Abstract:
A method for routing emergency calls is provided for emergency calls placed over a packet-switched network ( 310 ) from a Customer Premises Equipment (CPE) ( 110 ) at a remote location ( 100 ). The method includes: registering the CPE ( 110 ) with a home Internet Service Provider (ISP) ( 260 ) through a remote ISP ( 130 ) that is providing the CPE ( 110 ) access to the packet-switched network ( 310 ); determining that the CPE is at a remote location ( 100 ); obtaining a local Internet Protocol (IP) address that corresponds to a Public Safety Answering Point (PSAP) ( 170 ) serving the remote location ( 100 ); routing non-emergency calls to the home ISP ( 260 ) for call processing; and, handling emergency calls locally at the remote ISP ( 130 ) in accordance with the obtained local IP address.

Description:
FIELD 
   The present inventive subject matter relates to the telecommunication arts. Particular application is found in conjunction with emergency telecommunication services (e.g., emergency 9-1-1 calls), and the specification makes particular reference thereto. However, it is to be appreciated that aspects of the present inventive subject matter are also amenable to other applications. 
   BACKGROUND 
   With reference to  FIG. 1 , as is known in the art, the Public Switched Telephone Network (PSTN)  10  includes mechanisms for directing certain calls, such as an enhanced emergency 9-1-1 (E 9-1-1) call, to a Public Safety Answering Point (PSAP)  20 . For example, consider an end office (EO)  30  serving Customer premises equipment (CPE)  40  (i.e., a telephone or other like CPE) from which an E 9-1-1 call is placed. The EO  30  commonly includes a telecommunications switch  32  (e.g., a class  5  switch such as the Lucent Technologies 5ESS or another like switch) that is operatively connected to the CPE  40 . When the switch  32  recognizes an E 9-1-1 call, the call is routed, e.g., over the PSTN  10 , to the PSAP  20  serving the geographic region in which the CPE  40  is located, optionally, said PSAP  20  being designated by a directory number (DN) assigned thereto. 
   While only one CPE is shown, it is to be appreciated that typically a plurality of similarly situated CPE are likewise served by the EO  30  and switch  32 . Optionally, if the switch  32  serves multiple CPE in different geographic regions served by different PSAPs, a selective router (SR)  34  (access via the PSTN  10 ) is employed to route E 9-1-1 calls to the appropriate PSAP. For example, the switch may query a localized database of the SR  34  which relates the DN of the calling CPE to the DN of the PSAP that serves the geographic region in which the CPE is located. In this manner, the E 9-1-1 calls can be directed to the appropriate PSAPs. More frequently, the EO switch may route the call to a tandem office which may then query a localized database of the SR  34  which relates the DN of the calling CPE to the DN of the PSAP that serves the geographic region in which the CPE is located. In this manner, the E 9-1-1 calls can be directed to the appropriate PSAPs. 
   Typically, upon receiving an E 9-1-1 call, the PSAP  20  queries an Automatic Line Identification (ALI) database (DB) using the DN of the calling CPE  40 . The ALI DB provides the PSAP  20  with information associated with the DN of the calling CPE  40 , such as: the geographic and/or physical location of the CPE  40  (i.e., a street address or other positional identification); optionally, any special conditions (e.g., medical conditions of the CPE&#39;s registered owner or user, repeat call patterns from the CPE  40 , etc.); and/or any other such relevant information. In this manner, a proper response to the E 9-1-1 call can be quickly and readily coordinated. 
   One of the advantages of what is known as voice-over-packet-network telephony (which includes, but is not limited to Voice over Internet Protocol (VoIP) telephony) is the ability for “remote” users to access the PSTN through their “home” access network and/or switch. This is a beneficial arrangement since other callers can still reach the user by dialing their normal DN. For example, an individual (i.e., a remote user) that is traveling (e.g., in Cleveland, Ohio) or otherwise away from their home office or location (e.g., in Phoenix, Ariz.) may still be reached at their normal DN (i.e., their Phoenix number). Similarly, calls made by the remote user appear to come from their normal DN (i.e., their Phoenix number) and benefit from showing that DN on a caller ID. Further, the remote user has the ability to utilize any Private Branch Exchange (PBX) or Centrex features supported by the home location, home access network and/or home switch. 
