205 results about "Time domain correlation" patented technology

A method and apparatus for joint time and frequency synchronization for orthogonal frequency division multiplexing (OFDM) systems. A multitone pilot signal is sent in a designated OFDM symbol period. The receiver synchronizes to the pilot signal in a two-stage procedure. The first stage estimates the frequency offset coarsely with a frequency-domain correlation method and estimates the time offset with smoothed time-domain correlation. In a multipath channel, the smoothed time offset estimate is used to locate a cyclic prefix interval which captures the maximum total signal energy. The second stage improves the frequency estimate with a computationally efficient numerical optimization method.

Methods and systems are described for predicting the likely causes of service outages using only time information, and for predicting and the likely costs of service outages. The likely causes are found by defining a narrow likely cause window around an outage based on service quality and/or service usage data, and correlating service events to the likely cause window in the time domain to find a probability distribution for the events. The likely costs are found by measuring usage loss and duration for a given point during an outage and using cost component functions of the time and usage to extrapolate over the outage. These cause and cost predictions supply service administrators with tools for making more informed decisions about allocation of resources in preventing and correcting service outages.

The invention belongs to the field of communication technologies, and provides a D2D device discovery method and device based on an LTE cellular communication system. The method includes the steps that step 1, timing information of first D2D UE is obtained by the first D2D UE through the LTE cellular communication system; step 2, device discovery signals sent by second D2D UE through a discovery subframe are received in the discovery subframe according to the timing information; step 3, the time when the device discovery signals of the second D2D UE reach the first D2D UE is obtained through time domain correlation on pilot frequency OFDM symbols of the device discovery signals received in the discovery subframe and local pilot frequency sequences, device information OFDM symbols of the device discovery signals received in the discovery subframe are analyzed, device information of the second D2D UE is obtained, and therefore device discovery of the D2D UE is achieved. According to the D2D device discovery method and device, one D2D UE can effectively discover other D2D UE, system efficiency is improved, and power of the D2D UE is saved.

The invention provides a method and a device of multiple description video coding based on a relevance optimization rule, belonging to the field of video coding. The device comprises a coder, a decoder, a channel 1 and a channel 2, wherein the coder comprises a similarity optimization rule module, a preprocessor, an odd and even frame separator, a standard coder 1 and a standard coder 2; and the decoder comprises a standard decoder 1, a standard decoder 2, an odd and even frame interleaver and a postprocessor. The video coding method better keeps time domain relevance in a video subsequence by using the relevance optimization rule aiming at different motion information on the premise of guaranteeing the compression performance of each video sequence, thereby ensuring that a one-way decoder can more effectively restore lost information so as to improve the reconstruction quality of the one-way decoder.

The invention provides a method for detecting the signals randomly accessed to a signal channel. The method comprises the steps: A. after a base station acquires N time domain correlation values R(m) of the u root sequence, and all m values corresponding to the N time domain correlation values are used as detection points; B. among all detection points, the detection point m_max corresponding to the biggest time domain correlation value is found out, when the biggest time domain correlation value R(m_max) is bigger than the peak detection threshold, whether lead codes randomly accessed to the signal channel is detected by a circular shift search window corresponding to the m_max is judged, the m_max and the point m1 and/or point m2 of the present detection points are used as non-detection points, wherein m1=(N+m_max-du)mod N, and m2=(m_max+du)mod N; C. if detection points are still left, the biggest time domain correlation value of the remained detection points is bigger than the peak detection threshold, the step B is jumped to, N is more than and equal to Nzc.

A hybrid beamforming apparatus and method are proposed for a communication system. The hybrid beamforming apparatus includes a plurality of antennas, a plurality of FFT, a plurality of hybrid weight-coefficient generators and a plurality of adders. In each of the hybrid weight-coefficient generators, the weight coefficient for each subcarrier is calculated by a time-domain correlation matrix and a cross-correlation vector, which is calculated by a frequency domain signal and a training signal. The hybrid beamforming apparatus and method according to the present invention can enhance immunity for multipath effect with lower system complexity.

A low complexity RACH preamble detector is described herein. The RACH preamble detection algorithm uses the peak detection of the time domain correlation function through frequency domain processing. The frequency domain processing considers the reference signals generated directly from frequency domain CAZAC sequence or time domain CAZAC sequence with DFT conversion. A low-complexity poly-phase LPF along with down sampling is implemented before the FFT to reduce the required length of the long FFT operation N-folded.

