Background of the invention The background of the invention is discussed briefly in the following.

Prior to 3GPP Release 5, there didn't exist any generally accepted offline charging nodes CCF (CCF, Charging Collec- tion Function) that could be used by the network elements (NE, Network Element) for sending and receiving charging information. This meant that the offline charging solu- tions applied were usually very operator and vendor spe- cific.

Furthermore, currently in Offline Charging and Billing so- lutions in traditional telecom networks, end user billing and settlements between operators has been based on Call Detail Records (CDR, Call Detail Record) generated after service usage e. g. a call has been completed.

The exchanges normally outputs these CDRs in batch mode, and eventually, the CDRs are sent to billing systems, per- haps via a mediation device, for post-processing. FTP and FTAM are examples of protocols used for transferring CDR files. In addition to billing, CDRs are also used for fraud detection, statistics for trend analysis and network

engineering, analysis of customer behaviour e. g. data warehousing, etc.

During the last few years, prepaid charging and billing solutions i. e. Online Charging and Billing solutions, have become very popular. Today, approximately 50 % of all GSM subscribers in the world pay their telephone calls in ad- vance. Real-time charging protocols such as the CAMEL Ap- plication Part are used to support prepaid payment schemes.

Real-time charging mechanisms provide charging data to prepaid systems prior, during and after service usage.

This allows the prepaid systems to decide before or during service usage if the service in question shall be allowed to continue.

Supporting simultaneously two different mechanisms for charging means a lot of overhead for operators. More spe- cifically, it means unnecessarily high processor load in network elements and high costs for operation and mainte- nance. For vendors, two charging mechanisms mean high de- velopment costs and complex products. Every time a new ac- cess type (e. g. WLAN) or application (e. g. web service) is specified two interfaces have to be developed to terminate offline charging in CCF and online charging in OCS.

In 3GPP Release 5 two different mechanisms are specified to support offline and online charging for IMS. The off- line charging is handled in a logical node called Charging Collection Function (CCF) and the online charging is han- dled in the Online Charging System (OCS) logical node.

The same protocol, Diameter, is used for both offline and online charging but since the protocol is terminated in

two distinct entities, the IMS node has to send the same information twice, once to the CCF and once to the OCS.

There is a need for a solution, which can provide both a single point of contact on-line for the network elements, and convert to offline communications towards those user systems that do not implement the generic real-time proto- col.

There is a need for a charging mechanism, which would make a number of different billing alternatives and charging related services possible in a cost-efficient way.

In current mobile networks, there is no centralized node or function where to send the charging data. So there is a need for a common architecture for a specific function where the network elements could send all the charging data for off-line and on-line charging.

To solve the problem described above, charging related in- formation shall be sent from network elements to a new centralized charging proxy in the home network (HPLMN, Home Public Land Mobile Network). A possible scenario also includes sending charging related information from network elements in a visited network (VPLMN, Visited Public Land Mobile Network) to a charging proxy located in HPLMN in real-time.

Another problem is that the network elements don't know where to send charging data, unless a static configuration is used in the network elements. This means that extra configuration of the network elements is needed in order to find out the CCF/OCS location. Alternatively the charg- ing proxy address can be configured in the network ele- ment, and the charging proxy will find the relevant CCF/OCS location.

For this purpose there is a need of being able to specify the CCF/OCS or charging proxy address, on a subscriber ba- sis, and to distribute it to the network elements generat- ing charging information. If the charging proxy address has been specified on a subscriber basis, the network ele- ments will then use the charging proxy address as a con- tact point for sending or receiving charging information.

Summary of the present invention It is an object of the present invention to overcome or at least mitigate the disadvantages of the prior art. The present invention provides a system and a method for charging in a communication network and a communication network charging server.

According to a first aspect of the present invention there is provided a system for charging in a communications net- work having an off-line charging system for non-real time users, an on-line charging system for real-time users, other user system for business support functions, a number of different network domains including one or more network elements providing services to subscribers associated with the network, a multitude of network elements connected to said domains and a charging proxy server so that the charging proxy server handles combined off-line and on- line charging of the said network elements and collects the charging data from the number of different network do- mains in a communications based on requirements from the user systems, and that the charging proxy server provides a single point of contact to the network elements, and that the charging proxy server handles the distribution of the collected data to user charging systems.

