Application Of Chaotic Sequence In Spread Spectrum Communication System

Now, with the rapid development of spread spectrum communication technology, there are more and more high-quality requirements. With the principle of spread spectrum communication, in the spread spectrum communication system, the performance of spreading sequences has an influence on the advantages and disadvantages of communication systems. So, on the source side, improving the capability of spreading sequences will be the key of spread spectrum communication system.The discovery of chaos provides a new way to research on the spreading sequences. Chaotic system is a nonlinear dynamic system, similar to random process, this process is non-periodic, seemingly without the rules of moving, but is extremely sensitive to the initial value. Compared to spread spectrum codes which are now applied widely such as m-sequences and Gold-sequences, chaotic sequences can provide more codes with better correlation and stronger confidentiality, and these codes are easy to generate and regenerate.This paper makes some researches on chaotic sequences used in spread spectrum communication system, and takes the Logistic_Map chaotic spreading sequences as an example, introduces an improved method of generating digital chaotic spreading sequences. The method uses the technique of mid multi-bit quantifying and the technique of truncation to quantify, after a large number of simulations, this method retaining good quality of the two-valued quantitative method is verified. And then, the method not only reduces the number of iteration and omits a lot of processes of initial value selection and judgment, but also avoids regenerating the system, which helps to enhance the system's security. Mainly divided into the following sections:1. Studied on m-sequences and Gold-sequences which are representative in Spread Spectrum Communication, analyzed the disadvantage in the current spread-spectrum communication system.2. Analyzed some representative chaotic maps, and compared the advantages and capabilities between chaotic spreading sequences and traditional sequences. Then generalized the selection criteria of chaotic spreading sequences.3. Suggested an improved method of generating chaotic spread spectrum sequences based on hardware implementation. Described the improved method particularly, verified the performances of the improved chaotic spread spectrum sequences and made a large amount of simulation of the codes.4. Established a simulation model of spread spectrum communication system. Simulated the improved methods of chaotic spread spectrum. Analyzed and compared the performances between the improved method and the tradition method.