This
is also known as a centralized system. A localized system is where each and every RFID
reader has its own LBT sensor.
A centralized LBT system is as shown in Figure 7.3. The LBT sensor will constantly
monitor all the channels allocated for RFID operation, and dynamically assign available
channels to all the readers connected to it. The central control system has to be con?¬?gured
FIGURE 7.3
Centralized LBT system, where readers are connected to one LBT
sensor in nearby surroundings. (From Leong, K.S., M.L. Ng, and P.H.
Cole. 2006a. Synchronization of RFID readers for dense RFID reader
environments. International Symposium on Applications and the Internet.
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.)
Reader
LBT Sensor
Reader Reader ??? ??? ???
Antenna
130 RFID Handbook: Applications, Technology, Security, and Privacy
during the initial setup of the system. A ?¬?ne-tuned centralized LBT system offers high
reliability. However, it requires additional network hardware to connect all the readers to
the LBT sensor. In addition, a centralized LBT system will not be able to be implemented
effectively when mobile readers are dominant in the surroundings. Although the readers
can communicate with the centralized LBT sensor through a wireless link, it is very
dif?¬?cult for the centralized LBT sensor to estimate the position of mobile readers, and
hence is not possible to allocate the best channels for mobile readers.
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