JP2008270875A - Reception level estimation system - Google Patents

Abstract

It takes time to estimate the reception level of radio waves from a base station in a mobile station in a cellular mobile communication system.
A parameter input unit 102 inputs a base station position and height, a mobile station position and height, an estimation target area, and a radio frequency.
The line-of-sight determining unit 103 determines whether or not there is a line of sight between the base station and the mobile station from the input data from the parameter input unit 102 and the accumulated data in the building database unit 101.
When there is a line of sight, the first reception level calculation unit 104 calculates the estimated reception level using the input data from the parameter input unit 102.
When there is no line of sight, the second reception level calculation unit 105 calculates the estimated reception level using the input data from the parameter input unit.
[Selection] Figure 1

Description

  The present invention relates to a reception level estimation system for a mobile station in a cellular mobile communication system.

  In a cellular mobile communication system, it is necessary to estimate the reception level of a mobile station at a certain location when a base station is installed at a certain location when designing a radio link. As one of the estimation methods, it is known that a method of performing ray-trace calculation based on position information and surface information of structures (buildings, etc.) existing in an area whose reception level is to be estimated is effective. In addition, even when a mobile station exists indoors, a method of performing ray trace calculation considering the structure of the building where the mobile station exists is effective.

  Ray-trace calculation regards the radio wave radiated from the transmission point as Ray, and first traces the ray that reaches the reception point with reflection, transmission and diffraction by surrounding structures. . Next, the electric field due to the traced ray is obtained by geometric optics theory. Here, by using the information of the propagation distance of each ray and the incident angle to the receiving point, it is possible to estimate the characteristics of propagation loss, propagation delay, and arrival angle necessary for the evaluation of the mobile communication system. In this way, the ray tracing method can estimate the propagation characteristics relatively simply by obtaining the ray between transmission and reception.

However, ray tracing calculation increases the time to search for a path that can be reached from the base station to the mobile station as the number of surrounding structures to be considered and the number of reflections / diffractions increase, resulting in an increase in calculation time. was there.
In view of the above problems, an object of the present invention is to provide a system that can estimate the reception level of a mobile station existing in a building without increasing the amount of calculation.

The reception level estimation system according to the present invention includes a building database unit, a parameter input unit, a line-of-sight determination unit, a first reception level calculation unit, and a second reception level calculation unit.
The building database unit accumulates information on buildings existing in each area.
The parameter input unit is a part for inputting parameters necessary for estimating the position and height of the base station, the position and height of the mobile station, the estimation target area, the frequency of radio waves, and other reception levels.
The line-of-sight determination unit determines whether or not there is a line-of-sight between the base station and the mobile station from the input data from the parameter input unit and the accumulated data in the building database unit.

The first reception level calculation unit calculates the estimated reception level using the input data from the parameter input unit when there is a line of sight.
The second reception level calculation unit calculates the estimated reception level using the input data from the parameter input unit when there is no line of sight.

  According to the present invention, it is possible to configure a system that estimates a reception level of a mobile station existing in a building with a small amount of calculation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings used for the following description, the same parts are denoted by the same reference numerals. Moreover, those names and functions are also the same, and description thereof will not be repeated.

[First Embodiment]
FIG. 1 is a functional configuration example of a reception level estimation system 100 of the present invention. FIG. 2 is a processing flow.
The reception level estimation system 100 of the present invention includes a building database unit 101, a parameter input unit 102, a line-of-sight determination unit 103, a first reception level calculation unit 104, and a second reception level calculation unit 105.
The building database unit 101 stores information for each building existing in a certain area. Specifically, information such as the shape, position, and height in the horizontal plane and the vertical plane is stored.
The parameter input unit 102 inputs parameters necessary for calculating the position and height of the base station, the position and height of the mobile station, the estimation target area, the frequency of radio waves, and other estimated reception levels (S1). In addition, information on the shape, position, and height of a building that is not stored in the building database unit 101 may be input from here and stored in the building database unit 101.

The estimation target area is input, for example, by displaying the horizontal plane information accumulated in the building database unit 101 on a map and displaying it on the screen.
The line-of-sight determination unit 103 extracts the accumulated data of the building database unit 101 based on the input data from the parameter input unit 102 (S2), and determines whether there is a line-of-sight between the base station and the mobile station using this as basic data To do.

A method for determining the outlook will be described.
First, it is determined whether or not there is a line of sight between the base station and the mobile station on the horizontal plane based on the positions of the base station (BS) and the mobile station (MS) and the arrangement of the buildings in the selected area (hereinafter referred to as a profile). (S3). In the horizontal plane profile, when the line segment connecting the base station (BS) and the mobile station (MS) does not intersect any building as shown in FIG. 3, it is determined that there is a line of sight between the base station and the mobile station.

