interactive toys, sensor and automation needs.
- 802.16
- “Air Interface for Fixed Broadband Wireless Access Systems” An IEEE standard for fixed broadband wireless access system or MAN (Metropolitan Area Network), initially in 10 and 66 GHz band, branded as WiMAX. ETSI has BRAN with similar objectives.
- 802.1x
- IEEE standard for strong user authentication and centralised key management for WLAN (wireless LAN), improving on WEP. Based on IEEE EAP (extensible authorisation protocol), allowing WLAN access points and users to share and exchange WEP encryption keys automatically. The access point acts as a proxy, carrying the heavier computational load of encryption over the radio link. Has multiple options for user authentication. Typically used with an authentication server based on RADIUS or LDAP.
- 802.X
- IEEE set of standards describing physical layer and link layer of a LAN. Physical layers include both wired and wireless, as in 802.11 series.
- A
- INDEX: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
- A Interface
- The interface between MSC and BSC in GSM. The corresponding interface in UMTS is Iu-cs.
- A/D
- see analogue/digital.
- A3
- GSM subscriber authentication algorithm. Uses the shared secret key Ki, the mobile identity IMSI, and a random number, RAND, to generate a check value SRES simultaeneously in both mobile and network. Only RAND is sent from network to mobile and SRES is extremely difficult to forge because Ki is never transmitted, the algorithm is difficult to invert and RAND is new at every authentication.
- A38
- Combination of the A3 and A8 processes for GSM subscriber authentication and cipher key generation.
- A5
- GSM encryption algorithm. Uses the Kc key generated by the A8 process to encrypt and decrypt data exchanged between mobile and network. Since the same key is used for encryption and decryption this is an instance of symmetrical encryption with the key kept secret, so this is private key encryption.
- A8
- GSM cipher key generation algorithm. Uses the shared secret key Ki, the mobile identity IMSI, and a random number, RAND, to generate an encryption key Kc which is used for encryption and decryption of data exchanged between mobile and network. Only RAND is exchanged between mobile and network but it is new for every session and Ki remains a shared secret between mobile and network. This makes inverting the algorithm to produce Ki difficult.
- AAA
- The Internet standards topic, Authentication, Authorisation (or Authorization) and Accounting. The authentication process assures communicating parties that each is who it claims to be. Authentication is more precisely described as "peer entity authentication". Authorisation determines what privileges and services each party is entitled to. Accounting tracks usage of privileges and services. In the Internet, RADIUS is the standard authentication technique for point-to-point connections, typically using the PPP protocol. In the mobile context, 3GPP is working with IETF to support the newer Diameter Base Protocol. Commercial peer entity authentication for e-commerce typically uses public key encryption to exchange shared secret information encrypted using algorithms such as RSA (devised by Rivest, Shamir and Adleman). Related topics include non-repudiation, micropayment, DRM (Digital Rights Management) and EFT (Electronic Funds Transfer).
- Abis
- The interface between BTS and BSC (GSM), contrast A Interface.
- Accounting Rate System
- Long established ITU system of international Interconnect Billing. Allowing networks to pay each other for handling transit network and terminating network costs for handling calls on behalf of the originating network. Uses direct accounting. Often abbreviated to ARS.
- ACD
- Automatic Call Distribution in the context of CTI.
- ACK
- Acknowledgement of receipt of data - usually applied to simple character based protocols which use SAW (send and wait) techniques. ACK is an ASCII or EBCDIC control character.
- ACQ
- All Call Query. A number portability routing technique (as in MNP) using IN. IN-related MNP uses a database which is interrogated to identify whether the called number has been ported and, if so, to which destination. ACQ requires all calls to visit the central database. Contrast the QoR (Query on Release) technique and the GSM SR (Signaling Relay) technique.
- acquirer
- In electronic commerce, the bank which processes a merchant's transactions and passes them into the clearing system.
- ACTS
- Advanced Communications Technologies; a EU initiative supporting early work on 3G and 4G mobile.
- ADC
- Analogue to Digital converter. See analogue/digital.
- ADPCM
- Adaptive Differential Pulse Code Modulation; long-standing A/D conversion standard for wireline networks.
- ADSL
- Asymmetric Digital Subscriber Line. The most common of the DSL techniques. ADSL uses sophisticated and dynamic modulation techniques to enable high bit rate services (typically 500 Kbps uplink and 2 Mbps downlink) to be delivered over standard telephone wiring (the standard twisted pair). Ultimate bandwidths are often limited by cross-talk. ADSL is the basis for the much-anticipated "broadband revolution" given that twisted pairs are already universal but fibre and co-axial cable are not.
- aggregator
- In the context of SMS messaging, a company which provides MO and MT SMS access to mobile networks, typically via an email (typically SMTP) or web-like, HTTP, interface. Gives access to all the networks in at least one country and handles the network operator relationships on behalf of the customer. Usually aggregators add value through services such as marketing expertise, short code allocation and billing aggregation.
- AID
- Application Identifier: the unique code associated with a smart card application, which allows the terminal to select a suitable application within the card for a given operation.
- air interface
- The radio interface in a mobile network.
- airtime provider
- Mobile network service supplier, dealing directly with individual mobiles users directly or via retailers. Acts as an intermediary to a network service supplied by a network operator.
- alert
- In the mobile context, a message to a mobile to notify the user of a significant event (e.g. a voice message, a goal scored or a share price movement). Often used to stimulate a mobile user action such as a voice call or a WAP session. Alerts can be by pager, CMT or SMS. Alerts provide the essential push capability needed for services which must be initiated by the network, such as MMS delivery, but which use mobile-initiated bearers, such as early GPRS services.
- AM
- Amplitude modulation. Using continuous, analogue, variation of the amplitude (transmitted power) of a radio signal to convey information, as in AM radio.
- AMA
- Automatic Message Accounting. See CDR (Call Detail Record).
- AMPS
- Advanced Mobile Phone Service/System - North American First Generation analogue mobile phone technology. See also TACS and NMT. Contrast Second Generation, IS-95, IS-136 and GSM. Contrast Third Generation UTRA and cdma2000.
- AMPU
- Average Margin Per User. A vital factor in mobile network, and other business, profitability. Focuses on profit margin, in contrast to ARPU (Average Revenue Per User), which measures the total amount billed. Value added services (VAS) can enhance both factors but overheads associated with VAS implementation and operation may increase ARPU while decreasing ARPU.
- AMR
- The GSM/3GPP adaptive multirate codec. Originally intended for use in 3GPP UMTS 3G phones but being rolled out with GSM and EDGE phones. AMR allows for different bit rates conveying speech, dependent on the available bandwidth and signal to noise ratio. It is also compatible with the voice channel bit rates of IS-136 TDMA and PDC. Contrast the EFR, FR and HR codecs.
- analog
- (American English spelling of analogue) Transmission of information through a continuously variable signal. Contrast digital and see also analogue/digital.
- analog/digital
- American English spelling of analogue/digital.
- analogue
- Transmission of information through a continuously variable signal, like most forms of pre-electronic human communication. Contrast digital and see also analogue/digital.
- analogue/digital
- Usually used in the context of conversion from analogue to digital (or vice-versa). Analogue signals are continuously varying, as in speech into a GSM phone or audible music. Digital signals have discrete values, as in GSM transmission of speech or sheet music.
- anchor MSC
- The first MSC (Mobile Switching Centre) involved in a wireless call. As the mobile moves during the call, other MSCs may take over the call.
- ANSI
- American National Standards Institute, official owner of some 2G and 3G mobile standards, in practice these are driven by bodies such as 3GPP and 3GPP2.
- AOA
- Angle of Arrival. A technique for locating a (radio) mobile by estimating the angle of signal arrival at multiple points. Compare with TOA Time of Arrival, Cell Identity - CI, Observed Time Difference - OTD, GPS, and Timing Advance in the context of LCS (Location Services).
