Abstract:
The present invention relates to a method and system for providing access from a first network ( 30 ) to a service of a second network, wherein an authentication signaling is used to transfer a service selection information to the second network ( 70 ). Based on the service selection information, a connection can be established to access the desired service. Thereby, cellular packet-switched services can be accessed over networks which do not provide a context activation procedure or corresponding control plane signaling function.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method and system for providing access via a first network, for example a Wireless Local Area Network (WLAN), to a service of a second network, for example a service subscribed to in a General Packet Radio Service (GPRS) network or a Universal Mobile Telecommunications System (UMTS) network. 
     BACKGROUND OF THE INVENTION 
     Over recent years, the market for wireless communications has enjoyed tremendous growth. Wireless technology now reaches or is capable of reaching virtually every location on the earth. With tremendous success of wireless telephony and messaging services, it is hardly surprising that wireless communication is beginning to be applied to the realm of personal and business computing. No longer bound by the harnesses of wired networks, people will be able to access and share information on a global scale nearly anywhere they venture. 
     The major motivation and benefit from WLANs is increased mobility. Network users can move about almost without restriction and access LANs from nearly everywhere. In addition to increased mobility, WLANs offer increased flexibility. Meetings can be arranged, in which employees use small computers and wireless links to share and discuss future design plans and products. Such “ad hoc” networks can be brought up and torn down in a very short time as needed, either around the conference table and/or around the world. WLANs offer the connectivity and the convenience of wired LANs without the need for expensive wiring or re-wiring. 
     However, even with the fastest laptop, productivity while travelling can fall because of poor access to the Internet or company Internet. Despite the revolution of the Global System for Mobile communication (GSM), laptop users need faster access to download large files and to synchronize their e-mails quickly. The emerging mobile information society demands that data is available whenever and wherever. As a solution to this problem an operator WLAN solution has been proposed which brings broadband access to the laptop or terminal device in specific places like airports, convention centers, hotels and meeting rooms. Thus, mobile network operators are able to offer broadband access to the internet, corporate intranets or other service machineries from virtually anywhere in the world. Thus, a public WLAN service with own WLAN roaming feature can be provided. 
     In packet-switched cellular networks, such as the GPRS or UMTS network, the users service descriptions are specified by Access Point Names (APN). GPRS is a common packet domain core network used for both GSM and UMTS networks. This common core network provides packet-switched services and is designed to support several quality of service levels in order to allow efficient transfer of non real-time traffic and real-time traffic. The Serving GPRS Support Node (SGSN) keeps track of the individual location of a mobile terminal and performs security functions and access control. The Gateway GPRS Support Node (GGSN) provides interworking with external packet-switched networks, and is connected with SGSNs via an IP-based packet domain backbone network. In the backbone network, the APN is in practice a reference to the GGSN to be used. In addition, the APN may, in the GGSN, identify the external network and optionally a service to be offered. Further details concerning the use and structure of APNs are defined e.g. in the 3GPP specification TS 23.003. 
     When a user connects to a GPRS service, i.e. establishes a Packet Data Protocol (PDP) context as specified e.g. in the 3GPP specifications TS 23.060, the APN information selected by the terminal device or user equipment (UE) or the user of the terminal device is sent from the terminal device to the network in a PDP context establishment signaling. This information consists of APN and optionally user-name and password if required to access the service behind the selected APN. In the GPRS network, this information is used to select suitable GGSN. The information also arrives to the selected GGSN and the GGSN uses this information further to establish a connection to a network node behind the GGSN, e.g. a corporate Internet or an operator service node. If provided, the username and password are delivered to the concerned network node behind the GGSN to allow authorization of the connection. 
     However, in the proposed public or operator WLAN systems, an operation similar to the GPRS PDP context activation is not provided. In particular, there is no dedicated signaling for setting up services between a WLAN terminal device, i.e. WLAN UE, and the WLAN network or network behind the WLAN network. Therefore, GPRS type of service selection and activation is not possible via the WLAN network, which thus forms a drawback in the proposed public or operator WLANs. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a method and system for providing access from a WLAN network or any other first network to a service provided by a GPRS or any other second network. 
     This object is achieved by a method of providing access via a first network to a service facilitated by a second network, the method comprising the steps of:
         using an authentication message to signal a service selection information via said first network to an authentication server means of said second network; and   using said service selection information to connect to services provided over an access point indicated by said service selection information.       

     Furthermore, the above object is achieved by an authentication server device for providing an authentication mechanism, said authentication being arranged:
         to extract from a received authentication message a service selection information for selecting a service; and   to use said service selection information for establishing a connection to services provided over an access point indicated by said service selection information.       

     Additionally, the above object is achieved by a terminal device for providing access to a network service, said device being arranged to set in an authentication message a service selection information for selecting said network service. 