  Next, consider a case where a line segment connecting a base station (BS) and a mobile station (MS) intersects several buildings in a horizontal profile as shown in FIG. In such a case, first, the intersecting buildings are extracted. Then, a profile of a vertical plane as shown in FIG. 4 is created using the information on the height of each intersecting building stored in the database unit 101. At this time, an intersection of a straight line drawn in parallel with the ground from the mobile station (MS) toward the base station (BS) and a building where the mobile station exists is defined as a point A. Then, it is determined whether or not the line segment connecting the base station (BS) and the point A intersects the building in the vertical plane (S4). If the line segment and the building do not intersect, there is a line of sight, and if it intersects as shown in FIG. 5, it is determined that there is no line of sight.

If it is determined in step S4 that there is a line of sight, the first reception level calculation unit 104 calculates the estimated reception level using the input data from the parameter input unit.
An example of a method for calculating the estimated reception level when there is a line of sight is described (S5a).

First, the propagation loss L _LOS is obtained. The propagation loss is obtained from the free space loss L _f and the building entry loss L _i .
The free space loss L _f is calculated from the distance d between the base station and the point A obtained from the position and height of the base station and the point A and the frequency f of the radio wave for estimating the reception level by the equation (1). calculate. Here, λ = 3 · 10 ⁸ / f.
L _f = 20 log (4πd / λ) (1)
Building entry loss L _i is calculated by the distance d _i from the height h _m of the ground of the mobile station (2) between the mobile station and the point A (S6).
L _i = 0.6 d _i −0.6 h _m +10 (2)
Then, the propagation loss L _LOS is calculated by the equation (3) (S7a).
L _LOS = L _f + L _i (3)
Finally, the estimated reception level P is calculated by the equation (4) (S8). Here, the transmission power of P _t is the base station, G _BS antenna gain of the base station, G _MS is an antenna gain of the mobile station.
_{P = P t + G BS +} G MS -L LOS (4)
When it is determined in step S4 that there is no line of sight, the second reception level calculation unit 105 calculates the estimated reception level using the input data from the parameter input unit.

An example of a method for calculating the estimated reception level when there is no line of sight is described (S5b).
First, the propagation loss _LNLOS is obtained. The propagation loss is obtained from the space loss L _n and the building entry loss L _i .
The space loss L _n is calculated by the equation (5) from the distance d between the base station and the point A, the frequency f of the radio wave for estimating the reception level, and the height h _b of the base station from the ground.
L _n = 40 log (d) -30 log (h _b ) +21 log (f) +54 (5)
The building entry loss L _i is calculated by the above equation (3) (S6).
Then, the propagation loss _{L NLOS} (6) is calculated by equation (S7b).
_{L NLOS = L n + L i} (6)
Finally, the estimated reception level P is calculated by the equation (7) (S8). Here, the transmission power of P _t is the base station, G _BS antenna gain of the base station, G _MS is an antenna gain of the mobile station.
_{P = P t + G BS +} G MS -L NLOS (7)

As described above, according to the present embodiment, a complicated path search and a complicated calculation for obtaining reflection and diffraction loss are not performed as in the ray tracing method, so that a mobile station existing in a building can be received with a small amount of calculation. The level can be estimated.
Moreover, although it is inferior to the ray trace method in terms of accuracy, a necessary and sufficient accuracy can be obtained for designing a radio channel.

[Second Embodiment]
A functional configuration example of the reception level estimation system 200 of the present invention is also shown in FIG.
The reception level estimation system 200 according to the present invention includes a building database unit 101, a parameter input unit 102, a line-of-sight determination unit 103, a first reception level calculation unit 204, and a second reception level calculation unit 105. That is, except for the first reception level calculation unit 204 that calculates the estimated reception level when there is a line of sight, the configuration is the same as in the first embodiment, and the method for determining the line of sight and the method for calculating the estimated reception level when there is no line of sight are as follows. This is the same as in the first embodiment.

The first reception level calculation unit 204 obtains an estimation value of the reception level by geometric optical calculation using the input data from the parameter input unit 202 when there is a line of sight. Hereinafter, an example of the geometric optical calculation method will be described.
As shown in FIG. 6, considering the wedges with window frames modeled above and below the mobile station (MS), two paths diffracted by these wedges are directly connected to the base station (BS) and the mobile station (MS). The estimated reception level P is obtained by synthesizing a total of three paths with the paths. As shown in FIG. 7, when the direct path is shielded by the window frame, the estimated reception level P is obtained by combining only two diffraction paths.

