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MIN-based IMSI to TRUE IMSI Transitioning Proposal

MIN-based IMSI to TRUE IMSI Transitioning Proposal. Alain Bouvier & Hanan Ahmed alain.bouvier@ericsson.com hanan.ahmed@ericsson.com CDG International Roaming Team Meeting Boca Raton, FL, June 23-24, 2005. Table of Content. Definitions; IRM Exhaustion; IS-751:

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MIN-based IMSI to TRUE IMSI Transitioning Proposal

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  1. MIN-based IMSI to TRUE IMSI Transitioning Proposal Alain Bouvier & Hanan Ahmed alain.bouvier@ericsson.comhanan.ahmed@ericsson.com CDG International Roaming Team Meeting Boca Raton, FL, June 23-24, 2005

  2. Table of Content • Definitions; • IRM Exhaustion; • IS-751: • Upgrade Scheduling Constraints; • Backward Compatibility; • MIN-based versus True IMSI; • IMSI Discrimination: • Current Status; • MSID Numbering Plan Escape Code; • Migration Proposal: • Overview; • MSC/VLR Upgrade; • HLR/AC Upgrade; • MC/OTAF and SCP Upgrade; • Other Considerations; • Ericsson’s Roadmap; • Conclusion. TAKING YOU FORWARD

  3. Definition - IMSI • The IMSI (International Mobile Station Identity) is defined by the ITU-T Recommendation E.212. (referred to as IMSI_T in IS-95B and IS-2000). MCC MNC MSIN 3 digits 1-3 digits NMSI IMSI (<= 15 digits) MCC MNC MSIN NMSI IMSI Mobile Country Code Mobile Network Code Mobile Station Identification Number National Mobile Station Identity International Mobile Station Identity

  4. Definition - MIN-based IMSI • An IMSI using the lower 10 digits of the NMSI to store the MIN/IRM (Introduced in IS-95B as IMSI_M); MCC MNC MIN/IRM 3 digits 2 digits 10 digits MIN-based IMSI (15 digits) MCC MNC MIN IRM Mobile Country Code Mobile Network Code Mobile Identification Number International Roaming MIN

  5. Definition - MIN/IRM • The MIN is a 10-digit number that traditionally has been identical to the domestic Mobile Directory Number (MDN) and is defined in ANSI/EIA/TIA-553 (AMPS); • The IRM (International Roaming MIN) is a MIN adhering to the following format: • 0-XXX+6d or 1-XXX+6d (2000 IRM Network Ids); • NXX-0+6d or NXX-1+6d (1600 IRM Network Ids); The 4-digit prefix is allocated by the IFAST to facilitate international roaming by minimizing conflicts with North American MINs. The last 6 digits are allocated by the carriers.

  6. Definition - Numbering Plan Escape Code • NP Escape code: "An escape code is an indicator consisting of one or more digits which is defined in a given Numbering Plan and is used to indicate that the digits that follow are from a specific Numbering Plan which is different from the given Numbering Plan. For example, escape codes are currently used with the X.121 numbering plan to inter-work with E.164 (ISDN) and F.69 (Telex) numbering plans. An escape code can be carried forward through the originating network and can be carried across inter-network and international boundaries. Therefore, the digits used for escape codes should be standardized.“ Source:ITU-T Recommendation E.160 "Definitions Relating to National and International Numbering plans".

  7. Definition - MSID NP Escape Code • MSID NP Escape code: In the Mobile Identification context, an escape code is an indicator consisting of three to five digits which is defined in a given MSID Numbering Plan and is used to indicate that the digits that follow are from a specific MSID NP which is different from the given MSID NP. For example, mobile stations are assigned an IMSI number as per the IMSI MSID NP (i.e. the E.212 NP). For that MSID NP, the last 10 digits represent the last 10 digits of the IMSI number. By defining three to five digits indicators, the last ten digits of the IMSI can now be interpreted as the MIN/IRM as per the MIN-based MSID NP (i.e. MCC - MNC - MIN/IRM).

  8. IRM Exhaustion - % IRM Used Source:IRM Administrator’s Report (March 29th, 2005)

  9. After Expansion IRM Exhaustion - % IRM Used Source:IRM Administrator’s Report (March 29th, 2005)– June figure added!

  10. IRM Exhaustion - Conclusion • Without the expanded IRM codes range, the IRM code utilization would have been at 90%! Currently at 50% utilization, there is a reasonable amount of available IRM codes although it is not possible to get contiguous blocks of codes from the new range; • There are too many variables to predict when the IRM codes will be exhausted. For example: • If UPS discontinues its current system based on AMPS data transfer, 100 IRM code ranges would be returned - almost 3%; • The phasing out of certain technologies may return additional IRM code ranges; • China Unicom, KDDI and SK Telecom may have enough codes for the next 5 years considering the current IRM codes allocation status; • IRM code splitting can spare some codes. We will probably be okay for the next 5 years, but there is no guarantee. What is certain is that IRM codes won't last forever. Source:David Crowe, IFAST administrator.