     Accordingly, a service selection information or service description is forwarded to the second network by using an authentication signaling between the terminal device and an authentication server of the second network, which then uses the service selection information to establish a connection to the desired or subscribed service. Thereby, access to network services of third parties is possible over the first network, e.g. the WLAN. Thus, dynamic service selection and multiple simultaneous connections to different services are enabled, and service continuity is obtained between different networks, such as WLANs and cellular packet-switched networks. Thereby, network flexibility and user mobility can be enhanced and service logics can be unified in different networks. 
     From the network operator&#39;s point of view, the proposed solution is advantageous in that current service description mechanisms, such as the APN mechanism in GPRS, can be used in new operator WLANs to thereby support legacy solutions. The authentication message may be a message of the Extensible Authentication Protocol (EAP). In particular, the authentication message may be an EAP response message. 
     The service selection information may comprise at least one APN parameter. This at least one APN parameter may comprise an APN, a username and a password of the desired service. Furthermore, the APN parameter may be encrypted in the authentication message. The applied encryption for different APN parameters may be selected differently, so that selected APN parameters may be forwarded by the authentication server to the selected access point in encrypted format, and that the selected APN parameters are decrypted only at the access point or selected service network. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, the invention will be described in greater detail based on a preferred embodiment with reference to the accompanying drawings, in which: 
         FIG. 1  shows a schematic block diagram indicating the basic principles underlying the present invention; 
         FIG. 2  shows a schematic block diagram of a WLAN connected via a WLAN gateway of a GPRS network to an application server; 
         FIG. 3  shows an EAP signaling according the preferred embodiment of the present invention; and 
         FIG. 4  shows the format of an enhanced EAP Response Challenge packet according to the preferred embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment will now be described on the basis of a network architecture as indicated in  FIGS. 1 and 2 , where a WLAN user is authenticated to access a WLAN network by an EAP authentication to thereby get access to a cellular packet-switched service. 
       FIG. 1  shows a schematic block diagram of a network architecture comprising a WLAN  30  and a GPRS network  70 . A terminal device or UE  10  which is subscribed to a GPRS service and wishes to get access to the service, first transfers a service selection information indicating at least one APN parameter and an optional username and password via the WLAN  30  to an authentication server  50  of the GPRS network  70  by using an authentication signaling, e.g. an authorisation request message (1 st  step). Then, the authentication server  50  selects a WLAN gateway  60  arranged in the GPRS network  70 , signals the service information to the WLAN gateway  60 , and as a response receives from the WLAN gateway  60  a connection information for establishing a connection between an access server  40  of the WLAN  30  and an application server  80  providing the requested service and being identified by the at least one APN parameter (2 nd  step). In particular, the authorisation request may be forwarded further to the application server  80  or another external AAA server together with the username and password and the WLAN gateway  60  first receives a response from there and then proxies this response to the access server  40 . 
       FIG. 2  shows a more detailed block diagram of a network architecture in which the preferred embodiment of the present invention can be implemented. In  FIG. 2 , a WLAN UE  10  is connected via a wireless connection to an access point  20  of a WLAN  30 . It is noted that the access point  20  has a similar functionality as a base station in a general cellular network. The access point  20  is not mobile and forms part of the wired network infrastructure. Further details regarding the architecture and function of the WLAN network  30  can be gathered e.g. from the IEEE specification 802.11. 
     Furthermore, the WLAN  30  comprises a WLAN access server  40  for establishing a connection to external networks such as a GPRS network  70  or another packet-switched network  90 , e.g. the Internet or an operator or company Internet. The GPRS network  70  comprises an authentication server  50 , with an allocated authentication server database  55  in which subscriber information such as service profile information of each connected terminal device or UE are stored after retrieval of that information from a permanent subscriber database  110  at subscriber&#39;s home network  110 . It is noted that the functionality of the authentication server  50  can also be located at users home network or a WLAN backbone or subsystem. The authentication signaling with the UE  10  may be based on the EAP SIM authentication protocol in case a GSM SIM card is used within the UE  10 . Alternatively, the authentication may be based on the EAP AKA (Authentication and Key Agreement) authentication protocol in case. a UMTS SIM card is used within the UE  10 . 
     The EAP protocol mechanism is used for authentication and session key distribution by means of the GSM SIM or the USIM. Authentication is based on a challenge-response mechanism, wherein the authentication algorithm which runs on the SIM or USIM card can be given a random number (RAND) as a challenge. The SIM or USIM runs an operator-specific confidential algorithm which takes the RAND and a secret key stored on the SIM or USIM as input, and produces a response (SRES) and a key as output. The key is originally intended to be used as an encryption key over the air interface. The authentication server  50  has an interface to the GSM or UMTS home network  100  of the UE  10  and operates as a gateway between the packet-switched AAA (Authentication, Authorization and Accounting) networks and the GSM or UMTS authentication infrastructure. After receiving an EAP identity response including user identification mappable to the user&#39;s International Mobile Subscriber Identity (IMSI) the authorization server  50  obtains n triplets or quintuplets from the authentication center at the home location register (HLR) or Home Subscriber Server (HSS)  110  of the user&#39;s home network  100 . From the triplets, the authentication server  50  derives the keying material based on a cryptographic algorithm. 
