A transform domain frequency offset estimation and compensation method based on 5G OFDM system

Abstract

This application relates to a transform domain frequency offset estimation and compensation method based on a 5G OFDM system, which achieves frequency offset estimation and compensation with low computational complexity and good estimation and compensation performance. This application first extracts the first N / 2 data points of multiple pilot symbols and performs an FFT transform to reduce the computational complexity of the estimation algorithm. Then, it extracts the effective frequency band data based on the user's frequency band location and uses the correlation method to obtain the frequency offset estimate for each user. The compensation mode is selected according to the number of users: time-domain compensation is selected for single-user scenarios, while simplified frequency-domain compensation is selected for multi-user scenarios. The method exhibits excellent performance in single-user scenarios and good performance in multi-user scenarios. Therefore, the method of this application can be better applied to practical systems.

Description

Technical Field

[0001] This application relates to the field of digital communication technology, and more specifically, to a transform domain frequency offset estimation and compensation method based on a 5G OFDM system. Background Technology

[0002] With the rise of low-Earth orbit (LEO) broadband satellite internet infrastructure such as Starlink and Globalstar, satellite mobile communication systems have developed rapidly. Typical examples include SpaceX's Starlink system, the Iridium satellite system, the OneWeb satellite system, the Teledesic satellite communication network system, and the Hongyan constellation system. These constellations primarily utilize LEO satellite communication. 5G satellite communication leverages satellites to provide 5G internet access services to users worldwide, achieving global 5G mobile communication with advantages such as wide coverage, high reliability, and high flexibility. In satellite communication systems, Doppler frequency offset is a significant factor affecting communication performance. The high-speed relative movement of LEO satellites with ground platforms or user equipment generates substantial Doppler frequency offsets, severely impacting transmission performance and posing a significant challenge to high-quality transmission. Although terminals perform Doppler pre-compensation before accessing the system receiver, the residual Doppler frequency offset can still reach several kHz, far exceeding the Doppler frequency offset of terrestrial 5G communication, causing rapid deterioration of system performance.

[0003] To compensate for residual frequency offset, 5G satellite communication uses traditional frequency offset estimation algorithms, which estimate the frequency offset using 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] To overcome at least one deficiency in the prior art, this application provides a transform domain frequency offset estimation and compensation method based on a 5GOFDM system.

[0005] Firstly, a transform domain frequency offset estimation and compensation method based on a 5G OFDM system is provided, including:

[0006] The received time-domain signal is acquired, and all pilot symbols are determined based on their positions in the OFDM symbol set. The first N / 2 data points of each pilot symbol are extracted, and an N / 2-point FFT transform is performed to obtain the transform domain signal corresponding to each pilot symbol. Here, N is the number of data points in the received time-domain signal.

[0007] Based on the frequency domain offset of the user's pilot symbols and the number of pilot symbols, the transform domain signal is de-resource mapped to obtain the pilot reference signal corresponding to each pilot symbol for each user;

[0008] For each pilot symbol of each user, the two pilot reference signals before and after each pilot reference signal are cross-correlated to obtain the normalized frequency offset value of each user.

[0009] Based on the number of users, determine the time-domain frequency offset compensation value and the frequency-domain frequency offset compensation value for each user based on the normalized frequency offset value for each user.

[0010] The received time-domain signal is time-domain offset compensated according to the time-domain frequency offset compensation value of each user to obtain the time-domain offset signal;

[0011] The time-domain offset signal is subjected to cyclic prefix removal and FFT transformation to obtain the frequency domain signal corresponding to each OFDM symbol;

[0012] Based on the frequency domain offset of the user's pilot symbols 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 for each user;

[0013] Based on the frequency offset compensation value of each user, multiple frequency domain compensation factors are generated; these multiple frequency domain compensation factors form the Toplitz matrix for each user.

[0014] Based on the Toplitz matrix of each user, the frequency band data corresponding to each OFDM symbol of each user is subjected to frequency domain bias correction to obtain the frequency domain bias-corrected signal of each user.

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

[0016]

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

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

[0019]

[0020] Where, D(l,k) uY represents the pilot reference signal corresponding to the l-th pilot symbol of user u, where k is the index of the data point in the frequency domain. dft For transform domain signals, The frequency domain offset of the pilot symbol for user u. The number of pilot symbols for user u.

