15 results about "Spread spectrum communication systems" patented technology

This invention discloses a method for acquiring spread spectrum signals to eliminate the influence of high-speed data symbols, comprising the following steps: When down-converting the input signal obtained from the ADC sampling receiver, a fixed frequency offset is artificially introduced; a local pseudo-code sequence is correlated with the down-converted signal; the correlated signal is low-pass filtered; the I-path and Q-path of the filtered signal are multiplied, and the result is input to the FFT calculation module; the highest energy spectral line is found in the spectrum output by the FFT module, and the Doppler frequency offset of the input signal is calculated if the energy of this spectral line exceeds a threshold, then pseudo-code locking and carrier locking are performed; it is determined whether pseudo-code locking and carrier locking are completed: if locked, the acquisition process ends; if not locked, the phase of the local pseudo-code sequence is adjusted and the process returns to the down-conversion step. This invention can eliminate the influence of high-speed data symbol flipping on spread spectrum signal acquisition, is applicable to different data rates, and significantly enhances the communication capability of spread spectrum communication systems.

The present invention discloses a capture method compatible with multiple modes and multiple sampling rates, and relates to the field of spread spectrum and non-spread spectrum communication systems in satellite communications. The present invention mainly adopts two parallel codewords and matching, accumulation and other processing, and utilizes changes in parameters such as data bit width, matching method selection, and sampling rate adjustment to flexibly adapt the capture synchronization of various signals. The use of a universal capture method solves the problem of customizing capture modules under different modes or different sampling rates, and can also assist in achieving preliminary estimation of carrier frequency deviation and accelerate carrier synchronization. The present invention is simple to implement, occupies few resources, and is highly operational and portable. It is very suitable for FPGA implementation and is conducive to the rapid synchronization of spread spectrum and non-spread spectrum signals.

The application provides an anti-interference automatic synchronous frequency hopping method suitable for a wireless self-organizing network, and belongs to the technical field of radio communication transmission. The application extracts a signal form distortion variable while completing synchronous interaction at a physical layer through a node transmitting a composite waveform signaling carrying a precise timestamp and having a spread spectrum correlation characteristic, evaluates the channel quality of a current transmission frequency point, encapsulates a local channel quality evaluation result into a heartbeat signal and broadcasts the heartbeat signal in a network, and fuses to generate a global dynamic interference map. The node dynamically decides a frequency point and a frequency hopping sequence of frequency hopping communication based on the map, and broadcasts a synchronous guide signal through strong anti-interference coding. When a link is reconstructed, the node is guided to preferentially perform fast radio frequency scanning and synchronous acquisition based on a high-stability frequency point predicted based on the map. The application effectively avoids out-of-step disconnection caused by disturbed synchronous messages in traditional frequency hopping communication, and significantly improves the transmission reliability of a spread spectrum communication system in a severe electromagnetic environment.

This disclosure provides a spread spectrum communication system and method based on orthogonal pilots, comprising: a transmitter for spreading the spectrum using a first pseudo-random spreading code sequence and a fixed pilot sequence to obtain pilot branch signals and pilot pseudo-code phase information; spreading the spectrum using a second pseudo-random spreading code sequence and the original data sequence to obtain a data branch signal; orthogonally combining the pilot branch signals and the data branch signals to obtain a baseband signal; and a receiver for processing the baseband signal using a third pseudo-random spreading code sequence and a local carrier to obtain carrier frequency phase information and synchronization pseudo-code phase information; determining a demodulation carrier based on the carrier frequency phase information; demodulating the baseband signal using the demodulation carrier to obtain a demodulated data signal; performing phase adjustment on a fourth pseudo-random spreading code sequence based on the synchronization pseudo-code phase information; and despreading the demodulated data signal based on the phase adjustment result to obtain a target data sequence. This improves the efficiency of spread spectrum communication.

The present invention discloses a narrowband interference-resistant receiving device in a direct sequence spread spectrum communication system, belonging to the field of digital signal processing. The device comprises a DC module, an orthogonal downconverter, a decimation module, a low-pass filter module, a digital AGC module, an interference trap module, a sampling rate conversion module, a frequency estimation module, a parameter mapping module, and a table lookup module. The present invention implements interference trapping by combining sampling rate conversion with a table lookup, offering advantages such as simple processing, low resource usage, and high trapping accuracy. The device has a wide range of applications and can also be used in spaceborne equipment with limited hardware resources and stringent performance requirements.

