Abstract:
An IMS node communicating with a user node and an information node is provided. The information node is adapted to conduct access control based on IMS Public User Identity. The IMS node comprises: request mediation means for mediating an access request from the user node to the information node by converting a first protocol conforming to IMS into a second protocol interpretable to the information node; and response mediation means for mediating an access response from the information node to the user node by converting the second protocol into the first protocol. The access request includes the IMS Public User Identity and information identity specifying information which the information node is requested to retrieve.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates generally to the field of access control and, more particularly, but not by way of limitation, to access control based on IMS-related user identity conducted by an information repository server. 
       BACKGROUND 
     Abbreviations 
       [0002]    RFID: Radio Frequency Identification 
         [0003]    IMS: IP Multimedia Subsystem 
         [0004]    UICC: Universal Integrated Circuit Card 
         [0005]    SIM: Subscriber Identity Module 
         [0006]    USIM: Universal Subscriber Identity Module 
         [0007]    ISIM: IP multimedia Services Identity Module 
         [0008]    MSISDN: Mobile Subscriber ISDN Number 
         [0009]    IMSI: International Mobile Subscriber Identity 
         [0010]    UE: User Equipment 
         [0011]    ID: Identity 
         [0012]    TLS: Transport Layer Security 
         [0013]    SCM: Supply Chain Management 
         [0014]    Radio Frequency Identification (RFID) is a technology for automating identification of an object. The object is affixed by an RFID tag that stores identification information inside its embedded memory. Short-ranged radio frequency signal is used to transfer such information from the tag to a tag-sensing device called an RFID reader. The main use of this technology has been seen in supply chain management (SCM) application area in order to inventory goods more automatically than the case where inventory has much relied on manual operations. EPCglobal (EPCglobal Inc., http://www.epcglobalinc.org/) is the most active organization attempting to standardize the RFID system used in SCM. Its roles and techniques range from ID numbering assignment, RF (air) protocols, to ID resolution protocols and information access protocols etc. 
         [0015]      FIG. 1  shows a high-level architecture and information flow of an RFID application. For the time being, there&#39;s no standard protocol between each entities, which depends on the individual choice of each RFID application. The network infrastructure between the entities is build over IP-based network  101  and each protocol operates over some of transport protocols such as TCP, UDP, HTTP or SOAP etc. 
         [0016]    However, the basic architecture and information flow in  FIG. 1  can be applied for almost all kind of RFID applications. Note the name of each logical entity is also a non-standard name but conveniently named for easy understanding in this document. The brief functional descriptions of the entities are as follows: 
         [0017]    RFID reader client  102 : It consists of hardware for reading RFID via air interface and software for implementing services to enable data exchange between reader hardware and the servers on the network. 
         [0018]    RFID resolution server  103 : It resolves the location information (such as IP address, TCP/UDP port number or URL) of an information repository server  104  from a particular RFID value. The representative implementation of this would be ONS (Object Name Service) discussed in EPCglobal. 
         [0019]    Information repository server  104 : It is a database server that stores related information to the particular RFID value. The representative implementation of this would be EPC-IS (Electronic Product Code Information Service) proposed in EPCglobal. 
         [0020]    Tag  105 : It consists of a microchip attached to an antenna. 
         [0021]    In step S 101 , the reader client  102  reads an RFID value stored on the tag  105 . In step S 102 , the reader client  102  queries the RFID resolution server  103  about the network location of the information repository server  104  that holds the information associated to this RFID value. In step S 103 , the reader client  102  requests the information contents associated to this RFID value. 
         [0022]    One of security threats in the RFID application is illegal access to the information on the repository server. It is a likely case that sensitive information associated to the certain RFID may be stored on the repository server. Without any defence, it is obvious any information can be accessed unrestrictedly. Thus, it is a common idea that some kind of access control must be applied. 
         [0023]    Currently, access control mechanism mentioned above is always conducted by authenticating the reader identifier that is tightly bound to a physical hardware of the reader client. It may be a hardware serial number, MAC address, or possibly IP address assigned to the reader client. By setting one of these reader identifiers as a subject of the authentication, the access control has been performed. “Simple Lightweight RFID Reader Protocol,” P. Krishna et al., Internet Draft, March 2005 (work in progress) specifies how the RFID reader identity should be authenticated in the course of TLS (RFC 2246). 
