Abstract:
A system and method for routing calls from a communication system in a VoIP network to an external network. The communication system comprises a plurality of communicating nodes. The communication system is configured to request routing information from a register associated with the external network for routing a communication to a subscriber of the external network, receive routing information from the register, and establish an external connection from the VoIP network for routing the communication to the external network based on the routing information.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation of U.S. patent application Ser. No. 12/984,000 filed Jan. 4, 2011, entitled “Routing VOIP calls to an external network”, now U.S. Pat. No. 8,477,691, which is a continuation of U.S. patent application Ser. No. 11/285,805, filed Nov. 22, 2005, entitled “Interaction of VoIP Calls and Cellular Networks”, now U.S. Pat. No. 8,223,776, which is a continuation of U.S. patent application Ser. No. 09/653,680 filed on Sep. 1, 2000, entitled “Interaction of VoIP Calls and Cellular Networks”, now U.S. Pat. No. 6,982,985, which claims the benefit of U.S. Provisional Application No. 60/152,039 filed on Sep. 2, 1999 and entitled “Interaction of VoIP Calls and Cellular Networks”. Each of the aforementioned applications is hereby incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates generally to telephone communications, and more particularly to telephoning via Voice-over-IP (VoIP) and wireless networks. 
         [0004]    2. Description of the Background Art 
         [0005]      FIG. 1  shows a prior art telephony system  100  that includes a corporate network  120 , a traditional Public Switched Telephone Network (PSTN)  140 , and a wireless network  160 . System  100  routes a communication  124  from a Caller  122  in corporate network  120  to a wireless network Subscriber  190 . 
         [0006]    The corporate network  120  includes a traditional Private Branch Exchange (PBX)  128 . The PSTN  140  includes a Local Exchange Carrier (LEC)  144 , which in turn includes a Central Office (CO)  148 . PBX  128 , which receives communication  124  from Caller  122 , establishes connection  130  to Central Office (CO)  148 , which in turn establishes connection  150  to wireless network  160 . Those skilled in the art will recognize that, instead of communication  124 , a comparable communication may also be initiated by a direct telephone call from a home telephone (not shown). Passing through PBX  128 , in addition, PSTN  140  may be replaced by an Integrated Services Digital Network (ISDN). 
         [0007]    Wireless network  160  includes a Gateway Mobile Switching Center (GMSC)  164 , a Home Location Register (HLR)  166 , and a Visited Mobile Switching Center (VMSC)  168 . GMSC  164 , communicating via connection  171  with a base station (BS)  165  within Subscriber  190 &#39;s “home” wireless network  160 , is the control element for managing wireless network  160 , and is responsible for switching cellular cells, providing for backup, interfacing with telephone networks, and monitoring telephony traffic. 
         [0008]    A wireless Subscriber  190  may “register” merely by turning on his or her cell-phone. This example assumes that Subscriber  190  is currently registered and is not currently engaged in a call. Upon establishment of connection  150  from CO  148 , GMSC  164  via signal path  170  gathers information from HLR  166  to determine how to route connection  150 . Note that establishment of connection  150  may involve one or more intermediate exchanges. 
         [0009]    Wireless network  160  uses HLR  166  and VMSC  168  to locate Subscriber  190  and thereby establish final wireless connection  180 . Each Subscriber belongs to one HLR  166  associated with a cellular operator or a commercial network provider. HLR  166  stores information (accounting, subscribed services, profile information, etc.) about Subscriber  190 . HLR  166 , via one of several (not shown) VMSCs (i.e. VMSC  168 ), which report back on signal path  174 , keeps track of the location of Subscriber  190 . VMSC  168  informs HLR  166  when Subscriber  190  is on the system of VMSC  168 , and HLR  166  in turn updates its profile record for the new location of Subscriber  190 . When a call is placed to Subscriber  190 , HLR  166  determines whether Subscriber  190  is a valid subscriber, and if so, which VMSC  168  is currently serving Subscriber  190 . Subsequently HLR  166 , via signal path  172 , requests routing instructions from VMSC  168  for Subscriber  190 . VMSC  168 , having received information about Subscriber  190  from HLR  166 , assigns a routing number N for connection  150 , and then returns this routing number N via signal path  174  to HLR  166 . The HLR  166  then returns the routing number N via signal path  176  to GMSC  164 . The GMSC  164  uses this routing number N to establish connection  178  to VMSC  168 . This step may involve one or more intermediate exchanges and/or networks. Once connection  178  is established with the VMSC  168 , wireless connection  180  is completed to Subscriber  190  using standard wireless call processing which is not described herein. 
