Keeping in Touch!
How SMS Works
Q.1 What is SMS?
Ans. Short message service (SMS) is a globally accepted
wireless service that enables the transmission of alphanumeric messages between
mobile subscribers and external systems such as electronic mail, paging and
voice mail systems.
- Top -
Q.2 What are the benefits of SMS?
Ans. SMS provides a powerful vehicle for service
differentiation. The benefits of SMS to the service provider are:
- Increased call completion on wireless and wire-line networks by leveraging the notification capabilities of SMS.
- An alternative to alphanumeric paging services
- Enabling wireless data access to corporate users
- Provision of value added services as email, voicemail, and fax mail integration, reminder service, stock and currency quotes, and airline schedules
- Provision of key administrative services such as advice of charge, over the air downloading and service provisioning
- Top -
Q. 3 What are the Elements of the SMS Architecture?
SMS Architecture
The above figure shows the basic network structure of the SMS. It consists of
the following:
- 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 center
- Short Message Service Center: SMSC is responsible for the relaying, storing and forwarding of a short message between an SME and mobile station.
- SMS-Gateway MSC: 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.
- Home Location Register: 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.
- Mobile Switching Center: The mobile switching center (MSC) performs the switching functions of the system and controls calls to and from other telephone and data systems
- Visitor Location Register: (VLR) is a database that contains temporary information about subscribers. This information is needed by the MSC in order to service visiting subscribers
- Top -
Q.4 What is the Short Message Service Center?
Ans. See SMS Architecture
- Top -
Q.5 What are the basic MAP operations necessary to
provide end-to-end Short Message Service?
Ans. The following basic MAP operations are necessary to
provide end to end short message service:
- Routing Information Request: The SMSC needs to retrieve routing information from the HLR, in order to determine the serving MSC for the addressed mobile station. This process is carried out before delivering the message.
- Point to Point Short Message Delivery: The mechanism provides a means for the SMSC to transfer a short message to the MSC, which is serving the addressed mobile station.
- Short message waiting indication: This operation is activated when a short message delivery attempt by the SMSC fails due to a temporary failure. This provides a means for the SMSC to request the HLR to add an SMSC address to the list of SMSC s to be informed when the indicated mobile station becomes accessible.
- Service Center 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.
- Top -
Q.6 What Service Elements, does the SMS comprise of?
Ans. The SMS comprises several service elements relevant to
the reception and submission of short messages:
- Validity Period: The validity period indicates how long the SMSC shall guarantee the storage of the short message before delivery to the intended recipient
- Priority: Priority is the information element provided by an SME to indicate the priority message
In addition, SMS provides a time stamp reporting the time of submission of
the message and an indication to the handset of whether or not there are more
messages to send (GSM) or the number of additional messages to send (IS41)
- Top -
Q.7 How is the message status notified to the SMSC?
Ans. The SMSC is notified of the message status through MAP
operations. Go to Basic Map Operations.
- Top -
Q.8 What Potential Applications can be envisaged, using the
SMS?
Ans. Some of the potential applications of SMS technology,
utilizing the Mobile Terminated and Mobile Originated SMS are:
- Notification Services
- E-mail Interworking
- Paging Interworking
- Information Services
- Top -
Q.9 What are the various steps involved in a
"Successful short message transfer attempt"?
Ans. The following steps are involved in a Successful short
message transfer attempt: the short message is submitted from the SME to the SMSC.
After completing its internal processing, the SMSC interrogates the HLR and receives the routing information for the mobile subscriber.
The SMSC sends the short message to the MSC using the Forward Short message operation.
The MSC retrieves the subscriber information from the VLR. This operation may include an authentication procedure.
The MSC transfers the short message to the MS. The MSC returns to the SMSC the outcome of the Forward Short message operation.
If requested by the SME, the SMSC returns a status report indicating delivery of the short message.
