Channel modeling method, modeling system, electronic equipment and medium

Abstract

The invention discloses a channel modeling method, a modeling system, electronic equipment and a medium. The method comprises a modeling method of a small-scale channel fading model; the modeling method of the small-scale channel fading model comprises the following steps: setting a simulation area; acquiring the position of the incident electromagnetic wave after stepping according to the specified step length, and if the position of the incident electromagnetic wave after stepping does not exceed the simulation area, judging whether the incident electromagnetic wave reaches the receiving terminal according to the current position of the incident electromagnetic wave by taking the search depth as a judgment basis; and if the incident electromagnetic waves arrive at the receiving terminal, counting the incident electromagnetic waves arriving at the receiving terminal at the current moment, performing multi-path clustering on the incident electromagnetic waves, and configuring a channel according to the multi-path clustering. According to the method and the device, the channel can be modeled accurately.

Description

Technical Field

[0001] The present application relates to the field of communication technology, and in particular to a channel modeling method, a modeling system, an electronic device and a medium. Background Art

[0002] The communication quality of the satellite-to-ground link is closely related to the channel environment of the application scenario. Different environments such as oceans, mountains, and cities will produce different channel characteristics. The simulation of the channel environment can complete the communication system protocol design and communication terminal product design in the laboratory at a lower cost. In the current research on satellite-to-ground channel models, there are few research papers on the satellite-to-ground ocean channel because the test environment in the ocean environment is more harsh than on land and there are relatively fewer application scenarios.

[0003] The time-varying ocean satellite-to-ground communication channel has the characteristics of large-scale fading and small-scale fading. Large-scale fading includes the Doppler frequency deviation caused by the relative motion between the satellite and the terminal, the propagation delay change caused by the change in propagation distance, and the signal power attenuation caused by rainfall, atmospheric absorption, clouds and fog in the propagation path. Small-scale fading is manifested as sea surface multipath. In sea surface multipath, due to the strong time-varying nature of the ocean environment, the number of multipaths and the attenuation of multipath path loss will fluctuate rapidly in a short period of time. Summary of the invention

[0004] In view of this, the present application provides a channel modeling method, a modeling system, an electronic device and a medium to achieve more accurate channel modeling.

[0005] The present application discloses a satellite-to-earth channel modeling method, which includes a modeling method for a small-scale channel fading model;

[0006] The modeling method of the small-scale channel fading model comprises:

[0007] Set the simulation area;

[0008] Obtaining the position of the incident electromagnetic wave after stepping according to the specified step length; if the position of the incident electromagnetic wave after stepping does not exceed the simulation area, judging whether the incident electromagnetic wave reaches the receiving terminal according to the current position of the incident electromagnetic wave and the search depth;

[0009] If the incident electromagnetic wave reaches the receiving terminal, the incident electromagnetic wave arriving at the receiving terminal at the current moment is counted and multipath clustering is performed on the incident electromagnetic wave, and channels are configured according to the multipath clustering.

[0010] Further, judging whether the incident electromagnetic wave reaches the receiving terminal based on the search depth includes:

[0011] The distance between the current position of the incident electromagnetic wave and the coordinate point of the receiving terminal is calculated. If the distance is less than or equal to the search depth, it indicates that the incident electromagnetic wave has reached the receiving terminal.

[0012] Furthermore, the counting of the incident electromagnetic waves arriving at the receiving terminal at the current moment and performing multipath clustering on the incident electromagnetic waves includes:

[0013] The incident electromagnetic wave arriving at the receiving terminal is divided into a plurality of clusters according to the multipath delay of the incident electromagnetic wave and the signal symbol period in the incident electromagnetic wave.

[0014] Further, configuring channels according to multipath clustering includes:

[0015] According to the average path loss of each cluster, the electromagnetic waves in each cluster are merged into a cluster head; the path loss of the cluster head is the average path loss of each cluster;

[0016] Selecting a cluster head from all the cluster heads as a first cluster head according to the time delay of each cluster head;

[0017] Determine whether the first cluster head belongs to the direct line of sight path. If the first cluster head belongs to the direct line of sight path, configure the small-scale multipath fading model as a Ricean channel; otherwise, configure it as a Rayleigh channel.

[0018] Furthermore, it also includes judging whether the incident electromagnetic wave reaches the sea surface based on the search depth;

[0019] The step of judging whether the incident electromagnetic wave reaches the sea surface based on the search depth includes:

[0020] The wave surface of the ocean wave is divided into a plurality of ocean surface grid points, each of which corresponds to a three-dimensional spatial coordinate. The distances between all the ocean surface grid points and the position point of the incident electromagnetic wave at the current moment are calculated respectively. If there is a distance less than or equal to the search depth among all the obtained distances, it indicates that the incident electromagnetic wave has reached the sea surface.

