CN113904904B - OFDM-based integer frequency offset estimation method, system, medium and equipment - Google Patents

Abstract

The application relates to an integer frequency offset estimation method, a system, a medium and equipment based on OFDM, which comprises the following steps: carrying out fractional frequency offset estimation and compensation on an OFDM signal which is received by a receiver and is preset with a preamble symbol, carrying out FFT (fast Fourier transform) to obtain frequency domain data, and extracting the preamble symbol of the frequency domain data; performing conjugate operation on the preamble symbol and the preset preamble symbol; performing differential operation on the result of the conjugate operation; and carrying out minimum value search on the accumulated sum of the differential operation results to obtain a minimum value, and taking the integer frequency offset corresponding to the minimum value as feedback output to obtain the correct integer frequency offset. The application can reduce the calculation complexity of the algorithm while ensuring the performance of the algorithm, and can be widely applied to the technical field of wireless communication.

Description

OFDM-based integer frequency offset estimation method, system, medium and equipment

Technical field

The present invention relates to the field of wireless communication technology, and in particular to an OFDM-based integer frequency offset estimation method, system, medium and equipment.

Background technique

Different from the traditional frequency division multiplexing system that divides the signal frequency band into N non-overlapping sub-channels for transmission, orthogonal frequency division multiplexing (OFDM) technology, while frequency division multiplexing, due to the Mutually orthogonal, allowing sub-channel spectra to overlap with each other for parallel data transmission, which can maximize spectrum utilization and have significant improvements in combating narrowband impulse noise and multipath fading.

Orthogonal frequency division multiplexing (OFDM) technology has the characteristics of high spectrum utilization and strong fading resistance, and has important applications in many wireless communication fields. However, receiver synchronization errors, especially frequency offset, have a great impact on the performance of OFDM systems. For example, unstable oscillator frequency mismatch, Doppler frequency shift and complex channel environment of the transceiver system will introduce carrier frequency offset (CFO) to the OFDM system, resulting in frequency offset of the subcarrier frequency. Since the frequency offset of the carrier frequency will destroy the orthogonality between subcarriers, the performance of the OFDM system will drop sharply. The carrier frequency offset consists of two parts: fractional frequency offset (FFO) and integer frequency offset (IFO). FFO will cause inter-carrier interference (ICI), while IFO will cause cyclic shifts of subcarriers in the frequency domain, both of which will affect the reliability of data processing at the receiving end. The implementation of OFDM receivers and transceivers requires a large amount of hardware resources. If the IFO estimation module can use fewer resources, the resource usage efficiency of the entire system will be improved.

Contents of the invention

In response to the above problems, the purpose of the present invention is to provide an OFDM-based integer frequency offset estimation method, system, medium and equipment, which can reduce the computational complexity of the algorithm while ensuring algorithm performance.

In order to achieve the above object, the technical solution adopted by the present invention on the one hand is: an integer frequency offset estimation method based on OFDM, which includes: performing fractional frequency offset estimation and compensation on the OFDM signal received by the receiver and preset with the preamble symbol. Finally, perform FFT transformation to obtain the frequency domain data, and extract the leading symbol of the frequency domain data; perform a conjugate operation on the leading symbol and the preset leading symbol; perform a differential operation on the result of the conjugate operation; The results of the differential operation are accumulated and summed to perform a minimum value search to obtain the minimum value. The integer frequency offset corresponding to the minimum value is used as feedback output to obtain the correct integer frequency offset.

Further, the OFDM signal with pre-set preamble symbols is: setting the frequency domain value of the preamble symbol sequence for the original OFDM signal at the transmitter end; the length of the preamble symbol sequence is 2048, and the subcarrier length used is 1198.

Further, the preamble symbol for extracting the frequency domain data is:

R(k)=P(k)H(k)+n

Wherein, P(k) is the preset preamble symbol of the transmitter, H(k) is the channel impulse response frequency domain expression, and n is the noise signal.

