Research On Collision Signal Separation Technology For Satellite-based Internet Of Things Massive Access

In recent years,the Internet of Things(Io T)technology has developed rapidly,and its application scenarios cover all aspects of social life.With its advantages of wide coverage,flexibility,and freedom from geographical and climatic factors,the satellite communication system can be used for objects placed in remote areas.Networked terminals provide access services,which can realize the true "Internet of Everything" on a global scale.However,the wide coverage and light control of satellites have brought about the problem of a large number of Io T terminal access collisions.How to reduce the impact of signal collision on system performance under the condition of massive satellite Io T connections is an urgent problem to be solved.Under the existing collision tolerant random access framework,the thesis comprehensively considers the access characteristics,channel characteristics,signal characteristics and other factors of the satellite Io T,and carried out the research and program design of the open-loop collision signal separation technology for short burst signals,and It has been verified by simulation and measured data.The main research contents of the thesis are as follows:In the service scenario of global coverage and massive connections,satellite Io T systems will inevitably encounter user signal collision problems,and the short burst signal separation technology at the receiving end is a key means to solve collision access.In response to this problem,the thesis analyzes the satellite channel characteristics under the existing collision tolerant random access framework,and gives the researched receiving collision signal model.In order to reconstruct a clean copy for subsequent collision separation operations,the thesis combines the characteristics of the satellite Io T signal to design an open-loop demodulation scheme suitable for short burst signal reception and demodulation.This scheme captures the signal through the sliding correlation method,and at the same time,uses FFT to estimate the carrier frequency offset and the initial phase difference to complete the carrier frequency offset estimation.Finally,the timing error is estimated by the timing error estimation algorithm,and the symbol timing synchronization is achieved by using interpolation filtering.Through simulation analysis,the feasibility of the proposed open-loop demodulation scheme is verified.Aiming at the problem of massive Io T terminal access collisions,the thesis combines satellite channel characteristics and Io T signal characteristics under the framework of Contention Resolution Diversity Slotted ALOHA(CRDSA)access framework,based on an open-loop demodulation scheme.A set of short burst collision signal separation scheme based on open-loop adaptive filtering is designed.The scheme mainly includes three parts: preprocessing,reconstruction parameter estimation,and adaptive filtering.First,analyze the frequency offset difference between the clean copy and the collision signal through demodulation preprocessing;second,use the parameter estimation method to estimate the frequency offset difference between the copies and compensate for the frequency offset difference;finally,use the correlation between the clean copy and the collision signal The separation of collision signals is based on adaptive filtering based on the minimum mean square error criterion.Through simulation analysis,the feasibility of the proposed collision separation scheme is verified.In order to further verify the feasibility of the scheme proposed in this thesis,on the basis of MATLAB theoretical simulation,the thesis uses signal generators,signal collectors and other equipment to build a signal separation experimental verification platform,which can simulate the collision signal scene and set the signal key Parameters,the computer software receives the collision signal through the signal collector.Finally,the performance of the proposed scheme is verified by processing the measured data through the collision separation and open-loop demodulation scheme proposed in this thesis.