GB2416272A - Dialling of short code numbers in a communication system - Google Patents

Abstract

A communication system is described which includes a plurality of mobile telecommunications networks (A and B). Both the telecommunications networks provide a respective virtual private network which allows members thereof to initiate calls to one another using a special code number or short dialling code. Calls between the members of the same VPN may be charged at a special rate and additional services may be provided to members of a VPN. The invention provides an arrangement whereby a member of a VPN hosted by network A is able to communicate with a member of a VPN hosted by network B using a short code of that member of the VPN of network B. Each network includes an intelligent node IN 18A, IN 18B which stores data relating to the local VPN. This data is pushed to an adapter 34A,34B, where it is modified into a standardised predetermined XML format and passed to central IMP system 30 and stored on central database 32. The IMP system 30 and database 32 allow network A to pull data relating to the VPN hosted by network B via adapter 34A for storage on IN 18A. When the data relating to the VPN hosted by network B is stored on IN 18A of network A, this allows the short dialling codes of network B to be used by a subscriber terminal 1A located in network A.

Description

DIALLING OF NUMBERS IN A COMMUNICATIONS SYSTEM

The present invention relates to a communications system including a plurality of telecommunications networks. The networks provide subscriber terminals with publicly-known telephone numbers. Each network allows selected subscriber terminals registered therewith to be associated together in a group (for example a private dialling plan or virtual private network (VPN)) such that those subscriber terminals can address communications to one another using a respective code allocated to each of the selected subscriber terminals. For example, this can be a short dialling code or a code corresponding to an extension number also used for making internal telephone calls on a fixed telephone network.

It is known for a mobile telecommunications network to provide selected subscribers (for example, those belonging to a particular organisation or company) with a private dialling plan or VPN. The subscribers within the VPN can address communications to one another using a code which is different to the publicly-known telephone number allocated to each of the subscriber terminals. The code will typically be a short dialling code (for example, a four digit code corresponding to the extension number of the user of the subscriber terminal in the fixed internal communications network of the organization).

Subscriber terminals within the VPN may be provided with special services not available outside the VPN and may be charged by the mobile telecommunications network on a different basis from subscribers which are not in the VPN.

Whilst such arrangements are convenient, such systems only allow subscribers of the network hosting the VPN to access the VPN (that is, to be able to address calls to other subscriber terminals using the codes).

According to a first aspect of the present invention, there is provided a communications system including a plurality of telecommunications networks, each of which: provides subscriber terminals thereof with a respective publicly- known telephone number for allowing communications to be addressed to each subscriber terminal, allows selected subscriber terminals thereof to be associated together in a group such that those subscriber terminals can address communications to one another using a respective code allocated to each of the selected subscriber terminals, and includes means for translating the code of each of the selected terminals into the corresponding publicly-known telephone number thereof; wherein the system further includes means for maintaining a database of the codes and corresponding publicly-known telephone numbers for each of said networks and for providing to one of said networks a publicly known telephone number corresponding to a code of a subscriber terminal of another one of said networks to allow communication from a subscriber terminal of said one of the networks to be addressed to a subscriber terminal of said other of the networks using the code of the latter subscriber terminal.

By providing the database of codes and corresponding publicly-known telephone numbers of each of the networks, this allows a subscriber terminal of one group (for example, a VPN) within one network to be able to address a terminal of another group (for example, another VPN) in another network using the code of that other terminal.

Further aspects of the invention are defined in the independent claims.

For a better understanding of the present invention an embodiment will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic drawing of two mobile telephone networks for use 1S in explaining the operation of those networks, the "roaming" arrangements between the two networks, and how codes for a VPN are handled; Figure 2 shows the exchange of data between the elements shown in Figure 1 when a subscriber to a VPN administered by a home network calls another subscriber in that VPN; Figure 3 shows the exchange of data between the elements shown in Figure I when a subscriber to a VPN administered by home network calls a subscriber in that VPN that is "roaming"; Figure 4 shows the data exchanges that occurs between the elements shown in Figure 1 when a subscriber to the VPN administered by a home network wishes to make a call to another subscriber of the VPN when the calling subscriber is "roaming".

Figure 5 shows example data for two VPNs hosted by the network A of Figure 1; Figure 6 is a diagrammatic drawing of two mobile telephone networks similar to that of Figure 1 but showing the additional elements provided in accordance with the invention; Figure 7 shows in more detail the connections between a central VPN database and the elements of networks A and B shown in Figure 6 and the data exchanges occurring therebetwocn; Figure 8 shows the architecture of the central VPN database; Figure 9 shows examples of VPN data stored by the central VPN database; s Figure 10 shows examples of data "pulled" by network A from the central VPN database stored by that network together with data for VPNs hosted by the network A; and Figure 11 shows the exchange of data between the elements shown in Figure 6 when a subscriber of a VPN administered by a one network calls a subscriber of a VPN administered by another network.

In the drawings like elements are generally designated with the same reference numeral.

Figure 1 diagrammatically explains the operation of two GSM networks between which there is a roaming agreement. Network A has the facility to provide a virtual private network (VPN) for groups of its subscribers. A group of subscribers in a VPN may be provided with additional facilities. For example, each subscriber in a VPN will be given a code number in addition to the conventional mobile telephone number (the MSISDN - Mobile Station International ISDN number). This code number will typically be of a fixed length and significantly shorter than an MS1SDN. For example, the number may be a four digit number in the form of an extension number allocated in the telephone exchange of the organisation for which the VPN is provided.

