A frequency offset estimation method, device and receiver

Abstract

The application relates to the field of signal processing and discloses a frequency offset estimation method, a device and a receiver, which comprises the following steps: removing modulation information from a to-be-tested signal multiple times to obtain a first signal; performing N-point FFT transformation on the first signal with a length of N to obtain a second signal; obtaining a coarse estimation value of a relative fractional frequency offset corresponding to the second signal, and sequentially performing correction, N-point time domain zero padding and 2N-point FFT transformation on the first signal by using the coarse estimation value to obtain a third signal; obtaining a fine estimation value of the relative fractional frequency offset corresponding to the third signal; and obtaining a frequency offset estimation value according to a maximum spectral line index value in a spectrum of the third signal, the coarse estimation value, the fine estimation value, a sampling frequency and a modulation order. The above method obtains an accurate relative fractional frequency offset estimation value through coarse estimation and fine estimation, and then can obtain a more accurate estimation value of a real frequency offset, thereby improving the frequency offset estimation performance.

Description

Technical Field

[0001] This invention relates to the field of signal processing, and in particular to a frequency offset estimation method, apparatus and receiver. Background Technology

[0002] In communication systems, the relative velocity between the transmitting and receiving ends can cause the Doppler effect, resulting in a Doppler frequency offset in the received signal. This affects demodulation performance and reduces system reliability. Therefore, the receiver needs to be designed with a frequency offset estimator to compensate for this offset in order to achieve normal signal communication.

[0003] Existing frequency offset estimation algorithms are mainly divided into two categories: data-assisted and non-data-assisted. Data-assisted schemes mainly remove modulation information from pilot signals before frequency offset estimation. This type of method leads to a decrease in link capacity due to the insertion of pilot data. Non-data-assisted schemes mainly use nonlinear methods to remove modulation information before frequency offset estimation. This method has relatively low estimation accuracy but strong versatility.

[0004] In non-data-aided schemes, the traditional power spectrum estimation frequency offset algorithm mainly uses a power to demodulate the received multi-level phase shift keying signal and then uses the maximum peak value in the spectrum to estimate the frequency offset. This algorithm has high estimation accuracy when the frequency offset value is an integer multiple of the frequency resolution. However, in reality, the frequency offset value is not always an integer multiple of the frequency resolution and there will be a fractional frequency offset. In this case, the estimation performance of the algorithm will deteriorate. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a frequency offset estimation method, apparatus, and receiver that can obtain accurate relative fractional frequency offset estimates and improve estimation performance. The specific solution is as follows:

[0006] A frequency offset estimation method includes:

[0007] The modulation information is removed by performing a power multiple on the signal to be tested to obtain the first signal;

[0008] The first signal of length N is subjected to an N-point FFT to obtain the second signal; where N is a positive integer.

[0009] Obtain a coarse estimate of the relative fractional frequency offset corresponding to the second signal;

[0010] The first signal is then corrected, padded with N-point time-domain zeros, and subjected to a 2N-point FFT transform using the coarse estimate to obtain the third signal.

[0011] Obtain a precise estimate of the relative fractional frequency offset corresponding to the third signal;

[0012] The estimated value of the true frequency offset of the signal under test is obtained based on the maximum spectral line index value in the spectrum of the third signal, the coarse estimate value, the fine estimate value, the sampling frequency, and the modulation order.

[0013] Preferably, in the frequency offset estimation method provided in the embodiments of the present invention, obtaining a coarse estimate of the relative fractional frequency offset corresponding to the second signal includes:

[0014] Search for the maximum spectral line index value in the spectrum of the second signal;

[0015] The DFT coefficients are calculated based on the maximum spectral line index value in the spectrum of the second signal and the first spectral line index value corresponding to the true frequency offset of the second signal; the first spectral line index value is the sum of the maximum spectral line index value in the spectrum of the second signal and the corresponding relative fractional frequency offset.

[0016] Based on the DFT coefficients, a coarse estimate of the relative fractional frequency offset corresponding to the second signal is obtained.

