WO2008113408A1

WO2008113408A1 - Method and apparatus for use in a communications network

Info

Publication number: WO2008113408A1
Application number: PCT/EP2007/052565
Authority: WO
Inventors: Jan Dahl; Manuel Cardeno Triano
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2007-03-19
Filing date: 2007-03-19
Publication date: 2008-09-25

Abstract

A method is disclosed for use in a telecommunications network in which two nodes engage in a negotiation procedure to establish the media components of a multimedia session between them, with information describing the media components being sent to a charging function of the network during the negotiation procedure for use in charging and/or rating the session, the method comprising sending information relating to the status of the media component information to the charging function. The status information may relate to the status of the media component information in the context of the negotiation procedure. The status information may indicate an extent to which the media component information for the session has been agreed in the negotiation procedure.

Description

TITLE OF THE INVENTION

Method and Apparatus for use in a Communications Network

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a method and apparatus for use in a communications network, for example a Universal Mobile Telecommunications System having an IP Multimedia Subsystem.

2. Description of the Related Art

IP Multimedia services provide a dynamic combination of voice, video, messaging, data, etc. within the same session. By growing the number 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, including so-called "combinational IP Multimedia" services.

The UMTS (Universal Mobile Telecommunications System) is a third generation wireless system designed to provide higher data rates and enhanced services to subscribers. UMTS is a successor to the Global System for Mobile Communications (GSM), with an important evolutionary step between GSM and UMTS being the General Packet Radio Service (GPRS). GPRS introduces packet switching into the GSM core network and allows direct access to packet data networks (PDNs). This enables high-data rate packets switch transmissions well beyond the 64 kbps limit of ISDN through the GSM call network, which is a necessity for UMTS data transmission rates of up to 2 Mbps. UMTS is standardised by the 3^rd Generation Partnership Project (3GPP) which is a conglomeration of regional standards bodies such as the European Telecommunication Standards Institute (ETSI), the Association of Radio Industry Businesses (ARIB) and others. See 3GPP TS 23.002 for more details. The UMTS architecture includes a subsystem known as the IP Multimedia Subsystem (IMS) for supporting traditional telephony as well as new IP multimedia services (3GPP TS 22.228, TS 23.228, TS 24.229, TS 29.228, TS 29.229, TS 29.328 and TS 29.329 Releases 5 to 7). IMS provides key features to enrich the end-user person-to-person communication experience through the use of standardised IMS Service Enablers, which facilitate new rich person-to-person (client-to-client) communication services as well as person-to-content (client-to-server) services over IP -based networks. The IMS is able to connect to both PSTN/ISDN (Public Switched Telephone Network/Integrated Services Digital Network) as well as the Internet.

Specific details of the operation of the UMTS communications network and of the various components within such a network can be found from the Technical Specifications for UMTS that are available from http://www.3gpp.org.

The IMS makes use of the Session Initiation Protocol (SIP) to set up and control calls or sessions between user terminals (or user terminals and application servers). The Session Description Protocol (SDP), carried by SIP signalling, is used to describe and negotiate the media components of the session. Whilst SIP was created as a user-to- user protocol, IMS allows operators and service providers to control user access to services and to charge users accordingly. The 3GPP has chosen SIP for signalling between a User Equipment (UE) and the IMS as well as between the components within the IMS.

Further details of the use of SIP within UMTS can be found from the 3GPP Technical Specification TS 24.228 V5.8.0 (2004-03).

Figure 1 of the accompanying drawings illustrates schematically how the IMS fits into the mobile network architecture in the case of a GPRS/PS access network (IMS can of course operate over other access networks). Call/Session Control Functions (CSCFs) operate as SIP proxies within the IMS. The 3GPP architecture defines three types of CSCFs: the Proxy CSCF (P-CSCF) which is the first point of contact within the IMS for a SIP terminal; the Serving CSCF (S-CSCF) which provides services to the user that the user is subscribed to; and the Interrogating CSCF (I-CSCF) whose role is to identify the correct S-CSCF and to forward to that S-CSCF a request received from a SIP terminal via a P-CSCF.

