44results about How to "Improve frequency offset estimation accuracy" patented technology

The invention provides an OFDM carrier frequency offset estimation method for packet transmission, which comprises the following steps: 1) performing IFFT conversion on frequency domain symbols to obtain time domain training symbols of two same repetition modules; 2) adding cyclic prefixes with the length of L on the front of the time domain training symbols to form integral OFDM symbols, and obtaining received OFDM signals carrying frequency offset epsilon through a multipath channel; 3) rotating phases with pi epsilon by N/2 spaced received sample values in the received OFDM signals to obtain fine frequency offset estimation epsilon [fine]; 4) performing fine frequency offset compensation on the received OFDM signals to obtain OFDM signals after the compensation; 5) performing FFT conversion on training symbol parts of the compensated OFDM symbols after the cyclic prefixes are removed so as to obtain receiving end modulation frequency domain symbols; 6) detecting peaks of cyclic shift of the receiving end frequency domain symbols and sending end frequency domain symbols to obtain coarse frequency offset estimation; and 7) performing coarse frequency offset compensation on the receiving end modulation frequency domain symbols in a receiving end frequency domain, and summing up the coarse frequency offset estimation and the fine frequency offset estimation to obtain the carrier frequency offset estimation.

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.

A carrier frequency estimation method and apparatus is provided for improving frequency estimation performance in an Orthogonal Frequency Division Multiplexing (OFDM) communication system. The frequency estimation method for a wireless communication system includes summing correlations of four pairs of reference symbols transmitted at different frequency-time resource blocks in a pattern, each pair including two closest reference symbols; calculating a statistical value (E) by accumulating the summed correlation in a frequency direction; and estimating a frequency offset using an angle extracted from the statistical value (E).

The invention relates to an MIMO-OFDM system frequency deviation estimation method. The method is used for performing frequency deviation estimation on signals which contain a short training sequence, a long training sequence and an SIG sequence and are received by a plurality of receiving antennas of the receiver of an MIMO-OFDM system. The method of the invention includes the following steps that: coarse frequency deviation is calculated through utilizing the short training sequence of the signals; long training sequence frequency deviation is calculated through utilizing the long training sequence of the signals; time-domain residual carrier frequency deviation is calculated through utilizing the SIG sequence; and the coarse frequency deviation, the long training sequence frequency deviation and the time-domain residual carrier frequency deviation are summated, and a summation result is adopted as the estimation result of carrier frequency deviation. The method has the advantages of high frequency deviation estimation accuracy and wide application range.

The invention relates to a frequency synchronization method based on joint estimation carrier of frequency offset, belonging to the technical field of wireless mobile communication. The frequency synchronization method comprises the steps of: carrying out coarse frequency synchronization by using a short training field so as to correct integer frequency offset and carrying out frequency offset compensation on the basis of a coarse frequency synchronization result; by using a signal subjected to frequency offset compensation and a long training field, in combination with a segmentation related algorithm, carrying out frequency estimation to obtain a carrier frequency offset 1; obtaining a carrier frequency offset 2 on the basis of an MMSE (Minimum Mean Square Error) criterion; further obtaining a carrier frequency offset 3 on the basis of a mean square error criterion, and giving frequency synchronization results in different wireless channel environments; and finally, on the basis of the frequency synchronization results, carrying out frequency offset correction on a received signal. According to the frequency synchronization method, the synchronization mean square error of a wireless system is greatly lowered and the synchronization precision is effectively improved.

The invention discloses a multicarrier synchronization method and system of a nested recurrent PN sequence. According to the method, a carrier frequency offset estimation step and a frequency offset correction step are carried out successively, in the carrier frequency offset estimation step, the separated nested recurrent PN sequence is processed; and in the frequency offset correction step, the carrier frequency offset of a received signal is corrected. According to technical schemes of the invention, the method and device can be applied to the digital communication fields with low signal to noise ratio transmission and severe clutter interference, as ground wireless communication and satellite and power line communication.

A method for implementing carrier frequency offset correction base on large-point FFT. Firstly, the receive signal is orthogonally mixed, convert to I, Q two-way signal, and then combining the outputsignals of I and Q into complex signals, the spectrum characteristics of complex signals are estimated by using the twice FFT matrix method, and then finding the position corresponding to the maximumpeak point on the spectrum characteristic and calculating the frequency offset value, Finally, the frequency offset value is converted into the frequency control word of the voltage controlled oscillator, so as to generate the same frequency as the frequency offset value. After passing through the feedback loop, I and Q signals are compensated by orthogonal mixing, and the high-frequency components are eliminated through the low-pass filter to output the correct baseband signal after the frequency offset is eliminated.

The invention discloses a frequency offset estimation method and system for a 32-system quadrature amplitude modulation signal. According to the method and system, the method comprises the steps: rotating a class II signal sequence and a class IV signal sequence in a received 32-system quadrature amplitude modulation signal sequence in the same direction to form a rotation modulation signal sequence, and then using each amplification coefficient with the maximum peak-to-average power ratio for amplifying the rotation modulation signal sequence to obtain an amplified modulation signal sequence;performing the fast Fourier transform of the fourth power of the amplified modulation signal sequence based on the above, thereby obtaining the frequency corresponding to the peak of the spectrum amplitude; finally determining the frequency offset estimation value of the 32-system quadrature amplitude modulated signal sequence according to the frequency corresponding to the peak value of the spectrum amplitude. The method and system provided by the invention have high frequency offset estimation precision, good signal to noise ratio threshold performance, strong practicability and good application prospect.

