GSM TutorialGSM is a globally accepted standard for digital cellular communications.

GSM uses narrowband Time Division Multiple Access (TDMA) for voice and Short Messaging Service (SMS).

This tutorial helps you to understand GSM Basics and should be your starting point.

GSM – Overview

What is GSM?If you are in Europe, Asia or Japan and using a mobile phone then most probably you must be using GSM technology in your mobile phone.

GSM stands for Global System for Mobile Communication and is an open, digital cellular technology used for transmitting mobile voice and data services.

The GSM emerged from the idea of cell-based mobile radio systems at Bell Laboratories in the early 1970s.

The GSM is the name of a standardization group established in 1982 to create a common European mobile telephone standard.

The GSM standard is the most widely accepted standard and is implemented globally.

The GSM is a circuit-switched system that divides each 200kHz channel into eight 25kHz time-slots. GSM operates in the 900MHz and 1.8GHz bands in Europe and the 1.9GHz and 850MHz bands in the US.

The GSM owns a market share of more than 70 percent of the world's digital cellular subscribers.

The GSM makes use of narrowband Time Division Multiple Access (TDMA) technique for transmitting signals.

The GSM was developed using digital technology. It has an ability to carry 64 kbps to 120 Mbps of data rates.

Presently GSM support more than one billion mobile subscribers in more than 210 countries throughout of the world.

The GSM provides basic to advanced voice and data services including Roaming service. Roaming is the ability to use your GSM phone number in another GSM network.

A GSM digitizes and compresses data, then sends it down through a channel with two other streams of user data, each in its own time slot. It operates at either the 900 MHz or 1,800 MHz frequency band.

Why GSM?

The GSM study group aimed to provide the followings through the GSM:

Improved spectrum efficiency. International roaming.

Low-cost mobile sets and base stations (BSs)

High-quality speech

Compatibility with Integrated Services Digital Network (ISDN) and other telephone company services.

Support for new services.

GSM Brief History:Following table shows many of the important events in the rollout of the GSM system; other events were introduced, but had less significant impact on the overall systems.

Years Events

1982CEPT establishes a GSM group in order to develop the standards for a pan-European cellular mobile system.

1985 A list of recommendations to be generated by the group is accepted.

1986Field tests are performed to test the different radio techniques proposed for the air interface.

1987Time Division Multiple Access (TDMA) is chosen as the access method (with Frequency Division Multiple Access [FDMA]). The initial Memorandum of Understanding (MoU) is signed by telecommunication operators representing 12 countries.

1988 GSM system is validated.

1989The responsibility of the GSM specifications is passed to the European Telecommunications Standards Institute (ETSI).

1990 Phase 1 of the GSM specifications is delivered.

1991Commercial launch of the GSM service occurs. The DCS1800 specifications are finalized.

1992The addition of the countries that signed the GSM Memorandum of Understanding takes place. Coverage spreads to larger cities and airports.

1993 Coverage of main roads' GSM services starts outside Europe.

1994Data transmission capabilities launched. The number of networks rises to 69 in 43 countries by the end of 1994.

1995 Phase 2 of the GSM specifications occurs. Coverage is extended to rural areas.

1996 June: 133 network in 81 countries operational.

1997 July: 200 network in 109 countries operational, around 44 million subscribers worldwide.

1999Wireless Application Protocol came into existence and 130 countries operational with 260 million subscribers

2000 General Packet Radio Service(GPRS) came into existence.

2001 As of May 2001, over 550 million people were subscribers to mobile telecommunications

GSM – ArchitectureA GSM network consists of several functional entities whose functions and interfaces are defined. The GSM network can be divided into following broad parts.

The Mobile Station(MS) The Base Station Subsystem (BSS )

The Network Switching Subsystem (NSS)

The Operation Support Subsystem(OSS)

Following is the simple architecture diagram of GSM Network.

The added components of the GSM architecture include the functions of the databases and messaging systems:

Home Location Register (HLR) Visitor Location Register (VLR)

Equipment Identity Register (EIR)

Authentication Center (AuC)

SMS Serving Center (SMS SC)

Gateway MSC (GMSC)

Chargeback Center (CBC)

Transcoder and Adaptation Unit (TRAU)

Following is the diagram of GSM Network along with added elements.

The MS and the BSS communicate across the Um interface, also known as the air interface or radio link. The BSS communicates with the Network Service Switching center across the A interface.

GSM network areas:In a GSM network, the following areas are defined:

Cell: Cell is the basic service area: one BTS covers one cell. Each cell is given a Cell Global Identity (CGI), a number that uniquely identifies the cell.

Location Area: A group of cells form a Location Area. This is the area that is paged when a subscriber gets an incoming call. Each Location Area is assigned a Location Area Identity (LAI). Each Location Area is served by one or more BSCs.

MSC/VLR Service Area: The area covered by one MSC is called the MSC/VLR service area.

PLMN: The area covered by one network operator is called PLMN. A PLMN can contain one or more MSCs.

The GSM SpecificationsSpecifications for different Personal Communication Services (PCS) systems vary among the different PCS networks. The GSM specification is listed below with important characteristics.

Modulation:Modulation is a form of change process where we change the input information into a suitable format for the transmission medium. We also changed the information by demodulating the signal at the receiving end.

The GSM uses Gaussian Minimum Shift Keying (GMSK) modulation method.

Access Methods:Because radio spectrum is a limited resource shared by all users, a method must be devised to divide up the bandwidth among as many users as possible.

GSM choose a combination of TDMA/FDMA as its method. The FDMA part involves the division by frequency of the total 25 MHz bandwidth into 124 carrier frequencies of 200 kHz bandwidth.

One or more carrier frequencies are then assigned to each BS. Each of these carrier frequencies is then divided in time, using a TDMA scheme, into eight time slots. One time slot is used for transmission by the mobile and one for reception. They are separated in time so that the mobile unit does not receive and transmit at the same time.

Transmission Rate:The total symbol rate for GSM at 1 bit per symbol in GMSK produces 270.833 K symbols/second. The gross transmission rate of the time slot is 22.8 Kbps.

GSM is a digital system with an over-the-air bit rate of 270 kbps.

Frequency Band:The uplink frequency range specified for GSM is 933 - 960 MHz (basic 900 MHz band only). The downlink frequency band 890 - 915 MHz (basic 900 MHz band only).

Channel Spacing:This indicates separation between adjacent carrier frequencies. In GSM, this is 200 kHz.

Speech Coding:GSM uses linear predictive coding (LPC). The purpose of LPC is to reduce the bit rate. The LPC provides parameters for a filter that mimics the vocal tract. The signal passes through this filter, leaving behind a residual signal. Speech is encoded at 13 kbps.

Duplex Distance:The duplex distance is 80 MHz. Duplex distance is the distance between the uplink and downlink frequencies. A channel has two frequencies, 80 MHz apart.

Misc: Frame duration: 4.615 mS Duplex Technique: Frequency Division Duplexing (FDD) access mode previously

known as WCDMA.

Speech channels per RF channel: 8.

GSM - Addresses and IdentifierGSM distinguishes explicitly between user and equipment and deals with them separately. Besides phone numbers and subscriber and equipment identifiers, several other identifiers have been defined; they are needed for the management of subscriber mobility and for addressing of all the remaining network elements. The most important addresses and identifiers are presented in the following:

International Mobile Station Equipment Identity (IMEI):

The international mobile station equipment identity (IMEI) uniquely identifies a mobile station internationally. It is a kind of serial number. The IMEI is allocated by the equipment manufacturer and registered by the network operator who stores it in the EIR. By means of IMEI one recognizes obsolete, stolen or nonfunctional equipment.

There are following parts of an IMEI:

Type Approval Code (TAC): 6 decimal places, centrally assigned. Final Assembly Code (FAC): 6 decimal places, assigned by the manufacturer.

Serial Number (SNR): 6 decimal places, assigned by the manufacturer.

Spare (SP): 1 decimal place.

Thus, IMEI = TAC + FAC + SNR + SP. It uniquely characterizes a mobile station and gives clues about the manufacturer and the date of manufacturing.

