Passive formation positioning method and device based on over-the-horizon scattering communication

Abstract

The application provides a passive formation positioning method and device based on over-the-horizon scattering communication, a plurality of base stations emit signals to targets in a target formation, so that the targets receive a plurality of emitted signals scattered by the troposphere; each target determines its three-dimensional coordinates according to the received signals and the relative coordinate difference between the targets; and the position of each target is determined according to the three-dimensional coordinates. In the application, a plurality of positioning targets are added to form a target formation in the case of large time delay error. In the positioning environment of the application, the signals emitted by the base stations have time delay error caused by multipath effect, so the relative positions between the targets are selected to improve the overall positioning accuracy.

Description

Technical Field

[0001] This invention belongs to the field of target positioning technology, specifically relating to a passive formation positioning method and device based on beyond-line-of-sight scattering communication. Background Technology

[0002] Electromagnetic waves can be scattered by particles in a non-uniformly distributed atmosphere, and this scattering propagation enables over-the-horizon radio communication, which is defined as scattering communication. The research and application of scattering communication has solved the challenge of over-the-horizon communication between users separated by hundreds of kilometers due to natural geographical factors (deep lakes, high mountains, jungles, etc.). Based on the scattering medium, scattering communication mainly includes tropospheric scattering communication, meteor trail communication or reflection communication, and artificial scattering body scattering communication. Currently, tropospheric scattering communication has gradually reached a mature application stage. Efforts are being made to overcome some of the technical difficulties of tropospheric scattering communication and introduce advanced communication technologies, such as new diversity combining techniques, better channel coding techniques, channel interleaving techniques, and adaptive modulation methods, enabling tropospheric scattering communication to achieve high-capacity and high-stability applications.

[0003] Currently, tropospheric scattering communication has attracted widespread attention from major military powers both domestically and internationally. Scattering communication boasts advantages such as long single-hop distance, strong confidentiality, excellent anti-jamming capabilities, and independence from environmental constraints such as weather and terrain. Battlefield communication environments are extremely harsh; artillery shells, nuclear explosions, and missiles can all impact wireless channels, and there are also enemy electronic jamming and information interception threats. Scattering communication utilizes tropospheric scatterers, thus it is unaffected by environmental limitations. In fact, extreme weather conditions can sometimes enhance its reliability. Furthermore, the narrow antenna beam of scattering communication makes its electromagnetic waves difficult for the enemy to intercept in the air. Tropospheric scattering communication offers unparalleled reliability and stability in military environments compared to other communication systems, and is considered one of the most important communication methods on the future battlefield. Therefore, scattering communication has a wide range of applications.

[0004] The inhomogeneity of the troposphere causes electromagnetic wave scattering, refraction, and reflection, which not only increases system power loss but also leads to fading characteristics in the scattering channel, resulting in increased multipath propagation and larger phase shifts. The uneven distribution of the medium within the electromagnetic sphere and the varying transmission capabilities of atmospheric radiation due to regional characteristics, along with the influence of the Earth's rotation and revolution on solar radiation, create different strata at varying electron densities and latitudes. These strata differ in the duration of their distribution, the suitable transmission frequencies for each layer, and the matching signal strength and transmission range. Due to the inherent scattering, refraction, and reflection of electromagnetic waves by scatterers, the signals arrive at the receiver via different transmission paths and at different times, resulting in multipath propagation effects. Relatively speaking, the number of multipath paths is higher in scattering communication. These multipath effects cause pulse spread in the received signal, leading to time delay spread.

[0005] From the perspective of Doppler spread, Doppler frequency shift leads to Doppler spread. In the troposphere, the disordered movement of charged ions, the irregular changes of scatterers, and the emission and refraction of electromagnetic waves can all cause Doppler frequency shifts per path, further leading to Doppler spread. Statistical and measurement data show that the degree of tropospheric movement and change is relatively small; therefore, the Doppler spread of the tropospheric scattering channel is relatively small, and the channel fading variation can be attributed to slow fading. The tropospheric Doppler spread varies throughout the day. Similar to time delay spread, generally, a large Doppler spread only occurs at sunrise and sunset, while the Doppler spread remains at a small value at other times of the day.

[0006] In the context of scattering communication, passive positioning is the most suitable method for localization. Currently, passive positioning is widely used in radar, sonar, and sensor networks, and was applied to electronic reconnaissance as early as the initial stages of electronic warfare. At that time, people simply used some simple equipment to repeatedly determine the direction of the radiation source and then used mapping methods to determine the target's position. With the development of science and technology and the increasing importance of passive positioning in electronic warfare, it has gradually become a specialized technology and has been vigorously developed. Today, research on passive positioning focuses on how to improve the accuracy of target localization, how to minimize localization time, and how to achieve rapid and accurate localization of moving targets and better estimate their trajectories.