Further, performing a conjugate operation on the leading symbol and the preset leading symbol includes: performing complex multiplication of the leading symbol and the preset leading symbol using real and imaginary parts respectively to obtain the operation result.

Further, performing a differential operation on the result of the conjugate operation includes: performing a differential operation on the used adjacent subcarriers by subtracting the previous term from the latter term based on the correlation of adjacent carriers.

Further, the difference operation is:

M(k)＝{[P ² (k-1)-P ² (k)]H(k)}+[P(k-1) ^* -P(k) ^* ]n

Among them, M(k) is the result of the differential operation, P(k) is the preset preamble symbol of the transmitter, P(k) ^* is the conjugate of P(k), and H(k) is the channel impulse response. Frequency domain expression, n is the noise signal; when P ² (k) is a constant, the {·} term in the above formula is the smallest.

Further, the cumulative summation of the results of the differential operation for minimum search includes: taking the absolute value of the result of the differential operation and performing cumulative summation, and performing a minimum search on the result of the differential operation to obtain At the minimum value, the corresponding correct integer frequency offset value is obtained.

On the other hand, the technical solution adopted by the present invention is: an OFDM-based integer frequency offset estimation method, which includes: a preprocessing module that performs fractional frequency offset estimation and After compensation, perform FFT transformation to obtain the frequency domain data, and extract the leading symbol of the frequency domain data; the conjugate operation module performs a conjugate operation on the leading symbol and the preset leading symbol; the differential operation module performs a conjugate operation on the pre-set leading symbol. The result of the conjugate operation is subjected to a differential operation; the cumulative summation module performs a minimum value search on the cumulative sum of the results of the differential operation to obtain the minimum value, and the integer frequency offset corresponding to the minimum value is used as a feedback output to obtain the correct Integer frequency offset.

On the other hand, the technical solution adopted by the present invention is: a computer-readable storage medium storing one or more programs, the one or more programs including instructions, which when executed by a computing device, causes the The computing device performs any of the above methods.

On the other hand, the technical solution adopted by the present invention is: a computing device, which includes: one or more processors, memories and one or more programs, wherein one or more programs are stored in the memory and configured For execution by the one or more processors, the one or more programs include instructions for performing any of the methods described above.

Since the present invention adopts the above technical solutions, it has the following advantages:

1. The present invention uses the similarity between adjacent subcarriers to estimate IFO, and replaces the square operation with the absolute value operation during the calculation process, which effectively reduces the calculation complexity and can save hardware implementation resources in the actual application process.

2. The present invention is based on OFDM technology and adopts the FPGA implementation method of signal integer frequency offset estimation at the receiving end. Through the conjugate operation register module and differential summation module, the cumulative summation module performs integer frequency offset estimation, solving the problem of realizing integer frequency offset. Frequency deviation time-sharing solves the problem of excessive resource consumption in FPGA.

The invention can be widely used in the field of OFDM communication technology.

Description of the drawings

Figure 1 is a schematic diagram of the overall flow of an estimation method in an embodiment of the present invention;

Figure 2 is a schematic diagram of the OFDM physical layer frame structure in an embodiment of the present invention;

Figure 3 is a schematic diagram of the signal processing flow of the OFDM receiving end in an embodiment of the present invention;

Figure 4 is a schematic diagram of an OFDM integer frequency offset estimation system in an embodiment of the present invention;

Figure 5 is a schematic structural diagram of a computing device in an embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art fall within the scope of protection of the present invention.

It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular forms are also intended to include the plural forms unless the context clearly indicates otherwise. Furthermore, it will be understood that when the terms "comprises" and/or "includes" are used in this specification, they indicate There are features, steps, operations, means, components and/or combinations thereof.

Assuming that the transmitted signal is x(n), then the OFDM baseband model of the passband signal y(n) is:

Among them, x(n) is the signal data output after the transmitter performs IFFT on the multi-carrier orthogonal modulation data. y(n) is the signal data of the transmitted signal reaching the receiver through the channel with frequency selective fading characteristics, w(n) is the noise in the channel, and the noise type is AWGN. h(l) is the channel impulse response (CIR). N is the number of points in FFT. ξ is the normalized frequency offset part, which consists of CFO and IFO, and k represents the sequence number of the subcarrier.

