PATENT DOCUMENT

Publication Number: US-9380610-B2
Application Number: US-201414501996-A
Country: US
Kind Code: B2

Title: System and method for performing emergency calls over WiFi when a cellular network is unavailable

Abstract:
A station that performs methods related to emergency calls. In one example, the station determines that a first connection to a cellular network is unavailable, the client station being associated with a home network having a home Public-Safety Answering Point (PSAP), the station disposed at a location outside the home network, the location having a remote PSAP. The station determines a second connection to a WiFi network is available, establishes the second connection to the WiFi network and performs an emergency call over the WiFi network. The emergency call being routed to the remote PSAP associated with the location. In another example, the station determines it is capable of performing an emergency call over a cellular network, receives a request to perform an emergency call, determines whether a circuit switched radio access technology (CS-RAT) is available and performs the emergency call over a WiFi network when the CS-RAT is unavailable.

Claims:
What is claimed is: 
     
       1. A method, comprising:
 at a client station: 
 determining that a first connection to a cellular network is unavailable, the client station being associated with a home network, the home network having a home Public-Safety Answering Point (PSAP) associated therewith, the client station disposed at a geographic location outside the home network, the geographic location having a remote PSAP associated therewith; 
 determining that a second connection to a WiFi network is available; 
 establishing the second connection to the WiFi network; and 
 performing an emergency call over the WiFi network by registering with an Internet Protocol (IP) Multimedia Subsystem (IMS), the registering including providing location information of the client station, the emergency call being routed to the remote PSAP associated with the geographic location corresponding to the location information. 
 
     
     
       2. The method of  claim 1 , further comprising:
 determining that the location information of the client station is unavailable; and 
 determining that the registering with the location information is unsuccessful. 
 
     
     
       3. The method of  claim 2 , further comprising:
 registering with the IMS by providing civic address information of the client station, the emergency call being routed to the home PSAP when one of the location information is unavailable or the registering is unsuccessful. 
 
     
     
       4. The method of  claim 3 , further comprising:
 determining, after registering with the IMS by providing civic address information, whether the first connection to the cellular network is available; and 
 performing the emergency call over the cellular network. 
 
     
     
       5. The method of  claim 4 , wherein performing the emergency call over the cellular network includes:
 determining whether a circuit switched radio access technology (CS-RAT) is available; and 
 deregistering from the IMS via the second connection when it is determined that the CS-RAT is available. 
 
     
     
       6. The method of  claim 5 , wherein performing the emergency call over the cellular network further includes:
 initiating a timer, wherein the CS-RAT is determined to be available prior to the timer expiring. 
 
     
     
       7. The method of  claim 1 , wherein the first connection is determined to be unavailable based on one of the client station not having a cellular capability, the cellular capability of the client station being disabled or the client station being outside a range of cellular coverage. 
     
     
       8. The method of  claim 1 , wherein the location information is determined from one of out-of-band crowd-sourced WiFi location information, a global positioning system (GPS) location, a satellite based location system, or a triangulation based location system. 
     
     
       9. The method of  claim 1 , further comprising:
 displaying an indication to a user of the client station when the first and second connections are unavailable. 
 
     
     
       10. A client station, comprising:
 wireless communications circuitry configured to establish a connection to at least one of a cellular network and a WiFi network; and 
 a processor; 
 wherein the processor and the wireless communications circuitry are configured to perform an emergency call by:
 determining that a first connection to the cellular network is unavailable, the client station being associated with a home network, the home network having a home Public-Safety Answering Point (PSAP) associated therewith, the client station disposed at a geographic location outside the home network, the geographic location having a remote PSAP associated therewith; 
 determining that a second connection to the WiFi network is available; 
 establishing the second connection to the WiFi network; and 
 performing an emergency call over the WiFi network by registering with an Internet Protocol (IP) Multimedia Subsystem (IMS), the registering including providing location information of the client station, the emergency call being routed to the remote PSAP associated with the geographic location corresponding to the location information. 
 
 
     
     
       11. The client station of  claim 10 , wherein the processor and the wireless communications circuitry is further configured to perform an emergency call by:
 determining that the location information of the client station is unavailable; and 
 determining that the registering with the location information is unsuccessful. 
 
     
     
       12. The client station of  claim 11 , wherein the processor and the wireless communications circuitry is further configured to perform an emergency call by:
 registering with the IMS by providing civic address information of the client station, the emergency call being routed to the home PSAP when one of the location information is unavailable or the registering is unsuccessful. 
 
     
     
       13. The client station of  claim 12 , wherein the processor and the wireless communications circuitry is further configured to perform an emergency call by:
 determining, after registering with the IMS by providing civic address information, whether the first connection to the cellular network is available; and 
 performing the emergency call over the cellular network. 
 
     
     
       14. The client station of  claim 10 , wherein the first connection is determined to be unavailable based on one of the client station not having a cellular capability, the cellular capability of the client station being disabled or the client station being outside a range of cellular coverage. 
     
     
       15. The client station of  claim 10 , wherein the location information is determined from one of out-of-band crowd-sourced WiFi location information, a global positioning system (GPS) location, a satellite based location system, or a triangulation based location system. 
     
     
       16. A method, comprising:
 at a client station: 
 determining the client station is capable of performing an emergency call over a cellular network; 
 receiving a request to perform an emergency call; 
 determining whether a circuit switched radio access technology (CS-RAT) of the cellular network is available; and 
 performing the emergency call over a WiFi network when the CS-RAT is unavailable, wherein the emergency call is routed to one of a home Public-Safety Answering Point (PSAP) associated with the client station or a remote PSAP associated with a geographic location where the client station is currently located. 
 
     
     
       17. The method of  claim 16 , further comprising: performing the emergency call over the cellular network when the CS-RAT is available. 
     
     
       18. The method of  claim 17 , wherein the client station is registered with an Internet Protocol (IP) Multimedia Subsystem (IMS), and the performing the emergency call over the cellular network further comprises:
 deregistering from the IMS. 
 
     
     
       19. The method of  claim 16 , further comprising:
 initiating a timer, wherein the emergency call is performed over the WiFi network when it is determined that the CS-RAT is not available prior to the timer expiring. 
 
     
     
       20. The method of  claim 16 , further comprising:
 registering the client station with an Internet Protocol (IP) Multimedia Subsystem (IMS) including one of the geographic location where the client station is currently located or a civic address associated with the client station, 
 wherein the emergency call is routed to the remote PSAP when the registering includes the geographic location where the client station is currently located and the home PSAP when the registering includes the civic address.

Description:
INCORPORATION BY REFERENCE/PRIORITY CLAIM 
     This application claims priority to U.S. Provisional Application Ser. No. 61/943,761 entitled “System and Method for Performing Emergency Calls Over WiFi,” filed on Feb. 24, 2014, U.S. Provisional Application Ser. No. 62/003,977 entitled “System and Method for Performing Emergency Calls Over WiFi,” filed on May 28, 2014 and U.S. Provisional Application Ser. No. 62/005,916 entitled “System and Method for Performing Emergency Calls Over WiFi,” filed on May 30, 2014. Each of the above-identified applications are incorporated herein, in their entirety, by reference. 
    