International Mobile Subscriber Identity ( IMSI):

Each registered user is uniquely identified by its international mobile subscriber identity (IMSI). It is stored in the subscriber identity module (SIM) A mobile station can only be operated if a SIM with a valid IMSI is inserted into equipment with a valid IMEI.

There are following parts of an IMSI:

Mobile Country Code (MCC): 3 decimal places, internationally standardized. Mobile Network Code (MNC): 2 decimal places, for unique identification of mobile

network within the country.

Mobile Subscriber Identification Number (MSIN): Maximum 10 decimal places, identification number of the subscriber in the home mobile network.

Mobile Subscriber ISDN Number ( MSISDN):

The real telephone number of a mobile station is the mobile subscriber ISDN number (MSISDN). It is assigned to the subscriber (his or her SIM, respectively), such that a mobile station set can have several MSISDNs depending on the SIM.

The MSISDN categories follow the international ISDN number plan and therefore have the following structure.

Country Code (CC) : Up to 3 decimal places. National Destination Code (NDC): Typically 2-3 decimal places.

Subscriber Number (SN): Maximum 10 decimal places.

Mobile Station Roaming Number ( MSRN):

The Mobile Station Roaming Number ( MSRN) is a temporary location dependent ISDN number. It is assigned by the locally responsible VLR to each mobile station in its area. Calls are also routed to the MS by using the MSRN.

The MSRN has same structure as the MSISDN.

Country Code (CC) : of the visited network. National Destination Code (NDC): of the visited network.

Subscriber Number (SN): in the current mobile network.

Location Area Identity (LAI):

Each LA of an PLMN has its own identifier. The Location Area Identifier (LAI) is also structured hierarchically and internationally unique as follows:

Country Code (CC) : 3 decimal places. Mobile Network Code (MNC): 2 decimal places.

Location Area Code (LAC): maximum 5 decimal places or, maximum twice 8 bits coded in hexadecimal (LAC < FFFF).

Temporary Mobile Subscriber Identity (TMSI):

The VLR, which is responsible for the current location of a subscriber, can assign a temporary mobile subscriber identity (TMSI) which has only local significance in the area handled by the VLR. It is stored on the network side only in the VLR and is not passed to the HLR.

Together with the current location area, TMSI allows a subscriber to be identified uniquely and it can consist of upto 4x8 bits.

Local Mobile Subscriber Identity (LMSI):

The VLR can assign an additional searching key to each mobile station within its area to accelerate database access. This unique key is called the Local Mobile Subscriber Identity (LMSI). The LMSI is assigned when the mobile station registers with the VLR and is also sent to the HLR.

An LIMSI consists of four octets ( 4 x 8 bits).

Cell Identifier (CI):

Within an LA, the individual cells are uniquely identified with a cell identifier (CI), maximum 2 x 8 bits. Together with the global cell identity (LAI + CI) calls are thus also internationally defined in a unique way.

GSM – OperationsThe operation of the GSM system can be understood by studying the sequence of events that takes place when a call is initiated from the Mobile Station.

Call from Mobile Phone to PSTN:When a mobile subscriber makes a call to a PSTN telephone subscriber, the following sequence of events takes place:

1. The MSC/VLR receives the message of a call request.2. The MSC/VLR checks if the mobile station is authorized to access the network. If so, the

mobile station is activated. If the mobile station is not authorized, service will be denied.

3. MSC/VLR analyzes the number and initiates a call setup with the PSTN.

4. MSC/VLR asks the corresponding BSC to allocate a traffic channel (a radio channel and a time slot).

5. The BSC allocates the traffic channel and passes the information to the mobile station.

6. The called party answers the call and the conversation takes place.

7. The mobile station keeps on taking measurements of the radio channels in the present cell and neighboring cells and passes the information to the BSC. The BSC decides if handover is required, if so, a new traffic channel is allocated to the mobile station and the handover is performed. If handover is not required, the mobile station continues to transmit in the same frequency.

Call from PSTN to Mobile Phone:

When a PSTN subscriber calls a mobile station, the sequence of events is as follows:

1. The Gateway MSC receives the call and queries the HLR for the information needed to route the call to the serving MSC/VLR.

2. The GMSC routes the call to the MSC/VLR.

3. The MSC checks the VLR for the location area of the MS.

4. The MSC contacts the MS via the BSC through a broadcast message, that is, through a paging request.

5. The MS responds to the page request.

6. The BSC allocates a traffic channel and sends a message to the MS to tune to the channel. The MS generates a ringing signal and, after the subscriber answers, the speech connection is established.

7. Handover, if required, takes place, as discussed in the earlier case.

The MS codes the speech at 13 Kbps for transmission over the radio channel in the given time slot. The BSC converts (or transcodes) the speech to 64 Kbps and sends it over a land link or radio link to the MSC. The MSC then forwards the speech data to the PSTN. In the reverse direction, the speech is received at 64 Kbps rate at the BSC and the BSC does the transcoding to 13 Kbps for radio transmission.

In its original form, GSM supports 9.6 Kbps data, which can be transmitted in one TDMA time slot. Over the last few years, many enhancements were done to the GSM standards (GSM Phase 2 and GSM Phase 2+) to provide higher data rates for data applications.

GSM - Protocol StackThe layered model of the GSM architecture integrates and links the peer-to-peer communications between two different systems. The underlying layers satisfy the services of the upper-layer protocols. Notifications are passed from layer to layer to ensure that the information has been properly formatted, transmitted, and received.

The GMS protocol stacks diagram is shown below:

MS Protocols:The signaling protocol in GSM is structured into three general layers, depending on the interface.

Layer 1: The physical layer, which uses the channel structures over the air interface. Layer 2: The data-link layer. Across the Um interface, the data-link layer is a modified

version of the Link access protocol for the D channel (LAP-D) protocol used in ISDN, called Link access protocol on the Dm channel (LAP-Dm). Across the A interface, the Message Transfer Part (MTP), Layer 2 of SS7 is used.

Layer 3: The third layer of the GSM signaling protocol is divided into three sublayers:

o Radio Resource management (RR)

o Mobility Management (MM) and

o Connection Management (CM).

The MS to BTS Protocols:The RR layer oversees the establishment of a link, both radio and fixed, between the MS and the MSC. The main functional components involved are the MS, the BSS, and the MSC. The RR layer is concerned with the management of an RR-session, which is the time that a mobile is in dedicated mode, as well as the configuration of radio channels, including the allocation of dedicated channels.

The MM layer is built on top of the RR layer and handles the functions that arise from the mobility of the subscriber, as well as the authentication and security aspects. Location management is concerned with the procedures that enable the system to know the current location of a powered-on MS so that incoming call routing can be completed.

The CM layer is responsible for CC, supplementary service management, and Short Message Service (SMS) management. Each of these may be considered as a separate sublayer within the CM layer. Other functions of the CC sublayer include call establishment, selection of the type of service (including alternating between services during a call), and call release.

BSC Protocols:After the information is passed from the BTS to the BSC, a different set of interfaces is used. The Abis interface is used between the BTS and BSC. At this level, the radio resources at the lower portion of Layer 3 are changed from the RR to the Base Transceiver Station Management (BTSM). The BTS management layer is a relay function at the BTS to the BSC.

The RR protocols are responsible for the allocation and reallocation of traffic channels between the MS and the BTS. These services include controlling the initial access to the system, paging for MT calls, the handover of calls between cell sites, power control, and call termination. The RR protocols provide the procedures for the use, allocation, reallocation, and release of the GSM channels. The BSC still has some radio resource management in place for the frequency coordination, frequency allocation, and the management of the overall network layer for the Layer 2 interfaces.

From the BSC, the relay is using SS7 protocols so the MTP 1-3 is used as the underlying architecture, and the BSS mobile application part or the direct application part is used to communicate from the BSC to the MSC.

MSC Protocols:At the MSC, the information is mapped across the A interface to the MTP Layers 1 through 3 from the BSC. Here the equivalent set of radio resources is called the BSS MAP. The BSS MAP/DTAP and the MM and CM are at the upper layers of Layer 3 protocols. This completes the relay process. Through the control-signaling network, the MSCs interact to locate and connect to users throughout the network. Location registers are included in the MSC databases to assist in the role of determining how and whether connections are to be made to roaming users.

