[0034] FIG. 3 is a schematic diagram of a telecommunications network including a pre-charging number portability formatter 10 . This example is illustrated with reference to a 3G network, but the principle could be applied to networks of other types. When a connection is set up the service switching point (SSP) 11 does not signal the SCP 12 directly with the B-party's number, as it would in a conventional system. Instead it signals the SSP via the formatter 10 . The formatter 10 determines the operator with which the B-number is associated and passes this to the SCP. In this example the formatter signals the identity of the operator to the SCP in the form of a subscriber identity prefix that is associated with that operator. That means that the SCP can operate as it normally does to identify the operator: i.e. by means of a prefix that is associated with the operator.

[0035] The operation of the system of FIG. 3 will now be described in more detail. FIG. 3 shows the relevant parts of a 3G telecommunications network. The network includes a charging control unit 12 , which in this example includes a first processing entity 12 a which acts as an SCP or SCF for pre-paid subscribers, and a second processing entity 12 b which acts as an SCP for account subscribers. Both processing entities cooperate to provide an integrated SCP function. The network includes at least one SSP 11 , which acts in a similar way to an MSC in a GSM network: that is to supervise switching and call control (including charging) as a connection is set up, proceeds and is terminated. For illustration mobile stations 13 , 14 , which can communicate by radio with the network 15 in which the units 10 to 12 operate.

[0036] The signalling that takes place during connection set-up in order to pass the tariff information to the SSP 11 is illustrated by steps 21 to 24 in FIG. 3 . At step 21 the SSP 11 transmits an IDP message to the formatter 10 . That IDP message includes the identity code of the A subscriber (the A number), the identity code of the B subscriber (the B number) and the service key. On receiving that message the formatter performs look-ups to determine the operator with which the B number is associated (the details of these look-ups will be described later) and then to determine a subscriber identity code prefix with which that operator is associated. This will be termed the operator prefix. Then in step 22 the formatter 10 transmits an IDP message to the charging control unit 12 . That IDP message comprises the A number, the operator prefix, the B number and the service key. On receiving that message the charging control unit 12 analyses the message and determines a tariff for the connection based on information including the operator prefix. This will be described in more detail below. On determining the tariff the charging control unit transmits information identifying the tariff to the SSP in an FCI tariff information message. (Step 23 ). It also transmits a continue message (step 24 ) to the SSP to authorise it to continue with the set-up of the connection. Charging of the connection is performed in accordance with the tariff indicated in the message sent at step 23 .

[0037] To contrast this mechanism with the one shown in FIG. 2 , FIG. 4 is a block diagram showing the units 10 , 11 and 12 and signalling steps 21 , 22 , 23 and 24 . It will be seen that the formatter 10 acts as an intermediary between the SSP or MSC 11 and the SCP or SCF 12 .

[0038] In this embodiment the formatter 10 performs a look-up to determine the operator prefix. It access a database to determine the operator with which the B number is associated. In a system such an GSM or UMTS that is the operator of the B subscriber's home network. The database could be that of an SSRi of the network, or an equivalent function. Performing a look-up on the B number using the SSRi can return the direction specific data (DIRE) that is associated with the B number. The DIRE includes a subscription network identifier (SNID) which can be used as the operator prefix. It will be appreciated that the formatter could use other mechanisms to derive the operator prefix; for example, the formatter could store its own database of subscriber numbers and the operator associated with each one, and a database of subscriber prefixes associated with each operator. Alternatively it could store a database of numbers that have been moved from one operator to another, with for each one an indication of the operator to which they have been moved, and a database indicating a subscriber prefix associated with each operator. In the latter case the database of numbers that have been moved would be analogous to a number portability database (NPDB) of some circuit switched (CS) networks.

[0039] The charging control unit determines the tariff to be used for the connection based on information including the operator with which the subscriber representing the B-party is associated. In the normal case, the charging control unit would analyse the prefix of the B-number as received in a message requesting a tariff for a connection. Based on that prefix it would determine the operator to which that prefix relates. Then it would determine a tariff for the connection. Other information that could also be taken into account in determining the tariff include the time of day, the day of the week and the service type of the connection. When the operator prefix is prepended to the B-number exactly the same processing can be performed to yield the same result. An illustration of this is given below.

