Key Technologies Of MIMO Non-Coherent Time Synchronization In Low Signal-to-Noise Ratio Environments

In the communication process,the received signal is affected by channel fading,electromagnetic interference and other factors,and the signal-to-noise ratio may be negative.For example,when a communication system with a transmitted signal power of50d Bm and a transmitted signal frequency point of 278MHz is used for long-distance communication of 120km,the signal to noise ratio of the received signal is-17.68d B after field test.This low signal-to-noise ratio environment puts forward higher requirements for time synchronization performance of communication system.Only when time synchronization is correct,communication system can determine the starting position of signal frame and complete subsequent signal processing.The MIMO technology can obtain diversity gain and array gain,which is conducive to increasing the signal-to-noise ratio of synchronization signals and improving the time synchronization performance in low signal-to-noise environment.Therefore,this thesis studies the key technologies of MIMO time synchronization in low signal-to-noise ratio environments.The main research contents are as follows:Firstly,a MIMO non-coherent time synchronization algorithm is proposed for low signal-to-noise ratio environment.The synchronization head structure and workflow of the algorithm are introduced in detail,and the algorithm is analyzed theoretically.The analysis shows that the synchronization head designed in this thesis is composed of multiple segments of the same synchronization sequence and has strong correlation.Therefore,the algorithm can increase the signal-to-noise ratio of10 log₁₀（Q）d B synchronization signal by summing and merging Q-segment signals within a group.The signal-to-noise ratio of10 log₁₀（N _r）d B synchronization signal can be increased by summation and merging of signals betweenN_r receiving antennas.Secondly,the simulation model of MIMO non-coherent time synchronization algorithm is designed.The theoretical performance of time synchronization algorithm,the influence of decision threshold on synchronization performance,the influence of different multipath number on synchronization performance,the influence of Doppler shift on synchronization performance,the influence of synchronization sequence length on synchronization performance are analyzed by simulation,which provides simulation support for setting different algorithm parameters according to different application scenarios.Thirdly,the FPGA implementation scheme of MIMO incoherent time synchronization algorithm is presented.The correctness and feasibility of the scheme are verified by simulation software.Software simulation shows that the proposed scheme can complete the time synchronization task correctly.Under Rayleigh and Gaos mixed channel,Zadoff-Chu sequence with 52 segments and 1024 points length is used to form the synchronization head.The MIMO system is configured with 16 sending and 16receiving.Time synchronization algorithm can achieve 100%correct detection probability in the environment with-38d B signal-to-noise ratio.In this thesis,the key technologies of MIMO time synchronization in low signal-to-noise ratio environment are studied.The results can be applied in engineering practice,and provide theoretical guidance and engineering reference for the design of communication systems suitable for low signal-to-noise ratio environment.