OFDM systems are very sensitive to synchronization deviations, especially frequency deviations. Frequency deviations are divided into fractional frequency deviations and integer frequency deviations relative to the subcarrier spacing, respectively referred to as fractional frequency offset (FFO) and integer frequency deviation ( IFO). Among them, fractional frequency offset will cause inter-subcarrier interference (ICI); integer frequency offset will not cause inter-subcarrier interference, but will cause cyclic shift of received data symbols, which will increase the error rate of demodulated information symbols. The signal y(n) after passing through the channel is compensated to eliminate the FFO, which can effectively avoid inter-subcarrier interference. Then the IFO frequency offset is estimated, and compensation is performed based on the estimated frequency offset value, which can effectively reduce the error rate of the demodulated signal. , improve transmission reliability.

The OFDM-based integer frequency offset estimation method, system, medium and equipment provided by the present invention include: setting an integer frequency offset estimation module in the OFDM receiver synchronization module, which includes a conjugate operation module, a differential operation module, and a cumulative calculation module. and modules. The conjugate operation module stores the real and imaginary part data of the locally known leading symbols, and performs operations on the real and imaginary parts of the serially entered signal. The specific operation method is described in the specific implementation below. The output from the conjugate operation module enters the differential operation module of the OFDM receiver. The length of a data symbol is 2048, and the subcarriers used are 1198. The adjacent subcarriers used are subjected to a difference operation of subtracting the previous term from the latter term. The result obtained by the differential operation enters the cumulative summation module. The cumulative summation module of the receiver calculates the absolute value of the data after the differential operation and then searches for the minimum value. When the minimum value occurs, the corresponding correct integer frequency offset value is obtained. Therefore, the present invention can reduce the computational complexity of the algorithm while ensuring the performance of the algorithm.

In one embodiment of the present invention, as shown in Figure 1, an OFDM-based integer frequency offset estimation method is provided. This embodiment illustrates the application of this method to a terminal. It can be understood that this method can also be applied For servers, it can also be applied to systems including terminals and servers, and is implemented through the interaction between terminals and servers. In this embodiment, the method includes the following steps:

1) After performing fractional frequency offset estimation and compensation on the OFDM signal received by the receiver with pre-set preamble symbols, perform FFT transformation to obtain frequency domain data, and extract the preamble symbols of the frequency domain data;

When used, the leading symbol in a frame of OFDM signal received by the receiver is pre-known information. After synchronizing the symbol timing of the received frame of OFDM signal, the receiver performs fractional frequency offset estimation and compensation, and then performs FFT. Transform to obtain the OFDM signal of frequency domain data;

2) Perform conjugate operation on the leading symbol and the preset leading symbol;

3) Perform differential operation on the results of the conjugate operation;

4) The cumulative sum of the results of the differential operation is searched for the minimum value to obtain the minimum value. The integer frequency offset corresponding to the minimum value is used as the feedback output to obtain the correct integer frequency offset.

In this embodiment, the OFDM signal physical layer frame structure is shown in Figure 2. In this frame structure, preamble symbol 1 and preamble symbol 2 are used for synchronization and channel estimation, each occupying 1 OFDM symbol. The Data field carries the data message. This embodiment performs integer frequency offset estimation based on the two leading symbols of the physical layer frame structure. Specifically: after receiving the frame data, the timing synchronization is completed first by relying on the two leading symbols. After finding the frame header, the OFDM signal data is estimated and compensated by FFO. After performing FFT, the first symbol is taken for integer frequency offset estimation.