A user registers with the IMS using the specified SIP REGISTER method. This is a mechanism for attaching to the IMS and announcing to the IMS the address at which a SIP user identity can be reached. In 3GPP, when a SIP terminal performs a registration, the IMS authenticates the user, and allocates an S-CSCF to that user from the set of available S-CSCFs. Whilst the criteria for allocating S-CSCFs is not specified by 3GPP, these may include load sharing and service requirements. It is noted that the allocation of an S-CSCF is key to controlling (and charging for) user access to IMS- based services. Operators may provide a mechanism for preventing direct user-to-user SIP sessions which would otherwise bypass the S-CSCF.

During the registration process, it is the responsibility of the I-CSCF to select an S- CSCF if an S-CSCF is not already selected. The I-CSCF receives the required S-CSCF capabilities from the home network's Home Subscriber Server (HSS), and selects an appropriate S-CSCF based on the received capabilities. [It is noted that S-CSCF allocation is also carried out for a user by the I-CSCF in the case where the user is called by another party, and the user is not currently allocated an S-CSCF.] When a registered user subsequently sends a session request to the IMS, the P-CSCF is able to forward the request to the selected S-CSCF based on information received from the S- CSCF during the registration process.

Within the IMS service network, Application Servers (ASs) are provided for implementing IMS service functionality. Application Servers provide services to end- users in an IMS system, and may be connected either as end-points over the 3GPP defined Mr interface, or "linked in" by an S-CSCF over the 3GPP defined ISC interface. In the latter case, Initial Filter Criteria (IFC) are used by an S-CSCF to determine which Applications Servers should be "linked in" during a SIP Session establishment. Different IFCs may be applied to different call cases. The IFCs are received by the S- CSCF from an HSS during the IMS registration procedure as part of a user's User Profile. Certain Application Servers will perform actions dependent upon subscriber identities (either the called or calling subscriber, whichever is "owned" by the network controlling the Application Server). For example, in the case of call forwarding, the appropriate (terminating) application server will determine the new terminating party to which a call to a given subscriber will be forwarded. In the case that an IFC indicates that a SIP message received at the S-CSCF should be forwarded to a particular SIP AS, that AS is added into the message path. Once the SIP message is returned by the AS to the S-CSCF, it is forwarded on towards its final destination, or forwarded to another AS if this is indicated in the IFCs.

In an IMS multimedia session between two entities, SIP requests and answers (see 3GPP TS 24.229) carry the SDP information when the entities try to arrive at a common view of the multimedia session. This is done via an offer-answer mechanism defined by RFC 3264.

The SDP information is passed on to a charging system that uses the information for rating purposes. 3GPP TS 32.260 defines when to send the charging information.

The applicant has appreciated the following problem with the mechanism currently proposed.

The Charging Function (e.g. OCS for online charging, or CDF for offline charging) might be triggered by an Accounting Request (ACR; for offline charging) or Credit Control Request (CCR; for online charging) before the SDP negotiation has been completed. The ACR/CCR does not specify if the included SDP is an offer or an answer. If it is an answer, the negotiation has been completed, but if it is an offer it has not been completed. If the SDP is an offer, the Charging Function will use SDP data that very soon might be changed.

Two examples of this will now be described with reference to Figures 2 and 3 of the accompanying drawings. A first example relates to an online charging situation where SDP data is included in the SIP INVITE message. Figure 2 of the accompanying drawings illustrates an example from the existing standard for online charging, where SDP is included in SIP INVITE.

On receipt of a SIP INVITE message, the Charging Triggering Function (CTF) sends the initial Credit-Control-Request (CCRi), including SDP data, to the Online Charging System (OCS). A SIP INVITE will not contain an SDP answer, only an SDP offer, so the rating of the session will not be accurate. A Credit-Control- Answer (CCA) from the OCS may cause the CTF, for example by arming a trigger, to send CCRu at changes in the media composition.

