In the study of three-dimensional underwater sensor networks, the nodes would produce changes in perception range under the influence of environmental factors and their own hardware. Requesting all nodes completely isomorphic is unrealistic. Ignoring boundary effects usually causes the coverage effect of the actual deployment of networks to not reach the anticipated result. This paper firstly presents an underwater sensing model with normal distributed node sensing radius. Secondly, it gives the relationship between expected deployment quality and the number of nodes in the premise of considering boundary effects. Then, it deduces nodes' redundancy formula based on the sensing model with normal distributed node sensing radius, making node could determine whether itself is a redundant node only based on the number of its neighbour nodes. Furthermore, this paper proposes a redundancy model and boundary effects based coverage-enhancing algorithm for three-dimensional underwater sensor networks (RBCT). Simulation results show that RBCT, compared to similar algorithms, has certain advantages in saving energy and enhancing coverage rate. Underwater sensor node Anchor Figure 1: Architecture of UWSN. nodes and buoy nodes while nodes communicate with each other via wireless communication between buoy nodes. The wireless communication module of buoy nodes has multiple power levels to maintain different communication radius. Buoy can also equip locating device like GPS receiver and energy supply device like solar panel. When buoy receives data from underwater sensor node, it transmits them to base station on the sea or shore and then the data is forwarded to communication satellite, ground network, and terminal user. In WSN, coverage rate is an important indicator to network service quality which is the same in UWSN. Optimizing underwater sensor network coverage has important significance for rationally allocating network space resources, better achieving environmental perception and information acquisition task, and improving the network viability. Terrestrial wireless sensor networks have been studied extensively. In [14] , Bai et al. propose and design a series of connected coverage models in three-dimensional wireless sensor networks with low connectivity and full coverage. In [15] , Alam and Haas study truncated octahedron deployment strategy to monitor network coverage situation. However, there are little researches on three-dimensional underwater sensor networks. In [16] , Alam and Haas point that an underwater sensor network can have significant height which makes it a three-dimensional network unlike a terrestrial network. There are many important sensor network design problems where the physical dimensionality of the network plays a significant role. One such problem is determining how to deploy minimum number of sensor nodes so that all points inside the network are within the sensing range of at least one sensor and all sensor nodes can communicate with each other, possibly over a multihop path. The solution to this problem depends on the ratio of the communication range and the sensing range of each sensor. Under sphere-based communication and sensing model, placing a node at the centre of each virtual cell created by truncated octahedron-based tessellation solves this problem when this ratio is greater than 1.7889. However, for smaller values of this ratio, the
The network coverage quality is studied with respect to the number of sensor nodes deployed in underwater WSNs REF .
Redundancy Model and Boundary Effects Based Coverage-Enhancing Algorithm for 3D Underwater Sensor Networks
International Journal of Distributed Sensor Networks
Computer Science