CN101592690A - Method for predicting electromagnetic wave propagation based on ray tracking method - Google Patents

Abstract

The present invention relates to a kind of method for predicting electromagnetic wave propagation based on ray tracking method.This method comprises searching of raypath, the calculating of reflection, diffraction ray, the calculating of received field strength, path loss.Its design is: the position of at first determining an emissive source, find out emissive source all travel paths according to building feature on the 3D map and distribution to each test point light, then according to definite reflections such as Fresnel equation and geometric theory of diffraction/consistance diffraction theory and diffraction loss etc., the corresponding like this field intensity that obtains every paths to each test point, the field intensity in all paths that same test point place is arrived is done coherence stack, obtains the total received field strength in each test point place.Superiority of the present invention is to compare with traditional statistical model, and better adaptability is arranged.The present invention can be used for adapting to wireless network planning, designing requirement in the radio wave propagation prediction of wireless communication system.

Description

Method for predicting electromagnetic wave propagation based on ray tracking method

Technical field

The present invention relates to a kind of radio wave propagation Forecasting Methodology of communication technical field, specifically is a kind of method for predicting electromagnetic wave propagation based on ray tracking method.

Background technology

Along with to the going deep into of next generation mobile communication technical research, how in next generation mobile communication system, further to improve the availability of frequency spectrum, for providing better business experience, the user becomes the problem of researcher's primary concern.When making up new generation network communication experiment environment, be extremely necessary in order to reduce the blindness of test and networking, at first to set up radio waves propagation model.

The electromagnetic wave propagation prediction realizes by the field survey method mostly, field survey need expend great amount of manpower and material resources and financial resources, and the estimated parameter of measurement result only is applicable to tested zone and the area close with its structure, usage range is very little, and test result is subjected to the influence of test condition at that time such as air humidity and accidental interference of electromagnetic field signal.

Moreover urban environment, especially metropolitan urban environment are very complicated, comprise many intensive buildings, circumferential highway, high speed straight way, viaduct and open ground etc., and the electromagnetic wave propagation form is varied, and direct projection, reflection, scattering, diffraction and transmission etc. are arranged.For example metallic glass curtain wall, rivers and lakes, smooth earth or metope etc. might form bigger reflection.Owing to do not have los path under most of communication environments, this just makes single order diffracted wave after electromagnetic second-order reflection ripple, the primary event and the single order reflection wave reception to signal in complicated urban environment behind diffraction have bigger contribution.The electromagnetic wave that engine ignition produces during simultaneously owing to vehicle ' can bring very high noise, causes certain interference to received signal.So all multifactor influence degrees in the necessary Analysis of Complex urban environment to link prediction.

By the analysis and the calculating of electromagnetic radiation, set up the deterministic models of radio wave propagation prediction, carry out computing machine and propagate the simulation analytical calculation, can remedy the defective of field survey labor intensive, material resources and financial resources effectively.

Summary of the invention

The objective of the invention is to overcome the deficiencies in the prior art and defective, a kind of novel method for predicting electromagnetic wave propagation based on ray tracking method that is applied in the complicated urban environment is proposed, can be under the prerequisite of saving human and material resources, set up the electromagnetic wave propagation forecast model of better adaptability, the condition of necessity is provided for the network analysis and the design of next generation mobile communication.Through theoretical analysis, with electromagnetic direct projection, primary event, two secondary reflections, diffraction, a primary event add diffraction, diffraction add primary event and twice diffraction to the contribution calculation of signal interior, thereby the field intensity that can accurately calculate acceptance point is determined the coverage of base station.

For achieving the above object, design of the present invention is: the present invention includes searching of raypath, the calculating of reflection, diffraction ray, the calculating of received field strength, path loss.In general, (dBm is one and examines the value of levying the power absolute value-75dBm, computing formula is: and 10lg (performance number/1mw), 1mw is 1dBm) incoming level be illustrated in the urban district buildings in general indoor can guarantee the conversation, the incoming level of-95dBm is illustrated in outdoor can the assurance and converses, and when incoming level is lower than above-mentioned thresholding, tentatively can think signal blind zone.Then just can estimate the coverage of base station according to the received field strength of acceptance point.

Searching of raypath based on image method.Image method is based upon on the basis of reflection law, refraction law and geometric theory, and by geometrical optics as can be known, reflected ray can obtain by the way of seeking mirror point, and then the travel path of definite ray.

