Short-wave sky-wave beyond-visual-range link unified channel modeling method for high-latitude area

Abstract

The invention belongs to the technical field of short-wave communication, and relates to a short-wave sky-wave beyond-visual-range link unified channel modeling method for a high-latitude region, which comprises the following steps of: acquiring an actually-measured channel parameter, acquiring a channel parameter of a channel propagation model, comparing the channel parameter with the actually-measured channel parameter, and if the channel parameter does not accord with the actually-measured channel parameter, determining that the channel propagation model is a short-wave sky-wave beyond-visual-range link. If so, driving a link observation system to measure the channel according to the channel parameter, obtaining a full-link channel characteristic parameter on an actual transceiving channel, and correcting the channel parameter of the channel propagation model; otherwise, calculating a link long-period channel parameter according to the channel parameter, and performing fitting modeling on the long-period channel parameter to obtain a channel transmission model; the high-latitude region ionosphere model is adopted, the high-latitude short-wave communication channel parameters of the specified link region are calculated through 3D ray tracing, and the cost for constructing a short-wave communication channel system in the given link direction in the high-latitude region can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of shortwave communications, and in particular relates to a unified channel modeling method for shortwave skywave over-the-horizon links in high-latitude areas. Background Art

[0002] Shortwave communication, with its strong anti-destruction, high mobility and low cost, provides strong support for military activities, disaster relief and other operations in poor communication environments. In addition, shortwave communication can achieve communication between low and medium latitudes and high latitudes, providing support for civil aviation, shipping and long-distance fishing in high-latitude communication environments.

[0003] The shortwave channel is subject to strong irregularities due to changes in factors such as station movement speed, communication time, ionospheric conditions, and carrier frequency, which is particularly evident in high-latitude areas. Frequent extreme weather and complex and changeable geomagnetic fields in high-latitude areas lead to changes in the ionospheric space environment, which can lead to abnormal deterioration of shortwave communication channels. The high-latitude ionospheric background model can simulate the complex characteristics of the ionosphere very well. The Empirical Canadian High Arctic Ionospheric Model (E-CHAIM) shows good performance in areas above 50 degrees north latitude, which provides guidance for building channel models that reflect the complex characteristics of high latitudes.

[0004] The Doppler spread and multipath spread of the shortwave channel seriously affect the performance of the shortwave communication system. The 3D ray tracing algorithm can calculate the Doppler shift and delay of the shortwave signal of a specified link based on Maxwell's equations, ray optics theory and consistent diffraction theory. Furthermore, the high-latitude ionospheric background model combined with the 3D ray tracing algorithm can obtain the Doppler shift, multipath and power loss of the received signal in a specific high-latitude scenario. At present, the research on 3D ray tracing in the shortwave field focuses on predicting the maximum usable frequency (MUF), high-frequency radar detection, radio wave propagation path analysis and channel parameter estimation. There is little research on using the shortwave channel parameters obtained by 3D ray tracing to construct a specific channel mathematical model, especially for the high-latitude shortwave channel model with large Doppler shift. For example, Yan Zhaowen and other scholars from the Beijing University of Aeronautics and Astronautics built 3D ray tracing based on the improved international reference ionosphere model to predict the electromagnetic parameters of high-frequency receiving points. Xue Rui and other scholars from Harbin Engineering University estimated the Doppler shift and propagation time of a 1,800 km high-latitude high-frequency link, but they did not build a specific communication channel model at the mathematical level.

[0005] Traditional shortwave channel models are empirical statistical models such as the Watterson model and the ITS model. The Watterson model is a widely accepted deterministic narrowband model recommended by the International Telecommunication Union (ITU). The ITS communication channel system is a broadband mathematical model system obtained through mathematical abstraction based on a large amount of measured data. However, both the communication systems based on the Watterson model and the ITS model rely on long-term, large-scale actual observation data, which is extremely unfriendly to high-latitude areas where communication facilities are already scarce, thereby increasing the economic cost of high-latitude shortwave channel models. Summary of the invention

