28 results about "Ofdm communication system" patented technology

The invention relates to an MIMO windowing OFDM communication system in a high-speed mobile scene and a space diversity utilization method thereof, and the method comprises the steps: dividing a system bandwidth into K subcarriers, and transmitting a signal through M transmitting antennas; modulating a frequency domain signal transmitted by a # imgabs0 # transmitting antenna through OFDM (Orthogonal Frequency Division Multiplexing) to obtain a time domain signal, multiplying the time domain signal by a window function and adding a cyclic prefix; coding the transmitting antenna signal according to the space-frequency repetition code, and transmitting the transmitting antenna signal to a receiving end through a dual-selective channel; receiving signals through N receiving antennas at a receiving end; decoding the received signal by adopting an MIMO (Multiple Input Multiple Output) frequency-varying Viterbi decoding scheme; and iteratively executing solution by using a surround viterbi algorithm in the decoding process until the result converges or reaches the maximum iteration times, thereby obtaining a decoding result and realizing space diversity utilization. By adopting the method, a windowing orthogonal frequency division multiplexing scheme can be expanded to a multi-input multi-output system in a high-speed moving scene, and space diversity is utilized.

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 kind of based on gradient estimation joint optimal solution search underwater acoustic OFDM system carrier synchronization algorithm, belong to underwater acoustic communication technical field.The specific method includes the following steps: step one: in underwater acoustic OFDM communication system, time domain method is used to underwater acoustic OFDM carrier synchronization.Step two: in an OFDM frame, first OFDM symbol is estimated based on optimal solution search carrier synchronization algorithm to carry out frequency offset estimation.Step three: from the second OFDM symbol, gradient descent-based carrier synchronization algorithm is used to estimate frequency offset value, and the frequency offset estimation result of the first OFDM symbol is used as the initial value of iteration.The present application can carry out more fine residual carrier frequency offset compensation by pilot symbol, improve the step of underwater acoustic system carrier synchronization algorithm using Adam method, reduce complexity while improving accuracy, realize reliable and effective underwater acoustic OFDM communication.

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.

The invention discloses an OFDM (Orthogonal Frequency Division Multiplexing) communication signal data set manufacturing method based on an FPGA (Field Programmable Gate Array) and programmable interception, solves the problems of few tag dimensions and lack of an OFDM communication system of the existing communication signal data set, and belongs to the field of computer vision. Comprising the following steps: adopting FPGA equipment as a transmitter, a cooperative end receiver and a non-cooperative detection receiver; the channel simulator simulates a channel type, multipath information and Doppler frequency offset required by non-cooperative detection and reception, and respectively sends obtained OFDM communication signals to the cooperative end receiver and the non-cooperative detection and reception machine; using a Kalman filter to clean and retain the intercepted OFDM communication signal meeting the amplitude threshold, calculating the signal power of which the score meets the task requirement, and adding Gaussian white noise to obtain a target OFDM communication signal; the method comprises the following steps: storing an OFDM communication signal data set in a pickle format through python; according to the invention, the production of the OFDM communication signal data set is realized.

The present invention provides a CP-free PS-OFDM communication system based on an autoencoder, comprising a transmitter, a channel and a receiver; the transmitter comprises a modulation module, a serial-to-parallel conversion module, an inverse Fourier transform module and a transmitter pulse shaping module connected in sequence, the transmitter pulse shaping module comprising a transmitting DNN, the transmitting DNN comprising a transmitting input layer connected to the output end of the inverse Fourier transform module, and a transmitting output layer; the channel is a multipath fading channel; the receiver comprises a receiving pulse shaping module, a coarse equalization module and a demodulation mapping module connected in sequence, the receiving pulse shaping module comprising a receiving DNN, the receiving DNN comprising a receiving input layer for inputting a received signal, and a receiving output layer, the receiving output layer being a receiving PS filter. The present invention can reduce the influence of inter-symbol interference and inter-carrier interference on signal detection, control the time and frequency characteristics of the OFDM signal, and realize flexible configuration of pulse shaping to flexibly support different communication scenarios.

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 present disclosure describes a method for carrier frequency offset (CFO) estimation of a physical channel in a mobile communication system. The method includes the following steps: performing channel estimation on a received signal on a physical channel based on a plurality of orthogonal frequency division multiplexing (OFDM) symbols in one or more reference signals (RS). The method includes: determining a plurality of phase rotation values Φ and corresponding time differences s between different OFDM symbols in one or more RS within a base phase rotation range including + / −π to obtain a first CFO estimation candidate value f0. Expanding the base phase rotation range to provide an extended phase rotation range greater than + / −π to obtain additional CFO estimation candidate values f1, f2... f n .

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 invention discloses an electric power cognitive radio NC-OFDM pilot frequency design method and system, and belongs to the technical field of communication, and the method comprises the steps: selecting M pilot frequencies from an available carrier wave set based on an NC-OFDM communication system, selecting a pilot frequency carrier wave position index each time to form an initial pilot frequency vector, taking the pilot frequency vector as an ant matrix, and initializing ant colony algorithm parameters; randomly generating initial positions of ants, and calculating pheromones and a state transition probability matrix of each ant; performing outer loop iteration and inner loop iteration to optimize ant positions; in the iteration process, taking the minimum weighted cross-correlation of a sampling matrix corresponding to a pilot frequency vector as a target, and determining an optimal pilot frequency position index; based on the optimal pilot frequency position index, pilot frequency power is determined according to a minimum cross-correlation method, and a pilot frequency design result of the NC-OFDM communication system is obtained. The performance of the sampling matrix can be improved, and the channel estimation performance is improved.

