5 USSD to/from gsmSCF

23.0783GPPCustomised Applications for Mobile network Enhanced Logic (CAMEL) Phase 4Release 17Stage 2TS

5.1 Architecture

5.1.1 Functional Entities used for CAMEL

This subclause describes the functional architecture needed to support CAMEL handling of USSD to/from gsmSCF. The functional model of USSD in an HLR that supports CAMEL is shown in figure 5.1. The phase 2 USSD handler is defined in 3GPP TS 23.090 [24]. Phase 1 USSD information flows may be relayed from the HLR to the gsmSCF. CAMEL introduces a "CAMEL USSD application" which is invoked by the USSD handler. The CAMEL USSD functional entities and application behaviour is specified in this subclause.

Figure 5.1: Handling of USSD to and from a CAMEL subscriber

HLR: The HLR stores for subscribers requiring CAMEL support the information relevant to the current subscription regarding U‑CSI. The UG‑CSI is stored as global data applicable to all subscribers. The U‑CSI and the UG‑CSI are stored in the HLR only.

gsmSCF: see subclause 3.1.

5.1.2 Interfaces defined for CAMEL

This subclause describes the different interfaces applicable to CAMEL. It specifies on a high level the functions specific to CAMEL.

5.1.2.1 gsmSCF – HLR interface

This interface is used for USSD information flows, both for gsmSCF-initiated dialogues and MS-initiated dialogues (relayed via HLR). It is a network operator option whether to support or not USSD information flows on this interface.

5.2 Description of CAMEL Subscriber Data

5.2.1 USSD CAMEL Subscription Information (U‑CSI)

The subscription information specified in this subclause is for information only.

This subclause defines the contents of the USSD CAMEL Subscription Information (U‑CSI). The U‑CSI consists of a list of pairs of the following two parameters.

5.2.1.1 Service Code

Service code for a specific application in a gsmSCF which interacts with the user by USSD.

5.2.1.2 gsmSCF address

Address to be used to access the gsmSCF for a particular subscriber and a particular service code. The address shall be an E.164 number to be used for routeing.

5.3 Content of the USSD General CAMEL Service Information (UG‑CSI)

The service information specified in this subclause is for information only.

This subclause defines the contents of the USSD General CAMEL Service Information (UG‑CSI). The allocation of the UG‑CSI is independent from a particular subscriber.

The UG‑CSI consists of a list of pairs of the following two parameters.

5.3.1 Service Code

Service code for a specific application in a gsmSCF which interacts with the user by USSD.

5.3.2 gsmSCF address

Address to be used to access the gsmSCF for a particular service code. The address shall be an E.164 number to be used for routeing.

5.4 Procedures

5.4.1 MS Initiated USSD

For the behaviour of the USSD handler in HLR when receiving a MS initiated USSD see 3GPP TS 23.090 [24].

When the USSD handler has determined that the service code present in the received USSD does not indicate that an USSD application in the HLR shall be invoked it shall route the USSD to the USSD application specific for CAMEL, i.e. the CAMEL USSD application.

The procedure at the CAMEL USSD application at the HLR is implementation dependent. The following text describes a recommended procedure.

The CAMEL USSD application shall check the U‑CSI data assigned to the specific subscriber. If the service code is present in the U‑CSI the USSD is routed to the gsmSCF given by the gsmSCF address stored against the service code in the U‑CSI.

If the service code is not present in the U‑CSI (or the subscriber does not have U‑CSI defined) then the CAMEL USSD application shall check the UG‑CSI data assigned to the HLR. If the service code is present in the UG‑CSI then the USSD is routed to the gsmSCF given by the gsmSCF address stored against the service code in the UG‑CSI.

If the service code is not present in U‑CSI or UG‑CSI an error (unknown application) is returned to the USSD handler.

5.4.2 gsmSCF Initiated USSD

The HLR may at any time receive a USSD information flow from the gsmSCF. If the subscriber can be contacted, the HLR shall set up a transaction to the VLR and forward the information flow unchanged. Any further information exchange between the gsmSCF and MSC shall be transparent to the VLR and the HLR. When one transaction is released, the HLR shall release the other. If an error is received from the MSC, the VLR shall release the transaction to the HLR and the HLR shall release the transaction to the gsmSCF.

5.5 Description of information flows

This subclause contains the detailed description of the information flows used by CAMEL for USSD handling.

Each Information Element (IE) is marked as Mandatory (M), Conditional (C), Specific conditions (S) or Optional (O) in the "Status" column.

An ‘M’ IE shall always be included. A ‘C’ IE shall be included if the sending entity has the necessary information to populate the IE. The conditions for the inclusion of an ‘S’ IE are shown in the ‘Description’ column of the definition table. An ‘O’ IE may be included or omitted as required by the service logic. This categorization is a functional classification, i.e. it defines the requirements for the stage 2 information. It is not a stage 3 classification to be used for the ASN.1 syntax of the protocol.

