CN111669192B - Method for identifying and suppressing short-time pulse interference in OFDM signal - Google Patents

Method for identifying and suppressing short-time pulse interference in OFDM signal Download PDF

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CN111669192B
CN111669192B CN202010544529.5A CN202010544529A CN111669192B CN 111669192 B CN111669192 B CN 111669192B CN 202010544529 A CN202010544529 A CN 202010544529A CN 111669192 B CN111669192 B CN 111669192B
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谢映海
李宏文
李先怀
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Zhonghui Microelectronics Co ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
    • H04B1/1027—Means associated with receiver for limiting or suppressing noise or interference assessing signal quality or detecting noise/interference for the received signal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
    • H04J11/0023—Interference mitigation or co-ordination
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2614—Peak power aspects
    • H04L27/2623—Reduction thereof by clipping

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Abstract

A method for identifying and suppressing short-time pulse interference in OFDM signals comprises the steps that after a receiving end receives signals, a cyclic prefix is removed, Fourier transform is carried out to obtain frequency domain signals, and energy values of the frequency domain signals of OFDM symbols and energy ratios and mean square errors of the frequency domain signals of adjacent OFDM symbols are calculated; sorting the energy values of the frequency domain signals of the OFDM symbols from large to small, wherein the OFDM symbols arranged in the second half are OFDM symbols which are not subjected to pulse interference; for a certain OFDM symbol which is not subjected to pulse interference, judging whether two adjacent OFDM symbols are subjected to pulse interference or not; if the interfered OFDM symbols exist, denoising all the interfered OFDM symbols, and replacing the original time domain signals of the OFDM symbols with the denoised time domain signals; and carrying out denoising processing on the interfered OFDM symbols to obtain a new received signal, and carrying out channel estimation and decoding on the new received signal by a receiving end and reporting.

Description

Method for identifying and suppressing short-time pulse interference in OFDM signal
Technical Field
The invention belongs to the technical field of signal processing, and particularly relates to a method for identifying and inhibiting short-time pulse interference in an OFDM signal.
Background
Orthogonal Frequency Division Multiplexing (OFDM) has become a communication technology used in many wired or wireless communication systems due to its high spectrum utilization efficiency. In the communication process, the communication system is inevitably affected by various types of interference, short-time pulse interference is a common interference mode, and is more common in wireless communication systems, such as vehicle-mounted communication, smart grid communication, underwater communication, cellular communication and the like. The sources of impulse interference are various, including ignition devices of automobiles, switches of electrical equipment, lightning in the atmosphere, and the like.
The pulse interference has the characteristics of random burst, short duration, high interference amplitude and the like in a time domain, for the short-time pulse interference, the conventional coping strategy is that a signal sending party adopts channel interleaving and channel coding, and the core mechanism of the method is to improve the decoding performance by dispersing and correcting continuous error information caused by the short-time pulse. However, for the communication system adopting the OFDM system, in the process of performing fourier transform on the received signal, the energy of the pulse interference signal occupying a small proportion in the time domain will be spread to all the frequency domain signals, thereby causing a decoding error in a large area, causing the decoding performance of the received signal to be sharply reduced, and causing more serious performance attenuation than that of other single carrier communication systems; in addition, if the impulse interference signal is located right on the OFDM symbol carrying the pilot signal, the accuracy of channel estimation of the symbol and some symbols nearby the symbol is also seriously affected, and the signal receiving performance is further deteriorated. Therefore, how to suppress the impulse interference in the OFDM system has become a hot research point in the communication field in recent years.
Since the short-time pulse interference signal causes a local signal of the communication signal to have a large amplitude, it is an effective method to perform energy suppression of the pulse interference signal by using a threshold, but since the OFDM signal has a high peak-to-average ratio in the time domain, and factors such as multipath transmission of the signal on the channel, time-varying property of the wireless channel, and noise in the receiver cause large interference to the existence of the pulse interference and the location of the time domain position, it is difficult to obtain an optimal threshold calculation result.
Disclosure of Invention
The invention aims to provide a method for identifying and inhibiting short-time pulse interference in an OFDM signal, which can improve the decoding performance of a received signal.
