Abstract:
An apparatus and a method for providing at least two identities to a subscriber unit of a mobile telephone system. A subscriber identity module (SIM) is provided which is inserted into the subscriber unit for selectively activating an identity. The module may be activated through a keypad on the subscriber unit allowing a subscriber to enter a code for selecting a specific identity, or it may be a card having a separate program circuit on either end so that when inserted into the unit with its first end, a first identity is activated, and when inserted into the unit with its second end, a second identity is activated. Each selected identity may be allocated a separate directory number or all identities may be allocated a single number.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of application Ser. No. 08/162,164, filed Apr. 20, 1994 now abandoned, which is a continuation of PCT/SE92/00227 filed Apr. 8, 1992. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to telephone systems, preferably mobile telephone systems, in which the subscriber units, preferably mobile units or stations, are controlled by a subscriber identity module. More specifically, the invention concerns a method in such a telephone system, wherein the subscriber identity module is utilised in a new way, as well as a subscriber identity module especially suited for use in connection with the method. 
     The invention is advantageously applied to a telephone system of the GSM type (Global System for Mobile Communication). Although the invention is by no means restricted to such an application, it will be described hereinafter with reference to a system of this type. 
     BACKGROUND OF THE INVENTION 
     GSM is a uniform, intelligent digital mobile telephone system which is not geographically confined to a single country. A subscriber may use any subscriber unit (Mobile Station—MS) by controlling it with the aid of a subscriber identity module (SIM), which may be an active card or a plug-in unit inserted in the subscriber unit and producing the subscriber&#39;s identity (IMSI) which is allocated to a directory number (Mobile Station International ISDN number—MSISDN) . Information on IMSI and MSISDN is stored, together with other information relating to the subscriber, in a home database (Home Location Register—HLR) with the operator of the network including the subscriber. The system comprises visitor databases (Visitor Location Register—VLR) and switches (Mobile Services Switching Centre—MSC) Information on an activated subscriber unit MS is temporarily stored in the VLR pertaining to the area of location of the subscriber unit MS. 
     Since the above concepts, as well as the design and operation of the system as a whole, are subjected to extensive standardisation, no detailed description seems required here. 
     Systems of the above type are widely used for service calls, but also to some extent for private calls. Distributing the costs for service and private calls usually cause problems or involves extra work. 
     One and the same subscription can also be used by different people, e.g. within one and the same company. Also in this case, distributing the costs among the different people concerned may cause problems or involve extra work. 
     OBJECT OF THE INVENTION 
     The object of the present invention is to eliminate the above inconveniences and also in other respects enable a more flexible use of subscriptions and subscriber identity modules. 
     SUMMARY OF THE INVENTION 
     This object is achieved by a method and a subscriber identity module having the distinctive features recited in the appended claims. 
     The invention is thus based on the insight that a subscriber identity module can be allocated at least two different identities which are selectively activable by the user. As will be appreciated, there may be two identities, e.g. a service identity and a private identity, which belong to the same user, which seems to be the currently preferred case. However, different identities might also be used, which correspond to several potential users of the subscriber identity module. 
     Preferably, only one identity can be activated at a time, i.e. a change of identity means that the previously activated identity must first be deactivated before the new identity can be regarded as activated. The associated home database is suitably made to store information on which identity is activated, so that calls can be set up, cost information stored and so forth in a correct way. 
     The subscriber identity module can be so designed that the selective identity activation, i.e. the selection of identity function in the subscriber identity module, can be carried out with the aid of keys or the like provided on the subscriber unit, or with the aid of special means provided on the subscriber identity module, e.g. so-called touch contacts when the module is an active card. The activation may then, for instance, take place in connection with the input of a so-called PIN code. In that case, each identity can be allocated a special code. This means that a number of different users (corresponding to the number of different identities) can share the subscriber identity module employed. It is also possible to have a user&#39;s PIN code supplemented with code elements for selecting the desired identity (for instance, service or private). 
     In a preferred embodiment of the subscriber identity module according to the invention, the module is an active card designed to be inserted in the subscriber unit in two different positions, preferably with one or the other end first, each position corresponding to an allocated identity. This enables an embodiment in which each identity function is clearly marked on the card, which thus becomes easy to handle. A change of identity is performed simply by taking out the card and then again inserting it, now in the other position, e.g. when switching from a service call to a private call, or vice versa. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a highly schematic diagram illustrating an embodiment of the invention. 
     FIG. 2, which is a diagram similar to that of FIG. 1, illustrates another embodiment of the invention. 
     FIG. 3 is a highly schematic diagram illustrating the information flow occurring when an identity is activated and deactivated in accordance with an embodiment of the invention. 
     FIG. 4 illustrates a supplementary addition to a home database in accordance with an embodiment of the invention. 
     FIG. 5 is a flow chart illustrating a mode of using a ‘Call Forwarding Unconditional’ function in accordance with the invention. 
     FIG. 6 is a schematic top plan view of an active card modified for use as a subscriber identity module in accordance with an embodiment of the invention. 