[0021] Furthermore, before obtaining the position of the incident electromagnetic wave after stepping according to the specified step length, the method further includes:

[0022] Determine relevant parameters of a signal transmitted by a satellite from a reference line to a sea surface; generate an incident electromagnetic wave above the sea surface according to the relevant parameters; the reference line is located at a preset distance above the sea surface and is parallel to the sea level.

[0023] Furthermore, the determination of relevant parameters in the process of transmitting the signal transmitted by the satellite from the reference line to the sea surface includes:

[0024] Determine the total number of incident electromagnetic waves, solve the incident power of each incident electromagnetic wave incident on the sea surface based on the satellite signal transmission power, propagation path loss, and the total number of incident electromagnetic waves, determine the search depth of the incident electromagnetic wave, and the initial position of the incident electromagnetic wave incident on the sea surface.

[0025] Furthermore, before determining the relevant parameters of the signal transmitted by the satellite from the reference line to the sea surface, the method further includes:

[0026] A sea surface model at the current moment is established, a grid size is set, and the sea surface is gridded according to the grid size; the step size of the incident electromagnetic wave is determined according to the grid size of the sea surface; and the step size of the incident electromagnetic wave step is of the same order of magnitude as the grid size.

[0027] Furthermore, it also includes:

[0028] If the position of the incident electromagnetic wave after stepping exceeds the simulation area, the subsequent calculation of the incident electromagnetic wave is stopped.

[0029] Furthermore, if the incident electromagnetic wave reaches the sea surface, the reflection angle, reflection loss, and direction of the reflected electromagnetic wave are calculated.

[0030] Furthermore, if the incident electromagnetic wave does not reach the sea surface and does not reach the receiving terminal, the incident electromagnetic wave is stepped forward again by one step, and the current position of the incident electromagnetic wave is updated, and it is re-determined whether the incident electromagnetic wave reaches the receiving terminal until the incident electromagnetic wave reaches the receiving terminal.

[0031] Furthermore, it also includes:

[0032] A large-scale channel fading model is established for the first transmission process; channel modeling is performed according to parameters determined by the large-scale channel fading model and the small-scale channel fading model; the first transmission process is a signal transmission process between a signal transmitted by a satellite and a reference line; the reference line is located at a preset distance above the sea surface and is parallel to the sea level.

[0033] Further, the parameters determined according to the large-scale channel fading model and the small-scale channel fading model include:

[0034] Determining large-scale parameters through the large-scale channel fading model; the large-scale parameters include large-scale fading, transmission delay and Doppler frequency shift; the large-scale fading includes various path losses caused by atmosphere, space environment, and wave shielding, as well as sea surface shadow fading;

[0035] Small-scale parameters are obtained through the small-scale channel fading model; the small-scale parameters include the average multipath path loss and multipath delay of each multipath channel cluster, and random fading coefficients that obey Rayleigh or Rice distribution are generated according to whether there is a direct line of sight path;

[0036] The noise power or signal-to-noise ratio is calculated according to the channel conditions, and noise data of the corresponding power is generated.

[0037] Further, the channel modeling includes:

[0038] Channel modeling can be performed by configuring the large-scale parameters, the small-scale parameters and the noise data in the relevant parameter configuration area of ​​the channel simulator.

[0039] Further, the channel modeling includes:

[0040] In the large-scale channel fading model, the signal transmitted by the satellite is multiplied by the large-scale fading to obtain a first result, and the first result is successively subjected to transmission delay and Doppler frequency shift to obtain a second result; in the small-scale channel fading model, the second result generates a number of multipath clusters according to the actual environment; each of the multipath clusters represents a multipath; in each of the multipaths, the signal successively passes through the average multipath path loss, multipath delay, Rayleigh or Ricean random fading corresponding to the multipath to obtain a third result; all the third results are summed, and the signal obtained by the sum is the signal that has experienced small-scale fading; the signal that has experienced small-scale fading and the noise data are summed to obtain the signal generated by the channel modeling.

[0041] The present application also discloses a satellite-to-ground channel modeling system, which includes a modeling device for a small-scale channel fading model;

[0042] The modeling device of the small-scale channel fading model comprises:

[0043] A judgment module is used to set a simulation area, obtain the position of the incident electromagnetic wave after stepping according to a specified step length, and if the position of the incident electromagnetic wave after stepping does not exceed the simulation area, judge whether the incident electromagnetic wave reaches the receiving terminal according to the current position of the incident electromagnetic wave and the search depth;

[0044] The modeling module is used for counting the incident electromagnetic waves arriving at the receiving terminal at the current moment and performing multipath clustering on the incident electromagnetic waves if the incident electromagnetic waves arrive at the receiving terminal, and configuring channels according to the multipath clustering.

