Gsm Services
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GSM Services
INTRODUCTION
The primary objective of a mobile telephony system is to allow mobile subscribers to communicate effectively. GSM system provide this by offering a number of different basic telecommunication services. There are two main types of telecommunications services as Basic Services and Supplementary Services.
Introduction contd..,
Basi c servi ces: These are available to all subscribers to a mobile network. For example, the ability to make voice telephone calls is a basic service. Sup pl ement ary servi ces: These are additional services that are available by subscription only. Call forwarding is an example of a supplementary service. In addition, basic telecommunication services can be divided into two main categories as Teleservices and Bearer Services.
Basic Services
Teleservi ce s: A teleservice allows the subscriber to communicate (usually via voice, fax, data or SMS) with another subscriber. It is a complete system including necessary terminal equipment. Bearer s ervices: A bearer service transports speech and data as digital information within the network between user interfaces.
BEARER SERVICES
A bearer service is the capability to transfer information and does not include the enduser equipment. Every teleservice is associated with a bearer service. For example, a bearer service associated with the speech telephony teleservice is the timeslot assigned to a call on a TDMA frame over the air interface.
BEARER SERVICES contd..,
GSM systems offer a wide range of bearer services. Tra ffic to PST N for data traffic external to PLMN, either with another PLMN or directly to PSTN Tra ffic to ISDN Tra ffic to In ter net : traditionally, an MSC accessed Internet nodes via existing networks such as the PSTN. However, the direct access function enables an MSC to communicate directly with Internet nodes, thus reducing call set-up time.
TELESERVICES
The major teleservices supported by GSM are mentioned below: Spee ch: This is normal telephony (two-way voice communication) with the ability to make and receive calls to/from fixed and mobile subscribers worldwide. This is the most fundamental service offered. Emer ge ncy cal ls: The emergency call function enables a subscriber to make an emergency call by using the emergency number.
Teleservices contd..,
Dua l Tone Mu lt i Frequency ( DT MF) : This is a tone signaling facility which is often used for various control purposes, such as remote control of answering machines and interacting with automated telephone services. Shor t Messa ge Servi ces (SM S): This service allows simple text messages consisting of a maximum of 160 alphanumeric characters to be sent to or from an MS.
Teleservices contd..,
Voic e mail: This service is an answering machine within the network that is controlled by the subscriber. Calls can be forwarded to the subscriber’s voice mailbox.
SMS
Short Message Services Allows users to send up to 160 chars. Can be broadcasted Only one extra node the SMSC included in the basic GSM network
SMS contd..,
One SMS message can contain at most 140 bytes (1120 bits) of data, so one SMS message can contain up to:
160 characters if 7-bit character encoding is used. (7-bit character encoding is suitable for encoding Latin characters like English alphabets.) 70 characters if 16-bit Unicode UCS2 character encoding is used. (SMS text messages containing non-Latin characters like Chinese characters should use 16-bit character encoding.)
What is an SMS Center/SMSC?
An SMS center (SMSC) is responsible for handling the SMS operations of a wireless network. When an SMS message is sent from a mobile phone, it will reach an SMS center first. The SMS center then forwards the SMS message towards the destination. An SMS message may need to pass through more than one network entity (e.g. SMSC and SMS gateway) before reaching the destination.
SMSC cont..,
The main duty of an SMSC is to route SMS messages and regulate the process. If the recipient is unavailable (for example, when the mobile phone is switched off), the SMSC will store the SMS message. It will forward the SMS message when the recipient is available.
SMSC contd..,
Very often an SMSC is dedicated to handle the SMS traffic of one wireless network. A network operator usually manages its own SMSC(s) and locates them inside its wireless network system. However, it is possible for a network operator to use a third-party SMSC that is located outside the wireless network system. One must know the address of the wireless network operator's SMSC in order to use SMS messaging with your mobile phone.
