Radio Frequency Identification (RFID) is a technology that uses non-contact two-way data communication to identify targets through wireless radio frequency. It is fast, accurate and reliable. Compared with traditional identification methods, RFID technology can directly input and process information without direct contact, without optical visualization, without manual intervention. It is very convenient and fast, so it can be widely used in production, logistics, transportation, transportation, medical treatment. Application areas that need to collect and process data, such as anti-counterfeiting, tracking, equipment and asset management. Since the advent of RFID, its technology and industry have been rapidly developed, and has begun to be applied in many fields such as industrial automation, commercial automation, transportation control management, etc., and has become a new economic growth point for the IT industry, with a very broad Market development prospects. From the development trend of RFID technology and application, RFID applications have the characteristics of identification, positioning and event driving. By identifying and locating, it is possible for humans to identify, lock and control marked objects in a virtual network world. Through the real-time events generated by RFID, business processes can be driven to realize the intelligence and automation of business processes.
The RFID middleware acts as an intermediary between the RFID tag and the application. The application side uses a set of common application programming interfaces (APIs) provided by the middleware to connect to the RFID reader to read the RFID tag data. In this way, even if the database software or the back end of the RFID tag information is changed, such as the application addition, replacement, or the number and type of RFID readers, the application end can be processed without modification, avoiding multiple pairs. Maintenance complexity of multiple connections.
1 RFID network framework and middleware system functionsThe RFID network framework defined by the Global Product Electronic Code Management Center (EPCglobal) includes RFID tags, RFID readers, RFID middleware, RFID reader management, electronic product code information service (EPCIS) capture applications, and EPCIS storage. Public services such as EPCIS access applications, local object naming services (ONS), and ONS root nodes, EPC issues, tag information conversion models, tag information discovery, etc. [1-3].
As shown in Figure 1, the RFID middleware system is located between an EPCIS capture application (such as an Enterprise Resource Planning (EPR) system, etc.) and an RFID reader, and the tag information obtained from the reader is processed according to the rules set by the EPCIS capture application. Filter and aggregate and report them in the format and manner they are specified.
The three main functions of RFID middleware:
(1) Interface difference between shielded readers: Traditional reader manufacturers provide control of the device by applying a set of drivers. These drivers provide the same device access function, but between vendors. But they have incompatible control modules, command parameters and even support different air interface protocols. Moreover, when the driver's driver is updated, the upper-layer application software has to change with the change of the corresponding API. Especially when the user uses a large number of devices of different manufacturers at the same time, the overall maintenance cost also increases. The RFID middleware shields the details of the reader interface and driver, and provides a standard ALE reporting interface to the application system, so that the application system does not have to care about the specific interface and driver of each physical device, but concentrates on the implementation of the application business logic.
(2) Label filtering: In the RFID network, there are a large number of readers and tags. For a particular application, it only focuses on the tags of the readers associated with its business. The RFID middleware can filter the label information that the application system does not pay attention according to the ALE rule set by the application system, thereby greatly reducing the processing amount of the label information by the application system and improving the processing efficiency of the application system.
(3) Aggregation of tags: When it comes to the aggregation of tags, we must first explain the concept of logical readers. A logical reader can contain one or more physical readers or antennas of one or more physical readers. The application system can define RFID readers to enable RFID middleware to aggregate and group RFID tags as needed. For example, an access control system, which contains two physical reader antennas at the entrance of the gate, can be defined by the application system as a logical reader called "gate entrance". When the RFID middleware reports the tag information, the tags of the two antennas can be collected in the group of the "gateway" logical reader, which is convenient for the application system to process the tag information.
2 LLRP protocol and ALE protocolIn the EPCglobal standard system, the two protocols most relevant to middleware are LLRP and ALE protocols. LLRP is called low-level because it provides control over air interface operations and air interface protocol command parameters, providing a lower level. Accessibility of reader operations. ALE is an interface specification between the RFID application system defined by EPCglobal and RFID middleware. Through the ALE interface, there is a set of APIs from the application side using middleware. Usually the RFID middleware interface defines a relatively stable high-level application environment. Regardless of how the underlying computer hardware and system software are updated, as long as the middleware is updated and updated, and the interface definition of the middleware RFID acquisition system remains unchanged, the application software requires almost no modification, thereby protecting the enterprise in application software development and maintenance. Significant investment. At the same time, the use of RFID middleware helps to reduce the burden on the secondary development of the enterprise, making them easy to upgrade existing software systems, while ensuring the relative stability of the software system and the expansion of the functionality of the software system, simplifying development. The complexity and so on.
LLRP is the second generation of reader-writer protocol announced by EPCglobal, which defines the interface between the RFID reader and the client. Compared with the previous generation reader protocol, LLRP is closer to the details of the air interface protocol required for the reader to run, or more specifically to the reader parameters and control parameters in the EPCglobal Class1 Gen2 protocol. In addition to the current support for EPCglobal C1G2, LLRP also provides the corresponding expansion capabilities, which can easily support other air interface protocols in the future.
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