Multi-gradient mountain wireless channel modeling method combining digital elevation model and ray tracing

Abstract

The invention relates to a multi-gradient mountain wireless channel modeling method combining a digital elevation model and ray tracing, and belongs to the field of wireless communication. The unmanned aerial vehicle base station is used for assisting communication, and the method is suitable for quickly deploying an efficient communication network in natural disasters or emergencies. Through the digital elevation model, real mountain environments with different gradients can be established, and the mountain gradient can be obtained; the signal propagation path can be predicted and the signal propagation characteristics can be obtained through a ray tracing method. According to the modeling method, firstly, a real mountain scene is established, the slope of the mountain is extracted, then, channel model parameters are obtained, channel characteristics are analyzed, finally, transmitter parameters are adjusted according to channel characteristic data, and multi-slope mountain wireless channel modeling is achieved. The main thought of the modeling method provided by the invention is to analyze a channel model through accurate topographic data and channel characteristic data, and to improve the reliability of a wireless communication system by adjusting parameters. And design suggestions are provided for emergency communication and technical innovation.

Description

Technical Field

[0001] The invention relates to a multi-slope mountain wireless channel modeling method combining a digital elevation model and ray tracing, and belongs to the field of wireless communications. Background Art

[0002] Drones as aerial base stations have attracted widespread attention in the field of wireless communications. By deploying drone base stations, temporary communications can be quickly established to ensure the communication needs of disaster relief and emergency response.

[0003] At present, wireless communication research mainly focuses on indoor environments, urban areas and residential areas, while research on mountainous environments is relatively rare. In addition, for wireless communication in mountainous environments, in-depth analysis of specific mountain slopes has not been conducted. The present invention uses a multi-slope mountain wireless channel modeling method combining digital elevation model and ray tracing to simulate wireless communication in mountains with different slopes, filling this research gap.

[0004] In order to deal with the complexity of signal propagation paths in mountainous environments, the present invention models mountainous wireless channel communication systems by combining a digital elevation model (DEM) and a ray tracing algorithm, and introducing mountain slopes. First, traditional wireless channel models are difficult to accurately reflect the terrain characteristics in mountainous environments, resulting in large errors in signal propagation path calculations. By introducing a digital elevation model, the study was able to obtain high-precision terrain data, thereby improving the accuracy of wireless channel models in mountainous environments. Secondly, a ray tracing algorithm is used to simulate the propagation path of the signal, providing a more realistic signal energy loss calculation. Finally, the mountain slope is introduced into the channel model, and the influence of different slopes on the signal propagation path is considered, thereby simulating the propagation characteristics of the signal under different slope conditions. Through the combination of these technologies, the authenticity and reliability of the channel model can be improved, making the communication design in a multi-slope mountainous environment more reliable. Summary of the invention

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

[0006] The technical solution of the present invention 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: Use ArcGIS to extract the mountain slope in the terrain and generate a slope layer;

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

[0011] S321: Use Wireless Insite to set the relative dielectric constant and conductivity of the terrain to complete the mountain environment simulation;

[0012] S322: Setting the signal center frequency, bandwidth and antenna configuration, and providing antenna selection for the receiver;

[0013] S4: Use Wireless Insite to place the receiver according to the sample point location and determine the receiver related parameters;

[0014] S5: Place the emitter above the center of the terrain and set the relevant parameters of the emitter;

[0015] S6: Set up the computing engine and the combined communication system;

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

[0017] Optionally, the digital elevation data is downloaded by downloading ASTER GDEM 30M resolution digital elevation data from the Digital Geography Cloud website. The digital elevation represents a finite sequence of three-dimensional vectors on the area D, which is represented by a function:

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

[0019] Among them, (X i ,Y i ) is the plane coordinate, Z i Yes (X i ,Y i ) corresponding elevation.

