A method for predicting diffraction loss of wireless signals
Through planar rasterization processing and single-edge diffraction model calculation, the problem of insufficient calculation of wireless signal diffraction loss in complex terrain environments is solved, and a higher accuracy and versatility of wireless signal diffraction loss prediction is achieved.
Patent Information
- Application Number
- CN202410530589.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-29
- Publication Date
- 2024-12-20
- Estimated Expiration
- 2044-04-29
AI Technical Summary
The traditional wireless signal diffraction loss simulation method is insufficient in complex terrain environments, making it difficult to support high-precision wireless communication signal prediction, especially in complex terrain scenarios.
By plane rastering the elevation data of the area to be predicted, marking the transmitting and receiving antennas, selecting the sampling points and calculating the elevation through interpolation, establishing a plane rectangular coordinate system, judging the relative peak points and calculating diffraction based on the single-edge diffraction model Loss, simplified to multiple single-edge diffraction models to obtain the total diffraction loss.
It improves the accuracy and versatility of the diffraction loss of wireless signals, breaks through the computing limitations of traditional methods in complex terrain environments, and can quickly and accurately obtain the diffraction loss of wireless signals in complex terrain scenarios.
Smart Images
Figure CN118300720B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for predicting diffraction loss of wireless signals, and belongs to the technical field of information automation. Background Art
[0002] Among the many sub-modules of wireless communication systems, signal propagation and coverage simulation are key issues. The geographical environment of the radio wave transmission path has a significant impact on propagation loss, which needs to be fully considered during the simulation process.
[0003] As an electromagnetic wave, radio waves are affected by complex terrain and surface coverage in the space environment, forming three propagation mechanisms such as reflection, diffraction and scattering. Among them, the diffraction propagation process is most affected by the terrain, and the calculation process varies greatly with the terrain undulation of the area to be predicted, which has great uncertainty. Traditional wireless signal diffraction loss simulation methods mostly use the blade diffraction loss calculation method, which divides the diffraction loss calculation into single blade, double blade, three blade and more than three blade scenarios. It is not enough to describe the signal loss in complex terrain. At the same time, the calculation process varies greatly between scenarios (such as terrain undulation, building obstruction, vegetation coverage, etc. during the propagation process), and the general integration is insufficient, which makes it difficult to support the current refined needs of wireless communication signal prediction in complex terrain application scenarios.
[0004] How to further consider the impact of real complex terrain environment and achieve high-precision prediction of diffraction propagation of wireless communication signals, especially the prediction of diffraction propagation of wireless communication signals under complex terrain scenarios, is a common concern in the fields of geographic information and communications. Summary of the invention
[0005] The technical problem to be solved by the present invention is to provide an accurate calculation method for the diffraction loss of wireless signals applicable to a general environment with complex terrain.
[0006] In order to solve the above technical problems, the technical solution proposed in the present invention is: a method for predicting diffraction loss of wireless signals, comprising the following steps:
[0007] Step 1: plane rasterizing the elevation data of the area to be predicted to obtain a raster map, and superimposing the elevation data of the transmitting antenna and the receiving antenna on the raster map;
[0008] Step 2: The transmitting antenna and the receiving antenna are regarded as a transmitting and receiving antenna group, and the terrain diffraction loss is calculated between the transmitting antenna and the receiving antenna, and the method is as follows:
[0009] 1) Mark the transmitting antenna as T and the receiving antenna as R, select n sampling points on the line TR between the transmitting antenna T and the receiving antenna R, the sampling points are the intersection points between the line TR and the grid map, and calculate the elevation of the sampling points by interpolation;
[0010] 2) Establish a plane rectangular coordinate system with the position of the transmitting antenna T as the origin, the horizontal direction as the horizontal axis, and the elevation direction as the vertical axis; sort the n sampling points from small to large according to the horizontal distances between them and the transmitting antenna T, where the horizontal distance between the i-th sampling point and the transmitting antenna T is recorded as d i , the elevation of the i-th sampling point is recorded as h i , where i=1, 2, …, n;
[0011] 3) Traverse the n sampling points and determine whether each sampling point is a relative peak point. The method for determining whether the i-th sampling point among the n sampling points is a relative peak point is as follows:
[0012] In the plane rectangular coordinate system, the distance between the i-th sampling point and the line connecting the transmitting antenna T and the receiving antenna R is recorded as the relative elevation H of the i-th sampling point. i , when the i-th sampling point is above the line TR, H i is a positive number, otherwise H i is a negative number;
[0013] For the first sampling point, when H 1 Greater than 0 and H 1 Greater than H 2 When H n Greater than 0 and H n Greater than H n-1 When H is , the nth sampling point is marked as the relative peak point; for the remaining sampling points, the relative elevation of the ith sampling point is compared with the two adjacent sampling points, i.e., the i-1th sampling point and the i+1th sampling point. i Greater than H i-1 And H i Greater than H i+1 When , the i-th sampling point is marked as a relative peak point;
[0014] 4) Traverse all relative peak points and obtain the relative elevation value H of the highest relative peak point max ;
[0015] When H max When it is less than 0, the diffraction loss generated by each relative peak point is calculated in turn according to the single-blade diffraction model;
[0016] When H maxWhen it is greater than 0, the relative peak point is marked as the main peak point, and the diffraction loss generated by the main peak point is calculated according to the single-blade diffraction model; then a receiving antenna R1 and a transmitting antenna T1 are respectively attached to the main peak point, and the transmitting antenna T and the receiving antenna R1, and the transmitting antenna T1 and the receiving antenna R form two new groups of transmitting and receiving antennas, and return to execute steps 1)-4 respectively);
[0017] Step 3: Add the diffraction losses of all relative peak points calculated in step 2 to obtain the total diffraction loss.
