Anti-interference frequency hopping sequence construction method based on sequence combination

Abstract

The invention discloses an anti-interference frequency hopping sequence construction method based on sequence combination, and belongs to the field of communication signal processing. The frequency band hopping sequence is constructed by adopting a wide interval sequence design means, and the frequency band interval dbw meets the condition that the interval between the selected frequency point and the other frequency points in the adjacent frequency band is greater than the minimum frequency hopping interval d, so that the probability that the adjacent working frequency points fall into an interference band during frequency hopping communication is greatly reduced, and the resistance to blocking interference is ensured. Randomization mapping is carried out on frequency points in a frequency band, a pseudo-random sequence with excellent balance is constructed, combination mapping is carried out on the pseudo-random sequence and a wide-interval frequency band hopping sequence, the random performance of the sequence is improved through random disturbance, and then the decoding risk is reduced. By adopting balance characteristics and approximate entropy evaluation criteria, flexible selection of a sequence proportion is realized, and optimization of anti-interference performance of the sequence is realized at the same time; a data link frequency hopping synchronization verification scene is adopted, a frequency hopping communication condition is simulated in a blocking interference environment, and accurate evaluation of the anti-interference performance of the sequence is realized.

Description

Technical Field

[0001] This invention belongs to the field of communication signal processing and relates to a wide-interval frequency hopping sequence design method for blocking interference in broadband communication scenarios. Background Technology

[0002] In frequency-hopping communication, the frequency-hopping sequence is a core factor determining the carrier hopping pattern of the system, and its performance directly affects the system's anti-interference capability, synchronization stability, and security. Therefore, researchers both domestically and internationally have long been committed to the optimal design of frequency-hopping sequences, proposing various theoretical limits and construction methods. In recent years, the construction methods for frequency-hopping sequences have been continuously expanded, gradually introducing more mathematical tools, such as construction methods based on circle division classes and generalized circle division classes, and frequency-hopping sequence optimization methods based on the Chinese Remainder Theorem, etc., to improve the controllability of the sequence and the flexibility of engineering implementation.

[0003] To improve the anti-interference performance of frequency-hopping sequences, research mainly focuses on the construction of wide-interval frequency-hopping sequences and low / collision-free frequency-hopping sequences. Regarding the construction of wide-interval sequences, researchers have proposed optimization methods such as the dual-band method and the random shift substitution method, or they have adopted frequency-hopping design methods corresponding to wide intervals in their construction principles. However, these methods often fail to produce effective anti-interference sequences when many frequency points are contaminated; or the overly fixed sequence intervals reduce the sequence's randomness and weaken its anti-decryption capabilities.

[0004] In the field of UAV communication, frequency hopping communication, as a spectrum spreading method, is highly dependent on the frequency hopping sequence used by the system for its anti-interference performance. Therefore, in UAV communication scenarios, using a frequency hopping sequence design with superior anti-interference capabilities and robustness can better mitigate interference and improve communication quality. Summary of the Invention

[0005] The purpose of this invention is to provide an anti-interference frequency hopping sequence design method based on sequence combination. When dealing with blocking interference, the frequency hopping communication system uses a frequency hopping mechanism to ensure the minimum interval between adjacent operating frequencies, avoid the operating frequency from continuously falling into the interference range, achieve a higher synchronization probability between UAV terminals, and improve the anti-lockdown capability.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution.

[0007] This invention discloses an anti-interference frequency hopping sequence design method based on sequence combination, comprising the following steps:

[0008] S1. Within the specified operating frequency band, set a certain number of frequency hopping points, and the interval between each frequency point should be as equal as possible.

[0009] S2 divides the frequency hopping point set in S1 into several sub-bands, each containing the same number of frequency points.

[0010] When the frequency hopping frequency point set in S1 contains N frequency points, the frequency point set is divided into M sub-bands F with equal proportions. i Each sub-band F i It contains W frequency points;

[0011] S3, when the proportion of the blocking interference coverage band occupying the working frequency band is known, a wide-spaced frequency band hopping sequence is designed for the sub-frequency band obtained in S2, resulting in the wide-spaced sequence B = {b} m This gives the final frequency hopping sequence a basic wide spacing characteristic.

