CN111490952A

CN111490952A - Ray tracing method

Info

Publication number: CN111490952A
Application number: CN202010233725.0A
Authority: CN
Inventors: 纪腾飞; 王健; 黄翔东
Original assignee: Tianjin University
Current assignee: Chen Liang
Priority date: 2020-03-27
Filing date: 2020-03-27
Publication date: 2020-08-04
Anticipated expiration: 2040-03-27
Also published as: CN111490952B

Abstract

The invention discloses a ray tracing method, which comprises the following steps: importing scene data and determining a propagation ray path; acquiring a dominant path in the propagation ray path according to the ant colony algorithm; setting an error threshold; multithreading parallel acceleration is carried out, and an optimal ray path and a propagation loss value are output on the premise that an error threshold value is met; the acquiring of the dominant path in the propagation ray path according to the ant colony algorithm specifically includes: counting a dominant ray path combination scheme according to an ant colony algorithm; establishing a tabu table for storing a dominant ray path combination scheme after the ant colony algorithm is traversed; and finding the optimal ray path combination scheme in the tabu table. On the premise of ensuring the precision, the method reduces the traversal time of the rays in the scene, and selects the dominant rays to replace all the rays; the applicability of ray tracing is improved, and the channel characteristics of a complex scene are predicted.

Description

Ray tracing method

Technical Field

The invention relates to the field of channel estimation in communication, in particular to a ray tracing method.

Background

Research and development of wireless communication systems requires extensive knowledge of channel characteristics, and ray tracing is an effective method of predicting channel characteristics. The ray tracing method is suitable for simulating the radio wave propagation of various specific scenes due to the fact that the ray tracing method is completely based on the physical principle of the radio wave propagation.

Foreign researchers Eamonn M.Kenny and Eamonn O.Nuallin put forward a point-to-multipoint-based three-dimensional convex space ray tracing technology^[1]Drawing the indoor building modelDividing into freely filled convex space, generating a computable and storable visibility list, obtaining an effective image reflection and diffraction path generation algorithm, which can effectively optimize the position of the base transceiver station and has high calculation efficiency compared with the traditional ray tracing technology; hosseina zodi, Uwe Siart and Thomasf^[2]The flexibility of the ray tracker is improved by defining the measured geometric figure through a voxelization technology. The illumination matrix can identify the contributing rays of all observation points and simplify the calculation process of field intensity superposition. Due to the fact that the matrixes with the same size are used, cycle counting is avoided, and calculation efficiency of ray tracing is improved; in reference [3 ]]In the prior art, Andres Navarro provides a new receiving ball-based technology, and the tracking efficiency of ray tracking is greatly improved by combining a numerical method and a three-dimensional ray tracking model to simulate multipath propagation in an indoor environment on the premise of ensuring the precision.

Domestic researchers put forward a local oral surface grid optimization algorithm in a reference document [4], divide the total oral surface of a ray tube into local oral surface grids, extract a sampling ray tube on each local oral surface for judging the contribution level of the sampling ray tube, and determine whether to actually calculate the ray tube in the local oral surface according to the calculation level, thereby avoiding a large number of non-contribution ray tubes participating in intersection calculation and saving ray intersection calculation time; the reference document [5] [6] respectively proposes that the ray tracing efficiency is improved by a shortcut method and a neighborhood auxiliary track method, the shortcut method is used for actually calculating and recording the track of one ray tube and is used as a priority reference for intersection calculation of a plurality of subsequent ray tubes, so that the purpose-free traversal intersection is avoided, and the number of the ray tubes for actually calculating is greatly reduced; the neighborhood track auxiliary method is improved on the basis of a common track method, and for the target data in a surface element form, intersection calculation is carried out on adjacent units of a reference surface element on a reference path by increasing from the aspect of improving the success rate of incident point solution, so that the dependence of the common track method on the dividing density of a ray tube is overcome; reference [7] utilizes Gmsh software to divide a three-dimensional indoor environment into a plurality of seamless and non-overlapping tetrahedral units, and by studying the passing trajectory of rays in each tetrahedron, the tracking trajectory of each ray in the whole indoor environment can be obtained. The field distribution fast algorithm provided in the text does not need to be intersected with a polyhedral surface in the environment in the ray tracing process, so that the calculation efficiency is improved; reference [8] introduces a polygon triangulation algorithm, which aims to filter invalid rays before ray emission, and greatly improves the calculation efficiency of ray tracing while ensuring the precision.

In summary, researchers at home and abroad improve the calculation efficiency of ray tracing and reduce the complexity by reducing the intersection time, the intersection number and the like of the model and the ray elements. However, the above improvement techniques each emit many rays, increasing the ray traversal time in the scene.

Reference to the literature

[1]Kenny E M,Nuallain E O.Convex space building discretization forray-tracing[J].IEEE Transactions on Antennas and Propagation,2017,65(5):2578-2591.

[2]Azodi H,Siart U,Eibert T F.A fast 3-D deterministic ray tracingcoverage simulator including creeping rays based on geometry voxelizationtechnique[J].IEEE Transactions on Antennas and Propagation,2015,63(1):210-220.

