wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

RFID Technology and Its Industrial Applications 9-3
distance; normally, a larger antenna offers more area to capture electromagnetic energy from the reader
and, hence, provides a greater communication distance. There are several kinds of antennas like rectangular
planar spiral antenna, fractal antennas, microstrip patch antenna (monopole, dipole), etc.
Different types of tags have different kinds of antennas, e.g., low frequency and high frequency tags
usually have a coiled antenna that couples with the coiled antenna of the reader to form a magnetic field
[RFGA06]. UHF tag antennas look more like old radio or television antennas because UHF frequency is
more electric in nature [SWEE05]. Recent advanced in technology have even facilitated the deployment
of printed antennas to achieve similar functionality like the traditional antennas. One possible way of
printing antennas is to use silver conductive inks on plastic substrates or papers [TECS05]. The main
advantage of printed antennas is that they are cheap.
RFID Reader Antenna: Every RFID reader is equipped with one or more antennas. These antennas
generate the required electromagnetic field to sense the RFID tags. There are many different kinds of
antennas like linearly polarized, circularly polarized, or ferrite stick antennas. Several antennas can
connect a single reader at the same time. There are different kinds of antennas that are equipped with
standard readers, e.g., the IP3 Intellitag Portable Reader (UHF) [INTE06] comes with an integrated
circular polarized antennas. The advantage of such antennas is that it can read tags in any orientation.
9.2.4 rFID Middleware
In general, the RFID middleware manages the readers and extracts electronic product code (EPC) data
from the readers, performs tag data filtering, aggregating, and counting, and sends the data to the enterprise
warehouse management systems (WMS), the backend database, and the information exchange
broker [CHA07]. Figure 9.1 shows the relationship between tag, reader, RFID middleware, and backend
database. An RFID middleware works within the organization, moving information (i.e., EPC data) from
the RFID tag to the integration point of high-level supply-chain management systems through a series
of data related services. From the architectural perspective, RFID middleware has four layers of functionality:
reader API, data management, security, and integration management. The reader Application
Programming Interface (API) provides upper layer the interface interacting with the reader. Meanwhile, it
supports flexible interaction patterns (e.g., asynchronous subscription) and active “context-ware” strategy
to sense the reader. The data management layer mainly deals with filtering redundant data, aggregating
duplicate data, and routing data to appropriate destination based on the content. Integration layer provides
data connectivity to legacy data source and supporting systems at different integration levels and, thus, can
be further divided into three sublayers as specified in [LEAV05]: application integration, partner integration,
and process integration. The application integration provides varieties of reliable connection mechanisms
(e.g., messaging, adaptor, or the driver) that connect the RFID data with the existing enterprise
systems such as Enterprise Resource Planning (ERP), or WMS. The partner integration enables the RFID
middleware to share the RFID data with other RFID systems via other system communication components
(e.g., the data exchange broker in Figure 9.2). The process integration provides capability to orchestrate
the RFID-enabled business process. The security layer obtains input data from the data management
layer and detects data tampering, which might occur either in the tag by wicked RFID reader during the
transportation or in the backend internal database by malicious attacks. The overall architecture of RFID
middleware and its related information systems in an organization are depicted in Figure 9.2.
Backend database component stores the complete record of RFID items. It maintains the detailed
item information as well as tag data, which has to be coherent with those read from the RFID. It is worth
noting that the backend database is one of the data tampering sources, where malicious attacks might
occur to change the nature of RFID item data by circumventing the protection of organization firewall.
The WMS integrates mechanical and human activities with an information system to effectively manage
warehouse business processes and direct warehouse activities. WMS automates receiving, put-away,
picking, and shipping in warehouses and prompts workers to do inventory cycle counts. The RFID middleware
employs the integration layer to allow real-time data transfer toward WMS. The data exchange
© 2011 by Taylor and Francis Group, LLC