     FIG. 7 is a flow chart illustrating a method for transferring a call to another directory number linked to an active subscriber identity and setting up the call against the activated identity when the identity allocated to the call directory number is not activated. 
     FIG. 8 is flow chart illustrating a method for setting up calls to one of a plurality of subscriber identities in a digital telephone system. 
    
    
     DETAILED DESCRIPTION 
     A summary of the present invention is depicted in FIG.  8  and is provided later on in this specification. Reference to FIG. 8 is made throughout the specification. 
     It will be appreciated that the subscriber identity module according to the invention may be provided with specially programmed circuits  13 ,  17  (FIG. 6) which contain either integrated identity functions or separate, ‘parallell’ identity functions. With an active card having two different positions, the latter design is readily achieved by the provision of a first circuit  13  at one end of the card end a second circuit  17  at the other end of the card, all in compliance with current standards for such cards in respect of the positioning of the contact means, and so forth. Thus, one side of the card is able to identify one identity, while the other side identifies the other identity. 
     As to the allocation of directory numbers in a home database, there are different alternatives in accordance with the invention. 
     In a first alternative, as depicted in FIG. 1, the different identities of the subscriber identity module are allocated to one and same directory number at the home data base (HLR) (FIG. 8, block  60 ). The home database is designed to set up calls against and register cost information etc. for the current combination of directory number and identity. For properly performing this, the home database should be informed of which identity is activated. This can be done in that only one identity can be activated at a time, so that when a ‘new’ identity is activated, the preceding identity is always deactivated and the home database informed thereof. Such deactivation may, for instance, be performed by using a function of the type ‘Cancel IMSI’ (FIG.  3 ), which is employed in GSM-type systems. Such deactivation means that information on this identity is cancelled from the visitor database employed, and that the home database is always informed when the identity is again activated. 
     An incoming call is set up against the activated identity, controlled by the information in the home database  100 . 
     If there is no information on the activated identity, an incoming call can first be set up against a selected identity among the possible identities (e.g., IMSI  1 , IMSI  2 ). If the selected identity is found to be non-activated, the call can be transferred so as to be set up against the next possible identity etc., in accordance with the information in the home database. 
     It should be observed that a network operator can modify the function of his home database without coming into conflict with the standard of e.g. a system of GSM type. 
     In a second alternative, as depicted in FIG. 2, the different identities of the subscriber identity module are each allocated to a unique directory number. Of these directory numbers, one particular number is the subscriber&#39;s external telephone number, while the other number(s) is (are) only used in the home database  200  and may be unknown to the subscriber and to the public. It is convenient also in this case that only one identity can be activated at a time and that the home database is informed thereof, e.g. as in the first alternative (see FIG.  3 ). 
     When there is an outgoing call, the selected and activated identity is used together with the allocated directory number in conventional manner. 
     Incoming calls are always set up against the identity allocated to the special directory number, as shown in block  34  of FIG. 7, provided that this identity is activated (block  32 ). If not, the call can be transferred to the subscriber&#39;s next directory number with associated identity (block  36 - 42 ). It will be appreciated that this transfer can be performed directly, without the call being set up against the first-mentioned identity, if the home database knows which identity is activated. 
     For call transfer, use may, according to the invention, advantageously be made of a function of the type ‘Call Forwarding Unconditional’ (CFU), which is a well-known standard function adapted to be controlled by the subscriber as shown in FIGS. 4 and 5. By adding a corresponding function, controlled by the network operator, to the home database, one or more of the subscriber&#39;s directory numbers can be supplemented for direct transfer in the event of the associated identity being non-activated and provided that the subscriber has not himself made any arrangements for other direct call transfer, as shown in FIG.  5 . 
     In a third alternative, which is a further development of the second alternative, two of the subscriber&#39;s directory numbers are external telephone numbers, of which one suitably is a service number and the other is a private number. Informing of the activated identity and the direct call transfer can be performed as in the second alternative. 
     Thus, it will be appreciated that the present invention provides several different options for a subscriber as to different identities and amounts of external telephone numbers, while using a single subscriber identity module. 
     The invention will be illustrated in more detail below with the aid of non-restricting embodiments, reference being made to the accompanying drawings. 
     FIG. 1 schematically illustrates how an embodiment of the invention can be implemented in a mobile telephone system of the GSM type. The home database HLR and the visitor database VLR communicate with one another, as indicated by the arrows  1  and  3 . The visitor database VLR is in wireless communication with the mobile station MS, which is controlled by a SIM card which is activable to give the identity IMSI  1  or the identity IMSI  2 . The directory number MSISDN corresponds to these identities. Information on MSISDN and the linkage to the two identities IMSI  1  and IMSI  2  are stored in the home database HLR. 
     When IMSI  1  or IMSI  2  is activated by means of the SIM card in the mobile station MS (FIG. 8, block  62 ), information thereon is signalled to the home database HLR (FIG. 8, block  64 ), which transmits information on the current combination MSISDN-IMSI  1 , or MSISDN-IMSI  2 , to VLR in customary manner. Then, the call is set up in the usual way in consideration of the selected combination. 
