CHAPTER 23
ANTI-COLLISION ALGORITHM AND SMART ANTENNAS FOR RFID SYSTEMS
23.1 INTRODUCTION
The growing popularity in the radio-frequency identification (RFID) system is pushing for more efficient and reliable multiple access methods to automatically identify multiple tagged objects at once. Optical barcodes have dominated the identification and tracking market from their inception in 1970s. The limitations of optical barcodes and several available technologies for identifications are well known and have been discussed in the preceding chapters. RFID has the capability to identify objects uniquely and has the feature of automated non-line-of-sight reading. However, reliability becomes an issue when the reader attempts to read multiple tags in close proximity. This is due to the fact that data collision occurs during simultaneous transmission of multiple tags. To mitigate the collision problem of reading multiple tags at once by a reader or a set of readers connected to a data processing unit, various anti-collision algorithms have been proposed. A comprehensive account of RFID anti-collision protocols can be found in [1]. In this chapter a comprehensive overview of anti-collision protocols is presented first. The influence of smart antennas, especially MIMO antennas, to improve the anti-collision features of RFID tags is presented ...