   While generally acceptable for its intended purpose, the foregoing approach for handling emergency calls has certain drawbacks, in particular when dealing with VoIP emergency calls initiated by roaming and/or remote users. That is to say, e.g., when the aforementioned remote user is accessing the PSTN via their home access network and/or home switch in Phoenix, an E 9-1-1 call placed by the remote user would appear to be coming from their normal DN in Phoenix which is associated with their home location (i.e., Phoenix). Accordingly, the PSAP serving the home location in Phoenix would receive the E 9-1-1 call. However, the remote user is actually in Cleveland. Therefore, it would be advantageous to in fact have the E 9-1-1 call directly routed to an appropriate PSAP serving the remote user&#39;s location in Cleveland. 
   Accordingly, a new and improved system and/or method for handling VoIP E 9-1-1 calls is disclosed that overcomes the above-referenced problems and others. 
   SUMMARY 
   In accordance with one preferred embodiment, a method of routing emergency calls is provided for emergency calls placed over a packet-switched network from a Customer Premises Equipment (CPE) at a remote location. The method includes: registering the CPE with a home Internet Service Provider (ISP) through a remote ISP that is providing the CPE access to the packet-switched network; determining that the CPE is at a remote location; obtaining a local Internet Protocol (IP) address that corresponds to a Public Safety Answering Point (PSAP) serving the remote location; routing non-emergency calls to the home ISP for call processing; and, handling emergency calls locally at the remote ISP in accordance with the obtained local IP address. 
   In accordance with another preferred embodiment, a system is provided for routing emergency calls placed over a packet-switched network from a Customer Premises Equipment (CPE) at a remote location. The system includes: means for registering the CPE with a home Internet Service Provider (ISP) through a remote ISP that is providing the CPE access to the packet-switched network; means for determining that the CPE is at a remote location; means for obtaining a local Internet Protocol (IP) address that corresponds to a Public Safety Answering Point (PSAP) serving the remote location; means for routing non-emergency calls to the home ISP for call processing; and, means for handling emergency calls locally at the remote ISP in accordance with the obtained local IP address. 
   In accordance with yet another preferred embodiment, a method is provided for handling calls placed from an Internet Protocol (IP) telephone located at a remote location served by a first Public Safety Answer Point (PSAP) that is different from a second PSAP serving a home location. The handling includes selectively routing calls via one of a home network at the home location and a remote network at the remote location. The remote network provides the IP telephone access to an IP network linking the home and remote networks. The method includes: sending a registration message from the IP telephone through the remote network over the IP network to the home network; determining that the IP telephone is at a remote location; obtaining an IP address local to the remote location that corresponds to the first PSAP; defining a set of rules that differentiate calls into a first type of call and a second type of call; handling the first type of calls locally at the remote network in accordance with the obtained local IP address; and, routing the second type of calls to the home network for handling thereby. 
   Numerous advantages and benefits of the inventive subject matter disclosed herein will become apparent to those of ordinary skill in the art upon reading and understanding the present specification. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The inventive subject matter may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating preferred embodiments and are not to be construed as limiting. Further, it is to be appreciated that the drawings are not to scale. 
       FIG. 1  is a block diagram illustrating an example of a conventional telecommunications network for handling E 9-1-1 calls. 
       FIG. 2  is a block diagram illustrating an exemplary telecommunications network suitable for practicing aspects of the present inventive subject matter. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   For clarity and simplicity, the present specification shall refer to structural and/or functional elements, entities and/or facilities, relevant communication standards, protocols and/or services, and other components and features that are commonly known in the telecommunications art without further detailed explanation as to their configuration or operation except to the extent they have been modified or altered in accordance with and/or to accommodate the preferred embodiment(s) presented herein. 
