Initial test runs of RFID deployment show encouraging
results (Rendon, 2005), and hence large-scale RFID deployment is planned. However,
before any successful deployment can be achieved, some RFID issues have to be resolved.
One of them is the RFID reader collision problem, which is the focus of this chapter.
The term ??????reader collision(s)??™??™ is discussed extensively in Engels and Sarma (2002) and
Carbunar et al. (2005). In this chapter, reader collision is simply de?¬?ned as the phenomenon
where an interrogation signal from a certain reader disrupts the communication
between a tag and another reader, and this reader collision problem is potentially magni-
?¬?ed in a dense reader environment such as in a warehouse. To visualize a simple reader
collision situation, we can imagine a situation as shown in Figure 7.1.
In addition, the band RFID is using is an industrial, scienti?¬?c, and medical (ISM) band.
Normally, there is other electronic equipment, intentional or nonintentional radiators that
are operating in this band. Unlike some of the other signaling equipment permitted to use
the band, RFID antennas use comparatively intense RF power to energize passive tags
within their interrogating zones and hence can interfere with nearby electronic equipment
operating in the band of interest. Due to this reason, RFID is subjected to very strict
regulations around the world.
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