Being calculated as follows of reflection, diffraction ray:

Mirror field (E ^r) or diffraction field (E ^d) fundamental formular is:

E ^r＝E ⁱ×A _s×R×e ^-jks (1)

E ^d＝E ⁱ×A _d×D×e ^-jks (2)

E ⁱBe the incident field, R, D are respectively dyad reflection coefficient and dyad diffraction coefficient; A _s, A _dBe respectively the propagation factor of reflection wave and the propagation factor of diffracted wave; S is the distance of source point and acceptance point; K is a wave number.

$R=\left(\begin{array}{cc}{R}_{\′\′}& 0\\ 0& R_{\⊥}\end{array}\right)$

$R_{\′\′}=\frac{\mathrm{\ϵ}\·\left|(\stackrel{\‾}{n_b},\stackrel{\‾}{r})\right|-\sqrt{\mathrm{\ϵ}-1+{(\stackrel{\‾}{n_b},\stackrel{\‾}{r})}^2}}{\mathrm{\ϵ}\·\left|(\stackrel{\‾}{n_b},\stackrel{\‾}{r})\right|+\sqrt{\mathrm{\ϵ}-1+{(\stackrel{\‾}{n_b},\stackrel{\‾}{r})}^2}}$ $R_{\⊥}=\frac{\left|(\stackrel{\‾}{n_b},\stackrel{\‾}{r})\right|-\sqrt{\mathrm{\ϵ}-1+{(\stackrel{\‾}{n_b},\stackrel{\‾}{r})}^2}}{\left|(\stackrel{\‾}{n_b},\stackrel{\‾}{r})\right|+\sqrt{\mathrm{\ϵ}-1+{(\stackrel{\‾}{n_b},\stackrel{\‾}{r})}^2}}$

R _"And R _⊥Be respectively reflection coefficient to horizontal polarized wave and vertically polarized wave, ε=ε _r-j60 σ λ, ε _rBe relative dielectric constant, σ is a conductivity, and λ is a beam wavelength.n _b, r represents the unit vector of reflecting interface normal direction and incident ray direction, (n respectively _b, r) expression n _b, the inner product between the r.

$D=-\left(\begin{array}{cc}{D}_{\′\′}& 0\\ 0& D_{\⊥}\end{array}\right)$

$D_{\′\′}^{\⊥}=\frac{{-e}^{-j\frac{\mathrm{\π}}{4}}}{2n\sqrt{2\mathrm{\π}k\sin {\mathrm{\β}}_0}}\left\{\cot \right[\frac{\mathrm{\π}+(\mathrm{\φ}-{\mathrm{\φ}}^{\′})}{2n}]\·F[{\mathrm{kLg}}^{+}(\mathrm{\φ}-{\mathrm{\φ}}^{\′})]$

$+\cot \left[\frac{\mathrm{\π}-(\mathrm{\φ}-{\mathrm{\φ}}^{\′})}{2n}\right]\·F\left[\mathrm{kL}{g}^{-}(\mathrm{\φ}-{\mathrm{\φ}}^{\′})\right]+R_{0^{\′\′}}^{\⊥}\cot \left[\frac{\mathrm{\π}-(\mathrm{\φ}+{\mathrm{\φ}}^{\′})}{2n}\right]\·F\left[{\mathrm{kLg}}^{-}(\mathrm{\φ}+{\mathrm{\φ}}^{\′})\right]$

$+R_{n^{\′\′}}^{\⊥}\cot \left[\frac{\mathrm{\π}+(\mathrm{\φ}+{\mathrm{\φ}}^{\′})}{2n}\right]\·F\left[{\mathrm{kLg}}^{+}(\mathrm{\φ}+{\mathrm{\φ}}^{\′})\right]$

D _"And D _⊥Be the diffraction coefficient to horizontal polarized wave and vertically polarized wave, φ, φ ' are respectively incident angle and diffraction angle, and F in the formula (x) comprises a fresnel integral:

$F\left(x\right)=2j\sqrt{x}{e}^{\mathrm{jx}}\stackrel{\∞}{\∫}\sqrt{x}{e}^{{\mathrm{j\τ}}^2}\mathrm{d\τ}(x=\mathrm{kL}{g}^{\±}(\mathrm{\φ}\±{\mathrm{\φ}}^{\′}))$

$g^{\±}(\mathrm{\φ}\±{\mathrm{\φ}}^{\′})={2\cos }^2\left[\frac{2\mathrm{n\π}{N}^{\±}-(\mathrm{\φ}\±{\mathrm{\φ}}^{\′})}{2}\right]$

N ^±Be the integer that approaches following four equations most:

2nπN ⁺-(φ±φ′)＝π 2nπN ^--(φ±φ′)＝π

It is the angle that diffraction is split.