[0007] In the field of passive positioning, the following existing technologies exist:

[0008] (1) Chan Algorithm: The Chan algorithm, also known as the two-step weighted least squares method, is an approximation of the maximum likelihood estimation. Its core idea is to first transform the nonlinear equations established by the Time Difference of Arrival (TDOA) observations and base station location information into a linear equation system composed of unknowns and intermediate variables. Then, using the least squares method, a preliminary value for the sound source location is obtained. Finally, based on the relationship between the intermediate and unknown variables, the least squares method is used to calculate the improved sound source location. The advantages of this algorithm are low computational cost and high positioning accuracy in environments where the noise follows a Gaussian distribution. However, in NLOS (non-line-of-sight) environments, the positioning accuracy of the Chan algorithm will significantly decrease.

[0009] (2) Taylor Series Algorithm: The Taylor series algorithm is a recursive algorithm that requires an initial estimated position. In each recursion, the local least squares (LS) of the TDOA measurement error is solved to improve the estimated position. It is not easy to directly solve the nonlinear equation system shown in Equation (2-16). The equations are expanded by Taylor series and solved iteratively. This is the Taylor series method for solving the localization problem.

[0010] The Taylor series method is a recursive algorithm that requires initial target position estimation. When the initial target position is well-chosen, the Taylor series method achieves high positioning accuracy and converges quickly. However, if the initial target position is poorly chosen, the Taylor series method becomes computationally intensive and easily falls into local minima, making convergence difficult to guarantee.

[0011] (3) Constrained Weighted Least Squares Algorithm: See reference Figure 1 First, assume z a =[x,y,z,r1] o [inner x,y,z,r1] o They are mutually independent, transforming nonlinear equations into pseudolinear equations; secondly, utilizing... The relationship between x, y, and z improves positioning accuracy. This is achieved by using pseudo-linear equations to solve for x, y, and z. Because the quadratic term of the noise is ignored during the process, a threshold effect will occur when the noise is large. Therefore, this scheme adds a constraint to the traditional WLS algorithm: in the first step of the WLS algorithm, the distance from the radiation source to base station 1 is used. Using the constraint that z must always be a non-negative number as a condition, the CWLS algorithm is used to obtain z. a In the second step, (u-s1)⊙(u-s1)≥0 is used as a constraint condition, and the location of the radiation source is finally obtained, where u=[x,y,z] T Let be the target coordinates and be the base station coordinates. i =[x i ,y i ,z i ]T (i = 1, 2, ..., N). This scheme requires multiple iterations to calculate the distance from the target to the observation station in order to obtain the location of the radiation source, thus its complexity is high. Summary of the Invention

[0012] To address the aforementioned problems in the existing technology, this invention provides a passive formation positioning method and apparatus based on beyond-line-of-sight scattering communication. The technical problem to be solved by this invention is achieved through the following technical solution:

[0013] In a first aspect, the present invention provides a passive formation positioning method based on beyond-line-of-sight scattering communication, comprising:

[0014] S100 transmits signals to targets in a target formation through multiple base stations, so that the targets receive multiple transmitted signals scattered by the troposphere;

[0015] S200: Each target determines its own three-dimensional coordinates based on the received signals and the relative coordinate differences between targets;

[0016] S300 determines its own position based on three-dimensional coordinates.

[0017] Secondly, a passive formation positioning device based on beyond-line-of-sight scattering communication includes:

[0018] A transmitting device for transmitting signals to targets in a target formation via multiple base stations, so that the targets receive multiple transmitted signals scattered by the troposphere;

[0019] A positioning device is used to determine the three-dimensional coordinates of each target based on the received signals and the relative coordinate differences between targets;

[0020] A positioning device used to determine its own position based on three-dimensional coordinates.

[0021] Thirdly, an electronic device includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus.

[0022] Memory, used to store computer programs;

[0023] When a processor executes a program stored in memory, it implements the steps of the method described in the first aspect.

[0024] Fourthly, a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method described in one aspect.

