GSM module 2

7/28/2019 GSM module 2

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GSM Basics, Version 2.2 T.O.P. BusinessInteractive GmbH Page 1 of 15

2 GSM Services




2 GSM Services.........................................................................1 2.1 Classification (1/2)..............................................................3 2.1 Classification (2/2)..............................................................4 2.2 Bearer Services ..................................................................5 2.3 Teleservices ........................................................................6 2.4 Supplementary Services....................................................7 2.4.1 Line Identification Services............................................8 2.4.2 Call Offering Services .....................................................9 2.4.3 Call Completion Services .............................................10 2.4.4 Multi Party Supplementary Services ...........................11 2.4.5 Closed User Groups (CUG) ..........................................12 2.4.6 Advice of Charge ...........................................................13 2.4.7 Call Restriction Services ..............................................14 2.5 Value Added Services......................................................15




2.1 Classification (1/2)

The GSM services subdivide into the Bearer Services and the Teleservices. These baseservices are supplemented by the Supplementary Services. In addition, we have the Value Added Services.The Bearer Services are telecommunication services that guarantee the transmission of signals between access points in telecommunication networks. They are used exclusively for transport and define the services a network can offer, for example data transmissionbetween a corporate network and a mobile notebook, or data download from the web.The Teleservices are telecommunication services as well as functions that enablecommunication between users, and are based on protocols agreed on by the networkoperators. Teleservices affect the final link in the communication process - the end user.They include telephone services, emergency calls, the Short Message Service, E-mail andfax.




2.1 Classification (2/2)

Supplementary Services modify or add to the basic telecommunication services. They are

only offered in combination with a Bearer Service or a Teleservice. The same SupplementaryService can be applied to a range of Telecommunication Services. Most of these serviceshave been inherited directly from fixed networks, with some concessions as regards their adjustment to the mobile radio network. Supplementary Services include e.g. lineidentification and call forwarding. Value-Added Services depend on the service provider or network operator they are supplied by. They are not predefined in specifications, and includee.g. reservation or information services.Let's have a closer look at the services.




2.2 Bearer Services

GSM specifies a huge variety of Bearer Services for data transmission. Bit rates between300 and 9,600bps can be chosen according to data terminal equipment and the interferencesituation of the air interface. With HSCSD, the data rate may increase to 57.6 kbps. All Bearer Services are handled as circuit-switched services between the mobile dataequipment and the NSS requiring a permanent link between the involved components. A converter, called Packet Assembler-Disassembler or PAD, is used to adapt these signalsto the packet-switched mode in public data networks, e.g. the Internet. With GPRS, a totalpacket-switched transmission is provided between all data terminal equipment at a maximumbit rate of 171.2 kbps.




2.3 Teleservices

Teleservices provide voice and non-voice services. Voice services include normal speechtelephony and emergency calls. Non-voice services include the Short Message Service, for example, that is the sending, receipt and broadcast of short messages.Short messages can be received at any time, even during a call, and are transmitted over signalling channels. Whereas normal short messages are stored temporarily in the ShortMessage Service Center SMSC, with Cell Broadcast they are stored in the Base StationController BSC.The fax services, also referred to as Group 3 facsimile, provide automatic fax servicebetween a mobile fax and a fax machine within a PSTN, or between 2 mobile fax terminals,each with its own MSISDN at a maximum speed of 9.6 kbps.






2.4.1 Line Identification Services

The Line Identification Services include the Calling Line Identification Presentation (CLIP),

that is the display of the caller's number on the called party's mobile station. The networktransmits the call number at call set-up, provided that both parties are ISDN or GSMcustomers.Using Calling Line Identification Restriction (CLIR), the calling party can restrict its callnumber, so it cannot be identified by the called party. An appropriate instruction is sent fromthe caller's network to the network of the recipient. Some networks allow particular user groups, such as the police, to identify a call number even if the CLIR service is activated.In accordance with CLIP and CLIR, there is the Connected Line Identification Presentation,COLP, for identification of the called party by the caller, and Connected Line IdentificationRestriction, COLR, if the called party does not want to be identified by the caller. COLP andCOLR come into play when the called party has diverted its number to another number.




2.4.2 Call Offering Services

Call Offering Services are services which allow a customer to forward incoming calls to other

target numbers.Call Forwarding Unconditional CFU ensures that all incoming calls are diverted to a number specified by the customer, independent of the conditions of the call.Call Forwarding on mobile Subscriber Busy CFB diverts calls only if the called subscriber ismaking a call and the line is busy. Calls can also be diverted if the called party can't bereached - because it currently has no network access, because the phone is switched off, or because the call is not accepted.Supported by the Optimal Routing Service SOR - a GSM Phase 2+ feature - calls are routeddirectly to the subscriber's current location. This service is based on the information providedby the called subscriber's home network. As an option, the network may permit or deny SORon a per call basis. SOR has not yet been implemented.




2.4.3 Call Completion Services

Call Completion Services allow the customer to postpone incoming calls which he is currently

not able to accept, as well as to hold calls while simultaneously making another call.Call Waiting CW notifies the customer of an incoming call when no traffic channel isavailable, and the customer is engaged in an active or held call. The customer now has fromhalf a minute to two minutes time to decide whether to accept, reject or ignore the postponedcall.The Call Holding Service HOLD permits the customer to interrupt communication on theactive call for another call, without losing the connection to the first call. This is because thetraffic channel remains assigned to the customer even after interruption of the active call, sohe can resume the communication.




2.4.4 Multi Party Supplementary Services

Multi Party Services, also called conferencing services, allow the customer to communicate

with more than one party simultaneously. The Multi Party Service can be initiated if acustomer is in control of at least one active call and one call on hold. After it has beeninitiated, parties can be added, disconnected or separated. Thus the subscriber initiating theservice can add more parties to the Multi Party Call and exclude others from conversation. Atthe same time, he can have a private conversation with another party, which the other participants cannot hear. During all this, the participants of the Multi Party Call can stillcommunicate with each other.




2.4.5 Closed User Groups (CUG)

Closed User Group (CUG) gives a particular group of customers the opportunity tocommunicate with each other in PLMN or ISDN networks. The members of a Closed User Group can't communicate with subscribers outside the group. If desired, one or moresubscribers in this group can be authorised to call subscribers outside, or to receive callsfrom them.Emergency calls are not subject to the restrictions of this service.




2.4.6 Advice of Charge

The service Advice of Charge (AOC) is a supplementary service that allows a mobilesubscriber who uses services to receive service-related billing details.With Reverse Charging, on the other hand, a called subscriber can be charged for certaincalls. For this purpose, each individual call is analyzed and evaluated. Reverse Charging isactivated at request by the calling subscriber, and must be permitted by the calledsubscriber. At present, Reverse Charging is not implemented in GSM networks.




2.4.7 Call Restriction Services

There are basically two categories of Call Restriction Services: one refers to outgoing calls,and the other to incoming calls. The service offers several possibilities, such as:

• Barring all outgoing and incoming calls• Barring all outgoing international calls

or

• Barring all incoming calls except those coming from the country of the home network.

The calls can be barred manually by the subscriber, or by network configuration.




2.5 Value Added Services

Value Added Services are supplied by the respective Service Provider or network operator,and can be transmitted either via a normal telephone call or via SMS. These services offer the supplier a further opportunity - apart from price - to attract customers.

• Value Added Services are, for example:• Information on cultural events or traffic announcements via Cell Broadcast• Reservation of a hotel, a flight or a hire car • Help in the event of a car breakdown• Information services• Medical advice• Ticket reservation• Sports news

Delivery services, like sending flowers to a particular person and many more.

GSM module 2

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