- AoC
- Advice of Charge - "how much did this call cost?" - information to a telephone subscriber.
- API
- Application Programming Interface. Typically an interface specification of the function calls and other software environment which an application can use to get access to services. Contrast the concept of a communications protocol, a definition of the information to be exchanged between two communicating pieces of software or hardware. TCP is one of the most widely used protocols and standard API to this is defined by the XTI specification (X/Open Transport Interface).
- ARIB
- Association of Radio Industries and Businesses. Responsible for standardisation of telecommunications protocols in Japan. Major participant in 3GPP.
- ARP
- Address Resolution Protocol in the IPS (Internet Protocol Suite).
- ARPA
- Advanced Research Projects Agency of the US Department of Defense; Sponsor of ARPANET, the ancestor of the Internet.
- ARPU
- Average Revenue Per User. One of the vital factors in mobile network, and other business, profitability. Value Added Services, VAS, services are often cited as ways of increasing ARPU. More specifically, others are SMS & MMS, m-commerce, voice mail and CCBS (call completion). AMPU, Average Margin Per User, which focuses on profit margin may be more significant. Another major factor in profitability is churn.
- ARQ
- Automatic Repeat Request - for retransmission of a PDU. ARQ provides for error recovery when data is lost or corrupted. Corruption is detected using a CRC or FCS field. Contrast FEC.
- ARS
- See Accounting Rate System.
- ASCII
- American Standard Code for Information Interchange; de facto (i.e. informally recognised) world standard for representation of printable/displayable and control characters. The de jure (i.e. formally recognised) world standards are numerous and include IA5. The most common proprietary standard is IBM EBCDIC. See www.asciitable.com.
- ASIC
- Application-Specific Integrated Circuit
- ASN.1
- Abstract Syntax Notation 1. An ITU standard metalanguage which can be used to write a formal definition, in textual form, of the messages sent and received by a communications protocol. To fully define a protocol, a definition of the state machine which defines the behaviour of an implementation is also required. Other standards, such as TTCN, support this. ASN.1 is part of OSI, but is also used in non-OSI protocols, such as GSM.
- ATM
- Asynchronous Transfer Mode, The ITU standard for "cell relay" - information for multiple types of services (voice, video, data) is conveyed in small, fixed size, data blocks called "cells" (a mobile network cell is a very different concept!), used for multi-megabit corporate data services.
- AuC
- Authentication Centre. GSM network component which stores information for authentication of mobiles, and for encrypting their voice and data transmissions. An AuC receives Ki and IMSI values per mobile from the HLR. It computes RAND, Kc using the A8 algorithm and SRES using the A3 algorithm , either per-session or in batches for download to HLR and/or VLR.
- authentication
- The process of establishing the identity of a communicating party. Typical example is a GSM mobile phone which communicates with the network at registration time to establish its identity using A3 algorithm. More precisely this is "peer entity authentication" because the two parties involved are the same levels in the protocol stack and are hence, peers. GSM and other mobile networks have a dedicated AuC (Authentication Centre). Also applied to personal authentication including techniques such as password, PIN or biometric - typically used in m-commerce and e-commerce where a digital signature establishes identity and where non-repudiation may also be required. Authentication is related to encryption and the whole area is dealt with as AAA (Authentication, Authorisation and Accounting) in the Internet world.
- AVL
- Automatic Vehicle Location. See LCS (Location Services).
- AWT
- Abstract Window Toolkit in the context of J2ME and Java, AWT supports GUI (Graphical User Interface) programming. Providing user interface, event-handling, graphics / imaging independent of a particular window size or screen resolution.
- B
- INDEX: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
- B-ISDN
- Broadband - ISDN at bit rates greater than PRI (Primary Rate ISDN).
- Baby Bell
- One of the original 7 local exchange companies formed from the breakup of AT&T: NYNEX, Bell Atlantic, BellSouth, Southwestern Bell, Pacific Bell, US West and Ameritec. See also RBOC.
- backhaul
- Network connections from a remote site, such as a mobile base station, to a point of concentration such as an MSC or a BSC.
- bandwidth
- The raw transmission capacity of a channel. In digital systems, measured in bps (bits per second). In analogue and radio systems, measured in Hz (cycles per second). In both cases, bandwidth is measured before vital factors such as compression, errors and overheads are taken into account so the figure can be misleading unless factors such as BER (bit error rate in digital systems) and signal to noise ratio (analogue systems) are also considered.
- base station
- A cellular, mobile or other radio transmitter and receiver, for the GSM context see BTS.
- baseband
- The original signal impressed on a radio transmission and the spectrum it occupies by the process of modulation. For example, the baseband for a telephone service is analogue speech.
- Basic Rate Interface
- The Basic Rate Interface within ISDN. See BRI.
- BCC
- In GSM this is the Broadcast Control Channel - a channel that broadcasts information (about a cell, base station and its network) to mobiles in that cell.
- BCD
- Binary Coded Decimal. Decimal digits 0-9 encoded as 4 bit numbers (nibbles), so that two fit within a byte or octet.
- BER
- two menaings
Bit Error Rate - the proportion of bits received incorrectly in a digital channel.
Basic Encoding Rules. The basic set of syntax rules for ASN.1. - BER (ASN.1)
- see BER.
- billing
- In telecommunications, billing is the process of obtaining payment for telecommunications services. In wireline telecommunications and in Postpaid mobile billing, the billing process takes place after calls have been made. In prepay mobile billing the call activity must be monitored in real-time. Mobile systems usually allow for roaming to other networks and the cost of calls then has to be transferred between networks, possibly using a clearing house as intermediary. For both fixed and mobile billing, networks must also arrange to settle for calls which they carry on behalf of each other, this is Interconnect Billing.
- biometric
- Identification of a person by a physical or behavioural characteristic (such as the way they sign their name, their fingerprint or the marks on the iris of their eye) as distinct from a PIN (personal id number). Part of an authentication process.
- Bluetooth
- Short range radio technology interconnecting portable devices. Controlled by the Bluetooth SIG. Sometimes cited as a rival to Wi-Fi standards but arose from a different requirement, has shorter range and incorporates a voice-specific capability used for mobile phone headsets.
- BNF
- Backus-Naur Form. A way of describing the syntax of information. A precursor to ASN.1, Abstract Syntax Notation 1 and XML. Each of these is a metalanguage, a language for defining other languages. For example, the entries in this glossary may be described by the BNF -
<glossary entry> ::= <word or phrase><description> . - BOC
- Bell Operating Company. One of the companies formed from the break-up of AT&T (a.k.a. “Ma Bell”). Sometimes referred to as Baby Bells but these are big babies! See also RBOC (Regional BOC).
- bps
- Bits per second. A measure of the speed of a transmission link.
- BPSK
- Binary PSK (phase shift keying), used for some services in WCDMA for UTRAN.
- BRAN
- Broadband Radio Access Network, ETSI standards for wireless LAN and MAN networks following on from Hiperlan. BRAN work includes HIPERLAN/2, a mobile broadband short-range access network (up 54 Mbps), HIPERACCESS, a fixed wireless broadband access network working with IEEE 802.16, and HIPERMAN, a fixed wireless access network which operates below 11 GHz. Arguably this is a 4G mobile service.
- BRI
- Basic Rate Interface within ISDN, abbreviated BRI. A digital interface to the PSTN over standard telephone wiring (twisted pair). Delivering SS7 interfaces to an end user at the Basic Rate - two 64k bits per second B channels carrying user data, with signaling on a 16k bits per second D channel.
- bridging
- The process of extending link layer protocols across other networks. For example, MAC layer bridging between LANs is common and is simpler than routing but may be less efficient.
- BS7799
- British Code of Practice for Information Security Management.
- BSC
- Base Station Controller. The GSM network area controller for a base station cluster (a BTS in GSM).