  11. This constraint does not apply to CDMA since all accesses already use the IMSI. These constraints do not apply when using certain vendor’s MSC. IS-751 - Upgrade Scheduling Constraints Upgrade AC (if required) Program MS with IMSI Upgrade HLR Note:This constraint can be avoidedif a pseudo-IMSI is used and the serving system can recognize this situation and substitute MIN in IS-41 messages. Upgrade MC Allow term. to SME using IMSI Upgrade VLR Upgrade MSC Allow BS to accept access using IMSI Upgrade neighbor MSC Allow IMSI on E-Int. for HO/Inter-MSC paging

  12. IS-751 - Backward Compatibility • A Serving, Border or Anchor System sends the IMSI towards an MS's HLR if it is received from the MS, unless the received IMSI is recognized as a MIN-based IMSI; • A Serving, Border or Anchor System must be able to identify a MIN-based IMSI and treat the 10 (ten) least significant digits from that IMSI as the MS's MIN and include the “MobileIdentificationNumber”parameter in messages sent to the MS's Home System's HLR or in other messages in which that parameter should be included if the MIN is known.

  13. IS-751 - MIN-based versus True IMSI • IS-751 defines a method to identify a MIN-based IMSI: • An IMSI of the form MCC+00+10D shall be recognized as a potential MIN-based IMSI; • A number shall be recognized as a MIN-based IMSI if the MCC is one that has been designated by the associated country's numbering authorities for this use (since most countries are only assigned one MCC by the ITU-T, this is not be a viable method); • An IMSI of the form 000+00+10D should also be treated as a MIN-based IMSI.

  14. IS-751 - Conclusion • A Serving, Border or Anchor System must be able to identify a MIN-based IMSI when received in a message from the RAN; • The IS-751 proposed method to identify a MIN-based IMSI is not viable since most countries are only assigned 1 (one) MCC; • In order to fully support True IMSI subscriptions, the MSC, VLR, HLR, AC and MC should comply to the IS-751 Recommendation (“TIA/EIA-41-D Modifications to support IMSI”);

  15. IMSI Discrimination - Current Status • Both MIN-based IMSI and True IMSI can be used to identify a mobile subscriber; • IMSI is used to identify the mobile subscriber in the Radio Access Network (RAN) while the MIN/IRM is used to identify the subscriber in the IS-41 network. RAN IS-41 IMSI MIN/IRM MSC/VLR

  16. Regulated by independent countries and operators NO AGREEMENT Regulated by IFAST. IMSI Discrimination - Current Status (cont…) • Most (probably all) Serving, Border or Anchor Systems assume that the IMSI received from the RAN is a MIN-based IMSI (i.e. the MIN/IRM is represented by the last 10 (ten) digits of the received IMSI). In such Systems, True IMSI roamers can not be guaranteed service because of a potential clash with the last 10 (ten) digits of a MIN-based IMSI number. MCC MNC MSIN MCC MNC MIN/IRM : 1 to 3 Digits

  17. IMSI Discrimination - Current Status (cont…) • IS-751 does not provide a viable method for a Serving, Border or Anchor System to guarantee that an IMSI received from the RAN is a MIN-based IMSI or a True IMSI; RAN IS-41 IMSI ? MSC/VLR

  18. ESC Code 3 to 5 Digits IMSI Discrimination - MSID NP Escape Code • During the MIN-based to True IMSI transitioning period, the existing CDMA networks must support both types of IMSI. In order to achieve that, the MSC must be able to discriminate the IMSI type (MIN-based or True). This can be accomplished by introducing the concept of Escape Code. True IMSI MCC MNC MSIN MIN-based IMSI MCC MNC MIN/IRM : 1 to 3 Digits

  19. IMSI Discrimination - MSID NP Escape Code (cont…) • The following is proposed: • The MSID Numbering Plan Escape Code is to be used by the Serving, Border or Anchor System to identify the IMSI type (MIN-based or True). In other words, the MIN-based IMSI and True IMSI number series should be identified by Escape Codes; • Escape Codes are to be managed by the carriers; • Escape Codes are to be made known to roaming partners.