         [0024]    At the present, the important criteria of this access control are put on the fact whether from which asset of reader hardware or from which location the information is being accessed. This hardware-dependent access control is sufficient for the current major RFID applications such as SCM in which the readers are put or located within hardware facilities (e.g., entrances of warehouses, carriers of trucks) in the closed environment. 
         [0025]    &lt;Discussions Around Existing Technology&gt; 
         [0026]    Problem-1: The filter management of the access control is sometimes troublesome if the reader device is broken, stolen or replaced because the reader identifier on the access control list has to be changed. Even in use of IP addresses of the reader devices as the filtering criteria, it is obvious that frequent updates of the access control list may happen when the reader device obtains IP addresses by DHCP (RFC 2131). 
         [0027]    Problem-2: On the other hand, it is foreseen that consumer-oriented RFID applications will be emerging into the market in the near future. There, since everyone will carry a portable RFID reader and a huge number of products around us will be embedded with RFID tags, it will be possible that everybody can reads RFID tags and solicits the information bound to the RFID very easily. This emergence is strongly supported by recent development of mobile phones equipped with RFID reader devices (Nokia Mobile RFID Kit, http://www.nokia.com/nokia/0,,55738,00.html), (http://www.kddi.com/english/corporate/news_release/2005/0324/index.html). 
       SUMMARY 
       [0028]    It is an object of the present invention to provide a new access control technology in which an access control is conducted based on “user” identities. 
         [0029]    This invention provides the nodes, the system, and the method with which such RFID applications or the like can identify users for the purpose of the user identity-based access control. 
         [0030]    According to an aspect of the present invention, there is provided with an IMS node communicating with a user node and an information node, wherein the information node is adapted to conduct access control based on IMS Public User Identity, the IMS node comprising: request mediation means for mediating an access request from the user node to the information node by converting a first protocol conforming to IMS into a second protocol interpretable to the information node; and response mediation means for mediating an access response from the information node to the user node by converting the second protocol into the first protocol; wherein the access request includes the IMS Public User Identity and information identity specifying information which the information node is requested to retrieve. 
         [0031]    According to another aspect of the present invention, there is provided with an information node communicating with an IMS node, wherein the IMS node is adapted to mediate between a user node and the information node, the information node comprising: receiving means for receiving an access request from the IMS node; retrieving means for retrieving information specified by information identity included in the access request; access control means for determining available information to the retrieving means based on IMS Public User Identity included in the access request; generating means for generating an access response including retrieved information by the retrieving means; and sending means for sending the access response to the IMS node. 
         [0032]    According to another aspect of the present invention, there is provided with a user node communicating with an IMS node, wherein the IMS node is adapted to mediate between the user node and an information node, the user node comprising: retrieving means for retrieving information identity specifying information which the information node is requested to retrieve; generating means for generating an access request including IMS Public User Identity and the information identity; sending means for sending the access request to the IMS node; and receiving means for receiving, from the IMS node, an access response including information specified by the information identity. 
         [0033]    According to another aspect of the present invention, there is provided with an access control system comprising the IMS node, the information node, and the user node described above. 
         [0034]    According to another aspect of the present invention, there is provided with a method for mediating between a user node and an information node, wherein the information node is adapted to conduct access control based on IMS Public User Identity, the method comprising: request mediation step of mediating an access request from the user node to the information node by converting a first protocol conforming to IMS into a second protocol interpretable to the information node; and response mediation step of mediating an access response from the information node to the user node by converting the second protocol into the first protocol; wherein the access request includes the IMS Public User Identity and information identity specifying information which the information node is requested to retrieve. 
         [0035]    According to another aspect of the present invention, there is provided with a method for communicating with an IMS node, wherein the IMS node is adapted to mediate between a user node and an information node, the method comprising: receiving step of receiving an access request from the IMS node; retrieving step of retrieving information specified by information identity included in the access request; access control step of determining available information in the retrieving step based on IMS Public User Identity included in the access request; generating step of generating an access response including retrieved information in the retrieving step; and sending step of sending the access response to the IMS node. 
