Research On Channel Modeling For Wireless Sensor Networks Based On Time Reversal Electromagnetic Wave Transmission

Wireless Sensor Network(WSN)is a new network technology. It can sense, collect and process information of monitoring regional environment or detectied object in real time. then the sensors transfer the processed information to the network user terminals. Now WSN is widely used in many fields, such as intelligent transportation, military, medical and health. In the international arena WSN is considered one of the top second network after internet.But because of the shortage of spectrum resources and the complexity of the deployment environment, the coexistence of WSN nodes pose severe challenge to system designers. Especially the electromagnetic interference and multipath interference in WSN has become the top constraint problems in WSN. Time Reversal(TR) technique can use the multipath in the environment, complete the signal synchronization forcused at the sensor location with space and time. Therefore WSN based on TR electromagnetic wave transmission has advantages in overcoming multipath interference and same frequency interference. Research on the propagation of TR electromagnetic wave in WSN has important significance for the development of WSN.In the first chapter the research background and significance of this thesis is introduced. Next we describe briefly the recent development of the TR channel model. In the second chapter the basic features of wireless sensor nodes and WSN system architecture is presented. After that the interference problems in WSN are given. Then the introduction of the traditional ways to anti-interference in the WSN are introduced. But the traditional ways have their own unique flaw. Therefore WSN based on TR electromagnetic wave transmission is proposed for the drawbacks of traditional ways.The third chapter based on the plane wave theory, regard the electromagnetic wave arrived the sensor nodes as the plane wave. Adopted local ray tracing method to establish a single node focus model. Through this model to study the focusing of TR electromagnetic wave at a single sensor node. We can be targeted for WSN node deployment through this model to improve the coexistence performance. In the fourth chapter we equal the TR communication process to a correlation model. TR equivalent channel is correlation operations between different channel. This model is used to find ways to reduce TR focusing radius, and improve the coexistence performance of the WSN based TR technology. Based on the correlation model is proposed in this paper, we add local scatterer, change the time which is the ray finally arrives at different receiving sensor node to achieve the super-resolution focusing of TR electromagnetic wave. In the fifth chapter aiming at the limitation of TR technology which need channel detection, we use the time delay channel model and ignoring the multipath attenuation, present a method for simplified TR technology. The sixth chapter the summary of this thesis and directions for future research are given at last.