Each user of a GSM MS is assigned a HLR that is used to contain the user's location and subscribed services. A separate register, the VLR, is used to track the location of a user. As the users roam out of the area covered by the HLR, the MS notifies a new VLR of its whereabouts. The VLR in turn uses the control network (which happens to be based on SS7) to signal the HLR of the MS's new location. Through this information, MT calls can be routed to the user by the location information contained in the user's HLR.

GSM - User ServicesGSM has much more to offer than voice telephony. Additional services allow you greater flexibility in where and when you use your phone. You should contact your local GSM network operator for information on the specific services available to you.

But there are three basic types of services offered through GSM which you can ask for:

Telephony (also referred to as teleservices) Services Data (also referred to as bearer services) Services.

Supplementary Services

Teleservices or Telephony Services:A Teleservice utilises the capabilities of a Bearer Service to transport data, defining which capabilities are required and how they should be set up.

Voice Calls:

The most basic Teleservice supported by GSM is telephony. This includes Full-rate speech at 13 Kbps and emergency calls, where the nearest emergency� service provider is notified by dialing three digits. A very basic example of emergency service is 911 service available in USA.

Videotext and Facsmile:

Another group of teleservices includes Videotext access, Teletex transmission, Facsimile alternate speech and facsimile Group 3, Automatic facsimile Group 3 etc.

Short Text Messages:

SMS (Short Messaging Service) service is a text messaging which allow you to send and receive text messages on your GSM Mobile phone. Services available from many of the world's GSM networks today - in addition to simple user generated text message services - include news, sport, financial, language and location based services, as well as many early examples of mobile commerce such as stocks and share prices, mobile banking facilities and leisure booking services.

Bearer Services or Data ServicesUsing your GSM phone to receive and send data is the essential building block leading to widespread mobile Internet access and mobile data transfer. GSM currently has a data transfer rate of 9.6k. New developments that will push up data transfer rates for GSM users are HSCSD (high speed circuit switched data) and GPRS (general packet radio service) are now available.

Supplementary ServicesSupplementary services are provided on top of teleservices or bearer services, and include features such as caller identification, call forwarding, call waiting, multi�party conversations, and barring of outgoing (international) calls, among others. A brief description of supplementary services is given here:

Multiparty Service or conferencing: The multiparty service allows a mobile subscriber to establish a multiparty conversation.that is, a simultaneous conversation between three or more subscribers to setup a conference call. This service is only applicable to normal telephony.

Call Waiting: This service allows a mobile subscriber to be notified of an incoming call during a conversation. The subscriber can answer, reject, or ignore the incoming call. Call waiting is applicable to all GSM telecommunications services using a circuit-switched connection.

Call Hold: This service allows a subscriber to put an incoming call on hold and then resume this call. The call hold service is only applicable to normal telephony.

Call Forwarding: The Call Forwarding Supplementary Service is used to divert calls from the original recipient to another number, and is normally set up by the subscriber himself. It can be used by the subscriber to divert calls from the Mobile Station when the subscriber is not available, and so to ensure that calls are not lost. A typical scenario would be a salesperson turns off his mobile phone during a meeting with customers, but does not with to lose potential sales leads while he is unavailable.

Call Barring: The concept of barring certain types of calls might seem to be a supplementary disservice rather than service. However, there are times when the subscriber is not the actual user of the Mobile Station, and as a consequence may wish to limit its functionality, so as to limit the charges incurred. Alternatively, if the subscriber and user are one and the same, the Call Barring may be useful to stop calls being routed to international destinations when they are routed. The reason for this is because it is expected that the roaming subscriber will pay the charges incurred for international re-routing of calls. So, GSM devised some flexible services that enable the subscriber to conditionally bar calls.

Number Identification: There are following supplementary services related to number identification:

o Calling Line Identification Presentation: This service deals with the presentation of the calling party's telephone number. The concept is for this number to be presented, at the start of the phone ringing, so that the called person can determine who is ringing prior to answering. The person subscribing to the service receives the telephone number of the calling party.

o Calling Line Identification Restriction: A person not wishing their number to be presented to others subscribes to this service. In the normal course of event, the restriction service overrides the presentation service.

o Connected Line Identification Presentation: This service is provided to give the calling party the telephone number of the person to whom they are connected. This may seem strange since the person making the call should know the number they dialled, but there are situations (such as forwardings) where the number connected is not the number dialled. The person subscribing to the service is the calling party.

o Connected Line Identification Restriction: There are times when the person called does not wish to have their number presented and so they would subscribe to this person. Normally, this overrides the presentation service.

o Malicious Call Identification: The malicious call identification service was provided to combat the spread of obscene or annoying calls. The victim should subscribe to this service, and then they could cause known malicious calls to be identified in the GSM network, using a simple command. This identified number could then be passed to the appropriate authority for action. The definition for this service is not stable.

Advice of Charge (AoC): This service was designed to give the subscriber an indication of the cost of the services as they are used. Furthermore, those Service Providers who wish to offer rental services to subscribers without their own Subscriber Identity Module (SIM) can also utilize this service in a slightly different form. AoC for data calls is provided on the basis of time measurements.

Closed User Groups (CUGs): This service is provided on GSM to enable groups of subscribers to only call each other. This type of services are being offered with special discount and is limited only to those members who wish to talk to each other.

Unstructured supplementary services data (USSD): This allows operator-defined individual services.

GSM - Security and EncryptionThe security methods standardized for the GSM System make it the most secure cellular telecommunications standard currently available. Although the confidentiality of a call and anonymity of the GSM subscriber is only guaranteed on the radio channel, this is a major step in achieving end-to- end security.

The subscriber's anonymity is ensured through the use of temporary identification numbers. The confidentiality of the communication itself on the radio link is performed by the application of encryption algorithms and frequency hopping which could only be realized using digital systems and signaling.

This chapter gives an outline of the security measures implemented for GSM subscribers.

Mobile Station Authentication:The GSM network authenticates the identity of the subscriber through the use of a challenge-response mechanism. A 128-bit random number (RAND) is sent to the MS. The MS computes the 32-bit signed response (SRES) based on the encryption of the random number (RAND) with the authentication algorithm (A3) using the individual subscriber authentication key (Ki). Upon receiving the signed response (SRES) from the subscriber, the GSM network repeats the calculation to verify the identity of the subscriber.

Note that the individual subscriber authentication key (Ki) is never transmitted over the radio channel. It is present in the subscriber's SIM, as well as the AUC, HLR, and VLR databases as previously described. If the received SRES agrees with the calculated value, the MS has been successfully authenticated and may continue. If the values do not match, the connection is terminated and an authentication failure indicated to the MS.

The calculation of the signed response is processed within the SIM. This provides enhanced security, because the confidential subscriber information such as the IMSI or the individual subscriber authentication key (Ki) is never released from the SIM during the authentication process.

Signaling and Data Confidentiality:

The SIM contains the ciphering key generating algorithm (A8) which is used to produce the 64-bit ciphering key (Kc). The ciphering key is computed by applying the same random number (RAND) used in the authentication process to the ciphering key generating algorithm (A8) with the individual subscriber authentication key (Ki). As will be shown in later sections, the ciphering key (Kc) is used to encrypt and decrypt the data between the MS and BS.

An additional level of security is provided by having the means to change the ciphering key, making the system more resistant to eavesdropping. The ciphering key may be changed at regular intervals as required by network design and security considerations. In a similar manner to the authentication process, the computation of the ciphering key (Kc) takes place internally within the SIM. Therefore sensitive information such as the individual subscriber authentication key (Ki) is never revealed by the SIM.

Encrypted voice and data communications between the MS and the network is accomplished through use of the ciphering algorithm A5. Encrypted communication is initiated by a ciphering mode request command from the GSM network. Upon receipt of this command, the mobile station begins encryption and decryption of data using the ciphering algorithm (A5) and the ciphering key (Kc).

