Patent Application
20080126230
The present invention relates to flexible charging mechanisms for IP multimedia services and which are applicable in particular, though not necessarily, to Push-to-talk over Cellular services.
IP Multimedia (IPMM) services provide a dynamic combination of voice, video, messaging, data, etc. within the same session. By growing the numbers of basic applications and the media which it is possible to combine, the number of services offered to the end users will grow, and the inter-personal-communication experience will be enriched. This will lead to a new generation of personalised, rich multimedia communication services.
IP Multimedia Subsystem (IMS) is the technology defined by the Third Generation Partnership Project (3GPP) to provide IP Multimedia services over 3G mobile communication networks. IMS provides key features to enrich the end-user person-to-person communication experience through the integration and interaction of services. IMS allows new rich person-to-person (client-to-client) as well as person-to-content (client-to-server) communications over an IP-based network. The IMS makes use of the Session Initiation Protocol (SIP) and Session Description Protocol (SDP) to set up and control calls or sessions between user terminals and/or servers. IMS sits on top of an access network which would typically be a General Packet Radio Service (GPRS) network but which might use some alternative technology, e.g. WLAN, Fixed access.
Existing cellular telephone network operators have recently experienced tremendous growth in the numbers of subscribers choosing to use so-called “prepaid” subscriptions, i.e. where subscribers deposit an amount of cash (the credit balance) with their operators which is consumed by the subsequent use of services by the subscribers. It is anticipated that the prepaid subscription option will prove equally popular with the users of IMS services. Indeed, the provision of pre-paid services is likely to be a must for widespread take-up of IMS services. The prepaid payment method has the following main characteristics:
An Online/Real-time charging mechanism has been defined by 3GPP and is the preferred way to handle prepaid subscribers. The mechanism has the following characteristics:
In the Session-based Credit Control scenario considered by 3GPP, an OCS receives a request for credit reservation from an IMS SE, rates the request, reserves a suitable amount of money from the user's account and returns the corresponding amount of credit resources to the IMS SE. Note that credit resource may not imply actual monetary credit; credit resources may be granted in the form of units (e.g. data volume, or time) to be metered. Upon reception of a successful credit authorisation answer with a certain amount of credit resources, the IMS SE allows service delivery to the end user and starts monitoring the usage of the granted resources. When the credit resources granted to the end user have been consumed, or the service has been successfully delivered or terminated, the IMS SE reports back to the OCS the used amount. The OCS deducts the used amount from the user's account; the OCS may perform rating and make a new credit reservation if the service delivery is continuing. This process is accomplished with the Session-based Credit Control scenario that includes first interrogation, possible intermediate interrogations, and the final interrogation. Both IMS SEs and the OCS are required to maintain credit control session state. Although 3GPP considers other charging scenarios, the Session-based Credit Control scenario is considered appropriate for most IMS services.
There are a number of IMS Charging Principles which need to be considered when applying the 3GPP OCS charging mechanism to IMS based services. Chief amongst these are:
In today's cellular networks prepaid payment is typically used for services such as Circuit-Switched (CS) voice, GPRS data, Short Message Service (SMS), Multimedia Messaging Service (MMS). Whether subscription-based charging (e.g. a service package for a flat monthly fee) or per-usage charging applies, service-usage is measured using one single mechanism for each service, as follows:
In the above cases, the relevant SEs (MSC, GSN, MMSC) always know what parameter to monitor for each service. In contrast, an IMS service may be charged based on a number of possible service-specific chargeable events. For example, a user of an (IMS-based) Push-to-Talk over Cellular (PoC) service (a walkie-talkie type service) may be charged based on the number of sent and/or received talk bursts, or the duration in seconds of the sent and/or received talk bursts, or the session time, etc. In addition, a user may be charged differently based on whether he/she originates or terminates the session, whether he/she is the “session-owne” or a session-participant. Moreover, different charging models may apply to different categories of user (e.g. based on the type of subscription) for the same service/feature, within an operator's network (e.g. based on type of subscription).
It would be desirable for an operator to be able to manage charging models for IMS services and subscribers in a flexible manner and from a centralised element, e.g. the OCS.
According to a first aspect of the present invention there is provided a method of processing service related accounting requests at an Online Charging System of an IP Multimedia Subsystem, the method comprising:
Embodiments of the invention provide the following advantages over the state of the art:
Preferably, the method of the first aspect comprises checking the account of the subscriber associated with the request prior to sending to the Serving Element said accounting response. Said steps of selecting one or more of the supported measuring methods and determining an amount of granted service units may be based upon the account balance and/or the subscription type of the subscriber.
According to a second aspect of the present invention there is provided a method of controlling subscriber charging at an IP Multimedia Subsystem Serving Element of an IP Multimedia Subsystem, the method comprising:
The chargeable events measuring methods supported by the Serving Element include one or more of: IMS service session time, service sent and/or received talk bursts, sent and/or received data volume. Table 1 below provides further details.
The invention is applicable in particular to Push-to-talk Over Cellular (PoC) services. In this scenario, the IP Multimedia Subsystem Serving Element is a PoC server. A charging model may be provided for each PoC user and/or feature.
Preferably, said accounting request and response are Diameter-Accounting-Request (ACR) and Diameter-Accounting-Answer (ACA) messages respectively.