Preferably, the charging proxy server in the charging sys- tem also coordinates the requirements that the different user systems have on the collected data. The sum of all data items required by different user systems is what must be required from the network element.

More preferably, the charging proxy server in the charging system also is capable of changing the format of the data before distributing it further. More preferably, the charging proxy server co-ordinates the distribution of the requirements and information of the charging system to the network elements. More preferably, the charging proxy server supports a subscriber specific registration mecha- nism.

Preferably, the charging system allows a user system to inform the charging proxy server of whether real-time con- trol is required. More preferably, the charging system al- lows the user system to indicate which data items it is interested in. More preferably, the registration mechanism is manual. Alternatively, the registration mechanism is automatic.

Preferably, the charging proxy server in the charging sys- tem supports a distribution mechanism of incoming charging messages.

More preferably, an incoming message is first distributed to the user system, which has the real-time control, and based on the response, a control message is sent back to the network element. More preferably, the charging is initiated by the Network Elements. More preferably, there is more than one Network Element for each subscriber. More preferably, the start of service is flexible on a basis of a call or a session, or other event.

More preferably, when sending charging messages to other user systems, the data sent to the different user systems is filtered out from the superset of data received from the network element. More preferably, in high-load situa- tions, data to non-real-time applications is buffered and distributed when there is enough capacity available in the proxy.

Preferably, the charging proxy server in the charging sys- tem supports a co-ordination mechanism for the require- ments from the different user systems. More preferably, when used charging protocol allows the charging system to control when and which data items are required, the charg- ing proxy server co-ordinates the requirements from the different user systems.

Preferably, in a roaming situation, when the services are provided by the visited network, the charging proxy relays the online credit control requests to the subscriber's home network.

Preferably, when using WLAN access the charging proxy transfers the credit check requests for the usage of WLAN access in the visited network. Preferably, when special- ized services are provided in the visited network the charging proxy sends the credit control request to the lo- cal OCS for rating.

Preferably, when the rating has been performed the charg- ing proxy further relays the request to the user's home network for checking whether there is enough money on the user's account to cover the cost of the service and to monitor the credit control of the service.

Preferably, the charging proxy server in the charging sys- tem provides standardized bi-directional interfaces to-

wards network elements and elements in the service domain, both for real-time and non real-time charging purposes.

More preferably, the offline charging system, on-line charging system or charging proxy address is added as a new subscriber data in HLR/HSS. Alternatively, the offline charging system, online charging system or charging proxy address is sent to PLMN with MAP messages in CS and PS do- mains. Alternatively, the offline charging system, online charging system or charging proxy address is returned from the HSS to the S-CSCF over a Cx interface when requesting subscriber information.

Preferably, the S-CSCF further distributes the offline charging system, online charging system or charging proxy address to a P-CSCF over a SIP interface. Alternatively, the S-CSCF further distributes the offline charging sys- tem, online charging system or charging proxy address to a MRFC over a SIP interface. More preferably, the S-CSCF further distributes the offline charging system, online charging system or charging proxy address to an applica- tion server over an ISC interface.

According to a second aspect of the present invention there is provided a method for charging in a communica- tions network, the charging system having an off-line charging system for non-real time users, an on-line charg- ing system for real-time users, other user system for business support functions, a number of different network domains, including one or more network elements providing services to subscribers associated with the network, a multitude of network elements connected to said domains, and a charging proxy server, the method having the steps of the charging proxy server handling combined the off- line charging and the on-line charging of the said network elements and collecting the charging data from the number of different network domains in a communications network

based on requirements from the user systems, and the charging proxy server provides a single point of contact to the network elements, and the charging proxy server handling the distribution of the collected data to user charging systems.

Preferably, the charging proxy server is providing stan- dardized bi-directional interfaces towards network ele- ments and elements in the service domain, both for real- time and non real-time charging purposes. More preferably, the charging proxy server is providing standardized bi- directional interfaces towards network elements and ele- ments in the service domain, both for real-time and non real-time charging purposes More preferably, the offline charging system, online charging system or charging proxy address is being added as a new subscriber data in HLR/HSS. More preferably, the offline charging system, online charging system or charg- ing proxy address is being sent to PLMN with MAP messages in the existing CS and PS domains.

