Patent Publication Number: US-2007111738-A1

Title: Method for providing roaming using a mobile identification number based on an international mobile station identity

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates generally to telecommunications, and, more particularly, to wireless communications.  
      2. Description of the Related Art  
      In the field of wireless telecommunications, such as cellular telephony, a system typically includes a plurality of base stations distributed within an area to be serviced by the system. Various users within the area, fixed or mobile, may then access the system, and, thus, other interconnected telecommunications systems, via one or more of the base stations. Typically, a mobile device maintains communications with the system as the mobile device passes through an area by communicating with one and then another base station, as the user moves. The mobile device may communicate with the closest base station, the base station with the strongest signal, the base station with a capacity sufficient to accept communications, etc.  
      Many mobile devices are programmed by a service provider with a 10-digit, unique subscription identifier called a Mobile Identification Number (MIN). In particular, service providers in the United States utilize MIN, rather than the International Mobile Subscriber Identity (IMSI). The MIN may be used by the service provider to validate, provide customized service, and bill correctly. However, there are several shortcomings associated with the use of MIN. For example, with the explosion of cellular telephony, the number of unique MINs is in danger of being exhausted. Further, there is no international standard for MIN usage, and thus, international roaming standards do not support MIN. A mobile device using IMSI cannot roam to a cellular system that only employs MIN and mobile device using MIN cannot roam into a cellular system that only employs IMSI because routing based on MIN is not supported.  
     SUMMARY OF THE INVENTION  
      The present invention is directed to overcoming, or at least reducing, the effects of one or more of the problems set forth above.  
      In one aspect of the instant invention, a method is provided. The method comprises receiving at least a portion of an identifier from a mobile device wherein the identifier is comprised of a mobile identification number (MIN) and a home network identifier (HNI). The MIN and HNI are stored. Both the MIN and HNI are used for routing calls from a base station to the mobile device in response to the mobile device roaming. Only the MIN is used for routing calls from the base station to the mobile device in response to the mobile device being in a home network. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:  
       FIG. 1  is a block diagram of a typical communications system in which the instant invention may be employed;  
       FIG. 2A  is a stylistic representation of an IMSI numbering scheme that employs at least some aspects of the instant invention and may be used in the communications system of  FIG. 1 ;  
       FIG. 2B  is a stylistic representation of the IMSI numbering scheme used in the United States today; and  
       FIGS. 3 and 4  are flow diagrams stylistically illustrating messages exchanged between the various components of the communications system of  FIG. 1  based on at least some aspects of the instant invention in which a variety of mobile devices may seek to communicate with a variety of service providers. 
    
    
      While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.  
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS  
      Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions may be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but may nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.  
      Turning now to the drawings, and specifically referring to  FIG. 1 , a communications system  100  is illustrated, in accordance with one embodiment of the present invention. For illustrative purposes, the communications system  100  of FIG. I is a Code Division Multiple Access (CDMA) system, although it should be understood that the present invention may be applicable to other systems that support data and/or voice communications. The communications system  100  allows one or more mobile devices  120  to communicate with a data network  125 , such as the Internet, and/or a Publicly Switched Telephone Network (PSTN)  128  through one or more base stations  130 . The mobile device  120  may take the form of any of a variety of devices, including cellular phones, personal digital assistants (PDAs), laptop computers, digital pagers, wireless cards, and any other device capable of accessing the data network  125  and/or the PSTN  128  through the base station  130 .  
      In one embodiment, a plurality of the base stations  130  may be coupled to a Radio Network Controller (RNC)  138  by one or more connections, such as T1/EI lines or circuits, ATM circuits, cables, optical digital subscriber lines (DSLs), and the like. Those skilled in the art will appreciate that a plurality of RNCs  138  may be utilized to interface with a large number of base stations  130 . Generally, the RNC  138  operates to control and coordinate the base stations  130  to which it is connected. The RNC  138  of  FIG. 1  generally provides replication, communications, runtime, and system management services. The RNC  138 , in the illustrated embodiment handles calling processing functions, such as setting and terminating a call path and is capable of determining a data transmission rate on the forward and/or reverse link for each user  120  and for each sector supported by each of the base stations  130 .  