[0045] The present application also discloses an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the satellite-to-ground channel modeling method described in any one of the above items is implemented.

[0046] The present application also discloses a computer-readable storage medium, which includes a computer program or instruction. When the computer program or instruction is executed on a computer, the computer executes any one of the above-mentioned satellite-to-ground channel modeling methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of the present application. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0048] Figure 1 A schematic flow chart of a satellite-to-ground channel modeling method according to an embodiment of the present application;

[0049] Figure 2 A schematic diagram of an incident electromagnetic wave incident on a sea surface model according to an embodiment of the present application;

[0050] Figure 3 A schematic diagram of path clustering in an embodiment of the present application;

[0051] Figure 4 A schematic diagram of the relationship between the sea surface model and the small-scale model of an embodiment of the present application;

[0052] Figure 5 A schematic flow chart of another satellite-to-ground channel modeling method according to an embodiment of the present application;

[0053] Figure 6 A schematic diagram of the modeling process of the large-scale channel fading model according to an embodiment of the present application. DETAILED DESCRIPTION

[0054] The present application is further described in conjunction with the accompanying drawings and embodiments, and the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field should fall within the scope of protection of the embodiments of the present application.

[0055] See also Figure 1 and Figure 5 , the present application provides an embodiment of a satellite-to-earth channel modeling method, which includes a modeling method for a small-scale channel fading model;

[0056] The modeling method of the small-scale channel fading model includes:

[0057] Set the simulation area;

[0058] Obtain the position of the incident electromagnetic wave after stepping according to the specified step length. If the position of the incident electromagnetic wave after stepping does not exceed the simulation area, determine whether the incident electromagnetic wave reaches the receiving terminal based on the current position of the incident electromagnetic wave and the search depth;

[0059] If the incident electromagnetic wave reaches the receiving terminal, the incident electromagnetic waves arriving at the receiving terminal at the current moment are counted and multipath clustering is performed on them;

[0060] Channels are configured based on multipath clustering.

[0061] In one embodiment of the present application, judging whether the incident electromagnetic wave reaches the receiving terminal based on the search depth includes:

[0062] Calculate the distance between the current position of the incident electromagnetic wave and the coordinate point of the receiving terminal. If the distance is less than or equal to the search depth, it indicates that the incident electromagnetic wave has reached the receiving terminal; otherwise, it indicates that the incident electromagnetic wave has not reached the receiving terminal.

[0063] Optionally, after the incident electromagnetic wave hits the sea surface, it is reflected multiple times before reaching the receiving terminal. If the signal power is very small after three or more reflections, it will no longer participate in the subsequent judgment and calculation of whether it reaches the sea surface and the receiving terminal. Figure 2 The incident electromagnetic wave enters the sea surface and then reaches the receiving terminal after one reflection and two reflections.

[0064] In one embodiment of the present application, counting incident electromagnetic waves arriving at a receiving terminal at a current moment and performing multipath clustering on the incident electromagnetic waves includes:

[0065] The incident electromagnetic wave arriving at the receiving terminal is divided into a plurality of clusters according to the multipath delay of the incident electromagnetic wave and the signal symbol period in the incident electromagnetic wave.

[0066] The present application performs clustering through ray (incident electromagnetic wave) propagation, and can accurately simulate satellite-to-ground channels.

[0067] In one embodiment of the present application, configuring channels according to multipath clustering includes:

[0068] According to the average path loss of each cluster, the electromagnetic waves in each cluster are merged into a cluster head; the path loss of the cluster head is the average path loss of each cluster;

[0069] According to the delay of each cluster head, a cluster head is selected from all cluster heads as the first cluster head;

[0070] It is determined whether the first cluster head belongs to the direct line of sight path. If the first cluster head belongs to the direct line of sight path, the small-scale multipath fading model is configured as a Ricean channel, otherwise, it is configured as a Rayleigh channel.

[0071] In this embodiment, two common probability statistical models are considered: Rice distribution and Rayleigh distribution. In addition, when modeling small-scale multipath clustering, the ray tracing method is used to calculate the path of each incident electromagnetic wave from a reference line (the reference line is located at a preset distance above the sea surface and parallel to the sea surface) to the receiving terminal in a certain space, the path loss (path attenuation value) of each incident electromagnetic wave to the receiving terminal, and the propagation delay of each incident electromagnetic wave. Finally, multipath clustering is performed according to the period T of signal code element transmission, and the paths with a delay difference of less than 0.25T are grouped into one cluster. Finally, several clusters can be obtained, such as Figure 3 For example, the number of incident electromagnetic waves, the path delay and the path loss of the incident electromagnetic waves in the multipath cluster can be solved directly by program calculation, so that the channel modeling is more accurate.