The invention relates to network technology, discloses a DDoS attack detecting method and a device thereof, wherein the DDoS attack detecting method comprises: acquiring a signal flow matrix which describes a signal flow of a path to a destination node; decomposing the signal flow matrix to acquire an abnormal space flow matrix; according to the abnormal space flow matrix, calculating the average frequency domain correlation coefficient of a path signal flow on a frequency domain; matching the average time domain correlation coefficient with the presetting time domain condition; matching the average frequency domain correlation coefficient with the presetting frequency domain condition; if the average time domain correlation coefficient accords with the presetting time domain condition, and/or the average frequency domain correlation coefficient accords with the presetting frequency domain condition, detecting DDoS attack with a attack destination node. The technical proposal provided by the embodiment of the invention can detect DDoS attack according to abnormal flows of a plurality of paths.

The invention discloses a synchronization method for orthogonal frequency division multiplexing system, including: the launcher firstly constructs the originated / synchronous sequence that is sent out with OFDM data symbols together. Based on the correlation of CP effective length in OFDM symbols form the receiving end, the correlation result conducts a time domain processing to the correlation sequence energy to get the best synchronization points set after one synchronization. Based on the originated sequence and CP, the departure estimation and departure compensation of fractional part DF several times are processed. During a range of synchronization points set output at once, the long pre-symbol received after the compensation is made time-domain correlation with the symbol to find the second time synchronization point. Then after time-domain of the short pre-symbol and the received pre-sequence is made frequency departure compensation, time-domain-related operations is conduct to get the DF departure estimation of integer times, and departure compensation is conduct.

The embodiment of the invention provides an intelligent monitoring method and device, a storage medium and electronic equipment. The method comprises: acquiring collected monitoring data and monitoring video data of a monitoring site in the monitoring data collection process are acquired; identifying abnormal data caused by system state change or manual operation in the monitoring data and acquisition time corresponding to the abnormal data; identifying behavior actions existing in the monitoring video data and the occurrence time corresponding to the behavior actions; and detecting the behavior type of the behavior action and the correlation between the abnormal data and the behavior action or the system state change according to the time domain correlation between the abnormal data and the behavior action. According to the invention, data distortion caused by system state change or misoperation of related personnel can be automatically sensed and judged, and data counterfeiting caused by artificial interference can be avoided, so that the authenticity and effectiveness of monitoring data can be automatically ensured, and effective automatic supervision can be realized.

The invention discloses a frequency spectrum sensing method based on signal frequency spectrum envelope. The frequency spectrum sensing method comprises the following steps of: firstly, receiving a time domain continuous radio frequency signal by using two receiving antennae; secondly, carrying out down conversion and time domain sampling processing on the time domain continuous radio frequency signal to obtain a time domain discrete base band signal; carrying out discrete Fourier transform on the time domain discrete base band signal to obtain a signal frequency spectrum; calculating a signal frequency spectrum enveloped crosscorrelation coefficient; and finally, judging whether a frequency band is occupied by other wireless communication services by comparing the signal frequency spectrum enveloped crosscorrelation coefficient with a decision threshold and realizing the frequency spectrum cognition. According to the frequency spectrum sensing method disclosed by the invention, the defects that the frequency spectrum cognition is failed when the time-domain correlation among a plurality of antenna receiving signals is lower or uncorrelated in a traditional covariance matrix detection method and a characteristic value detection method are overcome.

A method of determining a boundary of a subframe in a time division duplexing (TDD) system is provided. The method detects a power level of a signal on at least one radio frequency, the signal comprising at least one subframe. A time-domain correlation is done on the detected signal with a first reference signal, wherein the first reference signal represents at least one subframe. The location in time of a boundary of the at least one subframe of the detected signal is determined based on the correlation of the detected signal and the first reference signal.

The invention discloses an airplane target classification method based on time domain correlation characteristics, and relates to the technical field of radar. The method includes the steps that firstly, a training sample peak value function is calculated; secondly, the variance, the entropy, the number of peaks with the values larger than a first training peak value threshold and a time domain point corresponding to the first peak with the value larger than a second training peak value threshold of the training sample peak value function are calculated; thirdly, the amplitude variance and the amplitude entropy of training samples are calculated; fourthly, training sample characteristic vectors are normalized, and a classifier is trained; fifthly, a test sample peak value function is calculated; sixthly, the variance, the entropy, the number of peaks with the values larger than a first test peak value threshold and a time domain point corresponding to the first peak with the value larger than a second test peak value threshold of the test sample peak value function are calculated; seventhly, the amplitude variance and the amplitude entropy of test samples are calculated; eighthly, test sample characteristic vectors are normalized and input into the classifier for class judgment. The method has good advantages at low repetition frequency and can be used for classification of three classes of airplane targets.