In order to achieve the purpose, the invention adopts the following technical solutions:
a method for identifying and suppressing short-time pulse interference in OFDM signals comprises the following steps:
s1, identifying impulse interference;
a. a receiving end receives a signal, the received signal contains K OFDM symbols, a time domain signal is obtained after a cyclic prefix of the received signal is removed, Fourier transform is carried out on the time domain signal to obtain a corresponding frequency domain signal, and energy values of the frequency domain signal of the K OFDM symbols are respectively calculated;
b. sequentially calculating the energy ratio and the mean square error value between the frequency domain signals of two adjacent OFDM symbols from the 1 st OFDM symbol;
c. sequencing the energy values of the frequency domain signals of the K OFDM symbols from large to small, and judging the OFDM symbols arranged in the second half order as the OFDM symbols which are not subjected to pulse interference;
d. based on the OFDM symbols judged not to be subjected to impulse interference, the rest OFDM symbols not judged are judged, whether the symbols subjected to impulse interference exist is judged, and the judgment process is as follows:
for a certain OFDM symbol which is judged not to be subjected to pulse interference, respectively judging whether two adjacent OFDM symbols are subjected to pulse interference, and judging whether the OFDM symbol positioned on the left side of the OFDM symbol which is not subjected to pulse interference is subjected to pulse interference under the conditions that:
Figure GDA0002579618690000021
the conditions for judging whether the OFDM symbol located at the right side of the OFDM symbol which is not subjected to the impulse interference is:
Figure GDA0002579618690000022
in the formulakRepresenting the energy ratio, MSE, between the frequency domain signals of two adjacent OFDM symbolskRepresenting the mean square error value between the frequency domain signals of two adjacent OFDM symbols, wherein C is a judgment threshold value;
repeating the judging process until all the OFDM symbols judged not to be subjected to pulse interference have no undetermined symbol on the left side and the right side;
s2, an interference suppression step; if all the K OFDM symbols received by the receiving end are judged to be non-interference symbols, the signal receiving is considered to be failed, the result of the receiving failure is reported, if the received OFDM symbols have the OFDM symbols judged to be interference, the impulse interference suppression is carried out on all the OFDM symbols judged to be interference, and the steps are as follows:
for a certain OFDM symbol judged to have interference, performing peak clipping and denoising processing according to the following method:
Figure GDA0002579618690000031
in the formulacTo de-noise the threshold, sc,nAn nth value representing a c-th OFDM symbol in time domain,
Figure GDA0002579618690000032
representing the denoised time domain signal of the OFDM symbol judged to have interference, and the denoised time domain signal
Figure GDA0002579618690000033
Replacing the original time domain signal of the OFDM symbol judged to have interference;
and all the OFDM symbols judged to have interference are subjected to denoising processing to obtain new received signals, the receiving end carries out channel estimation and channel decoding on the new received signals again, and decoding results are reported.
More specifically, when all the left and right sides of the OFDM symbol decided as not subject to impulse interference have no undetermined OFDM symbol, but there still exists an undetermined OFDM symbol, for a certain undetermined OFDM symbol, it is assumed to be the a-th OFDM symbol, and the decision is made according to the following decision conditions:
Figure GDA0002579618690000034
in the formula PaIs the energy value, P, of the frequency domain signal of the a-th OFDM symbolbIs the energy value of the frequency domain signal of the b-th OFDM symbol, the b-th OFDM symbol is the OFDM symbol which is judged not to be subjected to impulse interference and has the smallest distance with the a-th OFDM symbol on the time axis, Sa,nN-th value, S, representing the a-th OFDM symbol in the frequency domainb,nRepresents the nth value of the b-th OFDM symbol in the frequency domain.
More specifically, the mean square error value between the frequency domain signals of two adjacent OFDM symbols
Figure GDA0002579618690000035
Sk,nRepresenting the nth value of the kth OFDM symbol in the frequency domain.
More specifically, the determination threshold C is equal to 2 times the minimum value of all the mean square error values.
According to the technical scheme, the method introduces the short-time pulse interference signal identification and inhibition in the signal processing process of the signal receiving end, comprehensively identifies the existence and the time domain position of the short-time pulse interference signal in the received signal based on the energy ratio of the frequency domain signals of adjacent OFDM symbols and the change situation of the mean square error value of the frequency domain signals with high accuracy, and accordingly realizes the pulse interference energy inhibition based on the adaptive threshold value, thereby improving the decoding performance of the received signal.
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In order to illustrate the embodiments of the present invention more clearly, the drawings that are needed in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings can be obtained by those skilled in the art without inventive effort.
