Unmanned aerial vehicle identification method and device, and storage medium

Abstract

The invention relates to the technical field of unmanned aerial vehicles, and discloses an unmanned aerial vehicle identification method, which comprises the following steps: acquiring a to-be-searched sequence of OFDM signals of an unmanned aerial vehicle; generating a first ZC search sequence; determining a first to-be-searched sequence from the to-be-searched sequences; determining the position of an effective data sequence of the first pilot symbol sequence according to the first ZC search sequence; determining effective data sequences of the second pilot symbol sequence and the third pilot symbol sequence according to the position of the effective data sequence of the first pilot symbol sequence; generating a plurality of second ZC search sequences; respectively determining root values of the second pilot symbol sequence and the third pilot symbol sequence according to the plurality of second ZC search sequences and effective data sequences of the second pilot symbol sequence and the third pilot symbol sequence; and when the root value of the second pilot symbol sequence is the same as the root value of the third pilot symbol sequence, identifying the unmanned aerial vehicle according to the root value of the second pilot symbol sequence. In this way, the accuracy of unmanned aerial vehicle identification is improved.

Description

Technical Field

[0001] This application relates to the field of unmanned aerial vehicle (UAV) technology, specifically to a UAV identification method, device, and storage medium. Background Technology

[0002] LTE-OFDM type drones refer to drones that use LTE (Long Term Evolution) communication technology and OFDM (Orthogonal Frequency Division Multiplexing) modulation technology. These drones typically use the Zadoff-Chu sequence as a reference signal to achieve synchronization between the drone and ground control stations or other network elements.

[0003] Existing technologies typically utilize the autocorrelation properties of ZC sequences to perform correlation searches on OFDM signals in order to identify drones emitting OFDM signals. However, relying solely on a single ZC sequence for drone identification is insufficient if other similar signals or signals using the same ZC sequence as a reference signal exist in the environment. This can lead to different drones being identified as the same drone, reducing the accuracy of drone identification. Summary of the Invention

[0004] In view of the above problems, embodiments of this application provide a drone identification method, device and storage medium, which improves the accuracy of drone identification.

[0005] According to one aspect of the embodiments of this application, a method for identifying unmanned aerial vehicles (UAVs) is provided. The method includes: acquiring a search sequence of an OFDM signal from the UAV, wherein the OFDM signal includes multiple symbols, and the search sequence includes a first pilot symbol sequence, a second pilot symbol sequence, and a third pilot symbol sequence, wherein the first, second, and third pilot symbol sequences correspond to different symbols of the OFDM signal, the first and second pilot symbol sequences are separated by a first symbol length, and the first and third pilot symbol sequences are separated by a second symbol length; generating a first ZC search sequence based on a preset length and a preset root value; determining a first search sequence from the search sequence based on the symbol positions of the symbols corresponding to the first pilot symbol sequences in the OFDM signal; performing correlation detection on the first search sequence using the first ZC search sequence to determine the position of the valid data sequence of the first pilot symbol sequence; and determining the position of the valid data sequence of the first pilot symbol sequence based on the first pilot symbol sequence. The effective data sequence of the symbol sequence is determined from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the first symbol. The effective data sequence of the third pilot symbol sequence is determined from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the second symbol. Multiple second ZC search sequences are generated based on each root value within a preset length and preset root value range. The root value corresponding to the second ZC search sequence with the largest correlation value with the effective data sequence of the second pilot symbol sequence is determined as the root value of the second pilot symbol sequence. The root value corresponding to the second ZC search sequence with the largest correlation value with the effective data sequence of the third pilot symbol sequence is determined as the root value of the third pilot symbol sequence. When the root value of the second pilot symbol sequence is the same as the root value of the third pilot symbol sequence, the UAV is identified based on the root values ​​of the second and third pilot symbol sequences.

[0006] In one optional approach, the sequence to be searched further includes a fourth pilot symbol sequence, the first symbol length being either the length of a first sub-symbol or a third sub-symbol, and the second symbol length being either the length of a second sub-symbol or a fourth symbol; the first ZC search sequence is used to perform correlation detection on the first sequence to be searched to determine the position of the effective data sequence of the first pilot symbol sequence, further including: determining the largest correlation value among the correlation values ​​of the first ZC search sequence and the first sequence to be searched as a first maximum correlation value; determining the position of the effective data sequence of the first pilot symbol sequence based on the first maximum correlation value; the method further includes: determining a second sequence to be searched and a third sequence to be searched from the sequence to be searched based on the position of the effective data sequence of the first pilot symbol sequence; The search sequence is defined as follows: the second search sequence and the third search sequence correspond to the preceding and following symbols of the first pilot symbol sequence, respectively; the largest correlation value between the first ZC search sequence and the second search sequence is determined as the second maximum correlation value; the largest correlation value between the first ZC search sequence and the third search sequence is determined as the third maximum correlation value; the first power difference between the second maximum correlation value, the third maximum correlation value, and the first maximum correlation value is calculated respectively; if the first power difference between the second maximum correlation value and the first maximum correlation value is less than a first preset power difference, the first symbol length is the first sub-symbol length, the second symbol length is the second sub-symbol length, and the first pilot symbol sequence is used as the basis for the search. The method further includes: determining the effective data sequence of the second pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the first symbol length; determining the effective data sequence of the third pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the second symbol length; and determining the effective data sequence of the third pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the second symbol length. If the first power difference between the third maximum correlation value and the first maximum correlation value is less than the first preset power difference, the first... The symbol length is the third sub-symbol length, the second symbol length is the fourth sub-symbol length, the effective data sequence of the second pilot symbol sequence is determined from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the first symbol length, and the effective data sequence of the third pilot symbol sequence is determined from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the second symbol length, further including: determining the effective data sequence of the second pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the third sub-symbol length; determining the effective data sequence of the third pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the fourth sub-symbol length.

[0007] In one optional approach, the largest correlation value among the correlation values ​​between the first ZC search sequence and the first search sequence is determined as the first maximum correlation value. The position of the effective data sequence of the first pilot symbol sequence is determined based on the first maximum correlation value. This further includes: starting from the first sampling point of the first search sequence, sequentially selecting sampling points of a preset length as first subsequences to obtain multiple first subsequences, wherein in two adjacent first subsequences, the first sampling point of one first subsequence is adjacent to the first sampling point of the other first subsequence; sequentially calculating the correlation value between the first ZC search sequence and each first subsequence to obtain the correlation values ​​corresponding to each of the multiple first subsequences; determining the largest correlation value among the correlation values ​​corresponding to each of the multiple first subsequences as the first maximum correlation value; and determining the first sampling point of the first subsequence corresponding to the first maximum correlation value as the position of the effective data sequence of the first pilot symbol sequence.

[0008] In an optional embodiment, the method further includes: determining the second search sequence as the effective data sequence of the fourth pilot symbol sequence when the first power difference between the second maximum correlation value and the first maximum correlation value is less than the first preset power difference; determining the third search sequence as the effective data sequence of the fourth pilot symbol sequence when the first power difference between the third maximum correlation value and the first maximum correlation value is less than the first preset power difference; determining the position of the effective data sequence of the fourth pilot symbol sequence; selecting sampling points of a continuous preset sequence length as the first sequence, centered on the position of the effective data sequence of the first pilot symbol sequence; selecting sampling points of a continuous preset sequence length as the second sequence, centered on the position of the effective data sequence of the fourth pilot symbol sequence; determining the frequency offset of the search sequence based on the first sequence and the second sequence; performing frequency offset correction on the search sequence based on the frequency offset to obtain the frequency offset-corrected search sequence; determining the effective data sequence of the second pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the first sub-symbol length; and determining the effective data sequence of the second pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the second sub-symbol length. The determination of the effective data sequence of the third pilot symbol sequence from the search sequence based on the sub-symbol length further includes: determining the effective data sequence of the second pilot symbol sequence from the frequency offset corrected search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the first sub-symbol length; determining the effective data sequence of the third pilot symbol sequence from the frequency offset corrected search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the second sub-symbol length; determining the effective data sequence of the second pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the third sub-symbol length; determining the effective data sequence of the third pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the fourth sub-symbol length; further including: determining the effective data sequence of the second pilot symbol sequence from the frequency offset corrected search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the third sub-symbol length; determining the effective data sequence of the third pilot symbol sequence from the frequency offset corrected search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the fourth sub-symbol length.

[0009] In one optional approach, the root value corresponding to the second ZC search sequence with the largest correlation value to the effective data sequence of the second pilot symbol sequence among multiple second ZC search sequences is determined as the root value of the second pilot symbol sequence. This further includes: starting from the first sampling point of the effective data sequence of the second pilot symbol sequence, sequentially selecting sampling points of a preset length as second subsequences to obtain multiple second subsequences, wherein in two adjacent second subsequences, the first sampling point of one second subsequence is adjacent to the first sampling point of the other second subsequence; sequentially calculating the first correlation value between each second ZC search sequence and each second subsequence to obtain the first correlation values ​​corresponding to the multiple second ZC search sequences respectively; determining the second ZC search sequence corresponding to the largest first correlation value among the multiple second ZC search sequences; and determining the root value corresponding to the second ZC search sequence with the largest first correlation value as the second pilot symbol sequence. The process further includes: determining the root value of the third pilot symbol sequence by selecting sampling points of a preset length as third subsequences, starting from the first sampling point of the effective data sequence of the third pilot symbol sequence, obtaining multiple third subsequences, wherein in two adjacent third subsequences, the first sampling point of one third subsequence is adjacent to the first sampling point of the other third subsequence; calculating the second correlation value between each second ZC search sequence and each third subsequence, obtaining the second correlation value corresponding to each of the multiple second ZC search sequences; determining the second ZC search sequence corresponding to the largest second correlation value among the multiple second ZC search sequences; and determining the root value corresponding to the second ZC search sequence corresponding to the largest second correlation value as the root value of the third pilot symbol sequence.

