Abstract:
A system and method of PSTN based network roaming and SCP based subscriber management for internet telephony systems. When a call is incoming to the central office  60  of a subscriber&#39;s home service area which supports packet data network telephony  10 , such as for instance IP telephony, a home location register  40  translates the directory number into an IP address, URL address, or electronic mail address much the same that a local number portability node re-routes calls for non-IP telephony systems. When a subscriber is roaming in another network  100 , the roamed into (visited) gateway  130  signals back to the home location register  40  of the subscriber&#39;s network  20  and registers its (i.e., the visited gateway&#39;s) public switching telephone network  70  telephone directory number and the IP address assigned to the subscriber while connected to the visited network  100 . When subsequent calls are incoming to the subscriber&#39;s home network switch, the home location register  40  provides the ten (10) digit directory number of the visited gateway  130  and the new IP address rather than the home gateway telephone number and IP address of the subscriber.

Description:
TECHNICAL FIELD 
     The present invention relates to using a signaling control point to act as a home location register for a wireless or wireline telephone switch that supports internet protocol (IP) telephony. 
     BACKGROUND AND RELATED ART 
     Currently, wireless subscriber profile data is configured in a home location register (HLR). The HLR resides either on a computing module (CM) which is an end office telephony switch or in an off-board node that supports IS-41 protocol signaling. The subscriber data profile is retrieved from the HLR upon registration and stored in a visitor location register (VLR) while the subscriber is actively roaming. By contrast, wireline subscriber profile data, which includes internet (IP) telephones, is stored within the computing module in the form of table data. Wireline subscribers currently do not have public switching telephone network (PSTN) roaming capability. 
     The present invention addresses several shortcomings of the current configuration. First, the current subscriber profile data in the computing module does not provide the ability to map E.164 telephone directory numbers into internet addresses, e-mail addresses or universal resource locators (URLs) as may be used by IP telephones. Second, current systems have no provision for wireline mobility because an assumption is made that the address of a wireline is fixed, tied to a physical interface, and only moved by changes to the provisioned tables. 
     SUMMARY OF THE INVENTION 
     As with standard wireline telephony subscribers, IP telephony subscribers are assigned a standard ten (10) digit E.164 directory number (hereinafter “directory number”) comprised of a three (3) digit area code, a three (3) digit exchange within the area code, and a four (4) digit unique extension within the exchange. When a call is incoming to the central office of a subscriber&#39;s home service area which supports computer network telephony, such as for instance IP telephony, a signaling control point translates the directory number into an IP address, URL address, or electronic mail address much the same that a local number portability node re-routes calls for non-IP telephony systems. The signaling control point is signaled from an advanced intelligent network (AIN) termination attempt trigger point and provides the directory number of an H.323 gateway and the IP address of the subscriber&#39;s H.323 IP telephony end point. If the subscriber has de-registered from the signaling control point, an overflow route to a land line or voice mail is provided. 
     Local number routing (LNR) fields are re-used with the local number becoming the ten (10) digit directory number of the gateway, and the called directory number (CDN) becoming the IP address, or a new transmission control application protocol (TCAP) field could be introduced specifically for the IP address. 
     When a subscriber is roaming in another network, the roamed into (visited) gateway signals back to the home location register/signaling control point of the subscriber&#39;s network and registers its (i.e., the visited gateway&#39;s) public switching telephone network telephone directory number and the IP address assigned to the subscriber while connected to the visited network. When subsequent calls are incoming to the subscriber&#39;s home network switch, the home location register/signaling control point provides the ten (10) digit directory number of the visited gateway and the new IP address rather than the home gateway telephone number and IP address of the subscriber. 
     This provides the subscriber with a virtual private network for placing telephone calls over IP terminals. Thus, subscribers have the ability to roam among networks and continue placing or receiving telephone calls ubiquitously. The subscriber maintains a single telephone directory number and receives service no matter which IP network he is currently connected to. Under the present invention, subscribers can, for instance, move from a static network connection at work to a dial in network connection from home. 
