| CDMA is a kind of advanced wireless spread spectrum technique. It has been widely applied in personal communications , mobile communications and the field of broad band wireless access, and it has also been regarded as the main air access of the third generation mobile communications, because comparing with TDMA and FDMA, CDMA has greater system capacity, higher frequency efficiency and stronger anti-interference ability, at the same time it still has the potential of solving the conflict of limited frequency resource and limitless user request.However, in CDMA system there are multi-path interference, multi-access interference and the interference resulted from absence of synchronization which will limit the user content of the system. So based on the theory of complementary series and OND , the essay presents a new type of SpreadSpectrum series-Modified complementary series, which has been applied inCDMA communication system. And by use of the properties of modified complementary series, we try to cancel the effect of disturbance including multiple-access interference and multiple-path interference.On the basis of theory analysis and reasoning, CDMA single user system models based upon binary complementary sequences and complete complementary sequences are successfully built by use of S-FUNCTION. And respectively taken 8-bit, 16-bit binary complementary sequence and one subset of 4-order complete complementary sequence as examples, the simulations of all the functions of the system are realized. The result proves that it is proper and feasible to use the modified complementary sequences to cancel multi-path interference. It provides a new measure to restrain the single user multi-path noise in the CDMA communication system. Further more, the essay provides hardware design and implementation of some function modules of the system toprove the practicality of the theory of this essay and to establish the base to popularize this technology further. |
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