[0020] Optionally, the digital elevation data segmentation is to generate a plurality of subsets of output feature classes after segmenting the input elements. The specific operation is: firstly, the digital elevation data downloaded in step S1 is imported into ArcGIS in the form of .img file, and segmentation is selected in the extraction and analysis column, and the number of output terrains is set. Then, the required terrain is selected and the terrain is exported in .tif format.

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

[0022]

[0023] Where ATAN is the inverse tangent function.

[0024] Optionally, the sampling points are selected by selecting certain points on the slope layer to obtain the mountain slope values ​​of the sample points. The sampling point positions are selected by first drawing a line every 30 meters on the x-axis of the terrain, and then drawing a line every 30 meters on the y-axis, and taking the intersection of the two straight lines as the sample points.

[0025] Optionally, the relative dielectric constant is used to describe the ability of the terrain material to store electrical energy in an electric field, and the conductivity represents 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 relevant configurations of the antenna include the polarization mode of the antenna, the waveform of the antenna combination, the maximum gain of the antenna, and the receiving threshold.

[0027] Optionally, the receiver is placed in the Wireless insite software by opening the selected terrain and placing the receiver according to the sampling point location. The relevant parameters of the receiver include the type, orientation, noise coefficient and height of the antenna.

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

[0029] Optionally, the computing engine is an algorithm model that calculates the propagation of signals from a transmitter to a receiver within a specified area, and sets the number of reflections, transmissions, and diffractions of the ray tracing algorithm. The combined communication system is a communication system that sets one or more groups of transmitters and receivers during the modeling process, thereby realizing the calculation of the required data.

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

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

[0032] Among them, P Ris the received power generated by the transmitter, N total is the sum of the powers of all noise sources. N total Set the parameters according to the wireless communication scenario. If the SNR value is generally lower than -10dB, return to step S5 to adjust the antenna type, direction, input power and height used by the transmitter to achieve good communication effects 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 elevation 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 of (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 beneficial effect of the present invention is that the present invention enables the channel model to more accurately simulate the propagation characteristics of signals under different slope conditions. Studying the influence of slope on signal propagation helps to optimize the design and deployment of wireless communication systems, especially in natural disasters or emergencies, and can quickly deploy 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 THE DRAWINGS

[0041] Figure 1 It is a flow chart of the multi-slope mountain wireless channel modeling method of the present invention;

[0042] Figure 2 It is a mountain topographic map with a slope of 0-9.8 degrees;

[0043] Figure 3 It is a mountain topographic map with a slope of 16.9-33.2 degrees;

[0044] Figure 4 It is a mountain topographic map with a slope of 40.2-62.6 degrees;

[0045] Figure 5 These are the SNR data graphs for three terrains with different slopes. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods.

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

[0048] At present, most of the research on wireless communication is focused on indoor, urban and residential areas, and relatively less on mountainous environments. In addition, wireless communication in mountainous environments has not been deeply analyzed for a certain mountain slope. Different slopes will cause changes in the signal propagation path, thereby affecting the path loss and received power, etc. These factors will affect the signal strength and coverage.

[0049] The method of the invention comprises the steps of establishing a real mountain scene, extracting the mountain slope, obtaining channel model parameters, analyzing channel characteristics, adjusting transmitter parameters and the like.

[0050] Embodiment 1: A specific implementation example of the present invention provides a multi-slope mountain wireless channel modeling method combining a digital elevation model and ray tracing, the method is as follows Figure 1 As shown, the following steps are included:

[0051] like Figure 1As shown, first proceed to step S1 to download digital elevation data

[0052] As an example, the digital elevation data is downloaded by downloading ASTER GDEM 30M resolution digital elevation data from the Digital Geography Cloud website. On the website, the required surface data can be selected according to the spatial location such as administrative area, longitude and latitude and strip number, or the required surface data can be circled by point, rectangle or polygon.

[0053] like Figure 1 As shown, proceed to step S2, use ArcGIS to segment the digital elevation data and select the required terrain;

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

[0055] like Figure 1 As shown, proceed to step S311, use ArcGIS to extract the mountain slope in the terrain and generate a slope layer;

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

[0057]

[0058] Where ATAN is the inverse tangent function.

