A 6G Communication and Navigation Signal Fusion Method, Device and System for Space-Air-Ground Integration

Abstract

This application relates to a 6G communication and navigation signal fusion method, device and system for the integration of space-air-ground. The method includes: generating a communication and navigation fusion signal at the transmitting end; modulating the communication and navigation fusion signal from the time-delay - Doppler domain to the time-delay - time domain and performing a parallel-to-serial conversion to obtain a time-domain communication and navigation fusion signal; quickly capturing a satellite at the receiving end; after capturing the satellite, transforming and restoring the received time-domain communication and navigation fusion signal to obtain a precisely estimated fractional Doppler value and a fractional time delay, and then reconstructing a channel matrix, and demodulating data using the channel matrix to obtain the navigation message information of the captured satellite; performing Doppler positioning using the fractional Doppler value and satellite information to obtain a rough estimate of the receiver's position; calculating a Doppler positioning correction value based on four sets of navigation message information and four sets of pseudorange to correct the rough estimate of the receiver's position, so as to achieve 6G communication and navigation signal fusion transmission. Using this method can improve the signal spectrum efficiency and satellite utilization rate.

Description

Technical Field

[0001] This application relates to the field of satellite navigation technology, and in particular, to a 6G communication and navigation signal fusion method, device and system for air-space-ground integration. Background Art

[0002] The services obtained by mobile communication phone users globally mainly come from terrestrial communication networks, but they only cover about 6% of the Earth's surface. To achieve the goal of "anyone, anytime, anywhere" communication, mobile phone direct connection to satellites has become a hot topic in the air-space-ground integrated network application for the general public. At the same time, due to the advantages of high ground level and small delay, low-Earth orbit satellites can provide higher-precision positioning services and are important supplements to medium- and high-Earth orbit navigation satellites such as Beidou. Both communication and navigation systems are developing in the direction of low-Earth orbit satellites. However, in traditional space-based information systems, communication and navigation satellite systems are isolated and information is separated, making it difficult to meet the demands of mass, high-timeliness, and integrated satellite application services. There are the following severe problems:

[0003] 1) Enormous cost due to duplicate construction: Many countries around the world are promoting the construction of large-scale low-Earth orbit satellite constellations. Some countries' planned tens of thousands of satellites are expected to cost billions of yuan. If the constellation is limited to communication and another navigation constellation is built separately, it will lead to waste of resources and unnecessary high expenses.

[0004] 2) Increasingly tense spectrum resources: With the rapid increase in the number of satellite systems, the spectrum resources for communication and navigation have become particularly tense. Low-Earth orbit satellite systems serve the global population, and sharing the same frequency bands easily causes interference. And dedicated frequency bands are very scarce. If communication and navigation systems each occupy their own dedicated bands, it will further exacerbate the spectrum shortage.

[0005] 3) Lagging performance due to separate development: The information of communication and navigation satellites is separated and the services are lagging. Currently, only relying on terminals for "relay fusion" makes it difficult to meet the requirements of "one network with multiple functions" and "integrated services" in the future 6G.

[0006] With the exploration of 6G technology, there has been a two-way interaction trend between mobile communication and navigation positioning. Therefore, the integrated design of mobile communication and satellite navigation is the general trend. The communication-navigation integrated system based on low-Earth orbit satellites has become an important development direction for 6G air-space-ground integration technology. It is very necessary to carry out relevant technical research and design compatible communication and navigation fusion signals. At present, certain achievements have been made in the research and construction of 6G low-Earth orbit satellite communication-navigation integrated systems at home and abroad. However, the main LEO systems in the world have different focuses on communication and navigation functions. For example, existing systems such as the Starlink system, the second-generation Iridium (Iridium-NEXT) system, and the Beidou short message system cannot well deeply couple the two systems to meet the requirements of the new generation of 6G communication application scenarios.

[0007] Different from medium and high Earth orbit satellites and terrestrial communications, low Earth orbit satellites have extremely fast transit speeds. Traditional OFDM modulation will generate severe inter-carrier interference, and the performance will deteriorate sharply. When adding a navigation and positioning function to a low Earth orbit communication system, the following system difficulties need to be solved:

[0008] 1) The scale of the low Earth orbit satellite constellation is large, and the complexity of multi-satellite acquisition is high. The "Starlink" plan intends to launch up to 40,000 satellites. If the traditional CDMA algorithm is used, the signal acquisition time may be extended to 30 minutes or even longer, which cannot meet the real-time requirements of 6G.

[0009] 2) The low Earth orbit satellite channel has high dynamicity, and it is difficult to accurately track. Accurately estimating the Doppler frequency is crucial for subsequent positioning and communication. However, the high dynamic effect of low Earth orbit satellites poses a severe challenge to signal processing. The risk of losing lock of the traditional frequency-locked loop technology when dealing with this high dynamic scenario is as high as 49.7%.

[0010] 3) The requirements for communication and navigation signals are significantly different, and the real-time positioning accuracy is poor. In a low Earth orbit communication system, if the four-star positioning method of medium and high Earth orbit satellites is used, although the accuracy is high, quadruple coverage is required, which does not conform to the single-coverage standard of the communication system.

[0011] Therefore, designing a new communication and navigation deep fusion signal system, realizing multi-functional in one network, improving the signal spectrum efficiency and satellite utilization rate, and empowering the construction of 6G space-air-ground integration, has great practical significance. Summary of the Invention

[0012] Based on this, in view of the above technical problems, it is necessary to provide a 6G communication and navigation signal fusion method, device and system for space-air-ground integration that can realize multi-functional in one network and improve the signal spectrum efficiency and satellite utilization rate.

[0013] A 6G communication and navigation signal fusion method for space-air-ground integration, the method includes:

[0014] At the transmitter, obtain navigation data and communication service data and generate a pseudo-random sequence; perform channel coding, BPSK mapping and QPSK mapping on the navigation data and communication service data, and then input them into the delay-Doppler domain grid based on OTFS together with the pseudo-random sequence to generate a communication and navigation fusion signal;

[0015] According to the symplectic inverse Fourier transform and the Heisenberg transform, modulate the communication and navigation fusion signal from the delay-Doppler domain to the delay-time domain, and perform parallel-to-serial conversion. After obtaining the time-domain communication and navigation fusion signal, transmit it using an antenna;

[0016] Generate the same pseudo-random sequence as that at the transmitting end at the receiving end to perform serial-to-parallel conversion to generate a time-domain sequence, perform correlation operation on the time-domain sequence and the received time-domain communication-navigation integrated signal, and perform fast acquisition of the satellite at the location where the correlation value is the largest; after capturing the satellite, perform parallel-to-serial conversion, Wigner transform and SFFT transform on the received time-domain communication-navigation integrated signal, restore it to the delay-Doppler domain grid and perform correlation operation with the pseudo-random sequence to obtain the accurately estimated fractional Doppler value and the accurately estimated fractional delay;

[0017] Reconstruct the channel matrix according to the accurately estimated fractional Doppler value and the accurately estimated fractional delay, and use the channel matrix to demodulate the communication service data and navigation data to obtain the navigation message information of the captured satellite;

[0018] Track the loop according to the accurately estimated fractional delay, obtain the signal propagation time and multiply it by the speed of light to obtain the signal propagation distance, use the signal propagation distance as the distance between the satellite and the target receiver, and define it as the pseudo-range;

[0019] Perform Doppler positioning using the fractional Doppler value and satellite information to obtain a rough estimate of the receiver's position; when at least four satellites are accumulated and the navigation message information of the four satellites is obtained, calculate the Doppler positioning correction value according to the four sets of navigation message information and the four sets of pseudo-ranges;

[0020] Correct the rough estimate of the receiver's position according to the Doppler positioning correction value to achieve the integrated transmission of 6G communication-navigation signals.