   With reference to  FIG. 2 , a remote user in a remote location  100  uses customer premises equipment (CPE)  110  to selectively place telephone calls over a PSTN  300 . The CPE  110 , as illustrated, is an IP telephone, suitably, a hardphone or a softphone running as an application on a general purpose computer or the like. However, the CPE  110  may be any traditional IP-based CPE, e.g., used to engage in Voice over IP (VoIP), facsimile, data or other like calls. 
   In the usual manner, the CPE  110  operatively connects with an IP network  310 , such as the Internet or another managed or unmanaged packet-switched network. Suitably, the CPE  110  is served in this capacity by a remote Internet Service Provider (ISP)  130  which is accessed from a remote access network  140 , e.g., a Local Area Network (LAN), to which the CPE  110  is operatively connected in the usual manner. 
   When at a home location  200 , the user similarly uses CPE  210  to selectively place telephone calls over the PSTN  300 . As illustrated, the CPE  210  is again an IP telephone, suitably, a hardphone or a softphone running as an application on a general purpose computer or the like. However, the CPE  210  may again be any traditional IP-based CPE, e.g., used to engage in Voice over IP (VoIP), facsimile, data or other like calls. Note that suitably the CPE  210  is optionally provisioned and/or programmed with its own DN, id and/or other information from which its DN is discernable. 
   In the usual manner, the CPE  210  also operatively connects with the IP network  310 . Suitably, the CPE  210  is served in this capacity by a home ISP  230  which is accessed from a home access network  240 , e.g., a LAN, to which the CPE  210  is operatively connected in the usual manner. 
   Before calls are placed with the CPE  210 , it is first registered with the home ISP  230 . At registration, the home ISP  230  recognizes the CPE  210  as home-based insomuch as it is accessing the home ISP  230  from the home access network  240 . For example, the home ISP  240  checks the originating IP address of the registering CPE  210  to determine that the CPE  210  is accessing the home ISP  230  from the home access network  240  and it is therefore in the home location  200 . Accordingly, when calls are placed from the home-based CPE  210 , they are routed over the home access network  240  to the home ISP  230  which recognizes from the registration that the CPE  210  is at the home location. In this case, the routing of all outgoing calls (i.e., emergency calls such as E 9-1-1 calls, and regular or non-emergency calls) are handled by the home ISP  230  so as to appear as coming from the DN of the CPE  210  which is associated with it&#39;s home location  200 . Regular (i.e., non-emergency) outgoing VoIP calls are routed in the normal manner to the respective called parties, while E 9-1-1 calls are routed to a home EO  250  serving the DN of the CPE  210 . Suitably, regular calls and emergency calls are differentiated from one another by the telephone number dialed. 
   Suitably, the home EO  250  includes a telecommunications switch  252  (e.g., a class 5 switch such as the Lucent Technologies 5ESS or another like switch) that is operatively connected to the PSTN  300  in the usual manner. An IP gateway  260  is operatively connected between the switch  252  and the IP network  310  thereby bridging the IP network  310  with the PSTN  300  in the usual manner. That is to say, the IP gateway  260  acts as a point of entry for packet-switched calls from the IP network  310  headed into the PSTN  300 , and similarly acts as a point of entry for circuit-switched calls from the PSTN  300  headed into the IP network  310 . In the usual manner, the IP gateway  260  selectively converts and/or translates packet-switched calls into circuit-switched calls and vice versa depending on the direction of traffic flow. Alternately, the switch  252  and gateway  260  combination is replaceable by a softswitch that acts as a functional equivalent of the combination. 
   When the home switch  252  recognizes the E 9-1-1 call, the call is routed, e.g., over the PSTN  300 , to the home PSAP  270  serving the home location  200  in which the CPE  210  is located, optionally, said home PSAP  270  being designated by a directory number (DN) assigned thereto. 