      Each of the RNCs  138  is coupled to one of a plurality of Mobile Switching Centers (MSCs)  140 . The MSCs  140  are generally responsible for providing look-up information regarding call routing for the mobile device  120 . Generally, as discussed in greater detail below, the MSC  140  uses the Mobile Station IDentity (MSID) provided by the mobile device  120  to control call routing.  
      The MSC  140  is also coupled to a Core Network (CN)  150  via a connection, which may take on any of a variety of forms, such as T1/EI lines or circuits, ATM circuits, cables, optical digital subscriber lines (DSLs), and the like. Generally the CN  150  operates as an interface to the data network  125  and/or to the PSTN  128 . The CN  150  performs a variety of functions and operations, such as user authentication, however, a detailed description of the structure and operation of the CN  150  is not necessary to an understanding and appreciation of the instant invention. Accordingly, to avoid unnecessarily obfuscating the instant invention, further details of the CN  150  are not presented herein.  
      The data network  125  may be a packet-switched data network, such as a data network according to the Internet Protocol (IP). One version of IP is described in Request for Comments (RFC) 791, entitled “Internet Protocol,” dated September 1981. Other versions of IP, such as IPv 6 , or other connectionless, packet-switched standards may also be utilized in further embodiments. A version of IPv6 is described in RFC 2460, entitled “Internet Protocol, Version 6 (IPv6) Specification,” dated December 1998. The data network  125  may also include other types of packet-based data networks in further embodiments. Examples of such other packet-based data networks include Asynchronous Transfer Mode (ATM), Frame Relay networks, and the like.  
      As utilized herein, a “data network” may refer to one or more communication networks, channels, links, or paths, and systems or devices (such as routers) used to route data over such networks, channels, links, or paths.  
      Thus, those skilled in the art will appreciate that the communications system  100  facilitates communications between the mobile devices  120  and the data network  125  and/or the PSTN  128 . It should be understood, however, that the configuration of the communications system  100  of  FIG. 1  is exemplary in nature, and that fewer or additional components may be employed in other embodiments of the communications system  100  without departing from the spirit and scope of the instant invention.  
      Unless specifically stated otherwise, or as is apparent from the discussion, terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical, electronic quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system&#39;s memories or registers or other such information storage, transmission or display devices.  
      Those skilled in the art will appreciate that in the United States, each of the mobile devices  120  has historically used a unique Mobile Station IDentity (MSID) that is comprised of a Mobile Identification Number (MIN). In existing standards, the MIN is 10-digits long. MIN is assigned and administered by a MIN Block Administrator for wireless service providers in North America and an International Roaming MIN Administrator for wireless service providers outside North America. Under existing standards, each mobile device  120  is allowed to be programmed with two identifiers. One identifier is a 15-digit “true IMSI” and the other is a “MIN-based-IMSI” consisting of a 10-digit MIN preceded by a 5-digit “default” network identifier that is not unique and, therefore, can&#39;t be used for routing. In one embodiment of the instant invention, the true IMSI is not programmed into each mobile device  120 , or at least is not employed by the instant invention. Rather, only the MIN-based-IMSI field of the mobile device  120  is used in routing calls in one embodiment of the instant invention.  