[0021] The above-mentioned 6G communication and navigation signal fusion method, device and system for integrated space-air-ground communication. In this application, the navigation signal, communication signal and pseudo-random sequence are respectively placed in the time-delay Doppler domain grid to generate the communication and navigation fusion signal. By jointly placing the communication and navigation data and the pseudo-random sequence in the time-delay - Doppler domain, the inter-symbol fusion of communication and navigation data is realized, which can provide a unified terminal and integrated service for the general public and various industries. The receiving end uses the pseudo-random sequence for channel estimation to avoid interference between the two. The fusion signal is modulated on the 6G alternative signal OTFS. Compared with the traditional time-frequency domain, the sparsity of the OTFS time-delay Doppler domain has very strong robustness to the high-dynamic channel of low-earth orbit satellites; due to the fast moving speed of low-earth orbit satellites, the Doppler and time-delay differences of different satellite signals are relatively large, and the same pseudo-random sequence can also be used to distinguish satellites, shortening the acquisition time to one-thousandth of the traditional method. By using the commonality of the application of the pseudo-random sequence in the satellite navigation system and the satellite communication system, the proposed accurate channel estimation in the time-delay Doppler domain can simultaneously complete functions such as pseudo-range measurement, Doppler positioning, and data demodulation; at the same time, considering the contradiction between the single-coverage requirement of communication satellites and the single-coverage of navigation satellites, Doppler positioning is used when there are less than four satellites, and pseudo-range positioning is used for correction after accumulating data of four satellites, greatly improving the positioning accuracy. Starting from the signal system design, this application realizes the deep integration of navigation and communication, providing a navigation and communication solution for the construction of the 6G integrated space-air-ground system with low construction cost, high spectrum efficiency, obvious performance advantages, advanced technical route and rich application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 FIG. is a schematic flow chart of a 6G communication and navigation signal fusion method for integrated space-air-ground communication in one embodiment;

[0023] Figure 2 FIG. is a modulation diagram in the time-delay Doppler domain in one embodiment;

[0024] Figure 3 FIG. is a field diagram of a semi-physical test in one embodiment;

[0025] Figure 4 FIG. is a comparison diagram of demodulation constellations in another embodiment; (a) is the OFDM demodulation constellation diagram; (b) is the OTFS demodulation constellation diagram;

[0026] Figure 5 FIG. is a structural block diagram of a 6G communication and navigation signal fusion device for integrated space-air-ground communication in one embodiment;

[0027] Figure 6 FIG. is a structural diagram of a 6G communication and navigation signal fusion system for integrated space-air-ground communication in one embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] To make the objectives, technical solutions and advantages of this application clearer, the following further details this application in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for explaining this application and are not intended to limit this application.

[0029] In one embodiment, as Figure 1 shown, a 6G communication and navigation signal fusion method for integrated space-air-ground is provided, including the following steps:

[0030] Step 102, obtain navigation data and communication service data at the transmitter and generate a pseudo-random sequence; perform channel coding, BPSK mapping, and QPSK mapping on the navigation data and communication service data, and then input them together with the pseudo-random sequence into the time-delay Doppler domain grid based on OTFS to generate a communication and navigation fusion signal.

[0031] Channel-code the navigation data s nav [n] and the communication service data s com [n], then perform BPSK and QPSK mapping respectively, and place them together with the pseudo-random sequence c[n] for navigation acquisition and channel estimation in the time-delay Doppler domain grid of OTFS as Figure 2 shown, to form the communication and navigation fusion signal x[k, l], k = 0,..., N - 1, l = 0,..., M - 1. Since the low-earth orbit satellites move extremely fast, the Doppler and time-delay of different satellites arriving at the receiver at the same moment will have large differences. Therefore, the pseudo-random sequences inserted by all satellites are the same, avoiding the traversal search for satellites and shortening a large amount of search time. At the same time, placing the communication and navigation data together with the pseudo-random sequence in the time-delay Doppler domain realizes the inter-symbol fusion of communication and navigation data, and can provide a unified terminal and integrated service for the general public and various industries.

[0032] Step 104, modulate the communication and navigation fusion signal from the time-delay Doppler domain to the time-delay time domain according to the symplectic inverse Fourier transform and the Heisenberg transform, and perform serial-to-parallel conversion. After obtaining the time-domain communication and navigation fusion signal, transmit it using an antenna.

[0033] Step 106, generate the same pseudo-random sequence as that at the transmitter at the receiver, perform serial-to-parallel conversion to generate a time-domain sequence, perform correlation operation on the time-domain sequence and the received time-domain communication and navigation fusion signal, and quickly capture the satellite at the point where the correlation value is the largest; after capturing the satellite, perform parallel-to-serial conversion, Wigner transform, and SFFT transform on the received time-domain communication and navigation fusion signal, restore it to the time-delay Doppler domain grid, and perform correlation operation with the pseudo-random sequence to obtain the accurately estimated fractional Doppler value and the accurately estimated fractional time-delay.

[0034] During the channel transmission process, h(τ, v) can be used to represent the channel response:

[0035] h(τ,v) = h0δ(τ - τ0)δ(v - v0)

[0036] For the transmitted signal s(t), τ0 and v0 respectively represent the time delay and Doppler frequency shift of the channel. On the DD domain grid, let l τ and l τ respectively represent the integer values of the channel delay and Doppler grid, which are defined as

[0037]

[0038] where: represents the fractional part of the Doppler frequency, and l τ and k v take integer values respectively. The received signal after passing through the channel can be expressed as:

[0039]

[0040] where: v(t) is the additive noise.