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

[0060] like Figure 1 As shown, proceed to step S312, use Wireless Insite to set the relative dielectric constant and conductivity of the terrain to complete the mountain environment simulation;

[0061] As an example, the sampling point locations are selected by first drawing a line every 30 meters on the x-axis of the terrain, and then drawing a line every 30 meters on the y-axis, and taking the intersection of the two straight lines as the sampling point.

[0062] like Figure 1 As shown, proceed to step S321, using Wireless Insite to set the relative dielectric constant and conductivity of the terrain;

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

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

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

[0066] like Figure 1 As shown, proceed to step S4, use Wireless Insite to place the receiver according to the sample point location, and determine the receiver related parameters;

[0067] As an example, in the Wireless insite software, open the same terrain and place the receiver according to the sample point location. The antenna type used by the receiver is a half-wave dipole antenna, facing vertically upward, with a noise coefficient of 3dB and a height of 1.5m.

[0068] like Figure 1 As shown, proceed to step S5, placing a transmitter above the center of the terrain and setting relevant parameters of the transmitter;

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

[0070] like Figure 1 As shown, proceed to step S6, setting the computing engine and combining 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 consists of a transmitter and a group of receivers.

[0072] like Figure 1As shown, step S7 is performed to analyze the channel characteristic 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, and 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 the parameters according to the wireless communication scenario. If the SNR value is generally lower than -10dB, return to step S5 to adjust the antenna type, direction, input power and height used by the transmitter to achieve good communication effects 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 elevation 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 of (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 in the figure, the SNR value variation range is small in flat terrain, and the receiver cannot communicate in steep terrain. This phenomenon occurs partly because the hillside blocks the line-of-sight transmission of the signal, resulting in the failure to receive the signal; another part of the reason is that the height of some areas in the steeper mountains exceeds the height of the transmitter. Since the transmitter uses a directional antenna and the antenna is facing downward, the receiver does not receive the signal. Therefore, it is necessary to study the impact of slope on mountain wireless communication.

[0083] The multi-slope mountain wireless channel modeling method designed above combines digital elevation model and ray tracing. The modeling method mainly includes the steps of establishing a real mountain scene, extracting mountain slope, obtaining channel model parameters, analyzing channel characteristics, adjusting transmitter parameters, etc. When applied to practice, more types of antennas, as well as the signal frequency and bandwidth used, can be selected. As the mountain slope increases, the probability of a smaller SNR value increases. In relatively flat mountains, wireless communication is more reliable.

[0084] The method of the present invention provides a wireless communication channel modeling method that introduces mountain slopes, which can be configured according to the actual mountain slopes, and can better simulate the SNR value of multi-slope mountain wireless channels; the proposed modeling method covers the parameters of digital elevation model, ray tracing method and channel modeling, and can adjust the height of the transmitter, the transmission power and the type of antenna used according to the simulation results, so as to achieve the best communication effect. By analyzing the characteristics of the wireless communication channel, the base station site selection and communication parameter configuration can be optimized, providing a theoretical basis for improving the communication quality and coverage in the mountain environment.

[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 multi-slope mountain wireless channel modeling method combining digital elevation model and ray tracing, characterized in that: The method comprises the following steps: S1: Download digital elevation data; S2: Use ArcGIS to segment the digital elevation data and select the required terrain; S311: Use ArcGIS to extract the mountain slope in the terrain and generate a slope layer; S312: sampling points on the generated slope layer; S321: Use Wireless Insite to set the relative dielectric constant and conductivity of the terrain to complete the mountain environment simulation; S322: Setting the signal center frequency, bandwidth and antenna configuration, and providing antenna selection for the receiver; S4: Use Wireless Insite to place the receiver according to the sample point location and determine the receiver related parameters; S5: Place the emitter above the center of the terrain and set the relevant parameters of the emitter; S6: Set up the computing engine and the combined communication system; S7: Analyze the channel characteristics SNR and implement multi-slope mountain wireless channel modeling.

