For example, the
antenna placement found using an M value of 20 results in an actual coverage of about
63%, which is much smaller than the 72% that can be found by using a larger value of M. In
the three reader antenna placement case, the optimal placement is found even whenMis as
small as 20. But for the two reader placement problem, a smaller value of M can result in a
suboptimal solution, which covers as much as 10% less than the tag space than the best
solution. In the example problems, the optimal two reader placement solution can only be
found when the value of M is greater than 100.
Figure 10.11 shows the optimal 90% read accuracy coverage with different numbers
of antennas. The marginal bene?¬?t is diminishing as n0 increases. With three readers,
40
45
50
55
60
65
70
75
80
85
90
0 0.1 0.2 0.3 0.4 0.5
Search resolution (m)
Optimal coverage percentage (%)
Coverage
percentage for
two reader
antennas
placement
Coverage
percentage for
three reader
antennas
placement
FIGURE 10.9
Optimal coverage percentage for different
search resolutions.
TABLE 10.1
Two Types of Errors for Different Values of M
M 20 44 80 246 450 984 1454
Type 1 Error Percentage (%) 38.18 3.76 11.01 2.67 0.22 0.22 0.44
Type 2 Error Percentage (%) 0.56 3.90 0.29 0.18 0.33 0.18 0.06
Maximizing Read Accuracy by Optimally Locating RFID Interrogators 195
about 86.
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