A multi-slope mountainous wireless channel modeling method combining digital elevation model and ray tracing

Abstract

The present application relates to a kind of multi-gradient mountainous wireless channel modeling method of combining digital elevation model and ray tracing, belong to wireless communication field.It is unmanned aerial vehicle base station assisted communication, applicable in natural disaster or emergency, quickly deploy efficient communication network.Through digital elevation model, real different gradient mountainous environment can be established and mountain gradient is obtained;Through ray tracing method, signal propagation path can be predicted and signal propagation characteristics are obtained.The modeling method first establishes real mountainous scene, extracts mountain gradient, then obtains channel model parameters, analyzes channel characteristics, finally adjusts transmitter parameters according to channel characteristic data, realizes multi-gradient mountainous wireless channel modeling.The main idea of the modeling method proposed in the present application is to analyze the channel model through accurate terrain data and channel characteristic data, and to improve the reliability of wireless communication system by adjusting parameters.Design suggestions are proposed for emergency communication and technical innovation.

Description

TECHNICAL FIELD

[0001] The present application relates to a multi-slope mountain wireless channel modeling method combining digital elevation model and ray tracing, belonging to the field of wireless communication. BACKGROUND

[0002] Unmanned aerial vehicles as air base stations have attracted widespread attention in the field of wireless communication. By deploying unmanned aerial vehicle base stations, temporary communication can be quickly established to ensure communication needs for disaster relief and emergency response.

[0003] Current wireless communication research mainly focuses on indoor environments, urban areas and residential areas, while relatively little research has been conducted on mountainous environments. Moreover, for wireless communication in mountainous environments, specific mountain slopes have not been thoroughly analyzed. The present application uses a multi-slope mountain wireless channel modeling method combining digital elevation model and ray tracing to simulate wireless communication in different slope mountains, filling this research gap.

[0004] To address the complexity of signal propagation paths in mountainous environments, the present application models a mountainous wireless channel communication system by combining a digital elevation model (DEM) and a ray tracing algorithm, and introducing mountain slope. First, traditional wireless channel models cannot accurately reflect the topographic features of mountainous environments, resulting in large errors in signal propagation path calculations. By introducing a digital elevation model, high-precision topographic data can be obtained, thereby improving the accuracy of the wireless channel model in mountainous environments. Second, the ray tracing algorithm is used to simulate the signal propagation path, providing a more realistic calculation of signal energy loss. Finally, the mountain slope is introduced into the channel model to consider the impact of different slopes on signal propagation paths, thereby simulating the propagation characteristics of signals under different slope conditions. Through the combination of these technologies, the authenticity and reliability of the channel model can be improved, making communication design in multi-slope mountainous environments more reliable. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a multi-slope mountain wireless channel modeling method combining digital elevation model and ray tracing, which addresses the complexity of wireless communication signal propagation paths in mountainous environments.

[0006] The technical solution of the present application is: a multi-slope mountain wireless channel modeling method combining digital elevation model and ray tracing, the specific steps are:

[0007] S1: download digital elevation data;

[0008] S2: use ArcGIS to segment the digital elevation data and select the required terrain;

[0009] S311: Extract the mountain slope in the terrain using ArcGIS, and generate a slope layer;

[0010] S312: Sample points on the generated slope layer;

[0011] S321: Set the relative dielectric constant and conductivity of the terrain using Wireless Insite, and complete the mountain environment simulation;

[0012] S322: Set the signal center frequency, bandwidth and related configuration of the antenna, and provide the antenna selection for the receiver;

[0013] S4: Place the receiver according to the sample point position using Wireless Insite, and determine the related parameters of the receiver;

[0014] S5: Place the transmitter above the center of the terrain and set the related parameters of the transmitter;

[0015] S6: Set the calculation engine and combine the communication system;

[0016] S7: Analyze the channel characteristics SNR, and realize the multi-slope mountain wireless channel modeling.

[0017] Optionally, the downloaded digital elevation data is ASTER GDEM 30M resolution digital elevation data downloaded through the digital geographic cloud website. The digital elevation represents a finite sequence of three-dimensional vectors on the region D, which is represented by a function as:

[0018] V i =(X i ,Y i ,Z i )(i=1,2,3,...n)

[0019] Where (X i ,Y i ) is the plane coordinate, and Z i is the corresponding elevation of (X i ,Y i ).