         [0036]    According to another aspect of the present invention, there is provided with a method for communicating with an IMS node, wherein the IMS node is adapted to mediate between a user node and an information node, the user node comprising: retrieving step of retrieving information identity specifying information which the information node is requested to retrieve; generating step of generating an access request including IMS Public User Identity and the information identity; sending step of sending the access request to the IMS node; and receiving step of receiving, from the IMS node, an access response including information specified by the information identity. 
         [0037]    The main advantage of the present invention is as follows: when a user node requests an access to an information node to retrieve information, IMS node mediates the access request. Therefore, the information node can conduct access control based on IMS Public User identity. Because IMS Public User identity is independent of hardware of the user node, a user can easily change the user node with maintaining the same IMS Public User identity. 
         [0038]    This summary of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features. 
         [0039]    Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0040]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
           [0041]      FIG. 1  illustrates a high-level architecture and sequence flow of RFID application; 
           [0042]      FIG. 2  illustrates user identifiers-based access control on RFID information repository; 
           [0043]      FIG. 3  shows a high-level architecture of the invention; 
           [0044]      FIG. 4  shows the message sequence flow of the invention; 
           [0045]      FIG. 5  illustrates an overview of the procedure performed by the IMS AS; 
           [0046]      FIG. 6  shows an example of the INVITE request; 
           [0047]      FIG. 7  illustrates an overview of the procedure performed by the information repository server; and 
           [0048]      FIG. 8  illustrates an overview of the procedure performed by the UE. 
       
    
    
     DETAILED DESCRIPTION 
       [0049]    &lt;Overview&gt; 
         [0050]    An embodiment of implementing user identity-based access control is described below. 
         [0051]    An example scenario of this user identity-based access control can be depicted in  FIG. 2 . 
         [0052]      FIG. 2  shows how information associated with the particular RFID are stored in the repository server  104 . In this figure, n items of information are associated with RFID value ‘103’, each of which provides the defined users with Read/Write access privilege. In this example, User-A, B and C can read/write # 1 ˜# 3  items of the information, User-D can read # 3 ˜# 5  items, User-E and F can read/write # 5 ˜# 7  items, and anyone can read # 8 ˜#n items. 
         [0053]    In order to realize this user identifier-based access control to RFID information, a method to identify and distinguish users is required by such RFID applications. However, the problem is there&#39;s no effective method proposed. 
         [0054]    In this embodiment, an effective method to identify and distinguish users is provided using IP Multimedia Subsystem (IMS). 
         [0055]    &lt;IP Multimedia Subsystem (IMS)&gt; 
         [0056]    3GPP IMS is a standard that enables IMS-enabled mobile terminal users to perform IP-based multimedia communications. IMS consists of two major capabilities that are user registration and session control between registered users&#39; terminals. The user registration capability includes user authentication phase to check if user attempting to register IMS domain has the right to register. For this purpose, IMS supports mechanisms for user authentication based on subscription to relevant IMS service provider. In 3GPP IMS standards, ISIM based subscription and authentication technology is used, and also there is the option in which USIM is used for that purpose. 
         [0057]    UICC (Universal Integrated Circuit Card) 
         [0058]    Central to the design of 3GPP terminals is the presence of a UICC. The UICC is a removable smart card that contains a limited storage of data. The UICC is used to store, among other things, subscription information, authentication keys, a phone book, and messages. The UICC allows users to easily move their user subscriptions from one terminal to another. The user simply removes the smart card from a terminal and inserts it into another terminal. 
         [0059]    A UICC may contain several logical applications, such as a SIM (Subscriber Identity Module), a USIM (Universal Subscriber Identity Module), and an ISIM (IP multimedia Service Identity Module). 
         [0060]    ISIM 
         [0061]    ISIM (3GPP TS 31.103) is an application present in UICC. ISIM is of especial importance for the IMS, because it contains the collection of parameters that are used for user identification, user authentication etc. when the terminal operates in the IMS. The relevant parameters, among others, stored in ISM are: 
         [0062]    Private User Identity: ISIM stores the Private User Identity allocated to the user. There can only one Private User Identity stored in ISIM. This is an identity that is used for authentication purpose only during the registration phase, not for SIP message routing. It is equivalent to what in GSM is known as IMSI; it is never displayed to the user. 
