Abstract:
A method is provided for routing a message through a telecommunications network. The method includes receiving an identifying number (eg: a MIN or ESN) from a wireless terminal and prepending at least one character to the identifying number to form a pseudo-global title. The message is then routed through the telecommunications network to a destination determined by the pseudo-global title. Upon arrival at the destination, the method further includes converting the pseudo-global title to a home location register address. The message is then routed to a home location register having the home location register address.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to wireless telecommunications services, and, in particular, to international roaming of wireless terminals.  
         BACKGROUND OF THE INVENTION  
         [0002]    The operation of obtaining service outside of a wireless subscriber&#39;s home service area is commonly referred to as roaming. The ability of a subscriber to roam outside of his or her home service area depends on the relationship between the subscriber&#39;s home service provider and the service provider in the area being visited. This relationship ideally includes the ability to exchange information between the two systems. In order to provide a consistent exchange of information, with minimal user intervention, the telecommunications industry has developed standard protocols for communications between mobile switching centers, making it possible for roaming subscribers to originate, receive, and maintain calls as they cross system boundaries.  
           [0003]    Reference in this regard can be had, by example, to Telecommunications Industry Association Interim Standard 41 (TIA IS-41), also referred to as ANSI/TIA/EIA 41-D-1997 (ANSI-41), entitled “Cellular Radiotelecommunications Intersystem Operations.” 
           [0004]    ANSI-41 specifies two types of databases to facilitate roaming, the home location register (HLR) and the visitor location register (VLR). The home location register resides with the subscriber&#39;s home service provider and contains pertinent information about the subscriber&#39;s equipment and the services the subscriber is entitled to. The HLR also contains the current location and status of the subscriber&#39;s terminal. Access to the HLR is controlled by the subscriber&#39;s mobile identification number (MIN), which is stored in the terminal. The visitor location register (VLR) resides with the system being visited, referred to as the serving system, and contains information, including the MIN and the electronic serial number (ESN), regarding the terminals currently in the serving system service area.  
           [0005]    When a terminal enters a serving system, it attempts to register in that system. As part of the registration process, the serving system&#39;s mobile switching center (MSC) records information about the terminal, including the terminal&#39;s MIN and ESN, in its VLR. The serving system&#39;s VLR then attempts to contact the subscriber&#39;s HLR for authentication that the subscriber is entitled to access the system.  
           [0006]    ANSI-41 wireless networks worldwide use the MIN, mentioned above, to identify their subscribers within their own country. In North America, the MIN is often used as the subscriber&#39;s mobile directory number (MDN). ANSI-41 wireless networks in the United States and Canada also use the subscriber&#39;s 10 digit MIN to direct messages from the serving system to the subscriber&#39;s HLR. While MIN-based routing is generally supported in the ANSI networks of North America, it is not recognized as a valid global address type, also referred to as a title, by the International Telecommunications Union (ITU). As a result, using a subscriber&#39;s MIN to locate the subscriber&#39;s HLR is not generally supported by networks outside of North America. Thus, a subscriber&#39;s MIN is not necessarily a valid global title.  
           [0007]    New protocol extensions to ANSI-41 are being developed to provide true global title formats, specifically E.212, however, since the ITU has not yet accepted E212 as an officially sanctioned translation type, the useful application of E.212 is not expected to be available globally for some time.  
           [0008]    The International Forum for AMPS Standards Technology (I FAST) has issued unique network codes to operators outside of North America for use as the most significant four digits of their subscribers&#39; MINs. MINs using these special codes are called International Roaming MINs (IRMs). The use of IRMs ensures that a globally unique identification is available for mobile subscribers, and IRMs provide a generally accepted global title for directing a visited system to a subscriber&#39;s HLR. The IRM always begins with a “0” or a “1” to ensure that they never conflict with MINs used in North America, as North American MINs never start with a “0” or a “1.” While IRMs provide a generally accepted method for designating a subscriber&#39;s HLR, North American MINs, because they never begin with a “0” or “1”, remain unacceptable as global titles.  
