JP6967368B2 - Radio field intensity map generation method, propagation loss estimation method and indoor positioning system - Google Patents

Description

The present invention relates to a method for generating a radio wave intensity map showing the radio wave intensity of radio waves from a radio station in each indoor location such as a large-scale building, a method for estimating propagation loss, and an indoor positioning system.

It is known that the radio wave strength received by a terminal from a radio station such as an access point depends on the distance. There is an RSSI (Received Signal Strength Indicator) method as a method of determining the position by converting the distance from the position information of the access point and the transmitted radio wave strength. In order to estimate the position by the RSSI method, the radio field strength data at the position to be detected is acquired in advance to create a radio field strength map, and the position is based on the similarity with the received radio field strength of the terminal by referring to the radio field strength map. Can be determined.

By the way, in a large-scale building such as a terminal station facility, a complex commercial facility, or a university hospital, radio waves are scattered and absorbed by walls, floors, and the like. Therefore, the ITU-R recommends a method of estimating the approximate propagation loss only from the frequency, the distance between the access point and the terminal, and the floor difference between the access point and the terminal. The propagation loss estimation method according to the ITU-R recommendation is given by the following equation.
L = _{20log 10} f + Nlog ₁₀ d + Lf (n) -28 [dB]
L: Propagation loss expressed in dB value f = frequency [MHz]
N: Parameter indicating distance dependence d: Distance between access point and terminal [m]
Loss due to penetration through walls, ceilings, and floors expressed as Lf = dB [dB]
n = Number of walls, ceilings, and floors between the access point and the terminal

In addition, the radio field strength from multiple radio stations at each indoor position is measured in advance, a radio wave strength map that associates each position with the radio field strength is created, and the position of the terminal is estimated from the radio field strength received by the terminal. (For example, see Patent Document 1).

Japanese Unexamined Patent Publication No. 2011-99859

However, the work of creating a radio wave strength map requires enormous human labor, time, and cost because it is necessary to manually measure the radio wave strength of the radio wave received from each access point at each position.

In addition, in the propagation loss estimation method based on the ITU-R recommendation, obstacles such as walls and doors must be counted one by one in order to calculate Lf (n), so construction of such data and databases Is unrealistic.

The present invention has been made in view of these points, and is a method for generating a radio field intensity map, which can easily create a radio wave strength map in which the position of a terminal indoors can be estimated from the received radio wave strength from a radio station, and propagation loss. It is an object of the present invention to provide an estimation method and an indoor positioning system.

The method for generating a radio wave intensity map of the present invention is a method for generating a radio wave intensity map referred to for estimating the position of a terminal device on a floor of an indoor space in a facility building, and the position of the terminal device on the floor. The first division step that divides the position estimation target space that is the estimation target and the transmission space that is not the position estimation target of the terminal device, and the position estimation target space that are close to each other after the execution of the first division step. A second division step that divides the narrow space sandwiched by the transmission space into a normal space that is not the narrow space, a block division step that divides the floor into blocks that serve as position identification units, and the position estimation target. The amount of loss according to the linear distance between each block in the space and at least one radio station that emits radio waves that can be received by the block, and the length transmitted through the transmitted space in the straight line. The calculation step of subtracting the loss amount from the transmitted radio wave strength of the radio station to calculate the radio wave strength estimated value received by the block, and the matrix formed by the plurality of blocks and the plurality of radio stations, the matrix. In the calculation step, the straight line forms the narrow space in the calculation of the radio wave intensity estimation value. It is characterized in that an increase amount according to the passing length is added to the transmitted radio wave intensity of the radio station.

According to this method, it is possible to create a radio wave strength map without actually measuring the received radio wave strength at each position on the floor, and achieve cost reduction by reducing human labor and shortening the work time. Can be done. Further, in the above configuration, in calculating the radio wave intensity estimated value of each block, the loss amount according to the length transmitted through the transmission space is subtracted from the transmitted radio wave strength of the radio station. This eliminates the need to count obstacles one by one as in the conventional propagation loss estimation method, and makes it possible to easily create a radio field intensity map. Further, it can be calculated that the radio field intensity estimated value increases according to the tendency of the radio wave strength to be amplified in a narrow space such as a relatively long passage, and the accuracy of the radio wave strength estimated value can be improved.

In the method for generating a radio field intensity map of the present invention, the radio wave strength estimated value in the calculation step may be calculated by the following equation.
Estimated signal strength = transmitted signal strength- (Nlog ₁₀ D) (1 + (A1-1) L1 / D + (A2-1) L2 / D)
N is the reference value [dB] of the radio wave propagation loss from the radio station, D is the distance [m] between the radio station and the block, A1 is the loss coefficient in the transmission space, and L1 is the propagation distance [m] in the transmission space. ], A2 is the loss coefficient in the narrow space, and L2 is the propagation distance [m] in the narrow space.

