Reasearch On The Blind Estimation Of Non-cooperative Spread Spectrum Code

Direct Sequence Spread Spectrum(DSSS)communication technology is a significant method on spreading spectrum.In this decade,the DSSS communication technology has been applied diffusely in mobile communications,tactical communications,and remote telemetry.Based on its advantages such as: anti-interference ability,confidentiality,and easy to implement multiple access communication,DSSS communication technology has been attached more and more importance and the spreading code detection technology has also become a significant study issue.However,the blind estimation of sequence spread spectrum communication system on a small amount of priori conditions has been an urgent problem of non-cooperative communication needs to be solved and the research on the blind estimation of spreading sequences at low SNR condition is very significance.This paper has three contents.In the first contents,the composition working principle of the DS system was introduced;then,a blind estimation method of spreading sequences,which is based on principal component analysis(PCA)was established and some simulation experiments have been conducted.The results showed that,the detection performance of principal component analysis method on detecting different code lengths of spreading sequences has great differences and the computation of this method is so excessive that this principal component analysis method is not easy to be achieved.This paper studied the blind estimation of long and short codes of spreading sequences on the basis of principal component analysis method.For researching the blind estimation of short code spreading sequence,the projection approximation subspace tracking(PASTd)algorithm was studied.A combined blind estimation method was proposed based on the singular value decomposition to solve the reverse space vector combination problem of PASTd algorithm asynchronous.This method uses a special time window for information interception and restructuring,and separating the spreading sequence information sequence on the decomposition method of the singular values,combing with blind estimation of information sequences and spreading sequences of vector space 2 norm and removing polar blur,respectively.Finally,this method can improve the detection performance of the system.For the blind long code spreading sequence estimation,a segmentation cross-correlation algorithm had been researched.Based on this algorithm,a discrete cosine transform(DCT)blind estimation algorithm was proposed.Firstly,this method matched portion of the signal with filtering(PMF);then using the DCT transform refactoring the output.Finally,the detection performance has been effectively improved.