[0017] Preferably, in the frequency offset estimation method provided in the embodiments of the present invention, obtaining a precise estimate of the relative fractional frequency offset corresponding to the third signal includes:

[0018] Search for the maximum spectral line index value in the spectrum of the third signal;

[0019] Based on the maximum spectral line index value in the spectrum of the third signal and the second spectral line index value corresponding to the true frequency offset of the third signal, the maximum amplitude value of the spectrum of the third signal is calculated, and the amplitude value of the spectral line at half the distance to the left and right of the maximum spectral line index value in the spectrum of the third signal is calculated in combination with the DTFT; the second spectral line index value is the sum of the maximum spectral line index value in the spectrum of the third signal and the corresponding relative fractional frequency offset;

[0020] Based on the maximum amplitude of the spectrum of the third signal and the calculated amplitude of the spectral line, a precise estimate of the relative fractional frequency offset corresponding to the third signal is obtained.

[0021] Preferably, in the frequency offset estimation method provided in the embodiments of the present invention, the second signal is obtained using the following formula:

[0022]

[0023] x[n]=z[n] M +w'[n]n=0,1,...,N-1;

[0024] w'[n]=w[n] M ;

[0025]

[0026] g(n) = e j2πi / M i = 0, 1, ..., M-1;

[0027] Where X[k] is the second signal, f Δ f represents the frequency offset between the local reference frequency and the carrier frequency. s Sampling frequency, Let w[n] be the initial phase, and w[n] represent a zero mean and a variance of σ. 2 The complex Gaussian white noise, g(n) is the signal to be received, k is the subscript of the sequence element of the X[k] sequence, and M is the modulation order.

[0028] Preferably, in the frequency offset estimation method provided in the embodiments of the present invention, the coarse estimate of the relative fractional frequency offset corresponding to the second signal is obtained by the following formula:

[0029]

[0030] in, Y is a coarse estimate of the relative fractional frequency offset corresponding to the second signal. 0.5 Y represents the DFT coefficient of the spectral line 0.5 units to the right of the maximum spectral line in the frequency domain of the second signal. -0.5 It is the DFT coefficient of the spectral line 0.5 to the left of the maximum spectral line in the frequency domain of the second signal.

[0031] Preferably, in the frequency offset estimation method provided in the embodiments of the present invention, the following formula is used to perform a 2N-point FFT transform on the signal after N-point time-domain zero-padding:

[0032]

[0033]

[0034]

[0035] Wherein, X1'[k] is the third signal, x1[n] is the corrected signal, and x1'[n] is the signal after N-point time-domain zero-padding of x1[n].

[0036] Preferably, in the frequency offset estimation method provided in the embodiments of the present invention, the precise estimate of the relative fractional frequency offset corresponding to the third signal is obtained by using the following formula:

[0037]

[0038] in, m' is the precise estimate of the relative fractional frequency offset corresponding to the third signal. p The index value of the maximum spectral line in the spectrum of the third signal is |X′1[m' p| represents the maximum amplitude of the spectrum of the third signal, |X′1[m' p -0.5]| and |X′1[m' p +0.5]| represents the amplitude of the spectral line at half the distance to the left and right of the maximum spectral line index value in the spectrum of the third signal.

[0039] Preferably, in the frequency offset estimation method provided in the embodiments of the present invention, the estimated value of the true frequency offset of the signal under test is obtained by the following formula:

[0040]

[0041] in, This is an estimate of the true frequency offset of the signal under test.

[0042] This invention also provides a frequency offset estimation device, comprising:

[0043] The modulation information removal module is used to remove the modulation information from the signal under test by multiple powers to obtain the first signal;

[0044] The signal processing module is used to perform an N-point FFT transformation on the first signal of length N to obtain a second signal; where N is a positive integer.