Subscriber Identity Confidentiality:To ensure subscriber identity confidentiality, the Temporary Mobile Subscriber Identity (TMSI) is used. The TMSI is sent to the mobile station after the authentication and encryption procedures have taken place. The mobile station responds by confirming reception of the TMSI. The TMSI is valid in the location area in which it was issued. For communications outside the location area, the Location Area Identification (LAI) is necessary in addition to the TMSI.

GSM – Billingo their customers. All the parameters are simple enough to charge a customer for the provided services.

In this chapter we will discuss about most frequently used billing techniques and parameters to charge a GSM subscriber.

Telephony Service:

These services can be charged on per call basis. Only call initiator has to pay the charges and now a days, all the incoming charges are free. A customer can be charged based on different parameters like:

International call or long distance call. Local call

Call made during peak hours.

Call made during night time

Discounted call during weekends.

Call per minute or per second.

Many more other criteria can be designed by a service provider to charge their customers.

SMS Service:

Till the time this tutorial is written, most of the service providers are charging their customer's SMS services based on number of text messages sent from their mobile phone. There are other prime SMS services available where service providers are charging more than normal SMS charge. These services are being used in collaboration of Television Networks or Radio Networks to demand SMS from the audiences

Most of time charges are paid by the SMS sender but for some services like stocks and share prices, mobile banking facilities and leisure booking services etc. recipient of the SMS has to pay for the service.

GPRS Services

Using GPRS service you can browse Internet and can play games on the Internet, you can download movies or music etc. So a service provider will charge you based on the data uploaded as well as data downloaded on your mobile phone. These charges will be based on per Kilo Byte data downloaded/uploaded.

Additional parameter could be a Quality of Service provided to you. If you want to watch a movie then a low quality may work because some data loss may be acceptable to you but if you are downloading a zip file then a single byte loss will corrupt your complete downloaded file.

Another parameter could be peak and off peak time to download a data file or to browse the Internet.

Supplementary Services

Most of the supplementary services are being provided based on monthly rental or absolutely FREE. Like Call Waiting, Call Forwarding, Calling Number Identification, and call on hold are available at very low or zero prices.

Call Baring is a service which service providers use just to recover their dues etc. otherwise this service is not being used by any subscriber.

Call conferencing service is a form of simple telephone call where customer will be charged for multiple calls made at a time. No service provider charges extra charge for this service.

Closed User Group (CUG) is very popular and is mainly being used to give special discounts to the users if they are making calls to a particular defined group of subscribers.

Advice of Charge (AoC) can be charged based on number of queries made by a subscriber.

GSM - Mobile PhonesToday, GSM Arena is the biggest source of information about latest GSM Mobile Phones. This page is being displayed here as a courtesy of GSM Arena. So if you are planning to buy a GSM

Mobile phone then I would strongly suggest you to go through all the review comments and then decide which phone is suitable for you

GSM – SummaryHope, now you are aware of GSM Technology. We have taught you all the basic concepts related to GSM technology.

You have learnt about GSM basic overview, its architecture along with a description about all important GSM elements and a brief GSM specification. You have gone through all the important GSM Addresses and Identifiers also.

Further, We have given a short description of GSM protocol stack and available GSM services and their billing techniques.

A list of all the important GSM Acronyms has been given for your quick reference. So you can book mark this page for future reference.

What is Next?

To enhance the current data capabilities of GSM, operators and infrastructure providers have specified new extensions to GSM Phase II. These extensions are:

High Speed Circuit Switched Data (HSCSD): by using several circuit channels. General Packet Radio Service (GPRS) to provide packet radio access to external packet

data networks (such as X.25 or Internet)

Enhanced Data rate for GSM Evolution (EDGE): using a new modulation scheme to provide up to three times higher throughput (for HSCSD and GPRS)

Universal Mobile Telecommunication System (UMTS): a new wireless technology using new infrastructure deployment.

GSM - Useful Acronyms1GThe first generation of analogue mobile phone technologies including AMPS, TACS and NMT

2GThe second generation of digital mobile phone technologies including GSM, CDMA IS-95 and D-AMPS IS-136

2.5GThe enhancement of GSM which includes technologies such as GPRS

3GThe third generation of mobile phone technologies covered by the ITU IMT-2000 family

3GPP

The 3rd Generation Partnership Project, a grouping of international standards bodies, operators and vendors with the responsibility of standardising the WCDMA based members of the IMT-2000 family

3GPP2The counterpart of 3GPP with responsibility for standardising the CDMA2000-based members of the IMT-2000 family. 3GPP2 is spearheaded by ANSI

8PSKOctantal Phase Shift Keying

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A5/1/2/3/8XEncryption algorithms for GSM networks

AALATM Adaptation Layer

ABRAvailable Bit Rate

A-bisInterface between the BSC and BTS in a GSM network

ABAccess Burst; used for random access and characterised by a longer guard period to allow for burst transmission from a MS that does not know the correct timing advance when first contacting a network

ACTEApprovals Committee for Terminal Equipment

ACTSAdvanced Communications Technologies and Services . a European technology initiative

ACUAntenna Combining Unit

ADPCMAdaptive Differential Pulse Code Modulation; a form of voice compression that typically uses 32kbit/s

AFCAutomatic Frequency Control

AGCHAccess Grant Channel; downlink only, BTS allocates a TCH or SDCCH to the MS, allowing it access to the network

Air interfaceIn a mobile phone network, the radio transmission path between the base station and the mobile

terminal

A-interfaceInterface between the MSC and BSS in a GSM network

AMAmplitude Modulation

AMPSAdvanced Mobile Phone System, the analogue mobile phone technology used in North and South America and in around 35 other countries. Operates in the 800MHz band using FDMA technology

AMRAdaptive Multi-Rate codec. Developed in 1999 for use in GSM networks, the AMR has been adopted by 3GPP for 3G

AnalogueThe representation of information by a continuously variable physical quantity such as voltage

ANSIAmerican National Standards Institute. An non-profit making US organisation which does not carry out standardisation work but reviews the work of standards bodies and assigns them category codes and numbers

ANSI-136See D-AMPS

APIApplication Program Interface

AoCAdvice of Charge

ARIBAssociation of Radio Industries and Businesses. An organisation established by Japan.s Ministry of Posts and Communications to act as the standardisation authority for radio communication and broadcasting

ARPUAverage Revenue Per User

ASCIIAmerican Standard Code for Information Interchange

ASICApplication Specific Integrated Circuit

ASPApplication Service Provider

Asymmetric Transmission

Data transmissions where the traffic from the network to the subscriber is at a higher rate than the traffic from the subscriber to the network

A-TDMAAdvanced Time Division Multiple Access

ATMAsynchronous Transfer Mode; a multiplexed information transfer and switching method in which the data is organised into fixed length 53-octet cells and transmitted according to each application.s instantaneous need

AUCAuthentication Centre; the element within a GSM network which generates the parameters for subscriber authentication

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BandwidthA term meaning both the width of a transmission channel in terms of Hertz and the maximum transmission speed in bits per second that it will support

BCHBroadcast Channels; carry only downlink information and are mainly responsible for synchronisation and frequency correction (BCCH, FCCH and SCH)

BCCHBroadcast Control Channel; the logical channel used in cellular networks to broadcast signalling and control information to all mobile phones within the network

B-CDMABroadband Code Division Multiple Access

B-ISDNBroadband ISDN

BERBit Error Rate; the percentage of received bits in error compared to the total number of bits received

BERTBit Error Rate Test

BitA bit is the smallest unit of information technology. As bits are made up using the binary number system, all multiples of bits must be powers of two i.e. a kilobit is actually 1024 bits and a megabit 1048576 bits. Transmission speeds are given in bits per second (bit/s)

BluetoothA low power, short range wireless technology designed to provide a replacement for the serial cable. Operating in the 2.4GHz ISM band, Bluetooth can connect a wide range of personal, professional and domestic devices such a laptop computers and mobile phones together

wirelessly.

