Chaos Impulse Control,Filtering,and It's Application

As an important branch of nonlinear science,chaos theory and application of chaos in communication are a frontier topic in the field of science and engineering,which promote new research field for conventional communication theory and provide a broader stage for non-linear science.The research on chaotic systems and its application in communication has practical significance for human to understand and utilize non-linear phenomena.The chaotic impulsive control,chaotic shape-forming filter and c orresponding matched filter,chaotic spread spectrum communication and chaotic ranging detection are presented in this paper.The main contents and conclusions are listed as follows:1.An impulsive perturbation control method and a Chaotic Shape-Forming(CSF)filter are proposed,respectively,to deal with the effective modulating and demodulating in chaotic symbolic dynamical communication.The impulsive perturbation control can effectively modulate arbitrary information sequence without constraint.A matched filter at receiver is composed of a simple resistor-capacitor,which not only maximizes the Signal-to-Noise Ratio(SNR)of received signal,but also has a simple electronic circuit and easy to be implemented.The CSF filter is designed by using a linear convolution of a binary symbol sequence and a fixed basis function,and a Matched Filter(MF)is implemented by using the correlation operation between the received signal and the time reverse of the basis function,thus improving the SNR of the receiver and the performance of the communication system.An electronic circuit is designed to validate the effectiveness of the proposed impulsive perturbation control method and a TMS 320C6713 DSP is used to realize the digital implementation of the CSF and the corresponding MF.Moreover,the theoretical BER performances in both Additive White Gaussian Noise(AWGN)channel and multipath fading channel are analyzed,and a time-varying threshold is designed,which according to the information entropy of the received signal is unaltered after the chaotic signal transmitted via the wireless channel.It is used to resist the Inter-Symbol-Interference(ISI)caused by multipath propagation.The Bit Error Rate(BER)comparisons between the proposed method and Binary Phase Shift Keying(BPSK)with Minimum Mean Squared Error(MMSE)equalizer are performed in AWGN channel and multipath fading channel.The simulation results show that the proposed method is slightly inferior to BPSK about 0.5dB in the AWGN channel,due to the ISI caused by the chaotic signal.However,the proposed method outperforms the BPSK with MMSE significantly by using the time-varying threshold in multipath fading channel.Then,the communication experiments in the AWGN channel and in the multipath fading channel are carried out,respectively,by using a channel simulator and two TMS320C6713 DSPs,the experimental results show the similar BER compared with the simulation results2.A Differential Chaotic Shift Keying based on Hybrid System(HS-DCSK)is proposed to ensure the reliability of the communication system under complicated channel.In the proposed method,the chaotic signals are generated by the hybrid system rather than the logistic map in the conventional DCSK,and a matched filter is used at the receiver to maximize the SNR HS-DCSK not only inherits the advantages of the conventional DCSK,i.e.,the demodulation process is performed without chaotic synchronization and channel estimation,but also has ability to resist the ISI caused by multipath propagation.Moreover,the BER is further reduced by using the MF,which has characteristic of low pass filtering and can be used to resist additive high frequency jamming signal effectively as well.In addition,the HS-DCSK provides an extra bit stream by encoding the bit information into the chaotic symbols according to the work described in(1).Gaussian approximation method and Monte Carle simulation verify the superiority of the HS-DCSK,and the BER comparisons are analyzed between the HS-DCSK and other improved DCSK variants.The results show that the HS-DCSK has better BER performance and stronger anti-jamming ability in both AWGN channel and multipath fading channel.3.A Phase Separation DCSK using a second order Hybrid System(HS-PS-DCSK)is proposed to avoid the usage of delay units and to encode an additional bit stream transmission in the chaotic signal to achieve higher data transmission rate as compared to HS-DCSK and conventional DCSK.The chaotic signal containing Low Priority(LP)information bits is used as the reference signal and the information bearing signal after multiplying with the High Priority(HP)information bits.Then,the reference signal and information bearing signal are transmitted separated by orthogonal sinusoidal carriers rather than using the delay units.Due to the carriers being transmitted simultaneously in the same time slot,HS-PS-DCSK not only achieves double bit transmission rate,but also avoids the difficulty with the implementation of delay units faced by the conventional DCSK,and achieves an additional bit stream transmission The frequency modulation operation makes the HS-PS-DCSK compatible with the conventional transducer and antenna,and suitable for high reliability communication under complicated channel.The indoor and outdoor communication experiments are carried out by using Wireless Open-Access Research Platform(WARP),the experimental results show the effectiveness and practicability of the proposed methods4.A M-ary DCSK based on Hybrid System is proposed to provide different qualities of service for transmitted bits according to the levels of important data information,including a High Priority(HP)sub-stream to transmit the important data information and a Low Priority(LP)sub-stream to transmit the lower important data information,such as voice information The HP sub-stream is mapped into a symbol which is represented by one row of the orthogonal Walsh matrix,and the LP sub-stream is encoded into a chaotic continuous waveform rather than the logistic map widely used in current methods.The matched filter is used for the received signal to maximize the SNR of the receiver,thus improving the noise resistance performance of the system.Moreover,HS-M-DCSK provides an optimal solution over an AWGN channel in the category of non-coherent detection of chaotic system by employing the Generalized Maximum Likelihood(GML)decision rule.The parameters of the HS-M-DCSK,such as the order of Walsh and the length of the chaotic signal,are analyzed in both AWGN channel and multipath fading channel.The numerical simulation result and WARP-based experiment show that the HS-M-DCSK has better BER performance and better ability to resist the multipath propagation.5.An underwater chaotic acoustic positing method based on multipath suppression technology is proposed,where the chaotic signal of hybrid system is used as the detection signal for ranging,and the corresponding matched filter is used to filter out the effect of ambient noise,and the multipath suppression technology is used to reduce the influence of the multipath propagation.The proposed method achieves more accurate ranging results as compared to conventional cosine detection signal and linear frequency modulation detection signal.Then,the target coordinates are obtained by using the ranging results and the detection angle.The simulation of underwater acoustic channel model approves that the proposed method outperforms the compared methods,and has better resistance to multipath propagation and more accurate positioning performance in the complex channel.The experimental acoustic ranging system was designed by using TMS6713DSP,microphone and speaker,the experiment result shows that the proposed method not only achieve better performance,but also simplify the system structure,and avoid high fidelity sampling of the chaotic signal6.Two secure communications based on Chen system with time-delay and one way coupled map lattice(OCOML),respectively,are proposed.The Chen system with time-delay is an infinite-dimensional system with more than one positive Lyapunov exponents.The plaintext is encrypted with a hyperchaotic signal generated by the Chen system with time-delay and multi-shift cipher function.This encryption makes different for an eavesdropper to reconstruct the attractor by using time-delay embedding techniques and return map reconstruction.The OCOML system has positive Lyapunov exponents equaling to the dimension of the system.Therefore,the phase space of the signal would be complex.The plaintext signals and a group of key signals are fed into the nonlinear encryption module,then,the output signal and another group of key signals are fed into the linear encryption module,which are further confused the plaintext signal and hides the statistical characteristics of the plaintext signal and key signals The ciphertext signal transmitted through the channel is used as the driven signal after a mean filter,which improves the noise robustness of the secure communication system.Then,the simulation results using multi-frequency sinusoidal signal and voice signal show the effectiveness of the proposed two methods.Experiments on TI TMS6713DSP show the feasibility of the proposed methods in practical communication equipment.