[0040] In this illustration it is assumed that the format of the B-number is conventionally such that the first five digits of the B-number represent the operator with which it is associated. Thus in this example the B-number has two fields. One is represented by the first five digits of the number. It conventionally indicates the operator to which the number is assigned, although it does not do so when the number has been ported from one operator to another. The other field is represented by the remainder of the number. It will be appreciated that the two fields could take other forms than a prefix and a suffix.

[0041] The charging control unit stores a table (table 1) indicating tariffs for connections of different types to different operators. For simplicity the table in this example uses only two variables, but in a practical example more could be used. 1

[0042] The charging control unit also stores a table (table 2) indicating the operator conventionally associated with each of a number of B-number prefixes. 2

[0043] The charging control unit is configured to perform the following steps when it receives a request for a tariff for a connection of a certain type to a certain B-number.

[0044] 1. Look up the first five digits of the B-number in table 2 to determine the corresponding operator.

[0045] 2. Look up the determined operator and the connection type in table 1 to determine the tariff.

[0046] 3. Return the tariff to the entity that requested it.

[0047] Thus if the charging control unit received a request for a tariff for a connection of type X to B-number 07198 154786 it would:

[0048] 1. Look up digits 07198 in table 2 and thereby determine that they relate to operator B.

[0049] 2. Look up operator B and type X in table 1 and thereby determine that the tariff should be tariff 3.

[0050] 3. Return an indication of tariff 3 to the requesting entity.

[0051] Now, in the system described above, the B-number as transmitted to the charging control unit is modified by the pre-pending of an operator prefix. For example the number 07198 154786 might have been moved to being associated with operator C. In that case the operator prefix 07115 could be pre-pended by the formatter so that the B-number as received by the charging control unit is now 0711507198 154786. In this case the first five digits of the B-number as received by the charging control unit are 07115 so the steps performed are:

[0052] 1. Look up digits 07115 in table 2 and thereby determine that they relate to operator C.

[0053] 2. Look up operator C and type X in table 1 and thereby determine that the tariff should be tariff 5.

[0054] 3. Return an indication of tariff 5 to the requesting entity.

[0055] Thus the charging control unit can operate just as it did before, but the system as a whole will operate consistently with number portability.

[0056] In the system of FIG. 3 the IDP service requests are served against the intelligent network system. Core INAP (intelligent network application protocol) and CAP (CAMEL (customised applications for mobile networks enhanced logic) application part) signalling can be used.

[0057] FIGS. 5 and 6 show two alternative embodiments of the system. In FIGS. 5 and 6 like components are numbered as for FIG. 3 .

[0058] FIG. 5 shows an embodiment consistent with implementation in an IP Multimedia Subsystem (IMS) network (as specified in 3GPP TS 23.228 v.5.3.0) using CAP/INAP. A CAMEL/INAP SSF 30 takes the place of the SSP 11 of FIG. 3 . The SSF 30 is connected to a CPS 31 over an ISC (SIP) interface 32 . The CPS includes an S-CSCF as in a normal IMS network. This embodiment is useful when the IMS subscribers have E.164 addresses (in addition to logical IMS addresses).

[0059] In this embodiment the messages are sent as follows:

[0060] Step 21 : IDP message specifying A number, B number and service key

[0061] Step 22 : IDP message specifying A number, B number prefixed by the determined operator prefix and service key

[0062] Step 23 : FCI tariff information message

[0063] Step 24 : CONTINUE message

[0064] Subsequently the SCP or SCF 12 continues a dialogue with the SSF 30 for exchanging tariff information during the pendency of the connection.

[0065] FIG. 6 shows an embodiment consistent with implementation in an IP Multimedia Subsystem (IMS) network using ISC/SIP signalling. A CPS 40 takes the place of the SSP 11 of FIG. 3 . The CPS is connected to the formatter 10 and the SCP or SCF 12 over ISC (SIP) interfaces 41 , 42 . A more generic name, Application Server APSE), for the unit providing the functionality of the SCP or SCF, is often used in IMS networks

[0066] In this embodiment the messages sent at steps 21 , 22 and 23 are sent as SIP INVITE messages. The parameters of the messages are as follows:

[0067] Step 21 : To: B number

[0068] From: A number

[0069] P-header- 1 : service key

[0070] Route: formatter 10 , CPS 40

[0071] Step 22 : To: B number

[0072] From: A number

[0073] P-header- 1 : service key

[0074] P-header- 2 : Operator prefix (“origin network ID”)

[0075] Route: SCP 12 , CPS 40

[0076] Step 23 : To: B number

[0077] From: A number

[0078] P-header- 2 : Operator prefix (“origin network ID”)

[0079] P-header- 3 : Tariff identification

[0080] Route: CPS 40

[0081] Thus in this embodiment the basic SIP protocol can be used.