         [0010]      FIG. 2  shows a prior art system  200  comprising a corporate network  120  as in system  100  of  FIG. 1 , a VoIP Virtual Private Network (VPN)  240 , and a wireless network  160  as in system  100  of  FIG. 1 . System  200  uses VPN  240  instead of PSTN  140  of system  100  to route a communication  124  from a Caller  122  to a wireless network Subscriber  190 . Connection  130  is established between PBX  128  and GW-1  242 , residing within the VoIP VPN  240 . 
         [0011]    VoIP VPN  240  includes a Command Center (CC)  244 , a Gateway (GW-1)  242 , and a second Gateway (GW-2)  246 . In the preferred embodiment of the invention, CC  244 , GW-1  242 , and GW-2  246  are command center and gateway products of Clarent Corporation of Redwood City, Calif. In system  200 , as in system  100 , instead of communication  124  passing through PBX  128 , a comparable communication may also be initiated by a direct telephone call from a home telephone. 
         [0012]    The gateways GW-1  242  and GW-2  246  support an Internet Protocol (IP) such as Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) connection via the VoIP VPN  240  to the Internet (not shown). GW-1  242  and GW-2  246  support both telephone-to-telephone communications and PC-to-telephone communications. 
         [0013]    The originating exchange PBX  128  within the corporate network  120  (or possibly a Central Office, not shown) determines that VPN  240  is on-net. GW-1  242  via signal path  250  requests routing information from CC  244 . CC  244  verifies that connection  130  is allowed and translates the called Subscriber  190 &#39;s number into an IP address. CC  244  via signal path  252  notifies GW-2  246  about the incoming connection  258 , and GW-2  246  via signal path  254  notifies CC  244  of its readiness to accept connection  258 . CC  244  via signal path  256  returns the translated IP address to GW-1  242 . GW-1  242  establishes connection  258  with GW-2  246 . GW-2  246  continues routing based upon the called Subscriber  190 &#39;s number via path  262  to a GMSC  164  within the called Subscriber  190 &#39;s home wireless network  160 . This step may involve one or more intermediate exchanges and/or networks. 
         [0014]    From this point on, standard wireless call processing is used. The GMSC  164  via signal path  170  queries HLR  166  containing the Subscriber  190 &#39;s profile to determine how to continue routing. This example assumes that the subscriber is registered and is not currently engaged in a call. Registration may occur merely by Subscriber  190  turning on his cell-phone. The HLR  166  determines that the Subscriber  190  is valid and determines which VMSC  168  is currently serving him or her. HLR  166  via signal path  172  queries VMSC  168  for routing instructions. The VMSC  168  determines that Subscriber  190  is registered within its service area and assigns a temporary routing number N. VMSC  168  returns this temporary routing number N via signal path  174  to HLR  166 , which in turn returns temporary routing number N via signal path  176  to GMSC  164 . The GMSC  164  uses the temporary routing number N to route connection  178  to VMSC  168 . This step may involve one or more intermediate exchanges and/or networks. Once the connection is established with VMSC  168 , wireless call  180  is completed to Subscriber  190  using standard wireless call processing, which is not described herein. 
         [0015]    In both prior art systems  100  and  200 , GMSC  164  is fixed in the home service area of Subscriber  190 . System  200  changes between using VMSCs  168  in different locations based upon the location of Subscriber  190 , and regardless of the subscriber&#39;s location, connections are always routed to GMSC  164  before being transmitted to the VMSC  168  closest to the subscriber, generally, and then to Subscriber  190 . The GMSC  164  being fixed in the home service area for Subscriber  190  creates inefficiency. For example, suppose Subscriber  190  has a home base in Los Angeles (LA), Calif., and travels to San Francisco (SF), Calif., where Caller  122  resides. Consequently, GMSC  164  is in LA (or some nearby locality) and VMSC  168  is in SF (or some nearby locality). As Caller  122  uses either system  100  or  200  to call Subscriber  190 , routing must go from SF to GMSC  164  in LA, then to VMSC  168  in SF, and eventually to Subscriber  190  in SF. As a result, even if Caller  122  and Subscriber  190  are in the same locale of SF, routing must first go through LA before reaching Subscriber  190 , who is in SF. Further, in a traditional wireless call as depicted in system  100 , Caller  122  would incur two long distance toll charges, one from SF to LA, and one from LA back to SF. 