     According to the preferred embodiment, the WLAN authentication signaling is used for signaling GPRS service subscription or selection information via the authentication server  50  to the GPRS network  70 . The GPRS service information or service selection information comprises the APN of the desired service and an optional username and password required to connect to the service via the indicated APN. The authentication server  50  uses the obtained service selection information to select the WLAN gateway  60  having a similar function to a GGSN, from where the user can get access to the subscribed service. The subscribed service can be e.g. an access to a corporate Internet or to services of a mobile operator. 
       FIG. 3  shows a signaling diagram indicating an EAP-SIM authentication signaling between the UE  10  and the authentication server  50  of the GPRS network  70 . The first EAP request (not shown) issued by the network is an EAP Identity Request. The client or UE  10  responds with an EAP Identity Response (step  1 ) comprising a pseudonym or IMSI. The pseudonym is used when an identity privacy support is being used by the UE  10 . In response to the EAP Identity Response message or packet, the authentication server  50  sends an EAP challenge request comprising the n random numbers RAND among other parameters (step  2 ). In response thereto, the UE  10  issues an EAP Challenge Response including the calculated response value SRES. Furthermore, according to the preferred embodiment of the present invention, the EAP Challenge Response also includes at least one encryped APN parameter specifying the desired GPRS service to be accessed. The encrypted APN parameters my comprise the APN of the desired service and an optional username and password for getting access to the service (step  3 ). The applied encryption for different APN parameters may be selected differently. I.e., the APN itself may be the only APN parameter which is required for AP selection, and therefore only this parameter has to be in a format which is to be decrypted and/or read by the access server. The username and password parameters may be forwarded by the authentication server to the selected access point in encryped format, and these parameters are decrypted only at the access point or selected service network. It is thus not possible to access them while transferred via the first network. If the authentication procedure was successful, the authentication server  50  responds with an EAP Success message (step  4 ). 
     The above authentication signaling procedure enables a signaling of service selection parameters to the authentication server  50  without requiring any additional context activation function as would be required in a conventional GPRS network without WLAN functionality. To achieve this enhanced functionality of the authentication signaling, the client software at the UE  10  is modified or programmed to add the respective service selection information to the EAP Challenge Response message. In particular, if a user has selected to connect to a specific service identified by its APN, the service information or service selection information is configured in the client software at the UE  10 . For each service the following settings may be performed. Firstly, a free text entry identifying the service for the user may be set. Secondly, the APN, i.e. the identification of the Public Land Mobile Network (PLMN) plus the Domain Name Server (DNS) name assigned by the Mobile Operator (MO) may be set to point to the specific service, and, thirdly, a setting indicating whether the username and password are required (e.g. a Yes/No setting) can be made in the client software. The third setting may comprise a setting indicating either a predefined or a dynamic username or/and password setting. 
     At the latest after reception of the EAP request message, the UE  10  gets the required service selection related information from the user and encrypts it as specified by the utilised signalling protocol such as EAP-SIM. The UE  10  then inserts the APN parameter information to the EAP Challenge Response message and sends it via the WLAN  30  to the authentication server  50 . 
       FIG. 4  shows a format of the enhanced EAP SIM Challenge Response message according to the preferred embodiment as generated at the SIM. A “code” field is used to identify the message as a response message. An “identifier” field is one octet and aids in matching replies to responses. In particular, the “identifier” field must match the “identifier” field of the message to which it is sent in response. The “length” field indicates the length of the EAP message or packet. The “type” and “sub-type” fields are set to specific values specifying the EAP SIM Challenge Response message. The “reserved” fields are set to zero upon sending and ignored on reception. The “AT_SRES” field indicates an attribute value and is followed by an additional “length” field indicating the length of the following SRES value and by a “reserved” field. Finally, the proposed APN parameters specifying the requested service may be added e.g. as encrypted values. 
     It is noted that the present invention is not restricted to the described WLAN and GPRS service and can be used in any network architecture where a control plane signaling required for accessing a packet-switched service is not provided in the access network. The functionalities of the authentication server  50  and the gateway  60  not necessarily have to be GPRS functionalities, but can be located in any backbone network or subsystem of the WLAN or any other network accessible by the WLAN  30 . They may be provided in standalone server devices or in GPRS GGSN or SGSN functionalities, respectively. Also, the accessed service does not have to be a GPRS service. Thus, the WLAN UE  10  can be a single-mode WLAN terminal without GPRS functionality but with a functionality to access external services via an authentication signaling, e.g. by a similar mechanism as the GPRS service selection mechanism. Furthermore, any given authentication message can be used for transferring the service selection information. The preferred embodiments may thus vary within the scope of the attached claims.