    
     BACKGROUND 
     A client station may be configured to connect to a variety of different wireless networks based on the hardware and software configurations thereof. For example, a client station may be able to connect to a cellular network and/or a WiFi network, depending on how the client station is configured. While connected to a wireless network, the client station may execute a call application via which a voice call may be performed. A specific implementation of the voice call is an emergency call in which the call is routed to a Public-Safety Answering Point (PSAP). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exemplary network arrangement. 
         FIG. 2  shows an exemplary network arrangement in more detail than  FIG. 1  that is used to perform an emergency call. 
         FIG. 3  shows an exemplary client station configured to perform the emergency call. 
         FIG. 4  shows an exemplary method for performing the emergency call. 
         FIG. 5  shows an exemplary method for performing a cellular option. 
     
    
    
     DETAILED DESCRIPTION 
     The exemplary embodiments may be further understood with reference to the following description and the related appended drawings, wherein like elements are provided with the same reference numerals. The exemplary embodiments are related to a system and method for performing an emergency call with a client station. Specifically, the client station may be able to perform a voice call using either a cellular network or an Internet Protocol (IP) network. The term “cellular network” refers to any type of radio access network (“RAN”) having distributed cells for communicating with client stations. In one example, a cellular network may include networks utilizing legacy circuit-switched (CS) or packet-switched (PS) communications such as a 2G radio access network (RAN) or a 3G RAN. In another example, a cellular network may also include networks utilizing next generation technology such as a Long Term Evolution Radio Access Network (LTE-RAN). The IP network may represent networks that are IP-only such as a WiFi network (e.g., as defined by IEEE 802.11a/b/g/n/ac). While connected to the WiFi network, the client station may specifically be configured to perform an emergency call. The exemplary embodiments provide a mechanism for an emergency call placed over the WiFi network to be properly routed to a nearest PSAP relative to the client station rather than a home PSAP associated with the client station. 
       FIG. 1  shows an exemplary network arrangement  100 . The exemplary network arrangement  100  includes client stations  110 - 114 . In this example, it is assumed that the client stations  100 - 114  are associated with a single user. For example, the client station  110  may be the user&#39;s mobile phone, the client station  112  may be the user&#39;s tablet computer and the client station  114  may be the user&#39;s desktop computer. Those skilled in the art will understand that, in addition to the examples provided above, the client stations may be any type of electronic component that is configured to communicate via a network, e.g., smartphones, phablets, embedded devices, etc. It should also be understood that an actual network arrangement may include any number of client stations associated with any number of users and that the user may be associated with more or less client stations. The example of three (3) client stations associated with one (1) user is only provided for illustrative purposes. 
     Each of the client stations  110 - 114  may be configured to communicate directly with one or more networks. In this example, the networks with which the client stations  110 - 114  may communicate are a legacy radio access network (RAN)  120 , a Long Term Evolution radio access network (LTE-RAN) network  122  and a wireless local area network (WLAN)  124 . In this example, each of the networks  120 - 124  is a wireless network with which the client stations  110 - 114  may communicate wirelessly. However, it should be understood that the client stations  110 - 114  may also communicate with other types of networks using a wired connection. It should also be understood that not all of the client stations  110 - 114  may communicate directly with each of the networks  120 - 124 . For example, the client station  114  may not have an LTE chipset and therefore may not have the ability to communicate with the LTE-RAN  122 . Again, the use of three (3) networks is only exemplary and there may be any other number of networks with which the client stations  110 - 114  may communicate. 
     The legacy RAN  120  and the LTE-RAN  122  are portions of cellular networks that may be deployed by cellular providers (e.g., Verizon, AT&amp;T, Sprint, T-Mobile, etc.). These networks  120  and  122  may include, for example, base client stations (Node Bs, eNodeBs, HeNBs, etc.) that are configured to send and receive traffic from client stations that are equipped with the appropriate cellular chip set. Examples of the legacy RAN may include those networks that are generally labeled as 2G and/or 3G networks and may include circuit switched voice calls and packet switched data operations. Those skilled in the art will understand that the cellular providers may also deploy other types of networks, including further evolutions of the cellular standards, within their cellular networks. The WLAN  124  may include any type of wireless local area network (WiFi, Hot Spot, IEEE 802.11x networks, etc.). Those skilled in the art will understand that there may be thousands, hundreds of thousands or more of different WLANs deployed in the United States alone. For example, the WLAN  124  may be the user&#39;s home network, the user&#39;s work network, a public network (e.g., at a city park, coffee shop, etc.). Generally, the WLAN  124  will include one or more access points that allow the client stations  110 - 114  to communicate with the WLAN  124 . 
     In addition to the networks  120 - 124 , the network arrangement also includes a cellular core network  130  and the Internet  140 . The cellular core network  130 , the legacy RAN  120  and the LTE-RAN  122  may be considered a cellular network that is associated with a particular cellular provider (e.g., Verizon, AT&amp;T, Sprint, T-Mobile, etc.). The cellular core network  130  may be considered to be the interconnected set of components that manages the operation and traffic of the cellular network. The interconnected components of the cellular core network  130  may include any number of components such as servers, switches, routers, etc. The cellular core network  130  also manages the traffic that flows between the cellular network and the Internet  140 . 
     The network arrangement  100  also includes an IP Multimedia Subsystem (IMS)  150 . The IMS  150  may be generally described as an architecture for delivering multimedia services to the client stations  110 - 114  using the IP protocol. The IMS  150  may include a variety of components to accomplish this task. For example, a typical IMS  150  includes an HSS server that stores subscription information for a user of the client stations  110 - 114 . This subscription information is used to provide the correct multimedia services to the user. Other exemplary components of the IMS  150  will be described below, as needed. The IMS  150  may communicate with the cellular core network  130  and the Internet  140  to provide the multimedia services to the client stations  110 - 114 . The IMS  150  is shown in close proximity to the cellular core network  130  because the cellular provider typically implements the functionality of the IMS  150 . However, it is not necessary for this to be the case. The IMS  150  may be provided by another party. 
     Thus, the network arrangement  100  allows the client stations  110 - 114  to perform functionalities generally associated with computer and cellular networks. For example, the client stations  110 - 114  may perform voice calls to other parties, may browse the Internet  140  for information, may stream multimedia data to the client devices  110 - 114 , etc. 
     However, as described above, not every client station  110 - 114  may have the same communication capabilities with the networks  120 ,  122 ,  124 ,  130 ,  140 . This lack of communication with one or more of the networks may be due to the capabilities of the client device  110 - 114 , e.g., the client device does not include a cellular chip, or may be due to a limitation of the network, e.g., a cellular network does not have a base client station within range of the client station. This lack of communication with one or more networks may result in the client station being unable to avail itself of the functionalities that are available via one or more of the networks. 
     In addition to the elements already described, the network arrangement  100  also includes a network services backbone  160  that is in communication either directly or indirectly with the Internet  140  and the cellular core network  130 . The network services backbone  160  may be generally described as a set of components (e.g., servers, network storage arrangements, etc.) that implement a suite of services that may be used to extend the functionalities of the client stations  110 - 114  in communication with the various networks. These extensions may include the functionalities to which the client device  110 - 114  does not have access because of limitations of the device and/or network, some examples of which were described above. The network services backbone  160  interacts with the client devices  110 - 114  and/or the networks  120 ,  122 ,  124 ,  130 ,  140  to provide these extended functionalities. 
