Abstract:
A system and method for providing local service to non-local subscribers in a telecommunications network. The systems and methods employ mapping of a subscriber IMSI with a unique local identifier for use by the local system for locally originating and terminating calls.

Description:
TECHNICAL FIELD 
   The invention relates in general to systems and methods for providing local wireless service to non-local subscribers in a wireless telecommunications network. More particularly, the invention relates to systems and methods for providing services to non-local subscribers for locally originating and terminating calls without alteration of standard mobile terminals, and without alteration of roaming service from the home network. 
   BACKGROUND OF THE INVENTION 
   Wireless telecommunications systems exist and overlap throughout the world providing both local, national and international calling services. Although many wireless telecommunications exist, increasingly, dual and multiple band phones permit international roaming for subscribers using the same wireless terminal. For example dual band global system for mobile communications (GSM) “world phones” permit international roaming for GSM subscribers, e.g., between GSM 900 and GSM 1900 public land mobile networks (PLMN). A GSM subscriber with a dual band GSM device can roam between two or more countries and continue to receive service provided the operators in the various countries have a roaming agreement. 
   A serious disadvantage with international roaming as it exists today is that local callers must dial an international number to reach the GSM subscriber even if the GSM subscriber is geographically located in their local area. This is expensive in terms of both utilization of network resources and costs to the callers and subscribers. 
   An example of the current state of international roaming is shown in FIG.  1 . If a roaming GSM subscriber represented by handset  10  is located in a country  12  not local to his home PLMN  14 , a local caller  16  must dial the GSM subscriber&#39;s  10  home system telephone number resulting in a connection to the home PLMN  14  as indicated by signal path  18 . The Home Location Register (HLR)  20  of the home PLMN  14  routes the call to the roaming subscriber  10  in the distant country  13 . The call is connected via the local PLMN  22  and as indicated by signal paths  24  and  26 . 
   It would be desirable to have a visiting wireless subscriber access the local wireless services while roaming in distant lands using improved local calling techniques. Such calling techniques would result in improved customer service, improved operator efficiency, lower costs, and other advantages. 
   SUMMARY OF THE INVENTION 
   The invention provides methods and systems for offering local subscriber number and wireless telecommunication services to a non-local subscriber according to prearrangements between a local network operator and a non-local network operator. 
   The invention provides a method of providing local wireless telecommunication service to a non-local subscriber. According to the invention, a non-local subscriber obtains a local subscriber number from a local operator such that the local operator provides service to the non-local subscriber via the local subscriber number. 
   According to one aspect of the invention, a unique visitor identifier e.g., a Local MSISDN (LMSISDN), is mapped to the globally unique International Mobile Subscriber Identifier (IMSI) of the non-local subscriber. 
   According to another aspect of the invention, a registry of the local network associates the non-local subscriber IMSI with a unique visitor identifier, e.g., LMSISDN. 
   According to yet another aspect of the invention, the method includes steps for dissociating the unique visitor identifier from the non-local subscriber IMSI. 
   A system of the invention includes means for providing a non-local subscriber with a unique visitor identifier in a local registry and means for providing local wireless services via the unique visitor identifier. 
   The invention provides numerous technical advantages including increased efficiency for network operators providing services to non-local subscribers, improved service to subscribers, and decreased costs for local callers, subscribers, and network operators. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above advantages, as well as specific embodiments of the present invention, will be more clearly understood from consideration of the following descriptions in connection with the accompanying drawings in which: 
       FIG. 1  is a block diagram depicting the general features of international roaming known in the arts; 
       FIG. 2A  is a message flow diagram showing an example of a handshake between two service providers using the invention prior to providing a non-local subscriber service in a local network; 
       FIG. 2B  is a message flow diagram showing an example of a location update sequence using the invention; 
       FIG. 3  is a flow diagram illustrating an example of the invention used by the non-local subscriber to originate a call to a local number; 
       FIG. 4  is a flow diagram illustrating an example of the invention used to provide a terminating local call to a non-local subscriber; 
       FIG. 5  is a flow diagram illustrating an example of disassociating a non-local subscriber from a LMSISDN; and 
       FIG. 6  is a message flow diagram illustrating an example of the invention wherein a non-local subscriber moves from a first local operator service area to a second local operator service area. 
     Corresponding numerals and symbols in the various figures refer to corresponding parts unless otherwise indicated. Some features of embodiments shown and discussed are simplified or exaggerated for illustrating the principles of the invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts which can be embodied in a wide variety of specific contexts. Examples of the invention are given in the context of GSM, however, it should be understood that the invention may be practiced with wireless devices and networks of various types and in various configurations. 
