16 results about "Ofdm communication system" patented technology

The application discloses a kind of FPGA implementation methods for time-frequency synchronization of multi-path parallel transmission millimeter wave OFDM communication system, according to the frame structure of transmission signal physical layer and the number of parallel transmission paths of FPGA implementation time base, training sequence with specific structure is generated in time domain;Correlation operation is carried out on baseband multi-path parallel receiving signal using delay autocorrelation method, and the coarse timing synchronization position is found by the method of flow experience threshold comparison;The angle information carried by autocorrelation result is used to realize the frequency offset estimation calculation of system;The correlation operation is carried out on local cache sequence and receiving signal sequence, and the fine timing synchronization position is obtained;The final system symbol timing synchronization result position index is obtained by adding coarse synchronization and fine synchronization result, and the data sequence after symbol timing synchronization is output;Corresponding complex exponential signal is generated simultaneously, and frequency offset compensation operation is carried out on the sequence after timing synchronization, to complete system synchronization task.The application can improve system synchronization accuracy, reduce hardware implementation time cost and complexity.

The application discloses an FPGA-based adaptive OFDM frequency hopping system and method, and solves the problem of poor anti-interference ability of the current OFDM communication system, which leads to the decline of the system transmission information ability.The application combines the OFDM system with the frequency hopping system, and adds an adaptive control module; the receiver part of the system can detect the quality of the channel in real time, and can change the frequency hopping frequency points and the symbol modulation and demodulation modes of the transmitter and the receiver in real time according to the interference degree, so that the problem of the decline of the transmission information ability is effectively solved, the anti-interference ability of the OFDM communication system is improved, and the transmission reliability is improved.The application can be applied to the field of communication technology.

The application discloses a time-frequency synchronization method of a non-cooperative OFDM communication system, a blind synchronization algorithm of cyclic prefix autocorrelation is used to perform initial frame synchronization on a received signal to realize frame header positioning, a sliding correlation window is used to position a time domain position of a synchronization sequence of the received signal, clustering decision is performed on the synchronization sequence in continuous multiple frames of signals, and an initial synchronization sequence is extracted through autocorrelation peak value statistics of multiple frame decision results. According to autocorrelation characteristics and cycle characteristics of the synchronization sequence, the application provides a fast symbol synchronization and optimal sampling point synchronization method, and frequency offset estimation is realized based on a Moose algorithm. After the received signal is subjected to time-frequency synchronization, the synchronized sequence is fed back to the clustering decision step to perform iterative updating on a local synchronization sequence, and the overall system performance is further improved.

A method for suppressing peak-to-average power ratio (PAPR) of reserved subcarriers in OFDM communication systems includes the following steps: Step 1: digital clipping using a shearing method; Step 2: acquiring clipping noise; Step 3: suppressing out-of-band noise to obtain new clipping noise; Step 4: filtering out in-band noise to obtain canceled noise; Step 5: inversely superimposing the noise into the original signal; Step 6: repeating steps 1-5 to reach the maximum number of iterations; Step 7: outputting the signal after PAPR suppression. This invention expands the range of reserved subcarriers, combining the resources of out-of-band and in-band empty subcarriers, and uses them to generate a signal that suppresses high peak values ​​and cancels noise, thereby improving PAPR suppression gain and retaining the distortion-free characteristics of the reserved subcarrier method.

The invention discloses a self-adaptive channel estimation method and device for a power line OFDM (Orthogonal Frequency Division Multiplexing) communication system. The method comprises the following steps: S1, acquiring an initial frequency domain response estimation value of a current channel; s2, calculating a first channel parameter according to the initial frequency domain response estimation value; s3, calculating a second channel parameter according to the initial frequency domain response estimation value; s4, dynamically determining filtering configuration based on the first channel parameter and the second channel parameter, the filtering configuration comprising an application interval and a filtering order; s5, taking the subcarrier determined by the application interval as a node, and performing channel estimation on the corresponding node subcarrier in a first channel estimation mode according to the filtering order to obtain a node subcarrier channel estimation value; and S6, for non-node subcarriers, performing channel estimation based on the channel estimation values of the adjacent node subcarriers by using a second type of channel estimation mode, thereby realizing the effect of maximally reducing the operand on the premise of not sacrificing the system performance.