     The network services backbone  160  may be provided by any entity or a set of entities. In one example, the network services backbone  160  is provided by the supplier of one or more of the client stations  110 - 114 . In another example, the network services backbone  160  is provided by the cellular network provider. In still a further example, the network services backbone  160  is provided by a third party unrelated to the cellular network provider or the supplier of the client stations  110 - 114 . 
     The exemplary embodiments described herein provide an example of different types of functionalities that may be extended to a client station  110 - 114  and also provide an example of components and services that may be included in the network services backbone  160 . In this example, the network services backbone  160  is used to provide emergency calls over WLAN networks by the client stations  110 - 114 ]. However, it should be understood that the network services backbone  160  may include many other components and services that may be used to enhance the operations of the client stations  110 - 114  and networks. 
     One of the services provided by the network services backbone  160  may be to store and update associations among the different client stations  110 - 114 . As described above, in this example, each of these client stations  110 - 114  are associated with the same user. Thus, the network services backbone  160  may store information that indicates this association of the user with each of the client stations  110 - 114  and may then also store (or link) the relationship of the client stations  110 - 114  with each other based on their association with the user. This association among client stations  110 - 114  may be used as one of the bases for the network services backbone  160  to provide the enhanced operations of the client stations  110 - 114 . 
     A client station (e.g., client stations  110 - 114 ) may be able to connect to a legacy RAN and/or or a WiFi network, depending on its capabilities. For example, the client station may include wireless communications circuitry that is capable of communicating with the legacy RAN. More specifically, the legacy RAN may be for a particular cellular service provider. The wireless communications circuitry may include any component or combination of components to perform communications via the legacy RAN. In another example, the client station may include wireless communications circuitry for communications with a WiFi network. In various embodiments, a client station may include wireless communications circuitry for communicating (a) only with legacy RANs, (b) only with WiFi networks, or (c) for communicating with both legacy RANs and WiFi networks. Further details regarding wireless communications circuitry that may be included in a client station are provided below with reference to  FIG. 3 . 
     While the client station is connected to the legacy RAN  120 , the client station may execute a call application to establish a voice call with a target user over the legacy RAN  120 . While the client station is connected to the LTE-RAN  122  or the WLAN  124 , the client station may execute a variety of different applications to exchange data with other electronic devices. In a specific example of communicating with other electronic devices, the client station may be configured to also perform the voice call over the WLAN  124 . In view of the manner in which the voice call is performed over the WLAN  124 , the voice may be transmitted using, for example, the IMS  150  when the client station uses the WLAN  124 . An exemplary manner of performing the voice call over the WLAN  124  is the call application performing a Voice over Internet Protocol (VoIP) call. More specifically, the VoIP call may be a Voice over Long Term Evolution (VoLTE) call. 
     Throughout this description, it will be described that the IMS  150  is used for a voice call to be performed over the LTE-RAN  122  or WLAN  124 . However, those skilled in the art will understand that the use of the IMS  150  is only exemplary and that any network functionality that enables a station to perform a voice call over the LTE-RAN  122  or WLAN  124  may be used. For example, the IMS  150  may enable this functionality by being an interface between the LTE-RAN  122  or WLAN  124  (more specifically the cellular core network  130 ) and other networks (such as a public switched telephony network (PSTN)) for the voice call to be performed by the client station and a target destination. Therefore, the IMS  150  may represent any network functionality that provides this interface. 
     A specific type of voice call that may be performed over the legacy RAN  120 , the LTE-RAN  122 , or the WLAN  124  is an emergency call. In many countries, the public telephone network has a single emergency telephone number (e.g., “911” in North America, “112” in European countries, etc.) that allows a caller to contact emergency services for assistance. Thus, when the caller inputs the emergency telephone number into the call application of the client station, the voice call may be routed to a PSAP. The PSAP is a call center responsible for answering calls to an emergency telephone number for police, firefighting, ambulance services, and other emergency services. Therefore, there are a plurality of PSAPs disposed in select geographic locations that handle the emergency calls that are performed within the respective geographic area assigned to the PSAPs. 
     When a landline is used to perform an emergency call, a location of the stationary telephone is known. Specifically, the use of the PSTN with the related service provider may indicate the location that the emergency call is originating. When the location is known, the emergency call may be routed to a local PSAP relative to the caller. 
     With a client station that is mobile, the location of the user may change. When a client station registers with a home network, the client station may be associated with the region of the home network (e.g., the assumption being the client station is disposed in the region of the home network a majority of the time it is used). When the client station is configured to use the legacy RAN  120  or the LTE-RAN  122  to perform the voice call using the call application, the location of the client station may be known by the respective base station that the client station has associated to connect to the respective network. Thus, an emergency call performed by the client station may be properly routed to the local PSAP. For example, when the client station is in the region of the home network, the connection to the legacy RAN  120  provides the location of the client station such that an emergency call is routed to the local PSAP responsible for the region of the home network. In another example, when the client station is in a remote region away from the home network, the connection to the legacy RAN  120  or the LTE-RAN  122  still provides the location of the client station such that an emergency call is routed to the local PSAP responsible for this remote region. 
     As discussed above, the call application may be performed by the client station using the WLAN  124  as well. However, unlike the legacy RAN  120  and the LTE-RAN  122 , a connection to the WLAN  124  does not include a location of the client station. When using the call application for a non-emergency voice call with a target destination, the location information may be irrelevant. In contrast, the location of the client station may be highly relevant when performing the emergency call. Specifically, the location may indicate a manner in which the emergency call is to be routed to a desired PSAP. Using the WLAN  124  and without a known location of the client station, the emergency call may be handled in a sub-optimal manner. Specifically, the client station may be associated with a home network. The emergency call may always be routed to the PSAP responsible for the region of the home network. When the client station is in this region, the routing to this PSAP may be preferred. However, again, due to its mobile nature, the client station may not be in this region but in a remote region. Nevertheless, the emergency call is still routed to the PSAP responsible for the region of the home network. This may cause undue delay or other complications in handling the emergency. 
     The exemplary embodiments provide a manner of routing emergency calls performed over the WLAN  124  to the local PSAP relative to the location of the client station. Specifically, the emergency call may be performed when connected to the WLAN  124  by registering with an IMS  150  in the location of the client station. By including this location information when registering with the IMS  150 , the emergency call may be routed to the local PSAP rather than a home PSAP which may not be the optimal PSAP to handle the emergency call. In this manner, though using the WLAN  124  to perform the emergency call, the local PSAP may still receive the emergency call rather than the PSAP of the home network. The exemplary embodiments also provide a default mechanism for the standard location-free emergency call to be performed but also include a modification for the location to be used if available. 