The problem for online charging is that the negotiated SDP may not be available when 3GPP TS 32.260 prompts a CCR should be sent. When the OCS receives the CCRi message, it starts to work with the received SDP data (which constitutes an offer). When the CCRu message is received, the SDP data (which constitutes an answer) might have been changed, and the OCS must re-rate the session.

A second example relates to an offline charging situation where SDP data is not included in the SIP INVITE message. The second example is illustrated in Figure 3 of the accompanying drawings, which shows an example from the existing standard for offline charging in which SDP is not included in SIP INVITE message, but instead the offer is included in the 200 OK message.

When the CDF receives the ACR (Start) message, it starts to work with the received SDP data (which constitutes an offer). Later, when the ACR (Interim) message is received at the CDF, the SDP data might have been changed and CDF must re-rate the session.

It is desirable to address the problem of incorrect rating in the above-mentioned online and offline charging scenarios.

SUMMARY OF THE INVENTION According to a first aspect of the present invention there is provided a method for use in a telecommunications network in which two nodes engage in a negotiation procedure to establish the media components of a multimedia session between them, with information describing the media components being sent to a charging function of the network during the negotiation procedure for use in charging and/or rating the session, the method comprising sending information relating to the status of the media component information to the charging function.

The status information may relate to the status of the media component information in the context of the negotiation procedure.

The status information may indicate an extent to which the media component information for the session has been agreed in the negotiation procedure.

The negotiation procedure may be one that uses an offer-answer mechanism.

The status information may indicate whether the media component information relates to an offer or to an answer.

The media component information may comprise Session Description Protocol, SDP, information.

The method may comprise sending the status information around the time the media component information is sent to the charging function.

The method may comprise sending the status information when the media component information is sent to the charging function.

The method may comprise sending the media component information.

The method may comprise sending the status information and the media component information in a single message. The status information and the media component information in at least one such message may be encapsulated in different respective parts of the message.

The status information in at least one such message may be encapsulated within a part of the message holding the media component information.

The media component information in at least one such message may be encapsulated in a part of the message holding the status information.

Each such part may comprise at least one Attribute Value Pair.

The method may comprise sending multiple items of media component information in the message, each having its own respective status information.

The network may be a Universal Mobile Telecommunications System comprising an IP Multimedia Subsystem, IMS.

The charging function may comprise an IMS Online Charging System, OCS.

The method may comprise sending the status information in a Credit Control Request message.

The method may comprise sending the status information in a Credit Control Request (Initial) message.

The method may comprise sending the status information in a Credit Control Request (Update) message.

The method may comprise sending the status information in a Credit Control Request (Terminate) message.

The charging function may comprise an IMS Charging Data Function, CDF. The method may comprise sending the status information in an Accounting Request message.

The method may comprise sending the status information in an Accounting Request (Start) message.

The status information in the message may indicate that the media component information relates to an offer.

The method may comprise sending the status information in an Accounting Request (Interim) message.

The method may comprise sending the status information in an Accounting Request (Stop) message.

The status information in the message may indicate that the media component information relates to an answer.

The method may be performed by a Charging Triggering Function of the network.

According to a second aspect of the present invention there is provided an apparatus for use in a telecommunications network in which two nodes engage in a negotiation procedure to establish the media components of a multimedia session between them, with information describing the media components being sent to a charging function of the network during the negotiation procedure for use in charging and/or rating the session, the apparatus comprising means for sending information relating to the status of the media component information to the charging function.

According to a third aspect of the present invention there is provided a program for controlling an apparatus to perform a method according to the first aspect of the present invention or which, when loaded into an apparatus, causes the apparatus to become an apparatus according to the second aspect of the present invention. The program may be carried on a carrier medium. The carrier medium may be a storage medium. The carrier medium may be a transmission medium.

According to a fourth aspect of the present invention there is provided an apparatus programmed by a program according to the third aspect of the present invention.