[0041] r(t) is first processed by the RF front-end and transformed into a digital intermediate frequency signal. The receiver generates the same pseudo-random sequence and continuously correlates it with the received signal r(t) to perform a two-dimensional traversal search for the channel parameters. The intersection point of a Doppler frequency value and a time delay value is called a search unit (τ est , v est ). Through the two-dimensional traversal search, calculate the correlation function to find the channel parameters (τ est , v est ) with strong correlation characteristics, so that it satisfies to complete the rough estimation of the channel parameters and the rapid acquisition of the satellite.

[0042] It should be noted that due to the relatively fast movement speed of the satellite, the Doppler and time delay differences between different satellites are relatively large. Therefore, different satellites can still be distinguished by using the same pseudo-random sequence, avoiding the three-dimensional search for the satellite and greatly improving the acquisition speed.

[0043] After completing the satellite acquisition and time synchronization, the receiver performs a serial-to-parallel conversion on the received signal r(t), reconstructs the time delay-time domain grid, and performs the Wigner transform and SFFT transform on the time delay-time domain grid to restore the time delay-Doppler domain grid. Further, use the pseudo-random sequence in the time delay-Doppler domain for correlation operations to achieve accurate estimation of the fractional Doppler and fractional time delay. The specific process is as follows:

[0044] The receiving end restores the received signal y C (t) affected by the channel according to the parameter values of the center point of the search unit:

[0045]

[0046] Further perform the Wigner transform and the SFFT transform on y C (t) to obtain the time-delay - Doppler domain symbol y C [k, l]:

[0047]

[0048] Wherein: obeys the Gaussian distribution, and h w (·) is the sampled impulse response function:

[0049]

[0050] h w (ν′, τ′) represents the circular convolution of the windowed channel response

[0051]

[0052] In order to accurately estimate the parameters in the channel transmission, select the upper and lower boundary values of the Doppler frequency corresponding to the search unit to recover y U [k, l] and y L [k, l]. Among them, the Doppler frequency corresponding to y U [k, l] (y L [k, l]) is higher (lower) than the Doppler frequency used in y C [k, l] by half a search step (higher v bin / 2).

[0053] Perform cross-correlation on the three PN sequences y U [k, l], y C [k, l] and y L [k, l] recovered according to different Doppler frequencies respectively with y[k, l] generated by the pseudo-random sequence generator to obtain the cross-correlation results R(y, y U ), R(y, y C ), R(y, y L ). If there is an estimation deviation, the estimation deviation δ v of the Doppler frequency can be obtained through the early-late method:

[0054]

[0055] By comparing R(y, y U ) and R(y, y L) The relevant results are used to calculate the position of the peak of the PN code autocorrelation function, and then after passing through the energy discriminator of the code based on the pseudo-random sequence, the Doppler frequency estimate value is corrected

[0056]

[0057] where δ v represents the correction amount, and the corrected estimate is moved to the center position of the search unit. After multiple loops, until R(y,y U ) ≈ R(y,y L ) is satisfied, the final accurate Doppler estimated frequency is output. The time delay adopts the same principle, and the accurate time delay estimate

[0058] is output. The pseudo-random sequence in the time delay-Doppler domain is used to estimate the fractional Doppler and fractional time delay, improve the channel estimation accuracy, and can be used for navigation signal tracking, pseudo-range measurement, and Doppler positioning at the same time.

[0059] Step 108, reconstruct the channel matrix according to the accurately estimated fractional Doppler value and the accurately estimated fractional time delay, and use the channel matrix to demodulate the communication service data and navigation data to obtain the navigation message information of the captured satellite.

[0060] Reconstruct the channel matrix G according to the Doppler and time delay information, perform channel equalization according to the channel matrix G and the minimum mean square error criterion, and recover the time delay-Doppler domain communication and navigation integrated signal

[0061]

[0062] where: is the noise variance, I MN is the identity matrix, and then perform BPSK / QPSK demapping and channel decoding on the communication and navigation data to obtain the communication service data and navigation message information, and further obtain the satellite operation status and satellite coordinate information.

[0063] The signal and the channel are characterized in the time delay-Doppler domain, and the channel response of the satellite-ground high-dynamic channel is sparsified, greatly reducing the impact of the high-dynamic channel on signal transmission.

[0064] Step 110, perform loop tracking according to the accurately estimated fractional time delay, obtain the propagation time of the signal and multiply it by the speed of light to obtain the propagation distance of the signal, and use the propagation distance of the signal as the distance between the satellite and the target receiver, which is defined as the pseudo-range.

[0065] Track the loop using the accurately estimated fractional time delay to obtain the signal propagation time. Multiply the signal propagation time by the speed of light to get the signal propagation distance, which is used as the distance between the satellite and the target receiver and is defined as the pseudorange.

[0066]

[0067] Among them, c represents the speed of light.

[0068] Step 112: Perform Doppler positioning using the fractional Doppler value and satellite information to obtain a rough estimate of the receiver's position. When at least four satellites are accumulated and the navigation message information of the four satellites is obtained, calculate the Doppler positioning correction value according to the four sets of navigation message information and the four sets of pseudoranges. Correct the rough estimate of the receiver's position according to the Doppler positioning correction value to achieve the integrated transmission of 6G communication and navigation signals.

[0069] Let the satellite position be The velocity is The satellite transmission frequency is f s ; The receiver position is The velocity is The receiving frequency at the station is f r , The Doppler frequency is Then, for a stationary receiver, the Doppler frequency can be expressed as

[0070]

[0071] Among them, is the radial unit vector pointing from the satellite to the receiver. Considering the receiver clock error δf r and the frequency measurement error εf, the instantaneous Doppler observation equation at the station can be written as

[0072]

[0073] Among them, is the three-dimensional coordinate and clock error of the station, which are the parameters to be solved. Let the initial estimated values of the target position and clock error be

[0074]

[0075] After performing Taylor expansion and linearization on the observation equation in sequence, for the observed values at n moments, the least squares form of Doppler positioning is as follows

[0076]

[0077] Among them: G′ is the transfer matrix, ∈ is the error vector, k is the iteration number, is the solution estimate obtained in the k-th iteration, and Δf is the difference matrix between the Doppler observation value and the estimated value. It can be seen that the entire equation is a linear equation about the increment at this time.

[0078] Therefore, the change in the receiver position can be calculated

[0079]

[0080] After that, update the value to obtain a rough estimate of the receiver position

[0081]

[0082] After further accumulating the pseudorange data of four satellites, the Doppler positioning value is corrected using the Doppler positioning correction value to obtain the final receiver position estimate.

[0083]

[0084] Where: represents the Doppler positioning correction value calculated according to the four groups of navigation message information and the four groups of pseudoranges. The process of calculating the Doppler positioning correction value according to the four groups of navigation message information and the four groups of pseudoranges is a prior art and will not be elaborated too much in this application.