- BSS
- Two meanings -
Base Station Subsystem. In GSM; the cluster of several radio base stations, BTS, controlled by a BSC, base station controller.
Business SubSystem. In telecomms networks, the NSS (Network Subsystem) is the network itself, the OSS (Operations SubSystem) manages the network and the BSS (Business SubSystem) takes care of billing and customer management. - BTS
- Base Transceiver System - a mobile radio base station in GSM terminology. Provides radio coverage in a specific area and therefore effectively defines the cell of the GSM cellular system. The corresponding UMTS component is a Node B.
- bundled
- When applied to tariffing, the practice of charging a flat rate per period of service up to a certain limit of call time (for voice calls) or data transmitted (for data services like GPRS).
- BW
- see bandwidth
- byte
- An 8 bit unit of data storage. Byte meaning 8 bits was (is?) an IBM-specific term so octet is the preferred term in standards documents.
- C
- INDEX: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
- C/I
- Carrier to Interference Ratio. The signal to noise ratio at the radio level as distinguished from the S/N (signal noise ratio) in the baseband.
- C7
- See SS7.
- CA
- Certification Authority: a body able to certify the identity of one or more parties to an exchange or transaction- as in secure e-commerce.
- Call Detail Record
- See CDR.
- Called Party Pays
- See CPP.
- Calling Party Pays
- See CPP.
- CAMEL
- CAMEL (Customised Applications for Mobile network Enhanced Logic) is a feature of later versions of GSM to provide support for operator-specific services when roaming. Can be viewed as integration of IN into GSM. IN is a telecommunications concept which separates the service logic from the switches to support advanced services such call forwarding. The UMTS development of CAMEL is VHE (Virtual Home Environment).
- cascade accounting
- A method of Interconnect Billing. Where a call (or data conversation) transits several networks, each network bills the network from which the call immediately came, rather than the originating network. So, for each call, only one interconnect bill item needs to be paid by the originating network, to the adjacent network only. The adjacent network will have been billed by another adjacent network until the terminating network is reached. The bill cascades back to the originating network growing as it travels. The payment cascades back, each network taking its cut as it goes until the remainder is paid to the terminating network. Contrast direct accounting.
- CB
- In GSM, broadcast of an SMS-like message to all mobiles in a specific set of cells. See cell broadcast. Not to be confused with Citizens Band (CB radio)!.
- CBC
- Cell Broadcast Centre - The cell broadcast control centre in a GSM network.
- CBR
- Constant Bit Rate.
- CC
- E.164 Country Code within ITU-T standard dialing plan. Appears in the GSM IMSI and LAC, amongst other places.
- CCBS
- two meanings -
Completion of Call to Busy Subscriber. Notify caller when called telephone becomes free and automate reconnection. One of a number of ways ensuring that a billable call happens as often as possible, increasing ARPU. Many of these are CF, call forwarding, techniques.
Customer Care and Billing System. Computer system supporting both customer service representatives in a call centre and batch billing of postpay (as opposed to prepay) telephone subscribers. Interfaces to rating, mediation, Interconnect Billing and subscriber provisioning. - CCI
- Call Clarity Index. An ITU-T measure of telephone VQ (voice quality) derived from monitoring ordinary user calls. Defined by Standard ITU-T P.562. Contrast PSQM which uses agreed input signals and measures the quality of transmission and MOS (mean opinion score) using subjective, statistical methods.
- CCITT
- International Telegraph and Telephone Consultative Committee (abbreviated from the word order of the name in French). Now the ITU. ITU-T and ITU-R are responsible for Telecommunications and Radio respectively.
- CDB
- Call drop back. A number portability routing technique (as in MNP). CDB is an enhancement of OR (Onward Routing). When the donor network receives the call, it releases the call and returns a message indicating that the number has been ported (and providing routing information). This drop back message is used by a transit network or an originating network to route the call onward to the new destination.
- CDC
- Connected Device Configuration. A J2ME environment which uses the "classic" JVM (Java virtual machine) as used on a desktop system. Intended for high end mobiles with profiles such as the "Personal Profile" profile standard. Personal Profile. The CDC is intended for devices with memory greater than 512KB, smaller devices use CLDC.
- CDF
- Cumulative Distribution Function. The probability distribution of a variable. For every value of the variable, the cdf is the probability that the variable takes on a value less than or equal to some fixed value. Important in analysis of performance in analogue transmission systems and of the effectiveness of spread spectrum modulation techniques such as CDMA.
- CDG
- CDMA Development Group. The consortium of companies supporting the 2G cdmaOne and 3G cdma2000 mobile network standards. Its equivalent for GSM is the GSM Association.
- CDMA
- Code Division Multiple Access. Technique for sharing radio bandwidth between mobile telephones (or other radio users) by mixing a digital bit-stream representing the user information (such as a voice channel) with a higher rate bit-pattern unique to the specific user. Reversing the process at the receiver recovers the user information. CDMA is called a direct-sequence spread-spectrum technique; contrast other spread-spectrum techniques, such as frequency-hopping. CDMA is used in both Second Generation and Third Generation mobile systems including UMTS (and W-CDMA), TD-SCDMA, cdma2000 and cdmaOne.
- cdma2000
- Brand name for North American CDMA air interface standard aimed at Third Generation mobile requirements (see also 3G and IMT-2000). A rival to UMTS, cdma2000 includes a number of steps from cdmaOne to a full IMT-2000 3G specification. They include evolved narrowband CDMA schemes - 1X for higher capacity voice and data, 1xEV-DO (DO for packet data only) is asymmetric - claiming four times the speed for downlink vs. uplink and speeds of 300-700 Kbps for mobile users, and as high as 2.4 Mbps for fixed users. Eventually cdma2000 will be a hybrid system with a wideband option in the uplink and multiple narrowband CDMA channels in the downlink. See also its ancestor cdmaOne and its industry body, CDG.
- cdmaOne
- Brand name for Second Generation narrowband CDMA air interface standard. Replaces AMPS first-generation systems. Standardised by TIA IS-95. cdmaOne is available in most of North America and in Japan, Korea, Hong Kong, Australia, New Zealand and China with some countries in eastern Europe also building cdmaOne alongside existing GSM networks. Roaming between some cdmaOne networks also possible. See also its 3G descendant cdma2000 and its industry body, CDG.
- CDPD
- Cellular Digital Packet Data. A packet-radio protocol that uses 30 KHz AMPS radio channels to transmit packets of data on idle AMPS FDMA channels. Standardised by TIA/EIA/IS-732. See TIA.
- CDR
- Call Detail Record - typically sent by an MSC via a mediation device to a CCBS (billing system) to provide billing details for a particular call.
- cell
- Two meanings
The coverage area of a single radio base station or sector in a mobile communications system.
Fixed size packet in a cell relay system such as ATM. - cell broadcast
- Broadcast of an SMS-like message to all GSM mobiles in a specific set of cells. Mobiles can opt to receive CB messages in specific categories. Analagous to broadcast teletext for television (Ceefax in the UK). The Cell Broadcast Forum promotes CB services worldwide. The principal specification of the CB standard is GSM 03.41 / 3GPP 23.041.
- Cell Identity
- The identity of a cell or sector in a mobile communications system. See CI.
- cell relay
- The protocol principle of ATM. Cells in this context are fixed size data packets. By contrast, Frame Relay conveys frames, which are variable sized packets.
- cellular
- A mobile radio telecommunications concept using many radio base stations or cells to cover an area, reusing frequencies as much as possible. Examples of this technology include AMPS, TACS, NMT, GSM, D-AMPS, cdmaOne, PDC, UMTS, cdma2000.
- CELP
- Code Excited Linear Prediction - An analogue-to-digital voice coding scheme used in low bit-rate wire-line communications. Contrast ADPCM used in standard 64 Kbps channels.
