Short
Message Service Center also known as SMSC is a network element in the mobile
telephone network. Its purpose is to store, forward, convert and deliver SMS
messages.
All
messages are sent to the SMSC. The SMSC stores the messages, extracts the
destination from it and tries to deliver the message. If the message cannot be
delivered, the SMSC will try again to deliver the message in a so-called
retry-schedule. If the mobile phone is turned on or comes within reach of the
network, the SMSC will also retry to deliver the message. If a mobile telephone
received a message, it will send an acknowledgement back. Usually the message
will be discarded after two days if the destination can not be reached.
The
tasks of an SMSC can be described as;
- Reception of text messages (SMS) from wireless network users
- Storage of text messages
- Forwarding of text messages
- Delivery of text messages (SMS) to wireless network users
- Maintenance of unique time stamps in text messages
When
a user sends a SMS message to another user, the message gets stored in the SMSC,
which delivers it to the destination user when they are available. This is a
store and forward option.
Store
and forward switching centers are usually implemented in mobile service
stations where the messages that are sent from the sender are first sent to
these centers. If the destination address is not available then the center
stores this message and tries sending it later. This improves the probability
of the message to be delivered. In the other case, if the destination is
available at that time, then the message is immediately sent.
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.
- 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 or when the message's expiry period is exceeded.
An SMS message is stored temporarily in the SMS center if the
recipient mobile phone is unavailable. It is possible on most mobile handset to
specify an expiry period after which the SMS message will be deleted from the
SMS center. Once deleted, the SMS message will no longer be available for
dispatch to the recipient mobile phone (even if it becomes online). The
validity period should be regarded by the handset user as a request, as the
SMSC itself can be configured to ignore or otherwise handle message delivery
schedules.
The SMS sender needs to set a flag in the SMS message to
notify the SMS center that he wants the status report about the delivery of
this SMS message. This status report is sent to the SMS sender in the form of
an SMS.