[0010] In one optional embodiment, the method further includes: determining a second subsequence of the largest first correlation value among the first correlation values ​​corresponding to the plurality of second ZC search sequences; determining the second subsequence of the largest first correlation value as the position of the effective data sequence of the second pilot symbol sequence; calculating the position difference between the position of the effective data sequence of the first pilot symbol sequence and the position of the effective data sequence of the second pilot symbol sequence; determining whether the position difference and the first symbol length are less than or equal to a preset difference; if so, performing the step of determining the root value corresponding to the second ZC search sequence of the largest first correlation value as the root value of the second pilot symbol sequence.

[0011] In one optional approach, after determining the second ZC search sequence corresponding to the largest second correlation value among the multiple second correlation values ​​corresponding to the second ZC search sequences, the method further includes: determining the largest second correlation value among the multiple second correlation values ​​corresponding to the second ZC search sequences; calculating a second power difference between the largest second correlation value and the largest first correlation value; determining whether the second power difference is less than or equal to a second preset power difference; if so, performing the step of determining the root value corresponding to the second ZC search sequence corresponding to the largest second correlation value as the root value of the third pilot symbol sequence.

[0012] In one optional embodiment, the method further includes: acquiring the sampling rate and subcarrier spacing of the OFDM signal; calculating the length of the effective data sequence of the search sequence based on the sampling rate and subcarrier spacing; calculating the length of the CP sequence of the search sequence based on the subcarrier spacing; determining the symbol length of the search sequence based on the length of the effective data sequence and the length of the CP sequence; determining the first search sequence from the search sequence based on the symbol position of the symbol corresponding to the first pilot symbol sequence in the OFDM signal, further including: selecting sampling points of consecutive symbol lengths from the search sequence as the first search sequence based on the symbol position of the symbol corresponding to the first pilot symbol sequence in the OFDM signal; and determining the symbol length of the search sequence based on the effective data sequence length of the first pilot symbol sequence. The method further includes determining the effective data sequence of the second pilot symbol sequence from the search sequence based on the position of the sequence and the length of the first symbol, and selecting sampling points of the length of a continuous effective data sequence from the search sequence as the effective data sequence of the second pilot symbol sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the first symbol. The method also includes determining the effective data sequence of the third pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the second symbol, and selecting sampling points of the length of a continuous effective data sequence from the search sequence as the effective data sequence of the third pilot symbol sequence.

[0013] According to another aspect of the embodiments of this application, an electronic device is provided, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the drone identification method provided in any of the above embodiments.

[0014] According to another aspect of the embodiments of this application, a computer-readable storage medium is provided, on which a computer program is stored, which, when executed by a processor, implements the drone identification method provided in any of the above embodiments.

[0015] This application embodiment determines the first search sequence from the search sequence of the OFDM signal by determining the symbol position of the corresponding symbol in the first pilot symbol sequence. Then, by generating a first ZC search sequence and performing correlation detection on the first search sequence, the position of the effective data sequence of the first pilot symbol sequence can be determined. Next, based on the characteristic that the first pilot symbol sequence is separated from the second and third pilot symbol sequences by a first symbol length and a second symbol length, respectively, in the search sequence of the UAV's OFDM signal, the second pilot symbol sequence can be determined from the search sequence according to the position of the effective data sequence of the first pilot symbol sequence and the first symbol length. The system first obtains the effective data sequence of the symbol sequence and determines the effective data sequence of the third pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the second symbol length. Then, it generates multiple second ZC search sequences and determines the root of the second pilot symbol sequence and the root value of the third pilot symbol sequence based on the maximum correlation value between each second ZC search sequence and the effective data sequences of the second and third pilot symbol sequences, respectively. Finally, when the root of the second pilot symbol sequence and the root value of the third pilot symbol sequence are the same, the UAV can be identified based on the root values ​​of the second and third pilot symbol sequences. Based on the identical root values ​​of the second and third pilot symbol sequences of the UAV's OFDM signal, the UAV's OFDM signal can be distinguished from the signals of other UAVs, thus differentiating the UAV from other UAVs. This reduces the misclassification rate of different UAVs being identified as the same UAV due to identification based on the root value of a single ZC sequence, and improves the accuracy of UAV identification.

[0016] The above description is merely an overview of the technical solutions of the embodiments of this application. In order to better understand the technical means of the embodiments of this application and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of this application more obvious and understandable, specific implementation methods of this application are described below. Attached Figure Description

[0017] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0018] Figure 1 A flowchart illustrating the drone identification method provided in an embodiment of this application is shown; Figure 2 The frame format of the OFDM signal provided in the embodiments of this application is shown; Figure 3 This illustration shows a schematic diagram of the correlation values ​​between the first ZC search sequence and the first and third search sequences provided in an embodiment of this application. Figure 4 This illustration shows a schematic diagram of the first correlation values ​​between multiple second ZC search sequences and the first subsequence provided in an embodiment of this application; Figure 5 The flowchart of the steps following step 182 is shown; Figure 6 This illustration shows a schematic diagram of the first correlation values ​​between multiple second ZC search sequences and second subsequences, and the second correlation values ​​between them and third subsequences, provided in an embodiment of this application. Figure 7 The flowchart of the steps following step 192 is shown; Figure 8(a) illustrates the frame format of an OFDM signal provided in another embodiment of this application; Figure 8(b) illustrates the frame format of the OFDM signal provided in the embodiments of this application; Figure 9 A flowchart illustrating another embodiment of the drone identification method provided in this application is shown; Figure 10 A schematic diagram of the structure of an electronic device provided in an embodiment of this application is shown. Detailed Implementation

[0019] Exemplary embodiments of the present application will now be described in more detail with reference to the accompanying drawings. Although exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application may be implemented in various forms and should not be limited to the embodiments set forth herein.

[0020] OFDM is a signal transmission technology widely used in modern wireless communication systems. Due to its high spectral efficiency and strong resistance to multipath interference, it is widely applied in systems such as Wi-Fi (IEEE 802.11a / g / n / ac / ax), LTE, and 5G. OFDM technology can effectively combat multipath effects in wireless channels, ensuring the reliability of data transmission.

[0021] ZC sequences are a special type of complex sequence with constant envelope properties and good autocorrelation characteristics. These properties make ZC sequences commonly used in communication systems for critical stages such as channel estimation, synchronization, and random access. In complex multipath and low signal-to-noise ratio (SNR) environments, ZC sequences can significantly improve system performance, reduce errors, and enhance the accuracy of data transmission.

[0022] LTE-OFDM UAVs refer to UAVs that employ LTE communication technology and OFDM modulation technology. For LTE-OFDM UAVs, the ZC sequence is typically used as a reference signal, primarily for synchronization between the UAV and ground control stations or other network elements.

[0023] In existing technologies, the autocorrelation properties of ZC sequences are typically used to perform correlation searches on OFDM signals to identify drones emitting OFDM signals. However, relying solely on a single ZC sequence for drone identification is ineffective if other similar signals or signals using the same ZC sequence as a reference signal exist in the environment. This can lead to different drones being identified as the same drone, reducing the accuracy of drone identification.

[0024] A frame of OFDM signal transmitted by a drone using a specific type of LTE-OFDM standard includes two RS0 symbols and two RS1 symbols. The LTE wireless communication system of this type of drone uses the same ZC sequence as a reference signal to generate the two RS0 symbols and the same ZC sequence as a reference signal to generate the two RS1 symbols. Thus, the root values ​​of the two RS0 symbols and the two RS1 symbols can uniquely identify each other. Specifically, for this type of LTE-OFDM drone, different drones use the same fixed ZC sequence as a reference signal for their two RS1 symbols and the same ZC sequence as their two RS0 symbols, but the ZC sequences of the two RS0 symbols are different for each drone. In this case, the root values ​​of the two RS0 symbols for each drone are unique. Therefore, the drone transmitting the OFDM signal can be uniquely identified by the same root values ​​of the two RS0 symbols, effectively distinguishing this drone from other drones.

[0025] The applicant discovered that in a single frame of OFDM signal transmitted by the aforementioned UAV, the positions of the two RS0 symbols and RS1 symbols are generally fixed, and the interval between them is also fixed. Therefore, the RS1 symbol can be located by its position. Then, by generating a ZC search sequence with fixed root values ​​and performing correlation detection on the RS1 symbol, the position of the valid data of the RS1 symbol can be determined. Furthermore, based on the position of the valid data of the RS1 symbol, the valid data of the two RS0 symbols can be determined from the OFDM signal. Subsequently, by traversing the root values ​​of all ZC sequences to generate different ZC search sequences, and performing correlation detection on the two RS0 symbols using these different ZC search sequences, the root values ​​of the two RS0 symbols can be accurately found. When the root values ​​of the two RS0 symbols are the same, the UAV can be identified based on these root values, distinguishing the UAV's OFDM signal from those of other UAVs. This reduces the misclassification rate of different UAVs being identified as the same UAV due to identification based on the root values ​​of a single ZC sequence, thus improving the accuracy of UAV identification.

[0026] Figure 1 A flowchart of a drone identification method provided in an embodiment of this application is shown. This method is executed by drone countermeasures equipment (such as drone detection equipment and drone jamming equipment), electronic devices such as computers, servers, or tablets. Figure 1 As shown, the method includes the following steps: Step 110: Obtain the search sequence of the OFDM signal of the UAV. The OFDM signal includes multiple symbols. The search sequence includes a first pilot symbol sequence, a second pilot symbol sequence, and a third pilot symbol sequence. The first pilot symbol sequence, the second pilot symbol sequence, and the third pilot symbol sequence correspond to different symbols of the OFDM signal. The first pilot symbol sequence and the second pilot symbol sequence are separated by a first symbol length, and the first pilot symbol sequence and the third pilot symbol sequence are separated by a second symbol length.

