Abstract:
A system and method for proactively detecting cloning fraud in a cellular mobile telephone environment are discussed. Information is collected which corresponds to registration notifications of the cellular telephones as they operate within the cellular mobile telephone environment. The registration information is used to detect time-space peculiarities. Specifically, registrations having the same mobile identification number and occurring in different mobile switching centers within a predetermined time interval are identified. This time interval, based on a reasonable travel time between cells covered by the different mobile switching centers where the registrations originated, is used as a threshold for detecting cloning fraud.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to cellular/PCS (Personal Communications Services) telephone communications. Specifically, the present invention relates to detecting cloning fraud in a cellular/PCS environment. 
     2. Related Art 
     Cellular mobile telephone systems provide direct-dial telephone service to mobile users by using radio transmission. The service area of a cellular mobile telephone system is divided into regions called cells. Within each cell is a base station which includes a transmitter and a receiver. Each base station is connected to a mobile switching center (MSC) which processes calls to and from mobile users located in the cell. Each transmitter and receiver operates on a voice channel (frequency). A single channel may be used for many simultaneous conversations (voice signals) in cells which are sufficiently separated from one another such that excessive interference is avoided. However, as the number of mobile users increases within a cell, the cell may become too crowded to provide adequate separation. When a cell becomes overcrowded, the cell must be split into smaller cells with each cell covering a smaller geographic area. Each new cell requires a new base station which is connected to the original MSC. Thus, as the number of cells increases, each MSC may be processing calls for multiple cells. 
     As a mobile user travels with his cellular telephone powered up, the cellular telephone autonomously registers the mobile user by sending signals with information identifying the mobile user to the MSC serving the cell where the mobile user is currently located. The sending and receipt of such information is referred to as registration notification. The information included in a registration notification is the mobile user&#39;s mobile identification number (MIN) and an electronic serial number (ESN). The MIN uniquely identifies each mobile user in a manner similar to a conventional telephone number. The ESN is encoded into each cellular telephone. The ESN functions as a security password verifying the validity of the MIN and allowing the mobile user access to the cellular mobile telephone system. 
     The MSC collects registration notifications and provides them to other facilities in the cellular mobile telephone system. These facilities primarily use the registration notifications to facilitate incoming and outgoing calls. Typically, a mobile user subscribes for services with the MSC covering the cell, or group of cells, where the mobile user primarily resides or conducts business. This MSC is referred to as the mobile user&#39;s home MSC. All other MSCs in the cellular mobile telephone system are known as visited MSCs with respect to the mobile user. When a mobile user ventures beyond the cells covered by the home MSC, the mobile user is said to be “visiting.” For purposes of this discussion, a mobile user inside a cell of a visited MSC is referred to as a visiting mobile user. 
     When a mobile user powers on his cellular telephone or crosses cell boundaries covered by different MSCs, the cellular telephone, at some point, autonomously sends a signal representing a registration notification. The MSC covering the cell (i.e., either a home MSC or a visited MSC) receives the registration notification. Based on the MIN and ESN contained in the registration notification, the MSC queries a Roamer Validation and Call Delivery (RVCD) facility to validate the mobile user&#39;s subscription information. The RVCD stores the subscription information for all mobile users in the cellular mobile telephone system in a Home Location Register (HLR). The HLR identifies each of the mobile users home MSC, the services to which each mobile user is subscribed, and whether each subscription is valid. 
     After receiving a query from the MSC, the RVCD responds by sending the requested the information included in the HLR back to the querying MSC. The MSC maintains this information to provide cellular mobile telephone services to the mobile user as long as the mobile user remains in cells covered by the MSC. 
     Registration notification is important for several reasons. Primarily, registration notification is used to provide cellular mobile telephone services to mobile users outside of the cells of the home MSC (as described above). Thus, a mobile user can utilize cellular mobile telephone services throughout the cellular mobile telephone system. 