When used, as shown in Figure 3, the receiving end antenna receives the OFDM signal and performs time synchronization, frequency offset estimation and compensation, removal of cyclic prefix, and correct decoding only after steps such as FFT and channel equalization. The frequency offset estimation and compensation step includes extracting the preamble symbol as shown in Figure 2 and performing IFO estimation. After obtaining the frequency offset value and feeding it back, subsequent receiver operations are performed until the OFDM receiver is correctly demodulated.

In this embodiment, the time domain sampling data of the OFDM preamble symbol is y(t). In order to estimate the integer frequency offset IFO, it is necessary to perform a correlation operation on the FFO compensated OFDM preamble symbol and the original OFDM preamble symbol. In order to achieve this goal, the receiving end extracts y(t), performs Fourier transform on it to obtain frequency domain data, and performs related calculations based on the frequency domain data to obtain the estimated value of IFO.

In the above step 1), the OFDM signal with preamble symbols is preset as follows: the frequency domain value of the preamble symbol sequence is set to the original OFDM signal at the transmitter end; the length of the preamble symbol sequence is 2048, and the subcarrier length used is 1198.

Specifically: set the frequency domain values of the leading symbol sequence to the following four types: 0-j, 0+j, 1, -1. Obviously, the modular value of each value is 1, and the length of the leading symbol sequence is 2048. Register the real part and imaginary part in local storage respectively; from the previous OFDM baseband model, that is, formula (1), ξ is the normalized frequency offset part, which consists of FFO and IFO. FFO is denoted as ε ₀ and IFO ε ₁ respectively. , the preamble symbol is recorded as x(n) at the transmitting end, and the signal y(n) at the receiving end has the following expression:

After FFO compensation, that is, after eliminating ε ₀ , only IFOε ₁ remains, which has the following expression

The parameter meanings are consistent with the previous formula (1).

In the above step 1), the mathematical expression after Fourier transform of y(n) at the receiving end is:

Y(k)＝FFT[y(t)] (4)

That is, the frequency domain representation of the y(t) signal obtained at the receiving end is Y(k), and k is the subcarrier number.

In equation (4), FFT(·) represents the Fourier transform; Y(k) is the signal on the k-th subcarrier of the OFDM symbol.

The preamble symbol signal extracted after the Y(k) signal undergoes symbol timing synchronization and FFO compensation is recorded as R(k).

R(k)=P(k)H(k)+n

Among them, P(k) is the preset preamble symbol of the transmitter, H(k) is the frequency domain expression of the channel impulse response, and n is the noise signal. After the received signal is compensated by FFO, only the IFO value ε ₀ remains.

In the above step 2), the leading symbol and the preset leading symbol are subjected to a conjugate operation. Specifically, the leading symbol and the preset leading symbol are judged to perform complex multiplication using real and imaginary parts respectively to obtain the operation result.

In this embodiment, a conjugate operation is performed on R(k) and the locally stored preamble symbol data P(k). From the complex operation rules and the above-mentioned leading symbol settings, it can be seen that the operation result after the complex multiplication of the signal entering the conjugate operation module and the leading symbol can be recorded as T(k).

T(k)＝R(k)P(k) ^* (6)

have

T(k)＝R(k)P(k) ^* =P ² (k)H(k)+P(k) ^* n (7)

Due to the particularity of the leading symbol, operations such as multipliers will not be used directly when implemented in FPGA. The method used is to determine the real and imaginary parts separately.

In the above step 3), the result of the conjugate operation is subjected to a differential operation. Specifically, according to the correlation of adjacent carriers, the adjacent sub-carriers used are subjected to a differential operation of subtracting the previous term from the latter term.

Among them, the difference operation is:

M(k)＝T(k-1)-T(k) (8)

Since the channel response is slowly changing, it can be obtained:

M(k)＝{[P ² (k-1)-P ² (k)]H(k)}+[P(k-1) ^* -P(k) ^* ]n (9)

Among them, M(k) is the result of the differential operation, P(k) is the preset preamble symbol of the transmitter, P(k) ^* is the conjugate of P(k), and H(k) is the channel impulse response frequency domain In the expression, n is the noise signal; when the leading symbols are aligned, it can be seen from the value of the preset leading symbols that when P ² (k) is a constant, the term {·} of the above formula is minimum.