         [0063]    Public User Identity: ISIM stores one or more Public User Identities allocated to the user in the form of SIP URI or TEL URL. They publicly represent the user identities in the IMS. The user can choose one preferred public user identity when creating a session and the user can be uniquely recognized with the Public User Identity. 
         [0064]    USIM 
         [0065]    USIM (3GPP TS 31.102) is another example of an application that resides in UICC. USIM provides another set of parameters which include user subscriber information, authentication information, payment methods etc. A USIM is required if a CS (Circuit Switched) or PS (Packet Switched) terminal needs to operate in a 3G network. USIM stores, among others, the following parameters: 
         [0066]    IMSI: IMSI is an identity assigned to each user. This identity is not visible to users themselves, but only to the network. IMSI is used as the user identification for authentication purpose. 
         [0067]    The Private User Identity is the equivalent of the IMSI in the IMS. 
         [0068]    MSISDN: This field stores one or more telephone numbers allocated to the user. A Public User Identity is the equivalent of the MSISDN in the IMS. 
         [0069]    In case the IMS terminal is equipped with a UICC that does not contain an ISIM application, the user can still register with the IMS network. Of special interest in the USIM from the IMS perspective is the IMSI. The terminal extracts the IMSI from the USIM in order to build a temporary Private User Identity and a temporary Public User Identity etc. These parameters are only used during registration, re-registration, and deregistration procedures. When the user is eventually registered the Serving—Call and Session Control Function (S-CSCF) sends a collection of the regular Public User Identities allocated to the user. The IMS terminal only uses these Public User Identities for any SIP traffic other that REGISTER requests. As a consequence, the temporary identities are never known or used outside the home networks (e.g. in a session setup). 
         [0070]    IMS Application Server 
         [0071]    In the IMS network, there will be several Application Servers; each specialized in providing a particular service. All these Application Servers are characterized by implementing a SIP interface, which is called IMS Service Control (ISC), toward the S-CSCF. The Application Servers can be located in the home network or in a third-party service provider network. When an Application Server is located in the home networks, it can optionally implement an interface to the HSS. The implementation of the interface depends on whether the actual service logic needs to further interact with the HSS or not. The optional interface from the Application Server to the HSS is ‘Sh’, and the protocol is based on Diameter (RFC 3588). If the Application Server is located in a third-party service provider network, it cannot implement the Sh interface in the HSS, as Sh is just an intra-operator interface. 
       DETAILED DESCRIPTION OF THE EMBODIMENT 
       [0072]    As described above, end users with the IMS terminals can identify each other with the Public User Identity. An IMS Application Server can also identify each end user with the Public User Identity. The basic idea of this invention is to present these Public User Identities used in the IMS to the information repository server so that it can perform the user identity-based access control with these user identities. 
         [0073]      FIG. 3  shows the high-level architecture of the invention. The differences from  FIG. 1  are as follows: 
         [0074]    The ISIM  301  (and/or USIM) inserted UE  302  has RFID reader client functionality. 
         [0075]    The dedicated IMS Application Server  303  mediates RFID information request from the UE  302 , which is done directly between the reader client  102  and the information repository server  104  in the past. 
         [0076]      FIG. 4  shows the message sequence flow of the invention. First of all, the IMS terminal (i.e. UE  302 ) reads the RFID value from the RFID tag  304  (S 401  in  FIG. 4 ). The IMS Application Server (AS)  303  receives a SIP INVITE message from the IMS terminal  302 , soliciting the RFID-associated information (S 402  in  FIG. 4 ). Note that other methods such as OPTION and SUBSCRIBE may also be used, but are not described here. 
         [0077]    Here, the Public User Identity, which was the asserted identity of the user using the IMS terminal, is present in P-Asserted-Identity header in the INVITE message. 