[0072] In one embodiment of the present application, it further includes judging whether the incident electromagnetic wave reaches the sea surface based on the search depth;

[0073] Based on the search depth, determine whether the incident electromagnetic wave reaches the sea surface, including:

[0074] The wave surface of the ocean wave is divided into multiple ocean surface grid points, each of which corresponds to a three-dimensional spatial coordinate. The distances between all ocean surface grid points and the current position of the incident electromagnetic wave are calculated respectively. If there is a distance less than or equal to the search depth among all the obtained distances, it indicates that the incident electromagnetic wave has reached the sea surface; otherwise, it indicates that the incident electromagnetic wave has not reached the sea surface.

[0075] The present application uses ray tracing to perform multipath modeling, which can accurately simulate and model the multipath distribution of electromagnetic waves incident on the sea surface, can simulate the time-varying ocean multipath channel environment in real time, and perform more accurate modeling of satellite-to-ground channels. Among them, the incident electromagnetic waves propagate in the form of rays.

[0076] In one embodiment of the present application, before obtaining the position of the incident electromagnetic wave after stepping according to the specified step length, the method further includes:

[0077] Determine relevant parameters of a signal transmitted by a satellite from a reference line to a sea surface; generate an incident electromagnetic wave above the sea surface according to the relevant parameters; the reference line is located at a preset distance above the sea surface and is parallel to the sea surface.

[0078] In one embodiment of the present application, determining relevant parameters of a signal transmitted by a satellite during transmission from a reference line to a sea surface includes:

[0079] Determine the total number of incident electromagnetic waves, solve the incident power of each incident electromagnetic wave entering the sea surface based on the satellite signal transmission power, propagation path loss, and the total number of incident electromagnetic waves, determine the search depth of the incident electromagnetic wave, and the initial position of the incident electromagnetic wave entering the sea surface.

[0080] Exemplarily, the incident angle of the electromagnetic wave of the satellite transmission signal near the sea surface is determined according to the elevation angle of the communication link from the satellite to the receiving terminal at the current moment. Since the satellite is very far away from the terminal, the incident electromagnetic wave near the sea surface can be considered as a parallel wave. After comprehensively considering factors such as the size of the sea area, solution accuracy, and calculation time, the total number of incident electromagnetic waves is determined, and then the incident power of each incident electromagnetic wave near the sea level is solved according to the satellite signal transmission power, propagation path loss, and the total number of rays. Then, the search depth of the incident electromagnetic wave is determined, and finally the initial position of the incident electromagnetic wave entering the sea surface is determined.

[0081] In one embodiment of the present application, before determining the relevant parameters in the process of transmitting the signal transmitted by the satellite from the reference line to the sea surface, the method further includes:

[0082] Establish the current sea surface model, set the grid size, and divide the sea surface into grids according to the grid size; determine the step size of the incident electromagnetic wave according to the grid size of the sea surface; the step size of the incident electromagnetic wave is of the same order of magnitude as the grid size, which can reduce the amount of calculation and prevent erroneous searches.

[0083] For example, see Figure 4 , set the simulation area. The sea surface model at time t is established through the three-dimensional irregular short-peak wave model based on the PM spectrum. The sea surface grid is divided using an appropriate grid size after comprehensively considering factors such as the size of the sea area, solution accuracy, and calculation time.

[0084] The method of establishing the sea surface model using the three-dimensional irregular short-peak wave model based on PM spectrum is as follows:

[0085] In the simulation of two-dimensional irregular long-peaked waves, for any sub-wave, its wave frequency specifies the wave height, and the wave comes from only one direction of the sea surface. In fact, the waves have three-dimensional irregularity. The waves on the sea not only have different wave heights and frequencies, but also propagate to a certain point from all directions. In addition to the main wave direction generated along the main wind direction, the harmonics have diffusion within the ±π / 2 angle range on both sides of the main wave direction. Such waves are three-dimensional irregular short-peaked waves. The sea surface model can be simulated using the double summation model, that is:

[0086]

[0087] Where x represents the coordinate of the horizontal X-axis position point, y represents the coordinate of the vertical Y-axis position point, t represents the simulation time, z(x,y,t) represents the wave height at the coordinate (x,y) at time t, i represents the number of the cosine wave number, j represents the number of the cosine wave direction angle, n represents the total number of cosine wave numbers, m represents the total number of cosine wave direction angles, and ζ aij represents the cosine wave amplitude, k i Represents the wave value of the cosine wave numbered i, ω i represents the angular frequency of the cosine wave numbered i, θ j represents the direction angle of the cosine wave numbered j, ε ij Indicates the initial phase. g represents the acceleration due to gravity, and the initial phase ε ij is a random variable that follows a uniform distribution in the interval [0, 2π].