       FIG. 2  shows an exemplary network arrangement  200  in more detail than the network arrangement  100  of  FIG. 1  that is used to perform an emergency call. The network arrangement  200  may represent a variety of different pathways for an emergency call to be routed to reach a PSAP. The pathway may depend upon a network type being utilized to perform the emergency call. The pathway may also depend upon location information of the client station performing the emergency call. As illustrated in  FIG. 2 , a client station  205  may utilize a legacy RAN  210 , a LTE-RAN  215 , or a WiFi network  220 . The client station  205  may be any of the client stations  110 - 114  illustrated in  FIG. 1 . 
     As discussed above, the legacy RAN  210  may be any cellular network that operates in defined cellular frequency bands and managed by a cellular service provider. For example, the legacy RAN  210  may be a 2G RAN or a 3G RAN. Thus, the client station  205  may connect to the legacy RAN  210  via a cellular base station. The LTE-RAN  215  may also be a cellular network that utilizes an IP-based network that operates in defined cellular frequency bands and may also be managed by the cellular service provider. Thus, the client station  205  may connect to the LTE-RAN  215  via an evolved Node B (eNB). The WiFi network  220  may be any WiFi network that operates in defined WiFi frequency bands and managed by WiFi servers that may include public WiFi servers (e.g., HotSpots provided by cellular service providers) or private servers (e.g., a personal home access point, router, etc.). Thus, when further servers are included, the WiFi network  220  may be connected to other networks  225  such as an Internet Service Provider (ISP). As described above, a WiFi network is a type of WLAN  124 . Thus, throughout this description, the term WiFi network should be understood to include any type of WLAN. 
     Each of the legacy RAN  210 , the LTE-RAN  215 , and the WiFi network  220  (as well as the other networks  225 ) may be connected to a respective cellular core network  230  as also shown in  FIG. 1 . As shown in  FIG. 2 , the cellular core network  230  is illustrated as a single unit that includes a variety of different components that handles data transmissions with the various different types of networks. However, it should be noted that such a configuration is only exemplary and is used for illustrative purposes only. Specifically, the cellular core network  230  may be separated to include corresponding components for each type of network. As shown in  FIG. 2 , the cellular core network  230  may include a mobile switching center (MSC)  235  and a gateway MSC  240  for the legacy RAN  210 ; a serving gateway (SGW)  245  and a packet data network gateway (PDNGW)  250  for the LTE-RAN  215 ; and an evolved packet data gateway (ePDG)  255  and the PDNGW  250  for the WiFi network  220 . 
     With the legacy RAN  210 , the cellular core network  230  may include components for, for example, a Global System for Mobile Communications (GSM) core network or a Code Division Multiple Access (CDMA) core network. The MSC  235  may be responsible for routing voice calls, SMS, conference calls, fax, circuit switched data, etc. in GSM/CDMA cellular networks. Other functions such as set up and release of the end-to-end connections, mobility and call hand-overs, and account monitoring may be handled by the MSC  235 . Those skilled in the art will understand that the MSC  235  may have different functionalities that may be performed by the same MSC or may include further components to perform these further functionalities. Specifically, the GMSC  240  may be the MSC that determines which visited MSC the subscriber who is being called is currently located. The GMSC  240  also interfaces with the PSTN (as will be described below). All mobile to mobile calls and PSTN to mobile calls are routed through the GMSC  240  when using the legacy RAN  210 . 
     With the LTE-RAN  210 , the cellular core network  230  may include, for example, components for an Evolved Packet Core (EPC) or a System Architecture Evolution (SAE) Core providing an all-IP architecture. The SGW  245  is a packet based server that routes data packets. The SGW  245  also is a mobility anchor for inter-eNB handovers and for mobility between LTE and other 3GPP technologies (e.g., terminating S4 interface and relaying the traffic between 2G/3G systems and the PDNGW  250 ). The PDNGW  250  provides connectivity from the client station  205  to external packet data networks by being the point of exit and entry of traffic for the client station  205 . Examples of functionalities performed by the PDNGW  250  include policy enforcement, packet filtering, billing support, lawful interception and packet screening. The PDNGW  250  may also anchor mobility between 3GPP and non-3GPP technologies such as WiMAX and 3GPP2 (CDMA 1X and EvDO). Accordingly, the PDNGW  250  may be configured to interface with an IMS  265  (as will be described below). 
     The cellular core network  230  may also include, for example, an ePDG  255 , which may be used when the client station  205  communicates data to/from the cellular core network  230  via the WiFi network  220 . The ePDG  255  secures the data transmission with the client station  205  connected to the cellular core network  230  over an untrusted non-3GPP access such as the WiFi network  220 . The ePDG  255  may act as a termination node when an IPsec tunnel is established between the cellular core network  230  and the client station  205 . The ePDG  255  may also be connected to the PDNGW  250 . 
     As discussed above, the GMSC  240  may interface with the PSTN. The PSTN may be part of other networks  260  which is constructively shown in  FIG. 2  as being between the cellular core network  230  and PSAPs  285 ,  290  for the legacy RAN  210 . For example, the PSTN may be used as one of the other networks  260  to determine a manner of routing the emergency call to the target PSAP  285 ,  290 . The cellular core network  230  for the LTE-RAN  215  and the WiFi network  220  may also interface with the other networks  260 . However, in view of the manner in which the voice call is performed over these IP-based architectures, an IMS  265  may be utilized. Specifically, the PDNGW  250  may interface with the IMS  265 , which interfaces with the other networks  260 . 
     The IMS  265  provides an architectural framework for delivering IP multimedia services such as a VoIP call, a VoLTE call, etc. performed over the LTE-RAN  215  or the WiFi network  220 . The IMS  265  may provide this interface between the cellular core network  230  and the other networks  260  using a call session control function (CSCF). The CSCF provides signaling that controls the communication of the client station  205  with the IMS  265 . The CSCF may control session establishment and teardown, user authentication, network security and QoS (Quality of Service). The IMS  265  may include a plurality of different CSCFs. As shown in  FIG. 2 , the IMS  265  may include a proxy-CSCF (P-CSCF)  270 , a serving-CSCF (S-CSCF)  275 , and an emergency-CSCF (E-CSCF)  280 . Those skilled in the art will also understand that the IMS  265  may further include an interrogating-CSCF (I-CSCF). 
     The P-CSCF  270  may be an interface between the client station  205  and the IMS  265 . Specifically, the P-CSCF  270  may act as a session initiation protocol (SIP) proxy and may be located in either the user&#39;s home network or in the visited network for handling roaming. Thus, all SIP requests and responses from/to the client station  205  traverse the P-CSCF  270 . The P-CSCF  270  supports various functionalities such as validating the correctness of SIP messages with the client station  205  according to SIP standard rules; ensuring the security of the messages between client station  205  and the IMS  265  using IPsec or TLS security associations; authenticating and asserting the identity of the client station  205 ; compressing the messages ensuring the efficient transmission of SIP messages over narrowband channels; etc. The P-CSCF  270  may support policy enforcement capabilities for authorizing media plane resources, bandwidth, and QoS management. In addition, the P-CSCF  270  may also generate billing information to be collected by charging network nodes. 
     The S-CSCF  275  may act as a SIP registrar and/or a SIP redirect server. The S-CSCF  275  may be responsible for processing the location registration of the client station  205 , user authentication, and call routing and processing. As will be described in further detail below, the location registration may be utilized in accordance with the exemplary embodiments. All of the SIP signaling from/to the client station  105  traverses their serving S-CSCF  275  allocated during the registration process. The S-CSCF  275  may also provide SIP message routing and services triggering as well as enforcing the policy of the network operator to keep users from performing unauthorized operations. Those skilled in the art will understand that the S-CSCF may be located in the home network. However, a number of S-CSCFs  275  may be deployed for scalability and redundancy. 
