This page presents illustrative flows for USSD requests initiated by a UE . The USSI features are described in the administration guide.

A balance query example

A signalling diagram for a balance query operation is shown below.

ussi-ue-initiated-full

1 - The INVITE has an SDP offer as per TS 24.390 section 4.5.2. The INVITE body is as per 24.390. It is a multi-part body with both an SDP and a USSD message. An example of a USSD message is

Content-Type: application/vnd.3gpp.ussd+xml

<?xml version="1.0" encoding="UTF-8"?>
<ussd-data>
    <language>en</language>
    <ussd-string>*100*1#</ussd-string>
</ussd-data>

2 - An iFC is used to match USSD requests. An example is shown in INVITE Request containing USSD content

3 - A 2xx to the INVITE is sent, confirming the dialog. The SDP answer reflects the offer. The response contains a Recv-Info header field set to g.3gpp.ussd

4 - Forwarded to the UE

5 - ACK

6 - Forwarded to the IPSMGW/USSIGW

7 - A MAP Process-Unstructured-SS-Request containing the USSD message is sent to the HLR addressed using the MSISDN

8 - The HLR sends it towards the Prepaid SCP

9 - The SCP responds with the balance information in a USSD message

10 - Forwarded to the IPSMGW/USSIGW

11 - The IPSMGW/USSIGW converts the USSD message in the response into an XML document. It is placed in the body of the BYE request

An example is

Content-Type: application/vnd.3gpp.ussd+xml

<?xml version="1.0" encoding="UTF-8"?>
<ussd-data>
    <language>en</language>
    <ussd-string>
        Hello, your credit is $175.50. Thanks for your query.
        We are happy to assist. Your operator
    </ussd-string>
</ussd-data>

12 - Proxied to the UE

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