An intelligent anti-interference method based on interference deletion

Abstract

The present application relates to the field of communication technology, and more particularly to a kind of intelligent anti-interference method based on interference deletion;Including the following steps: S1.to the signal scrambling of sending source data, then the turbo coding of the data after scrambling;S2.turbo coding is carried out to the data block for OFDM modulation;S3.control transmitting end through transmitting frequency hopping;S4.receiving end obtains demodulated data;S5.adjusting is carried out to the demodulated data obtained from S4;S6.the limiting of adjusted signal;S7.getting signal-to-noise ratio mean;S8.according to signal-to-noise ratio threshold, the demodulated data obtained from S4 is screened;S9.turbo decoding and signal descrambling are carried out to the data after interference deletion.The present application has the advantages of simple algorithm, less resource consumption, adaptive adjustment threshold and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of communication technology, in particular to an intelligent anti-interference method based on interference deletion. BACKGROUND

[0002] With the continuous development and innovation of information systems, wireless communication technology has experienced a leap from early simple radio communication to today's highly complex and diversified information systems that use radio as the core transmission medium. These systems are widely used in data link communication, navigation and control, intelligence reconnaissance, and enemy-ally identification, greatly improving the efficiency and flexibility of military, civilian and commercial activities. However, while enjoying the convenience brought by technological progress, wireless communication also faces serious challenges brought by its inherent characteristics.

[0003] Due to the spatial openness of wireless communication, i.e. signals are easily received by any device within the signal coverage range during transmission, the security boundary of information becomes blurred. In addition, the non-cooperative nature of spectrum resources, i.e. limited spectrum resources need to be shared by multiple users, and the lack of central coordination mechanism, leads to competition and conflict for spectrum resources, further exacerbating the uncertainty of information transmission. These factors provide a convenient path for various intentional or unintentional interference sources and non-desired signals to enter the information system, seriously threatening the reliability and security of information transmission.

[0004] In particular, in recent years, with the continuous progress of reconnaissance technology, the intelligent development of interference technology, and the significant improvement of communication equipment performance, the interference means for wireless communication systems has become more efficient, concealed and intelligent. Advanced reconnaissance equipment can accurately locate and analyze communication signals, while intelligent interference systems can dynamically adjust interference strategies according to real-time conditions, effectively weakening or even blocking communication links. In addition, some new network attack methods, such as man-in-the-middle attack, signal injection attack, etc., have posed unprecedented challenges to the security of wireless communication systems.

[0005] In response to the requirements of anti-interference, the industry widely adopts spread spectrum communication system or frequency hopping communication system as an effective means to improve anti-interference capability. These two methods mainly use spread spectrum gain to improve the recognition of signals in noise, or use rapid changes in operating frequency to avoid conflicts with interference signals in the same frequency band, thereby effectively reducing the impact of interference signals on normal communication. However, although these methods have achieved remarkable results in improving anti-interference performance, they mainly focus on physical layer technology implementation, and have not fully realized intelligent processing of received signals at a higher level. SUMMARY

[0006] The application provides an intelligent anti-interference method based on interference deletion, which aims to solve the problem that the prior art has not realized anti-interference processing on received signals.

[0007] To achieve the above object, the technical scheme of the application is as follows:

[0008] The application provides an intelligent anti-interference method based on interference deletion, which comprises the following steps:

[0009] S1. Signal scrambling is performed on the source data, the scrambling sequence is a specific PN code sequence, and then turbo coding is performed on the scrambled data;

[0010] S2. Interleaving is performed on the turbo coded data, and after phase coding modulation, block OFDM modulation is performed;

[0011] S3. The transmitting end is controlled to perform frequency hopping transmission, so as to ensure that the duration of each frequency point covers one OFDM symbol;

[0012] S4. The receiving end performs capture, timing, frequency calibration and OFDM demodulation to obtain demodulated data;

[0013] S5. According to the I and Q signal component sizes and modulation types of the data, certain mapping is performed on the demodulated data obtained from S4, and the I and Q signals of the demodulated signal are adjusted;

[0014] S6. The adjusted signal is amplitude limited, and if the signal of any one of the I and Q paths exceeds the threshold, the signal at this moment is set to zero, so that the large interference signal is deleted in this way;

[0015] S7. The amplitude adjusted data is estimated in terms of OFDM symbols to obtain the signal-to-noise ratio of each OFDM symbol and the average signal-to-noise ratio of all symbols, so as to calculate a first threshold Th1;

[0016] S8. The demodulated data obtained from S4 is screened according to the signal-to-noise ratio threshold, if the signal-to-noise ratio of the OFDM symbol is lower than Th1, a 0 with the same length as the demodulated signal is output; if the signal-to-noise ratio of the OFDM symbol is higher than the first threshold Th1, it is judged whether the signal-to-noise ratio of the OFDM symbol is higher than a second threshold Th2, if yes, the data is output, otherwise, a 0 with the same length as the demodulated signal is output;

[0017] S9. Turbo decoding and signal descrambling are performed on the interference deleted data to obtain the required data.