- CEN
- Centre Européen pour la Normalisation (CEN is the European Standards Centre). For mobile telecommunications ETSI is more significant.
- CEPT
- Conference des administrations Europeennes des Postes et Telecommunications.CEPT represents European PTT bodies such as France Telecom.
- CF
- Call Forwarding - Transferring a telephone call or data connection to another endpoint, for example a voice messaging system. See the various CF conditions - CFB. CFNA, CFNR and CFU.
- CFB
- Call Forwarding when subscribing telephone is busy.
- CFNA
- Call forward on no-answer.
- CFNR
- Call forward on not-reachable - typically if a mobile is not registered or does not respond to paging.
- CFU
- Call Forwarding Unconditional (i.e. every incoming call will be forwarded). In effect, "do not disturb".
- CHAP
- Challenge Handshake Authentication Protocol. Defined in IETF RFC 1994, provides authentication for PPP.
- chip rate
- The rate of modulation of the pseudo-random code used in direct sequence spread spectrum modulation, as used in CDMA. For example UMTS radio access, UTRAN in FDD mode, has a chip rate of 3.84 Mcps.
- CHTML
- Compact HTML, a derivative of HTML for mobile devices. Used in the IMode system. See also HDML and WML.
- churn
- The rate at which subscribers leave one mobile network to go to another (or cease using mobiles altogether). A major expense for the network and/or Service Provider. Other important issues in profitability are ARPU and AMPU.
- CI
- Cell Identity. Identifying a base station. Applications may use this as a rough location of a mobile, see LCS.
- Cibernet
- A company originating in the CTIA (Cellular Telecomms Industry Association) but now owned by GTE; deals with payment resolution for roaming mobiles within North America.
- CIMD
- Computer Interface to Message Distribution. The) Nokia SMSC interconnect protocol, similar functionality to Logica SMPP and Sema OIS.
- CIR
- Committed Information Rate. Guaranteed bandwidth in a Virtual Circuit on a Frame Relay service.
- circuit network
- Network that switches multiple streams of data in circuit-mode. The ordinary PSTN, ISDN and cable networks are all examples. See CSD for mobile network examples.
- circuit-mode
- Data transmitted in a continuous stream instead of discrete packets. See CSD (circuit switched data) for mobile circuit-mode and circuit network for the more General case. Contrast packet-mode.
- circuit-switched
- See circuit-mode.
- circuit-switched data
- See CSD.
- CK
- Cipher Key in GSM authentication, see triplet.
- CLDC
- connected limited device configuration. A mobile device environment for J2ME (Java 2 micro edition). A J2ME environment which uses the K Virtual Machine, a small footprint virtual machine. The CLDC is intended for devices with memory between 128-512KB, contrast CDC for more sophisticated devices.
- clearing house
- A central point for the gathering and redistribution of usage records between networks, such as billing records (CDRs), For example, a roaming mobile will generate a CDR. This will be added to a file of CDRs to be sent back to the home network, either directly or via a clearing house.
- CLI
- Calling Line Identity. The number from which a call has come.
- CLIP
- Calling Line Identification Presentation. Showing the calling number, the CLI, to the receiving subscriber. Overridden by CLIR.
- CLIR
- Calling Line Identification Restriction.
- CLR
- Cell Loss Ratio; performance statistic in an ATM network, where the fixed length packets are called cells (nothing to do with a mobile cell). CLR is the ratio of discarded cells to cells that are successfully transmitted. Equivalent of signal to noise ratio in analogue systems.
- CLTS
- ConnectionLess mode Transport Service. OSI concept also used elsewhere as datagram service. Contrast COTS, Connection Oriented Transport Service. Internet UDP is, approximately, a ConnectionLess mode Transport Service.
- CMT
- Cellular Messaging Teleservice. North American messaging standards equivalent of GSM SMS, used in IS-95 and IS-136 systems. CMT also provides an alert mechanism for voice messaging.
- CN
- see core network.
- codec
- Coder Decoder; converts analogue signals to digital and digital to analogue (e.g. voice codec, video codec). Codecs began as simple analogue/digital converters but now universally use compression techniques to minimise the required bandwidth. The simplest compression technique, companding (i.e. non-linear A/D conversion), is universal in wireline telecommunications. Mobile codecs, such as the GSM codecs, all add predictive coding. The GSM codecs are, in order of evolution, FR (full rate), HR (half rate), EFR (enhanced full rate) and AMR (adaptive multi-rate). UMTS uses the AMR codec.
- Combined Delivery
- OMA DRM (Digital Rights Management) concept which supports access rules built-in to the content, for example to allow preview before purchase and/or a fixed number of viewings before deletion.
- command line mode
- A mode of interaction where a simple command executed with attached parameters. The Unix shell and the MSDOS (Microsoft) command line are the most common examples. Contrast the transaction mode of IS.136 (see TN3270) and the web (see HTML and HTTP).
- Common Channel Signaling
- Transmission signaling information on a common channel shared between multiple service channels, as in mobile systems like GSM or fixed systems such as ISDN. Telecommunications core networks also use SS7, which is, formally, "Common Channel Signaling System Number 7". MAP is the application layer above SS7 in the GSM core network.
- Compact HTML
- A derivative of HTML for mobile devices. Used in the IMode system. See also WML and HDML.
- companding
- Non-linear treatment of an analogue signal to achieve compression of an audio signal in a codec. Lower level signals are converted with more precision than high level signals since human hearing is more sensitive to inaccuracies at lower sound levels.
- compression
- using an algorithm to decrease the number of bits of user data to be transmitted, thereby increasing the efficiency of a communications channel. A related algorithm will expand the data back to its original form when it is received. In data communications compression is usually lossless, the original data is restored exactly as sent. For analogue services like speech (see codec) and pictures (see pixels), compression with some loss is often acceptable and a mobile phone codec will exploit this to achieve very high compression factors.
- CON
- Connection Oriented Network Services - an OSI concept establishing a fixed relationship between two communicating systems so that data packets do not need to carry addressing information. See also connection-oriented.
- concatenation
- Joining together as in a train of railway coaches. In data communications, messages or packets may be concatenated where the underlying transport mechanism only supports a limited amount of data per message or PDU. In GSM SMS concatenation uses the SMS UDH (user data header) to tell the recipient that each message is part of a concatenated long message.
- connection-oriented
- Describing communication between two systems over a VC (virtual circuit) where data packets do not need to carry addressing information. Typically data transfer is a reliable byte-stream, as in Internet TCP or ITU X.25. Contrast connectionless.
- connectionless
- Describing communication between two systems where data packets are sent singly and each must carry addressing information. Each data packet is a separate datagram. Typically data transfer is unreliable, as in Internet UDP and IP. This makes network architecture simpler and potentially more efficient. However, unless the application is insensitive to this potential loss, higher layer protocols must use error recovery, as in ARQ, to preserve the integrity of data. Contrast connection-oriented.
- CORBA
- Common Object Request Broker Architecture. A scheme for distributed object interaction between ORBs (Object Request Brokers). See the CORBA definition. CORBA defines a protocol, IIOP (Internet Inter-ORB Protocol), for communication although SOAP is a more recent rival, especially in the context of Java.
- core network
- In mobile networks, a distinction is made between the RAN (radio access network) and the core network. Both are part of the NSS (network system) as distinct from the BSS (business support system) and the OSS (operations support system). The core network consists of the main switching and other radio independent functions, many of them being similar to the components of a fixed network. The UMTS RAN, UTRAN, supports an number of core network architectures. A UTRAN RNC (radio network controller) can link through its Iu interfaces to a circuit-switched MSC in a GSM core network or to a packet-switched SGSN in a GPRS core network. The GPRS core network can, also, optionally support the IM (IP Multimedia Subsystem) through interfaces to its CSCF (Call Session Control Function) to allow an entirely IP based, packet-switched, core network to support all mobile services, including voice using IETF SIP.
