Method for Controlling Quality of Service in a Communication System by Using Policy Decision Function Module

Description

I. Technical Field

This invention relates to a method for controlling quality of service in a communication system by using a policy decision function module, and particularly, to a method for controlling quality of service in a communication system by using a policy decision function module in a third generation mobile communication network.

II. Technical Background

Nowadays, the communication environment has expanded from simple telegram and telephone communication to diversified communication including voice, data and multimedia communications. A common solution by operators is to have one service corresponding to one service network, thus forming a situation of coexistence of a plurality of service networks. The object of network integration is to conduct communication of all types of information through a unified network, which would help to realize a user's "universal experience" while enjoying many types of communication services. Currently, the integration that people in the trade are concerned with includes the integration between the telecommunication network and Internet, the integration between the mobile network and the fixed line network, etc. Among them, it was proposed by the 3 ^rd Generation Partnership Project (3GPP) in Release 5 (R5) that technology based on IP Multimedia Subsystem (IMS) had provided a basis for integration between IP based mobile and

fixed communications; and it was considered by those in the trade as an important stage for network evolvement.

The core features of IMS include the adoption of Session Initiation Protocol (SIP) and the irrelevancy of a connect-in. Currently, IMS supports 2.5G and 3G General Packet Radio Service (GPRS) mobile connect-in methods, and at the same time IMS is integrated into Next Generation Network (NGN) to support fixed connect-in methods. Under the trend of network integration, 3GPP, the European Telecommunications Standards Institute (ETSI) and the International Telecommunication Union- Telecommunication (ITU-T) are all studying IMS-based network integration schemes for the purpose of making IMS into a universal platform for SIP-based sessions, and at the same time supporting a plurality of connect-in methods such as fixed, mobile and Wireless Local Area Network (WLAN) , thus realizing the integration of fixed networks and mobile networks.

The core network in a third generation mobile communication system includes in its vertical direction from top downwards, respectively, an application layer, a control layer, a transmission layer and a connect-in layer. The application layer is responsible, on the basis of established calls, for providing all kinds of value-added services and management functions; the control layer is responsible for completing all kinds of call control and the transmission of corresponding operation processing information; the transmission layer is responsible for converting information sent by users into the formats that can be transmitted over the network and sending the information to its destination via a selected route, and this layer includes all kinds of gateways and is responsible for the exchange/route-selection between the peripheries and the core of the network; and the connect-in layer is responsible for connecting users to the network, pooling the operation volume together and sending the operation to destinations, including all kinds of connect-in means and connect-in nodes .

As the mobile communication technology combines with IP technology, mobile networks have developed from the electric- circuit exchange of the Global System for Mobile Communications

(GSM) networks to the packet exchange GPRS networks, and eventually to the 3G Universal Mobile Telecommunication System

(UMTS) networks providing high-speed real-time data services. According to differences in the services' sensitivity to time- delay, the UMTS system has defined four categories of bearing services: session type, flow type, interaction type and background type. In the communication field, more and more attention has been paid to the issue of how to ensure the requirements to Quality of Service (QoS) in a mobile network, so as to provide, through the mobile network, satisfactory services to users according to features of different services. Operator requirements in practical operation have been fully considered in IMS and relevant protocols regarding QoS have been formulated.

Fig. 1 illustrates a QoS system structure in UMTS packet domain and multimedia domain in the latest Release 6 (R6) of the 3GPP. This system structure is realized on the basis of a service policy control mechanism, which provides a dynamic control of QoS. In Fig. 1, functional entities concerned in the system structure include the User Equipment (UE) , Gateway GPRS Supporting Node (GGSN) , Policy Decision Function (PDF) and Application Function (AF) . Wherein, the GGSN is located in a transmission layer, the PDF in a control layer and the AF in an application layer.

The policy decision function PDF is a separate functional entity, which provides service-based QoS policy control to all packet domain services. PDF receives application requests from servers, establishes application sessions, pre-books different types of media resources required, and formulates specific policy rules according to users and applications. Decisions by PDF are sent to the IP bearing management function of GGSN and

GGSN maps the parameters of said service directly to the Packet Data Protocol context (PDP context) or to the parameters of the IP layer (such as Resource Reservation Protocol, RSVP) . The PDP context is database recorded information for use in the management of information on the data route between the UE and the GGSN. A Go interface between the PDF and the GGSN adopts the COPS protocol which IETF is responsible for, and a Gq interface between the PDF and AF adopts a Diameter protocol, for transmitting QoS relevant information and policy.

The QoS management packets are mainly performed by UE and GGSN, using Differentiated Service (DiffServ) defined by IETF and Differentiated Services Code Point (DSCP) function; the packets are classified and different priority classes are given to different types of packets during their transmission. The GGSN can extract from the PDP context or from the RSVP attribute parameters. Terminal UE can also provide DiffServ and DSCP functions, but it is not essential. The application function AF applies for or modifies the medium at the establishment of a session or during a session.