[0085] To improve the positioning accuracy, when there are less than four visible satellites, Doppler positioning is used for rough estimation of the positioning position. After accumulating up to four satellites, pseudorange positioning is used for correction. The "Doppler + pseudorange" fusion positioning greatly improves the positioning accuracy. At the same time, the technical route of this application is not limited to the space-ground channel and is applicable to both UAV air nodes and ground network nodes.

[0086] The above 6G communication and navigation signal fusion method for the integration of space, air, and ground. In this application, the navigation signal, communication signal, and pseudo-random sequence are respectively placed in the time-delay Doppler domain grid to generate the communication and navigation fusion signal. By jointly placing the communication and navigation data with the pseudo-random sequence in the time-delay - Doppler domain, the inter-symbol fusion of communication and navigation data is achieved, which can provide a unified terminal and integrated service for the general public and various industries. The receiver uses the pseudo-random sequence for channel estimation to avoid interference between the two. The fusion signal is modulated on the 6G alternative signal OTFS. Compared with the traditional time-frequency domain, the sparsity of the OTFS time-delay Doppler domain has very strong robustness to the high-dynamic channels of low-earth orbit satellites; due to the fast movement speed of low-earth orbit satellites, the Doppler and time-delay differences of different satellite signals are relatively large, and the same pseudo-random sequence can also be used to distinguish satellites, shortening the acquisition time to one-thousandth of the traditional method. By utilizing the commonality of the application of the pseudo-random sequence in the satellite navigation system and the satellite communication system, the proposed accurate channel estimation in the time-delay - Doppler domain can simultaneously complete functions such as pseudo-range measurement, Doppler positioning, and data demodulation; at the same time, considering the contradiction between the single-coverage requirement of communication satellites and the single-coverage of navigation satellites, Doppler positioning is adopted when there are less than four satellites, and pseudo-range positioning is used for correction after accumulating data of four satellites, greatly improving the positioning accuracy. Starting from the signal system design, this application realizes the deep integration of navigation and communication, providing a navigation and communication solution for the construction of the 6G space-air-ground integrated system with low construction cost, high spectrum efficiency, obvious performance advantages, advanced technical route, and rich application scenarios.

[0087] In one embodiment, after channel encoding, BPSK mapping, and QPSK mapping are performed on the navigation data and communication service data, they are input together with the pseudo-random sequence into the time-delay Doppler domain grid based on OTFS to generate the communication and navigation fusion signal, including:

[0088] The navigation data is converted into binary, and then channel encoded to generate a navigation data stream. The communication service data is also channel encoded to generate a communication data stream. After the navigation data stream and the communication data stream are subjected to BPSK mapping and QPSK mapping, they are modulated together with the pseudo-random sequence on the time-delay Doppler domain grid based on OTFS with a size of M×N to generate the communication and navigation fusion signal as

[0089] x[k,l], k = 0,..., N - 1, l = 0,..., M - 1

[0090] where k is the time-delay axis index, l is the Doppler axis index, M is the number of subcarriers, and N is the number of symbols.

[0091] In one embodiment, according to the symplectic inverse Fourier transform and the Heisenberg transform, the communication and navigation fusion signal is modulated from the time-delay Doppler domain to the time-delay time domain, and serial-to-parallel conversion is performed to obtain the time-domain communication and navigation fusion signal, including:

[0092] Discretize the time-delay - Doppler domain into an \(M\times N\) grid, and use the symplectic inverse Fourier transform to transform the pilot - data fusion signal \(x[k, l]\) in the time-delay Doppler domain to the time - frequency domain \(X[n, m]\) as

[0093]

[0094] Set the time - frequency grid as a discrete \(M\times N\) grid, and then through the Heisenberg transform, generate the time - domain pilot - data fusion signal from the symbol \(X[n, m]\) on the time - frequency grid through the pulse waveform \(g\) tx (t) as

[0095]

[0096] where \(n\) is the time - axis index, \(m\) is the frequency - axis index, \(t\) is time, \(T\) is the symbol duration, and \(\Delta f\) is the sub - carrier spacing.

[0097] In one embodiment, the received time - domain pilot - data fusion signal is

[0098]

[0099] where \(v(t)\) is the additive noise, \(h_0\) represents the amplitude response, and \(\tau_0\), \(v_0\) represent the time - delay and Doppler frequency shift of the channel respectively.

[0100] In one embodiment, perform a correlation operation on the time - domain sequence and the received time - domain pilot - data fusion signal, and perform fast acquisition of the satellite at the point where the correlation value is the largest, including:

[0101] The received time - domain pilot - data fusion signal \(r(t)\) is first processed by the RF front - end to transform it into a digital intermediate - frequency signal. Continuously perform correlation between the time - domain sequence and the received time - domain pilot - data fusion signal, and perform a two - dimensional traversal search for the channel parameters. The intersection of a Doppler frequency value and a time - delay value is called a search unit (\(\tau\) est , \(v\) est ). Through the two - dimensional traversal search, calculate the correlation function and find the channel parameters (\(\tau\) est , \(v\) est ) with strong correlation characteristics. When is satisfied, the fast acquisition of the satellite is completed.

[0102] In one embodiment, after capturing the satellite, perform serial - to - parallel conversion, Wigner transform, and SFFT transform on the received time - domain pilot - data fusion signal, restore it to the time - delay - Doppler domain grid, and perform a correlation operation with the pseudo - random sequence to obtain the accurately estimated fractional Doppler value and the accurately estimated fractional time - delay, including:

[0103] After capturing the satellite, perform serial-to-parallel conversion on the received time-domain communication and navigation integrated signal to recover the received signal y affected by the channel C (t):

[0104]

[0105] Perform Wigner transform and SFFT transform on y C (t) to obtain the symbol y C [k, l] in the time delay-Doppler domain:

[0106]

[0107] Where: obeys Gaussian distribution, and h w (·) is the sampled impulse response function:

[0108]

[0109] Where h w (ν′, τ′) represents the circular convolution of the windowed channel response, τ est is the time delay estimation, and v est is the Doppler estimation;

[0110] Select the upper and lower boundary values of the Doppler frequency corresponding to the search unit to recover y U [k, l] and y L [k, l], where the Doppler frequency corresponding to y U [k, l] or y L [k, l]) is higher or lower than the Doppler frequency used in y C [k, l] by half a search step (higher by v bin / 2);

[0111] Perform cross-correlation on the three PN sequences y U [k, l], y C [k, l] and y L [k, l] recovered according to different Doppler frequencies with the y[k, l] generated by the pseudo-random sequence generator respectively to obtain the cross-correlation results R(y, y U ), R(y, y C ), R(y, y L ). If there is an estimation deviation, obtain the estimation deviation δ v of the Doppler frequency according to the early-late method:

[0112]

[0113] By comparing R(y, y U ) and R(y, y L)Based on the relevant results, the position at the top of the main peak of the PN code autocorrelation function is deduced. Then, after passing through the energy discriminator of the code based on the pseudo-random sequence, the Doppler frequency estimate value is corrected.

