SMS is a service that allows subscribers to send short messages (up to 160 characters) to other
mobile subscribers. Rather than having to set up a call on a traffic channel, SMS uses spare
capacity on the Standalone Dedicated Control Channel (SDCCH).
• Categorised under GSM as a Teleservice
• Text-based messaging
• Uses GSM signalling channels (SDCCH) .
• 160-character messages
• Uses store-and-forward packet switching protocol
• Three SMS Teleservice types defined:
• TS 21 – Mobile terminated point-to-point messaging
• TS 22 – Mobile originated point-to-point messaging
• TS 23 – Short Message cell broadcast (SMSCB)
SMS is classified as a GSM Teleservice and three SMS teleservices (TS21-23) have been
defined:
· TS 21 – Mobile terminated point-to-point messaging. A mobile can terminate an SMS
message either from another MS or from the fixed network.
· TS 22 – Mobile originated point-to-point messaging. A mobile can send a message
either to another MS or into the fixed network (as an Email for example).
· TS23 – SMS Cell Broadcast (SMSCB). A more recent variation of SMS is SMSCB.
SMSCB messages are generally broadcast only in a specific network region. An MS
cannot initiate such a message and does not acknowledge receipt of one. Only MSs in
idle mode can receive SMSCB messages. These messages differ from standard SMS
messages in that they are only 92 characters long. However, procedures exist to
concatenate up to 15 SMSCB messages using a special reassembly mechanism.
In order to implement SMS, a network operator must establish a SMS Service Centre which
receives and processes SMS messages in a store-and-forward mode. Messages can be initiated
in the fixed or mobile network and delivered to either the fixed or mobile network.
SME may be located in the fixed network, a mobile station, or another service centre.
Short Message Service Centre
Short message service centre (SMSC) is responsible for the relaying and store-and-forwarding
of a short message between an SME and mobile station.
short message from an SMSC, interrogating a home location register (HLR) for routing
information, and delivering the short message to the visited MSC of the recipient mobile
station. The SMS interworking MSC (SMS–IWMSC) is an MSC capable of receiving a short
message from the mobile network and submitting it to the appropriate SMSC. The SMS–
GMSC/SMS–IWMSC are typically integrated with the SMSC.
service profiles. Upon interrogation by the SMSC, the HLR provides the routing information
for the indicated subscriber. The HLR also informs 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.
Mobile Switching Centre
The MSC performs the switching functions of the system and controls calls to and from other
telephone and data systems.
The visitor location register (VLR) is a database that contains temporary information about
subscribers. This information is needed by the MSC to service visiting subscribers.
The Base Station System
All radio-related functions are performed in the base-station system (BSS). The BSS consists of
base-station controllers (BSCs) and the base-transceiver stations (BTSs), and its primary
responsibility is to transmit voice and data traffic between the mobile stations.
messages as well as voice calls. The wireless network signalling infrastructure is based on
signalling system 7 (SS7). SMS makes use of the mobile application part (MAP), which defines
the methods and mechanisms of communication in wireless networks, and uses the services
of the SS7 transaction capabilities application part (TCAP). An SMS service layer makes use of
the MAP signalling capabilities and enables the transfer of short messages between the peer
entities.
mobile subscribers. Rather than having to set up a call on a traffic channel, SMS uses spare
capacity on the Standalone Dedicated Control Channel (SDCCH).
Shorrtt Message Serrviice ((SMS))
• Categorised under GSM as a Teleservice
• Text-based messaging
• Uses GSM signalling channels (SDCCH) .
• 160-character messages
• Uses store-and-forward packet switching protocol
• Three SMS Teleservice types defined:
• TS 21 – Mobile terminated point-to-point messaging
• TS 22 – Mobile originated point-to-point messaging
• TS 23 – Short Message cell broadcast (SMSCB)
SMS is classified as a GSM Teleservice and three SMS teleservices (TS21-23) have been
defined:
· TS 21 – Mobile terminated point-to-point messaging. A mobile can terminate an SMS
message either from another MS or from the fixed network.
· TS 22 – Mobile originated point-to-point messaging. A mobile can send a message
either to another MS or into the fixed network (as an Email for example).
· TS23 – SMS Cell Broadcast (SMSCB). A more recent variation of SMS is SMSCB.
SMSCB messages are generally broadcast only in a specific network region. An MS
cannot initiate such a message and does not acknowledge receipt of one. Only MSs in
idle mode can receive SMSCB messages. These messages differ from standard SMS
messages in that they are only 92 characters long. However, procedures exist to
concatenate up to 15 SMSCB messages using a special reassembly mechanism.
In order to implement SMS, a network operator must establish a SMS Service Centre which
receives and processes SMS messages in a store-and-forward mode. Messages can be initiated
in the fixed or mobile network and delivered to either the fixed or mobile network.
SMS Architecture
Short Messaging Entities
Short messaging entity (SME) is an entity which may receive or send short messages. TheSME may be located in the fixed network, a mobile station, or another service centre.
Short Message Service Centre
Short message service centre (SMSC) is responsible for the relaying and store-and-forwarding
of a short message between an SME and mobile station.
SMS Gateway Mobile Switching Centre
The SMS–gateway mobile switching centre (SMS–GMSC) is an MSC capable of receiving ashort message from an SMSC, interrogating a home location register (HLR) for routing
information, and delivering the short message to the visited MSC of the recipient mobile
station. The SMS interworking MSC (SMS–IWMSC) is an MSC capable of receiving a short
message from the mobile network and submitting it to the appropriate SMSC. The SMS–
GMSC/SMS–IWMSC are typically integrated with the SMSC.
Home Location Register
The HLR is a database used for permanent storage and management of subscriptions andservice profiles. Upon interrogation by the SMSC, the HLR provides the routing information
for the indicated subscriber. The HLR also informs 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.
Mobile Switching Centre
The MSC performs the switching functions of the system and controls calls to and from other
telephone and data systems.
Visitor Location Register
The visitor location register (VLR) is a database that contains temporary information about
subscribers. This information is needed by the MSC to service visiting subscribers.
The Base Station System
All radio-related functions are performed in the base-station system (BSS). The BSS consists of
base-station controllers (BSCs) and the base-transceiver stations (BTSs), and its primary
responsibility is to transmit voice and data traffic between the mobile stations.
The Mobile Station
The mobile station (MS) is the wireless terminal capable of receiving and originating shortmessages as well as voice calls. The wireless network signalling infrastructure is based on
signalling system 7 (SS7). SMS makes use of the mobile application part (MAP), which defines
the methods and mechanisms of communication in wireless networks, and uses the services
of the SS7 transaction capabilities application part (TCAP). An SMS service layer makes use of
the MAP signalling capabilities and enables the transfer of short messages between the peer
entities.