The present invention relates to an OFDM communication system and method for discrete shared spectrum, and belongs to the field of mobile communication technology. The system includes a transmitting end, a receiving end, and a shared information module. The present invention independently encodes the data carried by each subcarrier in the OFDM communication system and independently adds verification information; the subcarriers of the OFDM time-frequency resource block are continuously allocated in the time domain and discretely allocated in the frequency domain; each subcarrier uses an independent pilot signal and independently performs channel estimation and channel equalization; the time-frequency resource block of the OFDM system adopts a method of first mapping the time domain and then mapping the frequency domain; so that the receiving end can receive the correct data block when there are multiple subcarrier interferences in the OFDM system and the subcarriers in the discrete shared frequency domain are unevenly distributed, thereby making the OFDM system suitable for discrete shared spectrum resource systems.

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 provides a channel estimation and blocking diagnosis method for an RIS (Radio Information System)-assisted MIMO-OFDM (Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing) system, which comprises the following steps of: constructing an RIS-assisted millimeter wave MIMO-OFDM communication system, and blocking a part of RIS elements in the system; designing a frame-based structured training protocol, and modeling a received signal into a low-rank fourth-order tensor; analyzing uniqueness of tensor decomposition, and analyzing conditions which need to be met by a time frame number and a pilot frequency number; decomposing the received signal by using a non-iterative algorithm so as to obtain a factor matrix which is not influenced by a blocking vector and a coupling factor matrix containing residual channel parameters and the blocking vector; and channel parameters and RIS blocking vectors related to all factor matrixes are jointly estimated by using the sparse characteristic of the millimeter wave channel. According to the method, the problems of channel estimation and blocking diagnosis when part of RIS is blocked are solved, RIS blocking and channel parameters can be estimated, and then a cascade channel is recovered through the channel parameters.

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.

Described is a method of performing carrier frequency offset (CFO) estimation of physical channels in a mobile communications system. The method comprises the step of performing channel estimation of a received signal on a physical channel based on multiple orthogonal frequency division multiplex (OFDM) symbols in one or more reference signals (RSs). The method includes determining multiple phase rotation values Φ and corresponding time differences s between different OFDM symbols in the one or more RSs over a base phase rotation range comprising + / −π to obtain a first CFO estimation candidate ƒ0. The base phase rotation range is extended to provide an extended phase rotation range of greater than + / −π to obtain additional CFO estimation candidates ƒ1, ƒ2 . . . ƒn within the extended phase rotation range.

The present invention provides a PAPR suppression method based on pulse shaping modulation, belonging to the field of communications. The method comprises: establishing an end-to-end OFDM communication system model, comprising a transmitter, a channel, and a receiver; the PS module at the transmitting end is implemented by a transmitting DNN, which comprises a transmitting input layer connected to an S / P module and a transmitting output layer; the channel is a multipath fading channel; the receiver comprises an equalization module and a demodulation mapping module connected in sequence; and step S2, jointly training the neural network composed of the transmitter, channel, and receiver using a joint loss function L = α1L1 + α2L2. The present invention can reduce the PAPR at the transmitting end without affecting the transmission rate and bit error rate, and enables flexible configuration of pulse shaping to flexibly support different communication scenarios.

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 an intelligent reflecting surface (IRS) assisted OFDM communication system, which adjusts its phase shift by deploying an IRS to improve system throughput. By modeling a design problem of joint subcarrier allocation, base station transmit beamforming and IRS phase shift optimization, the application aims to maximize system throughput. In the method, multiple DQNs are used to solve the problem of excessive discrete action space, and DDPG is used to solve the problem of continuous action allocation. Simulation results show that, compared with other methods, the proposed DQN-DDPG based method can learn from the environment and continuously improve behavior, significantly improve the sum rate of the system, and has good convergence effect.

The invention relates to a signal design and iterative channel estimation method for deep sea underwater sound OFDM communication. The method comprises the following steps: step 1, establishing a ZP-OFDM communication system model; and 2, carrying out iterative channel estimation based on a channel cluster structure. According to the method, a channel cluster structure is fully utilized, a channel is divided into a plurality of clusters to be processed respectively, the iterative channel estimation and pilot frequency design technology is combined, channel parameters can be accurately estimated under the complex interference condition, and compared with a traditional method, the channel estimation performance is better, so that the reliability of a communication system is remarkably improved; aiming at serious IBI and ICI in a deep sea underwater acoustic channel, through iterative channel estimation and pilot frequency design, the interference influence is effectively inhibited, especially in a fast time-varying channel environment, stable estimation performance can still be maintained, it is ensured that communication quality is not significantly influenced by interference factors, and the method has efficient interference elimination capability and can be widely applied to the field of underwater acoustic communication. And the method has higher practical value in a dynamic deep sea environment.

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.