It is known to provide this type of VPN to subscribers of a mobile telecommunications system. By providing the mobile terminals registered with the VPN with a code number corresponding to the extension number used by the organisation for which the VPN is provided, the user of a mobile terminal can make and receive calls as if it were a standard fixed extension to the switchboard of the organization. The "conventional" MSISDN can also be used to make and receive calls from the mobile terminal.

In addition to simplifying the dalling of numbers between mobile terminals within the VPN, members of the VPN may be provided by the mobile telecommunications network with special call rates between members of the VPN. Special facilities may be provided to members of the VPN - for example, centralised billing to the organization, rather than the issuance of separate bills to each subscriber in the VPN.

The elements of the two mobile telecommunications networks, and their operation, will now briefly be described with reference to Figure 1.

Each base station (BS) corresponds to a respective cell of its telecommunications network and receives calls from and transmits calls to a mobile terminal In that cell by wireless radio communication. Such a subscnber's mobile terminal is shown at 1A. The base stations are arranged in groups and each group of base stations Is controlled by a mobile switching centre (MSC), such as MSC 2A for base stations 3A,4A and 5A. As shown in Figure 1, the network A has another MSC 6A, which is controlling a further three base stations 7A,8A and 9A. In practice, the network A will incorporate many more MSCs and base stations than shown in Figure 1.

Each subscriber to the network is provided with a smart card or SIM which, when associated with the user's mobile terminal identifies the subscriber to the network. The SIM card is pre-programmed with a unique identification number, the "International Mobile Subscriber Identity" (IMSI) which is not visible on the card and is not known to the subscriber. The subscriber is issued with a publicly known number, that is, the subscriber's telephone number, by means of which calls to the subscriber are initiated by callers. This number is the MSISDN. In addition, the mobile terminal 1A is a member of a VPN, and also has a code number, as described above.

The network includes a home location register (HER) lOA which, for each subscriber to the network, stores the IMSI and the corresponding MSISDN together with other subscriber data.

When the subscriber wishes to activate their mobile terminal in a network (so that it may make or receive calls subsequently), the subscriber places their SIM card in a card reader associated with the mobile terminal (terminal 1A in this example). The mobile terminal 1A then transmits the IMSI (read from the card) to the base station 3A associated with the particular cell in which the terminal IA is located. The base station 3A then transmits this IMSI to the MSC 2A with which the BS 3A is registered.

MSC2A now accesses the appropriate location in the HER lOA present in the network core 12A and extracts the corresponding subscriber MSISDN and other subscriber data from the appropriate storage location, and stores it temporarily in a location in a visitor location register (VLR) 14A. In this way, therefore the particular subscriber is effectively registered with a particular MSC (MSC 2A), and the subscriber's information is temporarily stored in the VLR (VLR 14A) associated with that MSC.

Each of the MSCs of the network (MSC 2A and MSC 6A) has a respective VLR ( 14A and l l A) associated with it and operates in the same way as already described when a subscriber activates a mobile terminal in one of the cells corresponding to one of the base stations controlled by that MSC.

When the subscriber using mobile terminal 1A wishes to make a call, having already inserted the SIM card into the reader associated with this mobile terminal in the manner described, a call may be made by entering the telephone number of the called party in the usual way. This information is received by the base station 3A and is then routed to the called party via the MSC 2A. By means of the information held in the VLR 14A, MSC 6A can associate the call with a particular subscriber and thus record information for charging purposes.

Similarly, when a calling party (whether a subscriber within the network A or outside it) makes a call for the subscriber using mobile terminal IA, MSC2A is able to route this call to mobile terminal IA via base station 3A using the information relating to that subscriber which is temporarily stored in VLR 14A.

The foregoing is intended to be merely a simplified description of the normal operation of the GSM network. In practice, other procedures will be carried out. In particular, an authcutication procedure will take place when a subscriber activates a mobile terminal using their SIM.

Also shown in Figure I is a second GSM network B. Items in network B corresponding to those in network A are similarly referenced, but with the suffix "B" instead of "A". Of course, the network "B" is likely to have a different arrangement and number of MSCs and base stations but operates in a similar manner to network A. As explained above, for a subscriber to network A, the respective IMSI and MSISDN and other relevant data particular to that subscriber will be stored in HER lOA. If that subscriber now roams to network B and activates a mobile such as MS IB in that network, the procedure described above is substantially repeated.

Thus, the subscriber inserts their SIM card into the card reader of mobile terminal 1B. The mobile terminal IB then transmits the IMSI from the card to the adjacent base station (3B) and thence to MSC 2B.

However, MSC 2B will now recognise, from the structure of the lMSI, that the subscriber is not a subscriber to network B but a subscriber to network A. Therefore, MSC 2B will access, via core 12B, HLR lOA instead of HLR lOB using the interconnection 16 between network A and network B. The subscriber's information, including the relevant MSISDN and other subscriber data, will be accessed and temporarily stored in the VLR 14B. All this information is thus ready for use in processing calls to or from mobile terminal 1B. Any charging information associated with any such calls can then be associated with the subscriber information in VLR 1 4B and eventually transmitted back to HLR lOA and then billed to the relevant subscriber.