Fig. 1 is a schematic diagram of an undecided OFDM symbol existing between two OFDM symbols determined to have interference;
FIG. 2 is a graph of the amplitude of a received time domain signal when simulating the method of the present invention;
FIG. 3 is a graph of energy ratio between adjacent symbols of 16 OFDM symbols when the method of the present invention is simulated;
fig. 4 is a graph of the MSE values between adjacent symbols of 16 OFDM symbols when the method of the present invention is simulated;
FIG. 5 is a diagram of the denoising and limiting threshold value obtained by the method of the present invention.
Detailed Description
In order to make the aforementioned and other objects, features and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
For an OFDM communication system using phase modulation (PSK), one OFDM symbol has N subcarriers, and its transmission signal in the frequency domain is X ═ X (X)1,X2,…,XN)T，(·)TThe method is characterized in that vector transposition is represented, a frequency domain signal X of a sending end is subjected to inverse Fourier transform, and then is converted into an OFDM signal X (F X) X (X) on a time domain1,x2,…,xN) Wherein F denotes the normalized discrete fourier transform matrix, and F denotes the conjugate transpose operation of the matrix F. The time domain signal x at the transmitting end is recorded as a cyclic prefix signal with the length of M after being inserted into the cyclic prefix
Figure GDA0002579618690000041
Will signal
Figure GDA0002579618690000042
Sending the data into a channel for transmission.
Receiving signal received by receiving end
Figure GDA0002579618690000051
Where H denotes a channel matrix, i denotes a glitch signal, and w denotes noise satisfying a gaussian distribution. And after the cyclic prefix of the received signal R is removed, Fourier transform is carried out to obtain a frequency domain signal R ═ Lambda X + Fi + Fw of the receiving end, and Lambda is a diagonal matrix.
As can be seen from the expression of the frequency domain signal R at the receiving end, although the short-time pulse interference signal i has a short duration in the time domain, when the receiving end performs fourier transform on the received signal without performing denoising, the pulse interference energy will be spread to all the frequency domain signals, thereby causing degradation of signal decoding performance.
Theoretically, since a short-time pulse interference signal i can cause a large number of points with large amplitude at the local position of the received signal in the time domain, performing peak clipping processing on the signal in this region is a simple and effective denoising mechanism. However, in the practical application process, the following problems must be solved:
1. the OFMD signal has a peak-to-average ratio characteristic, so that the time domain transmission signal of the OFMD signal is likely to have amplitude fluctuation, and the judgment of the existence of pulse interference is influenced;
2. multipath transmission of the signal and receiver noise can further aggravate the amplitude fluctuation condition of the received signal;
3. the wireless channel generally has strong time variability, and the occurrence frequency and the instantaneous amplitude of the pulse signal are both random processes, so that the fixed threshold-based denoising mechanism has poor flexibility and an undesirable denoising effect;
4. under the condition that the channel condition changes rapidly, if the signal length is long, the fading condition difference of signals with far difference on the time axis is large, so that under the condition of not suffering from pulse interference, different OFDM symbols can also have obvious energy fluctuation conditions, and therefore, the accuracy of judging whether a receiving symbol suffers from pulse interference by singly depending on the energy magnitude is poor.
For an OFDM communication system which is possibly interfered by short-time pulse and adopts phase modulation, one OFDM symbol which is not interfered by the pulse and one OFDM symbol which is interfered by the pulse have difference in the amplitude of a frequency domain signal. At the receiving end, if the CRC detection result of a packet signal received at a certain time is wrong, the packet signal is considered to be possibly interfered by the short pulse, and the short pulse interference is identified and noise suppression is carried out on the packet signal.
