AU718887B2 - Roaming process and appurtenant devices - Google Patents

Abstract

The roaming process allows a subscriber of a home public land mobile network (HPLMN) to be connected to a visitor public land mobile network (VPLMN). This is done without a roaming agreement with the home public land mobile network, when an international mobile subscriber identity (IMSI-PPLMN) is made available by a partner unit (PPLMN) having a roaming agreement with both mobile networks. The connection to the visitor public land mobile network can be established by replacing the international mobile subscriber identification (IMSI) for the home public land mobile network with the partner network identification on the subscriber identification module card (SIM).

Description

Roaming Process and Appurtenant Devices Technical Field The present invention relates to roaming in a radio network, particularly in a mobile radio network.

Although the following description deals particularly with the problem of roaming between mobile networks of the GSM type, the invention also relates to roaming between any kinds of mobile radio networks, terrestrial or via satellite, as well as roaming between different kinds of networks.

State of the Art Mobile telephone networks of the GMS type have existed since the beginning of the nineties. At present more than 200 networks of this type exist worldwide. In addition, other mobile radio networks exist which operate with other different analog or numeric standards. These different networks generally cover various geographical regions, for example various countries.

However, there is some overlapping between networks and, for example in some countries, several mobile networks exist alongside one another in the same region.

The mobile radio subscribers have generally concluded a subscription or another type of agreement with a certain mobile network which is generally operated at their place of residence, for example with a national network. This particular network for a certain subscriber is called a home mobile radio network, or more frequently by the English acronym HPLMN (Home Public Land Mobile Network). Still, it is desirable for a subscriber to be able to make and receive calls even when he leaves his HPLMN, that is, when he goes to a visited mobile radio network (VPLMN, Visited Public Land Mobile Network). In the same way, it is necessary that the calls which are made by a mobile radio subscriber during a visit to a VPLMN may be billed to the subscriber by the operator of the HPLMN and that the sums accruing may be i' redistributed between the HPLMN and the VPLMN. These possibilities presently require the conclusion of bilateral agreements between the operators of the GMS networks. These agreements are known as roaming agreements.

Roaming processes are described, for example by I. Brini et al. in "International roaming in digital cellular networks," CSELT Technical Reports, Volume XX, No. 6, Italy, December 1992, pp. 531-536, or by the same authors in "European roaming related technical problems" CSELT Technical reports, Volume XX, No. 3, Italy, June 1992, pp. 209-215. Bent Gabelgaard gives more exact information on the concept of the home file (HLR, Home Location Register) in a GSM environment in "The (GSM) HRL Advantages and lo Challenges," 1994, Records of the Third Annual International Conference on Universal Personal Communications, San Diego, 27 September-1 October 1994, published by IEEE in New York, 1994, pp. 335-339. More exact information concerning the establishment of connections in a GSM network are to be found above all in WO95/10174.

An older mobile network in a populated country may have concluded numerous bilateral roaming agreements, for example more than 50. For a newer mobile network it is difficult or impossible to conclude a comparable number of roaming agreements quickly, particularly if this network covers a geographical region which is sparsely settled or in which the potential of 2o possible mobile telephone subscribers is slight. Moreover, the costs which arise through the conclusion of a roaming agreement between two networks, for the testing of the roaming connections, and for the periodic preparation of exchanged billing files (TAP files) may prove to be troublesome when the traffic between these two networks is light. Hence the incentive for new networks is limited since the subscribers do not have the possibility of using their terminals in a large number of countries. The restriction of the number of roaming agreements thus represents a competitive disadvantage for the operators of new mobile networks.

Patent specification W096/13954 (Ericsson) describes a process which enables the subscribers of a home mobile radio network to establish a telephone connection from a visited mobile radio network without roaming q Nagreement to the home mobile radio network. The process comprises a step of -3a manual entry in a visitor table. This step of the manual entry is troublesome for the traveling subscriber. This patent relates only to the signaling problems but in no way to the problem of invoicing and clearing.

Patent specification W095/27382 (Ericsson) describes a process which enables the subscribers of a radio network of the PDC type (Personal Digital Cellular) to use their terminals in a network of the GSM type ("Inter Standard Roaming"). The arrangement described comprises, besides the two networks, PDC and GSM, a roaming arrangement which carries out the necessary formal conversion for the signals exchanged between the GSM network and the PDC network. The roaming arrangement is looked upon by the subscriber file HLR1 of the PDC network as a local exchange center and is looked upon by the local exchange center of the region of the GSM network in which the traveling subscriber is situated as subscriber file HLR. The roaming arrangement described contains a roaming file (ILR) with a list of all subscribers in the PDC network who are entitled also to use the GSM network. When the PDC network is extensive, the size of the roaming file may become considerable and its administration costly. Hence this solution strives for the possibility of a roaming agreement between two radio networks which use different standards but does not enable the operator of a new network to extend the number of roaming agreements quickly and more costeffectively. Here, too, this patent does not allude to the problem of invoicing and clearing.

Patent specification GB-A-2280085 describes a telecommunications method with which a subscriber of a AMPS/D-AMPS network can log onto a GSM network. The operator of the AMPSID-AMPS network needs a cooperation agreement with at least one GSM network A. The subscriber needs a new GSM-SIM card and a GSM mobile device in order to be able to telephone in network A or in another network with a roaming agreement with A. The bills are nevertheless sent to him by the operator of the AMPS/D-AMPS network Hence a task of the invention is the broadening of the roaming possibilities which can be offered to the subscribers by a network operator without having to conclude a large number of roaming agreements.

