The Coverage Problem Of Wireless Sensor Networks In A Shadow Fading Environment

Wireless sensor networks are self-organized and multi-hop networks, consisted of a large number of tiny sensor nodes. Wireless sensor networks implement the interaction between human and nature by monitoring surrounding environment and transmitting sensing data, and has vast and substantial prospects.The coverage problem of wireless sensor networks is one of the basic problems which have to solve to operate networks. It reflects the sensor networks'sensing quality of service. Because wireless sensor networks depend on the application, the coverage problem has close relationship to environment. In a free space environment, the coverage area of each node is a disk. However, a shadow fading caused by obstructions in the surroundings of transmitting has an important effect on practical sensor networks, and allows for random power variations around the area mean. So, the coverage problem of the wireless sensor networks in shadow fading environment is the major research object in this paper.In this paper, according to the characteristics of wireless sensor networks, we analyze the major factors effected by the shadow fading environment, and make main contribution as follows:(1) For the complete coverage problem of wireless sensor networks, we derive an explicit expression, which for the minimum number of sensor nodes in the active mode and the distance between two adjacent nodes in shadow fading environment. It is suggested that the relationship between the minimum number of active nodes and the strength of shadow fading, the sensing range.The simulation results show that the effectiveness of the derived formula.(2) In this paper, according to the probabilistic sensing model and collaborative features between nodes, we presents a collaborative sensing model based on probability which can satisfy the certain quality requirements of coverage, and work out the minimum working number. It provides a reasonable and effective evaluation criterion. The experimental results show that the theoretical analysis is effectivt.