Transform domain frequency offset estimation compensation method based on 5G OFDM system

Abstract

The invention relates to a transform domain frequency offset estimation compensation method based on a 5G OFDM system. Frequency offset estimation compensation is completed with low calculation complexity and good estimation compensation performance. The method comprises the following steps: firstly, extracting first N / 2 data of a plurality of pilot symbols, and carrying out FFT (Fast Fourier Transform) to reduce the calculation complexity of an estimation algorithm; extracting effective frequency band data according to user frequency band positions, and obtaining a frequency offset estimation value of each user by using a correlation method; according to the method, the offset compensation modes are selected according to the number of the users, single-user time domain offset compensation is selected, multi-user simplified frequency domain offset compensation is selected, the single-user scene performance is excellent, the multi-user scene performance is good, and therefore the method can be better applied to an actual system.

Description

Technical Field

[0001] The present application relates to the field of digital communication technology, and in particular, to a transform domain frequency offset estimation and compensation method based on a 5G OFDM system. Background Art

[0002] With the rise of low-orbit broadband satellite Internet construction such as Starlink and Globalstar, satellite mobile communication systems have developed rapidly. Typical representatives include the Starlink system built by SpaceX, the Iridium satellite system, the Oneweb satellite system, the Teledesic system, and the Hongyan constellation system. The above-mentioned constellations mostly use low-orbit satellite communications. 5G satellite communications use satellites to provide 5G Internet access services to global users and realize global 5G mobile communications. It has the advantages of wide coverage, high reliability, and high flexibility. In satellite communication systems, Doppler deviation is an important factor affecting communication performance. The relatively high-speed movement of low-orbit satellites and ground platforms or user equipment will produce a non-negligible Doppler deviation, which will seriously affect the transmission performance of communications and pose a huge challenge to the high-quality transmission of communication systems. Although the terminal will perform Doppler pre-compensation before accessing the system receiver, its residual Doppler deviation can still be as high as several kHz, which is much larger than the Doppler deviation of ground 5G communications, causing the system performance to deteriorate rapidly.

[0003] In order to compensate for the residual frequency offset, 5G satellite communications use traditional frequency offset estimation algorithms to estimate the frequency offset through cyclic prefix or pilot information. However, with the increase in the number of users and limited hardware resources, the applicability of traditional frequency offset estimation algorithms is poor. Summary of the invention

[0004] In order to overcome at least one deficiency in the prior art, the present application provides a transform domain frequency offset estimation and compensation method based on a 5G OFDM system.

[0005] In a first aspect, a transform domain frequency offset estimation and compensation method based on a 5G OFDM system is provided, comprising:

[0006] Obtain the received time domain signal, determine all pilot symbols according to the position of the pilot symbol in the OFDM symbol; extract the first N / 2 points of data of each pilot symbol, perform an N / 2-point FFT transform, and obtain the transform domain signal corresponding to each pilot symbol; where N is the number of data points of the received time domain signal;

[0007] De-resource mapping is performed on the transform domain signal according to the frequency domain offset of the user's pilot symbol and the number of pilot symbols to obtain a pilot reference signal corresponding to each pilot symbol of each user;

[0008] Performing a cross-correlation operation on the two preceding and following pilot reference signals in the pilot reference signals corresponding to each pilot symbol of each user to obtain a normalized frequency offset value for each user;

[0009] According to the number of users, determining a time domain frequency offset compensation value and a frequency domain frequency offset compensation value for each user based on a normalized frequency offset value of each user;

[0010] Performing time domain offset compensation on the received time domain signal according to the time domain frequency offset compensation value of each user to obtain a time domain offset compensated signal;

[0011] The cyclic prefix is ​​removed from the time-domain offset-compensated signal, and an FFT transform is performed to obtain the frequency domain signal corresponding to each OFDM symbol.

[0012] According to the frequency domain offset of the user's pilot symbol and the number of pilot symbols, the frequency domain signal corresponding to each OFDM symbol is de-resource mapped to obtain the frequency band data corresponding to each OFDM symbol of each user;

[0013] Generate multiple frequency domain compensation factors according to the frequency domain frequency offset compensation value of each user; the multiple frequency domain compensation factors form a Toeplitz matrix of each user;

[0014] The frequency band data corresponding to each OFDM symbol of each user is frequency-domain offset-compensated according to the Toeplitz matrix of each user to obtain a frequency-domain offset-compensated signal of each user.