[0114]

[0115] where δ v represents the correction amount, and the corrected estimate is moved to the center position of the search unit, and the accurately estimated fractional Doppler value is output Using the same principle, the accurately estimated fractional time delay is output

[0116] In one embodiment, according to the accurately estimated fractional Doppler value and the accurately estimated fractional time delay, the channel matrix is reconstructed, and the channel matrix is used to demodulate the communication service data and the navigation data, and the navigation message information of the captured satellite is obtained. It further includes:

[0117] According to the accurately estimated fractional Doppler value and the accurately estimated fractional time delay, the channel matrix G is reconstructed. According to the channel matrix G and the minimum mean square error criterion, channel equalization is performed, and the time delay-Doppler domain communication and navigation fusion signal is restored as

[0118]

[0119] where: is the noise variance, and I MN is the identity matrix;

[0120] Perform BPSK / QPSK demapping and channel decoding on the time delay-Doppler domain communication and navigation fusion signal to obtain the navigation message information of the captured satellite.

[0121] In one embodiment, Doppler positioning is performed using the fractional Doppler value and satellite information to obtain a rough estimate of the receiver's position, including:

[0122] Assume the satellite position is the speed is the satellite transmission frequency is f s , the receiver position is the speed is the station receiving frequency is f r , the Doppler frequency is Considering the receiver clock offset δf r and the frequency measurement error εf, the instantaneous Doppler observation equation of the station is calculated as

[0123]

[0124] where, Let the three-dimensional coordinates and clock offset of the measurement station be. Set the initial estimates of the target position and clock offset as

[0125]

[0126] After performing Taylor expansion and linearization on the observation equation successively, for the observables at n moments, the least squares form of Doppler positioning is as follows

[0127]

[0128] where, G′ is the transfer matrix, ∈ is the error vector, k is the number of iterations, Δf is the difference matrix between the Doppler observation value and the estimated value, and the change in the receiver position is calculated as

[0129]

[0130] After that, update to obtain a rough estimate of the receiver position

[0131]

[0132] In a specific embodiment, Figure 3 shows the semi-physical test scenario of this method. Select the real satellite ephemeris to make a channel simulator and obtain the navigation message information. Apply the 6G communication-navigation signal fusion method for space-air-ground integration proposed in this application. Complete the signal transmission, reception and demodulation through USRP software radio, and display the communication and positioning results in real time at the receiving end.

[0133] The channel simulator sets the space-ground scenario parameters according to the 3GPP specification. At the same time, set the parameters of this method according to the real satellite ephemeris. The range of the Doppler frequency change rate is -300 to 300 Hz / s, the number of subcarriers M = 256, the number of Doppler grids N = 64, the subcarrier interval is 30 kHz, the center frequency is 975 MHz, and the Carrier-to-Noise Ratio at the receiving end is 10.32 dB.

[0134] Comparison scheme: Use the orthogonal frequency division multiplexing (OFDM) technology that has been widely used in 5G currently as the basis for transmitting the communication-navigation fusion signal, that is, after superimposing the communication signal and the navigation signal in the power domain, modulate them to the carrier through OFDM. At the receiving end, use the traditional algorithm. The power ratio of the communication signal is set to 90%, and the power ratios of the navigation and pseudo-random sequences are each 5%. The test result figures are as Figure 4 (a) and as Figure 4 (b) shown.

[0135] It can be seen from the test results that compared with the method of this application under the same configuration, this comparison scheme:

[0136] In terms of the bit error rate of signal demodulation, with the same power configuration, the constellation diagram of this solution is significantly more concentrated. The bit error rate of the communication and navigation integration solution based on OTFS is lower than that of the communication and navigation integration solution based on OFDM, reaching 10 -6 , meeting the communication requirements, while OFDM cannot meet the communication requirements in high-dynamic scenarios. This shows that the communication and navigation integrated signal system based on OTFS can better cope with the impact of high-dynamic channels, thus achieving better transmission reliability.

[0137] In terms of receiver positioning and calculation, due to the adoption of algorithms such as fast acquisition, high-precision channel estimation, and integrated positioning in this application, the positioning speed and positioning accuracy of this solution have been greatly improved. The positioning error at the 10-meter level can be reduced to the meter level. At the same time, due to the lower bit error rate of this solution, higher-precision positioning can be achieved under low signal-to-noise ratios.

[0138] In addition, this solution has been widely tested in UAV scenarios and ground scenarios. The test results show that this method can fully meet the satellite application service requirements of the entire space-air-ground scenario and can provide an important reference for the construction of 6G space-air-ground integration.

[0139] In summary, a 6G communication and navigation signal integration method, device, and system of this application have the following advantages:

[0140] This application completes the integration of communication and navigation symbols for the entire space-air-ground scenario of 6G at the signal system level, provides a unified terminal for the general public and various industries, is conducive to improving the spectrum utilization rate, empowering the construction of 6G systems, and reducing the cost of the integrated system.

[0141] All satellites use the same pseudo-random sequence, and the Doppler effect and time delay of low-earth orbit satellites are used to distinguish satellites, greatly shortening the acquisition time of the giant constellation.

[0142] The integrated signal is modulated by the 6G alternative signal OTFS modulation method and then sent. Since OTFS can represent the signal and channel in the time delay-Doppler domain, compared with the traditional time-frequency domain, the time delay-Doppler domain has extremely strong robustness to the high-dynamic channels of low-earth orbit satellites.

[0143] The channel is accurately estimated through the pseudo-random sequence in the time delay-Doppler domain, and the fractional estimated values of Doppler and time delay are obtained through the redshift and blueshift of the energy discriminator, greatly improving the performance of communication and navigation.

[0144] When the number of visible satellites is less than 4, Doppler positioning is used. When the number of satellites reaches 4 cumulatively, pseudo-range positioning is used for correction to meet the positioning requirements in different environments and improve the positioning accuracy and the applicability of the system.