SMSC contd..,
Typically an SMSC address is an ordinary phone number in the international format. A mobile phone should have a menu option that can be used to configure the SMSC address. Normally, the SMSC address is pre-set in the SIM card by the wireless network operator, which means you do not need to make any changes to it.
What is an SMS Gateway?
One problem of SMS messaging is that SMSCs developed by different companies use their own communication protocol and most of these protocols are proprietary. For example, Nokia has an SMSC protocol called CIMD whereas another SMSC vendor, CMG, has an SMSC protocol called EMI. It is not possible to connect two SMSCs if they do not support a common SMSC protocol.
SMS Gateway contd..,
To deal with this problem, an SMS gateway is placed between two SMSCs. The SMS gateway acts as a relay between the two SMSCs. It translates one SMSC protocol to another one. This way can be used by two different wireless carriers to interconnect their SMSCs for purposes such as enabling the exchange of inter-operator SMS messages.
Signaling Elements
An SMS service layer makes use of the MAP signaling capabilities and enables the transfer of short messages between the peer entities. Both American and international standards bodies have defined a MAP layer using the services of the signaling system No. 7 transaction capabilities part. The American standard is published by Telecommunication Industry Association and is referred to as IS-41. The international standard is defined by the European Telecommunication Standards Institute and is referred to as GSM MAP.
MAP operations contd..,
The following basic MAP operations are necessary to provide the end-to-end short message service: Ro uting in forma tio n requ es t: Before attempting short message delivery, the SMSC needs to retrieve routing information in order to determine the serving MSC for the mobile station at the time of the delivery attempt. This is accomplished by way of an interrogation of the HLR which is accomplished via the use of the SMS request and send RoutingInfoForShortMsg mechanisms in IS41 and GSM respectively.
MAP operations contd..,
Point -t o-poi nt shor t messa ge deli very: The mechanism provides a means for the SMSC to transfer a short message to the MSC which is serving the addressed mobile station and attempts to deliver a message to an MS whenever the MS is registered, even when the MS is engaged in a voice or data call. The short message delivery operation provides a confirmed delivery service.
Shor t messa ge wa iti ng indi cation: The operation is activated when a short message delivery attempt by the SMSC fails due to a temporary failure and provides a means for the SMSC to request the HLR to add an SMSC address to the list of SMSCs to be informed when the indicated mobile station becomes accessible.
Se rvic e cent er alert : The operation provides a means for the HLR to inform the SMSC which has previously initiated unsuccessful short message delivery attempts to a specific mobile station, that the mobile station is now recognized by the mobile network to be accessible.
Subscriber Services
SMS comprises two basic point-to-point services:
Mobile-originated short message (MO-SM) Mobile-terminated short message (MT-SM)
Mobile-originated short messages are transported from the handset to the SMSC and can be destined to other mobile subscribers. Mobile-terminated short messages are transported from the SMSC to the handset
Subscriber Services contd..,
For MT-SM, a report is always returned to the SMSC either confirming the short message delivery to the handset or informing the SMSC of the short message delivery failure and identifying the reason for failure. Similarly, for MO-SM, a report is always returned to the handset either confirming the short message delivery to the SMSC or informing the handset of the encountered failure identifying the reason.
Services contd..,
For messages requiring immediate delivery, only one message delivery attempt is made per service request. For messages not requiring immediate delivery, one or more delivery attempts are made until an acknowledgment is received.
Mobile-Terminated Short Message Example
MT-SM contd.., 1. The short message is submitted from the SME to the SMSC. 2. After completing its internal processing, the SMSC interrogates the HLR and receives the routing information for the mobile subscriber. 3. The SMSC sends the short message to the MSC using the forward Short Message operation.
MT-SM contd.., 4. The MSC retrieves the subscriber information from the VLR. This operation may include an authentication procedure. 5. The MSC transfers the short message to the MS. 6. The MSC returns to the SMSC the outcome of the forwardShortMessage operation. 7. If requested by the SME, the SMSC returns a status report indicating delivery of the short message.