The invention discloses a passive channel correction method and system of a rotary array of an outer transmitter-based radar. An array antenna is rotated two or more times, the strongest path signal of every rotation is separated out through time domain correlation operation, a channel amplitude mismatching coefficient is estimated by the utilization of the strongest path signals with the high signal to noise ratio, and amplitude correction is achieved; a channel phase mismatching coefficient is estimated by the utilization of the strongest path signals with the corrected amplitude and the rotation angle information of the array antenna, and phase correction is achieved. Any auxiliary signal source is not needed any more, and the passive channel correction method and system are the real passive channel correction technical scheme. The passive channel correction method and system have the advantages that echo interference, the multipath effect and other problematic issues involved in an active channel correction method do not exist; by the utilization of the strongest path signal of every array rotation, good precision and robustness are achieved, and operation is easy; the application flexibility of the radar is improved greatly, and while the detection performance is improved, the development cost and maintenance expense of the radar are lowered largely.

The invention discloses a Sagnac/Mach-Zehnder interferometer profile fiber sensing system and a time domain positioning method thereof. The system comprises a nested structure of a Sagnac interferometer consisting of three fiber couplers and four fibers and a Mach-Zehnder interferometer, wherein the Sagnac/Mach-Zehnder interferometers are respectively connected with an incoherent light source and two photoelectric detectors. In the time domain correlation positioning method, the cross-correlation operation of disturbing signals detected by the Sagnac interferometer and the Mach-Zehnder interferometer are utilized to determine the time used from disturbance propagation to one end of a sensing fiber, the delay time of a maximum value point of a cross-correlation curve corresponds to the time, and a disturbance position is determined by using the time. The invention overcomes the defects of limit positioning distance and positioning precision of a traditional Sagnac nterferometer profile fiber sensing system.

The invention discloses a time-domain correlation and coding aiding based carrier synchronization method which achieves carrier synchronization by the aid of time-domain correlation functions of pilot frequency and output soft information of an iterative decoder of a coding system. Firstly, a pilot frequency and data add-drop frame structure is adopted, namely the pilot frequency is equally divided into two sections to be inserted into an initial position and a middle position of a data block; secondly, rough carrier estimation is performed by the aid of the time-domain correlation function of the pilot frequency, and a received signal is compensated by the aid of a rough estimation value; and finally, fine carrier estimation is performed by the aid of the time-domain correlation functions of the pilot frequency and the Turbo decoding soft information, and a fine estimation value is utilized for compensating the received signal to achieve effective carrier synchronization. The method includes the specific steps of baseband complex signal receiving, rough estimation, signal correction, soft demodulation, data demultiplexing, Turbo decoding expansion, hard decision, decoding termination condition, data multiplexing, and modulation and fine estimation. The method overcomes the defects of the prior art, and carrier frequency estimation accuracy is improved while operation complexity is lowered.

The invention discloses a method for rapidly capturing a Beidou satellite signal based on FFT. The method comprises steps of determining a local carrier frequency and a search step according to the range of the intermediate frequency and the Doppler frequency shift for receiving the Beidou satellite signal, generating a local carrier signal and performing a carrier-removing operation on the input signal to generate a mixed signal x1 (n); dividing the x1 (n) into P parts and subjecting each part to FFT calculation to obtain the frequency domain result Xi (k); dividing the Beidou satellite signal I branch ranging code CB2I code h1 (n) into P parts for the FFT calculation and performing the conjugate operation to get the frequency domain results Hi * (k); obtaining the frequency domain multiplication result Y1 (k) by the fusion algorithm; performing the IFFT operation on the frequency domain multiplication result Y1 (k) to obtain the time domain correlation result y1 (n); detecting whether there is a peak exceeding a threshold in the time domain correlation result y1 (n); and when the peak exceeds the threshold, indicating that the capture succeeds. The fusion algorithm of the invention is simple and easy to implement, the satellite signal is quickly captured without increasing the cost of the algorithm resources, and the acquisition algorithm is realized on the resource-limited embedded platform.