     The present invention provides a method of managing call origination for subscribers on a packet data telephony network which includes a home location register. A subscriber registers a packet data communication (IP telephony) device with the home location register of the subscriber&#39;s home packet data (IP) network, and uses the home location register to translate the subscriber&#39;s packet data (IP) address into a E.164) telephone directory number. 
     The present invention also provides a method of managing call termination (i.e., call reception) for subscribers on a packet data telephony network which includes a home location register. The subscriber registers a packet data communication (IP telephony) device with the home location register of the subscriber&#39;s home packet data (IP) network, and uses the home location register to translate the subscriber&#39;s E.164) telephone directory number into a packet data (IP) address. 
     The present invention further provides a method of public switching telephone network based roaming call origination for IP telephony devices. The subscriber registers his IP telephony device on a remote IP network, and may originate calls from the IP telephony device on the remote network to a third party. 
     The present invention still further provides a method of public switching telephone network based roaming call termination (i.e., call reception) for IP telephony devices. An IP subscriber registers his IP telephony device on a remote IP network, and may receive calls on the IP telephony device on the remote network from a third party. 
     It is therefore an object of the invention to provide PSTN based network roaming for IP telephony devices. 
     It is a further object of the invention to provide SCP based management for IP telephony devices. 
     Some of the objects of the invention having been stated hereinabove, other objects will become evident as the description proceeds, when taken in connection with the accompanying drawings as best described hereinbelow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram illustrating the hardware nodes present in a subscriber&#39;s home area network and a link to outside networks; 
     FIG. 2 is a block diagram illustrating the hardware nodes required for roaming on a public network; 
     FIG. 3 is a block diagram illustrating the hardware nodes required for roaming on a private network. 
     FIG. 4 illustrates the method or process steps for subscriber registration within the home area network; 
     FIG. 5 illustrates the method or process steps for call origination for a subscriber within the home area network; 
     FIG. 6 illustrates the method or process steps for call termination within the home area network; 
     FIG. 7 illustrates the method or process steps for subscriber registration while roaming on a remote area network; 
     FIG. 8 illustrates the method or process steps for call origination while roaming on a remote area network; and 
     FIG. 9 illustrates the method or process steps for call termination while roaming on a remote area network. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIGS. 1-3, a packet data telephony network is shown in each figure. In FIGS. 2 and 3, two (2) packet data telephony networks are shown linked together by a public switching network and a virtual private network, respectively. It is to be understood that multiple (more than two) packet data telephony networks may be linked together. Each network has a number of common elements which include home location registers (HLR)  40 , visitor location registers (VLR)  120 , gatekeepers (GK)  30 , 110 , gateways (COGW)  50 , 130 , central offices (CO)  60 , 140 , and various packet data telephony devices  10 , 25 , 35 . Other devices may be connected to the packet data network without departing from the spirit or scope of the present invention. 
     FIG. 1 illustrates a home switch call scenario. Registration, call origination, and call termination functions are described for a subscriber utilizing his home network. Registration refers to the process of provisioning the home location register (or the visitor location register if roaming) with the subscriber&#39;s relevant data. Call origination refers to placing a call while call termination refers to receiving a call. 
     Registration is initiated when a subscriber logs into his computer at work. Once the subscriber connects his IP telephone  10  to his home IP network  20 , registration is initiated with a local serving gatekeeper (GK)  30 . Gatekeeper  30  forwards the registration information to a serving home location register (HLR)  40  which validates the subscriber. Home location register  40  responds with authentication data and subscriber profile data which is then stored within gatekeeper  30 . Home location register  40  stores the directory number (DN) of the central office gateway (COGW)  50 , the directory number of the subscriber, and the assigned IP address of the subscriber&#39;s IP telephone  10 . 