[0006] In view of the above problems, in order to obtain an economical high-latitude shortwave channel model, the present invention uses a 3D ray tracing algorithm based on Maxwell equations and ray optics as a calculation driver, a high-latitude ionosphere background model as a propagation environment, and a dual-dispersion modeling method for characterizing the shortwave channel of a high-latitude designated link. A unified channel modeling method for shortwave skywave over-the-horizon links in high-latitude areas is proposed. The shortwave unified channel model includes a channel propagation model and a channel transmission model; wherein the construction of the channel transmission model includes:

[0007] S1. Obtain measured channel parameters;

[0008] S2. Acquire channel parameters of the channel propagation model, wherein the channel parameters include transmit power, antenna, frequency, and measurement waveform obtained by using a high-latitude ionosphere model and a 3D ray tracing algorithm;

[0009] S3, comparing the channel parameters with the measured channel parameters, if they do not match the measured channel parameters, executing step S4, otherwise executing step S6;

[0010] S4, driving the link observation system to measure the channel according to the channel parameters, and obtaining the full-link channel characteristic parameters on the actual transceiver channel;

[0011] S5, modifying the channel parameters of the channel propagation model according to the full-link channel characteristic parameters on the actual transceiver channel, and returning to step S3;

[0012] S6. Calculate the link long-period channel parameters according to the channel parameters, perform fitting modeling on the long-period channel parameters, and obtain a channel transmission model.

[0013] Beneficial effects of the present invention:

[0014] The present invention adopts a high-latitude ionosphere model and calculates the high-latitude shortwave communication channel parameters of a specified link area through 3D ray tracing, which can reduce the cost of constructing a shortwave communication channel system in a given link direction in a high-latitude area. The shortwave communication channel system of the present invention is effective on high-latitude shortwave links, can solve the problem of strict limitations on channel measurement in high-latitude areas, and has a certain reference value for waveform design and signal prediction of high-latitude shortwave links. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a shortwave unified channel model framework diagram of the present invention;

[0016] Figure 2 An overall flow chart for constructing the shortwave unified channel model of the present invention;

[0017] Figure 3 It is a schematic diagram of 3D ray tracing of high-latitude ionospheric environment of the present invention;

[0018] Figure 4 It is the 3D ray tracing DD domain source data graph of the present invention;

[0019] Figure 5 The present invention is different Comparison chart of the amplitude corresponding to the DPP function;

[0020] Figure 6 It is a data distribution diagram of the high latitude channel fading model of the present invention;

[0021] Figure 7 is a time-varying impulse response diagram of the present invention;

[0022] Figure 8 A dual dispersion diagram of a high-latitude channel of the time-varying transfer function of the present invention;

[0023] Fig. 9 is a scattering function diagram of the present invention;

[0024] Fig.10 This is a diagram of the channel scattering function measured in high latitude areas according to the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] A unified channel modeling method for shortwave skywave over-the-horizon links in high-latitude areas, such as Figure 2 As shown, the method includes: the shortwave unified channel model includes a channel propagation model and a channel transmission model; wherein the construction of the channel transmission model includes:

[0027] S1. Obtain measured channel parameters;

[0028] S2. Acquire channel parameters of the channel propagation model, wherein the channel parameters include transmit power, antenna, frequency, and measurement waveform obtained by using a high-latitude ionosphere model and a 3D ray tracing algorithm;

[0029] S3, comparing the channel parameters with the measured channel parameters, if they do not match the measured channel parameters, executing step S4, otherwise executing step S6;

[0030] S4, driving the link observation system to measure the channel according to the channel parameters, and obtaining the full-link channel characteristic parameters on the actual transceiver channel;

[0031] S5, modifying the channel parameters of the channel propagation model according to the full-link channel characteristic parameters on the actual transceiver channel, and returning to step S3;

[0032] S6. Calculate the link long-period channel parameters according to the channel parameters, perform fitting modeling on the long-period channel parameters, and obtain a channel transmission model.

[0033] In this embodiment, the channel propagation model includes a shortwave channel propagation model and a high-latitude ionosphere model.