The estimated reception field strength E _LOS of the direct path is calculated from the transmission field strength E ₀ from the base station, the distance d between the base station (BS) and the mobile station (MS), and the frequency f of the radio wave to be estimated. Calculated using equation (8). Here, λ = 3 · 10 ⁸ / f and k = 2π / λ.
E _LOS = E ₀ (λ / 4πd) e ^−jkd (8)
The combined estimated received field strength E _DLOS of the two diffraction paths is obtained as the sum of the estimated received field strength E _d1 of the first diffraction path and the estimated received field strength E _{d2 of} the second diffraction path.
E _DLOS = E _d1 + E _d2 (9)

E _d1 and E _d2 are obtained as follows.
First, s1 is a vector between the window frame upper part (A ₁ ) and the mobile station (MS), s1 ′ is a vector between the base station (BS) and the window frame upper part (A ₁ ), and s2 is a window frame lower part A vector between (A ₂ ) and the mobile station (MS), s2 ′, is defined as a vector between the base station (BS) and the lower part of the window frame (A ₂ ). FIG. 8 shows an image of the diffraction path viewed in the vertical plane, and FIG. 9 shows an image of the diffraction path viewed in the horizontal plane. FIG. 10 shows a three-dimensional image of FIGS.

The calculation is performed according to the following equations. Incidentally, E _d1 is the unit vector of the vector s1 to _{s u, s u} unit vector s1' the 'distance s1 to s, a E _d obtained by substituting the distance s1' in s', E _d2 is the unit vector of the vector s2 of Figure 6 in _{s u,} a _{s u} '= distance of the unit vector of the vector s2', the s s2, _{E d} obtained by substituting the distance s2 'in s'. Also, _eu is a unit vector in the tangential direction of each window frame.

ここで、(18)式のＤ_ｓ、Ｄ_ｈは以下の各式から求められる。

Here, D _s and D _{h in the} equation (18) are obtained from the following equations.

※ε_０は壁面の誘電率

* Ε ₀ is the dielectric constant of the wall

From the above, the estimated value P of the reception level in the case of FIG. 6 (in the case of three paths including the direct path) can be obtained by P = (E _LOS + E _DLOS ) ² , and in the case of FIG. 7 (including the direct path) The estimated value P of the reception level in the case of no two paths) can be obtained by P = E _DLOS ² .
By applying geometric optical calculation, since only three paths are taken into consideration while improving measurement accuracy as compared with the first embodiment, it is possible to estimate the reception level of a mobile station existing in a building with a small amount of calculation.

[Third Embodiment]
A functional configuration example of the reception level estimation system 300 of the present invention is also shown in FIG.
The reception level estimation system 300 according to the present invention includes a building database unit 101, a parameter input unit 102, a line-of-sight determination unit 103, a first reception level calculation unit 304, and a second reception level calculation unit 105. In other words, except for the first reception level calculation unit 304 that calculates the estimated reception level when there is a line of sight, the configuration is the same as in the first embodiment, and the method for determining the line of sight and the method for calculating the estimated reception level when there is no line of sight are as follows. This is the same as in the first embodiment.

The first reception level calculation unit 304 obtains an estimation value of the reception level by geometric optical calculation using the input data from the parameter input unit 302 when there is a line of sight. Hereinafter, an example of the geometric optical calculation method will be described.
In the third embodiment, considering the wedges with window frames modeled above and below the mobile station (MS), two paths diffracted by these wedges and a direct path connecting the base station (BS) and the mobile station (MS) The process is the same as in the second embodiment up to the point of obtaining a total of three paths.

However, in the third embodiment, the estimated received electric field strengths of the direct path and the diffraction path are further obtained in consideration of reflection by the wall surface in the room. FIG. 11 shows an image of reflection indoors.
The estimated reception field strength of the direct path is the sum of the transmission field strength E ₀ from the base station, the total propagation distance d (the distance between the base station (BS) and the mobile station (MS), and the indoor propagation distance. ), reflected from a radio wave of frequency f that estimates, (8) divided into a vertical component and a horizontal component E _LOS calculated by equation reflection coefficient calculated by respectively (25) R _v, R _h Calculate by multiplying by the number of times. Here, θ is the incident angle on the wall surface (see FIG. 12), and ε ₀ is the dielectric constant of the wall surface.

回折パスの推定受信電界強度についても(10)〜(24)式により算出されたＥ_d1（及びＥ_d2）を垂直成分と水平成分とに分け、それぞれに反射係数Ｒ_ｖ、Ｒ_ｈを反射回数分掛け合わせることにより求める。ただし、Ｅ_d1（及びＥ_d2）を算出する際には、sには回折後の伝搬路長を代入する。

For the estimated received field strength of the diffraction path, E _d1 (and E _d2 ) calculated by the equations (10) to (24) is divided into a vertical component and a horizontal component, and the reflection coefficients R _v and R _h are respectively calculated as the number of reflections. Calculate by multiplying. However, when calculating E _d1 (and E _d2 ), the propagation path length after diffraction is substituted for s.

