Chaotic Spread Spectrum Communication System And Its Interference

Chaos spread-spectrum communication has become a hotspot in the field of chaotic application research. Combined theoretical analysis with simulation approaches, the key technologies of multi-user chaotic direct sequence spread spectrum(DS-SS) communication are analyzed, especially in the generation of chaotic sequence, the optimizing of the chaotic sequence, the method of chaotic synchronization, and the simulation and performance analysis of the system. The chaos DS-SS communication's availably jamming becomes the key to get the electronic war's victory, so it is very important to research the effectiveness of jamming and interference referred to the chaos DS-SS communication system.In the first part, the relation between the performance of balance and the parameter of four typical chaotic maps (Chebyshev, Logistic, Improved Logistic and Tent) is studied. The new numeric ranges of initial value and fractal parameter are decided, which provides reference for the generation of chaotic spread-spectrum sequence. The performance of balance and correlated characteristic of these four chaotic sequences with the length of 2000 to 3000 are studied. Compared with conventional spreading sequence (m sequence and Gold sequence), they have better performance of balance and correlated characteristic.In the second part, the techniques of Costas carrier tracking and non-coherent PN sequence tracking in digital receiver are studied. Besides, based on m sequence, a new chaotic sequence synchronization method which has excellent anti-jamming capability is proposed. Through the capture of m sequence, the synchronization of chaotic sequence between transmitter and receiver is realized. This method not only solves the synchronization of the chaotic sequences with the finite length, but also founds the technology foundation for the practical application of chaotic DS-SS communication. In the third part, multi-user chaotic DS-SS communication systems are designed. The error-bit rate performance of this system with parameter of chaotic maps, signal to noise ratio, number of users, the length of sequence is investigated, and the results show that it has many merits, such as good anti-interference, low BER, great capacity, ideal secure properties, and good flexibility.In the fourth part, the optimum jamming bandwidth and optimum jamming frequency for direct sequence system are mathematically analyzed. Based on DS-SS technology, the proposed chaos-based noise jamming technology is studied. Based on chaos DS-SS technology, this Master Dissertation profoundly studies five kinds of different jamming signals, including the white noise, the chirp signal, the noise AM jamming, the noise FM jamming and the noise PM jamming, evaluates the effectiveness of them and makes simulation. Combined theoretical deduction and the computer simulation results, jamming strategy in different situations and get relevant jamming condition is analyzed.