In the above step 4), the results of the difference operation are accumulated and summed to search for the minimum value, including:

The absolute value of the result of the difference operation is taken and then the cumulative sum is performed. The result of the difference operation is searched for the minimum value. When the minimum value is obtained, the corresponding correct integer frequency offset value is obtained.

Since the traditional method is to first calculate the modulus value of the signal on each subcarrier for the previously obtained signal sequence M(k), and then accumulate and sum the modulus values of the signals on all subcarriers, multiplication operations in FPGA will consume a lot of resources. In this embodiment, the absolute value operation is replaced by the square operation, and simulation has proven that the performance is feasible, and multiplication operations are reduced to save resources. The following equation (10) is the square modulus expression in the traditional method, and equation (11) is the absolute value expression, which is the method proposed and used in the present invention.

Among them, N is the number of FFT points. Based on equation (9), the minimum value is searched. When the minimum value appears, the corresponding correct integer frequency offset value is obtained. There is the following formula:

It can be seen from equation (12) that when the pilot symbols are aligned, k is the ideal subcarrier position. The estimated integer frequency offset can be obtained through multiple calculations using equation (12) Recorded as an integer frequency offset nsc.

In summary, the present invention aims to reduce the impact of the channel impulse response on subsequent operation steps by performing differential operations on adjacent subcarriers within the OFDM preamble symbol. Combined with the cumulative sum operation, it can effectively reduce the computational complexity and reduce the use of FPGA resources. . And in the process of performing related operations to obtain integer frequency offsets, the absolute value summation operation is used instead of the square summation operation in the cumulative summation stage. Simulation has proven that this method is feasible, and the use of absolute value summation can greatly reduce calculations. quantity and save resources.

In one embodiment of the present invention, as shown in Figure 4, an OFDM-based integer frequency offset estimation system is provided, which includes:

The preprocessing module performs fractional frequency offset estimation and compensation on the OFDM signal with pre-set preamble symbols received by the receiver, performs FFT transformation to obtain frequency domain data, and extracts the preamble symbols of the frequency domain data;

The conjugate operation module performs conjugate operation on the leading symbol and the preset leading symbol;

The differential operation module performs differential operations on the results of the conjugate operation;

The cumulative summation module searches for the minimum value by cumulatively summing the results of the differential operation to obtain the minimum value. The integer frequency offset corresponding to the minimum value is used as feedback output to obtain the correct integer frequency offset.

In summary, at the receiving end of the OFDM system, the present invention first performs fractional frequency offset estimation and compensation on the received OFDM signal, performs FFT transformation on the signal after fractional frequency offset compensation to obtain frequency domain data, and extracts the leading symbols in the signal. ; Integer frequency offset estimation is performed through correlation operations, and the conjugate operation and storage of data are performed in the conjugate operation module; the data obtained by the conjugate operation module is sent to the difference operation module for differential operation of the data; the data obtained by the differential operation enters the accumulation The summation module searches for the minimum value, obtains the minimum value, and performs feedback based on the minimum value to output the correct integer frequency offset nsc.

The system provided by this embodiment is used to execute each of the above method embodiments. Please refer to the above embodiments for specific processes and details, which will not be described again here.

As shown in Figure 5, it is a schematic structural diagram of a computing device provided in an embodiment of the present invention. The computing device may be a terminal, which may include: a processor (processor), a communication interface (Communications Interface), a memory (memory), a display screens and input devices. Among them, the processor, communication interface, and memory complete communication with each other through the communication bus. The processor is used to provide computing and control capabilities. The memory includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. When the computer program is executed by the processor, it implements an integer frequency offset estimation method; the internal memory is Non-volatile storage media provide an environment for the execution of operating systems and computer programs. The communication interface is used for wired or wireless communication with external terminals. The wireless mode can be implemented through WIFI, manager network, NFC (Near Field Communication) or other technologies. The display screen may be a liquid crystal display or an electronic ink display. The input device may be a touch layer covered on the display screen, or may be a button, trackball or touch pad provided on the housing of the computing device, or may be an external Keyboard, trackpad or mouse, etc. The processor can call logical instructions in memory to perform methods such as:

After estimating and compensating the fractional frequency offset of the OFDM signal received by the receiver with pre-set preamble symbols, perform FFT transformation to obtain the frequency domain data, and extract the preamble symbols of the frequency domain data; the preamble symbols are shared with the preset preamble symbols. Yoke operation; perform difference operation on the results of the conjugate operation; sum up the results of the difference operation to search for the minimum value to obtain the minimum value. The integer frequency offset corresponding to the minimum value is used as the feedback output to obtain the correct integer frequency offset.

In addition, the above-mentioned logical instructions in the memory can be implemented in the form of software functional units and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on this understanding, the technical solution of the present invention essentially or the part that contributes to the existing technology or the part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including Several instructions are used to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage media include: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), magnetic disk or optical disk and other media that can store program code. .

Those skilled in the art can understand that the structure shown in Figure 5 is only a block diagram of a partial structure related to the solution of the present application, and does not constitute a limitation on the computing device to which the solution of the present application is applied. The specific computing device can May include more or fewer parts than shown, or combine certain parts, or have a different arrangement of parts.

In one embodiment of the present invention, a computer program product is provided. The computer program product includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions. When the program instructions When executed by a computer, the computer can execute the methods provided by the above method embodiments, which include, for example: performing fractional frequency offset estimation and compensation on the OFDM signal received by the receiver and preset with preamble symbols, and then performing FFT transformation to obtain the frequency domain Data, extract the leading symbol of the frequency domain data; perform conjugate operation on the leading symbol and the preset leading symbol; perform differential operation on the result of the conjugate operation; perform a minimum search by summing the results of the differential operation to obtain the minimum value , the integer frequency offset corresponding to the minimum value is used as the feedback output to obtain the correct integer frequency offset.

In one embodiment of the present invention, a non-transitory computer-readable storage medium is provided. The non-transitory computer-readable storage medium stores server instructions. The computer instructions cause the computer to execute the methods provided in the above embodiments, for example, including : After estimating and compensating the fractional frequency offset of the OFDM signal received by the receiver with a pre-set preamble symbol, perform FFT transformation to obtain the frequency domain data, and extract the preamble symbol of the frequency domain data; perform a comparison between the preamble symbol and the preset preamble symbol. Conjugate operation; perform differential operation on the results of the conjugate operation; sum up the results of the differential operation to search for the minimum value to obtain the minimum value. The integer frequency offset corresponding to the minimum value is used as feedback output to obtain the correct integer frequency offset.

The implementation principles and technical effects of the computer-readable storage medium provided by the above embodiments are similar to those of the above method embodiments, and will not be described again here.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each process and/or block in the flowchart illustrations and/or block diagrams, and combinations of processes and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing device to produce a machine, such that the instructions executed by the processor of the computer or other programmable data processing device produce a use A device for realizing the functions specified in one process or multiple processes of the flowchart and/or one block or multiple blocks of the block diagram.

These computer program instructions may also be stored in a computer-readable memory that causes a computer or other programmable data processing apparatus to operate in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including the instruction means, the instructions The device implements the functions specified in a process or processes of the flowchart and/or a block or blocks of the block diagram.

