DetermineRoamingFromHlr

Note: The default values for both RoamingStatus and RoamingIndicator are UNKNOWN and false respectively. If this feature is unable to determine the roaming status for any reason, it will leave the pre-set values.

The feature uses configuration data from the HLR MAP Configuration, the SIP Sentinel Configuration and the Determine International and Roaming Status Configuration.

DetermineRoamingFromHlr statistics are tracked by the DetermineRoamingFromHlr feature and can be found under the following parameter set:
SLEE-Usage ▶ sentinel.volte.sip service ID ▶ sentinel.volte.sip SBB ID ▶ DetermineRoamingFromHlr.

This feature uses the CGIN MAP RA to query the HLR with an ATI for subscriber location information.

Each time the feature is invoked, it checks the call type and determines the subscriber number that it should use to query the HLR.

When invoked on a SIP response the feature checks whether a request to the HLR has not already been made and whether there is an OC-Terminating-Domain present in the SIP responses with value CS. If either is not the case then the feature finishes execution.

The feature attempts to extract "phone number digits" from the CMSISDN session state field set by FetchCMSISDN, and if it cannot, from the Subscriber field set by SubscriberDetermination. If the feature cannot form a MSISDN it raises a Feature Error and finishes execution.

The feature then requests subscriber location info by sending a AnyTimeInterrogation request to the configured HLR.

In order to form the ATI request the feature:

If a successful result is received, it retrieves location information from the ATI result. The location information can be in either of the CellGlobalIdOrServiceAreaIdFixedLength or LaiFixedLength fields. If neither field is present, the feature increments the RoamingDataMissingFromHlrResponse stat. It will then check whether the MAPLocationInformation contains an MSC number, and if so, it will write this to the session state field SubscriberLocationMscAddress.

If the location information is found, the MCC and MNC are evaluated using the PLMN ID Analyser Component to determine whether the subscriber is roaming or not. If the fallbackToISOCCRoamingIdentification field of the Determine International and Roaming Status Configuration table is set to true and the PLMN ID Analyser finds that the MCC does not match the home MCC, then the feature falls back to an ISO CC comparison. If the home and visited ISO CCs match then the RoamingStatus is set to NATIONAL and the RoamingIndicator is set to false. If the ISO CCs do not match then the RoamingStatus is set to INTERNATIONAL and the RoamingIndicator is set to true. If the fallbackToISOCCRoamingIdentification field is set to false then mismatching MCCs immediately sets RoamingStatus to INTERNATIONAL. When the MCCs do match the MNCs are compared by the PLMN ID Analyser Component and the RoamingStatus and RoamingIndicator session state fields are set accordingly. The default values of RoamingStatus and RoamingIndicator in the case of incomplete information or feature failure are UNKNOWN and false respectively.

If found, the location information is also used to generate a discovered network access information. If no other access network information is available, this will be used in charging content AVPs. The format for the generated information is 3GPP-GERAN;cgi-3gpp=<cgi>;network-provided, where <cgi> is the Cell Global ID, made up of the MCC, MNC, Location Area Code (in hex) and Cell Id (in hex) concatenated. If the Cell Id is not provided by the HLR, it will default to 0000.