Recovering group data between mobile systems

ES 2 290 992 T3

DESCRIPTION

Group data recovery between mobile systems.

Background of the invention

The present invention refers to a method for retrieving group data between mobile systems, which incorporate at least a first mobile system, which comprises a first database, at least a second mobile system, which comprises a second database and a service area, and incorporating said mobile systems mobile stations as subscribers, The method comprising the steps in which group data is maintained in said first database of said first mobile system, and group data is maintained in said second database of said second mobile system.

The invention relates to a plurality of mobile systems, in particular mobile systems which comprise control centers, one or more databases, base stations and radiotelephones, the mobile systems presenting a cellular structure and each of the cells presenting at the same time. least one base station which communicates via one or more radio connections with at least one mobile station. The radio connection can be established by channels, one or more of which are typically used for signaling and the rest for traffic.

Document WO 96/29838 discloses an example of a subscriber data update and mobile system in such a system.

The method of the invention is intended to be used particularly in so-called mobile trunking systems, which are typically company networks or private mobile radio communications networks used by the authorities, all the channels of these networks being assigned to one or more companies or government organizations. In these networks, the subscribers, apart from their own subscriber numbers, have group numbers, which indicate to which group of group calls said subscriber belongs, with which calls, particularly group calls, that are intended for all subscribers in that group, they can be switched to those subscribers in the group.

The invention is applicable to mobile systems with either digital or analog radio paths. Analog mobile systems are described, for example, in British Ministry of Trade and Industry publications MPT 1327, A Signaling Standard for Trunked Private Land Mobile Radio Systems, January 1988, revised and reprinted in November 1991, published by the Agency Radiocommunications, and MPT 1343, Performance Specification, January 1988, revised and reprinted in September 1991, published by the Radiocommunication Agency.

A group call is one of the key functions in a private mobile radio network. A group call is used, among other things, in various operations involving several participants, particularly when an entire group must constantly be aware of how issues are evolving. A group call is a call in which all participants take turns talking and listening to each other. In group calls, the entire group is called using a call number. A single radio unit, for example a mobile station or a radiotelephone, ie a subscriber station, may belong to a plurality of groups that are programmed into the mobile station. The programming can be carried out permanently, although it can also be changed by the user or even by the system. Each mobile system can maintain a file on base stations in relation to each group number. A group call can encompass one, several or all base stations in the service area of ​​a mobile services switching center and a plurality of mobile services switching centers, or a group call can be established within the service area of various mobile systems.

When a group call is established, a traffic channel is assigned to all base stations related to the group, and each of these base stations transmits a group call request which comprises the group number and information about the channel. of assigned traffic. If the mobile station identifies the group number included in the group call request, it is transferred to the traffic channel indicated by the group call request. In this way, the mobile station which is registered in the predetermined operating area for the group, is in principle always available for a group call.

In connection with cellular radio communication networks, it is known that the group data of the radiotelephones registered in said mobile system is stored in the database of the mobile system with link concentrations, for example, in the switching center or in its visitor position register or in the base position register.

The group data (group profile) contains data that informs the subscribers of that group, or some subscribers of the group, about available or activated services, for example, about supplementary services. The group profile can also contain a definition of the importance, that is, the priority, of that group or its subset. On the other hand, the group profile can contain information about which subscribers belong to said group, that is, a list which includes the identifiers of those subscribers who have permission to participate in the communication.

ES 2 290 992 T3 within said group, for example, in a group call, in the service area of ​​said mobile system, in its specific location areas (Location Area) or its specific base stations.

This group profile is stored, for example, in volatile RAM, from which the data disappears, for example, when the power supply corresponding to the database is turned off, and at regular intervals in non-volatile memory means , for example, on a hard drive on which data is kept permanently. When the database in RAM sometimes reboots itself, the pool profile stored in volatile memory disappears. Only group data stored in non-volatile memory remains, for example on the hard disk.

