WO2004066659A1

WO2004066659A1 - Method for using a special apn for application level signalling

Info

Publication number: WO2004066659A1
Application number: PCT/FI2004/000026
Authority: WO
Inventors: Sami Ala-Luukko; Kai Väänänen
Original assignee: Teliasonera Finland Oyj
Priority date: 2003-01-22
Filing date: 2004-01-20
Publication date: 2004-08-05
Also published as: EP1590981A1; NO20053865L; FI115688B; FI20030100A0; NO20053865D0; FI20030100A

Abstract

A method for transmitting multimedia traffic in a telecommunications system and a telecommunications system comprising information on at least one predefined access point name for multimedia signalling traffic for use in generating a PDP context for the transfer of multimedia signalling traffic and/or at least one predefined access point name for multimedia user data traffic for use in generating a PDP context for the transfer of multimedia user data traffic; the telecommunications system being arranged to select, when generating a PDP context for multimedia signalling traffic or multimedia user data traffic transmission, the name of the access point depending on whether the multimedia traffic to be transmitted is signalling or user data by selecting as the access point name one of the access point names predefined for the multimedia traffic type in question, if at least one access point name has been predefined for said multimedia traffic type.

Description

Method for using a special APN for application level signalling

BACKGROUND OF THE INVENTION

[0001] The invention relates to transmitting multimedia traffic in a telecommunications system and especially in a telecommunications system that comprises a packet-switched access network for providing a connection for at least one terminal to one or more packet-switched data networks through one or more access points of the access network.

[0002] IMS (IP Multimedia Subsystem) is a generic service technology that can be run for instance on the packet-switched portion of GPRS (General Packet Radio Service) and UMTS (Universal Mobile Telecommunications System), which uses Internet Protocol (IP) to combine different multimedia communications elements in one call, for instance. IMS is also known as All IP. 3GPP (3^rd Generation Partnership Project) is responsible for the standardization of the IMS technology for the 3G GPRS environment. However, IMS is independent per se of the used access network technology, so it can also be applied to WLAN (Wireless Local Area Network) or 2.5G mobile systems, for example.

[0003] IMS traffic is divided into signalling and actual user. traffic. Conventionally, in mobile systems, when visiting the network of a foreign operator, the user has only paid for the services that s/he has initiated or received (in other words, user traffic). In GPRS network visitation, the end user pays for both the transmitted and received data. For GPRS network components (e.g. the serving GPRS support node SGSN), all IMS traffic is user data. In other words, a serving GPRS support node SGSN according to the specification 3GPP release 99 cannot distinguish between IMS signalling and IMS user data, which means that it is not necessarily possible to separate signalling and user data in billing. IMS components can distinguish between signalling and user data traffic, and this information can be transmitted to the gateway GPRS support node GGSN. However, when a user visits the GPRS network of a foreign operator, GGSN remains in the home network, and the visited network cannot separate IMS signalling and IMS user data.

[0004] One problem in the arrangement described above is that it may be difficult for an end user to understand that s/he must pay for signalling that s/he has not explicitly generated.

[0005] In the 3GPP specifications (3GPP TS 23.207 v5.2.0, page 30), there is a standardized procedure, in which a special PDP context is reserved for signalling, which the user/terminal can use for signalling only. In this case, a secondary PDP context (3GPP TS 23.060 v4.2.0, pages 124 to 126) is always generated for transmitting actual user data traffic. However, according to the procedure, the separation takes place in GGSN, which means that SGSN, for example, cannot identify a signalling PDP context and consequently distinguish between the signalling traffic and user data traffic. In such a case, during a network visit, the elements of the visited network do not know what type of traffic is transmitted within each context, and the above-mentioned problem in billing, for example, still exists.

BRIEF DESCRIPTION OF THE INVENTION

[0006] It is thus an object of the invention to develop a method and an apparatus implementing the method so as to solve the above-mentioned problems or to at least alleviate them. The object of the invention is achieved by a method, telecommunications system and terminal that are characterized by what is stated in independent claims 1 , 9, and 18. Preferred embodiments of the invention are set forth in the dependent claims.

[0007] The invention is based on defining in advance at least one access point name for use in generating a PDP context for multimedia signalling traffic transmission and/or at least one access point name for use in generating a PDP context for multimedia user data traffic transmission, and when generating a PDP context for multimedia signalling traffic or multimedia user data traffic transmission, the name of the access point is selected from the predefined access point names depending on whether the multimedia traffic to be transmitted is signalling or user data, if at least one access point name is defined for use for the multimedia traffic type in question.

