Unraveling Impact of Critical Sensing Range on Mobile Camera Sensor Networks.

In camera sensor networks (CSNs), full view coverage, meaning that any direction of any point in the operational region is covered by at least one camera sensor, plays a significant role in object identification. While prior work is dedicated to static CSNs for the sake of critical condition to achieve full view coverage, such performance still remains unknown in mobile CSNs. In this paper, we take the initiative to address this issue, where a centralized parameter, i.e., equivalent sensing radius (ESR), is defined to unravel the critical requirement for asymptotic full view coverage in mobile heterogeneous CSNs in the sense that camera sensors of different sensing capabilities are moving around in target area. Specifically, we derive ESR under three different mobilities, i.e., 1-dimensional and 2-dimensional random walks and random rotating model, and then explore respectively the corresponding critical conditions to achieve almost surely coverage.(1) The static network is introduced as a baseline in order to gain a clear understanding of how mobility affects coverage performance differently. Interestingly, we find that both 1-dimensional and 2-dimensional random walks exhibit a smaller ESR than static one whereas ESR is even larger in random rotating mobility than that in static CSNs. Moreover, the almost surely coverage is found to be around 1.225 times of the critical condition to achieve coverage with high probability,(2) and therefore turns out to be a stronger result compared to the traditional coverage with high probability. We then turn to the impact of various mobility patterns on sensing energy consumption, a metric that is closely related to ESR, and show that it can be decreased by random walks under certain delay tolerance. The relationship between ESR and percentage of full view coverage is also discussed and the results unify those under homogeneous CSNs.