Short Message Service Center

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;

1. Reception of text messages (SMS) from wireless network users
2.  Storage of text messages
3.  Forwarding of text messages
4.  Delivery of text messages (SMS) to wireless network users
5.  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.

1.  When an SMS message is sent from a mobile phone, it will reach an SMS center first. 
2. The SMS center then forwards the SMS message towards the destination.
3. 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.
4.  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.