| With the development of communication, in the third generation mobile communication system, CDMA which based on DS-SS technology has got more and more attention for its superiority. The PN sequence used by a DS-CDMA direct affects the performance of system. The PN sequence selected is crucial to the DS-CDMA system.Because the chaotic system depends on the its initial condition sensitively, a large number of uncorrelated, random-like, deterministic and reproducible signals can be generated, which can be used in spread-spectrum communication System as spread-spectrum sequence and has a excellent foreground in the application of telecommunication.In this paper , we have a deep discuss in DS-CDMA system, analysis the structure, principium, the ability to resist disturbance and the Bit Error Rate of the system, then we come to probe into the performance of the PN sequence used in DS-CDMA system synthetically, based on witch we introduce chaos to the study of PN sequence.Aiming at the characteristic of asynchronous DS-CDMA system, some criteria on optimizing spreading sequences are proposed. The method of choosing is also presented. According to the method, chaotic spreading sequences with better performance are obtained. Calculation shows that optimized chaotic spreading sequences are much better than Gold sequences. At last, not only 2 kinds of chaotic sequences' performance are compared, also by dint of Monte Carlo simulation, we Simulated the performance Of optimized chaotic spreading sequences and Gold sequences used in the asynchronous DS-CDMA system at the condition of the channel full of some kinds of interferences. The results show the optimized chaotic spread-sequences can be applied in A-DS/CDMA system well. |
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