[0020] Optionally, the digital elevation data segmentation is to generate a subset of multiple output feature classes after segmenting the input features. The specific operation is: first, import the downloaded digital elevation data in step S1 into ArcGIS in the form of.img file, select segmentation in the extraction analysis column, and set the number of output terrains. Then select the required terrain and export the terrain in.tif format.

[0021] The mountain slope is the degree of inclination of the terrain surface relative to the horizontal plane, and the mountain slope is determined by calculating the elevation change rate of the surface center pixel in the horizontal direction (dz / dx) and the vertical direction (dz / dy). The calculation formula of the slope in degrees is:

[0022]

[0023] Wherein, ATAN is the inverse tangent function.

[0024] Optionally, the sampling point is selected on the slope layer to obtain the mountain slope value of the sampling point. The sampling point position is selected by first drawing a line every 30 meters on the x-axis of the terrain, then drawing a line every 30 meters on the y-axis, and taking the intersection point of the two straight lines as the sampling point.

[0025] Optionally, the relative dielectric constant is used to describe the ability of the terrain material to store electric energy in the electric field, and the conductivity is used to represent the ability of the terrain material to conduct current. The relative dielectric constant and the conductivity are set according to the terrain material and the center frequency of the signal.

[0026] Optionally, the related configuration of the antenna includes the polarization mode of the antenna, the wave shape matched with the antenna, the maximum gain of the antenna, and the receiving threshold.

[0027] Optionally, the placement of the receiver is in the Wireless insite software, opening the selected terrain, and placing the receiver according to the sampling point position. The related parameters of the receiver include the type of the antenna, the direction, the noise coefficient, and the height.

[0028] Optionally, the related parameters of the transmitter include the type of the antenna used by the transmitter, the direction, the input power, and the height. The transmitter is used to simulate the unmanned aerial vehicle as a base station to send signals.

[0029] Optionally, the calculation engine is an algorithm model for calculating the signal propagation from the transmitter to the receiver within a specified area range, while setting the number of reflection, transmission, and diffraction of the ray tracing algorithm. The combined communication system is a communication system composed of one or more transmitters and receivers, which can realize the calculation of the required data.

[0030] Optionally, the SNR is calculated by the received power of a transmitter and the sum of the power of all noise sources, and the calculation formula is:

[0031] SNR (dB) = 10log 10 (P R )-10log 10 (N total )

[0032] Wherein, P Ris the received power generated by the transmitter, N total is the sum of the powers of all noise sources. N total Set parameters according to the wireless communication scenario. If the SNR value is generally lower than -10dB, return to step S5 and adjust the antenna type, direction, input power and height used by the transmitter to achieve good communication effect and realize multi-slope mountain wireless channel modeling. R The calculation formula is:

[0033]

[0034] Where θ is the angle between the z-axis and the horizontal plane, and φ is the angle between the x-axis and the y-axis on the horizontal plane. P is the total number of paths, λ is the signal wavelength, and β is the spectrum S of the transmitted signal T (f) and the spectrum S received by the receiver R (f) overlap, η0 is the free space impedance, E θ,i is the electric field strength in the pitch direction when the i-th ray reaches the receiver, E φ,i is the horizontal electric field strength of the i-th ray reaching the receiver, θ i and φ i is the angle of arrival of its ray, where g θ (θ,φ), g φ The calculation formulas for (θ, φ) and β are as follows:

[0035]

[0036] Among them, f T and B T are the center frequency and bandwidth of the transmitted waveform respectively. θ (θ,φ) and G φ The calculation formula for (θ,φ) is as follows:

[0037] G θ (θ,φ)=10log 10 [G max |f θ (θ,φ)| 2 ]

[0038] G φ (θ,φ)=10log 10 [G max |f φ (θ,φ)| 2 ]

[0039] Among them, G max is the maximum gain.

[0040] The present application has the beneficial effect that the present application enables the channel model to more accurately simulate the propagation characteristics of signals under different slope conditions. Studying the impact of slope on signal propagation helps optimize the design and deployment of wireless communication systems, especially in natural disasters or emergency situations, enabling the rapid deployment of efficient communication networks to ensure the reliability of information transmission. The communication system can realize wireless communication in mountainous environments with different slopes, and has important practical application value. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a flowchart of the multi-slope mountainous wireless channel modeling method of the present application;

[0042] Figure 2 is a mountainous terrain map with a slope of 0-9.8 degrees;

[0043] Figure 3 is a mountainous terrain map with a slope of 16.9-33.2 degrees;

[0044] Figure 4 is a mountainous terrain map with a slope of 40.2-62.6 degrees;

[0045] Figure 5 is a SNR data graph of three different slope terrains. DETAILED DESCRIPTION

[0046] The present application will be further described below in conjunction with the drawings and specific embodiments.

