In mobile telecommunications systems, such as the pan-European digital mobile communications system GSM (Global System for Mobile Com- munications), call prices depend usually on the time when the call is made. To be able to offer more versatile charging possibilities some operators offer pre- paid service for subscribers. A prepaid service is a service where a subscriber pays in advance his calls by buying vouchers. The prepaid service logic and prepaid service data are stored in the system. A prepaid SIM (Subscriber Identity Module) card comprises an MSISDN number which is associated with the prepaid service data, including the subscriber's credit, in the system. A prepaid service allows payment of a telephone bill in advance or setting an upper limit for the telephone bills. As another benefit, the prepaid service en- able roaming subscribers to pay their local calls at local tariffs, whereas the use of the SIM card of their home service provider results in paying interna- tional tariffs to their home network and back.

Usually a prepaid subscription is activated and money added to subscriber's prepaid account by means of vouchers. Some of the service pro- viders sell different types of vouchers, which differ from each other e. g. in the number of call units and the time the call time bought is valid. However, the calls are charged in the same way regardless of what kind of a voucher is used.

The above described possibilities for charging calls are insufficient, since the needs of mobile subscribers and their use of their mobile stations are becoming more and more differentiated. There are users making lot of calls during office hours whereas some other users call seldom and during eve- nings, for example. The charging of calls has to be diversified correspondingly.

Disclosure of the invention The object of the invention is to provide versatile charging possibili- ties that are easy to maintain and define by the operator. The object of the in-

vention is achieved with methods, a system, a network element and data- bases which are characterized in what is disclosed in the independent claims.

The preferred embodiments of the invention are set forth in the dependent claims.

The invention is based on defining at least two different kinds of tar- iff models and associating a subscriber's information directly or indirectly with a tariff model which is used when the subscriber makes a call. With tariff mod- els the charging of subscribers is easily diversified.

The advantages of the invention are that the service provider can customize the charging very easily and for example direct some users to call during times when the network is not very loaded.

In one embodiment of the invention, where the prepaid service is used, each voucher type has a tariff model. The further advantage of this em- bodiment is that a subscriber can change his tariff model by changing the voucher type he is using.

In another embodiment of the invention, where the prepaid service is used, voucher types allowed for subscribers are defined. The further ad- vantage of this embodiment is that the operator can restrict the subscriber's freedom to choose a tariff model to be used.

Brief description of the figures The invention will be described in further detail in the following by means of preferred embodiments with reference to the accompanying draw- ings, in which Figure 1 is a block diagram showing some relevant network ele- ments in a first preferred embodiment of the invention; Figure 2 is a block diagram showing some relevant elements of the SMP in the first preferred embodiment of the invention; Figure 3 is a flow chart illustrating charging in the first preferred em- bodiment; and Figure 4 is a flow chart illustrating depositing in the first preferred embodiment.

Detailed description of the invention Figure 1 is a block diagram of a telecommunications system S equipped with an arrangement according to a first preferred embodiment of the invention. The telecommunications network is assumed to be a public land

mobile network PLMN, without, however, limiting the invention to that kind of particular network. The invention can be used in any telecommunications systems where subscribers have subscription information stored in the system and the subscription information is used when calls are charged.

The embodiment illustrated in Figure 1 makes use of Intelligent Network technology. An intelligent network IN is able to provide a subscriber of a telecommunications network, such as a wired network or a mobile telephone network, with a plurality of services. An example of such an intelligent network is described in recommendations of the ITU-T Q-1200 series, of which Q-1210 to Q-1219 define a set of features known as CS-1 (Capability Set 1), and cor- respondingly, Q-1220 to Q-1229 define a set of features CS-2. The invention and its background will be described by the terminology of recommendation ETS 300 374-1 CoreINAP, but the invention can also be employed in intelli- gent networks implemented according to other intelligent network standards.

Figure 1 shows some elements of an intelligent network which are relevant to the understanding of the invention, such as what are known as in- telligent peripherals IP. Usually an IP is associated with a specialized resource function SRF which is an interface for network mechanisms associated with interaction with a subscriber. Thus an IP may comprise e. g. more advanced speech handling functions than do exchanges in general. The IVR application is usually located in the IP. The IVR application, also called the PrePaid serv- ice IVR application, is an interactive voice response application that allows the subscriber to make a deposit (add money, recharge) into his PrePaid SIM ac- count by entering the identification number of a prepaid voucher. The IP is connected to an SSP using for example ISUP (ISDN User Part) signalling and one or more voice transports.

