JPH09119955A - Field strength calculation apparatus and field strength estimation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To calculate the field strength at a receiving point quickly by finding the position of each subelement obtained by decomposing a road linearly based on a road data, finding the distance between buildings on the opposite sides, the width of road and the position of continuous wall surface from a building data, and then finding the track of radio wave from a transmitting point to a receiving point. SOLUTION: A node subelement processing section 42 decomposes a road rectilinearly based on a road data 47 indicative of the position of road and calculates the position of subelement. A road width processing section 44 calculates a road width data from the distance between buildings on the opposite sides of each element based on a building data 48 storing the position of building with respect to the road and stores the data as a position of continuous wall face in a memory. A ray trace section 54 binds the track of radio wave from a transmitting point to a receiving point based on the wall surface position and a receiving level calculating section 56 calculates the field strength at receiving point based on the track thus quickening the calculation according to ray trace method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric field strength calculating apparatus and method for calculating electric field strength in a service area in mobile communication. In particular, the present invention relates to an electric field strength calculation device and an electric field strength estimation method for calculating electric field strength using a ray trace method which is one of electric field strength estimation methods.

[0002]

2. Description of the Related Art A ray trace method is a method for calculating the electric field strength in a service area in mobile communication. As shown in FIG. 1, in the ray tracing method, a ray (ray), which is an elementary wave of a radio wave radiated from a wave source (transmission point), is repeatedly reflected, transmitted, and diffracted by a structure such as a wall or a pillar, and received. Trace the trace that reaches. The electric field strength is calculated by adding the powers of all the rays that have reached the reception point. An image method is known as a method of obtaining a ray trajectory from a transmission point to a reception point.

FIG. 2 shows a calculation method by the image method. In the image method, a reflection point and a transmission point between the transmission point BS and the reception point P are geometrically obtained. According to the image method, the ray reaching the reception point P can be accurately calculated. However, in order to determine the reflection surface and the diffraction point between the transmission point and the reception point, it is necessary to search the ray reaching the reception point among all the combinations of the reflection surface and the diffraction point of all the structures. Therefore, there is a drawback that the amount of calculation increases exponentially when the number of reflection surfaces and diffraction points of the structure increases. This point is described in detail in, for example, Ken Takahashi et al .: “Radio wave propagation simulation using the image method”, IEICE Technical Report, RCS94-125 (1994-11).

[0004]

FIG. 3 shows a search example in which a ray reaching from a transmission point on the road to a reception point on the road is searched by the image method. Here, for simplicity, only the case where the number of reflections is one is shown. In this way, by recognizing the reflecting surface of the building and searching for a combination of the transmitting point, the receiving point, and the building, it is determined whether or not it can actually exist as a reflected wave. Assuming that the number of buildings is N and the number of walls is M per building, the number of combinations of reflective surfaces when the number of reflections is 1 is MN.
Individual. Since there are as many ray combinations as there are reflecting surfaces, the number of rays is MN.

Generally, it is necessary to consider not only single reflection but also rays reflected by a plurality of wall surfaces. K from one reflection
When considering rays with multiple reflections, the number of rays is

(Equation 1) Becomes

Therefore, the total number of combinations of reflecting surfaces is

(Equation 2) Becomes The number of ray searches is the same. Thus, as the number of buildings (the number of reflecting surfaces) increases, the number of combinations required for the search increases exponentially.

A groove model can be used to easily obtain the ray trajectory. In the groove model, it is assumed that there is a continuous wall surface (reflection surface) in the road width as shown in FIG. Then, the reflection point and the diffraction point between the transmission point and the reception point are obtained, and the ray trajectory is obtained. In the grooved model, the reflecting surfaces exist only on both sides of the road, so the ray reaching the receiving point can be easily searched. However, in this method, since it is considered that there is a continuous wall surface (reflection surface) at the road edge, it is necessary to know the road width in order to obtain the position of the reflection surface.

A method of using the width of the road as the road width as shown in FIG. 5 and a method of using the width including the sidewalk as the road width as shown in FIG. However, even if the road width of any method is used, the actual position of the reflecting surface of the building is not correctly calculated, and thus an error occurs in the determination of the electric field strength.

Therefore, the present invention provides an electric field strength calculation device and electric field strength capable of speeding up the calculation by the ray trace method in a street microcell in which a base station is placed on the road and a service area is formed along the road. The purpose is to provide a measuring method.