[0088] Cosine wave amplitude ζ aij According to the following formula:

[0089]

[0090] Among them, Δω and Δθ are the step increments of angular frequency and direction angle during the simulation, respectively, S ζ (ω i )and They are the PM (Pierson-Moskowitze) spectrum and wave energy diffusion function of the ocean waves, and their expressions are as follows:

[0091]

[0092]

[0093] Where v is the wind speed at a height of 19.5 m above sea level, and g is the acceleration due to gravity, which is taken as 9.81 m / s.

[0094] The step increments Δω and Δθ are calculated as follows:

[0095]

[0096] In the formula, ω max represents the maximum angular frequency, ω min Indicates the minimum angular frequency.

[0097] Then the angular frequency of a single cosine wave is ω i and direction angle θ j It can be expressed as:

[0098]

[0099] In one embodiment of the present application, it also includes:

[0100] If the position of the incident electromagnetic wave after stepping exceeds the simulation area, the subsequent calculation of the incident electromagnetic wave is stopped.

[0101] In one embodiment of the present application, if the incident electromagnetic wave reaches the sea surface, reflection will occur, and the reflection angle, reflection loss, and direction of the reflected electromagnetic wave can be calculated based on the reflection theorem of light.

[0102] In one embodiment of the present application, if the incident electromagnetic wave does not reach the sea surface and does not reach the receiving terminal, the incident electromagnetic wave is stepped forward again, and the current position of the incident electromagnetic wave is updated, and it is re-determined whether the incident electromagnetic wave reaches the receiving terminal until the incident electromagnetic wave reaches the receiving terminal.

[0103] In one embodiment of the present application, it also includes:

[0104] A large-scale channel fading model is established for the first transmission process; channel modeling is performed according to the parameters determined by the large-scale channel fading model and the small-scale channel fading model; the first transmission process is the signal transmission process from the signal transmitted by the satellite to the reference line; the reference line is located at a preset distance above the sea surface and parallel to the sea level.

[0105] In one embodiment of the present application, the parameters determined according to the large-scale channel fading model and the small-scale channel fading model include:

[0106] The large-scale parameters are determined through the large-scale channel fading model; the large-scale parameters include large-scale fading, transmission delay and Doppler frequency shift; large-scale fading includes various path losses caused by the atmosphere, space environment, and wave shielding, as well as sea surface shadow fading;

[0107] Small-scale parameters are obtained through a small-scale channel fading model; the small-scale parameters include the average multipath path loss and multipath delay of each multipath channel cluster, and random fading coefficients that obey Rayleigh or Rice distribution are generated according to whether there is a direct line of sight path;

[0108] The noise power or signal-to-noise ratio is calculated according to the channel conditions, and noise data of the corresponding power is generated.

[0109] Optionally, a Gaussian white noise model is used to establish an environmental noise model, and the Gaussian white noise acts on the signal in an additive interference manner.

[0110] In one embodiment of the present application, channel modeling is performed, including:

[0111] Channel modeling can be performed by configuring large-scale parameters, small-scale parameters and noise data in the relevant parameter configuration area of ​​the channel simulator.

[0112] In one embodiment of the present application, channel modeling is performed, including:

[0113] In the large-scale channel fading model, the signal transmitted by the satellite is multiplied by the large-scale fading to obtain the first result, and the first result is successively subjected to transmission delay and Doppler frequency shift to obtain the second result; in the small-scale channel fading model, the second result generates several multipath clusters according to the actual environment; each multipath cluster represents a multipath; in each multipath, the signal successively passes through the average multipath path loss, multipath delay, Rayleigh or Ricean random fading corresponding to the multipath to obtain the third result; all the third results are summed up, and the signal obtained by the sum is the signal that has experienced small-scale fading; the signal that has experienced small-scale fading and the noise data are summed up to obtain the signal generated by channel modeling.

[0114] For example, see Figure 5 If the channel model calculation results need to be reflected in the input signal, large-scale fading (large-scale power fading includes various path losses caused by the atmosphere, space environment, and sea wave shielding, and sea surface shadow fading) can be converted into the attenuation multiple multiplied by the input signal amplitude (the signal transmitted by the satellite is multiplied by various path losses caused by the atmosphere, space environment, and sea wave shielding, and the multiplication result is multiplied by the sea surface shadow fading). The transmission delay can simulate the path delay by the store-and-forward method, and the Doppler frequency shift is multiplied by the signal through the sine and cosine data of the corresponding frequency; in small-scale fading, the signal will generate several multipath clusters according to the actual environment, and each cluster represents a multipath. In each multipath, the signal will experience the average path loss, multipath delay, Rayleigh or Rice random fading corresponding to the multipath in turn, and finally the signals obtained after experiencing the effects of each multipath are summed up. The summed signal is the signal that has experienced small-scale fading; the noise is directly added to the summed signal.