The disappearance of group data from the databases causes a serious problem in the group of a plurality of mobile systems, since if a given group call is extended to the service areas of several mobile systems, the group data of the group call are stored in the databases of all the various mobile systems mentioned. Therefore, if the power level of the database of any of the mobile systems must be reduced, and because the database whose power level has been reduced cannot continuously update the changes that have taken place in the group profile corresponding to the group in question, this data may change in the meantime in the databases of other mobile systems, although they remain unchanged in said database whose power level has been reduced. As a consequence, the group data contained in the databases of different mobile systems are different, on the one hand in the database whose power level has been reduced and on the other hand in other databases that operate normally.

This difference between the group data in the databases can cause a situation where a given mobile station is allowed to join a group call in a first mobile system, although in a second mobile system said mobile station is not allowed You are allowed to join the same group call, because the data of that group has not been kept up-to-date in said mobile system, nor in its database.

US Patent No. 5,564,071 discloses an example of a trunking communication system and the updating of the attributes of the communication units in such a system.

According to the prior art, it is possible to try to keep the contents of the databases of various mobile systems in a consistent manner using so-called retrieval.

The recovery method uses a normal sequence of inter-network mobile systems, or the like, processing by means of said sequence the joining and detaching requests sent by subscriber terminals operating in the network, the requests being directed to a group of another network. In the TETRA mobile system, this sequence is an ANF-ISIMM sequence. This sequence is described in the TETRA ETS 300 392-3-5 specification, Part 3: Inter-working basic operations; Part 3-5: Additional Network Feature Inter-System Interface for Mobility Management (ANF-ISIMM), ETSI, March 1997, 167 pages.

A normal update sequence of a group profile begins when a subscriber terminal sends a request to join a mobile system and that mobile system is not the home mobile system of the group. In the TETRA mobile system, the home mobile system is the home SwMI and correspondingly, the visited mobile system is the visited SwMI. In this way, the visited mobile system communicates the request to join the mobile system of origin of the group, which stores information on the incorporation in its database and responds to the visited mobile system by sending it the group profile. The visited mobile system stores the incorporation and other group data in its database. The group data is kept stored in the database of the visited mobile system as long as there is at least one valid join request for said group.

When the visited mobile system receives a join request from the subscriber terminal, any of the following procedures can be applied:

1) If several subscriber terminals send join requests for the same group of a second mobile system in the same visited mobile system, the visited mobile system sends the join request only once to the home mobile system upon receiving the first join request. incorporation. The mobile system of origin of the group call is the system in whose database, for example, the group profile corresponding to said group is stored.

2) The procedure described above can be complemented with a definition of the so-called "important user": important users can be defined in the group, and the join request sent by them is always communicated to the mobile system of origin of the group. Thus, important users are priority users.

3) Alternatively, the visited mobile system always sends the join request to the home mobile system upon receiving a join request from a subscriber terminal.

According to an operating principle corresponding to that described above, the visited mobile system communicates one or more separation requests received from radio subscribers to the home mobile system. Separation requests are communicated one for each major or subscriber group or user. In this way,

ES 2 290 992 T3 enrollment data is removed from the home mobile system database and correspondingly enrollment data and other group data are removed from the visited mobile system databases.

If the visited mobile system sends the joining request to the originating mobile system only once when the first joining request is received, the separation request is sent to the originating mobile system only after it has been received from the last one. subscriber incorporated to said group in the visited mobile system. In this way, all the data of said group is removed from the database of the visited mobile system. Additionally, in relation to this subscriber, the registration data of said subscriber is removed from the database of the mobile home system of the group and the subscriber.

A detach request received from an important user always removes the attachment data for that subscriber from both databases. Additionally, the above rule applies to a separation request received from an important user, in the case that said user / subscriber was the last subscriber in the group.

If the visited mobile system always sends a join request to the home mobile system upon receiving a join request from a subscriber terminal, the detach request is always sent to the home mobile system as well. If the separation request comes from the last subscriber added to said group in the visited mobile system, all the data of said group is removed from the database of the visited mobile system. Additionally, in relation to this subscriber, the registration data of said subscriber is removed from the database of the mobile home system of the group and the subscriber.

