Development of Sensing and Computing Enhanced Passive RFID Tags Using the Wireless Identification and Sensing Platform

Passive RFID tags are becoming increasingly common in home and work environments. As RFID tags find new applications beyond shipment tracking, they are being embedded in objects throughout our environment. RFID tags are already being incorporated in credit cards for touch-free payments, in clothing for merchandise tracking, and in ID cards for building access control. All these “non-shipping” RFID tags are powered wirelessly and are capable of wireless communication and rudimentary computation. Thus they can be viewed as micro-computing platforms with wireless power and communication capabilities. While the functionality of today’s passive RFID tags is extremely limited, today’s tags can already be thought of as a layer of invisible computing that is seamlessly embedded in objects throughout the environment. This primitive layer of embedded intelligence could grow in sophistication if additional sensing and computation capabilities could be added to RFID tags. The authors’ goal is to evolve this layer of passively powered embedded intelligence by creating RFID tags that support sensors and can execute general purpose computer programs. This chapter reviews several years’ work on the development of our open, programmable passive RFID tag, the Wireless Identification and Sensing Platform (WISP). It also shows how to use the EPC Class 1 Generation 2 RFID protocol to implement advanced RFID sensing applications that go far beyond simple tag ID inventorying applications. Our first venture into sensor-enhanced RFID was the α-WISP shown in Figure 1 (Philipose et al., 2005). With this device, one bit of sensor data was encoded by using anti-parallel tilt switches to multiplex one of two RFID tag ICs to a single antenna. Thus, a reader could infer three states about a tagged item (tag right side up, upside down, or not present). This simple example of overloading the EPC ID to encode sensor data allowed inference of very coarse orientation information. However, the use of commercial RFID tag ICs restricted our ability to control the RFID communication channel and in turn our ability to configure WISPs for new applications.