A USSD request is a short combination of numbers that is dialed on a mobile phone and allows you to receive any necessary information or perform some action.
USSD stands for Unstructured Supplementary Service Data. This is one of the services in GSM networks that allows subscribers to quickly interact with the operator's service applications. The technology used to transfer data via USSD requests has certain technical and functional similarities with the SMS technology, but it has a number of differences.
Features of USSD technology
USSD is a session-oriented technology in which data transfer occurs within an established session. In this part of the construction of USSD is very similar to the service of interactive systems based on IVR - Interactive Voice Response. The main difference between USSD technology and IVR is the lack of a voice connection between the subscriber and the service.
The initial purpose of USSD communication was to provide the subscriber with the ability to independently manage the service profile in the HLR - a database with information about subscribers, as well as interact with the services built into the HLR. Over time, the function of connecting external applications was added to the technology, after which USSD communication became ideal for working with information services that have a dialog structure - information services, banking services, customer service, and others.
How the USSD service works
To explain the operation of the USSD service, you can use a specific example. For example, a subscriber needs to find out the status of settlements with his operators. The USSD system assigned a short number 100 to the “Balance check” service. In order to use this service, the client must dial * 100 # on his mobile phone and press the call key.
The symbols * and # at the beginning and end of the number are used so that the mobile operator understands that this is not a regular call, but a request for USSD service. During processing, the request is passed to the corresponding USSD application. Further, the USSD application interacts with the billing system database, receives the necessary information and sends it in the form of a USSD package to the subscriber's mobile phone. The content of this package is displayed as text on the device screen.
The USSD request system allows you to get the minimum possible delay between the subscriber's request and the operator's response to it, which is impossible to achieve when using applications based on SMS. However, USSD technology is not a competitor to SMS. These two services are complementary. They allow mobile operators to combine both methods, giving subscribers the opportunity to choose the most convenient one.