If a calling party wishes to make a call to a visiting subscriber who is using mobile terminal 1B, the call would initially be routed to network A (because this network would be the network identified by the subscriber's pubhcly known telephone number which the calling party would use). The core 12A would interrogate HLR IOA which would thus produce an indication that a copy of the subscriber's data was temporarily stored in VLR 14B, indicating, of course, that the subscriber had roamed to network B. Via the link 16 between networks A and B. network A interrogates network B to request a "roaming number". This is in effect a temporary telephone number for the subscriber, being a number appropriate to network B. This roaming number can now be used to route the calling party's call to network B and thence to mobile terminal l B. The calling party would of course not be aware of this roaming number or of the transferring process.

lO The foregoing description is merely a simplified description of the normal operation of the GSM network and roaming between GSM networks. Further details of all aspects of GSM networks and roaming are available in the ETSI Standards documentation.

As discussed above, in addition to the routing of calls using a conventional MSISDN, it is also known to allow selected subscribers of a mobile telecommunications network to form a VPN between them. The core 12A of network A Includes an intelligent node (IN) 18 which stores the database of code numbers associated with respective MSISDNs. That is, the IN18 comprises a look-up table or database, allowing the appropriate MSISDN corresponding to a particular code number to be identified, and vice versa.

If the user of mobile terminal 1A (who is a member of a VPN (VPN X)) administered by the core 12A of network A wishes to call another member of that VPN, the user dials the code number of that other mobile terminal. In this instance, the called mobile terminal Is mobile terminal 20. Mobile terminal 20 is a member of the VPN X and has its MSISDN stored in IN 18 alongside that mobile terminal's code number ("4573" in this example). Because mobile terminal 20 is in the same VPN as mobile terminal IA, the user of mobile terminal 1A need only dial the code number of mobile terminal 20.

The data exchanges taking place during initiation of such a call are shown in Figure 2. A call initiation message 1, which will include the code number dialled by the user of mobile terminal 1 A, is transmitted wirelessly from mobile terminal 1A to MSC 2A. The initiation message is then transmitted from MSC2A to core 12A, typically by a wired or fixed connection (message 2).

The initiation message includes a flag or other identifier which indicates that the call being initiated is for a call within a particular VPN (VPN X). This flag is identified by core 12A. On identification of the flag, the core 12A transmits the code number extracted from the initiation message to the IN 18 (message 3). The IN 18 then consults the look-up table or database present therein and obtains the MSISDN corresponding to the code number - in this example, "077712254573". The MSISDN is resumed to the core 12A (message 4), and is transmitted from the core 12A to the MSC 2A (message 5). The MSC 2A then modifies the call initiation message to include the MSISDN of the called mobile terminal 20 in place of the code number. The modified call initiation message is then transmitted to the core 12A (message 6), where it is handled in a similar manner to any other telephone call dialled using a conventional MSISDN. However, the flag indicating that the call is between members of VPN X is used by the core 12A to identify and make available any special services which it has been agreed by the network will be provided to members of the VPN X, and also to charge for the call according to the charging structure agreed for members of the VPN X. The modified call initiation message is then transmitted from core 1 2A to the MSC 6A connected to the BS 7A serving the mobile terminal 20 (message 7). The call initiation message is then passed by the MSC 7A to the mobile terminal 20 (message 8) , "hereafter the telephone call between mobile telephones 1A and 20 can proceed in the conventional manner.

If the mobile terminal 20 is roaming in network B. and is therefore served by base station 7B, MSC 6B and VLR 11B (Figure 1), it may be still possible for the call to be routed to the mobile terminal 20 by dialling the code number at terminal IA. That mobile terminal 20 is roaming in network B is recorded in HLR1OA in the manner described above. Figure 3 shows the messages exchanged between the elements shown in Figure I during call initiation.

Messages 1 to 6 are the same as those messages described in relation to Figure 2.

When message 6, initiating the call between mobile terminal 1A and mobile terminal 20 is received by core 12A, and the HLR lOA is consulted, the HER lOA will indicate that a copy of the data relating to the user of mobile terminal 20A was temporarily stored in the VLR llB associated with the MSC 6B which controls the base station 3B with which mobile terminal 20B is registered in network B. The core 12A of network A then transmits the call initiation message to the core 12B of network B via interconnection 16 (message 10). The message is then routed to the appropriate MSC (MSC 6B) (message 11), and thence to mobile terminal 20 (message 12). When the call is accepted by mobile terminal 20, communication between mobile terminal 1A and mobile terminal 20 can occur in the conventional manner. Although the call is between members of VPN X, the charge for making the call may be higher to reflect that mobile terminal 20 is roaming.

Figure 4 shows the call initiation procedure when a call is initiated by roaming mobile terminal 20 to another member of the VPN X. The call initiation message (message 20) includes the code number of the terminal within the VPN being called - for example, mobile terminal 1A. The call initiation message is received from mobile terminal 20 by MSC 6B (via a wireless link), and is then transmitted (via a fixed or wired link) to the core 12B (message 21). As indicated above, the call initiation message includes a flag which indicates that the message is a message for setting up a call from one member of VPN X to another member of VPN X. This flag is recognised by core 12B, where it is also determined that VPN X is administered by network A. Core 12B then extracts the code number from the call initiation message and sends this to core 12A of network A via interconnection 16 (message 22).

