Research On The Modulation Methods Of Parallel Combinatory Spread Spectrum Communication Systems

Parallel combinatory spread spectrum communication system is a high efficiency spreadspectrum communication system based on M-ary spread spectrum communication system.This system not only reserve the advantage of spread spectrum communication system, suchas anti-interference, anti-multipath, strong confidentiality, but also have a higher informationtransmission efficiency than tradition spread spectrum communication system.Firstly, this subject gives out a cyclic shift parallel arrangement spread spectrumcommunication system on the basis of transmission efficiency formula of parallelcombinatory spread spectrum communication system. The main feature of this system isgenerating sequential relation between spreading code sequences using a cyclic shift of thespreading code sequences so that the system changes itself from combinatory spreadspectrum to arrangement spread spectrum and improves the transmission efficiency. The keyto realization of the system is to find out the spreading code sequence which after a cyclicshift can still maintain good correlation. The theoretical analysis and simulation find out thatbalance Gold code sequences meets the above requirements. System modeling and MATLABsimulation prove that cyclic shift parallel arrangement spread spectrum communicationsystem is indeed feasible. Contrast traditional parallel combinatory spread spectrumcommunication system, the new system has higher transmission efficiency, but the cost of itis high computational complexity and real-time communication performance reduction.Secondly, facing the problem that the system transmission efficiency improving iscompany with system reliability decline this subject makes a study on the modulation methodof parallel combinatory spread spectrum communication system and gives out a new parallelcombinatory spread spectrum system Quadrature Phase Shift Keying (QPSK) matrix softdecision demodulation method. This method has a higher accuracy compared with thetraditional parallel combinatory spread spectrum system QPSK hard decision and softdecision demodulation methods. After theoretical analysis and simulation experiment, thissubject gives out the reason why QPSK matrix soft decision demodulation system has a lowerbit error rate than traditional QPSK hard decision or soft decision demodulation method inthe sameEb/N0on the perspective of the Euclidean distance and the Hamminng distance, and then gives out the best-fit mapping method in new demodulation mode.Finally, this subject makes analysis and outlook to the research content and then pointsout that synchronization will be the focus of future research. Above all, cyclic shift parallelarrangement spread spectrum communication system is suitable for the non-real-timecommunication system based on the store-processing model.