Research On Fundamental Issues In Wireless Sensor Networks

With the increasing in speed of science and technology, we have involved in the information age. Wireless Sensor Network (WSN) is a new generation of network technology followeded Computer Network, Internet and Mobile Communication Network, which has an extensive application and exerts a profound influence on all aspects of human production and life. Internet changed the way people interact, while WSN changed the one human-nature interactions. WSN, the hot topic in information technology field, involves network, computer, communication, signal processing, sensor, embedded system and micro electro mechanical system fields. At the same time, some new problems in research also offer grave challenges for people.Based on these challenges in research, some basic and key problems in WSN are studied in this dissertation, including Coverage, Identifying neighbor and Connectivity, Network hop count, and Data Fusion of WSN. And the main research contents and originality innovations are as follows:1. Study on Coverage in WSN.WSN always shoulder monitoring and sensing responsibilities to the examination area, and Coverage is just a measure of the monitoring and sensing ability to target area. Coverage is a key problem in WSN which affects the monitor to the examination area directly. In this paper, three kinds of coverage measures in random WSN based on Boolean sensing model and general sensing model, area coverage, node coverage and detectable are investigated respectively by establishing location and sensing model of sensor nodes. Moreover, corresponding effectiveness of coverage measure is checked by simulation2. Study on identifying neighbor node in WSN.Usually when the wireless sensor network is deployed, every node in WSN is no any information of other nodes within its transmission range. For effective communication with other sensor nodes in WSN, every sensor node needs identifying neighbor node. In this paper, the 1 st nearest neighbor node, the 2nd nearest neighbor node, the kth nearest neighbor node and isolated node are studied by establishing spatial node distribution model of sensor nodes. And probability distribution function of neighbor node distance and corresponding expression of critical transmitting range for sensor nodes are obtained. At last, the effectiveness of calculated probability distribution function of neighbor node distance and corresponding critical transmitting range of sensor nodes are checked by simulation.3. Study on Connectivity in WSN.Network connectivity is the necessary prerequisite to ensure normal operation of WSN. Because of the sensor nodes scattered randomly over area of interest, sensor nodes can be ensured to communicate with each other in order to aggregate sensing data hop by hop to the base stations by connectivity. In this paper, the connectivity of WSN in two-dimensional space is discussed. And the probability distribution functions of 1-connectivity,2-connectivity and k-connectivity and the expressions of corresponding critical transmitting range of sensor nodes are derived using above obtained probability distribution function of neighbor node distance respectively. Moreover, the effectiveness of network connectivity probability distribution function is checked by simulation analysis.4. Study on network hop count in WSN.In WSN, the network average hop count is one of the most important basic parameters often as the key metric of the comparison for different wireless multiple hops network routing protocols. We investigate mathematical expectation problem of network hop count between arbitrary source node and destination node in this paper. A mathematical model represented the relationship between network average hop count and some parameters in WSN, such as node transmission range, density of nodes deployed, monitoring areas, are acquired. Meanwhile, it is also proved that mathematical expectation of network hop count and the distance among sensor nodes are related to each other. Furthermore, the correctness of obtained models is verified by simulation. It is shown that the analytical results and simulation results are close to agreement.5. Study on Data Fusion in WSN.WSN is a kind of network that energy and communications bandwidth are strictly restricted. So untreated original sensor information transmit in network will take enormous communication bandwidth and energy consumption. The only solution is data fusion to sensing information. In this paper, we study data fusion in WSN under the parallel fusion pattern and serial fusion pattern respectively. And the mathematical descriptions of data fusion in two fusion mode are given. Moreover, corresponding local and global optimization rule are obtained. Finally, the effectiveness of obtained optimization rules is checked by simulation and performance analysis.