[0015] In one embodiment, the first N / 2 points of data of each pilot symbol are extracted, and an N / 2-point FFT transform is performed to obtain a transform domain signal corresponding to each pilot symbol, which is expressed by the following formula:

[0016]

[0017] Among them, Y dft is the transform domain signal, l is the number of the pilot symbol, k is the index of the data point in the frequency domain, N is the number of data points of the received time domain signal, y(n) is the received time domain signal, n is the number of the data point, N cp is the length of the cyclic prefix, and p(l) is the starting position of the lth pilot symbol in the received time domain signal.

[0018] In one embodiment, according to the frequency domain offset of the pilot symbol of the user and the number of pilot symbols, the transform domain signal is de-resource mapped to obtain a pilot reference signal corresponding to each pilot symbol of each user, which is expressed by the following formula:

[0019]

[0020] Among them, D(l,k) urepresents the pilot reference signal corresponding to the lth pilot symbol of user u, k is the index of the data point in the frequency domain, and Y dft is the transform domain signal, is the frequency domain offset of the pilot symbol of user u, is the number of pilot symbols of user u.

[0021] In one embodiment, two preceding and succeeding pilot reference signals in the pilot reference signals corresponding to each pilot symbol of each user are cross-correlated to obtain a normalized frequency offset value of each user, which is expressed by the following formula:

[0022]

[0023] Among them, ε u is the normalized frequency deviation value of user u, N is the number of data points of the received time domain signal, k is the index of the data point in the frequency domain, is the number of pilot symbols of user u, D(2,k) u represents the pilot reference signal corresponding to the second pilot symbol of user u, D(1,k) u represents the pilot reference signal corresponding to the first pilot symbol of user u, * represents conjugation, p(2) is the starting position of the second pilot symbol in the received time domain signal, p(1) is the starting position of the first pilot symbol in the received time domain signal, N cp is the length of the cyclic prefix.

[0024] In one embodiment, according to the number of users, the time domain frequency offset compensation value and the frequency domain frequency offset compensation value of each user are determined based on the normalized frequency offset value of each user, using the following formula:

[0025]

[0026] Among them, ε time is the time domain frequency offset compensation value for each user, ε 0 is the normalized frequency deviation value of user u=0, U is the number of users, ε u Normalized frequency deviation value of user u, is the frequency offset compensation value of user u in the frequency domain.

[0027] In one embodiment, the received time domain signal is time-domain offset compensated according to the time domain frequency offset compensation value of each user to obtain a signal after time domain offset compensation, using the following formula:

[0028]

[0029] Among them, y tc (n) is the signal after time domain offset compensation, n is the number of the data point, y(n) is the received time domain signal, ε timeis the time domain frequency offset compensation value for each user, and N is the number of data points of the received time domain signal.

[0030] In one embodiment, the cyclic prefix is ​​removed from the time-domain offset-compensated signal, and an FFT transformation is performed to obtain a frequency domain signal corresponding to each OFDM symbol, using the following formula:

[0031]

[0032] Among them, Y tc (i, k) is the frequency domain signal corresponding to the i-th OFDM symbol, N is the number of data points of the received time domain signal, n is the number of the data point, y tc (n) is the signal after time domain offset compensation, N cp is the length of the cyclic prefix, d(i) is the starting position of the i-th OFDM symbol in the received time domain signal, and k is the index of the data point in the frequency domain.

[0033] In one embodiment, according to the frequency domain offset of the user's pilot symbol and the number of pilot symbols, the frequency domain signal corresponding to each OFDM symbol is de-resource mapped to obtain the frequency band data corresponding to each OFDM symbol of each user, using the following formula:

[0034]

[0035] Among them, Y data (i,k) u is the frequency band data corresponding to the i-th OFDM symbol of user u, k is the index of the data point in the frequency domain, Y tc is the frequency domain signal, is the frequency domain offset of the pilot symbol of user u, is the number of pilot symbols of user u.

