USSD – Unstructured Supplementary Service Data

Term used in Cellular / Mobile
Service ,is a protocol used by GSM cellular telephones to communicate with the service provider’s computers.

USSD can be used for prepaid main balance check,data balance
check, wap browsing , prepaid callback service , mobile-money services , location based
content services , menu-based information services , and as part of configuring the phone on the network.

USSD messages are up to 182 alphanumeric characters in length.

Unlike SMS service messages, USSD messages create a real-time connection during a USSD session.

The connection remains open, allowing a two-way exchange of a sequence of data. This makes USSD more responsive than services that use SMS.

Example of USSD command –

To check main balance in Idea is *212# and in

Airtel it is *123#

By dialing this command you will get the message from server for main balance left in your prepaid sim account.Same process are followed to check Internet Data
Balance Check .