     Registration notification is also important for routing incoming calls to mobile users. When an incoming call is to be routed to a mobile user, the mobile user must be located so that the call can be routed through the proper MSC to the mobile user. In the case of a conventional telephone user (i.e., not a mobile user) attempting to place a call to a mobile user, the home MSC receives the incoming call from the regular telephone user and determines whether the mobile user is active, or operating, in the cell of the home MSC. If the mobile user is not active within the cell of the home MSC, the mobile user may: 1) not have his telephone powered up, or 2) be active in the cell of a visited MSC. In the first case, the incoming call cannot be routed to the mobile user. In the second case, the RVCD attempts to locate the mobile user within the cellular telephone system. 
     The RVCD functions as a clearing house for a cellular mobile telephone system. Specifically, the RVCD validates mobile users and manages activation, deactivation, and changes in subscription profiles of mobile users. The RVCD also stores a copy of each registration notification received from the MSCs. Furthermore, the RVCD updates the HLR to indicate the MSC where the latest registration notification originated (this is called the originating MSC). This allows the RVCD to track where each mobile user is currently located in the cellular mobile telephone system. 
     Tracking mobile users within the cellular mobile telephone system serves to facilitate the routing of incoming calls to mobile users. When an incoming call is placed to a mobile user who is not within the cell of the home MSC, the home MSC can query the RVCD to locate the mobile user based on the origination of the registration notification maintained in the HLR. The the incoming call can then be routed to the originating MSC which connects the incoming call via radio communication signals to the mobile user. In the preferred embodiment, two RVCD systems are used in parallel to provide backup for the cellular mobile telephone system in case one RVCD should fail. 
     A problem existing in current cellular mobile telephone systems is cloning fraud. Cloning fraud occurs when one mobile user (called an unauthorized user) obtains and fraudulently uses the MIN and ESN registered to another mobile user (called an authorized user) in order to obtain “free” service. As used herein, the term “valid MIN” refers to a MIN when being used by an authorized mobile user. The term “cloned MIN” refers to a MIN when being used by an unauthorized mobile user. 
     The cellular mobile telephone system uses the MIN and ESN associated with each mobile telephone call to bill the authorized mobile user registered with that MIN and ESN. When a MIN and ESN are “cloned”, the authorized mobile user gets billed for calls made with the valid MIN as well as those calls made using the cloned MIN. Cloning fraud costs the cellular telephone industry millions of dollars in lost revenue each year. What is needed is a means for detecting cloning fraud in a cellular/PCS environment. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a system  200  and method for proactively detecting cloning fraud in a cellular/PCS (Personal Communications Services) environment. According to the invention, the system detects cloning fraud by comparing the time and location of registration notifications having the same mobile identification number (MIN). Cloning fraud is reported when the computed time difference between such registration notifications is less than a reasonable travel time between the cells of the originating mobile switching centers (originating MSCs). 
     Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. Additionally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears. 
     FIG. 1 illustrates a cellular mobile telephone environment; 
     FIG. 2 illustrates a block diagram of a cellular mobile telephone system according to a preferred embodiment of the present invention; 
     FIG. 3 illustrates a block diagram of a clone detection system (CDS) according to a preferred embodiment of the present invention; 
     FIGS. 4 and 5 are flow charts depicting the preferred operation of the present invention; and 
     FIG.  6 . illustrates an example clone detection table used by the invention. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     FIG. 1 illustrates a cellular mobile telephone environment  100 . Cellular mobile telephone environment  100  includes a plurality of cells  110 . Each cell  110  includes a base station (not shown) for transmitting and receiving radio signals to and from mobile users  130 . Each base station is connected to a mobile switching center (MSC)  120 . One or more mobile users  130  may be positioned in each cell  110  at any time. For ease of discussion, it is assumed that each MSC  120  is connected to one base station, and that each MSC  120  covers one cell  110 . However, it will be apparent to one skilled in the art that such a limitation is unnecessary. In fact, each MSC  120  is usually connected to several base stations, and thus, is responsible for covering multiple cells  110 . 
