Method and apparatus in a wireless communication system for facilitating a handoff

• US 20050047435A1
• Filed: 08/29/2003
• Published: 03/03/2005
• Est. Priority Date: 08/29/2003
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Hirsbrunner, Alex P., Belkin, Anatoly S., Idnani, Ajaykumar, Segal, Niranjan N., Pierce, Jennifer
• Granted Patent: US 7,155,225 B2
• Time in Patent Office: Days
• US Class Current: 370/466
• CPC Class Codes: H04W 36/0011 for data sessions of end-to-end connection
• CPC Class Codes: H04W 36/14 Reselecting a network or an air interface
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection
• CPC Class Codes: H04W 76/20 Manipulation of established connections
• CPC Class Codes: H04W 8/26 Network addressing or numbering for mobility support
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• 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 dual-band wireless subscriber unit (SU) (112) having an enterprise address of E1 and a cellular address of C1, corresponding method (200), software program (310-320), and WLAN (104) determines (202) that the SU is about to leave a wireless local area network (WLAN) (104). In response, when the SU is involved in a call on E1, the SU sends (212, 208) to the WLAN a SIP message, for example a Refer message with a “Refer To” field of C1 if an ongoing call or a SIP Redirect message with a contact address of C1 if a new call is attempting to begin on E1. In response to receiving either message, the WLAN seamlessly transfers (210, 214) the call to C1.

Claims

1. A method in a subscriber unit (SU) that is SIP enabled for facilitating a handoff of the SU from a wireless local area network (WLAN) to a wireless wide area network (WAN), the WLAN including a SIP Call Control Function (CCF), the first SU assigned an enterprise address E1 and a cellular address C1, the method comprising:

determining whether the SU is about to leave the WLAN;

determining whether the SU is involved in a call on E1; and

in response to determining that the SU is about to leave the WLAN and that the SU is involved with a call on E1,

sending, a SIP message with a contact address of C1 to the WLAN, the SIP message resulting in transferring the call from E1 to C1.

2. The method of claim 1, wherein determining whether the SU is involved in the call on E1 comprises determining whether the SU has a new call attempting to begin on E1.

3. The method of claim 2, wherein sending the SIP message comprises sending a SIP Redirect message in response to determining that the SU has a new call attempting to begin on E1.

4. The method of claim 1, wherein determining whether the SU is involved in the call on E1 comprises determining whether the SU has an ongoing call on E1.

5. The method of claim 4, wherein sending the SIP message comprises sending a SIP Refer message with a “

Refer To”

field containing the contact address of C1 in response to determining that the SU has an ongoing call on E1.

6. A subscriber unit (SU) that is SIP enabled for facilitating a handoff of the SU from a SIP-enabled wireless local area network (WLAN), the handoff made to a wireless wide area network (WAN), the SU assigned an enterprise address E1 and a cellular address C1, the SU comprising:

a dual-band transceiver for communicating wirelessly on two frequency bands; and

a processor coupled to the dual-band transceiver for controlling the dual-band transceiver, wherein the processor is programmed to;

cooperate with the dual-band transceiver to determine whether the first SU is about to leave the WLAN;

determine whether the SU is involved in a call on E1; and

in response to determining that the SU is about to leave the WLAN, and that the SU is involved with the call on E1,

send a SIP message with a contact address of C1 to the WLAN, the SIP message resulting in transferring the call from E1 to C1.

7. The SU of claim 6, wherein the processor is further programmed to determine whether the SU has a new call attempting to begin on E1.

8. The SU of claim 7, wherein the processor is further programmed to send a SIP Redirect message in response to determining that the SU has a new call attempting to begin on E1.

9. The SU of claim 6, wherein the processor is further programmed to determine whether the SU has an ongoing call on E1.

10. The SU of claim 9, wherein the processor is further programmed to send a SIP Refer message with a “

Refer To”

field containing the contact address of C1, in response to determining that the SU has an ongoing call on E1.

11. A software program comprising executable instructions for programming a processor of a subscriber unit (SU), the software program for facilitating a handoff of the SU from a wireless local area network (WLAN) that is SIP enabled, to a wireless wide area network (WAN), the SU assigned an enterprise address E1 and a cellular address C1, wherein the software program, when executed by the processor of the SU, programs the processor to:

determine whether the SU is about to leave the WLAN;

determine whether the SU is involved in a call on E1; and

in response to determining that the SU is about to leave the WLAN, and that the SU is involved with the call on E1,

send a SIP message with a contact address of C1 to the WLAN, the SIP message resulting in transferring the call from E1 to C1.

12. The software program of claim 11, further programming the processor to determine whether the SU has a new call attempting to begin on E1.

13. The software program of claim 12, further programming the processor to send a SIP Redirect message in response to determining that the SU has a new call attempting to begin on E1.

14. The software program of claim 11, further programming the processor to determine whether the SU has an ongoing call on E1.

15. The software program of claim 14, further programming the processor to send a SIP Refer message with a “

Refer To”

field containing the contact address of C 1, in response to determining that the SU has an ongoing call on E1.

16. A wireless local area network (WLAN) assigned to a Session Initiation Protocol (SIP) domain, for facilitating a handoff of a subscriber unit (SU) from the WLAN to a wireless wide area network (WAN), the SU being a dual-band unit assigned an enterprise address E1 and a cellular address C1, the WLAN comprising:

the SU;

a WLAN transceiver for supporting wireless communications with the SU;

a SIP call control function (CCF) coupled to the WLAN transceiver for controlling the WLAN transceiver and further coupled to an external network for handling communications with the external network;

wherein the SU is arranged and programmed to;

determine whether the SU is about to leave the WLAN;

determine whether the SU is involved in a call on E1; and

in response to determining that the SU is about to leave the WLAN, and that the SU is involved with the call on E1,

send a SIP message with a contact address of C1 to the WLAN, and

wherein the WLAN is arranged and programmed

in response to receiving the SIP message, to transfer the call from E1 to C1.

17. The WLAN of claim 16, wherein the SU is further arranged and programmed to determine whether the SU has a new call attempting to begin on E1.

18. The WLAN of claim 17, wherein the SU is further arranged and programmed to send a SIP Redirect message in response to determining that the SU has a new call attempting to begin on E1.

19. The WLAN of claim 16, wherein the SU is further arranged and programmed to determine whether the SU has an ongoing call on E1.

20. The WLAN of claim 19, wherein the SU is further arranged and programmed to send a SIP Refer message with a “

Refer To”

field containing the contact address of C1, in response to determining that the SU has an ongoing call on E1.