[0034] The shortwave channel propagation model adopts the shortwave channel propagation model based on ray optics; that is, computational electromagnetics (CME) is to solve the numerical solution of the electromagnetic field, that is, to solve the Maxwell equations describing the electric field, magnetic field and their changing relationship. The CEM method obtains the approximate solution of the electromagnetic field distribution and other related quantities through discretization and numerical solution. Considering the simple harmonic change of the electromagnetic field over time, the Maxwell equations in the passive region are expressed as:

[0035]

[0036] in, Represent the complex vector of electric field intensity, magnetic field intensity, magnetic induction intensity and electric displacement respectively, ε, μ represent the dielectric constant and magnetic permeability of the medium respectively. For linear and isotropic media, the medium parameters are all scalars. For general non-ferromagnetic media, the magnetic permeability can be considered as a constant, so the first two equations can be transformed into:

[0037]

[0038] The geometric optics approximation method is used to solve the equation (2). In the case of high-frequency approximation, since the wavelength is very short, it is assumed that ε remains unchanged in the local range. At this time, the electromagnetic field is expressed as:

[0039]

[0040] Where λ is the wavelength of the ray, c is the speed of light in a vacuum, and φ is the phase function with respect to the spatial position (x, y, z).

[0041] Taking full account of the premise of high-frequency approximation of geometric optical conditions, it is assumed that the wavelength is very small and the parameter k0 approaches infinity. and The spatial position changes slowly, and its curl and divergence are both limited. The Maxwell equations in equation (1) can be transformed into equation (5):

[0042]

[0043] Simplifying the above formula, we can get:

[0044]

[0045] Among them, η is the wave impedance, χ is the refractive index of the medium. From formula (6), we can see that, The three are mutually orthogonal, and the geometric optics field considers high-frequency rays as plane waves. Solving equation (5) yields:

[0046]

[0047] Since φ varies with the spatial position (x, y, z), the refractive index χ is also a function of the spatial position. On the other hand, the refractive index of radio waves in the ionosphere can also be calculated by the following formula:

[0048]

[0049]

[0050] Where m is the mass of the electron, n and k represent the real and imaginary parts of the refractive index, e is the charge of the electron, f is the operating frequency of the electromagnetic wave, and B T ,B L are the projections of the geomagnetic field parallel and perpendicular to the propagation direction of the electromagnetic wave, respectively, e Represents the electron density at any point in the ionosphere, symbol This reflects that electromagnetic waves will split into extraordinary waves and ordinary waves after entering the ionosphere. It also reflects that the refractive index depends on the geomagnetic field and the electron density of the ionosphere. Furthermore, since the electron density of the ionosphere changes with spatial position and time, the resulting refractive index also changes with spatial position and time.

[0051] According to 3D ray tracing theory, using the concept of light path in Fermat's principle, the group path length of the ray passing through the atmospheric space is:

[0052]

[0053] Among them, α is the angle between the ray normal and the ray propagation direction, which is a function of height. From the above, it can be seen that the refractive index n is a function of spatial position and time.

[0054] Using the group path length obtained by ray tracing and ignoring the effect of the ionospheric space environment on the speed of light, the propagation time of the ray in free space (time of flight TOF) can be obtained:

[0055]

[0056] Where c is the speed of light in vacuum, and the TOF values ​​of all rays form a set:

[0057]

[0058] make:

[0059]

[0060] Finally, the delay vector for all rays can be obtained as:

[0061]

[0062] Bennett assumed that the ionosphere changes slowly in time and space, ignored the effect of electron collisions, and only considered the transmitter and receiver to be stationary, and obtained the calculation expression for the Doppler shift in ray tracing:

[0063]

[0064] In this embodiment, the high-latitude ionosphere model is an ionosphere electron density model; the upper electron density specification standard is implemented by parameterization of the NeQuick model, and the electron density profile is described by the semi-Epstein layer as follows:

[0065]

[0066] Where N e(h, t) is the electron density variation function with altitude h and time t, NmF2 is the monthly median electron density, hmF2 is the ionospheric peak height, r, g, H0 are three empirical parameter values, H0 is the altitude at the peak height of the F2 layer, g is the gradient of H, and r characterizes the gradualness of H.