In the method for generating a radio field intensity map of the present invention, the facility building is provided with a spatial connection portion provided across a plurality of floors adjacent to each other above and below, and the radio station installed on one floor in the calculation step. When a radio wave is transmitted from a station and leaks to another floor as a leaked radio wave through the spatial connection portion, it is considered that a virtual radio station that transmits the leaked radio wave is installed in the spatial connection portion and is received by the block. It is advisable to calculate the estimated radio field strength. According to this method, it is possible to calculate the radio wave intensity estimation value by assuming that the radio wave is transmitted from the spatial connection portion, and it is possible to increase the transmission position of the radio wave that is the reference of the position estimation to improve the accuracy of the radio wave strength estimation value. ..

Propagation loss estimation method of the present invention, in the floor of the indoor space in the facility building, a position estimation target space to be located estimation target of the terminal device, after divided into the transmitting space that do not position estimation target of the terminal device, the The position estimation target space is divided into a narrow space sandwiched between the transparent spaces that are close to each other and a normal space that is not the narrow space, and the floor is divided into blocks that serve as position identification units, and the radio station and the radio station. It is characterized in that the radio wave propagation loss with the block is calculated by the following equation.
Formula radio wave propagation loss = (Nlog ₁₀ D) (1+ (A1-1) L1 / D + (A2-1) L2 / D)
N is the reference value [dB] of the radio wave propagation loss from the radio station, D is the distance [m] between the radio station and the block, A1 is the loss coefficient in the transmission space, and L1 is the propagation distance [m] in the transmission space. ], A2 is the loss coefficient in the narrow space, and L2 is the propagation distance [m] in the narrow space. In such a method, the estimated value of the radio wave propagation loss between the radio station and the block can be calculated with high accuracy.

The indoor positioning system of the present invention includes a map generation means for generating a radio wave intensity map by the above-mentioned method for generating a radio wave intensity map, a storage means for storing the radio wave intensity map generated by the map generation means, and the terminal. The block corresponding to the received radio wave intensity measured by the device is extracted from the radio wave strength map stored in the storage means, and the block is provided with a position estimation means for estimating the block in which the terminal device is located. It is characterized by.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a radio wave intensity map generation method, a propagation loss estimation method, and an indoor positioning system that can easily create a radio wave intensity map that can estimate the position of a terminal indoors from the received radio wave strength from a radio station.

It is a flowchart which shows an example of the generation method of the radio wave intensity map which concerns on this embodiment. It is a top view schematically showing an example of a facility building for explaining a 1st division step. It is a top view which shows typically an example of the facility building for demonstrating the 2nd division step. It is a top view schematically showing an example of a facility building for explaining a block division step. It is a flow diagram for demonstrating a part of the flow of a calculation step. It is an enlarged view of the part A of FIG. 4 for explaining a calculation step. It is explanatory drawing which shows an example of the radio wave strength map. It is a graph which shows the actual measurement result of the received radio wave strength in a normal space. It is a graph which shows the actual measurement result of the received radio wave strength in a narrow space. It is sectional drawing for explanation of the facility building of a plurality of floors. It is a figure which shows the whole structure of an indoor positioning system. It is a functional block diagram which shows the configuration example of a server. It is a functional block diagram which shows the configuration example of a terminal apparatus. It is explanatory drawing which shows the verification place of the position estimation using a radio wave intensity map. It is explanatory drawing which shows the verification place of the position estimation using a radio wave intensity map.

Hereinafter, a method of generating a radio field intensity map according to the present embodiment will be described with reference to the attached drawings. FIG. 1 is a flowchart showing an example of a method of generating a radio wave intensity map according to the present embodiment. As shown in FIG. 1, the generation method according to the present embodiment includes a first division step (step (hereinafter referred to as “ST”) 100), a second division step ST200, a block division step ST300, a calculation step ST400, and a map. The generation step ST500 is performed in this order. It should be noted that these steps are merely examples and are not limited to this configuration. Here, the radio wave intensity map is referred to for measuring the position of the terminal device that receives the radio wave from the access point (radio station), and the radio wave intensity of the radio wave received by the terminal device from the access point at a plurality of indoor locations. It is a record of the estimated value obtained by simulation.

In the generation method of the present embodiment, the facility information of the facility building that generates the radio wave intensity map is acquired in advance before the first division step ST100 is carried out. The facility information includes, for example, the plan view data 60a (see FIG. 12) consisting of CAD data, image data, etc. corresponding to the plan view of the architectural drawing, the positions of the walls and pillars in the indoor space in the facility building, and the use by the user. The shape and size of the space can be obtained as coordinate values. The facility information also includes access point data 60b (see FIG. 12) from which the installation position of the access point in the indoor space and identification information (base station ID, observed radio wave condition, etc.) can be acquired. FIG. 2 is a plan view schematically showing an example of a facility building for explaining the first division step. The facility building is not particularly limited, but station facilities, airport facilities, and various other large-scale facilities can be exemplified.

