51 results about "Chaos shift keying" patented technology

The invention discloses a multi-carrier difference chaos shift keying modulation and demodulation method and a modem. The method comprises the following steps: acquiring a DCSK reference signal in a current symbol period; converting a to-be-transmitted M-N serial data bits into M-N parallel data bits; completing information modulation and generating M-N DCSK information signals; completing multi-carrier modulation and generating N-path modulated DCSK reference signals and M-N path modulated DCSK information signals; adding N-path DCSK reference signals and M-N path DCSK information signals and then sending; completing multi-carrier modulation and respectively recovering disperse DCSK reference signal sequences and disperse DCSK information signal sequences; acquiring averaged DCSK reference signal sequence and respectively relating to M-N path disperse DCSK information signal sequences, thereby acquiring M-N related values; completing threshold judgment and outputting M-N path demodulation data bits; merging M-N path demodulation data bits into one path serial demodulation data bit stream. According to the multi-carrier difference chaos shift keying modulation demodulation method, the noise component in the judged variable can be reduced and the bit error performance of the system can be increased.

The invention provides a correlation delay-differential chaos shift keying (CD-DCSK)-based modulation communication method with the advantages of high antijamming capacity, simple circuit structure and low cost. A chaos signal at a transmitting end is subjected to related delay transmission; in front and back two-half symbol periods, two useful signals are transmitted simultaneously; and at a receiving end, the useful signals are subjected to related delay operation of a correlator and are respectively demodulated into useful signals a and b, and the useful signals a and b are subjected to serial conversion to form the original transmitting signals. The method has the advantages of high security of correlation delay shift keying (CDSK), low error rate of differential chaos shift keying (DCSK) and the like; and signals transmitted in channels are more uniform, and have high security and low error rate, and the data transmission rate is 2 times that of the DCSK. Besides, on the implementation of hardware circuits, the CD-DCSK is simpler than QCSK (quadrature chaos shift keying). The method ensures high security, high data transmission rate, higher antijamming capacity and low cost, and is easy to promote.

The invention discloses a multivariate orthogonal chaos shift keying modulation/demodulation method. According to the method, Hilbert orthogonal transformation and orthogonal Walsh sequence weighting are carried out chaos signals to construct a plurality of mutually- orthogonal chaos carrier signals; and the modulation/demodulation is carried out by utilizing a multivariate orthogonal modulation method. According to the multivariate orthogonal chaos shift keying modulation/demodulation method, the delay units in the existing binary/N-nary DCSK receivers are eliminated, the delay units in transmitters are decreased, the realizing complexity is reduced, the bit transmission speed of the system is greatly improved and the bit error rate performance of the system is enhanced to a relatively great extent.

The invention discloses an MIMO secret communication method based on differential chaos shift keying (DCSK). Due to improvement, information is made to be dispersed on two channels for transmission, the reference signal of each way of information is transmitted on the other way, and therefore even when a certain way of information is intercepted in the transmission process, an original signal can not be decoded, and meanwhile, the problem that the utilization rate of the channels is low is solved. Meanwhile, in order to solve the multi-path fading problem, the MIMO technology is used for suppressing the channel noise and the multi-path fading, and the system bandwidth and the transmission power do not need to be increased. By comparing the bit error rate of an original system with the bit error rate of an improved system, it is found that the bit error rate of the MIMO-DCSK secret communication system is lower than that of a traditional system in data transmission, meanwhile, the utilization rate of the channels is higher, and the secrecy is higher.

The invention discloses a confidentiality communication method based on an improved type DCSK, and belongs to the technical field of signal transmission. In response to the confidentiality problem of the DCSK, after the improvement, information is scattered to two communication channels to be transmitted, a reference signal of the information in each channel is transmitted in the other channel, so that even the information in one channel is intercepted and captured in the transmission process, the original signal cannot be decoded, and the problem of low channel utilization rate is solved. Through the comparison of the original system bit error rate with the improved system bit error rate, the bit error rate of the improved type DCSK system is lower than the bit error rate of the traditional system in the data transmission process, and the channel utilization rate is much higher and confidentiality is much stronger. Through simulation it can be seen that the simulation result is consistent with the theoretical analysis, and confidentiality is greatly enhanced. Meanwhile, the improved type differential chaos shift keying DCSK confidentiality communication method is relatively low in complexity, easy for the project to be realized, and will has wide application prospect in the fields of images, military confidential information and the like.

