A Framework for Seamless Information Retrieval between an EPC Network and a Mobile RFID Network

Transcription

1 A Framework for Seamless Information Retrieval between an EPC Network and a Mobile RFID Network Min Kyu Han, Il Woo Paik, Byung Hee Lee and Jin Pyo Hong Hankuk University of Foreign Studies {hufs96mk, steigensonne, icebyung, jphong}@hufs.ac.kr Abstract The EPC network, a de facto standard of RFID network, provides a variety of services including Information (IS) and Discovery (DS), fully utilizing today s Internet capabilities, such as HTTP or SOAP communication protocols and HTML or XML contents formats. The mobile RFID network exploits the existing cellular network infrastructure and offers RFID-related information services to the subscribers with cellular phones which RFID reader chips are built in. However, in current cellular network environment, contents are usually represented in WML and delivered by WAP protocol, due to the limitations such as narrow network bandwidth, constraints in display resolution, processing power, and memory space for hand-held phones. Inherently, these bring the problems in information exchange between EPC network and mobile RFID network. In this paper, we investigate and suggest a framework to allow EPC network as well as mobile RFID users to seamless access the information located in the other network. Firstly, we propose an application level gateway which transforms the protocols and contents formats used in EPC network into those specially used in mobile RFID network, and vice versa. The transformation rules may be derived by name resolution at the local ONS installed in mobile RFID network. Moreover, it is suggested that the transformation rules may be automatically derived and transparently accomplished by writing well-formed pair of NAPTR resource records for the local ONS of mobile network, regardless of user s location. Finally, an module concept for RFID applications is proposed not only to lighten the workload of cellular phone equipped with RFID reader and save bandwidth, but also to accommodate the heterogeneity and evolution of cellular phone capabilities. 1. Introduction Radio Frequency Identification (RFID) network is for the systematic communication between RFID tag and reader for searching information by mapping tag with RFID code and storing the change of an object that has a RFID tag. The information service system can track an object, which is out of range of the product company network and offer services to users. From this, the users can have information from scanning RFID tag everywhere in the world. The EPC network, originally developed by the Auto-ID Center with its standards now managed by EPCglobal Inc., was designed to enable all objects to be linked via the Internet. The Electronic Product Code (EPC) is the unique object identifier which is stored in RFID tags. RFID subscribers can obtain useful information about objects which RFID tag is attached to through the EPC network by scanning tag[1]. On the other hand, mobile RFID service offers various RFID services with the mobile stations embedding RFID readers in order for contents users to search information about interesting contents everywhere though mobile communication network and wireless Internet. The Mobile RFID Forum has been formed in Korea and currently performs standardization activities on the service and network aspects for mobile RFID. The EPC network and the mobile RFID network inherently have different system environment, communication protocols, and data formats. While the former fully utilizes today s Internet capabilities, such as HTTP or SOAP communication protocols and HTML or XML contents formats, the latter usually delivers contents represented in WML via WAP protocol over the current cellular network environment. The reason why the wireless Internet services on This work is supported by SK Telecom, Korea

2 mobile networks adopts different protocols and contents formats against Internet is due to the narrow bandwidth of mobile networks and the intrinsic limitations on hand-held devices such as low display resolution, lack of processing power and memory space. Inherently, these bring the problems in information exchange between EPC network and mobile RFID network. Therefore systematic mechanisms such as protocol transformation and contents format translation are required to provide seamless services across the two different types of networks. In this paper, we present weak points of interoperability between EPC network, which is regarded as the standard of RFID network infrastructure, and mobile RFID network. And we also propose communication model and mobile RFID network components to foster interoperability between two networks. 