Mobile-Originated Short Message Example
MO-SM contd..,
1. The MS transfers the SM to the MSC. 2. The MSC interrogates the VLR to verify that the message transfer does not violate the supplementary services invoked or the restrictions imposed. 3. The MSC sends the short message to the SMSC using the forwardShortMessage operation.
MO-SM contd..,
4. The SMSC delivers the short message to the SME. 5. The SMSC acknowledges to the MSC the successful outcome of the forwardShortMessage operation. 6. The MSC returns to the MS the outcome of the MO-SM operation.
SUPPLEMENTARY SERVICES
This section describes the main supplementary services supported by GSM system. Ca ll forwa rd ing : This service provides the subscriber with the ability to forward incoming calls to another telephone number in the following situations: Call forwarding on MS not reachable Call forwarding on MS busy Call forwarding on no reply Call forwarding, unconditional
Supplementary Services contd..,
Barr ing of out goi ng calls : The subscriber can activate or deactivate this service from the MS with a variety of options for barring outgoing calls. For example, the subscriber can: Bar all outgoing calls Bar all outgoing international calls
Supplementary Services contd..,
Bar rin g of incomin g calls: With this function, the subscriber can prevent incoming calls. There are two incoming call barring options: Barring of all incoming calls Barring of incoming calls when outside home PLMN Ca ll wai tin g: This service notifies the mobile subscriber, usually by an audible tone, for incoming call. The call can then be answered, rejected or ignored.
Supplementary Services contd..,
The incoming call can be any type of basic service including speech or data . Ca ll hold : This supplementary service enables the subscriber to put the basic normal telephony service on hold in order to set up a new call or accept a waiting call. Communication with the original call can then be re-established.
Supplementary Services contd..,
Ca lli ng line id enti fi cation servi ce s: These supplementary services cover both the presentation and restriction of the calling line identity. The presentation part of the service supplies the called party with the MSISDN number of the calling party. The restriction service enables calling parties to restrict the presentation of their numbers on the MSs of called parties.
Supplementary Services contd..,
Cl osed Us er Gr oup (CU G): The CUG service enables subscribers connected to the PLMN to form groups. In a CUG subscribers can communicate with each other at low tariff. Mu lt ip ar ty s ervice : The multiparty service enables a mobile subscriber to establish a multiparty conversation, that is, a simultaneous conversation between up to six subscribers.
Data Services
HSCSD (High Speed Circuit Switched Data) GPRS (General Packet Radio Services) EDGE (Enhanced Data Rates for GSM Evolution)
HSCSD
Data Rate per one TS – 9.6 Kbps Cannot be used for bursty applications such as email browsing Can combine 4 TS and give to one subscriber.
GPRS
Data Rate 115-176 kbps Can be used for browsing internet, emails etc Can serve as a node for PCs, laptops, palmtops for providing internet Occupies more than one timeslot Does not need to follow the same time slot
GSM PHASES
In the late 1980s, the groups involved in developing the GSM standard realized that within the given time-frame they could not complete the specifications for the entire range of GSM services and features as originally planned. Because of this, it was decided that GSM would be released in phases with phase 1 consisting of a limited set of services and features.
Each new phase builds on the services offered by existing phases. Ph as e 1 Phase 1 contains the most common services including: Voice telephony International roaming Basic fax/data services (up to 9.6 kbits/s) Call forwarding Call barring Short Message Service (SMS)
Phase 1 also incorporated features such as ciphering and Subscriber Identity Module (SIM) cards. Phase 1 specifications were then closed and cannot be modified.
Phase 2
Additional features were introduced in GSM phase 2 including: Calling line identification Call waiting Call hold Conference calling Closed user groups
Phase 2+
The phase 2+ program will provide more enhancements and a variety of business oriented features. Some enhancements are quality equal to fixed network circuit switched data < 76.8 kbps efficient administration (routing, packet data) Introduction of GPRS
INTRODUCTION
The primary objective of a mobile telephony system is to allow mobile subscribers to communicate effectively. GSM system provide this by offering a number of different basic telecommunication services. There are two main types of telecommunications services as Basic Services and Supplementary Services.
