TDOA-FDOA combined positioning method based on LTE signals

Abstract

The invention belongs to the technical field of radar signal processing, and particularly relates to a TDOA-FDOA combined positioning method based on LTE signals. The method comprises the following steps: step 1, constructing a TDOA-FDOA combined positioning scene based on an LTE signal; step 2, determining an initial target state through a least square method in a TDOA-FDOA combined positioning scene based on an LTE signal; and step 3, according to the initial target state, accurately solving the position and the speed of the target through a conjugate gradient algorithm. According to the TDOA-FDOA combined positioning method based on the LTE signals, the rich LTE signals in the external environment can be utilized, the position and speed information of the target can be accurately determined, the operation complexity is low, the memory demand is low, and the robustness is high.

Description

Technical Field

[0001] The present application belongs to the field of radar signal processing technology, and in particular relates to a TDOA-FDOA joint positioning method based on LTE signals. Background Art

[0002] Target tracking first needs to determine the initial position of the target. Using external radiation source positioning technology can effectively hide our radar in electronic warfare, so that our radar has better RF stealth performance. In terms of signals, the signals irradiated by external radiation sources mainly include FM radio, TV signals, GSM, CDMA and LTE communication signals, among which LTE signals refer to mobile communication signals used by the 4th generation communication technology (4G). It is a long-term evolution of the Universal Mobile Telecommunications System (UMTS) technical standard formulated by the 3rd Generation Partnership Project (3GPP). It is a communication signal based on orthogonal frequency division multiplexing (OFDM) modulation, with two transmission modes: time division duplex (TDD) and frequency division duplexing (FDD). TDD mode means that the uplink and downlink share the same frequency band resources and use different non-overlapping time slot resources. In contrast, FDD mode means that the uplink and downlink of the signal use different frequency band resources. Since the frequency band resources used by LTE signals in TDD mode are the same, it has an adverse effect on the echo information of the target that can be clearly detected on the Doppler frequency shift, and it is more difficult to obtain the frequency shift information of the signal. In addition, LTE signals have abundant base stations for transmitting, and have a natural advantage in collaborative detection, which can effectively improve the target detection capability. Compared with other signals, it has a wider frequency bandwidth, faster data transmission speed and higher distance resolution.

[0003] In the algorithm for locating the target with the help of a third-party external radiation source, the time delay (TDOA) information of the echo signal and the direct wave signal is often used for fixed target positioning; when locating a moving target, the measurement information also includes the arrival time difference and arrival frequency difference (FDOA) information. By combining the TDOA-FDOA observation information, not only the position of the target can be estimated, but also the speed can be estimated, and more accurate target state information can be obtained. Technically speaking, the positioning system based on the arrival direction is more common, such as angle measurement cross positioning and single-station angle measurement positioning, but it is more susceptible to noise, resolution, etc., and the reliability is not high. Since TDOA and FDOA information are closely related and have high positioning accuracy, TDOA-FDOA is often used to locate the target. At present, there are many experts and scholars who study the use of TDOA-FDOA information to locate mobile radiation sources, but there is no report on how to locate mobile targets in the scenario of multiple LTE signal radiation sources at a single station.

[0004] Therefore, it is desired to have a technical solution to overcome or at least alleviate at least one of the above-mentioned defects of the prior art. Summary of the invention

[0005] The purpose of this application is to provide a TDOA-FDOA joint positioning method based on LTE signals to solve at least one problem existing in the prior art.

[0006] The technical solution of this application is:

[0007] A TDOA-FDOA joint positioning method based on LTE signals, comprising:

[0008] Step 1: Construct a TDOA-FDOA joint positioning scenario based on LTE signals;

[0009] Step 2: In the TDOA-FDOA joint positioning scenario based on LTE signals, the initial target state is determined by the least squares method;

[0010] Step 3: According to the initial target state, the position and speed of the target are accurately solved by the conjugate gradient algorithm.

[0011] In at least one embodiment of the present application, in step 1, constructing a TDOA-FDOA joint positioning scenario based on LTE signals includes:

[0012] Assume that there are N external radiation sources and one observation point in the three-dimensional space. The external radiation source transmits an LTE signal which passes through the target and reaches the observation station to form an echo signal. At the same time, the external radiation source transmits a radiation signal which reaches the observation station to form a direct wave signal. The target is located by observing the TDOA and FDOA information.