         [0016]    Additionally, VoIP VPN  240  of system  200  loses control of routing. As connection  262  leaves GW-2  246  and enters wireless network  160 , the wireless network  160  assumes complete control of routing. Once the connection  262  is passed from VoIP VPN  240  into the wireless network  160 , a traditional toll call takes place, even though Caller  124  and Subscriber  190  in this example are both located in SF. The VoIP VPN  240  eliminates the toll leg from SF to LA, but the wireless network  160  still creates a toll call from GMSC  164  in LA to VMSC  168  in SF. 
         [0017]    Moreover, in various situations, VoIP VPN  240  would benefit from maintaining control of a call up to the connection  262  with VMSC  168  for providing additional call completion services without being dependent upon wireless network  160 . 
         [0018]    What is needed, therefore, is a solution that can alleviate the above-discussed deficiencies by eliminating possible and/or unnecessary toll calls. 
       SUMMARY OF THE INVENTION 
       [0019]    The present invention provides a system and method for improving current telephony use of VoIP on a VPN to interact with a wireless network. The invention efficiently routes telephone calls to wireless subscribers and allows a VoIP VPN system to gain and maintain control of a call. The invention thereby extends capabilities of VoIP VPN services to permit intelligent call completion even after a call has been routed to a terminating wireless network or in the event that a wireless network subscriber cannot be reached. The invention also eliminates toll calls associated with traditional wireless calls and prior art VoIP VPN wireless calls. 
         [0020]    In accordance with the invention, if a called party does not answer a call then the calling party can control disposition of the call. Using the profile of the called party, the invention may provide the following services/capabilities: a caller may route a call to the called party&#39;s secretary, voice mail, pager or alternate destination; the system may automatically route the call to the most likely location of the called party; the system, based upon the identity of the calling party, may route the call to a specific location; and, when a call is established, the called party may control further capabilities, such as transferring the call or adding a third party, among other options. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a block diagram showing a prior art system for a traditional wireless telephone call. 
           [0022]      FIG. 2  is a block diagram showing a prior art system for wireless telephone calling using a VoIP Virtual Private Network. 
           [0023]      FIG. 3  is a block diagram showing an improved system for wireless telephone calling using a VoIP Virtual Private Network in accordance with the invention. 
           [0024]      FIG. 4  is a flowchart illustrating steps in a method for routing a call in accordance with the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]      FIG. 3  shows a system  300  comprising corporate network  320 , VoIP VPN  340 , and wireless network  360 . In this scenario, corporate network  320  remains the same as network  120  of  FIG. 1  and of  FIG. 2 . However, element numbers are modified for  FIG. 3  to aid in distinguishing elements related to the present invention. The VoIP VPN  340  product replaces the PSTN  140  of  FIG. 1  and the VoIP VPN  240  of  FIG. 2 , and wireless network  360  replaces the wireless network  160  of  FIG. 1  and of  FIG. 2 . In accordance with the invention, system  300  uses VoIP VPN  340  to route a communication  324 , initiated by a Caller  322  from PBX  328  in corporate network  320 , to a wireless network Subscriber  390 . Those skilled in the art will recognize that communication  324  may also be initiated by a direct telephone call from a home telephone via a telephone company provider or a local central office rather than PBX  328 . 
         [0026]    VoIP VPN  340  includes a CC  344 , GW-1  342 , GW-2  348 , and a Signaling System Seven (SS7) backbone  346 . CC  344  includes additional functionality over CC  244  of  FIG. 2 . The CC  344  is where most of the changes for routing occur. The CC  344  determines routing steps and instructs GW-1  342  and GW-2  348  how to communicate with each other. The originating exchange (PBX  328  or a CO such as CO  148  of  FIG. 1 ) within the corporate network  320  may use an ISDN Primary Rate Q.931 protocol to establish a connection  330  to GW-1  342 . 
         [0027]    Wireless network  360  includes an HLR  366  and a VMSC  368 . HLR  366 , as compared to HLR  166  of  FIG. 1 , may receive instructions from CC  344 , which was prohibited in prior art systems. Wireless network  360  does not include a GMSC  164  as in wireless network  160  because the function of GMSC  164  has been incorporated into VoIP VPN  340 . VMSC  368 , as compared to VMSC  168  of  FIG. 1 , receives connections  362  from GW-2  348  instead of from the GMSC  164  of system  100 . Therefore, this scenario is advantageous over prior systems because, in accordance with the invention, routing does not have to go through a GMSC  164 , which is normally fixed at a home base of the Subscriber  390 . Further, VoIP VPN  340  maintains control of connections  330 ,  358 , and  362 , and can thereby extend additional capabilities. Routing steps associated with system  300  is discussed below with respect to  FIG. 4 . 