The method for identifying and suppressing glitches in OFDM signals of the present invention is further described below, and the method of the present invention includes the following steps:
s1, identifying impulse interference;
a. the receiving signal received by the receiving end contains K OFDM symbols (K is more than or equal to 2), and the time domain signal is obtained after the cyclic prefix of the receiving signal is removed
Figure GDA0002579618690000061
Fourier transform is carried out on the time domain signal s to obtain a corresponding frequency domain signal
Figure GDA0002579618690000062
Respectively calculating the energy value P ═ P of the frequency domain signals of K OFDM symbols1,P2,…,PK]Energy value of frequency domain signal of kth OFDM symbol
Figure GDA0002579618690000063
Sk,nAn nth value representing a kth OFDM symbol in a frequency domain;
b. taking 1 OFDM symbol as a basic processing unit, and respectively calculating energy ratios R between frequency domain signals of two adjacent OFDM symbols from the 1 st OFDM symbolkAnd calculating the mean square error value MSE between the frequency domain signals of two adjacent OFDM symbolskMean square error value MSE between frequency domain signals of two adjacent OFDM symbolskThe average difference between the frequency domain signals of the two OFDM symbols (the frequency domain signal of the kth OFDM symbol and the frequency domain signal of the (k + 1) th OFDM symbol) is expressed to some extent, and a larger value indicates a larger difference between the two signals; if two adjacent OFDM symbols are not subjected to pulse interference, and the adjacent time is close, the fading values of the two symbols on the same subcarrier are relatively close, and the corresponding MSEkWill be relatively small, if only one of the two signals is pulsed, the corresponding MSEkRelatively large, if both signals are pulsed, taking into account the non-correlation of the interfering signals on the different signals, the corresponding MSEkShould also be relatively large;
Figure GDA0002579618690000064
c. the energy of the frequency domain signals of the K OFDM symbols is sequenced from large to small, and considering that the pulse signals have the sparse characteristic in the time domain, only the OFDM symbols with lower proportion in the received signals can be considered to be possibly subjected to pulse interference, so that the energy of the frequency domain signals of the K OFDM symbols is sequenced from large to small, and therefore the energy of the frequency domain signals of the K OFDM symbols is sequenced from small to largeAfter sorting from large to small, the OFDM symbols arranged in the second half are judged as OFDM symbols which are not subjected to impulse interference, the OFDM symbols are numbered, and Index _ No [ I ]1,I2,…,IK/2]；
d. Based on the OFDM symbols judged to be not subjected to impulse interference, the other half of the OFDM symbols not judged (i.e. the OFDM symbols ranked in the first half after descending order) are judged, and whether the symbols subjected to impulse interference exist is judged, wherein the judgment process is as follows:
for 1 OFDM symbol determined not to be subjected to impulse interference (assuming that the OFDM symbol not subjected to impulse interference is the kth OFDM symbol), respectively determining whether two OFDM symbols adjacent thereto are subjected to impulse interference, and for an OFDM symbol located on the left side of the OFDM symbol not subjected to impulse interference (the kth-1 OFDM symbol), determining whether they are subjected to impulse interference under the condition:
Figure GDA0002579618690000071
for the OFDM symbol (the (k + 1) th OFDM symbol) located on the right side of the OFDM symbol that is not subjected to impulse interference, the condition for determining whether it is subjected to impulse interference is as follows:
Figure GDA0002579618690000072
in the formulakRepresents the ratio between the energy value of the frequency domain signal of the (k + 1) th OFDM symbol and the energy value of the frequency domain signal of the (k) th OFDM symbol, i.e. the energy ratio R between the frequency domain signals of two adjacent OFDM symbolsk，MSEkRepresents the mean square error value between the frequency domain signals of the kth OFDM symbol and the (k + 1) th OFDM symbol, i.e. the mean square error value between the frequency domain signals of two adjacent OFDM symbols, Dk-1Denotes the judgment result of the k-1 th OFDM symbol, Dk+1Representing the judgment result of the (k + 1) th OFDM symbol, wherein C is a judgment threshold value; more specifically, the determination threshold C is equal to 2 times the minimum value of the K-1 calculated mean square error values, i.e., C is 2 × Min (MSE)1,MSE2,...,MSEK-1) (ii) a By adopting the judging method, all the OFDM symbols which are not judged are judged until all the OFDM symbols which are judged not to be subjected to pulse interferenceNeither the left nor the right of the scrambled OFDM symbol has an undetermined symbol.
After the above decision process is completed, there may still exist some symbols which are still undetermined, that is, undetermined OFDM symbols located between two OFDM symbols which are determined to have interference (as shown in fig. 1), and for a certain undetermined OFDM symbol, it is assumed to be the a-th OFDM symbol, and the decision is performed according to the following determination conditions:
Figure GDA0002579618690000081
in the formula PaIs the energy value, P, of the frequency domain signal of the a-th OFDM symbolbIs the energy value of the frequency domain signal of the b-th OFDM symbol, the b-th OFDM symbol is the OFDM symbol which is judged to be non-interference and has the smallest distance with the a-th OFDM symbol on the time axis, Sa,nN-th value, S, representing the a-th OFDM symbol in the frequency domainb,nRepresents the nth value of the b-th OFDM symbol in the frequency domain.
