Abstract:
There is disclosed a method for charging for services in an IP based communication system, comprising: establishing an accounting session between a network element and a charging function for the session; and initiating a change in the accounting session at the charging function.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to the provision of charging services in Internet protocol networks, and particularly to the updating of accounting sessions during charging.  
       BACKGROUND OF THE INVENTION  
       [0002]     The provision of centralised charging functionality is likely to be a key issue in all-IP (Internet protocol) networks, such as mobile communications networks in which a packet switched cellular network provides access for mobile users to services provided by external IP networks.  
         [0003]     Diameter is an IETF protocol that has been specifically designed for the Internet infrastructure. Diameter unifies authentication, authorization and accounting (AAA) transactions. The accounting related extension of the base Diameter protocol is likely to be used in networks which are all-IP (Internet Protocol) based for charging purposes.  
         [0004]     An essential feature of the provision of charging functions in all-IP based networks is that on-line charging must be provided for, which may require for the information associated with an accounting session to be updated dynamically. However, the existing Diameter protocol does not specifically allow for on-line charging capability.  
         [0005]     It is an object of the present invention to provide an improved technique for charging in IP networks, which addresses one or all of the above-stated problems.  
       SUMMARY OF THE INVENTION  
       [0006]     According to the present invention there is provided a method for charging for services in an IP based communication system, comprising: establishing an accounting session between a network element and a charging function for the session; and initiating a change in the accounting session at the charging function.  
         [0007]     The step of initiating a change in the accounting session may comprise transmitting a request to update the accounting session from the charging function to the network element.  
         [0008]     The request may be an update accounting request message. Responsive to the request the network element may implement a change in the charging of the accounting session.  
         [0009]     Responsive to the request the network element may transmit an acknowledgement to the charging function. The acknowledgement may be an update accounting acknowledgement message.  
         [0010]     The network element may be a controller of the communications session.  
         [0011]     The step of establishing an accounting session may include establishing an accounting session between the charging function and a further network element.  
         [0012]     The method may further comprise the step of establishing an accounting session between an application for the session and the charging function.  
         [0013]     The method may further comprise the step of establishing an accounting session between a control function for the session and the charging function.  
         [0014]     The change in the accounting session between the network element controlling the session and the charging function may be responsive to a change in the at least one further accounting session.  
         [0015]     The accounting session may be associated with a pre-paid charging function.  
         [0016]     The IP based communication system may support a Diamater IP protocol.  
         [0017]     According to a further aspect of the present invention there is provided an element for monitoring charging in an IP based communication system, comprising: means for establishing an accounting session with an application; means for informing a network element controlling an associated communication session of the accounting session; and means for initiating a change in the accounting session.  
         [0018]     The means for initiating a change in the accounting session may include means for transmitting a request to update the accounting session.  
         [0019]     The request may be an update accounting request message.  
         [0020]     A change in the charging of the accounting session may be implemented responsive to the request.  
         [0021]     Responsive to the request the network element may transmit an acknowledgement to the charging function.  
         [0022]     The acknowledgement may be an update accounting acknowledgement message.  
         [0023]     The network element may be a controller of the communications session.  
         [0024]     The communication system may support a Diameter IP protocol.  
         [0025]     The request signal may be transferred using a Diameter IP protocol. The acknowledgement signal may be transferred using a Diameter IP protocol.  
         [0026]     According to a still further aspect of the present invention there is provided a communication system in which charging for the provision of services is implemented in a session, the system comprising: a network element for controlling the session; an application for the session; a control function for the session; and a charging function, wherein at least one accounting session is established between the charging function and at least one of the network element, the application and the control function, wherein the charging function is adapted to initiate a change in the at least one accounting session.  
         [0027]     The charging is preferably pre-paid charging.  
         [0028]     There is preferably provided a plurality of accounting sessions, wherein the charging function initiates a change in one accounting session responsive to a change in another accounting session.  