[0027] When a drone uses a ZC sequence as a reference signal, the ZC sequence has a specific distribution in the OFDM signal, which allows linear frequency modulation (LFM) characteristics to be observed in the time-frequency plot of the OFDM signal, meaning that the signal frequency changes linearly with time. Furthermore, this LFM characteristic may also be observed to repeat periodically, for example, with a period of 0.5 ms.

[0028] Figure 2 The frame format of the OFDM signal provided in the embodiments of this application is shown, such as... Figure 2As shown, the OFDM signal includes 7 symbols: DATA, DATA, RS0, RS0, RS1, RS1, DATA. Among them, the first RS1 symbol is the first pilot symbol, the second RS1 symbol is the fourth pilot symbol, the first RS0 symbol is the second pilot symbol, and the second RS0 symbol is the third pilot symbol.

[0029] The valid data for the first, fourth, second, and third pilot symbols all use the ZC sequence as a reference signal. This means the root value of the ZC sequence uniquely identifies each pilot symbol. The root values ​​of the ZC sequences for the first and fourth pilot symbols are the same and fixed. The root values ​​of the ZC sequences for the second and third pilot symbols are the same, but they vary depending on the UAV's unique identifier. In other words, the root values ​​of the ZC sequences for each UAV are different. Therefore, based on the root values ​​of the ZC sequences for the second and third pilot symbols, this UAV can be distinguished from other UAVs.

[0030] The first pilot symbol sequence corresponds to the first pilot symbol, the second pilot symbol sequence corresponds to the second pilot symbol, and the third pilot symbol sequence corresponds to the third pilot symbol. Therefore, the first pilot symbol sequence and the second pilot symbol sequence are separated by a distance of one symbol length, that is, they are separated by two symbol lengths. The first pilot symbol sequence and the third pilot symbol sequence are separated by a distance of two symbol lengths, that is, they are separated by a distance of one symbol length.

[0031] Specifically, step 110 includes the following steps: Step 111: Acquire the OFDM signal of the drone.

[0032] The devices that acquire OFDM signals can be signal receivers, signal analyzers, UAV detection equipment, and UAV jamming equipment, etc. For example, after acquiring the OFDM signal, the signal receiver can directly sample the OFDM signal, or it can send the OFDM signal to a computer for sampling.

[0033] Step 112: Obtain the signal bandwidth, sampling rate, sampling time, and subcarrier spacing of the OFDM signal.

[0034] The signal bandwidth can be 10MHz or 20MHz, the sampling rate can be 30.72MHz, the sampling time can be 0.5ms, and the subcarrier spacing can be 15KHz.

[0035] Step 113: Sample the OFDM signal according to the sampling rate and sampling time to obtain the sequence to be searched.

[0036] By configuring the sampling rate of the analog-to-digital converter in the signal receiver and configuring the signal receiver to continuously sample the OFDM signal during the subsequent sampling time, the search sequence can be obtained. The formula for calculating the length of the search sequence is as follows: The length of the sequence to be searched = sampling rate × sampling time, Formula 1.

[0037] When the sampling rate is 30.72MHz and the sampling time is 0.5ms, the length of the sequence to be searched can be calculated to be 15360, that is, the number of sampling points of the sequence to be searched is 15360.

[0038] After the signal receiver samples the OFDM signal to obtain the search sequence, it can send the search sequence to the drone countermeasure equipment, computer or server, which will then analyze the search sequence to identify the drone.

[0039] Step 114: Calculate the length of the effective data sequence of the sequence to be searched based on the sampling rate and subcarrier spacing.

[0040] The length of the effective data sequence of the sequence to be searched is equal to the sampling rate divided by the subcarrier spacing. For example, when the sampling rate is 30.72MHz and the subcarrier spacing is 15KHz, the length of the effective data sequence of the sequence to be searched is 2048.

[0041] Step 115: Calculate the length of the CP sequence of the sequence to be searched based on the subcarrier spacing.

[0042] Wherein, the length of the CP sequence = 144 / (subcarrier spacing / 15^e3).

[0043] For example, when the subcarrier spacing is 15 kHz, the length of the CP sequence is 144.

[0044] Step 116: Determine the symbol length of the sequence to be searched based on the length of the valid data sequence and the length of the CP sequence.

[0045] The symbol length of the sequence to be searched is equal to the sum of the length of the effective data sequence and the length of the CP sequence. For example, when the length of the effective data sequence of the sequence to be searched is 2048 and the length of the CP sequence is 144, then the symbol length of the sequence to be searched is 2192.

[0046] Step 120: Generate the first ZC search sequence based on the preset length and preset root value.

[0047] In standard LTE systems, the root value of the first pilot symbol is typically 600. Therefore, the preset root value for generating the first ZC search sequence in this application is 600. When the signal bandwidth is 20MHz, the sampling rate is 30.72MHz, and the subcarrier spacing is 15kHz, the number of effective subcarriers is 600. Therefore, the preset lengths for generating the first ZC search sequence and the second ZC search sequence in subsequent steps in this application are both 600, and the preset root value range for generating the second ZC search sequence is [1:600].

[0048] The formula for the standard ZC sequence is as follows: , formula 2 Where length represents the length of the ZC sequence, and root represents the root value of the ZC sequence.

[0049] Substituting the preset length and preset root value into Formula 2 of the standard ZC sequence above, the first ZC search sequence can be obtained.

[0050] Step 130: Based on the symbol position of the symbol corresponding to the first pilot symbol sequence in the OFDM signal, determine the first search sequence from the search sequence.

[0051] Specifically, based on the symbol position of the symbol corresponding to the first pilot symbol sequence in the OFDM signal, sampling points of continuous symbol length can be selected from the search sequence as the first search sequence.

[0052] Please continue reading. Figure 2 The symbol corresponding to the first pilot symbol sequence is at symbol position 5 in the OFDM signal. When the length of the sequence to be searched is 15360, the symbol length is 2192, and the symbol position of the first pilot symbol sequence is 5, the first sampling point 8769 of the first pilot symbol sequence can be determined. Starting from the first sampling point 8769 of the first pilot symbol sequence, 2192 sampling points are selected consecutively to obtain the first sequence to be searched: 8769~10860.

[0053] Step 140: Use the first ZC search sequence to perform correlation detection on the first search sequence to determine the position of the effective data sequence of the first pilot symbol sequence.

[0054] Since the UAV uses a ZC sequence generated with a preset length and a preset root value as a reference signal to generate the effective data for the first pilot symbol, the correlation value between the first ZC search sequence and the effective data sequence of the first pilot coincidence sequence in the search sequence is the largest. Therefore, by calculating the correlation value between the first ZC search sequence and the first search sequence, and then determining the position of the first search sequence corresponding to the maximum correlation value, the position of the effective data sequence of the first pilot coincidence sequence can be determined.

[0055] Please see Figure 3 , Figure 3 The diagram illustrates the correlation values ​​between the first ZC search sequence and the first and third search sequences provided in this embodiment. The horizontal axis represents the correlation convolution length, which is the sum of the length of the search sequence and the length of the effective data sequence. The first correlation peak represents the correlation value between the first ZC search sequence and the first search sequence, and the second correlation peak represents the correlation value between the first ZC search sequence and the third search sequence. As shown, the correlation convolution position corresponding to the maximum correlation value between the first ZC search sequence and the first search sequence is 10962. Since the correlation convolution position corresponding to the maximum correlation value is the end position of the first pilot symbol sequence, the position of the effective data sequence of the first pilot symbol sequence can be obtained as 8915 based on the correlation convolution position corresponding to the maximum correlation value and the length of the effective data sequence.

[0056] After determining the position of the effective data sequence of the first pilot symbol sequence, since the interval between the first pilot symbol sequence and the second pilot symbol sequence is fixed, the interval between the effective data sequences of the first pilot symbol sequence and the second pilot symbol sequence is also fixed. Therefore, the position of the effective data sequence of the second pilot symbol sequence can be determined based on the position of the effective data sequence of the first pilot symbol sequence.

[0057] Step 150: Determine the effective data sequence of the second pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the first symbol.

[0058] Specifically, based on the position of the effective data sequence of the first pilot symbol sequence and the length of the first symbol, sampling points of the length of a continuous effective data sequence can be selected from the sequence to be searched as the effective data sequence of the second pilot symbol sequence.

[0059] For example, when the position of the effective data sequence of the first pilot symbol sequence is 8915, that is, the first sampling point of the effective data sequence of the first pilot symbol sequence is 8915. Since the first pilot symbol sequence and the second pilot symbol sequence are separated by a distance of one symbol length, the effective data sequences of the first pilot symbol sequence and the effective data sequences of the second pilot symbol sequence are separated by 4384 sampling points. Starting from the first sampling point 8915 of the effective data sequence of the first pilot symbol sequence, moving forward 4384 sampling points, the first sampling point of the effective data sequence of the second pilot symbol sequence can be determined to be 4530.

[0060] Starting from the first sampling point of the effective data sequence of the second pilot symbol sequence, continuously selecting sampling points of a valid data sequence length yields the effective data sequence of the second pilot symbol sequence. For example, when the first sampling point of the effective data sequence of the second pilot symbol sequence is 4530 and the length of a valid data sequence is 2048, the effective data sequence of the second pilot symbol sequence is 4530~6577.

