51 results about "Chaos communications" patented technology

A chaotic communication system employs transmitting and receiving chaotic oscillating circuits. In an embodiment of the invention employing a Chua circuit as the basic chaotic circuit, the transmitter has a tank circuit portion and a Chua diode portion linked through a resistance. The capacitance of the tank circuit is varied by selectively switching in and out of the tank circuit an auxiliary capacitance isolated by an optoisolator. Switching of the optosiolator is controlled by an information signal to generate a perturbed oscillation in the transmitting circuit. A voltage is tapped from the Chua diode circuit and transmitted to carry the information from the information signal. A receiver in another embodiment applies the transmitted signal to both the tank circuit and Chua diode portions of the receiving circuit. The transmitted signal is applied through a resistor to the Chua diode portion as well as the tank circuit portion. By applying the received signal to the Chua diode portion as well as the tank circuit, synchronization of the transmitter with the receiver is accelerated substantially. In still another embodiment, the tank circuit components are varied to generate a vocabulary of chaotic signals that can be decoded by various receiver embodiments that are described.

A pseudo-chaotic coding / modulation method. The coding method exploits symbolic dynamics of a chaotic map at the transmitter to encode data. The encoding synthesizes the chaotic map based upon the data to be transmitted. In a preferred embodiment, pseudo-chaotic iterates are generated from a digital implementation of a Bernoulli shift map. The output of the shift map is translated by a mapping, preferably implemented by a digital signal processor, to allow transitions between states in a transmitted signal to differ, and the translated map is used to drive a modulator (for example PPM, FSK, PSK, QAM, etc.). In the specific case of pulse-position modulation (PPM) the translated map is used to modulate pulse train positions within a periodic synchronization frame. The preferred embodiment uses a shift register to implement an approximation of the Bernoulli shift map acting as a form of convolutional code with a number of states equal to the symbolic states defined on the chaotic map. A receiver may use fewer states and still decode the data signal, allowing receiver scalability.

A method for generating a broadband chaotic signal similar to white noise comprises the steps that beat frequency is carried out on two paths of chaotic lasers through an optical fiber coupler, the two paths of chaotic lasers are divided into two paths with the equal intensity, balanced detection is carried out on the two paths of optical signals, and a difference value signal is extracted and converted into a corresponding electric signal. A device for generating the broadband chaotic signal similar to the white noise comprises two chaotic laser emission devices, the optical fiber coupler and a balance detector. The optical frequencies of the chaotic laser emission devices are not equal, and an optical frequency difference is the spectral line width of the chaotic lasers. The chaotic signal generated through the method has the wide and flat frequency spectrum similar to that of the white noise, no rectilinear oscillation exists on the frequency spectrum, and periodicity caused when the chaotic lasers are generated through a time delay system can be thoroughly eliminated; the security of chaotic communication, the measurement accuracy of a radar and an optical time domain reflector, and the randomness of physical random numbers are improved. The method and device can be applied to the fields of communication, remote sensing, sensing and the like.

The present invention teaches method and apparatus to transform a featureless, unpredictable, and non-repeatable chaos waveform into digital chaos waveforms that maintain featureless characteristics to serve as a for wireless communications protocol, whereby unintended observers cannot detect or disrupt yet imprint a small measure of predictability and repeatability to aid intend observers in recovering embedded information.

The invention provides a wavelength-hopping chaotic secure communication method and system based on multi-mode lasers and belongs to the field of secure communication. The system comprises a driving end and two two-way-coupled sending / receiving ends. The same external chaotic optical injection signals are provided for the sending / receiving ends through the driving end, so that chaotic synchronization of each mode of the multi-mode lasers of the sending / receiving ends is achieved, information is loaded into chaotic carrier waves of different modes of the lasers of the sending / receiving ends in different time slots, and two-way wavelength-hopping transmission of the information is realized. The method and the system utilize the enhanced information security features of chaotic communication technology and wavelength-hopping technology at the same time, can improve the physical-layer information transmission security, and is applicable to high-security communication services. Meanwhile, as the method and the system achieve multi-wavelength chaotic synchronization based on the multi-mode lasers, and the information secure transmission capacity of the system can be improved.