[0067] In this embodiment, the construction of the channel transmission model includes: using the channel propagation model to provide a high-latitude modeling data source and channel parameter support, the high-latitude ionosphere model as the propagation environment of the shortwave signal, and the transmission model as the basic framework, and proposing a high-latitude shortwave skywave unified channel model framework such as Figure 1 .

[0068] The ITS model includes: based on the channel scattering function, the transfer function of the HF broadband channel is derived. The channel model is given in the form of impulse response, which is defined as a function of time t and delay τ. The function is expressed as follows:

[0069]

[0070] The channel impulse response is composed of multiple impulse responses, among which h n (t,τ) represents the impulse response under different propagation modes. Each impulse response consists of three parts: the delay power function P that reflects the channel delay characteristics n (τ), a deterministic phase function D that reflects the Doppler frequency shift characteristics n (t,τ), and the random modulation function ψ that reflects the Doppler spread characteristics n (t,τ).

[0071] In this embodiment, the DPP function describes the power distribution of the channel in the delay domain. From the perspective of 3D ray tracing, the rays emitted by the transmitter will reach the receiver through different paths. Since the transmission distances of these paths are different, the ray amplitudes at the receiver are different.

[0072] The attenuation of ray amplitude mainly includes the first type of attenuation and the second type of attenuation. The first type of attenuation is the propagation loss of electromagnetic waves in free space. This is the famous Friis formula, which can be expressed as:

[0073]

[0074] Among them, G t ,G r are the gains of the transmitting antenna and the receiving antenna respectively, λ refers to the wavelength of the ray, and d is the distance between the transmitting and receiving ends.

[0075] The second type of attenuation considers the energy absorption of high-frequency rays by the ionosphere, which is expressed as:

[0076]

[0077] Wherein, k is the imaginary part of the refractive index in equation (10), and the physical meanings of the other parameters are the same as those in equation (11).

[0078] High-frequency rays are reflected by both the ionosphere and the ground, so the energy loss of the rays by the ground cannot be ignored. The scattering loss of the rays along the ground can be calculated by the following formula:

[0079] L g (dB)=L0+10log 10 (f·θ 2 ) (twenty three)

[0080] Among them, θ refers to the incident angle of the ray, and L0 is related to the specific properties of the ground and is the basic loss.

[0081] Considering the multipath accumulation effect of high-frequency rays, and in order to distinguish the multipath components from different propagation modes, the ray's exit angle, incident angle and delay are combined into a ray matrix:

[0082]

[0083] Choose an arbitrary column vector as the reference vector of the ray:

[0084]

[0085] Formula (24)-(25), Θ T ,Θ R ,τ represent the ray exit angle, incident angle and delay respectively, and R represents the number of rays that can reach the receiving end.

[0086] Through the above three elements, the geometric distances between other ray vectors and the reference vector are calculated as:

[0087]

[0088] Arrange these R-1 geometric distances from small to large:

[0089] r(1)<r(2)<...<r(R-1) (27)

[0090] Finally, select The reference vector The ray with smaller geometric distance is regarded as a multipath component.

[0091] Based on the attenuation calculation of (21)-(23), the power amplitude of any ray is calculated as:

[0092]

[0093] Where Ptx (dbm) is the power value of the transmitting signal, combined with the delay vector of formula (15), and formula (27) as a multipath component, formula (29) as the fitting function, each path is fitted:

[0094]

[0095] Where τ is the delay variable, Δ controls the width of the power function, and τ l is smaller than and close to the minimum delay value τ L The delay, A represents the maximum power, Γ is the gamma function, τ c represents the mean value of the delay, α determines the symmetry of the power profile, and the initial value of the fit is determined by the propagation model results:

[0096]

[0097] in, and τ i are the power amplitude and delay of the i-th ray respectively. δ is used to adjust the width of the power function and should be as small as possible.