[0045] The coarse estimate acquisition module is used to acquire a coarse estimate of the relative fractional frequency offset corresponding to the second signal;

[0046] The signal processing module is further configured to use the coarse estimate to sequentially correct the first signal, perform N-point time-domain zero-padding, and 2N-point FFT transformation to obtain the third signal;

[0047] The precise estimation value acquisition module is used to acquire a precise estimate of the relative fractional frequency offset corresponding to the third signal;

[0048] The frequency offset estimation module is used to obtain an estimate of the true frequency offset of the signal under test based on the maximum spectral line index value in the spectrum of the third signal, the coarse estimate, the fine estimate, the sampling frequency, and the modulation order.

[0049] This invention also provides a receiver, including a processor and a memory, wherein the processor is connected to the memory;

[0050] The processor is configured to: remove modulation information from the signal under test by multiple powers to obtain a first signal; perform an N-point FFT transform on the first signal of length N to obtain a second signal, where N is a positive integer; obtain a coarse estimate of the relative fractional frequency offset corresponding to the second signal; use the coarse estimate to sequentially correct the first signal, perform N-point time-domain zero-padding, and perform a 2N-point FFT transform to obtain a third signal; obtain a fine estimate of the relative fractional frequency offset corresponding to the third signal; and obtain an estimate of the true frequency offset of the signal under test based on the maximum spectral line index value in the spectrum of the third signal, the coarse estimate, the fine estimate, the sampling frequency, and the modulation order.

[0051] As can be seen from the above technical solution, the frequency offset estimation method provided by the present invention includes: removing modulation information from the signal under test by a power multiple to obtain a first signal; performing an N-point FFT transform on the first signal of length N to obtain a second signal; wherein N is a positive integer; obtaining a coarse estimate of the relative fractional frequency offset corresponding to the second signal based on the maximum spectral line index value in the spectrum of the second signal; using the coarse estimate value to sequentially correct the first signal, perform N-point time-domain zero-padding and 2N-point FFT transform to obtain a third signal; obtaining a fine estimate of the relative fractional frequency offset corresponding to the third signal; and obtaining an estimate of the true frequency offset of the signal under test based on the maximum spectral line index value in the spectrum of the third signal, the coarse estimate value, the fine estimate value, the sampling frequency and the modulation order.

[0052] The frequency offset estimation method provided by this invention obtains an accurate relative fractional frequency offset estimate through two steps: coarse estimation and fine estimation. This allows for a more accurate estimate of the true frequency offset, solving the problem of difficult frequency offset estimation in multi-level phase shift keying modulation, improving frequency offset estimation performance, and thus enhancing the performance of the communication system.

[0053] Furthermore, the present invention also provides a corresponding device and receiver for the frequency offset estimation method, which further makes the above method more practical, and the device and receiver have corresponding advantages. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0055] Figure 1 A flowchart of the frequency offset estimation method provided in the embodiments of the present invention;

[0056] Figure 2Here is a flowchart of the algorithm corresponding to the frequency offset estimation method provided in the embodiments of the present invention;

[0057] Figure 3a The constellation diagram before compensation provided in this embodiment of the invention;

[0058] Figure 3b The compensated constellation diagram provided in this embodiment of the invention;

[0059] Figure 4 The frequency offset estimation method provided in this embodiment of the invention has different estimation performance diagrams for different signal lengths.

[0060] Figure 5 A comparison chart of the estimation performance of the frequency offset estimation method provided in this embodiment of the invention with that of traditional algorithms within the theoretical frequency offset range;

[0061] Figure 6 The comparison curves of the normalized mean square error of the frequency offset estimation method provided in this embodiment of the invention with three other power spectrum estimation algorithms are shown.

[0062] Figure 7 This is a schematic diagram of the frequency offset estimation device provided in an embodiment of the present invention. Detailed Implementation

[0063] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] This invention provides a frequency offset estimation method, such as... Figure 1 As shown, it includes the following steps:

[0065] S101. Perform multiple operations on the signal to be tested to remove the modulation information and obtain the first signal.

[0066] It should be noted that the signal to be tested here can be a multi-phase shift keying (MPSK) signal or other signals, and there are no restrictions here.

