Abstract:
A communication network comprises a device configured to place a call for an emergency service, a call processing system in communication with the device and configured to receive and process the call to route the call to a public service answering point (PSAP), initiate a location determination process, and terminate the call, and a location provisioning system configured to execute the location determination process to determine the location of the device, wherein the location provisioning system comprises a plurality of sub systems, and wherein the call processing system communicates with only a first sub system of the plurality of sub systems to initiate the location determination process and communicates with the first sub system and a second sub system of the plurality of sub systems to terminate the call.

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 relates to telecommunications, and in particular, to emergency call services, provisioning and termination. 
     2. Description of the Prior Art 
     Telecommunication service providers are increasingly required to provide location determination services for emergency service calls. For instance, when a wireless caller places a 911 call, the service provider carrying or otherwise handling the call must have the capabilities to determine the physical location of the caller. The public service answering point (PSAP) selected to handle the call can then use the location information to locate, find, and respond to the caller. 
     Often times, service providers provision their networks regionally. Typically, a single call processing center is assigned to a single region, such as a metropolitan region. Most regions include multiple PSAPs. In most cases, location determination systems exist to assist the call processing center with determining the geographical location of a caller. 
     A call processing center typically interfaces with location determination systems to initiate location processes and otherwise service emergency calls. An important facet of emergency call provisioning is the selection and distribution of a key that is utilized during a call to correlate information on the call by a wide variety of network elements. The key is typically selected from a finite pool of keys by the location determination system with which the call processing center interfaces. The key selection is then communicated by the call processing center to other elements, such as a PSAP, that need the key for information correlation purposes. 
     In many regions, the location determination system includes multiple sub-systems. Often times, the sub-systems are redundant. In these cases, the call processing center in a region may still communicate with only one of the sub-systems when provisioning an emergency call. The multiple sub-systems select keys from a shared pool of finite keys. Thus, when a call processing center communicates with one of the sub-systems on an emergency call, the one sub systems selects and reserves a key from the pool of keys. The other sub-system is prohibited from using the same key for any other calls that may be initiated to that other sub-system. An example of a sub-system is a mobile positioning center. 
     Problematically, when a call terminates, only one of the sub-systems is typically alerted of the termination. The one sub-system then releases the reserved key back to the pool of keys. However, the other sub-systems still holds the key in a reserved state. As a result, the other sub-system has one less key available for new calls. In times of high volume or congestion, such a situation can hinder emergency call processing and response. 
       FIG. 1  illustrates communication network  100  in an example of the prior art further describing the problems described above. Communication network  100  includes caller  101 , communication network  110 , call processing system (CPS)  121 , public safety answering point (PSAP)  141 , PSAP  151 , and location provisioning system (LPS)  130 . LPS  130  includes sub system  131  and sub system  132 . Caller  101  is operatively coupled to communication network  110 . CPS  121  is operatively coupled with communication network  110  and LPS  130 , and in particular, with sub systems  131  and  132 . PSAP  141  and PSAP  151  are also operatively coupled with communication network  110 . 
       FIG. 2  illustrates an operational flow diagram describing the operation of communication network  100  in an example of the prior art. To begin, caller  101  places a 911 emergency services call to CPS  121 . CPS  121  generally processes the call or call request to setup and connect the call to one of PSAP  141  or PSAP  151 . CPS  121  selects either PSAP  141  or PSAP  151  based on the geographical location of caller  101 . In the context of this example, it will be assumed that CPS  121  selects PSAP  141 . 
     Sub system  131  and sub system  132  provide redundant location determination services for emergency calls placed to CPS  121 . CPS  121  typically alternates communications between sub system  131  and sub system  132 . 
     Upon receiving the call request, CPS  121  transmits a key request to sub system  131 . The key request is typically part of a message sequence exchanged between CPS  121  and sub system  131  to determine the geographical location of caller  101 . 
     Sub systems  131  and  132  store a pool of keys that are assigned to each 911 call initiated by CPS  121 . The key is used by CPS  121  and other call elements, such as those elements within PSAP  141 , to correlate call information for the emergency services call. After selecting the key, sub system  131  provides the key to CPS  131 . The key is thereafter reserved or restricted by both sub system  131  and  132  from any use on any other calls. 
