A ground receiving end positioning method and system based on OTFS modulation to enhance low-orbit satellite opportunity signal

Abstract

The present invention discloses a ground receiving end positioning method based on OTFS modulation enhanced low-orbit satellite opportunity signals, including: obtaining real-time position and speed information of E satellites to obtain first data; modulating E groups of random low-orbit satellite opportunity signals based on OTFS modulation technology to obtain a first signal set; performing satellite-to-ground communication link level simulation based on the first signal set in combination with a signal transmission model to obtain a second signal set; tracking and sampling E satellites according to the second signal set and obtaining sampling signals respectively to obtain a sampling signal set; obtaining Doppler frequency shift measurement values ​​of E satellites based on the sampling signal set in combination with a signal processing algorithm; constructing a positioning equation group based on the first data and the Doppler frequency shift measurement values ​​of E satellites in combination with the Doppler positioning principle; solving the positioning equation group to obtain the position information of the ground receiving end. The present invention also discloses a ground receiving end positioning system based on OTFS modulation enhanced low-orbit satellite opportunity signals.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a ground receiving terminal positioning method and system based on OTFS modulation enhanced low-orbit satellite opportunity signal. Background Art

[0002] The Global Navigation Satellite System (GNSS) has long been regarded as a standard technical tool for outdoor positioning and is widely used in daily life and industry needs. However, with the continuous improvement of positioning accuracy requirements and the consideration of device power consumption limitations, existing GNSS systems face challenges such as indoor positioning accuracy, anti-interference capabilities, and low power consumption and low complexity requirements. To meet the above challenges, low earth orbit (LEO) satellites have been proposed as an important supplement to the GNSS system. Compared with the GNSS system, LEO satellites have the advantages of stronger signal strength, lower propagation delay, diversified supplementary signals and wide coverage.

[0003] At present, the existing LEO constellations (such as SpaceX's Starlink, Amazon's Kuiper and OneWeb, etc.) are usually used as opportunity signals to locate the ground receiver through Doppler positioning. Most of the existing low-orbit satellite signal modulation technologies use Chirp spread spectrum modulation, direct sequence spread spectrum BPSK modulation and OFDM modulation technology. Although these modulation technologies support long-distance signal transmission, the characteristics of the existing signals make it impossible to effectively distinguish the Doppler shifts of different path signals in dynamic channels, and cannot adapt well to high-speed mobile wireless scenarios, resulting in inaccurate positioning results. In addition, the existing signal processing methods are mainly concentrated in the time-frequency domain, which cannot match the characteristics of the satellite-to-ground channel well. OTFS modulation can convert time-varying channels into quasi-time-invariant channels by mapping signals to the Delay-Doppler (DD) domain, so that all symbols experience the same channel conditions throughout the transmission process. However, OTFS is currently mainly studied for communication scenarios, and its advantages as a positioning waveform have not yet been explored.

[0004] Therefore, a new technical solution is urgently needed to solve the technical problem of how to improve the positioning accuracy of the ground receiving end. Summary of the invention

[0005] The present invention provides a ground receiving end positioning method and system based on OTFS modulation enhanced low-orbit satellite opportunity signal, which is used to solve the technical problem of how to improve the positioning accuracy of the ground receiving end.

[0006] To achieve the above object, the present invention provides a ground receiving end positioning method based on OTFS modulation enhanced low-orbit satellite opportunity signal, comprising the following steps:

[0007] Real-time position and speed information of E satellites are obtained to obtain first data; E is an integer greater than or equal to 4.

[0008] Based on the OTFS modulation technology, E groups of random low-orbit satellite opportunity signals are modulated to obtain the first signal set.

[0009] A satellite-to-ground communication link level simulation is performed according to the first signal set in combination with a signal transmission model to obtain a second signal set, wherein the second signal set includes E groups of ground receiving end simulation signals.

[0010] According to the second signal set, E satellites are tracked and sampled, and sampling signals are respectively acquired to obtain a sampling signal set; and Doppler frequency shift measurement values ​​of the E satellites are obtained according to the sampling signal set combined with a signal processing algorithm.

[0011] A positioning equation group is constructed based on the first data and the Doppler frequency shift measurement values ​​of E satellites in combination with the Doppler positioning principle; the positioning equation group is solved based on the Gauss-Newton method to obtain the position information of the ground receiving end.

[0012] Preferably, modulating the E group of random low-orbit satellite opportunity signals based on the OTFS modulation technology includes:

[0013] Generate E groups of random delay-Doppler domain symbols , expressed as ; Based on the inverse symplectic finite Fourier transform Mapped to the time-frequency domain, the time-frequency domain symbol is obtained , which can be expressed as:

[0014] ,

[0015] After the Heisenberg transformation, we get a set of time domain signals, that is, a set of random low-orbit satellite opportunity signals :

[0016] ,

[0017] in, Indicates the index of the symbol in the Doppler domain; Represents the index of the symbol in the delay domain; Represents the index of the symbol in the time domain; Represents the index of the symbol in the frequency domain; is a natural constant; represents an imaginary number; Indicates time; represents the transmit shaping filter, represents a random LEO satellite opportunity signal in the time domain; Indicates the number of subcarriers, and the subcarrier spacing is ; Indicates the number of time slots; Represents the time slot length, and the occupied bandwidth is .