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

[0022]

[0023] Where, ε u Let N be the normalized frequency offset value for user u, N be the number of data points in the received time-domain signal, and k be the index of the data point in the frequency domain. Let D(2,k) be the number of pilot symbols for user u. u D(1,k) represents the pilot reference signal corresponding to the second pilot symbol of user u. u Let N represent the pilot reference signal corresponding to the first pilot symbol of user u, * denotes conjugate, 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, and N cp The length of the cyclic prefix.

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

[0025]

[0026] Where, ε time The time-domain frequency offset compensation value for each user, ε 0 ε is the normalized frequency offset for user u=0, where U is the number of users. u Normalized frequency offset value of user u This is the frequency offset compensation value for 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 for each user to obtain the time-domain offset signal, using the following formula:

[0028]

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

[0030] In one embodiment, the time-domain offset signal is subjected to cyclic prefix removal and FFT transformation to obtain the frequency domain signal corresponding to each OFDM symbol, using the following formula:

[0031]

[0032] Among them, Y tc (i,k) represents the frequency domain signal corresponding to the i-th OFDM symbol, N is the number of data points in the received time domain signal, and n is the label of the data point. tc (n) represents the time-domain offset signal, N cp d 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, based on the frequency domain offset of the user's pilot symbols and the number of pilot symbols, resource demapping is performed on the frequency domain signal corresponding to each OFDM symbol to obtain the frequency band data corresponding to each OFDM symbol for each user, using the following formula:

[0034]

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

[0036] In one embodiment, multiple frequency domain compensation factors are generated based on the frequency domain offset compensation value for each user; these multiple frequency domain compensation factors form a Toplitz matrix, represented by the following formula:

[0037]

[0038]

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

[0040] In one embodiment, frequency domain offsetting is performed on the frequency band data corresponding to each OFDM symbol of each user based on the Toplitz matrix of each user, resulting in the frequency domain offset signal of each user, expressed by the following formula:

[0041] Y fc (u) =Y data (u) ·ψ (u)

[0042] in, The frequency-domain offset signal for user u. For the frequency band data of user u, ψ (u) Let be the Toplitz matrix of user u.

[0043] Compared with existing technologies, this application has the following advantages: The transform domain frequency offset estimation and compensation method based on 5G OFDM systems in this application achieves frequency offset estimation and compensation with lower computational complexity and better estimation and compensation performance. This application first extracts the first N / 2 data points of multiple pilot symbols and performs FFT transformation to reduce the computational complexity of the estimation algorithm; then, it extracts effective frequency band data based on the user's frequency band location and uses the correlation method to obtain the frequency offset estimate for each user; the compensation mode is selected according to the number of users: time-domain compensation is selected for single-user scenarios, and simplified frequency-domain compensation is selected for multi-user scenarios. The method exhibits excellent performance in single-user scenarios and good performance in multi-user scenarios. Therefore, the method in this application can be better applied to practical systems. Attached Figure Description

[0044] This application can be better understood by referring to the description given below in conjunction with the accompanying drawings, which, together with the detailed description below, are incorporated in and form part of this specification. In the drawings:

[0045] Figure 1 A flowchart 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 used for the simulation experiment is shown;

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

[0048] Figure 4 The estimation performance of the method of this application is shown in the figure under different frequency offsets and signal-to-noise ratios;

[0049] Figure 5The performance graphs of different frequency offset estimation algorithms are shown when the multi-user carrier frequency offset is 6kHz.

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

[0051] Exemplary embodiments of the present application will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of the actual embodiments are described in the specification. However, it should be understood that many embodiment-specific decisions can be made in the development of any such actual embodiment to achieve the developer’s specific objectives, and these decisions may vary as the embodiments differ.

[0052] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the device structure closely related to the solution according to this application is shown in the accompanying drawings, while other details that are not closely related to this application are omitted.

[0053] It should be understood that this application is not limited to the described embodiments by virtue of the following description with reference to the accompanying drawings. In this document, embodiments may be combined with each other, features may be substituted or borrowed between different embodiments, and one or more features may be omitted in one embodiment, where feasible.

