Chapter 5 Simulation Results
5.2 The performance of our proposed schemes
Figure 5.2 and Figure 5.3 show the variation of Circumcenter-based scheme among
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five different moving approaches and the Virtual force scheme on the performance of accumulated coverage and moving distances respectively. We see that the Circumcenter-based scheme with Dual-centroid moving approach has better performance in term of coverage than the rest four approaches and the Virtual force scheme. This is because that the directional sensor will distribute more eventually by moving to the centroid of its Voronoi polygon and the centroid of the polygon which is constructed by its Voronoi neighbor nodes. The moving distance of VOR, Minimax, Centroid and Dual-Centroid moving approaches are closely. This is because the circumscribed circle of the directional sensor easily covers all the vertices of its local Voronoi polygon, so directional should not move to new position.
Figure 5.2 The performance in coverage of Circumcenter-based scheme and Virtual Force scheme.
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VOR Minimax
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Dual-Centroid VirtualForce
Figure 5.3 The performance in moving distance of Circumcenter-based scheme and Virtual Force scheme.
Figure 5.4 and Figure 5.5 show the variation of Incenter-based scheme among five different moving approaches and the Virtual force scheme on the performance of accumulated coverage and moving distances respectively. We see that the Incenter-based scheme with Dual-Centroid moving approach also has better performance in term of coverage than the rest four approaches and Virtual force scheme. This is because the same reason we mentioned before that the Dual-Centroid moving approach will eventually make all sensors more and more evenly distributed in the network. And the moving distance of VEC is much larger than others because of the same reason that the directional sensor will be pushed by the neighboring sensors when the circumscribe circle of the neighboring sensor’s sensing sector covers all the vertices of its local Voronoi polygon in the VEC moving approach. However, the VOR moving approach takes more moving distance than the rest three approaches and the Virtual Force scheme in order to get better performance in coverage. This is because that the Incenter-based with VOR moving approach will try to move the incenters to cover the Vfar points.
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Figure 5.4 The performance in coverage of Incenter-based scheme and Virtual Force scheme.
Figure 5.5 The performance in moving distance of Incenter-based scheme and Virtual Force scheme.
From Figures 5.2 to 5.5, we can see that the Incenter-based scheme has better coverage performance than the Circumcenter-based on all five moving approaches.
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VOR Minimax
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However, the Incenter-based scheme will take more moving distances than Circumcenter-based scheme. This is because that the circumscribe circle is larger than the inscribe circle for a given sensing direction. This implies that it will take less moving distance to cover more vertices of polygon for circumscribe circles compared with inscribe circles.
And the virtual force scheme has better coverage performance than the Circumcenter-based with VEC, VOR and Minimax moving approach. And the virtual force scheme has approximate coverage performance to the Incenter-based with VOR and Minimax moving approach. But the moving distance is larger than the Circumcenter-based and Incenter-based schemes both with VEC, VOR and Minimax moving approach. This is because that the Circumcenter-based and Incenter-based schemes use the Voronoi diagram to make all sensors more and more evenly distributed in the network, but the virtual force scheme only use the virtual force between two sensors to repel the directional sensors from a densely to sparse area.
Figures 5.6 and 5.7 show the difference of coverage and moving distance between the Circumcenter-based scheme and Incenter-based scheme both with the Dual-Centroid moving approach under different communication range (Rc) after ten rounds, respectively.
When the Rc increase, we can see that the coverage also increases, but the moving distance will decline. When Rc = 100(m), we can see that the increasing tendency of coverage and decreasing tendency of moving distance toward stationary. This is because that when the Rc is low, the local Voronoi polygons constructed by directional sensors are incomplete and most of them are overlapped [22]. This will cause the directional sensors to determine the inaccurate locations to move which result in the long moving distance. But when the Rc is large, directional sensors will construct the Voronoi polygons completely and determine more accurate location to move. Therefore, the moving distance will gradually decrease.
Figure 5.6 The Coverage performance vs. communication range.
Figure 5.7 The Moving distance performance vs. communication range.
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Communication range (m) Circumcenter-based with Dual-Centroid Incenter-based with Dual-Centroid
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Communication range (m) Circumcenter-based with Dual-Centroid Incenter-based with Dual-Centroid
As shown in Figure 6.1,
sensor to construct the local Voronoi polygon incenter to construct the local Voronoi polygon large, so it doesn’t appropriate to
blue sector is the sensing region of a directional sensor
Figure 6.1 Employ the center point of the directional sensor to construct the local
And in Figure 6.2, if we employ the represent the sensing region of a
region of the directional sensor circumcenter-based scheme and the incenter