[0018] All Mapped to the time-frequency domain, E groups of random low-orbit satellite opportunity signals are obtained, that is, the first signal set is obtained.

[0019] Preferably, performing satellite-to-ground communication link-level simulation according to the first signal set in combination with the signal transmission model to obtain the second signal set includes:

[0020] Based on the 3GPP TR 38.811 standard, the NTN-TDL-B model is selected as the signal transmission model, which can be expressed as:

[0021] ,

[0022] ,

[0023] in, represents the channel impulse response; represents the delay of the first path; Indicates the total number of multipath components; Indicates Paths; Indicates The complex amplitude of the path; represents the unit impulse function; represents the path loss; Indicates the propagation distance from the satellite to the ground; Indicates the carrier frequency; Represents the speed of light.

[0024] Based on the signal transmission model, link-level simulation is performed on E satellites, and the receiving end simulates the signal It can be expressed as:

[0025] ,

[0026] is the channel expansion function in the delay-Doppler domain, which can be expressed as:

[0027] ,

[0028] ,

[0029] ,

[0030] in, Indicates the number of propagation paths; and Respectively represent Path gain, delay, and Doppler shift of each path; represents Doppler; Indicates Paths; Represents the fractional part of the Doppler shift measurement; Represents the integer part of the Doppler shift measurement; Represents the delay index of the i-th path.

[0031] The receiving end simulation signals of E satellites are obtained, that is, the second signal set is obtained.

[0032] Preferably, tracking and sampling the E satellites according to the second signal set and acquiring sampling signals respectively to obtain a sampling signal set; and obtaining the Doppler frequency shift measurement values ​​of the E satellites according to the sampling signal set in combination with a signal processing algorithm includes:

[0033] Track and sample E satellites, obtain the Doppler frequency of each satellite respectively, and obtain a sampling signal set; and obtain the Doppler frequency shift measurement values ​​of E satellites based on the sampling signal set and a signal processing algorithm.

[0034] The Doppler frequency shift measurement value includes an integer part and a fractional part; the signal processing algorithm includes respectively obtaining the integer part and the fractional part of the Doppler frequency shift measurement values ​​of E satellites according to the sampled signal set, and combining the integer part and the fractional part to obtain the Doppler frequency shift measurement values ​​of E satellites.

[0035] Preferably, respectively obtaining the integer part and the fractional part of the Doppler frequency shift measurement values ​​of E satellites according to the sampled signal set comprises:

[0036] Get the integer part of the Doppler frequency shift measurement value of E satellites, including:

[0037] The maximum power corresponds to the position of the integer Doppler shift; by searching The maximum power in the Doppler dimension estimates the integer part of the Doppler shift measurement; the integer part of the Doppler shift measurement can be expressed as:

[0038] ,

[0039] in, express The position index of the maximum power, Indicates the initial position of the pilot symbol in the Doppler dimension.

[0040] Obtaining the fractional part of the Doppler frequency shift measurement value of the E satellites, comprising:

[0041] The fractional part of the Doppler shift measurement is obtained based on the channel spread characteristic, which can be expressed as:

[0042] ,

[0043] ,

[0044] ,

[0045] in, represents the channel estimate; represents the noise term; and is a simplified intermediate quantity; Indicates the current path and the maximum power path index in the Doppler domain distance; Indicates phase offset.

[0046] The fractional part of obtaining the Doppler shift measurement is modeled as a linear regression problem:

[0047] The received signal Filter and retain symbols with power greater than the preset limit for fitting. Set the filter range to , .

[0048] Defining intermediate variables and To assist calculation:

[0049] ,

[0050] ,

[0051] According to the least squares method :

[0052] ,

[0053] use Phase Estimate the fractional part of the Doppler shift measurement :

[0054] .

[0055] Preferably, combining the integer part and the fractional part to obtain the Doppler frequency shift measurement values ​​of E satellites includes:

[0056] The integer part and the fractional part of the Doppler frequency shift measurement value are combined to obtain the Doppler frequency shift measurement value ,include:

[0057] ,

[0058] The integer part and the fractional part of the Doppler frequency shift measurement values ​​of the E satellites are respectively integrated to obtain the Doppler frequency shift measurement values ​​of the E satellites.

[0059] Preferably, constructing a positioning equation group according to the first data and the Doppler frequency shift measurement values ​​of E satellites in combination with the Doppler positioning principle includes:

[0060] When the Doppler shift measurement When received by the receiving end, it can be expressed as:

[0061] ,

[0062] in, represents the theoretically calculated Doppler frequency value, Indicates the Doppler frequency shift measurement value received by the receiving end, represents the satellite velocity vector, represents the satellite position vector, represents the position vector of the receiver, represents the atomic clock frequency deviation of the ath satellite, represents the receiver's atomic clock frequency deviation, Represents the Doppler frequency measurement error.