Figure 1 illustrates a radio subscriber "SwMI / MM visited" 101, a mobile visited system "SwMM / FE3 visited" 102 and a mobile home system "SwMI / FE2 Home" 103. The figure shows the parameters transmitted in each message or sign. The GTSI, ie Group Tetra Subscriber Identity, is a group identifier, the ITSI is a radio subscriber identifier. It is not necessary to transmit the ITSI identifier if the first request to join and the last request to leave the group are only communicated to the mobile home system, in other words, if important users are not favored or have no priority and not all incorporation requests are communicated.

In Figure 1, the mobile station 101 sends an enrollment request 105 whereby the mobile station wishes to join a group within the service area of ​​the visited mobile system in question. In response to the aforementioned request, the visited mobile system checks the database to see if the visited mobile system is ready to support the use of said group. If so, the visited mobile system forwards 106 the join request to the group's home mobile system FE2 103. The home mobile system checks its database to see if it is ready to support the use of said group in the visited mobile system corresponding to said subscriber. In the affirmative case, the home mobile system transmits 107 the data of said group to the visited mobile system which sends 108 an acknowledgment of receipt. After receiving it, the home mobile system 109 sends an acknowledgment to the visited mobile system 102 informing that the complete sequence has been successful. The visited mobile system further sends an acknowledgment 110 to the mobile station 101. The sequence described above is an example of a prior art procedure, in which the first subscriber / mobile station wishes to join a group in the service area of ​​said mobile system in a situation where the incorporation is feasible.

Brief description of the invention

The object of the invention is to provide a method and equipment that implements the method in order to solve the above problems.

This objective is achieved with a method characterized by the aspects set forth in claim 1.

The invention further relates to an arrangement for retrieving group data between mobile systems, in which there is at least a first mobile system which comprises a first database in which group data is maintained, at least one second mobile system which comprises a second database in which said group data is maintained, and in which mobile stations are available.

The arrangement according to the invention for recovering group data between mobile systems is characterized by the aspects set forth in claim 14.

The invention is based on the idea that subscriber group data retrieval can be carried out in such a way that a virtual join request, generated by the system, is sent to each visiting subscriber from a visited mobile system or a visited node towards the home mobile system or home node, whereby the group data and possibly the location and subscriber data relating to the subscriber in question are updated in all databases according to the normal attachment sequence.

The idea of ​​the invention consists in recovering the data of groups of group calls between interconnected mobile systems by sending, to the mobile system of origin of each group, an incorporation request, similar to a normal incorporation request, generated by the visited mobile system, for each other group

ES 2 290 992 T3 mobile system in operation in the visited mobile system, whereby the group data is updated in the mobile systems according to the normal incorporation sequence.

The invention also relates to an idea, according to which the home mobile system keeps a record, during retrieval, about which embed data is processed in retrieval. When the home mobile system receives a notification from the visited mobile system that the part corresponding to the visited mobile system has been completed, the home mobile system reviews its database and makes comparisons to see if there is onboarding data. regarding the visited mobile system that have been left unprocessed, because the visited mobile system did not notify them. The home mobile system transmits said joining data to the visited mobile system by means of a virtual joining request according to the normal joining sequence. Virtual onboarding requests include the age of such onboarding data. The visited mobile system accepts the join request received from the home mobile system in the event that the visited mobile system has not stored subsequent corresponding separation data. The visited mobile system may reject the join request also for some other reason, for example if the visited mobile system does not support the group in question.

Furthermore, alternatively, the home mobile system does not keep any record of the incorporation data transmitted by the visited mobile system, but rather retrieves from its database all its incorporation data regarding the visited mobile system and transmits them to said mobile system. visited. One of the advantages of this procedure is its simplicity, since no record keeping is necessary. However, in this case the consumption of resources is not optimal.

The invention relates to a method and arrangement for retrieving group call group data, ie a group profile, corresponding to visiting subscribers between mobile systems and / or mobile network databases.

The invention is used to detect and correct inconsistencies in group profiles in interconnected TETRA mobile networks.

One of the advantages of this type of method according to the invention is that it solves the problems of the prior art solutions.

The method and the arrangement according to the invention furthermore have the advantage that the method uses normal sequences for the processing of group data. This situation simplifies the implementation of recovery and improves reliability.