The SSP (Service Switching Point) is a network element performing service switching function (SSF). The SSP may be a mobile service switching centre MSC, which includes the SSF. The SSF is an interface between a con- ventional call control function CCF and the service control function SCF of an intelligent network. The network element performing the SCF is called a serv- ice control point SCP. An intelligent network service is produced by the service switching point SSP inquiring instructions from the service control point SCP by means of messages to be transmitted across the SSP/SCP interface upon the encounter of detection points associated with the service. In association with an intelligent network service, a service logic program is started at the

service control point SCP, the operation of the program determining the mes- sages transmitted by the SCP to the SSP at each stage of a call. During one call there may be several service logic programs started and ended. The service logic program handling a prepaid call runs during the whole call, since it controls credit updating. Usually the SCP controls the charging and adjusts the charging on the basis of information it gets from the SSP. The credit up- dating according to the invention is discussed in greater detail in Figure 3.

However, usually the SCP is not used in the service logic of the Prepaid SIM IVR recharge application, i. e. calls to the IVR are routed by the CCF directly to the IVR on the basis of the service number which the sub- scriber has dialled in order to recharge (deposit).

In the example illustrated in Figure 1, prepaid subscriber informa- tion, information about vouchers, prepaid profile definitions and tariff models- are in a database located in a service management point SMP as is described in greater detail in Figure 2. Alternatively, they may be located in different da- tabases and/or in some other network element, like a home location register HLR (not shown in Figure 1). The database may also be a decentralized data- base. The IVR interfaces the SMP database through a service management interface SMI. The SMP and the IP may be connected e. g. through a local area network (LAN) using TCP/IP (Transmission Control Protocol/Internet Protocol). The connection between the IP and the SMP, illustrated by a dashed line, represents only management connection without any signalling connection.

The service management access point SMAP provides some se- lected users, such as service providers and network operators, with access to the service data of the service management point SMP through a public tele- phone network, such as the PSTN or the ISDN, a cellular radio network (such as the GSM) or a public data network (X. 25, the Internet) and an open inter- face. The SMAP interacts directly with the SMP. Furthermore, the SMAP can provide access to a network element of another telecommunications network.

The operator can define and redefine tariff models via the SMAP. The SMAP is described in greater detail in PCT patent application W098/41038 which is incorporated herein by reference.

Network operators and service providers are nowadays separated.

A service provider buys the required bearer services from a network operator.

A network operator may also be a service provider. An operator may also have multiple service providers.

Figure 2 is a block diagram showing the relevant parts of the SMP in the first preferred embodiment of the invention. In the first preferred em- bodiment of the invention, each voucher type VT is associated with one tariff model TM-ID and subscriber information SI comprises information about the voucher type currently in use, VTu. With this information, the tariff to be used is easily found when needed. Besides the voucher type VT and the tariff model identifier TM-ID, voucher information VI may comprise also other information like a CV indicating how many months the credit is valid for recharge and a voucher price VP as is illustrated in the example in Figure 2.

The tariff model TM comprises a tariff model identifier ID, weekday definitions WD, time definitions T, prices per minute P and in the example il- lustrated in Figure 2, also prefixes Pr. With prefixes it is possible to have dif- ferent call prices within one tariff model to different telephone numbers. The price without a prefix is used when the dialled number does not match any prefix defined in caller's tariff model. Each tariff model comprises preferably a unique tariff scheme. For example tariff model 1 is for persons normally calling during office hours whereas tariff model 2 is for persons calling in the evenings and weekends. In the tariff model 1 the possibility to differentiate call prices by a prefix is used: certain calls to/in Finland are cheaper than other calls during office hours. The tariff models illustrated in Figure 2 are purely illustrative. The service provider can define various tariff models, change definitions and add new models. The tariff model may have different prices for data calls, multime- dia calls or messages, short messages, or prices for calls where also the called person is charged, for example. The simplest tariff model is a model where one price is used all the time.

Subscriber information SI comprises in the first preferred embodi- ment subscribers'phone numbers MSISDNs, each associated with a profile identifier P-ID and a voucher type currently in use VTu. Instead of or in addi- tion to MSISDNs, subscribers identifiers IMSIs may also be used in other em- bodiments. The profile identifier identifies the profile whose information is to be used with this subscriber.

