Research On The Channel Propagation Characteristics Of Narrow-Band Industrial Internet Of Things

In recent years,with the rapid development of Fifth Generation Mobile Communication System(5G),the maturity of Artificial Intelligence(AI)technology and the upgrading of industrial product demand,industrial manufacturing based on the Industrial Internet of Things(IIoT)is a promising technique to push forward the traditional manufacturing into "Industry 4.0"dominated by smart manufacturing,which can achieve the production with high efficiency,safety and intelligence.Therefore,it's important to study the characteristics of the wireless channel in industrial scenarios to promote IIoT technology.The wireless channel in the industrial environment is significantly different from the traditional cellular communication.In the industrial environment,buildings,metal obstructions,various mechanical equipment,numbers of workers and vehicles are densely distributed in a fixed-scale factory.These environmental factors have different effects on electromagnetic wave propagation and most of the wireless signals are in the Obstructed Line of Sight(OLOS)propagation condition.In this thesis,a narrow-band wireless channel measurement is performed on a typical automotive welding shop scenario to research the special and complex wireless channel.The wireless channel fading characteristics of different situations and time-varying channel in a complex automotive welding factory environment are studied by the related wireless channel measurement methods,parameter extraction and modeling results analysis.For the static wireless channel,the path loss,signal envelope fluctuation and the K factor are extracted.The Line of Sight(LOS)and the OLOS are compared and analyzed.Furthermore,a special case of the signal transmission in industrial manufacturing,i.e.,the receiving antenna or sensor inside the metal chassis or large machinery is also considered.The measurement results show that the signal attenuation is serious in OLOS propagation condition due to high density machinery,metal support and buildings in industrial environment.What's more,received signals in OLOS propagation condition are more seriously attenuated,multipath components are more abundant and the volatility of the signal envelope is more severe.When the receiving antenna is placed inside the metal chassis,the metal chassis will weaken the main path component of the signal and enrich the multipath components because of the signal multiple reflections inside the metal chassis,moreover,the volatility of the signal envelope is also more severe.As a result,under the same propagation conditions(LOS or OLOS),the path loss value inside the chassis is bigger,and the K factor is smaller on average compared with that outside the chassis.For the time-varying channel,the Mechanical Robot Arms(MRAs)channel and the Automated Guided Vehicles(AGVs)channel are studied in the automotive welding shop environment.For the MRAs time-varying channel,the Doppler frequency trajectory is mainly dominated by the relative position of the transmitting antennas,the receiving antennas and the motion of the MRAs.Based on the geometric relationship in the actual environment,the two-dimensional geometric model of MRAs is constructed to characterize the instantaneous Doppler frequency trajectory of MRAs.For AGVs time-varying channels,the Doppler shift should theoretically be the "pure Doppler frequency offset" dominated by the speed of the transport vehicle and the relative position of the transmitting and receiving antennas.However,the extraction results of actual measured data show that the Doppler frequency trajectory of AGVs contains random components,a random Doppler mathematical model is proposed to describe its variation.This thesis provide a reference for the wireless channel research in IIoT and contribute to the construction and development of the IIoT wireless system.