IMSI analysis is the process of examining a subscriber's IMSI to identify the network the IMSI belongs to, and whether subscribers from that network may use a given network (if they are not local subscribers, this requires a roaming agreement). If the subscriber is not from the provider's network, the IMSI must be converted to a Global Title, which can then be used for accessing the subscriber's data in the remote
HLR. This is mainly important for international mobile
roaming. Outside North America, the IMSI is converted to the Mobile Global Title (MGT) format, standard
E.214, which is similar to an
E.164 number.
E.214 provides a method to convert the IMSI into a number that can be used for routing to international
SS7 switches. E.214 can be interpreted as implying that there are two separate stages of conversion; first determine the MCC and convert to E.164
country calling code then determine MNC and convert to national network code for the carrier's network. But this process is not used in practice and the GSM numbering authority has clearly stated that a one-stage process is used . In North America, the IMSI is directly converted to an E.212 number with no modification of its value. This can be routed directly on American SS7 networks. After this conversion,
SCCP is used to send the message to its final destination. For details, see
Global Title Translation.
Example of outside World Area 1 This example shows the actual practice which is not clearly described in the standards. Translation rule: • match numbers starting 28401
(Bulgaria mobile country code + MobilTel MNC) • identify this as belonging to MobilTel-Bulgaria network • remove first five digits
(length of MCC+MNC) • prepend 35988 ''(Bulgaria
E.164 country code + a Bulgarian local prefix reaching MobilTel's network)'' • mark the number as having E.214 numbering plan. • route message on
Global Title across SCCP network Therefore, 284011234567890 becomes 359881234567890 under the E.214 numbering plan. Translation rule: • match numbers starting 310150
(America first MCC + Cingular MNC) • remove first
six digits
(length of MCC+MNC) • prepend 14054
(North America E.164 country code + Network Code for Cingular) • mark the number as having E.214 numbering plan. • route message on
Global Title across SCCP network Therefore, 310150123456789 becomes 14054123456789 under the E.214 numbering plan. The result is an E.214 compliant Global Title, (
Numbering Plan Indicator is set to 7 in the SCCP message). This number can now be sent to Global Title Analysis.
Example inside World Area 1 (North America) Translation rule: • match number starting 28401
(Bulgaria MCC + MobilTel MNC) • identify this as belonging to MobilTel-Bulgaria network • do not alter the digits of the number • mark the number as having E.212 numbering plan. • route message on
Global Title across SCCP network Therefore, 284011234567890 becomes 284011234567890 under the E.212 numbering plan. This number has to be converted on the ANSI to ITU boundary. For more details please see
Global Title Translation. == Home Network Identity ==