     Consider a situation in which the subscriber wishes to initiate a call to someone who lives in a different service area. The subscriber&#39;s gatekeeper  30  queries his home location register  40  supplying his IP address. Home location register  40  supplies the subscriber&#39;s directory number, authentication data and any other data needed to place the call. The subscriber&#39;s gatekeeper  30  initiates a call origination via the central office gateway  50  and central office (CO)  60  by supplying the subscriber&#39;s directory number as the calling party and called party&#39;s directory number. The call routes normally over a public switching telephone network (PSTN)  70  to the called party&#39;s serving central office  80 . 
     Now consider the reverse situation in which someone wishes to initiate a call to the subscriber (e.g., call termination). The caller  90  dials the subscriber&#39;s telephone directory number. The call routes normally over the public switching telephone network  70  from the caller&#39;s central office  80  to the subscriber&#39;s central office  60 . The subscriber&#39;s central office  60  queries home location register  40  by supplying the subscriber&#39;s directory number and retrieves the directory number of the subscriber&#39;s central office gateway  50  and the IP address of the subscriber&#39;s IP phone  10 . The subscriber&#39;s central office  60  routes the call to the subscriber&#39;s central office gateway  50  by supplying the IP address of the subscriber&#39;s IP phone  10 . Lastly, the subscriber&#39;s central office gateway  50  uses the subscriber&#39;s IP address to route the call to the subscriber&#39;s IP telephone  10 . Call origination may be optimized by duplicating the IP address to directory number mapping in the gatekeeper. 
     FIG. 2 illustrates the architecture necessary to place and receive calls while roaming on a public network. Consider a scenario where a subscriber is out of his home service area. The subscriber registers on a remote network by connecting to the remote network  100  and initiating contact with the remote network&#39;s gatekeeper  110  in which the subscriber supplies his home area directory number. The remote gatekeeper  110  receives the registration request and recognizes it as a non-local subscriber based on the supplied directory number. The remote gatekeeper  110  then forwards the request to a visitor location register (VLR)  120  which will validate the subscriber if his subscriber profile is already resident on remote visitor location register  120 . If the subscriber&#39;s profile is not yet resident on remote visitor location register  120 , then visitor location register  120  initiates a registration request to the subscriber&#39;s home location register  40  using the subscriber&#39;s supplied directory number and/or a system ID to locate home location register  40 . The subscriber&#39;s home location register  40  responds by forwarding his subscriber profile and authentication data. Remote visitor location register  120  stores the subscriber&#39;s home directory number, his assigned remote network IP address, and the directory number of the remote network central office gateway  130 . The subscriber&#39;s home location register  40 , in turn, stores the remote network&#39;s  100  central office gateway  130  directory number and/or IP address. Next, remote visitor location register  120  responds to remote gatekeeper  110  with the subscriber&#39;s profile and authentication information which is stored in remote gatekeeper  110 . Where possible, standard IS-41 or GSM-MAP protocols are used for communications among home location register nodes, visitor location register nodes, and gatekeeper nodes. The gatekeepers act as mobile switching centers (MSCs) with respect to IS-41 or GSM-MAP protocols. 
     Call origination for a public network roaming call scenario is performed as follows. When the subscriber wishes to call someone while roaming on a remote network, he dials the called party&#39;s directory number. The remote gatekeeper  110 , recognizing that the subscriber&#39;s IP address is dynamically assigned, queries remote visitor location register  120  supplying the subscriber&#39;s assigned IP address. Remote visitor location register  120  sends back the subscriber&#39;s home directory number as well as authentication data needed to place the call. Remote gatekeeper  110  initiates an origination via remote central office gateway  130  and central office  140  by supplying the subscriber&#39;s home directory number as the calling party and the called party&#39;s directory number. The call routes normally over public switching telephone network  70  to the called party&#39;s central office  80 . Call origination may be optimized by duplicating the IP address to directory number mapping in the gatekeeper. 