[0061] Step 160: Determine the effective data sequence of the third pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the second symbol length.

[0062] Specifically, based on the position of the effective data sequence of the first pilot symbol sequence and the second symbol length, sampling points of the length of a continuous effective data sequence can be selected from the sequence to be searched as the effective data sequence of the third pilot symbol sequence.

[0063] For example, when the position of the effective data sequence of the first pilot symbol sequence is 8915, since the first pilot symbol sequence and the third pilot symbol sequence are separated by the second symbol length, the effective data sequence of the first pilot symbol sequence and the effective data sequence of the third pilot symbol sequence are separated by 2192 sampling points. Starting from the first sampling point 8915 of the effective data sequence of the first pilot symbol sequence, after moving forward 2192 sampling points, the first sampling point of the effective data sequence of the third pilot symbol sequence can be determined to be 6722.

[0064] Starting from the first sampling point of the effective data sequence of the third pilot symbol sequence, continuously selecting sampling points of the length of an effective data sequence yields the effective data sequence of the third pilot symbol sequence. For example, when the first sampling point of the effective data sequence of the third pilot symbol sequence is 6722, the effective data sequence of the fourth pilot symbol sequence is 6722~8769.

[0065] Step 170: Generate multiple second ZC search sequences based on each root value within a preset length and preset root value range.

[0066] The preset length is 600, and the preset root value range of the second ZC search sequence is [1: number of effective subcarriers], which is [1: 600]. By combining the preset length with each root value within the preset root value range and then substituting them into Formula 2 of the standard ZC sequence above, multiple second ZC search sequences can be obtained.

[0067] Step 180: Determine the root value of the second pilot symbol sequence as the second ZC search sequence that has the largest correlation value with the effective data sequence of the second pilot symbol sequence among the multiple second ZC search sequences.

[0068] When the UAV uses one of multiple second ZC search sequences as the reference signal for the valid data of the second pilot symbol, the correlation value between this second ZC search sequence and the valid data sequence of the second pilot symbol sequence is the largest. Therefore, by calculating multiple correlation values ​​between the second ZC search sequence and the valid data sequence of the second pilot symbol sequence, and then determining the second ZC search sequence corresponding to the largest correlation value among these multiple correlation values, it can be determined that the valid data sequence of the second pilot symbol sequence includes this second ZC search sequence. Thus, the root value corresponding to this second ZC search sequence can be determined as the root value of the second pilot symbol sequence.

[0069] Specifically, step 180 includes the following steps: Step 181: Starting from the first sampling point of the effective data sequence of the second pilot symbol sequence, select sampling points of a preset length as the second subsequence in sequence to obtain multiple second subsequences. Among them, in two adjacent second subsequences, the first sampling point of one second subsequence is adjacent to the first sampling point of the other second subsequence.

[0070] The length of each second subsequence and the length of the second ZC search sequence are both preset lengths, i.e., 600. The length of the effective data sequence of the second pilot symbol sequence is 2048. When the effective data sequence of the second pilot symbol sequence is 4530~6577, multiple second subsequences of length 600 can be selected from the effective data sequence of the second pilot symbol sequence, for example: 4530~5129, 4531~5130, 4532~5131, ..., 5978~6577.

[0071] Step 182: Calculate the first correlation value between each second ZC search sequence and each second subsequence in turn to obtain the first correlation value corresponding to each of the multiple second ZC search sequences.

[0072] For example, for the second ZC search sequence 1, the first correlation value between the second ZC search sequence 1 and each second subsequence is calculated sequentially to obtain multiple first correlation values ​​corresponding to the second ZC search sequence 1; for the second ZC search sequence 2, the first correlation value between the second ZC search sequence 2 and each first subsequence is calculated sequentially to obtain multiple first correlation values ​​corresponding to the second ZC search sequence 2... and so on, to obtain multiple first correlation values ​​corresponding to each second ZC search sequence.

[0073] Step 183: Determine the second ZC search sequence corresponding to the largest first correlation value among the multiple second ZC search sequences.

[0074] Figure 4This illustration shows a schematic diagram of the first correlation values ​​between multiple second ZC search sequences and the first subsequence provided in an embodiment of this application. Figure 4 The horizontal axis represents the root of the second ZC search sequence, and the vertical axis represents the first relevance value, such as... Figure 4 As shown, the largest first correlation value among the multiple second ZC search sequences is 27.1765, and its corresponding second ZC search sequence is second ZC search sequence 50. Therefore, the second ZC search sequence corresponding to the largest first correlation value is second ZC search sequence 50.

[0075] Step 184: Determine the root value of the second pilot symbol sequence corresponding to the largest first correlation value as the root value of the second ZC search sequence.

[0076] When the second ZC search sequence corresponding to the largest first correlation value is the second ZC search sequence 50, then the root value corresponding to the second ZC search sequence 50 is the root value of the second pilot symbol sequence. For example, Figure 4 As shown, the root value corresponding to the second ZC search sequence 50 is 69, so the root value of the second pilot symbol sequence is 69.

[0077] Step 190: Determine the root value of the second ZC search sequence with the largest correlation value with the effective data sequence of the third pilot symbol sequence among the multiple second ZC search sequences as the root value of the third pilot symbol sequence.

[0078] When the UAV uses one of multiple second ZC search sequences as the reference signal for the valid data of the third pilot symbol, the correlation value between this second ZC search sequence and the valid data sequence of the third pilot symbol sequence is the largest. Therefore, by calculating multiple correlation values ​​between the second ZC search sequence and the valid data sequence of the third pilot symbol sequence, and then determining the second ZC search sequence corresponding to the largest correlation value among these multiple correlation values, it can be determined that the valid data sequence of the third pilot symbol sequence includes this second ZC search sequence. Thus, the root value corresponding to this second ZC search sequence can be determined as the root value of the third pilot symbol sequence.

[0079] Specifically, step 190 includes the following steps: Step 191: Starting from the first sampling point of the third pilot symbol sequence, select sampling points of a preset length in sequence as the third subsequence to obtain multiple third subsequences. Among them, in two adjacent third subsequences, the first sampling point of one third subsequence is adjacent to the first sampling point of the other third subsequence.

[0080] The length of each third subsequence is a preset length, i.e., 600. The length of the effective data sequence of the third pilot symbol sequence is 2048. When the effective data sequence of the third pilot symbol sequence is 6722~8769, multiple third subsequences of length 600 can be selected from the effective data sequence of the third pilot symbol sequence, for example: 6722~7321, 6723~7322, ..., 8170~8769.

[0081] Step 192: Calculate the second correlation value between each second ZC search sequence and each third subsequence in turn to obtain the second correlation values ​​corresponding to the multiple second ZC search sequences.

[0082] For example, for the second ZC search sequence 1, the second correlation value between the second ZC search sequence 1 and each third subsequence is calculated sequentially to obtain multiple second correlation values ​​corresponding to the second ZC search sequence 1; for the second ZC search sequence 2, the second correlation value between the second ZC search sequence 2 and each third subsequence is calculated sequentially to obtain multiple second correlation values ​​corresponding to the second ZC search sequence 2... and so on, to obtain multiple second correlation values ​​corresponding to each second ZC search sequence.

[0083] Step 193: Determine the second ZC search sequence corresponding to the largest second correlation value among the multiple second ZC search sequences.

[0084] Step 194: Determine the root value of the second ZC search sequence corresponding to the largest second correlation value as the root value of the third pilot symbol sequence.

[0085] When the second ZC search sequence corresponding to the largest second correlation value is the second ZC search sequence 60, then the root value corresponding to the second ZC search sequence 60 is the root value of the third pilot symbol sequence.

[0086] Step 200: When the root value of the second pilot symbol sequence is the same as the root value of the third pilot symbol sequence, the UAV is identified based on the root values ​​of the second and third pilot symbol sequences.

[0087] When the root of the second pilot symbol sequence is different from the root of the third pilot symbol sequence, it indicates that the OFDM signal emitted by the UAV does not conform to the frame format, or that the received OFDM signal is missing some symbols. In this case, the root value of the second pilot symbol sequence and the root of the third pilot symbol sequence can be used to determine that the OFDM signal originates from a UAV, but it cannot be determined which UAV the signal originates from. In this situation, the root values ​​of the second and third pilot symbol sequences cannot be used to identify the UAV; it is necessary to re-acquire the UAV's OFDM signal for analysis.

[0088] When the root values ​​of the second and third pilot symbol sequences are the same, for example, both being 69, it indicates that the OFDM signal emitted by the UAV conforms to the frame format. In this case, determining the root values ​​of the second and third pilot symbol sequences establishes the UAV's fingerprint information, distinguishing it from other UAVs and reducing the false positive rate of misidentifying it as another UAV. Subsequently, the UAV target can be tracked based on the root values ​​of the second and third pilot symbol sequences.

[0089] This application embodiment determines the first search sequence from the search sequence of the OFDM signal by determining the symbol position of the corresponding symbol in the first pilot symbol sequence. Then, by generating a first ZC search sequence and performing correlation detection on the first search sequence, the position of the effective data sequence of the first pilot symbol sequence can be determined. Next, based on the characteristic that the first pilot symbol sequence is separated from the second and third pilot symbol sequences by a first symbol length and a second symbol length, respectively, in the search sequence of the UAV's OFDM signal, the second pilot symbol sequence can be determined from the search sequence according to the position of the effective data sequence of the first pilot symbol sequence and the first symbol length. The system first obtains the effective data sequence of the symbol sequence and determines the effective data sequence of the third pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the second symbol length. Then, it generates multiple second ZC search sequences and determines the root of the second pilot symbol sequence and the root value of the third pilot symbol sequence based on the maximum correlation value between each second ZC search sequence and the effective data sequences of the second and third pilot symbol sequences, respectively. Finally, when the root of the second pilot symbol sequence and the root value of the third pilot symbol sequence are the same, the UAV can be identified based on the root values ​​of the second and third pilot symbol sequences. Based on the identical root values ​​of the second and third pilot symbol sequences of the UAV's OFDM signal, the UAV's OFDM signal can be distinguished from the signals of other UAVs, thus differentiating the UAV from other UAVs. This reduces the misclassification rate of different UAVs being identified as the same UAV due to identification based on the root value of a single ZC sequence, and improves the accuracy of UAV identification.

