METHOD IN MOBILE TELEPHONE SYSTEMS IN WHICH A SUBSCRIBER IDENTITY MODULE (SIM) IS ALLOCATED AT LEAST TWO IDENTITIES WHICH ARE SELECTIVELY ACTIVATED BY THE USER

Abstract: Method in mobile telephone systems, especially of the GSM type, in which a subscriber identity module (SIM) is allocated at least two identities (IMSI 1, IMSI 2) which are selectively activated by the user. A preferred embodiment of a subscriber identity module consists of an active card which can be inserted in two different positions corresponding to one and the other identity, respectively. Preferably, the positions pertain, respectively, to one and the other end of the card.

Description: METHOD IN MOBILE TELEPHONE SYSTEMS IN WHICH A SUBSCRIBER IDENTITY MODULE (SIM) IS ALLOCATED AT LEAST TWO IDENTITIES WHICH ARE SELECTIVELY ACTIVATED BY THE USER Field of the Invention The present invention relates to telephone systems, preferably mobile telephone systems, in which the sub¬ scriber units, preferably mobile units or stations, are controlled by a subscriber identity module. More speci¬ fically, the invention concerns a method in such a tele¬ phone 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 tele¬ phone 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 tele- phone 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 subscriber identity module (SIM), which may be an active card or a plug-in unit inserted in the subscriber unit a producing the subscriber's identity (IMSI) which is allo cated to a directory number (Mobile Station Internationa 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 sub¬ scriber. The system comprises visitor databases (Visitor Location Register - VLR) and switches (Mobile Services Switching Centre - MSC). Information on an activated sub scriber unit MS is temporarily stored in the VLR pertain ing 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 servi calls, but also to some extent for private calls. Distri buting 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 diffe rent people concerned may cause problems or involve extra work. Object of the Invention The ob ect of the present invention is to eliminate the above inconveniences and also in other respects enabl a more flexible use of subscriptions and subscriber iden¬ tity modules. Summary of the Invention This object is achieved by a method and a subscriber identity module having the distinctive features recited i 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 identi ties, e.g. a service identity and a private identity, which belong to the same user, which seems to be the cur¬ rently preferred case. However, different identities migh 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 pro¬ vided 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 con¬ nection 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 sub- scriber identity module employed. It is also possible to have a user'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 iden¬ tity. 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. It will be appreciated that the subscriber identity module according to the invention may be provided with specially programmed circuits which contain either inte¬ grated identity functions or separate, 'parallell' iden¬ tity functions. With an active card having two different positions, the latter design is readily achieved by the provision of a first circuit at one end of the card and a second circuit at the other end of the card, all in com- pliance 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 iden¬ tity, 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, the different identities of the subscriber identity module are allocated to one and same directory number. The home database is designed to set up calls against and register cost information etc. for the current combination of directory number and iden¬ tity. 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*, 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 data¬ base. 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. 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, 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's external telephone number, while the other number(s) is (are) only used in the home database 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. 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, provided that this identity is activated. If not, the call can be trans¬ ferred to the subscriber's next directory number with associated identity. 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 inven- tion, 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. By adding a corresponding function, controlled by the network operator, to the home database, one or more of the subscriber's directory numbers can be supplemented for direct transfer in the event of the associated identi¬ ty being non-activated and provided that the subscriber has not himself made any arrangements for other direct call transfer. In a third alternative, which is a further develop¬ ment of the second alternative, two of the subscriber's directory numbers are external telephone numbers, of which one suitably is a service number and the other is a pri¬ vate 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 inven¬ tion provides several different options for a subscriber as to dif erent identities and amounts of external tele¬ phone numbers, while using a single subscriber identity module. The invention will be illustrated in more detail below with the aid of non-restricting embodiments, refe¬ rence being made to the accompanying drawings. 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 data base in accordance with an embodiment of the inven¬ tion, Fig. 5 is a flow chart illustrating a mode of using a 'Call Forwarding Unconditional' function in accordance with the invention, and Fig. 6 is a schematic top plan view of an active card modified for use as a subscriber identity module in accord ance with an embodiment of the invention. Description of the Preferred Embodiments 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 identi- ties 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, information thereon is signalled to the home database HLR, 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 select¬ ed 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 infor¬ mation 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 the initial position (at the to ), IMSI 1 is assumed to have been activated 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, and deactivates IMSI 1 by emitting a signal 'Cancel ISMI 1'. 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 trans¬ mitted to the visitor database. The call can now be set up by using the combination MSISDN 2-IMSI 2. 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 num¬ ber whose identity is not activated, the call is trans¬ ferred 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 condi¬ tion 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 fields of the home data¬ base is conveniently carried out simultaneously with the signalling sequence according to Fig. 3. The entry is exemplified in the flow chart of Fig. 5. 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 ser- vice as usual. If he does not, the home database HLR will transfer an incoming call from the non-activated combina¬ tion 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-con¬ trolled 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 so as to provide a first identity function when inserted into a mobile station, as indicated by the arrow 15. The illu¬ strated 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 iden¬ tity marking.

