Abstract:
A communication network for emergency service call handling, the communication network comprising a mobile switching center (MSC) configured to receive an emergency call from a wireless end device and transmit first call signaling indicating a call key for the emergency call and a public safety answering point (PSAP) for the call, and a gateway system configured to receive the first call signaling, process the first call signaling to generate second call signaling indicating the call key and the PSAP, transmit the second call signaling to a routing system, and connect the emergency call from the MSC to the routing system.

Description:
RELATED APPLICATIONS 
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     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
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     MICROFICHE APPENDIX 
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     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is related to telecommunication technologies, and in particular, to converged emergency service call handling technologies. 
     2. Description of the Prior Art 
     Service providers, such as telecommunication carriers, are required to provide emergency call services to end users. For example, service providers are typically required to offer 911 calling capabilities. Specialized location determining systems are used to determine the physical location of callers when 911 calls are placed. 
     Currently, determining the location of a caller on a circuit switched network, such as the public switched telephone network (PSTN), is a relatively straight forward task because every end point in the PSTN is fixed. The physical address of an end point, such as a home address, can be stored in association with a calling number, such as a home phone number. When a 911 call is placed from the PSTN, a location determining system performs a look up to a database system to determine the physical address of the call based on the calling number. The location determining system also determines the appropriate public safety answering point (PSAP) for the call and provides the physical address to the PSAP. In the meantime, the call is transferred from the PSTN to the PSAP. 
     Traditional wireless networks, such as CDMA, TDMA, GSM, iDEN, and PCS networks, present additional challenges to the task of locating callers. Namely, wireless end points are not fixed. Thus, wireless users can roam to any location at will. As a result, the location of a wireless caller cannot be determined based on his calling number. In response to this problem, complex location determining systems have been developed to assist with determining the location of wireless callers. For example, radio frequency triangulation techniques are used to locate callers. 
     Packet communication networks, such as the public Internet, present challenge beyond even those of traditional wireless networks. Voice services are often times provided over packet communication networks. An example of a packet based voice service is Voice Over Internet Protocol (VOID). Like wireless networks, VOIP end points are not fixed. Therefore, the location of a VOW caller cannot be determined based on his calling number or other similar type of identification. In response, complex location determining systems have also been developed in the prior art for determining the location of VOIP callers. 
     Oftentimes, a service provider provides both traditional wireless services as well as VOIP service. As a result, the single service provider frequently bears the entire cost of operating multiple location determining systems for both a wireless network and a VOIP network. 
       FIG. 1  illustrates communication network  100  in the prior art whereby a single service provider operates multiple location determining systems for both a traditional wireless network and a VOIP network. Communication network  100  includes public safety answering point (PSAP)  110  coupled to wireless location system  145  and VOIP location system  135 . Wireless location system  145  is coupled to mobile switching center (MSC)  140 . VOW location system  135  is coupled to VOW gateway system  130 . MSC  140  is coupled to selective router  120  by trunk  101 . VOIP gateway system  130  is also coupled to selective router  120  by trunk  102 . Wireless phone  141  is in communication with MSC  140 . VOIP phone  131  is in communication with VOIP gateway system  130 . 
       FIG. 2  illustrates the operation of communication network  100  in an example of the prior art. A VOIP emergency call flow diagram is first described, followed by a description of a wireless emergency call flow diagram. 
     To begin, a VOIP user using VOIP phone  131  places an emergency call, such as by dialing 911. VOIP phone  131  responsively transmits the emergency call to VOIP gateway system  130 . For instance, VOIP phone  131  might transmit the dialed digits along with a user identification that identifies the user to VOIP gateway system  130 . 
     Upon receiving the emergency call and user identification, VOIP gateway system  130  initiates call setup for the emergency call by transmitting call setup signaling and the user identification to VOIP location system  135 . VOIP location system  135  continues the call setup process by determining the location of the user based on the user identification. For example, VOIP location system  135  typically includes a location database that stores the physical address of users in association with their user identifications. In this case, VOIP location system  135  would perform a look-up to the location database based on the user identification. 
