40results about How to "Obvious peak" patented technology

The invention provides a new method for OFDM time synchronization, which is based on a training sequence structure and a corresponding synchronization algorithm. A method of superimposing the OFDM synchronization training sequence to cyclic prefixes of transmission data is used for saving extra transmission cost; relevant peak value is more prominent by combing the training sequence structure and utilizing positive and negative alternating characteristic of the training sequence. Both the synchronization accuracy and the operating speed of the algorithm are increased by combining the corresponding synchronization algorithm.

The invention discloses a preamble symbol generation method in a physical frame and a frequency domain OFDM symbol generation method. The preamble symbol generation method in the physical frame comprises steps: fixed sequences and signaling sequences are generated respectively in the frequency domain; the fixed sequences and the signaling sequences fill effective sub carriers, and odd-even staggered arrangement exists between the fixed sequences and the signaling sequences; two sides of the effective sub carriers are filled with zero-sequence sub carriers respectively to form a frequency domain OFDM symbol with a preset length; discrete Fourier inverse transform is carried out on the frequency domain OFDM symbol to obtain a time domain OFDM symbol; a modulation signal of the time domain OFDM symbol is generated, and on the basis of the time domain OFDM symbol and the modulation signal, a preamble symbol is generated. The technical scheme of the invention solves the problem that in the current DVB_T2 standard and other standards, failure probability happens in the case of low-complexity receiving algorithm detection on the preamble symbol in a frequency selective fading channel.

The invention discloses a generation method of a preamble symbol and a generation method of a frequency-domain OFDM symbol. The generation method of the preamble symbol in a physical frame comprises that a fixed sequence and a signaling sequence are generated in the frequency domain; the fixed sequence and the signaling sequence are filled to an effective subcarrier, and the fixed sequence and the signaling sequence are in odd / even or even / odd staggered arrangement; zero-sequence subcarriers are filled to the two sides of the effective subcarrier to form a frequency-domain OFDM symbol in a predetermined length; inverse discrete Fourier transform is carried out on the frequency-domain OFDM symbol to obtain a time-frequency OFDM symbol; a modulation signal of the time-frequency OFDM symbol is generated; and the preamble symbol is generated on the basis of the time-frequency OFDM symbol and the modulation signal. According to technical schemes of the invention, the problem that the preamble symbol may cause detection failure via a low-complexity reception algorithm in a frequency selective attenuation channel in present DVB_2 and other standards is solved.

The invention discloses a generation method for a preamble symbol in a physical frame. The generation method comprises that a time-domain OFDM symbol is obtained; the length of a cyclic prefix is determined; a time-domain OFDM symbol in the cyclic-prefix length is cut from the time-domain OFDM symbol and serves as the cyclic prefix; a modulation signal is generated according to the cut time-domain OFDM symbol in the cyclic-prefix length; and the preamble symbol is generated on the basis of the cyclic prefix, the time-domain OFDM symbol and the modulation signal. On the premise that the length of the modulation signal is determined, different initial positions are selected from the part, used for cutting the cyclic prefix, of the time-domain OFDM symbol to transmit signaling information on the basis of the length of the modulation signal. The generation method of the invention can be used to solve the problems that a DVB_T2 time-domain structure in DVB_T2 and other standards at present cannot adapt to coherent detection due to lack of a cyclic prefix, and that detection via a low-complexity reception algorithm may cause failure when the preamble symbol is in a complex frequency selective fading channel.

The invention discloses a method for generating a frequency domain OFDM symbol. The method is characterized by further comprising the following steps before discrete Fourier transform is performed on the frequency domain OFDM symbol with a predetermined length to obtain a time domain OFDM symbol: determining an average power ratio of a fixed sequence to a signaling sequence; separately generating the fixed sequence and the signaling sequence on the frequency domain according to the average power ratio; filling the fixed sequence and the signaling sequence on an effective subcarrier, wherein the fixed sequence and the signaling sequence are arranged in an odd-even stagger manner; and respectively filling zero sequence subcarriers on both sides of the effective subcarrier to form the frequency domain OFDM symbol with the predetermined length. The problem that a failure probability is detected by a low- complexity receiving algorithm of a pilot symbol in a frequency selective fading channel in the existing DVB_T2 standard is solved.