The invention also alleviates the load problems of mobile systems since by means of it the load caused by the recovery is automatically adjusted according to the load conditions of each mobile system or of the connections between the mobile systems, in the case of that the recovery is carried out according to the most preferred embodiment, that is, synchronization of the transmission using acknowledgments.

Furthermore, the invention has the advantage that it is not necessary to delete data from the databases, unless more correct data is available compared to the data previously stored in the database.

The invention further has the advantage that the method of the invention allows to be started in a variety of ways, for example periodically, by a user command or as a consequence of a detected or suspected failure.

Another drawback of the invention is that it is suitable for background processing in the mobile system.

The invention also has the advantage that it is not intended for pulses from the subscriber terminals. For this reason, it is possible to perform recoveries with the method of the invention also in cases where no impulse is received from the subscriber.

One of the advantages of the invention is further that, with the same, it is possible to make the recovery speed and the load adjustable in accordance with other loads of mobile systems.

The invention has the advantage that the recovery speed implemented with it does not depend on a random arrival time of the pulses.

The invention has the advantage that it does not consume radio communication resources at all.

The invention has the advantage that by synchronizing the transmission of a new incorporation request with the acknowledgment of receipt of the previous one, the recovery load can be adjusted in accordance with the total load, when there is available capacity.

The invention has the advantage that the additional load caused by it is minimal, when for some other reason a load occurs in some part of the system.

ES 2 290 992 T3

The invention has the advantage that when the operation occurs in accordance with the same, a node of the mobile system loads another node or connection in a way that is unmanageable for them.

Brief description of the drawings

The invention will now be described in more detail in relation to preferred embodiments, with reference to the accompanying drawings, in which Figure 1 illustrates a message diagram of a prior art method, Figure 2 is a flow chart of operation of the method of the invention, Figure 3 is a block diagram of an arrangement according to the invention.

Detailed description of the invention

Recovery

Figure 2 shows a flow chart of the operation of the method of the invention. Correspondingly, Figure 3 shows an arrangement by means of which the method of Figure 2 can be implemented. The block diagram of Figure 3 illustrates an arrangement for retrieving GD group data between mobile systems S1, S2, S3, in which there is at least a first mobile system S1 comprising a first database DB1 and an area of service SA1, at least one second mobile system S2 comprising a second database DB2 and a service area SA2, and in which there are mobile stations MS1, MS2. The mobile systems described are interconnected with telecommunication connections T through the inter-system interface ISI located between the mobile systems. The ISI interface and its operation are described in the aforementioned ETSI specification ETS 300 392-3-5. Mobile systems have at least one mobile services switching center MX1 ​​to MX3, to which at least one database DB1 to DB2 and typically one or more radio communication units are connected, with a base station BS being able to act as said unit. .

Group data retrieval can be initiated at the initiative of either the group's home mobile system or the visited mobile system. Recovery can be triggered, for example, periodically, with a user command or as a result of a detected or suspected failure. Recovery may involve one or more visited mobile systems and one or more originating mobile systems. Recovery can be performed simultaneously or successively for a plurality of mobile systems.

If the recovery is established at the initiative of the originating mobile system, it transmits a request to initiate recovery to all those visited mobile systems with which recovery is desired. Upon receipt of the establishment request, the visited mobile systems begin to retrieve group data from said home mobile systems that exist in their databases.

If the recovery is established at the initiative of the visited mobile system, it transmits a notification of the initiation of recovery to the originating mobile systems with which they wish to carry out the recovery, and begins to recover data from the groups of said mobile systems, which exist in their databases.

If desired, group data retrieval can be combined with location and subscriber data retrieval, for example, by retrieving group data for each subscriber specifically for each subscriber immediately, or, for example, by retrieving subscriber data. group data after the location and subscriber data of all subscribers have been retrieved.

If desired, the arrival of setup messages can be guaranteed, for example, with a transmission protocol which comprises acknowledgments and with the retransmission of the setup message, if necessary.

The recovery can be carried out in such a way that the visited mobile system reviews its database and transmits, according to its normal joining sequence, one or more virtual joining requests for each group to the mobile system of origin of each group. second group on the network, found in your database and participating in recovery.