Predefined profile information PP comprises at least a profile identi- fier P-ID and voucher types allowed to that profile, VTa. With the allowed voucher types VTa, the service provider can restrict the vouchers the sub-

scriber is allowed to use. One subscriber may use all kind of vouchers, whereas another subscriber may be restricted to only one voucher type. These allowed voucher types are used during recharges as illustrated in greater de- tail in Figure 4. The predefined profile may also comprise values for different kind of prepaid service attributes, for example an indication how to calculate a new credit when a subscriber deposits.

In the second preferred embodiment of the invention, all subscrib- ers are required to use only one kind of tariffing and only one kind of voucher.

Thus the allowed voucher types VTa comprise only one voucher type. The tariff model identifier TM-ID is either in the voucher information (as in Figure 2) or in the prepaid profile definitions. In the second embodiment there is no need to store information indicating the currently used profile VTu in the subscriber information SI since it is the same as the only allowed voucher type VTa in the prepaid profile information.

The third preferred embodiment of the invention differs from the first preferred embodiment in that no prepaid profiles are used. Thus all subscrib- ers can use all kinds of vouchers. Naturally, in the third preferred embodiment of the invention no prepaid profile information is maintained.

In the fourth preferred embodiment of the invention, all subscribers are required to use only one kind of tariffing but some of them are allowed to use different kind of vouchers. This embodiment differs from the first embodi- ment of the invention in that the tariff model identifier is defined either in the prepaid profile information or in the subscriber information, not in the voucher information. In this embodiment the difference between vouchers could be the price of the vouchers. Also subscribers having a different prepaid profile can have different kinds of charging, even if they use the same voucher type.

In the fifth preferred embodiment, no prepaid profiles are used and the subscriber information SI also comprises information about allowed voucher types VTa.

In another embodiment of the invention one tariff model is defined to be a default model which is used when no other model is defined for that subscriber or voucher. The advantage of this embodiment is that there is no need to add a tariff model to old subscriber information or voucher information.

These embodiments are only illustrative and different kinds of fur- ther embodiments can be built by taking a single feature or features of them and combining them.

Figure 3 is a flow chart illustrating an example of how the charging base is determined according to the first preferred embodiment of the inven- tion. In this example it will be assumed that the IN and, more precisely, the SCP is responsible for keeping track of the available credit of the prepaid sub- scriber, but this is not necessary to the invention. It is also possible that it is the MSC (SSP) that keeps track of the available credit of the prepaid sub- scriber. Another assumption, made here, is that the SCP stores the available credit to an IN database called Service Data Point (SDP, not shown separately in Figure 1) which is a database for the SCP. It is also assumed that the call made here is not an emergency call.

Referring to Figure 3, a prepaid subscriber has dialled numbers in- dicating that he wants to make a call which is charged from him. The SSP no- tices that the caller is a prepaid caller and sends a prepaid service request to the SCP. In step 301, the SCP deduces from the service request the caller's identification, which in the first preferred embodiment of the invention is the MSISDN. In step 302, it is checked if the subscriber's available credit is zero, i. e. has he used all his money. Since the available credit is stored in the SDP, it did not have to be transferred to the SCP. If the available credit is zero, call connection is terminated in step 303. In some other embodiments some other credit limit than zero may be used.

If a subscriber still has some money on his account, the SCP ob- tains in step 304 the voucher type currently in use, VTu, from the subscriber information SI located in the SMP on the basis of the MSISDN. The SCP then obtains in step 305 the tariff model identifier TM-ID from voucher information VI located in the SMP on the basis of VTu. In step 306 the tariff scheme in the tariff model is obtained from the tariff model information TM located in the SMP on the basis of the TM-ID.

The SCP then notifies in step 307 the switching point (SSP) by sending an instruction message of the events which affect call price formation and are to be reported by the switching point (SSP) to the control point (SCP) in a report message.

When the call is connected, the SCP reduces in step 308 the value of available credit during the call according to the tariff scheme in the tariff model. Naturally, the SCP adapts, when needed, reduction of the available credit according to the messages received from the SSP.

In other embodiments of the invention described in Figure 2, the tariff model to be used may be searched differently from what is described above in Figure 3 depending where and what information is required to find out the tariff model.

In some other embodiments of the invention the SCP may send the MSISDN to the SMP, and SMP carries out the data search described in steps 304-306 and sends as a response to the SCP the tariff scheme in the tariff model.