[0025] Beneficial effects:

[0026] This invention provides a passive swarm positioning method and apparatus based on beyond-line-of-sight scattering communication. Multiple base stations transmit signals to targets within a target swarm, enabling each target to receive multiple transmitted signals reflected by the troposphere. Each target determines its own three-dimensional coordinates based on the received signals and the relative coordinate differences between targets, and then determines its position based on these three-dimensional coordinates. This invention addresses situations with significant time delay errors by adding multiple positioning targets to form a target swarm. In the positioning environment of this invention, the signals transmitted by the base stations exhibit time delay errors due to multipath effects; therefore, the relative positions between targets are used to improve overall positioning accuracy.

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0028] Figure 1 It is a model diagram of existing technology that uses the weighted least squares algorithm to locate the model under constraints;

[0029] Figure 2 This is a flowchart illustrating a passive formation positioning method based on beyond-line-of-sight scattering communication provided by the present invention.

[0030] Figure 3 This is a schematic diagram of the passive formation positioning method based on beyond-line-of-sight scattering communication provided by the present invention;

[0031] Figure 4 This is a performance comparison chart of different base station number positioning schemes provided by the present invention;

[0032] Figure 5 This is a performance comparison chart of different layout and positioning schemes provided by the present invention. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0034] Before introducing this invention, an example from existing research that is relatively close to this invention is given to illustrate the technical concept of this invention. This example uses a constrained weighted least squares algorithm, that is, a method of imposing constraints on the weighted least squares algorithm. (See references.) Figure 1 , Figure 1 This is a model diagram for constrained localization using the weighted least squares algorithm. To obtain the accurate target location, this example requires the following two steps:

[0035] The first step is to obtain a rough estimate of the target using the least squares (LS) algorithm:

[0036] θ=(G T G) -1 G T h

[0037] In the above formula

[0038]

[0039]

[0040] In formula (7) The measurement path from base station 1 to the target. in Let r be the measured path difference from base station L to the target between base station L and base station 1. L Let r1 be the true path difference from base station L to the target. Let n be the measured path difference from base station l to the target. l (l=1,2,...,L) represents the measurement noise, which is usually assumed to be zero-mean noise. Alternatively, it can be estimated using the WLS algorithm, and the corresponding WLS function is...

[0041] (Gθ-h) T W -1 (Gθ-h)

[0042] In the above formula, the weighting matrix W is

[0043] W = BQB -1

[0044] In the above formula, B is a variable of the form diag(r) 21 ,r 31 ,...,r l1 ) is a diagonal matrix, and Q is the noise variance matrix with prior knowledge.

[0045] The second step involves minimizing the second estimate of θ using another WLS process. It was obtained. It should be noted that, due to... These steps are not available at the start of the calculation, so in order to obtain the optimal solution, these two steps require several iterations.

[0046] In the existing technical solution that utilizes tropospheric scattering for long-distance communication, the inhomogeneity of the tropospheric medium causes electromagnetic waves to scatter and reflect, resulting in significant time delay spread caused by multipath effects on the signal received by the target. This makes it impossible for the algorithm to make accurate estimates in this environment.

[0047] The technical concept of this invention is to use the constrained weighted least squares method for positioning. Based on single targets, a formation is formed, and the relative coordinate differences between targets can be determined using a rangefinder. The target matrix is ​​then expanded to further solve the equations. Therefore, in the positioning environment of this invention, the signals transmitted by the base station suffer from time delay errors caused by multipath effects. Thus, the overall positioning accuracy is improved by utilizing the relative positions of the targets.

[0048] The technical solution of the present invention will be described in detail below.

[0049] refer to Figures 2-3 This invention provides a passive formation positioning method based on beyond-line-of-sight scattering communication, comprising:

[0050] S100 transmits signals to targets in the target formation through multiple base stations, so that the targets receive multiple transmitted signals reflected by the troposphere;

[0051] S200: Each target determines its own three-dimensional coordinates based on the received signals and the relative coordinate differences between targets;

[0052] The S200 of the present invention includes:

[0053] S210, Each target establishes a positioning equation based on the received signals;

[0054] The positioning equation is expressed as:

[0055] Gθ i =h

[0056]

[0057] In the above formula, Let be the path difference between base station L and base station 1 reaching target i after reflection from the troposphere. This represents the measured path length of base station L reaching target i after reflection from the troposphere. The measured path length r represents the distance from base station 1 to target i after reflection from the troposphere. L,i The actual path length of the wave from base station L to target i after reflection through the troposphere is represented by n. L,i Indicates path length r L,i Noise during transmission, r 1,i n represents the actual path length of base station 1 to target i after reflection from the troposphere. 1,i Indicates path length r 1,i Noise during transmission, Let m represent the three-dimensional coordinates of base station m, i and k both represent the target number, the superscript k indicates generality, and the subscript i or superscript i specifically refers to the i-th target, i∈k, (k=1,2,...K), K represents the total number of targets, and L represents the total number of base stations.

