Extension of a local area phone system to a wide area network with handoff feature

Abstract

A soft switch 134 providing wireless PBX voice services to a local area network (WLAN) is used to extend PBX functionality to the cellular domain. A dual mode remote unit is capable of receiving signals both in the cellular system as well as the WLAN. The cellular system is comprised of a data-bearing path and a voice-bearing path. When the dual mode remote unit is within the WLAN, it communicates both voice over IP (VoIP) signaling as well as session initiation protocol (SIP) control signaling over the WLAN. When the remote unit is outside the WLAN, it communicates voice signaling over the voice-bearing path of the cellular network using a standard cellular voice channel. In parallel, it uses the data-bearing path of the cellular network to transmit SIP control signaling.

What is claimed is: 
     
         1 - 20 . (canceled) 
     
     
         21 . A method comprising:
 determining, by a wireless device, whether a call routed over a wireless local area network (“WLAN”) via a switch is to be handed off to a cellular network;   transmitting, by the wireless device, a registration request to the switch via a data-bearing path of the cellular network, based at least in part on a result of the determining, the registration request including a request for establishment of an audio connection to the wireless device over a voice-bearing path of the cellular network prior to handing off the call to the cellular network, wherein the voice-bearing path and the data-bearing path are different paths; and   associating, by the wireless device, the audio connection via the voice-bearing path of the cellular network with the call.   
     
     
         22 . The method of  claim 21 , wherein the determining comprises monitoring, by the wireless device, a performance parameter associated with the WLAN. 
     
     
         23 . The method of  claim 22 , wherein the monitoring comprises monitoring an automatic gain control value or a receive signal strength indication value associated with the WLAN. 
     
     
         24 . The method  claim 23 , wherein the monitoring of a receive signal strength indication value associated with the WLAN comprises monitoring an averaged, filtered, smoothed, and/or integrated receive signal strength indication value associated with the WLAN. 
     
     
         25 . The method of  claim 21 , wherein the determining comprises monitoring for an access point associated with the WLAN, wherein the access point has a coverage area that covers an exit point or exit area of the WLAN. 
     
     
         26 . The method of  claim 21  further comprising:
 receiving, by the wireless device, a switch indication, wherein the switch indication is configured to indicate to the wireless device that the audio connection over the voice-bearing path of the cellular network has been established. 
 
     
     
         27 . The method of  claim 26 , wherein the receiving comprises receiving pulse-control modulation frames from the switch over the voice-bearing path of the cellular network. 
     
     
         28 . An article of manufacture comprising:
 a memory;   a plurality of programming instructions stored on the memory, wherein the plurality of programming instructions, in response to execution by a wireless device, enable the wireless device to:
 determine whether a call routed over a wireless local area network (“WLAN”) via a switch is to be handed off to a cellular network; 
 transmit a registration request to the switch via a data-bearing path of the cellular network, based at least in part on a result of the determining, the registration request including a request for establishment of an audio connection to the wireless device over a voice-bearing path of the cellular network prior to handing off the call to the cellular network, wherein the voice-bearing path and the data-bearing path are different paths; and 
 associating the audio connection via the voice-bearing path of the cellular network with call. 
   
     
     
         29 . The article of manufacture of  claim 28 , wherein said determine comprises monitor a performance parameter associated with the WLAN. 
     
     
         30 . The article of manufacture of  claim 29 , wherein said monitor a performance parameter comprises monitor an automatic gain control value or a receive signal strength indication value associated with the WLAN. 
     
     
         31 . The article of manufacture of  claim 30 , wherein said monitor of a receive signal strength indication value associated with the WLAN comprises monitor an averaged, filtered, smoothed, and/or integrated receive signal strength indication value associated with the WLAN. 
     
     
         32 . The article of manufacture of  claim 28 , wherein said determine comprises monitor for an access point associated with the WLAN, wherein the access point has a coverage area that covers an exit point or exit area of the WLAN. 
     
     
         33 . The article of manufacture of  claim 28 , wherein the plurality of programming instructions are further designed to enable the wireless device to receive a switch indication, wherein the switch indication is configured to indicate to the wireless device that the audio connection over the voice-bearing path of the cellular network has been established. 
     
     
         34 . The article of manufacture of  claim 33 , wherein said receive comprises receive pulse-control modulation frames from the switch over the voice-bearing path of the cellular network. 
     
     
         35 . An apparatus comprising:
 a first processor configured to facilitate transmission of a session initiation protocol (“SIP”) message to a wireless local area network (“WLAN”) switch via a data-bearing path of a wireless communication system, wherein the SIP message is configured to request establishment of an audio connection from the WLAN switch to the apparatus over a voice-bearing path of the wireless communication system, wherein the data-bearing path is different than the voice-bearing path;   a second processor configured to associate the connection via the voice-bearing path of the wireless communication system with a call on the data-bearing path of the wireless communication system; and   a controller configured to switch the call from the data-bearing path to the connection via the voice-bearing path.   
     
     
         36 . The apparatus of  claim 35 , wherein the first processor is further configured to send a registration message to the WLAN switch. 
     
     
         37 . The apparatus of  claim 35 , wherein the first processor is further configured to receive an invite message from the WLAN switch via the data-bearing path of the wireless communication system. 
     
     
         38 . The apparatus of  claim 35 , wherein the controller is further configured to determine whether the call is to be switched to the voice-bearing path. 
     
     
         39 . The apparatus of  claim 38  wherein the handoff determination is based at least in part on a performance parameter associated with the WLAN. 
     
     
         40 . The apparatus of  claim 39  wherein the performance parameter is an automatic gain control value associated with the WLAN.