Research On Synchronization Method Using Superimposed Training Sequence At Low SNR

Relying on the concealment and short-term characteristics,burst communication has attracted more and more attention.The burst communication channel often presents complex and highly dynamic characteristics,which puts forward higher requirements for the system to estimate the parameters required for each frame signal under low signal-to-noise ratio(SNR)condition.In order to meet the needs of burst communication,the new generation of communication systems must comprehensively utilize all resources such as the frequency domain,time domain,and code domain to the greatest extent to ensure efficient signal transmission.This dissertation mainly researches on the synchronization scheme in burst communication under low SNR,and proposes a reliable transmission scheme based on bit-level superimposed training sequence.The research work of this dissertation is divided into the following two aspects.On the one hand,this dissertation introduces the burst communication receiver model and commonly used synchronization algorithms,and analyzes several traditional carrier synchronization algorithms,including Mengali and Moreli(M&M)algorithm,Kay algorithm,Fitz algorithm,and Luise and Reggiannini(L&R)algorithm,based on the principles of carrier synchronization algorithms and performance evaluation indicators.In response to the problem of limited resources faced by burst communication systems to achieve synchronization at low SNR environment,a scheme based on bit-level superimposed training sequence is proposed at the transmitter.The scheme superimposes the training sequence on sparse mapped codewords at the transmitter.The sparseness can effectively reduce the impact of superposition on the correlation of the training sequence.Under this scheme,the commonly used frame synchronization,timing synchronization,and carrier synchronization algorithms are simulated and analyzed to verify the feasibility of the proposed scheme.On the other hand,aiming at the problems of large frequency offset and limited spectrum resources in burst communication systems at low SNR,a carrier synchronization scheme based on bit-level superimposed training sequence frame is proposed.At the transmitter,the signal design method based on bit-level superimposed training sequence is used.At the receiver,a carrier synchronization method with strong anti-interference ability is proposed.The method uses the hidden training sequence to complete the frequency offset estimation,and the coarse frequency estimation and the fine frequency estimation are combined to improve the estimation accuracy.The simulation results show that the proposed scheme has a large frequency offset capture range and is more accurate than the traditional transmission scheme based on training sequence.And the combination of sparse decoding and channel decoding algorithms can guarantee the reliable transmission of information.In addition,the proposed scheme can enhance the anti-interception ability of burst communication,and ensure fast and accurate estimation of frequency offset without occupying additional bandwidth resources.When the burst frame has fragment loss,the superposition scheme can still use the remaining hidden sequence to achieve synchronization,thereby ensuring the reliable transmission of information.