Introduction contd..,
Basi c servi ces: These are available to all subscribers to a mobile network. For example, the ability to make voice telephone calls is a basic service. Sup pl ement ary servi ces: These are additional services that are available by subscription only. Call forwarding is an example of a supplementary service. In addition, basic telecommunication services can be divided into two main categories as Teleservices and Bearer Services.
Basic Services
Teleservi ce s: A teleservice allows the subscriber to communicate (usually via voice, fax, data or SMS) with another subscriber. It is a complete system including necessary terminal equipment. Bearer s ervices: A bearer service transports speech and data as digital information within the network between user interfaces.
BEARER SERVICES
A bearer service is the capability to transfer information and does not include the enduser equipment. Every teleservice is associated with a bearer service. For example, a bearer service associated with the speech telephony teleservice is the timeslot assigned to a call on a TDMA frame over the air interface.
BEARER SERVICES contd..,
GSM systems offer a wide range of bearer services. Tra ffic to PST N for data traffic external to PLMN, either with another PLMN or directly to PSTN Tra ffic to ISDN Tra ffic to In ter net : traditionally, an MSC accessed Internet nodes via existing networks such as the PSTN. However, the direct access function enables an MSC to communicate directly with Internet nodes, thus reducing call set-up time.
TELESERVICES
The major teleservices supported by GSM are mentioned below: Spee ch: This is normal telephony (two-way voice communication) with the ability to make and receive calls to/from fixed and mobile subscribers worldwide. This is the most fundamental service offered. Emer ge ncy cal ls: The emergency call function enables a subscriber to make an emergency call by using the emergency number.
Teleservices contd..,
Dua l Tone Mu lt i Frequency ( DT MF) : This is a tone signaling facility which is often used for various control purposes, such as remote control of answering machines and interacting with automated telephone services. Shor t Messa ge Servi ces (SM S): This service allows simple text messages consisting of a maximum of 160 alphanumeric characters to be sent to or from an MS.
Teleservices contd..,
Voic e mail: This service is an answering machine within the network that is controlled by the subscriber. Calls can be forwarded to the subscriber’s voice mailbox.
SMS
Short Message Services Allows users to send up to 160 chars. Can be broadcasted Only one extra node the SMSC included in the basic GSM network
SMS contd..,
One SMS message can contain at most 140 bytes (1120 bits) of data, so one SMS message can contain up to:
160 characters if 7-bit character encoding is used. (7-bit character encoding is suitable for encoding Latin characters like English alphabets.) 70 characters if 16-bit Unicode UCS2 character encoding is used. (SMS text messages containing non-Latin characters like Chinese characters should use 16-bit character encoding.)
What is an SMS Center/SMSC?
An SMS center (SMSC) is responsible for handling the SMS operations of a wireless network. When an SMS message is sent from a mobile phone, it will reach an SMS center first. The SMS center then forwards the SMS message towards the destination. An SMS message may need to pass through more than one network entity (e.g. SMSC and SMS gateway) before reaching the destination.
SMSC cont..,
The main duty of an SMSC is to route SMS messages and regulate the process. If the recipient is unavailable (for example, when the mobile phone is switched off), the SMSC will store the SMS message. It will forward the SMS message when the recipient is available.
SMSC contd..,
Very often an SMSC is dedicated to handle the SMS traffic of one wireless network. A network operator usually manages its own SMSC(s) and locates them inside its wireless network system. However, it is possible for a network operator to use a third-party SMSC that is located outside the wireless network system. One must know the address of the wireless network operator's SMSC in order to use SMS messaging with your mobile phone.