[0063] Assume that the unknown quantities at the receiving end include the receiving end position and the atomic clock frequency deviation, and the unknown quantity of each satellite is the atomic clock frequency deviation. For E satellites, there are a total of E+4 unknown quantities.

[0064] Given Q Doppler shift measurements, ; can be expressed by the pseudo-range rate equation group as:

[0065] ,

[0066] in, represents the Doppler frequency shift measurement value of the a-th satellite, represents the velocity vector of the ath satellite, is the position vector of the ath satellite, is the atomic clock frequency deviation of the ath satellite, is the Doppler frequency measurement error of the ath satellite.

[0067] All unknown quantities are uniformly represented as a state vector :

[0068] ,

[0069] State Vector is an E+4-dimensional state vector, including the coordinate position of the receiving end .

[0070] Based on the state vector Establish the residual equation, and the actual measurement value is The theoretical value is , the residual equation is the positioning equation group It can be expressed as:

[0071] ,

[0072] ,

[0073] in, represents the Doppler frequency shift measurement value of the Qth satellite; Represents the theoretically calculated Doppler frequency value of the Qth satellite.

[0074] Preferably, solving the positioning equations based on the Gauss-Newton method to obtain the location information of the ground receiving end includes:

[0075] Will Linearize at the current state:

[0076] ,

[0077] in, represents the derivative symbol; represents the state vector; represents the state vector of the pth iteration.

[0078] Jacobian matrix of the residual It can be expressed as:

[0079] ,

[0080] in, represents the residual of the Qth satellite; Represents the atomic clock frequency deviation of the Eth satellite.

[0081] The derivative terms in the Jacobian matrix can be expressed as:

[0082] ,

[0083] in, represents the residual of the a-th satellite.

[0084] The Gauss-Newton method is used to iteratively solve the receiving end state:

[0085] ,

[0086] in, represents the residual of the pth iteration; represents the state vector of the p+1th iteration.

[0087] The state vector is continuously updated by iteration until the residual converges, thereby obtaining the position information of the ground receiving end and the atomic clock frequency deviations of the ground receiving end and each satellite.

[0088] Preferably, acquiring real-time position and speed information of E satellites to obtain the first data includes:

[0089] Obtain two lines of orbital data; obtain the satellite's orbital elements based on the two lines of orbital data; the satellite's orbital elements include semi-major axis, eccentricity, inclination, right ascension of ascending node, and argument of perigee.

[0090] The satellite's position and velocity information is obtained based on the satellite's orbital elements combined with a simplified conventional perturbation propagation model.

[0091] A sub-satellite point trajectory diagram is obtained according to the position information and speed information of the satellite; the sub-satellite point trajectory diagram includes the position information and speed information of a preset number of satellites.

[0092] The real-time position and speed information of E satellites are acquired according to the sub-satellite point trajectory diagram to obtain first data.

[0093] The present invention also provides a ground receiving end positioning system based on OTFS modulation enhanced low-orbit satellite opportunity signal, which is used in the method of the present invention. The system includes a data acquisition module, a signal modulation module, a simulation module, a sampling module, a Doppler frequency shift measurement value calculation module, a positioning equation group construction module and a positioning equation group solving module.

[0094] The data acquisition module is used to acquire the real-time position and speed information of E satellites to obtain first data; E is an integer greater than or equal to 4.

[0095] The signal modulation module is used to modulate E groups of random low-orbit satellite opportunity signals based on the OTFS modulation technology to obtain a first signal set.

[0096] The simulation module is used to perform satellite-to-ground communication link-level simulation according to the first signal set in combination with the signal transmission model to obtain a second signal set, wherein the second signal set includes E groups of ground receiving end simulation signals.

[0097] The sampling module is used to track and sample E satellites according to the second signal set and obtain sampling signals respectively to obtain a sampling signal set.

[0098] The Doppler frequency shift measurement value calculation module is used to obtain the Doppler frequency shift measurement values ​​of E satellites according to the sampling signal set combined with the signal processing algorithm.

[0099] The positioning equation group construction module is used to construct a positioning equation group according to the first data and the Doppler frequency shift measurement values ​​of E satellites in combination with the Doppler positioning principle.

[0100] The positioning equation group solving module is used to solve the positioning equation group based on the Gauss-Newton method to obtain the position of the ground receiving end.

[0101] The present invention has the following beneficial effects:

[0102] The ground receiving end positioning method based on OTFS modulation enhancement of low-orbit satellite opportunity signals of the present invention modulates low-orbit satellite opportunity signals based on OTFS technology for subsequent simulation. OTFS modulates signals in the delay-Doppler domain, which can make full use of the delay spread and Doppler spread characteristics of the channel. After OTFS maps the signal to the delay-Doppler domain, the dynamic characteristics of the channel are converted into quasi-static characteristics, reducing the impact of fast time-varying channels on system performance. The method performs signal processing by modulating the opportunity signal of the low-orbit satellite based on the OTFS technology, respectively obtaining the integer and decimal parts of the Doppler frequency shift, obtaining an accurate estimate, and solving the Doppler positioning equations according to the satellite orbit information, and finally obtaining accurate ground receiving end position information, thereby improving the positioning accuracy of the ground receiving end.