[0067] Specifically, such as Figure 2 As shown, assuming the signal to be measured is an MPSK signal, transmitted in an ideal Gaussian white noise channel, the signal to be measured after timing synchronization and sampling can be expressed as:

[0068]

[0069] In the formula, n = 0, 1, ..., N-1, f Δ This refers to the frequency offset between the local reference frequency and the carrier frequency, i.e., the residual frequency offset; f s The sampling frequency; The initial phase is given by w[n]. w[n] has a mean of zero and a variance of σ. 2 Complex Gaussian white noise, noise power ratio SNR = A 2 / 2σ 2 For MPSK modulation, g(n) can be expressed as:

[0070] g(n) = e j2πi / M i = 0, 1, ..., M-1 (2)

[0071] In the formula, M is the modulation order.

[0072] Next, as Figure 2 As shown, the modulation information is removed by raising the signal z[n] to the power of M, resulting in the second signal x[n]:

[0073] x[n]=z[n] M +w'[n] (3)

[0074] In the formula, w'[n] = w[n] M Based on statistical properties, it still follows a zero-mean Gaussian distribution. In this case, the signal x[n] can be considered as a single-frequency signal after M harmonics, with a frequency offset of Mf. Δ .

[0075] S102. Perform an N-point FFT transform on the first signal of length N to obtain the second signal; where N is a positive integer.

[0076] Specifically, such as Figure 2 As shown, an N-point FFT transform is performed on a first signal x[n] of length N to obtain a second signal X[k]. It should be noted that the second signal X[k] is an FFT transform of the first signal x[n], and the first signal x[n] is an M-th power processing of the signal z[n] to be measured. They are essentially the same in terms of frequency offset.

[0077] In practical implementation, the second signal can be obtained using the following formula in the frequency offset estimation method provided in the embodiments of the present invention:

[0078]

[0079] In the formula, k is the index of the sequence element of X[k].

[0080] S103. Obtain a coarse estimate of the relative fractional frequency offset corresponding to the second signal;

[0081] Specifically, such as Figure 2As shown, after obtaining the second signal X[k], a coarse estimate of the relative fractional frequency offset Υ1 corresponding to the second signal X[k] can be obtained. Υ1 can be understood as the relative fractional frequency offset of the true frequency offset of the second signal X[k] to the frequency corresponding to the maximum spectral line.

[0082] S104. The first signal is corrected sequentially using the coarse estimate, N-point time-domain zero-padding is performed, and 2N-point FFT transformation is performed to obtain the third signal.

[0083] Specifically, such as Figure 2 As shown, firstly, the coarse estimate of the relative fractional frequency offset Υ1 is obtained. If the first signal x[n] is corrected, the corrected signal is x1[n].

[0084]

[0085] In the formula, Δξ is f s / N represents the interval between adjacent spectral lines.

[0086] Then, assume that the actual frequency offset at this time is The modified signal x1[n] is padded with N-point time-domain zeros to obtain the signal x1'[n] after N-point time-domain zero-padding. The third signal X′1[k] is obtained by performing a 2N-point FFT transformation on it.

[0087] In practical implementation, in the frequency offset estimation method provided in the embodiments of the present invention, the following formula can be used to perform a 2N-point FFT transform on the signal after N-point time-domain zero-padding:

[0088]

[0089] S105. Obtain a precise estimate of the relative fractional frequency offset corresponding to the third signal;

[0090] Specifically, after obtaining the third signal X′1[k], a precise estimate of the relative fractional frequency offset Υ2 corresponding to the third signal X′1[k] can be obtained. Υ2 can be understood as the relative fractional frequency offset between the true frequency offset of the third signal X′1[k] and the frequency corresponding to the maximum spectral line.

[0091] S106. Based on the maximum spectral line index value, coarse estimate value, fine estimate value, sampling frequency and modulation order in the spectrum of the third signal, obtain the estimated value of the true frequency offset of the signal under test.

[0092] Specifically, based on the maximum spectral line index value m' in the spectrum of the third signal X′1[k] p A rough estimate of the relative decimal frequency deviation Precise estimate of relative decimal frequency deviation sampling frequency fs By combining the modulation order M, we obtain an estimate of the true frequency offset of the signal z[n] under test.