BHCABusy Hour Call Attempts; the number of call attempts made during a network.s busiest hour of the day

BSCBase Station Controller; the network entity controlling a number of Base Transceiver Stations

BSSBase Station System/Subsystem

BTSBase Transceiver Station; the network entity which communicates with the mobile station

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CAICommon Air Interface; a standard developed for the UK.s public CT2 networks which enabled the same handset to be used on different networks

CAMELCustomised Application for Mobile network Enhanced Logic; an IN feature in GSM networks that enables users to carry personal services with them when roaming into other networks that support CAMEL

CSECAMEL Service Environment

CapacityA measure of a cellular network.s ability to support simultaneous calls

CBCell Broadcast

CCCall Control; manages call connections

CCBCustomer Care and Billing

CCCHCommon Control Channels; a group of uplink and downlink channels between the MS and the BTS (see PCH, AGCH and RACH)

CCS7Common Channel Signalling No. 7

CDMACode Division Multiple Access; also known as spread spectrum, CDMA cellular systems utilise a single frequency band for all traffic, differentiating the individual transmissions by assigning

them unique codes before transmission. There are a number of variants of CDMA (see W-CDMA, B-CDMA, TD-SCDMA et al)

CDMAoneThe first commercial CDMA cellular system; deployed in North America and Korea; also known as IS-95

CDMA2000A member of the IMT-2000 3G family; backwardly compatible with cdmaOne

CDMA 1XThe first generation of cdma2000; the standardisation process indicated that there would be CDMA 2X and CDMA 3X but this no longer appears likely

CDMA 1X EV-DOA variant of CDMA 1X which delivers data only

CDPDCellular Digital Packet Data; a packet switched data service largely deployed in the USA. The service uses idle analogue channels to carry the packetised information.

CDPSKCoherent Differential Phase Shift Keying

CDRCall Detail Records; the record made within the cellular network of all details of both incoming and outgoing calls made by subscribers, The CDR is passed to the billing system for action

CellThe area covered by a cellular base station. A cell site may sectorise its antennas to service several cells from one locationCell siteThe facility housing the transmitters/receivers, the antennas and associated equipment

Cell splittingThe process of converting a single cell to multiple cells by sectorising the antennas in the cell site or constructing additional cells within a cell site

CELPCode Excited Linear Prediction; an analogue to digital voice coding scheme, there are a number of variants used in cellular systems

CEPTConference of European Posts and Telecommunications. A organisation of national posts, telegraphs and telephone administrations. Until 1988, when this work was take over by ETSI, the main European body for telecommunications standardisation. CEPT established the original GSM standardisation group

CFCall Forwarding

CICarrier to Interference ratio

CIBERCellular Intercarrier Billing Exchange Roamer Record

CIDCaller Identification

Circuit switchingA method used in telecommunications where a temporary dedicated circuit of constant bandwidth is established between two distant endpoints in a network. Mainly used for voice traffic; the opposite of packet switching

CLIDCalling Line Identification

CLIPCalling Line Identification Presentation

CLIRCalling Line Identification Restriction

CMConnection Management; is used to set up, maintain and take down call connections

CMOSComplementary Metal Oxide Substrate

CodecA word formed by combining coder and decoder the codec is a device which encodes and decodes signals. The voice codec in a cellular network converts voice signals into and back from bit strings. In GSM networks, in addition to the standard voice codec, it is possible to implement Half Rate (HR) codecs and Enhanced Full Rate (EFR) codecs

Control signalA signal sent to a cellular phone from a base station or vice versa which carries information essential to the call but not including the audio portion of a conversation

CPECustomer Premises Equipment; all the equipment on the end user.s side of the network interface

CPUCentral Processing Unit

CRCCyclic Redundancy Check

CRMCustomer Relationship Management

CSSCustomer Support System

CTCordless Telephony

CT0Zero generation cordless telephony; the earliest domestic cordless phones which used analogue technology and which had severe limitations in terms of range and security

CT1First generation cordless telephony; Improved analogue phones with greater range and security; a number of European nations produced CT1 standards

CT2Second generation cordless telephony; Using digital technology CT2 phones offered greater range, improved security and a wide range of new functionalities. Used in both domestic and cordless PABX deployments, CT2 was standardised as an interim ETS but was overwhelmed by DECT

CT2-CAISecond generation cordless telephony-common air interface

CTACordless Terminal Adaptor; a DECT term

CTMCordless Terminal Mobility

CTRCommon Technical Regulation; part of the ETSI standardisation process

CUGClosed User Group

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D/ADigital to Analogue conversion

DACDigital to Analogue Convertor

DAMADemand Assigned Multiple Access

D-AMPSDigital AMPS, a US wireless standard also known as IS-136

DANDECT Access Node

DCADynamic Channel Assignment

DCCHDedicated Control Channels; responsible for roaming, handovers, encryption etc. (See SDCCH, SACCH and FACCH)

DCEData Communications Equipment

DCHData Clearing House

DCPSKDifferentially Coherent Phase Shift Keying

DCS1800Digital Cellular System at 1800MHz, now known as GSM1800

DECTDigitally Enhanced Cordless Telecommunications system, a second generation digital cordless technology standardised by ETSI

DEPSKDifferential Encoded Phase Shift Keying

DESDigital Encryption Standard

DFSKDouble Frequency Shift Keying

Digitala method of representing information as numbers with discrete values; usually expressed as a sequence of bits

DPCMDifferential Pulse Code Modulation

DPSKDigital Phase Shift Keying

DQPSKDigital Quadrature Phase Shift Keying

DS-CDMADirect Sequence CDMA

DSPDigital Signal Processing

DSRRDigital Short Range Radio; a UK standard for a low power, short range radio system designed for small voice and data networks

DTEData Terminal Equipment

DTMFDual Tone MultiFrequency; better know as Touch Tone. The tones generated by touching the keys on the phone are used for a variety of purposes including voice mail systems and voice messaging

DTXDiscontinuous Transmission

Dual BandThe capability of GSM infrastructure elements and handsets to work across both the 900MHz and 1800MHz bands. The capability to seamlessly handover between the two bands offers operators major capacity gains

DBDummy Burst; transmitted as a filler in unused timeslots of the carrier

DuplexThe wireless technique where one frequency band is used for traffic from the network to the subscriber (the downlink) and another, widely separated, band is used for traffic from the subscriber to the network (the uplink)

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EDGEEnhanced Data rates for GSM Evolution; effectively the final stage in the evolution of the GSM standard, EDGE uses a new modulation schema to enable theoretical data speeds of up to 384kbit/s within the existing GSM spectrum. An alternative upgrade path towards 3G services for operators, such as those in the USA, without access to new spectrum. Also known as Enhanced GPRS (E-GPRS)

EEPROMElectrically Erasable Programmable Read Only Memory

EFREnhanced Full Rate; a alternative voice codec that provides improved voice quality in a GSM network (see codec)

EFTElectronic Funds Transfer

EGSMExtended (frequency range) GSM

EIREquipment Identity Register; a database that contains a list of all valid mobile stations within a network based on their IMEI

EIRPEffective Isotropic Radiated Power

EPOCThe mobile phone operating system developed by Symbian. Derived from epoch-the beginning of an era-EPOC is a 32-bit operating environment which comprises a suite of applications, customisable user interfaces, connectivity options and a range of development tools

EPROMErasable Programmable Read Only Memory

ErlangA dimensionless unit of average traffic density in a telecommunications network

ERMESEnhanced Radio Messaging System; a paging technology developed by ETSI which was intended to allow users to roam throughout Europe. Adopted by a number of European and Middle Eastern countries, ERMES, like paging in general, was overtaken by the ubiquity of GSM

EROEuropean Radiocommunications Office

ERPEffective Radiated Power

ESMREnhanced Special Mobile Radio; a US PMR variant (see SMR)

ESNElectronic Serial Number; a 32-bit number that uniquely identifies a mobile phone

ESPRITEuropean Strategic Programme for Research and Development in Information Technology

ETACSExtended TACS; the extension of TACS by the addition of new frequencies

ETSIEuropean Telecommunications Standards Institute: The European group responsible for defining telecommunications standards

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FACCHFast Associated Control Channel; similar to the SDCCH but used in parallel for operation of the TCH. If the data rate of the SACCH is insufficient borrowing mode is used

FBFrequency Correction Burst; used for frequency synchronisation of the mobile

FCCFederal Communications Commission; the US regulatory body for telecommunications

FCCHFrequency Correction Channel; downlink only, correction of MS frequencies, transmission of frequency standard to MS etc.