SMSC contd..,
Typically an SMSC address is an ordinary phone number in the international format. A mobile phone should have a menu option that can be used to configure the SMSC address. Normally, the SMSC address is pre-set in the SIM card by the wireless network operator, which means you do not need to make any changes to it.
What is an SMS Gateway?
One problem of SMS messaging is that SMSCs developed by different companies use their own communication protocol and most of these protocols are proprietary. For example, Nokia has an SMSC protocol called CIMD whereas another SMSC vendor, CMG, has an SMSC protocol called EMI. It is not possible to connect two SMSCs if they do not support a common SMSC protocol.
SMS Gateway contd..,
To deal with this problem, an SMS gateway is placed between two SMSCs. The SMS gateway acts as a relay between the two SMSCs. It translates one SMSC protocol to another one. This way can be used by two different wireless carriers to interconnect their SMSCs for purposes such as enabling the exchange of inter-operator SMS messages.
Signaling Elements
An SMS service layer makes use of the MAP signaling capabilities and enables the transfer of short messages between the peer entities. Both American and international standards bodies have defined a MAP layer using the services of the signaling system No. 7 transaction capabilities part. The American standard is published by Telecommunication Industry Association and is referred to as IS-41. The international standard is defined by the European Telecommunication Standards Institute and is referred to as GSM MAP.
MAP operations contd..,
The following basic MAP operations are necessary to provide the end-to-end short message service: Ro uting in forma tio n requ es t: Before attempting short message delivery, the SMSC needs to retrieve routing information in order to determine the serving MSC for the mobile station at the time of the delivery attempt. This is accomplished by way of an interrogation of the HLR which is accomplished via the use of the SMS request and send RoutingInfoForShortMsg mechanisms in IS41 and GSM respectively.
MAP operations contd..,
Point -t o-poi nt shor t messa ge deli very: The mechanism provides a means for the SMSC to transfer a short message to the MSC which is serving the addressed mobile station and attempts to deliver a message to an MS whenever the MS is registered, even when the MS is engaged in a voice or data call. The short message delivery operation provides a confirmed delivery service.
Shor t messa ge wa iti ng indi cation: The operation is activated when a short message delivery attempt by the SMSC fails due to a temporary failure and provides a means for the SMSC to request the HLR to add an SMSC address to the list of SMSCs to be informed when the indicated mobile station becomes accessible.
Se rvic e cent er alert : The operation provides a means for the HLR to inform the SMSC which has previously initiated unsuccessful short message delivery attempts to a specific mobile station, that the mobile station is now recognized by the mobile network to be accessible.
Subscriber Services
SMS comprises two basic point-to-point services:
Mobile-originated short message (MO-SM) Mobile-terminated short message (MT-SM)
Mobile-originated short messages are transported from the handset to the SMSC and can be destined to other mobile subscribers. Mobile-terminated short messages are transported from the SMSC to the handset
Subscriber Services contd..,
For MT-SM, a report is always returned to the SMSC either confirming the short message delivery to the handset or informing the SMSC of the short message delivery failure and identifying the reason for failure. Similarly, for MO-SM, a report is always returned to the handset either confirming the short message delivery to the SMSC or informing the handset of the encountered failure identifying the reason.
Services contd..,
For messages requiring immediate delivery, only one message delivery attempt is made per service request. For messages not requiring immediate delivery, one or more delivery attempts are made until an acknowledgment is received.
Mobile-Terminated Short Message Example
MT-SM contd.., 1. The short message is submitted from the SME to the SMSC. 2. After completing its internal processing, the SMSC interrogates the HLR and receives the routing information for the mobile subscriber. 3. The SMSC sends the short message to the MSC using the forward Short Message operation.
MT-SM contd.., 4. The MSC retrieves the subscriber information from the VLR. This operation may include an authentication procedure. 5. The MSC transfers the short message to the MS. 6. The MSC returns to the SMSC the outcome of the forwardShortMessage operation. 7. If requested by the SME, the SMSC returns a status report indicating delivery of the short message.