2. RFID Network s EPC Network s The EPC network consists of three major components: the Object Naming (ONS), the EPC-Information (EPC-IS), and the EPC- Discovery (EPC-DS). The ONS is an entity to resolve EPC number in the EPC network. It acts like Domain Name (DNS). Resolving system of ONS is based on DNS. For resolving of the domain name, the ONS manages EPC numbers classified using the Naming Authority Pointer DNS Resource Record (NAPTR RR) among the DNS RR. When RFID subscriber scans the EPC number of the object s RFID tag and sends it to the ONS, the ONS returns NAPTR RR list which has information of EPC-IS URL and accessing method[2] [5]. The EPC-IS is a publicly accessible database that contains information related to objects such as price, weight, packaging and so on. Information in the EPC- IS are shared between subscribers or companies. RFID subscribers can obtain change of objects and history using the EPC-IS[3]. When an object moves from one EPC-IS to other EPC-IS, EPC-DS saves the location of the EPC-IS related to an object in the Discovery Server. Through this process, EPC-DS provides a history or change of status an object to subscribers. Mobile RFID Network s Mobile RFID provides various services with mobile station which RFID reader is built in to users over mobile network. The users equipped with mrfid-ms can be serviced over mobile RFID network anywhere, any time. The proposed network architecture by the Mobile RFID Forum, Korea, is shown in Figure 1. Figure 1. Overview of Mobile RFID Network The user scans a RFID tag of object and the mobile RFID mobile station, shortly mrfid-ms, request the URL to local ODS, which is an ONS to resolve multiple code systems. After mapping the tag ID with URL, the local ODS will return the matched URL to the mrfid-ms. After obtaining the received URL, the mrfid-ms can access to the WAP server which includes the service information for the object. Due to the narrow bandwidth of mobile network and intrinsic limitation of hand-held devices, WAP protocol, which can reduce data by encoding HTTP protocol for low bandwidth, is currently being used with light-weighted language, WML[4]. 3. Transformation of Contents and Protocols and Transparent Access Requirements for Interworking A mobile RFID network is thought of as an overlay network to provide RFID services on a existing cellular network. The mrfid-ms in the mobile RFID network uses WAP protocol and WAP browser using WML data to display the service list or contents received from IS. On the other hand, EPC users in the EPC network usually use a web browser to display XML/HTML data, and use HTTP protocol for communication, fully exploiting today s Internet capabilities. As far as RFID information services are concerned, EPC network and mobile RFID network are separated, that is, they cannot exchange RFIDrelated information. EPC network provides RFID services only for EPC users, and RFID network provides services only for mobile RFID subscribers. To enable information exchange between EPC networks and mobile RFID networks, transformation functionality is required. If an EPC user need to obtain information from IS resident in the mobile RFID

3 network, translation of protocols and transformation of data format are required for the interoperability of services because each network has used different protocols and data formats, and vice versa for an mobile RFID user. Moreover, it should be allowed EPC user to use access method complying with EPC standards, and mobile RFID users to use their proprietary access method and contents format. That is, we need a mechanism to identify whether the direct delivery to IS is required or the indirect delivery through mrfid- ALG is required. The information with regard to protocol and contents transformation should be included, too. Application Level Gateway for Mobile RFID Network As an interworking unit between a mobile RFID network and an EPC networks, we propose the Mobile RFID Application Level Gateway (mrfid-alg) to support such transformation functions. The mrfid- ALG may be located in the boundary of mobile RFID networks and supports network interfaces to both of the mobile network and Internet. The mrfid-alg has transformation functions between WAP and TCP/IP and it support data compression for bandwidth efficiency. It is easy to add, modify and delete various modules. The functions of mrfid-alg are as below: protocol conversion: WAP to HTTP (or SOAP) conversion, and vice versa, data format conversion: WML to HTML (or XML) conversion, and vice versa. A series of transformation functions during a service execution are invoked by the mobile RFID (mrfid-sa) on behalf of a mrfid-ms. Different Interworking Cases As far as the interworking problems between EPC network and mobile RFID network are concerned, we can classify the following information access scenarios as shown in Figure 2: Figure 2. Different access cases to IS Case A: EPC user accesses the EPC-IS (i.e. in Internet) Case B: Mobile RFID user accesses the mrfid-is located in the