FDDFrequency Division Duplex; a radio technique which uses paired spectrum; UMTS has an FDD element

FDMA Frequency Division Multiple Access-a transmission technique where the assigned frequency band for a network is divided into sub-bands which are allocated to a subscriber for the duration of their calls

FECForward Error Correction

FHFrequency Hopping

FH-CDMAFrequency Hopping CDMA

FMCFixed Mobile Convergence

FMIFixed Mobile Integration

FPLMTSFuture Public Land Mobile Telecommunications System, the original title of the ITU.s third generation concept now known as IMT-2000

FRAFixed Radio Access; see WLL

FSDPSKFiltered Symmetric Differential Phase Shift Keying

FSKFrequency Shift Keying; a method of using frequency modulation to send digital information

FSOQFrequency Shift Offset Quadrature Modulation

FSS Fixed Satellite ServiceGbThe interface between the PCU and the SGSN in a GSM/GPRS network

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GcThe interface between the GGSN and the HLR in a GSM/GPRS network

GdThe interface between the SGSN and the SMSC in a GSM/GPRS network

GfThe interface between the SGSN and the EIR in a GSM/GPRS network

GiThe interface between the GGSN and the Internet in a GPRS network

GnThe interface between the GGSN and the SGSN in a GPRS network

GpThe interfaces between the GGSN/SGSN and the Border Gateway in a GPRS network

GrThe interface between the SGSN and the HLR in a GPRS network

GsThe interface between the SGSN and the MSC in a GSM/GPRS network

GAITGSM/ANSI 136 Interoperability Committee

GAPGeneric Access Profile; a DECT term

Gbit/sA unit of data transmission rate equal to one billion bits per second

GMSCGateway Mobile Services Switching Centre; the gateway between two networks

GCFGlobal Certification Forum

GeostationaryRefers to a satellite in equatorial orbit above the earth which appears from the surface to be stationary

GERANGSM-EDGE Radio Access Network; the name for the evolution of GSM towards 3G based on EDGE

GGRFGSM Global Roaming Forum

GGSNGateway GPRS Support Node; the gateway between a cellular network and a IP network.

GHzA unit of frequency equal to one billion Hertz per second

GMPCSGlobal Mobile Personal Communications by Satellite

GMSKGaussian filtered Minimum Shift Keying; a refinement of FSK which minimises adjacent channel interference

GPRSGeneral Packet Radio Service; standardised as part of GSM Phase 2+, GPRS represents the first implementation of packet switching within GSM, which is a circuit switched technology. GPRS offers theoretical data speeds of up to 115kbit/s using multislot techniques. GPRS is an essential precursor for 3G as it introduces the packet switched core required for UMTS

GPS Global Positioning System; a location system based on a constellation of US Department of Defence satellites. Depending on the number of satellites visible to the user can provide accuracies down to tens of metres. Now being incorporated as a key feature in an increasing number of handsets

GRXGPRS Roaming Exchange

GSMGlobal System for Mobile communications, the second generation digital technology originally developed for Europe but which now has in excess of 71 per cent of the world market. Initially developed for operation in the 900MHz band and subsequently modified for the 850, 1800 and 1900MHz bands. GSM originally stood for Groupe Speciale Mobile, the CEPT committee which began the GSM standardisation process

GSM MoUThe GSM Memorandum of Understanding, an agreement signed between all the major European operators to work together to promote GSM. The precursor of the GSM Association

GSM-RGSM-Railway, A variant of GSM designed to meet the special communications needs of international train operators

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HandoffThe transfer of control of a cellular phone call in progress from one cell to another, without any discontinuity

Hands-free

The operation of a cellular phone without using the handset; usually installed in vehicles.

HCSHierarchical Cell Structure; the architecture of a multi-layered cellular network where subscribers are handed over from the macro to the micro to the pico layer depending on the current network capacity and the needs of the subscriber

HDLCHigh level Data Link Control

HIPERLANHigh Performance Radio Local Access Network; a wireless local area network being standardised by ETSI (Also HIPERLAN2)

HLRHome Location Register; the database within a GSM network which stores all the subscriber data. An important element in the roaming process

HSCSDHigh Speed Circuit Switched Data; a special mode in GSM networks which provides higher data throughput By cocatenating a number of timeslots, each delivering 14.4kbit/s, much higher data speeds can be achieved

HSPSDHigh Speed Packet Switched DataIubThe interface between the Node B and the RNC in a UMTS network

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IurThe interface between RNCs in a UMTS network

IupsThe connection between the RNC and the packet switched network in a GSM/GPRS/UMTS network

IucsThe connection between the RNC and the circuit switched network in a GSM/GPRS/UMTS network

I-ETSInterim European Telecommunications Standard

I-modeA service developed by Japanese operator NTT DoCoMo, I-mode delivers a huge range of services to subscribers and has proved enormously popular with some 30 million regular users. The revenue sharing model used for I-mode is being adopted by other operators as the basis for the new services enabled by GPRS and 3G

IMEIInternational Mobile Equipment Identity

IMSIInternational Mobile Subscriber Identity; an internal subscriber identity used only by the network

IMT-2000The family of third generation technologies approved by the ITU. There are five members of the family: IMT-DS, a direct sequence WCDMA FDD solution IMT-TC, a WCDMA TDD solution IMT-MC, a multicarrier solution developed from cdma2000 IMT-SC, a single carrier solution developed from IS-136/UWC-136 IMT-FT, a TDMA/TDD solution derived from DECT

INIntelligent Network

INAPIntelligent Network Application Part

InternetA loose confederation of autonomous databases and networks. Originally developed for academic use the Internet is now a global structure of millions of sites accessible by anyone

IntranetA private network which utilises the same techniques as the Internet but is accessible only by authorised users

IPInternet Protocol

IPRIntellectual Property Rights

IPv6The next generation of IP addressing designed to replace the current system IPv4 which uses a 32 bit address code which limits the number of possible addresses. IPv6 uses a 128 bit code ensuring that the possible number of IP addresses will be virtually limitless

IrDAInfra red Data Association

IridiumA low earth orbit satellite communications system developed initially by Motorola.

IS-54The first evolution in the USA from analogue to digital technology. Used a hybrid of analogue and digital technology, superseded by IS-136

IS-95Cellular standard know also as cdmaOne

IS-136Cellular standard also known as TDMA or D-AMPS

ISDN

Integrated Services Digital Network

ISOInternational Standards Organisation

ISP Internet Service Provider

ITUInternational Telecommunications Union

ITU-RITU Telecommunications Radio Sector

ITU-TITU Telecommunications Standardisation Sector

IWFInterworking Function

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JavaA programming language developed by Sun Microsystems Java is characterised by the fact that programs written in Java do not rely on an operating system

JPEGJoint Photographic Experts Group

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LANLocal Area Network

LANSLocal Area Network Services

LAPLink Access Protocol

LEOLow Earth Orbit; refers to satellites which orbit the Earth at around 1,000 kilometres

LMSSLand Mobile Satellite Service

LOSLine of Sight

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MACMedia Access Control; the lower sublayer of the OSI system

MANMetropolitan Area Network

MAPMobile Application Part

Mbit/s Megabit: a unit of data transmission speed equal to one million bits per second

MHzMegahertz; a unit of frequency equal to one million Hertz

MCPAMulti Carrier Power Amplifier

MeXeMobile Execution Environment; likely to be based on Java, MeXe enables WAP-enabled devices to offer a wider range of features with greater security and flexibility, as well as greater control of telephony features

MFSKMultiple Frequency Shift Keying

MMIMan Machine Interface

MMSMultimedia Messaging Service; an evolution of SMS, MMS goes beyond text messaging offering various kinds of multimedia content including images, audio and video clips

MMSKModified Minimum Shift Keying

MNOMobile Network Operator

ModulationThe process of imposing an information signal on a carrier. This can be done by changing the amplitude (AM), the frequency (FM) or the phase, or any combination of these

MoUMemorandum of Understanding-see GSM MoU

MPEGMotion Picture Experts Group; MPEG4 is a technology for compressing voice and video so that

the information can be transmitted over normally difficult links such as mobile radio