[0093] In the frequency offset estimation method provided in the embodiments of the present invention, a precise relative fractional frequency offset estimate is obtained through two steps of coarse estimation and fine estimation, thereby obtaining a more accurate estimate of the true frequency offset. This solves the problem of difficult frequency offset estimation in multi-level phase shift keying modulation, improves the frequency offset estimation performance, and thus enhances the performance of the communication system.

[0094] Furthermore, in a specific implementation, in the frequency offset estimation method provided in the embodiments of the present invention, step S103, obtaining a coarse estimate of the relative fractional frequency offset corresponding to the second signal, may specifically include the following steps:

[0095] First, search for the maximum spectral line index value m in the spectrum of the second signal X[k]. p At this time, the index value m of the first spectral line corresponding to the true frequency offset of the second signal X[k] p +Υ1, then the assumed true frequency offset can be represented by m p Using Υ1 to represent, the specific expression is:

[0096] f Δ =(m p +Υ1)Δξ / M (7)

[0097] Where Δξ is f s / N represents the interval between adjacent spectral lines.

[0098] Substituting equation (7) into equation (3) yields the signal x[n] at this point:

[0099]

[0100] Then, based on the index value m of the maximum value in the frequency domain of the second signal X[k] p The index value m of the first spectral line corresponding to the true frequency offset of the second signal X[k] p +Υ1, calculate the DFT coefficients:

[0101]

[0102] Substituting equation (8) into equation (9) and simplifying, we get:

[0103]

[0104] Finally, based on the DFT coefficients, the estimated value of the relative fractional frequency offset Υ1 corresponding to the second signal X[k] is calculated.

[0105] In specific implementation, in the frequency offset estimation method provided in the embodiments of the present invention, such as Figure 2 As shown, the coarse estimate of the relative fractional frequency offset Υ1 corresponding to the second signal can be obtained using the following formula.

[0106]

[0107] In the formula, Y is a coarse estimate of the relative fractional frequency offset Υ1 corresponding to the second signal. 0.5 Y represents the DFT coefficient of the spectral line 0.5 units to the right of the maximum spectral line in the frequency domain of the second signal. -0.5 , where is the DFT coefficient of the spectral line 0.5 units to the left of the maximum spectral line in the frequency domain of the second signal.

[0108] Furthermore, in a specific implementation, in the frequency offset estimation method provided in the embodiments of the present invention, step S105, obtaining a precise estimate of the relative fractional frequency offset corresponding to the third signal, may specifically include the following steps:

[0109] First, search for the maximum spectral line index value m' in the spectrum of the third signal X′1[k]. p At this time, the index value of the second spectral line corresponding to the true frequency offset of the third signal X′1[k] is m' p +Υ2; then the assumed true frequency offset value is represented by m' p Using Υ2 to represent, the specific expression is:

[0110] f' Δ =(m' p +Υ2)Δξ' / M (12)

[0111] In the formula, Δξ' is f s / 2N represents the interval between adjacent spectral lines.

[0112] Then, calculate the maximum amplitude value |X′1[m'] of the spectrum of the third signal X1'[k]. p ]|, and combined with DTFT to calculate the spectral amplitude |X′1[m' 1 / 2" at the left and right of the maximum spectral line index value in the spectrum of the third signal X′1[k] p -0.5]| and |X′1[m' p +0.5]|, its theoretical value is as follows:

[0113]

[0114]

[0115]

[0116] From equations (13), (14), and (15), we obtain:

[0117]

[0118]

[0119] Then, based on the maximum amplitude value of the spectrum of the third signal X′1[k], |X′1[m' p ]| and the calculated spectral line amplitude |X′1[m' p -0.5]| and |X′1[m' p +0.5]|, to obtain the precise estimate of the relative fractional frequency offset Υ2 corresponding to the third signal X′1[k].

[0120] In specific implementation, in the frequency offset estimation method provided in the embodiments of the present invention, such as Figure 2 As shown, the estimated value of the relative fractional frequency offset Υ2 corresponding to the third signal X′1[k] can be obtained using the following formula.

