!!! Overview
[{$pagename}] ([TMSI]) is an [Pairwise Pseudonymous Identifier] with the [International Mobile Subscriber Identity] ([IMSI]) assigned by the [Visitor Location Register] ([VLR]) to every [Mobile Device] in the area when it joins[{$pagename}] is assigned by the [Visitor Location Register] upon the [Mobile Device] presenting the [International Mobile Subscriber Identity]

[{$pagename}] is local to a location area and has to be updated each time the mobile moves to a new geographical ([Visitor Location Register]) area.[{$pagename}] can be changed by the [Mobile Network] at any time and typically would to avoid the subscriber from being identified. [{$pagename}] is a part of the ability for "Paging" or [Peer-to-peer] communication between the [Mobile Device] and another [Mobile Network Operator]. The most important use of broadcast information is to set up channels for "paging". Every cellular system has a broadcast mechanism to distribute such information to a plurality of mobiles.

Size of TMSI is 4 octet with full hex digits and can't be all FF because the SIM uses 4 octets with all bits equal to 1 to indicate that no valid TMSI is available.[1]

!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]