           [0009]    These problems are compounded when using a global satellite communications system, such as one shown in U.S. Pat. No. 5,655,005, issued Aug. 5, 1997, entitled “Worldwide telecommunications System Using Satellites”, by Robert A. Wiedeman and Paul A. Monte and U.S. Pat. No. 5,715,297, issued Feb. 3, 1998, entitled “Wireless Telephone/Satellite Roaming System”, by Robert A. Wiedeman. In a global satellite communications system, a user&#39;s terminal is intended to have service anywhere within the coverage area of a satellite system, regardless of international boundaries.  
         OBJECTS AND ADVANTAGES OF THE INVENTION  
         [0010]    It is an object and advantage of this invention to provide a method and apparatus to allow subscribers of ANSI-41 based networks to roam internationally. It is a second object and advantage of this invention to provide a method and apparatus to allow subscribers of ANSI-41 based networks to roam internationally by correctly routing wireless signaling messages from a visited system to a subscribers home network using the terminal&#39;s MIN as the initial addressing format. It is a further object and advantage of this invention to provide a method and apparatus to allow subscribers of ANSI-41 based networks to roam internationally in a global satellite communications system.  
         SUMMARY OF THE INVENTION  
         [0011]    The foregoing and other problems are overcome and the objects of the invention are realized by methods and apparatus in accordance with embodiments of this invention.  
           [0012]    A method is provided for routing a message through a telecommunications network. The method includes receiving an identifying number (eg: a MIN or ESN) from a wireless terminal and prepending at least one character to the identifying number to form a pseudo-global title. The message is then routed through the telecommunications network to a destination determined by the pseudo-global title. Upon arrival at the destination, the method further includes converting the pseudo-global title to a home location register address. The message is then routed to a home location register having the home location register address. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The above set forth and other features of the invention are made more apparent in the ensuing Detailed Description of the Invention when read in conjunction with the attached Drawings, wherein:  
         [0014]    [0014]FIG. 1 shows a diagram of a system in which the invention may be practiced.  
         [0015]    [0015]FIG. 2 shows a block diagram of a mobile switching center coupled to a pseudo-global title translator as part of this invention.  
         [0016]    [0016]FIG. 3 shows a block diagram of an originating international signaling node and an international point code suitable for practicing the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    [0017]FIG. 1 shows a network environment that is suitable for practicing this invention. A wireless terminal  10  is shown roaming in a foreign serving network  15 . The foreign serving network includes a communications satellite  17 , satellite system gateway  20 , a mobile switching center  25 , and a pseudo-global title translator  30 . The pseudo-global title translator  30  is shown for convenience as being a unit coupled between the mobile switching center  25  and an originating international signaling node  35  through a local network  40 . The originating international signaling node  35  communicates with an international point code  45 , also through the local network  40 . The international point code  45  contains a global title translation and routing process  47 . The international point code  45  communicates with a destination international signaling node  50  through an international network  55 . The destination international signaling node  50  then communicates with the wireless terminal&#39;s home subscriber network  60  and the wireless terminal subscriber&#39;s HLR  65  through a local network  70 . The various aspects of this embodiment are now described in further detail.  
         [0018]    Assume first that the wireless terminal  10  roaming on the foreign serving system  15  attempts to register. Upon detecting the presence of the visiting wireless terminal  10 , the gateway  20  of the foreign serving system informs the foreign serving system&#39;s MSC  25  that it has received a registration message. The MSC  25  then communicates with the pseudo-global title converter  30  as will be described.  