[0145] It should be understood that although Figure 1 each step in the flowchart is shown in sequence according to the indication of the arrow, these steps are not necessarily executed in sequence according to the indication of the arrow. Unless there is a clear description in this article, there is no strict order limit for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 at least a part of the steps in

[0146] include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed alternately or in turn with at least a part of other steps or sub-steps or stages of other steps. Figure 5 In one embodiment, as

[0147] shown, a 6G communication and navigation signal fusion device for integrated space-air-ground is provided, including: a communication and navigation signal generation module 502, a communication and navigation signal transmission module 504, a satellite capture module 506, a channel estimation module 508, a data demodulation module 510, and a fusion positioning module 512, where:

[0148] The communication and navigation signal generation module 502 is configured to obtain navigation data and communication service data at the transmitting end and generate a pseudo-random sequence; perform channel coding, BPSK mapping, and QPSK mapping on the navigation data and communication service data, and then input them into the time-delay-Doppler domain grid based on OTFS together with the pseudo-random sequence to generate a communication and navigation fusion signal;

[0149] The communication and navigation signal transmission module 504 is configured to modulate the communication and navigation fusion signal from the time-delay-Doppler domain to the time-delay-time domain according to the inverse symplectic Fourier transform and the Heisenberg transform, perform serial-to-parallel conversion, and then transmit the time-domain communication and navigation fusion signal using an antenna after obtaining it;

[0150] The satellite capture module 506 is configured to generate the same pseudo-random sequence as the transmitting end at the receiving end, perform serial-to-parallel conversion to generate a time-domain sequence, perform correlation operation on the time-domain sequence and the received time-domain communication and navigation fusion signal, and perform fast capture of the satellite at the maximum correlation value; after capturing the satellite, perform serial-to-parallel conversion, Wigner transform, and SFFT transform on the received time-domain communication and navigation fusion signal, restore it to the time-delay-Doppler domain grid, and perform correlation operation with the pseudo-random sequence to obtain an accurately estimated fractional Doppler value and an accurately estimated fractional time delay;

[0151] The data demodulation module 510 is used to track the loop according to the accurately estimated fractional time delay, obtain the propagation time of the signal, multiply it by the speed of light to obtain the propagation distance of the signal, use the propagation distance of the signal as the distance between the satellite and the target receiver, and define it as the pseudo-range.

[0152] The fusion positioning module 512 is used to perform Doppler positioning by using the fractional Doppler value and satellite information to obtain a rough estimate of the receiver's position; when at least four satellites are accumulated and the navigation message information of the four satellites is obtained, calculate the Doppler positioning correction value according to the four groups of navigation message information and the four groups of pseudo-ranges; correct the rough estimate of the receiver's position according to the Doppler positioning correction value to achieve the integrated communication and navigation signal fusion transmission of 6G.

[0153] For the specific limitations of a 6G integrated communication and navigation signal fusion device for air-space-ground integration, reference can be made to the limitations of a 6G integrated communication and navigation signal fusion method for air-space-ground integration in the above text, which will not be elaborated here. Each module in the above 6G integrated communication and navigation signal fusion device for air-space-ground integration can be implemented in whole or in part by software, hardware, and their combination. The above modules can be embedded in the processor of the computer device in hardware form or be independent of it, or can be stored in the memory of the computer device in software form, so that the processor can call and execute the operations corresponding to the above modules.

[0154] In one embodiment, as Figure 6 shown, the system includes a satellite 610 and a receiver 620; a communication and navigation signal generation module and a communication and navigation signal transmission module are arranged in the satellite 610; a satellite acquisition module, a channel estimation module, a data demodulation module, and a fusion positioning module are arranged in the receiver 620, where:

[0155] The communication and navigation signal generation module is used to obtain navigation data and communication service data at the transmitting end and generate a pseudo-random sequence; perform channel coding, BPSK mapping, and QPSK mapping on the navigation data and communication service data, and then input them into the time delay-Doppler domain grid based on OTFS together with the pseudo-random sequence to generate a communication and navigation fusion signal.

[0156] The communication and navigation signal transmission module is used to modulate the communication and navigation fusion signal from the time delay-Doppler domain to the time delay-time domain according to the symplectic inverse Fourier transform and the Heisenberg transform, perform parallel-to-serial conversion, and then use the antenna to transmit the time-domain communication and navigation fusion signal after obtaining it.

[0157] The satellite capture module is used to generate the same pseudo-random sequence as that at the transmitting end at the receiving end, perform serial-to-parallel conversion to generate a time-domain sequence, perform correlation operations on the time-domain sequence and the received time-domain communication-navigation integrated signal, and quickly capture the satellite at the position where the correlation value is the largest; after capturing the satellite, perform parallel-to-serial conversion, Wigner transform, and SFFT transform on the received time-domain communication-navigation integrated signal, restore it to the delay-Doppler domain grid, and perform correlation operations with the pseudo-random sequence to obtain the accurately estimated fractional Doppler value and the accurately estimated fractional delay;

[0158] The channel estimation module is used to reconstruct the channel matrix according to the accurately estimated fractional Doppler value and the accurately estimated fractional delay, and use the channel matrix to demodulate the communication service data and navigation data to obtain the navigation message information of the captured satellite;

[0159] The data demodulation module is used to track the loop according to the accurately estimated fractional delay, obtain the propagation time of the signal, multiply it by the speed of light to obtain the propagation distance of the signal, use the propagation distance of the signal as the distance between the satellite and the target receiver, and define it as the pseudo-range;

[0160] The fusion positioning module is used to perform Doppler positioning using the fractional Doppler value and satellite information to obtain a rough estimate of the receiver's position; when at least four satellites are accumulated and the navigation message information of the four satellites is obtained, calculate the Doppler positioning correction value according to the four sets of navigation message information and the four sets of pseudo-ranges; correct the rough estimate of the receiver's position according to the Doppler positioning correction value to achieve the integrated transmission of 6G communication-navigation signals.

[0161] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0162] The above-described embodiments only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A 6G communication and navigation signal fusion method for the integration of space, air, and ground, characterized in that, The method includes: Obtaining navigation data and communication service data at the transmitting end and generating a pseudo-random sequence; performing channel coding, BPSK mapping, and QPSK mapping on the navigation data and communication service data, and then inputting them together with the pseudo-random sequence into the time-delay-Doppler domain grid based on OTFS to generate a communication-navigation integrated signal; Modulating the communication-navigation integrated signal from the time-delay-Doppler domain to the time-delay-time domain according to the symplectic inverse Fourier transform and the Heisenberg transform, and performing serial-to-parallel conversion. After obtaining the time-domain communication-navigation integrated signal, it is transmitted using an antenna; Generating a pseudo-random sequence identical to that at the transmitting end at the receiving end, performing serial-to-parallel conversion to generate a time-domain sequence, performing a correlation operation on the time-domain sequence and the received time-domain communication-navigation integrated signal, and quickly capturing the satellite at the location where the correlation value is the largest; after capturing the satellite, performing parallel-to-serial conversion, Wigner transform, and SFFT transform on the received time-domain communication-navigation integrated signal, restoring it to the time-delay-Doppler domain grid, and performing a correlation operation with the pseudo-random sequence to obtain an accurately estimated fractional Doppler value and an accurately estimated fractional time delay; Reconstructing a channel matrix according to the accurately estimated fractional Doppler value and the accurately estimated fractional time delay, and using the channel matrix to demodulate the communication service data and navigation data to obtain the navigation message information of the captured satellite; Tracking the loop according to the accurately estimated fractional time delay, obtaining the signal propagation time, multiplying it by the speed of light to obtain the signal propagation distance, using the signal propagation distance as the distance between the satellite and the target receiver, and defining it as the pseudo-range; Performing Doppler positioning using the fractional Doppler value and satellite information to obtain a rough estimate of the receiver's position; when at least four satellites are accumulated, after obtaining the navigation message information of the four satellites, calculating a Doppler positioning correction value according to the four sets of navigation message information and the four sets of pseudo-ranges; Correcting the rough estimate of the receiver's position according to the Doppler positioning correction value to achieve the integrated transmission of 6G communication-navigation signals; Reconstructing a channel matrix according to the accurately estimated fractional Doppler value and the accurately estimated fractional time delay, and using the channel matrix to demodulate the communication service data and navigation data to obtain the navigation message information of the captured satellite, further including: Reconstructing a channel matrix G according to the accurately estimated fractional Doppler value and the accurately estimated fractional time delay, and performing channel equalization according to the channel matrix G and the minimum mean square error criterion to restore the time-delay-Doppler domain communication-navigation integrated signal as Wherein: is the noise variance, I MN is the identity matrix, G H represents the conjugate transpose of the channel matrix, y C [k, l] represents the symbol in the delay-Doppler domain, where k is the delay-axis index and l is the Doppler-axis index; Performing BPSK / QPSK demapping and channel decoding on the time-delay-Doppler domain communication-navigation integrated signal to obtain the navigation message information of the captured satellite.