[0010]

In order to achieve such an object, the invention as set forth in claim 1 traces the locus of the radio wave radiated from the transmitting point and determines the intensity of the radio wave reaching the receiving point. In the electric field strength calculation device that calculates the electric field strength of the receiving point by adding, a node that calculates the position of each of the sub-elements obtained by dividing the road into straight lines based on the road data indicating the position of the road. Road width processing unit that calculates road width data based on the distance between buildings on both sides of the sub element using the sub element processing unit and building data that stores the position of the building with respect to the road, and road width data on both sides of the sub element Based on the position of the wall surface stored in the first memory, and a radio wave from the transmitting point to the receiving point based on the position of the wall surface stored in the first memory. Characterized by comprising a raytracing unit for obtaining a trajectory, and a reception level calculator for calculating the electric field intensity at the reception point based on the obtained locus by raytracing unit.

According to a second aspect of the present invention, in the electric field strength calculation apparatus according to the first aspect, the node / sub-element processing section is based on the road data, and forms nodes at both ends of each of the sub-elements. And a position of the node, a position of the wall surface stored in the first memory, and an intersection angle of the road at the node. The ray tracing unit further includes means for storing the position and the diffraction angle of the diffraction point at the node calculated based on the second memory in association with the node, and the ray tracing unit stores the data stored in the first memory. The radio wave from the transmitting point to the receiving point based on the position of the wall surface and the position and diffraction angle of the diffraction point stored in the second memory. Characterized by further comprising means for determining the trajectory.

According to a third aspect of the present invention, in the electric field strength calculation apparatus according to the second aspect, the building data is
Including the information indicating the position of the wall of the building, the node sub-element processing unit has means for calculating the positions of both ends of the sub-element, the road width processing unit, the position of both ends of the sub-element Based on the above, the means for selecting a wall surface whose distance from the sub-element is a predetermined value or less from the wall surfaces represented by the building data, and calculating the road width data based on the position of the selected wall surface. And means for doing so.

The invention as defined in claim 4 is based on claims 1 to 3.
In any one of the inventions described above, the road width processing unit sets the average distance between the wall surfaces existing on both sides of the sub-element as road width data, and the first storing means centers the sub-element and averages between the wall surfaces. The first memory is characterized in that the positions distant from each other are stored as continuous wall surface positions.

According to a fifth aspect of the present invention, the electric field strength estimating method for calculating the electric field strength of the receiving point by tracing the locus of the electric wave radiated from the transmitting point and adding the strengths of the electric waves reaching the receiving point In, the road is decomposed into straight line sub-elements based on the road data indicating the position of the road, and the distance between the buildings on both sides of the sub-element is calculated using the building data storing the position of the building with respect to the road. The road width of the sub-element is calculated based on the distance between the buildings, and the positions separated from each other by the road width with respect to the sub-element are stored in the first memory as the positions of the continuous wall surface. Also,
Calculated based on the intersection angle of the road at the road node and the wall surface position stored by the wall surface position storage means,
Data representing the position of the diffraction point and the diffraction angle at the node is stored in the second memory in association with the node. Based on the positions of the continuous wall surfaces stored in the first memory and the positions and diffraction angles of the diffraction points stored in the second memory,
It is characterized in that the trajectory of the radio wave from the transmission point to the reception point is traced, and the electric field strength at the reception point is calculated based on the trajectory.

[0015]

An embodiment of the present invention will be described below with reference to the drawings. (Embodiment 1) 1. Hardware configuration FIG. 8 is a block diagram showing an example of the configuration of a reception level determination device of the present invention. The reception level determination device includes a road width acquisition unit 40 and a reception level calculation processing unit 5 using ray tracing.
0.

The road width acquisition unit 40 has a database 46.
, The node / element processing unit 42, and the road width processing unit 4
And 4. The database 46 stores road data 47 represented as network information, and building data 48 that stores the position of the building and the position of the wall surface of each building. The node / element processing unit 42 uses the road data 47 to determine the positions of the node, the element, and the sub-element obtained by linearly approximating the element. The road width processing unit 44 searches the building data near the road for each sub-element to obtain the road width.

The database 46 corresponds to the "first memory" and the "second memory" described in the claims. However, the “first memory” and the “second memory” may be physically different memories. Although the database 46 is shown as an image of a hard disk in FIG. 8, the “first memory” and the “second memory” may be semiconductor memories, magnetic or optical memories. .

The reception level calculation processing section 50 is an interface 52 for inputting the positions of the transmission point and the reception point of the radio wave.
A ray trace unit 54 for tracking the trajectory of the radio wave radiated from the transmission point, and a reception level calculation unit 56 for calculating the electric field strength at the reception point.

2. Judgment of Road Width A method of judging the road width of each road will be described with reference to FIG. First, using the road information shown in FIG. 9A, the relationship between the intersection and the road is represented by the information of the node which is the branch point and the information of the element which is the line. Here, the node information can be represented by, for example, a node number and a node position. The element information can be represented by, for example, node numbers of nodes at both ends of the element and information indicating a line. Since each element may be a curve, FIG.
As shown in (B), it is decomposed into subelements approximated by straight lines. The positions of both ends of each sub-element are stored in the database 46.

