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It is often assumed in sensor network research that the node density is high enough to ensure that all nodes are within communication range of several other nodes at all times. We begin by understanding the effect of node density on the performance of our algorithm. In this experiment, we vary the number of nodes in the rectangular field, and observe the number of formed entities around the moving target. The experiment is repeated for different target speeds. A run is successful if only one entity is formed. In the experiments below, we choose the awareness horizon to be one hop, which as we show later, represents a worst case from the perspective of trackability at the target speeds considered.
Figure 3 demonstrates the results. We see that independent of event speed, our architecture is capable of maintaining the formed logical entity when the number of nodes is 200 or higher which corresponds to an average distance of about 140 meters between any two nodes. Thus, in the rest of this section we fixed the number of sensor nodes to 200, as a rough estimate of ``sufficient'' node density.