         [0019]    Referring first to FIG. 2, there is illustrated in greater detail the MSC  25  and pseudo-global title converter  30 . As shown in FIG. 2, the MSC  25  examines an internal database  75  to determine if the wireless terminal  10  is already registered in its service area. If the wireless terminal  10  is not registered, the serving MSC  25  updates the internal database  75  with the information that the wireless terminal  10  is present and sends an IS-41 message containing the MIN and ESN of the wireless terminal  10  to its VLR  80 , also referred to as the serving VLR. The serving VLR  80  then determines if the wireless terminal  10  is already registered in its database  85 . If not, the serving VLR  80  stores the information and then attempts to contact the wireless terminal&#39;s HLR  65  (FIG. 1) for authentication. In order to accomplish this, the serving VLR  80  creates an ANSI-41 roaming signaling message with a destination, or title, based on the wireless terminal&#39;s MIN. The title is used to route the message to the wireless terminal&#39;s HLR  65 . As stated above, MIN-based titles are generally accepted in North America, but not in the rest of the world. In order to accommodate global routing of the roaming signaling message, the pseudo-global title converter  30  is used. The pseudo-global title converter  30  is coupled to the serving VLR  80  from which it receives the ANSI-41 roaming signaling message with its MIN-based title  90 . The pseudo-global title converter  30  converts the MIN-based title to a generally accepted E.164 type title  95  by prepending it with a country code of “1.” The converted title  95 , as generated in accordance with an aspect of this invention, is referred to herein as a pseudo-global title.  
         [0020]    It is important to note that any country code or identifier may be prepended to the MIN-based title  90  to create the pseudo-global title  95 , as long as the resulting digit string is unique to all international nodes within the system. Based on the pseudo-global title  95 , the pseudo-global title converter  30  selects an appropriate originating international signaling node  35 . After selecting the appropriate originating international signaling node  35 , the pseudo-global title converter  30  functions as a message router, and sends the ANSI-41 roaming signaling message with the pseudo-global title  95  to the originating international signaling node  35  over the local network  40 .  
         [0021]    Referring now to FIG. 3, the originating international signaling node  35  contains a routing table  100  and, using the most significant digits of the pseudo-global title  95  as a key, functions as a message router, routing the message to the international point code  45 , as specified by the international point code address  105  in its routing table  100 .  
         [0022]    At the international point code  45 , the global title translation and routing process  47  receives the message. The global title translation and routing process  47  contains a translation table  110  which links pseudo-global titles with the corresponding true E. 164 destination addresses for a subscriber&#39;s home network elements, including a subscriber&#39;s HLR  65  (FIG. 1). The global title translation and routing process  105  looks up the pseudo-global title  95  in its translation tables  110  and substitutes the true E. 164 destination title  115  for the subscriber&#39;s HLR  65  as the new destination address. The global title translation and routing process  105  then determines the address of the next appropriate node  120  in accordance with its routing tables  125 , and functioning as a message router, routes the message to the next appropriate node  120 .  
         [0023]    It is important to note that the global translation process from a pseudo-global title  95  to a true E. 164 destination title  115  is not limited to using the translation table  110 . For example, an algorithm could also be used to determine the true E. 164 destination title  115  from the pseudo-global title  95 .  
         [0024]    It is also important to note that the global title translation and routing process  105  is not limited to substituting the true E. 164 destination title  115  for the pseudo-global title  95 . The global title translation and routing process  105  may substitute any other acceptable format for the true destination address for the home network element including, without limitation, E.212, MIN, SS7 point code, etc. types of addresses, or any other type of address suitable to permit routing to the terminal&#39;s HLR  65 .  
         [0025]    If required, other nodes in the system (not shown) then route the message in accordance with its intended destination through the international network  55 . As shown in FIG. 1, eventually the destination international signaling node  50  receives the message and routes it to the subscriber&#39;s HLR  65  based on the true E. 164 title  115 .  
         [0026]    Although described in the context of a satellite communications system, it should be understood that the teachings of this invention may also be practiced in a terrestrial based communications system.  
         [0027]    While, for convenience, the pseudo-global title translator  30  has been described as a separate unit, it should be understood that the pseudo-global title translator  30  may also be implemented as software running in the MSC  25 .  
         [0028]    Although the MIN, ESN, etc., have been described as being stored in the wireless terminal, they could as well be stored in a detachable storage module installed in the wireless terminal.  
         [0029]    Thus, while the invention has been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that changes in form and details may be made therein without departing from the scope and spirit of the invention.