- COTS
- Connection Oriented Transport Service as opposed to CLTS, Connectionless Transport Service. Connection oriented protocols include Internet TCP and ITU X.25.
- coverage
- In the context of mobile radio technologies, the quality and breadth of geographical coverage is a vital part of any service offering. Mobile networks boast of having better coverage than their rivals. Coverage is a major issue for the rivalry between Wi-Fi and 3G. GSM networks are unrivalled in terms of worldwide coverage for terrestrial systems. Satellite systems, both GEO and LEO, beat all others for outdoor coverage but with serious limitations for indoor coverage. This also applies to satellite vs terrestrial LCS (location services) such as GPS and EOTD. Wavelength or frequency, transmit power, receiver sensitivity, interference immunity, FEC and antenna efficiency all affect coverage.
- CPP
- Can mean "calling party pays" or "called party pays". Either the calling party pays for calls to a mobile (as usual in Europe), or that the mobile receiving the call pays for the mobile part of the call (usual in North America). CPP in the North American sense (called party pays) is often cited as a major reason for lower penetration of mobiles in North America. This is a controversial issue.
- CPRI
- Common Public Radio Interface - intended to be a publicly available specification for key internal interfaces of radio base stations. Defined by Ericsson, Huawei, NEC, Nortel Networks and Siemens. Objectives include faster development when introducing new technologies and allowing base station manufacturers to offer a wider portfolio of products to the operators with shorter time to market. See also the earlier OBSAI (Open Base Station Architecture Initiative).
- CRC
- Cyclic Redundancy Check. Checking data included in many digital protocols to allow the receiver to check for errors in transmitted messages. CRC is specific category of FCS (i.e. Frame Check Sequence). Contrast parity and FEC.
- CRNC
- A UTRA Controlling RNC. Each RNC is a CRNC to several base stations (called Node B in UTRA).
- CSCF
- In UMTS, the Call Session Control Function. See core network.
- CSD
- Circuit switched data. Data transmission of a continuous bit stream from sender to receiver, as in the GSM CSD service. Data transmitted over a dedicated channel. In a mobile context, amounts to using the voice channel for data with corresponding radio loading and cost implications. Compare with Packet data as in GSM GPRS (General Packet Radio Service) and other mobile packet services such as Ericsson Mobitex, Motorola DataTAC, CDPD in AMPS and PDC-P in Japanese PDC networks. CSD is also the most common mode for fixed line communications, as in ISDN or modem connections.
- CSMA
- Carrier-sense multiple access; a scheme where stations listen to network activity and wait until no carrier is detected before transmitting. CSMA is combined with Collision Detection (CD) is the basic access method (media access control or MAC) for Ethernet. Contrast DSMA in packet radio networks.
- CSPDN
- Circuit Switched Public Data Network, for example, an ISDN service.
- CTI
- Computer Telephony Integration; typically used in Call Centres and in support of Customer Care in CCBS (billing system).
- CTIA
- (USA) Cellular Telecommunications Industry Association.
- CUG
- Closed User Group. Network service where calls or data packets are restricted to within a fixed group - as in a VPN (Virtual Private Network).
- CWTS
- Chinese Wireless Telecommunications Standards group.
- D
- INDEX: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
- D-AMPS
- Digital AMPS (IS-54 and IS-136 TDMA) Digital derivative of the North American AMPS analogue cellular standard Uses TDMA to split the old AMPS 30 KHz radio channel into three digital channels.
- DAB
- Digital Audio Broadcasting. A broadcast radio standard developed by ETSI.
- DARPA
- US Defense Advanced Research Projects Agency (now ARPA).
- data integrity
- All communications protocols must provide some assurance that data is received as transmitted but additional mechanisms may also be required for secure m-commerce and e-commerce where manipulation of information such as account numbers and amounts is a commercial risk. The technique is similar to a FCS (frame check sequence) in a communications protocol. A related process, digital signature, using public key encryption, is used for mutual authentication of receiver and transmitter.
- datagram
- The individual packet transmitted in a connectionless network protocol, such as IP (accessible as UDP).
- DataTAC
- Motorola packet radio technology available in both private and public forms.
- dB
- Decibels. Used to express a logarithmic ratio in communications engineering. Zero dB equals one.
ratio in dB = log10 ratio. See dBm for a frequently used example of the use of dB. - dBm
- Decibels, dB, referenced to one milliwatt used in communications engineering as a measure of absolute power values. Zero dBm equals one milliwatt. S(dBm) = log10 P (milliwatts). So P = 10**(S/10). For example, the quoted mobile power levels for regulated UTRA - given in dBm translate as follows -
33 dBm = 1.9 watts
27 dBm = 0.5 watts (500 milliwatts)
24 dBm = 0.25 watts (250 milliwatts)
21 dBm = 0.125 watts (125 milliwatts)
. And typical received signal strengths at a mobile phone are -90 dBm = 0.001 nanowatts (10-9 watts), -80 dBm = 0.01 nanowatts (10-9 watts) and -70 dBm = 0.1 nanowatts (10-9 watts). - DBMS
- Data Base Management System.
- DCE
- Data Communications Equipment (e.g. a modem or an ISDN TA - Terminal Adapter), contrast DTE.
- DCS1800
- Digital Cellular System at 1800MHz, now called GSM1800.
- DDI
- Direct Dialing In - to a building so everyone has a number which is directly dial-able from the PSTN (public network). As opposed to use of a human switchboard operator ("Good morning, this is Flying Boat Mobile Communications, how may I direct your call?") or a DTMF controlled extension access facility (as in "if you know the extension you require, please dial it now"). DDI is only feasible where the number space is large; one of the reasons for dialing code changes (of which there have been several in the UK in recent years).
- DDN
- US Defense Data Network.
- de facto
- In discussion of standards, a de facto standard is one very commonly used in practice but not accepted by the relevant formal standards body. Which, by contrast, is called a de jure standard. Typical examples in the mobile world are SMPP and Nokia Smart Messaging, which are widely-used, and therefore de facto, standards in their fields.
- de jure
- In discussion of standards, a de jure standard is one defined by the relevant formal standards body rather than being simply used in practice, a de facto standard. Typical examples in the mobile world are IS-136 defined by TIA and EMS for GSM and UMTS defined by 3GPP. Lawyers may quibble with both of these however and insist that only ISO and ITU are de jure standards bodies.
- decryption
- The process of recovering an encrypted message using a decryption key and a known algorithm to make it readable again - the reverse of the encryption process. In private key systems, the same key is used for encryption and decryption. In public key systems the encryption and decryption keys are different. Both are used in mobile networks; examples from the GSM world include the A3, A5 and A8 algorithms. Encryption/decryption is related to authentication and the whole area is dealt with as AAA (Authentication, Authorisation and Accounting) in the Internet world.
- DECT
- Digital Enhanced Cordless Telecommunications (formerly Digital European Cordless Telecommunications); a cordless system standardised by ETSI supporting both domestic and corporate cordless telecommunications including a packet capability. DECT is intended by ETSI to be retained as a Third Generation standard alongside UMTS.
- demodulation
- Reversing the modulation process on reception of a radio signal to extract the baseband signal.
- demultiplexing
- Extracting a number of different channels from a single channel, the reverse of multiplexing. Contrast inverse multiplexing
- DES
- Data Encryption Standard - the most widely used algorithm for symmetric encryption (i.e. using the same key for encryption and decryption). The standard is ANSI (American National Standards Institute) X3.92.
- DGPS
- Differential GPS. Enhanced performance GPS using locally provided clock and position information from a fixed transmitter. One of the options for LCS (location services) for mobiles.
- DHCP
- Dynamic Host Configuration Protocol provides dynamic address allocation for the Internet protocol, IP.
- DHKE
- Diffie-Hellman key exchange - see Diffie-Hellman.
