JP2021132241A - Radio distribution map creation method and radio distribution map creation system - Google Patents

Abstract

To enable the creation of a distribution map indicating a radio field intensity only by measuring a field intensity at less measurement point.SOLUTION: In a first step of a radio heat map creation method, a field intensity in regard to each of a plurality of measurement points in an area is measured in regard to a field generated from an access point installed to a radio communication in the area. In a second step, a space transmission coefficient map in the area is created on the basis of each measured field intensity. In a third step, the field intensity in regard to the measurement points smaller than the number of the measurement points in the first step is measured in regard to the field submitted from the access point after the second step. In a fourth step, the heat map of the field intensity in the area is created in regard to the field submitted from the access point after the second step on the basis of the space transmission coefficient map created in the second step, and the field intensity measured in the third step.SELECTED DRAWING: Figure 3

Description

The present invention relates to a radio distribution map creation method and a radio distribution map creation system.

Conventionally, a radio distribution map has been created in order to visualize the radio wave intensity distribution related to the radio wave transmitted by the radio wave transmission source in the area near the radio wave transmission source. As the radio distribution map, for example, a radio heat map can be mentioned. Patent Document 1 discloses an electric field strength map corresponding to this type of radio distribution map.

The electric field strength map of Patent Document 1 is a map showing the geographical distribution of the electric field strength of radio waves transmitted by an access point. The electric field strength map is provided by the electric field strength map providing system. The electric field strength map providing system performs, for example, an electric field strength map maintenance process for updating the electric field strength map. At this time, the electric field strength map providing system acquires the electric field strength data from a plurality of mobile devices in order to update the electric field strength map.

JP-A-2018-195897

In the configuration of Patent Document 1, the electric field strength map providing system acquires electric field strength data from a plurality of mobile devices with respect to the electric field strength of the radio wave transmitted by the access point. Therefore, every time the electric field strength map is updated for some reason, it is necessary to measure the electric field strength at a plurality of measurement points using a plurality of mobile devices. Therefore, there is a problem that it takes time and effort to update the electric field strength map.

The present invention has been made in view of the above circumstances, and an object of the present invention is to make it possible to create a distribution map showing radio wave strength by measuring only a small number of measurement points.

Means and effects to solve problems

The problem to be solved by the present invention is as described above, and next, the means for solving this problem and its effect will be described.

According to the first aspect of the present invention, the following radio distribution map creation method is provided. That is, this radio distribution map creation method includes a first step, a second step, a third step, and a fourth step. In the first step, with respect to the radio wave transmitted from the radio wave transmission source installed for wireless communication in the area, the radio wave intensity is measured at each of a plurality of measurement points in the area. In the second step, a spatial propagation coefficient map showing the distribution of the spatial propagation coefficient for the area is created based on the radio wave intensity at each of the plurality of measurement points measured in the first step. In the third step, with respect to the radio wave transmitted from the radio wave transmission source after the second step, the radio wave intensity is measured at a smaller number of measurement points than in the first step. In the fourth step, radio waves transmitted from the radio wave source after the second step are based on the spatial propagation coefficient map created in the second step and the radio wave intensity measured in the third step. With respect to, a distribution map of radio field intensity in the area is created.

As a result, if the radio field intensity is measured once at multiple measurement points in the target area and a spatial propagation coefficient map is created, then the radio wave strength can be measured at fewer measurement points. Using the spatial propagation coefficient map, a distribution map of radio field intensity within the area can be obtained by calculation. Therefore, it is possible to significantly reduce the time and effort required to obtain the distribution map of the radio field intensity.

In the radio distribution map creation method, it is preferable that the measurement point in the third step includes a measurement point having the same position as any one of the plurality of measurement points in the first step.

As a result, a heat map can be obtained based on the change in radio field intensity at the same point. Therefore, the accuracy of the heat map can be improved.

In the method for creating a radio distribution map, in the second step, with respect to a region between at least one of the plurality of measurement points and the position of the radio wave transmission source in the spatial propagation coefficient map. , It is preferable to assign the value of the spatial propagation coefficient corresponding to the measurement point.

As a result, it is possible to easily create a spatial propagation coefficient map that reflects the tendency in a generally good manner.

In the radio distribution map creation method, in the second step, in the space propagation coefficient map, the space corresponding to the measurement point is relative to a predetermined region centered on each of the plurality of measurement points. It is preferable to assign a value of the propagation coefficient.

This makes it possible to easily create a spatial propagation coefficient map.

In the above radio distribution map creation method, it is preferable to do as follows. That is, in the fourth step, the spatial propagation coefficient at the measurement point where the radio wave intensity was measured in the third step is obtained based on the spatial propagation coefficient map. In the fourth step, the entire area is free space based on the measured value of the radio wave intensity in the third step and the spatial propagation coefficient at the measurement point in the third step. Obtain the ideal radio field intensity distribution, which is the radio wave strength distribution under the assumption. In the fourth step, a distribution map of radio field intensity in the area is created by applying a propagation loss to the ideal radio wave intensity distribution based on the distribution of the spatial propagation coefficient shown by the spatial propagation coefficient map. ..