     CPS  121  responsively initiates call setup to PSAP  141 , such as by transmitting call signaling. Included within the call setup process is a transfer of the key to PSAP  141 . PSAP  141  queries sub system  131  with the key to obtain location information for caller  101 . Sub system  131  initially responds with the location information. PSAP  141  continues a message dialogue with sub system  131  to maintain the location information. 
     Ultimately, a voice path is established between caller  101  and a termination point within PSAP  141 , such as a phone, terminal, or computer of personnel within PSAP  141 . The personnel can direct other personal, such as emergency service responders, to the location of caller  101 . 
     Eventually, the call ends and caller  101  terminates the call, such as by hanging up, powering off, or otherwise ending the call. Caller  101  responsively transmits a termination message to CPS  121  alerting CPS  121  that the call has ended. CPS  121  forwards or generates and transmits a termination message to sub system  131 . Sub system  131  responsively returns the reserved key to the pool of keys. 
     Unfortunately, a problem arises whereby sub system  131  is alerted of the call termination by CPS  121 , but sub system  132  remains uninformed of the call termination. Thus, while sub system  131  returns the key to the key pool stored internally to sub system  131 , sub system  132  maintains the key in a reserved or restricted state. As a result, the total number of keys available for emergency service calls is reduced. In times of high call volume, the pool of keys available to sub system  132  could become severely limited, if not exhausted entirely. 
     SUMMARY OF THE INVENTION 
     An embodiment of the invention helps solve the above problems and other problems by transmitting multiple termination messages to multiple sub systems so that a previously reserved key is completely released and available for future use. In an embodiment of the invention, a communication network comprises a device configured to place a call for an emergency service, a call processing system in communication with the device and configured to receive and process the call to route the call to a public service answering point (PSAP), initiate a location determination process, and terminate the call, and a location provisioning system configured to execute the location determination process to determine the location of the device, wherein the location provisioning system comprises a plurality of sub systems, and wherein the call processing system communicates with only a first sub system of the plurality of sub systems to initiate the location determination process and communicates with the first sub system and a second sub system of the plurality of sub systems to terminate the call. 
     In an embodiment, the call processing system transfers a key request to the first sub system to initiate the location determination process and wherein the first sub system returns a key to the call processing system in response to the key request and wherein the call processing system transfers the key to the PSAP. 
     In an embodiment, the PSAP queries the location provisioning system with the key to obtain the location of the device. 
     In an embodiment, the first sub system selects the key from a pool of keys. 
     In an embodiment, the first sub system the key from use on other calls. 
     In an embodiment, the second sub system reserves the key from use on the other calls. 
     In an embodiment, the call processing system transmits a first termination message to the first sub system to terminate the call. 
     In an embodiment, the first sub system releases the key for use on the other calls in response to the first termination message. 
     In an embodiment, the call processing system transmits a second termination message to the second sub system to terminate the call. 
     In an embodiment, the second sub system releases the key for use on the other calls in response to the second termination message. 
     In an embodiment, a method of operating communication network comprises, in a device, placing a call for an emergency service, in a call processing system in communication with the device, receiving and processing the call to route the call to a public service answering point (PSAP), initiating a location determination process, and terminating the call, in a location provisioning system, executing the location determination process to determine the location of the device wherein the location provisioning system comprises a plurality of sub systems, and in the call processing system, communicating with only a first sub system of the plurality of sub systems to initiate the location determination process and communicating with the first sub system and a second sub system of the plurality of sub systems to terminate the call. 
    
    
     
       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  is 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 a flow diagram in an embodiment of the invention. 
         FIG. 5  illustrates a flow diagram in an embodiment of the invention. 
         FIG. 6  illustrates a call processing system in an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIGS. 3-6  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. 
