68 results about "Direct-sequence spread spectrum" patented technology

The invention discloses a direct sequence spread spectrum underwater acoustic communication Doppler rapid estimation method and system based on a GPU. The method comprises the following steps: modeling a received signal of a direct sequence spread spectrum underwater acoustic communication system; performing resampling and FFT operation on a local pilot signal in sequence, and storing an FFT operation result to obtain a Doppler matching matrix based on an equipment memory preloading method of a GPU (Graphics Processing Unit); a two-step Doppler estimation process is adopted, in the rough search stage, cross ambiguity function calculation is carried out based on GPU complex number multiplication, reduced module value normalization calculation is carried out based on GPU parallel, and a rough Doppler factor to be estimated is obtained through threshold detection; in the fine search stage, a plurality of Doppler branches near the coarse Doppler factor are selected, cross ambiguity function calculation is carried out based on GPU complex number multiplication, reduced module value normalization calculation is carried out based on GPU parallel, and a fine Doppler factor to be estimated is obtained through threshold detection.

The invention relates to the technical field of backscatter communication, and particularly discloses a backscatter method suitable for a ZigBee excitation source in an uncontrolled environment, which specifically comprises the following steps: a ZigBee transmitter maps binary data into data symbols, maps each data symbol into a chip sequence by using direct sequence spread spectrum, and modulates each chip sequence onto a carrier wave; a label modulation sequence is generated for the label data, and the label modulates a carrier wave in the excitation signal based on the label modulation sequence to generate a backscattering signal; and processing the excitation signal and the backscattering signal to obtain a pre-reflection code word corresponding to the excitation signal and a post-reflection code word corresponding to the backscattering signal, and obtaining label data according to the pre-reflection code word and the post-reflection code word. The invention aims to reduce the limitation of the excitation source and improve the throughput of the system at the same time, thereby further improving the universality of the ZigBee backscattering system.

Some methods may involve receiving a first content stream that includes first audio signals, rendering the first audio signals to produce first audio playback signals, generating first direct sequence spread spectrum (DSSS) signals, generating first modified audio playback signals by inserting the first DSSS signals into the first audio playback signals, and causing a loudspeaker system to play back the first modified audio playback signals, to generate first audio device playback sound. The method(s) may involve receiving microphone signals corresponding to at least the first audio device playback sound and to second through Nth audio device playback sound corresponding to second through Nth modified audio playback signals (including second through Nth DSSS signals) played back by second through Nth audio devices, extracting second through Nth DSSS signals from the microphone signals and estimating at least one acoustic scene metric based, at least partly, on the second through Nth DSSS signals.

Wireless digital communication of information over sound waves is provided using near near-ultrasonic acoustic (audio)-spectrum. A method includes receiving a modulated data signal generated from coupled direct sequence spread spectrum (DSSS) and orthogonal frequency division multiplexing (OFDM) at a transmitter. The modulated data signal has a phase-shift key (PSK) modulated data signal spread by different Q length chip sequence. The method includes demodulating a synchronized data signal by extracting each OFDM data block having a data symbol and preamble and postamble symbols which were transmitted on an orthogonal sub-carrier with variable Q length chip sequence for multi-user communication over air as a transmission medium. This enables synchronization of communication over the air between transmitters and receivers in multiple user devices in the presence of multiple path propagation and different signal to noise ratios. Simultaneous communication over air between transmitters and receivers in multiple user devices can be done.

The invention discloses a data processing method and a related device. In the method, the electronic equipment can generate a communication frame, processes the communication frame by respectively or in combination with technical means such as polarization coding, direct sequence spread spectrum and pilot frequency insertion, and modulates the processed communication frame by using a GFSK (Gaussian Frequency Shift Keying) technology to obtain a modulation signal. By applying the method, the processed communication frame has a high-performance GFSK frame structure, the receiving sensitivity and the anti-interference performance of a communication system where the electronic equipment is located can be improved, and more transmission rate selections can be provided.