[0103] The ground receiving end positioning system based on OTFS modulation enhanced low-orbit satellite opportunity signal of the present invention is used in the method of the present invention and has the same beneficial effects as the method of the present invention.

[0104] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0105] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0106] Figure 1 It is a schematic diagram of a method flow of a preferred embodiment of the present invention.

[0107] Figure 2 It is a sub-satellite point trajectory diagram of four low-orbit satellites in a preferred embodiment of the present invention.

[0108] Figure 3 1 is a Doppler frequency shift curve diagram of four low-orbit satellites in a preferred embodiment of the present invention.

[0109] Figure 4 It is a Doppler frequency shift change rate curve diagram of four low-orbit satellites in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0110] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0111] See also Figure 1 In a preferred embodiment of the present invention, a ground receiving end positioning method based on OTFS modulation enhanced low-orbit satellite opportunity signal is provided, comprising the following steps:

[0112] S1. Acquire the real-time position and speed information of E satellites to obtain first data; E is an integer greater than or equal to 4. Specifically including:

[0113] Obtain two lines of orbital data; obtain the satellite's orbital elements based on the two lines of orbital data; the satellite's orbital elements include semi-major axis, eccentricity, inclination, right ascension of ascending node, and argument of perigee.

[0114] The satellite's position and velocity information is obtained based on the satellite's orbital elements combined with a simplified conventional perturbation propagation model.

[0115] A sub-satellite point trajectory diagram is obtained according to the position information and speed information of the satellite; the sub-satellite point trajectory diagram includes the position information and speed information of a preset number of satellites.

[0116] The real-time position and speed information of E satellites are acquired according to the sub-satellite point trajectory diagram to obtain first data.

[0117] In a preferred embodiment of the present invention, the longitude and latitude of the sub-satellite point are calculated:

[0118] ,

[0119] in, Indicates the longitude of the subsatellite point; Indicates the latitude of the subsatellite point; and Indicates the coordinate position of the satellite in the geocentric inertial coordinate system.

[0120] Using the WGS-84 ellipsoid model of the earth and combining it with the real-time position information, the satellite's trajectory is projected onto the correct longitude and latitude coordinates on the earth's surface. Finally, for ease of observation, it is converted to the Northeastern Universe (ENU) coordinate system to obtain the final sub-satellite point trajectory map.

[0121] In the preferred embodiment of the present invention, see Figure 2, shows the sub-satellite point trajectory diagrams of four low-orbit satellites, Satellite 1, Satellite 2, Satellite 3 and Satellite 4. The sub-satellite point trajectory reflects the movement path of the satellite on the earth's surface, that is, the dynamic coverage of the satellite relative to the rotation of the earth. The trajectory lines show that the satellite moves in a curve on the earth's surface, which is related to the satellite's orbital inclination and the earth's rotation. The trajectory of each satellite in the figure is different, indicating that they are operating on different orbital planes. The orbital inclination determines the coverage of the sub-satellite point. Satellite trajectories with larger inclinations cover high latitudes, while satellites with smaller inclinations mainly cover medium and low latitudes. The distribution of sub-satellite point trajectories directly affects the positioning geometric distribution conditions (GDOP, geometric sparsity factor). The trajectories of the four satellites are relatively independent, and the angles between the trajectories are well distributed. This geometric distribution helps to reduce positioning errors.

[0122] S2. Modulate E groups of random low-orbit satellite opportunity signals based on OTFS modulation technology to obtain a first signal set. Specifically including:

[0123] Generate E groups of random delay-Doppler domain symbols , expressed as ; Based on the inverse symplectic finite Fourier transform Mapped to the time-frequency domain, the time-frequency domain symbol is obtained , which can be expressed as:

[0124] ,

[0125] After the Heisenberg transformation, we get a set of time domain signals, that is, a set of random low-orbit satellite opportunity signals :

[0126] ,

[0127] in, Indicates the index of the symbol in the Doppler domain; Represents the index of the symbol in the delay domain; Represents the index of the symbol in the time domain; Represents the index of the symbol in the frequency domain; is a natural constant; represents an imaginary number; Indicates time; represents the transmit shaping filter, represents a random LEO satellite opportunity signal in the time domain; Indicates the number of subcarriers, and the subcarrier spacing is ; Indicates the number of time slots; Represents the time slot length, and the occupied bandwidth is .

[0128] All Mapped to the time-frequency domain, E groups of random low-orbit satellite opportunity signals are obtained, that is, the first signal set is obtained.

[0129] S3, performing satellite-to-ground communication link-level simulation based on the first signal set in combination with the signal transmission model to obtain a second signal set, wherein the second signal set includes E groups of ground receiving end simulation signals. Specifically, it includes:

[0130] Based on the 3GPP TR 38.811 standard, the NTN-TDL-B model is selected as the signal transmission model, which can be expressed as:

[0131] ,

[0132] ,

[0133] in, represents the channel impulse response; represents the delay of the first path; Indicates the total number of multipath components; Indicates Paths; Indicates The complex amplitude of the path; represents the unit impulse function; represents the path loss; Indicates the propagation distance from the satellite to the ground; Indicates the carrier frequency; Represents the speed of light.