Systems (100) and methods for selectively controlling access to data streams communicated from a first communication device (FCD) using a timeslotted shared frequency spectrum and shared spreading codes. Protected data signals (1301, . . . , 130S) are modulated to form first modulated signals (1321, . . . , 132S). The first modulated signals are combined with first chaotic spreading codes to form digital chaotic signals. The digital chaotic signals are additively combined to form a protected data communication signal (PDCS). The PDCS (136) and a global data communication signal (GDCS) are time division multiplexed to form an output communication signal (OCS). The OCS (140) is transmitted from FCD (102) to a second communication device (SCD) over a communications channel. The SCD (106, 108, 110) is configured to recover (a) only global data from the OCS, or (b) global data and at least some protected data from the OCS.

The invention provides a repetitive correlation delay shift keying method for improving performance of a wireless chaos communication system. According to the method, a switch is added to a correlation delay shift keying (CDSK) emission end, namely an emission end of a repetitive correlation delay shift keying R-CDSK is in two symbol periods, a chaos modulation signal and a differential chaos modulation signal corresponding to one same information are continuously sent, and a common reference chaos signal of the chaos modulation signal and the differential chaos modulation signal is further sent. The method makes full of time diversity of a wireless channel, a transmission bit error rate is reduced through repetitively sending the mutually-differential chaos modulation signals, CDSK reliability is effectively improved, moreover, the information sent by the R-CDSK is a differential modulation symbol of the bearing information, so safety communication performance of the system is improved. Compared with schemes in the prior art, the method has relatively lower complexity, and an information transmission mode which is more reliable than a CDSK mode and is safer than a DCSK mode is realized.

The invention provides a time delay hiding and frequency spreading system based on laser chaos self-modulation and a method for generating laser chaos through employing same. The system comprises a chaos external cavity semiconductor laser and a frequency spreading module. A chaos optical signal generated by the chaos external cavity semiconductor laser passes through the frequency spreading module for frequency spreading conversion, thereby achieving the flat and wide spectrum and the time delay hiding of the laser chaos signal, wherein the frequency spreading module consists of a drive signal, a photoelectric phase modulator and an FBG (Fiber Bragg Grating). The above time delay hiding and frequency spreading system enables the safety of the chaotic communication to be greatly improved.

The invention relates to a communication method combining chaos and MIMO (Multiple Input Multiple Output) and belongs to the technical field of communication. According to the method, for the defects of low transmission rate, high error rate and low confidentiality of a correlation delay shift keying (CDSK) chaotic communication scheme, a frequency modulated signal is dispersed in multiple channels for transmission, a delayed signal is equally divided into M sections by a segmentation cyclic shifter, and the M signal sections are cyclically shifted right for n sections according to information code elements and added into an original chaotic signal to form an output signal. Therefore, the confidentiality is remarkably improved and the information transmission rate is remarkably increased in comparison with an FM-CDSK scheme; under the same error rate, the signal-noise ratio is greatly improved in comparison with the FM-CDSK scheme; an improved chaotic confidential communication system adopting the method has wide application prospects in the fields of images, military confidential information and the like.

The invention discloses an improved orthogonal multi-user differential chaotic communication system, and belongs to the field of communication systems. Reference signals and information signals are separated by replacing traditional time division multiple access with I / Q modulation, so that the transmission rate is increased, and the problem of radio frequency delay is solved; in order to furtherimprove the transmission rate, Hilbert transform and Walsh codes are combined to transmit 2N user information. The receiving end multiplies the received information signal by the corresponding sine and cosine carriers by adopting a non-correlation demodulation mode, and then respectively sends the obtained signals to a matched filter so as to respectively demodulate an information estimation signal and a reference estimation signal. After I / Q demodulation, correlation operation is performed on the reference estimation signal, the information estimation signal and the corresponding Walsh code to demodulate the first N user information; and meanwhile, the same operation is executed on the reference estimation signal and the information estimation signal after the Hilbert transform to demodulate the N user information. Compared with a traditional multi-user chaotic communication system, the scheme has more excellent performance, so that the scheme has a good application prospect in the field of wireless communication.