     After determining the location of the user, VOIP location system  135  generates a key that is used to identify the call. VOIP location system  135  continues the call setup process by transmitting the location of the user and the call key to PSAP  110 . At the same time, VOIP location system  135  transmits the identity of the PSAP and the call key to VOIP gateway system  130 . The PSAP is often times identified by a phone number. PSAP  110  receives the location information and the call key and waits for an incoming call associated with the call key. 
     VOIP gateway system  130  initiates call setup with selective router  120  by transmitting the PSAP identification and the call key to selective router  120 . Selective router  120  responsively processes the PSAP identification to select the appropriate PSAP from a group of PSAPs. Selective router  120  then transmits call setup signaling to the selected PSAP, PSAP  110 , indicating the call key. PSAP  110  receives the call setup signaling, recognizes the call key, and looks up the location of the caller based on the key provided by selective router  120 . A bearer connection is established from VOIP phone  131  through VOIP gateway system  130 , selective router  120 , to PSAP  110 . An operator at PSAP  110  is then able to direct emergency responders, such as the police, to the location of the caller. 
     In a wireless example, a wireless user using wireless phone  141  places an emergency call, such as by dialing 911. Wireless phone  141  responsively transmits the emergency call to MSC  140 . Typically, wireless phone  141  transmits a user identification, such as a calling number, that MSC  140  can associate with the user. 
     Upon receiving the emergency call and user identification, MSC  140  initiates call setup for the emergency call by transmitting call setup signaling and the user identification to wireless location system  145 . Wireless location system  145  continues the call setup process by determining the location of the user. Often times, the location of the user is determined using the global position system (GPS). Other times, the location of the user is determined using radio frequency triangulation techniques. 
     After determining the location of the user, wireless location system  145  generates a key that is used to identify the call going forward. Wireless location system  145  continues the call setup process by transmitting the location of the user and the call key to PSAP  110 . At the same time, wireless location system  145  transmits the identity of the PSAP and the call key to MSC  140 . The PSAP is often times identified by a phone number. PSAP  110  receives the location information and the call key and waits for an incoming call associaied with the call key. 
     MSC  140  initiates call setup with selective router  120  by transmitting the PSAP identification and the call key to selective router  120 . Selective router  120  responsively processes the PSAP identification to select the appropriate PSAP from a group of PSAPs. Selective router  120  then transmits call setup signaling to the selected PSAP, PSAP  110 , indicating the call key. PSAP  110  receives the call setup signaling, recognizes the call key, and looks up the location of the caller based on the key provided by selective router  120 . A bearer connection is established from wireless phone  141 , through MSC  140  and selective router  120 , to PSAP  110 . An operator at PSAP  110  is then able to direct emergency responders, such as the police, to the location of the caller. 
     As illustrated, communication network  100  in the prior art requires separate call handling processes for wireless emergency calls and VOIP emergency calls. Such a configuration is costly and inefficient. For example, two distinct trunks, trunks  101  and  102 , are utilized to couple MSC  140  and VOIP gateway system  130  to selective router  120 . Additionally, duplicate call handling processes are required in MSC  140  and VOIP gateway system  130  for routing emergency calls to selective router  120 . Owning and operating multiple location determining systems for both wireless service and packet phone service problematically increases expenses and reduces operating efficiencies. 
     SUMMARY OF THE INVENTION 
     An embodiment of the invention helps solve the above problems and other problems by providing a converged communication network for emergency service call handling that utilizes the resources of both a wireless network and a VOIP network to handle emergency calls. In an embodiment of the invention, a communication network comprises a mobile switching center (MSC) configured to receive an emergency call from a wireless end device and transmit first call signaling indicating a call key for the emergency call and a public safety answering point (PSAP) for the call. The communication network also comprises a gateway system configured to receive the first call signaling, process the first call signaling to generate second call signaling indicating the call key and the PSAP, transmit the second call signaling to a routing system, and connect the emergency call from the MSC to the routing system. 
     In an embodiment of the invention, the gateway system is configured to process the first call signaling to select the routing system from a group of routing systems based on the PSAP. 
     In an embodiment of the invention, the MSC is configured to transmit a key request indicating the emergency call, receive a key response identifying the call key for the emergency call and identifying the public safety answering point (PSAP). 
     In an embodiment of the invention, the gateway system is configured to receive user communications for the emergency call from the MSC and transmit the user communications to the routing system. 
