Method and apparatus for enabling roaming of subscriber among plural mobile radio systems, using mobile equipment accepting removable subscriber identity module

• US 5,675,628 A
• Filed: 08/01/1994
• Issued: 10/07/1997
• Est. Priority Date: 08/01/1994
• Status: Expired due to Term

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Telecommunications Oy (Nokia Corporation)
• Inventors: Hokkanen, Petri
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): TROST IV, WILLIAM GEORGE
• Application Number:
  US08/285,123
• Time in Patent Office: 1,163 Days
• Field of Search: 379/58, 379/59, 379/60, 379/62, 379/356, 379/357, 455/33.1, 455/33.2, 455/33.4, 455/54.1, 455/54.2, 455/56.1
• US Class Current: 455/433
• CPC Class Codes: H04L 63/0414 during transmission, i.e. party's identity is protected against eavesdropping, e.g. by using temporary identifiers, but is known to the other party or parties involved in the communication
• CPC Class Codes: H04W 12/06 Authentication
• CPC Class Codes: H04W 12/75 Temporary identity
• CPC Class Codes: H04W 48/18 Selecting a network or a communication service
• CPC Class Codes: H04W 8/183 Processing at user equipment or user record carrier
• CPC Class Codes: H04W 8/205 Transfer to or from user equipment or user record carrier
• CPC Class Codes: H04W 8/26 Network addressing or numbering for mobility support
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals

Abstract

A subscriber identification module (SIM) for storing user-identities and other user specific information and thereby enabling access to the service of the radio system. One of the user identities is a Temporary Mobile Subscriber Identity (TMSI) used for user anonymity purposes by utilizing the TMSI as an alias for the actual user identity in order to avoid sending the actual user identity in the clear on the radio path. A part of the TMSI is a random number which cannot be used to identify the user/terminal without mapping information to the actual user identity, which is found in the telecommunications network entity that allocated the random number. SIM roaming from one radio system to another is possible by utilizing predetermined bits of TMSI to differentiate between different TMSI'"'"'s of different systems by indicating in a uniform manner in all mobile radio systems the mobile radio system which has allocated the TMSI. The remaining bit locations of the TMSI provided in a mobile radio system-specific format. During an inter-system SIM roaming, the old TMSI will be copied from SIM and forwarded to a new mobile radio system. The new system will use the predetermined bits of the TMSI to identify the old system in order to request the actual user identity.

Claims

1. An inter-system roaming method, comprising the steps of:

allocating a temporary mobile subscriber identity for a mobile subscriber in a first mobile radio system having a first radio interface, including indicating the identity of said mobile radio system in predetermined bit locations in said temporary mobile subscriber identity in a system-independent format,

sending said temporary mobile subscriber identity to a first mobile station of said mobile subscriber, said mobile station comprising a removable subscriber identification module for storing data related to an identification and authentication of a mobile subscriber, as well as a first mobile equipment capable of operating in said first mobile radio system,

storing said temporary mobile subscriber identity in a predetermined storage location in said removable subscriber identification module,

removing said mobile subscriber identification module from said first mobile station,

inserting said mobile subscriber identification module in a second mobile station comprising a second mobile subscriber equipment capable of operating in a second mobile radio system having a second radio interface,

copying said temporary mobile subscriber identity from said mobile subscriber identification module to said second mobile subscriber equipment,

sending said temporary mobile subscriber identity to a fixed network of said second mobile radio system,

analyzing said predetermined bit locations in said temporary mobile subscriber identity in order to find said identity of said first mobile radio system, and

requesting an actual identity of said mobile subscriber from said first mobile radio system according to said identity of said first mobile radio system as found by said analyzing, and said temporary mobile subscriber identity.

2. Roaming method as claimed in claim 1, wherein said step of allocating said temporary mobile subscriber identity is performed by a visitor location register in said first mobile radio system.

3. Roaming method as claimed in claim 1, wherein said steps of analyzing and requesting are performed by a visitor location register in said second mobile radio system.

4. A mobile radio system, comprising:

a mobile exchange,

a plurality of mobile stations each including a removable subscriber identification module for storing data related to an identification and authentication of a mobile subscriber, as well as a first mobile equipment capable of operating in said mobile radio system, and

a visitor location register, including;

means for allocating temporary mobile subscriber identities for mobile subscribers in said mobile radio system, an identity of said mobile radio system being indicated in predetermined bit locations in said temporary mobile subscriber identity in a, system-independent format,

means for analyzing said predetermined bit locations in a temporary mobile subscriber identity received from a mobile station in order to find an identity of a mobile radio system which has allocated the temporary mobile subscriber identity, and

means for requesting an actual identity of said mobile subscriber from a mobile radio system which has allocated said temporary mobile subscriber identity according to said identity of said analyzed first mobile radio system identity and said temporary mobile subscriber identity.