MSMobile Station

MSCMobile Switching Centre; the switching centre of a mobile phone network, the MSC has interfaces to the BSCs, HLR, VLR and other MSCs

MSISDNMobile Station International ISDN Number

MSK Minimum Shift Keying; Another term for FFSK

MultiplexingA telecommunications technique where several channels can be combined to share the same transmission medium. The most common forms are Time Division Multiplexing (TDM) and Frequency Division Multiplexing (FDM)

MVPNMobile Virtual Private Network

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N-AMPSNarrowband AMPS

NBNormal Burst; used to carry traffic and control channels except RACH

NETNorme Europeenne de Telecommunications

NMTNordic Mobile Telephone system; an analogue cellular technology deployed in the Nordic countries in the late 1970.s; variations were also deployed in the Benelux countries and in Russia. NMT operated in the 450 and 900MHz bands and was the first technology to offer international roaming, albeit only in the Nordic countries

Node BThe element in a UMTS network which interfaces with the mobile station, analogous to a BTS in a GSM network

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OTAOver the air activation (of services and tariff changes)

O&M

Operations and Maintenance

OMCOperations and Maintenance Centre

OMC-RThe radio OMC

OMC-SThe switching OMC

OSIOpen Systems Interconnection; a seven layer model for protocols defined by ISO

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PACSPersonal Access Communication System; a digital cordless technology developed initially by Bell Labs in the US, PACS was designed to compete with DECT

Packet switchingA communication system wherein the information is transmitted in packets of a set size. These packets have address headers and find their way to their destination by the most efficient route through the network. Compared to circuit switching where a connection is occupied until the traffic exchange is completed, packet switching offers considerable efficiencies as connections can be used by a number of users simultaneously

PAMRPublic Access Mobile Radio; Commercial service using trunking techniques in which multiple groups of users can set up their own closed systems within a shared public network

PAPPublic Access Profile; a DECT term

PCHPaging Channel; downlink only, the MS is informed of incoming calls by the BTS via the PCH

PCMPulse Code Modulation; the standard digital voice format at 64kbit/s

PCMCIAPersonal Computer Memory Card Interface Association the body responsible for defining the standards and formats for memory expansion cards for laptop computers and PDAs. Now extended to cover cards for mobile phones

PCNPersonal Communications Network; a designation initially used in the UK to refer to networks operating in the 1800MHz band (see also DCS1800). No longer in use

PCS 1900Personal Communications Systems 1900MHz; the terminology used in the US to describe the

new digital networks being deployed in the 1900MHz band; rarely used today

PCUPacket Control Unit; an element in a GPRS/UMTS network

PDAPersonal Digital Assistant

PDCPersonal Digital Communications; a digital cellular technology developed and deployed uniquely in Japan. A TDMA technology, PDC is incompatible with any other digital cellular standard

PEDCPan European Digital Communications; A designation occasionally used in the early 1990.s to describe GSM. No longer in use

Penetration The percentage of the total population which owns a mobile phone

PHS / PHPPersonal HandyPhone System/Phone; a digital cordless technology developed in Japan which achieved great success. Deployed by NTT DoCoMo and other Japanese operators PHS offered two-way communications, data services and Internet access and eventually won some 28 million customers. Now in decline as cellular.s wide area capabilities offer better service

PINPersonal Identifier Number

PKIPublic Key Infrastructure

PLMNPublic Land Mobile Network; any cellular operator.s network

PMRPrivate Mobile Radiocommunications; two-way radio technology widely used for despatch and delivery services, taxi companies and the like. See TETRA

POCSAGPost Office Code Standardisation Group; a now defunct industry grouping which standardised pager addressing systems

PoPPoints of Presence; a method of measuring the value of a cellular licence; the approximate number of potential customers within a geographical area

POTSPlain Old Telephone Service

PROMProgrammable Read Only Memory

PSKPhase Shift Keying

PSRCPPublic Safety Radio Communications Project; an initiative by the UK Government to standardise all emergency services communications on to a single digital technology (see TETRA)

PSDNPublic Switched Data Network

PSPDNPublic Switched Packet Data Network

PSTNPublic Switched Telephone Network

PSUPower Supply Unit

PTOPublic Telecommunication Operator

PTTPosts, Telephone and Telegraph Administration

PTTPush-to-Talk; a feature of PMR systems

PWTPersonal Wireless Telecommunications; a variant of DECT developed for use in the USA

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QAMQuadrature Amplitude Modulation

QAPSKQuadrature Amplitude Phase Shift Keying

QCELPQuadrature Code Excited Linear Prediction

QoSQuality of Service; a broad term to describe the performance attributes of an end-to-end connection

QPSKQuadrature Phase Shift Keying

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RACEResearch in Advanced Communications in Europe

RACHRandom Access Channel; uplink only, allows the MS to request an SDCCH in response to a page or for a call

RAMRandom Access Memory

RFPRadio Fixed Part; equivalent to a base station in a DECT system

RCCRadio Common Carrier

RELPRegular pulse Excitation Linear Prediction coding

ReuseThe assignment of frequencies or channels to cells so that adjoining cells do not use the same frequencies and cause interference whereas more distant cells can use the same frequencies. Reuse expands the capacity of a cellular network by enabling the use of the same channels throughout the network

RP Radio Part

RNCRadio Network Controller; the element which controls the Node Bs within a UMTS network. It is roughly analogous to a BSC in a GSM network

RoamingA service unique to GSM which enables a subscriber to make and receive calls when outside the service area of his home network e.g. when travelling abroad

Router A device which forwards information in a network on a connectionless basis

RRMRadio Resource Management, part of the UMTS infrastructure

RTRemote Terminal

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SACCHSlow Associated Control Channel; transmits continuous measurements in parallel with operation of TCH or SDCCH; needed for handover decisions

SARSpecific Absorption Rate

SBSynchronisation Burst; used for time synchronisation of the mobile

S-CDMASynchronous CDMA (see CDMA)

SCHSynchronisation Channel; downlink only frame synchronisation and identification of base station

SCPSwitching/Service Control Point

SDCCHStand-alone Dedicated Control Channel; communications channel between the MS and the BTS. Used for signalling during call set-up before a TCH is allocated

SDLCSynchronous Data Link Control

SDMASpatial Division Multiple Access

SGSNServing GPRS Support Node; the gateway between the RNC and the core network in a GPRS/UMTS network

SIMSubscriber Identity Module; A smart card containing the telephone number of the subscriber, encoded network identification details, the PIN and other user data such as the phone book. A user.s SIM card can be moved from phone to phone as it contains all the key information required to activate the phone

SoHoSmall Office/Home Office

StreamingAn Internet derived expression for the one-way transmission of video and audio content

STKSIM ToolKit: specified within the GSM standard, this allows operators to add additional functions to the phone menu in order to provide new services such as mobile banking or email

SMRSpecialised Mobile Radio; the US term for private mobile radio (See PMR)

SMSShort Message Service; a text message service which enables users to send short messages (160 characters) to other users. A very popular service, particularly amongst young people, with 400 billion SMS messages sent worldwide in 2002

SMSCSMS Centre-the network entity which switches SMS traffic

SMSCBSMS Cell Broadcast

SMS-MOSMS Mobile Originated

SMS-MTSMS Mobile Terminated

SMS-PPSMS Point to Point

SPService Provider

SQAMStaggered Quadrature Amplitude Modulation

SQPSKStaggered Quadrature Phase Shift Keying

SSSupplementary Service Support; handles special services

SS7Signalling System Number 7 (See CCS7)

SSPService Switching Point

STMSynchronous Transfer Mode

SymbianA company created by Psion, Nokia, Ericsson and Motorola in 1998 with the aim of developing and standardising an operating system which enable mobile phones from different manufacturers to exchange informationThe operating system is known as EPOC. Matsushita has subsequently joined Symbian

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TACSTotal Access Communications System (an AMPS variant deployed in a number of countries principally the UK)

TAPTransferred Account Procedure; the essential charging methodology for international GSM

roaming. There have been four TAP standards, TAP1, TAP2, TAP2+ and TAP3. The latter offers variable record length and is sufficiently flexible to support all future requirements arising from the move to 3G