According to a fifth aspect of the present invention there is provided a storage medium containing a program according to the third aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1, discussed hereinbefore, illustrates schematically the integration of an IP Multimedia Subsystem into a 3 G mobile communications system;

Figure 2, also discussed hereinbefore, illustrates the existing standard in an online charging situation where SDP is included in SIP INVITE;

Figure 3, also discussed hereinbefore, illustrates the existing standard in an offline charging situation where SDP is not included in SIP INVITE;

Figure 4 illustrates an approach taken in an embodiment of the present invention in an online charging situation where SDP is included in SIP INVITE; and

Figure 5 illustrates an approach taken in an embodiment of the present invention in an offline charging situation where SDP is not included in SIP INVITE.

The following abbreviations are used in the above Figures and elsewhere herein:

ACA Accounting Answer

ACR Accounting Request

AVP Attribute-Value-Pair

CCA Credit-Control-Answer CCR Credit-Control-Request

CCRi Credit-Control-Request (Initial)

CCRu Credit-Control-Request (Update) CCRt Credit-Control-Request (Terminate)

CDF Charging Data Function

CTF Charging Triggering Function

OCS Online Charging System SDP Session Description Protocol

SIP Session Initiation Protocol

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As described above, at the time the CTF sends the SDP data to the Charging Function (OCS or CDF), the CTF knows the status of the SDP negotiation, i.e. whether the received SDP data constitutes an offer or an answer. According to a basic concept underlying an embodiment of the present invention, information relating to the status of the SDP information is passed on to the OCS or CDF. If the SDP is an offer, the OCS or CDF is able to do a simple rating and wait with some actions until it receives the SDP answer.

For a direct comparison with the previously-considered approach as described above, an embodiment of the present invention will be described in relation to the same two examples described above. It is only necessary to explain here any differences between an approach according to an embodiment of the present invention and the corresponding previously-considered approach.

As before, the first example relates to an online charging situation where the SDP data is included in the SIP INVITE message. The approach taken in the first example embodying the present invention is illustrated in Figure 4.

With an embodiment of the present invention, unlike in the previously-considered approach, information relating to the status of the SDP information is sent from the CTF to the OCS around the time of sending the CCRi message, most preferably in the CCRi message itself together with the SDP information. In the example shown in Figure 4, an indication is included in the CCRi message that the SDP information included in the CCRi message relates to an SDP Offer (rather than to, for example, an SDP Answer). Since the CCRi message includes information indicating that the SDP information is an offer, the OCS can defer some charging actions until it later receives an SDP answer in the CCRu message.

In this respect, therefore, with an embodiment of the present invention, unlike in the previously-considered approach, information relating to the status of the SDP information is sent from the CTF to the OCS around the time of sending the CCRu message, most preferably in the CCRu message itself together with the SDP information. In the example shown in Figure 4, an indication is included in the CCRu message that the SDP information included in the CCRu message relates to an SDP Answer. Information relating to the status of the SDP information can, of course, also be included in other such messages, for example in a CCRt message.

As before, the second example relates to an offline charging situation where the SDP data is not included in the SIP INVITE message. The approach taken in the second example embodying the present invention is illustrated in Figure 5.

With an embodiment of the present invention, unlike in the previously-considered approach, information relating to the status of the SDP information is sent from the CTF to the CDF around the time of sending the ACR (Start) message, most preferably in the ACR (Start) message itself together with the SDP information.

In the example shown in Figure 5, an indication is included in the ACR (Start) message that the SDP information included in the ACR (Start) message relates to an SDP Offer (rather than to, for example, an SDP Answer). Since the ACR (Start) message includes information that the SDP information relates to an offer, the CDF can defer some charging actions until it later receives an SDP answer in the ACR (Interim) message.