This makes it possible to appropriately create a distribution map of radio field intensity.

In the radio distribution map creation method, when a plurality of radio wave transmission sources are provided, the first step, the second step, the third step, and the fourth step are provided for each of the radio wave transmission sources. It is preferable to do.

As a result, it is possible to obtain a radio distribution map focusing on each radio wave transmission source.

In the radio distribution map creation method, when the radio wave transmission source can perform wireless communication in a plurality of frequency bands, the first step, the second step, and the first step are performed for each of the frequency bands. It is preferable to carry out the three steps and the fourth step.

This makes it possible to appropriately obtain a radio distribution map according to the frequency band.

In the radio distribution map creation method, the radio wave transmission source is preferably an access point in wireless communication.

As a result, a radio distribution map for the access point can be obtained.

According to the second aspect of the present invention, a radio distribution map creating system having the following configuration is provided. That is, this radio distribution map creation system includes a map creation device. The map creation device creates a distribution map of radio wave intensity with respect to radio waves transmitted from radio wave transmission sources installed for wireless communication in the area. The map creation device includes a spatial propagation coefficient map creation unit and a distribution map creation unit. The spatial propagation coefficient map creation unit determines the number of spatial propagation cases for the area based on the radio wave intensity measured at each of a plurality of measurement points in the area with respect to the radio wave transmitted from the radio wave transmission source. Create a spatial propagation coefficient map showing the distribution. The distribution map creation unit measures a number of radio waves transmitted from the radio wave source after the spatial propagation coefficient map is created, which is smaller than the number of measurement points when the spatial propagation coefficient map is created. Based on the radio wave intensity measured for the point, a distribution map of the radio wave intensity in the area is created by using the spatial propagation coefficient map.

As a result, if the radio field intensity is measured once at multiple measurement points in the target area and a spatial propagation coefficient map is created, then the radio wave strength can be measured at fewer measurement points. Using the spatial propagation coefficient map, a distribution map of radio field intensity within the area can be obtained by calculation. Therefore, it is possible to significantly reduce the time and effort required to obtain the distribution map of the radio field intensity.

The plan view which shows typically the wireless heat map making system which concerns on one Embodiment of this invention. A block diagram showing the relationship between the mapping system and the access point. A flowchart illustrating processing performed by the control unit of the map creation device. The figure which shows a mode that the measuring apparatus measures the radio field intensity at a plurality of measurement points in the 1st step. The figure which shows the spatial propagation coefficient map created in the 2nd step. The figure which shows the heat map initially created in the map making apparatus. The figure which shows the state that the measuring apparatus measures the radio field strength at a measuring point in the 3rd process. The figure which shows the heat map created in the 4th process.

Next, an embodiment of the present invention will be described with reference to the drawings.

The wireless heat map creation system (radio distribution map creation system) 1 shown in FIG. 1 can create a heat map (radio distribution map) of radio wave intensity by the map creation method described later. In the following, the heat map of radio wave intensity may be simply referred to as a heat map.

The heat map is created for the area 2 where the access point (radio wave transmission source) 3 is installed. The heat map visualizes the intensity distribution of the radio waves transmitted by the access point 3 in the area 2 in accordance with the heat map which visualizes the temperature distribution.

As the area 2, for example, the internal space of the factory where the wireless device is used is assumed. In the present embodiment, the access point 3 is installed at a point P0 in the area 2. Various structures 5 such as walls or partitions shown in FIG. 1 are arranged in the area 2. Therefore, with respect to the radio waves transmitted by the access point 3, the radio wave intensity in the area 2 changes in a complicated manner depending on the location. The use, shape, position of the access point 3 and the like of the area 2 are not particularly limited.

The access point 3 functions as an access point in the infrastructure mode defined in IEEE 802.11. As shown in FIG. 2, the access point 3 includes an AP communication unit 31. Here, AP is an abbreviation for an access point.

A known computer is built in the access point 3. This computer includes a CPU, ROM, RAM, and the like. Programs and the like for realizing wireless communication are stored in the ROM and RAM. By the cooperation of the above hardware and software, the computer can be operated as the AP communication unit 31 and the like.

The Associated Press communication unit 31 can wirelessly communicate with various communication devices (for example, the measuring device 4). This wireless communication is performed in accordance with a known standard.

The state of the access point 3 can change with use. As this change, for example, the antenna used by the access point 3 to transmit radio waves may be deformed for some reason such as an accident. Further, for example, a change in the performance of a component that amplifies an electric signal at the access point 3 with the passage of time or the environment can be regarded as a change in the state of the access point 3. In the present invention, the case where the access point 3 is physically completely replaced (for example, when the access point 3 is replaced with another access point due to a failure) is also included in the change in the state of the access point 3.

The wireless heat map creation system 1 includes a measuring device 4 and a map creating device 10.

The measuring device 4 includes a wireless communication unit 41, a measuring unit 42, and a wired communication unit 43.