[0036] In one embodiment, multiple frequency domain compensation factors are generated according to the frequency domain frequency offset compensation value of each user; the multiple frequency domain compensation factors form a Toeplitz matrix, which is expressed by the following formula:

[0037]

[0038]

[0039] Where ψ(m) (u) is the frequency domain compensation factor of user u, M is the number of frequency domain compensation factors, m is an integer related to M, is the frequency offset compensation value of user u in the frequency domain, N is the number of data points of the received time domain signal, ψ (u) is the Toeplitz matrix of user u, ψ (u) The number of columns and rows is is the number of pilot symbols of user u.

[0040] In one embodiment, frequency domain offset compensation is performed on the frequency band data corresponding to each OFDM symbol of each user according to the Toeplitz matrix of each user to obtain a frequency domain offset compensated signal of each user, which is expressed by the following formula:

[0041] Y fc (u) =Y data (u) ·ψ (u)

[0042] in, is the frequency domain offset-compensated signal of user u, is the frequency band data of user u, ψ (u) is the Toeplitz matrix of user u.

[0043] Compared with the prior art, the present application has the following beneficial effects: the transform domain frequency offset estimation and compensation method based on the 5G OFDM system of the present application completes the frequency offset estimation and compensation with lower computational complexity and better estimation and compensation performance. The present application first extracts the first N / 2 data of multiple pilot symbols and performs FFT transformation to reduce the computational complexity of the estimation algorithm; then extracts the effective frequency band data according to the user frequency band position, and uses the correlation method to obtain the frequency offset estimation value of each user; selects the compensation mode according to the number of users, selects time domain compensation for a single user, and selects simplified frequency domain compensation for multiple users. The performance of the single-user scenario is excellent, and the performance of the multi-user scenario is good. Therefore, the method of the present application can be better applied to actual systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present application may be better understood by referring to the following description given in conjunction with the accompanying drawings, which together with the following detailed description are included in this specification and form a part of this specification. In the drawings:

[0045] Figure 1 A flow chart of a transform domain frequency offset estimation and compensation method based on a 5G OFDM system is shown;

[0046] Figure 2 The system framework diagram for simulation experiments is shown;

[0047] Figure 3 The pilot structure used in the simulation experiment is shown;

[0048] Figure 4 The estimated performance diagram of the method of the present application under different frequency offsets and signal-to-noise ratios is shown;

[0049] Figure 5shows the performance graph of different frequency offset estimation algorithms when the multi-user carrier frequency offset is 6kHz;

[0050] Figure 6 The system performance diagram of different frequency offset estimation algorithms when the multi-user carrier frequency offset is 6kHz is shown. DETAILED DESCRIPTION

[0051] The exemplary embodiments of the present application will be described below in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features of the actual embodiments are described in the specification. However, it should be understood that many implementation-specific decisions can be made in the process of developing any such actual embodiments in order to achieve the specific goals of the developer, and these decisions may vary from embodiment to embodiment.

[0052] It is also necessary to explain here that, in order to avoid obscuring the present application due to unnecessary details, only the device structure closely related to the scheme according to the present application is shown in the drawings, while other details that are not closely related to the present application are omitted.

[0053] It should be understood that the present application is not limited to the described implementation forms due to the following description with reference to the accompanying drawings. In this article, where feasible, the embodiments can be combined with each other, features between different embodiments can be replaced or borrowed, and one or more features can be omitted in one embodiment.

[0054] The embodiment of the present application provides a transform domain frequency offset estimation and compensation method based on a 5G OFDM system, OFDM (Orthogonal Frequency Division Multiplexing), i.e., orthogonal frequency division multiplexing technology. Figure 1 A flowchart of a transform domain frequency offset estimation and compensation method based on a 5G OFDM system is shown in FIG. Figure 1 , methods include:

[0055] Step S1, obtain the received time domain signal, determine all pilot symbols according to the position of the pilot symbol in the OFDM symbol; extract the first N / 2 points of data of each pilot symbol, perform N / 2 points of FFT transformation, and obtain the transformed domain signal corresponding to each pilot symbol; wherein N is the number of data points of the received time domain signal.