The present invention may offer to a network, for example a new network or one which has concluded few roaming agreements, the roaming possibility of another partner network, preferably of a network which has concluded a large number of roaming agreements.

According to one aspect of the present invention there is provided telecommunication process which enables a subscriber of a home mobile radio network to log onto a visited mobile radio network (VPLMN, Visitor Public Land "Mobile Network) without a roaming agreement with the home mobile radio o *network, wherein a computer program replaces the identification data of the subscriber with identification data made available by a partner radio network having a roaming agreement with the home mobile radio network, on the one hand, and with the visited mobile radio network, on the other hand.

According to a further aspect of the present invention there is provided a chip card which is intended for use in a mobile radio apparatus and makes possible the storage of subscriber identification data, said chip card including: a 25 processor which makes possible a replacement of the subscriber identification data, dependent on the visited mobile radio network in which the mobile radio apparatus is presently situated, by identification data corresponding to a subscriber in a partner radio network having a roaming agreement with the home mobile radio network in which the subscriber has subscribed, on the one hand, and with the visited mobile radio network, on the other hand.

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The description mentions several exemplary embodiments of the invention, W tall of which may enable the operator of a new mobile radio network which has rr MJP C:WINWORD\MARIE\GABNODEL,40077C.DOC concluded few roaming agreements to offer his subscribers the roaming possibilities of another network which has concluded a large number of roaming agreements. The advantage consists in the fact that the subscribers of the new mobile network can immediately profit by all roaming agreements of the other mobile network. Consequently, the mobile network which makes its roaming agreements available is called a partner network or PPLMN (Partner Public Land Mobile Network).

According to a first exemplary embodiment of the invention, the tasks of the invention may be addressed substantially by means of a programmable device, for example a SIM (Subscriber Identity Module) card, provided with a novel program which is hereafter called UBICOM program for SIM card, as well as by means of a turntable controlled by software which is hereafter called UBICOM Manager administration program. The turntable can access both the home file (HLR) of the home network HPLMN and the home file HLR of the °•"partner network PPLMN.

tO oo According to this first exemplary embodiment, the SIM card may contain in a conventional manner a first set of subscriber identifying data (IMSI-HPLMN, International Mobile Subscriber Identity) in the home mobile radio network HPLMN. The card may further contain a second set of subscriber identifying data i: (IMSI-PPLMN) in a partner mobile radio network (PPLMN) administered by an operator which has a roaming agreement with the home mobile radio network.

Means for modifying the identifying data (identity) may make possible a 25 replacement of the data set used according to the mobile radio network in which 0 the terminal is currently situated. Through this mechanism, the subscriber of HPLMN can be recognized by the operator of the visited VPLMN network as a subscriber of PPLMN and can thus use the VPLMN network with the same roaming possibilities as are offered to the subscribers of PPLMN.

-6- However, this exemplary embodiment requires updating or an exchange of the SIM cards of all subscribers of the HPLMN network who wish to take advantage of the roaming possibilities offered by the PPLMN partner network.

According to a second exemplary embodiment of the invention, presuppose the connection requirements which are set out by a subscriber of the home mobile radio network (HPLMN) from a visited mobile radio network (VPLMN-NR) without a roaming agreement with the home mobile radio network, the sending-out of signals, for example of an authentication inquiry, to an intermediate turntable which is administered by an operator of a partner network (PPLMN) having a roaming agreement with the home network HPLMN, on the one hand, and with the visited network VPLMN-NR, on the other hand. In these signals, the turntable replaces the subscriber's location information (LI-HPLMN) by data corresponding to a subscriber in the partner radio network (LI-PPLMN).

The second exemplary embodiment of the invention may comprise a step "in which these location data (LI) of the subscriber are modified in such a way that a connection can be established. In this second exemplary embodiment, however, the means for data modification may be integrated in a turntable and not implemented in the form of an information module in the subscriber's SIM card.

Still, these two exemplary embodiments are not completely transparent to the operators of the radio network since they do not know the identity and/or the exact location of the subscriber. Some operators propose to their subscribers bargain subscription possibilities which exclude calls from or into certain regions of the world. Such restrictions could be circumvented in certain cases through the use of one or the other of these exemplary embodiments.

According to a third exemplary embodiment of the invention, establishment of the connections from the visited mobile radio network (VPLMN) may take place via at least one intermediate turntable with which both the home mobile radio MJP C:\WINWORD\MARIEGABNODEL477C.DOC -6a network and the visited mobile radio network have signed a roaming agreement.

Yet the connections established from the visited mobile radio network (VPLMN) do not necessarily go via the turntable.