Push-to-talk over Cellular is a walkie-talkie type of service defined by an industry consortium. For further details see Push-to-Talk over Cellular (PoC) Release Phase 1. Four types of PoC talk session have been defined, namely Instant Personal Talk, Ad-hoc Instant Group Talk, Instant Group Talk, and Chat Group Talk. Table 1 shows examples of PoC talk session charging model that may be supported via the OCS mechanism.
For Instant Personal Talk and Ad-hoc Instant Group Talk the following charges may apply:
For Instant Group Talk and Chat Group Talk the following charges may apply:
The different charging basis for these different services, as well as the differing charging models of different users, necessitates a flexible mechanism for defining in real-time what credits must be issued and what session data must be collected in order to control service use by prepaid subscribers. It is proposed here to introduce a process for the communication of service-specific supported measurement methods (in addition to service-specific rating input) from IMS SEs to the OCS, at the time that a IMS SE requests credit authorisation, such that, based on received inputs and the charging model in force, the OCS is able to select the types and amount of granted credit resources to be returned to the IMS SE.
This approach is be further illustrated by the following example:
When an IMS service is invoked, the responsible IMS SE, i.e. PoC server, shall send to OCS a Diameter Accounting-Request (ACR) message including:
The OCS shall rate the IMS service request (centralised rating), check the user's balance, and, based on the charging model in force (centralised management of charging model), reserve a suitable amount and type of credit units. The OCS shall send to IMS SE a Diameter Accounting-Answer (ACA) message including:
Upon IMS service invocation, the concerned IMS SE performs credit authorisation with money reservation towards PPS (session-based charging scenario). The IMS SE provides the following service-specific information to PPS in a Diameter Accounting-Request (ACR) command:
The PPS rates the IMS service request (centralised rating), checks the user's balance, and, based on the charging model in force (centralised management of charging model), reserves a suitable amount and type of credit units. The PPS provides the following service-specific information to the IMS SE in a Diameter Accounting-Answer (ACA) command:
NOTE: more than one set of “service-specific event to be measured” and “granted service-unit” may be sent to IMS SE if, for a given service, the user shall incur multiples charges, e.g. both session-time and sent-talk-burst.
To provide service-specific rating input and to notify support for several measuring methods for the same service from IMS SE to PPS, as well as to provide the charging model in force from PPS to IMS SE, it is proposed to include in the Diameter ACR/ACA commands the Multiple-Services-Credit-Control AVP (M-S-C-C) (see IETF DCC).
The Multiple-Services-Credit-Control AVP may also be used when multiple IMS services are invoked in the same IMS session.
The SE initiates an accounting session towards the PPS prior to service execution. The PPS determines the price of the service and reserves the corresponding monetary amount from the user's account. The PPS authorises the service execution by granting service units (e.g. time, data volume) to the IMS SE that may initiate service execution. The reservation from the user's account is valid for a certain duration after which the reservation expires; the interim interval is used to guarantee that the SE reports the used service units before the reservation in the users account expires.
When all the granted service units are spent by the service, when there is a change in the rating conditions (e.g. change in media components), or when the interim interval expires, the SE reports the used service units and requests a new credit reservation from the PPS. The PPS refunds the reserved credit amount and deducts the used monetary amount from the end user's account. The PPS authorises the continued service execution by granting service units (e.g. time, data volume) to the SE. Note that if the service execution time is so short that neither the interim interval nor the granted units expires, additional interim reports are not needed.
When the subscriber terminates the service delivery, the SE reports back the last used service units. The PPS refunds the reserved credit amount and deducts the used monetary amount from the user's account.
1. Before the service can be provided to the end user, the IMS SE needs to know if the subscriber has enough credit in his/her account. In this case the SE requests to have the service rated
2. An ACR is sent to the PPS. The ACR includes:
NOTE: in this example two M-S-C-C AVPs are shown. In general, several M-S-C-C AVPs may be included, one for each measurement method supported by the IMS SE for the concerned service-type and party-role combination.
3. The PPS rates the service, based on the contents of the received Service-parameter-info, makes a credit-reservation from the end-user's account (that covers the cost of the service). For the purpose of this scenario the user's credit balance is assumed to be sufficient.
4. A successful result is returned from the PPS in an ACA, the ACA including the granted amount of events and the granted reservation lifetime (in the Accounting-Interim-Interval AVP). The ACA includes:
5. Service delivery starts and the reserved units are concurrently controlled
6. During the service delivery, when the granted units have been consumed by the service, when there is a change in the rating conditions (e.g. media component changes) or the Acct-Interim-Interval expires, the SE sends an ACR to report the Used-Service-Unit to PPS. The ACR includes:
7. The PPS deducts the amount used from the account. PPS rates the service, based on the contents of the Service-Parameter-Info AVP, checks the subscriber's account balance and performs a new reservation of the checked amount from the account
8. A successful result is returned from PPS in an ACA, the ACA including the granted amount of events and the granted reservation lifetime (in the Accounting-Interim-Interval AVP). The ACA includes:
The SE continues monitoring the usage of the granted-service-units.
9. Service delivery continues and the reserved units are concurrently controlled. Steps from 6 to 9 can be repeated several times
10. When service delivery is completed (or the granted units have been consumed), the SE sends an ACR to terminate the accounting session and report the used units. The ACR includes:
11. The PPS deducts the used units
12. The PPS sends back an ACA indicating successful operation
It will be appreciated by the person of skill in the art that various modifications may be made to the above described embodiments without departing from the scope of the present invention.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP04/51063 | 6/8/2004 | WO | 00 | 9/5/2007 |
