IMS to CS Handover for IMS Systems for Legacy CS UE with Home Node B Access

• US 20100074224A1
• Filed: 09/17/2009
• Published: 03/25/2010
• Est. Priority Date: 09/18/2008
• Status: Active Grant

• Current Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Futurewei Technologies Incorporated (Huawei Investment & Holding Co., Ltd.)
• Inventors: Zhang, Zhaohui, Mahdi, Kaniz
• Granted Patent: US 8,830,953 B2
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04W 36/00226 wherein the core network technologies comprise IP multimedia system [IMS], e.g. single radio voice call continuity [SRVCC]
• CPC Class Codes: H04W 76/10 Connection setup
• CPC Class Codes: H04W 76/30 Connection release
• CPC Class Codes: H04W 84/045 using private Base Stations, e.g. femto Base Stations, home Node B

Abstract

A system and method for allowing legacy circuit switch user equipment (CS UE) to operate via a packet switch system, such as an IP Multimedia Subsystem (IMS) system, is provided. The mobility and session control aspects of communications with the legacy CS UE is separated. A user agent is placed in the receiving node (e.g., a home node B) that acts as the SIP agent for the CS UE for session control. An interworking function is provided to allow mobility between the macro CS network and the PS (e.g., IMS) network. Hand-back and hand-in procedures with service continuity are also provided.

Claims

1. A method for performing wireless communications, the method comprising:

facilitating a communications session extending between a user equipment (UE) and a remote end, the communications session including a circuit-switched (CS) communications path with the UE;

determining a service state of the communications session; and

transmitting a first message, the first message indicating the service state of the communications session and a home node B (HNB) indicator, the HNB indicator identifying sessions originally established with an HNB.

2. The method of claim 1, wherein the transmitting is performed by the HNB.

3. The method of claim 1, wherein the service state indicates that the communications session is in a held state.

4. The method of claim 1, wherein the service state indicates that the communications session is in an active state.

5. The method of claim 1, wherein the transmitting is performed in response to determining a handover is required to a 2G network.

6. The method of claim 1, further comprising handing over the CS communications path with the UE to a base station system (BSS).

7. A method for performing wireless communications, the method comprising:

establishing a communications session between a user equipment (UE) and a remote end, the communications session including a first communications path extending between the UE, a Home Node B (HNB), and the remote end;

handing the communications session over from the first communications path to a second communications path extending between the UE, the HNB, a Media Gateway (MGW), and the remote end; and

handing the communications session over from the second communications path extending between the UE, a base station system (BSS), a mobile switching center (MSC), the MGW, and the remote end.

8. The method of claim 7, wherein the handing the communications session over from the first communications path to the second communications path includes providing by the HNB service state information.

9. The method of claim 7, wherein the handing the communications session over from the first communications path to the second communications path includes providing by the HNB a session transfer identifier.

10. The method of claim 7, wherein the handing the communications session over from the first communications path to the second communications path includes providing by the HNB an HNB indication.

11. The method of claim 7, wherein the UE attaches to the HNB via a circuit-switched communications path.

12. The method of claim 7, wherein the second communications path includes a circuit-switched bearer path between the MGW and the HNB.

13. A method for performing wireless communications, the method comprising:

establishing a first session between user equipment (UE) and a first remote end via an IP multimedia system (IMS) network, the first session being in an active state;

establishing a second session between the UE and a second remote end via the IMS network, the second session being in a hold state;

communicating a request to an inter-working function (IWF) for handover from the IMS network to a circuit switch (CS) network;

establishing a CS bearer channel between the UE and the CS network;

handing the first session over to the CS network, the first session remaining in the active state; and

handing the second session over to the CS network, the second session remaining in the hold state.

14. The method of claim 13, wherein the request comprises an Initial UE message, a Setup message, and a Relocation Required message sent from a home node B (HNB) to the IWF.

15. The method of claim 14, wherein the Initial UE message and the Setup message are communicated via a NAS PDU IE.

16. The method of claim 13, wherein the request comprises a multi-purpose message having a parameter indicating handover is requested.

17. The method of claim 13, wherein the request comprises a message type indicating handover is requested.