  Considering reflection on the wall surface indoors, the measurement accuracy is further improved than in the second embodiment, but only three paths are considered as in the second embodiment. The reception level of the station can be estimated.

[Fourth Embodiment]
A functional configuration example of the reception level estimation system 400 of the present invention is also shown in FIG.
The reception level estimation system 400 according to the present invention includes a building database unit 101, a parameter input unit 102, a line-of-sight determination unit 103, a first reception level calculation unit 404, and a second reception level calculation unit 105. That is, except for the first reception level calculation unit 404 that calculates the estimated reception level when there is a line of sight, the configuration is the same as that of the first embodiment, and the method for determining the line of sight and the method for calculating the estimated reception level when there is no line of sight are as follows. This is the same as in the first embodiment.

The first reception level calculation unit 404 obtains an estimation value of the reception level by physical optical calculation using the input data from the parameter input unit 302 when there is a line of sight. Hereinafter, an example of a physical optical calculation method will be described.
In the fourth embodiment, considering wedges in which window frames (width a × length b) are modeled above and below a mobile station (MS), two paths diffracted by these wedges, a base station (BS), and a mobile station The process is the same as in the second and third embodiments until a total of three paths including the direct path connecting (MS) are obtained.

However, in the fourth embodiment, the estimated received electric field strength E _d1 of the first diffraction path and the estimated received electric field strength E _d2 of the second diffraction path are not the expressions (10) to (24), but the expressions (26) to (32). Ask for. E _d1 is E _d obtained by substituting the distance of s1 for s and the distance of s1 ′ for s ′, and E _d2 is the distance of s2 for s and the distance of s2 ′ for s ′. E _d obtained. Further, θ ₁ and θ ₂ are the incident and exit angles to the window frame (see FIG. 9).

第４実施形態は、幾何光学計算ではなく物理光学計算を用いることにより、フレネルゾーンの影響をより正確に考慮した計算結果が得られる。

In the fourth embodiment, by using physical optical calculation instead of geometric optical calculation, a calculation result in which the influence of the Fresnel zone is more accurately taken into consideration can be obtained.

  In the fourth embodiment, reflection by an indoor wall surface can be taken into consideration by the same means as in the third embodiment. Thereby, the measurement accuracy can be further increased as compared with the fourth embodiment.

  INDUSTRIAL APPLICABILITY The present invention is useful for estimating the reception level of a mobile station at a certain location when a base station is installed at a certain location when designing a radio link in cellular mobile communication.

Configuration of reception level estimation system of the present invention Processing flow of reception level estimation system of the present invention Profile of the segment in the horizontal plane (case where there is no horizontal plane intersection) Profile of the segment in the horizontal plane (case with horizontal plane crossing) Profile of segment in vertical plane (case with vertical plane crossing) Profile of segment in vertical plane (no direct path occlusion) Profile of segment in vertical plane (with direct path shielding) Image of diffraction path viewed from vertical plane Image of diffraction path seen in horizontal plane Three-dimensional diffraction path image Image of reflection on indoor wall Image of reflection on the wall

Claims (6)

A reception level estimation system in a mobile communication system,
A building database section that accumulates information on buildings existing in each area;
A parameter input unit for inputting parameters necessary for calculation of the position and height of the base station, the position and height of the mobile station, the estimation target area, the radio frequency, and other estimated reception levels;
A line of sight determination unit for determining the presence or absence of line of sight between the base station and the mobile station from the input data from the parameter input unit and the accumulated data of the building database unit;
A first reception level calculation unit that calculates an estimated reception level using input data from the parameter input unit when there is a line of sight;
A second reception level calculation unit that calculates an estimated reception level using input data from the parameter input unit when there is no prospect,
A reception level estimation system comprising: The reception level estimation system according to claim 1,
The line-of-sight determination unit determines whether or not the building and the line connecting the base station and the mobile station intersect on a horizontal plane, and when intersecting, the line connecting the base station and the mobile station on the vertical plane A reception level estimation system characterized by determining whether or not a building intersects. The reception level estimation system according to claim 1 or 2,
The reception level estimation system, wherein the first reception level calculation unit calculates an estimated reception level by geometric optical calculation. In the reception level estimation system according to claim 3,
A reception level estimation system characterized in that the geometric optical calculation takes into account reflections from an indoor wall surface. The reception level estimation system according to claim 1 or 2,
The reception level estimation system, wherein the first reception level calculation unit calculates an estimated reception level by physical optical calculation. The reception level estimation system according to claim 5,
A reception level estimation system, wherein the physical optical calculation takes into account reflections from an indoor wall surface.

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