[0082] Note that even though the message sent at step 22 is from the formatter 10 , the message's source is indicated in the message as being the CPS 40 . This means that the response at step 23 can be sent back to the CPS 40 , which originated the request for a tariff at step 21 . (See the ISC specifications 3GPP TS 23.218 and RFC 3261). The formatter 10 does not include mention of itself in the Record-Route field of the SIP message sent at step 22 so that it will not be included on the route of subsequent SIP messages in the same session. Such messages could be sent to proceed with the connection setting (e.g. PRACK, UPDATE) or to release an active connection (BYE).

[0083] The same functionality can be provided also with IDP messages. (See FIG. 3 ). The formatter 10 does not include mention of itself when sending the message to the SCP 12 . The message source is indicated in the message as being the SSP 11 . This means that the response at steps 23 and 24 can be sent back to the SSP 11 which originated the request for a tariff at step 21 .

[0084] To implement a system of the type illustrated in FIG. 6 , the service profile of the A party could include the address of the formatter 10 but not that of the SCP 12 . The formatter 10 could then include processing logic that can invoke a service interface or normal SIP interface towards the appropriate SCP/APSE etc. based on (for instance) the service identifier received in the P-header- 1 of the message of step 21 .

[0085] The SCP/APSE could omit the operator prefix, or “origin network ID”, from the message sent at step 23 , since the tariff information carried (in this example) in P-header- 3 could be used by other services invoked from the CPS after APSE services have been completed.

[0086] The messages described above in connection with FIG. 6 make use of the P-header concept specified in IETF. Another mechanism for delivering the additional information carried in this example by the P-headers is the use of a special body part in the SIP message.

[0087] Providing a formatter 10 to provide the charging control unit 12 with an indication of the B subscriber's network has a number of advantages over other solutions. It requires little if any modification to existing charging control units—especially if the indication of the operator's network is passed in a similar form to that in which the charging control unit would process normally. For example, if the indication of the operator's network is normally a prefix to the B number then the indication of the operator's network can prefix the B number when it is sent by the formatter to the charging control unit. Other formats of subscriber ID are suitable for use in a similar way. For example if the indication of the operator's network is normally a suffix to the B number then the indication of the operator's network can suffix the B number when it is sent by the formatter to the charging control unit. Or if the indication of the operator's network is normally indicated by a flag in the B number then the indication of the operator's network can be indicated by a flag in the B number when it is sent by the formatter to the charging control unit

[0088] Since little if any modification to conventional SCFs/SCPs is needed to implement the present invention it is especially suitable for operation in a multi-vendor environment.

[0089] The formatter 10 may be termed a number portability database (NPDB), especially a pre-SCP NPDB or a pre-gsmSCF NPDB.

[0090] The formatter needs to know which charging control unit it should access to determine the tariff. A given formatter could always access the same charging control unit. Alternatively, one way for it to determine which charging control unit to use is by analysis of the service key: the MSC (or the like) which sends the step 21 message to the formatter could modify the service key in such a way that it indicates the charging control unit that is to be used. Alternatively it could be formed from the service key using GT translations. FIG. 7 shows signalling between an MSC 60 (which could take the place of the SSP of FIG. 3 ), a formatter 61 (which could be integrated or closely linked with an SRRi) and a charging control function 62 (which could be an SCP or SCF) in order to use GT translations in this way.

[0091] The signalling in FIG. 7A is as follows.

[0092] Step 63 : GT analysis at the VMSC/GMSC determines the SRRi's address.