A method for synchronizing OFDM symbols, comprising: generating local frequency domain data, the local frequency domain data includes a plurality of pilot data, and the positions of the selected plurality of pilot data in the frequency domain are non-equal intervals; Perform inverse Fourier transform on the local frequency domain data to obtain local time domain data; add a cyclic prefix to the local time domain data to form time domain reference data, wherein the length of the cyclic prefix is ​​the OFDM symbol generated by the sending end Determine the length of the cyclic prefix; intercept multiple data sequences from the received OFDM time domain data, and perform correlation operations with the time domain reference data respectively to obtain multiple correlation calculation values; based on multiple correlation calculation values The maximum value is used to determine the timing point of the OFDM symbol. The technical solution solves the problem that in the prior art, there are many interference peaks, which cause offset and jitter in the theoretical optimal peak point, resulting in inaccurate timing of OFDM symbols.

The invention discloses a production method of frequency domain OFDM symbols. The production method comprises the following steps: separately generating fixed sequences and signaling sequences in frequency domain, filling the fixed sequences and the signaling sequences into a valid subcarrier, wherein the fixed sequences and the signaling sequences are arranged in an even-odd alternate array; and filling zero sequence subcarriers on both sides of the valid subcarrier to form the frequency domain OFDM symbol of a predetermined length. wherein according to the length and the number of the signaling sequences, root values in a CAZAC sequence generation formula are determined, different q values are selected to generate CAZAC sequences, the CAZAC sequences are subjected to cyclic shift, the signaling sequences are selected from all the CAZAC sequences based on the determined number of the signaling sequences. According to the method, the problem that the generated signaling sequences have the characteristics of cyclic shift or cyclic shift and phase shift in time domain is avoided, and also the problem of descending performance of the frequency domain channel estimation is solved, which further ensures that a receiving end still can receive and process the signal under the condition of carrier frequency deviation in the range of -500 kHz to 500 kHz.

The invention provides a generating method and a receiving method for a preamble symbol. The generating method is characterized by comprising the steps of: generating a time domain symbol having an arbitrarily three-segment structure based on an obtained time-domain main body signal; and generating a preamble symbol based on one or two time domain symbols. The generating method and the receiving method solve the problems that a DVB_T2 time domain structure in the existing DVB_T2 standard and other standards cannot be applied to coherent detection and the failure probability of the preamble symbol occurs in low-complexity receiving algorithm detection under a complex frequency selective fading channel.

The invention discloses a generation method for a frequency domain orthogonal frequency division multiplexing (OFDM) symbol. The generation method for the frequency domain OFDM symbol comprises the steps of respectively generating a fixed sequence and a signaling sequence in a frequency region, wherein the fixed sequence and the signaling sequence are constant-modulus sequences, and complex numbers in the fixed sequence and the signaling sequence are equal in modulus; filling the fixed sequence and the signaling sequence into an effective sub-carrier, wherein the fixed sequence and the signaling sequence are arranged in an odd-even staggered manner; and respectively filling zero-sequence sub-carriers on two sides of the effective sub-carrier to form the frequency domain OFDM symbol with predetermined length, wherein in the constant-modulus sequence generation step of the fixed sequence and the signaling sequence, a same sequence generation formula is acquired by endowing a CAZAC sequence with a same root value. According to the technical scheme of the method provided by the invention, a characteristic that the generated signaling sequence has cyclic shift or cyclic shaft and phase shift in the time domain is avoided, and the problem of reduction of frequency domain channel estimation performance is solved.

The invention discloses a frequency domain OFDM symbol generation method. The frequency domain OFDM symbol generation method includes the steps: respectively generating a fixed sequence and a signaling sequence on a frequency domain; filling an effective subcarrier with the fixed sequence and the signaling sequence, wherein the fixed sequence and the signaling sequence are arranged in a parity-alternative way; and respectively filling two sides of the effective subcarrier with zero sequence subcarriers to form a frequency domain OFDM symbol with a preset length. The technical scheme of the frequency domain OFDM symbol generation method solves the problem of the failure probability, for a lead symbol, for low complexity reception algorithm detection under a frequency selective fading channel, in the present DVB_T2 standard and other standards.

The invention discloses a generation method for a frequency domain OFDM symbol. The generation method for the frequency domain OFDM symbol comprises the following steps of determining an average power ratio of fixed sequences to signaling sequences; respectively generating the fixed sequences and a signaling sequence set on the frequency domain according to the average power ratio R; selecting one signaling sequence from the signaling sequence set and filling an effective subcarrier with the fixed sequences and the signaling sequences, wherein the fixed sequences and the signaling sequences are arranged in an odd-even interleaving manner; and respectively filling zero-sequence subcarriers at two sides of the effective subcarrier to form a frequency domain OFDM symbol with a preset length, wherein a sequence number of the selected signaling sequence in the set is signaling information carried by the OFDM symbol. According to the technical scheme, the problem of detection failure probability of a precursor symbol in a frequency selective fading channel by using a low-complexity receiving algorithm in the current DVB_T2 standard and other standards is solved.