[0121]

[0122] Where, m' p Let |X′1[m'] be the index of the maximum spectral line in the spectrum of the third signal X′1[k] p | represents the maximum amplitude of the spectrum of the third signal X′1[k], |X′1[m' p -0.5]| and |X′1[m' p +0.5]| represents the amplitude of the spectral line at half the distance to the left and right of the maximum spectral line index value in the spectrum of the third signal X′1[k].

[0123] In specific implementation, in the frequency offset estimation method provided in the embodiments of the present invention, such as Figure 2 As shown, the true frequency offset f of the signal z[n] to be measured can be obtained using the following formula. Δ The estimated value

[0124]

[0125] in, f is the true frequency offset of the signal z[n] to be measured. Δ The estimated value.

[0126] Assuming the original received signal length is N = 2048, the sampling frequency is 1.024MHz, the signal-to-noise ratio is 10dB, and the frequency offset is 100.2kHz. Figure 3a and Figure 3b The images show the modulation information constellation diagrams before and after compensation using the algorithm of this invention.

[0127] To further illustrate the effects of the present invention, the frequency offset estimation method provided by the embodiments of the present invention will be described in detail below with several specific examples.

[0128] For an MPSK signal, where M is 4, the modulation signal is a QPSK signal. The sampling frequency is 1.024MHz, such as... Figure 4 As shown, the signal length N is 512, 1024, and 2048. In these cases, the normalized frequency offset is 20.48kHz / 1.024MHz = 0.02. Figure 4 It can be seen that the larger the number of N points, the better the estimation performance of the frequency offset estimation method provided by this invention under low signal-to-noise ratio.

[0129] like Figure 5 As shown, the signal length N is 1024, and it can be seen that the frequency offset estimation method provided by this invention has a much better performance than the traditional power spectrum estimation algorithm.

[0130] like Figure 6 As shown, the signal length N is 1024 and the normalized frequency offset is -0.01, indicating that the frequency offset estimation method provided by this invention has the best estimation performance.

[0131] Based on the same inventive concept, this embodiment of the invention also provides a frequency offset estimation device. Since the principle of this device in solving the problem is similar to that of the aforementioned frequency offset estimation method, the implementation of this device can refer to the implementation of the frequency offset estimation method, and the repeated parts will not be described again.

[0132] In specific implementation, the frequency offset estimation device provided in the embodiments of the present invention, such as... Figure 7 As shown, it specifically includes:

[0133] The modulation information removal module 11 is used to remove the modulation information from the signal under test by multiple powers to obtain the first signal;

[0134] Signal processing module 12 is used to perform an N-point FFT transformation on a first signal of length N to obtain a second signal; where N is a positive integer.

[0135] The coarse estimation value acquisition module 13 is used to acquire a coarse estimate of the relative fractional frequency offset corresponding to the second signal;

[0136] The signal processing module 12 is also used to sequentially correct the first signal using the coarse estimate, perform N-point time-domain zero-padding and 2N-point FFT transformation to obtain the third signal;

[0137] The fine estimate acquisition module 14 is used to acquire the fine estimate of the relative fractional frequency offset corresponding to the third signal;

[0138] The frequency offset estimation module 15 is used to obtain the estimated value of the true frequency offset of the signal under test based on the maximum spectral line index value, coarse estimate value, fine estimate value, sampling frequency and modulation order in the spectrum of the third signal.

[0139] In the frequency offset estimation device provided in the embodiments of the present invention, a more accurate frequency offset value can be estimated through the interaction of the above four modules, which solves the problem of difficult frequency offset estimation in multi-level phase shift keying modulation, improves the frequency offset estimation performance, and thus enhances the performance of the communication system.

[0140] For more detailed information on the working process of each of the above modules, please refer to the relevant content disclosed in the foregoing embodiments, which will not be repeated here.