same mobile RFID network Case C: EPC user accesses the mrfid-is located in a mobile RFDI network Case D: Mobile RFID user accesses the EPC-IS in EPC network 4. Transparent Transformation Invocation based on ONS Resolution Preparation of NAPTR RR for mobile RFID To enable transparent transformation invocation regardless of user s resident network type, we suggest a mechanism based on ordinary ONS resolution. For instance, in case C, when an EPC user wants to access the mrfid-is of a mobile RFID network, the ONS resolution procedure should return URL representing the location of mrfid-alg together with location of target IS. In other words, a local ONS in the mobile RFID network should let the user know the location of the mrfid-alg for transformation in order to connect IS, because EPC user cannot access IS of the mobile RFID network directly. To solve this problem, NAPTR RRs of local ONS in the mobile RFID network need to be carefully prepared. To locate EPC-IS for a RFID in case A and D, NAPTR RRs preparation is out of concern, because we will comply with EPC ONS standards. NAPTR RRs for these case have the prefix epc+ in the service field of the RR. Consider a mobile RFID tag sensed by a RFID reader. The information about the RFID might be stored in mrfid-is. To locate mrfid-is for a mobile RFID in case B, the NAPTR RR should have different prefix, for instance, mrfid+, and it may be written as shown in Table 1. To locate mrfid-is as a mobile RFID tag is read by RFID reader owned by EPC user in case C, access to the mrfid-is should be passed through mrfid- ALG. For this case, the NAPTR RR should be prepared, compying with EPC standards as shown in Table 1, starting with prefix epc+, which denotes this RR is for EPC user s access. But, the difference is that URL of the ultimate mrfid-is is included as an parameter, which will be interpreted within mrfid- ALG. And it should be noted that the NAPTR RR with service prefix with mrfid+ must have higher priority than the NAPTR RR with service prefix epc+.

4 Consequently, these two NAPTR RRs should be stored in the local ONS in the mobile RFID network for direct access to mrfid-is and indirect access via mrfid-alg. Table 1. NAPTR RRs for IS in mobile RFID network epc+epcis mrfid+epcis Regular expression!^.*$! mis.mobile.net/pocket_service.php!!^.*$! ONS Resolution in Mobile RFID Networks The ONS resolver retrieves all the NAPTR RRs matched with FQDN (fully qualified domain name) which is derived from a given RFID code[6][7]. Consider the case C. EPC user s ONS resolver do not know the service with prefix mrfid+, so it would silently ignore this RR. Therefore, the NAPTR RRs with service prefix epc+ remain, then one or more URL might be derived by evaluation of the corresponding regular expression. Finally, the EPC application sends the HTTP request to the mrfid- ALG mrfid_alg.mobile.net, attaching URL of mrfid-is mis.mobile.net /pocket_service.php. Without any modification of EPC ONS resolver, EPC users are allowed to mrfid-is via mrfid-alg, and transformation is performed without intervention. The ONS resolvers in mobile RFID networks should comply with EPC standards. But only the difference is that the both of service prefixes epc+ and mrfid+ are allowed. Consider the case B. A mobile RFID user wants to know the URL of mrfid-is in the same mobile RFID network. The ONS resolver in mobile RFID network will receive two kinds of NAPTR RRs as in Table 1. Since the NAPTR RR with service prefix mrfid+ has higher priority, URL for direct access to mrfid-is mis.mobile.net is taken. Consider the case D. A mrfid-ms senses a RFID tag, and its information is in EPC network. The ONS resolver for the mrfid-ms will receive NAPTR RRs with service prefix epc+ from some ONS within EPC network domain. At this time, the ONS resolver for mrfid-ms should return the URL of mrfid- ALG and a parameter containing the URL of EPC-IS. Then, the requests will be forwarded to mrfid-alg, and mrfid-alg will forward this request to the target EPC-IS. 5. Mobile RFID Applications and their Modules Mobile RFID Applications We propose agents for mrfid services not only to lighten the workload of cellular phone equipped with RFID reader and save bandwidth, but also to accommodate the heterogeneity and evolution of cellular phone capabilities. A application for a mobile RFID service is divided into two pieces: a service application resident in mrfid-ms and a service agent resident in mobile RFID. Therefore, we have been designed SA model so as to work for processing service parts of mrfid-ms[8]. Figure 4. shows applications in SA for mobile RFID services. Mobile RFID Mobile Station Application Application Application Communicator Common Profile Interest Visits Mobile RFID Network Resolver Module Accessing Module BaseProfile Module Session Management Module Compressor Module mrfid-alg Communicator Web Module mrfid-alg