[0012] S31. Based on the proportion ζ of the number of interfered frequency points in the working frequency band to the total number of available frequency points N, the frequency point interval is designed to be greater than d to ensure that the frequency points of two adjacent frequency hopping are not consecutively falling into the interference band. The minimum frequency interval of the frequency hopping sequence is obtained according to Equation (1).

[0013]

[0014] S32, After the frequency band division in step S3, the equivalent minimum frequency band spacing d is obtained by equation (2). bw This ensures that all operating frequencies within a frequency band satisfy the minimum frequency interval d with other frequencies within the adjacent hopping frequency bands in the frequency hopping sequence.

[0015]

[0016] S33, Given the minimum bandwidth d bw With the number of sub-bands M, a wide-interval sequence is designed using a sequence concatenation method according to equation (2), ensuring that the interval d is maintained. bw Satisfy equation (3).

[0017] gcd(M,d bw = gcd(M,d) bw +1)=1 (3)

[0018] The generated wide-interval sequence B = {b m} is represented as:

[0019]

[0020] Sequence B = {b m The elements in} are mapped to each frequency band F i This ensures that the minimum frequency band spacing d between the sub-bands mapped by adjacent elements is achieved. B Satisfy d B ≥d bw, where B = {b m Sequence to frequency band set F = {F i The mapping relationship of |i=1,2,...M} satisfies equation (5).

[0021]

[0022] S4, based on the wide-interval frequency band hopping sequence constructed in S3, maps and associates each sub-band with the sequence B = {b}. m The elements of} are randomized within each sub-band to obtain a pseudo-random frequency point mapping sequence P = {p w}

[0023] S41 adopts a sequence design method based on linear congruence to design the frequency point mapping sequence P, which is used to randomize the sequence in the frequency band. The randomized sequence is used as the pseudo-random sequence part in the combined sequence, thereby ensuring both the flexibility of construction and the uniformity of frequency point usage.

[0024] S42, in the form of the linear congruential method, is as follows:

[0025]

[0026] Where D is the modulus, a is the multiplier, r is the increment, x0 is the initial value, and ξ is a random number. The parameter settings must satisfy the Hull-Dobell theorem to achieve the maximum balanced sequence period. The Hull-Dobell theorem is as follows.

[0027] ①gcd(r,D)=1;

[0028] ②For any prime factor p of D, the multiplier a≡1 (mod p);

[0029] ③If 4|D, then a≡1 (mod 4)

[0030] S43, Given the number of frequency points W within the band, design the frequency point mapping sequence according to the sequence design method based on the linear congruence method to obtain the pseudo-random sequence P = {p j |j=1,2,...,W} represents the pseudo-randomized mapping relationship of frequency points within the band.

[0031] S5, based on S3, design a wide-interval frequency band jump sequence to obtain the wide-interval sequence B = {b} m}, and based on S4, randomize the sub-band mapping to obtain the pseudo-random frequency point mapping sequence P = {p w The final frequency hopping sequence Y = {y} is constructed using an index traversal method. k}

[0032] S51, select the i-th element b of sequence B. i Its physical mapping to frequency band Then select the i-th element p in sequence P. i This element is mapped to a frequency band. frequency Its position in the original working frequency set is as shown in equation (7), where The element with the lowest frequency in the corresponding working frequency set.

[0033]

[0034] S52, based on the sequential selection of frequency elements in S51, the final frequency hopping sequence Y = {y} can be obtained. k}。 y k It is the kth element of the final sequence, and the correspondence between each element in the sequence and the actual communication bandwidth and frequency point is shown in the formula.

[0035]

[0036] S6. Based on the anti-interference frequency hopping sequence constructed in S5, and according to the proportion of sequence B and sequence P when constructing the final sequence, simulate its balance performance and approximate entropy, select the length ratio of the best-performing sequence B and sequence P, and the corresponding frequency hopping sequence, to realize the design of the anti-interference frequency hopping sequence.

