A method for suppressing distortion of OFDM signal by time-frequency cooperative equalization

Abstract

The application discloses a time-frequency collaborative equalization distortion suppression method for an OFDM signal, and belongs to the field of wireless communication. The application solves the problems of high complexity and poor transmission reliability of the existing short cyclic prefix method. The application adopts an OFDM system based on time domain oversampling and frequency domain interpolation equalization at a receiving end. The oversampling algorithm can enhance the power of useful signals by appropriately widening the equalization frequency band, thereby enhancing the equalization effect. The frequency domain interpolation equalization algorithm can better capture spectral details by performing weighted interpolation processing on the frequency domain receiving signals, thereby realizing compensation and correction of the energy migration phenomenon of spectral lines in the frequency band caused by the channel effect. Through time-frequency collaborative processing at the receiving end, the application can efficiently suppress interference, ensure stable and reliable demodulation accuracy and communication quality, avoid the spectral resource loss caused by the extra lengthening of the cyclic prefix, and further significantly improve the spectral utilization efficiency of the system. The application can be applied to the field of wireless communication.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, specifically relating to a time-frequency cooperative equalization distortion suppression method for OFDM signals with short cyclic prefixes. Background Technology

[0002] Driven by the continued deepening of 5G commercialization and the explosive growth of IoT terminals, the supply and demand imbalance of spectrum resources has become a core bottleneck restricting the development of wireless communication technology towards high speed and wide connectivity. Orthogonal Frequency Division Multiplexing (OFDM), as a core modulation technology in 4G systems, effectively resists inter-symbol interference (ISI) and inter-subcarrier interference (ICI) caused by multipath propagation by introducing a cyclic prefix (CP), ensuring the orthogonality of signal transmission. However, the introduction of the cyclic prefix requires additional spectrum resources, leading to a significant reduction in system spectral efficiency. This contradicts the core development goal of pursuing high spectrum utilization in wireless communication systems. Therefore, OFDM signal distortion suppression technology for short cyclic prefix (short CP) scenarios has become an important research direction. However, some existing CP-less or short CP transmission algorithms suffer from high computational complexity, and the performance of some schemes is highly dependent on channel conditions, making it difficult to guarantee stability in complex channel environments.

[0003] Both oversampling and frequency domain interpolation equalization techniques exhibit excellent interference suppression and signal recovery performance. Given the complementarity and compatibility of their core advantages, by rationally integrating and coordinating these techniques, and fully leveraging the advantages of oversampling in fine-grained reconstruction of time-domain signals and the characteristics of frequency domain interpolation equalization in channel distortion compensation, it is expected to further improve the transmission reliability and spectral efficiency of the system in short-CP scenarios. Therefore, how to integrate and apply these two techniques has become one of the key research directions worthy of attention in this field. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of high complexity and poor transmission reliability of existing short cyclic prefix methods, and to propose a time-frequency cooperative equalization distortion suppression method for OFDM signals with short cyclic prefixes.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is: a method for time-frequency cooperative equalization distortion suppression of OFDM signals with short cyclic prefixes, the method specifically including the following steps:

[0006] Step 1: Denote the raw bit stream to be transmitted generated by the digital source as... ,in, This represents the total number of bits in the original bitstream. , Then convert the original bitstream Divided into Each bit group contains 1 bit group. 1 bit, within each group One OFDM symbol is composed of 10 bits. Total number of OFDM symbols;

[0007] Step 2: Modulate the data subcarrier for each OFDM symbol to obtain the data subcarrier modulation symbol sequence corresponding to each OFDM symbol. The data subcarrier modulation symbol sequence corresponding to each OFDM symbol is denoted as . ,in, , Indicates the first The first OFDM symbol corresponding to the data subcarrier modulation symbol sequence A symbol, This refers to the number of data subcarriers in an OFDM symbol.