The invention relates to high anti-interference wireless communication for a battery management system. Techniques for improving the interference immunity of wireless battery systems by transmitting recoded signals, for example, using a plurality of chips of a sequence for each information bit, in response to interference or interference immunity in data rate exchange upon identification of a noisy environment. These techniques provide the system with an anti-noise mode of operation (or a highly anti-interference transmit and receive mode), which may improve resilience to interference or interference by reducing the data rate. One choice for reducing the data rate is to reduce the transmission bit rate so as to reduce the occupied transmission bandwidth, so that the probability of collision with interference signals is reduced to the greatest extent. Another choice is a digital coding method using forward error correction, such as convolutional coding, Reed-Solomon coding and Turbo coding. The third choice is to use a radio frequency spread spectrum technique, such as direct sequence spread spectrum (DSSS) or frequency hopping spread spectrum (FHSS).

The present invention discloses a folding capture method of a direct sequence spread spectrum long code, the method comprising: performing partial matching correlation with a local folding code after preprocessing and mixing a high frequency spread spectrum signal, storing the correlation result in a two-dimensional register, performing group FFT operation and accumulation on the correlation result, obtaining a power spectrum with the same code phase of the correlation result, performing square sum of the I / Q path power spectrum module to obtain a maximum peak value much larger than other power spectrum amplitudes, comparing the maximum peak value with a threshold value, if it is greater than the threshold value, then the local spread spectrum code phase offset corresponding to the peak value is consistent with the code offset of the input signal, and the Doppler frequency deviation estimation value of the input signal can be obtained through the corresponding local spread spectrum code. The local code is folded, multiple code phases can be searched for in one correlation, and the correlation results are grouped for FFT, which can reduce the difficulty of operation and reduce the calculation time.

The invention discloses a satellite communication physical layer codeword security enhancement method based on spatiotemporal chaos. First, the information transmitting end generates a spatiotemporal chaotic two-dimensional signal matrix, and uses a part of the information group to generate a chaotic keying index value of the spatiotemporal chaotic space dimension, and the other part of the information group and the spatiotemporal chaotic time dimension signal determined by the index value are quantized and sent by direct sequence spread spectrum; the information receiving end generates a spatiotemporal chaotic two-dimensional signal matrix based on the same initial parameters, quantizes the matrix and processes it with the received signal, determines the index value of spatial dimension information demodulation, and performs integral cleaning processing of despreading the corresponding time dimension chaotic sequence and the received signal based on the index value, and performs spatiotemporal dimension information demodulation, thereby obtaining demodulated information after security enhancement. The invention uses the same spatiotemporal chaotic mechanism to achieve the security enhancement of the expanded-dimensional codewords while reducing the complexity of implementation and improving the frequency band utilization.

The present invention relates to a satellite navigation signal system design method based on hybrid modulation of direct sequence spread spectrum and frequency hopping. The method comprises: spreading code sequences of multiple signal components being modulated and being then hybrid-multiplexed with signal components corresponding to a same frequency point, and forming a baseband code sequence on the basis of power allocation ratios of the signal components; on the basis of environment conditions, performing signal separation on the signal components corresponding to the baseband code sequence, in order to obtain separated radio frequency signals, and performing recombination and modulation on the signals; if the separated radio frequency signals are authorized signals, controlling a frequency hopping pattern by means of a frequency hopping code sequence, and performing hybrid frequency synthesis modulation on the basis of a center frequency point of the frequency hopping pattern and the frequency of the authorized signals; if the separated radio frequency signals are unauthorized signals, performing direct combining and radio frequency modulation on the unauthorized signals on the basis of a signal frequency point, in order to obtain recombined signal components; and performing signal power amplification on the basis of a center frequency point difference of the recombined signal components, in order to obtain direct sequence spread spectrum navigation signals. The method can greatly improve the anti-jamming capability of navigation signals.

A DSSS (Direct Sequence Spread Spectrum) receiver operates in a duty cycle mode to reduce its power consumption. The DSSS receiver uses fast DSSS preamble detection to determine if an incoming signal is a DSSS preamble symbol of a desired channel. In duty cycle mode, the DSSS receiver further reduces power consumption by selectively disabling at least one of its power domains during the power-on period of a duty cycle if a desired signal is not detected, and by selectively disabling at least one power domain during the power-off period of the duty cycle.