     FIG. 2 schematically illustrates another embodiment of the invention, in which each identity IMSI  1  and IMSI  2  is allocated to a directory number MSISDN  1  and MSISDN  2 , respectively, which both are external telephone numbers. For the activated combination MSISDN-IMSI, the call is set up etc. in customary manner. 
     FIG. 3 illustrates the essential steps in the information flow that may be used for ensuring that the home database HLR is informed of which of the identities IMSI  1  and IMSI  2  is activated. 
     In an alternate embodiment, a module storing a plurality of identities is used. The subscriber can select between these identities by keying in a code with the aid of keys  10  (FIGS. 1 and 2) located on the subscriber unit. 
     Alternatively, the code may be entered through touch contacts (not shown) located on the module when the module is an active card. 
     In the initial position (at the top), IMSI  1  is assumed to have been activated at a prior time by the insertion of the SIM card with one end first into the mobile station. Now, the user pulls out the card and inserts it again with the other end first in order to activate IMSI  2 . Then, IMSI  2  is signalled to the visitor database VLR which, noting that the IMSI is a non-registered one, transmits updating signals to the home database HLR, which stores information on IMSI  2  being activated (FIG. 8, block  66 ), and deactivates IMSI  1  by emitting a signal ‘Cancel IMSI  1 ,’ as shown in FIGS. 3 and 5. Thus, the temporary activation of IMSI  1  is cancelled from the current visitor database VLR that belongs to the area of location of the mobile station MS. Thereafter, data on IMSI  2  is transmitted to the visitor database. The call can now be set up by using the combination MSISDN  2 -IMSI  2  (FIG. 8, block  68 ). When the user once again turns the SIM card, i.e. changes identities, a corresponding activation of IMSI  1  and a corresponding deactivation of IMSI  2  take place. 
     When there is an incoming call to the directory number whose identity is not activated, the call is transferred directly to the other directory number by using ‘Call Forwarding Unconditional’. To this end, the home database is extended with one field for each directory number, as illustrated in FIG.  4 . The added field is the one at the very bottom. For MSISDN  1  is here entered: call transfer to MSISDN  2 , and vice versa. The call transfer in accordance with these added fields takes place on condition that the user has not himself initiated any transfer of this kind, which in that case would appear from the field immediately above. 
     The entry of the additional data into the fields of the home database is conveniently carried out simultaneously with the signalling sequence according to FIG.  3 . An example of the entry of additional fields is shown in FIG.  5 . The subscriber turns the SIM card so as to insert the card&#39;s IMSI  2  end into the subscriber unit (block  40 ). A determination is made at the VLR if IMSI  1  is registered at the VLR (block  42 ). If it is, IMSI  1  is canceled at the VLR (block  44 ). After IMSI  1  is canceled or if IMSI  1  is not registered at the VLR, a determination is made if the subscriber Call Forwarding Unconditional IMSI  1  field has been programmed by the subscriber (block  46 ). If it has not been programmed, the network controllable MSISDN  2  is loaded into the database as the Call Forward Unconditional directory number (block  48 ). A flag may be set on the IMSI  1  field signifying a temporary call forwarding to MSISDN 2  (block  48 ). If the subscriber has programmed the Call Forwarding Unconditional field or if MSISDN  2  has been down loaded into the database Call Forwarding Unconditional IMSI  1  field, a determination is made if the Call Forwarding Unconditional IMSI  2  field has been marked by a temporary flag or if MSISDN  1  has been set as the call forwarding number in the IMSI  2  field (block  50 ). If it is, the subscriber controllable call forwarding number (MSISDN  1 ) is canceled from the IMSI  2  field (block  52 ). If not, or if MSISDN  1  is canceled from the IMSI  2  field, the entry is completed. 
     Thus, the ‘Call Forwarding Unconditional’ can be implemented only if the subscriber has not himself requested such call transfer to another number. In other words, the subscriber may still use this subscriber service as usual. If he does not, the home database HLR will transfer an incoming call from the non-activated combination MSISDN-IMSI to the combination as last activated and registered. 
     Thus, it will be appreciated that the subscriber has several different options: one or two external telephone numbers; automatic transfer of service calls to the private number, and vice versa; or other personally-controlled call transfer. 
     FIG. 6 schematically illustrates an activated card that has been modified in accordance with the invention so as to provide two identity functions. At one end, the card  11  is equipped in conventional manner with a circuit  13  so as to provide a first identity function when inserted into a mobile station, as indicated by the arrow  15 . The illustrated side of the card may be a service side and have a suitable and clear marking to this effect. 
     The other side of the card is the private side. For this purpose, a second, completely separate circuit  17  is provided at the other end of the card and on the private side, in accordance with current standards for the arrangement of circuits and contacts. When the private side is to be used, the card is inserted with said other end first, as indicated by the arrow  19  on the private side. This side may also have a suitable and clear identity marking. 
     In an alternate embodiment, a card storing a plurality of identities is used. The subscriber can select between these identities by keying in a code with the aid of keys  10  (FIGS. 1 and 2) located on the subscriber unit. Alternatively, the code may be entered through touch contacts (not shown) located on the card.