As shown in FIG. 2, in the first division step ST100, the floor plan data of the facility building is separated into 11 floor units. In this separation, one floor 11 does not straddle a plurality of floors but is on the same floor. Even if it is on the same floor of the facility building, it may be separated into a plurality of floors 11 at arbitrary positions such as walls.

Next, in the first division step ST100, the separated floor 11 is divided into a position estimation target space 12 and a transmission space 13. In FIG. 2, in order to distinguish the position estimation target space 12 and the transmission space 13 for easy visual recognition, the region to be the transmission space 13 is surrounded by a thick line, and the outer region (surrounded by the thick line) of the region surrounded by the thick line is shown. The area that is not covered) is represented as the position estimation target space 12. The position estimation target space 12 is a space on the floor 11 that is the position estimation target of the terminal device, and the transmission space 13 is a space that is not the position estimation target of the terminal device on the floor 11 on the contrary. For example, as the position estimation target space 12, a meeting place, a space such as a plaza, a passage, or the like that can be normally used by a user of the floor 11 can be mentioned. Examples of the transmission space 13 include obstacles themselves such as pillars and walls that do not transmit radio waves, as well as spaces surrounded by walls that are generally inaccessible, such as stairs, elevator installation spaces, and employee waiting rooms.

FIG. 3 is a plan view schematically showing an example of a facility building for explaining the second division step. After performing the first division step ST100, as shown in FIG. 3, the second division step ST200 for further dividing the position estimation target space 12 into the normal space 14 and the narrow space 15 is performed. In FIG. 3, in order to distinguish between the normal space 14 and the narrow space 15 for easy visual recognition, the normal space 14 is shaded and the narrow space 15 is shown with halftone dots. The narrow space 15 is a region sandwiched between transparent spaces 13 that are close to each other and face each other, and can be exemplified as a narrow passage or the like. Specific examples of the narrow passage 15 include a passage that intersects in a continuous region of 20 m or more with a passage width of 7 m or less and a narrow passage that has no space. The normal space 14 is a space that is not a narrow space 15 in the position estimation target space 12. The criteria for selecting and setting the normal space 14 and the narrow space 15 will be further described.

FIG. 4 is a plan view schematically showing an example of a facility building for explaining the block division step. After performing the second division step ST200, as shown in FIG. 4, the block division step ST300 for further dividing the position estimation target space 12 into blocks is performed. In the block division step ST300, the position estimation target space 12 is subdivided into two orthogonal directions and divided into blocks B as position identification units. In other words, the position estimation target space 12 is composed of the set of blocks B. In the present embodiment, the planar shape of the block B is a square shape, but the present invention is not limited to this, and other various shapes and sizes such as a rectangular shape, a triangular shape, a polygonal shape such as a hexagon, and a circular shape are used. Can be adopted, and the shape and size may differ depending on the block B. A serial number (nth block (n is a natural number)) is also assigned to each block B for identification.

The order of the second division step ST200 and the block division step ST300 may be reversed or may be processed so as to be performed at the same time.

After executing the second division step ST200 and the block division step ST300, the calculation step ST400 is executed. In the calculation step ST400, when a terminal device (not shown) is arranged in each block B, an estimated value of the received radio wave intensity of the radio wave received by the terminal device from the access point AP which is a radio station is calculated. The communication method between the terminal device and the access point AP is WiFi (Wireless Fidelity), and as the terminal device, a mobile terminal such as a mobile phone or a tablet type terminal can be used.

In the calculation step ST400, the radio field intensity estimate from the access point AP in each block B is calculated. Here, assuming that the number of blocks on the same floor is n, the estimated radio field intensity is calculated for all the first to nth blocks. The order of calculation is arbitrary, and may be calculated in the order of serial numbers of blocks. If the number of access point APs installed on the same floor 11 is m, a serial number (mth access point (m is a natural number)) is assigned for identification, and all of the first to m access points are assigned to each block. Calculate the estimated radio field intensity transmitted from the sequence in the order of serial numbers.

The calculation of the estimated radio field intensity is performed using the following equations (1) and (2).
Equation (1)
Radio wave propagation loss = (Nlog ₁₀ D) (1+ (A1-1) L1 / D + (A2-1) L2 / D)
Equation (2)
Estimated signal strength = AP transmitted signal strength-Radio wave propagation loss = AP transmitted signal strength- (Nlog ₁₀ D) (1+ (A1-1) L1 / D + (A2-1) L2 / D)
The variables of equations (1) and (2) are as follows.
N: Reference value of radio wave propagation loss [dB]
D: Distance between the access point and the block [m]
A1: Loss coefficient in transmission space L1: Propagation distance in transmission space [m]
A2: Loss coefficient in a narrow space L2: Propagation distance in a narrow space [m]

The reference value N is a distance-dependent parameter, and is a coefficient that becomes a different value when calculating the upper limit value and the lower limit value of the allowable value in the radio field intensity estimation value for each block. In the present embodiment, the reference value N is 20 when calculating the upper limit of the estimated radio field intensity, 30 when calculating the lower limit, 0.83 for A1 and 2 for A2. The grounds for setting these values and the setting method will be described later.