The invention discloses a method and system for improving low signal-to-noise ratio direct sequence spread spectrum signal code tracking performance, and the method comprises the steps: generating an I-path bipolar code information source, and obtaining a baseband signal; performing convolution operation with the matched filter coefficient to obtain a matched filtering result; time lag and time lead are respectively carried out according to a specified length, so that a lag branch signal and a lead branch signal are respectively obtained; coherent integration is carried out on the local pseudo code sequence at a PL end, and an envelope value is solved; setting an incoherent accumulation length at a PS end, performing incoherent accumulation operation on the envelope value, and selecting a code phase discrimination mode to obtain a code phase discrimination value; and a phase change value is obtained through the linear filter and a loop filter of the code loop, and the phase change value is used for correcting the NCO of the local pseudo code sequence to realize closed-loop feedback. Code tracking performance is improved, signals can be accurately transmitted in a complex interference environment, error codes are reduced, inter-symbol crosstalk is effectively reduced, signal decoding accuracy is improved, and communication quality is guaranteed.

This application proposes a method and system for transmitting time synchronization signals based on general-purpose software-defined radio (SDR). The method includes: constructing a time synchronization signal data frame based on input time information; performing direct sequence spread spectrum (DSSS) on the time synchronization signal data frame to obtain a spread digital sequence; modulating and mapping the spread digital sequence into a digital baseband IQ signal; transmitting the digital baseband IQ signal to a general-purpose software-defined radio peripheral; processing the signal through the peripheral; transmitting it via an antenna; and performing time delay calibration on the system before transmission to compensate for internal system delays. This application, by employing a software-defined radio architecture combined with a high-precision clock reference, achieves software-based, general-purpose, and high-precision processing throughout the entire process of time synchronization signal generation, processing, transmission, and calibration. The overall approach offers multiple advantages, including high flexibility, high precision, high reliability, low cost, easy scalability, and open research potential.

The present invention discloses a synchronous time - synchronization type Internet of Things spread - spectrum communication control device, belonging to the technical field of communication equipment. The device includes a housing, in which a synchronous time - synchronization system and a spread - spectrum communication system are installed. The synchronous time - synchronization system includes a master clock source, a GNSS receiving module, a clock drift calibration circuit module and a backup power management module that are electrically connected to each other; the spread - spectrum communication system includes a DSSS direct - sequence spread - spectrum modulation module, a frequency planning module, and an adaptive power control module that are electrically connected to each other. A base is provided at the bottom of the housing, a limiting mechanism is provided in the base, and a mounting structure is provided on one side of the housing. By integrating the synchronous time - synchronization system and the spread - spectrum communication system in the housing, the clock synchronization accuracy is improved, ensuring the normal operation of the system and the accuracy of data. The anti - interference ability is improved, accurate measurement is achieved, communication security is guaranteed, which helps to ensure the security of the communication process.

The invention provides a narrow-band interference suppression method and system for a direct sequence spread spectrum system, and relates to the technical field of satellite communication anti-interference. The method comprises the following steps: determining the noise power of an obtained receiving signal, wherein the receiving signal is a frequency domain signal; determining an interference threshold according to the noise power of the received signal; determining an interference signal and an interference parameter thereof according to the interference threshold; and according to the interference parameter, performing interference filtering on the received signal through a high-pass filter to obtain a signal after interference suppression. According to the method, interference parameters can be accurately estimated in a frequency domain, the most matched high-pass filter is determined according to the determined interference parameters, interference is filtered through the high-pass filter to obtain the signal after interference suppression, the suppression capability of the direct sequence spread spectrum system on strong narrow-band interference can be remarkably improved, the complexity of the mode is greatly reduced, and the method is suitable for large-scale popularization and application. And the practicability is higher.

The application relates to a satellite-ground ranging method suitable for a multi-satellite measurement and control situation, and relates to a satellite-ground ranging method. The application aims to solve the problem that a physical layer of advanced on-orbit system system service data stream and pseudo code data stream cannot be compatible in a multi-satellite measurement and control scene. The process is as follows: at a transmitting end: a downlink telemetry uplink remote control signal is directly sequence spread through a CA code at the transmitting end I path, so as to realize transmission of measurement and control information between a satellite and the ground; a pseudo code ranging sequence is directly sequence spread through the CA code at the transmitting end Q path, so as to realize a ranging function between the satellite and the ground; at a receiving end: 1, transmitting signals of different satellites are separated, and a pseudo code phase and a Doppler frequency shift are obtained; 2, a carrier tracking loop and a pseudo code tracking loop are realized to stably work; 3, I path coherent integration output is carried out to output continuous bits; Q path coherent integration output is carried out to output continuous bits, transmission time is solved, and then actual satellite-ground distance is obtained. The application is used in the field of space technology.