[0056] In the current 5G OFDM system, the pilot format uses a pilot block inserted every two subcarriers starting from the even subcarriers. An OFDM time slot has a total of L ofdm OFDM symbols, L dmrs pilot symbols, the starting position of the lth pilot symbol in the received time domain signal is p(l), l = 0, 1, ..., L dmrs-1, the starting position of the i-th OFDM symbol in the received time domain signal is d(i), i = 0, 1, ..., L ofdm -1. An OFDM symbol consists of multiple subcarriers, and the frequency domain offset of the user u pilot symbol is The number of pilot symbols for user u is Since the pilot signal is inserted every other two, the number of data subcarriers is twice as much. Indicates the time slot structure corresponding to this parameter.

[0057] Specifically, the transform domain signal corresponding to each pilot symbol is expressed by the following formula:

[0058]

[0059] Among them, Y dft is the transform domain signal, l is the number of the pilot symbol, k is the index of the data point in the frequency domain, N is the number of data points of the received time domain signal, y(n) is the received time domain signal, n is the number of the data point, N cp is the length of the cyclic prefix, and p(l) is the starting position of the lth pilot symbol in the received time domain signal.

[0060] Step S2: De-resource-map the transform domain signal according to the frequency domain offset of the user's pilot symbol and the number of pilot symbols to obtain a pilot reference signal corresponding to each pilot symbol of each user. Specifically, the following formula can be used to represent this:

[0061]

[0062] Among them, D(l,k) u represents the pilot reference signal corresponding to the lth pilot symbol of user u, k is the index of the data point in the frequency domain, and Y dft is the transform domain signal, is the frequency domain offset of the pilot symbol of user u, is the number of pilot symbols of user u.

[0063] Step S3: performing a cross-correlation operation on the two preceding and succeeding pilot reference signals in the pilot reference signals corresponding to each pilot symbol of each user to obtain a normalized frequency offset value of each user.

[0064] Here, the first and second pilot reference signals may be used to perform a cross-correlation operation, which may be expressed by the following formula:

[0065]

[0066] Among them, ε u is the normalized frequency deviation value of user u, N is the number of data points of the received time domain signal, k is the index of the data point in the frequency domain, is the number of pilot symbols of user u, D(2,k) u represents the pilot reference signal corresponding to the second pilot symbol of user u, D(1,k) u represents the pilot reference signal corresponding to the first pilot symbol of user u, * represents conjugation, p(2) is the starting position of the second pilot symbol in the received time domain signal, p(1) is the starting position of the first pilot symbol in the received time domain signal, N cp is the length of the cyclic prefix.

[0067] Step S4, according to the number of users, based on the normalized frequency offset value of each user, determines the time domain frequency offset compensation value and the frequency domain frequency offset compensation value of each user. Specifically, it can be expressed by the following formula:

[0068]

[0069] Among them, ε time is the time domain frequency offset compensation value for each user, ε 0 is the normalized frequency deviation value of user u=0, U is the number of users, ε u Normalized frequency deviation value of user u, is the frequency offset compensation value of user u in the frequency domain.

[0070] Step S5, performing time domain offset compensation on the received time domain signal according to the time domain frequency offset compensation value of each user, to obtain a signal after time domain offset compensation. Specifically, it can be expressed by the following formula:

[0071]

[0072] Among them, y tc (n) is the signal after time domain offset compensation, n is the number of the data point, y(n) is the received time domain signal, ε time is the time domain frequency offset compensation value for each user, and N is the number of data points of the received time domain signal.

[0073] Step S6, remove the cyclic prefix operation on the time-domain offset-compensated signal, and perform FFT transformation to obtain the frequency domain signal corresponding to each OFDM symbol. Specifically, it can be expressed by the following formula:

[0074]

[0075] Among them, Y tc (i, k) is the frequency domain signal corresponding to the i-th OFDM symbol, N is the number of data points of the received time domain signal, n is the number of the data point, y tc (n) is the signal after time domain offset compensation, N cp is the length of the cyclic prefix, d(i) is the starting position of the i-th OFDM symbol in the received time domain signal, and k is the index of the data point in the frequency domain.