In this case, the turntable has the task of a central roaming turntable between all radio networks. The turntable is preferably administered by a partner unit, for example by the operator of a radio network (PPLMN) which has already concluded roaming agreements with a large number of networks. If need be, these agreements must be replaced or supplemented by subsidiary agreements which make it possible to carry out the process of the invention.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings wherein: Figure 1 shows diagrammatically a radio system which shows a home mobile radio network (HPLMN), a visited mobile radio network (VPLMN), and a partner radio network (PPLMN), as well as means according to the first exemplary

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embodiment of the invention which enable a subscriber of HPLMN to use his terminal in the VPLMN; *7 MJ o. 9 C C o VRAI 0 Figure 2 is a flow chart showing the program which is carried out by the SIM card according to the first exemplary embodiment of the invention; Figure 3 is a flow chart showing another embodiment of the program which is carried out by the SIM card according to the first exemplary embodiment of the invention when the SIM Toolkit GSM11.14 is available; Figure 4 shows diagrammatically a radio system comprising a home mobile radio network (HPLMN), a visited mobile radio network (VPLMN), and a partner radio network (PPLMN), as well as means according to the second exemplary embodiment of the invention which enable a subscriber of HPLMN to io use his terminal in the VPLMN; Figure 5 shows diagrammatically a radio system comprising a home mobile radio network (HPLMN), a visited mobile radio network (VPLMN), and a turntable administered by a partner unit, as well as means according to the third exemplary embodiment of the invention which enable a subscriber of HPLMN to use his terminal in the VPLMN; Figure 6 is a flow chart showing certain steps of the clearing and invoicing process which are carried out by the clearing and invoicing unit of the turntable according to the third exemplary embodiment of the invention; Figure 7 shows diagrammatically the course of invoicing and payment in a radio system according to the third exemplary embodiment of the invention comprising a home mobile radio network (HPLMN), a visited mobile radio network (VPLMN), and a turntable administered by a partner unit.

An embodiment of the first variant of the invention will now be discussed with reference to Figures 1 to 3. The radio system of the invention depicted as an example comprises a home mobile radio network (HPLMN, Home Public Land Mobile Network), for example a radio network according to the GSM standard, a partner radio network (PPLMN, Partner Public Land Mobile Network), as well as a visited radio network (VPLMN, Visited Public f Land Mobile Network). The three networks HPLMN, PPLMN, and VPLMN each comprise at least one home file HLR (Home Location Register), which is called HLR-HPLMN, HLR-PPLMN, or HLR-VPLMN. The other elements which form the mobile networks, such as terminals (mobile telephones), cells, base stations, base station control units, exchanges, etc., are known according to the state of the art and are thus not depicted. The visited network VPLMN has no roaming agreement with the home network HPLMN, which is indicated by the acronym VPLMN-NR (VPLMN with No Roaming Agreement).

It goes without saying that the radio system depicted here is intended only as a non-restricting example and that the invention is applicable io also to more complex radio systems comprising a large number of mobile radio networks which operate according to one or more standards and only some of which are connected by bilateral roaming agreements.

The letter S designates a subscriber of the home mobile radio network HPLMN. When he is in the geographical region served by his home network HPLMN, the subscriber 1 can telephone by means of his terminal, for example a portable telephone, and use the services offered by his HPLMN in a quite normal manner. The terminal 1 contains a programmable device 10, for example a chip card which in the GSM networks is called a SIM card (Subscriber Identification Module). SIM cards are described for example by Theodora Grogorova et al. in "SIM Cards," Telecommunication Journal of Australia, Vol. 43, No. 2, 1993, and make possible above all the storage of a subscriber identification code designated by the acronym IMSI (International Mobile Subscriber Identity). The SIM card further contains a processor 102 which can carry out various algorithms.

When the subscriber leaves his home network HPLMN and comes into a visited network which has a roaming agreement (not shown) with his HPLMN, subscriber S can use his terminal quite normally with the aid of the conventional roaming processes which are described for example in the abovementioned documents. However, when the subscriber S goes into a visited network VPLMN-NR which has not concluded any roaming agreement with his home network, the subscriber can no longer use the IMSI identification code of his card to log on since the visited network does not accept this identification code. According to the state of the art, the subscriber can thus neither carry out nor receive calls from the geographical zone covered by a VPLMN-NR.

According to the first exemplary embodiment of the invention, the SIM card 10 contains a computer program designated as UBICOM program.

The UBICOM program makes possible the exchange of the identification code of the subscriber from the HPLMN network (IMSI-HPLMN) for a corresponding identification code of a subscriber in the partner network PPLMN (IMSI- PPLMN). The subscriber S is thus considered in the visited network VPLMN- NR to be a traveling subscriber who comes from the partner network PPLMN.

Since the PPLMN network has a roaming agreement with the visited network VPLMN-NR, the subscriber S can thus log on and carry out or receive calls in the VPLMN-NR.

The partner network PPLMN contains in a conventional manner a location file HLR-PPLMN in which, according to a procedure conventional for a GSM network, the information is registered that the subscriber S (who is identified by the IMSI-PPLMN) is now in the VPLMN-NR. According to the invention, the PPLMN network further comprises a turntable with the designation UBICOM which is controlled by software hereafter called administration program UBICOM. The turntable 2 is informed by an alarm when the subscriber S is registered in the HLR-PPLMN files. The output of such alarm signals is known according to the state of the art and is for example already used when a short message SMS is temporarily stored and when a traveling subscriber again logs on in his network. In such a case, the administration center for short messages SMSC is informed by an alarm that the short message can now be sent out. This function may also be used in order to inform the file administration program UBICOM 2; however, it is also possible to use another function.

The turntable UBICOM 2 recognizes the correspondence between the IMSI-PPLMN and the IMSI-HPLMN of each subscriber. In the same way, the turntable UBICOM 2 recognizes the correspondence between the identification number MSISDN of the terminal 1 in the PPLMN (PPLMN- MSISDN, Mobile Station ISDN Number) and in the HPLMN (HPLMN-MSISDN).