       FIG. 3  illustrates communication network  300  in an embodiment of the invention. Communication network  300  includes caller  301 , communication network  310 , call processing system (CPS)  321 , public safety answering point (PSAP)  341 , PSAP  351 , and location provisioning system (LPS)  330 . LPS  330  includes sub system  331  and sub system  332 . Caller  301  is operatively coupled to communication network  310 . CPS  321  is operatively coupled with communication network  310  and LPS  330 , and in particular, with sub systems  331  and  332 . PSAP  341  and PSAP  351  are also operatively coupled with communication network  310 . 
     Communication network  310  could be any network or collection of networks that couple, link, or otherwise operatively connect caller  301  with CPS  321 , caller  301  with either PSAP  341  or PSAP  351 , and CPS  321  with either PSAP  341  or PSAP  351 . It should be understood that communication network  310  could also connect CPS  321  with LPS  330 , or PSAP  341  and PSAP  351  with LPS  330 . However, other secondary data networks could be used. In an example, communication network could include a backhaul network, a local network, a long distance network, or a packet network, or any combination thereof, as well as other types of networks. 
     Caller  301  could be any device, system, or other such communication platform capable of communicating with CPS  321  and PSAP  341  or PSAP  351  over communication network  310 . Caller  301  could be, for example, a mobile phone, a wireless phone, or a wireline phone, or any combination thereof, as well as any other type of device or system. Other types of communication platforms are possible. 
     CPS  321  could be any system or collection of systems capable of communicating with caller  301  and PSAP  341  or  351  to setup, tear-down, and otherwise handle an emergency service call. CPS  321  could also be capable of communicating with sub systems  331  and  332  to initiate location determination processes to determine the location of emergency service calls. CPS  321  could be, for example, a mobile switching center (MSC), a soft switch, a media gateway controller, or any combination or variation thereof, as well another type of call processing system. 
     Location provisioning system  330  could be any system or collection of systems, such as sub systems  331  and  332 , capable of determining the location of callers to emergency services. In an example, sub systems  331  and  332  could be mobile positioning centers (MPC). It should be understood that location provisioning system  330  could include additional elements not pictured for the sake of clarity. For example, position determining equipment (PDE) could be included. Furthermore, a gateway system could be included to interface between PSAPs  341  and  351  and sub systems  31  and  332 . An example of a gateway is an automatic location identification (ALI) gateway or database. 
       FIG. 4  illustrates an operational flow diagram describing the operation of communication network  300  in an example of the invention. To begin, caller  301  places a 911 emergency services call to CPS  321 . CPS  321  generally processes the call or call request to setup and connect the call to one of PSAP  341  or PSAP  351 . CPS  321  selects either PSAP  341  or PSAP  351  based on the geographical location of caller  301 . In the context of this example, it will be assumed that CPS  321  selects PSAP  341 . 
     Sub system  331  and sub system  332  provide redundant location determination services for emergency calls placed to CPS  321 . CPS  321  typically alternates communications between sub system  331  and sub system  332 . 
     Upon receiving the call request, CPS  321  transmits a key request to sub system  331 . The key request is typically part of a message sequence exchanged between CPS  321  and sub system  331  to determine the geographical location of caller  301 . 
     Sub systems  331  and  332  store a pool of keys that are assigned to each 911 call initiated by CPS  121 . The key is used by CPS  321  and other call elements, such as those elements within PSAP  341 , to correlate call information for the emergency services call. After selecting the key, sub system  331  provides the key to CPS  331 . The key is thereafter reserved or restricted by both sub system  331  and  332  from any use on any other calls. 
     CPS  321  responsively initiates call setup to PSAP  341 , such as by transmitting call signaling. Included within the call setup process is a transfer of the key to PSAP  341 . PSAP  341  queries sub system  331  with the key to obtain location information for caller  301 . Sub system  331  initially responds with the location information. PSAP  341  continues a message dialogue with sub system  331  to maintain the location information. 
     Ultimately, a voice path is established between caller  301  and a termination point within PSAP  341 , such as a phone, terminal, or computer of personnel within PSAP  341 . The personnel can direct other personal, such as emergency service responders, to the location of caller  301 . 