2. The method according to claim 1, wherein Performing channel coding, BPSK mapping, and QPSK mapping on the navigation data and communication service data, and then inputting them together with the pseudo-random sequence into the time-delay-Doppler domain grid based on OTFS to generate a communication-navigation integrated signal, including: Convert the navigation data into binary, and then generate a navigation data stream after channel coding. The communication service data is also channel-coded to generate a communication data stream. The navigation data stream and the communication data stream are modulated onto a time-delay Doppler domain grid based on OTFS with a size of M×N together with a pseudo-random sequence after BPSK mapping and QPSK mapping, and the generated communication-navigation integrated signal is x[k, l], k = 0, ..., N - 1, l = 0, ..., M - 1 where k is the time-delay axis index, l is the Doppler axis index, M is the number of subcarriers, and N is the number of symbols.

3. The method according to claim 2, characterized in that, According to the symplectic inverse Fourier transform and the Heisenberg transform, modulate the communication-navigation integrated signal from the time-delay Doppler domain to the time-delay time domain, and perform serial-to-parallel conversion to obtain the time-domain communication-navigation integrated signal, including: Discretize the time-delay Doppler domain into a grid of M×N, and use the symplectic inverse Fourier transform to transform the communication-navigation integrated signal x[k, l] on the time-delay Doppler domain to the time-frequency domain X[n, m] as Set the time-frequency grid as a discrete M×N grid, and then through the Heisenberg transform, generate the time-domain pilot-fused signal from the symbol X[n,m] on the time-frequency grid through the pulse waveform g tx (t) as where n is the time axis index, m is the frequency axis index, t is time, T is the symbol duration, and Δf is the subcarrier spacing.

4. The method according to claim 3, wherein The received time-domain communication-navigation integrated signal is where v(t) is additive noise, and τ0 and v0 respectively represent the time delay and Doppler frequency shift of the channel.

5. The method according to claim 4, characterized in that Perform a correlation operation on the time-domain sequence and the received time-domain communication-navigation integrated signal, and perform fast acquisition of the satellite at the location where the correlation value is the largest, including: The received time-domain navigation and communication integrated signal r(t) is first processed by the RF front-end and transformed into a digital intermediate-frequency signal. The time-domain sequence is continuously correlated with the received time-domain navigation and communication integrated signal, and a two-dimensional traversal search is performed on the channel parameters. The intersection of a Doppler frequency value and a time delay value is called a search unit (τ est , v est ). Through the two-dimensional traversal search, the correlation function is calculated and the channel parameters (τ est , v est ) with strong correlation characteristics are searched for. When is satisfied, the rapid acquisition of the satellite is completed. Among them, τ est is the time delay estimation, and v est is the Doppler estimation.