- Differ
- Differential routing. Mechanism defining how IP packets are classified and marked to receive a particular per-hop forwarding behavior on routing nodes along their path. Typically used to differentiate delay-sensitive traffic such as VoIP (Voice over IP) from interactive traffic such as web browsing and delay-insensitive traffic such as email. Defined by IETF RFC 2475. Architecture for Differentiated Services. A level of service is allocated to a traffic stream on entry to a differentiated services-capable network - this governs how that traffic is forwarded within that network. Inside a large WAN this will typically use MPLS (multi protocol label switching).
- Differential GPS
- See DGPS.
- Diffie-Hellman
- A secure key exchange algorithm, contrast RSA - The Rivest-Shamir-Adleman algorithm.
- digital
- Transmission of information through a signal that can take on only certain discrete values (e.g. a bit with values 0 or 1 or a modulation symbol with 2 or more values). Compare with analogue.
- digital signature
- An encrypted field, normally encrypted using the senders private key, which is attached to a message to prove its source and data integrity. Typically carried by SSL protocol in the Internet context. A more detailed explanation is at What is a Digital Signature.
- direct accounting
- The original manner of Interconnect Billing, as used by the Accounting Rate System. Where a phone call (or data conversation) transits several networks, each network billing the network from which the call originally came, the originating network. So, for each call, an interconnect bill item needs to be paid to each transit network separately, as well as to the terminating network. Contrast cascade accounting.
- direct mode
- In the context of mobile radio protocols, direct communication between mobile devices without intervention of a base station. Both Bluetooth and TETRA allow for direct mode communication and it is the normal mode of operation for unlicensed voice devices such as CB (citizens band) radio.
- diversity
- The use of multiple communication paths or channels to achieve efficiency and error protection. The main types of diversity used in mobile communications are - Antenna or spatial diversity: using multiple transmit and/or receive antennas to exploit multipath effects (typically in CDMA). Frequency diversity: transmitting on multiple frequencies as in spread spectrum techniques like CDMA and or frequency hopping as used in GSM. Time diversity: transmitting information at different times as in the spreading used in CDMA and interleaving as used in GSM. Diversity is especially effective in overcoming various types of interference. Spatial diversity overcomes multipath interference, frequency diversity overcomes single frequency interfering signals and time diversity overcomes short bursts of interference.
- DLCI
- data link connection identifier. Reference number identifying a VC (virtual circuit) in a Frame Relay network. Similar to a logical channel in a X.25 network.
- DNS
- Domain Name Service. - provides an IP address (e.g. 159.33.139.200) when handed a (more) human friendly domain address (e.g. flying-boat.co.uk). Hierarchies of DNS servers resolve client computer queries for Internet addresses.
- Doja
- Java profile used in IMode / IAppli (NTT DoCoMo). Contrast MIDP.
- DOML
- Document Object Model, an open interface supporting access and update of both content and structure of documents accessible in HTML or XML formats. DOML1 and DOML2 are part of the XML activity under the W3C.
- downlink
- In the mobile context, the channels from the mobile to the network are the uplink and from the network to the mobile are the downlink. Terminology borrowed from satellite communications.
- DPC
- Destination Point Code for an SS7 message, the destination address in the SS7 network.
- DQPSK
- Differential QPSK (quadrature phase shift keying) - a radio modulation technique.
- DRM
- Digital Rights Management - control of IPR (Intellectual Property Rights) over digital information. Commercially vital if rights to content - including images (including films and TV), sounds (including music) and software (including games and office applications) are to be exploited by the IPR owners. The effects of CD copying (both direct and via the Internet) on the recorded music business have shown the importance of this. DRM is especially important in mobiles now that MMS (multi-media messaging service) allows all of the above content to be transmitted and stored. Higher bit rate systems such as EDGE and the 3G standards such as UMTS will make sharing even easier. A number of open and proprietary schemes exist for controlling DRM, from a simple "do not forward" flag, ODI, in an SMS message to complex XML based schemes for MMS content defined by OMA (Open Mobile Alliance) including Forward-Lock, Combined Delivery, Separate Delivery, Rights Refresh and Superdistribution.
- DRNC
- A UTRA Drift RNC. A UMTS UE (mobile) may be in communication with several Drift RNCs but only one SRNC (Serving RNC) as part of the soft handover process (a spatial diversity process).
- DSL
- Digital Subscriber Line. A family of standards to deliver broadband service over existing telephone wires. Generically referred to as xDSL. Most commonly used to provide domestic broadband over ADSL.
- DSMA
- Digital Sense Multiple Access. Access to a shared uplink radio channel is controlled by sensing a digital flag encoded into a received downlink channel before attempting an access. Since mobiles cannot detect each other's transmissions, CSMA, as used in Ethernet is not feasible. So some downlink bandwidth is sacrificed to send the DSMA flag. Used by radio packet protocols such as CDPD and DataTAC. A more complex variant is the USF (Uplink Status Flag) used to control access to multiple uplink channels in GSM GPRS.
- DSP
- Digital Signal Processor. High speed processor typically used to implement most of the radio part of a mobile phone digital communications.
- DTE
- Data Terminal Equipment - the computer system connected to a modem or other communications device - which is termed a DCE (Data Communications Equipment).
- DTMF
- Dual Tone Multi Frequency. Tone signaling used by fixed phones to replace pulse dialling and by mobile phones and fixed phones to control VAS (value added services), such as information service access. DTMF is often called "Touch-Tone".
- DTN
- delay-tolerant network. Any network which works independent of delay times between nodes. Originally used to describe an astronautical overlay or "InterPlaNet" for Internet protocols like IP - using hop-by-hop transmission and storage to shuttle information across solar system sized distances and their inevitable speed-of-light delays. The relevant IETF group is DTNRG. Now DTN techniques are being applied to terrestrial systems. DTN uses the store and forward model of email or SMS and the diverse routing of fault tolerant networks.
- DTX
- Discontinuous Transmission. A mobile only transmits when the user is talking.
- dual-band
- A mobile that can support two different frequency ranges, such GSM900 and GSM1800. Three band mobiles, supporting GSM1900 too, are also available. Compare with dual-mode - a mobile that can support two different technologies such as analogue and digital.
- dual-mode
- A mobile that can support two different technologies, such as analogue AMPS and digital IS-136 TDMA. Compare with dual-band. Three or more modes may become necessary as technologies such as cdma2000, UMTS TDD and FDD and TD-SCDMA proliferate alongside GSM, PDC, IS-136 TDMA and IS-95 CDMA. In addition, the need to support wireless LAN or Wi-Fi networks and Bluetooth will make portable devices even more complicated.
- duplex
- In communications, point to point channels are either full duplex or half duplex. In full duplex, both ends can transmit at the same time. In half duplex, only one end can transmit at a time. Half duplex has advantages in saving bandwidth for mobile networks and is used, for example, in PoC and the FDM variant of WCDMA. Full duplex is easier to manage and is used wherever this is more important than saving bandwidth.
- DVB
- Digital Video Broadcasting.
- DWDM
- Dense Wave Division Multiplexing, see WDM.
- E
- INDEX: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
- E-cash
- Electronic money, often held on a smart card.
- e-commerce
- Electronic commerce, traditionally conducted over the Internet, now extending to other devices such as mobile phones, often called m-commerce.
- e-Ticket
- Electronically delivered ticket, in which the physical ticket may be dispensed with altogether.
- E.164
- the ITU-T dialing plan standard - the basis for all International telephone numbering.
- E.212
- the ITU-T mobile identification number standard.
- E.214
- the ITU-T standard that defines a mobile identification number or IMSI (International Mobile Subscriber Identity). In effect, a unique identifier for a SIM. Based on the ITU-T E.212 numbering plan, thus allowing the number to be mapped onto an E.164 number to allow routing through SS7 networks. Unfortunately, this mapping does not work in North America.