      Referring now to  FIG. 2A , in one embodiment of the instant invention, the MIN-based-IMSI takes the form of a 15-digit number: a 3-digit Mobile Country Code (MCC)  200  and a 2-digit Mobile Network Code (MNC)  202 , which together form a 5-digit Home Network Identifier (HNI)  204 . The Mobile Station Identification Number (MSIN)  206  located in the least significant 10-digits of the MIN-based-IMSI is formed from the conventional 10-digit MIN  206 . This scheme for establishing the IMSI differs from current standards for IMSI in North America, as shown in  FIG. 2B , in that the current standard for North America does not generally allow for a 5-digit HNI  214 , and the HNI  204  in this embodiment of the invention contains information that is assigned and actually identifies the mobile device&#39;s home network from the MCC  200  and the MNC  202 .  
      Additionally, the MIN  206  corresponds to and may be used as the MIN for the mobile device  120  when the home network of the mobile device supports the use of MINs  206 . It is anticipated that in one embodiment of the instant invention, each service provider will have authority to administer their own MINs. That is, each service provider is allowed to assign MINs  206  without regard to other service providers. Thus, those skilled in the art will appreciate that within the instant invention it is possible for two service providers to assign identical MINs  206  to two different mobile devices  120 . However, as discussed in greater detail below, the two mobile devices  120  will have non-identical HNIs  204 , yielding a 15-digit IMSI that is unique throughout the world. As the entire 15-digit IMSI is presented by a roaming mobile device  120  when it first attempts to access a serving system, the serving system can use the HNI to identify a roaming subscriber and the roaming subscriber&#39;s home service provider.  
      Those skilled in the art will appreciate that this numbering scheme will alleviate the near-term exhaustion of 10-digit MINs  206  currently facing the industry. Additionally, when a mobile device  120  is within its home network, it may continue to use its 10-digit MIN, rather than is 15-digit IMSI, as the 10-digit MIN  206  is sufficient to uniquely identify each mobile device  120  within its home network.  
      Some of the beneficial results from this numbering scheme include the fact that existing CDMA operations will support efficient use of the air interface by virtue of its ability to continue using the 10-digit MIN for its subscribers. Additionally, ANSI41 Call Delivery (receiving a Routing Request and paging the mobile to deliver the call) can continue to operate properly as long as the HLR provides a sender identification number (SENDERIN) in the format of an IMSI, with an assigned HNI, along with the IMSI_M_S —  (or MIN) for the phone with each intersystem operation message to the S-MSC  140 .  
      Further, since the proposed numbering scheme eliminates the use of 6-digit HNIs, modifications to enhanced Preferred Roaming List (ePRL) is not required. Use of the ePRL requires (a) the base station to broadcast a 5-digit HNI for the potential serving system to identify itself and (b) the mobile device  120  to use this 5-digit HNI to select a serving system to access by comparing it to a priority listing of 5-digit HNIs for preferred roaming partners programmed into the mobile device  120 . The 5-digit HNI is broadcast over the air by the base station  130  inside an Extended System Parameter Message (ESPM). With a 5-digit HNI inside the ESPM, mobile ePRLs with 5-digit HNIs do not need to be reprogrammed. Likewise, modifications to IS-2000 to support 6-digit HNIs and modifications IS-683 to provision mobiles over-the-air with a modified ePRL are not required.  
      Referring now to  FIGS. 3 and 4 , flow diagrams stylistically illustrate messages exchanged between the various components of the system  100  in a variety of scenarios in which a variety of mobile devices  120  may seek to communicate with a variety of service providers. For example,  FIG. 3  represents message flow that occurs when the mobile device  120  is communicating with its home network, whereas  FIG. 4  represents message flow that occurs when the mobile device  120  is communicating with a non-home network, or when the mobile device is roaming.  