     The E-CSCF  280  may be responsible for handling emergency call services. Once the P-CSCF  275  detects that the received SIP message request is for an emergency call, the SIP message for the emergency call may be forwarded to the E-CSCF  280  by the P-CSCF  275 . The E-CSCF  280  may then contact the Locating Retrieval Function (LRF) to determine the location of the client station  205  for routing the emergency call appropriately. The E-CSCF  280  may be located either in a home network or in a visited network. As will be described in further detail below, when the emergency call is performed using the WiFi network, the location information used to register with the IMS  265  may be utilized by the E-CSCF  280  for the routing. 
     It should be noted that the above mechanism of using the functionalities of the IMS  265  is only exemplary. Those skilled in the art will understand that the manner in which the different functionalities are used are dependent upon configurations and settings of the IMS  265 . For example, the use of the E-CSCF  280  by the P-CSCF  270  may be optional. 
     Once the IMS  265  provides its functionalities for the emergency call performed over the LTE-RAN  215  or the WiFi network  220  from the client station  205 , the emergency call may be routed based upon the information determined by the IMS  265  using the other networks  260  such as the PSTN. Subsequently, the routing may provide a communications connection between the client station  205  and the PSAP  285  or the PSAP  290 . Again, this may depend upon the location information that is used to register with the IMS  265 . 
     As discussed above, the PSAP  285  and the PSAP  290  may each be a call center that handles emergency calls that are routed thereto. For illustrative purposes, the PSAP  285  is described as a home PSAP while the PSAP  290  is described as a remote PSAP. The terms “home” and “remote” may be used with regard to a home network of the client station  205 . Thus, the home network of the client station  205  may be an area in which the home PSAP  285  is a local PSAP. In a similar manner, the remote network of the client station  205  may be an area in which the remote PSAP  290  is a local PSAP. Thus, as discussed above, when the client station  205  is located in the area of the home network, a preferred PSAP for an emergency call to be routed is the home PSAP  285 . When the client station  205  is located in the area of the remote network a preferred PSAP for an emergency call to be routed is the remote PSAP  290 . 
     As described above, devices in the network arrangement  200  may be configured to communicate with the PSAPs  285 ,  290  by executing a call application to perform an emergency call over the legacy RAN  210 , the LTE-RAN  215 , or the WiFi network  220 . As related to the exemplary embodiments, the emergency call may be performed over the WiFi network  220  by registering with the IMS  265 . According to the exemplary embodiments, based upon the location information used to register with the IMS  265 , the emergency call may be routed to the PSAP  285  or the PSAP  290 . Therefore, the client station  205  may include the required hardware and software components to provide the required data and information. 
       FIG. 3  shows an exemplary client station  205  configured to perform the emergency call. Specifically, the client station  205  may represent any portable device configured to perform an emergency call over the legacy RAN  210 , the LTE-RAN  215 , the WiFi network  220 , or any combination thereof. Thus, the client station  205  may be a cellular phone, a smartphone, a tablet, a phablet, a laptop, etc. The client station  205  may include a processor  305 , a memory arrangement  310 , a display device  315 , an input/output (I/O) device  320 , wireless communications circuitry  325 , and other components  330 . 
     The processor  305  may be configured to execute a plurality of applications of the client station  205 . For example, the applications may include a call application to perform a voice call with a further client station. Specifically, the voice call may be a specialized one such as an emergency call. In another example, the applications may include an emergency call routing application  335  that determines a manner in which the emergency call is to be performed dependent upon how the emergency call is to be routed. More particularly and as will be described in further detail below, the emergency call routing application  335  may provide location information while registering with the IMS  265  when performing the emergency call over the WiFi network  220 . Specifically, when the client station  205  is located in the area of the remote network, the emergency call may be routed to the local PSAP  290  instead of the home PSAP  285  by providing the location information. It should be noted that the call application and the emergency application  335  being a program executed by the processor  305  is only exemplary. The applications may also be represented as a separate incorporated component of the client station  205  or may be a modular component coupled to the client station  205 . 
     The memory arrangement  310  may be a hardware component configured to store data related to operations performed by the client station  205 . For example, the memory arrangement  310  may store the location information of the client station  205  to be used by the emergency call routing application  335 . The display device  315  may be a hardware component configured to show data to a user while I/O device  320  may be a hardware component configured to receive inputs from the user and output corresponding data. Specifically, the I/O device  320  may provide a numeric keypad in which an emergency telephone number may be entered to perform the emergency call. The other components  335  may include a portable power supply (e.g., battery), a data acquisition device, ports to electrically connect the client station  205  to other electronic devices, an audio I/O device, etc. 
     The wireless communications circuitry  325  may be one or more integrated circuits and/or other hardware components configured to transmit and/or receive data with the cellular network and/or the WiFi network. As described above, the client station  205  may be configured to connect to the legacy RAN  210 , the LTE-RAN  215 , the WiFi network  220 , or any combination thereof. Thus, the wireless communications circuitry  325  may includes components (such as one or more baseband processors, digital signal processing (DSP) circuits, transceivers, radio frequency (RF) front ends, and/or other components) that are configured for communication via the legacy RAN  210 , the LTE-RAN  215 , and/or the WiFi network  220 . In various embodiments, the wireless communications circuitry  325  may include components for communicating (a) only with cellular networks, (b) only with WiFi networks, or (c) for communicating with both cellular and WiFi networks. Although not shown in  FIG. 3 , the client station  205  may include one or more antennas, and the wireless communications circuitry  325  may be coupled to the one or more antennas. Whenever it is described herein that the client station  205  communicates data to/from a wireless network, that communication may be performed using the one or more antennas. 
     According to the exemplary embodiments, the emergency call routing application  335  may perform a P-emergency-calling-routable (PECR) functionality. The purpose of the packet header P is to convey to an IMS client of the client station  205  if a geolocation (e.g., latitude and longitude combination) provided during a registration procedure to the IMS is routable to a local PSAP. As discussed above, this may be performed by the IMS  265  when the packets are received thereby using the E-CSCF  280 . Again, when connected to the WiFi network  220  and performing the emergency call, the client station  205  may register with the IMS  265  since the IMS  265  provides the architectural framework for delivering IP multimedia services which include packet switching for, for example, an emergency call performed over the WiFi network  220 . It should be noted that the use of the P-header as well as the PECR functionality may be toggled to be enabled/disabled via settings in a carrier bundle and may also depend on whether a service provider, a carrier, and/or a country supports such a feature. 
     The IMS client may determine the location of the client station  205  using a variety of manners. For example, an out-of-band crowd-sourced WiFi location lookup may be used when associating with the WiFi base station for the first time, for every new WiFi base station, or service set identification (SSID). In another example, a global positioning system (GPS), a satellite based system, a triangulation system, etc. may be used to determine the location. The location may be stored in the memory arrangement  310  by the IMS client as a list against each WiFi base station for future use. Thus, when a subsequent connection is with a previously associated WiFi base station, the memory arrangement  310  may have the location information already stored. It should be noted that the list may be updated if the location information changes or a timer related to storing the information expires. For example, after a predetermined number of connections to a particular WiFi base station, the IMS client may perform the location determining functionality. In another example, after a predetermined time from a first determining of the corresponding location information, the IMS client may perform the location determining functionality. 
