초록 ▼

The invention is a virtual gateway that mediates between a dual-mode subscriber device and an IP-based PBX. In particular, the virtual gateway includes a WLAN interface for communicating with the dual-mode subscriber device and a network interface (wired or wireless) for communicating with the IP-ba

The invention is a virtual gateway that mediates between a dual-mode subscriber device and an IP-based PBX. In particular, the virtual gateway includes a WLAN interface for communicating with the dual-mode subscriber device and a network interface (wired or wireless) for communicating with the IP-based PBX over the Internet. As such, the virtual gateway may relay voice and call control instructions between the dual-mode subscriber device and the IP-based PBX, and may provide the same call control functions to the dual-mode subscriber device provided by the call control processor in existing dual-mode phones. The invention further provides a dual-mode subscriber device suitable for operation with the virtual gateway. Because the dual-mode subscriber device does not require a call control processor, the battery life and cost of the device are significantly improved.

대표청구항 ▼

1. A method of handing off a call at a dual-mode subscriber device from a wireless local area network to a wireless communication system comprising: creating, at a virtual gateway, a message in a first control signaling format initiating a call from an IP-based telephone switch to the dual-mode subs

1. A method of handing off a call at a dual-mode subscriber device from a wireless local area network to a wireless communication system comprising: creating, at a virtual gateway, a message in a first control signaling format initiating a call from an IP-based telephone switch to the dual-mode subscriber device via the wireless communication system;receiving, at the dual-mode subscriber device, the call from the wireless communication system;switching, at the dual-mode subscriber device, the call from the wireless local area network to the connection to the wireless communication system;performing, at the dual-mode subscriber device, at least one of (1) transmitting a WLAN-based handoff instruction to the virtual gateway and (2) receiving a WLAN-based handoff instruction from the virtual gateway;creating and sending, at the virtual gateway, a registration message to the IP-based telephone switch; andreceiving, at the dual-mode subscriber device, a call confirmation message from the virtual gateway via the wireless local area network, wherein the call confirmation message originated at the IP-based telephone switch. 2. The method of claim 1, wherein the first control signaling format is one of session initiation protocol (“SIP”) format and H.323 format. 3. The method of claim 1, comprising the step of receiving, at the virtual gateway, the WLAN-based request to hand off the call from the wireless local area network to the wireless communication system. 4. The method of claim 1, comprising the step of transmitting a WLAN-based switchover instruction from the virtual gateway to the dual-mode subscriber device. 5. The method of claim 1, wherein the registration message sent to the IP-based telephone switch initiates the call from the wireless communication system. 6. The method of claim 1, further comprising the step of receiving, at the virtual gateway, a SIP invite message from the IP-based telephone switch. 7. The method of claim 1 wherein the wireless communication system is a cellular system. 8. The method of claim 1, further comprising the step of determining whether a handoff to the wireless communication system is warranted. 9. The method of claim 8 wherein the handoff determination is made through monitoring at least one of an automatic gain control value, receive signal strength indication, packet error rate, signal to noise ratio, maximum allowable data rate, and current data transfer rate. 10. A dual-mode wireless communication device suitable for operation in a WLAN-based system including a wireless local area network, a virtual gateway and an IP-based telephone switch as well as in a wireless communication system, comprising: a VoIP processing module configured to establish a WLAN-based call with the IP-based telephone switch via the virtual gateway;a cellular processing module configured to establish a PSTN call with the wireless communication system while a call is in progress with the IP-based telephone switch via the WLAN and the virtual gateway, wherein the PSTN call is initiated from the IP-based telephone switch in response to receiving a message from the virtual gateway in a first control signaling format; anda controller module configured to switch between the WLAN-based call with the IP-based telephone switch via the virtual gateway and the PSTN call with the wireless communication system, wherein: the VoIP processing module is configured to at least one of (1) transmit a WLAN-based handoff instruction to the virtual gateway and (2) receive a WLAN-based handoff instruction from the virtual gateway;the virtual gateway creates and sends a registration message to the IP-based telephone switch; andthe VoIP processing module is further configured to receive a call confirmation message from the virtual gateway via the wireless local area network, wherein the call confirmation message originates at the IP-based telephone switch. 11. The device of claim 10, wherein the controller module is configured to switch the dual-mode wireless communication device from the call in progress over the WLAN and the virtual gateway to the call from the wireless communication system. 