Research On Methods For Getting The Minimum Number Of Mobile Sensors In WSN Sweep Coverage

Given the advantages of wireless sensor network, it has been widely developed in various fields. In application of building energy efficiency, the status of energy efficiency in a building can be concluded from the consumption of energy by that building and some environment physical parameters such temperature, humidity, wind speed, air pressure and so on. The monitoring of energy efficiency status is one of important steps for some application such as energy management, energy efficiency evaluation and energy efficiency audit. Because of the complexity of space structure, wireless sensor network can be applied by the energy efficient status monitoring process effectively. How to efficiently monitor the tasks as the energy efficient status by wireless sensor network is the key point.In the application of building energy efficient status monitoring, all interesting location in target area should be covered by wireless sensors for the acquisition of all interesting parameters. Coverage technologies such as carpet coverage and barrier coverage in wireless sensor network can be used for the coverage of each interesting location by the wireless sensor network. Both of them are continuous on time and space. In some applications as the application of wireless sensor networks aimed at building energy efficiency monitoring, the interesting location and its neighborhood in space is not continuous with other interesting location, and interesting information does not need to be collected in real time. With those two features as above, there are a great lot of wastes on information processing ability of sensor node in a wireless sensor network if the wireless sensor network is constructed with carpet coverage or barrier coverage technologies. However, in the process of sweep coverage, mobile node can be used to collect interesting information in monitoring location in right time.This coverage technology can effectively make up the deficiency of carpet coverage and barrier coverage. Therefore, the research for sweep coverage in wireless sensor network plays an important role in practical application.The paper describes the relevant scene of sweep coverage and the model of sweep coverage in wireless sensor network, discusses the feature of sweep coverage model, defines the problem of the minimum number of mobile sensors in sweep coverage and designs the search based method for solving the problem of the minimum number of mobile sensors. The paper also proves that the problem of path planning for mobile sensors is equivalent to MTSP. PSO is used for MTSP to get moving path of each mobile sensor. Two-phase TSP algorithm is proposed to get equilibrium and short paths quickly. At the same time, the paper analyzes that the problem of getting minimum number of mobile sensors is NP-Hard. Therefore, it is difficult to get the real minimum number of mobile sensors, we can only get the upper bound of minimum number of mobile sensors. On the basis of path planning, a search based method for getting the minimum number of mobile sensors is proposed. The experiment results show that two-phase TSP algorithm can quickly get equilibrium and short paths, and the search based method for getting the minimum number can quickly get the minimum number upper bound of mobile sensors.