     Eventually, the call ends and caller  301  terminates the call, such as by hanging up, powering off, or otherwise ending the call. Caller  301  responsively transmits a termination message to CPS  321  alerting CPS  321  that the call has ended. CPS  321  forwards or generates and transmits a termination message to sub system  331 . Sub system  31  responsively returns the reserved key to the pool of keys. Sub system  331  also responsively transmits a termination message to sub system  332 . Sub system  332  then also responsively returns the reserved key to the pool of keys. Advantageously, the previously reserved key is now available to both sub systems  331  and  332  for further use with new calls. 
       FIG. 5  illustrates an operational flow diagram describing the operation of communication network  300  in an example of the invention. To begin, caller  301  places a 911 emergency services call to CPS  321 . CPS  321  generally processes the call or call request to setup and connect the call to one of PSAP  341  or PSAP  351 . CPS  321  selects either PSAP  341  or PSAP  351  based on the geographical location of caller  301 . In the context of this example, it will be assumed that CPS  321  selects PSAP  341 . 
     Sub system  331  and sub system  332  provide redundant location determination services for emergency calls placed to CPS  321 . CPS  321  typically alternates communications between sub system  331  and sub system  332 . 
     Upon receiving the call request, CPS  321  transmits a key request to sub system  331 . The key request is typically part of a message sequence exchanged between CPS  321  and sub system  331  to determine the geographical location of caller  301 . 
     Sub systems  331  and  332  store a pool of keys that are assigned to each 911 call initiated by CPS  121 . The key is used by CPS  321  and other call elements, such as those elements within PSAP  341 , to correlate call information for the emergency services call. After selecting the key, sub system  331  provides the key to CPS  331 . The key is thereafter reserved or restricted by both sub system  331  and  332  from any use on any other calls. 
     CPS  321  responsively initiates call setup to PSAP  341 , such as by transmitting call signaling. Included within the call setup process is a transfer of the key to PSAP  341 . PSAP  341  queries sub system  331  with the key to obtain location information for caller  301 . Sub system  331  initially responds with the location information. PSAP  341  continues a message dialogue with sub system  331  to maintain the location information. 
     Ultimately, a voice path is established between caller  301  and a termination point within PSAP  341 , such as a phone, terminal, or computer of personnel within PSAP  341 . The personnel can direct other personal, such as emergency service responders, to the location of caller  301 . 
     Eventually, the call ends and caller  301  terminates the call, such as by hanging up, powering off, or otherwise ending the call. Caller  301  responsively transmits a termination message to CPS  321  alerting CPS  321  that the call has ended. CPS  321  forwards or generates and transmits a termination message to sub system  331 . Sub system  31  responsively returns the reserved key to the pool of keys. CPS  321  also forwards or generates and transmits a termination message to sub system  332 . Sub system  332  then also responsively returns the reserved key to the pool of keys. Advantageously, the previously reserved key is now available to both sub systems  331  and  332  for further use with new calls. 
       FIG. 6  illustrates call processing system  600  in an embodiment of the invention. Call processing system  600  includes interface  620 , processing system  630 , storage system  640 , and software  650 . Storage system  640  stores software  650 . Processing system  630  is linked to interface  620 . Call processing system  600  could be comprised of a programmed general-purpose computer, although those skilled in the art will appreciate that programmable or special purpose circuitry and equipment may be used. Call processing system  600  may use a client server architecture where operations are distributed among a server system and client devices that together comprise elements  620 - 650 . 
     Interface  620  could comprise a network interface card, modem, port, or some other communication device. Signaling interface  620  may be distributed among multiple communication devices. Interface  630  could comprise a computer microprocessor, logic circuit, or some other processing device. Processing system  630  may be distributed among multiple processing devices. Storage system  640  could comprise a disk, tape, integrated circuit, server, or some other memory device. Storage system  640  may be distributed among multiple memory devices. 
     Processing system  630  retrieves and executes software  650  from storage system  640 . Software  650  may comprise an operating system, utilities, drivers, networking software, and other software typically loaded onto a general-purpose computer. Software  650  could also comprise an application program, firmware, or some other form of machine-readable processing instructions. When executed by the processing system  630 , software  650  directs processing system  630  to operate as described above for call processing system  231 .