   With reference to  FIG. 2A , an example of a handshake between two wireless network operators using the invention is shown. This must occur prior to the local operator providing service to the non-local subscriber. A home network operator  30  is illustrated requesting a Local MSISDN (LMSISDN)  200  for a particular subscriber  32 , identified by a unique IMSI. A local operator  34  provides a LMSISDN  202  uniquely identifying the subscriber  32 . Preferably, the provision of a LMSISDN is performed according to prearrangements between network operators including billing arrangements and specification of service parameters. The local operator  34  creates a local subscription  204  for the subscriber  32  using the LMSISDN and the subscriber  32  IMSI and any additional service parameters provided by the home operator  30 . At a minimum, the local subscription, in addition to providing a LMSISDN, includes one or more purge conditions for triggering the termination of the local subscription for the non-local subscriber  32 . Examples of purge conditions include a selected expiration time and date, or usage of a selected number of air time minutes. The home operator  30  provisions a new Local MSISDN service in the home HLR  40 , step  206 . The service parameters typically include the LMSISDN and purge conditions. Typically, the network operators  30  and  34  maintain billing systems  208 ,  210  related to providing services using the invention. 
     FIG. 2B  depicts a non-local subscriber mobile station  32  performing a location update in a local PLMN  34  according to the invention. A location update message  300  passes from the local PLMN  34  to the home PLMN  30 . The home PLMN  30  then provides subscriber data to the local PLMN  34  with an Insert Subscriber Data (ISD) message  302  providing information as to the services this subscriber  32  is entitled to receive. Preferably, the ISD message  302  includes the information that this subscriber  32  is entitled to receive Local MSISDN service in the local PLMN  34  as well as specific local services, e.g., call forwarding, messaging and the like. Typically, details regarding the parameters and charges for such services are prearranged among PLMN operators. In GSM, the parameter information is preferably transmitted via the extension container of the ISD message  302 . In response, the local PLMN  34  sends an ISD acknowledgment message  304  to the home PLMN  30 . 
   The home PLMN  30  sends a location update acknowledgment message  306  to the local PLMN  34 . When the local PLMN  34  component serving the non-local subscriber  32 , typically an MSC/VLR  44  (Mobile Switching Center and Visitor Location Register) is notified that the subscriber  32  has a subscription for LMSISDN service, the serving MSC/VLR  44  sends a second location update message  308  to its local HLR  42 . The second location update message  308  is sent to the local HLR  42  by the serving MSC/VLR  44  using the LMSISDN as global title to address the local HLR  42 . The local HLR  42  sends an Insert Subscriber Data (ISD) message  310  to the serving MSC/VLR  44 . The local MSC/VLR  44  sends an ISD acknowledgment message  312  to the local HLR  42 , and the local HLR  42  responds with a location update acknowledgment  314 . Local callers, which may include mobile stations  36  and fixed local stations  38 , as depicted in  FIG. 2B  may use the LMSISDN in communications with the non-local subscriber  32 . Calls to the home MSISDN of the roaming subscriber  32  continue to be routed through the home PLMN  30 . 
     FIG. 3  is a process flow diagram showing an example of a non-local subscriber  32  originating a call to a local number  38  ( FIG. 2B ) using the invention. The non-local subscriber  32  originates a call to a local number  38 , step  400 . The local serving MSC/VLR  44  identifies the call as local in step  402 . The local MSC/VLR  44  serving the non-local subscriber  32  inserts the LMSISDN as the calling number, step  404 , in place of using the non-local MSISDN otherwise associated with the non-local subscriber  32 . The call setup then proceeds  406  as for any other locally originated call to a local number. 
     FIG. 4  is a process flow diagram illustrating an example of the invention used to provide a terminating local call to the non-local subscriber  32  according to the example described with respect to  FIG. 2. A  local caller  38  calls the unique visitor identifier, or temporarily assigned local MSISDN in this example, at step  300 . A local gateway MSC (GMSC), at step  302 , uses the local MSISDN to determine which HLR of the local PLMN  22  to interrogate regarding the whereabouts of the non-local subscriber  32 . At step  304 , the call is directed to the appropriate serving MSC by the HLR. The serving MSC, in step  306 , then inserts the LMSISDN and facilitates the connection with the non-local subscriber  32  according to local network procedures, step  308 . Preferably, the Local MSISDN includes means by which the LMSISDN is mapped to the IMSI of the non-local subscriber  10  in such a way that the local MSCs are provided with a the capability to identify circumstances in which services provided to a non-local subscriber are in fact local services. 
   In addition to calling services, the non-local subscriber  32  is preferably provided with other local services offered by the local PLMN operator  34  to its own subscribers. Additional services may also be provided to the non-local subscriber  32  by the local PLMN operator  34 . 
   It should be understood that the non-local subscriber  32  continues to receive terminating calls from its home PLMN  30  according to ordinary roaming call setup procedures. Similarly, calls originating from the non-local subscriber  32  to numbers in the home PLMN  30  are routed according to the ordinary procedures for roaming calls. It will be appreciated by those skilled in the arts that the specifics of the communications among PLMNs using the invention are not crucial to the invention, and are thus not shown or described in detail. Although the examples herein are described in terms of GSM, the invention may be adapted to operate with other implementations of wireless telecommunications PLMNs. 