[0134] Based on the signal transmission model, link-level simulation of E satellites is performed, and the receiving end simulates the signal It can be expressed as:

[0135] ,

[0136] is the channel expansion function in the delay-Doppler domain, which can be expressed as:

[0137] ,

[0138] ,

[0139] ,

[0140] Where P represents the number of propagation paths; and Respectively represent Path gain, delay, and Doppler shift of each path; represents Doppler; Indicates Paths; Represents the fractional part of the Doppler shift measurement; Represents the integer part of the Doppler shift measurement; Represents the delay index of the i-th path.

[0141] The receiving end simulation signals of E satellites are obtained, that is, the second signal set is obtained.

[0142] S4, tracking and sampling E satellites according to the second signal set and acquiring sampling signals respectively to obtain a sampling signal set; and obtaining Doppler frequency shift measurement values ​​of E satellites according to the sampling signal set combined with a signal processing algorithm. Specifically including:

[0143] Track and sample E satellites, obtain the Doppler frequency of each satellite respectively, and obtain a sampled signal set; obtain the Doppler frequency shift measurement value of E satellites based on the sampled signal set combined with the signal processing algorithm; the results are shown in Figure 3 to Figure 4 .

[0144] The Doppler frequency shift measurement value includes an integer part and a fractional part; the signal processing algorithm includes respectively obtaining the integer part and the fractional part of the Doppler frequency shift measurement values ​​of E satellites according to the sampled signal set, and combining the integer part and the fractional part to obtain the Doppler frequency shift measurement values ​​of E satellites.

[0145] In a preferred embodiment of the present invention, respectively obtaining the integer part and the fractional part of the Doppler frequency shift measurement values ​​of E satellites according to the sampled signal set specifically includes:

[0146] Get the integer part of the Doppler frequency shift measurement value of E satellites, including:

[0147] The maximum power corresponds to the position of the integer Doppler shift; by searching The maximum power in the Doppler dimension estimates the integer part of the Doppler shift measurement; the integer part of the Doppler shift measurement can be expressed as:

[0148] ,

[0149] in, express The position index of the maximum power, Indicates the initial position of the pilot symbol in the Doppler dimension.

[0150] Get the fractional part of the Doppler shift measurement value of E satellites, including:

[0151] The fractional part of the Doppler shift measurement is obtained based on the channel spread characteristic, which can be expressed as:

[0152] ,

[0153] ,

[0154] ,

[0155] in, represents the channel estimate; represents the noise term; and is a simplified intermediate quantity; Indicates the current path and the maximum power path index in the Doppler domain distance; Indicates phase offset.

[0156] The fractional part of obtaining the Doppler shift measurement is modeled as a linear regression problem:

[0157] The received signal Filter and retain symbols with power greater than the preset limit for fitting. Set the filter range to , .

[0158] Defining intermediate variables and To assist calculation:

[0159] ,

[0160] ,

[0161] According to the least squares method :

[0162] ,

[0163] use Phase Estimate the fractional part of the Doppler shift measurement :

[0164] ,

[0165] In a preferred embodiment of the present invention, the integral part and the fractional part are combined to obtain the Doppler frequency shift measurement values ​​of E satellites, including:

[0166] The integer part and the fractional part of the Doppler frequency shift measurement value are combined to obtain the Doppler frequency shift measurement value ,include:

[0167] ,

[0168] The integer part and the fractional part of the Doppler frequency shift measurement value of the E satellites are integrated respectively to obtain the Doppler frequency shift measurement value of the E satellites.

[0169] S5. Construct a positioning equation group based on the first data and the Doppler frequency shift measurement values ​​of E satellites in combination with the Doppler positioning principle. Specifically, it includes:

[0170] When the Doppler shift measurement When received by the receiving end, it can be expressed as:

[0171] ,

[0172] in, represents the theoretically calculated Doppler frequency value, Indicates the Doppler frequency shift measurement value received by the receiving end, represents the satellite velocity vector, represents the satellite position vector, represents the position vector of the receiver, represents the atomic clock frequency deviation of the ath satellite, represents the receiver's atomic clock frequency deviation, Represents the Doppler frequency measurement error.

[0173] Assuming that the unknown quantities at the receiving end include the receiving end position and the atomic clock frequency deviation, the unknown quantity of each satellite is the atomic clock frequency deviation. For E satellites, there are a total of E+4 unknown quantities.

[0174] Given Q Doppler shift measurements, ; can be expressed by the pseudo-range rate equation group as:

[0175] ,

[0176] in, represents the Doppler frequency shift measurement value of the a-th satellite, represents the velocity vector of the ath satellite, is the position vector of the ath satellite, is the atomic clock frequency deviation of the ath satellite, is the Doppler frequency measurement error of the ath satellite.