      Referring first to  FIG. 3 , a mobile device (MS)  120  that has only a MIN-based-IMSI (IMSI_M=311+12+IMSI_M_S) is attempting to communicate with a base station (BS)  130  of its home service provider, as indicated by its Extended System Parameter Message (ESPM) signaling, which has HNI set to 31112. The base station  130  is also signaling in the ESPM that a true 15-digit IMSI is not supported in the mobile application protocol by the serving MSC  140  (IMSI_T_SUPPORTED=0). In this scenario, the mobile device  120  recognizes that it is communicating with its home service provider because the received HNI matches its internally stored HNI, and thus, the mobile device  120  delivers a registration message that contains only the 10-digit MIN portion of its IMSI (RGM (IMSI=IMSI_M_S)). Those skilled in the art will appreciate that under the current standard, the mobile device  120  would always sends a less efficient 15-digit response that would include a 5-digit HNI value of MCC+00 (e.g. 31000 in the US). This is a default or non-assigned HNI value which is available for use by all service providers in a country in their subscriber&#39;s mobile devices. As such, MCC+00 does not uniquely identify a service provider and would not be used in an ePRL, an HNI in the ESPM, or for message routing. Thus, the HNI broadcast in the ESPM would never match the HNI of the IMSI_M in the mobile device  120  and the mobile device  120  would always send 15 digits to the base station  130 .  
      Referring still to  FIG. 3 , the base station  130  prepends its 5-digit HNI (31112 in this example) and forwards a 15-digit IMSI in a Location Updating Request (LUR) to the serving MSC  140 . Because the serving MSC  140  in this scenario does not support a 15 digit IMSI for mobile identification in the mobile application protocol, it stores the HNI portion of the IMSI as a MINExtension in its database  400 . The MINExtension is needed for subsequent call delivery. The serving MSC  140  then forwards a Registration Notification (REGNOT) with the MIN portion of the IMSI to a Home Location Register (HLR) located within the network or system  100 . The Registration Notification message is routed to the HLR through the network using either the MIN or 15-digit IMSI as the address for intra-system signaling. The serving MSC  140  sends an MSC Identification Number (MSCIN) (E.212 GT address) in a registration message to the HLR. The registration message identifies the serving MSC  140  as having an E.212 global title address to support international roaming and 15 digit mobile identifiers. The HLR stores the serving MSC GT address (MSCIN) to subsequently route messages to the serving MSC  140 . For example, when the HLR receives notification of an inbound call to the mobile device  120  registered at the serving MSC  140 , it sends a ROUTEREQ message to the serving MSC  140  using the MSCIN received in the registration message as the routing address. Because the serving MSC  140  sent the MSCIN in the registration message, the HLR responds by sending a Sender Identification Number (SENDERIN) (HNI+10 digits of the HLR) to the serving MSC  140 . The HNI of the HLR sent in the SENDERIN should be the same as the HNI of the mobile device  120  served by HLR. The serving MSC  140  prepends the HNI (31112 in this case) received in the SENDERIN to the MIN to uniquely identify the mobile device  120  within the MSC  140 .  
      When a call for the mobile device  120  arrives from the network  100  to the serving MSC  140  in the form of ROUTERREQ/TLDN(MIN=IMSI_M_S, MSCIN=E.212(O−MSC), SENDERIN=311+12+10d), the serving MSC  140  prepends the 5-digit HNI received in the SENDERIN (31112) to the MIN in order to form a 15-digit IMSI. This 15-digit IMSI is needed to match the 15-digit IMSI sent by the mobile device  120  when it registered. This IMSI was stored in the serving MSC database  400  as a MIN and MINExtension (5-digit HNI from the mobile device  120 ). The serving MSC  140  forms a Paging Request (PR) by prepending the mobile device&#39;s MINExtension to the MIN (IMSI_M_S), which is forwarded to the base station  130 . The base station  130  then issues a page to the mobile station  120  using only the 10-digit IMSI_M_S since this mobile device  120  is at home. This is a more efficient use of the air interface for an mobile device  120  at home than if a 15-digit IMSI were used for the page.  