   While only one home CPE is shown, it is to be appreciated that a plurality of similarly situated CPE may likewise be served by the EO  250  and switch  252 . Optionally, if the switch  252  serves such multiple CPE in different geographic regions served by a plurality of different PSAPs (for simplicity, only one is shown), a selective router (SR)  254  (accessible via the PSTN  300 ) is employed to route E 9-1-1 calls to the appropriate PSAP. For example, the switch  252  may query a localized database of the SR  254  which relates the DN of the calling CPE to the DN of the PSAP that serves the geographic region in which the CPE is located. Alternatively, the EO switch may route the call to a tandem office which may then query a localized database of the SR  254  which relates the DN of the calling CPE to the DN of the PSAP that serves the geographic region in which the CPE is located. In this manner, the E 9-1-1 calls can be directed to the appropriate PSAPs. 
   Upon receiving the home-based E 9-1-1 call from the CPE  210 , the home PSAP  270  queries an Automatic Line Identification (ALI) database (DB)  272  using the DN of the calling CPE  210 . The ALI DB  272  provides the PSAP  270  with information associated with the DN of the calling CPE  210 , such as: the geographic and/or physical location of the CPE  210  (i.e., a street address or other positional identification); optionally, any special conditions (e.g., medical conditions of the CPE&#39;s registered owner or user, repeat call patterns from the CPE  210 , etc.); and/or any other such relevant information. In this manner, a proper response to the E 9-1-1 call can be quickly and readily coordinated. Notably, the geographic and/or physical location information correctly corresponds to the actual location of the CPE  210  insomuch as the call has already been established by the home ISP  230  as being made from the home location  200 . 
   Returning attention now to the remote user using the remote CPE  110  in the remote location  100 , e.g., that is geographically distinct from the home location  200  at least insomuch as it is served by a different PSAP, namely, PSAP  170 . Suitably, the remote CPE  110  is also registered with the home ISP  230  before calls are placed therewith. Suitably, upon initialization of the remote CPE  110 , e.g., at the time of connection to the remote access network  140 , a registration message is sent from the remote CPE  110 , over the remote access network  140 , and through the remote ISP  130  and IP network  310  to the home ISP  230 . The home ISP  230  recognizes the CPE  110  as remote-based insomuch as it is accessing the home ISP  230  from the remote access network  140 . For example, the home ISP  240  checks the originating IP address of the registering CPE  110  to determine that the CPE  110  is accessing the home ISP  230  from the remote access network  140  and it is therefore in the remote location  100 . 
   In response to the remote registration, the home ISP  230  returns to the remote ISP  130  a response that includes a local IP address (i.e., local to the remote location  100 ) and a set of rules that define which calls are to be handled locally (e.g., emergency calls such as E 9-1-1 calls) and which call are to be handled via the home ISP  230  (e.g., regular non-emergency calls). Suitably, the rules of one embodiment are directed to distinguishing emergency calls (to be handled locally by the remote network) from non-emergency calls (to be handle by the home network). However, it is to be appreciated that the mechanism proposed would support other applications as well, so long as a distinction between which calls are to be handle by the remote network and which calls are to be handled by the home network can be expressed in the form of a suitable rule. 
   Suitably, the returned IP address is obtained from a PSAP DB  312  (e.g., accessible via the IP network  310 ) that relates the originating IP address from the registration message with an IP address associated with the PSAP  170  serving the remote location  100 . Alternately, the remote ISP  130  is provisioned with the local IP address associated with PSAP  170  serving the remote location  100 . The remote ISP  130  is then simply instructed to use this IP address for handling emergency calls locally. 
   Optionally, the location of the remote CPE  110  is identified from the originating IP address of the registration message. In an alternate embodiment, the CPE  110  is provisioned with terminal location equipment, e.g., a global position system (GPS)  112 , that identifies the location of the remote CPE  110 . In either case, the identified location of the CPE  110  is used to select the appropriate local IP address for E 9-1-1 call routing to the PSAP serving the location of the CPE  110 , in this case, namely the PSAP  170 . 