[0098] make:

[0099]

[0100] Therefore, taking the ray geometric distance as the standard, the unified DPP function calculated by ray tracing can be expressed as the sum of the propagation mode components:

[0101]

[0102] in, Represents the rounding down operation. The number of multipath rays selected It is related to the accuracy of the final DPP function. Without considering the computational cost, theoretically, the smaller its value is, the higher the horizontal resolution of the obtained DPP function is.

[0103] In this embodiment, the unified random modulation function includes: Rayleigh and Rice fading models can better reflect the fading characteristics of short-distance low-latitude shortwave channels, but it is too rough to use them to describe the fast fading characteristics of high-latitude shortwave channels for long-distance transmission. Nakagami observed fading phenomena more serious than Rayleigh fading in some long-distance communication channel measurements. The probability density function (PDF, the Probability Density Function) of the Nakagami-m distribution is:

[0104]

[0105] Where, Ω=E{X 2}, X is the amplitude random variable of the signal, A0 is the amplitude adjustment factor, m is the fading factor, 0.5≤m<1 means that the signal will experience a fading more severe than Rayleigh fading, and when m=1, this fading model is equivalent to Rayleigh fading.

[0106] When the time is less than the channel coherence time, the random modulation function can describe the time-varying nature of the channel, thereby characterizing the Doppler effect of the channel. Considering the application scenario in high-latitude areas, the Lorentz random modulation function is used:

[0107]

[0108] Among them, t coh is the channel coherence time, x is the amplitude value obtained by the Nakagami-m fading model, and the remaining parameters are obtained by statistical analysis of the propagation model parameters:

[0109]

[0110] Power scaling factor S V The power threshold and peak ratio that characterizes small-scale fading is difficult to obtain by ray tracing. Without loss of generality, we take S for the convenience of modeling. V =0.5.

[0111] Using the convolution theorem, we can get the Doppler power spectrum function of the channel as follows:

[0112]

[0113]

[0114] The above Doppler power function shows the theoretical profile of the channel energy in the Doppler domain calculated by ray tracing.

[0115] In this embodiment, the phase function includes: the deterministic phase function that characterizes the Doppler frequency shift characteristics of the transmission channel is defined as:

[0116]

[0117] In equation (40), b represents the rate of change of Doppler frequency shift relative to the time delay τ, and its value can be calculated by the following equation:

[0118]

[0119] Among them, f s ,f sL The delay τ c ,τ L The corresponding Doppler frequency shift value.

[0120] The deterministic phase function does not affect the shape of the impulse response in terms of amplitude, but since the channel scattering function is the impulse response after autocorrelation and Fourier transform, the deterministic phase function will affect the final shape of the scattering function.

[0121] In this embodiment, the ray tracing results calculated by the propagation model and the source data of the propagation model channel parameters are used to demonstrate the influence of the ray parameters of the unified delay power function on the horizontal resolution. A high-latitude Nakagami-m channel fading model is constructed through measured data from some high-latitude areas. Finally, a unified channel model is demonstrated, which mainly characterizes the channel characteristics through channel impulse response, transfer function and channel scattering function.

[0122] To show the simulation results of three channels, the parameters of the 3D ray tracing algorithm are set as shown in Table 1.

[0123] Table 1 3D ray tracing simulation parameters

[0124]

[0125] According to the parameter settings in Table 1, we can get Figure 3 The 3D ray tracing result shown in the figure, in addition, for the construction of the subsequent channel model, Figure 4 The Doppler-delay domain (DD) source data obtained by 3D ray tracing calculation is shown.

[0126] The number of rays selected when constructing the DPP function affects the final result of the DPP function. Figure 5 A comparison of DPP functions constructed with 10, 50, and 100 rays is presented. Figure 5 It can be seen that as the number of selected rays increases The increase of will reduce the horizontal resolution of the DPP function, and the obtained DPP function will be coarser and cannot accurately reflect the channel delay domain characteristics.

[0127] Through the Nakagami-m probability density function of formula (35), and with a small amount of Xinjiang-Kusamo actual communication link data as a reference, as follows Figure 6 (a) and Figure 6 (b), through mathematical fitting, we get the fading parameters m = 0.5109, Ω = 0.0529, Figure 6 (c) is the Nakagami-m fading model constructed using these measured data.