Hereinafter, with reference to FIGS. 5 and 6, a method of calculating the radio field intensity estimated value from the first access point in the first block in the calculation step ST400 will be described. FIG. 5 is a flow chart for explaining a part of the flow of calculation steps. FIG. 6 is an enlarged view of part A of FIG. 4 for explaining the calculation step.

The calculation step ST400 first acquires the strength of the radio wave transmitted from the first access point (AP transmission radio wave strength) (ST401). Next, after acquiring the coordinate values of the first block and the first access point, the first block and the first access point are connected by a straight line SL, and their straight line distance D (the length of the straight line SL) is calculated. (ST402). Next, it is determined whether or not the transmission space 13 is on the straight line SL connecting the first block and the first access point (ST403). When there is a transmission space 13 (ST403: Yes), the length L1 of the transmission space 13 existing on the straight line SL is calculated (ST404).

When there is no transmission space 13 (ST403: No), the length L1 = 0 (ST405). After setting the length L1 in ST404 or ST405, it is determined whether or not there is a narrow space 15 on the straight line SL (ST406). When there is a narrow space 15 (ST406: Yes), the length L2 of the narrow space 15 existing on the straight line SL is calculated (ST407). When there is no narrow space 15 (ST406: No), the length L2 = 0 (ST408). After setting the length L2 in ST407 or ST408, each value is input to the above equation (1) to calculate the radio wave propagation loss (ST409). At this time, two values of 20 and 30 are input as the reference value N, and the estimated maximum value and the estimated minimum value of the radio wave propagation loss are calculated. Here, the estimated value of the radio wave propagation loss may be a negative value, and in this case, it is a negative loss, that is, a value of the amplification amount of the propagating radio wave.

After calculating the radio wave propagation loss in ST407, the radio wave propagation loss and the AP transmission radio wave intensity of the first access point acquired in ST401 are input to the above equation (2), and the radio wave intensity estimated value is calculated (ST410). ). In this calculation, when the estimated maximum value of the radio wave propagation loss with the reference value N as 30 is used, the lower limit value of the allowable value in the radio wave intensity estimated value is obtained. On the other hand, when the estimated minimum value of the radio wave propagation loss with the reference value N as 20 is used, the upper limit of the allowable value in the radio wave intensity estimated value is obtained. The above-mentioned value of the reference value N is only an example and is not particularly limited, and is variously changed according to various conditions such as the building and the radio wave propagation condition. The method of setting the reference value N in this embodiment will be described later.

In the first block, the radio wave intensity estimated value transmitted from the other second to m access points arranged in the floor 11 is calculated in the same manner as the flow shown in FIG. Although the estimated radio wave intensity from all the access points in the floor 11 may be calculated, a threshold value is set for the distance from the access point to the first block, and the access point having a distance longer than the threshold value is used. , The calculation of the radio field intensity estimation value may be omitted. According to this, calculation processing can be omitted for access points that have a large floor area and cannot receive radio waves or are extremely weak, and in particular, when the number of access points installed is large, the effect of reducing the processing load is enhanced. be able to.

Then, in the same manner as the first block, the radio wave intensity estimated value is calculated for all the second to nth blocks on the same floor.

FIG. 7 is an explanatory diagram showing an example of a radio wave intensity map. After performing the calculation step ST400, as shown in FIG. 7, the map generation step ST500 for creating the radio field intensity map 20 is carried out. In the map generation step ST500, as the radio wave intensity map 20, a matrix is formed in which blocks are arranged in the order of serial numbers for identification in the vertical direction and access points are arranged in the order of serial numbers for identification in the horizontal direction. Then, the radio wave intensity estimated values (upper limit value, lower limit value) from each access point in each block calculated in the calculation step ST400 are input to each cell of the matrix in the radio wave intensity map 20. If the estimated radio field intensity from the access point is not calculated in each block, the cell corresponding to the access point is blank. In the radio wave intensity map 20 thus obtained, the identification information of the access point and the received radio wave intensity from the access point are specified, and the position of the block can be extracted.