     FIG. 5  is a process flow diagram illustrating an example of dissociation techniques for purging an LMSISDN in a local PLMN. As discussed above, upon initiation of a local subscriber number and local service for a non-local wireless subscriber, one or more purge conditions for the temporary subscription are established. For example, the expiration of a particular time and date, or the usage of a predetermined number of air-time minutes. Other purge conditions may be used such as a period of non-use of local services, or exhaustion of prepayment for services. Upon the occurrence of a purge condition  500 , the local PLMN preferably purges the local subscription in its HLR, step  502 . Shown in step  504 , the MSC&#39;s and VLR&#39;s of the local PLMN no longer permit the use of the LMSISDN previously assigned to the non-local subscriber to originate or terminate service. Typically, the LMSISDN is returned to a pool in the PLMN for eventual reassignment,  506 . 
     FIG. 6  is a diagram illustrating an example of a non-local subscriber  32  registered for local service with a first local PLMN operator  34  according to the invention as shown and described with reference to  FIG. 2A , in the event the subscriber  32  moves from a first local service area  34  ( FIG. 2A ) to a second local service area having a second PLMN operator  60 . In this example, a non-local subscriber  32 , has been provided local services according to the invention as in the example of  FIGS. 2A-B , in a non-local PLMN  34 . The home PLMN  30  has prearranged non-local service with the second local PLMN  60 . As in the previous example referring to  FIG. 2A , a handshake between the two PLMNs  30 ,  60  using the invention includes a request for a Local MSISDN (LMSISDN)  600  for the particular subscriber  32 , identified by a unique IMSI. The second local PLMN operator  60  provides a LMSISDN  602  uniquely identifying the subscriber  32 . Preferably, the provision of a LMSISDN is performed according to prearrangements between network operators including billing arrangements and specification of service parameters. The second local PLMN operator  60  creates a local subscription  604  for the subscriber  32  using the LMSISDN and the subscriber  32  IMSI and any additional service parameters provided by the home operator  30 . At a minimum, the local subscription, in addition to providing a LMSISDN, includes one or more purge conditions for triggering the termination of the local subscription for the non-local subscriber  32 . Examples of purge conditions include a selected expiration time and date, or usage of a selected number of air time minutes. The home operator  30  provisions new LMSISDN service in the home HLR  40 , step  606 . Service parameters typically include at least the LMSISDN and purge conditions. Typically, the network operators  30  and  60  maintain billing systems  608 ,  610  related to providing services using the invention. 
   Further referring to  FIG. 6 , the non-local subscriber mobile station  32  performing a location update in the second local PLMN  60  causes a location update message  612  to pass from the second local PLMN  60  to the home PLMN  30 . The home PLMN  30  provides subscriber data to the second local PLMN  60  with an Insert Subscriber Data (ISD) message  614  providing information as to the services this subscriber  32  is entitled to receive. Preferably, the ISD message  614  includes the information that this subscriber  32  is entitled to receive local service in the second local PLMN  60  as well as specific local services, e.g., call forwarding, messaging and the like. Preferably, details regarding the parameters and charges for such services are prearranged among PLMN operators. In GSM, the parameter information is preferably transmitted via the extension container of the ISD  614 . In response, the second local PLMN  60  preferably sends an ISD acknowledgment message  616  to the home PLMN  30 . The home PLMN  30  sends a location update acknowledgment message  618  to the second local PLMN  60 . 
   The second local PLMN  60  is adapted to use the LMSISDN as a global title for the non-local subscriber  32 . The second local PLMN  60  sends its second location update message  620  to its local HLR  66 . The second location update message  620  includes the LMSISDN assigned to the non-local subscriber  32  by the second local PLMN  60 . The local HLR  66  sends an Insert Subscriber Data (ISD) message  622  to the second local PLMN  60  component serving the non-local subscriber  32 , typically an MSC/VLR  64 . The local second PLMN  60  sends an ISD acknowledgment message  624  to the local HLR  66 , and the local HLR  66  responds with a location update acknowledgment  628 . Terminals local to the second PLMN  60 , which may include mobile stations  70  and fixed network stations  72 , use the LMSISDN in communications with the non-local subscriber  32 . Calls to the home MSISDN of the roaming subscriber  32  continue to be routed through the home PLMN  30 . 
   Thus, a non-local subscriber  32  is able to roam from PLMN-to-PLMN and/or country-to-country, while being provided a unique local identifier, or LMSISDN, for receiving local calls, while still retaining home-PLMN accessability. The embodiments shown and described above are only exemplary. Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description together with details of the invention, the disclosure is illustrative only and changes may be made within the principles of the invention to the full extent indicated by the broad general meaning of the terms used in the attached claims.