[0018] The present invention aims at the undulating characteristics of complex terrain, takes into account the key factor that irregular terrain affects the diffraction loss of wireless signals, reconstructs the terrain undulation, simplifies the diffraction loss calculation of complex terrain into the calculation of multiple single-blade diffraction models, and obtains a more accurate diffraction loss of wireless signals. It breaks through the limitations of the traditional knife-edge diffraction loss calculation method in calculating diffraction loss in complex terrain environments, thereby improving the accuracy of signal prediction.
[0019] The method of the present invention has strong versatility. Practice has proved that the method of the present invention can quickly and accurately obtain the diffraction loss of wireless signals in complex terrain scenarios, which can meet the needs of actual production. Compared with the traditional knife-shaped diffraction loss calculation method, it has stronger versatility and higher accuracy. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 It is a schematic diagram for selecting sampling points in a raster map.
[0021] Figure 2 It is a schematic diagram for establishing a plane rectangular coordinate system.
[0022] Figure 3 It is a schematic diagram of the principle of judging relative peak points.
[0023] Figure 4 It is a schematic diagram of the principle of the main peak iteration method.
[0024] Figure 5 It is a data diagram of the administrative divisions of Jiangning District, Nanjing City and its digital elevation model.
[0025] Figure 6 yes Figure 5 Topographic profile of path ①.
[0026] Figure 7 yes Figure 5 Schematic diagram of signal diffraction loss prediction data comparison for path ①.
[0027] Figure 8 yes Figure 5 Topographic profile of middle path ②.
[0028] Fig. 9 yes Figure 5 Schematic diagram of comparison of signal diffraction loss prediction data for path ②.
[0029] Fig.10 yes Figure 5 Topographic profile of path ③.
[0030] Fig.11 yes Figure 5 Schematic diagram of comparison of signal diffraction loss prediction data for path ③. DETAILED DESCRIPTION
[0031] The method for predicting the diffraction loss of wireless signals in this embodiment includes the following steps:
[0032] Step 1: Figure 1 As shown in the figure, the elevation data of the area to be predicted is processed into a grid map, and the elevation data of the transmitting antenna and the receiving antenna are superimposed on the grid map to prepare for the calculation of the signal diffraction loss. In the square regular grid map, the area to be predicted is divided into a series of two-dimensional dot matrixes, each of which contains the corresponding latitude and longitude position and elevation data of the point in the real surface environment. The DEM data can be regarded as a two-dimensional array, whose value is the height value of the point.
[0033] Step 2: The transmitting antenna and the receiving antenna are regarded as a transmitting and receiving antenna group, and the terrain diffraction loss is calculated between the transmitting antenna and the receiving antenna, and the method is as follows:
[0034] 1) If Figure 1 As shown, the transmitting antenna is marked as T, the receiving antenna is marked as R, and n sampling points are selected on the line TR between the transmitting antenna T and the receiving antenna R. The sampling points are the intersection points between the line TR and the grid map, and the elevations of the sampling points are calculated by interpolation to obtain information such as the height, longitude and latitude of each sampling point. Figure 1 Where T is the position of the transmitting antenna, R is the position of the receiving antenna, and numbers 1-11 are the positions of the sampling points.