[0115] Among them, the small-scale parameters (including the average multipath path loss and multipath delay of each multipath channel cluster, and the random fading coefficients obeying the Rayleigh or Rice distribution generated according to the presence or absence of a direct line of sight path) are convolved with the input signal (the signal output by the Doppler frequency shift).

[0116] In channel simulation, the influence characteristics of the channel can be loaded onto the actual signal to simulate the impact of the channel on the signal in a laboratory environment to the greatest extent, which is convenient for later factory testing of actual terminal products and early development of protocol systems.

[0117] In the above embodiment, the established large-scale channel fading model includes free space propagation loss, sea shadow fading, atmospheric absorption attenuation, rainfall attenuation, cloud attenuation, tropospheric scintillation, ionospheric scintillation, polarization loss, propagation delay, Doppler frequency shift, etc. The atmospheric absorption attenuation, rainfall attenuation, cloud attenuation, tropospheric scintillation, ionospheric scintillation, polarization loss, etc. models refer to ITU standards.

[0118] The free space propagation loss is calculated as:

[0119]

[0120] Among them, L f represents the free space propagation loss, P T Indicates the transmit power, P R represents the received power, d represents the distance between the satellite and the ground terminal, and f c represents the carrier operating frequency, and c represents the speed of light.

[0121] The calculation of sea shadow fading is as follows:

[0122] The random fluctuations of the sea level will block some of the incident waves, causing shadow fading, especially when the elevation angle of the incident light is small. Studies have shown that shadow fading in ocean scenes can be described by the shadow coefficient, that is:

[0123]

[0124]

[0125] Based on the above analysis, the shadow fading in the ocean multipath scenario can be calculated by the following formula:

[0126]

[0127] Among them, Loss sea represents the sea shadow fading, S sea represents the sea surface shadow coefficient, R represents the sea surface reflection coefficient, σ h represents the standard deviation of sea surface wave height, θ e represents the complementary angle of the electromagnetic wave incident angle, λ represents the signal wavelength, θ e =π / 2-θ i ,θ i Represents the incident angle of the electromagnetic wave.

[0128] The propagation delay is obtained by dividing the distance between the terminal and the satellite by the speed of light; the Doppler shift is obtained by the relative speed between the terminal and the satellite, that is:

[0129] Delay=d / c

[0130] Where Delay represents the propagation delay, d represents the distance between the satellite and the ground terminal, and c represents the speed of light.

[0131] The calculation formula for Doppler frequency shift is:

[0132]

[0133] Among them, f0 represents the signal frequency after Doppler frequency shift, r represents the distance between the satellite and the terminal vector, f represents the signal frequency before Doppler frequency shift, v represents the relative speed between the satellite and the terminal vector, and c represents the speed of light.

[0134] See also Figure 6 , the modeling process of the large-scale channel fading model is:

[0135] Input six satellite orbit numbers, terminal positions at each time point, simulation start and end time, and simulation step size; calculate satellite position and speed at each time according to the SGP4 orbit model; calculate free space propagation loss, atmospheric absorption attenuation, rainfall attenuation, cloud attenuation, tropospheric scintillation, ionospheric scintillation, and polarization loss on the communication link at each time through the large-scale standard model provided by ITU and historical environmental data; calculate sea surface shadow fading; calculate the propagation delay on the communication link at each time according to the position of the satellite and the terminal, and calculate the Doppler frequency deviation value at each time according to the relative speed of the satellite and the terminal; output large-scale parameters at each time; large-scale parameters include large-scale fading, transmission delay, and Doppler frequency shift; large-scale fading includes various path losses caused by the atmosphere, space environment, and wave obstruction, as well as sea surface shadow fading.

[0136] It should be noted that the small-scale channel fading model in the above embodiment is established for the second transmission process; the second transmission process is the signal transmission process between the reference line and the receiving terminal; the reference line is located at a preset distance above the sea surface and parallel to the sea surface. The large-scale channel fading model is used to describe the signal power changes, Doppler frequency shift and propagation delay over a long distance between the satellite and the receiving terminal. The signal power changes include transmission loss, dispersion, and shadow fading; the small-scale channel fading model is used to describe the rapid changes in signal power over a short distance and in a short time, including multipath fading.