   Accordingly, when a regular (i.e., a non-emergency call, e.g., as determined from the dialed telephone number) is placed from the remote CPE  110 , it is routed over the IP network  310  to be handled by the home ISP  230 , thereby receiving the benefits as if it were placed from the home access network  240 . That is to say, in regular operation, the remote CPE  110  would appear to be at the home DN and be able to utilize any PBX or Centrex features supported at the home location  200 . However, when an emergency call is placed from the remote CPE  110  (i.e., a E 9-1-1 call, e.g., as determined from the dialed telephone number), it is handled locally. For example, the remote ISP  130  uses the local IP address (e.g., the one contained in the response to the remote registration message, the one provisioned in the remote ISP  130 , etc.) to route the E 9-1-1 call to the remote PSAP  170 . As shown, the E 9-1-1 call is routed by the remote ISP  130  to the designated local IP address such that it proceeds through a gateway  160  (similar to gateway  260 ) to a remote EO  150  (similar to EO  250 ), or tandem office which then routes the E 9-1-1 call over the PSTN  300  to the PSAP  170  (similar to PSAP  270 ) serving the remote location  100 . Suitably, the remote EO  150 , or tandem office is provisioned with the DN of the PSAP  170  serving the remote location  100  such that E 9-1-1 calls received by the switch  152  are routed to the appropriate PSAP, namely, PSAP  170 . Again, optionally, the switch  152  and gateway  160  combination is replaceable by a softswitch that acts as a functional equivalent of the combination. 
   Suitably, the designated local IP address for routing E 9-1-1 calls made from the remote CPE  110  identifies either the gateway  160  serving the remote EO  150  or its softswitch, as the case may be. Alternately, the PSAP  170  is IP enabled or capable, e.g., having its own IP address. In this case, the PSAP&#39;s IP address itself is used to directly deliver E 9-1-1 calls from the remote CPE  110  to the PSAP  170  via the IP network  310 . 
   Upon receiving the E 9-1-1 call from the remote CPE  110 , the remote PSAP  170  queries its ALI DB  172  to obtain information associated with the calling CPE  110 , such as the geographic and/or physical location of the CPE  110  (i.e., a street address or other positional identification) and/or any other such relevant information. Optionally, if so equipped, the PSAP  170  may obtain the geographic location of the CPE  110  from its GPS  112 , e.g., via a location information server that provides the location information from the GPS  112  to the ALI DB  172  along with the IP address of the remote CPE  110 . Accordingly, by looking up the IP address from which the E 9-1-1 call originated in the ALI DB  172  the PSAP  170  obtains the corresponding location information for the CPE  110 . In this manner, a proper response to the E 9-1-1 call can be quickly and readily coordinated. Notably, the proper PSAP  170  serving the remote location  100  handles the E 9-1-1 call as opposed to the home PSAP  270 , and the geographic and/or physical location information correctly corresponds to the actual location of the CPE  110 . 
   It is to be appreciated that in connection with the particular exemplary embodiments presented herein certain structural and/or function features are described as being incorporated in defined elements and/or components. However, it is contemplated that these features may, to the same or similar benefit, also likewise be incorporated in other elements and/or components where appropriate. It is also to be appreciated that different aspects of the exemplary embodiments may be selectively employed as appropriate to achieve other alternate embodiments suited for desired applications, the other alternate embodiments thereby realizing the respective advantages of the aspects incorporated therein. 
   It is also to be appreciated that particular elements or components described herein may have their functionality suitably implemented via hardware, software, firmware or a combination thereof. Additionally, it is to be appreciated that certain elements described herein as incorporated together may under suitable circumstances be stand-alone elements or otherwise divided. Similarly, a plurality of particular functions described as being carried out by one particular element may be carried out by a plurality of distinct elements acting independently to carry out individual functions, or certain individual functions may be split-up and carried out by a plurality of distinct elements acting in concert. Alternately, some elements or components otherwise described and/or shown herein as distinct from one another may be physically or functionally combined where appropriate. 
   In short, the present specification has been set forth with reference to preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the present specification. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.