[0035] Because the actual terrain fluctuates greatly, it is not necessary to traverse all sampling points to calculate the wireless signal loss while considering the system operation efficiency and the accuracy of the results. Therefore, it is preferred that for the signal propagation path between the antenna groups to be predicted, the feature points and special terrain profiles on the path that can retain enough terrain information are found. When calculating the total diffraction loss, only the terrain feature points on the path are calculated and traversed, thereby simplifying the calculation and improving the efficiency of the prediction.
[0036] 2) If Figure 2As shown, a plane rectangular coordinate system is established with the position of the transmitting antenna T as the origin, the horizontal direction as the horizontal axis, and the elevation direction as the vertical axis; the n sampling points are sorted from small to large according to the horizontal distances between them and the transmitting antenna T, where the horizontal distance between the i-th sampling point and the transmitting antenna T is recorded as d i , the elevation of the i-th sampling point is recorded as h i , where i = 1, 2, ..., n. That is, the distance from each sampling point to the transmitting antenna is used as the horizontal coordinate, and the elevation of each point is the vertical coordinate.
[0037] 3) Traverse the n sampling points and determine whether each sampling point is a relative peak point. The method for determining whether the i-th sampling point among the n sampling points is a relative peak point is as follows:
[0038] like Figure 3 As shown, in the plane rectangular coordinate system, the distance between the i-th sampling point and the line connecting the transmitting antenna T and the receiving antenna R is recorded as the relative elevation H of the i-th sampling point i When the i-th sampling point is located above the line TR, H i is a positive number, otherwise H i There are many methods for determining whether the i-th sampling point is above or below the line TR. In this embodiment, the following method is preferably used: a vertical line perpendicular to the line TR is drawn to the i-th sampling point in the plane rectangular coordinate system. The elevation of the intersection of the vertical line and the line TR is recorded as h i0 , if the height h of the i-th sampling point i Greater than h i0 , the i-th sampling point is located above the line TR, otherwise, the i-th sampling point is located below the line TR.
[0039] For the first sampling point, when H 1 Greater than 0 and H 1 Greater than H 2 When H n Greater than 0 and H n Greater than H n-1 When H is , the nth sampling point is marked as the relative peak point; for the remaining sampling points, the relative elevation of the ith sampling point is compared with the two adjacent sampling points, i.e., the i-1th sampling point and the i+1th sampling point. i Greater than H i-1 And H i Greater than H i+1 When , the i-th sampling point is marked as a relative peak point;
[0040] 4) Traverse all relative peak points and obtain the relative elevation value H of the highest relative peak point max ;
[0041] When H max When it is less than 0, the diffraction loss generated by each relative peak is calculated in turn according to the single-blade diffraction model. Preferably, the radius of the first Fresnel zone of the transmitting antenna and the receiving antenna at a relative peak is recorded as r, and if the relative elevation of the relative peak is less than negative 0.6*r, at this time, the relative peak has no actual effect on signal transmission, and the diffraction loss generated by the relative peak is 0, that is, when the relative elevation of the relative peak is less than negative 0.6*r, the diffraction loss is no longer calculated, thereby further simplifying the calculation; and if the relative elevation of the relative peak is greater than negative 0.6*r, the relative peak does not cause line-of-sight obstruction but invades the first Fresnel zone to produce loss effects, at this time, the diffraction loss generated by the relative peak is calculated according to the single-blade diffraction model.
[0042] When H max When it is greater than 0, the relative peak point is marked as the main peak point, and the diffraction loss generated by the main peak point is calculated according to the single-blade diffraction model; then Figure 4 As shown, a receiving antenna R1 and a transmitting antenna T1 are respectively attached to the main peak point position, the parameters of the receiving antenna R1 are consistent with the parameters of the receiving antenna R, and the parameters of the transmitting antenna T1 are consistent with the parameters of the transmitting antenna T. The transmitting antenna T and the receiving antenna R1, and the transmitting antenna T1 and the receiving antenna R form two new groups of transmitting and receiving antennas, and return to execute steps 1)-4 respectively. At this time, for each group of transmitting and receiving antennas, the line of sight changes, and then a new relative peak point group is obtained, and the calculation is recalculated, that is, the new main peak is repeatedly found ( Figure 4 The terrain profile is divided until there are no relative peaks on the left and right sides that are above the line connecting the transmitting and receiving antennas.
[0043] In this embodiment, the above method for calculating the diffraction loss of the relative peak point is called the main peak iteration method, and its principle is as follows: Figure 4 In addition, the single-blade diffraction loss model is an existing technology and one of the simplest models in the calculation of diffraction loss. You can refer to relevant literature and will not repeat it here.
