Direct Sequence Spread Spectrum Signal Detection And Parameter Estimation

Because of the low frequency spectrum density, low intercepted probability, strong capacity of combating with multipath interference, similar to noise and other advantages, direct sequence spread spectrum signal is widely applied to the modern communication system. With a military projects for the background and based on the research of massive literature, this thesis aims to deal with the direct sequence spread spectrum signal detection and parameter estimation algorithms under a non-cooperative communication environment.The improved algorithms in this thesis will be implemented on DSP to achieve the direct sequence spread spectrum signal detection and parameter estimation system. Specifically, its main research work is:(1) Direct sequence spread spectrum signal detection algorithms based on average autocorrelation second moment and high order cumulants are analyzed; in order to solve the detection problems in multipath environment, a new detection factor is proposed. MATLAB simulation results show that the proposed detection factor can effectively achieve the detection of direct sequence spread spectrum signal in multipath environment; thus, the conventional detection algorithm used in additive white gaussian noise channel is extended to multipath channel.(2) The carrier frequency estimation algorithms based on the frequency doubling method and cyclic spectrum are discussed; the influence of the shaping filter on carrier frequency estimation is also analyzed. As the estimation algorithm of carrier frequency based on cyclic spectrum is only suitable for nonzero frequency, the new method which is based on complex power spectrum is proposed. MATLAB simulation and data test results on DSP show that the improved method can effectively estimates any form of carrier frequency.(3) The symbol rate estimation algorithms based on instantaneous amplitude spectrum and cyclic spectrum are considered; analyzed the influence of carrier frequency and roll-off factor to the estimation of symbol rate theoretically. MATLAB simulation results show that the larger roll-off factor is the better symbol rate estimation performance will be, at the same time the impact of small range of carrier deviation to the symbol rate estimation is not obvious.(4) Appropriate algorithm is selected to realize the direct sequence spread spectrum signal detection and parameter estimation system function on the hardware system based on DSPTMS320C6454, and a linear assembly language is used to optimize the core algorithm. The system test results verify the correctness and rationality of the system, and show that the optimized algorithm whether in precision or operation time are improved greatly than those with no optimization.In total, system-level simulation of direct sequence spread spectrum signal detection and parameter estimation as well as hardware-based system-level experiments are realized. The results of simulation and signal source measured experiments show that the system can achieve the standard of requirements and the improved algorithms compared to the original algorithm is more suited to the needs of this project.