The invention relates to a code multiplexing DCSK (Differential Chaotic Shift Keying) modulator-demodulator based on a PFDM (Orthogonal Frequency Division Multiplexing) technology, and relates to DCSK modulation and demodulation. By utilizing orthogonality of a Walsh code, orthogonality of a reference signal and an information carrying signal on a code domain and overlapping of the reference signal and the information carrying signal on a time domain are implemented, and the problems of different channel responses and poor transmission performance of the reference signal and the information carrying signal, which are caused by channel time selection, are solved; and by utilizing the OFDM technology, each code chip of one frame of signal is propagated on different sub carriers, so that the problem of intersymbol interference caused by channel frequency selection is avoided. Simulation under an Additive White Gaussian Noise (AWGN) channel and a multi-path time-varying channel shows that compared to conventional DCSK, the code multiplexing DCSK system based on the PFDM technology has good transmission performance under the AWGN channel and the multi-path time-varying channel and has resistance to time selection and resistance to frequency selection fading.

Provided are a wide band-differential chaos shift keying modulation method, a transmitting apparatus adopting the wide band-differential chaos shift keying modulation method, a wide band-differential chaos shift keying demodulation method, and a receiving apparatus adopting the wide band-differential chaos shift keying demodulation method. The wide band-differential chaos shift keying modulation method includes: generating a wide band chaotic signal; delaying the wide band chaotic signal; multiplying the delayed wide band chaotic signal by an information signal to output a multiplied signal; and performing a switching operation so as to alternately transmit the wide band chaotic signal and the multiplied signal. Thus, the invention can be realized without an APLL, a mixer, an FM modulator, and the like, to reduce power consumption and manufacturing cost for the transmitting apparatus. Thus, noise characteristics and security performance can be high, and the wide band-DCSK modulation method can be robust to multi-path.

The invention discloses a three-channel carrier index differential chaos shift keying modem and method, which belong to the technical field of chaos communication. Three-channel index modulation is realized by two layers in an inter-channel mutual reference mode, the two layers of modulation are distinguished by chaotic signals and Hilbert signals which are mutually orthogonal, and the signals aremodulated and demodulated by using an index mapping rule and an anti-index mapping rule. On the premise of occupying the same frequency band, in comparison with the existing carrier index differential chaos shift keying system whose reference signals only serve as reference of information signals but do not carry any information, the information signals of each layer in the invention can also serve as reference signals for other layers in the case of information bit transmission, independent reference signals do not need to be transmitted additionally, and thus, a higher bit transmission rate, a higher spectrum utilization rate and better data security can be acquired, and the bit error rate can also be reduced.

The invention provides a fusion code index-modulated multi-ary differential chaos shift keying modem and relates to the field of wireless communication, wherein a receiver is free of any delay unit. Meanwhile, the fusion code index-modulated multi-ary differential chaos shift keying modem improves the system transmission data rate. The subscript value of a Walsh code is adopted as a carrier for the transmission of information bits, so that the number of bits transmitted by the system is improved. The transmission data rate and the energy efficiency of the system are improved effectively. In the orthogonal code multiplexing manner, delay units are effectively eliminated, and the complexity of system implementation is lowered. The simulations of AWGN channels and multi-path rayleigh fading channels show that, compared with the conventional DCSK, the fusion code index-modulated multi-ary DCSK system has certain performance advantages.

The invention relates to a synchronization method of a differential chaos shift keying or frequency-modification differential chaos keying ultra wideband system. The synchronization method comprises the following steps: step 1, averagely dividing an initial search region into four secondary regions, compressing the search region into one of the secondary regions by a method of adopting the characteristics of quite high autocorrelation and quite weak cross correlation of chaos signals and comparing the energy of useful signals collected in each secondary region, and letting n be equal to 2; step n, averagely dividing the search region determined in the last step into two secondary regions, setting the midpoint of each secondary region as an integral start point, comparing the two obtained integral results, determining the region of the larger integral result as a new secondary region, setting the midpoint of the secondary region as an estimated synchronization time, letting n be equal to N+1, ending the algorithm if n is larger than N, otherwise executing the n step of algorithm. The method disclosed by the invention greatly shortens the time needed by synchronization and is quite low in computation complexity so that the implementation complexity of a receiver is effectively reduced.

The invention relates to a demodulation method for a bipolar chaos shift keying communication system, belonging to the technical field of communication. Aiming at the problem of high bit error ratio during the coherent demodulation process when the synchronizing characteristics are not ideal in the bipolar chaos shift keying communication system, the invention adopts the technical scheme that twodifferent chaotic signal trackers are used to respectively track the received modulated chaotic signals, and the mean square errors for the tracked signal and the received signal are calculated and compared to distinguish the transmitted data. The chaotic signal tracking method adopts two algorithms: extended Kalman filter and particle filter, and the results show that compared with the traditional coherent demodulation method, the demodulation method of the invention greatly reduces the bit error ratio when the synchronizing characteristics are not ideal; and the bit error ratio of the particle filter algorithm is superior to that of the extended Kalman filter algorithm.

