The Fast PN Acquisition Algorithm Research Based On DS-SS Communication System

At present, the Spread Spectrum (SS) communication technology has been madeprofound research as one of the wireless communication systems. Owing to its manyadvantages such as strong anti-jamming, good security and low power consumption, ithas been applied well both in military uses and in commercial business. However, theSS communication technology contains more complex technical problems comparedto the common communication systems. Pseudo random (PN) code synchronization iskey characteristic technology of the SS system. It is also the difficult problem in theresearch of the SS system. Only when this key technology is well dealt with, can theSS system work effectively and play its advantages.Generally speaking, pseudo random code can be achieved by acquire and track.While many of the researches presently has been made in the process of pseudo codecapture. The traditional pseudo code acquisition algorithm has some advantages, suchas long length of acquire and complicated realization of mathematic construction etc,which makes it hard to realize the PN acquisition under the low SNR and largeDoppler frequency shift condition. Aiming at the shortcomings of traditional PNacquisition, the research aim of this paper is research of PN code acquisitionalgorithm which is of high acquire probability and less acquire time.The main idea of this thesis is offered as follows:First of all, the author makes a brief introduction about the theory of the SScommunication system，and the generation, construction and characteristics of thepseudo code, then he illustrates several traditional PN acquisition method includingsliding correlation method and match filter method etc and especially analyses theiradvantages and disadvantages.Secondly, in the most condition of Doppler frequency shift to improveacquisition algorithm, firstly, use correlator combine fast Fourier transform tofrequency shift estimation of the Doppler frequency shift, and then estimate the valueof the Doppler frequency shift. In order to eliminate the effect of Doppler frequencyshift. More importantly is to improve algorithm so as to Code-Doppler frequency, twodimension searching is reduced to one dimension.Lastly, on the basis of researching tradition PN acquisition algorithm, a PN codeacquisition method based on boolean satisfiability is proposed. The process of boolean satisfiability intelligent searching are used to acquire sequence, judgetime-delay and errors, which thus reduce the influence of noise to acquisitionalgorithm. Only in this way, can the outcome of PN code sequence of coarsesynchronization with the receiver and the effect of rapid acquisition be achieved.Finally, the author analyzes its feasibility and effectiveness through simulation.