S2, an interference suppression step; if all the K OFDM symbols received by the receiving end are judged to be non-interference symbols, the signal receiving is considered to be failed, the result of the receiving failure is reported, and if interfered OFDM symbols exist, the pulse interference suppression is sequentially executed on the interfered OFDM symbols, and the method comprises the following steps:
for a certain OFDM symbol which is determined to have interference, assuming that the OFDM symbol is the c-th OFDM symbol, the OFDM symbol is determined according to the d-th OFDM symbol which is not interfered by the impulse, that is, in the sub-step d of the impulse interference identification step, the c-th OFDM symbol is determined to have interference through the d-th OFDM symbol, and the d-th OFDM symbol is a determined symbol corresponding to the c-th OFDM symbol;
according to the above decision condition, when an OFDM symbol has interference, the ratio of the energy value of the interfered OFDM symbol to the energy value of the non-interfering OFDM symbol is greater than 2, i.e. the ratio
Figure GDA0002579618690000082
Here, it can be considered that the excess energy is brought by the impulse interference signal, and then the noise is removed by setting the noise for the interfered OFDM symbol in the time domainIn the threshold mode, the amplitude of the signal is subjected to peak clipping and denoising processing to remove the energy of the pulse interference signal, and the method comprises the following steps:
Figure GDA0002579618690000083
in the formulacTo de-noise the threshold, sc,nAn nth value representing a c-th OFDM symbol in time domain,
Figure GDA0002579618690000084
representing a denoised time domain signal of the OFDM symbol judged to have interference; more specifically, the denoising threshold ΔcArranged to denoise a certain OFDM symbol decided to have interference
Figure GDA0002579618690000085
Is substantially the same as the energy value of its corresponding decision symbol (the d-th OFDM symbol that is not interfered by the pulse), i.e. the energy value of the decision symbol(s) is substantially the same as the energy value of the decision symbol(s) that are not interfered by the pulse(s)'
Figure GDA0002579618690000086
Using de-noised time-domain signals
Figure GDA0002579618690000091
And replacing the original time domain signal of the OFDM symbol to obtain a new received signal, carrying out channel estimation (if the interference signal has a symbol carrying a pilot signal) and channel decoding on the new received signal by the receiving end again, and reporting a decoding result.
As can be seen from the glitch recognition step, the design idea of the glitch recognition of the present invention is that, although the glitch has random burstiness, but it has sparseness on the time axis, so that the proportion of symbols interfered by the short pulse is low in one packet signal transmission (if it is high, even if it is correctly identified and noise threshold suppression is performed, it will exceed the error correction capability of general channel coding, and the result of decoding error cannot be changed), so that the half of symbols with smaller received signal energy are not interfered by default, and then, the characteristics of the frequency domain fading coefficients of the subcarriers with the same adjacent symbols are compared to be similar, and whether the symbol is interfered by the pulse is judged by utilizing the energy ratio and the mean square error value between the interference-free symbol and the symbol to be judged which are closer to each other on the time axis, so that the existence of the pulse interference and the high accuracy of the judgment of the time domain position by the algorithm are ensured.
In the interference suppression step, the basic idea of the denoising method is to use the energy of a symbol adjacent to the interference-free symbol as a reference to perform amplitude peak clipping processing on the area signal subjected to the impulse interference, and the energy value of the processed new signal is the same as that of the interference-free signal, so that the signal energy of the impulse interference is suppressed to the maximum extent, the channel estimation and decoding influence of the interference-free signal by the interference-free signal is reduced, and the overall receiving performance of the signal is improved.
The simulation tool of MATLAB software is used for verifying the pulse interference identification and the adaptive threshold denoising effect of the method.
The simulated signal parameters are: BPSK modulation is adopted, the format of subcarriers is 512, the cycle length is 1/8 symbols, 16 OFDM symbols are sent by a packet signal once, the channel is an AWGN channel, the packet signal is interfered by pulse interference signals with the length being 5% of the sent signal respectively at two positions in the time domain, the interference signals meet Gaussian distribution, the signal-to-noise ratio of an interference-free area is 0dB, and the signal-to-noise ratio of an area subjected to pulse interference is-8 dB and-10 dB. The amplitude of the received time domain signal interfered with 2 short pulses is shown in fig. 2, where the start positions of the interference signals are 2000 and 7000, respectively.