     FIG. 2 illustrates a block diagram of a cellular mobile telephone system  200  according to a preferred embodiment of the present invention. Cellular mobile telephone system could comprise a nationwide telephone system. Cellular mobile telephone system  200  includes a PCS Service Management System (PSMS)  202 , a first Roamer Validation and Call Delivery system (RVCD)  204 A, a second RVCD  204 B, a plurality of MSCs  120 , and a plurality of mobile users  130 . As discussed above, a base station (not shown) is positioned in each cell  110 . Each base station is connected to a MSC  120 . An MSC  120  may be connected to one or more base stations thus covering one or more cells  110 . Each of the MSCs  120  is connected to either RVCD  204 A or RVCD  204 B, which are centrally located within cellular mobile telephone system  200 . The RVCDs  204  are connected to each other to provide rerouting in the event that one fails. Both RVCDs  204  are connected to PSMS  202  which is also centrally located within cellular mobile telephone system  200 . In the preferred embodiment, the MSCs  120  are connected to the RVCDs  204  using IS-41 protocol over SS7 or X.25. The RVCDs  204  are connected to the PSMS  202  via an X.25 packet network. A person skilled in the art will recognize that other connection protocols and networks may alternatively be used. 
     In general, a mobile user  130  registers with a MSC  120  by sending its MIN and ESN using well known wireless communication techniques (i.e., via a radio signal  220 ). Radio signal  220  containing mobile user&#39;s MIN and ESN is sent at a predetermined time interval while the mobile user  130  is operating to notify the MSC  120  of its presence within the cell  110  where the MSC  120  is located. This is referred to as registration notification. The MSC  120  receives the radio signal  220  as a registration notification (REGNOT) query. A REGNOT query includes a MIN, a time stamp representing a time when the registration notification was received by the MSC  120 , and an originating MSC indicia identifying which MSC  120  received the registration notification. The MSC  120  sends the REGNOT query to one of the RVCDs  204  which processes the REGNOT query and creates a record of the query for subsequent retrieval by PSMS  202  (described below). 
     For example, at 10:30 am, a mobile user  130 G operating in a cell  110 G sends a radio signal  220  containing a registration notification. The MSC  120 G receives the signal  220  and creates a REGNOT query. The REGNOT query includes the mobile user  130 G&#39;s MIN, a time stamp of 10:30 am (i.e., the time when the registration notification was received), and an originating MSC indicia identifying MSC  120 G (i.e., the identity of the MSC receiving the registration notification). The REGNOT query is sent to either RVCD  204 A or RVCD  204 B which stores the query as a REGNOT record. 
     As discussed previously, each RVCD  204  functions as a clearing house for the cellular mobile telephone system  200  by maintaining information regarding the mobile users  130 . This information includes the cellular mobile telephone services to which each mobile user  130  subscribes and the cell where each operating mobile user  130  is currently located. RVCDs  204  maintain this information in a master list referred to as a Home Location Register (HLR). The information regarding the cell where each operating mobile user  130  is currently located is updated from REGNOT queries received from the MSCs  120 . At a predetermined time interval (i.e. determined by individual system implementation requirements), each RVCD  204  sends the REGNOT records to the PSMS  202  which performs various processing of the information. The PSMS  202  includes a clone detection system (CDS)  210  which processes the REGNOT records to identify instances of cloning fraud. 
     FIG. 3 illustrates a block diagram of the clone detection system (CDS)  210  according to a preferred embodiment of the present invention. The CDS  210  includes a REGNOT record collector  302 , a REGNOT record file  312 , a fraud manager  304 , a clone detection time table  306 , a clone detection window  308 , a clone record file  314 , and a report generator  316 . 
     The PSMS  202  receives the REGNOT records, indicated by reference number  318  in FIG. 3, from the RVCDs  204 . The REGNOT record collector  302  collects these REGNOT records  318  and stores them in the REGNOT record file  312 . In the preferred embodiment, the PSMS  202  receives new REGNOT records  318  from the RVCDs  204  every thirty minutes. The REGNOT records  318  received during each thirty minute interval are stored in the REGNOT record file  312  as a group. Each group of REGNOT records  318  so stored is referred to as a “half hour data group”  310 . 