[0008] Step 3: Construct the frequency domain signal vector corresponding to each data subcarrier modulation symbol sequence, and then... The frequency domain signal vector is denoted as , ;

[0009] Step 4: Perform serial-to-parallel conversion on each frequency domain signal vector, and then analyze the serial-to-parallel conversion results for each frequency domain signal vector. The inverse fast Fourier transform of each point yields the time-domain signal corresponding to each frequency domain signal vector. The time-domain signal corresponding to each frequency domain signal vector is denoted as . , ;

[0010] in, Time-domain signal The symbols in;

[0011] Step 5: Add a cyclic prefix to the time-domain signal corresponding to each frequency domain signal vector to obtain each time-domain signal after adding the cyclic prefix;

[0012] Step 6: Perform parallel-to-serial conversion on each time-domain signal after adding the cyclic prefix, according to the signal transmission order, to obtain... Then, the parallel-to-serial conversion result is sequentially subjected to digital-to-analog conversion and up-conversion processing, and the processing result is sent to the channel.

[0013] The beneficial effects of this invention are:

[0014] This invention employs an OFDM system based on oversampling and frequency-domain interpolation equalization at the receiver, suppressing inter-symbol interference and inter-subcarrier interference caused by insufficient cyclic prefix, thus acquiring accurate demodulated data. Compared to conventional OFDM systems with added cyclic prefixes, this invention retains the transmitter's cyclic prefix but optimizes it for scenarios with insufficient cyclic prefixes, eliminating the need to increase the cyclic prefix length. This reduces complexity and avoids wasting spectrum resources due to extended cyclic prefixes, improving spectrum utilization efficiency. Simultaneously, time-frequency co-processing at the receiver ensures communication quality and improves system transmission reliability. This invention effectively balances system performance and resource utilization. Attached Figure Description

[0015] Figure 1 This is a flowchart of a method for time-frequency co-equalization distortion suppression of OFDM signals with short cyclic prefixes according to the present invention;

[0016] Figure 2 This is a flowchart of time-domain oversampling and frequency-domain interpolation equalization at the receiving end;

[0017] Figure 3 These are simulation graphs of the bit rate performance of various methods in Rayleigh fading channels, 16QAM modulation, and a maximum Doppler frequency shift of 300Hz.

[0018] Figure 4 The figure shows the bit rate performance simulation of the traditional MMSE equalization method and the time-frequency co-equalization method of the present invention under Rayleigh fading channel, 16QAM modulation, and maximum Doppler frequency shifts of 30Hz, 300Hz, 3000Hz, and 30000Hz. Detailed Implementation

[0019] Specific implementation method one: Combining Figure 1 This embodiment describes a time-frequency cooperative equalization distortion suppression method for OFDM signals with short cyclic prefixes. The method's operation at the transmitter is as follows:

[0020] Step 1: Denote the raw bit stream to be transmitted generated by the digital source as... ,in, This represents the total number of bits in the original bitstream. , Then convert the original bitstream Divided into Each bit group contains 1 bit group. bits, The value is determined by the modulation scheme and the number of subcarriers in each OFDM symbol, within each group. One OFDM symbol is composed of 10 bits. Total number of OFDM symbols;

[0021] Step 2: Modulate the data subcarrier for each OFDM symbol to obtain the data subcarrier modulation symbol sequence corresponding to each OFDM symbol. The data subcarrier modulation symbol sequence corresponding to each OFDM symbol is denoted as . ,in, , Indicates the first The first OFDM symbol corresponding to the data subcarrier modulation symbol sequence A symbol, This refers to the number of data subcarriers in an OFDM symbol.

[0022] Step 3: Construct the frequency domain signal vector corresponding to each data subcarrier modulation symbol sequence, and then... The frequency domain signal vector is denoted as , ;

[0023] Step 4: Perform serial-to-parallel conversion on each frequency domain signal vector, and then analyze the serial-to-parallel conversion results for each frequency domain signal vector. The inverse fast Fourier transform (IFFT) of each point yields the time-domain signal corresponding to each frequency domain signal vector, and the first point... The time-domain signal corresponding to each frequency domain signal vector is denoted as . , ;

[0024] in, Time-domain signal The symbols in;

[0025] Step 5: Add a cyclic prefix to the time-domain signal corresponding to each frequency domain signal vector to obtain each time-domain signal after adding the cyclic prefix;

[0026] Step 6: Perform parallel-to-serial conversion on each time-domain signal after adding the cyclic prefix, according to the signal transmission order, to obtain... Then, the parallel-to-serial conversion result is sequentially subjected to digital-to-analog conversion and up-conversion processing, and the processing result is sent to the channel.