The code number is received by core 12A, which consults IN 18 to determine from the look-up table stored therein the MSISDN corresponding to the short code (message 23). The MSISDN corresponding to the short code is then transmitted from the IN18 to the core 12A (message 24). Core 12A then transmits the MSISDN to core 12B via interconnection 16 (message 25). The core 12B then modifies the call initiation message by replacing the code number with the MSISDN provided by IN 18 and sends this to MSC 6B (message 26). The call initiation procedure can then continue as for a conventional call (and will not be described further here for the sake of brevity).

In this specification, MSISDNs are referred to as being stored in the IN18.

However, it should be understood that any type of telephone number (or device address) may be stored and used to replace a corresponding code number. For example, the telephone number may be a fixed PSTN telephone number.

References In this specification to an MSISDN should be interpreted also to be references to any type of telephone number or device address.

Figure 5 shows an example of the data stored by IN 18. The IN 18 stores details of code numbers and MSISDNs or telephone numbers for two VPNs: VPN X and VPN Y. Of course, in practice, the IN 18 might store data for a multiplicity of VPNs. For each code number of a particular VPN the IN 18 stores the corresponding MSISDN. Several code numbers may correspond to a single MSISDN (that is, if a subscriber dials two different code numbers, the same MSISDN will be returned).

For example, for VPN X code number "0" corresponds to MSISDN (PSTN telephone number) "0207 225 1000". This might, for example, be the PSTN telephone number of the switchboard of the organization for which VPN X is provided. Other code numbers (4573.... 4965) correspond to respective MSISDWs (07771 225 4573...07771 225 4965). Other code numbers (4990,4491) correspond to PSTN telephone numbers of another country (in this

example Germany).

The IN 18 also lists code numbers and corresponding MSISDNs for VPN Y. The code numbers in VPN Y have a different length to the code numbers of VPN X. It is advantageous for the orgamsation for which a VPN is provided to use its existing extension numbers (for example, used for making internal calls within the organizations fixed telephone network) as code numbers without modification.

As indicated above, the call initiation message from a mobile terminal that is a member of a VPN will include a flag or other identifier which indicates of which VPN the mobile terminal is a member. In addition to the code number being forwarded by the core 12A to the IN 18, this flag or other identifier Is also forwarded. This enables the IN 18 to initially identify the relevant VPN, and subsequently, using the code number, to obtain the relevant MSISDN (or other telephone number).

It should be appreciated that, although the examples given above of the prior art, and the embodiments of the invention described below, concern GSM mobile telecommunications systems, the present invention is applicable to any type of mobile or cellular telecommunications system, including a UMTS (3G) mobile telecommunications system.

As described above, the known VPN arrangement can successfully route calls between members of a VPN when those members are roaming in a mobile telecommunications network (that is not hosting the VPN). However, in the prior art arrangement, it is not possible to route calls dialled using code numbers between members of VPNs hosted or administered by different networks. Such "different" networks may have separate network cores, controlling the authentication of subscribers and charging for use of the relevant network by subscribers. The different networks may be controlled and operated completely independently from one another, and may be different legal entities. Alternatively, different networks may be commonly owned but may be located in different countries or regions, each network having a respective core for controlling overall operation of that network.

The embodiment to be described enables data from VPNs or private dialling plans hosted by different mobile telecommunications networks to be shared.

Selected networks may agree in principle to allow the sharing of data of VPNs hosted thereby. When such an agreement is in place in principle, each network will specify, and only allow sharing of, selected VPNs hosted thereby. Further, there may be some entries of a VPN that are not to be shared between the networks. The IN of each network controls with which (if any) other networks VPN data are shared. By sharing data from VPNs hosted or administered by different networks, a subscriber registered with a VPN hosted by network A can dial a subscriber of a different VPN, hosted by network B. using the short code of the subscriber of the VPN hosted by network B. Such an arrangement is particularly advantageous, for example, when a multinational organisation, which has VPNs in several different countries and hosted by different networks (which might perhaps be commonly owned) wishes to provide its employees with the facility to use code numbers to make calls internationally but within the organisaton. Special services and call charges can be provided for such inter-VPN calls.

Figure 6 shows the two GSM networks of Figure 1, modified in accordance with an embodiment of the invention. In Figure 6, by way of illustration, an agreement exists between networks A and B to share data from all the VPNs hosted by each of the two networks. In addition to the components shown in Figure 1, Figure 6 further includes an International VPN Mediation and Provisioning system (IMP system) 30. IMP system 30 maintains a database 32 of code numbers and corresponding MSISDNs (and/or other telephone numbers or device addresses) from the lN18A and IN18B of networks A and B - i.e. the VPN data stored by each of the networks. Each of the networks A and B is provided with an IMP provisioning adapter 34A,34B, which provides an interface between the IN 18A,18B of networks A and B and the IMP system 30.

