User terminal-initiated hard handoff from a wireless local area network to a cellular network

• US 20070049276A1
• Filed: 10/12/2005
• Published: 03/01/2007
• Est. Priority Date: 09/01/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Rimoni, Yoram, Yacobi, Eitan
• Granted Patent: US 7,706,796 B2
• Time in Patent Office: Days
• US Class Current: 455/436
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/70 Admission control; Resource allocation
• CPC Class Codes: H04L 47/72 using reservation actions during connection setup
• CPC Class Codes: H04L 5/0058 Allocation criteria
• CPC Class Codes: H04M 15/8016 based on quality of service [QoS]
• CPC Class Codes: H04M 2207/18 wireless networks
• 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 36/30 by measured or perceived connection quality data
• CPC Class Codes: H04W 36/36 by user or terminal equipment
• CPC Class Codes: H04W 40/20 based on geographic position or location
• CPC Class Codes: H04W 48/06 based on traffic conditions
• 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 system and method are provided for supporting a multi-mode portable user terminal (UT) hard handoff procedure for a call from a wireless local area network (WLAN) to a cellular telephone network. The method includes: establishing a link between a UT and a serving WLAN; establishing a call via the established WLAN link; monitoring the WLAN link signal strength; simultaneously monitoring a serving cellular network; initiating a hard handoff to the cellular network, responsive to the monitored WLAN link signal strength falling below a minimum threshold; and, continuing the call via the cellular network. More specifically, the method initiates a call handoff to a Cellular Gateway (CGW) telephone number, responsive to the monitored WLAN link signal strength falling below the minimum threshold. Then, continuing the call via the cellular network includes continuing the call to the first telephone number via the CGW handoff telephone number.

Claims

1. In a multi-mode portable user terminal (UT), a method for supporting a hard handoff procedure for a call from a wireless local area network (WLAN) to a cellular telephone network, the method comprising:

establishing a link between a UT and a serving WLAN;

establishing a call via the established WLAN link;

monitoring the WLAN link signal strength;

simultaneously monitoring a serving cellular network;

initiating a hard handoff to the cellular network, responsive to the monitored WLAN link signal strength falling below a minimum threshold; and

,

continuing the call via the cellular network.

2. The method of claim 1 wherein establishing the call between the UT and the serving WLAN includes establishing a call in a format selected from the group consisting of packet data, voice over Internet Protocol (VoIP), and video telephony (VT).

3. The method of claim 1 wherein continuing the call via the cellular network includes continuing the call in a format selected from the group consisting of VoIP, packet data, and circuit switched (CS).

4. The method of claim 1 wherein establishing the call between the UT and the serving WLAN includes establishing the call with a WLAN selected from the group consisting of IEEE 802.11, Bluetooth, and IEEE 802.15 networks.

5. The method of claim 1 wherein continuing the call via the cellular network includes continuing the call via a cellular network selected from the group consisting of Code Division Multiple Access (CDMA), Global System for Mobile Communications (GSM), and Universal Mobile Telecommunications System (UMTS).

6. The method of claim 1 wherein establishing the call via the established WLAN link includes establishing a call with a first telephone number via the WLAN link;

wherein initiating a hard handoff to the cellular network, responsive to the monitored WLAN link signal strength falling below the minimum threshold, includes initiating a call handoff to a Cellular Gateway (CGW) telephone number; and

,

wherein continuing the call via the cellular network includes continuing the call to the first telephone number via the CGW handoff telephone number.

7. The method of claim 6 further comprising:

receiving cellular network resource allocations in a common control channel message, responsive to initiating the call to the CGW telephone number;

tuning to an allocated traffic channel within the cellular network; and

,

wherein continuing the call via the cellular network includes continuing the call using the allocated traffic channel.

8. The method of claim 6 wherein establishing the call with the first telephone number via the WLAN link includes establishing a call selected from the group consisting of a Mobile Originated (MO) call and a Mobile Terminated (MT) call.