[0137] The present application also provides an embodiment of a satellite-to-ground channel modeling system, which includes a modeling device for a small-scale channel fading model;

[0138] A modeling device for a small-scale channel fading model, comprising:

[0139] A judgment module is used to set a simulation area, obtain the position of the incident electromagnetic wave after stepping according to a specified step length, and if the position of the incident electromagnetic wave after stepping does not exceed the simulation area, judge whether the incident electromagnetic wave reaches the receiving terminal according to the current position of the incident electromagnetic wave and the search depth;

[0140] The modeling module is used for counting the incident electromagnetic waves arriving at the receiving terminal at the current moment and performing multipath clustering on the incident electromagnetic waves if the incident electromagnetic waves arrive at the receiving terminal, and configuring channels according to the multipath clustering.

[0141] An embodiment of the present application further provides an electronic device, which includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the satellite-to-ground channel modeling method described in the above embodiment is implemented.

[0142] An embodiment of the present application further provides a computer-readable storage medium, which includes a computer program or instructions. When the computer program or instructions are executed on a computer, the computer executes the satellite-to-earth channel modeling method described in the above embodiment.

[0143] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application rather than to limit it. Although the present application has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present application can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present application should be included in the scope of protection of the claims of the present application.

Claims

1. A satellite-to-ground channel modeling method, characterized in that: Includes modeling methods for small-scale channel fading models; The modeling method of the small-scale channel fading model comprises: Set the simulation area; Obtaining the position of the incident electromagnetic wave after stepping according to the specified step length, if the position of the incident electromagnetic wave after stepping does not exceed the simulation area, judging whether the incident electromagnetic wave reaches the receiving terminal according to the current position of the incident electromagnetic wave and the search depth; If the incident electromagnetic wave reaches the receiving terminal, the incident electromagnetic wave arriving at the receiving terminal at the current moment is counted and multipath clustering is performed on it, and channels are configured according to the multipath clustering.

2. The satellite-to-ground channel modeling method according to claim 1, characterized in that: The step of judging whether the incident electromagnetic wave reaches the receiving terminal based on the search depth includes: The distance between the current position of the incident electromagnetic wave and the coordinate point of the receiving terminal is calculated. If the distance is less than or equal to the search depth, it indicates that the incident electromagnetic wave has reached the receiving terminal.

3. The satellite-to-ground channel modeling method according to claim 1, characterized in that: The counting of the incident electromagnetic waves arriving at the receiving terminal at the current moment and performing multipath clustering on the incident electromagnetic waves includes: The incident electromagnetic wave arriving at the receiving terminal is divided into a plurality of clusters according to the multipath delay of the incident electromagnetic wave and the signal symbol period in the incident electromagnetic wave.

4. The satellite-to-ground channel modeling method according to claim 1, characterized in that: The configuring of channels according to multipath clustering includes: According to the average path loss of each cluster, the electromagnetic waves in each cluster are merged into a cluster head; the path loss of the cluster head is the average path loss of each cluster; Selecting a cluster head from all the cluster heads as a first cluster head according to the time delay of each cluster head; Determine whether the first cluster head belongs to the direct line of sight path. If the first cluster head belongs to the direct line of sight path, configure the small-scale multipath fading model as a Ricean channel; otherwise, configure it as a Rayleigh channel.

5. The satellite-to-ground channel modeling method according to claim 1, characterized in that: It also includes judging whether the incident electromagnetic wave reaches the sea surface based on the search depth; The step of judging whether the incident electromagnetic wave reaches the sea surface based on the search depth includes: The wave surface of the ocean wave is divided into a plurality of ocean surface grid points, each of which corresponds to a three-dimensional spatial coordinate. The distances between all the ocean surface grid points and the position point of the incident electromagnetic wave at the current moment are calculated respectively. If there is a distance less than or equal to the search depth among all the obtained distances, it indicates that the incident electromagnetic wave has reached the sea surface.

6. The satellite-to-ground channel modeling method according to claim 1, characterized in that: Before obtaining the position of the incident electromagnetic wave after stepping according to the specified step length, the method further includes: Determine relevant parameters of a signal transmitted by a satellite from a reference line to a sea surface; generate an incident electromagnetic wave above the sea surface according to the relevant parameters; the reference line is located at a preset distance above the sea surface and is parallel to the sea level.

7. The satellite-to-ground channel modeling method according to claim 6, characterized in that: The determination of the relevant parameters in the process of the signal transmitted by the satellite from the reference line to the sea surface includes: Determine the total number of incident electromagnetic waves, solve the incident power of each incident electromagnetic wave incident on the sea surface based on the satellite signal transmission power, propagation path loss, and the total number of incident electromagnetic waves, determine the search depth of the incident electromagnetic wave, and the initial position of the incident electromagnetic wave incident on the sea surface.