[0177] All unknown quantities are uniformly represented as a state vector :

[0178] ,

[0179] State Vector is an E+4-dimensional state vector, including the coordinate position of the receiving end .

[0180] Based on the state vector Establish the residual equation, and the actual measurement value is The theoretical value is , the residual equation is the positioning equation group It can be expressed as:

[0181] ,

[0182] ,

[0183] in, represents the Doppler frequency shift measurement value of the Qth satellite; Represents the theoretically calculated Doppler frequency value of the Qth satellite.

[0184] S6. Solve the positioning equations based on the Gauss-Newton method to obtain the location information of the ground receiving end. Specifically including:

[0185] Will Linearize at the current state:

[0186] ,

[0187] in, represents the derivative symbol; represents the state vector; represents the state vector of the pth iteration.

[0188] Jacobian matrix of the residual It can be expressed as:

[0189] ,

[0190] in, represents the residual of the Qth satellite; Represents the atomic clock frequency deviation of the Eth satellite.

[0191] The derivative terms in the Jacobian matrix can be expressed as:

[0192] ,

[0193] in, represents the residual of the a-th satellite.

[0194] The Gauss-Newton method is used to iteratively solve the receiving end state:

[0195] ,

[0196] in, represents the residual of the pth iteration; represents the state vector of the p+1th iteration.

[0197] The state vector is continuously updated through iteration until the residual converges, and the position information of the ground receiving end and the atomic clock frequency deviation of the ground receiving end and each satellite are obtained.

[0198] The ground receiving end positioning method based on OTFS modulation enhancement of low-orbit satellite opportunity signals of the present invention modulates low-orbit satellite opportunity signals based on OTFS technology for subsequent simulation. OTFS modulates signals in the delay-Doppler domain, which can make full use of the delay spread and Doppler spread characteristics of the channel. After OTFS maps the signal to the delay-Doppler domain, the dynamic characteristics of the channel are converted into quasi-static characteristics, reducing the impact of fast time-varying channels on system performance. The method performs signal processing by modulating the opportunity signal of the low-orbit satellite based on the OTFS technology, respectively obtaining the integer and decimal parts of the Doppler frequency shift, obtaining an accurate estimate, and solving the Doppler positioning equations according to the satellite orbit information, and finally obtaining accurate ground receiving end position information, thereby improving the positioning accuracy of the ground receiving end.

[0199] In a preferred embodiment of the present invention, a ground receiving end positioning system based on OTFS modulation enhanced low-orbit satellite opportunity signal is also provided, which is used for the method of the present invention. The system includes a data acquisition module, a signal modulation module, a simulation module, a sampling module, a Doppler frequency shift measurement value calculation module, a positioning equation group construction module and a positioning equation group solving module.

[0200] The data acquisition module is used to acquire the real-time position and speed information of E satellites to obtain first data; E is an integer greater than or equal to 4.

[0201] The signal modulation module is used to modulate E groups of random low-orbit satellite opportunity signals based on the OTFS modulation technology to obtain a first signal set.

[0202] The simulation module is used to perform satellite-to-ground communication link-level simulation according to the first signal set in combination with the signal transmission model to obtain a second signal set, wherein the second signal set includes E groups of ground receiving end simulation signals.

[0203] The sampling module is used to track and sample E satellites according to the second signal set and obtain sampling signals respectively to obtain a sampling signal set.

[0204] The Doppler frequency shift measurement value calculation module is used to obtain the Doppler frequency shift measurement values ​​of E satellites according to the sampling signal set combined with the signal processing algorithm.

[0205] The positioning equation group construction module is used to construct a positioning equation group according to the first data and the Doppler frequency shift measurement values ​​of E satellites in combination with the Doppler positioning principle.

[0206] The positioning equation group solving module is used to solve the positioning equation group based on the Gauss-Newton method to obtain the position of the ground receiving end.

[0207] The ground receiving end positioning system based on OTFS modulation enhanced low-orbit satellite opportunity signal of the present invention is used in the method of the present invention and has the same beneficial effects as the method of the present invention.

[0208] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A ground receiving end positioning method based on OTFS modulation enhanced low-orbit satellite opportunity signal, characterized in that: The following steps are involved: Acquire real-time position and velocity information of E satellites to obtain first data; E is an integer greater than or equal to 4; Modulating E groups of random low-orbit satellite opportunity signals based on OTFS modulation technology to obtain a first signal set; Perform satellite-to-ground communication link-level simulation according to the first signal set in combination with a signal transmission model to obtain a second signal set, wherein the second signal set includes E groups of ground receiving end simulation signals; Track and sample the E satellites according to the second signal set and obtain sampled signals respectively to obtain a sampled signal set; obtain Doppler frequency shift measurement values ​​of the E satellites according to the sampled signal set in combination with a signal processing algorithm; Constructing a positioning equation group according to the first data and the Doppler frequency shift measurement values ​​of the E satellites in combination with the Doppler positioning principle; The positioning equations are solved based on the Gauss-Newton method to obtain the position information of the ground receiving end.