The 3GPP specifies that when using a terminal UE in an IP-based environment, said UE needs to obtain two IP addresses, one of the IP addresses is used for signaling transmission , which is called Primary IP, and the other IP address is used for medium data transmission (voice, video), which is called Secondary IP. Corresponding to the primary IP there is a primary PDP context for recording the primary IP route, and corresponding to the secondary IP there is a secondary PDP context for recording the secondary IP route. The basic flow chart of QoS control provided by PDF in IMS as claimed by the 3GPP is shown in Fig. 2:

(1) The user equipment (UE) sends a service request message to an application function module (AF) , which provides voice or video service, via session initiation protocol

(SIP), this request message is usually an INVITE message .

(2) The AF sends an authorization request to the PDF via a Gq interface' s Authentication Authorization Request

(AAR) message, informing the PDF to use the QoS required by the user of said service.

(3) The PDF generates an Authorization Token (AT) , and transmits said AT to the AF via Gq interface's Authentication Authorization Answer (AAA) . The AT is a sequence of characters, indicating said PDF ' s IP address .

(4) The AF sends the received AT containing said PDF address to the UE via a SIP signalling.

(5) The UE activates the secondary PDP context and at the same time transmits the AT in the activated secondary PDP context to the GGSN. The purpose is to obtain the UE' s secondary IP address, so that the UE can notify the transmission layer of the GGSN location to get prepared for transmitting medium data.

(6) The GGSN sends a request via a Go interface's Request

(REQ), which request carries said AT.

(7) The PDF compares the AT it generated and sent via the Gq interface with the AT received via the Go interface, namely it executes an authentication process. If said two ATs are the same, the PDF sends an authentication decision message to the GGSN, notifying the GGSN that said user is successful in authentication, and can use the QoS required by the service; if said two ATs are not the same, said PDF sends an authentication decision message to said GGSN, notifying GGSN that said user failed authentication, so the user equipment cannot use the service.

However, if the UE is required to support the above-mentioned two IP addresses at the same time, as claimed by the 3GPP, it would require the UE to have very high processing capacity. Current UE can only support a primary IP, and cannot support a secondary IP, namely, it cannot support the above-mentioned

secondary PDP context. Therefore, the QoS control claimed by the 3GPP cannot be provided to networks before Release 6.

III. Contents of Invention

Therefore, the main object of this invention is to provide a method for controlling quality of service in a communication system by using a policy decision function module, so that the basic procedure of the above-mentioned QoS control provided by said PDF in IMS can be realized without a secondary PDP context, which would meet the status that the current UE cannot support secondary IP, while realizing IMS-based QoS control claimed by the 3GPP.

To achieve the above object, the technical solution of this invention is realized as follows:

A method for controlling quality of service in a communication system by using a policy decision function module, and for use in controlling quality of service in a network based on IP multimedia subsystem technology in a third generation mobile communication system, comprising one or more user equipment, one or more gateway GPRS supporting nodes, a policy decision function module and one or more application function modules, wherein said method comprises the following steps:

(a) sending by said user equipment a service request message to said application function module via a session initiation protocol; then

(b) generating by said application function module an authorization token 1, and sending via a Gq interface an authentication authorization request message carrying said authorization token 1 to said policy decision function module; then

(c) storing said authorization token 1 at said policy decision function module, and returning via the Gq interface an authentication authorization answer message carrying said authorization token 1 to said application function module;

(d) sending by said application function module an AF via a session initiation protocol message a response message to said user equipment; then

(e) sending by said user equipment an IP packet message to said gateway GPRS supporting node; then

(f) generating by said gateway GPRS supporting node an authorization token 2 identical to said authorization token, and sending via a Go interface a request message carrying said authorization token 2 to said policy decision function module; then

(g) comparing by said policy decision function module said authorization token 1 received from the application function module and said authorization token 2 from the gateway GPRS supporting node, wherein if said two authorization tokens are the same, said policy decision function module sends via the Go interface an authentication decision message to said gateway GPRS supporting node, notifying said gateway GPRS supporting node that said user is successful in authentication, and can use the quality of service required by the service; if said two authorization tokens are not the same, said policy decision function module sends via the Go interface an authentication decision message to said gateway GPRS supporting node, notifying said gateway GPRS supporting node that said user is not successful in authentication, so the user equipment cannot use the service.

According to one aspect of this invention, the format of said authorization token contains said user equipment's international identity number, said policy decision function module's IP address, and said user equipment's IP address.

According to another aspect of this invention, a pair of attribute values for sending said authorization token is added to the Diameter protocol.

According to yet another aspect of this invention, said IP packet message is a secondary packet data protocol context activation message.

According to another aspect of this invention, said IP packet message is generated by the application software of said user equipment or the hardware module of said user equipment.

According to another aspect of this invention, said service request message is an invite message based on the session initiation protocol.

As can be seen from the above solution, the key point of this invention is that the application function module generates an authorization token and sends said authorization token to said policy decision function module via the Gq interface.

