Patent Publication Number: US-2011053580-A1

Title: System and Method for Reusing Mobile Phone Numbers

Description:
FIELD OF THE INVENTION 
     The present invention is comprised within the field of mobile telecommunications, and more specifically in providing a method for reusing phone numbers, and it is specially used for prepaid subscriptions that are only valid for a limited short period of time (e.g. one week, one month). 
     BACKGROUND OF THE INVENTION 
     Mobile operators have limited dialing numbers (MSISDNs) available for new users due to the restrictions imposed by regulators. 
     In particular, there are prepaid users that stop using their subscription/MSISDN but the MNO cannot reuse the number typically for one year. 
     There are intelligent network (IN) solutions that translate the originating or the destination number of a call to a different number. For example, when a call is made to the professional mobile number of a user, the user might have activated an IN service that automatically forwards calls to his/her voicemail number after 6 pm. Similarly, the user might have another service activated so that when he/she sets up a call from his/her professional mobile number (e.g. 123456789), the originating address is changed so the receiving party does not see his/her number, but the number of his/her company (e.g. 123000000). 
     Existing solutions to reuse MSISDNs have a very long lead time due to legal and contractual implications but also because if a number is reused immediately, it is quite likely that, for a while, the new user will keep receiving calls from people that want to talk to the old user, the previous owner of the MSISDN, and that do not know yet that he has changed his number. 
     It is well-known that abbreviations and acronyms are frequently used in the mobile telephony field. Below is a glossary of acronyms/terms used throughout the present specification:
     GMSC Gateway Mobile Switching Centre   HLR Home Location Register   IMS IP Multimedia Subsystem   IMSI International Mobile Subscriber Identity   IN Intelligent Network   MNO Mobile Network Operator   MSC Mobile Switching Centre   MSISDN Mobile Station International ISDN Number   SIM Subscriber Identification Module   SMS Short Message Service   

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The single FIGURE of the drawings is a flow chart of an exemplary method according to the invention. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     The invention relates to a method for reusing mobile phone numbers according to claim  1 , and to a system according to claim  10 . Preferred embodiments of the system and of the method are defined in the dependent claims. 
     The present invention solves the above commented problems. The proposed invention supports prepaid subscriptions that are only valid for a limited short period of time (e.g. one week, one month), from now on “short term” prepaid users. Once this period expires, the subscription is over and the number can be reused for another prepaid user straight away. From this moment, calls made to the old user will be rejected (e.g. number does not exist) so the new user will not be bothered. 
     The invention is based on IN, but other technologies such as IMS are also valid. 
     The method is aimed to be applied on new subscriptions (from now on, short-term subscriptions) of a MNO. 
     As shown in the FIGURE of the Drawings, the method comprises the following steps: 
     S 10 , reserving a pool of free MSISDNs for short-term subscriptions; 
     whenever a user requests a short-term subscription:
         S 12 , removing a free MSISDN from the pool;   S 14 , choosing a determined n-digit number;   S 16 , appending said determined n-digit number to said free MSISDN removed from the pool, obtaining a new MSISDN;   S 18 , assigning said new MSISDN to said user;   S 20 , assigning, in the HLR of said MNO, said new MSISDN to an IMSI;   S 22 , providing the user with a SIM card having said IMSI associated       

     with the new MSISDN. 
     The method can further comprise, when appending a determined n-digit number to said free MSISDN removed from the pool, S 24 , including said determined n-digit number in a list of the last n-digit numbers used for said free MSISDN removed from the pool. 
     The method can also comprise, when choosing a determined n-digit number, S 26 , choosing an n-digit number not included in the list of the last n-digit numbers used for said free MSISDN removed from the pool. 
     The method can further comprise, S 28 , whenever a short-term subscription of a user ends, adding the MSISDN associated to said user (said MSISDN corresponding to the free MSISDN previously removed from the pool) back to the pool of free MSISDNs for short-term subscriptions. 
     The method can also comprise, S 30 , whenever a new MSISDN, which includes the appended n-digit number, is involved in the process of a mobile phone communication, checking that said new MSISDN is valid. The validation of the new MSISDN can be, S 32 , carried out by a HLR. It can also be, S 34 , validated by a MSC together with a HLR; the first one validates the appended n-digit number, whereas the latter validates the rest of the digits of the new MSISDN. 
     In a preferred embodiment n, the number of digits appended to the free MSISDN removed from the pool, is equal to 2. 
     The appendage of the n-digit number is preferably done at the end of the free MSISDN removed from the pool. 
     The present invention also includes a system for reusing mobile phone numbers, comprising: 
     data processing means configured for:
         reserving a pool of free MSISDNs for short-term subscriptions;   whenever a new user requests a short-term subscription:
           removing a free MSISDN from the pool;   choosing a determined n-digit number;   appending said determined n-digit number to said free MSISDN removed from the pool, obtaining a new MSISDN;   assigning said new MSISDN to said user;   assigning, in the HLR of said MNO, said new MSISDN to an IMSI;   
               

