Since the two
commands differ in length, the burst switch can be easily substituted in place of the active
receiver.
The temperature sensors are designed such that the only command they receive is the
temperature request command. When a burst of RF energy long enough to be the temperature
request command is observed the temperature sensors can take appropriate
action. In this case, they take a temperature reading and transmit that reading to the
router. With an appropriate anticollision protocol, the transmission of multiple temperature
readings to the router is regulated to prevent collisions. The sensors were modeled via
a Markov process, as shown in Figure 11.20.
This Markov model is identical in structure for both cases, with the energy consumption
portion of the model being different. With the models as a basis, the energy consumed by
each network for a period of 1 day was determined to be as shown, as in Table 11.4. Using
the burst switch receiver in place of the active receiver, the energy consumed by the burst
216 RFID Handbook: Applications, Technology, Security, and Privacy
switch-based sensor was approximately 56% lower than that of the sensor with the
RF receiver.
11.4.2 Smart Buffer
Broadcasting is the only communication method between RFID readers and tags. However,
RFID technology uses not only broadcast RFID commands but also point-to-point
(P2P) commands speci?¬?ed in ISO 18000 Part 7 and ANSI 256 active RFID standards.
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