[0018] Further, the Turbo coding selects a code rate of 1 / 3.

[0019] Further, the OFDM modulation selects to be completed by using IFFT.

[0020] Further, the OFDM demodulation is completed by using FFT.

[0021] Further, the first threshold Th1 is 1 / 4 of the average SNR.

[0022] The present application has the following advantages:

[0023] (1) The present application is based on FH_OFDM system, and uses frequency hopping communication mode to reduce the influence of interference signal on the communication system.

[0024] (2) The present application first limits the amplitude of the demodulated signal to avoid the maximum value caused by interference, which affects the subsequent SNR estimation and ensures the accuracy of SNR calculation.

[0025] (3) The SNR of each OFDM symbol is dynamically calculated according to the actual data, and the average SNR is used as the first threshold. The threshold value is also dynamically changed, which can adapt to different situations.

[0026] (5) The second threshold is a smaller SNR value, which is suitable for the case where all frequency points are interfered, and can avoid the continuous transmission of error data and reduce the processing pressure, and plays a double protection role.

[0027] (6) By comparing the SNR of each OFDM symbol with the threshold, the signal with less interference is intelligently selected, and the performance of turbo code is used to realize the final data recovery.

[0028] (8) Since the intelligent interference deletion method is based on FH_OFDM system, according to the data output by each OFDM symbol to the turbo decoding module, the frequency point of interference can be directly judged.

[0029] (9) The calculation of SNR has small amount of calculation, and only needs a small amount of resources to complete the SNR estimation and calculation on the basis of the original communication system. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of the drawings shown.

[0031] Figure 1 is the flow chart of the method disclosed by the present application; in the figure, Y branch is the branch higher than the threshold, and the output is the demodulated data; N branch is the branch lower than the threshold, and the output is the 0 equal to the signal.

[0032] Figure 2 is a constellation diagram before BPSK processing.

[0033] Figure 3 is a constellation diagram before QPSK processing.

[0034] Figure 4 is a constellation diagram after BPSK adjustment.

[0035] Figure 5 is a constellation diagram after QPSK adjustment.

[0036] Figure 6 is a flow chart of screening demodulated data according to a signal-to-noise ratio threshold in the present application.

[0037] Figure 7 is a data diagram of a bit error rate simulation experiment in the present application. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0039] It should be noted that if the embodiments of the present application involve directionality indications (such as up, down, left, right, front, back, etc.), the directionality indications are only used to explain the relative positional relationship, movement condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directionality indications also change accordingly.

[0040] In addition, if the embodiments of the present application involve descriptions of “first”, “second”, etc., the descriptions of “first”, “second”, etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features with “first” and “second” can explicitly or implicitly include at least one of the features. In addition, the meaning of “and / or” appearing throughout the text is that it includes three parallel schemes, for example, “A and / or B” includes A scheme, or B scheme, or A and B schemes are satisfied at the same time. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of a person skilled in the art, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist, and is not within the scope of protection claimed by the present application.

[0041] In order to improve the anti-interference ability of the system, aiming at the FH_OFDM system, the application provides an intelligent anti-interference method based on interference deletion, as shown in the figure, comprising the following steps: Figure 1

[0042] S1. Signal scrambling is carried out on the source data, the scrambling sequence is a specific PN code sequence, and then the turbo coding is carried out on the scrambled data.

[0043] Among them, the Turbo coding selects 1 / 3 code rate.

[0044] S2. Interleaving is carried out on the turbo coded data, after phase coding modulation, block OFDM modulation is carried out.

[0045] Among them, the OFDM modulation selects to complete by using IFFT (Inverse Fast Fourier Transform).

[0046] S3. The transmitting end is controlled to transmit frequency hopping, so as to ensure that the duration of each frequency point covers an OFDM symbol; so as to reduce the interference effect by the way of frequency hopping.

[0047] S4. The receiving end obtains the demodulated data by capturing, timing, frequency calibration and OFDM demodulation.

[0048] Among them, the OFDM demodulation is completed by using FFT, and the signal demodulation is completed by using the demodulation mode corresponding to the transmitting end.

[0049] S5. According to the I and Q two-way signal component size and modulation type of the demodulated data, a certain mapping (specifically, since the signal in this process is a vector, direct superposition will lose signal energy, therefore, according to the amplitude and phase of the signal, the signal is mapped to a fixed quadrant) is carried out on the I and Q two-way signals of the demodulated signal.