[0076] Step S7, according to the frequency domain offset of the user's pilot symbol and the number of pilot symbols, perform resource de-mapping on the frequency domain signal corresponding to each OFDM symbol to obtain the frequency band data corresponding to each OFDM symbol of each user. Specifically, it can be expressed by the following formula:

[0077]

[0078] Among them, Y data (i,k) u is the frequency band data corresponding to the i-th OFDM symbol of user u, k is the index of the data point in the frequency domain, Y tc is the frequency domain signal, is the frequency domain offset of the pilot symbol of user u, is the number of pilot symbols of user u.

[0079] Step S8, generating multiple frequency domain compensation factors according to the frequency domain frequency offset compensation value of each user; the multiple frequency domain compensation factors form a Toeplitz matrix of each user. Specifically, it can be expressed by the following formula:

[0080]

[0081] Where ψ(m) (u) is the frequency domain compensation factor of user u, M is the number of frequency domain compensation factors, m is an integer related to M, is the frequency offset compensation value of user u in the frequency domain, N is the number of data points of the received time domain signal, ψ (u) is the Toeplitz matrix of user u, ψ (u) The number of columns and rows is is the number of pilot symbols of user u. M∈{3,5,…,2N pilot -1}, sin[·] represents the sine function.

[0082] Here, the Toeplitz matrix of user u has a main diagonal of ψ(0) (u) , parallel to the main diagonal line above is ψ(m) (u) , , parallel to the main diagonal line below is ψ(m) (u) , , and the other positions are 0.

[0083] Step S9, frequency domain offset compensation is performed on the frequency band data corresponding to each OFDM symbol of each user according to the Toeplitz matrix of each user to obtain the frequency domain offset compensated signal of each user. Specifically, it can be expressed by the following formula:

[0084] Y fc (u) =Ydata (u) ·ψ (u)

[0085] in, is the frequency domain offset-compensated signal of user u, is the frequency band data of user u, ψ (u) is the Toeplitz matrix of user u.

[0086] In an optional implementation example of the present application, the method provided by the present invention is verified through experiments.

[0087] 1. Simulation conditions

[0088] Figure 2 The system framework diagram for simulation experiments is shown. Figure 3 The simulation system adopts the 5G OFDM system of 3GTPP standard, with 92.16MHz system bandwidth, 120kHz subcarrier spacing, 491.52MHz sampling rate and burst time slot parameters. The OFDM system of one time slot contains 12 OFDM symbols, and the corresponding pilots are located on the 3rd, 6th, 9th and 12th symbols. The simulation channel adopts Gaussian channel.

[0089] 2. Simulation Results

[0090] By comparing the traditional frequency offset estimation algorithm with the method provided in the present application, the performance of the method provided in the present application is further illustrated.

[0091] Figure 4 The estimated performance diagram of the method of the present application under different frequency offsets and signal-to-noise ratios is shown. Figure 4 It can be seen that this method can complete the frequency offset estimation and compensation in multi-user scenarios. The frequency offset estimation performance at the non-algorithm estimation boundary is independent of the frequency offset size. The estimation range is the same as that based on the received pilot correlation algorithm, which greatly reduces the complexity of frequency offset estimation and compensation.

[0092] Figure 5 The performance diagram of different frequency offset estimation algorithms when the multi-user carrier frequency offset is 6kHz is shown. Figure 5 It can be seen that under a given residual Doppler frequency offset, compared with the performance of the CP-based correlation algorithm, the performance of the proposed estimation algorithm is improved by about 12dB; compared with the received pilot-based correlation algorithm, the performance of the proposed estimation algorithm is reduced by about 4dB; compared with the local pilot-based correlation algorithm, the performance of the proposed estimation algorithm is improved by about 16dB.

[0093] Figure 6 The system performance diagram of different frequency offset estimation algorithms when the multi-user carrier frequency offset is 6kHz is shown. Figure 6 It can be seen that under a given residual Doppler frequency offset, in a single-user scenario, the system performance of the proposed algorithm coincides with the theoretical line and is at least 1 dB better than the other algorithms; in a multi-user scenario, compared with the patent [CN11657470A] algorithm, the performance of the proposed algorithm is the same; compared with the algorithm based on local pilot correlation, the performance of the proposed algorithm is improved by about 3 dB.