The invention discloses a CD-DCSK chaos communication scheme without signal mutual interference, and the scheme belongs to the technical field of communication. The conventional CDSK (Correlation Delay Shift Keying) modulation technology is combined with the DCSK (Differential Chaos Shift Keying) modulation technology, a simple orthogonal chaos signal generator is used, thus, an aim of improving error code performance without changing information transmission rate of a CDSK system can be realized. A receiving end extracts data information through related demodulation. Correlation operation isexecuted for received signals and corresponding delay signals thereof through a correlator, then, threshold decision making is executed respectively, thus, data information can be recovered. A threshold decision making criterion is as follows: if an output result of a correlation demodulator is greater than or equal to 0, judging that the sent information signal is '+1'; and otherwise, judging that the sent information signal is '-1'. The information transmission rate of the scheme is twice of the information transmission rate of a DCSK system, and error code performance is improved remarkablyin comparison with the CDSK system. So, the scheme provided by the invention has important application value in the field of communication.

The invention discloses an OFDM-DCSK (Orthogonal Frequency Division Multiplexing-Differential Chaos Shift Keying) communication system and relates to the wireless communication field. The purpose of the invention is that the data rate is increased in the OFDM-DCSK communication system to solve the delay problem of RF (radio frequency). As an irrelevant chaos communication solution, all subcarriers are divided into several groups, chaos reference sequences are transmitted by the central subcarrier in each group, and modulated data streams are transmitted by the subcarriers in the residual groups. Thus, in comparison with a traditional DCSK system, the spectrum utilization rate is improved by a transmitting structure. The received data on a receiving end isn't demodulated by a radio frequency delay circuit, so that a convenient condition is provided to the system in practical application. The system is applied to wireless communication occasions.

The invention requests for protecting an orthogonal multi-user chaos shift keying communication scheme, and belongs to the field of communication systems. A system utilizes an orthogonal chaos signalgenerator to generate two orthogonal chaos signals, and the two orthogonal chaos signals are added together to serve as a reference signal. Different information signals are distinguished by delayingfor different times; each information signal transmits N pieces of user information that are distinguished by Walsh codes; the first and second orthogonal chaos signals are sequentially taken to be multiplied with user information added together to acquire an information signal. By using the orthogonal chaos signal generated by the orthogonal chaos signal generator, the interference in the signalcan be thoroughly eliminated, and the bit error rate performance of the system can be effectively improved. The scheme deduces and simulates a bit error rate formula under AWGN and Rayleigh fading channels. A simulation result indicates that the system can enhance the transmission speed and improve the bit error rate, and has good application value.

The invention relates to the technical field of secret communication, in particular to a communication system for encrypting information through a chaotic signal. The communication system comprises a signal transmitting end and a signal receiving end, wherein an analog signal input port and an antenna A are arranged on a shell of the signal transmitting end; an analog signal output port and an antenna B are arranged on a shell of the signal receiving end; an A/D conversion module, a chaotic signal generating module, an FM-DCSK (Frequency-Modulated Differential Chaos Shift Keying) modulation module, a radiofrequency modulation module and a power transmitting module are arranged in the shell of the signal transmitting end; a filtering and amplifying module, a radio frequency demodulation module, an FM-DCSK demodulation module and a D/A conversion module are arranged in the shell of the signal receiving end; encryption processing of an input signal is realized through the signal transmitting end; and decryption of received encrypted information is realized through the signal receiving end. Through adoption of the communication system, the problem of poor secrecy in current wireless communication is solved, and chaotic encryption processing of transmitted signals is realized, so that the security and reliability of wireless communication are enhanced.

The invention relates to a differential chaos shift keying modulator with re-differential permutation indexing. In a DPI-DCSK single-user transmission scheme, reference signals of (n + 1) bits transmitted each time are information bearing signals of the first (n + 1) bits at the same time, so compared with a PI-DCSK system, chaotic reference signals without bearing bit information are transmitted; according to the DPI-DCSK scheme, the problem of waste of transmission energy is solved. Compared with the traditional PI-DCSK system, the method provided by the invention has better bit error performance, effectively reduces the bit error rate and saves half of transmission energy.

The invention discloses a dual-mode multi-carrier differential chaotic shift keying modulation method and a transmitter. The transmitter comprises a subcarrier generator, a chaotic signal generator, anormalization processor, an S/P converter, an index selector, a polarity converter, a modulation multiplier, a carrier multiplier, an N-IFFT processor, a CI code encoder and a P/S converter. Index modulation is introduced, and meanwhile CI codes are introduced to expand signals. On the basis of improving the frequency band utilization rate of the system, the effect of reducing the peak-to-averageratio of the system is more obvious.

