Research And Design Of Chaotic Spread-spectrum Sequence

With the rapid development of science and technology, people’s demand has produced a great challenge to the communication system. The traditional narrowband communication had not been able to content his with people’s demand. CDMA Spread-Spectrum technology arose at the historic moment, its appearance has brought about a revolutionary progress in the field of communication. Meanwhile the wideband communication obtains a chance of rapid development. The traditional Spread-Spectrum Code could not content his with the channel capacity, the communication’s security and reliability. That is why more and more scholars concentrated their energy on the study of new Spread-Spectrum Code.Chaotic Dynamics is an important complex disciplines. Chaotic Dynamics’s appearance apply a new research direction for the researchers to find new Spread-Spectrum Code. Chaotic system is a deterministic system and its movement is nonperiodicity, nonrepeatability, unpredictability. The length of the Chaotic Sequence can be arbitrarily long. So, the Chaotic Sequence can be in accordance with the Spread-Spectrum communication system’s requirement. The research of Chaotic Sequence has become a hotspot of modern communication field.In the paper, we have done a lot of research for the generation and its application of the Chaotic Spread-Spectrum Sequences. In chapter3, we have designed a two level parallel chaotic system based on the advanced Logistic Map and Chebyshev Map, as well as quantized the new Analogue Chaotic Sequence. The simulation results show us that the new chaotic Spread-Spectrum Sequence has excellent correlation, balance as well as the run characteristic. Compared with the advanced Logistic Map, the key space of New Sequence have been increased by a wide margin. In chapter4, the simulation results show us that the communication’s security and reliability have been improved.The research effort can be divided into the following sections:1. First, we have researched chaotics theory,one of the key technologies in the Chaotic Spread-Spectrum communication. And then we have researched the characteristics and the parameters of chaotic systems. Several common chaotic maps have been showed.2. First, we have researched the spread Spectrum-Theory and several performance indicators as well as five work forms of the Spread-Spectrum communication. And then we have studied of the defects and deficiencies of two traditional spreading sequences. The work we have done have Laid a foundation for the next two key chapters.3. There is just one parameter μ or a in the original chaotic systems and the key space Obvious insufficiency. In view of this shortcoming, we have designed a new chaotic system, there are three parameters in the new system:μ, a and which map iterated first, as well as the key space of the new system have been extended. These improvements make the new chaotic system more safety. The new chaotic system not only retains the original system’s excellent feature: simple structure, achieve convenient, and the simulation results show that the statistical characteristics have improved to the original sequences.4. First, we have established a communication system model. And then, the simulation results have been done under Gauss Channel and Rayleigh Channel. By studying the influence of SNR, spreading gain, number of users and different spreading Codes to the communication system, we find that the Spread-Spectrum performances of the new sequence have been improved. Theoretically, the new sequence is able to meet the communication system’s requirements of the spreading Code. This conclusion was consistent with the simulation results. The New Chaotic Spread-Spectrum Sequence was able to meet the requirement of the communication system.