The invention belongs to the technical field of chaotic communication carriers, particularly relates to a broadband white chaos generation method and device. The problems that a traditional white chaos generation device is complex in structure, high in cost, single in generated white chaos bandwidth and not high in adjustability are solved. According to the method, a VCSEL chaotic generator is used for outputting a total chaotic signal; a total chaotic signal is divided into two paths of optical signals through a polarization beam splitter; the polarization states of two paths are adjusted tobe consistent, the optical frequency difference is adjusted between 10 GHz and 20 GHz, frequency beating is conducted on the two paths, optical signals obtained after frequency beating are divided into two paths with the equal power intensity, balance detection is conducted on the two paths of optical signals through the equal optical path, and difference signals are converted into electric signals. The device comprises a VCSEL chaotic generator, a polarization beam splitter, a first polarized light detector, a second polarized light detector, a tunable polarization controller, a 2 * 2 opticalfiber coupler and a balance detector. The device is simple in structure and low in equipment cost, and broadband white chaotic bandwidth adjustment can be achieved through the method.

The invention requests to protect a multi-ary high-efficiency chaotic communication scheme based on Walsh codes, belonging to the field of communication system. By replacing the delay structure of a CDSK (Correlation Delay Shift Keying) system with a set of orthogonal Walsh code sequences, the purpose of eliminating inter-signal interference is achieved. A modulator modulates multi-ary symbols carrying N pieces of user information through chaotic sequences, and then, encodes the multi-ary symbols through a set of orthogonal Walsh code sequences. A demodulator carries out demodulation by meansof correlation demodulation. First, received signals are decoded together with Walsh code sequences correspondingly allocated by a sender. Then, the multi-ary symbol of each user is demodulated by a decision threshold. Finally, the binary data information flow sent by each user can be determined according to the multi-ary mapping relationship of the modulator. Compared with CDSK and RA-CDSK systems, the bit error performance and transmission rate of the scheme are greatly improved, and less bit energy is consumed. The good performance of MAHE-CDSK makes the scheme have a wide application prospect in the field of wireless communication.

A data transmission method and apparatus and a data receiving method and apparatus provide for multiple access in a chaotic communication system. The data transmission method includes arranging a template chaotic signal at a predetermined position of a data frame to be transmitted, the predetermined position being allocated to a user, modulating a data source signal using the template chaotic signal and arranging the modulated data source signal in the data frame, and transmitting the data frame.

The invention relates to a differential chaotic communication method and system based on polarization codes. The method comprises a coding modulation process and a demodulation decoding process. The code modulation process comprises the following steps: after a signal source generates a signal, inputting the signal into a polarization code encoder for encoding, then sending a code word encoded bya polarization code into a DDCSK-WC modulator for chaotic modulation, redesigning a data frame by utilizing an orthogonal Walsh code, and sending the redesigned data frame; wherein the demodulation and decoding process comprises the steps that after a receiving end receives a signal, a DDCSK-WC demodulator demodulates the received signal, soft information obtained through demodulation is input into a polarization code decoder, the polarization code decoder decodes the soft information through an SC decoding algorithm based on an MS algorithm, and finally a decoding result is obtained. According to the method and the system, the information transmission rate and performance of communication are improved, and the calculation complexity and the implementation cost are reduced.

The invention provides a high-efficiency and energy-saving differential chaos communication scheme. The scheme belongs to the field of communication systems. Through effective improvement of a prior frame structure of a DCSK system, transmission time of each frame is shortened. The DCSK system subjected to transformation remains a prior frame structure; the reference time slot length is changed to1 / P(P=beta / R) of the prior length and the data time slot length remains the same. The frame structure is composed of P times duplication, which carries 2 bit information, of the sum of the referencetime slot and the reference time slot of the last frame. A demodulation terminal adopts a non-coherent demodulation method. In order to demodulate each bit of information, a synchronization clock is adopted. The received reference time slot is correlated to the corresponding data time slot and finally sending information is acquired through demodulation with a judgment threshold. Namely, if the correlation value is greater than zero, +1 is judged; if the correlation value is not greater than zero, -1 is judged. The scheme provided by the invention achieves higher transmission rate than a DCSKsystem. At the same time, lower bit energy is consumed compared with the DCSK system. Good performance of SERT-DCSK enables a good application prospect in the wireless communication field.

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 discloses a transmission system based on coupled lasers for chaotic broadcast communication. The transmission system comprises a first laser, a second laser, a first plane mirror, a second plane mirror, a first collimating lens and a second collimating lens, wherein the second laser, the first laser, the first collimating lens and the first plane mirror are sequentially arranged, thesecond laser, the second collimating lens and the second plane mirror are sequentially arranged, the second laser is served as a transmitting end, and the first laser is served as a receiving end. According to the transmission system, the information of the sending end is received by utilizing the receiving laser so as to realize broadcast communication in a chaotic communication field, when boththe lasers of the transmitting end and the receiving end send '0' or '1', the two lasers are synchronous, and otherwise, the two lasers are in an asynchronous state; and the modulation and demodulation processes of the transmitting end and the receiving end of the broadcast transmission system are bits transmitted by the transmitting end decoded by means of the power error between the received information and the local information, so that the purpose of broadcasting information from one laser to another laser is achieved.