Virtual onboarding requests contain the age of such onboarding data. The home mobile system accepts the join request from the visited mobile system, in the event that the home mobile system has not stored subsequent corresponding separation data. The home mobile system then updates 308 the corresponding enrollment data in its database and transmits 309 the data for that group to the visited mobile system. The home mobile system may reject the join request also for some other reason, for example, in the event that said subscriber is not authorized to join the group. The home mobile system also checks, in accordance with the normal sequence, if the subscriber is registered in said visited mobile system according to the information of the home mobile system, if not, the home mobile system initiates a sequence of normal correction of location data and the like.

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The joining data and other groups (group profile) relating to the group are updated in both the visited mobile system and the home mobile system according to the normal joining / detaching sequence. On the other hand, the visited mobile system always verifies that the subscriber, who joins the group, also has the valid registration for said visited mobile system. If the record does not exist, the embedding data is removed according to the normal embedding / detaching sequence operating principle.

Mobile systems do not necessarily store any group call separation data in their databases after the normal separation sequence has been completed.

The visited mobile system transmits virtual join requests to the home mobile systems according to the same operating principles as normal join requests.

If the normal procedure is that the visited mobile system transmits the join request to the home mobile system only once after receiving the first join request for that group, in recovery only one virtual join request per group is transmitted .

If the aforementioned procedure is complemented by a definition of the so-called "important user", in the recovery a virtual joining request is transmitted for each important subscriber of the group, provided that the group call involves one or more important subscribers and with priority .

If the visited mobile system normally transmits an join request to the home mobile system each time it receives the join request from the subscriber terminal, in retrieval a virtual join request is transmitted for each subscriber joined the group.

If the normal sequence is optimized so that the home mobile system does not transmit the group profile corresponding to a group call to the visited mobile system each time it receives a join request from the visited mobile system, the sequence of The retrieval of the invention must be completed in such a way that the retrieval guarantees the transmission of the group profile. This option can be done so that, in recovery,

a) in the virtual join message, the visited mobile system requests, at least once for each relevant group, that the home mobile system transmit the group profile to said visited mobile system.

This solution requires a field for this purpose in the ISI onboarding message between different TETRA mobile systems, or

b) the home mobile system ensures that it transmits the group profile at least once for each relevant group to each relevant visited mobile system.

During recovery, the source mobile system keeps a record of what onboarding data is processed in recovery. When the home mobile system receives a notification from the visited mobile system that the part corresponding to the visited mobile system has been completed (see completion of recovery), it reviews the database and makes comparisons to see if the database contains incorporation data that refers to the visited mobile system and which remains raw, because the visited mobile system did not notify them. The home mobile system generates 310 second join requests and transmits 311 this virtual join data to the visited mobile system in virtual join requests according to the normal join sequence. Virtual requests contain the age of such data. The visited mobile system accepts the joining request from the home mobile system, in the event that the visited mobile system has not stored subsequent corresponding separation data. Next, the visited mobile system updates 312 in its database said group data, about which the home mobile system had notified. The visited mobile system may reject the join request also for some other reason, for example, in the event that it is not possible or not allowed to form the group in said visited mobile system.

Alternatively, the home mobile system does not keep any record of the incorporation data transmitted by the visited mobile system, but rather retrieves from its database all the incorporation data referring to said visited mobile system, generates 310 second incorporation requests and transmits them 311 to said visited mobile system. One of the advantages of this procedure is its simplicity since no record keeping is necessary. On the other hand, in this case the resource consumption is not optimal.

If desired, group data retrieval can be combined with location and subscriber data retrieval, for example, by retrieving group data for each subscriber specifically for each subscriber as soon as the subscriber data has been retrieved. location and subscriber data for the subscriber in question, or for example by retrieving group data after location and subscriber data for all subscribers have been retrieved.

If desired, group data recovery between the subscriber terminal and mobile systems can be combined with group data recovery between mobile systems. The order of execution of these recovery operations can be selected according to the desired manner.

ES 2 290 992 T3

If desired, the arrival of the messages sent in a sequence can be guaranteed, for example, with a transmission protocol that includes a retransmission of the message, should this be necessary.