[0013] In at least one embodiment of the present application, in step 2, in a TDOA-FDOA joint positioning scenario based on LTE signals, determining an initial target state by a least squares method includes:

[0014] Let the distance R and speed between the target and the observation station be It is expressed as:

[0015] R=||u||2

[0016]

[0017] In the formula,

[0018] u=(x,y,z) T

[0019]

[0020] Build About Quadratic equation of two variables:

[0021]

[0022] In the formula, (·) T Indicates transposition, A1, B1, C1 are:

[0023]

[0024] Among them, s k =(x k ,y k ,z k ) T , (k=1,2,...,N) are the positions of external radiation sources, is the distance between the external radiation source k and the observation station, r k is the observed value of the distance difference between the direct wave signal and the echo signal of the external radiation source k;

[0025] Combining formulas (1) and (2) to calculate R and

[0026] R and Substituting into the likelihood function:

[0027] X=(D T D) -1 D T B

[0028] In the formula,

[0029]

[0030] Where O is a zero matrix;

[0031] Calculate the initial solution X0 that maximizes the likelihood function.

[0032] In at least one embodiment of the present application, formulas (1) and (2) are combined to calculate R and include:

[0033] R is a positive real number, let The value of R is as follows:

[0034] When △<0, R can only take complex roots:

[0035] like but

[0036] like Then R = 0;

[0037] When △≥0, R Obtained and / or

[0038] if as well as If one of them is a positive root, then keep the positive root;

[0039] if as well as If they are all positive roots, they will be retained temporarily;

[0040] if as well as are all negative roots, then R = 0;

[0041] The distance between the corresponding target and the observation station is calculated by formula (2): R , substitute it into the equation (1) In the equation, the coefficients A2, B2, and C2 are solved as follows:

[0042]

[0043] In the formula,

[0044]

[0045] In formula (1) is the observed value of the difference between the path change rate of the direct wave signal and the echo signal of the external radiation source k, It is expressed as:

[0046]

[0047] when as well as When both are positive roots, calculate R and

[0048] In at least one embodiment of the present application, in step 3, according to the initial target state, the position and speed of the target are accurately solved by a conjugate gradient algorithm, including:

[0049] S31, initialization parameters, including: setting the number of iterations to l = 0, the running error to 0 < ε < < 1, the initial gradient direction to

[0050] The calculation formula for the gradient direction is:

[0051]

[0052] In the formula,

[0053]

[0054]

[0055] Among them, θ is the observation matrix, H is the measurement matrix, Q is the covariance matrix of the observation noise, is the distance between the lth external radiation source and the target;

[0056] Step 32: Determine whether || g l ||≤ε, if so, the optimal solution X of the target state is obtained, otherwise, go to step 33;

[0057] Step 33: Calculate the search direction:

[0058]

[0059] In the formula,

[0060]

[0061] Step 34: Determine the step size factor α using the Armijo criterion l ;

[0062] Step 35: Update target state X l+1 :

[0063] X l+1 =X l +α l d l

[0064] calculate:

[0065]

[0066] Step 36: Set the number of iterations l = l + 1, and determine whether l <lmax , l max Is the preset maximum number of iterations, if so, return to step 32.

[0067] The invention has at least the following beneficial technical effects:

[0068] The TDOA-FDOA joint positioning method based on LTE signals in the present application can utilize the abundant LTE signals in the external environment to accurately determine the position and speed information of the target. It has low computational complexity, low memory requirement, and strong robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 This is a schematic diagram of a TDOA-FDOA joint positioning scenario based on LTE signals according to an embodiment of the present application;

[0070] Figure 2 This is a flow chart of a TDOA-FDOA joint positioning method based on LTE signals according to an embodiment of the present application. DETAILED DESCRIPTION

[0071] In order to make the purpose, technical scheme and advantages of the implementation of this application clearer, the technical scheme in the embodiment of this application will be described in more detail below in conjunction with the drawings in the embodiment of this application. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described embodiments are part of the embodiments of this application, not all of them. The embodiments described below with reference to the drawings are exemplary and are intended to be used to explain this application, and should not be construed as limitations on this application. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. The embodiments of this application are described in detail below in conjunction with the drawings.

[0072] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the scope of protection of the present application.

[0073] The following is combined with Figure 1 to Figure 2 This application is described in further detail.

[0074] The present application provides a TDOA-FDOA joint positioning method based on LTE signals, comprising the following steps:

[0075] Step 1: Construct a TDOA-FDOA joint positioning scenario based on LTE signals;

[0076] Step 2: In the TDOA-FDOA joint positioning scenario based on LTE signals, the initial target state is determined by the least squares method;

[0077] Step 3: Based on the initial target state, the position and velocity of the target are accurately solved using the conjugate gradient algorithm.