[0037] Balance performance characterizes the number of times each frequency gap appears in a sequence period. Under non-ideal conditions, the closer the balance performance index δ is to 0, the better the balance of the sequence and the more uniform the frequency gap distribution of frequency hopping.

[0038] Approximate entropy is a statistic that measures the complexity of frequency-hopping sequences. The more random the frequency-hopping sequence, the lower the frequency of similar patterns, the higher the value of the approximate entropy, and the stronger the resistance to decryption of the frequency-hopping sequence.

[0039] The lengths M of B and P, and the number of W and the total number of working frequencies N satisfy M×W≤N. When the length ratio of the two is close to 1:1, the approximate entropy of the sequence reaches its maximum. At this time, the randomness of the sequence and its resistance to decryption are the best.

[0040] S7. Based on the anti-interference frequency hopping sequence constructed in S5, the sequence design method proposed in this invention has good anti-interference synchronization capability under the mainstream synchronization link establishment method M / N decision method in the UAV data link communication environment; and has good anti-interference and anti-lockdown capability under the communication lockout determination based on continuous out-of-synchronization decision.

[0041] Beneficial effects:

[0042] 1. This invention discloses an anti-interference frequency hopping sequence design method based on sequence combination, which uses a wide-interval sequence design technique to construct a frequency band hopping sequence with a frequency band interval d. bw The selected frequency point and the other frequency points in the adjacent frequency band are spaced apart by a distance greater than the minimum frequency hopping interval d. This significantly reduces the probability that adjacent operating frequency points will fall into the interference band during frequency hopping communication, thus ensuring resistance to blocking interference.

[0043] 2. The present invention discloses an anti-interference frequency hopping sequence design method based on sequence combination. It adopts randomized mapping of frequency points within the frequency band to construct a pseudo-random sequence with good balance, and combines it with a wide-interval frequency band hopping sequence. Compared with the general wide-interval construction method, the random perturbation improves the random performance of the sequence, thereby reducing the risk of being deciphered.

[0044] 3. The present invention discloses an anti-interference frequency hopping sequence design method based on sequence combination. It adopts the balance characteristic and approximate entropy evaluation criteria to achieve flexible selection of sequence ratio and optimize the anti-interference performance of the sequence. It adopts the data link frequency hopping synchronization verification scenario to simulate the frequency hopping communication situation under the blocking interference environment and achieve accurate evaluation of the anti-interference performance of the sequence. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a flowchart of the sequence design for an anti-interference frequency hopping sequence construction method based on sequence combination according to the present invention.

[0047] Figure 2 This is a schematic diagram illustrating the principle of an anti-interference frequency hopping sequence construction method based on sequence combination according to the present invention.

[0048] Figure 3 In the anti-interference frequency hopping sequence construction method based on sequence combination of the present invention, after the frequency set is divided into frequency bands, the actual working frequency band and the wide-interval hopping sequence B = {b m A schematic diagram of the mapping relationship of};

[0049] Figure 4 This is a schematic diagram illustrating the mapping relationship between in-band frequency points and pseudo-random sequence P in an anti-interference frequency hopping sequence construction method based on sequence combination according to the present invention.

[0050] Figure 5In the first embodiment of the present invention, the frequency of use of each working frequency in the frequency hopping sequence designed by the anti-interference frequency hopping sequence construction method based on sequence combination;

[0051] Figure 6 In the first embodiment of the present invention, the spacing distribution of adjacent frequency hopping points in the frequency hopping sequence designed by the anti-interference frequency hopping sequence construction method based on sequence combination;

[0052] Figure 7 In the first embodiment of the present invention, the synchronization probability simulation curve of the frequency hopping sequence designed by the anti-interference frequency hopping sequence construction method based on sequence combination is obtained by using the M / N detection decision method to synchronize the frequency hopping sequence under the frequency hopping communication system subjected to blocking interference.