Claims: CLAIMS 1. Method in telephone systems, preferably mobile telephone systems, especially of the GSM type, in which subscriber units (MS) are controlled by a subscriber identity module (SIM), c h a r a c t e r i s e d in that the subscriber identity module (SIM) is allocated at least two identities (IMSI 1, IMSI 2) which are selec- tively usable, the user selectively activating the desir¬ ed identity when using a subscriber unit (MS). 2. The method of claim 1, in which the subscriber identity module (SIM) is of the active-card type, c h a r a c t e r i s e d in that use is made of a sub- scriber identity module (SIM) which has double identity functions and is so designed that one identity (IMSI 1) is utilised when the module (SIM) is inserted in the subscri¬ ber unit (MS) in a first position, especially with one end first, and that the other identity (IMSI 2) is utilised when the module (SIM) is inserted in the subscriber unit (MS) in a second position, especially with the other end first. 3. The method of claim 1, c h a r a c t e r i s ¬ e in that use is made of a subscriber identity module (SIM) which has at least two identity functions, the desired identity being selectively activated with the aid of the keys of the subscriber unit (MS) or with the aid of activating means provided on the subscriber identity module. 4. The method of claim 3, c h a r a c t e r i s ¬ e d in that the desired identity is activated in connec¬ tion with the input of a PIN code. 5. The method of any one of the preceding claims, c h a r a c t e r i s e d in that the identities (IMSI 1, IMSI 2) of the subscriber identity module (SIM) are allo¬ cated to one and the same directory number (MSISDN), an incoming call being set up against one or the other iden- tity (IMSI 1 or IMSI 2), controlled by the subscriber's home database (HLR) in response to the selective identity activation. 6. The method of claim 5, c h a r a c t e r i s - e d in that an incoming call is first set up against one identity (IMSI 1) and, if this identity is found to be non-activated, then against the other identity (IMSI 2) b call transfer. 7. The method of any one of claims 1-4, c h a r - a c t e r i s e d in that the identities (IMSI 1, IMSI 2) of the subscriber identity module (SIM) are each allocate to a directory number (MSISDN 1 and MSISDN 2, respec¬ tively). 8. The method of claim 7, c h a r a c t e r i s - e d in that one directory number (MSISDN 1) is the sub¬ scriber's external telephone number, an incoming call being transferred to the other directory number (MSISDN 2) when the identity (IMSI 1) allocated to the telephone num¬ ber is not activated. 9. The method of claim 7, c h a r a c t e r i s ¬ e d in that the directory numbers (MSISDN 1, MSISDN 2) are external telephone numbers of the subscriber, e.g. a service telephone number and a private telephone number, an incoming call to a directory number (MSISDN 1 or MSISDN 2) whose allocated identity (IMSI 1 and IMSI 2, respec¬ tively) is not activated, being transferred to the other directory number (MSISDN 2 or MSISDN 1). 10. The method of claim 6, 8 or 9, c h a r a c ¬ t e r i s e d in that the call transfer relies on a func- tion of the type 'Call Forwarding Unconditional", provided that this function has not been used by the subscriber. 11. The method of any one of the preceding claims, c h a r a c t e r i s e d in that only one identity (IMSI 1 or IMSI 2) can be activated at a time. 12. The method of claim 11, c h a r a c t e r i s ¬ e d in that, when one identity (IMSI 1 or IMSI 2) is selectively activated, involving a change of identity, the previous identity is deactivated, controlled by the sub¬ scriber's home database (HLR). 13. Subscriber identity module (SIM) for use in con¬ nection with a subscriber unit in a telephone system, pre- ferably a mobile telephone system, especially of the GSM "type, c h a r a c t e r i s e d in that it includes at least two identity functions which are selectively acti- vatable. 14. The subscriber identity module of claim 13, c h a r a c t e r i s e d in that it is of the active- card type and is designed for insertion into the subscri¬ ber unit in two different positions, preferably relating, respectively, to one and the other end of the card, one position allowing activation of a first identity (IMSI 1) and the other position allowing activation of a second identity (IMSI 2). 15. The subscriber identity module of claim 14, c h a r a c t e r i s e d in that it is provided with two separate circuitries, of which one is allocated one iden- tity (IMSI 1) and the other is allocated the other identi¬ ty (IMSI 2).

Inventors: JULIN TOMAS, JULIN, TOMAS
Applicants: COMVIK GSM AB
Application year: 1992
Main classification: H04B7
IPC codes: H04W8