Research On FCrSK Multiple Access Technology For LEO Internet Of Things

In recent years,the Io T of LEO has received widespread attention.Its advantages of low loss,low latency,and wide coverage can make up for many shortcomings in the deployment of the Io T on the ground.However,there are also urgent issues to be addressed,such as high Doppler frequency shift and large node capacity requirements.Multiple Chirprate modulation technology utilizes the time-frequency invariance of Chirp slope dimension,which can provide good Doppler robustness.In response to the dual requirements of Doppler robustness and large capacity parallel multiple access in the Low Earth Orbit Internet of Things,this thesis focuses on the design of multiple access methods and the study of multiple access interference suppression algorithms based on fold Chirp-rate shift keying modulation.A wireless transceiver system has been built based on software radio platform and channel simulator,and the performance of the system and algorithms in Doppler environments was tested in practice.The main research contents of this thesis are as follows:1.First,it explains the research status of Lo Ra,multiple Chirp-rate modulation,and multiple access interference suppression technologies at home and abroad.Secondly,the principles of Lo Ra and FCr SK modulation and demodulation are introduced.Subsequently,an in band frequency division multiple access method was designed using the idle frequency band within the FCr SK bandwidth,providing new multiple access dimensions for multiple users without occupying additional spectrum resources,and analyzing its existing multiple access interference issues.2、An interference suppression algorithm is proposed to solve the interference problem caused by in band frequency division multiple access.From the perspectives of interference cancellation,phase precoding,and adaptive filtering,multiple access interference cancellation algorithms based on error correction feedback,multiple access interference suppression algorithms based on phase assistance,and multiple access interference suppression algorithms based on adaptive filtering are proposed.The performance of the algorithms is analyzed through numerical simulation,and it is verified that the above algorithms can effectively improve the system’s multiple access capacity and have good Doppler robustness.3.Based on the analysis of the detection performance of FCr SK under the time synchronization error,a time synchronization scheme based on signal sorting under the condition of oversampling is designed.Subsequently,a multi user wireless transceiver system is built based on the USRP platform and channel simulator.The feasibility of the synchronization scheme,in band frequency division multiple access design,and the robustness of the system to Doppler are verified through actual measurements.Subsequently,the basic performance of the phase assisted multiple access interference suppression algorithm and the adaptive filtering based multiple access interference suppression algorithm is verified using the system.