The invention discloses a method and a transmitting structure of a multicarrier differential chaos shift keying system PAPR. The method comprises the following steps: sorting input signals, performingpacket transmission on signals obtained by multiplying modulated signals by chaotic signals, and introducing CI codes to expand the signals; the transmitting structure comprises a chaotic signal generator, a normalization processor, an input signal module, a signal encoder, a PSK modulator, a serial-parallel converter, N modulation multipliers, a CI code encoder and an inverse Fourier processor.Compared with an existing method under a multi-carrier differential chaos shift keying system, the influence of a modulation signal system on the peak-to-average ratio of the system can be ignored, and the effect of reducing the peak-to-average ratio of the system is more obvious.

The invention discloses a multipath multivariate differential chaos shift keying iterative receiving method, and belongs to the technical field of demodulation in a wireless communication technology.The method comprises the steps of: transmitting a reference signal and a information bearing signal through a plurality of parallel paths, performing correlation operation on the received reference signal and the information bearing signal at a receiving end to obtain a correlation value and a likelihood value; and using the likelihood value as a weight to carry out weighted summation on each signal to obtain a new reference signal, so that the noise of the reference signal is reduced, feedback iteration is carried out by using the new reference signal, the BER performance of the system is improved, and finally, the effectiveness is verified by using computer simulation. Simulation under an AWGN channel and a Rayleigh fading channel shows that the multi-channel multivariate DCSK iterativereceiving method can provide the reliability of the system. By using the iterative receiver provided by the invention, the reference signal is iteratively updated at the receiving end without transmitting a copy of the reference signal, so that the noise is suppressed, the BER performance of the system is improved, and the transmission reliability of the system is improved.

The invention discloses a fractional order multi-carrier multi-code-shift multi-system differential chaos shift keying modulation and demodulation method and a modem, and relates to the technical field of communication signal processing. The modulation and demodulation method comprises the steps: carrying out the serial-parallel conversion of a to-be-transmitted multi-system information packet into P-path parallel multi-system information, carrying out the bit/symbol conversion to obtain P-path multi-system parallel constellation symbols, and meanwhile, generating a fractional order chaotic signal by a fractional order chaotic generator; generating a Walsh code by a Hadamard matrix, selecting a signal obtained by multiplying a first Walsh sequence by a fractional order chaos signal as a reference signal, multiplying other 2P different Walsh sequences by the fractional order chaos signal, inputting the multiplied signals into a multi-system DCSK modulator, respectively acquiring P paths of multi-system DCSK modulation signals through modulation, adding the reference signal and the P paths of multi-system DCSK modulation signals, after completing multi-carrier modulation, sending the information to a channel for transmission, and carrying out related demodulation at a receiving end to recover original information. According to the method, the bit error rate is lower, the higher data rate is realized, and the confidentiality is higher.

The invention discloses a multi-carrier multi-element differential chaos shift keying noise suppression system and method, and belongs to the field of noise suppression in a wireless communication technology. A system transmitting terminal comprises a chaotic signal generator, a serial/parallel converter, a bit/symbol converter, a multivariate DCSK modulator, a pulse shaping filter, a multiplier and an adder. And A receiving terminal comprises a matched filter, a sampling module, an averaging module, a noise suppression module and a multivariate DCSK modulator. A correlation coefficient of a received reference signal and an information bearing signal is used as a weight factor at a receiving terminal, the weight factor is used as feedback to update the previous reference signal and the information bearing signal and suppress noise in the transmission signal, and the effectiveness of the proposed method is verified by computer simulation. Under an additive white Gaussian noise channel and a multipath fading channel, the noise in a transmission signal is significantly reduced, and the bit error rate performance of the system is improved. And the system and method having a wide application prospect in future wireless communication application.

An all-digital spread-spectrum type communications system employing chaotic symbol modulation. The system includes a transmitter having a symbol mapper that converts a series of information bits to a series of bit symbols, a digital chaos modulator employing an M-ary chaotic shift keying (M-CSK) architecture for chaotically spreading the bit symbols in the digital domain, where the chaos modulator includes a separate chaos generator for each of the M-CSK symbols, and a digital-to-analog converter (DAC) for converting the chaotic modulated bit symbols to an analog signal for transmission. The system also includes a receiver responsive to the analog signal from the transmitter and generating a received signal therefrom. The receiver performs signal acquisition and tracking on the received signal using a look-up table, a transmitter ID and a receiver ID in the received signal, de-spreading and de-modulation on the received signal and bit removal from the symbols in the received signal.