The invention relates to a combination function projection synchronization method in chaotic communication systems. A concept of proportional function is introduced to change synchronization proportional factors in conventional multiple chaotic systems from specific numerical values to a proportional function. Combination function projection synchronization of the multiple chaotic systems is realized by designing a corresponding adaptive feedback controller. Therefore, higher security can be provided without adding more chaotic systems. In addition, the invention proposes to introduce a clocksynchronization module in a driving system and a response system after analyzing reasons that affect a projection synchronization speed of multiple combination functions, which reduces external disturbance of the chaotic systems caused by time factors, accelerates the synchronization of the chaotic systems, thereby enabling a combination mode of the multiple chaotic systems to be rapidly switchedaccording to time, and provides better security performance for the multiple chaotic systems under the premise of ensuring the robustness and reliability of a secure communication system.

The invention provides a method for chaotic communication decoding under a finite bandwidth condition. A signal can be decoded. According to the method, minimum values of a receiving time sequence are calculated to obtain a minimum value sequence map, whether a code element losing phenomenon happens or not and the moment of the code element losing phenomenon are determined according to time between two adjacent minimum values, a one-dimensional mapping phase diagram of continuous code elements is drawn, and the position of a lost code element in the phase diagram and the lost code element are determined according to the phase diagram and the positions of code elements before and after the lost code element. The method has the advantages that the dynamic characteristics of a receiving attractor can be changed when a channel has filter characteristics, all transmitted code elements cannot be acquired from received signals by the conventional method, while the losing moment of the lost code element and the lost code element can be obtained by the method provided by the invention, so that the problems caused to a communication terminal by the losing of the code elements are solved; and moreover, a low bit error rate can be obtained by adopting three-dimensional characteristic vectors of the code elements and a trained support vector machine.

A system for chaotic sequence spread spectrum communications includes a transmitter (402) for transmitting information symbols using a chaotic sequence of chips generated at the transmitter, the information symbols having a duration of transmission based on a threshold symbol energy value and the chips. The system also includes a receiver (404) for extracting the information symbols from the transmitted signal using a chaotic sequence of chips generated at the receiver and the threshold symbol energy value. In the system, the chips generated at the transmitter and the receiver are identical and synchronized in time, where the duration of transmission of the information symbols in the carrier is a total duration of a selected number of the chips used for transmitting, and where the number of the chips is selected for the information symbols to provide a total chip energy greater than or equal to the threshold symbol energy value.

The invention relates to an electro-optic phase mutual coupling bidirectional chaotic communication system, which comprises a transmitting end and a receiving end which are connected through an optical fiber, the transmitting end comprises a first chaotic laser, a first beam splitter, a first circulator, a first coupler, a first Mach-Zehnder interferometer, a first photoelectric detector, a first electric amplifier and a first phase modulator which are connected in sequence; the system further comprises a second chaotic laser, a second circulator, a second Mach-Zehnder interferometer, a second photoelectric detector and a second electric amplifier which are connected in sequence, the second electric amplifier is connected with the first phase modulator, and the first circulator and the second circulator are both connected with the second coupler. The second coupler and the first phase modulator are connected with the third circulator; and the receiving end and the sending end have the same structure. The chaotic communication system not only realizes chaos time delay hiding of chaos synchronous communication, but also has the characteristics of stable performance, high confidentiality and the like.

The invention discloses a device and a method for enhancing the safety of a co-driven chaos synchronization system, and relates to the technical field of chaos communication carriers, and the device comprises a transmitting end, a first receiving end, a first dispersion compensation device, a second receiving end and a second dispersion compensation device. The transmitting end generates a main chaotic signal, divides the main chaotic signal into a first path of main chaotic signal and a second path of main chaotic signal, and sends the first path of main chaotic signal and the second path of main chaotic signal to the first receiving end and the second receiving end; a first receiving end receives a first path of main chaotic signal, and after the first path of main chaotic signal is processed by a first dispersion compensation device, a first path of slave chaotic signal is generated; and the second receiving end receives the second path of main chaotic signal, and after the second path of main chaotic signal is processed by the second dispersion compensation device, a second path of slave chaotic signal is generated to realize chaotic synchronization with the first path of slave chaotic signal. According to the invention, two paths of chaotic signals with flat frequency spectrums and no time delay characteristic can be generated, high-quality chaotic synchronization is realized, and the safety of a co-driven chaotic synchronization system is improved.

