Research On Data Downlink Channel Estimation Algorithm For Tunnel Inspection UAV

With the rapid development of wireless communication technology and flight control systems nowadays,Unmanned Aerial Vehicle(UVA)is widely used in military,industrial,and civilian fields.When performing aerial photography,terrain mapping,and orbit inspections,UVA often faces a limited space communication environment.In the tunnel environment,the propagation characteristics of UVA signals are different from other open scenarios.With the influence of the tunnel walls and tunnel shapes,more reflection effect will be generated in the tunnel,and UVA signals will face serious fading,multipath effect and delay effect at the receiving end,which directly affects the quality of signals at the receiving end and the performance of UVA communication system in the tunnel.The UVA communication system adopts orthogonal frequency division multiplexing(OFDM)modulation technology,which can effectively resist the multipath effect of communication in the tunnel,and has the advantage of high frequency efficiency.As one of the key technologies of the OFDM system,channel estimation is also one of the research hotspots in the field of wireless communication.This thesis focuses on how to improve the performance of UVA signals in the tunnel,and mainly carries out the following work:(1)The propagation characteristics of wireless channels are studied and the statistical characteristics of wireless signals are analyzed from the aspects of large-scale fading and small-scale fading.In addition,the tunnel scenario was investigated to research the propagation characteristics of wireless signals in thetunnel,and a statistical model of tunnel wireless channel was established and analyzed.(2)based on the fundamentals of the OFDM system,a framework suitable for UVA communication transmission is built.Pilots are inserted both in time and frequency domains to research the channel estimation algorithms and channel interpolation algorithms based on pilot-assisted.The LS algorithm,MMSE algorithm and Kalman Filtering algorithm are analyzed,and by using frequency domain characteristics of Kalman filtering algorithm based on Singular Value Decomposition(SVD),the performance of different algorithms under tunnel channels is analyzed and compared by Matlab simulation.(3)A simulation platform of UVA wireless communication transmission system based on OFDM technology was built by using Simulink.The wireless channel model of tunnel environment was adopted in the platform.The LS algorithm and the improved Kalman filtering algorithm were implemented in the channel estimation module,and the performance of the two algorithms is analyzed and compared by simulation.