Protocol Conversion Data Conversion Figure 3. s and their modules ONS EPC IS EPC IS Internet (EPC Network) for Mobile RFID Applications The mobile RFID (mrfid-sa) is basically designed to overcome the physical limitation of a mobile station so that it reduces overhead of processing RFID services in it and offers various services to users. The mrfid-sa is set of agents which process each RFID service by using more than one module. Practically each module works the processes such as ONS resolution, service request, and service setup on behalf of a mobile station. The Common in the SA supports fundamental processes by resolver module, accessing module and baseprofile module before using real service contents : ONS resolver module gets the location of the IS which has information about objects, then ONS resolver returns it to mrfid-ms Access module takes charge of access to URL of IS. Basically, the IS require an authentication procedure to access. Then, the Access module delivers an authentication request message to mrfid-ms, when the IS requests an authentication for an access BaseProfile module requests baseprofile to IS using ID and password received from mrfid- MS. It receives and parses the baseprofile. The user can select service on display from the result. The baseprofile of IS contains the Profile URL

5 list for services. A service profile includes an interface list for an access Session Management module maintains connection status and procedure of each services by matching mrfid ID and service category Other service specific agent is for their own services using modules of the Common. 6. Interworking Procedures Accessing from mrfid Users to EPC IS After the subscriber in mobile RFID network service scan the interesting object, contents of the object delivered from EPC IS will be displayed. The Figure. as below presents the case of that a mobile RFID network subscriber connects to the IS located in EPC network. Depending on the characteristics of mrfid-ms, various protocols, IP, and WSP can be adapted. Hence, SA should be able to support the mobile RFID services according to the type of protocol and service. Figure 4. Accessing from mrfid Users to EPC IS Figure 4. shows the flows of the procedure that a mrfid-ms scans and connect to IS. This procedure shows how the SA work and the mrifd-alg converts the protocol and data format for interservicing. 1) A mrfid-ms gets tag information by scanning. It sends to the tag information to SA, and SA will query to local ONS which manages data of tag and the related object, using SA s ONS resolving module. The local ONS responses the tag information and the NAPTR RR list, and the SA references service field in the returned NAPTR RR s list for delivering to the mrfid-ms. 2) A mrfid-ms user selects the service type among the service list from the SA, and the chosen service type information will be transferred to the SA. A mrfid-ms has two types of lower protocol. Those are IP based - mrfid-ms and WAP based - mrfid-ms. If the mrfid-ms is based on IP, it requests as type of HTTP to AS, and if WAP based, the request type will be WSP. 3) SA, requested by mrfid-ms, also requests to a IS to Internet by using the Access module. When an SA gets the WSP request, it should send to the IS through mrfid-alg converting protocol (1- a). If the SA gets HTTP request, it can send the request to IS without any conversion (1-b). 4) After Access module s requesting to IS, the IS requires ID and password for an authentication. The Access module will deliver the interpreted data to the mrfid-ms. In this procedure, if the protocol used in mrfid-ms is WSP, the messages should go through mrfid-alg and be delivered to the SA. The Access module will create login form or send parameters for the authentication of the mrfid-ms by referencing a Connection status Table. 5) The mrfid-ms user inputs his ID and password, and the data will be delivered to the BaseProfile module in the SA. The information, obtained from the mrfid-ms for an authentication, will be added as a parameter in the request form. The Baseprofile module request baseprofile of the IS. The baseprofile presents service list that IS offers and the list can be different depending on the type of mrfid-ms. And then the BaseProfile module sends the baseprofile delivered from IS to mrfid-ms. As like the previous procedure, If protocol used in mrfid-ms is WSP, mrfid- ALG will convert data type and protocol. 6) If the mrfid user selects the service in the list, the service will be offered as the service providers. Accessing from Internet and EPC Users to mrfid IS On the contrary to the previous communication model, there can be the case that the users in Internet or EPC network want to access to IS in mobile RFID network for information of objects. Internet is based on HTML/XML, while the mobile RFID service is WSP/WML. Hence, mrfid-alg is required, too.