The measuring device 4 is configured as a known computer. This computer includes a CPU, ROM, RAM, HDD, and the like. By the cooperation of the above hardware and software, the computer can be operated as a wireless communication unit 41, a measurement unit 42, and a wired communication unit 43.

The wireless communication unit 41 can perform wireless communication with the AP communication unit 31 included in the access point 3. The wireless communication unit 41 acquires a radio wave transmitted from the access point 3 in order to measure the radio wave strength. (In this step, substantial data transmission / reception is not performed with / from the access point 3.) For example, in the so-called monitor mode, packets on the wireless LAN transmitted from the access point 3 are monitored. The measuring device 4 can measure the radio field strength by analyzing the packet acquired by such monitoring.

The measuring unit 42 is configured as, for example, a known electric field strength measuring device. The measuring unit 42 can measure the actual radio wave strength of the radio wave received from the access point 3 when the measuring device 4 and the access point 3 perform wireless communication.

The wired communication unit 43 performs wired communication with the map creation device 10 by an appropriate communication method. Through this wired communication, the measuring device 4 can transmit the radio field intensity measured by the measuring unit 42 to the map creating device 10. Information such as the radio wave intensity measured by the measuring unit 42 is stored in the measuring device 4, and the information is later input to the map creating device 10 (for example, by manual operation by the operator) together with the position information and the like. You can also do it.

The map creation device 10 is a computer used to create the above-mentioned heat map. The mapping device 10 is attached to a portable carriage together with the measuring device 4.

As shown in FIG. 2, the map creation device 10 includes a wired communication unit 11, a storage unit 12, a control unit 13, a display unit 14, and an input unit 15.

The map creation device 10 is configured as a known computer having a CPU, ROM, RAM, HDD, etc. (not shown). Various programs for realizing the wireless distribution map creation method of the present invention are stored in the HDD or the like. By the cooperation of the hardware and software, the computer can be operated as a wired communication unit 11, a storage unit 12, a control unit 13, a display unit 14, and an input unit 15.

The wired communication unit 11 is connected to the wired communication unit 43 included in the measuring device 4. The wired communication unit 11 enables the map creation device 10 to perform wired communication with the measuring device 4. The map creating device 10 acquires the radio field intensity measured by the measuring device 4 by this wired communication.

The storage unit 12 is composed of a ROM, a RAM, an HDD, and the like. The storage unit 12 stores the above-mentioned program, various parameters for creating a heat map, and the like.

Specifically, the storage unit 12 stores the position where the access point 3 is installed (relative position in the area 2). In addition, the storage unit 12 stores the obtained radio wave intensity in association with the position of the measurement point when the measuring device 4 at an appropriate point measures the radio wave intensity. The positions of the access point 3 and the measurement point can be represented by, for example, a plane orthogonal coordinate system defined with an appropriate position in the area 2 as the origin. When the shape of the area 2 is substantially rectangular, it is preferable that the Cartesian coordinate system is defined so that each coordinate axis is along the side of the rectangle. The positions of the access point 3 and the measurement point can be input to the map creation device 10 by, for example, an operator operating the input unit 15.

The control unit 13 has a first map creation unit (spatial propagation coefficient map creation unit) 17 and a second map creation unit (distribution map creation unit) 18.

The first map creation unit 17 creates a spatial propagation coefficient map showing the distribution of the spatial propagation coefficient with respect to the area 2. The details of the processing performed by the first map creating unit 17 and the details of the spatial propagation coefficient map will be described later.

The second map creation unit 18 creates a heat map of the radio field intensity with respect to the area 2. Details of the processing performed by the second map creating unit 18 and the heat map will be described later.

The spatial propagation coefficient map created by the first map creation unit 17 and the heat map created by the second map creation unit 18 are stored in the storage unit 12.

The display unit 14 is configured as a known dot matrix type display. The control unit 13 can display the created heat map on the display unit 14 according to an appropriate operation of the input unit 15. According to the instruction of the operator, the control unit 13 can also display the spatial propagation coefficient map on the display unit 14.

The input unit 15 is operated so that the operator gives some instruction to the map creation device 10. The input unit 15 is composed of, for example, a keyboard, a mouse, a touch panel, and the like.

In such a configuration, the heat map of the area 2 is created by the radio heat map creation method (radio distribution map creation method) of the present invention in a state where the access point 3 is installed at an appropriate point P0.

The wireless heat map creation method includes at least a first step, a second step, a third step, and a fourth step. In the flowchart of FIG. 3, step S101 corresponds to the first step, step S102 corresponds to the second step, step S104 corresponds to the third step, and step S105 corresponds to the fourth step. In the following, these four steps will be described in detail with reference to FIGS. 3 to 8.

First, with respect to the radio wave transmitted from the access point 3 installed at the point P0, the actual radio wave intensity at each of the plurality of measurement points P1 to P7 appropriately determined in the area 2 is measured by the measuring device 4. (Step S101 of FIG. 3: First step). The positions of the measurement points P1 to P7 are shown in FIG. The number and position of measurement points can be arbitrarily selected.