12. The device of claim 10, wherein the VoIP processing module is configured to establish a call with the IP-based telephone switch via the WLAN and the virtual gateway while a call is in progress over the wireless communication system, and wherein the controller module is configured to switch the dual-mode wireless communication device from the call in progress over the wireless communication system to the call with the IP-based telephone switch via the WLAN and the virtual gateway. 13. The device of claim 10, wherein the VoIP processing module is configured to receive the WLAN-based handoff instruction from the virtual gateway. 14. The device of claim 10, wherein the controller module is configured to cause the VoIP processing module to transmit the WLAN-based handoff instruction to the virtual gateway. 15. The device of claim 10, wherein the VoIP processing module is configured to transmit the handoff instruction to the virtual gateway and wherein the WLAN-based handoff instruction causes the virtual gateway to create and send a registration message to the IP-based telephone switch. 16. The device of claim 10, wherein the call confirmation message originates as a SIP invite message. 17. The device of claim 10, wherein the controller module is configured to determine whether a handoff of a call from the WLAN-based system to the wireless communication system is warranted. 18. The device of claim 17, wherein the controller module is configured to make the handoff determination by monitoring at least one of an automatic gain control value, receive signal strength indication, packet error rate, signal to noise ratio, maximum allowable data rate, and current data transfer rate. 19. The device of claim 10, wherein the cellular processing module is further configured to send a PSTN call initiation message to the wireless communication system specifying a surrogate called number that is assigned to the IP-based telephone switch. 20. The device of claim 19, wherein the VoIP processing module is further configured to send a WLAN call initiation message in the first control signaling format to a virtual gateway capable of converting the WLAN call initiation message to an initiation message specifying an actual called number in a second control signaling format. 21. The apparatus of claim 20 wherein the VoIP processing module is further configured to conduct a voice call to the actual called number via a call path that includes the virtual gateway and the IP-based telephone switch. 22. The device of claim 10, wherein the cellular processing module is configured to send over the wireless communication system a call initiation message in the first control signaling format specifying a telephone number associated with the IP-based telephone switch as a called party; and wherein the VoIP processing module is configured to send an WLAN invite message to the virtual gateway, andwherein the virtual gateway is configured to translate the WLAN invite message into an invitation message in a second control signaling format specifying an actual called party and further configured to forward the invitation message in the second control signaling format to the IP-based telephone switch. 23. The device of claim 10, wherein the VoIP processing module is configured to receive a WLAN call invitation message from the virtual gateway, the WLAN call invitation message specifying a calling party; and wherein the cellular processing module is configured to send a call initiation message over the wireless communication system in response thereto. 24. The device of claim 10, wherein the VoIP processing module is configured to receive a WLAN call invitation message from the virtual gateway, the message specifying a calling party; wherein the cellular processing module is configured to receive a call initiation message over the wireless communication system; andwherein the controller module is configured to correlate the WLAN call invitation message with the call initiation message. 25. The device of claim 24, wherein the controller module is configured to correlate the WLAN call invitation message with the call initiation message by comparing caller ID information received over the wireless communication system with the calling party. 26. The device of claim 24, wherein the controller module is configured to correlate the WLAN call invitation message with the call initiation message by comparing caller ID information received over the wireless communication system with one or more dummy numbers. 27. A method of establishing a telephone connection at a dual-mode wireless communication device suitable for operation in (1) a WLAN-based system including a wireless local area network, a virtual gateway and an IP-based telephone switch as well as in (2) a wireless communication system, comprising the steps of: establishing, at the dual-mode wireless communication device, a WLAN-based call with the IP-based telephone switch via the virtual gateway;establishing, at the dual-mode wireless communication device, a cellular-based call with the wireless communication system after the WLAN-based call with the IP-based telephone switch via the virtual gateway is in progress, wherein the cellular-based call is initiated from the IP-based telephone switch in response to receiving a message from the virtual gateway in a first control signaling format;switching, at the dual-mode wireless communication device, between the WLAN-based call established with the IP-based telephone switch via the virtual gateway and the cellular-based call with the wireless communication system;performing, at the dual-mode wireless communication device, at least one of (1) transmitting a WLAN-based handoff instruction to the virtual gateway and (2) receiving a WLAN-based handoff instruction from the virtual gateway;creating and sending, at the virtual gateway, a registration message to the IP-based telephone switch; andreceiving, at the dual-mode wireless communication device, a call confirmation message from the virtual gateway via the wireless local area network, wherein the call confirmation message originates at the IP-based telephone switch. 