;iD "I Pos When the turntable 2 discovers that the subscriber S is using the identification code PPLMN-IMSI of the PPLMN, it sends a message to the location file HPLR- HPLMN of S's home network (HPLMN), which activates or deactivates a call diversion (CFU, Call Forwarding Inconditional[sic]). This message causes the diversion of all calls intended for the MSISDN-HPLMN to the MSISDN-PPLMN.

Thus the identification code of the terminal MSISDN-HPLMN may be used for calling the subscriber S. The process is automatic and transparent to the subscriber.

When the subscriber S leaves the visited network VPLMN-NR and returns to his home network HPLMN, he first logs on with the aid of the identification code PPLMN-IMSI. This reconnection to the HPLMN network is registered in the location file of PPLMN through the mechanism described previously. The turntable UBICOM 2 now issues an alarm to the home network HPLMN for suppressing the diversion CFU.

The SIM card 10 of the subscriber S is informed in the same way upon reconnecting to the HPLMN that the subscriber S has returned to his home network. The UBICOM program of the SIM card again exchanges the identification code of the subscriber IMSI in the partner network PPLMN (IMSI- PPLMN) for a subscriber identification code in the home network HPLMN (IMSI-HPLMN). Thus, after the reconnection to his home network, the subscriber S can switch his terminal 1 off and on again in order to telephone again with his own IMSI and his MSISDN which are defined in his home network. The mechanism of the invention is reactivated only if the subscriber S again goes into a network without a roaming agreement VPLMN-NR.

The steps of the UBICOM program carried out by the SIM card of the invention will now be described with reference to Figure 2.

The UBICOM program of the SIM card is automatically run upon each resetting of the card, for example after switching the terminal 1 on. The SIM card of the invention contains, besides the usual files of the standard GSM, an additional file EFUBICOM containing the following information: A processing flag 100 indicating whether the UBICOM mechanism is activated or not.

The subscriber identification code in the home network IMSI-

HPLMN.

The subscriber identification code in the partner network IMSI-

PPLMN.

The home country code (MCC, Mobile Country Code) and the home network code (MNC, Mobile Network Code).

A list 101 of the MCC codes of all countries and of the MNC io codes of all VPLMN networks which have concluded a roaming agreement with the home network (VPLMN-WR, VPLMN With Roaming Agreement).

This list can be dynamically completed or updated, for example by means of a procedure known by the designation SICAP and described in patent application EP94810363.5 in the name of the applicant, or by means of any other suitable procedure such as ESMS, etc.

It is known to one skilled in the art that these different items of information are cited as an illustrative example and that they can just as well be divided up into several files.

The UBICOM program run by the processor of the SIM card begins with step 30 ATR (Answer to Reset). In step 31 the processing flag showing whether the UBICOM mechanism is activated is tested. The UBICOM program is immediately interrupted when the processing flag indicates that the UBICOM mechanism is not activated, and in this case the processor of the SIM card immediately continues carrying out the normal operations from step 37 on, which are carried out after a conventional reset.

If the UBICOM mechanism is activated, the program reads in step 32 the conventional file EFLOCI (Elementary File for Location Information). In step 33 the program checks whether the file EFLOCI contains the code of the mobile network (MNC, Mobile Network Code) of the home network HPLMN or the code of a network VPLMN-WR which is specified in the file EFUBICOM, that is, of a network which has concluded a roaming agreement with the HPLMN network.

In case of an affirmative result of the check 33, that is, if the file EFLOCI indicates that the subscriber S is currently in a network which recognizes the identification code IMSI of his home network HPLMN, the UBICOM program continues with the check 34 in which the subscriber to identification code IMSI is checked (file EFIMSI). If the subscriber identification code IMSI corresponds to an identification code in the partner network PPLMN, the program continues with the following step 35 in which the subscriber identification code IMSI-PPLMN is replaced by the identification code IMSI- HPLMN in the home network of the subscriber. The program thereafter carries out the operation 36 in which the file EFLOCI is deleted, for example by inputting the hexadecimal value "FF FF FF The UBICOM program is thereafter terminated, and the processor of the SIM card thereafter continues with step 37 in which the normal functions of the SIM card are carried out. If the subscriber S actually is in his HPLMN or in a VPLMN-WR, he can thus log on to the network normally using his IMSI- HPLMN. The file EFLOCI is now updated with the identification code of the mobile network to which the subscriber logs on.

If, however, the subscriber S is in a network VPLMN-NR without a roaming agreement, he cannot log on with his IMSI-HPLMN since no roaming agreement exists between the HPLMN and VPLMN-NR networks. Hence the subscriber S can neither telephone nor receive a call, so that the file EFLOCI is not updated and remains deleted. The subscriber then switches his terminal off and on again, which causes the UBICOM program to be re-run. One skilled in the art can imagine without difficulty another, more elegant way of restarting running of the UBICOM program.

In this re-running of the UBICOM program, the file EFLOCI is thus deleted. The result of the check 33 is thus negative, whereby it is indicated to the SIM card that the subscriber identification code in the home network IMSI- HPLMN cannot be used since the subscriber S is currently in a network without a roaming agreement with his home network HPLMN. In this case the UBICOM program continues with the check 38 in which the subscriber identification code IMSI is checked (file EFIMSI). If the subscriber identification code IMSI corresponds to an identification code in the home network HPLMN, the program continues with the following step 39 in which the subscriber identification code IMSI-HPLMN is replaced by the identification code IMSI- PPLMN in the partner network PPLMN, so that the subscriber S can log on.