Here, the above equations (1) and (2) used in the calculation step ST400 will be further examined. In the formula (1), the radio wave intensity that decreases until the radio wave transmitted from the access point AP propagates to the position of each block B is calculated as an estimated value of the radio wave propagation loss. The decomposition of equation (1) is as follows.
Radio wave propagation loss = (Nlog ₁₀ D) (1+ (A1-1) L1 / D + (A2-1) L2 / D)
= Nlog ₁₀ D
+ Nlog ₁₀ D ((A1-1) L1 / D)
+ Nlog ₁₀ D ((A2-1) L2 / D)
In the equation (1), when neither the transmission space 13 nor the narrow space 15 exists between the access point AP and the block B, L1 = 0 and L2 = 0, and the radio wave propagation loss = Nlog ₁₀ D. Therefore, as the distance D becomes longer, the radio wave propagation loss also increases, and when the distance D is 10 [m], the radio wave propagation loss = N [dB].

The loss coefficient A1 in the transmission space 13 is set to 2 as an example, but a value larger than 1 (A1> 1) may be set, and "(A1-1)" in the equation (1) means that the transmission space 13 is used. If it exists (L1> 0), it becomes a positive value. Further, "L1 / D" in the equation (1) is the ratio of the propagation distance in the transmission space 13 to the distance between the block B and the access point AP. Therefore, "Nlog ₁₀ D ((A1-1) L1 / D)" in the above equation is a value of the amount of radio wave loss according to the length transmitted through the transmission space 13 between the block B and the access point AP. Will be. In the formula (2), this value is _{subtracted from the AP transmission radio wave strength together with "Nlog 10} D" to calculate the radio wave strength estimation value.

On the other hand, the loss coefficient A2 of the narrow space 15 is 0.83 as an example, but it is larger than 0 and less than 1 (0 <A2 <1), and "(A2-1)" in the equation (1) is When the narrow space 15 exists (L2> 0), it becomes a negative value. Further, "L2 / D" in the equation (1) is the ratio of the propagation distance in the narrow space 15 to the distance between the block B and the access point AP. Therefore, the "Nlog ₁₀ D ((A2-1) L2 / D)" in the above equation is the amount of negative radio wave loss according to the length passing through the narrow space 15 between the block B and the access point AP. That is, it becomes the value of the amplification amount. By subtracting this value as the radio wave propagation loss in the equation (2), the radio wave intensity estimated value increased from the AP transmission radio wave strength can be calculated. It can be inferred that the reason for this increase is the influence of the reflected waves due to the walls of radio waves and the like.

In order to set the reference value N at the time of calculating the maximum value of the estimated radio field strength in the formula (2), the radio field strength [dB] from an arbitrary access point was actually measured by the terminal device on the first basement floor of Tokyo Station. The actual measurement was performed in a normal space where neither a transparent space nor a narrow space exists between the terminal device and the access point. The AP transmission signal strength of the access point was set to -20 dB. The actual measurement results are shown in FIG. FIG. 8 is a graph showing the actual measurement results of the received radio wave intensity in the normal space. In FIG. 8, the distance between the terminal device and the access point is on the horizontal axis, the radio wave intensity received by the terminal device is on the vertical axis, and the measured data is developed as a scatter diagram. In the graph, plot the measured data with a filled diamond "◆".

Further, in the graph of FIG. 8, the calculation results of the equation (2) are superposed. This calculation result is a cross mark "x" when the reference value N is 10, a white square "□" when the reference value N is 20, and a white triangle "△" when the reference value N is 30. Plot with. Here, in specifying the position of the block, the distance between the access point and the block, which is easily affected by the difference in radio wave intensity, is 50 m or less. In the graph of FIG. 8, when the upper limit value of the measured data in the range at each distance is compared with the plot of the calculation result of the equation (1), the value “□” at which the reference value N is 20 is approximated. ing. Therefore, when the maximum value of the estimated radio wave intensity is calculated by the equation (2) and the lower limit of the radio wave propagation loss is calculated by the equation (1), the value of the reference value N is set to 20.

Next, the method used to set the reference value N at the time of calculating the minimum value of the estimated radio field intensity and the loss coefficient A1 in the transmission space will be described by the equation (2). In this method, the radio field intensity [dB] from an arbitrary access point was actually measured by a terminal device in a plurality of blocks around an arbitrary access point on the first basement floor of Tokyo Station. In this actual measurement, the transparent space exists and does not exist between the access point and the block, and the narrow space does not exist. Further, the radio field intensity estimation value according to the equation (2) in those blocks was calculated by a plurality of combinations of the reference value N and the loss coefficient A1 shown in Table 1 below. Then, in each block, each calculation result of a plurality of combinations of the reference value N and the loss coefficient A1 according to the equation (2) is compared with the actually measured data, and the equation (2) is within a predetermined range centered on the actually measured data. The number of cases in which the calculation result of was settled was counted. The results are shown in Table 1.

As can be understood from Table 1, the number of cases was the largest in the combination of the reference value N of 30 and the loss coefficient A1 of 2.0. Therefore, when the loss coefficient A1 in the transmission space is set to 2.0, the minimum value of the estimated radio wave intensity is obtained by the equation (2), and the upper limit of the radio wave propagation loss is obtained by the equation (1), the reference value N is used. The value was set to 30.