[0047] In conjunction with the drawings, the embodiments of the technical solutions of the present application will now be described in detail. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, but the scope of protection of the present application is not limited to the following described embodiments.

[0048] Currently, research on wireless communication is mostly concentrated in indoor, urban and small cell environments, and relatively little in mountainous environments. Moreover, wireless communication in mountainous environments has not been thoroughly analyzed for a certain mountain slope. Different slopes will cause changes in signal propagation paths, thereby affecting path loss and received power, etc., which will affect the strength and coverage of the signal.

[0049] The method of the present application includes the steps of establishing a real mountainous scene, extracting the mountain slope, obtaining the channel model parameters, analyzing the channel characteristics, adjusting the transmitter parameters, etc.

[0050] Embodiment 1: The present application provides a multi-slope mountainous wireless channel modeling method combining digital elevation model and ray tracing, as shown in Figure 1 , which includes the following steps:

[0051] As shown in Figure 1As shown, first, step S1 is performed to download digital elevation data

[0052] As an example, the downloaded digital elevation data is ASTER GDEM 30M resolution digital elevation data downloaded from the Digital Globe website. On the website, the required surface data can be selected according to spatial positions such as administrative regions, latitude and longitude and strip numbers, or the required surface data can be circled by points, rectangles or polygons.

[0053] As shown, step S2 is performed to divide the digital elevation data using ArcGIS to select the required terrain Figure 1

[0054] As an example, the terrain division is to open the toolbox, find the extraction analysis column in the toolbox, then find the division, input the downloaded digital elevation data in the form of.img file as the input element, and set the number of lines required to be divided on the x-axis and y-axis. Among them, the terrain size with a slope of 0-9.8 degrees is about 990m×1065m, the mountain size with a slope of 16.9-33.2 degrees is about 750m×750m, and the mountain size with a slope of 40.2-62.6 degrees is about 360m×360m.

[0055] As shown, step S311 is performed to extract the mountain slope in the terrain using ArcGIS to generate a slope layer Figure 1

[0056] The mountain slope is determined by calculating the elevation change rate of the surface center pixel in the horizontal direction (dz / dx) and the vertical direction (dz / dy). The calculation formula of the slope in degrees is:

[0057]

[0058] Among them, ATAN is the inverse tangent function.

[0059] As an example, the extraction of the mountain slope is to open the toolbox, find the surface analysis column in the toolbox, and then open the slope dialog box. The selected terrain is input as the input data, the file name of the output raster is specified, and the measurement unit of the output slope is specified. In the case, the slope change ranges of the three terrains are 0-9.8 degrees, 16.9-33.2 degrees, and 40.2-62.6 degrees, respectively.

[0060] As shown, step S312 is performed to set the relative dielectric constant and conductivity of the terrain using Wireless Insite to complete the mountain environment simulation Figure 1

[0061] ​​​As an example, the selection of sample positions is first to draw a line every 30 meters in the x-axis of the terrain, and then to draw a line every 30 meters in the y-axis, and to take the intersection of the two straight lines as the sample point.

[0062] As shown in Figure 1 , step S321 is performed to set the relative permittivity and conductivity of the terrain using Wireless Insite;

[0063] As an example, the relative permittivity and conductivity of the ground are 25 and 0.02 (S / m), respectively.

[0064] As shown in Figure 1 , step S322 is performed to set the signal center frequency, bandwidth, and related configurations of the antenna to provide the receiver with antenna selection.

[0065] As an example, the signal center frequency is 2.4 GHz, the bandwidth is 10 MHz, the polarization mode of the antenna is vertical polarization, the waveform matched with the antenna is a sine wave, the maximum gain of the antenna is calculated by the software itself, and the receiving threshold is -250 dBm.

[0066] As shown in Figure 1 , step S4 is performed to place the receiver according to the sample position using Wireless Insite, and to determine the related parameters of the receiver;

[0067] As an example, in the Wireless Insite software, the same terrain is opened, and the receiver is placed according to the sample position. The type of antenna used by the receiver is a half-wave dipole antenna, the orientation is vertically upward, the noise factor is 3 dB, and the height is 1.5 m.