28. The method of claim 27, further comprising the step of switching, at the dual-mode wireless communication device, from the call in progress via the virtual gateway to the call from the wireless communication system. 29. The method of claim 27, wherein the step of establishing a call with the IP-based telephone switch via the virtual gateway is performed after the step of establishing a call with the wireless communication system, and wherein the step of switching comprises the step of switching the dual-mode wireless communication device from the call in progress over the wireless communication system to the call with the IP-based telephone switch via the virtual gateway. 30. The method of claim 27, comprising the step of receiving, at the dual-mode wireless communication device, the WLAN-based handoff instruction via the virtual gateway. 31. The method of claim 27, comprising the step of transmitting, by the dual-mode wireless communication device, the WLAN-based handoff instruction to the virtual gateway. 32. The method of claim 31, further comprising the steps of translating the WLAN-based handoff instruction into registration message and sending the registration message to the IP-based telephone switch. 33. The method of claim 27, wherein the call confirmation message originates as a SIP invite message. 34. The method of claim 27, further comprising the step of determining, at the dual-mode wireless communication device, whether a handoff of a call from the WLAN-based system to the wireless communication system is warranted. 35. The method of claim 34, wherein the step of determining includes the step of monitoring at least one of an automatic gain control value, receive signal strength indication, packet error rate, signal to noise ratio, maximum allowable data rate, and current data transfer rate. 36. The method of claim 27, further comprising the step of sending, by the dual-mode wireless communication device, a PSTN call initiation message to the wireless communication system specifying a surrogate called number that is assigned to the IP-based telephone switch. 37. The method of claim 36, further comprising the step of sending a WLAN call initiation message specifying an actual called number in the first control signaling format from the dual-mode wireless communication device to a virtual gateway capable of converting the WLAN call initiation message to an initiation message in a second control signaling format. 38. The method of claim 37 further comprising the step of conducting, from the dual-mode wireless communication device, a voice call to the actual called number via a call path that includes the virtual gateway and the IP-based telephone switch. 39. The method of claim 27, further comprising the steps of sending, by the dual-mode wireless communication device, over the wireless communication system a call initiation message specifying a telephone number associated with the IP-based telephone switch as a called party;sending, by the dual-mode wireless communication device, an WLAN invite message in the first control signaling format specifying an actual called party to the virtual gateway,translating the WLAN invite message into a message in a second control signaling format; andsending the message in the second control signaling format to the IP-based telephone switch. 40. The method of claim 27, further comprising the steps of receiving, at the dual-mode wireless communication device, a WLAN call invitation message from the virtual gateway, the WLAN call invitation message specifying a calling party; andsending, by the dual-mode wireless communication device, a call initiation message over the wireless communication system in response thereto. 41. The method of claim 27, further comprising the steps of receiving, at the dual-mode wireless communication device, a WLAN call invitation message from the virtual gateway, specifying a calling party;receiving, at the dual-mode wireless communication device, a call initiation message over the wireless communication system; andcorrelating, by the dual-mode wireless communication device, the WLAN call invitation message with the call initiation message. 42. The method of claim 41, wherein the step of correlating the WLAN call invitation message with the call initiation message includes the step of comparing caller ID information received over the cellular network with the calling party. 43. The method of claim 41 wherein the step of correlating the WLAN call invitation message with the call initiation message includes the step of comparing caller ID information received over the cellular network with one or more dummy numbers. 44. The device of claim 10, wherein: the virtual gateway comprises a portable computing device;the virtual gateway is adapted to establish a WLAN link with the dual-mode communication device;the virtual gateway is adapted to establish a communication link with the IP-based telephone switch. 45. The device of claim 44, wherein: the virtual gateway handles any of SIP and H.323 signaling on behalf of the dual-mode communication device;the dual-mode communication device does not handle any of SIP and H.323 signaling. 46. The method of claim 27, wherein the virtual gateway comprises a portable computing device, the method further comprising: establishing, by the virtual gateway, a WLAN link with the dual-mode communication device;establishing, by the virtual gateway, a communication link with the IP-based telephone switch. 47. The method of claim 46, further comprising handling, by the virtual gateway, of any of SIP and H.323 signaling on behalf of the dual-mode communication device, wherein the dual-mode communication device does not handle any of SIP and H.323 signaling.