[0027] Assuming the signal passes through a Rayleigh fading channel, the sampling interval of a conventional system is... The maximum delay spread of the channel is And the length of the added loop prefix Less than the actual maximum multipath delay spread of the channel This indicates a problem of insufficient cyclic prefix. The received signal at the receiver can be represented in the time domain as:

[0028]

[0029] in, express When a wireless signal is constantly input and transmitted through the channel, the channel is in The response made at any moment It is additive white Gaussian noise in the channel.

[0030] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the specific process of step three is as follows:

[0031] For the The data subcarrier modulation symbol sequence corresponding to each OFDM symbol In the sequence The front of the supplement zeros in the sequence Add after There are zeros, and the length of the zero padding satisfies ;

[0032] like If it is even, then ;

[0033] like If it is an odd number, then , ;

[0034] Modulation symbol sequence for data subcarriers After padding with zeros, we get the first... A frequency domain signal vector.

[0035] The other steps and parameters are the same as in Specific Implementation Method 1.

[0036] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the specific process of step five is as follows:

[0037] For time-domain signals Copying time-domain signals tail One symbol, and add the copied symbol to the time-domain signal. The first symbol before the loop prefix is ​​used as the loop prefix, and the loop prefix is ​​added to the first symbol. Time-domain signal for:

[0038]

[0039] in, Indicates a signal located in the time domain The end The symbol is the added cyclic prefix.

[0040] Other steps and parameters are the same as in specific implementation method one or two.

[0041] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the working process of the method at the receiving end is as follows:

[0042] Step 7: The receiving end performs down-conversion and analog-to-digital conversion on the signal received from the channel, and then applies the oversampling factor. The signal processed at the receiving end is sampled to obtain a discrete baseband digital signal;

[0043] in, oversampling factor It is an integer greater than 1. Indicates the oversampling factor;

[0044] Discrete baseband digital signals The sampled values ​​for each sampling point are:

[0045]

[0046] in, The sampled value of the received signal. The noise is sampled at the receiving end. The impulse response of an oversampled discrete channel represents the response of an input at... When a unit pulse is applied at a given time, at the time of receiving the oversampled pulse... The response generated at that location. And, for Discrete-time impulse response of a tap It is an oversampling of the input signal.

[0047] Then, the discrete baseband digital signal is converted from serial to parallel to obtain the time-domain samples corresponding to each OFDM symbol. The time-domain samples corresponding to each OFDM symbol are denoted as . , ;

[0048] Remove the headers of the samples in each time domain. The symbols are used to obtain the discrete time-domain signals, and the first symbol is used to obtain the second discrete time-domain signal. A discrete time-domain signal is denoted as ,in, Indicates the first A discrete time-domain signal The symbols in;

[0049] Step 8: Perform serial-to-parallel conversion on each discrete time-domain signal, and then perform Fast Fourier Transform (FFT) on the serial-to-parallel conversion result for each discrete time-domain signal to convert the time-domain signal from the time domain to the frequency domain, obtaining the frequency-domain received signal vector corresponding to each discrete time-domain signal. The frequency domain received signal vector corresponding to a discrete time-domain signal is denoted as ,and The length of the digital signal is ;

[0050] Then, weighted interpolation is performed on each frequency domain received signal vector to obtain the weighted interpolated signal vector corresponding to each frequency domain received signal vector. The length of each weighted interpolated signal vector is... ;

[0051] Step 9: Perform MMSE equalization on each weighted interpolated signal vector to obtain the equalized OFDM frequency domain signal, and then... The equalized OFDM frequency domain signal is denoted as ;

[0052] From the equalized OFDM frequency domain signal Extract an odd number of points from the sample, and use these odd numbers to form a balanced sample. OFDM frequency domain signal Extract the OFDM frequency domain signal The front of the middle Each point and after The extracted points are used to form a frequency domain signal. ;

[0053] Step 10: Remove frequency domain signals The leading zeros at the beginning and the trailing zeros at the end are used as the remaining part of the extracted raw data. This extracted raw data is then sent to a conventional OFDM receiver for conventional decision-making.