Hence there are four possible situations upon switching on the terminal: 1) The subscriber is in his home network HPLMN or in a visited network having a roaming agreement VPLMN-WR The file EFLOCI is read first of all. The UBICOM program determines in step 33 that the contained information corresponds to the identification code of HPLMN or of a VPLMN-WR. The subscriber identification code IMSI-HPLMN can continue to be used and the file EFLOCI be deleted for example with the data "FF FF FF." The UBICOM program is now terminated, and the processor of the SIM card can carry out the normal functions of the SIM card.

2) The subscriber S comes from a visited network without roaming agreement VPLMN-NR into his home network HPLMN or into a visited network having a roaming agreement VPLMN-WR.

The file EFLOCI is read first of all. The UBICOM program determines in step 33 that the contained information corresponds to the identification code of HPLMN or of a VPLMN-WR. The subscriber identification code IMSI-PPLMN is subsequently replaced by the identification code in the home network IMSI-HPLMN and the file EFLOCI then deleted, for example with the data "FF FF FF." The UBICOM program is now terminated, and the processor of the SIM card can carry out the normal functions of the SIM card.

3) The subscriber S comes into a visited network without roaming agreement VPLMN-NR from his home network HPLMN or from a visited network with a roaming agreement VPLMN-WR The SIM card cannot establish any connection to the VPLMN-NR network since the IMSI-HPLMN is not authorized in this network. The file EFLOCI is still deleted, for example with the data "FF FF FF." The mobile telephone is then switched off and switched on again, and the UBICOM program is run a further time. EFLOCI is still empty upon this second running. The processor now replaces, in step 39, the subscriber identification code IMSI-HPLMN by the identification code in the partner network IMSI-PPLMN.

The UBICOM program is now terminated, and the processor of the SIM card can carry out the normal functions of the SIM card.

4) The subscriber S is in a visited network without roaming agreement The file EFLOCI is read first of all. The UBICOM program determines in step 33 that the contained information corresponds to the identification code of a VPLMN-NR. The subscriber identification code IMSI- PPLMN can continue to be used.

The UBICOM program is now terminated, and the processor of the SIM card can carry out the normal functions of the SIM card.

Figure 3 shows a variant of the program carried out by the processor of the SIM card according to a first exemplary embodiment of the invention.

With reference to the variant depicted in Figure 2, this variant makes it possible for the terminal 1 not to have to be switched off and then switched on again in order to re-run the UBICOM program. For this purpose, in this variant the program comprises two additional steps 40 and 41 in which the SIM card sends directly to the terminal (ME, Mobile Equipment) an inquiry which makes it possible to obtain the subscriber identification code IMSI directly.

This additional possibility is made available above all by the io additional functions of the SIM cards according to the GSM11.14 toolkit.

It is known to one skilled in the art that the SIM card according to the invention is preferably provided with a conventional encoding key K1. This key is used for encoding both the IMSI-HPLMN and the IMSI-PPLMN. A prerequisite for faultless operation of the process of the invention is thus a correspondence between the identification code algorithm used by the PPLMN network and by HPLMN.

In the variant described before, for carrying it out the UBICOM program must be loaded in all SIM cards of subscribers in the mobile network HPLMN. This loading can be carried out for example with the SICAP process described in the already mentioned patent application EP94810363.5. If the operator of the HPLMN network has not yet used the SICAP process, or if the storage or processing capacity of the distributed SIM cards is not sufficient for reliable running of the UBICOM program, it may be necessary to exchange the SIM cards of the subscribers who want to use the novel roaming possibilities offered indirectly via a partner network PPLMN. In view of the slight cost of these cards and of the prospective increase in traffic, such an exchange is quite conceivable.

There will now be described with reference to Figure 4 a second exemplary embodiment of the invention which can be carried out without updating and without exchanging the SIM cards of subscribers.

This exemplary embodiment uses an international turntable 3 situated for example in the country or region which is served by the partner network PPLMN, or in another suitable region. Ideally, the turntable 3 should be disposed in an intermediate position between the HPLMN network and the VPLMN-NR network. Corresponding to the number of subscribing networks, it may be advantageous to use several turntables, for example one per continent.

The turntable 3 is preferably administered by the operator of a partner network PPLMN or by another appurtenant unit of the operator or a unit in touch with the operator. The PLMN networks which want to expand their io roaming offer by adding the turntable 3 must conclude a special roaming agreement with the operator of this turntable. As will be shown, only a few minor adaptations are necessary on the part of the PLMN networks in order to use the turntable 3. These special agreements can thus be concluded without difficulty with the mobile networks VPLMN which have already concluded a roaming agreement with the PPLMN network. On the other hand, bilateral agreements between all PPLMN networks which want to use the turntable 3 are not necessary.

Carrying out this second exemplary embodiment of the invention requires that the subscribing VPLMN networks accept the requests to log on of the other VPLMN networks even when they have no roaming agreement amongst themselves.

The turntable 3 preferably consists of a programmable device which can be connected simultaneously to the HPLMN network and every mobile network PLMN which has joined this mentioned, special agreement. The turntable 3 is preferably controlled by a computer program recorded on a recording carrier 30, as for example a diskette, hard disk, or an optical disk storage which can be read by the turntable 3.

For simpler representation, a single VPLMN network is drawn in Figure 4 in addition to the home network HPLMN of the subscriber S; it goes without saying, however, that a radio system according to this second exemplary embodiment offers an advantage above all when the number of 7 networks which have joined is large. Moreover, just as in Figure 1, only the structures of the HPLMN and VPLMN networks essential to the explanation of the invention are depicted.