The invention discloses a direct sequence spread spectrum signal detection method based on GPU parallel, and belongs to the technical field of wireless communication. According to the method, signal basic data information of an energy detection method and a cyclostationary analysis method is obtained, reliability models are constructed respectively, and the reliability of the reliability models is calculated; and based on the dynamic weight distribution model, fusing the energy statistics and the maximum peak value index of the spectral correlation density, reconstructing a weighted average judgment model to output a judgment value, and comparing the judgment value with a preset threshold value to realize signal detection. According to the method, GPU parallel acceleration calculation is utilized, so that the processing efficiency is remarkably improved; the advantages of energy detection and cyclostationary analysis are combined, and the detection robustness and accuracy in a complex environment are enhanced through normalized parameter modeling and dynamic weight optimization.

Some methods may include receiving a first content stream including a first group of audio signals, rendering the first group of audio signals to generate a first group of audio playback signals, generating a first group of direct sequence spread spectrum (DSSS) signals, generating a first group of modified audio playback signals by inserting the first group of DSSS signals into the first group of audio playback signals, and generating a first audio device playback sound by playing the first modified audio playback signal through a loudspeaker system. The method(s) may include receiving a group of microphone signals corresponding to at least the first audio device playback sound and second through Nth audio device playback sounds corresponding to second through Nth modified audio playback signals (including the second through Nth DSSS signals) played by second through Nth audio devices, extracting the second through Nth DSSS signals from the microphone signals, and estimating at least one acoustic scene metric based at least in part on the second through Nth DSSS signals.

The invention discloses a signal modulation method for spaceflight. Data are modulated based on a direct sequence spread spectrum and Gaussian minimum frequency shift keying modulation technology. Compared with DSSS-BPSK modulation, satellite EMC of multi-frequency-point emission is improved, the frequency spectrum captured by PMF-FFT is more characteristic, the phenomenon of mistaken capturing is not prone to occurring, and due to the fact that the single-path code rate is half of the DSSS-BPSK, the chip migration effect is easy to eliminate.

The application provides a kind of multi-beam coherent high reliability combination method, device, electronic equipment and storage medium, it relates to satellite communication technical field, the method comprises: the multi-channel signal of satellite retransmission is received coherently, multi-channel signal is BPSK symbol sequence after direct sequence spread spectrum modulation, in beam overlap area through multiple different beams equal gain is sent to the satellite;Based on cross-entropy optimization algorithm, the normalized channel gain corresponding to each multi-channel beam is jointly optimized, and the optimal normalized channel gain corresponding to each beam is obtained;Based on the optimal normalized channel gain corresponding to each beam, the weighted and combined multi-channel signal after despreading is obtained, and the combined signal is obtained.The application realizes the adaptive maximum ratio combination of multi-channel signal, can significantly improve the signal-to-noise ratio after signal combination, so that the communication system can still maintain high communication quality in weak channel environment, enhance the anti-interference ability and concealment of system, improve the reliability of link.

The invention belongs to the field of direct sequence spread spectrum signal parameter estimation, and particularly relates to a pseudo code period estimation method, a storage medium and equipment for direct sequence spread spectrum signals. The objective of the invention is to explain the problem that the accuracy of pseudo code period estimation is low due to the fact that a period spectrum peak of pseudo code period estimation for direct sequence spread spectrum signals is greatly influenced by a signal-to-noise ratio in the prior art. The method comprises the following steps: obtaining direct sequence spread spectrum signals of each group; obtaining code difference value results in all the segmented windows under different sliding times; accumulating the obtained code difference results in all the segmented windows under different sliding times to obtain accumulated code difference results SI (i) in all the segmented windows; calculating the autocorrelation of SI (i); normalizing the autocorrelation to obtain the autocorrelation after normalization; calculating a normalized average self-correlation second-order moment rho (k); and extracting peak values in rho (k), wherein the interval between adjacent peak values is a pseudo code period estimation result.