As shown in FIG. 10, buildings on both sides of the road corresponding to each sub-element are searched from the building data 48. Next, among all the wall surfaces of the searched building, a wall surface whose distance from the sub element is equal to or less than a certain threshold value Sth is selected. The distance from the sub-element to the wall surface is calculated using the positions of the buildings on both sides centering on the sub-element stored in the database 46. The spatial distance between the left and right wall surfaces is obtained using the selected right and left wall surfaces.

A method of calculating the road width W from the spatial distance between the left and right wall surfaces will be described with reference to FIG. It is divided into right and left of the road, (1) minimum value of spatial distance from sub-element to wall surface, (2) average value of spatial distance from sub-element to wall surface, or (3) statistical accumulation from sub-element to wall surface. Probability value (for example, 90% value) is obtained.
The road width W is calculated by adding the left and right values thus obtained.
Ask for.

The road width W is calculated from the building data by the above processing.
Can be requested. In addition, the spatial distances on the left and right sides of the sub-elements are not individually calculated.
As shown in 2, the distance between the left and right wall surfaces may be obtained, and the average value, the minimum value, the cumulative probability value (for example, 90% value, etc.) or the like may be set as the road width W. At this time, in the portion where there is no wall surface within the threshold value, the average value is calculated assuming that the wall surface exists at the position of the distance Sth from the sub element.

3. Calculation of Reflecting Surface and Diffraction Point FIG. 13 shows a process of setting a reflecting surface for each sub-element. First, one sub-element is selected (S11
0). Next, by using the road width W of the selected sub-element, a position separated from the sub-element by the road width is set as the wall surface position. This wall surface is a continuous reflecting surface having an infinite height (S120), and this is projected on the wall surface at the road edge (S130).

There is one kind of electrical information of the material forming the reflecting surface for each sub-element. However, all sub-elements may have the same value. The data obtained in S110 to S130 is stored in the database 46 as the reflection surface information in association with the information indicating the sub-element. This data is later used for ray tracing. S110 to S140 are repeated until the calculation for all sub-elements is completed (S150).

FIG. 14 shows the processing for setting diffraction points at each node. First, one node is selected (S210).
Next, a diffraction point having an infinite height whose diffraction angle is equal to the intersection angle of the road is set (S220) and projected onto the intersection of the road edge (S2).
30). The information obtained in S210 to S240 is stored in the database 46 as diffraction point information. S210 to S240 are repeated until the diffraction points of all nodes are calculated (S250).

FIG. 15 shows an example of the reflecting surface and diffraction points set by the processing shown in FIGS. 13 and 14. In this example, reflective surfaces are set on both sides of a road (sub-element) whose road width is W1 and W2. Data representing these reflection surfaces and diffraction points are stored in the database 46.

4. Ray Trace FIG. 16 shows an example of modeled data. Ray tracing is performed from the transmission point to the reception point based on the data representing the reflection surface and the diffraction points stored in the database 46. In FIG. 16, the subelement road widths W1 and W
2 is calculated. Ray tracing is performed on the road modeled in this way.

In FIG. 16A, the reception point is in the line-of-sight range from the transmission point. In this case, the information necessary for the ray trace is only the reflecting surfaces on both sides of the road in the subelement having the road width W1. In FIG. 16B, the reception point is outside the line of sight from the transmission point. However, the information necessary for the ray trace is the subelement of the road width W1 and the road width W2.
It is limited to the information of the reflecting surfaces on both sides of the road and the node (diffraction point) in the sub-element of.

Therefore, the number of reflection surfaces and diffraction points is extremely small compared with the conventional technique of directly retrieving reflection surfaces and diffraction points from building data and ray tracing. Therefore, the amount of information stored in the memory can be significantly reduced. Further, since the number of combinations of reflections between the transmitting point and the receiving point is significantly reduced, it is possible to speed up the ray trace calculation process.

(Others) Although the embodiments of the invention have been described above, the technical scope of the invention according to the present application is not limited to the above-mentioned embodiments. The invention described in the claims can be implemented by adding various changes to the above embodiment. It is obvious from the description of the claims that such an invention belongs to the technical scope of the invention according to the present application.

[0031]

According to the present invention, since the number of reflecting surfaces and diffraction points can be reduced, the amount of information stored in the memory can be reduced. In addition, the number of reflection combinations between the transmitting point and the receiving point is reduced, which speeds up the ray trace calculation.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an outline of a ray tracing method.

FIG. 2 is an explanatory diagram illustrating an outline of an image method.