- E911
- Enhanced 9-1-1 service. In the USA, the FCC (Federal Communications Commission US Telecoms regulator) requirement to provide the identity and the approximate location of the calling mobile phone when 911, the emergency number, is called. Similar requirements are being suggested in Europe. See LCS (location services).
- EAIF
- External Application Interface. Nokia proprietary definition of MMS MM7 functionality.
- EAP
- Extensible authorisation protocol, IETF standard used for WLAN security in conjunction with 802.1x. EAP methods include MD5, a one-way authentication scheme like WEP, and TLS (Transport Layer Security), a two-way authentication scheme based on SSL (Secure Socket Layer) protocol - as used for HTTPS for secure web transactions.
- ECC
- Elliptic Curve Cryptography: a more efficient alternative to RSA, which may be more suitable for battery-powered devices.
- ECMA
- European Computer Manufacturers Association.
- EDGE
- Enhanced Data-rates for Global Evolution (formerly "GSM Evolution"). Use of new modulation schemes to increase data rates within the existing RF bandwidth for GSM. EDGE supports three bits per symbol. EDGE is also part of the evolution of US TDMA IS-136 standard networks towards UMTS and some US networks have already deployed it. As GPRS as regarded as "2.5 generation", EDGE can be "2.75 generation". EDGE supports both more and better quality voice and faster GPRS, EGPRS. The RAN (radio access network) for EDGE is standardised by the GERAN group of 3GPP.
- EDI
- Electronic Data Interchange - long-established mechanism for B2B (business-to-business) e-commerce, traditionally conducted over the Internet or X.25 networks, now extending to other devices such as mobile phones. Specific sector standards in include HL7 (health) and SWIFT (airlines).
- EDIFACT
- Electronic Data Interchange for Commerce & Trade, early set of EDI standards sanctioned by the UN.
- EEPROM / E2PROM
- Electronically Erasable Programmable Read Only Memory - part of the chip used to store information that will change during the life of a smart card. It ‘remembers’ when the power is unavailable.
- EFR
- Enhanced Full Rate. GSM voice codec standard. Provides higher quality than the FR (full rate) or HR (half rate) standards. See also AMR.
- EFT
- Electronic Funds Transfer: electronic payment. EFT-POS is used in conventional retail while micropayment mechanisms are growing rapidly in the mobile world.
- EFT-POS
- Electronic Funds Transfer at Point of Sale: electronic payment as at a supermarket checkout.
- EGP
- Exterior Gateway Protocol.
- EGPRS
- Higher data rate variant of GSM GPRS using EDGE radio technology.
- EIA
- Electronics Industry Association.
- EIR
- Equipment Identity Register. Stores information about wireless terminals as opposed to subscriptions. Compare with HLR.
- EIRP
- Equivalent Isotropically Radiated Power. The power radiated by a radio transmitter including gain from the antenna. For example, an antenna with 3 dB gain concentrates the power in a particular direction such that twice as much power is transmitted in the concentrated direction. So if the total power transmitted is one watt then the EIRP is two watts. The regulator for a particular piece of spectrum will limit the EIRP because that figure gives a better indication of the possibility of interference from a transmitter.
- EMS
- Enhanced Messaging Service. An extension of GSM SMS to support audio/music, simple graphics and pictures. Uses the SMS UDH (user data header) and SMS concatenation. EMS is a standardised way of delivering the logo and ring-tone download capabilities long-supported by Nokia (the Nokia proprietary technology is called Smart Messaging). More about EMS in the FBMC EMS White Paper.
- EN
- Euronorm or European Standard. The official, de jure, designations for standards such as GSM. The ETSI designations are more widely understood (e.g. GSM 03.40 for short message service).
- encapsulation
- The process of wrapping one form of data in another, as in protocol layering. A classic metaphor for encapsulation is putting a letter in an envelope.
- encryption
- Manipulating data using an encryption key and a known algorithm to make it unreadable to anyone who does not possess the decryption key. Both public key and private key systems are used in mobile networks; examples from the GSM world include the A3, A5 and A8 algorithms. Encryption is related to authentication and the whole area is dealt with as AAA (Authentication, Authorisation and Accounting) in the Internet world.
- EOTD
- Enhanced Observed Time Difference. An enhancement of OTD (Observed Time Difference) for LCS (Location Services) proposed by Cambridge Positioning Systems.
- EPOC
- Operating system for handheld devices, developed by Symbian. Contrast Windows CE. A joint venture of Psion (the originators), Ericsson, Nokia and Motorola promotes EPOC as the standard operating system for handheld devices.
- EPROM
- Erasable PROM - a low-cost memory technology.
- Erlang
- Measure of traffic capacity of telecommunications networks. Calculated as rate at which calls arrive divided by the rate at which they are completed. An erlang is effectively the capacity to carry one phone call.
- ERMES
- European Radio Messaging System. An ETSI digital paging standard launched in the mid 90s. However, ERMES did not obtain the expected market penetration and the spectrum for it may be reallocated (see ERO). Contrast the older POCSAG standard.
- ERO
- The ERO office of CEPT in Denmark maintains lots of useful information about European mobile and radio networks, including spectrum policy, numbering plans / portability and type approval.
- ERP
- Effective Radiated Power - from a radio antenna.
- ETACS
- Extended spectrum for TACS (Total Access Communications System).
- Ethernet
- The universal wired LAN standards and services based on ideas from the Aloha packet radio network. Defined by IEEE 802 series standards. Wireless LAN standards delivering equivalent services are defined by 802.11 standards.
- ETR
- ETSI Technical Report.
- ETS
- European Telecommunication Standard.
- ETSI
- The European Telecommunications Standards Institute. Owner of the GSM, ERMES and DECT standards, amongst others. Leading participant in 3GPP, standardising Third Generation UMTS.
- F
- INDEX: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
- FA
- Foreign Agent see Mobile IP.
- FACCH
- Fast Associated Control Channel in GSM. Steals capacity from the associated TCH (traffic channel) temporarily to handle bandwidth-intensive activities such as handover between cells, relying on FEC to protect the speech or data traffic on the TCH.
- FCC
- US Federal Communications Commission. The regulator which sets requirements on US networks, such as E911.
- FCS
- Frame Check Sequence. Data added to a Frame to allow receiver to detect errors. A more powerful variant of the pparity bit added to a 7 bit ASCII character. A frame check sequence provides this using algorithms related to encryption which generate a message hash which is appended to the message. The algorithm can then be performed again on reception and the result compared with the received message hash to suggest strongly that the message is valid. One widely used category of FCS is the CRC (Cyclic Redundancy Check). FCS techniques are similar to those used for data integrity in m-commerce and e-commerce.
- FD-CDMA
- The FDD (Frequency Division Duplex) mode of operation for the 3G system, UMTS UTRA. FD-CDMA is the mainstream mode. Intended for wide area coverage using paired spectrum, unlike TDD (Time Division Duplex) which is intended to provide local area coverage and unsymmetrical uplink vs. downlink bit rates (in unpaired spectrum) at a higher bit rate than FDD.
- FDD
- Frequency Division Duplex. Separating transmit and receive (or uplink and downlink in the mobile context) channels by allocating different parts of the radio spectrum to them. Used in GSM, UMTS, IS-136, IS-95 and PDC. Contrast TDD (time division duplex).
- FDDI
- Fibre Distributed Data Interface. High speed token-based LAN protocol standard. No longer widely used?.
- FDMA
- Frequency Division Multiple Access. Channel separation by allocation of radio spectrum to different channels. Widely used in First Generation mobile systems such as AMPS and TACS. Compare with TDMA and CDMA.
- FEC
- Either Forward Error Correction; adding redundant information to a bit stream to allow error correction by the receiver. Essential precaution where errors are likely (as in mobile radio systems) and retransmission is not acceptable (as in speech communication). Contrast ARQ. Or Forwarding Equivalence Class, the packet priority associated with a label in MPLS (multi protocol label switching).
