A Study And Implementation Of Jamming Detection Technology Based On DSSS System

Wireless communication has been widely used in various fields so far. However, The reliability of the communication system is still threatened by interference in the complex electromagnetic environment of space. Direct Sequence Spread Spectrum(DSSS) system based on spread spectrum technology has strong anti-jamming, high security, low probability of intercept characteristics. It has become the most commonly communication system and applied to various fields. Although the direct sequence spread spectrum system can work properly with some interference in environment, when the strength of the interference signal exceeds the system tolerance, the reliability of the communication system can not be guaranteed. So the research on the communications jamming technology has become essential way to protect the communication reliability, the study of jamming detection technology is a key technology of the communications jamming technology, which has an important practical significance for the direct sequence spread spectrum communication system.Firstly, this paper introduces the theoretical foundation of direct sequence spread Spectrum system and jamming detection technology, including the basic principles of spread spectrum communication and jamming detection technology, the method of selecting jamming threshold and the calculations of false alarm probability.Secondly, the paper analyzes the common jamming model of the direct sequence spread spectrum system briefly, and studies the basic jamming detection algorithms used in the jamming detection technology: the general jamming detection algorithm, the Consecutive Mean Excision(CME), the Forward Consecutive Mean Excision algorithm(FCME), dual-threshold algorithm. Finally, the paper optimizes the FCME algorithms and analyses simulation results about the detect performance of the differences window function and the detection performance of different algorithms by the tool of MATLAB. Through simulation, analysis and comparison, the improved FCME algorithm with the Hamming window is better than the other algorithms at the same probability of detection,Finally, this paper designs the jamming detection communication system based on the optimization FCME algorithms by FPGA and tests the performance of the system about the detection of single-tone interference, multi-tone interference and narrowband interference in the silent period and the non-silent period.The tests draw the conclusions that the actual performance of the improved algorithm FCME is similar to the performance simulated by the software. With the different signal to noise ratio, the performance of the system about the interference signal detection are not the same. In the silent period, when the single-tone interference signal has the jam-to-noise ratio greater than-30 d B, the multi-tone interference signal has the jam-to-noise ratio greater than-26 d B and the narrowband interference signal has the noise ratio greater than-4d B, the system can detect their position of frequent correctly. In the non-silence period, when the signal to noise ratio is-15 d B, the system can detect the interference correctly that the tone signal has the jam-to-noise ratio greater than-29 d B, the multi-tone signal has the jam-to-noise ratio greater than-24 d B, and the narrowband signal has the jam-to-noise ratio greater than-3d B. When the signal to noise ratio is 0d B, the system can detect the interference correctly that the tone signal has the jam-to-noise ratio greater than-23 d B, the multi-tone signal has the jam-to-noise ratio greater than-18 d B, and the narrowband signal has the jam-to-noise ratio greater than 2d B. The jamming detection communication system shows good performance in the detection of the commom interference signal.