Chaos Sequences And Its Applications In Sepread Spectrum Communication

CDMA is a kind of main techinques of the third generation personal wireless communication system. The basic element of CDMA is to construct a kind of spread sequence which has the excellent self-correlation and inter-correlation, at the same time, it must have enough coding sequences to meet the multi-users need. Though, in the existing spread sequences system, the m and Gold sequences are used widely, which are generated by the longest linear shift register, they all have the limitation of length and number in some sense.The discovery of chaotic dynamic system broad the way of study of PN sequence. Chaos is a random kind course that appears in the nonlinear system. It is an unperiod and an irregular course. It is not convergence but dose have a bound, while it is sensitive to its initial valve. For all these special performance, they can generate many enough PN sequence with good correlation property.This paper centers on research of the chaotic digital spread-spectrum sequence. First, we introduced the chaotic digital spread-spectrum sequence's production method, the characteristic and the application performance, and made the PN characteristic simulation on the several kinds of chaotic spread-spectrum sequence produced by chaos mappings. Proved the good performance of the chaos sequence, so the chaotic sequence can indeed serve as spreading address code in spreading communication. Next, we proposed one kind of new chaotic mapping model-improved Tent chaotic mapping in the classics Tent mapping foundation, enhanced sequence complex, strengthened the sequence secrecy. And carried on this new chaotic sequence with four kind of classics chaotic sequences and the traditional m sequence the performance simulation analysis to compare, theoretically fully conformed the chaotic digital spread-spectrum sequence to replace the traditional spread-spectrum sequence the possibility and the superiority, specially the improved Tent chaotic spread-spectrum sequence. Finally used the CDMA communications system model and the Monte Carlo simulation method to the improved Tent chaotic spread-spectrum sequence, the m sequence and the Gold sequence carried on the system error rate simulation computation, compared with the different spread-spectrum sequence in the anti-multi-diameters disturbance and the anti-multi-sites disturbance performance fit and unfit quality, had proven the improved Tent chaotic spread-spectrum sequence in harms in the code performance the superiority.