Ds Signal Code Sequence Recovery Algorithm And System Performance Simulation Study

Direct sequence spreading spectrum signal has been widely used both in military and commercial telecommunication area, owing to the ability of working at low signal-to-noise ratio (SNR), strong anti-jamming, lower probability interception and mitigating the effects of multi-path fading effects. So the DSSS communication antagonism technology becomes an urgent research topic in the communication field. The blind detection, parameters estimation and recovery of spreading sequences are the main contents of DSSS communication antagonism. After having estimated some signal parameters, it need to recover the spreading sequences before de-spreading the DSSS signal and recovering the primitive information. Therefore the research on blind estimation of PN sequences shows the vital urgency and significance at present. This paper focuses on the blind code synchronization approach and the spreading sequences estimation algorithm. In this thesis, the spreading sequence restoration has been analyzed. The methods of code sequences restoration are explored and investigated, and the key work and innovations of the thesis mainly include:1. Set up the synchronous and non-synchronized base-band signal model, introduced the two programs of code sequence estimation and despreading, researched the principle of restoring the code sequence based on the principal eigenvector and computer simulation based on eigen-value decomposition algorithm.2. Studied the code synchronization technology, including delayed multiplication and modified sliding window, modified sliding window method is researched for code synchronization, combining algorithm of restoring code sequence a lot of simulations are done in synchronous and non-synchronous cases.3. Studied the code sequences restoration algorithm of the short-code modulation DSSS signal, including code sequences restoration algorithm based on neural network algorithm, code sequences restoration algorithm based on the projection approximation subspace tracking, code sequences restoration algorithm based on neural network by a novel information criterion. Through many computer simulation experiments, analysis of the feasibility of algorithms in the synchronous and asynchronous two signal models,the relevance of sequences and convergence performance are compared by the algorithms.4. For the problem of code sequences restoration in the lower SNR DSSS signal, researched pre-processing of DSSS signal by the use of wavelet denoising method, then we will proceed to restore code sequences and compare before and after denoising.5. Researched the code sequences restoration algorithm based on fast approximated power iteration, rapid extraction of the principal eigenvector achieves recovery of PN code sequences. Many simulation and algorithm analysis show that the algorithm can quickly extract the principal eigenvector at low SNR, so that spreading sequences can restore real-time implementation.6. For the problem of code sequence restoration of long-code modulation DSSS signal, researched the recovery method based on the subsection technique, many simulations show that this method can restore the code sequences at low SNR, and the performance can also achieve the request.7. Studied the basic ways of parameter estimation in the DSSS/BPSK signal, builded on the union processing system including the DSSS/BPSK signal detection, parameter estimation and code sequences restoration, and a lot of simulation and analysis are done for this system.