For the above signal, the case of the energy ratio between adjacent symbols of 16 OFDM symbols is shown in fig. 3, and the case of the MSE value between adjacent symbols of 16 OFDM symbols is shown in fig. 4. As can be seen from the results of fig. 3 and 4, two short pulse interference signals in the received signal cause local maxima and local minima in the energy ratio and MES values between adjacent symbols, while the correlation values are substantially the same between those non-interfering symbols. FIG. 5 is a diagram of the denoising and limiting threshold value obtained by the method of the present invention. According to the simulation results, compared with non-interference symbols, the short-time pulse interference signal can cause the difference of the energy ratio and the MSE value between the non-interference symbol and the interference symbol, and the method for comprehensively identifying the interference based on the two characteristics has stronger adaptability, thereby ensuring the high accuracy of the judgment method.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (4)

1. A method for identifying and suppressing glitches in an OFDM signal, comprising the steps of:
s1, identifying impulse interference;
a. a receiving end receives a signal, the received signal contains K OFDM symbols, a time domain signal is obtained after a cyclic prefix of the received signal is removed, Fourier transform is carried out on the time domain signal to obtain a corresponding frequency domain signal, and energy values of the frequency domain signal of the K OFDM symbols are respectively calculated;
b. sequentially calculating the energy ratio and the mean square error value between the frequency domain signals of two adjacent OFDM symbols from the 1 st OFDM symbol;
c. sequencing the energy values of the frequency domain signals of the K OFDM symbols from large to small, and judging the OFDM symbols arranged in the second half order as the OFDM symbols which are not subjected to pulse interference;
d. based on the OFDM symbols judged not to be subjected to impulse interference, the rest OFDM symbols not judged are judged, whether the symbols subjected to impulse interference exist is judged, and the judgment process is as follows:
for a certain OFDM symbol which is judged not to be subjected to pulse interference, respectively judging whether two adjacent OFDM symbols are subjected to pulse interference, and judging whether the OFDM symbol positioned on the left side of the OFDM symbol which is not subjected to pulse interference is subjected to pulse interference under the conditions that:
Figure FDA0002540102660000011
the conditions for judging whether the OFDM symbol located at the right side of the OFDM symbol which is not subjected to the impulse interference is:
Figure FDA0002540102660000012
in the formulakRepresenting the energy ratio, MSE, between the frequency domain signals of two adjacent OFDM symbolskRepresenting the mean square error value between the frequency domain signals of two adjacent OFDM symbols, wherein C is a judgment threshold value;
repeating the judging process until all the OFDM symbols judged not to be subjected to pulse interference have no undetermined symbol on the left side and the right side;
s2, an interference suppression step; if all the K OFDM symbols received by the receiving end are judged to be non-interference symbols, the signal receiving is considered to be failed, the result of the receiving failure is reported, if the received OFDM symbols have the OFDM symbols judged to be interference, the impulse interference suppression is carried out on all the OFDM symbols judged to be interference, and the steps are as follows:
for a certain OFDM symbol judged to have interference, performing peak clipping and denoising processing according to the following method:
Figure FDA0002540102660000021
in the formulacTo de-noise the threshold, sc,nAn nth value representing a c-th OFDM symbol in time domain,
Figure FDA0002540102660000022
representing the denoised time domain of the OFDM symbol determined to have interferenceSignals, using de-noised time-domain signals
Figure FDA0002540102660000023
Replacing the original time domain signal of the OFDM symbol judged to have interference;
and all the OFDM symbols judged to have interference are subjected to denoising processing to obtain new received signals, the receiving end carries out channel estimation and channel decoding on the new received signals again, and decoding results are reported.
2. The method of claim 1, wherein the method further comprises: when all the left and right sides of the OFDM symbols which are judged not to be subjected to impulse interference have no undetermined OFDM symbol, but there still exists an undetermined OFDM symbol, regarding a certain undetermined OFDM symbol, it is assumed to be the a-th OFDM symbol, and the judgment is performed according to the following judgment conditions:
Figure FDA0002540102660000024
in the formula PaIs the energy value, P, of the frequency domain signal of the a-th OFDM symbolbIs the energy value of the frequency domain signal of the b-th OFDM symbol, the b-th OFDM symbol is the OFDM symbol which is judged not to be subjected to impulse interference and has the smallest distance with the a-th OFDM symbol on the time axis, Sa,nN-th value, S, representing the a-th OFDM symbol in the frequency domainb,nRepresents the nth value of the b-th OFDM symbol in the frequency domain.
3. The method of claim 1, wherein the method further comprises: mean square error value between frequency domain signals of two adjacent OFDM symbols
Figure FDA0002540102660000031
Sk,nRepresenting the nth value of the kth OFDM symbol in the frequency domain.
4. The method of claim 1, wherein the method further comprises: the decision threshold C is equal to 2 times the minimum of all the mean square error values.
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