[0090] To improve the accuracy of drone identification, this application further proposes an implementation method, the details of which are available in the following documents: Figure 5 , Figure 5 The flowchart for the steps following step 182 is shown in the figure. Step 182 includes the following steps: Step 182a: Determine the second subsequence with the largest first correlation value among the first correlation values ​​corresponding to the multiple second ZC search sequences.

[0091] In step 182, when calculating the first correlation value between each second ZC search sequence and each second subsequence, the resulting multiple first correlation values ​​not only correspond one-to-one with each of the multiple second ZC search sequences, but also one-to-one with each of the multiple second subsequences. Thus, after determining the second ZC search sequence corresponding to the largest first correlation value in step 183, the second subsequence corresponding to the largest first correlation value can also be determined.

[0092] For example, the second ZC search sequence corresponding to the largest first relevance value is the second ZC search sequence 50, and the second subsequence corresponding to the largest first relevance value is the second subsequence 3.

[0093] Step 182b: Determine the position of the effective data sequence of the second pilot symbol sequence by the second subsequence with the largest first correlation value.

[0094] When the second subsequence corresponding to the largest first correlation value is the second subsequence 3, then the first sampling point of the second subsequence 3 is the first sampling point of the effective data sequence of the second pilot symbol sequence, which is also the position of the effective data sequence of the second pilot symbol sequence.

[0095] Figure 6 This illustration shows a schematic diagram of the first correlation values ​​between multiple second ZC search sequences and second subsequences, and the second correlation values ​​between them and third subsequences, provided in an embodiment of this application. Figure 6 The horizontal axis represents the correlation convolution length, and the vertical axis represents the first and second correlation values. In the graph, the first correlation peak represents the first correlation value, and the second correlation peak represents the second correlation value. For example... Figure 6 As shown, the correlation convolution position corresponding to the largest first correlation value is 6579. This correlation convolution position corresponding to the largest first correlation value is the end position of the second pilot symbol sequence. Therefore, based on the correlation convolution position corresponding to the largest first correlation value and the length of the effective data sequence, the position of the effective data sequence of the second pilot symbol sequence can be obtained as 4532, which is the first sampling point of the second subsequence 3.

[0096] Step 182c: Calculate the position difference between the position of the effective data sequence of the first pilot symbol sequence and the position of the effective data sequence of the second pilot symbol sequence.

[0097] For example, when the position of the effective data sequence of the first pilot symbol sequence is 8915 and the position of the effective data sequence of the second pilot symbol sequence is 4532, the position difference between them is 4383.

[0098] Step 182d: Determine whether the difference between the position difference and the length of the first symbol is less than or equal to the preset difference. If yes, proceed to step 184; otherwise, end.

[0099] The preset difference can be set to 10.

[0100] Specifically, when the difference between the position difference and the first symbol length is less than or equal to a preset difference, for example, when the position difference is 4383 and the first symbol length is 4384, it indicates that the relative position of the second pilot symbol sequence and the first pilot symbol sequence conforms to the fixed interval length in the frame format. Thus, the root value corresponding to the second ZC search sequence searched in step 183 is the root value of the second pilot symbol sequence. Next, step 184 is executed to determine the root value corresponding to the second ZC search sequence with the largest first correlation value as the root value of the second pilot symbol sequence.

[0101] When the difference between the position difference and the length of the first symbol is greater than a preset difference, it indicates that the relative positions of the second pilot symbol sequence and the first pilot symbol sequence do not conform to the fixed interval length in the frame format. This suggests that the second pilot symbol may be affected by noise or other interference signals, or that the OFDM signal in this frame did not capture the second pilot symbol due to the distance being too far. In this case, the root value corresponding to the second ZC search sequence searched in step 183 is not the root value of the second pilot symbol sequence. Therefore, the search for the root value of the second pilot symbol sequence ends, avoiding the use of incorrect root values ​​of the second pilot symbol sequence to identify the UAV and improving the accuracy of UAV identification.

[0102] Under normal circumstances, the root values ​​of the ZC sequences used in the second and third pilot symbol sequences are the same. When multiple second ZC search sequences are used to perform correlation searches on the second and third pilot symbol sequences, the maximum power of the correlated peaks should be similar. Thus, the power of the maximum peak values ​​correlated with the second and third pilot symbol sequences using multiple second ZC search sequences can be used to determine whether the second and third pilot symbol sequences conform to the frame format of a genuine OFDM signal emitted by a UAV, thereby improving the accuracy of UAV identification.

[0103] Please refer to the details. Figure 7 , Figure 7 The flowchart of steps after step 192 is shown, as follows: Figure 7 As shown, the steps following step 192 include the following steps: Step 192a: Determine the largest second correlation value among the second correlation values ​​corresponding to the multiple second ZC search sequences.

[0104] Step 192b: Calculate the second power difference between the largest second correlation value and the largest first correlation value.

[0105] Specifically, the second power difference between the largest second correlation value and the largest first correlation value can be obtained by calculating the absolute value of the difference between the largest second correlation value and the largest first correlation value.

[0106] Assuming the largest second correlation value is 26 and the largest first correlation value is 27.1765, then the second power difference is 1.1765 dB.

[0107] Step 192c: Determine whether the second power difference is less than or equal to the second preset power difference. If yes, proceed to step 194; otherwise, end.

[0108] The second preset power difference can be set to 3.5dB.

[0109] Specifically, when the second power difference is less than or equal to the second preset power difference, it indicates that the maximum peak power of the same second ZC search sequence is close to that of the second pilot symbol sequence and the third pilot symbol sequence, meaning that the second pilot symbol sequence and the third pilot symbol sequence represent the frame format of the OFDM signal emitted by the actual UAV. In this case, the root value corresponding to the second ZC search sequence searched in step 193 is the root value of the third pilot symbol sequence. Thus, step 194 is then executed to determine the root value corresponding to the second ZC search sequence with the largest second correlation value as the root value of the third pilot symbol sequence.

[0110] When the second power difference is greater than the second preset power difference, it indicates that the power of the maximum peak associated with the same second ZC search sequence and the second and third pilot symbol sequences is not close. This means the maximum peak associated with the second ZC search sequence and either the second or third pilot symbol sequence may be caused by noise or other interference signals. In this case, the root value corresponding to the second ZC search sequence found in step 193 may not be the root value of the third pilot symbol sequence. Therefore, the search for the root value of the third pilot symbol sequence ends to avoid using an incorrect root value of the third pilot symbol sequence for drone identification, thus improving the accuracy of drone identification.

[0111] In some cases, the signal receiver may be too far from the drone, causing signal interruption and resulting in the loss of part of a frame. Alternatively, the frame format transmitted by the drone may change, potentially leading to a frame of OFDM signal transmitted by the drone not conforming to the specified format. Figure 2 The frame format of the OFDM signal shown is illustrated in Figure 8(a), another embodiment of the present application, in which the first DATA symbol in a frame of OFDM signal transmitted by the UAV is located after the last DATA symbol.

[0112] In this case, based on Figure 1 In the illustrated embodiment, the determined first pilot symbol sequence corresponds to the second RS1 symbol, not the first RS1 symbol; the determined second pilot symbol sequence corresponds to the second RS0 symbol, not the first RS0 symbol; and the determined third pilot symbol sequence corresponds to the first RS1 symbol. Thus, the third pilot symbol sequence is incorrectly positioned, preventing the search for a second ZC search sequence identical to the second pilot symbol sequence. When verifying whether the OFDM signal originates from a real drone based on whether the root values ​​of the ZC sequences of the two RS0 symbols are the same, it may mistakenly determine that the OFDM signal is not emitted by a real drone, reducing the accuracy of drone identification.

[0113] Please continue reading. Figure 2 The sequence to be searched also includes the fourth pilot symbol sequence, wherein the fourth pilot symbol sequence corresponds to the fourth pilot symbol (i.e. Figure 2 (The second RS1 symbol in the text). Please continue to refer to Figure 8(a). When the first pilot symbol sequence corresponds to the fourth pilot symbol, and the fourth pilot symbol sequence corresponds to the first pilot symbol, the first pilot symbol sequence is separated from the second and third pilot symbol sequences by the length of the first sub-symbol and the length of the second sub-symbol, respectively, that is, separated by three symbol lengths and two symbol lengths, respectively. Please refer to Figure 8(b) for the frame format of the OFDM signal, where the frame format of the OFDM signal shown in Figure 8(b) is similar to... Figure 2 The OFDM signals shown have a consistent frame format. When the first pilot symbol sequence corresponds to the first pilot symbol and the fourth pilot symbol sequence corresponds to the fourth pilot symbol, the first pilot symbol sequence is separated from the second and third pilot symbol sequences by the lengths of the third and fourth sub-symbols, respectively—that is, by two symbol lengths and one symbol length. Thus, by determining the position of the fourth pilot symbol sequence, the position of the first pilot symbol sequence can be accurately determined, which in turn accurately determines the position of the second pilot symbol sequence, and consequently, the position of the third pilot symbol sequence. This ensures that the root values ​​of the two RS0 ZC sequences are found, avoiding misjudgments that the OFDM signal is not emitted by a real drone and improving the accuracy of drone identification.

