Unstructured Supplementary Service Data (USSD)

Unstructured Supplementary Service Data (USSD) is a protocol, providing session-based communication, used by GSM cell phones to communicate with the service provider's applications. This is using text based messaging within an open session between the user and the application. The USSC service, which is implemented in the USSD center, exchanges the USSD data between the mobile phone and the application server.

Is this similar to SMS? No, USSD is session based, unlike SMS, which is a store-and-forward technology with transaction capabilities. Most of the user interactive applications hug this standard because of the session-based feature and less response time.

The standard can be used to create value added services for operators, service providers, and enablers in the mobile interaction industry. Some of the well known USSD based applications offered by the telecom operators are prepaid balance inquiry, top-up, caller tune selections, balance transfer etc. In all these applications what we are doing is simply sending preformatted text messages to a short code published by the service provider. The USSD center which receives these messages interprets and invokes the corresponding applications to retrieve the desired results and present it to the user.