A synchronization method and apparatus and a location awareness method and apparatus in a chaotic communication system are provided. The location awareness method includes receiving a data frame which includes a template chaotic signal to be determined to be arranged at a predetermined position of the data frame, and a data source signal obtained by modulating the template chaotic signal, the position allocated to a user; detecting a position of the data frame in which the template chaotic signal is substantially arranged; and determining the distance between a device transmitting the data frame and a device receiving the data frame using the difference between the position of the data frame in which the template chaotic signal is substantially arranged and the predetermined position. Accordingly, it is possible to precisely detect the distance between devices.

The invention discloses a laser chaotic signal generating device capable of hiding a feedback delay characteristic. An adjustable polarizing film is led in an annular feedback cavity of a vertical cavity surface emitting laser, so that even under larger feedback strength, the feedback delay characteristic of a laser chaotic signal can be successfully hidden only if the angle of the adjustable polarizing film is adjusted reasonably. According to the device disclosed by the invention, on the basis of ensuring the generation of the laser chaotic signal, the delay hidden characteristic of a chaotic carrier wave under the larger feedback strength is realized, and the safety of a chaotic communication system based on the vertical cavity surface emitting laser is enhanced.

The invention provides a repetitive correlation delay shift keying method for improving performance of a wireless chaos communication system. According to the method, a switch is added to a correlation delay shift keying (CDSK) emission end, namely an emission end of a repetitive correlation delay shift keying R-CDSK is in two symbol periods, a chaos modulation signal and a differential chaos modulation signal corresponding to one same information are continuously sent, and a common reference chaos signal of the chaos modulation signal and the differential chaos modulation signal is further sent. The method makes full of time diversity of a wireless channel, a transmission bit error rate is reduced through repetitively sending the mutually-differential chaos modulation signals, CDSK reliability is effectively improved, moreover, the information sent by the R-CDSK is a differential modulation symbol of the bearing information, so safety communication performance of the system is improved. Compared with schemes in the prior art, the method has relatively lower complexity, and an information transmission mode which is more reliable than a CDSK mode and is safer than a DCSK mode is realized.

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.

Repeatable chaotic spread-spectrum DCSK modulation and demodulation method and modem, the aforementioned repeatable chaotic spread-spectrum DCSK modulation and demodulation method is to generate a repeated chaotic spread-spectrum sequence by copying the reference signal of the differential chaos shift keying modulation signal, and then combine the And the converted part of the data stream is multiplied to form RCSS‑DCSK signal, and the remaining parallel data stream is DCSK modulated to form DCSK signal, and then the RCSS‑DCSK signal and DCSK signal are added and sent to the channel for transmission, and finally received The terminal performs relevant demodulation to recover the original information. The bit error rate of the system using this modulation and demodulation method is lower than that of DCSK, CDSK and CD‑DCSK systems under the same spreading factor, and the smaller the spreading factor is, the lower the bit error rate is, and the system has higher confidentiality and is easier for eavesdropping. The latter is more difficult to detect and restore the original data, which can better meet the confidentiality requirements of the chaotic communication system in practical applications.

The invention discloses a differential chaos shift keying modem and a differential chaos shift keying modulation method based on two-path index modulation, and relates to the technical field of chaoscommunication. A two-path index modulation method is used for transmitting a chaos reference signal and a Hilbert reference signal orthorhombic with each other, and an index mapping rule and an inverted index mapping rule are used for modulating and demodulating the signals. According to the modulation method provided by the invention, delay units are used in a transmitting terminal and a receiving terminal; compared with an existing carrier-index differential chaos shift keying (CI-DCSK) technology, under the premise of occupying a same frequency band, the method synchronously transmits two information signals, so that a bit transmission rate of the system is doubled; in addition, the higher spectrum utilization rate and better data security are achieved, and the method provided by the invention is reduced in bit error rate (BER), and shows better bit error rate performance, and the advantages of the BER performance becomes more significant along with the increasing of a bit signal tonoise ratio.