Specifically, the measuring device 4 and the mapping device 10 are carried by the operator to the first point P1. When the measuring device 4 measures the radio field intensity at the point P1, the measurement result is stored in the storage unit 12 by the map creating device 10. At this time, the radio field intensity, which is the measurement result, is stored in the storage unit 12 in association with the information indicating the position of the point P1. The position (coordinates) of the point P1 is measured in advance by an appropriate method and input to the map creation device 10.

Next, the measuring device 4 and the map creating device 10 are carried by the operator to the next point P2, and the above-mentioned work is performed in the same manner. The radio field strength is sequentially measured at the remaining points P3 to P7.

Next, a spatial propagation coefficient map is created by the map creation device 10 based on the actual radio wave intensities at each of the plurality of measurement points P1 to P7 measured in the first step described above (step S102 in FIG. 3: Second step). The spatial propagation coefficient map shows the distribution of the spatial propagation coefficient in the area 2, and is configured as a two-dimensional map in the present embodiment.

In this step, the spatial propagation coefficient is calculated based on the radio wave intensity at each of the measurement points P1 to P7 stored in the storage unit 12. A known Fris transmission formula is used in this calculation.

Hereinafter, a detailed description will be given. According to Frith's transmission formula, the following formula (1) holds.

Here, P _T is the transmission power at the access point 3. G _T is the transmission gain in the access point 3. G _R is a reception gain in the measurement device 4. λ is the wavelength. D is the distance. P _R is the received power, which corresponds to the radio wave intensity.

In equation (1), (λ / 4πD) ² is the reciprocal of the free-space propagation loss. Free-space propagation loss refers to the loss that occurs when radio waves propagate in an ideal space with no obstacles. The free space propagation loss is represented by L _B, it can be derived equation (2).

Further, when expressing the expression of _{L B = 1 / (λ /} 4πD) 2 using a logarithmic function, Equation (3) is obtained. In Equation (3) and later, the unit of L _B is decibel.

The mathematical formulas shown above assume an ideal situation in which radio waves spread in a spherical shape in an unobstructed vacuum. However, in the actual communication environment, there are obstacles and / or reflective objects and the like. In order to deal with this situation, as a simple approximate expression, the mathematical expression (4) in which the coefficient n is introduced is used instead of the mathematical expression (3).

Here, the coefficient n is a dimensionless number and is called a spatial propagation coefficient. When n = 2.0, a communication environment that is an ideal space without obstacles is assumed. When n <2.0, a communication environment in which radio waves are transmitted while being reflected is assumed, and when N> 2.0, a communication environment in which radio waves are absorbed by obstacles and propagate while being attenuated is assumed. Will be done.

The mathematical formula (5) can be obtained by transforming the mathematical formula (4).

In the equation (2), the transmission power P _T and the transmission gain G _T of the access point 3 are known, and the reception gain G _R of the measuring device 4 is also known. Accordingly, deformed so that Equation (2) and L _B = · · ·, transmit power P _T, transmission gain G _T, and assigns the receive gain G _R, the measurement described above as a radio wave intensity P _R by substituting, it is possible to determine the value of the propagation loss L _B.

In equation (5), the wavelength λ is known. Further, the distance D can be obtained from the measurement point of the radio wave intensity and the position of the access point 3. Thus, for equation (5), by substituting the wavelength λ and the distance D, by substituting the value of the propagation loss L _B described above, it is possible to obtain the spatial propagation coefficient n.

The first map creation unit 17 calculates the spatial propagation coefficients of the measurement points P1 to P7. As a result, it is possible to obtain spatial propagation coefficients at a plurality of points P1 to P7 discretely determined in the area 2. Then, the first map creation unit 17 creates a spatial propagation coefficient map 61 for the entire area 2 based on the spatial propagation coefficient at the representative point of the area 2.

In this embodiment, the spatial propagation coefficient map 61 is created by the following algorithm. First, the first map creation unit 17 obtains the measurement point having the maximum distance from the position of the access point 3 (point P0) among the plurality of measurement points P1 to P7. In the example of FIG. 4, the point satisfying the condition is the measurement point P7. As the initialization process, the first map creation unit 17 assigns the value of the spatial propagation coefficient at the measurement point P7 to the entire region of the spatial propagation coefficient map. As a result, the measurement point P7 is already assigned.

Next, the first map creation unit 17 determines whether or not there is a quadrant that includes measurement points (measurement points P1 to P6) other than the above-mentioned measurement points P7 among the four quadrants based on the position of the access point 3. Find out. The four quadrants mean four regions separated by two coordinate axes when considering a plane orthogonal coordinate system with the position of the access point 3 (point P0) as the origin. Therefore, the four quadrants correspond to each region divided into a cross around the access point 3.

In the example of FIG. 4, the measurement points P1, P3, P5, and P7 are included in the upper left quadrant when viewed from the access point 3. On the other hand, the measurement points P2, P4, and P6 are included in the lower left quadrant when viewed from the access point 3. The measurement points are not included in the upper right quadrant and the lower right quadrant when viewed from the access point.