Subsequently, the method used to set the loss coefficient A2 in the narrow space in the equation (2) will be described. In this method, as a candidate for a narrow space, the radio field intensity [dB] from an arbitrary access point was actually measured by a terminal device in five passages having different widths at Tokyo Station. The actual measurement was carried out in a continuous passage (no intersection) of 20 m or more in which there is no transmission space between the terminal device and the access point. The AP transmission signal strength of the access point was set to -25 dB. The passage widths of the five passages were 5.0 [m], 7.5 [m], 10 [m], 16.25 [m], and 25 [m]. The actual measurement results are shown in FIG.

FIG. 9 is a graph showing the actual measurement results of the received radio wave intensity in a narrow space. In FIG. 9, the distance between the terminal device and the access point is on the horizontal axis, the radio wave intensity received by the terminal device is on the vertical axis, and the measured data is developed as a scatter diagram. In the graph of FIG. 9, as shown by the downward arrow, the three passages (passage width: 5.0 [m], 7.5 [m], 10 [m]) having a relatively small passage width are shown. Compared to the two passages (passage width: 16.25 [m], 25 [m]) having a relatively large passage width, the received radio wave strength is larger and the attenuation of the radio wave strength is smaller. Comparing these, the former has an attenuation amount of about 83% as compared with the latter, and the loss coefficient A2 in a narrow space is set to 0.83.

FIG. 10 is an explanatory sectional view of a facility building having a plurality of floors. As shown in FIG. 10, when floors 11 are adjacent to each other on the upper and lower floors and a space connection portion 18 such as a staircase is provided straddling the upper floor and the lower floor, an access point AP installed on the floor 11 on the upper floor transmits a radio wave. The generated radio wave W leaks to the floor 11 on the lower floor as a leaked radio wave Wa through the space connection portion 18. Focusing on this point, assuming that a virtual access point (virtual radio station) VAP that emits leaked radio waves Wa is installed at the installation position of the spatial connection unit 18 on the floor 11 on the lower floor, the radio wave strength in each block described above is assumed. Estimates may be calculated. In this case, in the virtual access point VAP, the identification information is the same as that of the access point AP on the upper floor, and it is preferable that the AP transmission radio field intensity is the measured value in the immediate vicinity of the virtual access point VAP. In addition, compared to the normal access point AP, the virtual access point VAP narrows the range of the block that the radio wave reaches, and the calculation of the radio wave strength estimation value is replaced with the formula (1), so that the radio wave strength estimation value is attenuated linearly. A calculation formula may be used. The space connection portion 18 is not particularly limited, and may be a stairwell, an escalator, or the like as long as a space for leaking radio waves is formed.

By calculating the radio wave intensity estimated value assuming that the virtual access point VAP is installed as described above, it is possible to increase the transmission points of the radio waves referred to in the radio wave strength map 20. As a result, the amount of information in the radio wave intensity map 20 increases, and the accuracy of the position estimation of the block B using the radio wave intensity map 20 can be improved.

Next, with reference to FIG. 11, an indoor positioning system using the radio field intensity map will be described. FIG. 11 is a diagram showing an overall configuration of an indoor positioning system. The indoor positioning system 50 includes a server 51 and a terminal device 52. The server 51 and the terminal device 52 are communicably connected to each other via the network 53. The terminal device 52 is equipped with software for realizing navigation or software for displaying or notifying the current position in the facility building. The terminal device 52 is connected to the network 53 by wireless communication such as WiFi via a plurality of access points (APs) 54 provided in the facility building.

FIG. 12 is a functional block diagram showing a configuration example of the server. As shown in FIG. 12, the server 51 includes a storage means 60, an input means 61, a map generation means 62, a communication means 63, and a position estimation means 64. Note that FIG. 12 mainly shows the functional blocks related to indoor positioning using the radio field intensity map in the present embodiment, and the server 51 also has other functional blocks necessary for other processing as appropriate. There is.

The storage means 60 is composed of a memory, a hard disk, and the like, and stores the radio wave intensity map 20 (see FIG. 7) in addition to the plan view data 60a and access point data 60b described above as facility information. Facility information is input to the storage means 60 remotely from an external server or from a personal computer via the input means 61.

The map generation means 62 generates the radio field intensity map 20 by the above-mentioned method based on the plan view data 60a and the access point data 60b stored in the storage means 60.

The communication means 63 constitutes an external communication interface of the server 51. The communication means 63 receives the received radio wave intensity measured by the terminal device 52 via the network 53, and transmits the block position information and the like of the terminal device 52 obtained by the position estimation means 64.