Figure 4 is a flow chart illustrating the depositing in the first pre- ferred embodiment of the invention. In this example it is assumed that the IVR is taking care of the depositing and the voucher is assumed to be valid. In the example illustrated in Figure 4, it is also assumed that the voucher identifica- tion numbers are used to identify the type of the voucher, so that e. g. when two types of vouchers are used, the identification numbers on list 1 are of type 1 and the missing numbers are of type 2. It is, however, irrelevant to the in- vention how the type of the voucher is determined.

Referring to Figure 4, a subscriber has bought a voucher from a shop, called to the IVR and selected to deposit the voucher. The subscriber is assumed to be a prepaid subscriber, otherwise he cannot deposit. It is also assumed that the IVR checks at the beginning of the call if the caller is a pre- paid subscriber, and if not, then the call is disconnected or connected to cus- tomer service.

Figure 4 begins in step 401, where the IVR deduces the caller's identification, which is in the first preferred embodiment the MSISDN. On the basis of the MSISDN the IVR obtains, in step 402, the caller's prepaid profile identifier P-ID from the subscriber information SI located in the SMP. On the basis of profile identifier P-ID, the IVR obtains, in step 403, the allowed voucher types VTas from the predefined profile information PP located in the SMP. In embodiments where the profile information also comprises other in- formation related to depositing, this information is also obtained in step 403. In step 404, the IVR prompts the subscriber for voucher identification ID. The voucher identification number ID is received in step 405. The validity of the voucher is checked (not shown in Figure 4) and after that, in step 406, the IVR determines the type T of voucher e. g. by using the identification number and going through list (s) in order to find out the types. After the voucher type T is determined, the IVR checks, in step 407, if the voucher type is an allowed one.

In other words, the IVR checks whether the type T belongs to the allowed voucher types VTas. If so, the IVR continues depositing in step 408, the de- tailed steps of which are not shown in Figure 4. The depositing is carried out according to prior art, but in the future the depositing may also be carried out by new depositing methods not known today. If the deposit was carried out (step 409), in step 410 the IVR sets in the subscriber information the voucher type currently in use VTu to voucher type T and then ends the depositing in step 411, the detailed steps of which are not shown in Figure 4.

If the deposit is not carried out (step 409), e. g. because the caller changes his mind due to losing current credit, then the IVR gives an audio message"goodbye"in step 412 and no subscriber-related information is changed. The call is disconnected.

If the voucher which the caller is trying to deposit is not one of the allowed voucher types (step 407), then the IVR quits without doing any updat- ing and gives in step 412 an audio message telling that the voucher type the caller is trying to deposit, is not an allowed one. The IVR also gives in the audio message the allowed voucher types VTas in step 412.

In some other embodiments of the invention the IVR may send the MSISDN to the SMP, and the SMP performs the data search described in steps 402 and 403 and sends as a response to the SCP the allowed voucher types VTas.

The steps have not been set out in absoute time sequence in Fig- ures 3 and 4. Some of the above steps may take place simultaneously or in a different order, for example steps 401-403 and 404-406. Some steps may also be skipped, like the step 402 in embodiments where subscriber information comprises allowed voucher types VTas. Other steps not shown in Figures 3 and 4 may also occur between the steps stated above. Instead of some steps shown in Figures 3 and 4, some other step having the same result, may be performed. For example in some embodiments, step 304 may be replaced by steps where the voucher number currently in use is used for determining the voucher type.

The present invention can be implemented in existing network ele- ments. They all have processors and a memory with which the inventive func- tionality described below can be implemented. The functions described above may be located in one network element or some of them may be in one ele-

ment and the others in other elements regardless of how they are located in the examples which illustrate the invention.

Although the invention is described above assuming that the sub- scriber is a prepaid subscriber and the system is a prepaid system, the inven- tion may be implemented also for conventional subscribers who are charged afterwards. When the implementation involves conventional subscribers, the tariff model identifier is preferably added to the subscriber information stored in the subscriber information database, such as a home location register in the GSM system. It is also possible to use profile definitions with conventional subscribers. This invention is not limited to mobile systems but it may be im- plemented in any kind of telecommunications system, e. g. fixed systems, storing subscriber information, like the PSTN (Public Switch Telephone Net- work) or the so called third generation system UMTS (Universal Mobile Tele- communications System) and IMT-2000 (International Mobile Telecommunica- tion 2000). It is also possible to provide prepaid service to fixed subscribers in a similar way as is illustrated here with the above figures.

The accompanying drawings and the description pertaining to them are only intended to illustrate the present invention. Different variations and modifications to the invention will be apparent to those skilled in the art, with- out departing from the scope and spirit of the invention defined in the ap- pended claims.