[0044] It can be seen that this embodiment simplifies the prediction of diffraction loss in complex terrain into the calculation of a group of single-blade diffraction losses, thereby breaking through the limitations of the traditional knife-edge diffraction loss calculation method in calculating diffraction loss in complex terrain environments, and can be suitable for the prediction of diffraction loss in various complex terrains, thereby improving versatility.
[0045] Step 3: Add the diffraction losses of all relative peak points calculated in step 2 to obtain the total diffraction loss.
[0046] This embodiment takes the administrative division data of Jiangning District, Nanjing City as an example. Figure 5As shown, the administrative division of Jiangning District is taken as the area to be predicted, and three direct paths of the receiving antenna and the transmitting antenna are designed, namely path ①-path ③, to verify the method of this embodiment. The principle of the three path design is to include terrain conditions of different complexities as much as possible. The parameters of the transmitting antenna and the receiving antenna used for verification are as follows: the radio wave frequency is 900MHz, and the antenna height ranges from 20 meters to 50 meters, and the values are different according to different base stations and receiving terminals.
[0047] Jiangning District is surrounded by mountains in the northeast and southwest, with large elevation differences and obvious terrain undulations, which can form sufficient blade-shaped barriers. From southwest to northeast, there are Penshan, Jilongshan, Niu Shoushan, Fangshan, Qinglongshan and Tangshan in Jiangning District. Compared with the overall low terrain of Nanjing, the existence of these mountains makes the terrain in the area undulate. At the same time, Jiangning District integrates Nanjing's aviation, shipping, railway and highway transportation systems in one district, and has scientific and educational gathering places such as Jiangning University Town, which is a typical complex terrain area.
[0048] The digital elevation model data of Jiangning District comes from the geospatial data cloud platform of the Computer Network Information Center of the Chinese Academy of Sciences (website: www.gscloud.cn). The dataset is GDEMV3 with a resolution of 30 meters. The communication base station distribution data, antenna parameters and other data of Jiangning District are obtained from communication operators or communication base station service providers.
[0049] It should be noted that: 1) Figure 6 , Figure 8 , Fig.10 The black curve in the middle is the terrain profile line, and the red straight line is the line between the transmitting and receiving antennas, also often called the line of sight. 2) Figure 7 , Fig. 9 , Fig.11 The black curve in the middle is the free space transmission loss calculated by the empirical formula. The applicant's experience shows that the free space transmission loss is close to the total loss between the measured transmitting and receiving antennas, and the diffraction loss is the main loss. Therefore, the free space transmission loss can be used to evaluate the accuracy of the diffraction loss prediction; the blue curve is the diffraction loss calculated using the original Durkin model, and the red curve is the diffraction loss predicted by this implementation method.
[0050] Path ① Prediction result verification: Figure 6 As shown in Figure 1, the path has a large terrain undulation and is about 11 km long. There are 367 sampling points on the path, including 278 sampling points that obviously block the direct path of the initial signal between the transmitting and receiving antenna groups. Figure 7It can be seen that the diffraction loss calculated by the original Durkin model and the diffraction loss calculated by the method of this embodiment have good responses to the sampling points that block the direct path, such as the highest peak of the terrain at 1500m to 2000m. However, compared with the original Durkin model, the diffraction loss calculated by the method of this embodiment does not converge after about 6500m due to the elongation of the distance, and the prediction ability does not disappear, which is better than the original Durkin model. This path reaches the highest diffraction loss value at about 10500m.
[0051] Path ② Prediction result verification: Figure 8 As shown in Figure 1, the path has a small overall undulation and is about 11 km long. There are 326 sampling points on the path, and none of them obviously blocks the direct path of the initial signal between the transmitting and receiving antenna groups. Fig. 9 It can be seen that the method of this embodiment has the highest diffraction loss value in the valley between 8500m and 9000m. This is because the terrain elevation changes sharply before and after the valley, so that a knife-shaped obstruction appears in the line of sight after the virtual receiving antenna is placed on these sampling points. When the receiving antenna returns to the original receiving antenna point, the diffraction loss tends to be normal. Since the sampling points that actually intrude into the 60% first Fresnel zone of this path are relatively small, the actual calculated diffraction loss value is about 4.2dB.
[0052] Path ③ Prediction result verification: Fig.10 As shown in the figure, the path has a large terrain undulation and is about 13.6 km long. There are 423 sampling points on the path, including 164 sampling points that obviously block the direct path of the initial signal between the transmitting and receiving antenna groups. These sampling points are distributed before 5000 m. Fig.11 It can be seen that the method of this embodiment reaches the highest diffraction loss value at about 5000m, which is caused by the blocking of multiple peaks before 5000m. The second highest diffraction loss value reached at about 13200m is close to the above-mentioned highest diffraction loss value. This is because most of the subsequent sampling points that are not obviously blocked invade the 60% first Fresnel zone, and diffraction loss is actually generated and accumulated.