Mobile-Originated Short Message Example
MO-SM contd..,
1. The MS transfers the SM to the MSC. 2. The MSC interrogates the VLR to verify that the message transfer does not violate the supplementary services invoked or the restrictions imposed. 3. The MSC sends the short message to the SMSC using the forwardShortMessage operation.
MO-SM contd..,
4. The SMSC delivers the short message to the SME. 5. The SMSC acknowledges to the MSC the successful outcome of the forwardShortMessage operation. 6. The MSC returns to the MS the outcome of the MO-SM operation.
SUPPLEMENTARY SERVICES
This section describes the main supplementary services supported by GSM system. Ca ll forwa rd ing : This service provides the subscriber with the ability to forward incoming calls to another telephone number in the following situations: Call forwarding on MS not reachable Call forwarding on MS busy Call forwarding on no reply Call forwarding, unconditional
Supplementary Services contd..,
Barr ing of out goi ng calls : The subscriber can activate or deactivate this service from the MS with a variety of options for barring outgoing calls. For example, the subscriber can: Bar all outgoing calls Bar all outgoing international calls
Supplementary Services contd..,
Bar rin g of incomin g calls: With this function, the subscriber can prevent incoming calls. There are two incoming call barring options: Barring of all incoming calls Barring of incoming calls when outside home PLMN Ca ll wai tin g: This service notifies the mobile subscriber, usually by an audible tone, for incoming call. The call can then be answered, rejected or ignored.
Supplementary Services contd..,
The incoming call can be any type of basic service including speech or data . Ca ll hold : This supplementary service enables the subscriber to put the basic normal telephony service on hold in order to set up a new call or accept a waiting call. Communication with the original call can then be re-established.
Supplementary Services contd..,
Ca lli ng line id enti fi cation servi ce s: These supplementary services cover both the presentation and restriction of the calling line identity. The presentation part of the service supplies the called party with the MSISDN number of the calling party. The restriction service enables calling parties to restrict the presentation of their numbers on the MSs of called parties.
Supplementary Services contd..,
Cl osed Us er Gr oup (CU G): The CUG service enables subscribers connected to the PLMN to form groups. In a CUG subscribers can communicate with each other at low tariff. Mu lt ip ar ty s ervice : The multiparty service enables a mobile subscriber to establish a multiparty conversation, that is, a simultaneous conversation between up to six subscribers.
Data Services
HSCSD (High Speed Circuit Switched Data) GPRS (General Packet Radio Services) EDGE (Enhanced Data Rates for GSM Evolution)
HSCSD
Data Rate per one TS – 9.6 Kbps Cannot be used for bursty applications such as email browsing Can combine 4 TS and give to one subscriber.
GPRS
Data Rate 115-176 kbps Can be used for browsing internet, emails etc Can serve as a node for PCs, laptops, palmtops for providing internet Occupies more than one timeslot Does not need to follow the same time slot
GSM PHASES
In the late 1980s, the groups involved in developing the GSM standard realized that within the given time-frame they could not complete the specifications for the entire range of GSM services and features as originally planned. Because of this, it was decided that GSM would be released in phases with phase 1 consisting of a limited set of services and features.
Each new phase builds on the services offered by existing phases. Ph as e 1 Phase 1 contains the most common services including: Voice telephony International roaming Basic fax/data services (up to 9.6 kbits/s) Call forwarding Call barring Short Message Service (SMS)
Phase 1 also incorporated features such as ciphering and Subscriber Identity Module (SIM) cards. Phase 1 specifications were then closed and cannot be modified.
Phase 2
Additional features were introduced in GSM phase 2 including: Calling line identification Call waiting Call hold Conference calling Closed user groups
Phase 2+
The phase 2+ program will provide more enhancements and a variety of business oriented features. Some enhancements are quality equal to fixed network circuit switched data < 76.8 kbps efficient administration (routing, packet data) Introduction of GPRS
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