[0054] This application provides a transform domain frequency offset estimation and compensation method based on a 5G OFDM system. OFDM (Orthogonal Frequency Division Multiplexing) is a technology that uses frequency division multiplexing. Figure 1 A flowchart of a transform domain frequency offset estimation and compensation method based on a 5G OFDM system is shown. (See attached diagram) Figure 1 The methods include:

[0055] Step S1: Obtain the received time-domain signal; determine all pilot symbols based on their positions in the OFDM symbols; extract the first N / 2 points of data for each pilot symbol; perform an N / 2-point FFT transform to obtain the transform domain signal corresponding to each pilot symbol; where N is the number of data points in the received time-domain signal.

[0056] In current 5G OFDM systems, the pilot format uses pilot blocks that start with an even-numbered subcarrier and are interleaved every two. One OFDM time slot contains L... ofdm One OFDM symbol, L dmrs There are 1 pilot symbol, and the starting position of the l-th pilot symbol in the received time-domain signal is p(l), where l = 0, 1, ..., L. dmrs-1, where 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 comprises multiple subcarriers, and the frequency offset of the user u pilot symbol is... The number of pilot symbols for user u is Because it uses a pilot spacing of two and interleaving of one, the number of data subcarriers is twice that of pilots. This indicates the time slot structure corresponding to this parameter.

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

[0058]

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

[0060] Step S2 involves de-resource mapping the transform domain signal based on the frequency domain offset and the number of pilot symbols for each user, to obtain the pilot reference signal corresponding to each pilot symbol for each user. This can be expressed using the following formula:

[0061]

[0062] Where, D(l,k) u Y represents the pilot reference signal corresponding to the l-th pilot symbol of user u, where k is the index of the data point in the frequency domain. dft For transform domain signals, The frequency domain offset of the pilot symbol for user u. The number of pilot symbols for user u.

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

[0064] Here, the first and second pilot reference signals can be cross-correlated, as expressed by the following formula:

[0065]

[0066] Where, ε u Let N be the normalized frequency offset value for user u, N be the number of data points in the received time-domain signal, and k be the index of the data point in the frequency domain. Let D(2,k) be the number of pilot symbols for user u. u D(1,k) represents the pilot reference signal corresponding to the second pilot symbol of user u. u Let N represent the pilot reference signal corresponding to the first pilot symbol of user u, * denotes conjugate, 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, and N cp The length of the cyclic prefix.

[0067] Step S4: Based on the number of users, determine the time-domain frequency offset compensation value and the frequency-domain frequency offset compensation value for each user, using the normalized frequency offset value for each user. This can be expressed using the following formula:

[0068]

[0069] Where, ε time The time-domain frequency offset compensation value for each user, ε 0 ε is the normalized frequency offset for user u=0, where U is the number of users. u Normalized frequency offset value of user u This is the frequency offset compensation value for user u in the frequency domain.

[0070] Step S5: The received time-domain signal is time-domain offset based on the time-domain frequency offset compensation value for each user, resulting in a time-domain offset-corrected signal. This can be expressed using the following formula:

[0071]

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

[0073] Step S6 involves removing the cyclic prefix from the time-domain offset signal and performing an FFT transform to obtain the frequency domain signal corresponding to each OFDM symbol. This can be expressed using the following formula:

[0074]

[0075] Among them, Y tc (i,k) represents the frequency domain signal corresponding to the i-th OFDM symbol, N is the number of data points in the received time domain signal, and n is the label of the data point. tc (n) represents the time-domain offset signal, N cp d 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: Based on the frequency domain offset of the user's pilot symbols and the number of pilot symbols, perform de-resource mapping on the frequency domain signal corresponding to each OFDM symbol to obtain the frequency band data corresponding to each OFDM symbol for each user. Specifically, this can be expressed using the following formula:

[0077]

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

[0079] Step S8: Based on the frequency offset compensation value for each user, generate multiple frequency domain compensation factors; these multiple frequency domain compensation factors form the Toplitz matrix for each user. Specifically, this can be expressed using the following formula:

[0080]

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

[0082] Here, the Topulitz matrix of user u has ψ(0) on its main diagonal. (u) Above the main diagonal, ψ(m) are respectively... (u) , The numbers parallel to the main diagonal below are ψ(m). (u) , , and 0 in other positions.

[0083] Step S9: Based on the Toplitz matrix of each user, perform frequency domain offsetting on the frequency band data corresponding to each OFDM symbol of each user to obtain the frequency domain offsetting signal for each user. Specifically, this can be expressed using the following formula:

[0084] Y fc (u) =Ydata (u) ·ψ (u)

[0085] in, The frequency-domain offset signal for user u. For the frequency band data of user u, ψ (u) Let be the Toplitz matrix of user u.