      Referring now to  FIG. 4 , a roaming mobile device (MS)  120  that has only a MIN-based-IMSI set with an HNI value of 31234 is attempting to communicate with a base station (BS)  130  of a non-home service provider, as indicated by its ESPM signaling, which has HNI set to 31112 (the HNI for the mobile device  120  is set to 31234). The non-home service provider base station  130  is also signaling in the ESPM that true IMSI is not supported (IMSI_T_SUPPORTED=0) in the mobile application protocol by the serving MSC  140 . The mobile device  120  sends a 15-digit registration message to the base station  130  formed from the MIN-based IMSI (IMSI_M=312+34+IMSI_M_S). The base station  130  delivers a 15-digit Location Updating Request (LUR) based on the same MIN-based-IMSI (LUR(IMSI_M=312+34+IMSI_M_S)). Again, because the serving MSC  140  does not support a true 15-digit IMSI for mobile identification in the mobile application protocol, it stores the HNI portion of the IMSI as a MINExtension in the serving MSC database  400  for subsequent call delivery. The serving MSC  140  then forwards a Registration Notification (REGNOT) with the MIN portion of the IMSI to a Home Location Register (HLR) located within the network or system  100 . The Registration Notification message is routed to the HLR through the network using the 15-digit IMSI for inter-system signaling. The serving MSC  140  also sends an MSC Identification Number (MSCIN) (E.212 GT address) in the registration message to the HLR. The registration message identifies the serving MSC  140  as having an E.212 global title address to support international roaming. The HLR stores the serving MSC GT address (MSCIN) to subsequently route messages to the serving MSC  140 . In response to receiving an MSCIN from the serving MSC  140 , the HLR then sends a Sender Identification Number (SENDERIN) (HNI+10 digits of the HLR) to the serving MSC  140  in subsequent messages to the serving MSC  140  about this mobile device  120 . The HNI of the HLR sent in the SENDERIN is the same as the HNI of mobile device  120  served by HLR.  
      When a call for the mobile device  120  arrives from the network  100  to the serving MSC  140  in the form of ROUTERREQ/TLDN(MIN=IMSI_M_S, MSCIN=E.212(O−MSC), SENDERIN=312+34+10d), the serving MSC  140  prepends the 5-digit HNI received in the SENDERIN (31234) to the MIN in order to form a 15-digit IMSI. This 15-digit IMSI is needed to match the 15-digit IMSI sent by the mobile device when it registered. This IMSI was stored in the serving MSC database  400  as a MIN and MINExtension (5-digit HNI from the mobile device  120 ). The serving MSC  140  forms a Paging Request (PR) by prepending the mobile&#39;s MINExtension to the MIN (IMSI_M_S), which is forwarded to the base station  130 . The base station  130  then issues a page to the mobile station  120  using the 15-digit IMSI_M since this mobile device  120  is not at home.  
      Those skilled in the art will appreciate that the various system layers, routines, or modules illustrated in the various embodiments herein may be executable control units. The control units may include a microprocessor, a microcontroller, a digital signal processor, a processor card (including one or more microprocessors or controllers), or other control or computing devices. The storage devices referred to in this discussion may include one or more machine-readable storage media for storing data and instructions. The storage media may include different forms of memory including semiconductor memory devices such as dynamic or static random access memories (DRAMs or SRAMs), erasable and programmable read-only memories (EPROMs), electrically erasable and programmable read-only memories (EEPROMs) and flash memories; magnetic disks such as fixed, floppy, removable disks; other magnetic media including tape; and optical media such as compact disks (CDs) or digital video disks (DVDs). Instructions that make up the various software layers, routines, or modules in the various systems may be stored in respective storage devices. The instructions when executed by the control units cause the corresponding system to perform programmed acts.  
      The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. Consequently, the method, system and portions thereof and of the described method and system may be implemented in different locations, such as the wireless unit, the base station, a base station controller and/or mobile switching center. Moreover, processing circuitry required to implement and use the described system may be implemented in application specific integrated circuits, software-driven processing circuitry, firmware, programmable logic devices, hardware, discrete components or arrangements of the above components as would be understood by one of ordinary skill in the art with the benefit of this disclosure. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.