System and method for circuit switched fallback in IMS centralized services

Patent metadata

Field	Value
Publication number	US-10341906-B2
Application number	US-201715727734-A
Country	US
Kind code	B2
Filing date	Oct 9, 2017
Priority date	Apr 30, 2015
Publication date	Jul 2, 2019
Grant date	Jul 2, 2019

Abstract

A method of performing CSFB in an IMS comprises receiving, at a TAS, an incoming voice call for a UE attached to an EPS; paging the UE by the first ICS GW; receiving, by a second ICS GW associated with a second CS RAN currently connected to the UE, a Location Update message from the UE, the Location Update message containing a first CSFB indicator; transmitting, by the second ICS GW, a Registration message to the TAS, the Registration message containing a second CSFB indicator in response to the first CSFB indicator in the Location Update message; transmitting, by the TAS, a Cancel message to the first ICS GW; and transmitting, by the TAS, an Invite message to the second ICS GW to complete the voice call with the UE.

First claim

What is claimed is:

1. A method of performing Circuit Switched Fallback (CSFB) in an IP Multimedia Subsystem (IMS), comprising:
receiving, at a Telephony Application Server (TAS), an incoming voice call for a User Equipment (UE) attached to an Evolved Packet Subsystem (EPS);
transmitting, by the TAS, an Invite message to a first network node associated with a first Circuit Switched Radio Access Network (CS RAN) connected to the UE;
paging the UE by the first network node;
receiving, by a second network node associated with a second CS RAN currently connected to the UE, a Location Update message from the UE, the Location Update message containing a first CSFB indicator;
transmitting, by the second network node, a Registration message comprising an IMS Registration message to the TAS, the Registration message containing a second CSFB indicator in response to the first CSFB indicator in the Location Update message;
transmitting, by the TAS, a Cancel message to the first network node, after the step of transmitting the Registration message; and
transmitting, by the TAS, an Invite message to the second network node to complete the voice call with the UE.

2. The method of claim 1 , wherein transmitting, by the TAS, an Invite message to a first network node comprises transmitting an Invite message to a ICS GW associated with the first CS RAN.

3. The method of claim 1 , wherein receiving, by a second network node a Location Update message from the UE comprises receiving, by an ICS GW the Location Update message containing the first CSFB indicator from the UE.

4. The method of claim 1 , wherein transmitting, by the second network node, a Registration message to the TAS, comprises transmitting, by an ICS GW, the Registration message containing a second CSFB indicator to the TAS.

5. The method of claim 1 , wherein transmitting a Registration message by the second network node comprises transmitting a Registration message having a unique reg-id to avoid the Registration message from the second network node to overwrite a previous IMS registration from the first network node.

6. The method of claim 1 , wherein transmitting a Registration message comprises transmitting a Registration message having a new SIP header to indicate a CSFB call.

7. The method of claim 1 , wherein transmitting a Registration message comprises transmitting a Registration message having a pre-existing message parameter to indicate a CSFB call.

8. The method of claim 1 , wherein transmitting a Location Update message comprises transmitting a Location Update message having a pre-existing message parameter to indicate a CSFB call.

9. A method of performing Circuit Switched Fallback (CSFB) in an IP Multimedia Subsystem (IMS), comprising:
receiving, at a Telephony Application Server (TAS), an incoming voice call for a User Equipment (UE) attached to an Evolved Packet Subsystem (EPS);
transmitting, by the TAS, an Invite message to a first network node associated with a first Circuit Switched Radio Access Network (CS RAN) connected to the UE;
paging the UE by the first network node;
receiving, by a second network node associated with a second CS RAN currently connected to the UE, a Location Update message from the UE, the Location Update message containing a first CSFB indicator;
transmitting, by the second network node, a Registration message to the TAS, the Registration message containing a second CSFB indicator in response to the first CSFB indicator in the Location Update message;
transmitting, by the TAS, a Cancel message to the first network node; and
transmitting, by the TAS, an Invite message to the second network node to complete the voice call with the UE;
wherein transmitting, by the TAS, an Invite message to a first network node comprises transmitting an Invite message to a MSC/VLR associated with the first CS RAN.