2. According to claim 1, a multi-slope mountain wireless channel modeling method combining digital elevation model and ray tracing is characterized in that: The downloading of digital elevation data is specifically as follows: Download ASTER GDEM 30M resolution digital elevation data from the Digital Geography Cloud website. Digital elevation represents a finite sequence of three-dimensional vectors in area D, which can be expressed as: V i =(X i ,Y i ,Z i )(i=1,2,3,...n) Among them, (X i ,Y i ) is the plane coordinate, Z i Yes (X i ,Y i ) corresponding elevation.

3. The multi-slope mountain wireless channel modeling method combining digital elevation model and ray tracing according to claim 1 is characterized by: In step S2, the digital elevation data segmentation is to generate multiple subsets of output feature classes after segmenting the input elements. The specific operation is: first, import the digital elevation data downloaded in step S1 into ArcGIS in the form of .img file, select segmentation in the extraction and analysis column, set the number of output terrains, and 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. The mountain slope is determined by calculating the elevation change rate of the center pixel of the surface in the horizontal direction (dz / dx) and the vertical direction (dz / dy). The calculation formula in degrees is: Where ATAN is the inverse tangent function.

5. The multi-slope mountain wireless channel modeling method combining digital elevation model and ray tracing according to claim 1 is characterized by: In step S312, the sampling points are selected by selecting certain points on the slope layer to obtain the mountain slope value of the sample points. The sampling point positions are selected by first drawing a line every 30 meters on the x-axis of the terrain, and then drawing a line every 30 meters on the y-axis, and taking the intersection of the two straight lines as the sample points.

6. The multi-slope mountain wireless channel modeling method combining digital elevation model and ray tracing according to claim 1 is characterized by: In step S321, the relative dielectric constant is used to describe the ability of the terrain material to store electrical energy in an electric field, and the conductivity represents 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.

7. The multi-slope mountain wireless channel modeling method combining digital elevation model and ray tracing according to claim 1 is characterized by: In step S322, the antenna configuration includes the polarization mode of the antenna, the waveform of the antenna, the maximum gain of the antenna, and the receiving threshold.

8. The multi-slope mountain wireless channel modeling method combining digital elevation model and ray tracing according to claim 1 is characterized by: In step S4, the receiver is placed by opening the selected terrain in the Wireless insite software and placing the receiver according to the sample point location. The relevant parameters of the receiver include the type of antenna, direction, noise coefficient and height.

9. The multi-slope mountain wireless channel modeling method combining digital elevation model and ray tracing according to claim 1, characterized in that: In step S6, the computing engine calculates the algorithm model of the signal propagating from the transmitter to the receiver within the specified area, and sets the number of reflections, transmissions, and diffractions of the ray tracing algorithm; the combined communication system sets one or more communication systems consisting of transmitters and receivers during the modeling process, thereby realizing the calculation of the required data.

10. The multi-slope mountain wireless channel modeling method combining digital elevation model and ray tracing according to claim 1, characterized in that: In step S7, the SNR is calculated by the sum of the received power of a transmitter and the power of all noise sources, and the calculation formula is: SNR(dB)=10log 10 (P R )-10log 10 (N total ) 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 Parameters are set according to the wireless communication scenario. If the SNR value is generally lower than -10dB, return to step S5 to 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; where P R The calculation formula is: Among them, θ is the angle between the z-axis and the horizontal plane, φ is the angle between the x-axis and the y-axis on the horizontal plane, and N 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 elevation 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: Among them, f T and B T are the center frequency and bandwidth of the transmitted waveform, G θ (θ, φ) and G φ The calculation formula of (θ,φ) is as follows: G θ (θ,φ)=10log 10 [G max |f θ (θ,φ)| 2 ] G φ (θ,φ)=10log 10 [G max |f φ (θ,φ)| 2 ] Among them, G max is the maximum gain.

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