$L=\frac{s{s}^{\′}}{s+s^{\′}}{\sin }^2{\mathrm{\β}}_0,$ Be apart from the factor, β ₀It is the angle on incident ray and diffraction limit.

Be that diffraction is split vertical polarization or the parallel-polarized reflection coefficient of cutting the surface,

Be the vertical polarization or the parallel-polarized reflection coefficient on method surface.

In practice, because environment is very complicated, most rays will be through repeatedly reflecting and diffraction before arriving acceptance point.When on the ray propagates path, running into reflection or diffraction, electric field need be resolved into two components, these two components are respectively and are parallel and perpendicular to plane of incidence, obtain reflection wave (diffracted wave) then.When ray arrived the field point, its electric field level was:

$E\left(R\right)=E^i\left(s\right)\·\underset{m}{\mathrm{\Π}}{R}_m\underset{n}{\mathrm{\Π}}{D}_n\·A_s\·e^{-\mathrm{jkd}}---\left(3\right)$

In the formula, E ⁱ(s) be the initial electric field vector, R _mBe reflection square formation, D _nBe diffraction square formation, A _sBe the coefficient of diffusion of ray on whole travel path, d is that ray is through the path total length.At last, suppose that it is E that total n bar ray has arrived the ray electric field intensity that receiver and i bar arrive _i,, promptly try to achieve a some field intensity E with all electric field intensity stacks that reaches a ray of point _Total:

$E_{\mathrm{total}}=\underset{i}{\overset{n}{\mathrm{\Σ}}}{E}_i---\left(4\right)$

After trying to achieve the field point, the path loss L from the source point to the acceptance point that can ask is:

$L=20\lg \left|\frac{{\mathrm{\λE}}_{\mathrm{total}}}{4\mathrm{\π}{E}_0}\right|---\left(5\right)$

E ₀Be the initial field intensity of transmitter radiation, λ is an operation wavelength.

According to the foregoing invention design, the present invention adopts following technical proposals:

A kind of method for predicting electromagnetic wave propagation based on ray tracking method is characterized in that operation steps is:

(a) gather the geographical environment data message;

(b) emissive source and a parameter of putting are set;

(c) raypath searches;

(d) calculating of acceptance point field intensity and path loss.

The concrete steps of definite geographical environment data message of above-mentioned steps (a) are:

A) determine the distribution and the shape of buildings;

B) feature of buildings is set, it comprises relative dielectric constant and the conductivity that building wall/ground is set.

The concrete steps of definite geographical environment data message of above-mentioned steps (b) are:

A) parameter of emissive source is set, it comprises the setting of position, polarization mode, radiation power, gain and the height of emitting antenna;

B) parameter of putting is set.

The concrete steps of searching of above-mentioned steps (c) raypath are:

A) searching of reflected ray: reflected ray obtains by the way of seeking mirror point, and then the travel path of definite ray; Source image point produces mirror point to reflecting surface simultaneously, and these mirror points produce new mirror point to all reflectings surface again as secondary source, and these new mirror points produce new mirror point, so continue;

B) searching of diffraction ray: when the wireless transmission between the transmitter and receiver during by the sharp keen object blocks in surface, diffraction takes place, this moment, secondaries was distributed in whole space even the diffraction back side to object;

According to above explanation,, repeat the path that above process finally finds ray if ray could arrive acceptance point through secondary and above secondary reflection, diffraction; Here only consider the contribution of direct rays, reflection and diffraction ray.

The step of the calculating of above-mentioned steps (d) acceptance point field intensity and path loss is:

After finding contributive to received signal all rays, carry out following calculating:

The field intensity of a) calculating reflection, diffraction ray;

Mirror field E ^rOr diffraction field E ^dFundamental formular be:

E ^r＝E ⁱ×A _s×R×e ^-jks (1)

E ^d＝E ⁱ×A _d×D×e ^-jks (2)

E in the formula ⁱBe the incident field, R, D are respectively dyad reflection coefficient, diffraction coefficient; A _s, A _dBe respectively the propagation factor of reflection wave and the propagation factor of diffracted wave; S is the distance of source point and acceptance point; K is a wave number.