     Fraud manager  304  collects several half hour data groups  310  from the REGNOT record file  312  and forms a clone detection window  308  (such half hour data groups  310  are stored in memory, such as random access memory). The clone detection window  308  collectively represents all registration notifications (represented by REGNOT records  318 ) received by the MSCs  120  within the cellular mobile telephone system  200  during a predetermined time frame. In the preferred embodiment, the fraud manager  304  forms a clone detection window  308  from the most recent thirteen half hour data groups  310  arranged from oldest in time to newest in time. Accordingly, the clone detection window  308  represents all registration notifications received within the past 6.5 hours by all MSCs  120  in the cellular mobile telephone system  200 . 
     Clone detection window  308  is a sliding window, representing registration notifications occurring within a specified time interval (i.e. the last 6.5 hours). As the window “slides” (i.e. time passes), new registration notifications are added to the window and old ones are removed. Thus, only those registration notifications occurring within the specified time interval are processed together by fraud manager  304 . 
     The fraud manager  304  determines whether cloning fraud exists by determining whether time-space peculiarities exist within the clone detection window  308 . A time-space peculiarity exists when registration notifications with the same MIN originated in different locations within a time insufficient to travel between the different locations. In such cases, at least one of the registration notifications is likely to be an instance of cloning fraud. 
     In the preferred embodiment, the fraud manager  304  detects cloning fraud by comparing the difference between the time stamps of the REGNOT records  318  in the clone detection window  308  having the same MIN with a reasonable travel time between the locations of the cells of the originating MSCs. For example, referring to FIG. 1, suppose the MSC  120 A receives a registration notification indicating a MIN of X from the mobile user  130 A at 10:00 a.m. Later, the MSC  120 C receives a registration notification also indicating a MIN of X from the mobile user  130 C at 10:45 a.m. Suppose that a reasonable travel time between cell  110 A and cell  110 C is 80 minutes. When the fraud manager  304  processes the REGNOT records  318  in the clone detection window  310 , it will locate these two registration notifications having the same MIN of X. The fraud manager  304  will determine that one registration notification was received by the MSC  120 A in cell  110 A while the other was received by the MSC  120 C in cell  110 C. The fraud manager  304  will determine that the registration notifications occurred 45 minutes apart from one another. By comparing this time difference (45 minutes) with the reasonable travel time (80 minutes), the fraud manager  304  will conclude that an instance of cloning fraud has occurred. 
     The previous example has been provided to illustrate the operation of the clone detection system  210  and not as a limitation. In the preferred embodiment, the clone detection window  308  is 6.5 hours wide (chosen as the minimum reasonable time to travel across the United States) and encompasses a much larger time frame than the example illustrates. Furthermore, it would be apparent for one skilled in the art to adjust the width of the clone detection window  308  depending on the geographic area covered by the cellular mobile telephone system  200 . 
     Referring again to FIG. 3, in the preferred embodiment, reasonable travel times between the cells  110  covered by different MSCs  120  of the cellular mobile telephone system  200  are stored in a clone detection time table  306 . The clone detection time table  306  includes the reasonable travel time between cells  110  covered by a pair of MSCs  120 . For cells  110  covered by a pair of adjacent MSCs  120  (e.g., MSC  120 A and MSC  120 B), the travel time is zero because a mobile user  130  could register with either MSC  120  as the mobile user  130  crosses cell boundaries. For each pair of nonadjacent MSCs  120  (e.g., MSC  110 A and MSC  110 D), a reasonable travel time is determined based on the time a mobile user  130  would take to travel out of cells  110  covered by a first MSC  120  and into cells  110  covered by a second MSC  120 . This reasonable travel time is stored in clone detection time table  306  and is retrieved using the originating MSC from each of the REGNOT records as indices into the table. An example clone detection time table  306  is illustrated in FIG.  6 . For example, the reasonable travel time between cells  110  covered by MSCs  120 A and  120 D is found by using the first REGNOT originating MSC as MSC A and the second REGNOT originating MSC as MSC D to retrieve  120  minutes as the reasonable travel time. 