[0086] In one optional embodiment of this application, the method provided by the present invention is verified through experiments.

[0087] I. Simulation Conditions

[0088] Figure 2 The system framework diagram used for the simulation experiment is shown. Figure 3 The pilot structure used in the simulation experiment is shown. The simulation system adopts a 5G OFDM system based on the 3GTPP standard, with a system bandwidth of 92.16MHz, a subcarrier spacing of 120kHz, a sampling rate of 491.52MHz, and burst time slot parameters. The input frequency is (4, 12, 4096, 1280, 768), the modulation scheme is 16QAM, MCS6, transform domain coding is enabled, the multi-user carrier frequency offset is 6kHz, the pilot format is pos3, and a one-slot OFDM system contains 12 OFDM symbols, with the corresponding pilots located on symbols 3, 6, 9, and 12. The simulated channel uses a Gaussian channel.

[0089] II. Simulation Results

[0090] The performance of the method provided in this application is further illustrated by comparing traditional frequency offset estimation algorithms with the method provided in this application.

[0091] Figure 4 The estimation performance of the method of this application is shown in the figure under different frequency offsets and signal-to-noise ratios. Figure 4 It can be seen that this method can complete frequency offset estimation and compensation in multi-user scenarios. The frequency offset estimation performance outside the algorithm estimation boundary is independent of the frequency offset magnitude. The estimation range is the same as that of the receiving pilot correlation algorithm, which greatly reduces the complexity of frequency offset estimation and compensation.

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

[0093] Figure 6 The system performance diagrams of different frequency offset estimation algorithms are shown when the multi-user carrier frequency offset is 6kHz. 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 1dB better than other algorithms; in a multi-user scenario, the proposed algorithm has the same performance as the algorithm in patent [CN11657470A]; and compared with the algorithm based on local pilot correlation, the proposed algorithm improves the performance by about 3dB.

[0094] III. Complexity Analysis

[0095] By comparing the complexity of traditional algorithms with that of the method in this application, the performance of the method in this 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 the compensation algorithms corresponding to all frequency offset estimations is shown in Table 2 below.

[0097] Table 1 Computational complexity of the frequency offset estimation algorithm

[0098]

[0099]

[0100] Table 2 shows the computational complexity of the compensation algorithm corresponding to frequency offset estimation.

[0101]

[0102] As can be seen from Tables 1 and 2, under the given parameter use cases, the method of this application significantly reduces the computational complexity compared with the receiver pilot correlation algorithm; compared with other traditional algorithms, the computational complexity of the method of this 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] This application presents a transform domain frequency offset estimation and compensation method based on a 5G OFDM system, which achieves frequency offset estimation and compensation with low computational complexity and good estimation and compensation performance. First, this application extracts the first N / 2 data points of the pilot symbols and performs an FFT transform to reduce the computational complexity of the estimation algorithm. Then, it extracts the effective frequency band data based on the user's frequency band location and uses the correlation method to obtain the frequency offset estimate for each user. The method selects the compensation mode based on the number of users: time-domain compensation is selected for single-user scenarios, while simplified frequency-domain compensation is selected for multi-user scenarios. The method exhibits excellent performance in single-user scenarios and good performance in multi-user scenarios. Therefore, this application's method can be better applied to practical systems.

[0105] The above descriptions are merely various embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the 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 the received time-domain signal and determine all pilot symbols based on their positions in the OFDM symbols; Extract the first N / 2 points of data for 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; Based on the frequency domain offset of the user's pilot symbols and the number of pilot symbols, the transform domain signal is de-resource mapped to obtain the pilot reference signal corresponding to each pilot symbol for each user; The pilot reference signals corresponding to each pilot symbol of each user are cross-correlated to the two pilot reference signals before and after each pilot reference signal to obtain the normalized frequency offset value of each user. Based on 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. The received time-domain signal is time-domain offset compensated according to the time-domain frequency offset compensation value of each user to obtain the time-domain offset signal; The time-domain offset signal is subjected to a cyclic prefix removal operation, and an FFT transformation is performed to obtain the frequency domain signal corresponding to each OFDM symbol. Based on the frequency domain offset of the user's pilot symbols 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 for each user; Based on the frequency offset compensation value of each user, multiple frequency domain compensation factors are generated; the multiple frequency domain compensation factors form the Toplitz matrix for each user; Based on the Toplitz matrix of each user, the frequency band data corresponding to each OFDM symbol of each user is frequency-domain biased to obtain the frequency-domain biased signal of each user.

