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

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.

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 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.

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 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 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.

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.

This invention relates to a method, storage medium, and device for estimating the pseudocode period of direct sequence spread spectrum signals. It belongs to the field of parameter estimation for direct sequence spread spectrum signals, and specifically relates to a method, storage medium, and device for estimating the pseudocode period. The purpose of this invention is to address the problem that existing methods for estimating the pseudocode period of direct sequence spread spectrum signals suffer from low accuracy due to the significant influence of the signal-to-noise ratio on the period spectral peak. The process is as follows: Obtain the direct sequence spread spectrum signal for each group; obtain the code difference values ​​within all segmented windows under different sliding numbers; accumulate the obtained code difference values ​​within all segmented windows under different sliding numbers to obtain the accumulated code difference value result S within all segmented windows. I (i); Calculate S I (i) Autocorrelation; normalize the autocorrelation to obtain the normalized autocorrelation; calculate the normalized average autocorrelation second moment ρ(k); extract the peak value in ρ(k), and the interval between adjacent peak values ​​is the pseudocode period estimation result.

The invention provides a random distributed space-time frequency coding and decoding method in relay cooperative cross-border communication. The problem that a relay node loses efficacy in cross-border or underwater magnetic induction communication is solved, and a decoding algorithm is improved. According to the method, on the basis of distributed space-time block coding matrixes, the distributed space-time block coding matrixes are linearly combined through a random matrix, and a randomized distributed space-time block coding matrix is obtained; and the relay node selects the corresponding row in the matrix for transmission, so that the randomness of the relay node does not influence the orthogonality of the space-time coding matrix, and the influence of the failure of the relay node on the coding structure is avoided. And then, the random distributed space-time coding is subjected to direct sequence spread spectrum coding, the frequency spectrum of a transmitted signal is expanded, a receiving end utilizes related reception of a spread spectrum signal, the signal is enhanced, the noise is suppressed, the received signal-to-noise ratio is remarkably improved, and the decoding performance of the space-time coding signal under the condition that the signal-to-noise ratio is extremely low is ensured.

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

The invention relates to the technical field of wireless communication, in particular to an intelligent anti-interference method for multi-physics coupling and polarization diversity, which integrates a material shielding effect, a dust scattering characteristic and a dynamic polarization optimization mechanism so as to improve the reliability and the stability of wireless communication in a deep well environment. The method comprises the following steps: firstly, establishing a path loss correction model based on an eddy current shielding effect of a metal support material and a Mie scattering theory of dust concentration; secondly, providing an intelligent anti-interference layered framework, combining a direct sequence spread spectrum (DSSS) technology and a wavelet adaptive filtering method, and introducing a game theory to optimize multi-source node power distribution; and further designing a polarization-time delay joint compensation strategy, and suppressing multipath fading and inter-symbol interference in a non-line-of-sight scene by adopting a circularly polarized antenna and a channel equalizer based on a convolutional neural network and a long-short term memory network. Compared with a traditional method, the method has the advantages that the bit error rate can be reduced by 42% in a high-dust-concentration (200 g / m) environment, and the signal to interference plus noise ratio can be increased by 15 dB in a strong electromagnetic interference area.

A control and management system using direct sequence spread spectrum radio within the 900 MHz frequency band may be configured act as a one-to-many bridge between a central access control system or server and a plurality of peripherally connected remote devices communicatively linked to the server through a wireless hub. The wireless hub acts as a wireless bridge between the central access control system and the plurality of peripherally connected remote devices to create an access control and building management system. The wireless hub and peripherally connected devices are configured to scan channels within the 900 MHz band to detect and reply to a transmitted data packet on a randomly selected channel. The disclosed technology allows the data rate to be dynamically adjusted to optimize the time on air. By dynamically adjusting time on air, a wireless repeater may be used to decrease any latency between the peripherally connected remote devices to approximately the same as higher data rate systems, while providing substantial increases to the range between the peripherally connected remote devices and the wireless hub.

A control and management system using direct sequence spread spectrum radio within the 900 MHz frequency band may be configured act as a one-to-many bridge between a central access control system or server and a plurality of peripherally connected remote devices communicatively linked to the server through a wireless hub. The wireless hub acts as a wireless bridge between the central access control system and the plurality of peripherally connected remote devices to create an access control and building management system. The wireless hub and peripherally connected devices are configured to scan channels within the 900 MHz band to detect and reply to a transmitted data packet on a randomly selected channel.

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.

The invention discloses a low-frequency time code system and method based on a two-dimensional composite chaotic sequence, and relates to the technical field of wireless communication, and the low-frequency time code system based on the two-dimensional composite chaotic sequence mainly comprises a transmitting end and a receiving end. The transmitting end comprises a time coding module, a direct sequence spread spectrum module, an amplitude shift keying modulation module and a frequency hopping spread spectrum module; and the receiving end comprises a de-hopping module, an amplitude shift keying module, a de-spreading module, a filtering module, a judgment module and a decoding module. According to the low-frequency time code system and method based on the two-dimensional composite chaos sequence, the complexity, randomness and statistical property of the chaos spread spectrum sequence can be improved, and the anti-jamming capability, safety and environmental adaptability of the low-frequency time code system are improved.

