SAINT, Phoenix, Arizona, USA,
#2006 by IEEE. With permission; Leong, K.S., M.L.Ng, A. Grasso, and
P.H. Cole. 2006d. J. Commun., 1, 9,#2006 by IEEE. With permission.)
RFID Reader Synchronization 131
from both of the antennas with the result that the tag is misread. This effect is known as the
tag confusion problem. The discussion of this issue is outside the scope of this chapter but a
simple solution to this is to alternate the operation of antenna A and antenna B every query
cycle.
7.5 Case Study
A case study on dense RFID reader deployment at the dock doors of a warehouse is
presented here. As shown in Figure 7.6, the dark color rectangles represent trucks loading
or unloading goods at the dock doors of a warehouse. Each door is around 3 m in width,
and has two RFID antennas facing each other for tag interrogation.
Since all the readers are synchronized in a way described in Section 7.3, they will start
??????Listening??™??™ at the same time and will be assigned a channel for interrogation at the
end of ??????Listen??™??™ period. The assignment of channels will be geographically in?¬‚uenced.
Two readers assigned to be operating in the same channel will be as far apart as possible.
In addition, the neighboring antennas will be using channels as far apart as
FIGURE 7.5
A typical antenna setting at dock door, with h being the
height of the antenna from the base of a dock door.
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