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

3. The method as described in claim 1, characterized in that, in, Based on the frequency domain offset and number of pilot symbols for each user, the transform domain signal is de-resource mapped to obtain the pilot reference signal corresponding to each pilot symbol for each user, expressed by the following formula: Where, D(l,k) (u) Y represents the pilot reference signal corresponding to the l-th pilot symbol of user u, where k is the index of the data point in the frequency domain. dft For transform domain signals, The frequency domain offset of the pilot symbol for user u. The number of pilot symbols for user u.

4. The method as described in claim 1, characterized in that, in, The pilot reference signals corresponding to each pilot symbol of each user are cross-correlated to each other to obtain the normalized frequency offset value of each user, which is expressed by the following formula: Where, ε (u) Let N be the normalized frequency offset value for user u, N be the number of data points in the received time-domain signal, and k be the index of the data point in the frequency domain. Let D(2,k) be the number of pilot symbols for user u. (u) D(1,k) represents the pilot reference signal corresponding to the second pilot symbol of user u. (u) Let N represent the pilot reference signal corresponding to the first pilot symbol of user u, * denotes conjugate, 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, and N cp The length of the cyclic prefix.

5. The method as described in claim 1, characterized in that, in, Based on the number of users, the time-domain frequency offset compensation value and the frequency-domain frequency offset compensation value for each user are determined using the following formula: Where, ε time The time-domain frequency offset compensation value for each user, ε (0) ε is the normalized frequency offset for user u=0, where U is the number of users. (u) Normalized frequency offset value of user u This is the frequency offset compensation value for user u in the frequency domain.

6. The method as described in claim 1, characterized in that, in, The received time-domain signal is time-domain offset compensated based on the time-domain frequency offset compensation value for each user, resulting in a time-domain offset compensated signal, using the following formula: Among them, y tc y(n) represents the time-domain offset signal, n is the data point label, y(n) is the received time-domain signal, and ε time Here, N represents the time-domain frequency offset compensation value for each user, and N is the number of data points in the received time-domain signal.

7. The method as described in claim 1, characterized in that, in, The time-domain offset signal is subjected to cyclic prefix removal and FFT transformation to obtain the frequency domain signal corresponding to each OFDM symbol, using the following formula: Among them, Y tc (i,k) represents the frequency domain signal corresponding to the i-th OFDM symbol, N is the number of data points in the received time domain signal, and n is the label of the data point. tc (n) represents the time-domain offset signal, N cp d 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 as described in claim 1, characterized in that, in, Based on the frequency domain offset of the user's pilot symbols and the number of pilot symbols, de-resource mapping is performed on the frequency domain signal corresponding to each OFDM symbol to obtain the frequency band data corresponding to each OFDM symbol for each user, using the following formula: Among them, Y data (i,k) (u) Y represents the frequency band data corresponding to the i-th OFDM symbol of user u, where k is the index of the data point in the frequency domain. tc For frequency domain signals, The frequency domain offset of the pilot symbol for user u. The number of pilot symbols for user u.

9. The method as described in claim 1, characterized in that, in, Based on the frequency offset compensation value for each user, multiple frequency domain compensation factors are generated; these multiple frequency domain compensation factors form a Toplitz matrix, expressed by the following formula: Where, ψ(m) (u) Let M be the frequency domain compensation factor for user u, M be the number of frequency domain compensation factors, and m be an integer related to M. Here, ψ is the frequency offset compensation value for user u in the frequency domain, N is the number of data points in the received time domain signal, and ψ is the frequency offset compensation value in the frequency domain. (u) Let ψ be the Topulitz matrix of user u. (u) The number of columns and rows is The number of pilot symbols for user u.

10. The method as described in claim 1, characterized in that, in, Based on the Toplitz matrix of each user, the frequency band data corresponding to each OFDM symbol of each user is subjected to frequency domain bias correction to obtain the frequency domain bias-corrected signal of each user, which is expressed by the following formula: AND fc (u) =Y data (u) ·ψ (u) in, The frequency-domain offset signal for user u. For the frequency band data of user u, ψ (u) Let be the Toplitz matrix of user u.

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