This invention belongs to the field of underwater communication security detection technology, and specifically relates to a clever jamming method and apparatus for direct sequence spread spectrum underwater acoustic communication links. It collects underwater acoustic communication signals from known interference source nodes, analyzes the signals to distinguish between spread spectrum and noise segments, and estimates key parameters, including carrier frequency, symbol rate, symbol period, and codeword sequence. Based on these parameters, a pseudo-spread spectrum signal is generated. This pseudo-spread spectrum signal is used to monitor the communication status of the interference source in real time. When the interference source is communicating, the local node sends the pseudo-spread spectrum signal for jamming defense. This invention employs an active defense strategy to specifically and reverse-jamming direct sequence spread spectrum underwater acoustic links with specific code sequences, blocking communication link information transmission, preventing command issuance, and hindering the transmission of eavesdropped data, thereby preventing further interference to legitimate underwater acoustic networks.

The invention discloses a universal acquisition method suitable for direct sequence spread spectrum and data transmission signals, which relates to the field of satellite measurement and control communication, and comprises the following steps of: demodulating a received baseband signal by using the center frequency of a current Doppler packet to generate a baseband Doppler demodulated signal; a corresponding local signal is selected and generated according to the working mode, in the spread spectrum mode, the local signal is a spread spectrum pseudo code signal containing the current Doppler grouping center frequency and the current time delay segmentation initial value, and in the data transmission mode, the local signal is the conjugate of the baseband Doppler demodulation signal; and dividing the baseband Doppler demodulation signal in the coherent accumulation time into a plurality of non-overlapped time periods, and combining signal data of two adjacent time periods to construct double blocks of the baseband Doppler demodulation signal. According to the invention, the problems of large occupation of on-satellite storage resources and low mode switching efficiency caused by non-uniform architecture in the prior art are solved.

Methods and apparatus are disclosed for assisting in the determination of the position of a wireless communication device. One wireless communication device is provided comprising a transmitter configured to broadcast a direct sequence spread spectrum reference signal in a predefined ISM band. Another wireless communication device is provided comprising a receiver that is configured to receive direct sequence spread spectrum reference signals in the predefined ISM band. The same transmitter and receiver are used to communicate between the respective wireless communication devices and one or more base stations in a wireless infrastructure network (of which each wireless communication device is a part).

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 a robust capture method and system for a deep pseudo-random sequence with a stop judgment function, in particular to a robust capture method and system for an m-sequence codebook of an important pseudo-random sequence for a direct sequence spread spectrum technology. The invention discloses an iMPA pseudo code capturing method and system with stop judgment based on a state backtracking and phase estimation technology under sliding window overlapping state estimation, and belongs to the field of communication signal processing. According to the method, a probability signal processing technology and m sequence construction features are combined, the capturing method which can achieve a better capturing effect under a limited number of receiving chip observation values and remarkably shorten the capturing time of a long PN sequence is designed in a probability domain, and the implementation complexity and the capturing time delay brought by related operation in a traditional pseudo code capturing algorithm can be reduced.

The invention relates to a duty cycle based receiver with reduced listening power consumption. A direct sequence spread spectrum (DSSS) receiver operates in a duty cycle mode to reduce power consumption of the DSSS receiver. The DSSS receiver uses fast DSSS preamble detection to determine whether the input signal is a desired channel DSSS preamble symbol, and uses one preamble symbol to determine whether the input signal is the desired channel DSSS preamble symbol. When operating in a duty cycle mode, the DSSS receiver selectively disables at least one power domain of a plurality of power domains of the DSSS receiver during an ON time of the duty cycle and when a desired signal is not detected, and selectively disables at least one power domain of the DSSS receiver during an OFF time of the duty cycle, and the power consumption is further reduced.

The invention discloses a high-speed hybrid spread spectrum underwater acoustic communication modulation and demodulation method. The method comprises the steps of parameter setting, information modulation and receiving end information demodulation of the high-speed hybrid spread spectrum underwater acoustic modulation and demodulation method. A sending end groups information streams according to fixed time, each group of information is sequentially used for realizing frequency hopping (FH) through frequency mapping, and the carrier frequency is determined; time hopping (TH) is realized through time slot mapping, and a signal emission time slot is determined; spreading codewords for transmission are determined by direct sequence spread spectrum (DSSS) modulation. And finally, the three are combined to complete the transmission of the hybrid modulation signal. And the receiving end performs a corresponding inverse process to demodulate the original information. According to the method, three spread spectrum technologies of DSSS, FH and TH are fused, the strong anti-interference performance and the concealment of a spread spectrum system are reserved, meanwhile, the three-dimensional freedom degrees of frequency, time and code words are used for transmitting information in parallel, the communication rate of the system is remarkably improved, and the method is particularly suitable for complex and changeable underwater acoustic channels.