Research On Synchronization Techniques Of Burst-Mode Direct Sequence Spread Spectrum Communication System

Burst communication has the characteristics of uncertain transmission time and short-time transmission,so it plays an extremely critical role in special scenarios such as emergency communication.The burst-mode direct sequence spread spectrum communication system combining burst communication and direct sequence spread spectrum communication can not only improve the anti-interference of burst communication,but also be compatible with the navigation system.Because burst signals have a shorter duration than continuous signals,burst direct sequence spread spectrum communication systems have higher requirements for synchronization technology.Therefore,in order to meet the emergency communication of emergency events such as rescue and disaster relief,this paper designs a burst direct sequence spread spectrum communication system,and conducts in-depth research on its synchronization technology.The main contents of this article include: 1).Combined with the characteristics of burst communication and synchronization implementation requirements,the frame structure of the burst signal is designed.At the same time,the overall design of the transmitting end of the burst direct sequence spread spectrum communication system and the signal synchronization strategy of the receiving end are given.Among them,the signal synchronization strategy at the receiving end includes acquisition,fine estimation of synchronization parameters and steady-state tracking,which is a synchronization strategy combining open-loop and steady-state tracking.2).Based on the basic principles of acquisition,the acquisition accumulation method,acquisition search method and signal detection method are deeply studied,and two signal acquisition schemes are given,namely,the acquisition scheme based on the parallel code phase search acquisition method and the PMF-FFT acquisition algorithm.The capture scheme and simulation analysis of its capture performance.Among them,the two schemes use the signal detection method that combines the maximum observation and the adaptive threshold detection method,which can reduce the probability of missed alarms while increasing the probability of capture detection.3).The traditional algorithm and the difference algorithm of FFT frequency offset estimation are studied,and the two simulation algorithms are compared and simulated.The frequency offset estimation error and the preamble overhead are comprehensively considered,and the frequency offset estimation scheme suitable for this system is given.The principles of the carrier loop and code tracking loop are thoroughly studied,and on the basis of FFT frequency offset estimation,the steady-state tracking and frame synchronization simulation of the carrier loop auxiliary code tracking loop are completed.The simulation shows that the system can complete the synchronization of the burst signal when the signal-to-noise ratio is -20 dB and the preamble is 151 bit.