It is assumed that a subscriber S who is a subscriber of the home network HPLMN goes into the network VPLMN-NR without a roaming agreement with the HPLMN network. Still, the home network HPLMN and the visited network VPLMN-NR have both concluded a special roaming agreement with the partner network PPLMN. When the subscriber S tries to log on with his terminal to the VPLMN-NR network, the latter determines based upon the io subscriber identification code HPLMN-IMSI that the subscriber S comes from the HPLMN network with which no bilateral roaming agreement has been concluded. In principle, the VPLMN-NR network would have to refuse the request to log on.

Because of the special roaming agreement with the partner network PPLMN, however, the subscribers of the HPLMN network are regarded in the VPLMN-NR as subscribers of the PPLMN network. The special roaming agreements thus require of the networks which have joined that they modify the home file HLR and/or the exchange centers MSC in order to identify the SIM cards of the subscribers of the other networks which have joined, especially of the home network HPLMN of the subscriber S, and that they treat these subscribers as subscribers of the partner network PPLMN. Consequently, in accordance with the GSM protocols, the VPLMN-NR network sends an authentication inquiry 7 to the PPLMN network. This inquiry is dealt with in the PPLMN network by the turntable 3 which has been set up especially for this purpose within the scope of this invention.

The authentication inquiry transmitted by the VPLMN-NR network contains in particular the information concerning the location of the subscriber S (LI, Location Information), so that the turntable 3 now knows that the subscriber S is in the VPLMN-NR network. The turntable 3 modifies this location information by replacing it with LI-PPLMN data indicating that the subscriber is in the PPLMN network and then transmits the thus modified authorization inquiry to the home network HPLMN of S (arrow Thus the turntable 2 [sic] "lies to" the HPLMN network by pretending that S is in the partner network PPLMN.

As already described, the home network HPLMN has concluded a roaming agreement with the PPLMN network. The home file HLR of the home network HPLMN first checks whether the subscriber S is authorized to use his terminal in the partner network PPLMN, and if the result of this check is affirmative, a corresponding reply 9 is sent to the turntable 3, which transmits it on to the visited network VPLMN-NR (arrow 11). This reply is compared in this network with a reply which has been received from the SIM card 10 of the io terminal 1 of the subscriber S, and if the result of this check is affirmative, the subscriber S is considered authorized and is entered in the visitor file VLR- VPLMN (Visitor Location Register of VPLMN). The complete log-on process may comprise several interrogations and replies additionally exchanged between the visited network VPLMN-NR and the home network HPLMN which run through the turntable 3 each time. For example, the visited network may ask the home network about special services for the use of which the subscriber S has an authorization.

At the end of this process of the subscriber S logging on to the visited network VPLMN-NR, the latter treats S as though he were a subscriber of PPLMN and transmits the connection requests carried out by S, which it cannot establish directly, to the turntable 3, which is administered by PPLMN.

Conversely, the HPLMN network transmits the calls intended for S to the turntable 3.

The connection requests and the calls from or for S, which are represented by the arrow 12, thus run via the PPLMN network and via the turntable 12 [sic]. For the particular case where the mobile networks HPLMN and VPLMN-NR have different standards, for example if a subscriber of a GSM network comes into a PDC network, the turntable 3 may comprise conversion means known according to the state of the art which make possible a conversion of the formats of the connection requests and calls.

In the VPLMN-NR network, the subscriber S is regarded as a subscriber of the partner network PPLMN. Further, the home network HPLMN does not know the exact location of S when he is in the VPLMN-NR network and assumes that he is in the partner network PPLMN. Hence this variant is not completely transparent to the home radio network HPLMN of the traveling subscriber S since it does not know the exact location of the subscriber. Some operators offer their subscribers bargain subscription possibilities which exclude calls from or into certain regions of the world. These restrictions may in certain cases be circumvented through the execution of this second exemplary embodiment.

A third exemplary embodiment of the invention which does not have these disadvantages will now be described with reference to Figure The third exemplary embodiment of the invention requires that all participating PLMN networks conclude a special roaming agreement with the operator of a turntable 5, for example with a partner network PPLMN or with a company which administers such a turntable. As will become obvious hereafter, through the conclusion of such a special agreement, each network which has joined can offer its subscribers roaming possibilities in every other network which has joined; hence no bilateral roaming agreements between all networks which have joined are necessary. When the number of networks which have joined is large, a new network having only few roaming agreements can thus offer its subscribers the same possibilities with a single roaming agreement concluded with the turntable 5 as those offered by already established networks which have joined. Upon the joining of new mobile networks, it is necessary only to reconfigure the turntable 5 and to check the connections between the new mobile network and the turntable; no adaptation is required on the part of the networks which have already joined.

The mobile networks need a special roaming agreement in order to be able to use the turntable. This agreement regulates the points ordinarily cited in a roaming agreement, which are recommended for example in the GSM Memory of Understanding, as well as the following points specific to the system of the invention: Naming of the other networks which have joined with which the new network would like to use the roaming possibilities via the turntable Routing of the necessary signaling signals for connecting via the turntable Initial tests for checking the quality of the connections between the new network which has joined and the turntable 5. A test of the bilateral connections with every other network which has joined is not necessary.

Periodical supplying of the invoicing files (TAP files)to the turntable Amount of the call charges billed by the new network which has joined.

etc.

