Research And Implementation Of Satellite Internet Of Things Modulation And Demodulation Algorithm Based On Chirp System

With the rapid popularization of Internet of Things applications,medical treatment,transportation,intelligent environment,and social networking are all the main application areas of Io T.The worldwide Internet of Things will become a reality in the near future.However,with the increasing number of Io T application scenarios,the traditional terrestrial Io T will lose its applicability in some special application scenarios.The terrain,climate and other conditions have restricted the construction of ground base stations and the use of corresponding networks.The ground Internet of Things has encountered a mismatch in service capabilities and performance requirements in remote areas,deserts,oceans,and disaster-prone areas where ground networks are vulnerable.In order to provide services in the above special application scenarios,the traditional Internet of Things technology has started to develop in the direction of Satellite Internet of Things.The Satellite Internet of Things can be seen as a supplement and extension of the ground Internet of Things,using low-orbit satellites and low-power wide-area networks for largescale data exchange between Io T terminal devices.However,the development of the Satellite Internet of Things is relatively slow,and there are no mature physical layer communication standards,networking schemes and protocol specifications.Therefore,it is very necessary to study a suitable Satellite Internet of Things modulation and demodulation scheme.This article first introduces the development status of the Satellite Internet of Things,Linear Frequency Modulation technology and Frequency Shift Linear Frequency Modulation technology.Through the analysis of the research status at home and abroad,it is found that a lot of research work needs to be carried out on the low-orbit Satellite Internet of things at home and abroad,especially in the communication system applicable to the Satellite Internet of Things.Through the research and analysis of the background,this article will conduct a detailed study on the modulation and demodulation scheme of the Satellite Internet of Things based on the Linear Frequency Modulation system,analyze the specific hardware and software implementation algorithm of the modem,and finally implement the modem model on the FPGA.This paper studies the modulation and demodulation scheme based on the LFM system,clarifies the generation method of the frequency-shifted LFM signal,and performs time-frequency and spectrum analysis on the frequency-shifted LFM signal,and then studies the orthogonality of the frequency-shifted LFM.The orthogonality of the signal is verified by simulation.After that,this paper studies the demodulation scheme of frequency-shifted chirp signal,and clarifies the method steps of frequency-shifted chirp demodulation.Based on the above analysis of the principle of frequency-shifted chirp modulation and demodulation technology,the design process for implementing the modem is given.The simulation and verification are carried out in combination with the AWGN channel and the satellite typical channel model,and the actual test of the Satellite Io T modem with chirp system on the Xilinx ZC706 development board is completed.Based on the in-depth study and analysis of the principle of frequency-shifted chirp modulation and demodulation,this paper puts forward the method steps of hardware implementation of a Satellite Io T modem based on chirp system,and finally implements the modem on FPGA.