[0008] The method and system of the invention provide the advantage that the traffic type transmitted within the PDP context, i.e. whether the transmitted multimedia traffic is signalling or user data, can be identified during billing, for example, on the basis of the access point name associated with the PDP context.

BRIEF DESCRIPTION OF THE FIGURES

[0009] The invention will now be described in greater detail by means of preferred embodiments and with reference to the attached drawing, in which Figure 1 is a simplified block diagram of a telecommunications system, to which the invention can be applied.

DETAILED DESCRIPTION OF THE INVENTION

[0010] The invention can be applied to different telecommunications systems. These systems comprise third-generation mobile systems, such as UMTS (Universal Mobile Telecommunications System). In the following, the invention will be described using a 3GPP IMS (IP Multimedia Subsystem) system, i.e. an UMTS system that is based on IP technology and defined by 3GPP rrl

(3 Generation Partnership Project), as an example, without limiting the invention thereto. The specifications for mobile systems and especially third- generation mobile systems progress rapidly; as a result of this, the invention may require additional changes. Therefore, all terms and expressions should be interpreted broadly, because they are only intended to illustrate and not restrict the invention.

[0011] Figure 1 shows an example of the network architecture of the UMTS system and the IM subsystem attached thereto. It should be noted that for the sake of clarity, the figure only shows the components that are essential for the invention. The system comprises a radio access network RAN that provides wireless access for terminals UE (user equipment), such as mobile stations. The radio access network RAN comprises (not shown in the figure) base stations BS under the control of radio network controllers RNC. The example of Figure 1 further comprises a packet-switched access network that comprises a serving GPRS (General Packet Radio Service) support node SGSN and gateway GPRS support node GGSN, home subscriber server HSS, call session control function CSCF, and domain name system DNS. A core network, such as an IP/ATM (Internet Protocol / Asynchronous Transfer Mode) network, typically connects the support nodes SGSN and GGSN to each other. The shown support nodes SGSN and GGSN may belong to the network of the same operator or the packet-switched access network of the figure may be formed of the subnetworks of different operators, in which case, when the terminal UE visits the network of a foreign operator, SGSN is in the visited network and GGSN in turn in the home network of the terminal UE. If SGSN and GGSN reside in the networks of different operators, there may be other network elements between them, which are, however, not shown in the figure for the sake of clarity. [0012] The serving GPRS support node SGSN is a node that serves the terminal UE in its area. In a cellular packet radio network, each support node SGSN provides a packet data service within its service area for terminals UE in the area of one or more cells. The gateway GPRS support node GGSN connects the GPRS network of the operator with external packet-switched data networks PSDN, such as IP networks. The term packet-switched data network should, in this context, be understood broadly, and it may refer to an Internet, intranet, WAP, or multimedia IP system, or merely to a single server element, or the like, directly connected to the gateway support node. GGSN serves as a router between an external address and internal routing data (e.g. SGSN). It should be noted that the functionalities of SGSN and GGSN could physically be in the same node. Logically the nodes are, however, separate nodes. Packet-switched access networks of other type can comprise other network elements. The packet-switched access network can be connected to external networks, such as IP networks and PSTN/ISDN networks, as shown in the figure. A gateway unit GW is used in the interworking of the IP access network and conventional circuit-switched networks, such as PSTN. It serves as a gateway for both media (user data) and signalling (transfer of signalling). The home subscriber server HSS logically corresponds to the home location register of the GSM system, where the subscriber information of each subscriber is stored permanently or semi-permanently in such a manner that the subscriber information is associated with a subscriber identifier, which in the GSM system is IMSI. The controlling element CSCF controls the setting up of calls and is responsible for routing calls and comprises, among other things, a function that corresponds to the switching function in an intelligent network. CSCF provides IP call services with end-to-end control. Signalling related to IP call traffic, such as H.323 and SIP (Session Initiation Protocol), terminates at the terminal and CSCF. The Session Initiation Protocol (SIP) developed by IETF (Internet Engineering Task Force) is an application-layer control (signalling) protocol for generating, changing, and ending sessions with one or more participants. These sessions comprise Internet multimedia conferences, Internet call connections, and multimedia distribution. The H.323 standard provides a base for audio, video and data connections in IP-based networks, including the Internet. The H.323 is a recommendation of the International Telecommunications Union (ITU). In other words, CSCF is a network node, to which IP call traffic terminal registers and through which signalling is transferred. CSCF comprises call state models for IP call traffic that are used in controlling call set-up with other network nodes. CSCF can also communicate with IP call traffic application servers (not shown in the figure). CSCF comprises a subscriber database that logically corresponds to the visitor location register of the GSM system. CSCF is responsible for generating both call traffic billing information and service billing information. It should be noted that the location of the state control function CSCF could vary in the system; CSCF may be a separate element or reside in the terminal UE, for instance. In this application, the term 'controlling element' refers generally to the element or entity controlling a call, while CSCF is only one example of such an element.