The IMP system 30 stores a copy of the code number and MSISDN (and/or other telephone numbers or device addresses) data stored in the IN 18A, 18B of each network served by the IMP system 30. The data is stored in database 32 in a predetermined format as an XML file. The format of data stored in the local IN 18A,18B of each network may be different from this predetermined format. The adapter 34A,34B of each local network modifies the data stored in the IN 18A,18B of each network to put it into the predetermined standard format, prior to the data being transmitted to the IMP system 30 and from there to the database 32.

Generally speaking, the IMP system 30 and database 32 will allow a subscriber to one network (network A) to call a subscriber of another network (network B) using a code number of the subscriber of network B relating to a VPN hosted by IN 18B of network B. When the code number is dialled by the subscriber of network A, the call initiation message is passed from mobile terminal 1A via base station 3A to MSC 2A, and from there to network core 12A. The code number is recognised as not being an MSISDN and is passed to IN 18A. The IN 18A in turn recognises that the code number is not for a VPN that it hosts.

What happens next depends upon the implementation of the IMP system 30.

In a first implementation the IN 18A generates a request for the MSISDN corresponding to the code number and sends this to its adapter 34A. The adapter 34A configures this request into the required XML format and transmits this to IMP system 30. The IMP system 30 interrogates database 32 to provide the MSISDN corresponding to the code number and returns this to the IN 18A via the adapter 34A. The IN 18A then returns the MSISDN to the MSC 2A in order to allow the call to continue in the conventional manner.

In a second, preferred, arrangement, the code numbers and MSISDNs of all the VPNs hosted by other networks (network B in this example) with which network A wishes to allow dialling using code numbers are copied to the IN 18A of network A. If such an arrangement is used, the IN 18A will be able to look up the relevant MSISDN for a code number of a VPN which is not hosted by the IN 18A using the downloaded information, without requiring an enquiry to IMP system 30 and database 32 via adapter 34A. Of course, as well as network A receiving a copy of all code numbers and MSISDNs for relevant VPNs hosted by the other networks, those other networks (network B in this example) will also require copies of relevant details from relevant VPNs which they do not host (the VPNs of network A in this example).

Whichever of the two arrangements is used, special services may be provided for, and special charges made be applied to, calls between VPNshosted by different networks, these being different from services and charges rendered by conventionally dialled calls using MSISDNs. If a call Is between subscriber terminals served by VPNs that have an association (that is, VPNs between which an agreement exists to allow calls to be routed therebetween using their code numbers), such calls are termed "online" calls. Calls which do not use the code numbers and which are not between subscriber terminals of associated VPNs are termed "off-line". Such off-lne calls are conventional calls between mobile telephone network subscribers, or between a mobile telephone subscriber and a subscriber to a fixed network. A different rate and services may be offered to a subscriber terminal making an on-line call depending upon whether that call is between subscriber terminals which are a member of the same VPN and where both subscriber terminals are in their home network. A different charge and services may be available when the subscriber terminals are both members of the same VPN but one of the subscribers is roaming in a visited network. A different charging structure and services may again be provided when a call is between two subscriber terminals that are members of different VPNs, and may further vary in dependence on whether the different VPNs are hosted by the same network or different networks, and on the location of the respective subscriber terminals between which the call is made.

In order for the database 32 to be compiled, the IN 18A, I 8B of each network must provide its contents to the database 32. As indicated above, provisioning adapters 34A,34B are operable to arrange the data of each hosted VPN in an appropriate XML predetermined form and this is passed to database 32. The database 32 will be regularly updated with additions, deletions and amendments to the VPNs hosted by each TN 1 8A, 1 8B. If the second arrangement described above applies, the copies of the VPN databases downloaded to each IN 1 8A,18B from the database 32 will also be periodically 1 5 updated.

As described above in relation to the conventional arrangement where a mobile telecommunications network provides VPNs for a plurality of organizations, it is necessary that the IN 18A can distinguish between code numbers for the respective VPNs hosted thereby.

In the embodiment described the networks A and B are located in different countries. A convenient arrangement for distinguishing short codes of VPNs associated with network A from those associated with network B is to automatically add to the short codes the standard country dialling code for the country where the VPN Is hosted when the short code is prepared in adapter 34A,34B for transmission to the IMP system 30. Therefore, the code numbers of VPNs hosted by network A, which is located in the United Kingdom, would all have added to them the prefix "44" by adapter 34A prior to them being transmitted to IMP system 30. The short codes of VPNs hosted by network B. which is located in Germany, would automatically have the prefix "49" added to them by adapter 34B prior to them being transmitted to IMP system 30. The country code prefix is in addition to the prefix that uniquely identifies each code number as a member of its VPN within the network hosting the VPN.

In the discussion hereinafter, an implementation of the second arrangement referred to above, where the IN of each network maintains a copy of VPN data from each of the associated VPNs hosted by other networks, will be described.

VPN data are "pushed" from each IN (IN 18A and IN 18B) to the IMP system into primary ways. Data may be pushed selectively. For example, when a new member joins a VPN hosted by network A, the relevant information (short code, MSISDN, country code and VPN identifier) are pushed to the IMP system 30. An alternative updating mode is where the entire content of the IN, or of a particular VPN hosted by the IN, is pushed to the IMP system 30. This mode will be used when initially setting up the IMP system 30 (because it will have no record of any entries of the IN of network A). This mode may subsequently be used to perform a reconciliation of the data stored by the IN of network A and the data for network A stored by the IMP system 30. If there are any discrepancies between the data these can be identified and resolved.