In this respect, therefore, with an embodiment of the present invention, unlike in the previously-considered approach, information relating to the status of the SDP information is sent from the CTF to the CDF around the time of sending the ACR (Interim) message, most preferably in the ACR (Interim) message itself together with the SDP information. In the example shown in Figure 5, an indication is included in the ACR (Interim) message that the SDP information included in the ACR (Interim) message relates to an SDP Answer. Information relating to the status of the SDP information can, of course, also be included in other such messages, for example in an ACR (Stop) message.

Some more information will now be provided concerning how the SDP status information can be represented in an embodiment of the present invention.

The SDP data itself is sent in the ACR or CCR message by way of the following AVPs:

* [SDP-Session-Description]

* [SDP-Media-Component]

The first AVP above contains all attribute lines (one instance for each line) related to the whole session, and the second AVP above contains all data related to one media component. Both AVPs can thus occur more than once in a request, and the transfer of SDP status can be outside these AVPs or inside.

Perhaps the more straightforward solution is to do it outside, which can be achieved in at least the following two ways.

In a first approach, a new optional "SDP-Status" AVP is added to the existing SDP AVPs. The "SDP-Status" AVP could take the value "offer" or "answer", for example. This would make it possible to define, per ACR or CCR message, whether the included SDP information relates to an offer or an answer.

The AVPs in the first approach are summarised below: [SDP-Status]

* [SDP-Session-Description]

* [SDP-Media-Component]

In a second approach, two new grouped AVPs, both optional, are added that encapsulate the existing SDP AVPs. The CTF could send one or both of these grouped AVPs, depending on availability of information. Sending both SDP-Offer and SDP-Answer can give the Charging Function extra information that can be useful.

The AVPs in the second approach are summarised below:

[SDP-Offer]

* [SDP-Session-Description]

* [SDP-Media-Component] [SDP-Answer]

* [SDP-Session-Description]

* [SDP-Media-Component]

A variant of the first approach above would be to send the SDP status information inside the existing AVPs. This will still only make it possible to send offer or answer, not both at the same time. Sending the SDP status inside could entail insertion of a new

<type>=<value> line representing the SDP status, e.g. with "f=" as type and "offer" and

"answer" as possible values. A new instance of the SDP-Session-Description AVP could be created containing the status and it could be placed first of all SDP-Session- Description instances.

An embodiment of the present invention offers one or both of the following advantages.

The status of the SDP information will facilitate CDF and OCS rating decisions and make it apparent that an ACR or CCR with the SDP answer will arrive shortly.

It will give the OCS an improved basis for a decision as to when to arm triggers. It will be appreciated that operation of one or more of the above-described components can be controlled by a program operating on the device or apparatus. Such an operating program can be stored on a computer-readable medium, or could, for example, be embodied in a signal such as a downloadable data signal provided from an Internet website. The appended claims are to be interpreted as covering an operating program by itself, or as a record on a carrier, or as a signal, or in any other form.

It will also 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 as defined by the appended claims. In particular, it will be appreciated that, although described in relation to a Universal Mobile Telecommunications System having an IP Multimedia Subsystem, the present invention is also applicable to other types of network.

For example, although the above examples are described in the context of a negotiation performed based on the SIP INVITE message, it will be appreciated that RFC 3264 describes other scenarios and possibilities for SDP negotiation that are also applicable to an embodiment of the present invention. The invention is also applicable where a type of negotiation procedure other than the SDP negotation procedure is used.

Furthermore, although 3GPP mentions the Diameter protocol (e.g. ACR/ACA) in relation to the sending of charging data in the offline charging scenario, it will readily be apparent to the skilled person that the RADIUS protocol or another protocol such as

FTP could be used to send a file with charging data in the offline charging scenario. It will also be readily apparent to the skilled person that an embodiment of the present invention need not be implemented in a CTF, but can be implemented in any suitable network node or function.

Claims

WHAT IS CLAIMED IS:

1. A method for use in a telecommunications network in which two nodes engage in a negotiation procedure to establish the media components of a multimedia session between them, with information describing the media components being sent to a charging function of the network during the negotiation procedure for use in charging and/or rating the session, the method comprising sending information relating to the status of the media component information to the charging function.