[0114] Specifically, Figure 9 A flowchart of another embodiment of the drone identification method provided in this application is shown, such as... Figure 9 As shown, the method includes the following steps: Step 210: Obtain the search sequence of the OFDM signal of the UAV. The OFDM signal includes multiple symbols. The search sequence includes a first pilot symbol sequence, a second pilot symbol sequence, and a third pilot symbol sequence. The first pilot symbol sequence, the second pilot symbol sequence, and the third pilot symbol sequence correspond to different symbols of the OFDM signal. The first pilot symbol sequence and the second pilot symbol sequence are separated by a first symbol length, and the first pilot symbol sequence and the third pilot symbol sequence are separated by a second symbol length.

[0115] Wherein, the length of the first symbol is either the length of the first sub-symbol or the length of the second sub-symbol, and the length of the second symbol is either the length of the third sub-symbol or the length of the fourth sub-symbol.

[0116] Step 220: Generate the first ZC search sequence based on the preset length and preset root value.

[0117] Step 230: Based on the symbol position of the symbol corresponding to the first pilot symbol sequence in the OFDM signal, determine the first search sequence from the search sequence.

[0118] For detailed procedures of steps 210-230, please refer to [link / reference]. Figure 1 Steps 110-130 of the illustrated embodiment will not be repeated here.

[0119] Step 240: Determine the largest correlation value among the correlation values ​​of the first ZC search sequence and the first search sequence as the first maximum correlation value.

[0120] Specifically, step 240 includes the following steps: Step 241: Starting from the first sampling point of the first search sequence, select sampling points of a preset length as the first subsequence in sequence to obtain multiple first subsequences. Among them, in two adjacent first subsequences, the first sampling point of one first subsequence is adjacent to the first sampling point of the other first subsequence.

[0121] The length of each first subsequence is a preset length, which is 600. The length of the first search sequence is 2192. When the first search sequence is 8769~10860, multiple first subsequences of length 600 can be selected from the first search sequence, such as: 8769~9368, 8770~9369, ..., 10261~10860.

[0122] Step 242: Calculate the correlation value between the first ZC search sequence and each first subsequence in turn to obtain the correlation values ​​corresponding to the multiple first subsequences.

[0123] Step 243: Determine the largest correlation value among the correlation values ​​corresponding to the multiple first subsequences as the first maximum correlation value.

[0124] Step 250: Determine the position of the effective data sequence of the first pilot symbol sequence based on the first maximum correlation value.

[0125] Specifically, the first sampling point of the first subsequence corresponding to the first maximum correlation value is determined as the position of the effective data sequence of the first pilot symbol sequence.

[0126] When the first subsequence corresponding to the first maximum correlation value is the first subsequence 10, then the first sampling point of the first subsequence 10 is the first sampling point of the effective data sequence of the first pilot symbol sequence, that is, the position of the effective data sequence of the first pilot symbol sequence. For example, Figure 3 As shown, the correlation convolution position corresponding to the first maximum correlation value is 10962, and the end position of the first pilot symbol sequence is 10962. That is, the last sampling point of the second subsequence 10 is 10962, and the first sampling point of the second subsequence 10 is 8915. The position of the effective data sequence of the first pilot symbol sequence is 8915.

[0127] Step 260: Based on the position of the effective data sequence of the first pilot symbol sequence, determine the second search sequence and the third search sequence from the search sequence, wherein the second search sequence and the third search sequence correspond to the symbol before and the symbol after the symbol of the first pilot symbol sequence, respectively.

[0128] For example, when the position of the effective data sequence of the first pilot symbol sequence is 8915, since the fourth pilot symbol sequence is adjacent to the first pilot symbol sequence, the effective data sequence of the first pilot symbol sequence and the effective data sequence of the fourth pilot symbol sequence are spaced 2192 sampling points apart.

[0129] In this case, starting from the first sampling point 8915 of the effective data sequence of the first pilot symbol sequence, moving forward 2192 sampling points, we can obtain the first sampling point of the second search sequence as 6722. Moving backward 2192 sampling points, we can obtain the first sampling point of the third search sequence as 11108.

[0130] Starting from the first sampling point 6722 of the second search sequence, continuously selecting sampling points of the length of a valid data sequence yields the second search sequence 6722~8769. Starting from the first sampling point 11108 of the third search sequence, continuously selecting sampling points of the length of a valid data sequence yields the third search sequence 11108~13155.

[0131] Step 270: Determine the largest correlation value between the first ZC search sequence and the second search sequence as the second maximum correlation value.

[0132] Step 280: Determine the largest correlation value among the correlation values ​​of the first ZC search sequence and the third search sequence as the third maximum correlation value.

[0133] The specific processes of steps 270 and 280 are similar to those of steps 241-243 above, and will not be repeated here.

[0134] Step 290: Calculate the first power difference between the second and third maximum correlation values ​​and the first maximum correlation value, respectively.

[0135] After determining the second and third maximum correlation values, the first power difference between the second and first maximum correlation values ​​can be calculated first, and then the first power difference between the third and first maximum correlation values ​​can be calculated.

[0136] Step 300: If the first power difference between the second maximum correlation value and the first maximum correlation value is less than the first preset power difference, then the second search sequence is determined as the effective data sequence of the fourth pilot symbol sequence, the first symbol length is the first sub-symbol length, and the second symbol length is the second sub-symbol length.

[0137] When the first power difference between the second maximum correlation value and the first maximum correlation value is less than the first preset power difference, it indicates that the second search sequence uses the same ZC sequence as the first pilot symbol sequence. This means that the second search sequence is a valid data sequence of the fourth pilot symbol sequence. Therefore, the second search sequence is determined to be a valid data sequence of the fourth pilot symbol sequence.

[0138] Step 310: Determine the effective data sequence of the second pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the first sub-symbol.

[0139] When the second search sequence is a valid data sequence of the fourth pilot symbol sequence, the fourth pilot symbol sequence corresponds to the first pilot symbol, and the first pilot symbol sequence corresponds to the fourth pilot symbol. In this case, the length of the first symbol is the length of the first sub-symbol. Therefore, it can be determined that the first pilot symbol sequence and the second pilot symbol sequence are separated by the length of the first sub-symbol, that is, by the length of three symbols. Thus, based on the position of the valid data sequence of the first pilot symbol sequence and the length of the first symbol, sampling points of the length of consecutive valid data sequences can be selected from the search sequence as the valid data sequence of the second pilot symbol sequence.

[0140] For example, when the position of the effective data sequence of the first pilot symbol sequence is 8915, since the first and second pilot symbol sequences are separated by 3 symbol lengths, the effective data sequences of the first and second pilot symbol sequences are separated by 6576 sampling points. Starting from the first sampling point 8915 of the effective data sequence of the first pilot symbol sequence, moving forward 6576 sampling points, the first sampling point of the effective data sequence of the second pilot symbol sequence can be determined as 2338. Finally, starting from the first sampling point 2338 of the effective data sequence of the second pilot symbol sequence, continuously selecting sampling points of one effective data sequence length, the effective data sequence of the second pilot symbol sequence 2338~4385 can be obtained.

[0141] In some embodiments, the local oscillators of the wireless transmitter and signal receiver on the UAV may have slight frequency deviations. These deviations can cause frequency offsets in the search sequence of the OFDM signal, affecting the subsequent location of the second pilot symbol sequence and consequently the accuracy of ZC sequence search based on the second pilot symbol sequence. Therefore, to avoid the above problems, the following steps may be included before step 310: Step a1: Determine the position of the valid data sequence of the third pilot symbol sequence.

[0142] The specific process of this step and Figure 9 The specific processes of steps 240 and 250 in the illustrated embodiment are similar and will not be described again here.

[0143] Please continue reading. Figure 3 The correlation convolution position corresponding to the third maximum correlation value is 13155, which is also the end position of the third pilot symbol sequence. Therefore, the position of the effective data sequence of the third pilot symbol sequence is 11108.

[0144] Step a2: Using the position of the effective data sequence of the first pilot symbol sequence as the center, select sampling points of a continuous preset sequence length as the first sequence.

[0145] The preset sequence length can be set to 11. For example, assuming the effective data sequence position of the first pilot symbol sequence is 8915, with the sampling point 8915 as the center, select 5 consecutive sampling points forward and backward to obtain the first sequence 8910~8920.

[0146] Step a3: Using the position of the effective data sequence of the third pilot symbol sequence as the center, select sampling points of a continuous preset sequence length as the second sequence.

[0147] For example, assuming the effective data sequence position of the third pilot symbol sequence is 11108, with the sampling point 11108 as the center, select 5 consecutive sampling points forward and backward to obtain the second sequence 11103~11113.

[0148] Step a4: Determine the frequency offset of the sequence to be searched based on the first sequence and the second sequence.

[0149] First, the instantaneous phase difference between each sampling point of the first sequence and each sampling point of the second sequence can be calculated. Then, the average phase difference between the first sequence and the second sequence can be calculated based on all instantaneous phase differences. After that, the average phase difference can be converted into a frequency offset value, and the frequency offset of the sequence to be searched can be obtained.

[0150] Step a5: Correct the frequency offset of the sequence to be searched based on the frequency offset to obtain the frequency offset corrected sequence to be searched.

[0151] Once the frequency offset of the sequence to be searched is determined, the frequency offset can be corrected using the following formula: , formula 3 in, This represents the search sequence after frequency offset correction. Indicates frequency offset. This indicates the sequence to be searched.

