Points in call and detection points
The various events such as call origination, answer, and disconnection during establishing, maintaining, or tearing down a call are referred as the points in call (PICs). The PICs provide a view of a state or an event in which call processing logic within the MSC/VLR/SGSN may initiate an appropriate action.
Detection points (DPs) represent transitional events that occur between PICs. The gsmSSF makes these DPs visible to the gsmSCF as and when they are encountered. This allows gsmSCF to control subsequent handling of the call.
The service logic that is loaded in the network nodes to carry out the call processing on encountering the detection points is termed a trigger.
The DP can be armed or disarmed. "Arming" a DP means that the gsmSSF must notify the gsmSCF on encountering it. If the DP is not armed, the processing node continues processing of a call on its own, without involvement of the gsmSCF. The DPs can be armed statically or dynamically.
The CAMEL specifications identify three different types of DP:
■ Trigger detection point-request (TDP-R): The DP is statically armed. The processing is suspended when the TDP is encountered.
■ Event detection point-request (EDP-R): The DP is dynamically armed within the context of a CAMEL-controlled relationship. The processing is suspended on encountering the EDP. The gsmSSF then processes the call according to the instructions from the gsmSCF.
■ Event detection point-notification (EDP-N): Like EDP-R, this DP is also dynamically armed within the context of a CAMEL-controlled relationship. However, the processing of the call continues without suspension on encountering an EDP-N
CAMEL subscriber information
The HLR stores the following CAMEL subscription information (CSI): (1) that CAMEL support is required for the subscriber and (2) the identities of the CAMEL-specific entities (CSEs) to be used for that support.
Circuit-switched call CSIs. Table 8-2 lists CSIs relevant to circuit-switched calls.
TABLE 8-2 Circuit-Switched Call CSIs
|
CAMEL subscription information (CSI) |
Description |
|
O-CSI Originating CSI |
The O-CSI identifies the roamer as having originated CAMEL services. It contains the trigger information that is required to invoke CAMEL service logic for the roamer-originated call. The HPLMN HLR sends O-CSI to the VPLMN VLR/MSC in the insert subscriber data operation during the location update procedure or whenever it gets changed, e.g., because of administrator action. It is also transferred to the interrogating network when a GMSC receives an incoming call for a subscriber roaming in a visited network and interrogates the HLR for routing information, using the send routing information procedure. |
|
D-CSI Dialed service CSI |
The D-CSI contains trigger information that is required to invoke CAMEL service logic for subscriber-dialed services. The HPLMN HLR sends D-CSI to the VPLMN VLR/MSC in the insert subscriber data operation as part of the location update procedure or whenever it gets changed, e.g., because of administrator action. It is also transferred to the interrogating network when a GMSC receives an incoming call for a subscriber roaming in a visited network and interrogates HLR for routing information using the send routing information procedure. |
|
T-CSI Terminating CSI |
The T-CSI identifies the roamer as having terminated CAMEL services. It contains the trigger information that is required to invoke CAMEL service logic for a mobile-terminating call in the GMSC. |
|
VT-CSI Visited-MSC-terminating CSI |
The VT-CSI contains trigger information that is required to invoke CAMEL service logic for mobile-terminating calls in the VMSC. The HPLMN HLR sends VT-CSI to the VPLMN VLR/MSC in the insert subscriber data operation as part of the location update procedure. |
|
TIF-CSI Translation information flag CSI |
The TIF-CSI is used in the HLR for registering short forwarded-to Numbers (FTNs). When TIF-CSI is present, the subscriber is allowed to register short FTNs. When the subscriber invokes call deflection, the TIF-CSI in the VPLMN allows the subscriber to deflect to short deflected-to numbers. The TIF-CSI is transferred to the VPLMN in the insert subscriber data. |
|
N-CSI Network CSI |
The N-CSI identifies services offered on a per-network basis by the serving PLMN operator for all subscribers. This CSI is stored in the MSC. |
Each CSI contains a set of information elements. Table 8-3 lists information elements for each CSI.
TDP list. The TDP list indicates on which detection point triggering shall take place. The list of all detection points on which triggering takes place is as follows:
For O-CSI, the detection points are:
■ DP collected info
■ DP route select failure
For T-CSI, the detection points are:
■ DP terminating attempt authorized
■ DPT busy
■ DP T no answer
For VT-CSI, the detection points are:
■ DP terminating attempt authorized
■ DP T busy
■ DP T no answer
gsmSCF address. The gsmSCF address indicates the address to be used to access the gsmSCF for a particular subscriber. The address is based on the E.164 addressing scheme and is used for routing. There may be more than one gsmSCF associated with a TDP.
Service key. The service key identifies to the gsmSCF the service logic to be used. A service key is associated with each DP criterion.