The application discloses an OFDM communication signal dataset manufacturing method based on FPGA and programmable interception, solves the problems of few label dimensions and lack of OFDM communication system in current communication signal datasets, and belongs to the field of computer vision; the method comprises the following steps: adopting an FPGA device as a transmitter, a cooperative terminal receiver and a non-cooperative detection receiver; a channel simulator simulates the channel type, multipath information and Doppler frequency offset required by non-cooperative detection, and sends the obtained OFDM communication signals to the cooperative terminal receiver and the non-cooperative detection receiver; a Kalman filter is used to clean and retain the intercepted OFDM communication signals meeting the amplitude threshold, the signal power meeting the task requirement is calculated, Gaussian white noise is added to obtain a target OFDM communication signal; the OFDM communication signal dataset is stored in a pickle format through python; and the application realizes the manufacturing of the OFDM communication signal dataset.

The invention provides a frequency band detection method of an OFDM (Orthogonal Frequency Division Multiplexing) communication system and related equipment. The method comprises the following steps: performing sliding discrete Fourier transform on a received signal sampling sequence to obtain sliding discrete Fourier transform output corresponding to each subcarrier index; constructing a frequency band energy sequence of each candidate frequency band based on the sliding discrete Fourier transform output; defining an adaptive threshold value of each candidate frequency band based on the noise statistical parameter of each candidate frequency band in the preset noise interval; constructing a detection window based on the obtained window starting position; based on the frequency band energy sequence of each candidate frequency band, calculating the detection statistics of each candidate frequency band in the detection window and the corresponding confidence; and if the detection statistical magnitude is greater than the adaptive threshold and the confidence coefficient is greater than a preset confidence coefficient, determining each candidate frequency band as an effective communication frequency band. According to the invention, low time delay, low power consumption and accuracy of communication frequency band detection in the OFDM communication system can be considered.

The application discloses an OFDM signal-based underwater acoustic time-varying Doppler estimation method, and belongs to the technical field of underwater acoustic communication and underwater acoustic signal processing. The application is used to solve the problem of realizing joint accurate estimation of relative speed and relative acceleration parameters of a transmitting-receiving party in an underwater acoustic OFDM communication system without improving sampling rate and without complex frequency search, and the time-varying Doppler model containing the speed parameter and the acceleration parameter is constructed by modeling the received signal through nonlinear resampling; the phase and amplitude information is extracted by using the autocorrelation characteristics of adjacent OFDM symbols, the cost function is constructed through multi-branch parallel autocorrelation processing, and the speed and acceleration parameters are jointly estimated by combining the constraint relationship of the phase changing with the symbol serial number. The application can realize joint parameter estimation under the acceleration condition without improving the sampling rate and without large-range frequency search, effectively reduces the system bit error rate, and improves the reliability of the underwater acoustic mobile OFDM communication system.

The present disclosure discloses systems and methods of calculating a near-maximum likelihood detection (MLD) performance capability signal to interference plus noise ratio (SINR) according to instructions stored in non-transitory computer readable memory that when executed by a processor of a multiple-input, multiple output orthogonal frequency-division multiplexing (MIMO-OFDM) wireless communications receiver device cause the processor to perform operations including the processor acquiring Hi and noise variance σn2 for each subcarrier of a set of subcarriers between a MIMO-OFDM wireless communications transmitter device and the wireless communications receiver device, computing an average received bit mutual information rate (RBIR) over all subcarriers, converting the average RBIR to an effective SINR; and selecting a modulation coding scheme (MCS).

The invention discloses an underwater acoustic OFDM (Orthogonal Frequency Division Multiplexing) adaptive communication method based on two-dimensional channel characteristics and an XGBoost classifier, and belongs to the technical field of underwater acoustic communication. The invention solves the problems of high bit error rate and low transmission efficiency of the traditional method. According to the method, the m value obtained through Nakagami-m distribution fitting and the PSNR are used for constructing the two-dimensional channel features as input, the XGBoost multi-classification model optimized through PSO is used for completing modulation mode selection, and therefore finer and more reliable parameter configuration is achieved. By introducing the machine learning algorithm into the adaptive modulation process, the accuracy of modulation coding scheme selection is improved, and the transmission efficiency is maximized while the communication reliability is ensured. The adaptive communication performance of the underwater acoustic OFDM communication system under the condition of the fast time-varying underwater acoustic channel is comprehensively improved from the two aspects of reliability and effectiveness, and the bit error rate of the underwater acoustic OFDM communication system is reduced. The method provided by the invention can be applied to underwater acoustic OFDM adaptive communication.

The invention discloses an RFSoC (radio frequency system-on-chip) low-delay optimization method oriented to a communication sensing integrated system. The method comprises the following steps: firstly, establishing a transmitting link and a receiving link of an OFDM (orthogonal frequency division multiplexing) communication system in a programmable logic PL of an RFSoC; data interaction with a processing system PS is realized by adopting an AXI-based streaming interface; a pseudo-random noise PN sequence is inserted into the initial position of a transmission link in a time division multiplexing mode, and cooperative operation of communication and sensing is achieved; carrying out pipelined delay optimization processing on the transmitting link; dMA data path optimization is carried out on a data transmission path on the PS side, and system-level data paths and signal interface modes of an OFDM transmitting link and an OFDM receiving link are optimized on the PL side. According to the method, the parameterization relationship between communication and sensing performance is constructed, so that the system can select proper PN code configuration according to application requirements, and the performance balance between the communication and sensing functions is realized.