         [0029]     In summary, therefore, in embodiments the present invention provides an enhancement to the Diameter IP protocol&#39;s on-line charging capability, by specifying a new message pair for charging information updating purposes. This new message pair is, in a preferred embodiment, a charging function server initiated update-accounting-request, and a corresponding update-accounting-answer.  
         [0030]     Advantageously, the present invention enables effective on-line charging in all-IP networks. The charging function server is adapted to update an accounting session dynamically. Especially advantageously, the Diameter protocol is adapted to enable more flexible charging functionality.  
         [0031]     The invention thus provides for an operator to be able to use the Diameter protocol in a flexible way. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]     For a better understanding of the present invention and as to how the same can be carried into effect, reference will now be made by way of example to the accompanying drawings in which:  
         [0033]      FIG. 1  illustrates the main network elements in an example implementation of the present invention;  
         [0034]      FIG. 2  illustrates the signaling in a preferred embodiment of the present invention; and  
         [0035]      FIG. 3  is a flow chart illustrating the principle steps in implementing the preferred embodiment of  FIG. 2 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0036]     The present invention is described herein with reference to a particular illustrative embodiment. However, such embodiment is presented for the purposes of illustrating the present invention, and does not limit the scope thereof.  
         [0037]     In particular, the present invention is described herein with reference to a particular example of a UMTS network supporting user equipment, such as a mobile station, and providing connections for the user equipment to external IP networks.  
         [0038]     Referring to  FIG. 1 , there is illustrated the main elements of a UMTS network implementing an all-IP Diameter protocol system for the purposes of describing the present invention. In  FIG. 1  only those elements of a UMTS system necessary for supporting the Diameter protocol charging in accordance with the present invention are illustrated. The full implementation of such a system will be apparent to one skilled in the art.  
         [0039]      FIG. 1  illustrates generally a UMTS network infrastructure  10  including a serving GPRS support node (SGSN)  3 , a gateway GPRS support node (GGSN)  5 , a serving call state control function (S-CSCF)  4 , a charging framework (CF)  8  preferably including a combined charging collector function (CCF) and online charging system (OCS), and an application server (AS)  6 . The SGSN  3  provides access over the radio access network  7  for a user equipment  2  to the UMTS network  10 . The SGSN  3  is connected to the GGSN  5  by a link  9 . The GGSN is connected to the S-CSCF  4  by a link  17 . The SGSN and the GGSN represent the packet domain of the network  10  of  FIG. 1 . They provide control and transfer of packets between the UE  2  and applications provided in the network  10  or in other external networks.  
         [0040]     The S-CSCF  4  supports a call session for the user equipment, such as user equipment  2 , connected in the UMTS network  10 . The CF  8  provides the centralized charging function for on-line and off-line charging, and is connected to the S-CSCF  4  by communication link  13 . The CF  8  is additionally connected to the GGSN  5  and the AS  6  by respective communication links  11  and  19 . The AS  6  is connected to the S-CSCF  4  by communication links  15 .  
         [0041]     It should be noted that the elements and connections shown in  FIG. 1  are for the purposes of illustrating an exemplary embodiment of the invention only, and one skilled in the art will fully understand the implementation of a UMTS network  10 .  
         [0042]     The S-CSCF  4  additionally has a connection  12  to an IP network or element of an IP network external to the UMTS network  10 , as described further hereinbelow. In particular, the connection  12  connects to a service provider or terminating part with which the user equipment  2  establishes a session.  
         [0043]     The UMTS network provides access to other, external IP services or networks for the user equipment  2 . For the purposes of the present example, it is assumed that a call session is to be established between the user equipment  2 , and a B-subscriber  22  in a further IP network  18 . The further IP network  18  supports the call session for the E-subscriber  22  with a serving call state control function (S-CSCF)  20 . For the purposes of this example, as the initiating caller the user equipment  2  is considered to be an A-subscriber. For the purposes of supporting the call session, the connection  12  is between the respective S-CSCFs of the respective subscribers.  