[0053] Figure 8 In the first embodiment of the present invention, the frequency hopping sequence designed by the anti-interference frequency hopping sequence construction method based on sequence combination is used to simulate the loss probability curve of the frequency hopping sequence under the frequency hopping communication system subjected to blocking interference, using the continuous detection decision method for loss simulation. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0055] Example 1

[0056] like Figure 1 As shown in the figure, this embodiment discloses an anti-interference frequency hopping sequence construction method based on sequence combination. The specific implementation steps are as follows:

[0057] S1. Within the specified operating frequency band, set a certain number of frequency hopping points, and the intervals between each frequency point should be as equal as possible.

[0058] This embodiment considers setting a certain number of frequency hopping points within a specified operating frequency band, f = {f1, f2, f3, ..., f...}. N}, where N = 130, meaning there are 130 frequency hopping operating frequencies within the frequency band, with equal frequency intervals;

[0059] S2 divides the N=130 frequency points in S1 into 13 frequency bands, with each group consisting of 10 frequency points, i.e., M=13 and W=10.

[0060] S3, in this embodiment, it is considered that the known blocking interference coverage band occupies 35% of the working frequency band, i.e., 35% of the frequency points are interfered with. A wide-spaced frequency band hopping sequence is designed for the sub-frequency band obtained in S2, resulting in a wide-spaced sequence B = {b}. m This gives the final frequency hopping sequence a basic wide spacing characteristic.

[0061] S31. Based on the proportion ζ of the number of interfered frequency points in the working frequency band to the total number of available frequency points N, the frequency point interval is designed to be greater than d to ensure that the frequency points of two adjacent frequency hopping are not consecutively falling into the interference band. The minimum frequency interval of the frequency hopping sequence is obtained according to Equation (9).

[0062]

[0063] After the frequency band is divided, with each sub-frequency band transition, d > 0.35 × N, the frequency band spacing can then be calculated. That is, the interval of the frequency band jump sequence is 5;

[0064] S32, After the frequency band division in step S3, the equivalent minimum frequency band spacing d is obtained by equation (10). bw This ensures that all operating frequencies within a frequency band satisfy the minimum frequency interval d with other frequencies within the adjacent hopping frequency bands in the frequency hopping sequence.

[0065]

[0066] At this point, the bandwidth can be calculated. That is, the interval of the frequency band jump sequence is 5.

[0067] S33, Given the minimum bandwidth d bw With the number of sub-bands M, a wide-interval sequence is designed using a sequence concatenation method according to equation (2), ensuring that the interval d is maintained. bw It satisfies equation (11).

[0068] gcd(M,d bw )=gcd(13,5)=1=gcd(M,d bw +1)=gcd(13,6) (11)

[0069] The generated wide-interval sequence B = {b m} can be represented as:

[0070]

[0071] Sequence B = {b m The elements in} can be mapped to each frequency band F i This ensures that the minimum frequency band spacing d between the sub-bands mapped by adjacent elements is achieved. B Satisfy d B ≥d bw , where B = {b m Sequence to frequency band set F = {F i The mapping relationship of |i=1,2,...M} satisfies equation (13).

[0072]

[0073] The complete sequence B is as follows:

[0074] B={1,7,13,6,12,5,11,4,10,3,9,2,8,2,9,3,10,4,11,5,12,6,13,7,1,8} (14)

[0075] S4, based on the wide-interval frequency band hopping sequence constructed in S3, maps and associates each sub-band with the sequence B = {b}. m The elements of} are randomized within each sub-band to obtain a pseudo-random frequency point mapping sequence P = {p w}

[0076] S41 adopts a sequence design method based on linear congruence to design the frequency point mapping sequence P, which is used to randomize the sequence in the frequency band. The randomized sequence is used as the pseudo-random sequence part in the combined sequence, thereby ensuring both the flexibility of construction and the uniformity of frequency point usage.

[0077] S42, in the form of the linear congruential method, is as follows:

[0078]

[0079] Where D is the modulus, a is the multiplier, r is the increment, x0 is the initial value, and ξ is a random number. The parameter settings must satisfy the Hull-Dobell theorem to achieve the maximum balanced sequence period. The Hull-Dobell theorem is as follows.