6. The method according to claim 5, wherein After capturing the satellite, perform serial-to-parallel conversion, Wigner transform, and SFFT transform on the received time-domain communication-navigation integrated signal, restore it to the time-delay Doppler domain grid, and perform a correlation operation with the pseudo-random sequence to obtain an accurately estimated fractional Doppler value and an accurately estimated fractional time delay, including: After capturing the satellite, perform serial-to-parallel conversion on the received time-domain communication-navigation integrated signal to recover the received signal y C (t): For y C Perform the Wigner transform and the SFFT transform on (t) to obtain the symbol y in the time delay-Doppler domain C [k, l]: Wherein: obeys a Gaussian distribution, h w (·) is the sampled impulse response function: where h w (ν′,τ′) represents the circular convolution of the windowed channel response, and τ est is the delay estimate, and v est is the Doppler estimate; Restore y by selecting the upper and lower boundary values of the Doppler frequency corresponding to the search unit U [k, l] and y L [k, l], where y U [k, l] or y L [k, l] corresponds to a Doppler frequency that is higher or lower by half a search step than the Doppler frequency used in y C [k, l]; The three PN sequences y U [k, l] recovered according to different Doppler frequencies, y C [k, l], and y L [k, l] are respectively cross-correlated with y[k, l] generated by the pseudo-random sequence generator to obtain the cross-correlation results R(y, y U ), R(y, y C ), R(y, y L ). If there is an estimation deviation, the estimation deviation δ v of the Doppler frequency is obtained according to the lead-lag method: By comparing the relevant results of R(y, y U ) and R(y, y L ), the position of the peak of the autocorrelation function of the PN code is deduced. Then, after passing through an energy discriminator for the code based on the pseudo-random sequence, the estimated Doppler frequency is corrected Among them, δ v represents the correction amount, and the corrected estimator is moved to the central position of the search unit, and the accurately estimated fractional Doppler value is output. Using the same principle, the accurately estimated fractional time delay 7. The method according to claim 1, wherein Use the fractional Doppler value and satellite information for Doppler positioning to obtain a rough estimate of the receiver's position, including: Let the satellite position be and the velocity be The satellite transmission frequency is f s , the receiver position is and the velocity is The receiver frequency measured at the station is f r , and the Doppler frequency is Considering the receiver clock error δf r and the frequency measurement error εf, the instantaneous Doppler observation equation at the station is calculated as Among them, are the three-dimensional coordinates and clock bias of the measuring station. Let the initial estimates of the target position and clock bias be After performing Taylor expansion and linearization on the observation equation in sequence, for the observations at n moments, the least squares form of Doppler positioning is as follows where G′ is the transfer matrix, ∈ is the error vector, k is the iteration number, Δf is the difference matrix between the Doppler observation value and the estimated value, and the receiver position change is calculated as Among them, G′ T represents the transpose operation on the transition matrix; Subsequent update The value gives a rough estimate of the receiver position 8. A 6G communication and navigation signal fusion device for integrated space-air-ground, characterized in that The device includes: A communication-navigation signal generation module, configured to obtain navigation data and communication service data at the transmitter end and generate a pseudo-random sequence; perform channel coding, BPSK mapping, and QPSK mapping on the navigation data and communication service data, and input them into a time-delay Doppler domain grid based on OTFS together with the pseudo-random sequence to generate a communication-navigation integrated signal; A communication-navigation signal transmission module, configured to modulate the communication-navigation integrated signal from the time-delay Doppler domain to the time-delay time domain according to the symplectic inverse Fourier transform and the Heisenberg transform, perform serial-to-parallel conversion, and use an antenna to transmit the obtained time-domain communication-navigation integrated signal; A satellite acquisition module, which is used to generate the same pseudo-random sequence as that at the transmitting end at the receiving end, perform parallel-to-serial conversion to generate a time-domain sequence, perform correlation operation on the time-domain sequence and the received time-domain navigation and communication integrated signal, and quickly acquire the satellite at the position where the correlation value is the largest; after acquiring the satellite, perform serial-to-parallel conversion, Wigner transform and SFFT transform on the received time-domain navigation and communication integrated signal, restore it to the delay-Doppler domain grid and perform correlation operation with the pseudo-random sequence to obtain the accurately estimated fractional Doppler value and the accurately estimated fractional delay; A channel estimation module, which is used to reconstruct the channel matrix according to the accurately estimated fractional Doppler value and the accurately estimated fractional delay, and use the channel matrix to demodulate communication service data and navigation data to obtain the navigation message information of the acquired satellite; reconstruct the channel matrix according to the accurately estimated fractional Doppler value and the accurately estimated fractional delay, and use the channel matrix to demodulate communication service data and navigation data to obtain the navigation message information of the acquired satellite, and further includes: Reconstruct the channel matrix G according to the accurately estimated fractional Doppler value and the accurately estimated fractional delay, and perform channel equalization according to the channel matrix G and the minimum mean square error criterion to restore the delay-Doppler domain navigation and communication integrated signal as Wherein: is the noise variance, I MN is the identity matrix, G H represents the conjugate transpose of the channel matrix, y C [k, l] represents the symbol in the delay-Doppler domain, where k is the delay-axis index and l is the Doppler-axis index; Perform BPSK / QPSK demapping and channel decoding on the delay-Doppler domain navigation and communication integrated signal to obtain the navigation message information of the acquired satellite; A data demodulation module, which is used to track the loop according to the accurately estimated fractional delay, obtain the propagation time of the signal and multiply it by the speed of light to obtain the propagation distance of the signal, use the propagation distance of the signal as the distance between the satellite and the target receiver, and define it as the pseudo-range; A fusion positioning module, which is used to perform Doppler positioning using the fractional Doppler value and satellite information to obtain a rough estimate of the receiver's position; when at least four satellites are accumulated and the navigation message information of the four satellites is obtained, calculate the Doppler positioning correction value according to the four sets of navigation message information and the four sets of pseudo-ranges; correct the rough estimate of the receiver's position according to the Doppler positioning correction value to achieve the integrated transmission of 6G navigation and communication signals.

9. A 6G communication and navigation signal fusion system for integrated space-air-ground scenarios, characterized in that, The system includes a satellite and a receiver; a navigation and communication signal generation module and a navigation and communication signal transmission module are arranged in the satellite; a satellite acquisition module, a channel estimation module, a data demodulation module and a fusion positioning module are arranged in the receiver; A navigation and communication signal generation module, which is used to acquire navigation data and communication service data at the transmitting end and generate a pseudo-random sequence; perform channel coding, BPSK mapping and QPSK mapping on the navigation data and communication service data, and then input them into the delay-Doppler domain grid based on OTFS together with the pseudo-random sequence to generate a navigation and communication integrated signal; A navigation and communication signal transmission module, which is used to modulate the navigation and communication integrated signal from the delay-Doppler domain to the delay-time domain according to the symplectic inverse Fourier transform and the Heisenberg transform, perform parallel-to-serial conversion, and then use an antenna to transmit the obtained time-domain navigation and communication integrated signal; A satellite acquisition module, which is used to generate the same pseudo-random sequence as that at the transmitting end at the receiving end, perform serial-to-parallel conversion to generate a time-domain sequence, perform correlation operation on the time-domain sequence and the received time-domain communication-navigation integrated signal, and quickly acquire the satellite at the position where the correlation value is the largest; after acquiring the satellite, perform parallel-to-serial conversion, Wigner transform and SFFT transform on the received time-domain communication-navigation integrated signal, restore it to the delay-Doppler domain grid and perform correlation operation with the pseudo-random sequence to obtain the accurately estimated fractional Doppler value and the accurately estimated fractional delay; A channel estimation module, which is used to reconstruct the channel matrix according to the accurately estimated fractional Doppler value and the accurately estimated fractional delay, and demodulate the communication service data and navigation data by using the channel matrix to obtain the navigation message information of the acquired satellite; Reconstructing the channel matrix according to the accurately estimated fractional Doppler value and the accurately estimated fractional delay, and demodulating the communication service data and navigation data by using the channel matrix to obtain the navigation message information of the acquired satellite, further including: Reconstructing the channel matrix G according to the accurately estimated fractional Doppler value and the accurately estimated fractional delay, performing channel equalization according to the channel matrix G and the minimum mean square error criterion, and restoring the delay-Doppler domain communication-navigation integrated signal as Wherein: is the noise variance, I MN is the identity matrix, G H represents the conjugate transpose of the channel matrix, y C [k, l] represents the symbol in the delay-Doppler domain, where k is the delay-axis index and l is the Doppler-axis index; Performing BPSK / QPSK demapping and channel decoding on the delay-Doppler domain communication-navigation integrated signal to obtain the navigation message information of the acquired satellite; A data demodulation module, which is used to track the loop according to the accurately estimated fractional delay, obtain the signal propagation time and multiply it by the speed of light to obtain the signal propagation distance, use the signal propagation distance as the distance between the satellite and the target receiver, and define it as the pseudo-range; A fusion positioning module, which is used to perform Doppler positioning by using the fractional Doppler value and satellite information to obtain a rough estimate of the receiver's position; when at least four satellites are accumulated and the navigation message information of the four satellites is obtained, calculate the Doppler positioning correction value according to the four sets of navigation message information and the four sets of pseudo-ranges; correct the rough estimate of the receiver's position according to the Doppler positioning correction value to achieve the integrated transmission of 6G communication-navigation signals.

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