2. The ground receiving end positioning method based on OTFS modulation enhanced low-orbit satellite opportunity signal according to claim 1 is characterized in that: The modulation of the E group of random low-orbit satellite opportunity signals based on the OTFS modulation technology includes: Generate E groups of random delay-Doppler domain symbols , expressed as ; Based on the inverse symplectic finite Fourier transform Map to the time-frequency domain to obtain the time-frequency domain symbol , which can be expressed as: ， After the Heisenberg transformation, we get a set of time domain signals, that is, a set of random low-orbit satellite opportunity signals : ， in, Indicates the index of the symbol in the Doppler domain; Represents the index of the symbol in the delay domain; Represents the index of the symbol in the time domain; Represents the index of the symbol in the frequency domain; is a natural constant; represents an imaginary number; Indicates time; represents the transmit shaping filter, represents a random LEO satellite opportunity signal in the time domain; Indicates the number of subcarriers, and the subcarrier spacing is ; Indicates the number of time slots; Represents the time slot length, and the occupied bandwidth is ; All Mapped to the time-frequency domain, E groups of random low-orbit satellite opportunity signals are obtained, that is, the first signal set is obtained.

3. The ground receiving end positioning method based on OTFS modulation enhanced low-orbit satellite opportunity signal according to claim 2 is characterized in that: According to the first signal set combined with the signal transmission model, a satellite-to-ground communication link level simulation is performed to obtain a second signal set including: Based on the 3GPP TR 38.811 standard, the NTN-TDL-B model is selected as the signal transmission model, which can be expressed as: ， ， in, represents the channel impulse response; represents the delay of the first path; Indicates the total number of multipath components; Indicates Paths; Indicates The complex amplitude of the path; represents the unit impulse function; represents the path loss; Indicates the propagation distance from the satellite to the ground; Indicates the carrier frequency; represents the speed of light; Based on the signal transmission model, link-level simulation is performed on E satellites, and the receiving end simulates the signal It can be expressed as: ， is the channel expansion function in the delay-Doppler domain, which can be expressed as: ， ， ， in, Indicates the number of propagation paths; and Respectively represent Path gain, delay, and Doppler shift of each path; represents Doppler; Indicates Paths; Represents the fractional part of the Doppler shift measurement; Represents the integer part of the Doppler shift measurement; represents the delay index of the i-th path; The receiving end simulation signals of E satellites are obtained, that is, the second signal set is obtained.

4. The ground receiving end positioning method based on OTFS modulation enhanced low-orbit satellite opportunity signal according to claim 3 is characterized in that: Tracking and sampling the E satellites according to the second signal set and acquiring sampling signals respectively to obtain a sampling signal set; Obtaining the Doppler frequency shift measurement values ​​of the E satellites according to the sampled signal set in combination with a signal processing algorithm includes: Tracking and sampling E satellites, respectively acquiring the Doppler frequency of each satellite, and obtaining the sampled signal set; Obtaining Doppler frequency shift measurement values ​​of the E satellites according to the sampled signal set in combination with a signal processing algorithm; The Doppler frequency shift measurement value includes an integer part and a fractional part; the signal processing algorithm includes respectively acquiring the integer part and the fractional part of the Doppler frequency shift measurement values ​​of the E satellites according to the sampled signal set, and combining the integer part and the fractional part to obtain the Doppler frequency shift measurement values ​​of the E satellites.

5. The ground receiving end positioning method based on OTFS modulation enhanced low-orbit satellite opportunity signal according to claim 4 is characterized in that: Acquiring the integer part and the fractional part of the Doppler frequency shift measurement values ​​of the E satellites respectively according to the sampled signal set comprises: Obtaining the integer part of the Doppler frequency shift measurement values ​​of the E satellites, comprising: The maximum power corresponds to the position of the integer Doppler shift; by searching The maximum power in the Doppler dimension estimates the integer part of the Doppler shift measurement; the integer part of the Doppler shift measurement can be expressed as: ， in, express The position index of the maximum power, represents the initial position of the pilot symbol in the Doppler dimension; Obtaining the fractional part of the Doppler frequency shift measurement value of the E satellites, comprising: The fractional part of the Doppler shift measurement is obtained based on the channel spread characteristic, which can be expressed as: ， ， ， in, represents the channel estimate; represents the noise term; and is a simplified intermediate quantity; Indicates the current path and the maximum power path index in the Doppler domain distance; Indicates phase shift; The fractional part of obtaining the Doppler shift measurement is modeled as a linear regression problem: The received signal Filter and retain symbols with power greater than the preset limit for fitting. Set the filter range to , ; Defining intermediate variables and To assist calculation: ， ， According to the least squares estimation : ， use Phase Estimate the fractional part of the Doppler shift measurement : 。 6. The ground receiving end positioning method based on OTFS modulation enhanced low-orbit satellite opportunity signal according to claim 5 is characterized in that: Combining the integer part and the fractional part, the Doppler frequency shift measurement values ​​of the E satellites are obtained, including: The integer part and the fractional part of the Doppler frequency shift measurement value are combined to obtain the Doppler frequency shift measurement value ,include: ， The integer part and the fractional part of the Doppler frequency shift measurement values ​​of the E satellites are respectively integrated to obtain the Doppler frequency shift measurement values ​​of the E satellites.