[0080] ①gcd(r,D)=1;

[0081] ②For any prime factor p of D, the multiplier a≡1 (mod p);

[0082] ③If 4|D, then a≡1 (mod 4)

[0083] S43, Given the number of frequency points W within the band, design the frequency point mapping sequence according to the sequence design method based on the linear congruence method to obtain the pseudo-random sequence P = {p j |j=1,2,...,W} represents the pseudo-randomized mapping relationship of frequency points within the band.

[0084] Given that the frequency band has been divided and the number of frequency points W within the band is determined, a pseudo-random sequence P = {p j |j=1,2,...,W}, when W=10, according to equation (15), a complete pseudo-random sequence P can be constructed as shown in equation (16).

[0085] P={10,7,4,1,8,5,2,9,6,3} (16)

[0086] S5, based on S3, design a wide-interval frequency band jump sequence to obtain the wide-interval sequence B = {b} m}, and based on S4, randomize the sub-band mapping to obtain the pseudo-random frequency point mapping sequence P = {p w The final frequency hopping sequence Y = {y} is constructed using an index traversal method. k}

[0087] S51, select the i-th element b of sequence B. i Its physical mapping to frequency band Then select the i-th element p in sequence P. i This element is mapped to a frequency band. frequency Its position in the original working frequency set is as shown in equation (7), where The element with the lowest frequency in the corresponding working frequency set.

[0088]

[0089] It is the i-th element of the final sequence, and so on, to obtain the frequency hopping sequence y = {y} k |k=1,2,...,2M×W / gcd(2M,W)}, where the correspondence between each element in the sequence and the actual communication bandwidth and frequency point is shown in the following formula:

[0090]

[0091] The final sequence y is as follows:

[0092]

[0093] Calculate the interval between adjacent elements in the sequence and analyze the distribution map of adjacent frequency point intervals, such as... Figure 5 As shown, the minimum interval distribution of the sequence is 53. For continuous narrowband interference with an interference ratio ζ of 35%, the maximum number of interference frequency points can reach 46, which is less than the frequency hopping interval distribution of the generated sequence;

[0094] S6, based on the anti-interference frequency hopping sequence constructed in S5 using sequence combination, simulate its balance performance and approximate entropy according to the proportion of sequence B and sequence P in the final constructed sequence. Select the optimal length ratio of sequence B and sequence P, and the corresponding frequency hopping sequence, to achieve the design of the anti-interference frequency hopping sequence. Based on the above sequence description results, simulate its balance performance, approximate entropy randomness, synchronization performance, and lockout performance.

[0095] S61, its equilibrium value δ is calculated using equation (20).

[0096]

[0097] Wherein, the smaller δ is, the better the sequence balance performance, and the more uniform the frequency of each frequency. Calculations show that the balance performance of the above sequence y is δ = 0. Combined with... Figure 4 This indicates that the frequency of use of each frequency point in sequence y is basically consistent, and the balance is excellent;

[0098] S62 uses time series approximate entropy to measure the irregularity and complexity of frequency hopping sequences;

[0099] S621, a frequency hopping sequence of length L {y(1),y(2),...,y(L)}, with subsequence length metric m, is reconstructed to obtain L-m+1 subsequences Y(i):

[0100] Y(i)=[y(i),y(i+1),...,y(i+m-1)],1≤i≤L-m+1 (21)

[0101] S622, define the Chebyshev distance d[Y(i),Y(j)] between sequences Y(i) and Y(j) as the maximum difference between corresponding elements in the two sequences:

[0102]

[0103] S623, Given a threshold r representing similarity comparison, for each i, count the number of distances d < r, and record the ratio of this number to the total number of distances Nm:

[0104]

[0105] S624, Take the logarithm and calculate its average over all i, denoted as:

[0106]

[0107] S625, add 1 to the dimension, making it m+1, and repeat steps S621 to S625 to obtain... and φ m+1 (r);