     Call termination for a public network roaming call scenario is performed as follows. This time, the subscriber receives a call from someone while he is roaming in another network. The caller dials the subscriber&#39;s telephone directory number. The call routes normally over public switching telephone network  70  from the caller&#39;s serving central office  80  to the subscriber&#39;s home central office  60 . The subscriber&#39;s central office  60  queries its home location register  40  by supplying the subscriber&#39;s directory number. Home location register  40  returns the directory number of the central office gateway  130  of the network  100  in which the subscriber is roaming. The subscriber&#39;s home central office  60  routes the call to the remote network central office  140  using the remote central office gateway  130  directory number and supplying the subscribers home directory number and/or URL or electronic mail address. If the directory number only is supplied, remote central office  140  queries remote visitor location register  120  by supplying the subscriber&#39;s home directory number and retrieves the subscriber&#39;s remote assigned IP address. Remote central office  140  routes the call to remote central office gateway  130  by supplying the subscriber&#39;s dynamically assigned IP address. Lastly, remote central office gateway  130  uses the subscriber&#39;s IP address to route the call to the subscriber. 
     Private network roaming, illustrated in FIG. 3, is achieved in almost identical fashion as public network roaming with the following exceptions. IS41/GSM-MAP messages can be sent over a virtual private network (VPN)  160  instead of the IS-41 or GSM-MAP public network  150 , thereby lowering costs. Second, the local gatekeeper can make least cost routing and/or quality of service decisions and choose to route a call over a public switching telephone network or a virtual private network. 
     FIGS. 4-9 illustrate method or process steps for various functions of the present invention. It is to be understood that each of the method or process steps illustrated herein are readily implementable by those of ordinary skill in the art as a computer program product having a medium with a computer program embodied thereon. The computer program product is capable of being loaded and executed on the appropriate computer processing device(s) in order to carry out the method or process steps described. 
     FIG. 4 illustrates the method or process steps for subscriber registration within the home area network. Once a subscriber connects  402  his IP telephone to his home IP network, registration is initiated and an IP address is assigned  404  to the IP phone. A registration initiation message is sent  406  to the IP network gatekeeper. The gatekeeper forwards  408  the registration information to the serving home location register (HLR) which validates the subscriber&#39;s service and authentication data. The home location register responds  410  with authentication data and subscriber profile data. At this point, the authentication data and subscriber profile data can be stored within the gatekeeper  412  or the network gateway directory number, IP phone directory number, and assigned IP address can be stored in the home location register  414 . 
     FIG. 5 illustrates the method or process steps for call origination for a subscriber within the home area network. Once a subscriber has registered his IP telephony device with his home area IP network, he may place or receive calls. To place a call (call origination), the subscriber dials and the gatekeeper sends  502  the IP address previously assigned during registration to the home location register. The home location register returns  504  the subscriber&#39;s directory number, authentication data and any other data needed to place the call to the gatekeeper. The subscriber&#39;s gatekeeper then originates  506  the call origination by supplying the subscriber&#39;s directory number as the calling party and called party&#39;s directory number to the central office gateway and central office (CO). The call routes  508  normally over a public switching telephone network (PSTN) to the called party&#39;s serving central office. 
     FIG. 6 illustrates the method or process steps for call termination within the home area network. A caller dials the subscriber&#39;s telephone directory number. The call routes normally over the public switching telephone network from the caller&#39;s central office to the subscriber&#39;s central office  602 . To retrieve the call (call termination), the subscriber&#39;s central office queries  604  home location register by supplying the subscriber&#39;s directory number and retrieves  606  the directory number of the subscriber&#39;s central office gateway and the IP address of the subscriber&#39;s IP phone. The subscriber&#39;s central office routes  608  the call to the subscriber&#39;s central office gateway by supplying the IP address of the subscriber&#39;s IP phone Lastly, the subscriber&#39;s central office gateway uses the subscriber&#39;s IP address to route  610  the call to the subscriber&#39;s IP telephone. 