[0013] For the terminal UE, the GPRS interface of the packet- switched access network comprises one or more individual packet data protocols, i.e. PDP (Packet Data Protocol) contexts, that identify the packet data address that UE can use for transmitting and receiving data packets when the PDP context is active. The PDP context can, thus, be seen as a connection. One multimedia connection can comprise two or more PDP contexts in such a manner, for example, that one PDP context is for signalling and one PDP context is for user data. The PDP context defines various data transfer parameters, such as PDP type (e.g. X.25 or IP), PDP address (e.g. IP address), quality of service QoS, access point name APN and NSAPI (Network Service Access Point Identifier. APN in particular is a logical name that in accordance with the DNS naming conventions identifies the actual access point; in the GPRS system, for instance, APN is a reference to the used gateway GPRS support node GGSN and to an external data network PSDN connected to it. APN indicates to the serving GPRS support node SGSN the name of the used gateway GPRS support node GGSN. APN indicates to the gateway GPRS support node GGSN the external data network PSDN, with which a connections is to be established. APN has two parts: an APN network identifier and an APN operator identifier. The APN network identifier is compulsory and identifies the external data network PSDN, with which a connection is to be established. The APN operator identifier, which is optional, indicates the network to be used during a network visit. When activating a PDP context, the terminal UE can indicate the desired access point name to the support node SGSN, which then, assisted by the domain name system DNS, interprets the name and the actual access point associated with it, and starts to generate the PDP context with the selected access point (GGSN). In practice, IP call traffic is in- visible to the elements of the packet-switched access network. For the support nodes SGSN and GGSN, IP call traffic is just a PDP context with certain service quality requirements. The signalling associated with IP call traffic terminates at the terminal UE and CSCF, so SGSN or GGSN need not understand it.

[0014] IP multimedia traffic or IP call traffic is a general term covering services from a standard VoIP (Voice over IP) to multimedia applications that use IP data, audio and video in IP call traffic. In addition to IP multimedia traffic, the system described above can also support other applications, such as access to the Internet or intranet. Similarly, an IP call refers to a call that utilizes IP-based user data flow and signalling. The user data may comprise several different components, such as audio, video, and data. In addition to calls, IP call traffic may comprise call-like services that may for instance be unidirectional, directed to a group (or groups) and broadcast in a certain area. In IP call traffic, mobile systems utilize new protocols, such as WAP (Wireless Application Protocol).

[0015] According to the invention, at least one access point name (APN) is defined in advance for multimedia signalling traffic for use in generating a PDP context for the transfer of multimedia signalling traffic and/or at least one access point name for multimedia user data traffic for use in generating a PDP context for the transfer of multimedia user data traffic. The access point name can be defined to explicitly or implicitly indicate the type of traffic it is reserved for without this being significant with respect to the basic idea of the invention. Examples of suitable APNs are 'IMS signalling' and 'IMS data'. The only essential thing for the invention is, however, that it is possible to determine on the basis of the access point name, what type of traffic it is at least mainly reserved for, or at least that a PDP context reserved for signalling and/or user data traffic can be identified. It should be noted that the transferred traffic could also comprise other traffic than multimedia signalling or multimedia user data traffic without this affecting the basic idea of the invention. Because the access point name (APN) is a logical reference to the actual access point (e.g. GGSN) and an external data network PSDN, it is possible that the access point names reserved for generating a PDP context for the transfer of multimedia signalling traffic and/or multimedia user data traffic refer to the same physical access point and external data network, even though the actual access point names differ from each other. Information on the predefined access point names should preferably be delivered to all the network elements of the telecommunications system that possibly need the information, for instance to the terminal UE and support nodes SGSN and GGSN of the system. The system administrator of one or more network operators or other systems, for instance, can predefine the names. How the access point names are predefined and who does it is, however, not significant for the basic idea of the invention.