The invention relates to a Doppler and channel joint estimation method of an OFDM (Orthogonal Frequency Division Multiplexing) system under an impulse noise background, which comprises the following steps of: constructing an OFDM communication system model in which a channel has Doppler frequency shift and a sending signal is an OFDM modulation signal, and then respectively calculating a cyclic autocorrelation function of the sending signal and a cyclic autocorrelation function of a receiving signal in the OFDM communication system model; the method comprises the following steps of: constructing a cyclic correlation matrix equation by using the difference of an OFDM signal, AWGN noise and impulse noise in cyclic correlation function energy distribution, and finally obtaining a Doppler frequency shift estimation value and a channel parameter by solving the matrix equation, thereby realizing Doppler frequency shift and channel estimation of an OFDM system under the impulse noise background. And better robust performance is shown in an impulse noise environment.

The invention discloses a noise estimation method and device for an orthogonal frequency division multiplexing communication system, and the method comprises the following steps: S1, calculating respective initial noise estimation matrixes on subcarriers based on a received training sequence; s2, on the basis of the initial noise estimation matrix, a measurement parameter vector used for representing noise characteristics of each subcarrier is obtained through calculation, and the dimension of the measurement parameter vector is equal to the number of the subcarriers; s3, dynamically and adaptively dividing all the subcarriers into one or more continuous frequency segments according to the measurement parameter vector, and determining the dividing boundary by the change characteristic of the measurement parameter vector in the frequency domain; and S4, for each frequency segment obtained by division, based on the initial noise estimation matrix corresponding to the subcarriers contained in the segment, calculating a noise covariance matrix of the segment, so that colored noise can be more effectively converted into white noise, the detection error of the signal is remarkably reduced, and the receiving performance and demodulation reliability of the whole communication system are improved.

The invention provides a 5G OFDM communication system and method of a PDF probability model assisted FFT, relates to the technical field of wireless communication, and solves the technical problems of insufficient signal identification precision and weak anti-interference capability in the prior art. The system comprises a transmitting end module, an interference monitoring module and a receiving end module, the sending end module is used for generating a packaging signal through signal generation, coding, PDF-FFT preprocessing, OFDM modulation and frame formatting processing; the interference monitoring module is used for acquiring interference parameters in real time, respectively transmitting the interference parameters to the transmitting end and the receiving end, and forwarding the packaging signal at the same time; and the receiving end module is used for carrying out OFDM (Orthogonal Frequency Division Multiplexing) demodulation and inverse PDF-FFT decoding on the received packaging signal, and finally recovering a decoded signal. The present application is used in a wireless communication process.

The application discloses a water acoustic MIMO communication multi-channel different carrier frequency offset two-stage joint estimation method and relates to the technical field of water acoustic communication. In view of the problem that the estimation performance is reduced due to model mismatch in the multi-channel different CFO scene, the method adopts a coarse-precise two-stage estimation framework: in the coarse estimation stage, the minimum cost function value is searched to determine and compensate the multi-channel consistent CFO component through candidate CFO compensation, tentative channel estimation and equalization; in the fine estimation stage, the multi-channel different residual CFO and the channel are jointly estimated based on the sparse Bayesian learning technology, and a low-complexity closed-form solution is obtained through Taylor series expansion by using the small characteristic of the residual CFO. The application does not need to configure zero subcarriers, effectively solves the model mismatch problem while maintaining high spectral efficiency, reduces the estimation difficulty, improves the CFO estimation precision, and is suitable for actual water acoustic MIMO-OFDM communication systems.

The application discloses a gain control method and device, a communication node and a medium. The method comprises the following steps: determining an initial average power value of a sampling signal in a current statistical period; determining a target average power value of the sampling signal in the current statistical period based on a target average power value of the sampling signal in a first statistical period, a target average power value of the sampling signal in a second statistical period, the initial average power value of the sampling signal in the current statistical period, and a weight value of each statistical period; determining a target communication gain value based on a communication gain value of the current statistical period, the target average power value and an optimal power threshold value; and taking the target communication gain value as a communication gain value of a next statistical period of a variable gain power amplifier. The application reduces the influence of wireless channel fading and burst interference on the wireless communication quality in a large-scale MIMO-OFDM communication system.