[0053] Through the verification of path ①-path ③, it is found that the diffraction loss calculated by the original Durkin model is often greater than the actual total loss. The method of the present invention effectively extracts the factors that produce diffraction loss in the actual terrain by reconstructing the terrain information, and the diffraction loss prediction during wireless signal propagation is more accurate. In addition, the calculation method is simpler, which can meet actual needs and provide effective support for the development of wireless communication systems.
Claims
1. A method for predicting diffraction loss of wireless signals, comprising the following steps: Step 1: plane rasterizing the elevation data of the area to be predicted to obtain a raster map, and superimposing the elevation data of the transmitting antenna and the receiving antenna on the raster map; Step 2: The transmitting antenna and the receiving antenna are regarded as a transmitting and receiving antenna group, and the terrain diffraction loss is calculated between the transmitting antenna and the receiving antenna, and the method is as follows: 1) Mark the transmitting antenna as T and the receiving antenna as R, select n sampling points on the line TR between the transmitting antenna T and the receiving antenna R, the sampling points are the intersection points between the line TR and the grid map, and calculate the elevation of the sampling points by interpolation; 2) Establish a plane rectangular coordinate system with the position of the transmitting antenna T as the origin, the horizontal direction as the horizontal axis, and the elevation direction as the vertical axis; sort the n sampling points from small to large according to the horizontal distances between them and the transmitting antenna T, where the horizontal distance between the i-th sampling point and the transmitting antenna T is recorded as d i , the elevation of the i-th sampling point is recorded as h i ,in, i=1, 2, …, n; 3) Traverse the n sampling points and determine whether each sampling point is a relative peak point. The method for determining whether the i-th sampling point among the n sampling points is a relative peak point is as follows: In the plane rectangular coordinate system, the distance between the i-th sampling point and the line connecting the transmitting antenna T and the receiving antenna R is recorded as the relative elevation H of the i-th sampling point. i , when the i-th sampling point is above the line TR, H i is a positive number, otherwise H i is a negative number; For the first sampling point, when H1 is greater than 0 and H1 is greater than H2, the first sampling point is marked as a relative peak point. For the nth sampling point, when H n Greater than 0 and H n Greater than H n-1 When H is , the nth sampling point is marked as the relative peak point; for the remaining sampling points, the relative elevation of the ith sampling point is compared with the two adjacent sampling points, i.e., the i-1th sampling point and the i+1th sampling point. i Greater than H i-1 And H i Greater than H i+1 When , the i-th sampling point is marked as a relative peak point; 4) Traverse all relative peak points and obtain the relative elevation value H of the highest relative peak point max ; When H max When it is less than 0, the diffraction loss generated by each relative peak point is calculated in turn according to the single-blade diffraction model; When H max When it is greater than 0, the relative peak point is marked as the main peak point, and the diffraction loss generated by the main peak point is calculated according to the single-blade diffraction model; Then, a receiving antenna R1 and a transmitting antenna T1 are respectively attached to the main peak position, and the transmitting antenna T and the receiving antenna R1, and the transmitting antenna T1 and the receiving antenna R are formed into two new groups of transmitting and receiving antennas, and the steps 1) to 4 are respectively returned to execute); Step 3: Add the diffraction losses of all relative peak points calculated in step 2 to obtain the total diffraction loss.
2. The method for predicting diffraction loss of wireless signals according to claim 1, wherein: In step 2, the method for determining whether the i-th sampling point is located above or below the line TR is as follows: a vertical line perpendicular to the line TR is drawn to the i-th sampling point in the plane rectangular coordinate system, and the elevation of the intersection of the vertical line and the line TR is recorded as h i0 , if the height h of the i-th sampling point i Greater than h i0 , the i-th sampling point is located above the line TR, otherwise, the i-th sampling point is located below the line TR.
3. The method for predicting diffraction loss of wireless signals according to claim 1, wherein: In step 2, when H max Less than 0. When calculating the diffraction loss generated by each relative peak point according to the single-blade diffraction model, the radius of the first Fresnel zone of the transmitting antenna and the receiving antenna at a certain relative peak point is recorded as r. If the relative elevation of the relative peak point is less than negative 0.6*r, the diffraction loss generated by the relative peak point is 0.