The HLR fails to provide the requested USSD service when a USSD message sent

from the MSC indicates that MAP phase 1 is supported.

The HLR processes relevant USSD services successfully when a USSD message

sent from the MSC indicates that MAP phase 2 is supported.

When the USSD message sent from the MSC indicates that MAP phase 2 is

supported, and the value of the parameter PUssdOption is 2 in the hdusys.cfg file,

the HLR responds normally. The value 2 of the parameter PUssdOption indicates

that the HLR includes the VLR number in the message to be sent to the USSD center

over the TCAP layer.

When the USSD message sent from the MSC indicates that MAP phase 1 is

supported, the HLR transparently transfers the message according to the 3GPP

23.090 specification, which states:

When a network entity is to process a USSD request locally, the request shall be

handled by an appropriate application.

The location, nature and contents of USSD applications is, by definition, service

provider and network operator dependent, but may include:

- Setting up or releasing signaling and/or speech channels

- Passing the request to another network entity (unchanged or changed)

- Passing a different USSD request to another network entity

and/or

- Requesting further information from the MS (one or more times)

Upon completion of handling the request, the network entity shall respond to the

request and release the transaction.’

For messages indicating that MAP phase 2 is supported, the HLR sends the VLR

number to the USSD center. This indicates that the VLR number is required for the

USSD center to send a response. For messages indicating that MAP phase 1 is

supported, the HLR does not send the VLR number to the USSD center. Therefore,

the requested USSD service is not provided.

The HLR is designed to transparently transfer received messages to the USSD

center. The function of including the MSISDN, the VLR number, both, or neither is

customized only for messages indicating that MAP phase 2 is supported. Therefore,

the function is not available for messages indicating that MAP phase 1 is supported.

For messages indicating that MAP phase 2 is supported, the HLR sends the

MSISDN, the VLR number, both, or neither to the USSD center. For messages

indicating that MAP phase 1 is supported, the HLR transparently transfers received

messages to the USSD center.

thanks for the doc

useful information

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helpful indeed. thanks

thanks for the document. really useful.