         [0078]    Optionally, if the AS  303  can communicate with the HSS  305  through the Sh interface (i.e., the AS  303  is located within the same IMS operator&#39;s network), then the AS  303  can pull more user identity information out from the HSS (S 402   a , S 402   b  in  FIG. 4 ). In this case, the AS  303  can present different Public User Identity (SIP URI, TEL URL) or MSISDN owned by this user to the information repository server  306 . Which user identity format is used depends on the configuration of the information repository server  306 . 
         [0079]    Then, the AS  303  mediates the request by converting the protocols from the IMS to RFID application network and sending a request message to the information repository server  306  presenting the RFID value and the user identity, for example, in the form of SIP URI (S 403  in  FIG. 4 ). 
         [0080]    By using this presented user identity, the information repository server can perform the user identity-based access control against the requested information (S 404  in  FIG. 4 ). Again, the user identity presented to the information repository server is derived from the ISIM or USIM application on the UICC that has to be inserted into the RFID reader-enabled UE  302 . It should be noted that the access control includes authorization but does not include authentication. That is, the UE  302  is authenticated to access the IMS infrastructure comprising the AS  303  in advance, for example, when the UE  302  is turned on (not shown in  FIG. 4 ). Then, in step S 404 , whether or not the authenticated UE is allowed to access certain information is determined based on the user identity (authorization). 
         [0081]    The information repository server sends a response (i.e., e.g., the requested information) to the UE  302  via IMS AS  303  (S 405 , S 406  in  FIG. 4 ), or directly to the UE  302  (not shown). 
         [0082]      FIG. 5  illustrates an overview of the procedure performed by the AS  303 . The AS  303  comprises two functional elements: the IMS Function  501  and the RFID Application Function  502 . 
         [0083]    The IMS Function  501  comprises a request mediation module  504  and a response mediation module  505 . These modules may be implemented by a computer program executed by a CPU (not shown) of AS  303 . The request mediation module  504  mediates an access request and the response mediation module  505  mediates an access response between the UE  302  and the information repository server  306  (as will hereinafter be described in detail). 
         [0084]    The following outlines the procedure: 
         [0085]    In step S 501 , the IMS Function  501  receives an INVITE request, which is addressed and routed to the AS  303 . In  FIG. 6 , an example of the INVITE request is shown. The Request-URI is filled with the Public Service Identity of the AS  303  so that the INVITE is routed to this AS  303  via the IMS infrastructure. In this example, “sip:rfid_ims_as@imsop.net” is used. The Request-URI also contains a special URI parameter named ‘rfid’ that holds the RFID value so that the AS  303  can receive the RFID value. That is, RFID value specifies information which the UE  302  wants the information repository server  306  to retrieve. Alternatively, any of SIP headers or a message body may be used for the purpose, which contains the RFID value as well. Since any SIP entity must ignore unknown URI parameters such as ‘rfid’, this URI parameter should not affect operation of other IMS entities (e.g. CSCFs). It should also be noted that P-Asserted-Identity is presented in the INVITE request by which the AS  303  is granted, by the IMS infrastructure, the authenticity of a request source of the INVITE. 
         [0086]    In step S 502 , the request mediation module  504  in the IMS Function  501  extracts both the Public User Identity from the P-Asserted-Identity header field and the RFID value from the ‘rfid’ URI parameter. Then, the request mediation module  504  generates a HTTP Request message comprising the extracted Public User Identity and RFID value. In other words, the request mediation module  504  transforms the SIP INVITE message (which is a kind of a SIP Request message) into the HTTP Request message. This step is necessary because the UE  302  sends an access request using a SIP protocol, whereas the information repository server  306  receives the access request using a different protocol such as HTTP. 
         [0087]    In step S 503 , the IMS Function  501  invokes the RFID Application Function  502  with the transformed access request (i.e. the HTTP Request message). 
         [0088]    In step S 504 , the RFID Application Function  502  may need to contact an RFID resolution server  503  to determine a target location of the information repository server  306  (e.g. a HTTP URL) as discussed above. The location of the RFID resolution server  503  may be pre-configured in the RFID Application Function  502 . 
         [0089]    In step S 505 , the RFID Application Function  502  requests the Information repository server  306  in order to retrieve the information associated with the RFID value. The request message generated in step S 502  at least contains the Public User Identity and the RFID value so that the Information Repository server  306  can perform the access control based on the Public User Identity and send the information associated with the requested RFID value, respectively. The access control is done in order to determine available information. 