The present invention discloses a system and method for optimizing the logic circuit complexity of a spread-spectrum communication system. The system includes a data buffer module (RxBuffer), a local spread-spectrum sequence generation module (LocalCSSGen), an FFT-based time-domain circular correlation despreading module (RxDeCSS), and a despreading parameter control module (RxCtrlModul). The system utilizes a joint mechanism technology that combines local coarse correlation despreading of a low-sampling-rate complete symbol period sequence with fine correlation despreading of a high-sampling-rate truncated symbol period sequence for despreading spread-spectrum symbols. By dynamically setting the compression ratio of the buffer module and the local spread-spectrum sequence, accessing the initial index, and truncating the spread-spectrum sequence length, the system performance requirement for the FFT length is reduced, thereby reducing the complexity and difficulty of implementing the FFT logic circuit of the spread-spectrum communication chip, achieving chip area optimization, and promoting optimization of the overall area of ​​the spread-spectrum communication chip while ensuring high sensitivity and large capacity system requirements.

The invention relates to the field of communication signal processing, and provides a satellite-ground link Doppler effect compensation method and device for a low-orbit satellite spread spectrum communication system, and the method comprises the steps: extracting a downlink auxiliary carrier from a downlink receiving signal; performing Doppler frequency offset real-time estimation by using the extracted downlink auxiliary carrier; performing pulse shaping processing on an input spread spectrum modulation symbol based on a Doppler frequency offset real-time estimation result, and generating a baseband sending signal pre-compensated by a clock Doppler error; based on the Doppler frequency offset real-time estimation result, Doppler carrier frequency offset pre-compensation is carried out on the baseband sending signal subjected to clock Doppler error pre-compensation, and a final sending signal is generated. According to the invention, the communication capacity and transmission performance of the low-orbit satellite spread spectrum communication system can be improved.

The application discloses a spread spectrum communication interference sensing method based on an attention mechanism, which comprises the following steps: 1, collecting common interference signal types in a spread spectrum communication task and modeling; 2, modeling a channel environment, constructing a received signal model according to a spread spectrum communication system, generating a large number of interference-free signals and interfered signals under different jamming signal-to-signal ratios, and constructing a training data set; 3, establishing an interference sensing Transformer network, which is composed of an embedding module, a twin transformer module and a gating module, wherein the twin transformer module comprises two transformers, which are respectively used for learning the correlation characteristics between subcarriers and the correlation characteristics between real parts and imaginary parts; 4, training the interference sensing Transformer network constructed by using the training data set to obtain network parameters; and 5, fixing the network parameters, inputting a real-time spread spectrum received signal spectrum, and completing interference type identification by the network.

The invention provides an anti-interference automatic synchronization frequency hopping method suitable for a wireless ad hoc network, and belongs to the technical field of radio communication transmission. According to the method, the node sends the composite waveform signaling which carries the precise timestamp and has the spread spectrum related characteristics, the signal form distortion amount is extracted while synchronous interaction is completed in the physical layer so as to evaluate the channel quality of the current transmission frequency point, and the local channel quality evaluation result is packaged into the heartbeat signal and broadcasted in the network. And fusing to generate a global dynamic interference map. The nodes update frequency points and frequency hopping sequences of frequency hopping communication based on the map dynamic decision, broadcast synchronous guide signals through strong anti-interference codes, and guide the nodes to preferentially carry out rapid radio frequency scanning and synchronous capture based on map prediction high-stability frequency points during link reconstruction. According to the method, the out-of-step and chain breakage caused by interference of the synchronous message in the traditional frequency hopping communication are effectively avoided, and the transmission reliability of the spread spectrum communication system in the severe electromagnetic environment is remarkably improved.

The invention discloses a quasi-cyclic double diagonal LDPC (Low Density Parity Check) coding device, system and method capable of efficiently utilizing resources, and belongs to the field of LDPC coding, and the device comprises an RAM (Random Access Memory) storage module, a read address calculation module, a check bit operation module and a control module; the RAM storage module is used for storing data to be coded; the read address calculation module is used for circularly reading the data to be coded in the RAM; the check bit operation module is used for executing exclusive-or operation on the read data to be coded to directly generate check data; and the control module is used for dynamically adjusting the working state of the encoder so as to realize compatibility with different spread spectrum rates. The method is suitable for a spread spectrum communication system, and has the advantages of few storage resources, simplicity in operation, controllable coding rate and high universality.