The turntable 5 may, like the turntable 3 in the second exemplary embodiment, be disposed in the country or region served by the partner network PPLMN or in some other suitable region. Several turntables, geographically distributed, may prove to be suitable. The turntable is preferably administered by the operator of the partner network PPLMN or by another appurtenant unit of the operator or a unit in touch with the operator.

The international turntable 5 preferably consists of a programmable device which can be simultaneously connected to the HPLMN network and to every PLMN network which has joined this particular said agreement. It is preferably controlled by a computer program recorded on a recording carrier as for example a diskette, hard disk, or an optical disk storage which can be read by the turntable It is assumed that a subscriber S who is a subscriber of the home network HPLMN goes into the network VPLMN-NR without a roaming agreement with the HPLMN network. Still, the home network HPLMN and the visited network VPLMN-NR have both concluded a special roaming agreement with the partner network PPLMN. When the subscriber S tries to log on with his terminal to the VPLMN-NR network, the latter determines based upon the subscriber identification code HPLMN-IMSI that the subscriber S comes from a network (HPLMN) with which no bilateral roaming agreement has been concluded. In principle, the VPLMN-NR network would have to refuse the request to log on.

However, the VPLMN-NR has storage means 13 containing a list of the network identification codes (NC) of the networks joined to the intermediate lo turntable 5. Thus, the VPLMN-NR determines that the subscriber S comes from a network joined to the intermediate turntable 5. In this case, based on the mentioned special roaming agreements, the VPLMN-NR network sends an authentication inquiry 14 to this turntable 5. The turntable 5 transmits this inquiry immediately to the home file HLR of the home network HPLMN (arrow 15) without changing the possibly contained location information LI-VPLMN.

The home file HLR-HPLMN first checks whether the subscriber S is authorized to use his terminal in the networks which have joined, and if the result of this check is affirmative, a corresponding reply 16 is sent to the intermediate turntable 5, which transmits it to the visited network VPLMN-NR (arrow 17). This reply is compared in this network with a reply obtained from the SIM card 10 of the terminal 1 of the subscriber S, and if the result of this check is affirmative, the subscriber is regarded as authorized and entered in the visitor file VLR-VPLMN (Visitor Location Register of VPLMN). As in the second exemplary embodiment described previously and as in the conventional roaming protocols, the complete log-on process may comprise several interrogations and replies additionally exchanged between the visited network VPLMN-NR and the home network HPLMN, which run through the intermediate turntable 5 each time. For example, the subscriber identification code IMSI- HPLMN may, of course, also be transmitted between the visited network and the home network via the turntable 5. Moreover, the visited network may ask the home network about special services for the use of which the subscriber S has an authorization.

22 According to this third exemplary embodiment, the home file of the home network HLP-HPLMN stores the correct location of the subscriber S in the visited network VPLMN-NR; this information is not changed by the intermediate turntable 5. Conversely the visitor file VLR of the visited network VPLMN correctly stores the identification code of the home network HPLMN of the subscriber S and thus does not consider S a subscriber of the partner network PPLMN. The connection requests 18 which are intended for the subscriber S and come for example from his home network HPLMN can consequently be routed directly between the home network HPLMN and the io visited network VPLMN-NR without running via the turntable 5. Conversely, the calls made by S intended for a subscriber outside the visited network VPLMN- NR are routed directly via the location file HRL-HPLMN of S's home network without running via the turntable Depending on the type of network, various signals can be exchanged between the visited network and the home network upon the subscriber S's logging-on in the visited network. According to the third exemplary embodiment of the invention, at least some of these signals are transmitted between the visited network and the home network via the intermediate turntable 5 which is administered by a network partner PPLMN.

The connection requests from or for S thus run via the turntable In the particular case where the mobile networks HPLMN and VPLMN-NR have different standards, for example if a subscriber comes from a GSM network into a PDC network, the turntable 5 may comprise conversion means known according to the state of the art which make possible a conversion of the formats of the connection requests.

The turntable 5 comprises a clearing and invoicing unit 6.

According to the special roaming agreement previously described, each mobile network PLMN which has joined must undertake to supply the turntable 5 with files containing data relating to all calls with roaming use which have come from subscribers or were intended for subscribers who were visiting this network. Similar files are already used in the conventional roaming procedures and are called "TAP files." According to the invention, however, these files need not be distributed to every other PLMN network which has joined; the operators can group the files containing the data concerning the calls which comprise the subscribers of every other network which has joined in order to send them to the turntable 5. It is possible to send either one TAP file for each HPLMN network which has joined or a single combined file containing all data relating to the calls with all other networks. If no subscriber of a HPLMN network has used his terminal in a VPLMN network since the last sending of the TAP file, the operator of the VPLMN network preferably so 0io informs the clearing and invoicing unit by means of a certain notification.

The TAP files and the notifications may be sent to the turntable 5 in electronic form, for example using the well-known exchange format EDI (Electronic Data Interchange). Other carriers, for example magnetic tapes, may naturally be used within the scope of this invention. The TAP files are transmitted to the turntable at a rate fixed in advance, preferably daily.

The clearing unit 6 in the turntable 5 receives and deals with the received TAB [sic] files of various mobile networks (VPLMN) which have joined and distributes the received information to each home network HPLMN. The clearing unit is preferably controlled by a computer program registered on a recording carrier 50 as, for example, a diskette, hard disk, or an optical disk storage. The clearing unit may be provided from the same server as the turntable 5 or executed on another machine administered by the same operator as the turntable 5. Under the control of this program, the clearing unit preferably carries out a process, the main steps of which are depicted in the flow chart of Figure 6.