8. The satellite-to-ground channel modeling method according to claim 6, characterized in that: Before determining the relevant parameters in the process of transmitting the signal transmitted by the satellite from the reference line to the sea surface, the method further includes: A sea surface model at the current moment is established, a grid size is set, and the sea surface is gridded according to the grid size; the step size of the incident electromagnetic wave is determined according to the grid size of the sea surface; and the step size of the incident electromagnetic wave step is of the same order of magnitude as the grid size.

9. The satellite-to-ground channel modeling method according to claim 1, characterized in that: Also includes: If the position of the incident electromagnetic wave after stepping exceeds the simulation area, the subsequent calculation of the incident electromagnetic wave is stopped.

10. The satellite-to-ground channel modeling method according to any one of claims 1 to 9, characterized in that: If the incident electromagnetic wave reaches the sea surface, the reflection angle, reflection loss, and direction of the reflected electromagnetic wave are calculated.

11. The satellite-to-ground channel modeling method according to any one of claims 1 to 9, characterized in that: If the incident electromagnetic wave does not reach the sea surface and does not reach the receiving terminal, the incident electromagnetic wave is stepped forward again, and the current position of the incident electromagnetic wave is updated, and it is re-determined whether the incident electromagnetic wave reaches the receiving terminal until the incident electromagnetic wave reaches the receiving terminal.

12. The satellite-to-ground channel modeling method according to claim 1, characterized in that: Also includes: Establishing a large-scale channel fading model for the first transmission process; performing channel modeling according to parameters determined by the large-scale channel fading model and the small-scale channel fading model; The first transmission process is a signal transmission process between a signal transmitted by a satellite and a reference line; The reference line is located at a preset distance above the sea surface and is parallel to the sea surface.

13. The satellite-to-ground channel modeling method according to claim 12, characterized in that: The parameters determined according to the large-scale channel fading model and the small-scale channel fading model include: Determining large-scale parameters through the large-scale channel fading model; the large-scale parameters include large-scale fading, transmission delay and Doppler frequency shift; the large-scale fading includes various path losses caused by atmosphere, space environment, and wave shielding, as well as sea surface shadow fading; Small-scale parameters are obtained through the small-scale channel fading model; the small-scale parameters include the average multipath path loss and multipath delay of each multipath channel cluster, and random fading coefficients that obey Rayleigh or Rice distribution are generated according to whether there is a direct line of sight path; The noise power or signal-to-noise ratio is calculated according to the channel conditions, and noise data of the corresponding power is generated.

14. The satellite-to-ground channel modeling method according to claim 13, characterized in that: The channel modeling comprises: Channel modeling can be performed by configuring the large-scale parameters, the small-scale parameters and the noise data in the relevant parameter configuration area of ​​the channel simulator.

15. The satellite-to-ground channel modeling method according to claim 13, characterized in that: The channel modeling comprises: In the large-scale channel fading model, the signal transmitted by the satellite is multiplied by the large-scale fading to obtain a first result, and the first result is successively subjected to transmission delay and Doppler frequency shift to obtain a second result; in the small-scale channel fading model, the second result generates a number of multipath clusters according to the actual environment; each of the multipath clusters represents a multipath; in each of the multipaths, the signal successively passes through the average multipath path loss, multipath delay, and random fading corresponding to the multipath to obtain a third result; all the third results are summed, and the signal obtained by the sum is the signal that has experienced small-scale fading; the signal that has experienced small-scale fading and the noise data are summed to obtain the signal generated by the channel modeling.

16. A satellite-to-ground channel modeling system, characterized in that: A modeling device including a small-scale channel fading model; The modeling device of the small-scale channel fading model comprises: A judgment module is used to set a simulation area, obtain the position of the incident electromagnetic wave after stepping according to a specified step length, and if the position of the incident electromagnetic wave after stepping does not exceed the simulation area, judge whether the incident electromagnetic wave reaches the receiving terminal according to the current position of the incident electromagnetic wave and the search depth; The modeling module is used for counting the incident electromagnetic waves arriving at the receiving terminal at the current moment and performing multipath clustering on the incident electromagnetic waves if the incident electromagnetic waves arrive at the receiving terminal, and configuring channels according to the multipath clustering.

17. An electronic device, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the satellite-to-ground channel modeling method according to any one of claims 1 to 15 is implemented.

18. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a computer program or an instruction. When the computer program or the instruction is executed on a computer, the computer is enabled to execute the satellite-to-ground channel modeling method according to any one of claims 1 to 15.

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