The Research On Signal Propagation Characteristics Of The Wireless Sensor Networks Based On GNU Radio

With the widespread of wireless communication and wireless sensor networks,there is a great demand for the research on the related technology.The wireless channel is a necessary propagation medium for wireless communication,which is an important basic field in the research of wireless communication.Different scenarios and environment will lead to different propagation characteristics,which will cause different fading during the wireless signal propagation.Thus,it is significant to make a study of the signal propagation characteristics for wireless sensor networks.It can provide reference and theoretical support for the design and optimization of the system,the deployment scheme of nodes,the improvement of network coverage as well as the choice of key technologies.This paper is based on the 433MHz signal of the ISM Band as the transmit signal frequency and the software radio platform of GNU Radio and USRP as the experimental platform,and majorly researched on the time domain statistical characteristics of small-scale propagation channel sounding both in the agricultural environment and indoor environment.First of all,this paper made a research on the wireless sensor networks,channel models and software defined radio,especially the large-scale and small-scale fading models as well as the channel impulse response model.Then,it studied the measurement methods of multipath fading and summarized the basic characteristics of measuring signal.From the standpoint of the time domain and frequency domain,it made a reaserch and analysis on three kinds of the small-scale channel sounding method.Besides,the capability of GNU Radio and USRP is also introduced.In this paper,two different kinds of the small-scale channel sounding system with 433MHz signal are established based on the GNU Radio and USRP platform.In the agricultural environment,this paper used the sliding correlative sounder that transmited the PN sequence in the wheat field with different antenna heights and propagation distance conditions.In the indoor environment,the linear frequency modulated signal,also known as Chirp,is introduced as transmit signal of the new sounder,and the idea of sweeping frequency steply is applied.This modified frequency domain sounder designed to increase the system bandwidth and improve the time delay resolution accomplishs the indoor experiment with diffrernt scenario conditions.In the end,this paper obtained and analysed all the channel parameters in both channel sounding experiments based on Matlab.The channel small-scale characteristic parameters and results researched by this paper provide a practical reference value for the study of signal propagation characteristics and channel fading models of the wireless sensor network in corresponding scenarios.