FIG. 3 is an explanatory diagram illustrating the number of ray combinations between a transmission point and a reception point when the image method is used.

FIG. 4 is an explanatory diagram illustrating the number of ray combinations between a transmission point and a reception point when a groove model is used.

FIG. 5 is an explanatory diagram illustrating an example of a road width defining method in the case of using a groove model.

FIG. 6 is an explanatory diagram illustrating an example of a road width defining method when a groove model is used.

FIG. 7 is an explanatory diagram illustrating an example of a method of defining a road width when a groove model is used.

FIG. 8 is a block diagram showing a configuration of an electric field strength calculation device according to an embodiment of the present invention.

FIG. 9 is an explanatory diagram illustrating expansion from road data to sub-elements.

FIG. 10 is an explanatory diagram illustrating a search for a wall surface near a sub-element.

FIG. 11 is an explanatory diagram showing a method of calculating a distance from a sub-element to a wall surface.

FIG. 12 is an explanatory diagram showing a method of obtaining a road width.

FIG. 13 is a flowchart showing a method of calculating a wall surface position.

FIG. 14 is a flowchart showing a method of calculating diffraction points.

FIG. 15 is an explanatory diagram showing the shape of a groove model.

FIG. 16 is an explanatory diagram showing a ray tracing method using a groove model.

[Explanation of symbols]

 40 road width acquisition unit 42 node / sub-element processing unit 44 road width processing unit 46 database 47 road data 48 building data 50 reception level calculation processing unit 52 interface 54 ray tracing unit 56 reception level calculation unit

Claims (5)

[Claims] 1. A field strength calculation apparatus for calculating the electric field strength of the reception point by tracing the locus of the radio wave radiated from the transmission point and adding the strengths of the radio waves reaching the reception point. Based on the road data showing, by using the node / sub-element processing unit that calculates the position of each sub-element obtained by dividing the road into straight lines, and the building data that stores the position of the building with respect to the road A road width processing unit that calculates road width data based on a distance between buildings on both sides of the sub-element, and a position based on the road width data on both sides of the sub-element as a continuous wall surface position. A first storage means for storing in the memory, and a locus of the radio wave from the transmitting point to the receiving point is obtained based on the position of the wall surface stored in the first memory. Based on the trace obtained by Itoresu portion and the ray trace portion, the electric field intensity calculation apparatus characterized by comprising a reception level calculator for calculating the electric field intensity in the reception point. 2. The node / sub-element processing unit,
Means for calculating the positions of the nodes forming both ends of each of the sub-elements and the positional relationship of the sub-elements with respect to the node based on the road data, and the position of the node stored in the first memory. And a means for storing the position and diffraction angle of the diffraction point at the node calculated based on the position of the wall surface and the intersection angle of the road at the node in the second memory in association with the node. The ray trace unit, based on the position of the wall surface stored in the first memory, and the position and diffraction angle of the diffraction point stored in the second memory, from the transmission point to the reception point. The electric field strength calculation apparatus according to claim 1, further comprising means for obtaining a trajectory of the radio wave. 3. The building data includes information indicating a position of a wall of the building, the node / sub-element processing unit has means for calculating positions of both ends of the sub-element, and the road width processing. The section selects a wall surface whose distance from the sub element is a predetermined value or less from the wall surfaces represented by the building data, based on the positions of both ends of the sub element, and the selected wall surface. 3. The electric field strength calculation device according to claim 2, further comprising means for calculating the road width data based on a position. 4. The road width processing unit uses the average distance between wall surfaces existing on both sides of the sub-element as the road width data, and the first storing means has the sub-element as a center, and the mutual storage is performed. The electric field strength calculation device according to claim 1, wherein a position separated by an average distance is stored in the first memory as a position of the continuous wall surface. 5. The electric field strength estimation method for calculating the electric field strength of the receiving point by tracing the trajectory of the electric wave radiated from the transmitting point and adding the strengths of the electric waves reaching the receiving point, the position of the road Is decomposed into linear sub-elements based on the road data, and using the building data that stores the position of the building with respect to the road, the distance between the buildings on both sides of the sub-element is calculated, The road width of the sub-element is calculated based on the sub-element, and the positions apart from each other by the road width are stored in the first memory as positions of continuous wall surfaces with the sub-element as the center, Data representing the position and the diffraction angle of the diffraction point at the node, which is calculated based on the intersection angle and the position of the wall surface, is associated with the node to generate the second data. Stored in the memory, the position of the said continuous wall which is stored in the first memory,
And tracing the locus of the radio wave from the transmitting point to the receiving point based on the position and the diffraction angle of the diffracting point stored in the second memory, and calculating the electric field strength at the receiving point based on the locus. A method for estimating electric field strength, which is characterized by calculating.