[0108] S626, the approximate entropy of the sequence is calculated as follows:

[0109] ApEn(m,r,N)=φ m (r)-φ m+1 (r) (25)

[0110] According to equations (21) to (25), the approximate entropy of the frequency hopping sequence in this embodiment can be calculated to be 0.4277;

[0111] S63, the anti-interference capability of this sequence under blocking interference with different spectral characteristics, is measured by its synchronization performance in the interference environment. A narrowband interference scenario with a proportion of 35% is constructed, in which frequency points falling within the interference band cannot achieve communication synchronization;

[0112] S631 uses the ZC sequence as the synchronization sequence, with parameter N selected. ZC =128, u=127, construct the ZC sequence as shown in equation (26).

[0113]

[0114] S632, based on the relevant peak detection method, the false alarm probability P is obtained. fa Detection probability P d As shown in equation (27).

[0115]

[0116] S64, using the M / N decision method, M / N = 3 / 6, calculate the synchronization probability of the communication system when actually using the frequency hopping sequence of this invention. The relationship between the synchronization probability and SNR is as follows: Figure 7 As shown, the highest synchronization success probability can be achieved after -9dB; using the continuous decision method, the lock is lost after two consecutive missed detections. This method is used to calculate the lock loss probability of a communication system when actually using the frequency hopping sequence of this invention. When the signal-to-noise ratio is high, narrowband interference can be completely avoided, preventing communication from continuously falling into the interference band. Simulation results are as follows. Figure 8 As shown.

[0117] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for constructing anti-interference frequency hopping sequences based on sequence combination, characterized in that: Includes the following steps, S1. Within the specified operating frequency band, set a certain number of frequency hopping points, and the interval between each frequency point should be as equal as possible. S2, divide the frequency hopping frequency point set in S1 into equal parts to obtain several sub-bands, each of which contains the same number of frequency points; S3, when the proportion of the blocking interference coverage band occupying the working frequency band is known, a wide-spaced frequency band hopping sequence is designed for the sub-frequency band obtained in S2, resulting in the wide-spaced sequence B = {b} m This gives the final frequency hopping sequence the basic wide-interval characteristic; S4, based on the wide-interval frequency band hopping sequence constructed in S3, maps and associates each sub-band with the sequence B = {b}. m The elements of} are randomized within each sub-band to obtain a pseudo-random frequency point mapping sequence P = {p w }; S5, based on S3, design a wide-interval frequency band jump sequence to obtain the wide-interval sequence B = {b} m }, and based on S4, randomize the sub-band mapping to obtain the pseudo-random frequency point mapping sequence P = {p w The final frequency hopping sequence Y = {y} is constructed using an index traversal method. k }; S6. Based on the anti-interference frequency hopping sequence constructed in S5, and according to the proportion of sequence B and sequence P when constructing the final sequence, simulate its balance performance and approximate entropy, select the length ratio of the best-performing sequence B and sequence P, and the corresponding frequency hopping sequence, to realize the design of the anti-interference frequency hopping sequence.

2. The method for constructing an anti-interference frequency hopping sequence based on sequence combination as described in claim 1, characterized in that: In S2, if the frequency hopping frequency point set in S1 contains N frequency points, the frequency point set is divided equally to obtain M sub-bands F. i Each sub-band F i It contains W frequency points.