         [0028]      FIG. 4  is a flowchart illustrating the steps of a method  400  that corresponds to the routing steps of  FIG. 3 . In step  410 , Caller  322  initiates a communication  324  with PBX  328  in corporate network  320 . In step  415 , the originating exchange within the corporate network  320  (PBX  328 , or CO  148  as in  FIG. 1 ) determines that communication  324  is an on-net VoIP VPN  340  communication, and thus, routes via connection  330  to GW-1  342 . In step  420 , GW-1  342  via signal path  350  requests routing information from CC  344 . 
         [0029]    In step  425 , new functionality in CC  344  determines whether the called telephone number of Subscriber  390  is a valid subscribed wireless number, and if so, CC  344  determines the characteristics of the home network (e.g., Electronics Industries Association EIA-41 standard or Global System for Mobile (GSM) communications standard) for the Subscriber  390 . This functionality provides enhanced VPN call processing. CC  344 , via signal path  352 , uses SS7 gateway (backbone)  346 , which via signal path  370  queries HLR  366  for routing information. 
         [0030]    In step  430 , HLR  366  determines whether Subscriber  390  is a valid subscriber, and, if so, queries the serving VMSC  368  for routing information via signal path  372 . This is standard wireless routing interrogation. In accordance with the invention, the query to the HLR  366  appears as if it were from a GMSC (such as GMSC  164  of system  100 ), although the query is instead from CC  344 . Policing table(s) in HLR  366  may need to be updated to allow CC  344  to perform the interrogation since most wireless networks restrict this capability to GMSCs within their own network. The invention is thus advantageous over prior art techniques because the invention does not need to use GMSC  164 , which is always at the home base of the called subscriber. 
         [0031]    In step  435 , VMSC  368  determines whether Subscriber  390  is registered, and if so, VMSC  368  assigns a temporary routing number N and passes this number N on signal path  374  to HLR  366 . In step  440 , HLR  366  returns temporary routing number N via signal path  376  through SS7  346 , and then via signal path  354 , to CC  344  (which HLR  366  interacts with as if it were a GMSC). In prior art, such as in system  100 , HLR  166  returns a temporary routing number N to GMSC  164  instead of to a CC such as CC  344  of system  300 . 
         [0032]    In step  445 , new functionality in CC  344 , based on temporary routing number N, determines the capabilities of the terminating mobile wireless network  360 . Existing functionality of CC  344  also determines the identity of GW-2  348  that serves the temporary routing number N and, via signal path  355 , informs GW-2  348  of the incoming connection  358 . In step  450 , GW-2  348  via signal path  356  informs CC  344  that GW-2  348  is ready to receive connection  358 , and in step  455 , CC  344  via signal path  357  returns instructions and a VoIP IP address to GW-1  342 . The instructions are extended to include an indication that routing is to a mobile Subscriber  390  as well as to include the capabilities of the terminating mobile wireless network  360 . Steps  445 ,  450 , and  455  comprise additional enhancements for VoIP VPN call processing. Since all the long distance service is provided through the VoIP VPN  340 , local connections  330  and  362  are the only traditional telecom or telephony links used. 
         [0033]    In step  460 , GW-1  342  establishes connection  358  to GW-2  348 . In step  465 , GW-2  348  uses temporary routing number N to route connection  362  to VMSC  368 . In accordance with the invention, step  465  may involve one or more intermediate exchanges and/or networks. In step  470 , VMSC  368  uses standard wireless call processing to complete wireless connection  380  to Subscriber  390 . 
         [0034]    In accordance with the invention, method  400  is advantageous over prior art techniques as method  400  efficiently and directly routes to where Subscriber  390  is located, rather than first through a home location for Subscriber  390  and then to Subscriber  390 , thereby incurring toll call charges. The invention also provides intelligent call completion services if Subscriber  390  is not reachable (e.g., if the phone line is busy or if Subscriber  390 &#39;s phone is turned off or out of the wireless service area). These services are also applicable to calls terminating to fixed subscribers. 
         [0035]    Appended to this specification are one or more claims, which may include both independent claims and dependent claims. Each dependent claim makes reference to an independent claim, and should be construed to incorporate by reference all the limitations of the claim to which it refers. Further, each dependent claim of the present application should be construed and attributed meaning as having at least one additional limitation or element not present in the claim to which it refers. In other words, the claim to which each dependent claim refers is to be construed and attributed meaning as being broader than such dependent claim. 
         [0036]    While the invention has been described herein with reference to certain exemplary embodiments, these embodiments are provided for illustrative purposes only and are not intended to be limiting. Therefore, those skilled in the art will recognize that other embodiments can be practiced without departing from the scope and spirit of the claims set forth below.