[0128] Based on the channel parameters of the channel propagation model, three shortwave channel models with the link of Xinjiang-Kusamo, the carrier frequency of 15MHz, and the ionospheric conditions of quiet and storm are obtained through the DPP function construction method, the Nakagami-m fading model and the Lorentz random modulation function. Figure 7 is a time-varying impulse response. Figure 8 The channel time-varying transfer function is shown, which indicates that the high-latitude channel is also a doubly selective fading channel. Fig. 9 are the three scattering functions of the channel, which characterize the dual dispersion of the high-latitude channel.

[0129] superior Figure 4-6 It reflects the characteristics of high-latitude channels from different angles. High-latitude channels will change with the communication time and ionospheric conditions. Figure 8 It is clear that the delay spread and Doppler spread in summer are both increased compared to winter. This is because the enhanced solar activity in summer intensifies the changes in the ionosphere environment, which increases the number of signal transmission paths that can reach the receiving end. At the same time, the strong time variability of the high-latitude ionosphere environment also enhances the Doppler effect. Figure 6 and Figure 7 It can be seen that the high-latitude channel exhibits strong time-varying characteristics. From equations (17) and (18), it can be seen that the high-latitude ionosphere model is a time-varying model, which causes the impulse response and transfer function to be time-varying as well, which is ultimately reflected in the existence of Doppler expansion and frequency shift in the scattering function.

[0130] In order to verify the effectiveness of the proposed high-latitude channel model, the following four sets of measured channel scattering functions are provided: Fig. 9 and Fig.10 Since the channel model in this paper is a theoretical model, the influence of noise on the channel is not considered. Excluding the influence of noise, the channel model in this paper has certain accuracy and effectiveness. Table 2 is a comparative analysis of the multipath delay and Doppler spread characteristics of the channel model in this paper and the actual channel measurement.

[0131] Table 2 Model and measured parameters

[0132]

[0133] By comparing the proposed model with the measured data, it is found that there is a certain degree of error between the high-latitude channel model proposed in this paper and the measured data. There are several reasons for this result. First, the 3D ray tracing algorithm principle uses the geometric optics approximation principle, which will cause the channel parameters to deteriorate. Second, the deviation between the ionospheric background model data and the actual communication channel environment will also cause errors.

[0134] Since the traditional shortwave channel model that relies on long-term, large-scale actual observation data is not economical in high-latitude regions, this paper proposes a more economical shortwave channel model driven by 3D ray tracing calculation for high-latitude regions, taking the high-latitude ionospheric background model as the propagation environment.

[0135] Taking the ITS model as the basic framework, the DPP function and the Lorentz random modulation function are constructed by calculating the channel parameters of the Xinjiang-Kusamo designated link, and then the channel model is obtained.

[0136] Compared with the scattering function obtained from actual channel measurements, the channel model proposed in this paper is effective on high-latitude shortwave links to meet the challenge of strictly limited channel measurements in high-latitude areas, and has certain reference value for waveform design and signal prediction of high-latitude shortwave links.

[0137] The channel modeling research in this paper has not fully considered the phase characteristics of the channel. The phase characteristics of the channel can provide certain support for channel estimation and thus improve its accuracy. Therefore, the phase characteristics of high-latitude shortwave channels can be examined in subsequent studies.

[0138] A person skilled in the art can understand that all or part of the steps in the various methods of the above embodiments can be completed by instructing the relevant hardware through a program, and the program can be stored in a computer-readable storage medium, which can include: ROM, RAM, disk or CD, etc.