[0054] The other steps and parameters are the same as those in one of the specific implementation methods one to three.

[0055] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the weighted interpolation of each frequency domain received signal vector is performed to obtain the weighted interpolated signal vector corresponding to each frequency domain received signal vector; specifically:

[0056] Construction dimension Receiver frequency domain interpolation matrix The construction method is as follows:

[0057]

[0058] in, Representation matrix The Middle Line 1 Column elements, Representation matrix The Middle Line 1 Column elements, Representation matrix The Middle Line 1 The element in the column is set to 0, and all other elements are set to 0;

[0059] With the first Take, for example, the frequency domain received signal vector corresponding to a discrete time-domain signal:

[0060] Using frequency domain interpolation matrix For the frequency domain received signal vector Perform a linear transformation, that is, the frequency domain interpolation matrix With frequency domain received signal vector Perform multiplication operations and use the results of the multiplication operations as the weighted interpolated signal vector. .

[0061] The other steps and parameters are the same as those in one of the specific implementation methods one to four.

[0062] Let the frequency domain received signal vector The frequency domain signal vector after weighted interpolation is The weighted interpolation process is equivalent to transforming the frequency domain received signal vector... The first in Each sample point is directly placed in the output vector. The At each position; and in the vector The sample points and the sample points Insert a new sample point between the two points, and the value of the new sample point is and The weighted sum, with weights respectively and New sample points are placed in the output vector. The One position, which can be written as:

[0063]

[0064] In the input vector The last sample point Then a new sample point is inserted, whose value is determined solely by... and Decide, .

[0065] Among them, the weighting coefficient and For maximum multipath delay spread and maximum Doppler frequency shift The function, coefficient Specifically:

[0066]

[0067] in, , For maximum multipath delay spread, , For the maximum Doppler frequency shift, All are polynomial coefficients;

[0068] coefficient Specifically:

[0069]

[0070] in, All of these are polynomial coefficients, and the values ​​of the polynomial coefficients range from -50 to 50.

[0071] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One through Five in that the MMSE equalization is performed on each weighted interpolated signal vector, specifically as follows:

[0072] With the first Taking a weighted interpolated signal vector as an example:

[0073] Step 91, constructing the dimension as frequency domain transformation matrix ;

[0074] Step 92: Based on Discrete-Time Channel Impulse Response Construction dimension is Time-domain channel matrix ;

[0075] Step 93: Calculate the matrix when the cyclic prefix is ​​insufficient. Frequency domain representation :

[0076]

[0077] in, The dimension is The fast Fourier transform matrix, express The conjugate transpose of ;

[0078] The frequency domain representation of the equivalent channel matrix after frequency domain interpolation is:

[0079]

[0080] in, express The inverse matrix, It is the frequency domain representation of the equivalent channel matrix after frequency domain interpolation;

[0081] Step 94, according to Construction dimension Equalizer coefficient matrix:

[0082]

[0083] in, Indicates the average power of the signal. Indicates the average noise power. Represents the identity matrix. express The conjugate transpose of . Represents the equalizer coefficient matrix;

[0084] Step 95: Interpolate the signal vector in the frequency domain. With equalizer coefficient matrix Multiply, we get OFDM frequency domain signal after point equalization .

[0085] The other steps and parameters are the same as those in one of the specific implementation methods one to five.

