USSD Meaning | What is USSD does for a subscriber

USSD is for unstructured data service between the mobile handset and mobile operator home network. What is unstructured data mean? In telephony protocols, all data formats are predefined in specs. E.g., IMSI, which is the identity of the subscriber, is well structured in a 3gpp specification.

A USSD message carries user-entered data to the network node or USSD gateway, which can handle the USSD request. E.g., Balance check. The user can enter the data for which no format is specified in 3GPP. Because of this, it is called unstructured data.

Although the data coding schemes are standardized in 3GPP.