DP criteria. The DP criteria indicate if the gsmSSF needs to request instructions from the gsmSCF.
TABLE 8-3 Circuit-Switched Call CSI Contents
|
Contents |
O-CSI |
D-CSI |
T-CSI |
VT-CSI |
TIF-CSI |
N-CSI |
|
TDP list |
X |
X |
X |
X |
||
|
gsmSCF address |
X |
X |
X |
X |
||
|
Service key |
X |
X |
X |
X |
||
|
DP criteria |
X |
X |
X |
X |
||
|
Default call handling |
X |
X |
X |
X |
||
|
CAMEL capability handling |
X |
X |
X |
X |
||
|
CSI state |
X |
X |
X |
X |
||
|
Notification flag |
X |
X |
X |
X |
X |
|
|
Translation information flag |
X |
|||||
|
List of services |
X |
Default call handling. The default call handling element indicates whether the call shall be released or continued as requested if there is an error in the dialogue between gsmSSF and gsmSCF or if the call is subject to call gapping in the gsmSSF. A default call handling element is associated with each service key.
CAMEL capability handling. The CAMEL capability handling element indicates the phase of CAMEL that is requested by the gsmSCF for the service. The HLR does not include in a CSI that it sends to a GMSC any data for a CAMEL phase later than that which the CAMEL capability handling indicates. The CAMEL capability handling may be different for the different CSIs. For example, O-CSI may have a CAMEL capability handling value to indicate CAMEL Phase 3, while T-CSI may contain a value indicating CAMEL Phase 2 support.
To enable interworking between networks supporting different phases of CAMEL, the HLR decides on a subscriber basis to apply operator-determined barring, perform normal call handling, or perform operator-specific handling.
CSI state. This indicates whether the CSI (i.e., O-CSI/D-CSI/T-CSI/VT-CSI) is active or not.
Notification flag. The notification flag indicates whether a change in the CSI shall trigger a notification or not.
Translation information flag. The TIF-CSI in the CAMEL subscriber data indicates that:
■ When the subscriber registers a forwarded-to number supplementary service, the HLR shall not attempt to perform any translation, number format checks, prohibited FTN checks, or call barring checks.
■ When the subscriber invokes the call deflection supplementary service, the VLR shall not attempt to perform any translation, number format checks, prohibited DTN checks, or call barring checks.
List of Services. The list of services in N-CSI identifies services offered on a per-network basis by the serving PLMN operator for all subscribers.
USSD CSIs. Table 8-4 lists CSIs to support USSD services. The contents of USSD CSIs are:
Service code. The service code identifies a specific application in a gsmSCF that interacts with the user via the USSD.
gsmSCF address. The gsmSCF address indicates the address to be used to access the gsmSCF for a particular service. The address is based of on the E.164 addressing scheme and is used for routing.
TABLE 8-4 USSD-CSI
|
CAMEL subscription information (CSI) |
Description |
|
U-CSI USSD CSI |
The U-CSI contains trigger information that is used to invoke a USSD application in the CAMEL service environment for the served subscriber. The U-CSI is held in the HLR and never sent to any other node. The U-CSI was introduced in CAMEL Phase 2. |
|
UG-CSI USSD general CSI |
The UG-CSI contains trigger information that is used to invoke a USSD application in the CAMEL service environment for all subscribers. The UG-CSI is held in the HLR and never sent to any other node. The UG-CSI was introduced in CAMEL Phase 2. |
SS notification CSI. Table 8-5 lists the supplementary services notification CSI and its functions. The SS notification CSI contents are:
Notification criteria. This data indicates for which supplementary services notifications shall be sent. The supplementary services that may be indicated are ECT, CD, CCBS, and MPTY.
gsmSCF address. This is the E.164 address of a gsmSCF. It is used for routing purposes to access the gsmSCF for a particular subscriber.
CSI state. The CSI state indicates whether the SS-CSI is active or not.
Notification flag. The notification flag indicates whether the change of the SS-CSI shall trigger a notification on change of subscriber data or not.
GPRS CSI. Table 8-6 lists the CSI to support GPRS. The contents of the GPRS CSI are:
gsmSCF address. This is the address of the gsmSCF in ITU-T E.164 format. It is used for routing purposes to access the gsmSCF for a particular subscriber.
