The Research Of Spread-spectrum Communication System Based On The Technology Of Chaos

Chaos is the pseudorandom behavior that appears in confirmed no-linear system, The characteristic of chaotic system is just the same as that of modem cryptology,and the characteristic like noise make it has the nature of concealment, so chaos has abroad application foreground in field of information security. This paper researches its way used in communication.Chaotic spread-spectrum sequences are created by iteration method based on Logistic-map. We discuss the performances of the chaotic sequence, after a good study on chaos-based encryption methods, we put forward a new chaotic sequence encryption method based on parameters changed, the performance of correlation is destroyed by this encryption method. This method enhances the security of the system.The PN sequence used by a DSSS direct affects the performance of system. DSSS usually takes m sequences or Gold sequences as address codes, but they all have the limitation of length and number in some sense. Through asynchronous DS/CDMA system model, we analyze the key points of chaotic spread-spectrum CDMA system performances. Multiple access interference of multi-user system in chaotic DS/CDMA is analyzed. The BER is discussed under the condition of synchronization among the signal of users. In order to generate the security of CDMA system, depress the multiple access interference and improve the capacity of the system, an optimization algorithm for selecting chaotic binary sequence were proposed. Finally, the paper discusses the realization of the optimal chaotic sequences. Three different chaotic spread-spectrum series are used in DS/CDMA system. We compare their capabilities based on the numbers of the optimal chaotic sequences and the performance of the DS/CDMA system. The results show that the Improvable Chebyshev sequence is better than others,which can be used in DS/CDMA system as spread-spectrum sequence.