6.2.1 Handling of USSD request at MS

23.0903GPPRelease 17Stage 2TSUnstructured Supplementary Service Data (USSD)

When the user or the application in the MS makes a request which the MS determines is to make use of USSD, the MS shall set up a transaction to the network, send the request to the MSC and await a response. When the MS receives the response, it shall display the information contained to the user or relay the message to the application in the MS.

While awaiting the response, the MS may receive a network initiated USSD request or notification on the same transaction. If this occurs, the MS shall process that operation (see clause 1) and continue to await the response to the mobile initiated request.

If, when the MS determines that a user request is to make use of USSD, the MS is already involved in a USSD or a non-call related supplementary service transaction, the MS shall reject the request.