[0094] 3. Complexity Analysis

[0095] By comparing the complexity of the traditional algorithm and the method of the present application, the performance of the method of the present application is further illustrated.

[0096] The computational complexity is measured by the number of complex multiplications and complex additions. The total complexity of all frequency offset estimation algorithms is shown in Table 1 below, and the total complexity of all compensation algorithms corresponding to frequency offset estimation is shown in Table 2 below.

[0097] Table 1 Calculation of frequency offset estimation algorithm

[0098]

[0099]

[0100] Table 2 Computational amount of compensation algorithm corresponding to frequency offset estimation

[0101]

[0102] It can be seen from Tables 1 and 2 that, under given parameter use cases, compared with the algorithm based on receiving pilot correlation, the method of the present application greatly reduces the computational complexity; compared with other traditional algorithms, the computational complexity of the method of the present application is slightly higher, but the estimation performance and applicability to multi-user scenarios are greatly improved.

[0103] In summary, this application has the following technical effects:

[0104] The transform domain frequency offset estimation and compensation method based on the 5G OFDM system of the present application completes the frequency offset estimation and compensation with low computational complexity and good estimation and compensation performance. The present application first extracts the first N / 2 data of the pilot symbol and performs FFT transformation to reduce the computational complexity of the estimation algorithm; then extracts the effective frequency band data according to the user frequency band position, and uses the correlation method to obtain the frequency offset estimation value of each user; selects the compensation mode according to the number of users, and selects time domain compensation for single users and simplified frequency domain compensation for multiple users. The performance of the single-user scenario is excellent and the performance of the multi-user scenario is good. Therefore, the method of the present application can be better applied to actual systems.

[0105] The above are only various implementations of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A transform domain frequency offset estimation and compensation method based on a 5G OFDM system, characterized in that: include: Acquire a received time domain signal, and determine all pilot symbols according to the positions of the pilot symbols in the OFDM symbols; Extract the first N / 2 points of data of each pilot symbol, perform N / 2-point FFT transformation, and obtain the transform domain signal corresponding to each pilot symbol; where N is the number of data points of the received time domain signal; De-resource-map the transform domain signal according to the frequency domain offset of the user's pilot symbol and the number of pilot symbols to obtain a pilot reference signal corresponding to each pilot symbol of each user; Performing a cross-correlation operation on two preceding and succeeding pilot reference signals in the pilot reference signals corresponding to each pilot symbol of each user to obtain a normalized frequency offset value for each user; Determine, according to the number of users, a time domain frequency offset compensation value and a frequency domain frequency offset compensation value for each user based on the normalized frequency offset value of each user; Performing time domain offset compensation on the received time domain signal according to the time domain frequency offset compensation value of each user to obtain a time domain offset compensated signal; Performing a cyclic prefix removal operation on the time-domain offset-compensated signal, and performing an FFT transformation to obtain a frequency domain signal corresponding to each OFDM symbol; Perform resource de-mapping on the frequency domain signal corresponding to each OFDM symbol according to the frequency domain offset of the user's pilot symbol and the number of pilot symbols to obtain frequency band data corresponding to each OFDM symbol of each user; Generate a plurality of frequency domain compensation factors according to the frequency domain frequency offset compensation value of each user; the plurality of frequency domain compensation factors form a Toeplitz matrix of each user; Frequency domain offset compensation is performed on the frequency band data corresponding to each OFDM symbol of each user according to the Toeplitz matrix of each user to obtain a frequency domain offset compensated signal of each user.

2. The method according to claim 1, characterized in that in, Extract the first N / 2 points of data of each pilot symbol, perform N / 2-point FFT transformation, and obtain the transform domain signal corresponding to each pilot symbol, which is expressed by the following formula: Among them, Y dft is the transform domain signal, l is the number of the pilot symbol, k is the index of the data point in the frequency domain, N is the number of data points of the received time domain signal, y(n) is the received time domain signal, n is the number of the data point, N cp is the length of the cyclic prefix, and p(l) is the starting position of the lth pilot symbol in the received time domain signal.