[0016] Further, according to the invention, when generating a PDP context for the transfer of multimedia signalling or multimedia user data traffic, the access point name is selected on the basis of whether the multimedia traffic is signalling or user data by selecting as the access point name one of the access point names predefined for the multimedia traffic type in question, if at least one access point name has been predefined for said multimedia traffic type. In other words, when generating a PDP context for the transfer of multimedia signalling traffic, an access point name predefined for the transfer of multimedia signalling traffic is selected as the access point name to be used (if at least one such name is predefined) and/or when generating a PDP context for the transfer of multimedia user data traffic, an access point name predefined for the transfer of multimedia user data traffic is selected as the access point name to be used (if at least one such name is predefined). It is possible to predefine one or more access point names for signalling traffic only or for user data traffic only. In such a case, an access point name can be selected on other grounds for traffic for which no predefined access point name to be used exists; for instance, it is possible to use a default name of the system.

[0017] According to a preferred embodiment of the invention, the access point name is selected in the terminal UE, and the selected access point name is preferably transmitted from the terminal UE to the packet- switched access network when generating the PDP context. Preferably, this takes place in the Access Point Name field of the Activate PDP Context Request message that is transmitted from the terminal UE to the serving GPRS support node SGSN. The terminal UE is preferably arranged to select the access point name on the basis of whether the multimedia traffic to be transferred is signalling or user data, when it generates the PDP context with the packet-switched access network, and to transmit the selected access point name to the packet-switched access network. For this purpose, the terminal UE preferably comprises information on at least one predefined access point name for use in PDP context generation for multimedia signalling traffic only and/or on at least one predefined access point name for use in PDP context generation for multimedia user data traffic only. It is also possible that another network element selects the access point name.

[0018] Further, according to the preferred embodiment of the invention, the name of the access point used for multimedia traffic is stored in a charging record generated for traffic billing. The charging record, i.e. CDR, is generated from the PDP context in the serving GPRS support node SGSN, for instance, and it contains all the necessary information on traffic within the PDP context for billing, with the exception of the actual price information which is typically generated in a later process. For instance, in the present GPRS systems, the access point name APN is stored in charging records CDR, so for this part the invention does not necessarily require changes to the existing systems. By means of the access point name in the charging record and the invention, the support node SGSN or another network element in a network of a foreign operator can identify whether the charging record is associated with a PDP context generated for the transfer of signalling or user data traffic. According to the preferred embodiment of the invention, the charging records that contain the access point name defined for use in generating a PDP context for the transfer of multimedia signalling traffic only are rejected in the later charging record CDR processing, in which the actual billing information is generated for billing the subscriber. This later charging record processing is typically done for each operator in the operator's billing centre or post-processing system (not shown in the figure), and the resulting invoice is delivered to the home system of the subscriber that used the services. For this purpose, the billing system preferably also comprises information on the predefined access point names. By means of the preferred embodiment of the present invention, it is possible to avoid billing the subscriber for the transfer of signalling traffic and to bill only for the transfer of actual user data traffic even in a situation, in which the terminal UE of the subscriber visits the network of a foreign operator.

[0019] It is obvious to a person skilled in the art that while the technology advances, the basic idea of the invention can be implemented in many different ways. The invention and its embodiments are thus not restricted to the examples described above, but can vary within the scope of the claims.

Claims

1. A method for transmitting multimedia traffic in a telecommunications system that comprises at least one terminal and a packet-switched access network for providing a connection for said at least one terminal to one or more packet-switched data networks through one or more access points of the access network, the method comprising the step of: generating at least one packet data protocol, i.e. PDP, context for the transfer of multimedia signalling traffic between the terminal and access point and/or at least one PDP context for the transfer of multimedia user data traffic between the terminal and access point, wherein the used access point is determined on the basis of a selected access point name, characterized in that the method also comprises the steps of: defining in advance at least one access point name for multimedia signalling traffic for use in generating the PDP context for the transfer of multimedia signalling traffic and/or at least one access point name for multimedia user data traffic for use in generating the PDP context for the transfer of multimedia user data traffic; and selecting, when generating the PDP context for multimedia signalling traffic or multimedia user data traffic transmission, the name of the access point depending on whether the multimedia traffic to be transmitted is of the signalling or user data type by selecting as the access point name one of the access point names predefined for the multimedia traffic type in question, if at least one access point name has been predefined for said multimedia traffic type.

2. A method as claimed in claim 1, characterized in that the access point name is selected in the terminal, in which case the method comprises the step of transmitting the selected access point name from the terminal to the packet-switched access network when generating the PDP context.

3. A method as claimed in claim 1 or 2, characterized by storing the name of the access point used for multimedia traffic in a charging record generated for traffic billing.

4. A method as claimed in claim 3, characterized by rejecting in the billing the charging records that contain the access point name de- fined for use in generating a PDP context for the transfer of multimedia signalling traffic only.