[0141] Accordingly, this invention also discloses a receiver, including a processor and a memory; the processor is connected to the memory; wherein, the processor is used to perform a power-wise removal of modulation information from the signal under test to obtain a first signal; perform an N-point FFT transform on the first signal of length N to obtain a second signal; wherein N is a positive integer; obtain a coarse estimate of the relative fractional frequency offset corresponding to the second signal; use the coarse estimate to sequentially correct the first signal, perform N-point time-domain zero-padding and 2N-point FFT transform to obtain a third signal; obtain a fine estimate of the relative fractional frequency offset corresponding to the third signal; and obtain an estimate of the true frequency offset of the signal under test based on the maximum spectral line index value in the spectrum of the third signal, the coarse estimate, the fine estimate, the sampling frequency and the modulation order.

[0142] For a more detailed explanation of the functions of the aforementioned processor, please refer to the relevant content disclosed in the foregoing embodiments, which will not be repeated here.

[0143] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus and receiver disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0144] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0145] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0146] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0147] The frequency offset estimation method, apparatus, and receiver provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A frequency offset estimation method, characterized in that, include: The modulation information is removed by performing a power multiple on the signal to be tested to obtain the first signal; For length of N The first signal is performed N Point FFT transformation yields the second signal; where, N It is a positive integer; Obtain a coarse estimate of the relative fractional frequency offset corresponding to the second signal; The first signal is then corrected sequentially using the coarse estimate. N Point-time zero-padding and 2 N Point FFT transformation yields the third signal; Search for the maximum spectral line index value in the spectrum of the third signal; Based on the maximum spectral line index value in the spectrum of the third signal and the second spectral line index value corresponding to the true frequency offset of the third signal, the maximum amplitude value of the spectrum of the third signal is calculated, and the amplitude value of the spectral line at half the distance to the left and right of the maximum spectral line index value in the spectrum of the third signal is calculated in combination with the DTFT; the second spectral line index value is the sum of the maximum spectral line index value in the spectrum of the third signal and the corresponding relative fractional frequency offset; Based on the maximum amplitude of the third signal spectrum and the calculated spectral line amplitude, the precise estimate of the relative fractional frequency offset corresponding to the third signal is obtained using the following formula: ； in, This is a precise estimate of the relative fractional frequency offset corresponding to the third signal. The index value of the largest spectral line in the spectrum of the third signal. The maximum amplitude of the spectrum of the third signal. and The amplitude of the spectral line located at approximately 1 / 2 of the maximum spectral line index value in the spectrum of the third signal. The estimated value of the true frequency offset of the signal under test is obtained based on the maximum spectral line index value in the spectrum of the third signal, the coarse estimate value, the fine estimate value, the sampling frequency, and the modulation order.

2. The frequency offset estimation method according to claim 1, characterized in that, Obtaining a coarse estimate of the relative fractional frequency offset corresponding to the second signal includes: Search for the maximum spectral line index value in the spectrum of the second signal; The DFT coefficients are calculated based on the maximum spectral line index value in the spectrum of the second signal and the first spectral line index value corresponding to the true frequency offset of the second signal; the first spectral line index value is the sum of the maximum spectral line index value in the spectrum of the second signal and the corresponding relative fractional frequency offset. Based on the DFT coefficients, a coarse estimate of the relative fractional frequency offset corresponding to the second signal is obtained.

3. The frequency offset estimation method according to claim 2, characterized in that, The second signal is obtained using the following formula: ； ； ； ； ； in, The second signal, The first signal, The frequency offset between the local reference frequency and the carrier frequency. Sampling frequency, For the initial phase, This indicates that the mean is zero and the variance is... Complex Gaussian white noise, For the signal to be received, k for The sequence element index of the sequence. M The modulation order, To address complex Gaussian white noise do M The noise term after the second operation.

4. The frequency offset estimation method according to claim 3, characterized in that, The following formula is used to obtain a coarse estimate of the relative fractional frequency offset corresponding to the second signal: ； in, This is a coarse estimate of the relative fractional frequency offset corresponding to the second signal. The DFT coefficients are the spectral lines located 0.5 units to the right of the maximum spectral line in the frequency domain of the second signal. It is the DFT coefficient of the spectral line 0.5 to the left of the maximum spectral line in the frequency domain of the second signal.

