How Does SMS Work?

Short message service or SMS allows users to send short text messages from one cell phone to another. A SMS message can accommodate up to 160 characters.

SMS work on a store-and-forward basis. SMS messages travel through various nodes before reaching the final recipient.

SMS message is first reaches the wireless service provider's SMS center. SMS center then sends a request to the Home Location Register (HLR) and receives the routing information for the recipient.  

The SMS center sends the message to the Mobile Switching Center (MSC). The MSC collects the recipient's information from the Visitor Location Register (VLR).

The MSC forwards the message to a mobile server. If the recipient has a Treo or VisorPhone the SMS is placed on the SIM. That is why; Treo or VisorPhone can store hundreds of SMSs, whereas GSM cell phones can store only a few.

The MSC returns the outcome of the Forward Short operation to the SMS Center and the SMS Center reports delivery status of the short message back to the sender.