     According to the exemplary embodiments, when the IMS client has location information available, the IMS client may include the location information in the P-header during a registration procedure with the IMS (when performing an emergency call). The IMS client may include the location information in, for example, a presence information data format (PIDF)-location object (LO) in accordance with RFC 4119 which defines a LO format. The LO may be included in a message body with content type application/PIDF+XML, and include a content identification universal resource locator (URL) that refers to the message body as the geolocation header field value in the P-header in accordance with RFC 6442 which defines location conveyance for a SIP procedure such as that used in registering with the IMS  265 . 
     It should be noted that for devices with no cellular baseband (e.g., a WiFi only capable device), the location obtained, for example, via the out-of-band crowd-sourced WiFi location lookup may be used to determine the location of a closest cell site per Radio Access Technology (RAT) for a given carrier of interest. This lookup may be done either by the IMS client or the carrier network. Depending on the distance between the IMS client location and location of the closest cell site, the cell site information (e.g., syntax as defined by RFC 3455) may be used by the IMS client to comply with P-Access-Network Information (PANI). 
     As will be described in further detail below, the exemplary embodiments provide a mechanism to perform an emergency call such that location information may be utilized more often such that a local PSAP may have the emergency call routed thereto, even when the emergency call is performed over a WiFi network. The exemplary embodiments may determine the capabilities of the client station performing the emergency call as well as the configurations to determine the manner of performing the emergency call (e.g., over the legacy RAN  210 , over the LTE-RAN  215 , or over the WiFi network  220 ). When performed over the WiFi network  220 , the exemplary embodiments provide a manner of further including location information such that the local PSAP has the emergency call routed thereto or, as a fallback option, a standard routing to a home PSAP may be performed. 
     Specifically, when the emergency call is performed over the legacy RAN  210  or the LTE-RAN  215 , the emergency call may be routed to the home PSAP  285  when the client station  205  is located in the area of the home network or may be routed to the remote PSAP  290  when the client station  205  is located in the area of the remote network. Again, when using the LTE-RAN  215 , the emergency call may also be routed through the IMS  265 . Using location information already known by the networks, the appropriate routing may be performed. When the client station  205  is connected to the WiFi network  220  and an emergency call is performed over the WiFi network  220 , location information (when known) may be provided when registering with the IMS  265 . Thus, using location information known by the networks, the appropriate routing may be performed. However, when the location information is not known, the emergency call may use the fallback option of always being routed to the home PSAP  285  regardless of the location of the client station  205 . 
       FIG. 4  shows an exemplary method  400  for performing the emergency call by the client station  205 . In the method  400  of  FIG. 4 , the client station  205  determines whether an emergency call is to be performed over the WiFi network  220  or the legacy RAN  210 . For illustrative purposes and as discussed above, the LTE-RAN  215  may also be represented by the legacy RAN  210 . Thus, the description of the method  400  describing the legacy RAN  210  may also incorporate the LTE-RAN  215 . The method  300  further includes the client station  205  determining whether the emergency call performed over the WiFi network  220  utilizes location information for a local PSAP to have the emergency call routed thereto. The method  400  will be described with regard to the network arrangement of  FIG. 2  and the components of the client station  205  of  FIG. 3 . 
     In step  405 , the emergency call routing application  335  determines the configurations of the client station  205 . For example, the configurations may relate to a WiFi capability, a cellular capability, other configurations that are enabled/disabled, etc. The configurations of the client station  205  may affect the manner in which the emergency call is to be performed. Thus, in step  410 , the emergency call routing application  335  determines whether the client station  205  is cellular capable. That is, the wireless communications circuitry  325  is configured to communicate with the legacy RAN  210 . 
     If the client station  205  is cellular capable, the emergency call routing application  335  continues the method  400  to step  415 . For example, as shown in  FIG. 1 , the client station  205  may be configured to connect to the legacy RAN  210  via a cellular base station. In step  415 , the emergency call routing application  235  determines whether the cellular capability has been disabled. For example, the cellular capability may be manually disabled by the user of the client station  205  by enabling an airplane mode. If the airplane mode is enabled, the emergency call routing application  335  continues the method  400  to step  430  that will be discussed below. However, if the airplane mode is disabled, the emergency call routing application  335  continues the method  400  to step  420 . 
     In step  420 , the emergency call routing application  335  determines whether the enabled cellular capability has a cellular coverage associated therewith. For example, the client station  205  may be disposed in a geographic location where an operating area of the legacy RAN  210  does not extend. Therefore, although the cellular capability is enabled, the legacy RAN  210  is not accessible and there is no cellular coverage. When no cellular coverage exists, the emergency call routing application  335  continues the method  400  to step  430 , which will be discussed below. However, with the cellular capability enabled and cellular coverage being provided, the emergency call routing application  335  continues the method  400  to step  425 . 
     In step  425 , the emergency call routing application  335  determines that emergency calls that are performed are done over the legacy RAN  210 . Since the emergency call is performed over the legacy RAN  210 , the location of the client station  205  is known (e.g., based on the cellular network base station that is being used). Accordingly, the emergency call from the client station  205  may be routed to the local PSAP. Specifically, when the client station  205  is located in the home network, the emergency call may be routed to the home PSAP  285  which is the local PSAP. When the client station  205  is located in the remote network, the emergency call may be routed to the remote PSAP  290 , which is the local PSAP. Thus, as shown in  FIG. 2 , the emergency call may originate from the client station  205  having a connection to the legacy RAN  210 , forwarded through the cellular core network  230  (specifically the MSC  235 , and the GMSC  240 ) to the other networks  260  (such as the PSTN) to the local PSAP (depending on the location of the client station  205 ). 
     Returning to step  410 , if the emergency call routing application  335  determines that the client station  205  does not have a cellular capability, the emergency call routing application  335  continues the method  400  to step  430 . For example, the wireless communications circuitry  325  may not include cellular capabilities. In a specific example, the client station  205  may be an iPad with WiFi only as manufactured by Apple Inc. in comparison to an iPad with 4G and WiFi capability. 
     In step  430 , the emergency call routing application  335  determines whether the client station  205  has a WiFi capability enabled. It should be noted that since the exemplary embodiments relate to performing an emergency call, it may be assumed that the client station  205  has at least one of a cellular capability, a WiFi capability, or both. That is, the client station  205  does not have both capabilities absent. If the emergency call routing application  335  determines that the client station  205  has the WiFi capability disabled, the emergency call routing application  335  continues the method  400  to step  435 . In step  435 , the emergency routing application  335  is configured to display instructions to the user via the display device  315  when an emergency call is performed under these circumstances. For example, the instructions under this scenario may indicate that the WiFi capability must be enabled for the emergency call to be performed. The emergency call routing application  335  may continue the method  400  to return to step  405 . Specifically, if the WiFi capability has been enabled while all other conditions remain the same, the emergency call routing application  335  continues the method  400  to step  440 . 
