| As the energy consumption of the sensor is proportional to d k in the wireless sensor network ,where d is transmission distance ,and k is a constant not less than 2,So long distance transmisstion in wireless sensor network is very costly.In order to prolong the lifetime of wireless sensor network ,at the same time, guarantee the connectivity of the whole network , deploying addition more powerful relay nodes has been the main solution.In this dissertation, we mainly study the problem of the relay node deploy in heterogeneous two-tiered wireless sensor networt. The whole dissertation is organized as following:Chapter1 outlines the background of our subject. Give some introduction for basic concepts in graph theory, combinatorial optimization, algorithms and complexity.Chapter2 introduces relay node deployment problem in wireless sensor network and related research. In the following, we introduces the definition and classification of the relay node deployment.we summary the literatures considering the difference research objectives of the deployment problem.Chapter3 we discuss the connected problem of heterogeneous two-tiered wireless sensor network ,in other words,we find the minimum number of relay nodes such that the full network is connected with the condition that all the radius of sensor nodes is not equal and the sensor nodes will not participate in packet forwarding.At the same time, we discuss the reliable problem of heterogeneous two-tiered wireless sensor network,and give the performance ratio.Chapter4 presents the improved algorithm about the connected problem of heterogeneous two-tiered wireless sensor network with base station.It achieves its objective by placing the next relay node at the transmission boundary of already selected relay nodes,at a position which covers the maximum number of sensor nodes until all the sensors are covered.The improved algorithm has a low complexity of (ΟN~3 ).Chapter5 summarizes the paper and propose the prospects. |
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