[0058] S220, Based on the relative coordinate difference between itself and other targets and the positioning equation, establish a cost function; this step can use the relative coordinate difference to transform the positioning equation to obtain an optimization problem; solve the cost function of the optimization problem.

[0059] Assume that each target in the formation receives signals from all base stations, and calculate the fuzzy distance between the target and each base station based on the time delay of the received signals. The three-dimensional coordinates of the target k are represented as U. k =[x k ,y k ,z k ] T The relative coordinate difference between target i and target j is expressed as ΔU = [x i -x j ,y i -y j ,z i -z j ] T , is the coordinate difference between targets in the formation measured by instruments, and carries the subscript j or superscript j to specifically refer to the j-th target, j∈k.

[0060] Derived through formula:

[0061] G k θ k =h k ;

[0062] Furthermore, if the target i is located, then the θ-th... k With θ i The relationship between them is represented as

[0063]

[0064] From this, we can deduce that...

[0065]

[0066] The optimization problem can then be expressed as:

[0067]

[0068]

[0069]

[0070]

[0071]

[0072] Where Σ represents a diagonal matrix, Σ=diag(1,1,1,-1), This represents the estimated three-dimensional coordinates of the i-th target.

[0073] The cost function is expressed as:

[0074] L(θ i ,λ)=(Gθ i -h) T W -1 (Gθ i -h)+λθ i T Σθ i ;

[0075] Where λ is the Lagrange multiplier.

[0076] S230, take the partial derivative of the cost function to obtain its own three-dimensional coordinates.

[0077] For L(θ) i Find the partial derivative of λ with respect to θ, and then set the result to 0 to obtain the optimal estimate.

[0078] S300 determines its own position based on three-dimensional coordinates.

[0079] This invention provides a passive formation positioning device based on beyond-line-of-sight scattering communication, comprising:

[0080] A transmitting device used to transmit signals to multiple targets via multiple base stations, so that the multiple targets receive the multiple transmitted signals reflected by the troposphere;

[0081] A positioning device is used to determine the three-dimensional coordinates of each target based on the received signals and the relative coordinate differences between targets;

[0082] A positioning device used to determine its own position based on three-dimensional coordinates.

[0083] This invention provides an electronic device including a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus;

[0084] Memory, used to store computer programs;

[0085] The processor, when executing a program stored in memory, implements the steps of passive formation positioning based on beyond-line-of-sight scattering communication.

[0086] The present invention provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a passive formation positioning method based on beyond-line-of-sight scattering communication.

[0087] This invention provides a passive swarm positioning method and apparatus based on beyond-line-of-sight scattering communication. Multiple base stations transmit signals to targets within a swarm, enabling each target to receive multiple transmitted signals scattered by the troposphere. Each target determines its own three-dimensional coordinates based on the received signal and the relative coordinate differences between targets, and then determines its position based on these three-dimensional coordinates. This invention addresses situations with significant time delay errors by adding multiple positioning targets to form a target swarm. In the positioning environment of this invention, signal transmission between base stations, observation stations, and targets is considered linear, eliminating time delay errors caused by multipath effects. Therefore, the overall positioning accuracy can be improved by considering the relative positions of the targets.

[0088] To verify the reliability and effectiveness of the novel algorithm, simulation tests are conducted on the proposed algorithm in this section. The advantages of the algorithm are demonstrated by calculating the positioning accuracy of the Chan algorithm, the single-target constrained weighted least squares algorithm, and the formation constrained weighted least squares algorithm of this invention under different numbers and arrangements of base stations affected by time delay errors in an AWGN noise environment.

[0089] refer to Figure 4 As shown, Figure 4 The error accuracy of target positioning using 4 base stations and 5 base stations was demonstrated. It can be seen that increasing the number of base stations under the same base station layout can make the positioning more accurate, and compared with other existing algorithms, the present invention has a performance advantage.

[0090] Next, keeping the number of fixed base stations unchanged, we will compare the algorithm performance of different base stations in different arrangements.

[0091] Figure 5 This paper demonstrates the accuracy of target localization using different base station arrangements. It shows that changing the base station arrangement can improve accuracy even with the same number of base stations. The Chan algorithm and single-target constrained weighted least squares algorithm are commonly used localization methods, with the single-target constrained weighted least squares algorithm showing the best performance among these methods. However, it still exhibits significant localization errors under conditions of large time delay. Compared to other existing algorithms, this invention offers superior performance.