[0050] S6. The adjusted signal is limited, if the signal of any one of I and Q exceeds the threshold, the signal at this moment is set to zero, and in this way, the large interference signal is deleted first.

[0051] ​Specifically, the above two steps involve adjusting the demodulated data based on the two orthogonal components of the signal. The demodulated signal can be expressed as R(i)=I(i)+1i*Q(i); where R(i) is the demodulated signal, and I(i) and Q(i) are two orthogonal components. abs(I(i)) and abs(Q(i)) are the moduli of the two signal components. First, the large signal is deleted. This operation can be expressed as (abs(I(i))>th)||(abs(Q(i))>th), when R(i)=0, where th is the judgment threshold (this judgment threshold is an empirical value, and the selected limit depends on the bit width limit of subsequent processing). Since large signals are generally generated by external interference signals, resulting in excessive signal energy at that moment, setting the data at that moment to zero can prevent the signal-to-noise ratio from being affected by extreme values ​​and ensure the accuracy of the signal-to-noise ratio calculation.

[0052] In order to avoid the energy loss caused by vector summation, the signal energy is then concentrated. Due to the phase coding adopted, R(i) is currently distributed according to the phase modulation method of the transmitter, such as Figure 2 and 3 shown.

[0053] For BPSK signals, the adjustment method can be expressed as:

[0054] I(n)<0, Rb(n)=-I(n)+1i*Q(n)

[0055] For QPSK signals, the adjustment method can be expressed as:

[0056] abs(I(n))>=abs(Q(n)), I(n)>=0:Rb(n)=I(n)+1i*Q(n);

[0057] abs(I(n))>=abs(Q(n)), I(n)<0:Rb(n)=-I(n)-1i*Q(n);

[0058] abs(I(n))<abs(Q(n)),Q(n)> =0:Rb(n)=-1i*I(n)+Q(n);

[0059] abs(I(n)) <abs(Q(n)),Q(n)<0:Rb(n)=1i*I(n)-Q(n);

[0060] Among them, Rb(n) is the adjusted data. The adjusted signal constellation diagram is as follows Figure 4 and 5 shown.

[0061] S7. The amplitude-adjusted data is used to estimate the signal-to-noise ratio of each OFDM symbol, and the signal-to-noise ratio of each OFDM symbol and the average signal-to-noise ratio of all symbols are obtained to calculate the first threshold Thl.

[0062] The signal-to-noise ratio is calculated as follows. The amplitude-adjusted data Rb(n) is expressed as Rb(n) = X(n) + N(n), where n = 1, 2,..., N; X(n) represents the actual effective signal; N(n) represents random noise, which is selected as additive white Gaussian noise with a mean of 0 for simplification; n represents the signal position; and N represents the length of a single OFDM symbol.

[0063] The signal energy Ps can be approximately expressed as:

[0064]

[0065] wherein, The additive white Gaussian noise property is used.

[0066] The total signal power P can be expressed as:

[0067]

[0068] Therefore, the noise power Pn can be expressed as Pn = P - Ps.

[0069] The signal-to-noise ratio calculation expression is

[0070]

[0071] wherein, fix represents rounding; and c is an adjustment coefficient related to the phase encoding mode. The signal-to-noise ratio of each OFDM symbol is calculated by the formula. Since the number of OFDM blocks sent by the sending module in a single sending is fixed, the average signal-to-noise ratio of the received OFDM symbol in one receiving can be calculated by the receiving end, and the average signal-to-noise ratio is used as the subsequent decision threshold Thl.

[0072] S8. Filtering the demodulated data from S4 according to the signal-to-noise ratio threshold, if the signal-to-noise ratio of the OFDM symbol is lower than Thl, outputting 0 with the same length as the demodulated signal; if the signal-to-noise ratio of the OFDM symbol is higher than the first threshold Thl, judging whether the signal-to-noise ratio of the OFDM symbol is higher than the second threshold Th2, outputting data if yes, otherwise outputting 0 with the same length as the demodulated signal; specifically, filtering the OFDM signal by using the threshold Thl, if the signal-to-noise ratio of the OFDM symbol is lower than Thl, judging that the symbol is obviously interfered, and the data of the symbol does not participate in subsequent processing. If the signal-to-noise ratio of the OFDM symbol is higher than the first threshold Thl, judging whether the signal-to-noise ratio of the OFDM symbol is higher than the second threshold Th2, if lower than the threshold Th2, considering that all the frequency points of the FH_OFDM system are interfered, and selecting the signal with better signal quality.

[0073] Since the interfered OFDM symbol is deleted, the influence of the error data on turbo decoding is avoided. Since the turbo encoding is followed by interleaving processing, there is a probability to restore the source data after deleting the interfered signal.