[0086] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that, since this invention addresses a scenario with insufficient cyclic prefixes, the channel does not satisfy cyclic stationarity; therefore, the time-domain channel matrix... It is a non-cyclic Topletz matrix, the time-domain channel matrix. Make vector multiplication The result is mathematically equivalent to the effective data portion of the transmitted signal. Channel impulse response The linear convolution of the time-domain channel matrix for:

[0087]

[0088] Among them, matrix ,matrix The first in Line 1 The elements of the column are:

[0089]

[0090] in, Representation matrix The first in Line 1 Column elements, Indicates the number of channel taps. As an intermediate variable, express Divide by The remainder of the matrix makes the matrix Each row has a maximum of only One non-zero element, Indicates the oversampling time of the received signal. The corresponding number The discrete-time impulse response of each channel tap (can be obtained from a known channel; when the channel is unknown, the transmitter can send a pilot signal to estimate the channel, and then obtain the response based on the channel estimation result).

[0091] The other steps and parameters are the same as those in one of the specific implementation methods one to six.

[0092] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the frequency domain transformation matrix... The first in Line 1 The elements of the column are set to 1, where, All other elements are set to 0.

[0093] The other steps and parameters are the same as those in any of the specific implementation methods one to seven.

[0094] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the specific process of step ten is as follows:

[0095] like If it is even, then from the frequency domain signal The Starting from a single sample point, continuously extract... For each sample, the extracted data will be used as part of the extracted original data.

[0096] like If it is odd, then from the frequency domain signal The Starting from a single sample point, continuously extract... The data extracted from each sample point will be used as part of the extracted raw data.

[0097] The other steps and parameters are the same as those in one of the specific implementation methods one to eight.

[0098] Simulation section

[0099] The simulation input parameter settings for the method of this invention are shown in Table 1:

[0100]

[0101] Step 1: The transmitting end first generates the random binary bit stream to be transmitted and maps the data bits to be transmitted. The modulation method is selected based on the amount of data to be transmitted; 16QAM digital signal modulation is selected in the simulation. Then, serial-to-parallel conversion is performed, converting the serial data into 192 parallel data subcarriers. Due to the large number of subcarriers, OFDM modulation is performed using inverse Fast Fourier Transform to generate an OFDM signal. Then, the last 32 subcarriers are truncated and added to the signal front end as a cyclic prefix. Finally, after converting the parallel data back to serial data, the resulting serial data undergoes digital-to-analog conversion before being transmitted through the transmitting antenna.

[0102] Step 2: Establish a Rayleigh fading channel model based on Gaussian white noise and Doppler effect for the OFDM signal to simulate the noise interference, phase shift, and signal attenuation process of the OFDM signal as it passes through the channel environment. The simulation signal-to-noise ratio range is set to 0~20dB, and the simulation is run 1000 times under each signal-to-noise ratio environment.

[0103] Step 3: After oversampling and removing the cyclic prefix at the receiving end, perform frequency domain interpolation on the OFDM signal;

[0104] Step 4: Perform MMSE equalization on the frequency-domain interpolated OFDM signal to obtain... Then, the equalized signal Perform extraction;

[0105] Step 5: Demodulate the extracted signal using 16QAM demapping, and finally convert the signal from parallel to serial to output a bit stream for subsequent result processing.

[0106] Simulation results are as follows Figure 3 and Figure 4 As shown, all of these demonstrate that the method of the present invention has better bit rate performance.

[0107] In summary, this invention proposes a signal processing scheme for OFDM system receivers in scenarios with insufficient cyclic prefixes. Its core objective is to address the technical challenge of deteriorated inter-symbol and inter-subcarrier interference and impaired communication performance caused by the failure of the cyclic prefix length configured at the transmitter in an OFDM system to match the actual maximum channel delay spread. This invention employs a combination of time-domain oversampling and frequency-domain interpolation equalization techniques in the receiver. For frequency-dispersion channels, since channel energy extends beyond the original signal bandwidth, the oversampling algorithm can appropriately widen the equalization bandwidth to recover previously ignored signal energy, enhancing the power of the useful signal and thus improving the equalization effect. Based on this, the frequency-domain interpolation equalization algorithm inserts a third spectral line between two adjacent spectral lines according to the waveform's continuity characteristics, performing weighted interpolation processing on the received signal in the frequency domain. This captures previously unnoticed spectral details, compensating for and correcting the energy migration phenomenon caused by channel effects on spectral lines within the frequency band. Subsequently, an equalizer is designed based on the minimum mean square error criterion to perform equalization processing on the oversampled frequency-domain interpolated signal to complete data recovery. This invention, through the optimized processing mechanism at the receiver, can efficiently suppress interference, ensure stable and reliable demodulation accuracy and communication quality, and avoid spectrum resource loss caused by the additional extension of the cyclic prefix, thereby significantly improving the spectrum utilization efficiency of the system. It also effectively addresses the frequency shift and time-varying effects caused by high-speed time-varying channels, as well as the inter-symbol interference caused by insufficient CP.