[0152] After frequency offset correction is performed on the search sequence in step a5, in this step 310, the effective data sequence of the second pilot symbol sequence can be determined from the frequency offset corrected search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the first sub-symbol. This improves the accuracy of the effective data sequence of the second pilot symbol sequence.

[0153] Step 320: Determine the effective data sequence of the third pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the second sub-symbol.

[0154] When the second search sequence is a valid data sequence of the fourth pilot symbol sequence, the second symbol length is the second sub-symbol length. Therefore, the interval between the first and third pilot symbol sequences can be determined to be the second sub-symbol length, or two symbol lengths. Thus, based on the position of the valid data sequence of the first pilot symbol sequence and the second sub-symbol length, sampling points of consecutive valid data sequence lengths can be selected from the search sequence as the valid data sequence of the third pilot symbol sequence.

[0155] For example, when the position of the effective data sequence of the first pilot symbol sequence is 8915, since the first and third pilot symbol sequences are separated by two symbol lengths, the effective data sequences of the first and third pilot symbol sequences are separated by 4384 sampling points. Starting from the first sampling point 8915 of the effective data sequence of the first pilot symbol sequence, moving forward 4384 sampling points, the first sampling point of the effective data sequence of the third pilot symbol sequence can be determined as 4530. Finally, starting from the first sampling point 4530 of the effective data sequence of the third pilot symbol sequence, continuously selecting sampling points of one effective data sequence length, the effective data sequence of the third pilot symbol sequence 4530~6577 can be obtained.

[0156] After frequency offset correction is performed on the search sequence in step a5, in this step 320, the effective data sequence of the third pilot symbol sequence can be determined from the frequency offset corrected search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the second sub-symbol length. This improves the accuracy of the effective data sequence of the third pilot symbol sequence.

[0157] Step 330: If the first power difference between the third maximum correlation value and the first maximum correlation value is less than the first preset power difference, then the third search sequence is determined as the effective data sequence of the fourth pilot symbol sequence, the first symbol length is the third sub-symbol length, and the second symbol length is the fourth sub-symbol length.

[0158] When the first power difference between the third maximum correlation value and the first maximum correlation value is less than the first preset power difference, it indicates that the third search sequence uses the same ZC sequence as the first pilot symbol sequence. This means that the third search sequence is a valid data sequence of the fourth pilot symbol sequence. Therefore, the third search sequence is determined as a valid data sequence of the fourth pilot symbol sequence.

[0159] Step 340: Determine the effective data sequence of the second pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the third sub-symbol.

[0160] When the third search sequence is a valid data sequence of the fourth pilot symbol sequence, the fourth pilot symbol sequence corresponds to the fourth pilot symbol, and the first pilot symbol sequence corresponds to the first pilot symbol. In this case, the length of the first symbol is the length of the third sub-symbol. Therefore, it can be determined that the first pilot symbol sequence and the second pilot symbol sequence are separated by a distance of three sub-symbol lengths, i.e., two symbol lengths. Thus, based on the position of the valid data sequence of the first pilot symbol sequence and the length of the third sub-symbol, sampling points of the length of a continuous valid data sequence can be selected from the search sequence as the valid data sequence of the second pilot symbol sequence.

[0161] For example, when the position of the effective data sequence of the first pilot symbol sequence is 8915, since the first and second pilot symbol sequences are separated by two symbol lengths, the effective data sequences of the first and second pilot symbol sequences are separated by 4384 sampling points. Starting from the first sampling point 8915 of the effective data sequence of the first pilot symbol sequence, moving forward 4384 sampling points, the first sampling point of the effective data sequence of the second pilot symbol sequence can be determined as 4530. Finally, starting from the first sampling point 4530 of the effective data sequence of the second pilot symbol sequence, continuously selecting sampling points of one effective data sequence length, the effective data sequence of the second pilot symbol sequence 4530~6577 can be obtained.

[0162] After frequency offset correction is performed on the search sequence in step a5, in this step 340, the effective data sequence of the second pilot symbol sequence is determined from the frequency offset corrected search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the third sub-symbol. This improves the accuracy of the effective data sequence of the second pilot symbol sequence.

[0163] Step 350: Determine the effective data sequence of the third pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the fourth sub-symbol.

[0164] When the third search sequence is a valid data sequence of the fourth pilot symbol sequence, the second symbol length is the fourth sub-symbol length. Therefore, it can be determined that the first and third pilot symbol sequences are separated by a distance of four sub-symbol lengths, or one symbol length. Thus, based on the position of the valid data sequence of the first pilot symbol sequence and the fourth sub-symbol length, sampling points of consecutive valid data sequence lengths from the search sequence can be selected as the valid data sequence of the third pilot symbol sequence.

[0165] For example, when the position of the effective data sequence of the first pilot symbol sequence is 8915, since the first and third pilot symbol sequences are separated by one symbol length, the effective data sequences of the first and third pilot symbol sequences are separated by 2192 sampling points. Starting from the first sampling point 8915 of the effective data sequence of the first pilot symbol sequence, moving forward 2192 sampling points, the first sampling point of the effective data sequence of the third pilot symbol sequence can be determined as 6722. Finally, starting from the first sampling point 6722 of the effective data sequence of the third pilot symbol sequence, continuously selecting sampling points of one effective data sequence length, the effective data sequence of the third pilot symbol sequence 6722~8769 can be obtained.

[0166] After frequency offset correction is performed on the search sequence in step a5, in this step 350, the effective data sequence of the third pilot symbol sequence can be determined from the frequency offset corrected search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the fourth sub-symbol. This improves the accuracy of the effective data sequence of the third pilot symbol sequence.

[0167] Step 360: Generate multiple second ZC search sequences based on each root value within a preset length and preset root value range.

[0168] Step 370: Determine the root value of the second pilot symbol sequence as the second ZC search sequence that has the largest correlation value with the effective data sequence of the second pilot symbol sequence among the multiple second ZC search sequences.

[0169] Step 380: Determine the root value of the second ZC search sequence with the largest correlation value with the effective data sequence of the third pilot symbol sequence among the multiple second ZC search sequences as the root value of the third pilot symbol sequence.

[0170] Step 390: When the root value of the second pilot symbol sequence is the same as the root value of the third pilot symbol sequence, the UAV is identified based on the root values ​​of the second and third pilot symbol sequences.

[0171] For detailed instructions on steps 360-390, please refer to [link / reference]. Figure 1 The specific processes of steps 170-200 shown in the embodiment are similar and will not be repeated here.

[0172] The second and third search sequences are selected from the search sequences by using the position of the effective data sequence of the first pilot symbol sequence. A first ZC search sequence is then used to perform a correlation search on the second and third search sequences, determining the second and third maximum correlation values ​​between them and the first ZC search sequence, respectively. Then, by calculating the first power difference between the second and third maximum correlation values ​​and the first maximum correlation value, it can be determined which of the second and third search sequences uses the same ZC sequence as the first pilot symbol sequence as a reference signal, thus determining the position of the fourth pilot symbol sequence. This accurately determines the pilot symbols corresponding to the first and fourth pilot symbol sequences, and consequently, the positions of the second and third pilot symbol sequences. This ensures that the root values ​​of the ZC sequences of the two RS0 symbols can be found subsequently, avoiding misjudgments when verifying whether the OFDM signal originates from a real drone based on the root values ​​of the ZC sequences of the two RS0 symbols, thereby improving the accuracy of drone identification.

[0173] Figure 10 The diagram shows a structural schematic of an electronic device provided in an embodiment of this application. The specific embodiments of this application do not limit the specific implementation of the electronic device.

[0174] like Figure 10 As shown, the electronic device 400 may include a processor 402 and a memory 404.

[0175] The memory 404 is used to store the computer program 406. The memory 404 may include high-speed RAM, and may also include non-volatile memory, such as at least one disk drive. The computer program 406 may include computer-executable instructions.

[0176] The processor 402 is used to execute the computer program 406 to implement the above-described embodiment of the drone identification method.

[0177] Processor 402 may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of this application. The electronic device may include one or more processors of the same type, such as one or more CPUs; or it may include processors of different types, such as one or more CPUs and one or more ASICs.

[0178] This application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described drone identification method embodiment.

[0179] This application provides a computer program that can be executed by a processor to implement the above-described drone identification method embodiment.

[0180] This application provides a computer program product, which includes a computer program that, when executed by a processor, implements the above-described drone identification method embodiment.

[0181] In the several embodiments provided in this application, any function, if implemented as a software functional module / unit and sold or used as an independent product, can be stored in a computer-readable storage medium. Based on this understanding, part or all of the technical solutions of this application can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or other electronic device) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing computer program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

Claims

1. A method for identifying unmanned aerial vehicles (UAVs), characterized in that, The method includes: The search sequence of the OFDM signal of the UAV is obtained. The OFDM signal includes multiple symbols. The search sequence includes a first pilot symbol sequence, a second pilot symbol sequence, and a third pilot symbol sequence. The first pilot symbol sequence, the second pilot symbol sequence, and the third pilot symbol sequence correspond to different symbols of the OFDM signal. The first pilot symbol sequence and the second pilot symbol sequence are separated by a first symbol length, and the first pilot symbol sequence and the third pilot symbol sequence are separated by a second symbol length. Generate the first ZC search sequence based on the preset length and preset root value; Based on the symbol position of the first pilot symbol sequence in the OFDM signal, a first search sequence is determined from the search sequence; The first ZC search sequence is used to perform correlation detection on the first search sequence to determine the position of the effective data sequence of the first pilot symbol sequence. The effective data sequence of the second pilot symbol sequence is determined from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the first symbol. The effective data sequence of the third pilot symbol sequence is determined from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the second symbol. Generate multiple second ZC search sequences based on each root value within a preset length and preset root value range; The root value corresponding to the second ZC search sequence with the largest correlation value with the effective data sequence of the second pilot symbol sequence among multiple second ZC search sequences is determined as the root value of the second pilot symbol sequence; The root value corresponding to the second ZC search sequence with the largest correlation value with the effective data sequence of the third pilot symbol sequence among multiple second ZC search sequences is determined as the root value of the third pilot symbol sequence; When the root value of the second pilot symbol sequence is the same as the root value of the third pilot symbol sequence, the UAV is identified based on the root values ​​of the second pilot symbol sequence and the third pilot symbol sequence.