[0092] This invention addresses the high latency characteristics of tropospheric scattering communication by proposing a formation-based positioning method after experimenting with and comparing commonly used positioning methods. Simulation results demonstrate that the formation-based positioning method provided by this invention achieves more accurate positioning with higher latency errors compared to existing methods.

[0093] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0094] Although this application has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, the disclosure, and the appended claims in carrying out the claimed application. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality.

[0095] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A passive formation positioning method based on beyond-line-of-sight scattering communication, characterized in that, include: S100 transmits signals to targets in a target formation through multiple base stations, so that the targets receive multiple transmitted signals scattered by the troposphere; S200: Each target determines its own three-dimensional coordinates based on the received signals and the relative coordinate differences between targets. S300 determines its own position based on three-dimensional coordinates; S200 includes: S210, Each target establishes a positioning equation based on the received signals; S220, establish a cost function based on the relative coordinate difference between itself and other targets and the positioning equation; S230, take the partial derivative of the cost function to obtain its own three-dimensional coordinates; The positioning equations in S210 are expressed as follows: In the formula, For base stations Reaching the target via scattering from base station 1 The path difference, let , Indicates base station Reaching the target after scattering The measured path, This indicates that base station 1 reaches the target via scattering. The measured path, Represented as base station Reaching the target after scattering Actual path Indicates path Noise during transmission, This indicates that base station 1 reaches the target via scattering. The actual path length, Indicates path Noise during transmission, Indicates base station The three-dimensional coordinates and Both represent the target's sequence number, carrying a superscript. Indicates general applicability, carries a subscript. or superscript Specifically refers to the first One goal, , , Indicates the total number of targets. L Indicates the total number of base stations; Target The three-dimensional coordinates are represented as ,Target With the goal The relative coordinate difference between them is expressed as Carrying a corner mark or superscript Specifically refers to the first One goal, ; S220 includes: S221, The positioning equation is transformed using the relative coordinate difference to obtain an optimization problem; S222, Solve the cost function of the optimization problem; The optimization problem is expressed as: ； ； ； ； ； ； ； in, Represents a diagonal matrix. , Indicates the estimated first The three-dimensional coordinates of the target.

2. The passive formation positioning method based on beyond-line-of-sight scattering communication according to claim 1, characterized in that, The cost function is expressed as: ； in, It is a Lagrange multiplier.

3. A passive formation positioning device based on beyond-line-of-sight scattering communication, characterized in that, include: A transmitting device for transmitting signals to targets in a target formation via multiple base stations, so that the targets receive multiple transmitted signals scattered by the troposphere; A positioning device is used to determine the three-dimensional coordinates of each target based on the received signals and the relative coordinate differences between targets; The positioning device is used to determine its own position based on three-dimensional coordinates; specifically, the positioning device is used for: S210, Each target establishes a positioning equation based on the received signals; S220, establish a cost function based on the relative coordinate difference between itself and other targets and the positioning equation; S230, take the partial derivative of the cost function to obtain its own three-dimensional coordinates; The positioning equations in S210 are expressed as follows: In the formula, For base stations Reaching the target via scattering from base station 1 The path difference, let , Indicates base station Reaching the target after scattering The measured path, This indicates that base station 1 reaches the target via scattering. The measured path, Represented as base station Reaching the target after scattering Actual path Indicates path Noise during transmission, This indicates that base station 1 reaches the target via scattering. The actual path length, Indicates path Noise during transmission, Indicates base station The three-dimensional coordinates and Both represent the target's sequence number, carrying a superscript. Indicates general applicability, carries a subscript. or superscript Specifically refers to the first One goal, , , Indicates the total number of targets. L Indicates the total number of base stations; Target The three-dimensional coordinates are represented as ,Target With the goal The relative coordinate difference between them is expressed as Carrying a corner mark or superscript Specifically refers to the first One goal, ; S220 includes: S221, The positioning equation is transformed using the relative coordinate difference to obtain an optimization problem; S222, Solve the cost function of the optimization problem; The optimization problem is expressed as: ； ； ； ； ； ； ； in, Represents a diagonal matrix. , Indicates the estimated first The three-dimensional coordinates of the target.

4. An electronic device, characterized in that, It includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus; Memory, used to store computer programs; A processor, when executing a program stored in memory, implements the steps of the method described in any one of claims 1-2.

5. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the method described in any one of claims 1-2.

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