A video abstraction method based on attention expansion coding and decoding network comprises: regarding a video abstract as a sequence-to-sequence learning process; using time domain correlation between video frames is utilized to obtain a video frame feature sequence from an original video in the SumMe or the TVSum through a pre-training network; taking the video frame feature sequence as inputof an encoder network in an attention expansion coding and decoding network to obtain a semantic information sequence of the video frames, and then obtaining a score corresponding to each video framethrough a multiplicative attention decoding network; the scores of all the video frames forming an abstract sequence; obtaining a semantic information sequence of an abstract sequence through a retrospective encoder, constructing global semantic discrimination loss, introducing a moving average model, learning semantic correlation between the abstract sequence and a video frame feature sequence, obtaining a new abstract sequence retaining important information of an original video, and finally selecting a set final abstract through the new abstract sequence. The robustness of the model is enhanced.

The invention discloses a GPS (Global Positioning System) signal acquisition method based on an FPGA (Field Programmable Gate Array), which comprises the following steps of: firstly, carrying out down sampling on a medium-frequency acquisition signal by adopting an average sampling method; taking data obtained by averaging the energy of a point during each sampling period as sample data subjectedto down sampling, wherein the averagely-sampled points meet 2FFT (Fast Fourier Transformation) operation; finishing initial acquisition of the GPS signal to obtain an initial phase range of a pseudocode and initial carrier frequency; and carrying out further fine acquisition by using a time domain correlation algorithm to obtain accurate initial phase of the pseudocode and carrier frequency. An FPGA hardware platform is set up in the acquisition system and is combined with a radio-frequency front-end chip of a GSP receiver; and the acquisition system comprises a clock generation module, a main control module realized by a state machine, a GPS signal storage module, a carrier oscillator module, a carrier stripping module, a pseudocode reading module, an average sampling module, an FFT(FastFourier Transformation)/IFFT (Inverse Fast Fourier Transform) module, a threshold decision and initial phase calculation module and a fine acquisition module realized by a correlator.

The invention discloses an HEVC (High Efficiency Video Coding) prediction mode fast selection method based on time domain correlation and mainly solves the problem of high computation complexity of prediction mode selection during HEVC inter-frame coding. The HEVC prediction mode fast selection method includes the following steps: (1) classifying the movement intensity of a video sequence into three states: slow movement, moderate movement and fast movement; (2) counting the probability relations of the optimum prediction modes of a coding unit and the optimum prediction modes of a coding unit adjacent to the time domain of the coding unit at the movement intensity of slow movement and moderate movement respectively; (3) building a candidate prediction mode list according to the probability relations; (4) coding inter-frame coding units according to the candidate prediction mode list to obtain the optimum prediction mode. The HEVC prediction mode fast selection method effectively reduces the computation complexity of prediction mode selection on the premise of hardly changing the video frequency distortion performance, improves the prediction mode selection speed, reduces coding time, and can be applied to real-time video compression.

A method for Doppler shift estimation for channel estimation of a received signal, comprising the steps of: calculating time domain correlations; providing a Hamming window over the calculated time domain correlations; calculating a power spectrum by using FFT; calculating an adaptive threshold based on a noise floor and an average power density calculated from the power spectrum; and estimating a Doppler shift based on the adaptive threshold.

A method for time sequence analysis based on a tensor time-domain correlation decomposition model comprises the steps that time sequences are encoded into tensors; the initial tensor is converted into a dimension decrease form; a self-regression model is applied to the obtained tensors with the dimension decrease form, so that time-domain continuity can be maintained and course update results are learned dynamically till algorithm convergence is achieved, and result optimization is achieved. The method for the time sequence analysis based on the tensor time-domain correlation decomposition model provided by the invention is characterized in that the time-domain correlation model is introduced to a tensor decomposition framework, so a space-domain dimension and a time-domain dimension of the time sequences can be processed at the same time in an anisotropic manner; noise and redundant information in the time sequence space domain can be removed; internal relations among time sequence time-domain information can be controlled; and the time-domain continuity of the time sequences is maintained. According to the invention, accuracy for time sequence prediction is enhanced especially for a high-dimensional time sequence prediction issue.

The invention discloses a method, a device and equipment for detecting lead code of random access channel, which are used for reducing the complexity of lead code detection. The method for detecting lead code of random access channel comprises: carrying out multiplication operation equivalent to time domain correlation operation on a lead code to be detected which is acquired from the received signals and any sequence selected as the lead code in the frequency domain to obtain a group of correlation values; confirming the module value of each correlation value and arranging all the module values in a descending order, and extracting the module values with the identical number which are arranged forward according to the numbers of all the sequences which can be selected as the lead code; confirming the judgment variable corresponding to each extracted module value according to all the module values, and detecting that the sequence corresponding to the extracted module value is selected as the lead code when the judgment variable corresponding to the extracted module value is larger than or equal to the confirmed judgment threshold.