Note that only GSM gateway supports this feature.
Unstructured Supplementary Service Data (USSD), sometimes referred to as "Quick Codes" or "Feature codes", is a communications protocol used by GSM cellular telephones to communicate with the mobile network operator's computers. USSD can be used for WAP browsing, prepaid callback service, mobile-money services, location-based content services, menu-based information services
Unlike SMS 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. Basically, there is 2 types of sessions.
- First is the one-time session that you input a code, the carrier replies a result and then session closed automatically.
- Second is standby session that you input a code, the carrier replies a menu and you could input an option. If you don’t input, the session would keep alive until timeout. Or you could manually exit the standby session to perform other USSD session.
USSD session flow
- 1.1 GSM gateway sends the USSD request to GSM module.
- 1.2 GSM module sends the USSD request to cellular network.
- 1.3 Cellular network returns a result or a menu to GSM module.
- 1.4 GSM module returns a result, and session ends. Or it returns a meu to GSM gateway.
- 1.5 GSM gateway sends the USSD request to GSM module again. Or manually exit the session.
- 1.6 GSM module sends the USSD request to cellular network. Or manually exit the session.
No web configuration is related with USSD function.