It can be seen that the method for controlling quality of service in a communication system by using a policy decision function module provided by this invention has the following advantages and features:

(1) This invention can achieve the basic procedure of the above-mentioned QoS control provided by said PDF in IMS without a secondary PDP context, which would meet the status that the current user equipment cannot support secondary IP, while realizing IMS-based QoS control claimed by the 3GPP; and because it uses one user equipment IP address to accomplish operational service quality control, it can be deployed in networks before the 3G.

(2) In this invention, a pair of attribute values for sending authorization tokens is added to the Diameter protocol and the Gq interface is modified, which is simple and effective, and no modification is needed to the relatively complicated Go interface based on the COPS protocol.

(3) In this invention, no major change is needed to the policy decision function module PDF; therefore it saves manufacturing and operational costs.

IV. Description of Drawings

Fig. 1 is the end to end QoS system structure in the prior art

UMTS packet domain and multimedia domain.

Fig. 2 is a basic flow chart for providing quality of service to a policy decision function module in an IP-based multimedia subsystem in the prior art.

Fig. 3 is a basic flow chart for providing quality of service to a policy decision function module in an IP-based multimedia subsystem in this invention.

V. Preferred Embodiments

This invention is described hereinbelow in detail with reference to the drawings .

The prerequisite for realizing this invention is that the current user equipment can use the quality of service control function before it comes to the time of introducing 3G networks based on IMS technology and using a policy decision function for controlling quality of service QoS.

Based on the above prerequisite, a method for controlling quality of service QoS in a communication system based on IMS technology using a policy decision function PDF module in a 3G network is proposed in this invention, as shown in Fig. 3. A 3G network system using this method comprises at least: one or more user equipment, one or more gateway GPRS supporting nodes, a policy decision function module and one or more application function modules. The user equipment notifies the gateway GPRS supporting node GGSN of the service required by said user, and the QoS needed by the service is decided by the application

function module AF. In the process of its practical application, the method comprises at least the following steps:

(1) When user equipment initiates a call, said user equipment sends a service request message (usually an INVITE message based on SIP) to the application function module AF via a session initiation protocol SIP.

(2) The application function module AF generates an authorization token ATI, and sends via a Gq interface an authentication authorization request message AAR carrying said authorization token ATI to the policy decision function module PDF.

Different from the AT of confidential nature as claimed in the 3GPP protocol, said authorization token ATI is an open message, with a format of international identity number (MSISDN) + IP address of PDF + IP address of UE.

The user equipment's international identity number ISDN (MSISDN) is the authentication number for uniquely identifying the user equipment in the public exchange telephone network numbering program, and it has the format of: MSISDN = CC + NDC + SN, wherein CC is the country code, i.e. the code for international long distance telephone communication network, NDC is the national destination code, and SN is the Subscriber code. Since the Gq interface is based on a Diameter protocol, and since compared with the 3GPP protocol, this invention adds in an AAR message the contents for transmitting the authorization token ATI, needs to be added an attribute value { attribute, value } in Diameter protocol.

(3) The policy decision function module stores said authorization token ATI, and returns via the Gq interface an authentication authorization answer message AAA carrying said authorization token ATI to said application function module AF.

(4) The application function module AF returns a SIP response message, usually 200 OK.

(5) The user equipment sends an IP packet message to said gateway GPRS supporting node, its function being to notify GGSN to get prepared to authenticate the PDF request. A currently workable scheme is the user equipment UE sends a secondary PDP

activation request, but the user equipment UE cannot obtain a secondary IP address.

Said UE and GGSN may need to exchange messages for several times to eventually complete the transmission of the IP packet message .

The secondary PDP context claimed in the 3PGG protocol is completed in a specific module in the user equipment, while said IP packet message can be completed by such a specific module, and it can also be completed by application software in the user equipment.

(6) The gateway GPRS supporting node generates an authorization token AT2 identical to the above authorization token, and sends via a Go interface a request message REQ carrying said authorization token AT2 to said policy decision function module PDF.

(7) The policy decision function module PDF compares the authorization token ATI received from the application function module AF with the authorization token AT2 from the gateway GPRS supporting node, wherein if said two authorization tokens are the same, said policy decision function module sends via the Go interface an authentication decision message to said gateway GPRS supporting node, notifying said gateway GPRS supporting node that said user is successful in authentication, and can use the quality of service required by the service; if said two authorization tokens are different, said policy decision function module sends, via the Go interface, an authentication decision message to said gateway GPRS supporting node, notifying said gateway GPRS supporting node that said user is not successful in authentication, so the user equipment cannot use the service.

This invention can achieve the basic procedure of QoS control provided by said PDF in IMS without a secondary PDP context, which would meet the status that the current user equipment cannot support secondary IP, while realizing IMS-based QoS control claimed by the 3GPP; and because it uses one user

equipment IP address to accomplish operational service quality control, it can be deployed in networks before the 3G.