Accessing ip multimedia subsystem

• US 20040146040A1
• Filed: 12/02/2003
• Published: 07/29/2004
• Est. Priority Date: 06/08/2001
• Status: Active Grant

• Current Assignee: INVT SPE LLC (SoftBank Group Corp.)
• Original Assignee: Nokia Corporation
• Inventors: Phan-Anh, Son, Wolfner, Gyorgy, Sugar, Robert
• Granted Patent: US 7,304,966 B2
• Time in Patent Office: Days
• US Class Current: 370/349
• CPC Class Codes: H04L 65/1016 IP multimedia subsystem [IMS]
• CPC Class Codes: H04L 65/1043 Gateway controllers, e.g. media gateway control protocol [MGCP] controllers
• CPC Class Codes: H04L 65/1073 Registration or de-registration
• CPC Class Codes: H04L 65/1104 Session initiation protocol [SIP]
• CPC Class Codes: H04L 67/51 Discovery or management thereof, e.g. service location protocol [SLP] or web services

Abstract

A method and a system for providing access to an IP multimedia subsystem (IMS) for a subscriber roaming in a visited communication network are described. A subscriber equipment determines that a visited network IMS is not accessible and sends a register message for registering to an IMS to a control entity in the home communication network of the subscriber. The control entity recognizes that the register message is received directly from a subscriber equipment, and an access entity for accessing the IMS of the home network is assigned. Then, the control entity sends a message to the subscriber equipment which message comprises the address of the access entity.

Claims

1. A method of providing access to an IP multimedia subsystem (IMS) for a subscriber roaming in a visited communication network, said method comprising the steps of:

determining in a subscriber equipment that a visited network IMS is not accessible;

sending a register message for registering to an IMS from the subscriber equipment to a control entity in the home communication network of the subscriber;

recognizing at the control entity that the register message is received directly from a subscriber equipment;

assigning an access entity for accessing the IMS of the home network;

sending a message from the control entity to the subscriber equipment which message comprises the address of the access entity.

2. A method according to claim 1, further comprising the step of:

initiating an IMS registration by the subscriber equipment towards the access entity using the address of the access entity.

3. A method according to claim 1, wherein the address of the control entity is obtained by the subscriber equipment by using a DNS query.

4. A method according to claim 1, wherein the control entity address is directly hard-coded into the subscriber equipment.

5. A method according to claim 1, wherein the recognizing step comprises the step of:

detecting that a subscriber equipment address is present in the received register message as sending address.

6. A method according to claim 1, wherein the recognizing step comprises the step of:

detecting that mandatory fields set by an access entity in the register message are missing.

7. A method according to claim 1, wherein the assignment of the access entity is initiated by the control entity and the result is conveyed back to the subscriber equipment by the control entity.

8. A method according to claim 1, wherein the messages are SIP messages.

9. A system for providing access to an IP multimedia subsystem (IMS) for a subscriber roaming in a visited communication network, said system comprising:

a subscriber equipment for determining that a visited network IMS is not accessible and sending a register message for registering to an IMS to a control entity in the home communication network of the subscriber,

said control entity being arranged to receive the register message from said subscriber equipment, recognize that the register message is received directly from said subscriber equipment and send a message to said subscriber equipment which message comprises the address of an access entity for accessing the IMS of the home network.

10. A system according to claim 9, wherein said subscriber equipment is further arranged to initiate an IMS registration towards the access entity using the address of the access entity.

11. A system according to claim 9, wherein said subscriber equipment is arranged to perform a DNS queryfor obtaining the address of said control entity.

12. A system according to claim 9, wherein the control entity address is directly hard-coded into the subscriber equipment.

13. A system according to claim 9, wherein said control entity is arranged to detect that a subscriber equipment address is present in the received register message as sending address.

14. A system according to claim 9, wherein said control entity is arranged to detect that mandatory fields set by an access entity are missing in the received register message.

15. A system according to claim 9, wherein said control entity is further arranged to select the access entity.

16. A system according to claim 9, wherein said control entity is further arranged to initiate the assignment of the access entity by a different entity.

17. A system according to claim 9, wherein said control entity is an I-CSCF in the home network IMS of the subscriber.

18. A system according to claim 9, wherein the access entity is a P-CSCF in the home network IMS of the subscriber.

19. A subscriber equipment in a system for providing access to an IP multimedia subsystem (IMS) for a subscriber roaming in a visited communication network, said subscriber equipment being arranged to determine that a visited network IMS is not accessible, send a register message for registering to an IMS to a control entity in the home communication network of the subscriber and receive a message from said control entity which message comprises the address of an access entity for accessing the IMS of the home network.

20. A subscriber equipment according to claim 19, being further arranged to initiate an IMS registration towards the access entity using the address of the access entity.

21. A subscriber equipment according to claim 19, being arranged to perform a DNS query for obtaining the address of said control entity.

22. A subscriber equipment according to claim 19, having the control entity address directly hard-coded.

23. A control entity in a system for providing access to an IP multimedia subsystem (IMS) for a subscriber roaming in a visited communication network, said control entity being arranged to receive a register message for registering to an IMS from a subscriber equipment, recognize that the register message is received directly from said subscriber equipment and send a message to said subscriber equipment which message comprises the address of an access entity for accessing the IMS of the home network of the subscriber.

24. A control entity according to claim 23, being located in the home communication network of the subscriber.

25. A control entity according to claim 23, further being arranged to detect that a subscriber equipment address is present in the received register message as sending address.

26. A control entity according to claim 23, further being arranged to detect that mandatory fields set by an access entity are missing in the received register message.

27. A control entity according to claim 23, being further arranged to select the access entity.

28. A control entity according to claim 23, further being arranged to initiate the assignment of the access entity by a different entity.

29. A control entity according to claim 23, being an I-CSCF in the home network IMS of the subscriber.