Chaos Digital Sequences And Its Applications In Spread Spectrum Communication

CDMA is a main technique of the third generation wireless personal communication system. It adopts to the method of spread spectrum (SS), so the quality of the SS sequence affects the system performances directly. This thesis focused on the chaotic digital sequence of Direct Spread Spectrum CDMA communication system, including its generation,characteristics and application properties analyzing. At first, the thesis did a summary of generation methods and properties that has been known, pointing out their limitations. The next in order, according to the characteristics of nonlinear system, the generation methods were deeply studied. Based on this, a new method is put forward—drawing out from the middle of the sequence. Then taken four kinds of maps for examples, comparing with m-sequence, their properties are calculated, verifying the advantages of the chaotic sequence generated by the new method. After this, an improved scheme is discussed--using m-sequence to change the sequence's turn and verifying that the permutation parameters have effect on improving the sequence's properties. In chapter 5, Monte Carlo simulation method is used to test performances of our sequences'applications in the given model of Direct Spread Spectrum CDMA system, and results of error rate of the system are given; the comparing resuls of performances of anti-Multi-Access interference and anti-Multi- Address interference of different PN sequence is also shown in this thesis. At last, conclusions are drawn out and the expectations are put forward.