3. The method according to claim 1, characterized in that in, According to the frequency domain offset of the user's pilot symbol and the number of pilot symbols, the transform domain signal is de-resource mapped to obtain a pilot reference signal corresponding to each pilot symbol of each user, which is expressed by the following formula: Among them, D(l,k) u represents the pilot reference signal corresponding to the lth pilot symbol of user u, k is the index of the data point in the frequency domain, and Y dft is the transform domain signal, is the frequency domain offset of the pilot symbol of user u, is the number of pilot symbols of user u.

4. The method according to claim 1, characterized in that in, The two preceding and succeeding pilot reference signals in the pilot reference signals corresponding to each pilot symbol of each user are cross-correlated to obtain a normalized frequency offset value of each user, which is expressed by the following formula: Among them, ε u is the normalized frequency deviation value of user u, N is the number of data points of the received time domain signal, k is the index of the data point in the frequency domain, is the number of pilot symbols of user u, D(2,k) u represents the pilot reference signal corresponding to the second pilot symbol of user u, D(1,k) u represents the pilot reference signal corresponding to the first pilot symbol of user u, * represents conjugation, p(2) is the starting position of the second pilot symbol in the received time domain signal, p(1) is the starting position of the first pilot symbol in the received time domain signal, N cp is the length of the cyclic prefix.

5. The method according to claim 1, characterized in that in, According to the number of users, the time domain frequency offset compensation value and the frequency domain frequency offset compensation value of each user are determined based on the normalized frequency offset value of each user, using the following formula: Among them, ε time is the time domain frequency offset compensation value for each user, ε 0 is the normalized frequency deviation value of user u=0, U is the number of users, ε u Normalized frequency deviation value of user u, is the frequency offset compensation value of user u in the frequency domain.

6. The method according to claim 1, characterized in that in, The received time domain signal is time-domain offset compensated according to the time domain frequency offset compensation value of each user to obtain a signal after time domain offset compensation, using the following formula: Among them, y tc (n) is the signal after time domain offset compensation, n is the number of the data point, y(n) is the received time domain signal, ε time is the time domain frequency offset compensation value for each user, and N is the number of data points of the received time domain signal.

7. The method according to claim 1, characterized in that in, The cyclic prefix operation is performed on the time-domain offset-compensated signal, and an FFT transformation is performed to obtain a frequency domain signal corresponding to each OFDM symbol, using the following formula: Among them, Y tc (i, k) is the frequency domain signal corresponding to the i-th OFDM symbol, N is the number of data points of the received time domain signal, n is the number of the data point, y tc (n) is the signal after time domain offset compensation, N cp is the length of the cyclic prefix, d(i) is the starting position of the i-th OFDM symbol in the received time domain signal, and k is the index of the data point in the frequency domain.

8. The method according to claim 1, characterized in that in, According to the frequency domain offset of the user's pilot symbol and the number of pilot symbols, the frequency domain signal corresponding to each OFDM symbol is de-resource mapped to obtain the frequency band data corresponding to each OFDM symbol of each user, using the following formula: Among them, Y data (i,k) u is the frequency band data corresponding to the i-th OFDM symbol of user u, k is the index of the data point in the frequency domain, Y tc is the frequency domain signal, is the frequency domain offset of the pilot symbol of user u, is the number of pilot symbols of user u.

9. The method according to claim 1, characterized in that in, According to the frequency domain offset compensation value of each user, a plurality of frequency domain compensation factors are generated; the plurality of frequency domain compensation factors form a Toeplitz matrix, which is expressed by the following formula: Where ψ(m) (u) is the frequency domain compensation factor of user u, M is the number of frequency domain compensation factors, m is an integer related to M, is the frequency offset compensation value of user u in the frequency domain, N is the number of data points of the received time domain signal, ψ (u) is the Toeplitz matrix of user u, ψ (u) The number of columns and rows is is the number of pilot symbols of user u.

10. The method according to claim 1, characterized in that in, The frequency band data corresponding to each OFDM symbol of each user is frequency-domain offset-compensated according to the Toeplitz matrix of each user to obtain a frequency-domain offset-compensated signal of each user, which is expressed by the following formula: AND fc (u) =And data (u) ·ψ (u) in, is the frequency domain offset-compensated signal of user u, is the frequency band data of user u, ψ (u) is the Toeplitz matrix of user u.

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