9. The method of claim 8 wherein establishing the call with the first telephone number via the WLAN link includes establishing an MT call;

and,

wherein continuing the call via the cellular network includes continuing the handoff call to the CGW telephone number as an MT call.

10. A multi-mode portable user terminal (UT) for supporting a hard handoff procedure for a call from a wireless local area network (WLAN) to a cellular telephone network, the UT comprising:

a WLAN subsystem for establishing a link between the UT and a serving WLAN, establishing a call via the established WLAN link, and monitoring the WLAN link signal strength; and

,

a cellular subsystem for monitoring a serving cellular telephone network, initiating a hard handoff to the cellular network responsive to the monitored WLAN link signal strength falling below a minimum threshold, and continuing the call via the cellular network.

11. The UT of claim 10 wherein the WLAN subsystem establishes a call with the serving WLAN in a format selected from the group consisting of packet data, voice over Internet Protocol (VoIP), and video telephony (VT).

12. The UT of claim 10 wherein the cellular subsystem continues the call via the cellular network in a format selected from the group consisting of packet data, VoIP, and circuit switched (CS).

13. The UT of claim 10 wherein the WLAN subsystem establishes the call with a WLAN selected from the group consisting of IEEE 802.11, Bluetooth, and IEEE 802.15 networks.

14. The UT of claim 10 wherein the cellular subsystem continues the call via a cellular network selected from the group consisting of Code Division Multiple Access (CDMA), Global System for Mobile Communications (GSM), and Universal Mobile Telecommunications System (UMTS).

15. The UT of claim 10 wherein the WLAN subsystem establishes a call with a first telephone number;

wherein the cellular subsystem initiates a call handoff to a Cellular Gateway (CGW) telephone number, responsive to the monitored WLAN link signal strength falling below the minimum threshold, and continues the call to the first telephone number via the CGW handoff telephone number.

16. The UT of claim 15 wherein the cellular subsystem receives cellular network resources in a common control channel, responsive to initiating the call handoff to the CGW telephone number, tunes to an allocated traffic channel, and continues the call using the allocated traffic channel.

17. The UT of claim 15 wherein the WLAN subsystem establishes a call selected from the group consisting of a Mobile Originated (MO) call and a Mobile Terminated (MT) call.

18. The UT of claim 17 wherein the WLAN subsystem initially establishes an MT call with the first telephone number;

and,

wherein the cellular subsystem continues the handoff call to the CGW telephone number as an MT call.

19. A system supporting a hard handoff procedure for transferring a call from a wireless local area network (WLAN) to a cellular network, the system comprising:

a user terminal (UT) comprising;

a WLAN subsystem to establish call through a link between the UT and a serving WLAN, and monitor the WLAN signal strength; and

,

a cellular subsystem registered with and monitoring a serving cellular telephone network, and initiating a call handoff to a Cellular Gateway (CGW), responsive to the monitored WLAN link signal strength falling below a minimum threshold;

a CGW having an interface to the UT cellular subsystem via a cellular network, for receiving the call handoff from the UT cellular subsystem, supplying cellular network resources to the UT cellular subsystem, and continuing the call initially established through the WLAN link.

20. The system of claim 19 wherein the UT WLAN subsystem initially establishes the call as a Mobile Terminated (MT) call;

and,

wherein the CGW records the call handoff as an MT call.

21. A multi-mode portable user terminal (UT) for supporting a hard handoff procedure for a call from a wireless local area network (WLAN) to a cellular telephone network, the UT comprising:

a means for establishing a call via a WLAN link;

a means for monitoring the WLAN link signal strength;

a means for initiating a hard handoff to a cellular network, responsive to the monitored WLAN link signal strength falling below a minimum threshold and,

a means for continuing the call via a cellular network.

22. The UT of claim 21 wherein the means for establishing the call via the WLAN link includes establishing a call to a first telephone number;

wherein the means for initiating the hard handoff includes initiating a call handoff to a Cellular Gateway (CGW) telephone number; and

,

wherein the means for continuing the call via the cellular network includes continuing the call to the first telephone number via the CGW call handoff telephone number.