[0093] Step 64 : The VMSC/GMSC transmits to the SSRi an IDP message including the A number, the B number and a service key denoting an intelligent networking tariff. The signalling parameters are:

[0094] CgPA: RI=GT, SSN,GT=MSC_GT

[0095] CdPA: RI=GT,SSN,GT=SCP_GT

[0096] OPC=MSC_PC, DPC=SRRi

[0097] Step 65 : The SCCP makes a GT analysis and the result is the subsystem of the SRRi's application. The SRRi's application changes the Translation Type (TT) for the signalling session. The SCCP makes another GT analysis and the result is the SCP. The SCCP changes the TT's value back to its original value before the IDP message is forwarded to the SCP.

[0098] Step 66 : The SSRi transmits to the SCP an IDP message including the A number, the B number prefixed by the operator prefix and the service key for the intelligent networking tariff. The signalling parameters are:

[0099] CgPA:RI=GT, SSN,GT=MSC_GT

[0100] CdPA:RI=GT,SSN,GT=SCP_GT

[0101] OPC=SRRi_PC,DPC=SCP_PC

[0102] Step 67 : Either the SCP changes its real address to the origGT address, or the routing indicator is changed to DPC+SSN

[0103] Step 68 : The SCP signals the tariff information to the VMSC/GMSC. Depending on the action taken at step 67 the signalling parameters are either:

[0104] Continue( )

[0105] CgPA:RI=GT,SSN,GT=real_SCP_GT

[0106] CdPA:RI=GT,SSN,GT=MSC_GT

[0107] OPC=SCP_PC,DPC=MSC_PC

[0108] or:

[0109] Continue( )

[0110] CgPA:RI=DPC+SSN,GT=SCP_GT

[0111] CdPA:RI=GT,SSN,GT=MSC_GT

[0112] OPC=SCP_PC,DPC=MSC_PC

[0113] Step 69 : The dialogue between VMSC and SCP can be arranged without the SRRi's intervention, if needed.

[0114] FIG. 7B shows an alternative method. The signalling in FIG. 7B is as follows.

[0115] Step 70 : GT analysis at the VMSC/GMSC determines the SRRi's address.

[0116] Step 71 : The VMSC/GMSC transmits to the SSRi an IDP message including the A number, the B number and a service key denoting an intelligent networking tariff. The signalling parameters are:

[0117] CgPA: RI=GT, SSN,GT=MSC_GT

[0118] CdPA: RI=GT,SSN,GT=xx+SCP_GT

[0119] OPC=MSC_PC, DPC=SRRi

[0120] Step 72 : The SCCP makes GT analysis for xx+SCP and the result is the subsystem of the SRRi's application. In the analysis the prefix xx is removed. Application level processing determines the operator prefix on the basis of B number and attaches it in front of the B number for the message of step 73 . The SCCP makes another GT analysis, and the result is then: DPC=SCP_PC, GT=SCP_GT. After that, the message of step 73 is sent to the SCP.

[0121] Step 73 : The SSRi transmits to the SCP an IDP message including the A number, the B number prefixed by the operator prefix and the service, key for the intelligent networking tariff. The signalling parameters are:

[0122] CgPA:RI=GT, SSN,GT=MSC_GT

[0123] CdPA:RI=GT,SSN,GT=SCP_GT

[0124] OPC=SRRi_PC,DPC=SCP_PC

[0125] Step 74 : In this case the SCP does not have to change its GT address. Subsequent messages can be directly routed to the SCP with GT=SCP_GT without intervention from the SRRi.

[0126] Step 75 : The SCP signals the tariff information to the VMSC/GMSC. The signalling parameters are:

[0127] Continue( )

[0128] CgPA:RI=GT,SSN,GT=SCP_GT

[0129] CdPA:RI=GT,SSN,GT=MSC_GT

[0130] OPC=SCP_PC,DPC=MSC_PC

[0131] Step 76 : The dialogue between VMSC and SCP can be arranged without the SRRi's intervention, if needed.

[0132] In addition to determining tariffs, as described above, the functionality of the formatter 10 could serve other purposes. For example, with knowledge of the B subscriber's network in a convenient form, by way of the subscriber prefix, a network could determine routings for a connection or could set one or more quality of service targets, for instance to meet inter-operator agreements.

[0133] The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any-problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. In view of the foregoing description it will be evident 1 to a person skilled in the art that various modifications may be made within the scope of the invention.