Its electric field level E (R) is during through repeatedly reflection and diffraction arrival acceptance point:

$E\left(R\right)=E^i\left(s\right)\·\underset{m}{\mathrm{\Π}}{R}_m\underset{n}{\mathrm{\Π}}{D}_n\·A_s\·e^{-\mathrm{jkd}}---\left(3\right)$

In the formula, E ⁱ(s) be the initial electric field vector, R _mBe reflection square formation, D _nBe diffraction square formation, A _sBe the coefficient of diffusion of ray on whole travel path, d is that ray is through the path total length;

B) carry out the field intensity stack; Suppose that it is E that total n bar ray has arrived the ray electric field intensity that receiver and i bar arrive _i,, promptly try to achieve a some field intensity E with all electric field intensity stacks that reaches a ray of point _Total: $E_{\mathrm{total}}=\underset{i}{\overset{n}{\mathrm{\Σ}}}{E}_i;$

C) calculating path loss L: $L=20\lg \left|\frac{{\mathrm{\λE}}_{\mathrm{total}}}{4\mathrm{\π}{E}_0}\right|$

E in the formula ₀Be the initial field intensity of transmitter radiation, λ is an operation wavelength.

The present invention compared with prior art, have following conspicuous outstanding substantive distinguishing features and remarkable advantage: the present invention at first determines the position of an emissive source, find out emissive source all travel paths according to building feature on the 3D map and distribution to test point light, then according to definite emission such as Fresnel equation and geometric theory of diffraction/consistance diffraction theory and diffraction loss etc., the corresponding like this field intensity that obtains every paths to each test point.Superiority of the present invention is to compare with traditional statistical model, and better adaptability is arranged.The present invention can be used for adapting to wireless network planning, designing requirement in the radio wave propagation prediction of wireless communication system.

Description of drawings

Fig. 1 is the process flow diagram that the present invention is based on the method for predicting electromagnetic wave propagation of ray tracking method.

The vertical view of Fig. 2 avenue.

Fig. 3 is all travel paths that emissive source arrives certain acceptance point light.

Fig. 4 seeks the raypath synoptic diagram in two dimensional surface.

Fig. 5 is the path loss at each acceptance point place of test zone.

Embodiment

Below in conjunction with accompanying drawing a preferred embodiment of the present invention is elaborated: present embodiment is being to implement under the prerequisite with the technical solution of the present invention; provided detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

With reference to Fig. 1, this operation steps based on the method for predicting electromagnetic wave propagation of ray tracking method is:

(a) determine geographical environmental data information;

(b) emissive source and a parameter of putting are set;

(c) raypath searches;

(d) calculating of acceptance point field intensity and path loss.

The buildings parameter at first is set, and wherein the distribution of buildings and feature are as shown in Figure 2.The concrete parameter of buildings is as follows: ground relative dielectric constant ε _r=15, conductivity=7S/m, metope relative dielectric constant ε _r=3, conductivity=0.005S/m.

Next is provided with an emissive source and a point, and emitting antenna is placed on the T place in Fig. 2, high 9m, and radiation power is 20dBm; Receiving antenna is from R ₀Moving to R ', highly is 1.5m.According to the needs of actual measurement, the parameter of dual-mode antenna is provided with as follows: the omni-directional antenna, vertical polarization is operated in the 3.5GHz frequency range, gains to be 10.5dBi.

Next find out emissive source all travel paths to each receiving position (test point) light according to building feature on the 3D map and distribution, as shown in Figure 4, promptly emitting antenna is to electromagnetic all travel paths of certain acceptance point.

Reflected ray can obtain by the way of seeking mirror point, and then the travel path of definite ray.Described by general image method, source image point produces mirror point to reflecting surface, and these mirror points produce new mirror point to all reflectings surface, and these new mirror points can produce new mirror point, so continue.And when the wireless transmission between the transmitter and receiver during by the sharp keen object blocks in surface, diffraction takes place, this moment, secondaries was distributed in whole space even the diffraction back side to object.The searching of raypath as shown in Figure 3 in two dimensional surface.