5. A method as claimed in any one of claims 1 to 4, characterize d in that said multimedia traffic is IP multimedia traffic.

6. A method as claimed in any on of claims 1 to 5, characterize d in that the terminal is wireless and that the telecommunications system comprises a wireless access network for providing a wireless connection between the terminal and the packet-switched access network.

7. A method as claimed in any on of claims 1 to 6, characterize d in that the packet-switched access network is a GPRS network.

8. A method as claimed in any on of claims 1 to 7, characterize d in that the packet-switched access network comprises two or more subnetworks managed by different network operators.

9. A telecommunications system that comprises: at least one terminal (UE); and a packet-switched access network for providing a connection for said at least one terminal (UE) to one or more packet-switched data networks (PSDN) through one or more access points (GGSN), the telecommunications system being arranged to generate at least one packet data protocol, i.e. PDP, context for the transfer of multimedia signalling traffic between the terminal (UE) and access point (PSDN) and/or at least one PDP context for the transfer of multimedia user data traffic between the terminal (UE) and access point (GGSN) in such a manner that the used access point is determined on the basis of a selected access point name, characterized in that the telecommunications system also comprises: information on at least one predefined access point name for multimedia signalling traffic for use in generating the PDP context for the transfer of multimedia signalling traffic and/or at least one predefined access point name for multimedia user data traffic for use in generating the PDP context for the transfer of multimedia user data traffic; and the telecommunications system is also arranged to select when generating the PDP context for multimedia signalling traffic or multimedia user data traffic transmission, the name of the access point depending on whether the multimedia traffic to be transmitted is of the signalling or user data type in such a manner that the telecommunications sys- tem is arranged to select as the access point name one of the access point names predefined for the multimedia traffic type in question, if at least one access point name has been predefined for said multimedia traffic type.

10. A telecommunications system as claimed in claim 9, characterized in that the terminal (UE) is arranged to select the access point name, and to send the name of the selected access point to the packet- switched access network when generating the PDP context.

11. A telecommunications system as claimed in claim 9 or 10, characterized in that the telecommunications system is arranged to store the name of the access point used for multimedia traffic in a charging record generated for traffic billing.

12. A telecommunications system as claimed in claim 11, characterized in that the telecommunications system is arranged to reject in the billing the charging records that contain the access point name defined for use in generating a PDP context for the transfer of multimedia signalling traffic only.

13. A telecommunications system as claimed in any one of claims 9 to 12, characterized in that the multimedia traffic is IP multimedia traffic.

14. A telecommunications system as claimed in any one of claims 9 to 13, characterized in that the terminal (UE) is wireless and that the telecommunications system comprises a wireless access network (RAN) for providing a wireless connection between the terminal and the packet-switched access network.

15. A telecommunications system as claimed in any one of claims 9 to 14, characterized in that the wireless access network (RAN) is a UMTS or GSM network.

16. A telecommunications system as claimed in any one of claims 9 to 15, characterized in that the packet-switched network is a GPRS network.

17. A telecommunications system as claimed in any one of claims 9 to 16, characterized in that the packet-switched network comprises two or more subnetworks managed by different network operators.

18. A terminal for a telecommunications system that comprises a packet-switched access network for providing a connection for the terminal (UE) to one or more packet-switched data networks through one or more access points (GGSN), and the terminal is arranged to: generate at least one packet data protocol, i.e. PDP, context for the transfer of multimedia signalling traffic between the terminal (UE) and access point (GGSN) and/or at least one PDP context for the transfer of multimedia user data traffic between the terminal (UE) and access point (GGSN), characterized in that the terminal (UE) comprises: information on at least one predefined access point name for multimedia signalling traffic for use in generating the PDP context for the transfer of multimedia signalling traffic and/or at least one predefined access point name for multimedia user data traffic for use in generating the PDP context for the transfer of multimedia user data traffic; and the terminal (UE) is also arranged, when generating the PDP context for multimedia signalling traffic or multimedia user data traffic transmission, to select the name of the access point depending on whether the multimedia traffic to be transmitted is of the signalling or user data type in such a manner that the terminal (UE) is arranged to select as the access point name one of the access point names predefined for the multimedia traffic type in question, if at least one access point name has been predefined for said multimedia traffic type, and to transmit the name of the selected access point to the packet- switched access network.

19. A terminal as claimed in claim 18, characterized in that the multimedia traffic is IP multimedia traffic.

20. A terminal as claimed in claim 18 or 19, characterized in that the terminal (UE) is wireless.