2. A method as claimed in claim 1, wherein the status information relates to the status of the media component information in the context of the negotiation procedure.

3. A method as claimed in claim 1 or 2, wherein the status information indicates an extent to which the media component information for the session has been agreed in the negotiation procedure.

4. A method as claimed in claim 1, 2 or 3, wherein the negotiation procedure is one that uses an offer-answer mechanism.

5. A method as claimed in claim 4, wherein the status information indicates whether the media component information relates to an offer or to an answer.

6. A method as claimed in any preceding claim, wherein the media component information comprises Session Description Protocol, SDP, information.

7. A method as claimed in any preceding claim, comprising sending the status information around the time the media component information is sent to the charging function.

8. A method as claimed in any preceding claim, comprising sending the status information when the media component information is sent to the charging function.

9. A method as claimed in any preceding claim, comprising sending the media component information.

10. A method as claimed in claim 9, comprising sending the status information and the media component information in a single message.

11. A method as claimed in claim 10, wherein the status information and the media component information in at least one such message are encapsulated in different respective parts of the message.

12. A method as claimed in claim 10 or 11, wherein the status information in at least one such message is encapsulated within a part of the message holding the media component information.

13. A method as claimed in claim 10, 11 or 12, wherein the media component information in at least one such message is encapsulated in a part of the message holding the status information.

14. A method as claimed in claim 11, 12 or 13, wherein each such part comprises at least one Attribute Value Pair.

15. A method as claimed in any preceding claim, comprising sending multiple items of media component information in the message, each having its own respective status information.

16. A method as claimed in any preceding claim, wherein the network is a Universal Mobile Telecommunications System comprising an IP Multimedia Subsystem, IMS.

17. A method as claimed in claim 16, wherein the charging function comprises an IMS Online Charging System, OCS.

18. A method as claimed in claim 16 or 17, comprising sending the status information in a Credit Control Request message.

19. A method as claimed in claim 18, comprising sending the status information in a Credit Control Request (Initial) message.

20. A method as claimed in claim 18, comprising sending the status information in a Credit Control Request (Update) message.

21. A method as claimed in claim 18, comprising sending the status information in a Credit Control Request (Terminate) message.

22. A method as claimed in claim 16, wherein the charging function comprises an IMS Charging Data Function, CDF.

23. A method as claimed in claim 16 or 22, comprising sending the status information in an Accounting Request message.

24. A method as claimed in claim 23, comprising sending the status information in an Accounting Request (Start) message.

25. A method as claimed in claim 19, 21 or 24, wherein the status information in the message indicates that the media component information relates to an offer.

26. A method as claimed in claim 23, comprising sending the status information in an Accounting Request (Interim) message.

27. A method as claimed in claim 23, comprising sending the status information in an Accounting Request (Stop) message.

28. A method as claimed in claim 20, 21, 26 or 27, wherein the status information in the message indicates that the media component information relates to an answer.

29. A method as claimed in any one of claims 16 to 28, the method being performed by a Charging Triggering Function of the network.

30. An apparatus for use in a telecommunications network in which two nodes engage in a negotiation procedure to establish the media components of a multimedia session between them, with information describing the media components being sent to a charging function of the network during the negotiation procedure for use in charging and/or rating the session, the apparatus comprising means for sending information relating to the status of the media component information to the charging function.

31. A program for controlling an apparatus to perform a method as claimed in any one of claims 1 to 29.

32. A program which, when loaded into an apparatus, causes the apparatus to become an apparatus as claimed in claim 30.

33. A program as claimed in claim 31 or 32, carried on a carrier medium.

34. A program as claimed in claim 33, wherein the carrier medium is a storage medium.

35. A program as claimed in claim 33, wherein the carrier medium is a transmission medium.

36. An apparatus programmed by a program as claimed in any one of claims 31 to

35.

37. A storage medium containing a program as claimed in any one of claims 31 to 34.