TBRTechnical Basis for Regulation (part of the ETSI standardisation process)

TCHTraffic Channel

TD-CDMATime Division CDMA

TD-SCDMATime Division-Synchronous CDMA; a CDMA variant developed by Chinese vendors which is claimed to offer high data rates and greater coverage

TDDTime Division Duplex; a radio technology for use in unpaired spectrum. WCDMA/UMTS includes a band for TDD mode usage and both PHS and DECT use this technology

TDMATime Division Multiple Access; a technique for multiplexing multiple users onto a single channel on a single carrier by splitting the carrier into time slots and allocating these on a as-needed basis

TelematicsA wireless communications system designed for the collection and dissemination of information, particularly refers to vehicle-based electronic systems, vehicle tracking and positioning, on-line vehicle navigation and information systems and emergency assistance

TETRATerrestrial Trunked Radio; a European developed digital private mobile radio technology which is now being extensively deployed worldwide

TetrapolA competitive digital PMR technology to TETRA developed by French vendors

TFTSTerrestrial Flight Telephone System

TimeslotA frame within a TDMA schema; has a time interval of 576 microseconds. Physical content of a timeslot is known as a burst. Five different burst types exist, they are distinguished by different TDMA frame divisions (see NB, FB, SB, AB and DB)

TIPHONTelecommunications and Internet Protocol Harmonisation over Networks; an ETSI project designed to support the market for voice communications and voice band communications. In particular TIPHON will ensure that users on IP-based networks can communicate with those on circuit switched networks

TMNTelecommunications Management Network

TMSITemporary Mobile Subscriber Identity; covers the IMSI to prevent over-the-air interception and tracing

TRAUTranscoder Rate Adapter Unit; the transport unit for a 16kbit/s traffic channel on the A-bis interface

Tri-bandRefers to a mobile phone able to operate on the three internationally designated GSM frequencies- 900, 1800 and 1900MHz

TrueSyncA technology which enables the optimal synchronisation of calendars, address books, action lists and memoranda. It enables multi-point, one-step synchronisation of wireless and wireline devices, desktop computers and server-based applications and services

TRXTransmitter/receiver (transceiver)

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UIUser Interface

UmThe air interface between the BTS and the MS in a GSM network

UuThe air interface between the Node B and the MS in a UMTS network.

UMTSUniversal Mobile Telecommunications System; the European entrant for 3G; now subsumed into the IMT-2000 family as the WCDMA technology.

UPNUniversal Personal Number

UPTUniversal Personal Telecommunications

URLUniform Resource Locator; the addressing system of the Internet

USOUniversal Service Obligation

UTRA

Universal Terrestrial Radio Access; the air interface component of WCDMA.

UTRANUniversal Terrestrial Radio Access Network; the UMTS radio access network comprising the RNC, Node B and the air interface

USIMUniversal Subscriber Identity Module; the 3G equivalent of the GSM SIM

UWBUltra Wide Band

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VASValue Added Services

VBRVariable Bit Rate

VHEVirtual Home Environment

VLRVisitor Location Register

VocoderVoice coder

VoIPVoice over Internet Protocol

VPNVirtual Private Network

VSATVery Small Aperture Terminal

VSELPVector Sum Excited Linear Prediction

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WAPWireless Application Protocol; a de facto standard for enabling mobile phones to access the Internet and advanced services. Users can access websites and pages which have been converted by the use of WML into stripped-down versions of the original more suitable for the limited display capabilities of mobile phones

WARC

World Administration Radio Conference; an ITU conference held at regular intervals to determine the allocation of spectrum for various services

WCDMA Wideband CDMA; the technology created from a fusion of proposals to act as the European entrant for the ITU IMT-2000 family

WLLWireless Local Loop; a technique for providing telephony and low speed data services to fixed customers using wireless. Regarded as having considerably potential for rapidly addressing the telecommunications gap in developing countries. A number of different WLL solutions have been marketed based on cellular and cordless technologies

WLANWireless Local Area Network; a short range radio network normally deployed in traffic hotspots such as airport lounges, hotels and restaurants. WLAN enables suitably equipped users to access the fixed network wirelessly, providing high speed access (up to 11Mbit/s download) to distant servers. The key WLAN technologies are the IEEE802.11 family and ETSI HIPERLAN/2

WMLWireless Markup Language; a markup language developed specifically for wireless applications. WML is based on XML

WQAMWeighted Quadrature Amplitude Modulation

WWWWorld Wide Web

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XMLeXtended Markup Language

The Consumer Mobile Glossary

Advice of chargeA service which provides the user with information on the cost of calls from a mobile phone

AirtimeThe amount of time a subscriber spends using his/her mobile phone

Battery status/Battery charge displayAn indication of the amount of battery life remaining

BatteryA chargeable device which provides the mobile phone with power. A variety of battery technologies have been used for mobile phones including nickel cadmium (NiCad), nickel metal hydride (NiMH) and lithium ion (Li-ion)

Call barring A service which enables users to bar certain incoming or outgoing calls on their mobile phones

Call timerA service which keeps track of the amount of airtime being used by the subscriber on a cumulative basis

Call divertThe capability to divert incoming calls to another phone (fixed or mobile) or to an answering service

Call holdThe ability to put an ongoing call on hold whilst answering or making a second call

Caller IDCaller Identification; displays the name/number of the person calling a mobile phone. Also known as CLI

CLISee Caller ID

CLRClear; the key on a cellular phone which is pressed to remove information from the display

Data capableMobile phones which have the capability to enable transmission of data from a laptop computer or PDA via the phone

Dual bandMobile phones which support transmission and reception of calls on the 900MHz and 1800MHz bands with seamless handover between the two frequency bands

EFREnhanced Full Rate (codec); an improved version of the standard voice codec used in GSM phones; offers improved speech quality without impacting on network capacity

ENDThe key on a cellular phone which is pressed to terminate a call

Infrared data portA facility on a mobile phone to allow information to be exchanged with other devices e.g. a PC using infra red technology

LockA function on a cellular phone which, when activated, prevents use of the phone until the user enters a security code

No ServiceAn indication on the display of a cellular phone that indicates that the user is in an area where cellular service is unavailable

One-touch dialling

The ability to dial frequently called numbers using a single key stroke; see Speed Dialling

PCNPersonal Communications Networks; an outdated term for GSM services in the 1800MHz band

PDAPersonal Digital Assistant; a sophisticated handheld device with advanced display facilities and a range of business-oriented software programs

Phone bookA list of personal names and numbers stored in a mobile phone.s internal memory or in the SIM card. These numbers can be called by accessing the appropriate memory and making a single key stroke

PINPersonal Identity Number; a number, usually four digits, that must be keyed into a mobile phone to make it work. A security measure to prevent unauthorised usage

RCLThe function on a cellular phone which recalls a phone number from memory

RoamingThe ability to make and receive calls on the same mobile phone when travelling outside the area of the home network operator

Smartphonea combination of mobile phone and personal digital assistant

SNDSend; The key on a cellular phone which initiates a call or answers an incoming call

Speed diallingSee One-touch dialling

Standby timeThe length of time a battery can power a mobile phone when it is switched on but not making or receiving calls

Talk-timeThe length of time a battery can power a mobile phone when making or receiving calls

VoicemailA service offered by network operators whereby calls received when the mobile is in use, switched off or out of coverage can be diverted to an answering service which can be personalised by the user

WAPWireless Application Protocol; a standard whereby mobile phones can gain access to specially tailored Internet websites

WML

Wireless Markup Language; a specially designed markup language used for tailoring WAP content. WML enables optimum usage of the limited display capabilities of the mobile phone 

GSM - Useful ResourcesIf you want to list down your website, book or any other resource on this page then please contact at webmaster@tutorialspoint.com

GSM World - Official Website of GSM Association. Find all the latest news, invetions and standards available at this site.

GSM @ Wikipedia - A very useful article on GSM technology and further more links to useful sites.

GSM Arena - A site providing comprehensive reviews, feedback and prices of all the available GSM Mobile Models in the market.

Introduction to GSM - A small article on GSM from Performance Technologies