The IN of each network will also need to "pull" data relating to VPNs hosted by other networks from IMP system 30. Again, this pulling of data may be either performed selectively, or all the data held for a particular VPN or IN (or a proportion of that data) may be downloaded - the latter mode being used typically during system set up and to perform a reconciliation operation of the type described above in relation to a data push by an IN.

The database 32 is a relational database and includes relevant provisioning data for all '1PNs. The database stores a corresponding code number, telephone number (or the like), VPN identifier and country code for each entry.

Figure 9 shows an example of the data stored in the database 32. Figure lo shows an example of the corresponding data pulled by the IN 18A of network A. As well as storing the code numbers, telephone numbers, etc., the database 32 also stores data indicating when entries therein were last updated, and when data from the database 32 has last updated the corresponding information stored at the IN of each relevant network. This information can be used to allow selective updating of the data stored at the IN of each relevant network.

The provisioning 34A,34B adapter of each network is responsible for all communication between the IN 18A,18B of that network and the IMP system 30. The provisioning adapter is a single Java application. The provisioning adapter includes a scheduler which triggers pull and push operations according to a pre-programmed and configurable schedule. In addition to allowing pull and push operations, as described above, the provisioning adapter also performs an archive operation, where the provisioning adapter periodically moves data stored in the IN to an archive store where the data is stored in compressed form.

The provisioning adapters communicate with a central system 30 by exchanging XML formatted files. The file transport protocol is SCP (Secure Copy Protocol). This protocol uses the encryption and authentication of secure shell (SSH). Secure shell is an industry standard for establishment and maintenance of secure connections. It uses DES and RSA algorithms for privatc/publc key management. Transferred data is encrypted and protected from manipulation. Secure shell tunnelling protection is equivalent to that provided by an IP virtual private network. Secure shell uses standard IP routing and it can also run within an IP virtual private network. All file transfer operations are initiated by the adapters 34A,34B.

The tunnel Is established only for the time needed to perform pull, push or archive operations. After these operations are completed, the tunnel is dismantled. This allows the system to operate using, for example, ISDN connections, which are established only when needed. The SSH server has a host certificate that must match the relevant entry in the IMP system 30 which stores details of each known adapter 34A,34B. The IMP system 30 stores a public key associated with each adapter 34A,34B to authorise access. Each adapter 34A,34B will use its own private key to access the IMP system 30.

Each adapter will store a IMP system 30 host certificate in its "known hosts list.

As a security measure, the IMP system may be configured such that it will only allow an IN 18A to pull data from the database 32 if that IN 18A has previously pushed data.

As shown in Figure 7 the IMP system 30 is provided with a graphical user interface (GUI) 36 for monitoring operation of the IMP system 30, fault tracing and manual connection to adapters 34A,34B.

With reference to Figure 7, an example will now be described of the data flows when network A uploads data to the IMP system 30 and network B downloads data.

Data flow 1: Network A, by means of IN 18A, provides VPN data of its subscribers to the adapter 18A. The network A specifies update (add or modify) and remove operations to carry out on the data stored by the IMP system 30. The update may be either a selective (differential) update or a complete or partial reconciliation of data concerning the VPN.

Data flow_: The adapter 34A uploads the data to the IMP system 30. The adapter 34A performs all communication and error handling with the IMP system 30.

The IMP system 30 will check that each code number and MSISDN received is valid. This may be done by a separate communication path to the relevant network which hosts the code number and the MSISDN. The database 32 will only be updated (see data flow 3 below) with valid code numbers and MSISDNs. For any code numbers or MSISDNs that are not valid, a report will be produced and returned to the adapter 34A (data flow 4 below).

Data flow 3: The IMP system 30 updates its database 32 according to the data received from the network A. Data flow 4: The IMP system 30 returns to the adapter 34A a report of the success or failure of each update operation.

When network B wishes to download VPN data, the following data flows occur.

Data flow 5: Network B. by means of its IN 18B, requests from its adapter 34B a download of some specified provisioning data relating to VPNs of other networks. Such requests may be scheduled periodically, or triggered manually by an operator. The requests may be for either a selective/differential update or for a full or partial reconciliation.

Data flow 6: The adapter 34B determines the VPNs of other networks with which network B has an association (i.e. between which inter-VPN or onnet calls may be made) and for which relevant provisioning data should be downloaded.

Data flow 7: The adapter 34B initiates a download from the IMP system 30, specifying a list of VPNs from which data are required. The adapter 34B performs all communication and error handling with the IMP system 30.

Data flow 8: The IMP system retrieves the relevant data for the VPNs from its database 32. The data includes code numbers, telephone numbers for the entries of all relevant VPNs except the VPNs hosted by network B. Data flow 9: The IMP system 30 returns the requested data to the adapter 34B.

Data flow 10: The adapter 34B returns the requested data from the VPNs of other networks to the IMP of network B. s The GUI 36 allows the internetwork VPN service 30 to be managed as follows.

Date flow ll:The GUI system 36 can add, update and remove network data from the IMP system 30, such as valid participating networks and VPN accounts.

Date flow 12:The GUI system 36 can correct data in the IMP system 30 database.

Data flow 13: The GUI system 36 can generate reports from the IMP system database.

