If you liked it, or content was helpful to you please add "+1" to article you used or share it on facebook or so.
Make it easier to find for others who could need those information, allow them find these articles on the spot. But.. it's your call.
Recommendations until now

Feb 15, 2012

IMSI, TMSI and GUTI - how they are created

IMSI, TMSI and GUTI - how they are created | LTE AND BEYOND |Tech-blog on LTE/4G and more..
Last time, in article about Network Attach, many times I was using IMSI, P-TIMSI, GUTI and few more numbers. This time I will try to explain most of them. It's good to know what consist on them, how they are created, and what's the purpose of using them.

As always is good to start with a big picture, that this time, we will start with general description of mentioned above.

Mobile subscribers identification

General information
A unique International Mobile Subscriber Identity (IMSI) shall be allocated to each mobile subscriber in every (GSM, UMTS, and EPS) system. In order to support the subscriber identity confidentiality service the VLRs, SGSNs and MMEs may allocate Temporary Mobile Subscriber Identities (TIMSI) to visiting mobile subscribers. The VLR, SGSN, and MME must be capable of correlating an allocated TIMSI with the IMSI of the Mobile Station (MS) to which it is allocated.
An MS may be allocated three TMSIs, one for services provided through the MSC, one for services provided through the SGSN (P-TIMSI for short) and one for the services provided via the MME (M-TIMSI which is part of GUTI).
For addressing on resources used for GPRS, a Temporary Logical Linkt Identity (TLLI) is used. The TLLI to use is built by the MS either on the basis of the P-TIMSI (local or foreign TLLI), or directly (random TLLI).
In order to speed up the search for subscriber data in the VLR a supplementary Local Mobile Station Identity (LMSI) is defined. The LMSI may be allocated by the VLR at location updating and is sent to the HLR together with the IMSI. The HLR makes no us of it but includes it together with the IMSI in all messages sent to the VLR concerning that MS.