These computer program instructions may also be loaded onto a computer or other programmable data processing device, causing a series of operating steps to be performed on the computer or other programmable device to produce computer-implemented processing, thereby executing on the computer or other programmable device. Instructions provide steps for implementing the functions specified in a process or processes of a flowchart diagram and/or a block or blocks of a block diagram.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that it can still be used Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent substitutions are made to some of the technical features; however, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (7)

1. An OFDM-based integer frequency offset estimation method, characterized by including: After performing fractional frequency offset estimation and compensation on the OFDM signal received by the receiver and preset with preamble symbols, perform FFT transformation to obtain frequency domain data, and extract the preamble symbols of the frequency domain data; Perform a conjugate operation on the leading symbol and the preset leading symbol; Perform a difference operation on the result of the conjugate operation; The results of the differential operation are accumulated and summed to perform a minimum value search to obtain the minimum value. The integer frequency offset corresponding to the minimum value is used as feedback output to obtain the correct integer frequency offset; The OFDM signal pre-set with preamble symbols is: setting the frequency domain value of the preamble symbol sequence for the original OFDM signal at the transmitter end; the length of the preamble symbol sequence is 2048, and the subcarrier length used is 1198; The preamble symbols for extracting the frequency domain data are: R(k)=P(k)H(k)+n Among them, P(k) is the preset preamble symbol of the transmitter, H(k) is the frequency domain expression of the channel impulse response, and n is the noise signal; Performing a conjugate operation on the leading symbol and the preset leading symbol includes: The real part and the imaginary part are respectively judged to perform complex multiplication of the leading symbol and the preset leading symbol to obtain an operation result. 2. The integer frequency offset estimation method according to claim 1, wherein performing a differential operation on the result of the conjugate operation includes: According to the correlation of adjacent carriers, the adjacent subcarriers used are subjected to a difference operation of subtracting the previous term from the latter term. 3. The integer frequency offset estimation method according to claim 2, wherein the difference operation is: M(k)＝{[P ² (k-1)-P ² (k)]H(k)}+[P(k-1) ^* -P(k) ^* ]n Among them, M(k) is the result of the differential operation, P(k) is the preset preamble symbol of the transmitter, P(k) ^* is the conjugate of P(k), and H(k) is the channel impulse response. Frequency domain expression, n is the noise signal; when P ² (k) is a constant, the {·} term in the above formula is the smallest. 4. The integer frequency offset estimation method according to claim 1, wherein the cumulative summation of the results of the difference operation to perform a minimum value search includes: The result of the difference operation is taken as an absolute value and then accumulated and summed. The result of the difference operation is searched for a minimum value. When the minimum value is obtained, the corresponding correct integer frequency offset value is obtained. 5. An OFDM-based integer frequency offset estimation method, characterized by including: The preprocessing module performs fractional frequency offset estimation and compensation on the OFDM signal with preset preamble symbols received by the receiver, performs FFT transformation to obtain frequency domain data, and extracts the preamble symbols of the frequency domain data; A conjugate operation module performs a conjugate operation on the leading symbol and the preset leading symbol; A differential operation module performs a differential operation on the results of the conjugate operation; The cumulative summation module performs a minimum value search by cumulative summing the results of the differential operation to obtain the minimum value, and the integer frequency offset corresponding to the minimum value is used as feedback output to obtain the correct integer frequency offset; The OFDM signal pre-set with preamble symbols is: setting the frequency domain value of the preamble symbol sequence for the original OFDM signal at the transmitter end; the length of the preamble symbol sequence is 2048, and the subcarrier length used is 1198; The preamble symbols for extracting the frequency domain data are: R(k)=P(k)H(k)+n Among them, P(k) is the preset preamble symbol of the transmitter, H(k) is the frequency domain expression of the channel impulse response, and n is the noise signal; Performing a conjugate operation on the leading symbol and the preset leading symbol includes: The real part and the imaginary part are respectively judged to perform complex multiplication of the leading symbol and the preset leading symbol to obtain an operation result. 6. A computer-readable storage medium storing one or more programs, characterized in that the one or more programs include instructions that, when executed by a computing device, cause the computing device to perform as claimed Any of the methods described in 1 to 4. 7. A computing device, characterized by comprising: one or more processors, a memory, and one or more programs, wherein one or more programs are stored in the memory and configured to be the one or more The processor executes, and the one or more programs include instructions for executing any one of the methods described in claims 1 to 4.