7. The ground receiving end positioning method based on OTFS modulation enhanced low-orbit satellite opportunity signal according to claim 6 is characterized in that: Constructing a positioning equation group according to the first data and the Doppler frequency shift measurement values ​​of the E satellites in combination with the Doppler positioning principle includes: When the Doppler shift measurement value When received by the receiving end, it can be expressed as: ， in, represents the theoretically calculated Doppler frequency value, Indicates the Doppler frequency shift measurement value received by the receiving end, represents the satellite velocity vector, represents the satellite position vector, represents the position vector of the receiver, represents the atomic clock frequency deviation of the ath satellite, represents the receiver's atomic clock frequency deviation, Represents the Doppler frequency measurement error; Assume that the unknown quantities at the receiving end include the receiving end position and the atomic clock frequency deviation, and the unknown quantity of each satellite is the atomic clock frequency deviation. For E satellites, there are a total of E+4 unknown quantities. Given Q Doppler shift measurements, ; can be expressed by the pseudo-range rate equation group as: ， in, represents the Doppler frequency shift measurement value of the a-th satellite, represents the velocity vector of the ath satellite, is the position vector of the ath satellite, is the atomic clock frequency deviation of the ath satellite, is the Doppler frequency measurement error of the ath satellite; All unknown quantities are uniformly represented as a state vector : ， State Vector is an E+4-dimensional state vector, including the coordinate position of the receiving end ; Based on the state vector Establish the residual equation, and the actual measurement value is The theoretical calculated value is , the residual equation is the positioning equation group It can be expressed as: ， ， in, represents the Doppler frequency shift measurement value of the Qth satellite; Represents the theoretically calculated Doppler frequency value of the Qth satellite.

8. The ground receiving end positioning method based on OTFS modulation enhanced low-orbit satellite opportunity signal according to claim 7 is characterized in that: Solving the positioning equations based on the Gauss-Newton method to obtain the location information of the ground receiving end includes: Will Linearize at the current state: ， in, represents the derivative symbol; represents the state vector; represents the state vector of the pth iteration; Jacobian matrix of the residual It can be expressed as: ， in, represents the residual of the Qth satellite; represents the atomic clock frequency deviation of the Eth satellite; The derivative terms in the Jacobian matrix can be expressed as: ， in, represents the residual of the a-th satellite; The Gauss-Newton method is used to iteratively solve the receiving end state: ， in, represents the residual of the pth iteration; represents the state vector of the p+1th iteration; The state vector is continuously updated by iteration until the residual converges, thereby obtaining the position information of the ground receiving end and the atomic clock frequency deviations of the ground receiving end and each satellite.

9. The ground receiving end positioning method based on OTFS modulation enhanced low-orbit satellite opportunity signal according to claim 8 is characterized in that: Acquire the real-time position and speed information of E satellites, and obtain the first data including: Acquire two lines of orbital data; obtain the orbital elements of the satellite according to the two lines of orbital data; the orbital elements of the satellite include semi-major axis, eccentricity, inclination, right ascension of ascending node, and argument of perigee; Obtaining the position information and velocity information of the satellite according to the orbital elements of the satellite in combination with a simplified conventional perturbation propagation model; Obtaining a sub-satellite point trajectory diagram according to the position information and speed information of the satellite; the sub-satellite point trajectory diagram includes the position information and speed information of a preset number of satellites; The real-time position and speed information of E satellites are acquired according to the sub-satellite point trajectory diagram to obtain the first data.

10. A ground receiving end positioning system based on OTFS modulation enhanced low-orbit satellite opportunity signal, used in the method according to any one of claims 1 to 9, characterized in that: The system includes a data acquisition module, a signal modulation module, a simulation module, a sampling module, a Doppler frequency shift measurement value calculation module, a positioning equation group construction module and a positioning equation group solution module; The data acquisition module is used to acquire real-time position and speed information of E satellites to obtain first data; E is an integer greater than or equal to 4; The signal modulation module is used to modulate E groups of random low-orbit satellite opportunity signals based on OTFS modulation technology to obtain a first signal set; The simulation module is used to perform satellite-to-ground communication link-level simulation according to the first signal set in combination with a signal transmission model to obtain a second signal set, wherein the second signal set includes E groups of ground receiving end simulation signals; The sampling module is used to track and sample the E satellites according to the second signal set and obtain sampling signals respectively to obtain a sampling signal set; The Doppler frequency shift measurement value calculation module is used to obtain the Doppler frequency shift measurement values ​​of the E satellites according to the sampled signal set in combination with a signal processing algorithm; The positioning equation group construction module is used to construct a positioning equation group according to the first data and the Doppler frequency shift measurement values ​​of the E satellites in combination with the Doppler positioning principle; The positioning equation group solving module is used to solve the positioning equation group based on the Gauss-Newton method to obtain the position of the ground receiving end.

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