[0078] The TDOA-FDOA joint positioning method based on LTE signals of the present application, in step 1, constructs a TDOA-FDOA joint positioning scenario based on LTE signals, including:

[0079] Assume that there are N external radiation sources and one observation point in the three-dimensional space. The external radiation source transmits an LTE signal which passes through the target and reaches the observation station to form an echo signal. At the same time, the external radiation source transmits a radiation signal which reaches the observation station to form a direct wave signal. The target is located by observing the TDOA and FDOA information.

[0080] Among them, the parameters related to LTE signals in subsequent derivation are mainly the location of the external radiation source sk , sk represents the position of the external radiation source k; the parameters related to TODA are mainly R and r k , R is the distance between the target and the observation station, r k It is the observed value of the distance difference between the direct wave signal and the echo signal of the external radiation source k; the parameters related to FDOA are mainly and The speed between the target and the observation station, It is the observed value of the difference in the rate of change of the direct wave signal and the echo signal of the external radiation source k.

[0081] In the TDOA-FDOA joint positioning method based on LTE signals of the present application, in step 2, in the TDOA-FDOA joint positioning scenario based on LTE signals, the initial target state is determined by the least squares method. X0 ,include:

[0082] Let the distance R and speed between the target and the observation station be It is expressed as:

[0083] R=||u||2

[0084]

[0085] In the formula,

[0086] u=(x,y,z)T

[0087]

[0088] Build About Quadratic equation of two variables:

[0089]

[0090] In the formula, (·) T Indicates transposition, A1, B1, C1 are:

[0091]

[0092] Among them, s k =(x k ,y k ,z k ) T , (k=1,2,...,N) are the positions of external radiation sources, is the distance between the external radiation source k and the observation station, r k is the observed value of the distance difference between the direct wave signal and the echo signal of the external radiation source k;

[0093] Combining formulas (1) and (2) to calculate R and

[0094] R and Substituting into the likelihood function:

[0095] X=(D T D) -1 D T B

[0096] In the formula,

[0097]

[0098] Where O is a zero matrix;

[0099] Calculate the initial solution X0 that maximizes the likelihood function.

[0100] In this embodiment, the TDOA-FDOA joint positioning method based on LTE signals is characterized in that R and include:

[0101] Since R must be a positive real number, let The value of R is as follows:

[0102] When △<0, R can only take complex roots:

[0103] like but

[0104] like Then R = 0;

[0105] When △≥0, R Obtained and / or

[0106] if as well as If one of them is a positive root, then keep the positive root;

[0107] if as well as If they are all positive roots, they will be retained temporarily;

[0108] if as well as are all negative roots, then R = 0;

[0109] The distance between the corresponding target and the observation station is calculated by formula (2): R , substitute it into the equation (1) In the equation, the coefficients A2, B2, and C2 are solved as follows:

[0110]

[0111] In the formula,

[0112]

[0113] In formula (1) is the observed value of the difference between the path change rate of the direct wave signal and the echo signal of the external radiation source k, It is expressed as:

[0114]

[0115] when as well as When both are positive roots, calculate R and

[0116] The TDOA-FDOA joint positioning method based on LTE signals of the present application, in step 3, accurately solves the position and speed of the target by using the conjugate gradient algorithm according to the initial target state, including:

[0117] S31, initialization parameters, including: setting the number of iterations to l = 0, the running error to 0 < ε < <, the initial gradient direction to

[0118] The calculation formula for the gradient direction is:

[0119]

[0120] In the formula,

[0121]

[0122]

[0123] Among them, θ is the observation matrix, H is the measurement matrix, Q is the covariance matrix of the observation noise, is the distance between the lth external radiation source and the target;

[0124] Step 32: Determine whether || g l ||≤ε, if so, the optimal solution X of the target state is obtained, otherwise, go to step 33;

[0125] Step 33: Calculate the search direction:

[0126]

[0127] In the formula,

[0128]

[0129] Step 34: Determine the step size factor α using the Armijo criterion l ;

[0130] Step 35: Update target state X l+1 :

[0131] X l+1 =X l +α l d l

[0132] calculate:

[0133]

[0134] Step 36: Set the number of iterations l = l + 1, and determine whether l <l max , l max Is the preset maximum number of iterations, if so, return to step 32.

[0135] According to the above steps, the optimal solution of the target state is obtained, and the target position and speed can be obtained according to the optimal solution of the target state.