Preferably, in IMS domain, the offline charging system, online charging system or charging proxy address is re- turned from the HSS to the S-CSCF over a Cx interface when requesting subscriber information. More preferably, the S- CSCF further distributes the offline charging system, online charging system) or charging proxy address to a P- CSCF over a SIP interface. Alternatively, the S-CSCF fur- ther distributes the offline charging system, online charging system or charging proxy address to a MRFC over a SIP interface. Alternatively, the S-CSCF further distrib- utes the offline charging system, online charging system or charging proxy address to an application server over an ISC interface.

According to a third aspect of the present invention there is provided a charging proxy server in a communications network, the a charging system of said communications net- work having an off-line charging system for non-real time users, an on-line charging system for real-time users, other user system for business support functions, a number of different network domains, including one or more net- work elements providing services to subscribers associated with the network, a multitude of network elements con- nected to said domains, and a charging proxy server, so that the charging proxy server handles combined off-line charging and the on-line charging of the said network ele- ments and collects the charging data from the number of different network domains in a communications network based on requirements from the user systems, and that the charging proxy server provides a single point of contact to the network elements, and that the charging proxy server handles the distribution of the collected data to user charging systems.

Preferably, the charging proxy server also coordinates the requirements that the different user systems have on the collected data. The sum of all data items required by dif- ferent user systems is what must be required from the net- work element. More preferably, the charging proxy server is capable of changing the format of the data before dis- tributing it further. More preferably, the charging proxy server co-ordinates the distribution of the requirements and information of the billing system to the network ele- ments.

Detailed description of certain embodiments As a solution to the problem there is a charging proxy in- troduced into the communication network architecture. The charging proxy provides standardized bi-directional inter-

face (s) towards Network elements in various domains, both for real-time and non real-time charging purposes.

A standardized charging proxy function makes it easier to define standardized interfaces for collecting charging in- formation from various sources (network elements, elements in service domain etc. ), thus avoiding proprietary charg- ing solutions. A centralized charging proxy function sim- plifies the charging information flow and also makes it easier to introduce new elements in the network.

The solution according to the present invention presents a new system for charging in a telecommunication network.

This new charging system enables a combined on-and off- line charging mechanism, which makes a number of different billing alternatives and charging related services possi- ble in a cost-efficient way.

The fact that a large and growing number of subscribers require real-time charging and the fact that real-time charging mechanisms provide a large part of the data which is included in CDRs, makes it feasible to combine on-and offline into one generic, real-time charging mechanism.

From a network element point-of-view, it would mean one charging protocol, and one point of contact to the charg- ing system. However, within the charging system, the in- formation must be filtered and distributed to a number of (legacy) user systems, such as prepaid applications, fraud management applications, billing systems, mediation de- vices etc.

Also the control of what kind of data that is required from the network element, when and how often this data is needed, etc must be a sum of all the requirements that the different systems using the charging data have.

The solution to the problems within the charging system is a charging proxy, which co-ordinates all the requirements that the different applications and systems have on the network elements.

It is also proposed in this patent application that a CCF/OCS/charging proxy address is added as a new sub- scriber data in HLR/HSS (HLR, Home Location Register; HSS, Home Subscriber Server). The CCF/OCS/charging proxy ad- dress is sent to PLMN (PLMN, Public Land Mobile Network), e. g. CS (CS, Circuit Switched), PS (PS, Packet Switched), WLAN (Wireless Local Area Network). When applied to the IMS domain, the CCF/OCS/charging proxy address is returned over a Cx interface to the S-CSCF (S-CSCF, Serving Call Session Control Function) when requesting subscriber in- formation. The CCF/OCS/charging proxy address is also sent to the Service domain to be used e. g. by a Multimedia Mes- saging (MMS) system.

When the CCF/OCS/charging proxy address is available in the Network elements as described above, it enables a more dynamic routing of charging data. This also means that it is quite easy to distribute the CCF/OCS/charging proxy ad- dress to various domains, thus making it possible to cor- relate charging data from different Network elements in- volved in the same call/session/service.

The usage of a CCF/OCS/charging proxy address specified in the HSS/HLR also means that the amount of pre-configured data in the Network elements decreases.

The fact that a large number of subscribers require real- time charging (and the number is likely to grow) and the fact that real-time charging mechanisms provide a large part of the data which is included in CDRs, makes it fea-

sible to combine on-and offline into one generic, real- time charging mechanism.

From a network element point-of-view, this would mean one charging protocol, and one point of contact to the charg- ing system. However, within the charging system, the in- formation must be processed and distributed to a number of (legacy) user systems, such as prepaid applications, fraud management applications, billing systems, mediation de- vices etc.