         [0090]    In step S 506 , the RFID Application Function  502  internally returns the received information, which was received in the form of a HTTP Response message, to the IMS Function  501 . 
         [0091]    In step S 507 , the response mediation module  505  in the IMS Function  501  extracts the received information from the HTTP Request message. Then, the response mediation module  505  generates a 200 OK message (a kind of a SIP Response message) comprising the extracted received information. In other words, the response mediation module  505  transforms the HTTP Response message into the SIP Response message. This step is necessary because of the similar reason as step S 502 . 
         [0092]    In step S 508 , the IMS Function  501  returns the received information to the request source over 200 OK. 
         [0093]      FIG. 7  illustrates an overview of the procedure performed by the information repository server  306 . The information repository server  306  comprises a communication unit  701  and a HDD (Hard Disk Drive)  704 . The information repository server  306  also comprises a retrieving module  702 , an access control module  703 , and a generation module  705 . These modules may be implemented by a computer program executed by a CPU (not shown) of the information repository server  306 . 
         [0094]    In step S 701 , the communication unit  701  receives an access request from the AS  303 . 
         [0095]    In step S 702 , communication unit  701  provides the retrieving module  702  with the access request. 
         [0096]    In step S 703 , the retrieving module  702  accesses the HDD  704  and retrieves the information associated with the information identity included in the access request. The retrieved information may consist of plural pieces of information; each piece has an access control attribute indicating which user can access the piece. 
         [0097]    In step S 704 , the access control module  703  compares the access control attributes of the retrieved information with the Public User Identity included in the access request, and determines which pieces of the retrieved information is available to the requesting user. For example, in case that the information identity (RFID value) is ‘103’ and the Public User Identity indicates User-A, items # 1 ˜# 3  and # 8 ˜#n are available (refer to  FIG. 2 ). Then the retrieving module  702  provides the available pieces of the retrieved information with the generation module  705 . 
         [0098]    In step S 705 , the generation module  705  generates an access response including the pieces of information provided in step S 704 . Then the generation module  705  provides the access response with the communication unit  701 . The access response is, for example, in the form of a HTTP Response message. 
         [0099]    In step S 706 , the communication unit  701  sends the access response to the AS  303 . 
         [0100]      FIG. 8  illustrates an overview of the procedure performed by the UE  302 . The UE  302  comprises an RFID Reader  801 , UICC  803  which comprises ISIM  804  and/or USIM  805 , and a communication unit  806 . The UE  302  also comprises a generation module  802  and an initiation module  807 . These modules may be implemented by a computer program executed by a CPU (not shown) of the UE  302 . 
         [0101]    In step S 801 , the RFID Reader  801  reads the RFID Tag  304  and retrieves an RFID value. 
         [0102]    In step S 802 , the RFID Reader  801  provides the retrieved RFID value with the generation module  802 . 
         [0103]    In step S 803 , the generation module  802  retrieves Public User Identity from the UICC  803 . The Public User Identity may be maintained in the ISIM  804 , or built using IMSI maintained in the USIM  805 . 
         [0104]    In step S 804 , the generation module  802  generates an access request including the retrieved RFID value and the retrieved Public User Identity. Then, the generation module  802  provides the access request with the communication unit  806 . The access request is, for example, in the form of an INVITE message shown in  FIG. 6 . 
         [0105]    In step S 805 , the communication unit  806  sends the access request to the AS  303 . 
         [0106]    In step S 806 , the communication unit  806  receives the access response in reply to the access request. 
         [0107]    The UE  302  can utilize the received access response in various ways. For example, in step S 807 , the initiation module  807  retrieves the SIP URI from the access response and initiates a SIP session using the retrieved SIP URI. 
         [0108]    The present invention can work as an effective mechanism to deliver IP-based multimedia services to users by combining the IMS with RFID applications, particularly when RFIDs are associated with multimedia services (see step S 807  in  FIG. 8 ). 