[3]Navarro A,Guevara D,Gómez J.A Proposal to Improve Ray LaunchingTechniques[J].IEEE Antennas and Wireless Propagation Letters,2018,18(1):143-146.

[4] Huangpei Lin, Wutai, an efficiency improvement algorithm study of ray tracing [ J ]. the university of Beijing aerospace, 2003, 29(7):607 + 610.

[5] Huangpei Lin, Wangbulin, Wutaimen, improve ray tracing efficiency by shortcut method [ J ]. the university of Beijing aerospace, 2004, 30(5):425 + 428.

[6] Huang Mingjie, Li Bing Yin, Wu Zheng. neighborhood auxiliary tracking method improves ray tracing efficiency [ J ]. the university of aerospace, Beijing, 2007,33(3): 298-.

[7] Yellow self-intensity, fast calculation of ray tracing field distribution and implementation [ D ]. Nanjing post and telecommunications university, 2015.

[8] Yoxinlong improvement study of ray tracing indoor algorithm [ D ] beijing post and telecommunications university, 2015.

Disclosure of Invention

The invention provides a ray tracing method, which reduces the traversal time of rays in a scene on the premise of ensuring the precision, and selects dominant rays to replace all rays; the applicability of ray tracing is improved, and the channel characteristics of a complex scene are predicted, which is described in detail in the following:

a ray tracing method, the method comprising the steps of:

importing scene data and determining a propagation ray path; acquiring a dominant path in the propagation ray path according to the ant colony algorithm;

setting an error threshold; multithreading parallel acceleration is carried out, and an optimal ray path and a propagation loss value are output on the premise that an error threshold value is met;

the acquiring of the dominant path in the propagation ray path according to the ant colony algorithm specifically includes:

counting a dominant ray path combination scheme according to an ant colony algorithm; establishing a tabu table for storing a dominant ray path combination scheme after the ant colony algorithm is traversed;

and finding the optimal ray path combination scheme in the tabu table.

The importing scene data and determining a propagation ray path specifically include:

determining 1 direct path L according to scene physical structure₀F primary reflection paths L₁₁、L₁₂、…L_1FS secondary reflection paths L₂₁、L₂₂、…L_2S…, N M-fold reflection paths L_M1、L_M2、…，L_MNWherein L_pqThe q-th path representing p reflections, then the total number of ray propagation paths in the scene environment L:

the method for establishing the tabu table and storing the combination scheme of the dominant ray paths traversed by the ant colony algorithm specifically comprises the following steps:

the ray direct path, the primary reflection path, the secondary reflection path, … and the M times of reflection path are respectively stored and arranged from high to low according to the energy of the received ray.

Further, the outputting the optimal ray path and the propagation loss value on the premise of meeting the error threshold specifically includes:

selecting ray path combination in tabu table to obtain scheme phi₁,φ₂,...,φ_LAnd calculating a solution phi₁,φ₂,...,φ_L-1Ray path combined loss value Pl in_ir；

Will scheme phi₁,φ₂,...,φ_L-1Phi and phi_LComparing the path loss of the first and second paths, and ensuring that the error is | P_ir-P_L1L satisfies 0 ≦_rIn this case, the dominant ray combination of the error minimization scheme is found, i.e., the finally determined dominant ray path.

The technical scheme provided by the invention has the beneficial effects that:

1) according to the method, 2-3 dominant ray paths are selected through an ant colony algorithm to replace all propagation paths, and a multi-thread parallel computing technology is combined, so that the accuracy is guaranteed, the number of ray emitting paths is reduced, the ray tracing speed is greatly improved, and the complexity is reduced;

2) when the traditional ray tracing method is adopted to predict the channel characteristics of the complex scene, n (n) is generated>>+ ∞) ray paths with a computational complexity of O (n)²) Researchers at home and abroad gradually reduce the complexity to O (n) and O (logn) at present by reducing the intersection time, the intersection number and the like of the model and the ray primitive. According to the method, the dominant ray path is selected through the ant colony algorithm, and the complexity is reduced to O (log2) -O (log 3);

3) according to the ray tracing technology improved by the ant colony algorithm, the channel characteristic prediction of different communication scenes of 5G or 6G in the future is accelerated, and the method has great engineering application value in the field of channel estimation in communication.

Drawings

FIG. 1 is a flow chart of a ray tracing method;

FIG. 2 is a flow chart of determining a dominant path according to an ant colony algorithm;

FIG. 3 is a multi-threaded parallel acceleration flow diagram;

FIG. 4 is an indoor two-dimensional environmental model;

FIG. 5 is an indoor three-dimensional environment model;

FIG. 6 is an indoor ray tracing path;

FIG. 7 is a ray tracing path for a single receiving point in a room;

fig. 8 is an indoor single receive point dominant ray tracing path.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention are described in further detail below.

Example 1

A ray tracing method, see fig. 1, comprising the steps of:

step 101: importing scene data and determining a propagation ray path;

step 102: referring to fig. 2, the method for obtaining the dominant path in the propagation ray path according to the ant colony algorithm includes the following specific steps:

1) counting a dominant ray path combination scheme according to an ant colony algorithm;

2) establishing a tabu table for storing a dominant ray path combination scheme after the ant colony algorithm is traversed;

3) and finding the optimal ray path combination scheme in the tabu table.