When another measurement point is included in a quadrant different from the quadrant containing the measurement point P7, the first map creation unit 17 determines the distance from the position of the access point 3 (point P0) in each of the quadrants. Find the measurement point where is the maximum. In the example of FIG. 4, in the lower left quadrant when viewed from the access point 3, the point satisfying the condition is the measurement point P6. Therefore, the first map creation unit 17 allocates the value of the spatial propagation coefficient at the measurement point P6 to overwrite the past value for the entire region corresponding to the relevant quadrant of the spatial propagation coefficient map. As a result, the measurement point P6 is already assigned.

Next, the first map creation unit 17 obtains the measurement point having the largest distance from the position of the access point 3 (point P0) among the measurement points that have not been assigned, regardless of the quadrant. In the example of FIG. 4, such a point is the measurement point P5. In the spatial propagation coefficient map, the first map creation unit 17 sets the value of the spatial propagation coefficient at the measurement point P5 in the past with respect to a rectangular area whose diagonal line is the position of the access point 3 and the measurement point P5. Assign to overwrite the value of. The rectangular area whose diagonal line is the position of the access point 3 and the measurement point P5 can be considered as an area between the position of the access point 3 and the measurement point P5. As a result, the measurement point P5 is already assigned.

Similarly, the first map creation unit 17 obtains the measurement point having the largest distance from the position of the access point 3 (point P0) among the unassigned measurement points. In the example of FIG. 4, such a point is the measurement point P4. In the spatial propagation coefficient map, the first map creation unit 17 sets the value of the spatial propagation coefficient at the measurement point P4 in the past with respect to a rectangular area whose diagonal line is the position of the access point 3 and the measurement point P4. Assign to overwrite the value of. As a result, the measurement point P4 is already assigned.

As described above, the first map creation unit 17 covers the unassigned measurement point having the largest distance from the position of the access point 3 (point P0) and the rectangular area having the access point 3 diagonally. After the value of the spatial propagation coefficient of the measurement point is overwritten, the processing of assigning the measurement point is performed. This process is repeated until all the measurement points P1 to P7 have been assigned. As a result, the spatial propagation coefficient map 61 as shown in FIG. 5 can be obtained. In FIG. 5, the magnitude of the value of the spatial propagation coefficient n in the spatial propagation coefficient map 61 is represented by the width of the hatching.

The spatial propagation coefficient map 61 obtained in the second step is stored in the storage unit 12. By referring to the spatial propagation coefficient map 61, the value of the spatial propagation coefficient n at an arbitrary point in the area 2 can be obtained.

Next, the second map creation unit 18 creates the heat map 62 (step S103 in FIG. 3). Specifically, the second map creation unit 18 pays attention to an arbitrary point in the area 2 and obtains the spatial propagation coefficient n of the point based on the spatial propagation coefficient map 61. Second map creation unit 18, by substituting the spatial propagation coefficient n obtained in Equation (4) described above, obtaining the propagation loss L _B at the point. Second map creation unit 18, by applying the propagation loss L _B in the formula (2), obtain the radio wave intensity P _R at the point. While moving little by little the point of interest in the area within 2 By repeating the above calculation, it is possible to obtain a heat map 62 of the radio wave intensity P _R as shown in FIG.

For convenience of representation by figures, the heat map 62 of FIG. 6, a strong area radio field intensity P _R is a color close to black, weakened region is represented by a color close to white. However, expression technique heatmap 62 can vary, for example, as thermography, strong forward wave intensity P _R are red, yellow, green, light blue, blue, be expressed as changes smoothly and black can.

As long as there is no change in the state of the access point 3, the distribution of radio field intensity should follow the heat map 62 of FIG. 6 created by the second map creation unit 18. However, as described above, there is a possibility that the state of the access point 3 may change, such as when the access point 3 fails and is replaced. In this case, the distribution of radio wave intensity is different from the initial heat map 62.

In consideration of this, in the present embodiment, the heat map can be updated by the following operations.

First, with respect to the radio wave transmitted from the access point 3, the actual radio wave intensity at the measurement point P8 appropriately determined in the area 2 is measured by the measuring device 4 (step S104 in FIG. 3: third step). The position of the measurement point P8 is shown in FIG. Unlike the case where the heat map 62 is created first, when updating the heat map, it is sufficient to measure the radio field intensity at only one point P8.

As can be seen by comparing FIG. 7 and FIG. 4, this measurement point P8 coincides with one of the initial measurement points P1 to P7 (measurement point P2). As a result, the accuracy of the updated heat map can be improved because it is not affected by the change of the measurement point. However, the measurement point P8 for updating the heat map may be different from any of the initial measurement points P1 to P7.

With respect to the radio wave transmitted by the access point 3, the measurement of the radio wave intensity at the measurement point P8 is performed by using the measuring device 4 in exactly the same manner as the measurement at the measurement points P1 to P7. The radio wave intensity obtained by the measuring device 4 is stored in the storage unit 12 of the map creating device 10 in a form associated with the position of the measuring point P8.