The invention discloses a method for generating a preamble in a physical frame. The method comprises the following steps: obtaining a time domain OFDM symbol; determining the length of a cyclic prefix; intercepting a part of the time domain OFDM symbol with the length of the cyclic prefix from the rear of the time domain OFDM symbol to serve as the cyclic prefix; generating a modulation signal according to the part of the time domain OFDM symbol; and generating the preamble based on the cyclic prefix, the time domain OFDM symbol and the modulation signal. The technical scheme solves the problem of reduced frequency domain channel estimation performance, and generates the modulation signal by using the part of the time domain OFDM symbol, so that the generated preamble has good small frequency offset and timing synchronization performance. Further, it is guaranteed that received signals can stilled be processed within a carrier frequency deviation of-500kHz to 500kHz.

The invention discloses an OFDM symbol timing deviation estimation method. The OFDM symbol timing deviation estimation method comprises: receiving a transmitting signal sent by a transmitting end, thetransmitting signal comprising an IEEE1901.1 protocol preamble sequence signal, and transmitting the transmitting signal to a receiving end through a low-voltage power line physical channel; processing the received transmitting signal by using a sliding window to obtain a symbol timing metric function of the received transmitting signal; and obtaining the symbol timing deviation of the OFDM system according to the symbol timing metric function. The purposes that the algorithm has higher accuracy in a low-voltage power line transmission environment and the overall performance of the system isimproved are achieved.

A method for synchronizing code element timing includes calculating correlation of sampling sequence and delay sampling sequence of sampling sequence delay length N for generating correlation sequence, generating cross correlation sequence by taking a moving average on correlation sequence, carrying out differential operation on cross correlation sequence to generate differential post sequence, generating a moving average post sequence by taking a moving average on differential sequence, detecting peak value position of moving average post sequence for obtaining correct code element timing.

The invention provides an image registration method combined with edge regions and cross-correlation. The image registration method can be used for effectively selecting the edge regions of images, and selecting and improving similarity measure functions and optimization algorithms, and aims to improve robustness and real-time performance of image registration on the premise of meeting image registration accuracy. The image registration method includes the first step of extracting the edges of reference images and images to be registered; the second step of obtaining edge region images of the reference images and the images to be registered through edge images of the two images; the third step of calculating cross-correlation coefficients of the two edge region images obtained at the second step, and using a squared value of the cross-correlation coefficients as a similarity measure function; the fourth step of searching for registration result parameters enabling the similarity measure function obtained at the third step to reach the maximum by means of a particle swarm optimization algorithm.

A calibration system for RDSS (Radio Determination Satellite Service) channel zero value comprises a spread spectrum signal source, a microwave signal source, a frequency converter, a power divider, a double-channel digital oscilloscope, a first attenuator, a second attenuator, a control and processing computer and a vector network analysis instrument, wherein the spread spectrum signal source generates simulated RDSS spread spectrum signals; spread spectrum signal source outcoming signals are subjected to frequency conversion by the microwave signal source and the frequency converter so as to generate frequency points suitable for RDSS service channel input; a high-sampling rate digital oscilloscope is used for synchronously sampling the input / output signals of the RDSS service channel; and the control and processing computer is used for completing initialization of the oscilloscope, acquisition and loading of the oscilloscope channel data, orthogonalization of the channel data, carrier rotation, circulating autocorrelation, peak value searching, and zero value calculation and processing, so as to eventually obtain the absolute time delay of the RDSS service channel. According to the system provided by the invention, the signals consistent with the RDSS service system are adopted to serve as the reference, the calibration zero value can reflect the real conditions and the calibration precision is high.

The present invention relates to a nonlinear transformation-based phase-modulated signal frequency offset estimation and tracking method. According to the method, on the basis of theoretical analysison two-phase BPSK, four-phase balanced QPSK and unbalanced four-phase UQPSK modulated signals, primary nonlinear transformation or secondary nonlinear transformation is utilized to obtain symbol influence-removed radio frequency single-carrier signals, and therefore, preconditions are created for FFT (fast Fourier transform) spectrum analysis to realize carrier frequency offset estimation fast andaccurately. Compared with existing satellite technology which directly performs processing such as FFT spectrum analysis on phase-modulated signals, the method of the invention can assist solving technical shortcomings of dispersion of envelop spectrum peak points and large frequency offset estimation error and greatly improving the accuracy and real-time performance of frequency offset estimation and tracking of the phase-modulated signals, and has a bright application prospect in realizing carrier frequency offset estimation and tracking of phase-modulated signals of different links of a satellite.