The following principles apply for the handling of the IEs by the receiving entity:

– The gsmSCF may silently discard any IE which it does not functionally support.

– The HLR shall return an error if it does not functionally support an IE which it receives.

Details of errors and exceptions to these rules are specified in are specified in 3GPP TS 29.002 [34].

5.5.1 gsmSCF to HLR information flows

5.5.1.1 Unstructured SS Request

5.5.1.1.1 Description

This IF is used for the gsmSCF to request data from the MS via the HLR.

5.5.1.1.2 Information Elements

Information element name	Status	Description
USSD String	M	This IE contains the string that will be sent to the MS.
Data Coding Scheme	M	This IE indicates the characteristics of the USSD string.
IMSI	S,E	This IE identifies the subscriber for which the information is requested. It shall be present if this IF is the first IF in a USSD dialogue, otherwise it shall be absent.
MSISDN	S,E	This IE identifies the subscriber for which the information is requested. It shall be present if this IF is the first IF in a USSD dialogue, otherwise it shall be absent.
Alerting Pattern	O	This IE indicates an alerting pattern to be sent to the MS.

5.5.1.2 Unstructured SS Notify

5.5.1.2.1 Description

This IF is used for the gsmSCF to send data to the MS via the HLR.

5.5.1.2.2 Information Elements

Information element name	Status	Description
USSD String	M	This IE contains the string that will be sent to the MS.
Data Coding Scheme	M	This IE indicates the characteristics of the USSD string.
IMSI	S,E	This IE identifies the subscriber for which the information is requested. It shall be present if this IF is the first IF in a USSD dialogue, otherwise it shall be absent.
MSISDN	S,E	This IE identifies the subscriber for which the information is requested. It shall be present if this IF is the first IF in a USSD dialogue, otherwise it shall be absent.
Alerting Pattern	O	This IE indicates an alerting pattern to be sent to the MS.

5.5.1.3 Process Unstructured SS Data ack

5.5.1.3.1 Description

This IF is used for the gsmSCF to send the response to the MS via the HLR for the MS initiated IF.

5.5.1.3.2 Information Elements

The following information element is required:

Information element name	Status	Description
SS User Data	C	This IE contains the string that will be sent to the MS.

5.5.1.4 Process Unstructured SS Request ack

5.5.1.4.1 Description

This IF is used for the gsmSCF to send the response to the MS via the HLR for the MS initiated IF.

5.5.1.4.2 Information Elements

Information element name	Status	Description
USSD String	S	This IE contains the string that will be sent to the MS. It shall be present if the Data Coding Scheme is present; otherwise it shall be absent.
Data Coding Scheme	S	This IE indicates the characteristics of the USSD string. It shall be present if the Data Coding Scheme is present; otherwise it shall be absent.

5.5.2 HLR to gsmSCF information flows

5.5.2.1 Unstructured SS Request ack

5.5.2.1.1 Description

This IF is used for the MS to send to the gsmSCF via the HLR for the gsmSCF initiated IF.

5.5.2.1.2 Information Elements

Information element name	Status	Description
USSD String	C	This IE contains the string that will be sent to the gsmSCF. It shall be present if the Data Coding Scheme is present; otherwise it shall be absent.
Data Coding Scheme	C	This IE indicates the characteristics of the USSD string. It shall be present if the Data Coding Scheme is present; otherwise it shall be absent.

5.5.2.2 Unstructured SS Notify ack

5.5.2.2.1 Description

This IF is used for the MS to via the HLR acknowledge to the gsmSCF that the notification was received.

5.5.2.2.2 Information Elements

This IE contains no information element.

5.5.2.3 Process Unstructured SS Data

5.5.2.3.1 Description

This IF is used for the MS to request data from gsmSCF via the HLR.

5.5.2.3.2 Information Elements

Information element name	Status	Description
SS User Data	M	This IE contains the string that was received from the MS.

5.5.2.4 Process Unstructured SS Request

5.5.2.4.1 Description

This IF is used for the MS to request data from the gsmSCF via the HLR.

5.5.2.4.2 Information Elements

Information element name	Status	Description
USSD String	M	This IE contains the string that will be sent to the gsmSCF, including the Service Code.
Data Coding Scheme	M	This IE indicates the characteristics of the USSD string
IMSI	M	This IE identifies the subscriber.
MSISDN	S	This IE contains the basic MSISDN of the subscriber who has requested the USSD IF. This IE is used as an operator option.
Originating Entity Number	M	This IE identifies the functional entity initiating the information flow. In this case, this shall be the address of the HLR.

5.5.2.5 Begin Subscriber Activity

5.5.2.5.1 Description

This IF is used by the HLR to start subscriber activity towards the gsmSCF for USSD purposes.

5.5.2.5.2 Information Elements

Information element name	Status	Description
IMSI	M	This IE identifies the subscriber.
Originating Entity Number	M	This IE identifies the functional entity initiating the subscriber activity. In this case, this shall be the address of the HLR.