     The preferred embodiment uses RVCDs  204  to store the HLR and collect the REGNOT queries for each of the MSCs  110 . One skilled in the art would recognize that other implementations or divisions of processing could be utilized for clone detection system  210 . For example, the PSMS  202  could be directly connected to each MSC  110  and handle the registration notifications without any RVCDs  204 . Furthermore, data could be processed in other that half hour increments, or in fact, immediately upon receipt. 
     FIG. 4 illustrates a flow diagram of a preferred implementation of the processing performed by the fraud manager  304  during clone detection. In a step  402 , the fraud manager  304  forms a clone detection window  308  from preferably the most recent in time thirteen half hour data groups  310  retrieved from REGNOT record file  312 . As discussed above, the data is arranged from the oldest REGNOT record to the newest REGNOT record. 
     In a step  404 , the fraud manager  304  reads a MIN from a first REGNOT record  318 , (i.e., the oldest record with respect to time) in the clone detection window  308 . In a step  406 , the fraud manager  304  reads a MIN from a second REGNOT record  318  in clone detection window  308 . In a decision step  408 , the fraud manager  304  compares the MIN from the first REGNOT record with the MIN from the second REGNOT record to determine if the MINs are the same. If the MINs are the same (indicating the same registered mobile user), processing continues at a step  410 ; otherwise, processing continues at a decision step  414 . 
     In step  410 , the fraud manager  304  handles a possible clone detection, as discussed in greater detail below. After handling a possible clone detection, the fraud manager  304 , in a step  412 , notes that it should use the second REGNOT record in place of the first REGNOT record in future performances of step  408  and  410 , so that future occurrences of the same MIN will be compared (in step  502 , as described below) with the time stamp of the second REGNOT record rather than that of the first. 
     In decision step  414 , the fraud manager  304  determines whether the entire clone detection window  308  has been searched for the occurrence of the MIN obtained in step  404 . If the entire clone detection window  308  has been searched, processing continues at a step  416 ; otherwise, processing returns to step  406  to get a new second REGNOT record  318  from the clone detection window  308  and continue searching for the same MIN. 
     In step  416 , the fraud manager  304  excludes from further consideration all REGNOT records  318  having the MIN obtained in step  404 . In a step  418 , the fraud manager  304  determines whether any REGNOT records  318  remain in the clone detection window  308  that contain MINs that have not yet been checked for cloning fraud. If no REGNOT records  318  remain to be checked, processing ends in a step  420 ; otherwise, processing returns to step  404  to get a new first REGNOT record  318  containing a new MIN to check for cloning fraud. 
     FIG. 5 illustrates the handling of possible clone detection of step  410  in greater detail. In a step  502 , the fraud manager  304  computes a difference between time stamps of the first and second REGNOT records. In a step  504 , the fraud manager  304  obtains the indicia identifying the originating MSCs from the first and second REGNOT records and uses them as indices to the clone detection time table  306  to retrieve a reasonable travel time between the respective cells of originating MSCs. In a decision step  506 , the fraud manager  304  determines whether the time stamp difference obtained in step  502  is less than the reasonable travel time obtained from the clone detection time table  308  in step  504 . If the time stamp difference is less than the reasonable travel time, then cloning fraud is likely to exist and processing continues at a step  508 ; otherwise, the handling of possible clone detection is complete (i.e., cloning fraud does not exist) and processing continues at step  412 . 
     In step  508 , the fraud manager  304  records a likely instance of cloning fraud in the clone record file  314 . The fraud manager stores the MIN, both originating MSCs, the clone detection time, and the time stamp difference for later action/reporting by the clone detection system  210 . In addition to a daily report of cloning activity, such action/reporting may include an alarm displayed to personnel in cellular mobile telephone system  200  or removal of the suspected clone from service. After step  508 , processing continues at step  412 . 
     While the invention has been particularly shown and described with reference to several preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.