In step 60 the clearing and invoicing unit 6 receives the TAP files and/or the notifications of each network which has joined, which have been transmitted for example all day long according to the file exchange protocol EDI. In step 62 the clearing unit 6 now checks for each PLMN network which has joined whether all TAP files and all notifications have been received in the fixed period of time, for example within 24 hours after the last sending of TAP files. In case of a negative result of this check, a manual or automatic inspection is carried out in step 64 at the PLMN networks which have not yet supplied the necessary files, and the program returns to step In step 66 the TAP files are checked, and in case of an error, the program goes to step 64 in order to clarify the problem with the network concerned. If the Tap[sic] files do not contain any errors, the clearing unit copies the received files in step 68 in a suitable format and then in step distributes to each home network HPLMN the information relating to the calls from or for the subscriber from the visited network into another network which has joined.

At regular fixed intervals, for example monthly, the clearing and invoicing unit 6 in the turntable 5 bills (71) each HPLMN network which has joined for an amount corresponding to the calls of the subscribers of HPLMN in the other, visited VPLMN networks which have joined. This amount is calculated from the information contained in the copies of the TAP files which have been supplied by each visited VPLMN network (arrow 75). The arrow 76 marks the distribution of the information from the Tap[sic] files to the HPLMN.

The bill is sent to the respective HPLMN network by any means, for example in electronic form (arrow 71). A copy of the bill is preferably sent for information to each respective VPLMN network (arrow 74).

After receipt of this bill, each HPLMN pays the operator of the turntable 5 (arrow 72). It is to be seen that the payment operations carried out by each HPLMN are clearly simplified since the amounts intended for each VPLMN can be regrouped into a single payment to a single recipient, the operator of the turntable 5. After receipt of the money remitted by the HPLMN, the clearing and invoicing unit distributes this money to each VPLMN (arrow 73), an amount concerning its costs being added to the same bill or shown separately. In the--frequent--event that the networks HPLMN and VPLMN do not use the same currency, the clearing unit 6 carries out the necessary conversions, preferably using an intermediate conversion with the SDR format.

Claims (13)

1. Telecommunication process which enables a subscriber of a home mobile radio network to log onto a visited mobile radio network (VPLMN, Visitor Public Land Mobile Network) without a roaming agreement with the home mobile radio network, wherein a computer program replaces the identification data of the subscriber with identification data made available by a partner radio network having a roaming agreement with the home mobile radio network, on the one hand, and with the visited mobile radio network, on the other hand.

2. Process according to claim 1, characterized in that the bills run over a unit administered by the partner radio network.

3. Process according to claim 1 or 2, characterized in that at least one of the mobile radio networks is a GSM network.

Process according to any one of the preceding claims, characterized in *o that the radio networks may be of different types.

5. Process according to the preceding claim, characterized in that the identification data of the subscriber are stored in a storage means for example in a SIM card, which is integrated in the mobile apparatus of the subscriber, and that using an identification modifying means the identification data of the subscriber, dependent upon the mobile radio network in which the mobile apparatus is 25 presently situated, are replaced in the terminal by identification data •corresponding to a subscriber in a partner radio network having a roaming agreement with the home mobile radio network, on the one hand, and with the visited mobile radio network, on the other hand.

6. Process according to the preceding claim, characterized in that the identification data of the subscriber are replaced in the storage means using a processor which runs a computer program stored in the storage means. MJP C:\WINWORD\MARIE\GABNODEL\400?7C.DOC -26-

7. Process according to the preceding claim, characterized by a step of checking a processing flag contained in the storage means, upon each reset or upon each switching-on of the mobile apparatus and in that the said computer program is run at the end of the check when the processing flag is set.

8. Chip card which is intended for use in a mobile radio apparatus and makes possible the storage of subscriber identification data, said chip card including: a processor which makes possible a replacement of the subscriber identification data, dependent on the visited mobile radio network in which the mobile radio apparatus is presently situated, by identification data corresponding to a subscriber in a partner radio network having a roaming agreement with the home mobile radio network in which the subscriber has subscribed, on the one hand, and with the visited mobile radio network, on the other hand.

9. Chip card according to the preceding claim, characterized in that the means for changing the subscriber identification data contain a computer program which is stored in the programmable device and can be run by a processor on the programmable device.

10. Chip card according to the preceding claim, characterized in that it further stores a processing flag which is checked upon each reset or upon each switching-on of the mobile radio apparatus.

11. Chip card intended for use in a mobile radio apparatus and containing a first set of subscriber identification data from the home radio network, characterized in that it further contains a second set of subscriber identification data from a partner radio network administered by an operator having a roaming agreement with the home mobile radio network.

12. A telecommunication process which enables a subscriber of a home J' obile radio network to log onto a visited mobile radio network without a roaming MJP C:\WINWORD\MARIE\GABNODEL\40077C.DOC -27 agreement with the home mobile radio network substantially as herein described with reference to the accompanying drawings.

13. A chip card which is intended for use in a mobile radio apparatus and makes possible the storage of subscriber identification data substantially as herein described with reference to the accompanying drawings. DATED: 29 October, 1999 PHILLIPS ORMONDE FITZPATRICK Attorneys for: SWISSCOM AG r t 6* **s 0*b *@9q a a a *6 a as -a a .0 oo MJP C:\WINWORD\MARIE\GABNODEL\4W77C.DOC