2. The method according to claim 1, characterized in that, The sequence to be searched further includes a fourth pilot symbol sequence, wherein the first symbol length is the length of the first sub-symbol or the length of the third sub-symbol, and the second symbol length is the length of the second sub-symbol or the length of the fourth symbol; The step of using the first ZC search sequence to perform correlation detection on the first search sequence to determine the position of the effective data sequence of the first pilot symbol sequence further includes: The largest correlation value among the correlation values ​​of the first ZC search sequence and the first search sequence is determined as the first maximum correlation value; The position of the valid data sequence of the first pilot symbol sequence is determined based on the first maximum correlation value; The method further includes: Based on the position of the effective data sequence of the first pilot symbol sequence, a second search sequence and a third search sequence are determined from the search sequence, wherein the second search sequence and the third search sequence correspond to the preceding and following symbols of the first pilot symbol sequence, respectively. The largest correlation value between the first ZC search sequence and the second search sequence is determined as the second maximum correlation value; The largest correlation value among the correlation values ​​of the first ZC search sequence and the third search sequence is determined as the third maximum correlation value; Calculate the first power difference between the second maximum correlation value and the third maximum correlation value and the first maximum correlation value, respectively; If the first power difference between the second maximum correlation value and the first maximum correlation value is less than a first preset power difference, the first symbol length is the first sub-symbol length, and the second symbol length is the second sub-symbol length. The step of determining the effective data sequence of the second pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the first symbol length, and determining the effective data sequence of the third pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the second symbol length, further includes: The effective data sequence of the second pilot symbol sequence is determined from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the first sub-symbol; The effective data sequence of the third pilot symbol sequence is determined from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the second sub-symbol; If the first power difference between the third maximum correlation value and the first maximum correlation value is less than the first preset power difference, the first symbol length is the third sub-symbol length, the second symbol length is the fourth sub-symbol length, and the step of determining the effective data sequence of the second pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the first symbol length, and determining the effective data sequence of the third pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the second symbol length, further includes: The effective data sequence of the second pilot symbol sequence is determined from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the third sub-symbol; The effective data sequence of the third pilot symbol sequence is determined from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the fourth sub-symbol.

3. The method according to claim 2, characterized in that, The step of determining the largest correlation value among the correlation values ​​of the first ZC search sequence and the first search sequence as the first maximum correlation value, and determining the position of the effective data sequence of the first pilot symbol sequence based on the first maximum correlation value, further includes: Starting from the first sampling point of the first search sequence, sampling points of the preset length are selected sequentially as the first subsequence to obtain multiple first subsequences. Among them, in two adjacent first subsequences, the first sampling point of one first subsequence is adjacent to the first sampling point of the other first subsequence. The correlation values ​​between the first ZC search sequence and each of the first subsequences are calculated sequentially to obtain the correlation values ​​corresponding to the multiple first subsequences respectively. The largest correlation value among the correlation values ​​corresponding to the multiple first subsequences is determined as the first maximum correlation value; The first sampling point of the first subsequence corresponding to the first maximum correlation value is determined as the position of the effective data sequence of the first pilot symbol sequence.

4. The method according to claim 2, characterized in that, The method further includes: When the first power difference between the second maximum correlation value and the first maximum correlation value is less than the first preset power difference, the second search sequence is determined as the valid data sequence of the fourth pilot symbol sequence; when the first power difference between the third maximum correlation value and the first maximum correlation value is less than the first preset power difference, the third search sequence is determined as the valid data sequence of the fourth pilot symbol sequence. Determine the position of the valid data sequence of the fourth pilot symbol sequence; Centered on the position of the effective data sequence of the first pilot symbol sequence, sampling points of a continuous preset sequence length are selected as the first sequence; Centered on the position of the effective data sequence of the fourth pilot symbol sequence, sampling points of the preset sequence length are selected as the second sequence; The frequency offset of the sequence to be searched is determined based on the first sequence and the second sequence; The search sequence is corrected for frequency offset based on the frequency offset to obtain the search sequence after frequency offset correction. The step of determining the effective data sequence of the second pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the first sub-symbol, and determining the effective data sequence of the third pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the second sub-symbol, further includes: The effective data sequence of the second pilot symbol sequence is determined from the frequency offset-corrected search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the first sub-symbol; The effective data sequence of the third pilot symbol sequence is determined from the frequency offset-corrected search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the second sub-symbol. The step of determining the effective data sequence of the second pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the third sub-symbol, and determining the effective data sequence of the third pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the fourth sub-symbol, further includes: The effective data sequence of the second pilot symbol sequence is determined from the frequency offset-corrected search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the third sub-symbol. The effective data sequence of the third pilot symbol sequence is determined from the frequency offset-corrected search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the fourth sub-symbol.

5. The method according to claim 1, characterized in that, The step of determining the root value of the second pilot symbol sequence as the root value of the second ZC search sequence, which has the largest correlation value with the effective data sequence of the second pilot symbol sequence among multiple second ZC search sequences, further includes: Starting from the first sampling point of the effective data sequence of the second pilot symbol sequence, sampling points of the preset length are selected sequentially as second subsequences to obtain multiple second subsequences. Among them, in two adjacent second subsequences, the first sampling point of one second subsequence is adjacent to the first sampling point of the other second subsequence. Calculate the first correlation value between each second ZC search sequence and each second subsequence in turn to obtain the first correlation values ​​corresponding to the multiple second ZC search sequences respectively; Determine the second ZC search sequence corresponding to the largest first relevance value among the multiple second ZC search sequences; The root value corresponding to the second ZC search sequence with the largest first correlation value is determined as the root value of the second pilot symbol sequence; The step of determining the root value of the third pilot symbol sequence as the root value of the second ZC search sequence that has the largest correlation value with the effective data sequence of the third pilot symbol sequence among a plurality of second ZC search sequences further includes: Starting from the first sampling point of the effective data sequence of the third pilot symbol sequence, sampling points of the preset length are selected sequentially as the third subsequence to obtain multiple third subsequences. Among them, in two adjacent third subsequences, the first sampling point of one third subsequence is adjacent to the first sampling point of the other third subsequence. The second correlation value between each second ZC search sequence and each third subsequence is calculated sequentially to obtain the second correlation values ​​corresponding to the multiple second ZC search sequences respectively; Determine the second ZC search sequence corresponding to the largest second correlation value among the multiple second ZC search sequences; The root value corresponding to the second ZC search sequence with the largest second correlation value is determined as the root value of the third pilot symbol sequence.

6. The method according to claim 5, characterized in that, The method further includes: Determine the second subsequence with the largest first correlation value among the multiple second ZC search sequences; The second subsequence with the largest first correlation value is determined as the position of the effective data sequence of the second pilot symbol sequence; Calculate the position difference between the position of the effective data sequence of the first pilot symbol sequence and the position of the effective data sequence of the second pilot symbol sequence; Determine whether the position difference and the length of the first symbol are less than or equal to a preset difference; If so, then the step of determining the root value of the second ZC search sequence corresponding to the largest first correlation value as the root value of the second pilot symbol sequence is performed.

7. The method according to claim 5, characterized in that, After determining the second ZC search sequence corresponding to the largest second correlation value among the multiple second ZC search sequences, the method further includes: Determine the largest second correlation value among the second correlation values ​​corresponding to the multiple second ZC search sequences; Calculate the second power difference between the largest second correlation value and the largest first correlation value; Determine whether the second power difference is less than or equal to the second preset power difference; If so, then the step of determining the root value of the second ZC search sequence corresponding to the largest second correlation value as the root value of the third pilot symbol sequence is performed.

8. The method according to claim 1, characterized in that, The method further includes: Obtain the sampling rate and subcarrier spacing of the OFDM signal; The length of the effective data sequence of the sequence to be searched is calculated based on the sampling rate and the subcarrier spacing. The length of the CP sequence of the sequence to be searched is calculated based on the subcarrier spacing; The symbol length of the sequence to be searched is determined based on the length of the effective data sequence and the length of the CP sequence; The step of determining the first search sequence from the search sequence based on the symbol position of the symbol corresponding to the first pilot symbol sequence in the OFDM signal further includes: Based on the symbol position of the symbol corresponding to the first pilot symbol sequence in the OFDM signal, sampling points of consecutive symbol length are selected from the search sequence as the first search sequence; The step of determining the effective data sequence of the second pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the length of the first symbol further includes: Based on the position of the effective data sequence of the first pilot symbol sequence and the length of the first symbol, sampling points of consecutive lengths of the effective data sequence are selected from the sequence to be searched as the effective data sequence of the second pilot symbol sequence; The step of determining the effective data sequence of the third pilot symbol sequence from the search sequence based on the position of the effective data sequence of the first pilot symbol sequence and the second symbol length further includes: Based on the position of the effective data sequence of the first pilot symbol sequence and the length of the second symbol, sampling points of consecutive lengths of the effective data sequence are selected from the sequence to be searched as the effective data sequence of the third pilot symbol sequence.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the drone identification method according to any one of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the drone identification method according to any one of claims 1 to 8.

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