     In an embodiment of the invention, the gateway system is configured to receive the user communications in a synchronous format and transmit the user communications in an asynchronous format. 
     In an embodiment of the invention, the gateway system is configured to receive the user communications in a synchronous format and transmit the user communications in the synchronous format. 
     In an embodiment of the invention, a method of operating a communication network for emergency service call handling comprises receiving an emergency call into a mobile switching center (MSC) from a wireless end device, transmitting first call signaling from the MSC indicating a call key for the emergency call and a public safety answering point (PSAP) for the call, receiving the first call signaling into a gateway system, processing the first call signaling in the gateway system to generate second call signaling indicating the call key and the PSAP, transmitting the second call signaling from the gateway system to a routing system, and connecting the emergency call from the MSC to the routing system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The same reference number represents the same element on all drawings. 
         FIG. 1  illustrates a communication network in an example of the prior art. 
         FIG. 2  illustrates a flow diagram in an example of the prior art. 
         FIG. 3  illustrates a communication network in an embodiment of the invention. 
         FIG. 4  illustrates the operation of a communication network in an embodiment of the invention. 
         FIG. 5  illustrates a communication network in an embodiment of the invention. 
         FIG. 6  illustrates the operation of a communication network in an embodiment of the invention. 
         FIG. 7  illustrates a gateway system in an embodiment of the invention. 
         FIG. 8  illustrates a gateway system in an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIGS. 3-8  and the following description depict specific embodiments of the invention to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these embodiments that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple embodiments of the invention. As a result, the invention is not limited to the specific embodiments described below, but only by the claims and their equivalents. 
     First Embodiment Configuration and Operation 
     FIGS.  3  and  4   
       FIG. 3  illustrates communication network  300  in an embodiment of the invention. Communication network  300  includes public switched telephone network (PSTN)  302 , VOIP network  303  and wireless network  304 . PSTN  302  includes routing system  320 . VOIP network  303  includes gateway system  330 . Wireless network  304  includes MSC  340  and wireless device  341 . Other elements could be included, such as base station systems, but are not shown for purposes of clarity. 
       FIG. 4  illustrates the operation of communication network  300  in an embodiment of the invention. To begin, MSC  340  receives an emergency call from wireless phone  341  (Step  410 ). The call could be, for example, a 911 call. MSC  340  initiates call setup for the call by transmitting first call signaling indicating a call key for the emergency call (Step  420 ). The first call signaling also identifies a PSAP for the call. A location determination system could provide the key and the PSAP identification to MSC  340 , as is commonly understood in the art. 
     Gateway system  330  receives and processes the first call signaling to continue the call setup process initiated by MSC  340  and generates second call signaling that identifies the call key and the PSAP (Step  430 ). Gateway system  330  then transmits the second call signaling to routing system  320  (Step  440 ) to setup a call leg for the call between gateway system  330  and routing system  320 . Gateway system  330  connects the emergency call from MSC  340  to routing system  320  (Step  450 ). Routing system  320  processes the second call signaling to route the call to the appropriate PSAP. The PSAP uses the call key to link the incoming emergency call with the location of the caller. The location of the caller could be provided to the PSAP by the above mentioned location determination system, as well as other location determination systems. 
     Advantageously, communication network  300  improves the efficiency of and reduces the costs of operating both a wireless network and a packet based phone network. For example, only one link to routing system  320  is needed to route emergency calls to a PSAP in PSTN  302  from either VOIP network  303  or wireless network  304 . This advantage significantly reduces costs because, often times, there are several MSCs serving a particular region. As such, rather than running several expensive TDM lines, such as DSOs, from each MSC to a routing system, such as a selective router, only one link is required between the routing system and the VOIP network. 
     Second Embodiment Configuration and Operation 
     FIGS.  5 - 8   
       FIG. 5  illustrates communication network  500  in an embodiment of the invention. Communication network  500  includes public safety answering point (PSAP)  510  coupled to wireless location system  545  and VOIP location system  535 . Wireless location system  545  is coupled to legacy mobile switching center (MSC)  540 . VOIP location system  535  is coupled to VOIP gateway system  530 . MSC  540  is coupled to VOIP gateway system  530 . VOIP gateway system  530  is also coupled to routing system  520 . Wireless phone  541  is in communication with MSC  540 . VOIP phone  531  is in communication with VOIP gateway system  530 . 