The application discloses a kind of inter-satellite microwave measurement communication link signal generation and chain building method, comprising: generating transmitting signal based on direct sequence spread spectrum mode, and transmitting signal is divided into mutually orthogonal I branch and Q branch, and the spread spectrum code sequence of different length is modulated to two branches respectively;I branch is used as measurement branch, fixed modulation long code is used and binary offset subcarrier modulation mode is used, and measurement data frame with fixed frame length and information rate is loaded on I branch;Q branch is set to pilot mode or communication mode, short spread spectrum code is modulated in pilot mode and no data is loaded, long spread spectrum code is modulated in communication mode and communication data with configurable information rate is loaded;The start bit of spread spectrum code period of I branch and Q branch is aligned with the start bit of data frame header to the local maintained second pulse, and the generation of inter-satellite microwave measurement communication link transmitting signal is completed.The application can realize acquisition complexity and pseudo-range measurement accuracy under the condition of given bandwidth.

The invention relates to an automatic frequency hopping image transmission communication system, the system comprises an unmanned aerial vehicle and a ground station in mutual wireless communication, the unmanned aerial vehicle comprises a data acquisition module used for acquiring unmanned aerial vehicle data, and the unmanned aerial vehicle data comprises any one or a combination of more of a flight control instruction, telemetry data and / or image transmission data; the DSSS sending module is used for carrying out direct sequence spread spectrum processing on the unmanned aerial vehicle data; the radio frequency transmitting module is used for transmitting the signal after direct sequence spread spectrum processing through an antenna after carrier modulation; the ground station comprises a radio frequency receiving module which is used for receiving the signal after the direct sequence spread spectrum processing through an antenna of the ground station; the DSSS receiving module is used for performing de-spreading processing on the signal after the direct sequence spread spectrum processing to obtain the unmanned aerial vehicle data; and the data output module is used for outputting the unmanned aerial vehicle data. By adopting the method, anti-interference communication can be realized.

The invention discloses a self-adaptive capturing method for a multi-rate direct sequence spread spectrum signal of a low earth orbit satellite, and belongs to the field of low earth orbit satellite communication. According to the method, the multi-rate direct sequence spread spectrum signal self-adaptive capturing method is constructed, multiple sets of direct sequence spread spectrum signal receivers at all rates do not need to be achieved, signal detection and synchronization can be conducted on the multi-rate direct sequence spread spectrum signals only through one set of receiver algorithm, and hardware resource consumption of the receivers is reduced; meanwhile, the capturing method is compatible with processing of multi-rate direct sequence spread spectrum signals, so that risks caused by program reconstruction and interruption of communication services can be avoided; in addition, under the condition that the transmitting power is not changed, the ground terminal adjusts the transmitting rate, on one hand, the transmitting rate can be increased, and the signal exposure time can be shortened; on the other hand, the transmission rate can be reduced to ensure the communication reliability, and the communication is more flexible; according to the invention, on the basis of a DSSS receiver algorithm, signal detection and synchronization of spread spectrum signals with different rates are completed through a self-adaptive adjustment capturing method.

The invention discloses an earth-moon space-oriented high-dynamic weak DSSS (direct sequence spread spectrum) signal capturing method, which relates to the technical field of direct sequence spread spectrum, and comprises the following steps of: demodulating a received complex baseband signal by using the center frequency of a current Doppler packet to generate a baseband Doppler demodulated signal, and generating a local pseudo code signal according to an initial value of a current time delay segment; segmenting the baseband Doppler demodulation signal and the local pseudo code signal according to partial correlation time, and respectively constructing received signal double blocks and local signal double blocks; performing frequency domain fast correlation operation on the received signal double blocks and the local signal double blocks to obtain a partial correlation result; and performing Keystone transformation on the partial correlation result, correcting pseudo code phase walking, generating a corrected partial correlation result, and establishing a symbol search matrix. According to the invention, high-efficiency coherent accumulation of signal energy in an extremely low carrier-to-noise ratio and extremely high dynamic environment is realized, and the capture sensitivity and reliability are improved.