6 The Figure 5. presents the flow that Internet/EPC network users hope to approach the mobile RFID network. Figure 5. Accessing from Internet and EPC Users to mrfid IS 1) EPC network user, who belongs to Internet, can obtain the location of IS in mobile RFID network by using ONS system. 2) An EPC network subscriber selects service type in the received NAPTR RRs list. The information of selected service type will be delivered to SA. At this time, the service request of the EPC network subscriber should go through protocol conversion and be delivered to the SA. 3) The Access module, requested from the user, requests to an appropriate IS in mobile RFID network. The IS will reply after an authentication. The response message from IS will be transformed from WSP to HTTP by mrfid-alg. 4) After the response from the IS, the EPC user sends ID and password to the SA. 5) The SA confirms to ID and password. The Baseprofile module in the SA requests baseprofile to IS and will return the result to the EPC network subscriber. 6) The subscriber replied from SA searches the baseprofile. The subscriber will select service in list if there is. 7. Conclusions We have proposed the models for unidirectional service in the mobile RFID network and the procedure for mrfid-ms to request service to content server as well as interworking for service compatibility between mobile RFID network and EPC network. The First proposal is the functional model that enables end user to enjoy both of services offered by each network, configuring the mrfid-alg as an accessing point between two networks. The service of mrfid-alg dose not follow the architecture proposed by mobile RFID network. So it belongs to the functional service area of EPC network (Internet). To support Transparency for all of users in EPC network and mobile RFID network is the second. ONS in the mobile RFID network let EPC network user know the URL of mrfid-alg by using modified NAPTR RRs so as to be able to connect to IS, located in the side of mobile RFID network, via mrfid-alg. We have also proposed the SA model to maximize the performance of service processing and to overcome the physical constraints and limitation such as power, memory, display, and etc in a mobile station. The SA consists of Common for ONS resolution, access, authentication and baseprofile and specific service agents for the respective services of IS. These modules can reduce load of mrfid-ms and provide flexibility and extensibility for service. Lastly, we have proposed the communication model for service internetworking and proved the possibility to realize. In this paper, our proposals for interworking service between the two networks are based on structural EPC network model of EPCglobal Inc. More various and different structure model and service over EPC network can be suggested and proposed, and we should focus on not only the service model, but also compatible service and interworking between Internet and mobile network. References EPCglobal, The EPCglobal Architecture Framework Final Version, EPCglobal, 1 July EPCglobal Object Name (ONS) 1.0, EPCglobal, 29 Nomber EPCglobal, Object Name Information (OIS) 1.0, EPCglobal, 8 March Mobile RFID Forum, Common Application Requirements Profile for Mobile RFID, Mobile RFID Forum, 30 August D. Senie, Encouraging the use of DNS IN-ADDR Mapping, INTERNET-DRAFT, April RFID ONS Guideline v1.0, NIDA, 7 Dec M. Mealling, Dynamic Delegation Discovery System (DDDS) Part two: The Algorithm, RFC3402, October Jin Pyo Hong, Technical Document The RFID Classification on Mobile Network Final Version, MCLAB-S-01, Sept WAP-230-WSP Approved Version 5 July