       FIG. 6  illustrates the operation of communication network  500  in an embodiment of the invention. A VOIP emergency call flow diagram is first described, followed by a description of a wireless emergency call flow diagram. 
     To begin, a VOIP user using VOIP phone  531  places an emergency call, such as by dialing 911. VOIP phone  531  responsively transmits the emergency call to VOIP gateway system  530 . For instance, VOIP phone  531  might transmit the dialed digits along with a user identification that identifies the user to VOIP gateway system  530 . 
     Upon receiving the emergency call and user identification, VOIP gateway system  530  initiates call setup for the emergency call by transmitting call setup signaling and the user identification to VOIP location system  535 . VOIP location system  535  continues the call setup process by determining the location of the user based on the user identification. For example, VOIP location system  535  typically includes a location database that stores the physical address of users in association with their user identifications. In this case, VOIP location system  535  would perform a look-up to the location database based on the user identification. 
     After determining the location of the user, VOIP location system  535  generates a key that his used to identify the call. VOIP location system  535  continues the call setup process by transmitting the location of the user and the call key to PSAP  510 . At the same time, VOIP location system  535  transmits the identity of the PSAP and the call key to VOIP gateway system  530 . The PSAP is often times identified by a phone number. PSAP  510  receives the location information and the call key and waits for an incoming call associated with the call key. 
     VOIP gateway system  530  initiates call setup with routing system  520  by transmitting the PSAP identification and the call key to routing system  520 . Routing system  520  responsively processes the PSAP identification to select the appropriate PSAP from a group of PSAPs. Selective router then transmits call setup signaling to the selected PSAP, PSAP  510 , indicating the call key. PSAP  510  receives the call setup signaling, recognizes the call key, and looks up the location of the caller based on the key provided by routing system  520 . A bearer connection is established from VOIP phone  531  through VOW gateway system  530 , routing system  520 , to PSAP  510 . An operator at PSAP  510  is then able to direct emergency responders, such as the police, to the location of the caller. 
     In a wireless example, a wireless user using wireless phone  541  places an emergency call, such as by dialing 911. Wireless phone  541  responsively transmits the emergency call to MSC  540 . Typically, wireless phone  541  transmits a user identification, such as a calling number, that MSC  540  can associate with the user. 
     Upon receiving the emergency call and user identification, MSC  540  initiates call setup for the emergency call by transmitting call setup signaling and the user identification to wireless location system  545 . Wireless location system  545  continues the call setup process by determining the location of the user. Often times, the location of the user is determined using the global position system (GPS). Other times, the location of the user is determined using radio frequency triangulation techniques. 
     After determining the location of the user, wireless location system  545  generates a key that is used to identify the call going forward. Wireless location system  545  continues the call setup process by transmitting the location of the user and the call key to PSAP  510 . At the same time, wireless location system  545  transmits the identity of the PSAP and the call key to MSC  540 . The PSAP is often times identified by a phone number. PSAP  510  receives the location information and the call key and waits for an incoming call associated with the call key. 
     MSC  540  initiates call setup with gateway system  530  by transmitting call signaling indicating the PSAP identification and the call key to gateway system  530 . Gateway system  530  responsively processes the call signaling to route the call to selective router  320 . In some cases, there may be multiple selective routers. In such a case, gateway system  530  processes the PSAP identification to select the appropriate selective router based on the PSAP identification. For example, if the PSAP is identified by a phone number, gateway system  530  could select the selective router based on the area code of the phone number. Gateway system  530  then transmits call signaling to the selected selective router, in this case routing system  520 , to setup a call leg for the call. The call signaling identifies the call key and the PSAP. 
     Upon having setup a call leg between gateway system  530  and routing system  520 , routing system  520  transmits call setup signaling to the selected PSAP  510  indicating the call key. PSAP  510  receives the call setup signaling, recognizes the call key, and looks up the location of the caller based on the key provided by routing system  520 . A bearer connection is established from wireless phone  541 , through MSC  540  to gateway system  530 , through gateway system  530  to routing system  520  and from routing system  520  to PSAP  510 . An operator at PSAP  510  is then able to direct emergency responders, such as the police, to the location of the caller. 