[0139] The above embodiments further illustrate the purpose, technical solutions and advantages of the present invention in detail. It should be understood that the above embodiments are only preferred implementation modes of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A unified channel modeling method for shortwave skywave over-the-horizon links in high-latitude areas, characterized in that: The shortwave unified channel model includes the channel propagation model and the channel transmission model; The construction of the channel transmission model includes: S1. Obtain measured channel parameters; S2. Acquire channel parameters of the channel propagation model, wherein the channel parameters include transmit power, antenna, frequency, and measurement waveform obtained by using a high-latitude ionosphere model and a 3D ray tracing algorithm; S3, comparing the channel parameters with the measured channel parameters, if they do not match the measured channel parameters, executing step S4, otherwise executing step S6; S4. Drive the link observation system to measure the channel according to the channel parameters to obtain the full-link channel characteristic parameters on the actual transceiver channel; S5, modifying the channel parameters of the channel propagation model according to the full-link channel characteristic parameters on the actual transceiver channel, and returning to step S3; S6. Calculate the link long-period channel parameters according to the channel parameters, perform fitting modeling on the long-period channel parameters, and obtain a channel transmission model.

2. According to claim 1, a unified channel modeling method for shortwave skywave over-the-horizon links in high-latitude areas is characterized in that: The channel propagation model includes the shortwave channel propagation model and the high-latitude ionosphere model.

3. According to claim 1, a unified channel modeling method for shortwave skywave over-the-horizon links in high-latitude areas is characterized in that: The calculation of the transmission power includes using the DPP function to obtain the power distribution of the channel in the delay domain; specifically, obtaining the signal's exit angle, incident angle, and delay, and constructing a ray matrix based on the exit angle, incident angle, and delay; using a column vector of the ray matrix as a reference vector; calculating the geometric distance between other ray vectors and the reference vector, and arranging the geometric distance from small to large; selecting The rays with a smaller geometric distance from the reference vector are taken as single-mode multipath components; the power amplitude of each ray is calculated according to the power attenuation mechanism; the single-mode multipath components are fitted according to the power amplitude; and the single-mode multipath components are summed according to the fitting results to obtain the transmission power.

4. The unified channel modeling method for shortwave skywave over-the-horizon links in high-latitude areas according to claim 3 is characterized in that: The power attenuation mechanism includes the propagation loss of electromagnetic waves in free space, the energy absorption loss of high-frequency rays by the ionosphere, and the scattering loss of rays along the ground.

5. The unified channel modeling method for shortwave skywave over-the-horizon links in high-latitude areas according to claim 4 is characterized in that: Calculating the power amplitude of each ray involves: Among them, P tx (dbm) is the power value of the transmitting signal, L1 (dB) is the propagation loss of electromagnetic waves in free space, L2 (dB) is the energy absorption loss of high-frequency rays by the ionosphere, and L g (dB) is the scattering loss of the ray along the ground.

6. The unified channel modeling method for shortwave skywave over-the-horizon links in high-latitude areas according to claim 1 is characterized in that: Comparing the channel parameters with the measured channel parameters includes determining the size of the parameters in the channel parameters and the measured channel parameters. If the channel parameters are smaller than the measured channel parameters, the channel parameters do not meet the requirements, otherwise they meet the requirements.

7. The unified channel modeling method for shortwave skywave over-the-horizon links in high-latitude areas according to claim 1 is characterized in that: The link long-term channel parameters include Doppler shift, phase and group path.

8. The unified channel modeling method for shortwave skywave over-the-horizon links in high-latitude areas according to claim 1 is characterized in that: Calculating the Doppler frequency shift includes calculating the Doppler frequency shift using a Doppler power spectrum function.

9. The unified channel modeling method for shortwave skywave over-the-horizon links in high-latitude areas according to claim 6 is characterized in that: The Doppler power spectrum function is: Among them, f D is the Doppler frequency shift, ψ(t) is the Lorentz random modulation function, represents the Fourier transform operation, x is the amplitude value obtained by the Nakagami-m fading model, σ f is the Doppler spread factor.

10. The unified channel modeling method for shortwave skywave over-the-horizon links in high-latitude areas according to claim 1, characterized in that: The phase is calculated by the phase function, and its calculation expression is: Among them, f s ,f sL are delays, τ c ,τ L are the corresponding Doppler frequency shift values, and b represents the rate of change of Doppler frequency shift relative to the time delay τ.

Images