The solution to the problems within the charging system described above, is a charging proxy server, which co- ordinates the charging information transfer on the offline and online interfaces and provides a single point of con- tact to the network elements.

Brief description of the drawings For a better understanding of the present invention and in order to show how the same may be carried into effect ref- erence will now be made to the accompanying drawings, in which: Figure 1 illustrates the initialisation of a system for charging in a communication network according to the pre- sent invention.

Figure 2 illustrates a system for charging in a communica- tion network according to the present invention.

Figure 3 illustrates a simplified inter-operator message sequence in the system for charging in a communication network according to the present invention.

Figure 4 illustrates another message sequence in the sys- tem for charging in a communication network according to the present invention.

Figure 1 illustrates the initialisation of a system for charging in a communication network according to the pre- sent invention. The charging system according to the pre- sent invention is connected to several domains: Circuit Switched (CS, Circuit Switched) domain 1, Packet Switched (PS, Packet Switched) domain 2, IP Multimedia (IMS, IP Multimedia Subsystem) domain 3, WLAN access 4, Service do- main 5, and other possibly emerging domains 55. The charg- ing system domains are also connected to a home network with a home location register/home subscriber server (HLR/HSS) 6. The charging system has a charging proxy server 7, a Charging Collection Function 8 (CCF), and an Online Charging System (OCS) node 9, and other user sys- tems 65 (e. g. fraud detection system, data warehouse).

The charging system according to the present invention has a charging proxy server 7 that handles all the charging from the different domains 1-5. The charging proxy server 7 handles all non-real-time charging mechanisms towards the Charging Collection Function (CCF) 8 and respectively handles all real-time charging mechanisms towards the Online Charging System (OCS) node 9.

The main purposes of the charging proxy server 7 are real- time and non-real-time charging mechanisms combining off- line charging and credit control (pre-paid is a part of this) and user spending Collection (for example monthly credit limit set by the user him/herself). In Real-time Charging the charging process is performed as part of ren- dering a service. In Non-real-time Charging the charging process is performed while or after the service has been rendered.

The charging proxy server 7 will handle all the connec- tions towards the Charging Collection Function (CCF) 8 and towards the Online Charging System (OCS) node 9. CCF 8 and

OCS 9 will in turn handle the connections towards the business support systems like billing system, interconnect system, data warehouses etc.

The charging proxy server 7 can also be used for other services and applications, which are not shown in the pic- ture.

The following mechanisms are the minimum that must be sup- ported by such a charging proxy server according to the present invention: A subscriber specific registration mechanism, a distribution mechanism of incoming charging messages, and a co-ordination mechanism for the require- ments from the different user systems (CCF, OCS, fraud de- tection system, data warehouse etc.).

A subscriber specific registration mechanism of the proxy server according to the present invention allows a user system to inform the proxy of whether real-time control is required. A practical limitation is that only one user system can have real-time control per subscriber. The reg- istration mechanism would also allow the user system to indicate which data items it is interested in. The regis- tration mechanism can be either automatic, or manual.

A distribution mechanism of incoming charging messages from the network element. An incoming message is first distributed to the user system, which has the real-time control. Based on the response from this user, a control message is sent back to the network element. This must be done in order not to keep the delay before the service is executed as small as possible. A short delay is important, in order not to increase the service establishment/execu- tion time. The charging can be initiated by the Network Elements and also by the end users. There can be more than one Network Elements for each subscriber. The start of

service can be flexible on a basis of a call or a session, or other event.

After this, charging messages to other user systems are sent. The data sent to the different user systems is fil- tered out from the superset of data received from the net- work element. In high-load situations, data to non-real- time applications may be buffered and distributed when there is enough capacity available in the proxy.

In case the charging protocol used allows the charging system to control when and which data items are required, the proxy must co-ordinate the requirements from the dif- ferent user systems. The sum of all data items required by different user systems is what must be required from the network element. The timing of when data should be pro- vided by the network element must be the strictest re- quirements of all the user systems.

This invention enables a combined on-and offline charging mechanism, which makes a number of different billing al- ternatives and charging related services possible in a cost-efficient way.