[0068] As shown in Figure 1 , step S5 is performed to place the transmitter above the center of the terrain and to set the related parameters of the transmitter;

[0069] As an example, the type of antenna used by the transmitter is a directional antenna, the orientation is vertically downward, the input power is 20 dBm, and the height is 200 m.

[0070] As shown in Figure 1 , step S6 is performed to set the calculation engine and to combine the communication system;

[0071] As an example, the calculation engine uses the X3D algorithm model, the number of reflections of the ray tracing algorithm is 6, the number of transmissions is 0, and the number of diffractions is 1. The communication system is composed of one transmitter and a group of receivers.

[0072] As shown in Figure 1As shown, step S7 is performed to analyze the channel characteristics SNR to achieve multi-slope mountain wireless channel modeling. SNR is calculated by the sum of the received power of a transmitter and the power of all noise sources. The calculation formula is:

[0073] SNR (dB) = 10log 10 (P R )-10log 10 (N total )

[0074] Among them, P R is the received power generated by the transmitter, N total is the sum of the powers of all noise sources. N total Set parameters according to the wireless communication scenario. If the SNR value is generally lower than -10dB, return to step S5 and adjust the antenna type, direction, input power and height used by the transmitter to achieve good communication effect and realize multi-slope mountain wireless channel modeling. R The calculation formula is:

[0075]

[0076] Where θ is the angle between the z-axis and the horizontal plane, and φ is the angle between the x-axis and the y-axis on the horizontal plane. P is the total number of paths, λ is the signal wavelength, and β is the spectrum S of the transmitted signal T (f) and the spectrum S received by the receiver R (f) overlap, η0 is the free space impedance, E θ,i is the electric field strength in the pitch direction when the i-th ray reaches the receiver, E φ,i is the horizontal electric field strength of the i-th ray reaching the receiver, θ i and φ i is the angle of arrival of its ray, where g θ (θ,φ), g φ The calculation formulas for (θ, φ) and β are as follows:

[0077]

[0078] Among them, f T and B T are the center frequency and bandwidth of the transmitted waveform respectively. θ (θ,φ) and G φ The calculation formula for (θ,φ) is as follows:

[0079] G θ (θ,φ)=10log 10 [G max |f θ (θ,φ)|2 ]

[0080] G φ (θ,φ)=10log 10 [G max |f φ (θ,φ)| 2 ]

[0081] Among them, G max is the maximum gain.

[0082] The channel SNR value data results are as follows Figure 5 As shown, the SNR value range is smaller on flat terrain, while on steep terrain, the receiver cannot communicate. This phenomenon is partly due to the slope blocking the signal's line of sight, resulting in a lack of signal reception. Another reason is that some areas of the steep mountain are higher than the transmitter. Since the transmitter uses a directional antenna pointed downward, the receiver cannot receive the signal. Therefore, it is necessary to study the impact of slope on wireless communication in mountainous areas.

[0083] The proposed method for modeling wireless channels in multi-slope mountainous areas, combining a digital elevation model and ray tracing, involves creating a realistic mountain scene, extracting the mountain slope, obtaining channel model parameters, analyzing channel characteristics, and adjusting transmitter parameters. In practical applications, this method allows for a wider range of antenna options, as well as signal frequencies and bandwidths. The probability of a smaller SNR value increases with increasing mountain slope, making wireless communication more reliable in flatter mountainous areas.

[0084] This method proposes a wireless communication channel modeling method that incorporates mountain slope. This method can be configured based on the actual mountain slope and effectively simulate the SNR values ​​of multi-slope mountain wireless channels. The proposed modeling method incorporates parameters from digital elevation models, ray tracing, and channel modeling, and can adjust the transmitter height, transmit power, and antenna type based on simulation results to achieve optimal communication results. By analyzing the characteristics of wireless communication channels, it is possible to optimize base station site selection and communication parameter configuration, providing a theoretical basis for improving communication quality and coverage in mountainous environments.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the design scheme and implementation functions of the present invention, and do not limit the present invention; all persons familiar with the technical field can modify and adjust the above embodiments based on the present invention according to specific application scenarios and corresponding parameter settings, and these modifications and adjustments still fall within the scope of the claims of the present invention.