         [0109]    For example, an RFID on a business card and/or consumer product may be associated with a VoIP service with a SIP URI of a customer or a help desk. In this case, the AS  303  (that converts the requested RFID value into the associated SIP URI) establishes a VoIP session automatically between the requesting user (represented by the Public User Identity of the INVITE) and the customer/help desk (represented by the SIP URI associated with the RFID value). 
         [0110]    Another example would be that an RFID on a CD/DVD package might be associated with a content streaming service with a SIP URI that represents content and its streaming server. In this case, the AS  303  (that converts the requested RFID value to the associated SIP URI) establishes a video/audio streaming session automatically between the requesting user (represented by the Public User Identity of the INVITE) and the streaming server (represented by the SIP URI associated with the RFID value). 
         [0111]    Another example would be that the UE  302  could obtain a coupon (an electronic coupon) for certain goods just by reading an RFID tag. Suppose the certain goods in a supermarket are affixed with RFID tags. The supermarket offers special membership service. A customer needs to tell his/her IMS Public User Identity (e.g. sip:User-A@imsop.net as described in  FIG. 6 ) to the supermarket so that the customer signs up to the membership service. Then the customerID (i.e. IMS Public User Identity) is registered in an access control list on an information repository server  306  managed by the supermarket. 
         [0112]    If the customer finds favorite goods affixed with a RFID tag in the supermarket, the membership service enables him/her to download the detailed product information and its special coupon (which may be included in the OK message described in  FIG. 4 ) by simply reading the RFID tag with his/her UE with RFID-reader. This indicates that other customers who don&#39;t sign up for the membership service cannot retrieve the coupons because their identities are not on the access control list of the repository server  306 . The coupon may be displayed on the display of the UE and the customer can use it by, for example, showing the display to a clerk. 
         [0113]    As the examples show, the present invention enables the IMS AS to establish variety of SIP sessions between the requesting user and the multimedia services associated with the RFID value (by using e.g. third party call control technique (Best Current Practices for Third Party Call Control in the SIP, RFC 3725)). This is possible because the IMS AS has both the IMS Function and RFID Application Function. This will benefit the user in that the user can automatically be a part of such a multimedia service only by sending RFID value to the IMS AS because the IMS AS performs all the necessary coordination of the multimedia service delivery ranging from converting the RFID value to e.g. SIP URI and establish a multimedia session between the users and the SIP URI associated with the RFID value. 
         [0114]    Alternatively, user equipment may be configured to establish a SIP session using SIP URI (or TEL URL) associated with a RFID value. That is, when user equipment receives a SIP Response message including SIP URI, it may automatically initiate a SIP session with the SIP entity represented by the SIP URI. 
       ADVANTAGES OF THE INVENTION 
       [0115]    The main advantage of the invention is just providing the valid method for RFID applications to securely identify users to perform user identity-based access control to the information repository server. Also, the following benefits would come together. 
         [0116]    (1) RFID Applications Do Not Need Their Own Naming and Authentication Infrastructure of User Identity 
         [0117]    Even without involvement of the IMS network, it is still possible that RFID applications can perform the user identity-based access control to the information repository servers by introducing both their own naming and authentication systems of user identity. However, it must require too much cost for RFID applications to prepare and manage the naming and authentication infrastructure on its own account with a huge number of RFID reader-embedded personal devices such as cellular phones. 
         [0118]    If the RFID application relies on and makes reuse of the existing IMS naming and authentication infrastructure, development and management cost of the user identity-based access control can be drastically decreased. 
         [0119]    (2) User Identities are Independent of RFID Reader Hardware 
         [0120]    The ISIM or USIM-based naming and authentication mechanism of user identity in the IMS is independent of hardware of the UE. The users can have flexibility in changing the UE hardware by simply inserting their own UICC with ISIM or USIM to desired UE hardware. The users and RFID applications can inherit this flexibility as it is, even when RFID-reader device is put on the UE hardware. They can be free against failure of the reader hardware and can easily change to new extended featured reader hardware without any change to user identity information. 
         [0121]    Although RFID tag has been exemplified as a source of identity that specifies information stored in the information repository server, it should be noted that other sources, such as bar code and QR-code, are also adoptable. Accordingly, an RFID reader may be replaced by a bar code reader, a QR-code reader, etc. 
         [0122]    While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.