Research On Synchronization Algorithm For Frequency Hopping Communication System In High Dynamic Environment

Frequency Hopping communication is one of the key technologies in the field of communication anti-jamming.As the core technology of frequency hopping communication,synchronization determines the performance of a frequency hopping system.In a high-dynamic environment with large frequency offsets,such as air-ground communication or air-to-air communication at high speeds,frequency offset has important influence on time synchronization performance,and time synchronization performance also determines the accuracy of frequency offset estimation.So how to achieve time synchronization and frequency synchronization efficiently in high dynamic environments is essential for synchronization.This thesis focuses on the synchronization technology of frequency hopping system in high dynamic environment.Two-stage acquisition algorithm and multi-level frequency offset estimation algorithm for high dynamic environment are proposed.Interpolation-based sequence correlation timing estimation algorithm and multi-level timing estimation method based on Gardner algorithm are studied.The theoretical analysis of the acquisition algorithm and frequency offset estimation algorithm is also performed in this thesis.And simulation analysis and verification of synchronous acquisition,timing synchronization and frequency offset estimation performance.The main content of this thesis is as follows:Firstly,the requirements of the frequency hopping system in high dynamic environment are analyzed and the frequency hopping system scheme is designed.Based on the scheme,the parameters such as system frequency hopping points and time slot length are determined,so as the system frame format and synchronization frame format.A synchronization scheme adapted to the high dynamic environment is proposed,and the two-stage aquisition algorithem and its sequence design proposed in this paper are elaborated in detail.Secondly,the commonly used synchronization acquisition algorithms in high dynamic environment are studied,and the theoretical performance of the two-stage acquisition algorithm proposed in this paper is derived,including the acquisition probability and false alarm probability.Then the performance of the two-stage acquisition method and Partial Matched Filtering(PMF-FFT)algorithm was simulated and compared.Then simulated the performance of two-stage acquisition and PMF algorithms.Simulation results showed that under the same false alarm probability,the complexity of the two-stage acquisition algorithm is much lower than the PMF-FFT algorithem.Next,this paper discussed the frequency synchronization method in high dynamic environment,derived the theoretical estimation range of traditional estimation methods,proposed a frequency offset estimation algorithm based on symbol-level phase differential,and deduces the Cramer-Rao Lower Bound(CRLB)of the frequency estimation in the AWGN channel.The performance of different frequency offset estimation algorithms is verified by simulation under different frequency offsets.The simulation results show that the multi-level frequency estimation algorithm can cope with the high frequency dynamic environment with large frequency offset better.Finally,the interpolation-based timing estimation method based and the timing estimation method based on Gardner algorithem in high dynamic environment are studied and verified by simulation.The simulation results show that the interpolation-based sequence correlation algorithm has a better performance than the method based on Gardner alogrithem,because the interpolation-based sequence correlation algorithm is assisted by pseudo-random sequence.