Research On Secure Waveform Design And Performance Optimization Or Satellite Communications

Satellite communications support a wide coverage area at a low cost,and provide a very useful supplement to terrestrial communication systems restricted by geographical and political factors.As the terrestrial communication system gradually develops to saturation,expanding the boundaries of the communication system and establishing an integrated space-aerial-terrestrial communication network are an important trend for communication technology.Satellite communication has security problems,which makes the signals easy to be detected,intercepted and processed by non-cooperative parties.It is necessary to use security technology in the satellite communication waveform.Spread spectrum is a classic secure technology used in traditional satellite communications,which once achieved good performance.However,with the development of low probability of interception signal detection problems,some technologies that can effectively detect the characteristics of spread-spectrum signals emerged.This dissertation designs a security waveform for satellite communications,proposes a time-based pseudo-random code generation mechanism on the base of spread spectrum communication,and uses the time-varying pseudo random sequence to control the selection of the spreading code.hopping frequency and modulation mode.These technologies can obtain ideal anti-interception performance.Satellite communication channels have the characteristics of high dynamics and low signal-to-noise ratio,and signal synchronization is hard to realize.Traditional DSSS technology can help signal's synchronization while improving the anti-interception performance.However,the satellite communication security waveform uses non-stationary technology,which suppresses the periodic characteristics of the signal,and puts forward higher requirements for synchronization technology.The PMF-FFT algorithm has excellent synchronization performance.However,because of the limitation of power and processing capability in the satellite communication environment,this signal detection algorithm still needs optimization.This dissertation proposes an energy detection algorithm based on double patterns of frequency hopping and code hopping spread spectrum,which can perform searching with symbol period as the step size.This dissertation analyzes the performance of this synchronization method,determines the best parameters by Monte Carlo simulation.Comparing the performance and complexity of the algorithm with some other algorithms,it is proved that when this algorithm is used as a coarse synchronization algorithm and PMF-FFT scheme is used as a fine synchronization scheme to form a synchronization mechanism,it can greatly reduce the calculation complexity without performance deterioration compared with the PMF-FFT algorithm.