The position estimation means 64 extracts the identification information of the access point 54 output from the terminal device 52 and the block corresponding to the received radio wave intensity from the radio wave intensity map 20, and estimates the block in which the terminal device 52 is located. Specifically, a block in which the radio field intensity received by the terminal device 52 falls within the range of the upper limit value and the lower limit value in each block of the radio wave strength map 20 is specified. If the specified block is one in the radio field intensity map 20, the position of the block is estimated as the position of the terminal device 52. If there are a plurality of the specified blocks in the radio field intensity map 20, the average distance between the blocks is estimated as the position of the terminal device 52. For example, as shown by the thick line in FIG. 7, when the received radio field intensity of the terminal device 52 is -20 or less and the lower limit value is -40 or more in both the second and third blocks, the terminal device 52 The position of is estimated to be an intermediate position between the second and third blocks.

FIG. 13 is a functional block diagram showing a configuration example of the terminal device. As shown in FIG. 13, the terminal device 52 includes an operation means 70, a display means 71, a storage means 72, an AP information acquisition means 73, a direction acquisition means 74, and a communication means 75. .. Note that FIG. 13 mainly shows the functional blocks related to indoor positioning using the radio field intensity map in the present embodiment, and the terminal device 52 also has other functional blocks necessary for other processing. There is.

The operation means 70 is composed of a device capable of converting an operation input from a user such as a key, a button, and a touch panel into an electric signal, and receives an input to the terminal device 52.

The display means 71 is composed of display devices such as a display and a monitor, and displays various images in which the position estimation result of the terminal device 52 can be visually recognized via a navigation application or the like. While the image is being displayed by the display means 71, the position estimation result may be output by voice by an output device such as a speaker.

The storage means 72 is composed of a memory, a hard disk, and the like, and stores an application for displaying the position estimation result of the terminal device 52 by the operation means 70 and various data transmitted from the server 51. The storage means 72 may be mounted on an external storage device (for example, an external server), and the terminal device 52 may be configured to use the storage means of the external server via the network 53 by the communication means 75. The AP information acquisition means 73 measures the radio wave intensity from the access point and acquires the identification information of the access point.

The orientation acquisition means 74 detects an orientation in the horizontal plane of the terminal device 52 (hereinafter, simply referred to as an orientation) and an angle in a vertical plane perpendicular to the floor surface (hereinafter, simply referred to as an angle). The directional acquisition means 74 is composed of, for example, an azimuth sensor and an angle sensor.

The communication means 75 includes a wireless module that wirelessly communicates with an access point 54 (see FIG. 11) and a wireless base station (not shown). The communication means 75 transmits an information distribution request to the server 51 via the access point 54 and the network 53, while acquiring the estimated position information of the terminal device 52 transmitted from the server 51.

The terminal device 52 may be provided with the map generation means 77 and the position estimation means 78 having the same functions as the map generation means 62 and the position estimation means 64 of the server 51. In this case, the terminal device 52 receives various information stored in the storage means 60 of the server 51 via the communication means 75 and the network 53, and maps the above-mentioned processes of the map generation means 62 and the position estimation means 64. The means 77 or the position estimation means 78 may be used. The map generation means 62, 77 and the position estimation means 64, 78 of the server 51 and the terminal device 52 may be in at least one of them.

Next, verification of position estimation using a radio field intensity map will be described. The verification locations were the station premises of Shinjuku Station as the facility building, the south exit / southeast exit concourse shown in Fig. 14, and the east exit / west exit / east exit central concourse shown in Fig. 15. A WiFi access point was installed at the point marked with a "★" in the floor diagram. On each floor, a radio field intensity map was created as described in the above embodiment. With reference to the created radio field intensity map, the block position, which is the own position of the terminal device, was estimated multiple times at the measurement points s01 to s028 and ss01 to ss12 shown in the figure. From a plurality of position estimates, the own position of the terminal device and the estimated block position were compared, and the error was evaluated when the error was the smallest. As an evaluation result, in 40 measurement points s01 to s028 and ss01 to ss12, 20 measurement points have an error within 10 m and 31 measurement points have an error within 20 m. In other words, of all the measurement points, 50% of the measurement points had an error of 10 m or less, and about 78% of the measurement points had an error of 20 m or less, which was a generally reasonable position estimation.

According to the above-described embodiment, the radio wave strength in each block B can be calculated based on the facility information without actually measuring the radio wave strength from the access point AP on the floor 11, and the measurement by the operator is possible. The work can be omitted. As a result, the work load for creating the radio wave intensity map 20 can be reduced, and the radio wave intensity map 20 can be created in a short time.

Moreover, in the calculation of the radio field intensity estimation value in each block B, the amount of loss according to the length transmitted through the transmission space 13 is subtracted, so that an obstacle such as the propagation loss estimation method according to the ITU-R recommendation is used. The count can be omitted. This also makes it possible to easily create the radio field intensity map 20 by reducing the work load and the processing load.