     a SIM card provided to each new user, said SIM card having said IMSI associated with the corresponding new MSISDN. 
     The data processing means can be further configured for: 
     when appending a determined n-digit number to said free MSISDN removed from the pool, including said determined n-digit number in a list of the last n-digit numbers used for said free MSISDN removed from the pool. 
     when choosing a determined n-digit number, choosing an n-digit number not included in the list of the last n-digit numbers used for said free MSISDN removed from the pool. 
     whenever a short-term subscription of a user ends, adding the MSISDN associated to said user, said MSISDN corresponding to the free MSISDN previously removed from the pool, back to the pool of free MSISDNs for short-term subscriptions. 
     whenever a new MSISDN, which includes the appended n-digit number, is involved in the process of a mobile phone communication, checking that said new MSISDN is valid. 
     DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
     Most MSISDN, in countries such as Spain, France and Holland, have 11 digits including country code (e.g. 34610123456), although MSISDN can have different number of digits (e.g., 12 digits in Germany and UK). 
     A range of 11 digits number will be reserved for the “short term” prepaid users, and two more digits will be added for the internal processing of the MNO. 
     The MNO will have a pool of 11-digit MSISDNs that will be used for short-term subscriptions. 
     Whenever a new user requests a short-term subscription, the MNO take a free one form the pool and assign it to the user. Before the assignment, the MNO appends two digits to the MSISDN so that the new user will be differentiated from the previous users that used said MSISDN in the recent past. 
     For instance, MSISDN 34610123456 is free in the pool. The operator removes it from the pool and chooses two digits, e.g. 83, and appends them to the number, obtaining 3461012345683, which is the new 13-digit MSISDN assigned to the user. Every MSISDN will have assigned a list of the last used two-digit combinations that should be avoided when reassigning the number (e.g. 92, 45, 28, 09, 82, 52, 10, 83); in this case 83 is the last two-digit used. Note that it can be added n digits instead of two (however two-digit addition should be enough). 
     The 13-digit MSISDN is now associated to the IMSI stored in the SIM card provided to the user. 
     Internal processes need to support this new provisioning mechanism. 
     Form this moment, the user can set up and receive calls/SMS/etc. as any other mobile user. 
     When the user sets up a call, the IMSI in his/her SIM is passed to the MSC and is used to get the 13-digit MSISDN from the HLR. The called person will see the 13-digit MSISDN on the screen of his phone when he receives the call. Other alternatives may include a generic gateway number for the originating address, or no number at all. 
     When the user receives a call, the call will be routed to the MNO through a GMSC (the MSC that determines which visited MSC the subscriber who is being called is currently located) and at this point the HLR will inform about the MSC from which the user is hanging. The call will be rerouted to said MSC. 
     There are two ways to validate that the last two digits are valid: 
     1) The HLR performs the check of the 13-digit MSISDN. 
     2) The HLR only checks the 11-digit MSISDN and then the MSC needs to check the validity of the last two digits. 
     Basically, a call will only be accepted if the last two digits correspond to the value assigned to the current user (83 in the example) 
     If any other value is received (e.g. 52 that was assigned to a previous user two weeks ago), the call will be rejected (e.g. with the message “Number not known”). This can be achieved through IN. 
     The method proposed by the present invention can be carried out by data processing means connected to the HLR of the MNO. The data processing means can be, for instance, a dedicated server connected to the HLR, a module contained in the HLR or a software module loaded in the HLR itself.