Next, a heat map 62x of the radio field intensity in the area 2 is created based on the spatial propagation coefficient map created in the above step and the radio wave intensity measured at the measurement point P8 (step S105: first). 4 steps).

Specifically, the second map creation unit 18 obtains the spatial propagation coefficient n corresponding to the position of the measurement point P8 with reference to the created spatial propagation coefficient map 61. Next, the second map creation unit 18 determines what the radio field intensity distribution by the access point 3 after the state change will be if the spatial propagation coefficient n is 2.0 over the entire area 2. calculate. Hereinafter, this hypothetical distribution may be referred to as an ideal radio field intensity distribution.

The calculation of the ideal radio field intensity distribution can be performed as follows. That is, the value of the space propagation coefficient n in the measurement point P8 by substituting the equation (4), obtains the propagation loss L _B. In the equation (4), the wavelength λ is known, and the distance D is substituted with the distance between the access point 3 and the measurement point P8.

Then, in the equation obtained by transforming Equation (2) such that G _T = · · ·, as a radio wave intensity P _R, by substituting the measured value of the radio wave intensity at the measurement point P8, as the propagation loss L _B, formula substituting the propagation loss L _B obtained in (4). Receive gain G _R, and the transmit power P _T is known. Thus, it is possible to determine the value of transmit gain G _T. The value of the transmit gain G _T obtained, when the value of transmit gain G _T by a change in the state of the access point 3 is assumed to have varied, which means the value of the transmit gain G _T after change.

Ideally radio wave intensity distribution, the value of the new transmit gain G _T By applying the equation (1) is obtained as a function of the distance D. In Equation (1), the wavelength lambda, reception gain G _R, and the transmit power P _T is known. Therefore, determining the value of the new transmit gain G _T is that substantially the same for obtaining the ideal wave intensity distribution.

Subsequently, the second map creation unit 18 updates the heat map. Specifically, the second map creation unit 18 pays attention to an arbitrary point in the area 2 and obtains the spatial propagation coefficient n of the point based on the spatial propagation coefficient map 61. The second map creation unit 18 substitutes the obtained spatial propagation coefficient n and the distance D between the access point 3 and the relevant point into the above-mentioned mathematical formula (4), thereby causing the propagation loss at the relevant point. determine the L _B. Second map creation unit 18, by applying the propagation loss L _B in the formula (2), obtain the radio wave intensity P _R at the point. While moving little by little the point of interest in the area within 2 By repeating the above calculation, (in other words, heat map 62x after update) the distribution of the radio wave strength P _R as shown in FIG. 8 can be obtained ..

The obtained heat map 62x corresponds to the result of applying the propagation loss to the above-mentioned ideal radio field intensity distribution based on the distribution of the spatial propagation coefficient shown by the spatial propagation coefficient map 61.

In this way, if the spatial propagation coefficient map 61 is prepared once for the area 2, when the state of the access point 3 changes, the actual radio field intensity in the area 2 does not need to be measured at a plurality of points. A new heat map 62x can be created by measuring only at one point.

As shown in the flowchart of FIG. 3, the processes of steps S104 and S105 can be repeated as many times as necessary. The heat map 62x may be updated (recreated) when a change in the state of the access point 3 is suspected, or simply periodically.

The work of measuring the radio wave strength involves the acquisition of the radio wave transmitted from the access point 3. Therefore, when the factory equipment uses the wireless communication of the access point 3, there is a high possibility that the operation of the factory equipment in the area 2 is hindered in order to create the heat maps 62 and 62x. In this regard, according to the present embodiment, in the second and subsequent heat map 62x creation (heat map update), the radio field intensity measurement work can be completed in a short time. Therefore, it is possible to continuously monitor the heat map 62x of the radio wave intensity by visualizing it without stopping the operation of the equipment of the factory for a long period of time.

As described above, the method for creating a wireless heat map of the present embodiment includes a first step, a second step, a third step, and a fourth step. In the first step, with respect to radio waves transmitted from the access point 3 installed for wireless communication in the area within 2 to measure the radio field intensity P _R for each of a plurality of measurement points P1~P7 in area 2. In the second step, based on the radio wave intensity P _R at each of a plurality of measurement points P1~P7 measured in the first step, the spatial propagation coefficient map 61 showing the distribution of the spatial propagation coefficient n intended for the area 2 create. In the third step, with respect to radio waves transmitted from the access point 3 after the second step, measuring the radio field intensity P _R for the measurement point P8 of fewer than the first step. In the fourth step, based on the radio wave intensity P _R measured in created space propagation coefficient map 61, and the third step in the second step, with respect to radio waves transmitted from the access point 3 after the second step, the area to create a heat map 62x of the radio wave intensity P _R in the 2.

As a result, if the radio field intensity is measured once at a plurality of measurement points P1 to P7 in the target area 2, the radio wave intensity at a smaller number of points (one point P8 in the present embodiment) thereafter. The heat map 62x of the radio field intensity in the area 2 can be obtained by calculation using the spatial propagation coefficient map 61 only by measuring. Therefore, the time and effort required to obtain the heat map 62x can be significantly reduced.