Further, since the calculation is made so that the estimated value of the radio field intensity in each block B increases based on the tendency that the radio wave intensity is amplified in the narrow space 15 found by the result of repeating the actual measurement and the verification, the radio wave intensity is estimated. The accuracy of the value can be improved.

The present invention is not limited to the above embodiment, and can be modified in various ways. In the above embodiment, the size, shape, direction, etc. shown in the attached drawings are not limited to this, and can be appropriately changed within the range in which the effect of the present invention is exhibited. In addition, it can be appropriately modified and implemented as long as it does not deviate from the scope of the object of the present invention.

For example, when the facility building has a plurality of floors, the radio field intensity map 20 may be generated on each of the plurality of floors and managed as a library. In this case, the floor number of the installation position is included as the identification information of the access point AP, and the floor number of the facility building can be included as the position estimation of the terminal device.

INDUSTRIAL APPLICABILITY The present invention is useful for generating a radio wave intensity map that estimates the current position of a pedestrian or the like moving in a building such as a large-scale station building based on the radio wave intensity received from an access point.

11 Floor 12 Position estimation target space 13 Transmission space 14 Normal space 15 Narrow space 18 Spatial connection 20 Radio intensity map 52 Terminal device AP access point (radio station)
B block VAP virtual access point (virtual radio station)

Claims (5)

It is a method of generating a radio field intensity map that is referred to for estimating the position of a terminal device on the floor of an indoor space in a facility building.
On the floor, the first division step that divides the position estimation target space that is the position estimation target of the terminal device into the transmission space that is not the position estimation target of the terminal device.
After the execution of the first division step, the second division step that divides the position estimation target space into a narrow space sandwiched between the transmission spaces adjacent to each other and a normal space that is a space that is not the narrow space.
A block division step that divides the floor into blocks that serve as position identification units, and
The amount of loss according to the linear distance between each block in the position estimation target space and at least one radio station that emits radio waves that can be received by the block, and the length transmitted through the transmission space in the straight line. A calculation step of subtracting the corresponding loss amount from the transmitted radio wave strength of the radio station and calculating the radio wave strength estimated value received by the block, and
A matrix is formed by the plurality of blocks and the plurality of radio stations, and the matrix is provided with a map generation step of inputting the radio field intensity estimated value calculated in the calculation step to obtain a radio field strength map.
Wherein the calculation step, the at radio strength estimate calculations, radio intensity map the straight line and said Rukoto added increasing amounts corresponding to the length of passing through the narrow space in the outgoing radio wave intensity of the radio station How to generate. The method for generating a radio field intensity map according to claim 1 , wherein the radio wave intensity estimated value in the calculation step is calculated by the following equation.
Estimated signal strength = transmitted signal strength- (Nlog ₁₀ D) (1 + (A1-1) L1 / D + (A2-1) L2 / D)
N is the reference value [dB] of the radio wave propagation loss from the radio station, D is the distance [m] between the radio station and the block, A1 is the loss coefficient in the transmission space, and L1 is the propagation distance [m] in the transmission space. ], A2 is the loss coefficient in the narrow space, and L2 is the propagation distance [m] in the narrow space. The facility building is provided with a spatial connection portion provided across a plurality of floors adjacent to each other in the vertical direction.
In the calculation step, a virtual radio station that emits a leaked radio wave when it is transmitted from the radio station installed on one floor and the radio wave leaks to another floor as a leaked radio wave through the space connection portion. The method for generating a radio wave intensity map according to claim 1 or 2 , wherein the radio wave intensity estimated value received by the block is calculated assuming that the space connection portion is installed. On the floor of the indoor space in the facility building, the position estimation target space that is the position estimation target of the terminal device and the transmission space that is not the position estimation target of the terminal device are divided, and then the position estimation target space is close to each other. The floor is divided into a narrow space sandwiched between the transmitted spaces and a normal space that is not the narrow space, and the floor is divided into blocks that serve as position identification units, and radio wave propagation loss between the radio station and the blocks. Is a propagation loss estimation method characterized by calculating by the following equation.
Formula radio wave propagation loss = (Nlog ₁₀ D) (1+ (A1-1) L1 / D + (A2-1) L2 / D)
N is the reference value [dB] of the radio wave propagation loss from the radio station, D is the distance [m] between the radio station and the block, A1 is the loss coefficient in the transmission space, and L1 is the propagation distance [m] in the transmission space. ], A2 is the loss coefficient in the narrow space, and L2 is the propagation distance [m] in the narrow space. A map generation means for generating a radio field intensity map by the method for generating a radio wave intensity map according to any one of claims 1 to 3.
A storage means for storing the radio field intensity map generated by the map generation means, and a storage means.
The block corresponding to the received radio wave intensity measured by the terminal device is extracted from the radio wave intensity map stored in the storage means, and the block is provided with a position estimation means for estimating the block in which the terminal device is located. An indoor positioning system characterized by being

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