Figure 2 illustrates a system for charging in a communica- tion network according to the present invention. The charging system according to the present invention has a home network 10 with a home subscriber server (HSS) 11, a Charging Proxy server 12, a charging collection function (CCF) 13, an Online Charging System (OCS) node 14, an S- CSCF server 15, a MRFC server 16, and an Application Server 17.

In the figure also another 3GPP visited network 18 with a Charging Proxy server 19, a charging collection function (CCF) 20, an Online Charging System (OCS) node 21, an P-

CSCF server 22, and an Application Server 23. In the fig- ure also a WLAN access network 24 is shown with an end user terminal 25.

The charging proxy is located in the architecture where both WLAN and IMS domains are combined. The charging proxy acts as a 3GPP Accounting server towards the WLAN access but combines also the offline and online charging inter- faces from the existing IMS network elements.

The concept can be used also for load-sharing purposes. By allocating several charging proxies the signalling load from the network elements can be distributed between nodes, thus avoiding over-loading one node and providing redundancy in the network in case of failure situations.

It has been proposed to use basic AAA architecture to sup- port charging for WLAN, where a 3GPP specific AAA server distributes offline and online messages to CCF and OCF, respectively. In a system for charging according to the present invention a more generic charging proxy is used thus extending the applicability of the above AAA server.

In addition to the existing solutions the proposed charg- ing proxy is used to provide one generic interface towards existing network elements, such as IMS nodes, as well as new emerging applications.

It is presented in this patent application that the CCF/OCS/charging proxy address is transferred from S-CSCF to other IMS nodes using appropriate signalling protocols e. g. SIP towards other IMS nodes, ISC towards Application Servers, a specific signalling protocol (e. g. DIAMETER) between the charging proxies belonging to different PLMNs etc.

Figure 3 illustrates a simplified message sequence in the system for charging in a communication network according to the present invention. The figure shows how the credit control for services in visited network can be offered us- ing charging proxies.

In a roaming situation, if the services are provided by the visited network, the charging proxy relays the online credit control requests to the subscriber's home network.

In case of WLAN the charging proxy transfers the credit check requests for the usage of WLAN access in the visited network.

In case some specialized services are provided in the vis- ited network (e. g. find the nearest restaurant'-type of service built using IMS application servers) the charging proxy can send the credit control request to the local OCS for rating since most likely the home OCS does not have knowledge about the rating plans of the services provided in the visited network. When the rating has been performed the charging proxy can further relay the request to the user's home network for checking whether there is enough money on the user's account to cover the cost of the ser- vice and to monitor the credit control of the service.

Figure 4 illustrates another message sequence in the sys- tem for charging in a communication network according to the present invention. The figure shows a simplified se- quence on how the offline and online interfaces can be combined using the charging proxy in home network. The network element (NE) might be located in a visited network and there can be additional charging proxies between the NE and the charging proxy but they have been left out of the figure for simplicity reasons.

After the user has been authenticated and authorized the network element sends an initial charging request (e. g.

Diameter Accounting Start record) to charging proxy. This request may contain the user's payment option information received prior to the request (e. g. during authentica- tion/authorization).

If the payment option is not known the charging proxy can optionally make a query to a subscriber database (e. g. HSS or OCS internal database) to find subscriber's payment op- tion and the addresses of the nodes to which the messages should be distributed. Alternatively the addresses can be configured in the charging proxy or be included in the messages from the NE.

In the sequence above, the initial request is relayed to the OCS for a credit check. The result containing credit control information (e. g. reporting thresholds) is re- turned to the NE via the charging proxy. The initial re- quest is also sent to the CCF (or other nodes utilizing the usage data information, e. g. fraud detection system).

When a reporting threshold expires (e. g. granted time du- ration) the NE sends an interim request to the charging proxy that distributes the message to the OCS and CCF (or other nodes utilizing the usage data information, e. g. fraud detection system). The same applies to the final re- quest when the service execution ends.

Different combinations of distributions are possible, e. g. the messages are only sent to OCS, only to CCF or both to OCF and CCF.

The charging proxy may contain more intelligent logic to handle the charging data. E. g. it can collect information from several charging requests coming from the NE, buffer

the information and send the information in one request to the CCF, since the reporting interval to the online nodes is likely more frequent than to the offline nodes.

This invention enables a combined on-and offline charging mechanism, which makes a number of different billing al- ternatives and charging related services possible in a cost-efficient way. The invention also provides a mecha- nism to support inter-operator credit control in IP net- works.