     In step  440 , the emergency call routing application  235  determines whether the client station  205  has a WiFi calling functionality enabled. As discussed above, the processor  305  may include the call application that enables voice calls to be performed. The voice call may be performed over the legacy RAN  210  or the WiFi network  220 . When performed over the WiFi network  220 , the call application may include the WiFi calling functionality. If the emergency call routing application  335  determines that the client station  205  has the WiFi calling functionality disabled, the emergency call routing application  335  continues the method  400  to step  435 . In step  435 , the emergency routing application  335  is configured to display instructions to the user via the display device  315  when the emergency call is performed under these circumstances. For example, the instructions under this scenario may indicate that the WiFi calling functionality must be enabled for the emergency call to be performed. The emergency call routing application  335  continues the method  400  to return to step  405 . Specifically, if the WiFi calling functionality has been enabled while all other conditions remain the same, the emergency call routing application  335  continues the method  400  to step  445 . 
     In step  445 , the emergency call routing application  335  determines whether the client station  205  has a WiFi association. Specifically, the emergency call routing application  335  of the client station  205  determines whether a connection to the WiFi network  220  has been established. In a substantially similar manner as the legacy RAN  210 , the client station  205  may be disposed outside an operating area of the WiFi network  220  such that the WiFi association is absent. If the emergency call routing application  335  determines that the client station  205  has no WiFi association, the emergency call routing application  335  continues the method  400  to step  435 . In step  435 , the emergency routing application  335  is configured to display instructions to the user via the display device  315  when the emergency call is performed under these circumstances. For example, the instructions under this scenario may indicate that the client station  205  is required to be connected to a WiFi network for the emergency call to be performed. The emergency call routing application  335  continues the method  400  to return to step  405 . Specifically, if the WiFi association has been established while all other conditions remain the same, the emergency call routing application  335  continues the method  400  to step  450 . 
     It should be noted that the above examples of the instructions relate to when the emergency call routing application  335  determines that the client station  205  has no cellular capability. However, as discussed above, the emergency call routing application  335  may perform the method  400  to proceed from step  415  and step  420  to step  430 . That is, when the airplane mode is enabled (as determined in step  415 ) such that the cellular capability is disabled or when the cellular capability is enabled with no cellular coverage (as determined in step  420 ), the emergency call routing application  335  performs the method  400  to continue to step  430 . For example, the client station  205  may be an iPhone with 4G and WiFi capability as manufactured by Apple Inc. but either with the airplane mode enabled or out of a cellular coverage of a cellular service provider (e.g., AT&amp;T, T-Mobile, Verizon, etc.). 
     Thus, returning to step  415 , if the emergency call routing application  335  determines that the client station  205  has a cellular capability but has airplane mode enabled, the method  400  continues to step  430 . Under these circumstances, when the WiFi capability is determined to be disabled (as determined in step  430 ), when the WiFi calling functionality is determined to be disabled (as determined in step  440 ), or when the client station  205  is determined to not have a WiFi association (as determined in step  445 ), the instructions to be displayed on the display device  315  may be that the user must disable the airplane mode to perform the emergency call. With these instructions, the user may manually change the configurations. Thus, with the method  400  returning to step  405 , a different path may be taken for subsequent processing. 
     Returning to step  420 , if the emergency call routing application  335  determines that the client station  205  has a cellular capability and has airplane mode disabled but has no cellular coverage, the emergency call routing application  335  continues the method  400  to step  430 . Under these circumstances, when the WiFi capability is determined to be disabled (as determined in step  430 ), or when the client station  205  is determined to not have a WiFi association (as determined in step  445 ), the instructions to be displayed on the display device  315  may be that the emergency call cannot be performed over the WiFi network. With these instructions, the user may manually change the configurations or move to a location in which an association to the legacy RAN  210  or the WiFi network  220  may be established. Thus, with the emergency call routing application  335  performing the method  400  is caused to return to step  405 , where a different path may be taken for subsequent processing. 
     When the emergency call routing application  335  determines that cellular service is not an option to perform the emergency call for the client station  205  but that the emergency call may be performed over the WiFi network  220 , the emergency call routing application  335  may continue with the method  400 . Therefore, returning to step  450 , the emergency call routing application  335  may determine whether location information is available. As discussed above, the location information may be determined in a variety of manners such as with out-of-band WiFi crowd-sourced location lookup. If the location information is unavailable, the emergency call routing application  335  continues the method  400  to step  475 , which will be discussed below. 
     When the location information is available, the emergency call routing application  335  continues the method  400  to step  455 , where the emergency call routing application  335  provides the location information during a registration procedure with the IMS  265  since the emergency call is being performed over the WiFi network  220 . As discussed above, the location information may be included in the P-header by the IMS client when registering with the IMS  265 . In step  460 , the emergency call routing application  335  determines whether the registration is successful. If unsuccessful, the emergency call routing application  335  continues the method  400  to step  435 . In such a scenario, the instructions may indicate that the emergency call cannot be performed over the WiFi network. 
     Returning to step  460 , if the registration is successful, the emergency call routing application  335  continues the method  400  to step  465 , where the emergency call routing application  335  verifies the registration with the location information with the WiFi network. For example, a 200 OK response may be received for the verification. In another example, the location information may be referenced as to whether the PECR functionality is possible. That is, the emergency call routing application  335  may determine or request whether a pathway may be established to the local PSAP based upon the location information. As discussed above, this may be performed by the E-CSCF  280  of the IMS  265 . If the verification fails, the emergency call routing application  335  continues the method  400  to step  475 , which will be discussed below. If the registration with the location information is successful and verified, the emergency call routing application  335  continues the method  400  to step  470 , where the emergency call may be performed using the WiFi network  220 . For example, a packet-switched emergency call may be performed by the client station  205  over the WiFi network  220 . Specifically, when the emergency call is performed over the WiFi network  220 , the local PSAP may have the emergency call routed thereto from the client station  205 . Thus, as shown in  FIG. 2 , the emergency call may originate from the client station  205  having a connection to the WiFi network  220 , forwarded through other networks  225  (e.g., an ISP), forwarded through the cellular core network  230  (specifically the ePDG  255  and the PDNGW  250 ) to the IMS  265  (specifically the E-CSCF  280 ) to the other networks  260  (e.g., the PSTN) to the local PSAP (depending on the location of the client station  205 ). 
     Returning to step  450  where the location information is unavailable, the emergency call routing application  335  continues the method  400  to step  475 . Also, returning to step  465  where the verification fails, the emergency call routing application  335  continues the method  400  to step  475 . In step  475 , the civic address is used to register with the IMS  265 . The civic address may correspond to the home network of the client station  205 . Thus, the civic address that is used to register with the IMS  265  may be within the area of the home network. When the client station  205  is located within the area of the home network, the location used for registration is the civic address which (in this case) may also be considered as the location of the client station  205  (although unaware by all network components). When the client station  205  is located within the area of the remote network, the location used for registration is the civic address, which is not the location of the client station  205 . It should be noted that the user may consent to providing the civic address and therefore be an option that the user of the client station  205  agrees to enabling. However, if disabled, the civic address may not be used during the registration procedure to the IMS  265 . 