In the wireless heat map creation method of the present embodiment, one point P8 in the third step has the same position as any of a plurality of measurement points P1 to P7 (point P2) in the first step.

As a result, the heat map can be updated based on the change in the radio field intensity at the same point. Therefore, the accuracy of the new heat map 62x can be improved.

In the method for creating a wireless heat map of the present embodiment, in the second step, at least one of a plurality of measurement points P1 to P7 (in the example of FIG. 4, measurement points P1 to P5) is used in the spatial propagation coefficient map. , The value of the spatial propagation coefficient corresponding to the measurement points P1 to P5 is assigned to the region between the position of the access point 3 (point P0).

As a result, the spatial propagation coefficient map 61 that reflects the tendency generally well can be easily created.

In wireless heat map creation method of this embodiment, in the fourth step, the spatial propagation coefficient n of the measuring point P8 where the radio wave intensity P _R in the third step was measured, determined based on the spatial propagation coefficient map 61. In the fourth step, the measured value of the radio wave intensity P _R in the third step, a space propagation coefficient n of the measurement point P8 in the third step, based on the entire area 2 is assumed to be free space Find the ideal radio field intensity distribution, which is the radio field strength distribution in the case. In the fourth step, to the ideal wave intensity distribution, by applying the propagation loss L _B based on the distribution of the spatial propagation coefficient n indicating the spatial propagation coefficient map 61, heatmap 62x field intensity P _R in the area 2 To create.

Thereby, the heat map 62x of the radio wave intensity can be appropriately created.

Further, the wireless heat map creation system 1 of the present embodiment includes a map creation device 10. The map creation device 10 creates a heat map 62x of radio wave intensity with respect to the radio waves transmitted from the access point 3 installed for wireless communication in the area 2. The map creation device 10 includes a first map creation unit 17 and a second map creation unit 18. First map creation unit 17, with respect to radio waves transmitted from the access point 3, based on the radio wave intensity P _R measured for each of a plurality of measurement points P1~P7 in area 2, intended for area 2 space A spatial propagation coefficient map 61 showing the distribution of the number of propagations is created. The second map creation unit 18 has a number smaller than the number of measurement points P1 to P7 when the spatial propagation coefficient map 61 is created with respect to the radio waves transmitted from the access point 3 after the spatial propagation coefficient map 61 is created. based on the wave intensity P _R measured measurement point P2 of the heat map 62x field intensity P _R in the area 2, made using space propagation coefficient map 61.

As a result, a new heat map 62x can be easily obtained while reducing the trouble of measuring the radio field strength.

Although preferred embodiments and modifications of the present invention have been described above, the above configuration can be changed as follows, for example.

In the above embodiment, one access point 3 is used for one area 2, but a plurality of access points 3 may be used for one area 2. In this case, the above-mentioned first step, second step, third step, and fourth step are performed for each access point 3. The above-mentioned first step, second step, third step, and fourth step may be performed in one measurement for a plurality of radio wave transmission sources, radio channels, and frequency bands.

The frequency band used by the access point 3 for wireless communication may be single or plural. However, as shown by the above-mentioned mathematical formula (1), the radio field intensity becomes less likely to be attenuated as the wavelength increases, so that the tendency of the radio wave strength distribution varies greatly depending on the frequency band. Therefore, when the access point 3 uses a plurality of frequency bands, it is appropriate to perform the above-mentioned four steps for each frequency band to create separate spatial propagation coefficient maps 61 and heat maps 62, 62x. For example, when the access point can selectively use either the 2.4 GHz band frequency or the 5 GHz band frequency for wireless communication, the above four steps are performed for each of the 2.4 GHz band and the 5 GHz band. , Separate spatial propagation coefficient maps 61 and heat maps 62, 62x are created. In this case, it is sufficient to create the spatial propagation coefficient map 61 and the heat maps 62, 62x corresponding to the 2.4 GHz band and the 5 GHz band, respectively, and it is not always necessary to create the individual spatial propagation coefficient map 61 and the individual spatial propagation coefficient map 61 for each channel included in each frequency band. It is not necessary to create heat maps 62 and 62x.

When creating a spatial propagation coefficient map, the region of the map to which the spatial propagation coefficient value is assigned is not limited to the above example. For example, when the radio field intensity can be measured at a large number of points, the space corresponding to the measurement points is relative to the area within a predetermined range centered on each measurement point (for example, the area of a circle having a radius of about several meters). Propagation coefficients can be assigned. In this case, the spatial propagation coefficient map can be created by a simple process.

The map-making device 10 may be fixedly installed and changed so that only the measuring device 4 moves between a plurality of measuring points. Information may be communicated wirelessly between the measuring device 4 and the map creating device 10 instead of being wired.

The map creating device 10 may be composed of the same hardware as the measuring device 4.