[0108] The above examples of the present invention are merely illustrative of the computational model and process of the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is impossible to exhaustively list all possible implementations here. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for time-frequency coordinated equalization distortion suppression of OFDM signals, characterized in that, The operation process of the method at the transmitting end is as follows: Step 1: Denote the raw bit stream to be transmitted generated by the digital source as... ,in, This represents the total number of bits in the original bitstream. , Then convert the original bitstream Divided into Each bit group contains 1 bit group. 1 bit, within each group One OFDM symbol is composed of 10 bits. Total number of OFDM symbols; Step 2: Modulate the data subcarrier for each OFDM symbol to obtain the data subcarrier modulation symbol sequence corresponding to each OFDM symbol. The data subcarrier modulation symbol sequence corresponding to each OFDM symbol is denoted as . ,in, , Indicates the first The first OFDM symbol corresponding to the data subcarrier modulation symbol sequence A symbol, This refers to the number of data subcarriers in an OFDM symbol. Step 3: Construct the frequency domain signal vector corresponding to each data subcarrier modulation symbol sequence, and then... The frequency domain signal vector is denoted as , ; Step 4: Perform serial-to-parallel conversion on each frequency domain signal vector, and then analyze the serial-to-parallel conversion results for each frequency domain signal vector. The inverse fast Fourier transform of each point yields the time-domain signal corresponding to each frequency domain signal vector. The time-domain signal corresponding to each frequency domain signal vector is denoted as . , ; in, Time-domain signal The symbols in; Step 5: Add a cyclic prefix to the time-domain signal corresponding to each frequency domain signal vector to obtain each time-domain signal after adding the cyclic prefix; Step 6: Perform parallel-to-serial conversion on each time-domain signal after adding the cyclic prefix, according to the signal transmission order, to obtain... Then, the parallel-to-serial conversion result is sequentially subjected to digital-to-analog conversion and up-conversion processing, and the processing result is sent to the channel; The working process of the method at the receiving end is as follows: Step 7: The receiving end performs down-conversion and analog-to-digital conversion on the signal received from the channel, and then applies the oversampling factor. The signal processed at the receiving end is sampled to obtain a discrete baseband digital signal; Then, the discrete baseband digital signal is converted from serial to parallel to obtain the time-domain samples corresponding to each OFDM symbol. The time-domain samples corresponding to each OFDM symbol are denoted as . , ; Remove the headers of the samples in each time domain. The symbols are used to obtain the discrete time-domain signals, and the first symbol is used to obtain the second discrete time-domain signal. A discrete time-domain signal is denoted as ,in, Indicates the first A discrete time-domain signal The symbols in; Step 8: Perform serial-to-parallel conversion on each discrete time-domain signal, and then perform Fast Fourier Transform on the serial-to-parallel conversion result for each discrete time-domain signal to obtain the frequency-domain received signal vector corresponding to each discrete time-domain signal. The frequency domain received signal vector corresponding to a discrete time-domain signal is denoted as ; Then, weighted interpolation is performed on each frequency domain received signal vector to obtain the weighted interpolated signal vector corresponding to each frequency domain received signal vector. The length of each weighted interpolated signal vector is... ; Step 9: Perform MMSE equalization on each weighted interpolated signal vector to obtain the equalized OFDM frequency domain signal, and then... The equalized OFDM frequency domain signal is denoted as ; From the equalized OFDM frequency domain signal Extract an odd number of points from the sample, and use these odd numbers to form a balanced sample. OFDM frequency domain signal Extract the OFDM frequency domain signal The front of the middle Each point and after The extracted points are used to form a frequency domain signal. ; Step 10: Remove frequency domain signals The leading zeros at the beginning and the trailing zeros at the end are used as the remaining part of the extracted raw data. This extracted raw data is then sent to a conventional OFDM receiver for conventional decision-making.

