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2. USSD overview

Unstructured Supplementary Service Data (USSD) is a 3GPP/GSM service that enables interactive, session-oriented communication between a subscriber handset (UE) and network service applications. USSD is designed for real-time dialogs (menus, prompts, and user responses) and is transported via the signaling plane rather than through a store-and-forward messaging system.

USSD is often contrasted with SMS:

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