The architecture of the IMP system 30 is shown in Figure 8. The dispatcher process module 40 is responsible for decoding XML requests or uploaded files received from the adapter of a network (in this example adapter 34A of network A). The dispatcher process 40 also updates the database 32 according to the uploaded files received and prepares XML return files for sending to the adapter 34A.

Maintenance (archiving) module 42 is responsible for archiving and purging old or obsolete XML files and purging odd entries from a store of past pull and push operations.

The log server 44 is responsible for writing log entries generated by all the components of the IMP system 30 to log files.

The application server 46 of the GUI system 36 provides for database access and associated business logic, and XSL style sheets. Web server 48 and web browser 50 provide a convenient means for implementing the graphical user interface from the GUI system 36. File system 52 manages pull and push requests from adapter 34A.

Referring now to Figure lo, the content of the lN 18A of network A is shown after that IN 18A has pulled relevant data from two VPNs (VPN MB and VPN NB from another network (network B) with which there is an agreement to allow inter-VPN on-net calling. The code numbers of VPN MB include a unique VPN identifier "2" and the country code "49" of the country (Germany) where VPN is hosted. These digits precede the basic code number " 12340....12347". Similarly, the code numbers of VPN NB have a unique VPN identifier "4" and the country code "49" preceding the relevant basic code number "1...8". As discussed above, the unique" VPN identifier is unique within that VPN's host network, but it might be repeated in another network.

The code numbers of VPN X and VPN Y. which are hosted by network A (and in Figure 10 a-e designated VPN XA and VPN YA) can be considered to be "local" VPNs. These will not have added to them a unique VPN identifier or a country code. When the data of VPN XA and YA are uploaded to IMP system 30, the adapter 34A will add a relevant unique VPN identifier and country code in order to put the VPN data in the required format for IMP system 30.

It should be understood that any network may host VPNs which are only required locally within that network, and where details of which are never passed to IMP system 30.

Because the code numbers of the local VPNs (VPN XA and VPN YA are not processed by adapter 34A and IMP system 30, and are not provided with a unique VPN identifier and country code, it is possible that a code number used by a local VPN is the same as the code number used in pulled VPN data. In Figure 10 the last entry of the left hand column for VPN XA has a code number "4491". The first code number of VPN No is also "4491", although the latter code number comprises unique VPN identifier "4", country code "49" and basic code number " 1".

Such a situation may be dealt with in a variety of different ways. The IN 18A may monitor for any clash between code numbers of different VPNS and produce a report which prompts manual intervention. For example, a message could be sent to network B. and in particular to the person responsible for administering VPN NB indicating that the subscriber with basic code number " l " of VPN NB must change that code number or they will not be able to access VPN NB when roaming in network A. If the conflict is not resolved, the IN l 8A of network A will, on receipt of the code number "4491 " in a call initiation message, assume that this is the code number of the local VPN XA and return the telephone number + 49 89 2399 4991".

Figure 9 shows the data present in IMP system database 32 following pushing of data for VPN XA and YA from network A and from VPN MB and VPN NB from network B. The clash between code numbers described in relation to Figure 9 does r ot occur because the code number "4491 " of VPN XA has added to it the unique VPN identifier " I " and the country code "44".

The database 32 does however monitor for clashes of code numbers when VPN data is being pushed from a network. If database 32 detects a clash between code numbers, this is reported using GUl 36 and user intervention is required to prevent two code numbers being present on database 32 that clash.

The exchange of data taking place between the elements shown in Figure 6 which occurs during initiation of a call from mobile terminal 1A which is a member of VPN XA hosted by network A to mobile terminal 20 which is a member of VPN MB hosted by network B. and dialled by mobile terminal IA using the short code for mobile terminal 20, will now be described with reference to Figure 11.

The user of mobile terminal IA will be aware that mobile terminal 20 is not a member of the same VPN as mobile terminal 1A. The user of mobile terminal IA will know that the VPN of which mobile terminal 20 is a member is hosted in Germany, and will therefore precede the code number by the country code for Germany "49".

A call initiation message 60, which will include the code number dialled by the user of mobile terminal 1A, is transmitted wirelessly from mobile terminal IA to MSC 2A. The initiation message is then transmitted from MSC 2A to core 12A (message 61). The initiation message includes a flag or other identifier which indicates that the call being initiated for a particular VPN (VPN MB) This flag is identified by core 12A. On identification of the flag, the core 12A transmits the code number extracted from the initiation message to the IN 18A (message 62). The IN 18A then consults the data stored therein to locate the relevant entry for the code number received. For example, if the code number of mobile terminal 20 is "12340", the IN 18A will then initially search data stored for its local VPNS (that is, VPNS that it hosts). If, as in this case, the code number is not identified as being one of a local VPN, the search is then extended to code numbers of VPNs previously pulled by the IN 1 8A from the IMP system 30 using adapter 34A. The IN 18A will identify code number 12340 stored for VPN MB and will obtain the relevant MSISDN "+49 65 4521 2340". The MSISDN is returned to the core 12A (message 63), and this is transmitted from the core 12A to the MSC 2A (message 64). The MSC 2A then modifies the call initiation message to include the MSISDN of the called mobile terminal 20 in place of the code number. The modified call initiation message is then transmitted to the core 12A (message 65), where it is handled in a similar manner to any other telephone call initiated using a conventional MSISDN. However, the flag indicating that the call is before a member of VPN MB is used by the core 12A to identify and make available any special services which it has been agreed will be provided to calls between VPNS XA and MB, and also to charge for the call according to the charging structure agreed between those VPNS. The core 12A will identify from the structure of the MSISDN that the call is for a mobile terminal that is a subscriber of network B. The core 12A of network A then transmits the call initiation message to the core 12B of network B via interconnection 16 (message 66).