     In step  480 , the emergency call routing application  335  determines whether the registration with the civic address is successful. If unsuccessful, the emergency call routing application  335  continues the method  400  to step  435  in which instructions are shown on the display device  315 . In such a scenario, the instructions may indicate that the emergency call cannot be performed over the WiFi network  220 . However, if the registration with the civic address is successful, the emergency call routing application  335  continues the method  400  to step  485 . 
     In step  485 , the emergency call routing application  335  determines again whether the client station  205  is cellular capable. This second determination may indicate whether the pathway through the method  400  relates to whether the airplane mode is enabled and/or cellular coverage is available versus when the cellular capability is absent. If the client station  205  does not have a cellular capability, the emergency call routing application  335  continues the method  400  to step  470 , where the emergency call may be performed over the WiFi network  220 . However, in contrast to registering with the location information, the use of the civic address causes the emergency call to be routed to the home PSAP instead of the local PSAP. For example, with the client station  205  in the area of the remote network, under these circumstances, an emergency call that is performed by the client station  205  is routed to the home PSAP  285  although preferred to be routed to the remote PSAP  290  (which would be local to the client station  205 ). 
     Returning to step  485 , if the client station  205  is cellular capable, the emergency call routing application  335  continues the method  400  to step  490 . In step  490 , the emergency call routing application  335  performs a cellular option such that the location of the client station  105  may still be utilized prior to using the civic address for emergency calls. The cellular option will be described in further detail below with regard to  FIG. 5 . If the cellular option is successful, then the emergency call routing application  335  continues the method  400  to step  425  in which the emergency call is performed over the legacy RAN  210 . As discussed above, the use of the legacy RAN  210  may enable the emergency call to be routed to the local PSAP. However, if the cellular option fails, the fallback position of using the WiFi network  220  to perform the emergency call in which the emergency call is routed to the home PSAP is performed. 
       FIG. 5  shows an exemplary method  500  for performing a cellular option by the client station  205 . In the method  500  of  FIG. 5 , the client station  205  is initially determined to have a cellular capability disabled and has a civic address that is used for registering with the IMS  265  when connected to the WiFi network  220 . For example, the client station  205  may be determined to have no cellular service and is registered to the IMS  265  using its civic address. Accordingly, the emergency call would be routed to the home PSAP  285  instead of the remote PSAP  290  when located in the area of the remote network. Specifically, the cellular option of the method  500  performed by the client station  205  corresponds to step  490  of the method  400  of  FIG. 4 . More specifically, the cellular option relates to when an emergency call is actively being performed. 
     In step  505 , the emergency call routing application  335  receives the request for an emergency call. For example, a user of the client station  205  may enter the emergency telephone number on the I/O device  320  (e.g., 911). In step  510 , the emergency call routing application  335  initiates a timer. 
     In step  515 , the emergency call routing application  335  signals for a quick scan to be performed to determine available circuit switched RATS. Since the cellular capability has already been determined to be available but that the cellular service is not, this may provide a subsequent determination of whether cellular service may be established (e.g., between the client station  205  and the legacy RAN  210 ). If no available legacy RAN  210  is found in step  520 , the emergency call routing application  335  continues the method  500  to step  525 , where the emergency call routing application  335  determines whether the timer expired. If still running, the emergency call routing application  335  continues the method  500  to return to step  515 . However, if the timer expired, the emergency call routing application  335  continues the method  500  to step  530 , where the emergency call is performed over the WiFi network  220  and the civic address is still used as the basis for routing the emergency call. This step may correspond to step  470  of the method  400  of  FIG. 4 . Accordingly, the emergency call performed over the WiFi network  220  by the client station  205  located in the area of the remote network results in a routing to the home PSAP  285 . 
     Returning to step  520 , if a circuit switched radio access technology (RAT) is found to be available, the emergency call routing application  335  continues the method  500  to step  535 , where the emergency call routing application  335  signals for the IMS  265  to be de-registered. Specifically, by using the legacy RAN  210  and the cellular core network  230 , the IMS  265  is not required. Furthermore, the connection to the legacy RAN  210  may be established. Thus, in step  540 , the emergency call may be performed over the legacy RAN  210  in which the location information of the client station  205  is used as the basis for routing the emergency call. That is, the emergency call performed by the client station  205  over the legacy RAN  210  results in a routing to the local PSAP. This step may correspond to step  425  of the method  400  of  FIG. 4 . 
     It should be noted that the above manner in which the emergency call routing application  335  performing the cellular option of the method  500  is only exemplary. For example, the use of the timer in step  510  is only exemplary and may not be included in the method  500 . However, further manners may be used by the emergency call routing application  335  to determine how the method  500  is to be performed such that it proceeds from step  525  to step  530 . 
     The exemplary embodiments provide a system and method for performing an emergency call and utilize location information of a station to route the emergency call. Specifically, the emergency call is routed to a local PSAP relative to the station. When the emergency call is performed over a legacy RAN, it may be routed to the local PSAP as location information is known. When the emergency call is performed over a WiFi network, the exemplary embodiments provide a mechanism to include the location information during a registration thereto such that an emergency call may be routed to the local PSAP instead of a home PSAP associated with a home network of the station that may potentially be located farther away than the local PSAP. 
     Those skilled in the art will understand that the above-described exemplary embodiments may be implemented in any suitable software or hardware configuration or combination thereof. An exemplary hardware platform for implementing the exemplary embodiments may include, for example, an Intel x86 based platform with compatible operating system, a Mac platform, MAC OS, iOS, Android OS, etc. In a further example, the exemplary embodiments of the above described method may be embodied as a program containing lines of code stored on a non-transitory computer readable storage medium that, when compiled, may be executed on a processor or microprocessor. 
     It will be apparent to those skilled in the art that various modifications may be made in the present invention, without departing from the spirit or the scope of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalent.

Metadata:
Filing Date: 20140930
Publication Date: 20160628
Grant Date: 20160628
Priority Date: 20140224
Inventors: YERRABOMMANAHALLI VIKRAM B.
PEREZ CESAR
LEE TECK YANG
Assignee: APPLE INC
CPC Classifications: [{"code": "H04L65/1016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1073", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W76/007", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W84/12", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W88/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04L65/1073", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W4/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W4/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1073", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W88/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W76/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W76/50", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W76/50", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W76/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W4/90", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L65/1016", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W84/12", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 53883604