Research On Chaotic Spread Spectrum Communication Based On Multi-carrier

In recent years,chaotic signals have been widely used in various fields due to their noiselike,wide spectrum,initial value sensitivity and impulse autocorrelation.Recently,same new properties of chaos are reported for communication applications e.g.chaotic baseband signal can be used to achieve maximum signal to noise ratio using very simple matched filter;Inter-symbol interference(ISI)caused by multi-path can be reduced by using chaos property,etc.In this paper,multi-carrier chaotic spread spectrum communication is studied by combining the chaotic shape forming filter.The main points are as follows:(1)Multi-carrier Differential Chaos Shift Keying Wireless Communication Based On Chaotic Shape-forming Filter is proposed.In this method,the chaotic shaping filter is used to generate chaotic signal and modulate data streams at the same time.This approach can transmit two information streams.The first stream is the information modulated by chaotic shape forming filter,which is called low priority information.The second stream is through the multi-carrier spread spectrum modulation,referred to as high priority information.In this approach,the chaotic signal generated by chaotic shape forming filter is used as the reference signal in DCSK.As the signal is narrowband signal,multi-carriers are used to realize the modulation of high priority information,which improved the data transmission rate.Due to the use of multi-carriers,this method avoids the use of delay unit and reduces the hardware implementation difficulty.The receiver used the corresponding matched filter to obtain the maximum signal to noise(SNR)of the signal for convolution,which improves the bit error rate performance of high priority information.The feasibility and superiority of the proposed scheme are verified by simulation and open-access research platform experiment.(2)Chaotic Shape-forming Filter and Cross Correction Based Quadrature Multi-carrier Differential Chaos Shift Keying Communication is proposed.Considering that the sinusoidal carrier and cosine carrier is orthogonal in same frequency,there are two orthogonal signals in each frequency band.Quadrature multi-carriers are used to transmit reference signals and information bearing signals to further improve the data transmission rate.When the number of carrier frequencies is M,this method can transmit 2M-1 high-priority bits within a high priority symbol duration.Because the reference signal carrying low priority information is transmitted together with 2M-1 identical or opposite data stream,these can be corrected with the high priority information after demodulation,so as to improve the performance of the low priority information.In return,the high priority bit error rate(BER)performance is improved as well by using the corrected reference signal to re-judge the high priority data.The performance of high priority and low priority BER is improved obviously by cross correction.The feasibility and superiority of the proposed scheme are verified by simulation and open-access research platform experiment.(3)Chaotic Shape-forming Filter and pulse position modulation Based Multi-carrier Differential Chaotic Shift Keying Communication is proposed.In this systems,the pulse position modulation is added on the basis of the last method.The transmitted rate is improved using the same bandwidth.This methods maps the high priority information to be transmitted in to the pulse position modulation and then multiplies the chaotic signal.Therefore,the high priority of this scheme can transmit two stream of information bits,namely pulse position modulation bit and direct modulation bit.When the number of carrier frequency is M and the number of pulse position modulation is h,the method can transmit(M-1)×(h+1)high priority bits.Considering channel redundancy of reference signals,cross correction can be used to processed high priority and low priority,so as to improve BER performance of both high priority and low priority.The feasibility and superiority of the proposed scheme are verified by simulation of Gauss channel and wireless channel.