51 results about "Chaos communications" patented technology

The invention concerns a chaotic communications system, method and apparatus having a transmitter configured to spread an input data signal over a wide intermediate frequency band, by digitally generating a first chaotic sequence of values to form a spreading code. The spreading code is then used to form a digital IF chaotic spread spectrum signal having a uniform sampling interval. The duration of the sampling interval is then selectively varied in accordance with a first pseudo-random sequence, thereby introducing a known dither in the digital IF chaotic spread spectrum signal. After introducing the known dither, the digital IF chaotic spread spectrum signal is converted to an analog RF spread spectrum signal at a conversion rate that exceeds the sampling interval of the chaotic spread spectrum signal. A corresponding receiver recovers the input data from the spread transmitted signal. This spreading may utilize a chaotic sequence employing discrete time chaos dithering.

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 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 discloses an analysis method of similar frequency-dependent delay electro-optic phase chaotic dynamics. The method is executed according to the following steps: step 1, building a dynamic mathematical model in a chaotic communication system; step 2, determining a relation between delay and frequency; step 3, dividing time interval and determining an equation initial value; step 4, solving a delay signal of each moment in one period of time after delay through Fourier time-frequency transformation; step 5, converting a delay differential equation into an ordinary differential equation; step 6, performing numerical solution for the ordinary differential equation of the step 5 through a Runge-Kutta method. The method provided by the invention can accurately solve a differential-integral equation having frequency-dependent delay, and can accurately analyze chaotic dynamics and chaotic communication having frequency-dependent delay feedback.

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.