The uninduced part of the visited mobile system ends for each home mobile system when it detects that data has been retrieved from all groups in said network. The visited mobile system transmits a notification about the completion of its part to the originating mobile system of each group call formed in its coverage area. The uninduced portion of the visited mobile system ends completely when all group calls from the home mobile system have been processed.

The home mobile system processes, for each visited mobile system, the incorporation data that has remained unprocessed in the part of the visited mobile system, when it receives a notification about the completion of the part of said visited mobile system. Recovery ends for said visited mobile system when the joining data is processed with said visited mobile system.

Recovery ends on the home mobile system, after the home mobile system has received a completion notification from all visited mobile systems with which the recovery was performed, and after the home mobile system has processed the data from the home mobile system. raw incorporation into your database. If desired, the home mobile system may also notify participating visited mobile systems of the completion of the recovery. This data can be used, for example, for user information.

In the method of the invention, the GD group data is kept 302 in the first database DB 1 of the first mobile system S1, and additionally, the GD group data is kept 303 in the second database DB2 of the second system mobile S2. In this case, as described in the previous descriptive part in connection with the problems of the prior art, the problem is how to keep the group data equal and consistent with each other in the databases DB1, DB2.

In the method of the invention, this problem is solved in such a way that a retrieval request is made 304 to retrieve the GD group data.

The second system S2 generates 306 a virtual join request for the first database DB1 and transmits 307 said request to the first database DB1 of the first mobile system S1.

In response to that virtual join request, the GD group data in the first database DB1 is updated 308.

According to one of the embodiments of the invention, the first mobile system S1 performs the aforementioned recovery request by transmitting a recovery establishment message towards all those other mobile systems S2, S3, with which recovery is desired, and in In response to this setup message the other mobile systems S2, S3 start to retrieve their group data.

Alternatively, the second mobile system S2 performs the retrieval request by sending a retrieval establishment notification to the first mobile systems S1, with which it wishes to perform group data retrieval. In response to the notification of recovery establishment performed, the second mobile system S2 begins to retrieve the group data (GD) from its second database DB2.

The invention also relates to the idea that during retrieval the home mobile system keeps a record of which embed data is processed in retrieval. When the home mobile system receives a notification from the visited mobile system about the completion of the part of the visited mobile system, it reviews its database and makes comparisons to see if the database has incorporation data which they refer to said visited mobile system and which have been left unprocessed, because the visited mobile system did not notify them. The home mobile system generates 310 and transmits 311 said second join data to the visited mobile system in a virtual join request according to the normal join sequence.

Furthermore, alternatively, the home mobile system does not keep any record of the incorporation data transmitted by the visited mobile system, but rather retrieves from its database all the incorporation data referring to the visited mobile system and transmits them to said system. visited mobile. One of the advantages of this procedure is its simplicity since no record keeping is necessary. On the other hand, in this case the consumption of resources is not optimal.

In the method of the invention, apart from the recovery of data from GD groups, location data and subscriber data corresponding to subscribers MS1, MS2 who have entered the group specified in said groups can be retrieved in a specific way for each subscriber. first DB1 and second DB2 databases.

In the method of the invention, the arrival of retrieval requests and said virtual join requests is guaranteed in such a way that retrieval requests and virtual join requests are retransmitted, if necessary.

ES 2 290 992 T3

Furthermore, according to the invention, the virtual join request contains information about the age of the join data. In response to the information about the age of the attachment data contained in the first virtual attachment request, the first mobile system S1 compares that information with the ages of possible separation data stored in the first mobile system S1, and whether the age of the incorporation request is less than the antiquities of the separation data previously stored in the first mobile system S1, the first mobile system S1 accepts the virtual join request transmitted from the second mobile system S2, the group data GD of said group call GC being updated in the first database DB1 in response to said virtual join request.

On the contrary, if the age of the join request is greater than the age of the separation data previously stored in the first mobile system S1, the first mobile system S1 rejects the virtual join request transmitted from the second mobile system S2.

If such separation data and the request for incorporation are the same age, the request for incorporation can either be accepted or rejected. This selection can be made to involve all relevant cases when the mobile system is implemented.

In a corresponding way, the second mobile system S2 processes the age of the second virtual join request transmitted by the first mobile system S1.