         [0044]     The B-subscriber may, for example, be a further user equipment or a service provided by a third party.  
         [0045]     The protocol interfaces for the various IP network elements of  FIG. 1  may be implementation dependent. In a preferred embodiment the S-CSCF  4  is connected to the AS  6  via an ISC interface. The ISC interface may, for example, be a session initiation protocol (SIP) interface. The CF  8  is preferably connected to the S-CSCF  4  via a Diameter protocol represented. The CF  8  is preferably connected to the AS  6  via a diameter protocol.  
         [0046]     Referring to  FIGS. 2 and 3 , an example embodiment of the present invention is now described.  
         [0047]     In a first step, user equipment  2  transmits an INVITE message  100  in the packet domain—as represented by block  101 —to the serving call state control function (S-CSCF)  4  allocated to the call session. In  FIG. 2 , the packet domain  101  represents the SGSN  3  and the GGSN  5 . The communication of signals through the packet domain is well-known to one skilled in the art. The INVITE message represents the initiation of an active communication session by the UE  2 , as represented by step  300  in  FIG. 3 , which requires an accounting session to be initiated to-charge the session.  
         [0048]     Responsive to the INVITE message, in the preferred embodiment an initial accounting is started by the S-CSCF  4 . The S-CSCF sends an ACR(START_RECORD) accounting request message  102  to the CF  8 . The CF  8  replies with an ACA accounting acknowledgement message  103 . If the user equipment  2  is a pre-paid user, an initial threshold value is also sent to the S-CSCF  4  by the CF  8 . The start of the accounting session is represented by step  302  in  FIG. 3 .  
         [0049]     As such, a first accounting session is established with the charging function.  
         [0050]     Following the start of the initial accounting, the S-CSCF  4  transmits an INVITE message  104  to the AS  6 . Responsive to the INVITE message  104 , the AS  6  preferably performs a session based service as represented by step  304  in  FIG. 3 . To perform the session based service, the AS  6  sends an accounting request ACR(START_RECORD) message  106  to the CF  8 . Responsive thereto, the CF  8  replies with an ACA accounting acknowledgement message  107 .  
         [0051]     As such, a second accounting session is established with the charging function.  
         [0052]     The session based service may be a one-time event, for example this ACR may include any sponsorship information, where the AS  6  confirms its identity and also that it will pay a percentage, or a predetermined fixed amount, of certain charges. For example, the AS  6  may inform the CF  8  that it intends to pay for 50% of the Call Control charges and 50% of the mobility management charges, as charged by the S-CSCF  4 . The CF  8  stores this information, and then replies with the ACA accounting acknowledgement message  107 .  
         [0053]     Thereafter, the AS  6  returns an INVITE message  108  to the S-CSCF  4 . The, S-CSCF  4  then forwards an INVITE message  110  towards the terminating party (the B-subscriber  22 ), i.e. the recipient of the call session initiated by the user equipment  2 .  
         [0054]     Responsive to satisfactory acceptance of the call, in accordance with known techniques, the terminating party returns a positive acknowledgement message to the S-CSCF  4 , which message may be a 200 OK message. Such message is not shown in  FIG. 2 , and will be familiar to one skilled in the art.  
         [0055]     Thereafter, a final session data protocol (SDP) takes place between the CF  8  and the UE  2 , as represented by message  111 . A secondary PDP context then takes place in the packet domain, as represented by block  113 . The secondary PDP context is well-known to one skilled in the art.  
         [0056]     The transmission of the final SDP  111  and the activation of the second PDP context  113  complete the establishment of the call between Subscriber A (UE  2 ) and Subscriber B  22 . This is represented in  FIG. 3  by step  306 .  
