An Introduction to RFID Technology
In recent years, radio frequency identification technology has moved from obscurity into mainstream applications that help speed the handling of manufactured goods and materials. RFID enables identification from a distance, and unlike earlier bar-code technology (see the sidebar), it does so without requiring a line of sight. RFID tags support a larger set of unique IDs than bar codes and can incorporate additional data such as manufacturer, product type, and even measure environmental factors such as temperature. Furthermore, RFID systems can discern many different tags located in the same general area without human assistance. In contrast, consider a supermarket checkout counter, where you must orient each bar-coded item toward a reader before scanning it. So why has it taken over 50 years for this technology to become mainstream? The primary reason is cost. For electronic identification technologies to compete with the rock-bottom pricing of printed symbols, they must either be equally low-cost or provide enough added value for an organization to recover the cost elsewhere. RFID isn’t as cheap as traditional labeling technologies, but it does offer added value and is now at a critical price point that could enable its large-scale adoption for managing consumer retail goods. Here I introduce the principles of RFID, discuss its primary technologies and applications, and review the challenges organizations will face in deploying this technology. RFID principles Many types of RFID exist, but at the highest level, we can divide RFID devices into two classes: active and passive. Active tags require a power source-they’re either connected to a powered infrastructure or use energy stored in an integrated battery. In the latter case, a tag’s lifetime is limited by the stored energy, balanced against the number of read operations the device must undergo. One example of an active tag is the transponder attached to an aircraft that identifies its national origin. Another example is a LoJack device attached to a car, which incorporates cellular technology and a GPS to locate the car if stolen. However, batteries make the cost, size, and lifetime of active tags impractical for the retail trade. Passive RFID is of interest because the tags don’t require batteries or maintenance. The tags also have an indefinite operational life and are small enough to fit into a practical adhesive label. A passive tag consists of three parts: an antenna, a semiRFID is at a critical price point that could enable its large-scale adoption. What strengths are pushing it forward? What technical challenges and privacy concerns must we still address? Intel Research About the Review Process This article was reviewed and accepted before Roy Want became research Pervasive Computing’s editor in chief. It went through our standard peerreview process and was accepted 28 Nov. 2005.-M. Satyanarayanan conductor chip attached to the antenna, and some form of encapsulation. The tag reader is responsible for powering and communicating with a tag. The tag antenna captures energy and transfers the tag’s ID (the tag’s chip coordinates this process). The encapsulation maintains the tag’s integrity and protects the antenna and chip from environmental conditions or reagents. The encapsulation could be a small glass vial (see figure 2a) or a laminar plastic substrate with adhesive on one side to enable easy attachment to goods (see figure 2b). Two fundamentally different RFID design approaches exist for transferring power from the reader to the tag: magnetic induction and electromagnetic (EM) wave capture. These two designs take advantage of the EM properties associated with an RF antenna-the near field and the far field. Both can transfer enough power to a remote tag to sustain its operation-typically between 10 W and 1 mW, depending on the tag type. (For comparison, the nominal power an Intel XScale processor consumes is approximately 500 mW, and an Intel Pentium 4 consumes up to 50 W.) Through various modulation techniques, near- and far-field-based signals can also transmit and receive data.
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