Step 103: setting an error threshold;

step 104: referring to fig. 3, multithreading parallel acceleration outputs the optimal ray path and propagation loss value on the premise of meeting the error threshold.

Example 2

The solution of example 1 is further described below with reference to fig. 1 to 8, as described in detail below:

step A: the method is characterized by comprehensively considering various communication application scenes, carrying out three-dimensional modeling on an actual measurement scene by adopting a modeling tool, counting electromagnetic parameters such as materials, relative dielectric constants and permeability coefficients in a scene environment, and importing electromagnetic simulation software or programming software to carry out modeling simulation. As shown in fig. 4 and 5, an indoor environment model is built:

TABLE 1 electromagnetic parameters of different materials in indoor environment

Material of	Magnetic permeability coefficient	Relative dielectric constant	Thickness of
				Floor and ceiling	0.01	9	15.0
Wall body	0.01	9	10.0
				Door with a door panel	10^-5	13	4.0
Table (Ref. Table)	10^-5	13	2.0
				Window	10^-12	7.6	1.0

Table 2 antenna parameter settings

Step B, determining 1 possible direct path L according to scene physical structure₀F primary reflection paths L₁₁、L₁₂、…L_1FS secondary reflection paths L₂₁、L₂₂、…L_2S…, N M-fold reflection paths L_M1、L_M2、…，L_MNWherein L_pqThe q-th path representing p reflections, then the total number of ray propagation paths in the scene environment L:

and C: and determining the dominant path according to the ant colony algorithm.

According to the path information quantity sensing principle in the ant colony algorithm, the path combination scheme with the highest pheromone concentration is optimal, so that on the premise of ensuring the precision, a part of dominant ray paths can be found to replace all propagation paths.

C1 selecting the dominant ray, counting all possible ray path transmission schemes, selecting 1 path from L paths according to permutation and combination principle

Species selection scheme phi₁：φ₁＝[{L₀},{L₁₁},{L₁₂},…,{L_MN}]；

Similarly, 2 paths selected from L paths correspond to each other when propagating

Species selection scheme phi₂：φ₂＝[{L₀,L₁₁},{L₀,L₁₂},…,{L_M(N-1),L_MN}]…, selecting L paths from L paths for propagation

Species selection scheme phi_L：φ_L＝[{L₀,L₁₁,L₁₂,…L_MN}]And thus share

A path selection scheme phi: phi is ═ phi₁,φ₂,...,φ_L]。

Step C2: setting an error threshold_rFor determining an optimal ray combination plan;

step C3, establishing L mutually independent taboo tables Chart₀,Chart₁,…,Chart_MAnd respectively storing a ray direct path after traversing according to the ant colony algorithm, a primary reflection path, a secondary reflection path, … and M times of reflection paths which are arranged from high to low according to the received ray energy.

Step C4: according to a selection scheme phi in a taboo table Chart_jSelecting ray path combination to obtain scheme phi in (j is more than or equal to 0 and less than or equal to M)₁,φ₂,...,φ_L(ii) a And calculates a solution phi₁,φ₂,...,φ_L-1Ray path combined loss value Pl in_ir；

Wherein, (i ═ 1,2, …, L-1;

) (ii) a Will scheme phi₁,φ₂,...,φ_L-1Phi and phi_LComparing the path loss of the first and second paths, and ensuring that the error is | P_ir-P_L1L satisfies 0 ≦_rIn the case of (2), find the error minimum squareThe dominant ray combination is the finally determined dominant ray path.

Setting an error threshold_rFig. 8 shows that 1dB is used to obtain the indoor optimal ray path according to the ant colony algorithm.

And step D, according to the multithreading parallel computing capability, accelerating the traversal process of the ray in the scene, and the principle of the ray is shown in FIG. 3.

And step E, as shown in the table 3, outputting the dominant ray and the propagated path loss value after traversing the scene.

TABLE 3 Single receiver ray paths and losses

Those skilled in the art will appreciate that the drawings are only schematic illustrations of preferred embodiments, and the above-described embodiments of the present invention are merely provided for description and do not represent the merits of the embodiments.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A ray tracing method, characterized in that it comprises the steps of:

and finding the optimal ray path combination scheme in the tabu table.

2. The ray tracing method according to claim 1, wherein the importing scene data and determining a propagation ray path specifically include:

3. the ray tracing method according to claim 1, wherein the combination scheme of the dominant ray paths after establishing the tabu table and storing the ant colony algorithm traversal specifically comprises:

4. The ray tracing method according to claim 1, wherein the outputting the optimal ray path and propagation loss value on the premise that the error threshold is satisfied specifically comprises:

Will scheme phi₁,φ₂,...,φ_L-1Phi and phi_LComparing the path loss of the first and second paths, and ensuring that the error is | P_ir-P_L1L satisfies 0 ≦_rIn the case of (1), finding the dominant ray combination of the error minimization scheme is the final determinationThe dominant ray path of (2).