The invention relates to a frequency offset estimation method and system for a burst-mode signal. The method comprises the steps of extracting pilot frequency information of each segment in a received burst frame to obtain at least two segments of initial pilot frequency sequences; according to the pilot frequency information of each segment of initial pilot frequency sequence and standard pilot frequency information, generating target pilot frequency sequences; carrying out phase angle obtaining processing on the target pilot frequency sequences to obtain phase angle sequences; segmenting the phase angle sequences and setting a spacing between each two adjacent phase angle sequences; and according to a difference of two adjacent phase angle values in the phase angle sequences, calculating a series of frequency offset estimated values. According to the scheme of estimating the frequency offset of the burst-mode signal, which is provided by the invention, under the condition that each segment of pilot frequency sequence in a burst sequence in short burst communication is relatively short, by processing each segment of pilot frequency sequence, frequency offset estimation can be carried out through utilizing multiple segments of pilot frequency information, and each segment of pilot frequency sequence is not requested to have an equal length, and thus, a frequency offset value of the short burst frame can be accurately estimated, and frequency offset estimation accuracy under the condition of a low signal-to-noise ratio can be improved.

The invention belongs to the technical field of communication, and relates to a multilevel frequency offset estimation method based on FFT. The method provided by the invention mainly comprises the following steps: setting carrier frequency offset estimation to multiple frequency offset estimation levels, which is characterized in that a lower extraction ratio corresponding to the frequency offset estimation increases with the increase of the frequency offset estimation levels; carrying out the frequency offset estimation starting from the first level frequency offset estimation, and calculating the frequency offset estimation result of each level before the frequency offset estimation level reaches a preset total level; and accumulating the frequency offset estimation result of each level, and using the obtained accumulated value as a final frequency offset estimation result. The multilevel frequency offset estimation method provided by the invention has the beneficial effects that compared with the traditional frequency offset estimation method based on the FFT, on the basis of guaranteeing the estimation range, the frequency offset estimation precision can be greatly improved.

The invention discloses a frequency deviation estimating method in the QAM (quadrature amplitude modulation). The frequency deviation estimating method is characterized by including steps of carrying out frame synchronization by means of relative detection and picking up frame header codes; pairwise corrugating and multiplying the frame header codes with the interval 32 for rough frequency deviation estimation,; then corrugating and multiplying two adjacent frame header codes in pairwise for fine frequency deviation estimation; and combining the rough frequency deviation estimation and the fine frequency deviation estimation to obtain accurate frequency deviation estimation. By the aid of the frequency deviation estimating method, high-order QAM modulation accuracy and frequency deviation estimating accuracy on the condition of low signal to noise ratio in the QAM communication system are effectively increased, and the frequency deviation estimating range is broadened.

The invention discloses a frequency offset estimation method for an orthogonal frequency division multiplexing (OFDM) communication system, which comprises the following steps of: extracting a frequency-domain original reference signal and a time shift parameter; obtaining a time-domain reference signal with cyclic time shift characteristics according to the frequency-domain original reference signal and the time shift parameter; transmitting the time-domain reference signal; receiving the time-domain reference signal; and extracting a time shift reference signal, and calculating an estimatedfrequency offset value according to the time-domain reference signal and the time shift reference signal. The invention also discloses a frequency offset estimation device for the OFDM communication system. By the method and the device, the frequency offset estimation accuracy in the OFDM communication system is improved, and a frequency offset estimation range in the OFDM system is widened.

Embodiments of the invention disclose a frequency offset estimation method and a frequency offset estimation device. The method comprises the following steps: carrying out frequency offset estimation according to the repeatability of cyclic prefix CP to get a first frequency offset estimated value; getting at least one second frequency offset estimated value through a preset pilot pair, and getting a wide range of frequency offset estimated values to be chosen according to the at least one second frequency offset estimated value and preset operation rules; and getting an optimal frequency offset estimated value according to the first frequency offset estimated value, the wide range of frequency offset estimated values to be chosen and a preset range value.

The invention provides a sampling frequency offset estimation method based on a pilot frequency, which can obtain a good estimation effect in such NG-DSL (Next Generation Digital Subscriber Line) environment with a high sub-carrier number and a high modulation level. Estimation accuracy, a convergence rate and algorithm stability are all greatly promoted.

The invention discloses a coding CPM signal frequency offset estimation and correction method based on waveform matching, and relates to the technical field of wireless measurement and control communication. According to the invention, the frequency offset estimation of the CPM receiving signal is carried out by adopting a method of correlatively matching the channel coding frame header waveform with the receiving signal waveform. Compared with a traditional frequency offset estimation method based on FFT frequency spectrum characteristics, the frequency offset estimation performance closer tothe corrected Cramer-Rao bound and the higher convergence speed can be obtained, the method is very suitable for an incoherent coding CPM receiver sensitive to residual frequency offset, and the error code performance better than that of a traditional frequency offset correction method can be obtained.

The invention discloses a fast frequency offset estimation and compensation method and system based on burst communication, and the method comprises the steps: obtaining a first signal, extracting a frame header signal of the first signal, demodulating the frame header signal, and obtaining a demodulated frame header signal; carrying out diversity combination on the demodulated frame header signal to obtain a frame header signal after diversity combination; performing coarse frequency offset estimation based on FFT on the frame header signal after diversity combining to obtain a coarse frequency offset estimation value, and performing coarse frequency offset compensation on the first signal according to the coarse frequency offset estimation value to obtain a second signal; extracting a pilot signal of the second signal, and demodulating the pilot signal to obtain a demodulated pilot signal; and carrying out FFT-based fine frequency offset estimation on the demodulated pilot signal to obtain a fine frequency offset estimation value, and carrying out fine frequency offset compensation on the second signal according to the fine frequency offset estimation value. According to the invention, the signal-to-noise ratio can be effectively improved, and the frequency offset estimation precision can be effectively improved.