  20. IMSI Discrimination - MSID NP Escape Code (cont…) • The MSC support for an IMSI Type discrimination mechanism is key in providing a smooth migration for all carriers. RAN IMSI or MIN/IRM IS-41 IMSI MSC

  21. Migration Proposal - Overview • The MSC/VLR should be upgraded first for the following reasons: • The MSC plays a key role in providing simultaneous support for IMSI and MIN-based IMSI mobile stations; • Upgrading the MSC/VLR to support IMSI Type discrimination allows an operator to provide access service to True IMSI inbound roamers (may require adjustments to relevant systems i.e. Charging System); • Roaming partners must review their roaming agreements to include MSID NP Escape Codes. When no Escape Code is available, MIN-based IMSI is assumed for backward compatibility reasons; • The HLR/AC should be upgraded next in preparation to support True IMSI subscriptions; • The Service Nodes (i.e. MC/OTAF and SCP) should then be upgraded to provide full service to IMSI subscriptions; • A Subscription Migration Plan should be defined for existing subscribers.

  22. MC HLR/AC HLR/AC MC MSC/VLR MSC/VLR IMSI MIN/IRM IMSI MIN/IRM MIN-based IMSI Network True IMSI Network IMSI MIN/IRM Migration Proposal - MSC/VLR HLR/AC MSC/VLR capable of handling both MIN-based and true IMSI MC/OTAF IMSI MIN/IRM

  23. CD Service [IMSI] Term. Service [IMSI] Orig. Service [IMSI] SCP HLR MSC/VLR MC/OTAF Migration Proposal - MSC/VLR (cont…) IMSI[A]-to-IMSI[B] – MINb[ServA]-&-MINb[ServB] MIN-based IMSI Operator MIN-based IMSI Operator Call Set-up A B MSC/VLR STP STP MSC/VLR ORIGINATION TERMINATION A SUB. HOME B SUB. HOME SCP HLR MSC/VLR True IMSI Operator True IMSI Operator MC/OTAF CD: Call Delivery

  24. SCP HLR MSC/VLR MSC/VLR STP STP MSC/VLR CD Service [MIN/IRM] Term. Service [MIN/IRM] Orig. Service [MIN/IRM] MC/OTAF SCP HLR MSC/VLR MC/OTAF Migration Proposal - MSC/VLR (cont…) MINb[A]-to-MINb[B] – IMSI[ServA]-&-IMSI[ServB] True IMSI Operator True IMSI Operator Call Set-up A B ORIGINATION TERMINATION A SUB. HOME B SUB. HOME IMSI MIN/IRM MIN-based IMSI Operator MIN-based IMSI Operator CD: Call Delivery

  25. MSC/VLR STP STP MSC/VLR CD Service [IMSI] Term. Service [IMSI] Orig. Service [MIN/IRM] SCP SCP HLR HLR MSC/VLR MSC/VLR MC/OTAF MC/OTAF Migration Proposal - MSC/VLR (cont…) MIN[A]-to-IMSI[B] – MINb[ServA]-&-IMSI[ServB] True IMSI Operator MIN-based IMSI Operator Call Set-up ORIGINATION TERMINATION A SUB. HOME B SUB. HOME MIN-based IMSI Operator True IMSI Operator CD: Call Delivery

  26. SCPs HLR MCs/OTAF Migration Proposal - HLR/AC Upgrade • The HLR/AC nodes are upgraded in preparation to support IMSI subscriptions; • All services must be madeavailable to True IMSIsubscriptions beforeprovisioning newsubscribers ormigrating existingsubscribers. STP IMSI RAN MSC/VLR

  27. Migration Proposal - MC/OTAF and SCP Upgrade • Service nodes are upgraded and made available for true IMSI subscriptions; • At this stage, the CircuitSwitched Core andService networks areready for theprovisioning ofnew subscribersor the migration ofexisting subscribers. SCPs STP IMSI RAN HLR MSC/VLR MCs/OTAF

  28. Other Considerations • Handset Provisioning - New and Existing subscriptions; • Charging System; • Other Systems (e.g. Mobile Positioning System); • GT Routing;“Global title routing has been implemented to some extent in GSM, but hardly at all in TIA/EIA-41 networks. GSM has attempted to simplify the usage of GT by using phone numbers according to ITU-T recommendation E.164 as their only global title. This requires mapping from E.212 IMSI to E.164 that breaks down in the North American Numbering Plan where numerous MCCs (e.g. 302 for Canada, 310-316 for the US, and 330-376 for the Caribbean) map onto a single E.164 country code (“1”). The ITU-T specified mapping between these country codes (E.214) assumes a 1:1 correspondence between MCC and CC.”For CDMA,Global Title Translation should be performed on the E.212 number. Not on the E.214 number.

  29. Ericsson’s Roadmap • Ericsson could support MIN-based IMSI to True IMSI transitioning depending on customer's requirements.

  30. Conclusion • A 3 (three) to 5 (five) digits Escape Code should be used by the Serving, Border or Anchor System to identify the IMSI type (MIN-based or True); • Global Title Translation should be performed on the full IMSI (E.212) even for MIN-based IMSI mobile stations (i.e. no translation on MIN/IRM); • To provide guidance to CDMA operators wishing to use True IMSI as mobile identities, CDG should publish a “True IMSI Migration Guideline.

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