[0136] The TDOA-FDOA joint positioning method based on LTE signals of the present application uses FDD mode downlink signals to locate the target. Considering that in three-dimensional space, N external radiation sources transmit LTE signals through the target to reach the observation station to form echo signals. At the same time, the external radiation sources transmit radiation signals to reach the observation station to form direct wave signals. The target is positioned with high precision by observing TDOA and FDOA information.

[0137] The TDOA-FDOA joint positioning method based on LTE signals of the present application first constructs a TDOA-FDOA joint positioning scenario based on LTE signals; then, the initial target state is determined by the least squares method; finally, the conjugate gradient target positioning is used to accurately solve the position and speed of the target. Through the above process, when the external radiation is an LTE signal, the target echo signal and the direct wave signal are used to observe the TDOA and FDOA information to perform high-precision positioning of the target. The present application can not only accurately determine the target position and speed, but also has low computational complexity, low memory requirements, and strong robustness.

[0138] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A TDOA-FDOA joint positioning method based on LTE signals, characterized in that: include: Step 1: Construct a TDOA-FDOA joint positioning scenario based on LTE signals; Step 2: In the TDOA-FDOA joint positioning scenario based on LTE signals, the initial target state is determined by the least squares method; Step 3: According to the initial target state, the position and speed of the target are accurately solved by the conjugate gradient algorithm.

2. The TDOA-FDOA joint positioning method based on LTE signals according to claim 1, characterized in that: In step 1, a TDOA-FDOA joint positioning scenario based on LTE signals is constructed, including: Assume that there are N external radiation sources and one observation point in the three-dimensional space. The external radiation source transmits an LTE signal which passes through the target and reaches the observation station to form an echo signal. At the same time, the external radiation source transmits a radiation signal which reaches the observation station to form a direct wave signal. The target is located by observing the TDOA and FDOA information.

3. The TDOA-FDOA joint positioning method based on LTE signals according to claim 2, characterized in that: In step 2, in the TDOA-FDOA joint positioning scenario based on LTE signals, the initial target state is determined by the least squares method, including: Let the distance R and speed between the target and the observation station be It is expressed as: R=||u||2 In the formula, u=(x,y,z) T Build About Quadratic equation of two variables: In the formula, (·) T Indicates transposition, A1, B1, C1 are: Among them, s k =(x k ,y k ,z k ) T , (k=1,2,...,N) are the positions of external radiation sources, is the distance between the external radiation source k and the observation station, r k is the observed value of the distance difference between the direct wave signal and the echo signal of the external radiation source k; Combining formulas (1) and (2) to calculate R and R and Substituting into the likelihood function: X=(D T D) -1 D T B In the formula, Where O is a zero matrix; Calculate the initial solution X0 that maximizes the likelihood function.

4. The TDOA-FDOA joint positioning method based on LTE signals according to claim 3 is characterized in that: Combining formulas (1) and (2) to calculate R and include: R is a positive real number, let The value of R is determined as follows: When △<0, R Only complex roots can be obtained: like but like Then R = 0; When △≥0, R Obtained and / or if as well as If one of them is a positive root, then keep the positive root; if as well as If they are all positive roots, they will be retained temporarily; if as well as are all negative roots, then R = 0; The distance between the corresponding target and the observation station is calculated by formula (2): R , substitute it into the equation (1) In the equation, the coefficients A2, B2, and C2 are solved as follows: In the formula, In formula (1) is the observed value of the difference between the path change rate of the direct wave signal and the echo signal of the external radiation source k, It is expressed as: when as well as When both are positive roots, calculate R and 5. The TDOA-FDOA joint positioning method based on LTE signals according to claim 4, characterized in that: In step 3, based on the initial target state, the position and velocity of the target are accurately solved by a conjugate gradient algorithm, including: S31, initialization parameters, including: setting the number of iterations to l = 0, the running error to 0 < ε < < 1, the initial gradient direction to The calculation formula for the gradient direction is: In the formula, Among them, θ is the observation matrix, H is the measurement matrix, Q is the covariance matrix of the observation noise, is the distance between the lth external radiation source and the target; Step 32: Determine whether || g l ||≤ε, if so, the optimal solution X of the target state is obtained, otherwise, go to step 33; Step 33, calculate the search direction: In the formula, Step 34: Determine the step size factor α using the Armijo criterion l ; Step 35: Update target state X l+1 : X l+1 =X l +a l d l calculate: Step 36: Set the number of iterations l = l + 1, and determine whether l <l max , l max Is the preset maximum number of iterations, if so, return to step 32.

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