     FIG. 7 illustrates the method or process steps for subscriber registration while roaming on a remote area network. The subscriber initiates registration on a remote IP network by connecting  702  his IP phone to the remote IP network. The remote IP network initiates  704  contact via a registration request message with its gatekeeper in which the subscriber supplies his home area directory number. The remote gatekeeper receives the registration request and recognizes it as a non-local subscriber based on the supplied directory number. The remote gatekeeper then forwards  706  the request to a visitor location register (VLR). If the subscriber&#39;s profile is not yet resident on remote visitor location register then visitor location register initiates  708  a registration request to the subscriber&#39;s home location register using the subscriber&#39;s supplied directory number and/or a system ID to locate home location register. The subscriber&#39;s home location register responds  710  by forwarding his subscriber profile and authentication data. Remote visitor location register stores  712  the subscriber&#39;s home directory number, his assigned remote network IP address, and the directory number of the remote network central office gateway. The subscriber&#39;s home location register in turn, stores  714  the remote network&#39;s central office gateway directory number and/or IP address. Next, remote visitor location register responds  716  to remote gatekeeper with the subscriber&#39;s profile and authentication information which is stored  718  in the remote gatekeeper. 
     Otherwise, the visitor location register will validate  720  the subscriber since his subscriber profile is already resident on remote visitor location register. The visitor location register sends  722  the service profile and authentication data to the remote IP network gatekeeper where it is then stored  724 . 
     FIG. 8 illustrates the method or process steps for call origination while roaming on a remote area network. When the subscriber wishes to call someone while roaming on a remote network, he dials the called party&#39;s directory number. The remote gatekeeper recognizing that the subscriber&#39;s IP address is dynamically assigned, queries  802  remote visitor location register supplying the subscriber&#39;s assigned IP address. Remote visitor location register sends  804  back the subscriber&#39;s home directory number as well as authentication data needed to place the call. Remote gatekeeper initiates  806  an origination via remote central office gateway and central office by supplying the subscriber&#39;s home directory number as the calling party and the called party&#39;s directory number. The call routes  808  normally over public switching telephone network to the called party&#39;s central office. 
     FIG. 9 illustrates the method or process steps for call termination while roaming on a remote area network. A caller dials the subscriber&#39;s telephone directory number. The call routes normally over public switching telephone network from the caller&#39;s serving central office to the subscriber&#39;s home central office  902 . The subscriber&#39;s central office queries its home location register by supplying the subscriber&#39;s directory number. Home location register returns  904  the directory number of the central office gateway of the network in which the subscriber is roaming. The subscriber&#39;s home central office gateway routes  906  the call to the remote network central office gateway using the remote central office gateway directory number and supplying the subscriber&#39;s home directory number and/or URL or electronic mail address. If the directory number only is supplied, remote central office queries  908  remote visitor location register by supplying the subscriber&#39;s home directory number and retrieves  910  the subscriber&#39;s remote assigned IP address. Remote central office routes  912  the call to the subscriber via remote central office gateway by supplying the subscriber&#39;s dynamically assigned IP address. 
     Alternatively, the call can be routed  914  from the home network gateway to the remote network gateway using the IP address of the subscriber&#39;s IP phone rather than using the subscriber&#39;s directory number. Remote central office would then routes  916  the call to the subscriber via remote central office gateway by supplying the subscriber&#39;s dynamically assigned IP address. 
     Appropriate computer program code in combination with hardware implements many of the elements of the present invention. This computer code is often stored on storage media. This media can be a diskette, hard disk, CD-ROM, or tape. The media can also be a memory storage device or collection of memory storage devices such as read-only memory (ROM) or random access memory (RAM). Additionally, the computer program code can be transferred to the appropriate hardware over some type of data network. 
     It is to be understood that the foregoing is illustrative of the present invention and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the appended claims. 
     For instance, an ATM or other packet data network may be substituted for the IP network used throughout the foregoing description. 
     Further, E.164 directory numbers to an IP address is only one mapping that the present invention contemplates. Universal resource locator (URL) addresses, electronic mail addresses, etc . . . may be substituted for the IP address mapping. 
     Still further, gateway protocols are freely substitutable. The present invention has been described using the H.323 protocol. Other protocols, including, but not limited to, internet protocol device control (IPDC), simple gateway control protocol (SGCP), and session initiation protocol (SIP) may also be implemented. 
     The invention is defined by the following claims, with equivalents of the claims to be included therein.