The invention discloses a self-adaptive anti-interference synchronization method for a spread spectrum communication system based on an FPGA (Field Programmable Gate Array). The method comprises the following steps: inputting a zero intermediate frequency signal containing a signal, interference and noise into the FPGA; converting the zero intermediate frequency signal from a time domain signal to a frequency domain signal; identifying an interference frequency point by comparing a real-time calculated dynamic interference threshold value with an actually received frequency domain signal; removing the influence of the interference signal and then converting back to the time domain; frequency slots are divided, and the time domain signals are subjected to synchronous frequency conversion to the corresponding frequency slots; performing matched filtering on the signal in each frequency slot; and repeatedly calling the summator by using the signal updating gap in the sliding correlation process of the local synchronization code and the filtered signal of each frequency slot to complete the synchronization process. According to the method, the interference signals can be quickly and accurately identified and eliminated, the anti-interference capability of the spread spectrum communication system in a complex interference environment is remarkably improved, the bit error rate is reduced, and the communication quality is improved.

The invention discloses a fast bit synchronization device and method for a high-dynamic incoherent spread spectrum communication system, and belongs to the field of communication signal processing. A multi-phase segmented integral structure is adopted to realize matched filtering and variable sampling rate speed reduction processing of data symbols; the synchronous clock capturing and tracking unit performs bit synchronization error estimation by using an input multiple symbol rate sampling signal, a bit synchronization error estimation value is filtered to generate a symbol synchronization clock error control signal, and a symbol synchronization clock pulse is synthesized according to the synchronization clock error control signal and a fixed frequency control word; and the bit synchronization data recovery unit judges and extracts the optimal sampling position of the input data symbol under the driving of the symbol synchronization clock pulse signal, and outputs final bit synchronization data. According to the invention, the transmission performance of the high-dynamic incoherent spread spectrum communication system is improved.

The application discloses a multipath diversity receiving spread spectrum communication system suitable for urban channels and relates to the technical field of signal processing, which solves the problem of passive multipath coherent combination in the prior art. The system comprises the following steps: at the transmitting end, after input data streams pass through channel coding, interleaving and symbol mapping, serial-parallel conversion is performed, a data block is formed by adding block pilots after direct sequence spread spectrum using a spread spectrum code sequence, IFFT transformation is performed to the time domain, a cyclic prefix is introduced, and after serial conversion, the data block is sent into a multipath fading channel; at the receiving end, after serial-parallel conversion, the cyclic prefix is removed, FFT transformation is performed to the frequency domain, pilot channel estimation is performed, the pilots are removed, de-spreading and de-mapping are performed, channel estimation results and de-spreading data are mapped to the time domain by IFFT for RAKE reception, finally, soft information is added, demodulation, de-interleaving and decoding are performed; the multipath coherent combination is changed from passive to active, the multipath components can be better extracted, and the system has more superior performance under urban multipath channels.

The present invention provides a satellite spread spectrum communication system and symbol synchronization method based on improved square variation. The method includes the following steps: S1: a receiving end performs matched filtering despreading on all sampling points of an input signal to convert the input signal into a complex signal; S2: preprocessing the complex signal; S3: comparing the preprocessed input signal with a preset signal amplitude threshold T, and determining the moment when the signal amplitude is greater than the threshold T as the current optimal sampling time point; S4: determining the phase based on the optimal sampling time point and generating a timing pulse sequence signal; S5: sampling the preprocessed signal using the timing pulse sequence signal, calculating the sum of the variation between the sampling value of the optimal sampling point and the two preceding and following sampling values as a correction variable; and S6: correcting the phase of the timing pulse sequence signal based on the correction variable. The present invention has a low computational complexity and can quickly and accurately perform symbol synchronization between a transmitting end and a receiving end.

The invention discloses a broadband interference signal elimination method in a spread spectrum communication system under a non-homologous clock. According to the method, an input signal is sampled and filtered, a cooperative interference signal is demodulated to obtain a corresponding data stream, then the cooperative interference signal is reconstructed according to a modulation mode of the cooperative interference signal to obtain a reconstructed interference signal, and non-homologous clock self-adaptive resampling is performed on the reconstructed interference signal to obtain a reconstructed interference signal. And the problem of sampling point number change caused by a non-homologous clock is corrected. And finally, performing alignment subtraction on the sampling signal and the reconstructed interference signal after adaptive resampling to complete interference elimination. According to the invention, non-homologous clock adaptive resampling is carried out after signal reconstruction to compensate for sampling point jitter, so that the problem that cooperative broadband interference signals are difficult to effectively eliminate in a non-homologous clock environment is solved, and the anti-interference capability and anti-interception capability of a spread spectrum communication system are improved.