SMS is Wireless Data
When a mobile phone user sends a message using the short message service (SMS) feature, the initial process is very similar to other uses of the mobile handset. The mobile phone user enters text on the phone's keyboard, and the phone's operating system interprets the input to create meaningful text messages. Software built into the phone translates the text input into small packets of data suitable for transmission over radio waves, encodes the data using the mobile carrier's proprietary encoding method and sends the message to a nearby cellular phone tower.
Messages Pass Through the SMSC
When a user sends a text message from a mobile phone, a nearby cellular tower receives the message, converts it from radio waves to electronic data and transfers it to a Short Message Service Center (SMSC). Most cell stations are not capable of processing an SMS message themselves; instead, they must forward the message to another device charged with the responsibility of routing the message. The SMSC, built into the operation of the cell station itself, serves the purpose of accepting the message and forwarding it on for processing.
SMSC Forwards Messages to the GMSC
When a cell site based Short Message Service Center forwards a message for processing, the entity where the message is forwarded is known as a Gateway Message Service Center, or GMSC. The GMSC operates at a higher hierarchical level than the SMSC, and generally serves as a contact point for transferring messages from one carrier's network to another. The GMSC uses a number of mobile network-based applications and databases to route the SMS message to its proper destination. Using information contained in the Signaling System Seven (SS7) headers of the message, the GMSC queries a proprietary database to determine which carrier and which region should receive the SMS message for processing. If the message must be routed to another carrier's network, the GMSC contacts that carrier's network equipment and forwards the message. If the message is destined for another subscriber on the GMSC's own network, the device determines which cell site should receive the message and forwards it accordingly.
Cell Site SMSCs Deliver Messages to Recipients
When the SMS message arrives at a cell site after being forwarded by the GMSC, it is first processed by the site's Short Message Service Center. If the SMSC determines that the destination device is available, it encodes the message into a radio transmission format, applies the proprietary headers that ensure the message is delivered to the correct subscriber and forwards the message for transmission by the cell tower. If the subscriber is not available, the SMSC stores the message for delivery when the subscriber's device is turned on or becomes available.
Tags: Message Service, Message Service Center, Service Center, carrier network, forwards message, mobile phone