The map creation device 10 may be configured to enable wired communication with the access point 3. In this case, the radio field intensity and the measurement position measured by the measuring device 4 are transmitted from the measuring device 4 to the access point 3, and the access point 3 transfers the information to the map creating device 10.

In step S104 of FIG. 3, the number of measurement points of radio field intensity may be two or more. In this case, the radio wave intensity at each measurement point, the value of the new transmit gain G _T in consideration of the change of state of the access point 3 can be obtained. The mean value is calculated from several new transmit gain G _T, by substituting the average value into Equation (2) can be obtained with high accuracy heatmap 62x.

The process of creating the heat map 62 shown in step S103 of FIG. 3 may be omitted.

The radio distribution map such as the heat map 62x may be output from the map creation device 10 to another device by communication instead of being output to the display unit 14.

The heat maps 62 and 62x are not limited to being output in a two-dimensional color-coded display, and can be displayed by, for example, contour lines or a three-dimensional graph.

In view of the above teachings, it is clear that the present invention can take many modified and modified forms. Therefore, it should be understood that the present invention may be practiced in a manner other than that described herein, within the scope of the appended claims.

1 Wireless heat map creation system 2 Area 3 Access point 4 Measuring device 10 Map creation device 61 Spatial propagation coefficient map 62x Heat map (wireless distribution map)
n Spatial propagation coefficient P1 to P8 Measurement points

Claims (9)

Regarding the radio waves transmitted from the radio wave transmission source installed for wireless communication in the area, the first step of measuring the radio wave intensity at each of a plurality of measurement points in the area, and
The second step of creating a spatial propagation coefficient map showing the distribution of the spatial propagation coefficient for the area based on the radio field intensity at each of the plurality of measurement points measured in the first step, and the second step.
With respect to the radio waves transmitted from the radio wave transmission source after the second step, the third step of measuring the radio wave intensity at a smaller number of measurement points than the first step, and
Based on the spatial propagation coefficient map created in the second step and the radio wave intensity measured in the third step, the radio waves transmitted from the radio wave source after the second step are in the area. The fourth step of creating a distribution map of radio field strength,
A method for creating a radio distribution map, which comprises. The method for creating a radio distribution map according to claim 1.
A method for creating a radio distribution map, wherein the measurement point in the third step includes a measurement point having the same position as any one of the plurality of measurement points in the first step. The method for creating a radio distribution map according to claim 1 or 2.
In the second step, the spatial propagation corresponding to the measurement point is made with respect to a region between at least one of the plurality of measurement points and the position of the radio wave transmission source in the spatial propagation coefficient map. A radio distribution map creation method characterized by assigning coefficient values. The method for creating a radio distribution map according to claim 1 or 2.
The second step is characterized in that the value of the spatial propagation coefficient corresponding to the measurement point is assigned to a predetermined region centered on each of the plurality of measurement points in the spatial propagation coefficient map. How to create a radio distribution map. The method for creating a radio distribution map according to any one of claims 1 to 4.
In the fourth step,
The spatial propagation coefficient at the measurement point where the radio field intensity was measured in the third step was obtained based on the spatial propagation coefficient map.
Based on the measured value of the radio wave intensity in the third step and the space propagation coefficient at the measurement point in the third step, the radio wave strength when it is assumed that the entire area is free space. Find the ideal radio field intensity distribution, which is the distribution,
A radio wave in which a distribution map of radio wave intensity in the area is created by applying a propagation loss to the ideal radio wave intensity distribution based on the distribution of the spatial propagation coefficient shown by the spatial propagation coefficient map. Distribution map creation method. The method for creating a radio distribution map according to any one of claims 1 to 5.
When a plurality of the radio wave transmission sources are provided, the radio wave distribution map is characterized in that the first step, the second step, the third step, and the fourth step are performed for each of the radio wave transmission sources. How to make. The method for creating a radio distribution map according to any one of claims 1 to 6.
When the radio wave transmission source is capable of performing wireless communication in a plurality of frequency bands, the first step, the second step, the third step, and the fourth step are performed for each of the frequency bands. A radio distribution map creation method characterized by. The method for creating a radio distribution map according to any one of claims 1 to 7.
A method for creating a radio distribution map, wherein the radio wave transmission source is an access point in wireless communication. Equipped with a map creation device for creating a distribution map of radio wave intensity for radio waves transmitted from radio wave transmission sources installed for wireless communication in the area.
The map creation device
With respect to the radio waves transmitted from the radio wave transmission source, a spatial propagation coefficient map showing the distribution of the number of spatial propagation cases in the area is created based on the radio wave intensities measured for each of a plurality of measurement points in the area. Spatial propagation coefficient map creation unit and
With respect to the radio waves transmitted from the radio wave source after the spatial propagation coefficient map is created, the radio wave intensity measured for a number of measurement points smaller than the number of measurement points when the spatial propagation coefficient map is created. Based on the above, a distribution map creation unit that creates a distribution map of radio wave intensity in the area using the spatial propagation coefficient map, and
A radio distribution map creation system characterized by being equipped with.

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