Lets see what is thisssss....
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).
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.
Short Messaging Entities
Short messaging entity (SME) is an entity which may receive or send short messages. The 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.
SMS Gateway Mobile Switching Centre
The SMS–gateway mobile switching centre (SMS–GMSC) is an MSC capable of receiving a 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.
Home Location Register
The HLR is a database used for permanent storage and management of subscriptions and 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.
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 short 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.
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