         [0057]     Thereafter, an accounting session is initiated from the GGSN  5  in the packet domain  101 , as represented by step  308 . In this example the GGSN  5  is the network element (NE) responsible for controlling the session. In alternatives, the network element controlling the &#39;session may, for example, be an application server such as AS  6  or an IP multimedia subsystem (IMS).  
         [0058]     The accounting session is initiated by the GGSN sending an ACT(START_RECORD) message  114  to the CF  8 . The CF  8  replies with an ACA accounting acknowledgement message  116 .  
         [0059]     As such, a third accounting session is established with the charging function.  
         [0060]     The ACA message  116  may include the new tariff. In a pre-paid user scenario, an initial threshold value is sent from the CF  8  to the GGSN  5 .  
         [0061]     Thereafter a 200 OK message  118  is transmitted through the network from the terminating network  18  to the UE  2 , to indicate that the session could be established.  
         [0062]     Thereafter, as represented by step  310  in  FIG. 3  and communication  120  in  FIG. 2 , a communication session is ongoing in which the cost thereof is monitored by the CF  8 .  
         [0063]     Once the session is established and ongoing, in accordance with the present invention the CF  8  may dynamically change the charging capabilities of the session.  
         [0064]     In the example of  FIG. 2 , at some time after the session has begun the CF  8  detects that after a certain time (e.g. after the session has been ongoing for one hour), the use of the packet domain is free for the particular application server being used. As such, the CF 8  sends a UAR (update-accounting-request) message  122  to the GGSN  5 . The UAR message  122  indicates to the GGSN  5  that the accounting session is free of charge from this point onwards.  
         [0065]     Responsive to the UAR message  122 , the GGSN  5  returns a UAA (update-accounting-answer) message  124  to the CF  8 , to acknowledge that the UAR message  122  has been received and acted on. The change to the charging capabilities of the network is indicated by step  312  in  FIG. 3 .  
         [0066]     It should be noted that the update could be performed also towards the S-CSCF  4  and/or the AS  6 .  
         [0067]     Thus the present invention provides for the dynamic change of the accounting session on the initiation of the charging function, particularly in a network utilizing a Diameter protocol for charging.  
         [0068]     The present invention particularly advantageously may be applied in prepaid charging scenarios. A charging function or framework may support pre-paid charging for GPRS or  3 G access and for access to the IP multimedia subsystem (IMS). The invention allows the charging function or framework to inform the network element controlling the session if charging parameters are changed at some point in the session.  
         [0069]     There are various different bases on which the charging parameters may be changed. For example the service provider may increase or decrease some part of the session charge at some stage during the session. This may be because the session has exceeded a certain length of time or cost, or the time of day is such that revised charging costs are in force. Possible alternatives for causing the charging function or framework to vary the cost of the charging session will be readily apparent to one skilled in the art.  
         [0070]     The invention advantageously provides a mechanism for flexible and effective on-line charging in all-IP networks. As the CF is the only node which can combine independent accounting sessions related to the same session, the CF initiated updating mechanism offers an important service.  
         [0071]     In the preferred embodiment, the invention provides for a new message pair in networks implementing charging using the Diameter protocol. The message pair comprises an updating accounting request (UAR) from the charging function or framework, and a corresponding update accounting answer (UAA) to the charging function or frame work. This enables the Diameter protocol to be effectively used for on-line charging in all-IP networks.  
         [0072]     The need for such an ability for the charging function or charging framework to provide dynamic adjustment of the charging parameters is especially applicable in scenarios where accounting sessions have interaction. In such scenarios, -one session may provide another with information about a change in its charging.  
         [0073]     In the example of  FIG. 2 , for example, three accounting sessions are established, as represented by steps  302 ,  304  and  308 .  
         [0074]     The invention may preferably be utilized for on-line charging.  
         [0075]     The present invention is described herein with reference to examples of preferred embodiments for the purpose of illustration, and is not limited to any such embodiments. The scope of the present invention is defined by the appended claims.