3. The method for constructing an anti-interference frequency hopping sequence based on sequence combination as described in claim 2, characterized in that: The S3 implementation method is as follows: S31, based on the proportion ζ of the number of interfered frequency points in the total number of available frequency points N within the working frequency band, the frequency interval is designed to be greater than d to ensure that the frequency points of two adjacent frequency hopping cycles do not fall into the interference band consecutively. The minimum frequency interval of the frequency hopping sequence is obtained according to equation (1): S32, After the frequency band division in step S3, the equivalent minimum frequency band spacing d is obtained by equation (2). bw This ensures that all operating frequencies within the frequency band satisfy the minimum frequency interval d with other frequencies within the adjacent hopping frequency band in the frequency hopping sequence. S33, Given the minimum bandwidth d bw With the number of sub-bands M, a wide-interval sequence is designed using a sequence concatenation method according to equation (2), ensuring that the interval d is maintained. bw Satisfy equation (3); gcd(M,d bw )=gcd(M,d bw +1)=1 (3) The generated wide-interval sequence B = {b m } is represented as: Sequence B = {b m The elements in} are mapped to each frequency band F i This ensures that the minimum frequency band spacing d between the sub-bands mapped by adjacent elements is achieved. B Satisfy d B ≥d bw , where B = {b m Sequence to frequency band set F = {F i The mapping relationship of |i=1,2,...M} satisfies equation (5); 4. The method for constructing an anti-interference frequency hopping sequence based on sequence combination as described in claim 3, characterized in that: The S4 implementation method is as follows: S41 adopts a sequence design method based on linear congruence to design the frequency point mapping sequence P, which is used to randomize the sequence in the frequency band. The randomized sequence is used as the pseudo-random sequence part in the combined sequence, thereby ensuring both the flexibility of construction and the uniformity of frequency point usage. S42, in the form of the linear congruential method, is as follows: Where D is the modulus, a is the multiplier, r is the increment, x0 is the initial value, and ξ is a random number; the parameter settings must satisfy the Hull-Dobell theorem to achieve the maximum balanced sequence period; the Hull-Dobell theorem is as follows; ①gcd(r,D)=1; ②For any prime factor p of D, the multiplier a≡1 (mod p); ③If 4|D, then a≡1 (mod 4) S43, Given the number of frequency points W within the band, design the frequency point mapping sequence according to the sequence design method based on the linear congruence method to obtain the pseudo-random sequence P = {p j |j=1,2,...,W} represents the pseudo-randomized mapping relationship of frequency points within the band.

5. The anti-interference frequency hopping sequence design method based on sequence combination as described in claim 4, characterized in that: The S5 implementation method is as follows: S51, select the i-th element b of sequence B. i Its physical mapping to frequency band Then select the i-th element p in sequence P. i This element is mapped to a frequency band. frequency Its position in the original working frequency set is as shown in equation (7), where The element with the lowest frequency in the corresponding working frequency set; S52, based on the method of selecting frequency elements sequentially in S51, the final frequency hopping sequence Y = {y} is obtained. k };y k It is the kth element of the final sequence, and the correspondence between each element in the sequence and the actual communication bandwidth and frequency point is shown in the formula.

6. The method for constructing an anti-interference frequency hopping sequence based on sequence combination as described in claim 5, characterized in that: In S6, Balance performance characterizes the number of times each frequency gap appears in a sequence period. Under non-ideal conditions, the closer the balance performance index δ is to 0, the better the balance of the sequence and the more uniform the frequency hopping gap distribution. Approximate entropy is a statistic that measures the complexity of frequency-hopping sequences. The more random the frequency-hopping sequence, the lower the frequency of similar patterns, the higher the value of the approximate entropy, and the stronger the resistance to decryption of the frequency-hopping sequence.

7. The method for constructing an anti-interference frequency hopping sequence based on sequence combination as described in claim 6, characterized in that: In S6, The lengths M of B and P, and the number of W and the total number of working frequencies N satisfy M×W≤N. When the length ratio of the two is close to 1:1, the approximate entropy of the sequence reaches its maximum. At this time, the randomness of the sequence and its resistance to decryption are the best.

8. A method for constructing an anti-interference frequency hopping sequence based on sequence combination as described in claims 1, 2, 3, 4, 5, 6, or 7, characterized in that: It also includes step S7, which constructs a UAV data link communication environment under blocking interference based on the anti-interference frequency hopping sequence constructed in S5 and improves the anti-interference synchronization capability under the mainstream synchronization link establishment method M / N decision method through sequence construction method; and improves the anti-interference and anti-lockdown capability under the communication lockout determination based on continuous out-of-synchronization decision.

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