       FIG. 7  illustrates gateway system  700  in an embodiment of the invention. Gateway system  700  could be illustrative of gateway systems, such as gateway systems  330  and  530  in  FIGS. 3 and 5  respectively. Gateway system  700  includes gateway  720 , gateway  710 , and gateway controller  730 . Other elements could be included, such as routers and packet switches, as well as other elements. 
     Gateway  710  is capable of receiving communications in one format and interworking the communications to a different format. Similarly, gateway system  720  is capable of receiving communications in one format and interworking the communications to a different format. For example gateway systems  710  and  720  could interwork communications between synchronous and asynchronous format. Examples of synchronous format include time division multiplexed (TDM) communications. Examples of asynchronous formats include packet formats, such as Internet Protocol (IP) based formats. Gateways  710  and  720  could also be referred to as media gateways, as well as by other terms. 
     Gateway controller  730  controls the operations of gateways  710  and  720 . For instance, gateway controller  730  provides incoming and outgoing connection information to gateway  710  and  720 . Gateway controller  730  is capable of receiving call signaling from external elements, such as mobile switching centers (MSCs) and routing systems. Gateway controller  730  is also capable of transmitting call signaling to external elements. Gateway controller  730  could also be referred to as a soft switch or a media gateway controller, as well as by other terms. 
     In operation, gateway controller  730  receives call signaling from external elements for calls. Gateway controller  730  processes the call signaling to setup the call. In some cases, the call could be incoming to gateway  720  and outgoing to gateway  710 . In such a case, gateway controller  730  would instruct gateway  720  to receive synchronous communications on a link connecting gateway  730  and an originating system. Gateway controller  730  further instructs gateway  720  to interwork the synchronous communications to an asynchronous format, and transmit the asynchronous communications for the call to gateway  710 . Gateway controller  730  also instructs gateway  710  to receive the asynchronous communications for the call and interwork the asynchronous call communications to a synchronous format. Gateway controller  730  further instructs gateway  710  to transmit the synchronous call communications on an outgoing link to a destination routing system, such as a selective router. The incoming and outgoing links could be, for example, TDM trunk lines incoming and outgoing from an MSC, a circuit switched routing system, or the like. 
       FIG. 8  illustrates gateway system  800  in an alternative embodiment of the invention. Gateway system  800  could be illustrative of gateway systems, such as gateway systems  330  and  530  in  FIGS. 3 and 5  respectively. Gateway system  800  includes gateway  810 , and gateway controller  830 . Other elements could be included, such as routers and packet switches, as well as other elements. 
     Gateway  810  is capable of receiving communications in one format and interworking the communications to a different format. For example, gateway system  810  could interwork communications between synchronous and asynchronous formats. Examples of synchronous format include time division multiplexed (TDM) communications. Examples of asynchronous formats include packet formats, such as Internet Protocol (IP) based formats. Gateway  810  could also be referred to as a media gateway, as well as by other terms. 
     Gateway controller  830  controls the operation of gateway  810 . For instance, gateway controller  830  provides incoming and outgoing connection information to gateway  810 . Gateway controller  830  is capable of receiving call signaling from external elements, such as mobile switching centers (MSCs) and routing systems. Gateway controller  830  is also capable of transmitting call signaling to external elements. Gateway controller  830  could also be referred to as a soft switch or a media gateway controller, as well as by other terms. 
     In operation, gateway controller  830  receives call signaling from external elements for calls. Gateway controller  830  processes the call signaling to setup the call. In some cases, the call could be both incoming and outgoing through gateway  810 . In such a case, gateway controller  830  instructs gateway  810  to bridge incoming communications to an outgoing link. The outgoing link could be, for example, a packet tunnel or another, similar type of virtual path. Gateway controller  830  further instructs gateway  810  to transmit the asynchronous call communications on the outgoing link to a destination routing system. The incoming links could be, for example, trunk lines incoming from MSCs, circuit switched routing systems, or the like. The destination routing system could be a packet communication network, a packet switch, a router, or the like.