Wait to determine reflection and diffraction loss etc. according to Fresnel equation and geometric theory of diffraction/consistance diffraction theory (GTD/UTD) then, here utilize above-mentioned formula (1), (2) to calculate the field intensity of reflection and diffraction ray respectively, can utilize above-mentioned formula (3) to calculate through repeatedly reflection, ray field intensity behind the diffraction tries to achieve, thereby obtain every road through arriving the field intensity of each test point, the field intensity in all paths that same test point place is arrived is done coherence stack, obtain the total received field strength in each test point place, concrete calculating formula such as above-mentioned formula (4).Utilize above-mentioned formula (5) can get the path loss at each acceptance point place.This method for predicting electromagnetic wave propagation based on ray tracking method is applied in the urban environment of certain avenue, can obtains received signal path loss synoptic diagram as shown in Figure 5.

Claims (2)

1. method for predicting electromagnetic wave propagation based on ray tracking method is characterized in that operation steps is:

(a) gather the geographical environment data message;

(b) emissive source and a parameter of putting are set;

(c) raypath searches;

(d) calculating of acceptance point field intensity and path loss.

2 method for predicting electromagnetic wave propagation based on ray tracking method according to claim 1 is characterized in that described step (a) determines that the concrete steps of geographical environmental data information are:

A) determine the distribution and the shape of buildings;

B) feature of buildings is set, it comprises relative dielectric constant and the conductivity that building wall/ground is set.

3 method for predicting electromagnetic wave propagation based on ray tracking method according to claim 1 is characterized in that the concrete steps of parameter that described step (b) is provided with an emissive source and a point are:

A) parameter of emissive source is set, it comprises the setting of position, polarization mode, radiation power, gain and the height of emitting antenna;

B) parameter of putting is set.

4 method for predicting electromagnetic wave propagation based on ray tracking method according to claim 1 is characterized in that the concrete steps of searching of described step (c) raypath are:

A) searching of reflected ray: reflected ray obtains by the way of seeking mirror point, and then the travel path of definite ray; Source image point produces mirror point to reflecting surface simultaneously, and these mirror points produce new mirror point to all reflectings surface again as secondary source, and these new mirror points produce new mirror point, so continue;

B) searching of diffraction ray: when the wireless transmission between the transmitter and receiver during by the sharp keen object blocks in surface, diffraction takes place, this moment, secondaries was distributed in whole space even the diffraction back side to object;

According to above explanation,, repeat the path that above process finally finds ray if ray could arrive acceptance point through secondary and above secondary reflection, diffraction; Here only consider the contribution of direct rays, reflection and diffraction ray.

5. the method for predicting electromagnetic wave propagation based on ray tracking method according to claim 1 is characterized in that the step of the calculating of described step (d) acceptance point field intensity and path loss is:

After finding contributive to received signal all rays, carry out following calculating:

The field intensity of a) calculating reflection, diffraction ray;

Mirror field E ^rOr diffraction field E ^dFundamental formular be:

E ^r＝E ⁱ×A ^s×R×e ^-jks (1)

E ^d=E ⁱ* A _d* D * e ^-jks(2) E in the formula ⁱBe the incident field, R, D are respectively dyad reflection coefficient, diffraction coefficient; A _s, A _dBe respectively the propagation factor of reflection wave and the propagation factor of diffracted wave; S is the distance of source point and acceptance point; K is a wave number.

Its electric field level E (R) is during through repeatedly reflection and diffraction arrival acceptance point:

$E\left(R\right)=E^i\left(s\right)\·\underset{m}{\mathrm{\Π}}{R}_m\underset{n}{\mathrm{\Π}}{D}_n\·A_s\·e^{-\mathrm{jkd}}$ (3) in the formula, E ⁱ(s)

Be initial electric field vector, R _mBe reflection square formation, D _nBe diffraction square formation, A _sBe the coefficient of diffusion of ray on whole travel path, d is that ray is through the path total length;

B) carry out the field intensity stack; Suppose that it is E that total n bar ray has arrived the ray electric field intensity that receiver and i bar arrive _i,, promptly try to achieve a some field intensity E with all electric field intensity stacks that reaches a ray of point _Total: $E_{\mathrm{total}}=\underset{i}{\overset{n}{\mathrm{\Σ}}}{E}_i;$

C) calculating path loss L: $L=20\lg \left|\frac{{\mathrm{\λE}}_{\mathrm{total}}}{4\mathrm{\π}{E}_0}\right|$

E in the formula ₀Be the initial field intensity of transmitter radiation, λ is an operation wavelength.

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