Claims

1. A method for modeling multi-slope mountainous wireless channels by combining digital elevation model and ray tracing, characterized in that, The method comprises the following steps: S1: downloading digital elevation data; S2: using ArcGIS to segment the digital elevation data and select the required terrain; S311: using ArcGIS to extract the mountain slope in the terrain and generate a slope layer; S312: sampling points on the generated slope layer; S321: using Wireless Insite to set the relative permittivity and conductivity of the terrain, and complete the simulation of the mountain environment; S322: setting the signal center frequency, bandwidth and antenna related configuration, and providing the antenna selection for the receiver; S4: placing the receiver according to the sample point position using Wireless Insite, and determining the related parameters of the receiver; S5: placing the transmitter above the center of the terrain and setting the related parameters of the transmitter; S6: setting the calculation engine and combining the communication system; S7: analyzing the channel characteristic SNR to realize the modeling of the multi-slope mountain wireless channel; In step S6, the calculation engine is an algorithm model for calculating the signal propagation from the transmitter to the receiver in a specified area range, and the number of reflection, transmission and diffraction of the ray tracing algorithm is set; the combined communication system is a communication system composed of one or more transmitters and receivers in the modeling process, so that the required data can be calculated; In step S7, the SNR is calculated by the received power of a transmitter and the sum of the powers of all noise sources, and the calculation formula is: ； wherein, is the received power produced by the transmitter, is the sum of the powers of all noise sources, According to the wireless communication scene, if the SNR value is generally lower than -10dB, return to step S5 to adjust the type, orientation, input power and height of the antenna used by the transmitter to achieve good communication effect and realize multi-slope mountain wireless channel modeling.

2. The method of claim 1, wherein, The downloaded digital elevation data is specifically: ASTER GDEM 30M resolution digital elevation data is downloaded through the digital geographic cloud website, and the digital elevation represents a finite sequence of three-dimensional vectors on the region D, which is represented by a function as: ； wherein, is a planar coordinate, is a corresponding elevation.

3. The method of claim 1, wherein: In step S2, the digital elevation data segmentation is to generate a subset of multiple output feature classes after segmenting the input features, and the specific operation is: first, import the digital elevation data downloaded in step S1 in the form of.img file into ArcGIS, select segmentation in the extraction analysis column, set the number of output terrains, then select the required terrain, and export the terrain in.tif format.

4. The multi-slope mountain wireless channel modeling method combining digital elevation model and ray tracing according to claim 1 is characterized by: In step S311, the mountain slope is the inclination of the terrain surface relative to the horizontal plane, and the mountain slope is determined by calculating the elevation change rate of the surface center pixel in the horizontal direction dz / dx and the vertical direction dz / dy, and the calculation formula in degrees is: ； Wherein, ATAN is the inverse tangent function.

5. The method of claim 1, wherein: In step S312, the sampling points are selected on the slope layer to obtain the mountain slope value of the sample points, and the selection of the sample point position is first to draw a line every 30 meters on the x-axis of the terrain, then to draw a line every 30 meters on the y-axis, and to take the intersection point of the two straight lines as the sample point.

6. The method of claim 1, wherein: In step S321, the relative permittivity is used to describe the ability of the terrain material to store electric energy in the electric field, and the conductivity is used to represent the ability of the terrain material to conduct current, and the relative permittivity and conductivity are set according to the terrain material and the center frequency of the signal.

7. The method of claim 1, wherein: In step S322, the related configuration of the antenna includes the polarization mode of the antenna, the waveform matched with the antenna, the maximum gain of the antenna and the receiving threshold.

8. The method of claim 1, wherein: In step S4, the placement of the receiver is in the Wireless insite software, open the selected terrain, according to the sample point position to place the receiver, the relevant parameters of the receiver have the type of antenna, orientation, noise coefficient and height.

9. The method of claim 1, wherein: The The calculation formula is: The calculation formula is: ； wherein is the angle between the z-axis and the horizontal plane, is the angle between the x-axis and the y-axis in the horizontal plane, is the total number of paths, is the signal wavelength, is the spectrum of the transmitted signal and the spectrum received by the receiver, the overlap of, is the free space impedance, is the electric field strength of the i-th ray in the elevation direction to the receiver, is the electric field strength of the i-th ray in the horizontal direction to the receiver, and is the angle of arrival of its rays, wherein , and are calculated as follows: ； ； ； wherein, and are the center frequency and bandwidth of the transmit waveform, respectively, and The calculation formula is as follows: ； ； in, is the maximum gain.

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