[0074] The first threshold Thl is a threshold obtained according to the mean value of the signal-to-noise ratio, and is generally 1 / 4 of the mean value of the signal-to-noise ratio. The second threshold Th2 is an empirical value, and a very small signal-to-noise ratio is selected.

[0075] The first threshold is an adaptive threshold, and the data less affected by the interference is selected according to the signal-to-noise ratio, and the seriously interfered signal is deleted, so as to ensure the correctness of turbo decoding. If the seriously interfered signal participates in turbo decoding, the performance of turbo decoding is even decreased.

[0076] For the second threshold, the case that all the frequency points are interfered is considered, at this time, the signal-to-noise ratio is relatively poor, the interference deletion effect brought by the first threshold is poor, and all the OFDM symbols with low signal-to-noise ratio are directly deleted according to the second threshold, so as to ensure the integrity of the interference deletion. The flow is as shown in Figure 6 .

[0077] Specifically, two scenarios are considered: the first scenario is that occasionally a few frequency points are interfered, the signal-to-noise ratio of the interfered frequency points is low, and the interfered frequency points can be deleted by Thl; the second scenario is that all the communication frequency points are interfered, at this time, the estimated signal-to-noise ratio of all the frequency points is very low, and the signal with larger signal-to-noise ratio is found for subsequent processing; therefore, TH2 needs to select a lower value, which is an empirical value, and the value has no size relationship with THl.

[0078] S9. Turbo decoding and signal descrambling are performed on the data after interference deletion, and the required data is obtained; the same PN code sequence as the sending end is used for descrambling operation.

[0079] The simulation parameters are as follows: sampling rate 12.8MHz, sending source data 256bit, using 1 / 3 code rate Turbo coding, DBPSK modulation after coding, and data is divided into 4 OFDM symbols. The BER performance under different OFDM symbol interference deletion at the receiving end is simulated respectively. Figure 7 It can be seen from the simulation results that in the FH_OFDM system, the source signal can be recovered even if some OFDM symbols are interfered, and the system has good anti-interference ability, but the recovery ability decreases with the increase of deleted OFDM symbols.

[0080] The above embodiments can be extended to FH_OFDM communication systems with different modulation modes, and have the advantages of simple algorithm, less resource consumption, adaptive threshold adjustment, etc.

[0081] The above only describes optional embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation, direct / indirect application in other related technical fields within the inventive concept of the present application and the content of the specification and drawings are included in the patent protection scope of the present application.

Claims

1. An intelligent anti-jamming method based on interference deletion, characterized in that, The method comprises the following steps: S1. Signal scrambling is performed on the source data, and the scrambling sequence is a specific PN code sequence, and then turbo coding is performed on the scrambled data; S2. Interleaving is performed on the turbo coded data, and after phase coding modulation, block OFDM modulation is performed; S3. The transmitting end is controlled to perform frequency hopping transmission, so as to ensure that the duration of each frequency point covers one OFDM symbol; S4. The receiving end obtains the demodulated data through capturing, timing, frequency calibration, and OFDM demodulation; S5. According to the I and Q signal components and the modulation type of the data, the I and Q signals of the demodulated data are mapped and adjusted; S6. The adjusted signal is limited, and if the signal of any one of the I and Q channels exceeds the threshold, the signal at this moment is set to zero, so as to delete the large interference signal in this way; S7. The signal-to-noise ratio of the amplitude-adjusted data is estimated in OFDM symbols, and the signal-to-noise ratio of each OFDM symbol and the average signal-to-noise ratio of all symbols are obtained, so as to calculate a first threshold Th1; S8. The demodulated data obtained from S4 is screened according to the signal-to-noise ratio threshold, if the signal-to-noise ratio of the OFDM symbol is lower than Th1, 0 with the same length as the demodulated signal is output, if the signal-to-noise ratio of the OFDM symbol is higher than the first threshold Th1, it is judged whether the signal-to-noise ratio of the OFDM symbol is higher than a second threshold Th2, if yes, the data is output, otherwise, 0 with the same length as the demodulated signal is output; S9. Turbo decoding and signal descrambling are performed on the interference-removed data, and the required data is obtained.

2. The intelligent anti-jamming method based on interference cancellation according to claim 1, characterized in that: The turbo coding selects 1 / 3 code rate.

3. The intelligent anti-jamming method based on interference cancellation according to claim 1, characterized in that: The OFDM modulation is completed by using IFFT.

4. The intelligent anti-jamming method based on interference cancellation according to claim 1, characterized in that: The OFDM demodulation is completed by using FFT.

5. The intelligent anti-jamming method based on interference cancellation according to claim 1, characterized in that: The first threshold Th1 is 1 / 4 of the average signal-to-noise ratio.

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