Figure 3 is a block diagram of an arrangement according to the invention. In the arrangement of Figure 3, there is a group of mobile systems S1, S2, S3, in which there are at least a first mobile system S1 comprising a first database DB1, in which data of groups Gd, at least one second mobile system S2 comprising a second database DB2 in which group data GD is maintained, and in said group are mobile stations MS1, MS2 of which at least some communicate in the group call established within the service area SA2 of at least said second mobile system S2.

The group of mobile systems may also include a third mobile system S3, in which a group call GC2 is maintained. This group call may be a second group call or a subset of the group call that is maintained in the service area of ​​the second mobile system S2, said group call being described in more detail herein.

In the arrangement according to the invention, the second mobile system S2 comprises generating means GM2 for generating a virtual attachment request for the first database DB1 and for transmitting the aforementioned virtual attachment request towards the first database DB1 of the first mobile system S1, whereby the first database DB1 is arranged to update the group data GD in the first database DB1 in response to said virtual join request.

In the arrangement according to the invention, the first mobile system S1 comprises generating means GM1 for generating a virtual joining request for the second DB2 database and for transmitting the aforementioned virtual joining request towards the second DB2 database of the second mobile system S2, whereby the second DB2 database is arranged to update GD group data in the second DB2 database in response to said virtual join request.

In the method of the invention, the arrival of messages can be guaranteed, for example with a transmission protocol which comprises the retransmission of a completion message, if necessary. For example, acknowledgment messages can be used, which inform the sender whether the receiver has received the transmitted message.

If desired, group data retrieval can be combined with location and subscriber data retrieval, for example, by specifically retrieving for each subscriber group data relating to each subscriber as soon as said subscriber data has been retrieved. location and subscriber data, or, for example, by retrieving group data after location and subscriber data for all subscribers have been retrieved.

The recovery speed and the recovery load can be automatically adjusted based on the load factor of both the visited database and the source database in such a way that join requests are transmitted one at a time in order that the network does not send a new virtual join request until the previous one has been processed on both networks. In this way, the network will not start processing the new virtual join request until it has received an acknowledgment for the previous virtual join request from the other network. In the event that the network does not receive any acknowledgment from the other network, the continuity of a sequence can be guaranteed in such a way that the network continues with the recovery in a predetermined period of time in the event that it is not received. the acknowledgment of receipt.

If desired, the synchronization can be limited to the transmission of only one new message: the network can process the new virtual join request even before receiving the acknowledgment corresponding to the previous request, and consequently the new message can be transmitted faster.

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The method of the invention can be supplemented with decision priorities between virtual join requests and other transactions such as normal join requests.

Alternatively, speed and load can be adjusted, for example by pausing between transmitting virtual join requests.

If desired, the home mobile system may notify the participating visited mobile systems of the completion of the recovery. This information can be used, for example, to inform users that either group data or even subscriber data and subscriber location data have been retrieved for a subscriber, a mobile system, a database or a specific group call.

If desired, the arrival of the messages to be transmitted in the recovery sequence can be guaranteed, for example, with a transmission protocol which includes, if necessary, the retransmission of the message. Ensuring the arrival of messages is an advantageous procedure as it increases reliability.

One of the advantageous ways of combining group data retrieval with location and subscriber data retrieval is by retrieving group data for each subscriber specifically for each of the latter as soon as the subscriber data has been retrieved. location and subscriber corresponding to the subscriber in question, as it is easier to handle a failure in which conflicting location data is detected in the mobile source systems in relation to group data recovery. Therefore, the conflict can be corrected by restarting a subscriber-specific retrieval sequence from the location data retrieval, and the sequence corrects both location and group data.

A successful implementation is to synchronize the transmission of virtual join requests with the acknowledgments of the originating mobile systems, since with this implementation the recovery speed and recovery load can be automatically adjusted according to the load factor of both visited and home mobile systems. This method is also easy to implement.

It is apparent to those skilled in the art that the basic idea of ​​the invention can be implemented in a variety of ways as technology advances. Thus the invention and its embodiments are not limited to the above-described examples, but may vary within the scope of the appended claims.