TABLE 8-5 SS Notification CSIs
|
CAMEL subscription information (CSI) |
Description |
|
SS-CSI Supplementary services invocation notification CSI |
The SS-CSI is used to notify the CSE about the invocation of certain supplementary services at the VLR/MSC. The HPLMN HLR sends SS-CSI to the VMSC in the insert subscriber data element as part of the location update procedure or whenever it gets changed, e.g., because of administrator action. The SS-CSI was introduced in CAMEL Phase 2. |
TABLE 8-6 GPRS-CSI
|
CAMEL subscription information (CSI) |
Description |
|
GPRS CSI GPRS CAMEL subscription information |
The GPRS-CSI contains trigger information that is required to invoke CAMEL service logic for GPRS sessions and PDP contexts. The HPLMN HLR sends GPRS-CSI to the SGSN during GPRS attach and inter SGSN routing area update procedure or whenever it gets changed, e.g., because of administrator action. The GPRS-CSI was introduced in CAMEL Phase 3. |
Service key. The service key identifies to the gsmSCF the service logic to be used.
Default GPRS handling. The default GPRS handling indicates if the GPRS session or PDP context shall be released or continued as requested in case of error in the gprsSSF to gsmSCF dialogue.
TDP list. The TDP list indicates the detection point on which triggering shall take place.
CAMEL capability handling. To enable interworking, CAMEL capability handling indicates the phase of CAMEL that gsmSCF requests for the service.
CSI state. The CSI state indicates whether the GPRS-CSI is active or not.
Notification flag. The notification flag indicates whether the change of the GPRS-CSI shall trigger a notification on change of subscriber data or not.
SMS CSIs. Table 8-7 lists CSIs to support SMS. The contents of the MO-SMS CSI are:
gsmSCF address. This is the E.164 address of a gsmSCF. It is used for routing purposes to access the gsmSCF for a particular subscriber.
Service key. The service key identifies to the gsmSCF the service logic to be used.
Default SMS handling. The default SMS handling element indicates whether the SMS submission/short message delivery shall be released or continued as requested in case of error in the dialogue between gprsSSF and gsmSCF/gprsSCF.
TDP list. The TDP list indicates on which detection point triggering shall take place.
TABLE 8-7 SMS CSIs
|
CAMEL subscription information (CSI) |
Description |
|
MO-SMS CSI Mobile-originated short message service CSI |
The HPLMN HLR sends MO-SMS-CSI to the VMSC in the insert subscriber data element as part of the location update procedure or whenever it gets changed, e.g., because of administrator action. The MO-SMS-CSI was introduced in CAMEL Phase 3. |
|
MT-SMS CSI Mobile-terminated short message service CSI |
The HPLMN HLR sends MT-SMS-CSI to the VMSC in the insert subscriber data element as part of the location update procedure or whenever it gets changed, e.g., because of administrator action. The MT-SMS-CSI was introduced in CAMEL Phase 3. |
■ For MO-SMS-CSI, the only defined DP is SMS collected info.
■ For MT-SMS-CSI, the only defined DP is SMS delivery request. DP criteria. The DP criteria indicate whether the SMS SSF shall request the gsmSCF for instructions. This information element is present only in case of MT-SMS-CSI.
CAMEL capability handling. The CAMEL capability handling indicates the phase of CAMEL that is asked by the gsmSCF for the service. This parameter is set to CAMEL Phase 3 for MO-SMS-CSI and CAMEL Phase 4 for MT-SMS-CSI.
CSI state. The CSI state indicates whether the MO-SMS-CSI/MT-SMS-CSI is active or not.
Notification flag. The notification flag indicates whether the change of the MO-SMS-CSI/MT-SMS-CSI shall trigger notification on change of subscriber data.
Mobility management-CSI. Table 8-8 lists the CSIs to support mobility management.
The contents of the mobility management CSI are:
Mobility management triggers. This data indicates which mobility management events shall result in a notification to the gsmSCF. One or more events may be marked per subscriber. These events are:
■ Location update in the same VLR service area.
■ Location update to another VLR service area.
■ IMSI attach.
TABLE 8-8 Mobility Management CSIs
|
CAMEL subscription information (CSI) |
Description |
|
M-CSI Mobility management CSI |
M-CSI is used to notify the CSE about mobility management events for the CAMEL subscriber. The HPLMN HLR sends M-CSI to the VMSC in the insert subscriber data element as part of the location update procedure or whenever it gets changed, e.g., because of administrator action. |
|
MG-CSI Mobility management GPRS CSI |
The MG-CSI is used to notify the CSE about mobility management events for the GPRS subscriber. The HPLMN HLR sends MG-CSI during the routing area update, or restore data procedure, or whenever it gets changed, e.g., because of administrator action. |
■ MS-initiated IMSI detach (explicit detach) and network-initiated IMSI detach (implicit detach).
gsmSCF address. This is the E.164 address of the gsmSCF to which the mobility management event notification needs to be sent. It is used for routing purposes to access the gsmSCF for a particular subscriber.
Service key. The service key identifies to the gsmSCF the service logic to be used.
CSI state. The CSI state indicates whether the M-CSI is active or not.
Notification flag. The notification flag indicates whether the change of the M-CSI shall trigger a notification on change of subscriber data or not.