The present disclosure provides a method and an apparatus for tracking a direct sequence spread spectrum (DSSS) signal in a fractional Fourier domain (FRFD). The method includes the steps of: receiving an intermediate frequency (IF) DSSS signal; removing a Doppler frequency component by mixing with local sine and cosine waveforms generated by a carrier numerically controlled oscillator (NCO) to obtain in-phase (I) and quadra-phase (Q) carrier-stripped samples; performing code tracking and integration / dumping operations in the FRFD using chirp-signal modulation; discriminating carrier phase errors via I and Q prompt correlations and code chip errors via I and Q early / late correlations through carrier and code discriminators; filtering the discriminated errors through low-pass loop filters; and using filter outputs to generate carrier and code measurements while adjusting carrier and code NCOs for real-time tracking in subsequent epochs.

Techniques to improve the immunity of wireless battery systems by transmitting heavily-coded signals, e.g., using multiple chips of a sequence for each bit of information, to trade data rate for interference or jamming immunity as a response once a noisy environment is identified. The techniques provide the system with a noise immunity operating mode (or high-immunity transmit and receive mode) that can improve resilience to interference or jamming by reducing the data rate. One option for reducing the data rate is by slowing down the transmission bit rate to reduce the occupied transmit bandwidth to minimize the probability of collisions with interfering signals. Another option is though digital coding methods using Forward Error Correction such as Convolutional Coding, Reed-Solomon Coding and Turbo coding. A third option is with RF spread spectrum techniques such as Direct Sequence Spread Spectrum (DSSS) or Frequency Hopped Spread Spectrum (FHSS).

The present invention relates to the technical field of demodulation and despreading of direct sequence spread spectrum system, and in particular to a soft bit joint demodulation and despreading method based on GMSK, comprising the following steps: grouping a received data sequence according to the number of oversampling points based on the spread multiple; using a Gold pseudo-random sequence to generate a local spread spectrum code, and multiplying the spread spectrum code with a corresponding NCO signal to obtain a local modulation sequence; using an effective sampling point signal to multiply the received data sequence with a local modulation sequence and its conjugate sequence to obtain a corresponding correlation sequence; accumulating and integrating the two multiplication results according to the sequence grouping length, respectively, to obtain a correlation integral value of each code element and a local reference signal, and calculating the average value of the correlation integral value; calculating the power of the two average values, and outputting the power difference as the final demodulation and despreading soft bit data. Compared with the implementation scheme of demodulation before despreading of conventional FSK-type modulation, the present invention effectively improves the demodulator performance.

The invention discloses a method for capturing and tracking a time-hopping direct sequence spread spectrum signal, which comprises the following steps of: carrying out matched filtering on the signal to obtain an incoherent detection quantity; judging whether a target signal exists or not; determining the existence time of the target signal and obtaining a time hopping sequence of the signal according to the existence time and the receiving time interval sequence; mixing the time hopping sequence of the signal with a local carrier to obtain an I / Q demodulation signal, determining an error value of a pseudo code phase according to the I / Q demodulation signal and the pseudo code, and adjusting the phase of the local pseudo code to realize accurate synchronization of the pseudo code at the receiving end and the pseudo code at the sending end; coherent integration is carried out on an I / Q demodulation signal and an instant code of a local pseudo code to obtain a phase difference between a received signal carrier and a local reference carrier, and the output frequency and phase of a voltage-controlled oscillator are controlled. According to the invention, signals can be rapidly and accurately captured and stably tracked in a complex communication environment, and the overall performance of a communication system is improved.

Wireless digital communication of information over sound waves is provided using near near-ultrasonic acoustic (audio)-spectrum. A method includes receiving a modulated data signal generated from coupled direct sequence spread spectrum (DSSS) and orthogonal frequency division multiplexing (OFDM) at a transmitter. The modulated data signal has a phase-shift key (PSK) modulated data signal spread by different Q length chip sequence. The method includes demodulating a synchronized data signal by extracting each OFDM data block having a data symbol and preamble and postamble symbols which were transmitted on an orthogonal sub-carrier with variable Q length chip sequence for multi-user communication over air as a transmission medium. This enables synchronization of communication over the air between transmitters and receivers in multiple user devices in the presence of multiple path propagation and different signal to noise ratios. Simultaneous communication over air between transmitters and receivers in multiple user devices can be done.