- FER
- Frame Error Rate. The ratio of incorrectly received frames to correctly received frames, contrast BER and see also frame.
- First Generation
- Applied to mobile telecommunications systems, using analogue transmission of speech, such as AMPS, TACS and NMT. Contrast Second Generation and Third Generation, 3G.
- Flash
- E-memory type based on EPROM technology, but which is electronically erasable. Used in PDAs and digital cameras.
- Floor Control
- In PoC (push-to-talk over cellular) only one person can talk at a time, so a user must ask for the “floor” before talking by pressing the push-to-talk button. This acts as a request into the Floor Control mechanism, which also has to handle contention for the "floor" and release of the "floor" when a speaker has finished or is preempted.
- FM
- Frequency Modulation. Using continuous, analogue, variation of the frequency of a radio signal to convey information, as in FM radio. Digital variant is FSK (frequency shift keying).
- FMCG
- Fast Moving Consumer Goods, as in mobile telephones perhaps. A marketing term. See also churn.
- FOMA
- DoCoMo's 3G service in Japan. FOMA, Freedom of Mobile Access, is based on early UMTS standards so worldwide roaming is doubtful. KDDI's 3G service based on cdma2000 is a serious rival.
- footprint
- Amount of memory taken up by an application (e.g. on a smart card or other embedded device).
- Forward-Lock
- OMA DRM (Digital Rights Management) concept which supports single purchase, single delivery, the content is delivered but forwarding is prevented. Similar to the simple "do not forward" flag in later versions of the GSM SMS messaging standard.
- FPLMTS
- Future Public Land Mobile Telecommunications Systems. Now called IMT-2000.
- FQDN
- Fully Qualified Domain Name. The full name of a system or service within the DNS naming scheme. Fully qualified because including a TLD (top-level domain). For example, "flying-boat.co.uk" is a FQDN with a TLD of "uk". An FQDN should be sufficient to determine a unique Internet address for any host on the Internet. This process, called "name resolution", uses the Domain Name System (DNS).
- FR
- In GSM, Full Rate. Referring to the original GSM voice codec, contrast EFR, HR and AMR. In WAN Technology, Frame Relay, a well-established set of standards and services.
- frame
- In a TDMA system, like GSM, frames are the fixed-size repeating sequences of data in the TDM bit stream. GSM and other TDMA systems have many overlapping sizes of frames repeating at different intervals. Contrast Frame Relay, which has variable sized frames.
- Frame Relay
- Packet-based virtual circuit data communication protocol similar to X.25 but assuming lower BER and improving performance by reducing error protection. The basic unit transmitted is a variable length frame, rather than a fixed length cell, in contrast with ATM.
- Freephone
- Phone call paid for by the terminating organisation, often used for flat rate services like some ISP services. Effectively wholesale reverse billing. The terminating network has also to reverse the normal flow of money in Interconnect Billing. Compare revenue sharing and premium rate. Freephone is called Toll Free in the USA.
- frequency hopping
- A simple form of spread spectrum where the transmitted signal is changed periodically in an pseudo-random pattern across a wide range frequencies in the radio spectrum. One of the advantages of this is to produce frequency diversity. Where the baseband signal is modulated directly onto the carrier then this is direct sequence spread spectrum, as used in CDMA (code division multiple access). Where the spreading is separated from the modulation then process is indirect as in OFDM (orthogonal frequency division multiplexing) and in the frequency hopping which is supported by GSM.
- FSA
- Finite State Automaton. Formal name for the state machine which drives the succession of handshake-like exchanges between the two communicators in a communications protocol.
- FSK
- Frequency Shift Keying. Using variation of frequency to convey digital information. See also FM (frequency modulation).
- ftp
- File Transfer Protocol (normally written lower case "ftp"). The Internet connection-oriented protocol defining how to transfer files, for example to download software, pictures or music. ftp uses IP connectionless protocol as its bearer. Contrast HTTP.
- FTP
- see ftp.
- G
- INDEX: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
- Gateway MSC
- See GMSC.
- Gb interface
- In GPRS, the interface between a GSM BSC and a GPRS SGSN. The corresponding interface in UMTS is Iu-ps.
- GEO
- Geostationary Orbit (for a satellite). Commonly used for telecommunications satellites. Apparently stationary from the earths surface but altitude of 38,000 kilometres implies delay of 38,000/c = about 130 milliseconds for uplink and downlink, so leading to echoes and difficulty in telephone conversation, unlike LEO (low earth orbit) and MEO systems.
- GERAN
- GSM / EDGE RAN (Radio Access Network). The higher-speed TDMA radio access network defined by the EDGE TDMA standard. The original GSM TDMA radio technology is based upon GMSK modulation but EDGE uses 8PSK, eight-way phase shift keying). EDGE can share spectrum, and even TDMA timeslots, with GSM, unlike UTRAN. UTRAN uses BPSK and QPSK with WCDMA for multiple access. GERAN standards are defined by 3GPP.
- GGSN
- Gateway GPRS Support Node. A gateway and router which connects a GPRS network to external networks, either IP or X.25. See also GSN and SGSN.
- GHz
- One thousand million Hz (hertz) = one thousand MHz = one million KHz. A measure of radio frequency. Most mobile communications is in the MHz or GHz range of frequencies.
- glossary
- As in this FBMC Glossary. Other useful glossaries in this subject area include US Federal Standard 1037C (1996 - so a bit old but very large and cross-referenced, like this glossary), Termite database from ITU (short definitions and document references). In the wider communications world Webopedia and Connected - An Internet Encyclopedia are both useful. Roke Manor Research have a good radio-oriented glossary. The FBMC Briefings and White Papers cover topics in the mobile space in more detail. More widely, try the Imperial College FOLDOC (Free Online Dictionary of Computing) and don't forget good old Google! The FBMC glossary has been adopted elsewhere, for example by Purple Patch Wireless.
- GMSC
- Gateway MSC. An MSC designated to receive phone calls from the PSTN. Contrast IWMSC (interworking MSC).
- GMSK
- Gaussian Minimum Shift Keying, modulation scheme used by GSM, contrast EDGE.
- GPRS
- General Packet Radio Service. A packet radio protocol extension to GSM to support packet data over the air interface, services supported include IP, SMS and X.25. Contrast CSD (circuit switched data). The major components of GPRS networks are GGSN, SGSN, PCU. User data is carried across GPRS networks by SNDCP and GTP protocols and between GPRS networks by GRX (GPRS Roaming eXchange). More about GPRS in the FBMC GPRS Briefing.
- GPS
- Global Positioning System. A LCS (location services) system. Determines location based on comparing signals and accurate clocks from US military satellites. Compare with AOA, TOA, OTD, CI (Cell Identity), Timing Advance and see also DGPS (Differential GPS).
- GRX
- GPRS Roaming eXchange. The interconnecting network between GPRS networks carrying roaming traffic. Uses a variant of GTP to tunnel between networks.
- GSM
- Global System for Mobile Communications. A Second Generation world standard for digital cellular networks (formerly Groupe Speciale Mobile). GSM network components are -
- MS (mobile station, the GSM phone, consisting of ME and SIM),
- BTS (base station),
- BSC / BSS,
- MSC (mobile switching centre, the mobile telephone exchange),
- HLR (home location register, the real-time subscriber database),
- AuC, EIR, SMSC, GWMSC and IWMSC.
- GSM Association
- GSM [MoU] Association. The consortium of companies supporting the GSM standard. Formerly the GSM MoU Association. The GSM Association owns the TAP (transferred accounts procedure) standard used to convey CDR information for roamed subscribers. Its equivalent for cdmaOne and cdma2000 is CDG (CDMA Development Group). Contrast ETSI (which owns the GSM standard), 3GPP and the