The message is then routed to the appropriate MSC (MSC 6B) (message 67), and thence to mobile terminal 20 (message 68). When the call is accepted by mobile terminal 20, communication between the mobile terminal IA and the mobile terminal 20 can occur in the conventional manner. l

The use of the country codes described above is not necessary if the code numbers used by all VPNs are unique and there is no duplication of code numbers.

It should be appreciated that the invention is also applicable to an arrangement where some or all of the networks A and B are not cellular telecommunications networks but are some other type of commumcations network. For example, one or more of the networks could be a satellite communications network.

l O There may be more than two networks.

The networks A,B are separate or discrete in the sense that they have a separate core for routing data between devices registered therewith and/or In the sense that they do not share a radio access network/base station transceivers. The networks may be operated by different (legal) entities and/or have separate facilities for authenticating user devices and charging users of devices registered therewith for use of the network.

Claims (15)

1. A communications system including a plurality of telecommunications networks, each of which: provides subscriber terminals thereof with a respective publicly-known telephone number for allowing communications to be addressed to each subscriber terminal, allows selected subscriber terminals thereof to be associated together in a group such that those subscriber terminals can address communications to one another using a respective code allocated to each of the selected subscriber terminals, and includes means for translating the code of each of the selected terminals into the corresponding publicly-known telephone number thereof; wherein the system further includes means for maintaining a database of the codes and corresponding publicly-known telephone numbers for each of said networks and for providing to one of said networks a publicly-known telephone number corresponding to a code of a subscriber terminal of another one of said networks to allow communication from a subscriber terminal of said one of the networks to be addressed to a subscriber terminal of said other of the networks using the code of the latter subscriber terminal.

2. The system of claim 1, wherein each network is provided with respective interface means for exchanging data with the database maintaining means.

3. The system of claim 2, wherein the interface means is operable to transmit data indicative of its networks codes and corresponding publiclyknown telephone numbers to the database maintaining means.

4. The system of claim 3, wherein the interface means is operable to generate said data in a predetermined format for use by the database maintaining means.

5. The system of claim 4, wherein the interface means is operable to generate said data using XML.

6. The system of any one of claims 2 to 5, wherein the interface means is operable to receive data indicative of codes and corresponding publicly known telephone numbers of other ones of said networks from the database maintaining means.

7. The system of any one of claims 1 to 6, including means for modifying said codes to provide them with an indicator of the group and/or network with which they are associated.

8. The system of any one of claims 1 to 7, including means for detecting two identical codes.

9. The system of any one of claims 1 to 8, wherein said group comprises a virtual private network (VPN).

10. The system of any one of claims 1 to 9, including means for identifying communications initiated using a said code and for applying a special charging or service scheme to such communications.

A method of enabling communication between a plurality of telecommunications networks, the method including: providing subscriber terminals of each network with a respective publicly-known telephone number for allowing communications to be addressed to each subscriber terminal, associating selected subscriber terminals of each network together in a group such that those subscriber terminals can address communications to one another using a respective code allocated to each of the selected subscriber terminals, and maintaining a database of the codes and corresponding publicly-known telephone numbers for each ol said networks and providing to one of said networks a publicly-known telephone number corresponding to a code of a subscriber terminal of another one of said networks to allow communication from a subscriber terminal of said one of the networks to be addressed to a subscriber terminal of said other of the networks using the code of the latter subscriber terminal.

12. A method of enabling a telephone call initiated by a subscriber terminal of a first mobile telecommunications network to be routed to a subscriber terminal of a second telecommumcations network, wherein the telephone call is addressed by the terminal of the first mobile telecommunications network to lO the terminal of the second mobile telecommunications network using a code allocated by the second telecommunications network, the method including maintaining a database of codes allocated by the second mobile telecommunications network and respective publicly-known telephone numbers corresponding thereto and providing the codes and publicly-known telephone numbers to the first mobile telecommunications network for enabling the first mobile telecommunications network to translate the code used to address the telephone call to be converted into the corresponding publicly- known telephone number.

13. Apparatus for enabling a telephone call initiated by a subscriber to involve a first mobile telecommunications network to be routed to a subscriber terminal of a second mobile telecommunications network, wherein the telephone call is addressed by the terminal of the first mobile telecommunications network to the terminal of the second mobile telecommunications network using a code allocated by the second mobile telecommunications network, the apparatus including a database which stores the codes allocated by the second mobile telecommunications network and respective publicly-known telephone numbers corresponding thereto and for providing the codes and publicly-known telephone numbers to the first mobile telecommunications network for enabling a first mobile telecommunications network to translate the code used to address the telephone call to be converted into the corresponding publicly-known telephone number.

14. A system substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of Figures 6 to 11 of the accompanying drawings.

15. A method substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of Figures 6 to 11 of the accompanying drawings.