10. A method of performing Circuit Switched Fallback (CSFB) in an IP Multimedia Subsystem (IMS), comprising:
receiving, by a gateway network node associated with a Circuit Switched Radio Access Network (CS RAN) currently connected to a User Equipment (UE), a first message to update its location from the UE containing a first CSFB indicator;
transmitting, by the current gateway network node, a second message comprising an IMS Registration message to register the UE to an application server node handling an incoming voice call for the UE, the second message containing a second CSFB indicator in response to the first CSFB indicator in the first message;
transmitting, by the application server node, a third message to a prior gateway network node associated with a prior CS RAN previously connected to the UE to cancel a prior pending invite request in response to the second CSFB indicator in the second message; and
transmitting, by the application server node, a fourth message to the current gateway network node to complete the voice call with the UE.

11. The method of claim 10 , wherein transmitting an IMS Registration message comprises transmitting an IMS Registration message having a unique reg-id assigned to avoid the IMS Registration message from the current gateway network node to overwrite a previous IMS registration from the prior gateway network node.

12. The method of claim 10 , wherein transmitting an IMS Registration message comprises transmitting an IMS Registration message having a new SIP header.

13. The method of claim 10 , wherein transmitting an IMS Registration message comprises transmitting an IMS Registration message having a pre-existing message parameter to indicate a CSFB call.

14. The method of claim 10 , wherein transmitting a Location Update message comprises transmitting a Location Update message having a pre-existing message parameter to indicate a CSFB call.

15. A non-transitory computer-readable medium having encoded therein a method of performing Circuit Switched Fallback (CSFB) in an IP Multimedia Subsystem (IMS), the method comprising:
receiving, by a first network node associated with a current Circuit Switched Radio Access Network (CS RAN) connected to a User Equipment (UE), a Location Update message from the UE containing a first CSFB indicator;
transmitting, by the first network node, a Registration message comprising an IMS Registration message to a Telephony Application Server (TAS) handling an incoming voice call for the UE, the Registration message containing a second CSFB indicator in response to the first CSFB indicator in the Location Update message;
transmitting, by the TAS, a Cancel message to a second network node associated with a prior CS RAN previously connected to the UE in response to the second CSFB indicator in the Registration message; and
transmitting, by the TAS, an Invite message to the first network node to complete the voice call with the UE.

16. The method of claim 15 , wherein receiving, by a first network node associated with a current Circuit Switched Radio Access Network (CS RAN) connected to a User Equipment (UE), a Location Update message comprises receiving, by a current IMS Centralized Services Gateway (ICS GW) associated with a current Circuit Switched Radio Access Network (CS RAN) connected to a User Equipment (UE), a Location Update message containing the first CSFB indicator from the UE.

17. The method of claim 15 , wherein transmitting, by the first network node, a Registration message to a Telephony Application Server (TAS) comprises transmitting, by a current IMS Centralized Services Gateway (ICS GW), a Registration message to a Telephony Application Server (TAS) handling an incoming voice call for the UE, the R

Assignees

• Mavenir Systems Inc

Inventors

• Wallis Michael Brett
• Chen Dan

Classifications

• H04L65/1073

  Registration or de-registration · CPC title

• H04L65/1063

  Application servers providing network services (systems providing special services to telephonic subscribers H04M3/42) · CPC title

• H04W80/10

  adapted for {application} session management, e.g. SIP [Session Initiation Protocol] {(connection management H04W76/00; arrangements for session management H04L67/14)} · CPC title

• H04W8/06

  Registration at serving network Location Register, VLR or user mobility server · CPC title

• H04L65/1006

  Electricity · mapped topic