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A directional sensor network DSN consists of directional sensors instead of the omnidirectional ones in the conventional wireless sensor networks. The sensing coverage of a DSN depends on the directionality and size-specific sensing angle of the sensors. The conditions are dissimilar from those of omnidirectional sensor networks for researches, especially on the sensing coverage. For coverage problem in DSNs, the geometric structures of Voronoi diagram and Delaunay triangulation have not drawn the attention of researchers. This study utilised Voronoi diagram and Delaunay triangulation and proposed four basic distributed and localised sensor direction adjustment algorithms with the characteristics of these two geometric structures to explore the field coverage improvement in DSNs. The simulation results and comparisons of coverage performance of the proposed four basic algorithms are provided. They can give the clarity of the performance results and have a reference value for future advanced studies on various coverage issues in DSNs.

In this paper, an adaptive video packet transmission mechanism under WLAN is proposed. In terms of the following characteristics: optimal packet length, layering and scalability of MPEG-4 FGS and Unequal Error Protection (UEP), the low calculation complication is applicable to real-time environments. The findings show that the optimal packet length can be obtained through mathematical analysis according to the current wireless network transmission status and the header overhead. Compared to several distinct scalable video transmission schemes, the simulation results reveal that our transmission scheme is capable of reacting to the varying channel condition with less and smoother quality degradation.

The deployment of wireless sensor devices is one of the most fundamental and important issues in wireless sensor network applications, and coverage is a chief consideration in deployment requirements. This paper proposes a hexagonal cell-based sensor deployment strategy that adopts a mobility-assisted hybrid wireless sensor network. Calculation of coverage hole size, the corresponding hole-healing process and discovery of nearly redundant sensors are based on the hexagonal cells into which the sensing field is virtually divided. Simulations show that the proposed algorithm achieves significantly improved field coverage, and indicates both the number and the influence of nearly redundant sensors in the wireless sensor network.