This metric can be described as
how fast a reader can identify whether a certain tag exists within its reader??™s range.
In order for an application to make this metric meaningful, we consider an application
where the state of the tags are to be checked out in real time. It is meaningless to use
the quiet state in such applications, and a method that wakes up tags at appropriate
time must be considered. There has been little investigation on such a method, and
we compare the probabilistic tag anticollision protocols without quiet state with the
deterministic ones.
Accordingly, we can apply the conveyer belt to this. In a conveyer belt, the interval and
the moving speed of the tag can be regarded as the speed of the belt and the rate of change
of samples, respectively. Figure 9.11b shows the changing rate of samples and the number
of readable slots per unit time. The number of readable slots per unit time is the number of
readable slots when a reader identi?¬?es all tags within its range.
Since even probabilistic protocols without quiet state achieve high identi?¬?cation ratio
over 98%, we present the results from 40 ms in interval. ABS and AQS show desirable
results while the other protocols are comparable. The reason why the readable slots
increase as the speed decreases is that the time taken for tags to pass by increases.
Therefore, the identi?¬?cation process is performed during a number of rounds.
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