5. The frequency offset estimation method according to claim 4, characterized in that, The following formula is used to analyze the process. N The signal after zero-padding in the time domain is subjected to 2 N Point FFT Transform: ； ； ； in, The third signal, The corrected signal; To conduct N The signal after zero-padding in the time domain, The interval between adjacent spectral lines.

6. The frequency offset estimation method according to claim 5, characterized in that, The estimated value of the true frequency offset of the signal under test is obtained using the following formula: ； in, This is an estimate of the true frequency offset of the signal under test.

7. A frequency offset estimation device, characterized in that, include: The modulation information removal module is used to remove the modulation information from the signal under test by multiple powers to obtain the first signal; The signal processing module is used to process signals of length... N The first signal is performed N Point FFT transformation yields the second signal; where, N It is a positive integer; The coarse estimate acquisition module is used to acquire a coarse estimate of the relative fractional frequency offset corresponding to the second signal; The signal processing module is further configured to sequentially correct the first signal using the coarse estimate. N Point-time zero-padding and 2 N Point FFT transformation yields the third signal; The precise estimation module is used to search for the maximum spectral line index value in the spectrum of the third signal; calculate the maximum amplitude value of the spectrum of the third signal based on the maximum spectral line index value and the second spectral line index value corresponding to the true frequency offset of the third signal, and calculate the spectral line amplitude value at half the distance to the left and right of the maximum spectral line index value in the spectrum of the third signal using DTFT; the second spectral line index value is the sum of the maximum spectral line index value in the spectrum of the third signal and the corresponding relative fractional frequency offset; based on the maximum amplitude value of the spectrum of the third signal and the calculated spectral line amplitude value, the precise estimation value of the relative fractional frequency offset corresponding to the third signal is obtained using the following formula: ； in, This is a precise estimate of the relative fractional frequency offset corresponding to the third signal. The index value of the largest spectral line in the spectrum of the third signal. The maximum amplitude of the spectrum of the third signal. and The amplitude of the spectral line located at approximately 1 / 2 of the maximum spectral line index value in the spectrum of the third signal. The frequency offset estimation module is used to obtain an estimate of the true frequency offset of the signal under test based on the maximum spectral line index value in the spectrum of the third signal, the coarse estimate, the fine estimate, the sampling frequency, and the modulation order.

8. A receiver, characterized in that, It includes a processor and a memory, wherein the processor is connected to the memory; The processor is configured to perform a power-wise removal of modulation information from the signal under test to obtain a first signal; and to process the signal of length... N The first signal is performed N Point FFT transformation yields the second signal; where, N The first signal is obtained by using a positive integer; a coarse estimate of the relative fractional frequency offset corresponding to the second signal is obtained; the first signal is then corrected sequentially using the coarse estimate. N Point-time zero-padding and 2 N A point FFT transform is performed to obtain a third signal; the maximum spectral line index value in the spectrum of the third signal is searched; based on the maximum spectral line index value in the spectrum of the third signal and the second spectral line index value corresponding to the true frequency offset of the third signal, the maximum amplitude value of the spectrum of the third signal is calculated, and the amplitude value of the spectral line at half the distance to the left and right of the maximum spectral line index value in the spectrum of the third signal is calculated using DTFT; the second spectral line index value is the sum of the maximum spectral line index value in the spectrum of the third signal and the corresponding relative fractional frequency offset; based on the maximum amplitude value of the spectrum of the third signal and the calculated spectral line amplitude value, the precise estimate of the relative fractional frequency offset corresponding to the third signal is obtained using the following formula: ； in, This is a precise estimate of the relative fractional frequency offset corresponding to the third signal. The index value of the largest spectral line in the spectrum of the third signal. The maximum amplitude of the spectrum of the third signal. and The amplitude of the spectral line at half the distance to the left and right of the maximum spectral line index value in the spectrum of the third signal is given. Based on the maximum spectral line index value in the spectrum of the third signal, the coarse estimate, the fine estimate, the sampling frequency, and the modulation order, the estimated value of the true frequency offset of the signal under test is obtained.

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