5 Network initiated unstructured supplementary service data operations

04.903GPPTSUnstructured Supplementary Service Data (USSD)

5.1 Unstructured supplementary service data request

5.1.1 Normal operation

The network invokes an USSD request by sending a REGISTER message containing a UnstructuredSS‑Request invoke component to the MS.

The MS shall respond to the request by sending a FACILITY message containing the user’s mobile subscriber’s response in a return result component. The network shall pass the data received in the response to the application handling USSD operations and shall wait for the response of the application. The application may either continue or terminate the dialogue.

When the application continues the dialogue, it may initiate another USSD operation by sending a FACILITY message (see figure 5.2). The operation may either be an USSD request or notification (see subclause 5.1.2).

When the application terminates the dialogue, the network shall clear the transaction by sending a RELEASE COMPLETE message. The MS may also clear the transaction at any time by sending a RELEASE COMPLETE message upon the request of the user.

If the MS is unable to process the request received from the network, it shall return an error indication by sending a FACILITY message containing a return error component. Error values are specified in GSM 04.80.

When the MS receives an USSD operation in parallel to any call independent supplementary service transaction, it shall respond with a return error component in a RELEASE COMPLETE message, containing the "USSD‑Busy" error as specified in GSM 04.80, to indicate the failure in handling a parallel USSD operation. However, the network is allowed to initiate USSD operations in parallel to call related transactions.

MS Network

REGISTER

<————————————————————————————————————————

Facility (Invoke = UnstructuredSS-Request (ussd-DataCodingScheme, ussd-String))

FACILITY

————————————————————————————————————————>

Facility (Return result = UnstructuredSS-Request (ussd-DataCodingScheme, ussd-String))

FACILITY

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->

Facility (Return error (Error))

FACILITY

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->

Facility (Reject (Invoke_problem))

RELEASE COMPLETE

<————————————————————————————————————————

NOTE: The MS may clear the transaction at any time by sending a RELEASE COMPLETE upon request of the user.

Figure 5.1: Single network initiated USSD request

MS Network

REGISTER

<————————————————————————————————————————

Facility (Invoke = UnstructuredSS-Request (ussd-DataCodingScheme, ussd-String))

FACILITY

————————————————————————————————————————>

Facility (Return result = UnstructuredSS-Request (ussd-DataCodingScheme, ussd-String))

FACILITY

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->

Facility (Return error (Error))

FACILITY

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->

Facility (Reject (Invoke_problem))

FACILITY

<————————————————————————————————————————

Facility (Invoke = UnstructuredSS-Request (ussd-DataCodingScheme, ussd-String))

FACILITY

————————————————————————————————————————>

Facility (Return result = UnstructuredSS-Request (ussd-DataCodingScheme, ussd-String))

FACILITY

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->

Facility (Return error (Error))

FACILITY

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->

Facility (Reject (Invoke_problem))

.

.

.

RELEASE COMPLETE

<————————————————————————————————————————

NOTE 1: The MS may clear the transaction at any time by sending a RELEASE COMPLETE upon request of the user.

NOTE 2: The second USSD operation may also be an USSD notification. The network may use the on‑going transaction for sending further USSD operations. Only one additional USSD request is shown.

Figure 5.2: Multiple network initiated USSD request

5.2 Unstructured supplementary service data notification

5.2.1 Normal operation

The network invokes an USSD notification by sending a REGISTER message to the MS containing a UnstructuredSS‑Notify invoke component.

The MS shall acknowledge the operation by sending a FACILITY message containing an empty result component to the network. The application may either continue or terminate the dialogue.

When the application continues the dialogue, it may initiate another USSD operation by sending a FACILITY message (see figure 5.4). The operation may either be an USSD request (see subclause 5.1.1) or notification.

When the application terminates the dialogue, the network shall clear the transaction by sending a RELEASE COMPLETE message. The MS may also clear the transaction at any time by sending a RELEASE COMPLETE message upon request of the user.

If the MS is unable to process the request received from the network, it shall return an error indication by sending a FACILITY message containing a return error component. Error values are specified in GSM 04.80.

When the MS receives an USSD operation in parallel to any call independent supplementary service transaction, it shall respond with a return error component in a RELEASE COMPLETE message, containing the "USSD‑Busy" error as specified in GSM 04.80, to indicate the failure in handling a parallel USSD operation. However, the network is allowed to initiated USSD operations in parallel to call related transactions.

MS Network

REGISTER

<————————————————————————————————————————

Facility (Invoke = UnstructuredSS-Notify (ussd-DataCodingScheme, ussd-String))

FACILITY

————————————————————————————————————————>

Facility (Return result)

FACILITY

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->

Facility (Return error (Error))

FACILITY

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->

Facility (Reject (Invoke_problem))

RELEASE COMPLETE

<————————————————————————————————————————

NOTE: The MS may clear the transaction at any time by sending a RELEASE COMPLETE upon request of the user.

Figure 5.3: Single network initiated USSD notification

MS Network

REGISTER

<————————————————————————————————————————

Facility (Invoke = UnstructuredSS-Notify (ussd-DataCodingScheme, ussd-String))

FACILITY

————————————————————————————————————————>

Facility (Return result)

FACILITY

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->

Facility (Return error (Error))

FACILITY

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->

Facility (Reject (Invoke_problem))

FACILITY

<————————————————————————————————————————

Facility (Invoke = UnstructuredSS-Notify (ussd-DataCodingScheme, ussd-String))

FACILITY

————————————————————————————————————————>

Facility (Return result)

FACILITY

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->

Facility (Return error (Error))

FACILITY

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – ->

Facility (Reject (Invoke_problem))

.

.

.

RELEASE COMPLETE

<————————————————————————————————————————

NOTE 1: The MS may clear the transaction at any time by sending a RELEASE COMPLETE upon request of the user.

NOTE 2: The second USSD operation may also be an USSD request. The network may use the on‑going transaction for sending further USSD operations. Only one additional USSD notification is shown.

Figure 5.4: Multiple network initiated USSD notification