2. The OFDM signal time-frequency cooperative equalization distortion suppression method according to claim 1, characterized in that, The specific process of step three is as follows: For the The data subcarrier modulation symbol sequence corresponding to each OFDM symbol In the sequence The front of the supplement zeros in the sequence Add after There are zeros, and the length of the zero padding satisfies ; like If it is even, then ; like If it is an odd number, then , ; Modulation symbol sequence for data subcarriers After padding with zeros, we get the first... A frequency domain signal vector.

3. The OFDM signal time-frequency cooperative equalization distortion suppression method according to claim 2, characterized in that, The specific process of step five is as follows: For time-domain signals Copying time-domain signals tail One symbol, and add the copied symbol to the time-domain signal. The first symbol before the loop prefix is ​​used as the loop prefix, and the first symbol after the loop prefix is ​​added is the loop prefix. Time-domain signal for: in, Indicates a signal located in the time domain The end The symbol is the added cyclic prefix.

4. The OFDM signal time-frequency cooperative equalization distortion suppression method according to claim 3, characterized in that, The step involves performing weighted interpolation on each frequency domain received signal vector to obtain the weighted interpolated signal vector corresponding to each frequency domain received signal vector; specifically: Construction dimension Receiver frequency domain interpolation matrix The construction method is as follows: in, Representation matrix The Middle Line 1 Column elements, Representation matrix The Middle Line 1 Column elements, Representation matrix The Middle Line 1 The element in the column is set to 0, and all other elements are set to 0; Using frequency domain interpolation matrix For the frequency domain received signal vector Perform a linear transformation, that is, the frequency domain interpolation matrix With frequency domain received signal vector Perform multiplication operations and use the results of the multiplication operations as the weighted interpolated signal vector. .

5. The OFDM signal time-frequency cooperative equalization distortion suppression method according to claim 4, characterized in that, The step of performing MMSE equalization on each weighted interpolated signal vector is as follows: Step 91, constructing the dimension as frequency domain transformation matrix ; Step 92: Based on Discrete-Time Channel Impulse Response Construction dimension is Time-domain channel matrix ; Step 93: Calculate the matrix Frequency domain representation : in, The dimension is The fast Fourier transform matrix, express The conjugate transpose of ; The frequency domain representation of the equivalent channel matrix after frequency domain interpolation is: in, express The inverse matrix, It is the frequency domain representation of the equivalent channel matrix after frequency domain interpolation; Step 94, according to Construction dimension Equalizer coefficient matrix: in, Indicates the average power of the signal. Indicates the average noise power. Represents the identity matrix. express The conjugate transpose of . Represents the equalizer coefficient matrix; Step 95: Interpolate the signal vector in the frequency domain. With equalizer coefficient matrix Multiply, we get OFDM frequency domain signal after point equalization .

6. The OFDM signal time-frequency cooperative equalization distortion suppression method according to claim 5, characterized in that, The time-domain channel matrix for: Among them, matrix The first in Line 1 The elements of the column are: in, Representation matrix The first in Line 1 Column elements, Indicates the number of channel taps. As an intermediate variable, express Divide by The remainder, Indicates the oversampling time of the received signal. The corresponding number Discrete-time impulse response of each channel tap.

7. The OFDM signal time-frequency cooperative equalization distortion suppression method according to claim 6, characterized in that, The frequency domain transformation matrix The first in Line 1 The elements of the column are set to 1, where, All other elements are set to 0.

8. The OFDM signal time-frequency cooperative equalization distortion suppression method according to claim 7, characterized in that, The specific process of step ten is as follows: like If it is even, then from the frequency domain signal The Starting from a single sample point, continuously extract... For each sample, the extracted data will be used as part of the extracted original data. like If it is odd, then from the frequency domain signal The Starting from a single sample point, continuously extract... The data extracted from each sample point will be used as part of the extracted raw data.

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