Method for determining arrangement of antennas, device, program, and object detection system

Abstract

To determine an antenna arrangement which allows an object to be detected highly accurately with a small load.SOLUTION: According to an antenna arrangement determination method of the present disclosure, a target region to detect an object using an access point (AP) and a single terminal (STA) including a plurality of antennas is virtually divided into a plurality of sub-regions. Next, a first type of scores (a first score S1 and a second score S2a) which become larger as the number of sub-regions on a path of a direct wave between a position of the STA and a position candidate of the antenna becomes larger and a second type of scores (third score S2b) which becomes larger as the number of sub-regions on a path of a reflection wave becomes larger are computed. Then, an evaluation index value S which becomes larger as the first type of scores is larger and which becomes smaller as the second type of score is larger is computed for each combination of position candidates of the antennas. Finally, a combination of positions to arrange the antennas is determined from among a high-order predetermined number of combinations of position candidates with the evaluation index value S selected in ascending order.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a technique for determining the arrangement of antennas in a system for detecting an object using radio waves. [Background technology]

[0002] As a method for estimating the position of an object using radio waves such as Wi-Fi, a method is known in which the object is detected based on the state of multipath waves (CSI: Channel State Information) that changes due to an object in a detection area. For example, Patent Document 1 proposes a method in which the object position is used as a label to create training data together with the corresponding CSI, a learning model is generated by machine learning using the training data, and the CSI is input into the learning model to detect an object in a target area.

[0003] FIG. 11 shows one embodiment of the object detection method disclosed in Patent Document 1. In this example, the target area for object detection is divided vertically into eight and horizontally into four, resulting in a total of 32 small areas. Then, using the conventional method described above, it is estimated in which small area (numbered 1 to 32) an object exists. A wireless LAN conforming to the IEEE802.11ac or later standard (ac / ax / be, etc.) is used as the wireless system, and object detection is performed based on the CSI between one access point (AP) and one terminal (STA). The AP has four antennas. The STA has one antenna.

[0004] In the example shown in Figure 11, twelve candidate positions for antenna placement are set around the target area, indicated by circled numbers from 1 to 12. Antennas are placed at four positions selected from behind these twelve positions. Since the accuracy of object detection varies depending on the combination of the four antenna positions, the detection accuracy is calculated by computer-based simulation for all 495 combinations of the four antenna positions. However, if simulations such as ray tracing or experiments with real objects were to be performed for all of the enormous number of antenna placement patterns, the load required would be extremely large.

[0005] Therefore, the inventors of the present application have been researching a new method for determining antenna layout without performing simulations or experiments, or without requiring simulations or experiments with many layout patterns. One of the things considered in the new method is the experimental results reported in Non-Patent Document 1. Non-Patent Document 1 reports experimental results showing that in high frequency bands, the object detection rate deteriorates in areas where the influence of direct waves is large and areas where the influence of reflected waves is small. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-034878 [Non-patent literature]

[0007] [Non-Patent Document 1] Murakami et al., “Experimental Evaluation of Wireless Sensing Using 5GHz and 28GHz CSI,” 2021 IEICE Society Conference, B-1-82 Summary of the Invention [Problem to be solved by the invention]

[0008] Figures 12 and 13 are diagrams showing the results of an experiment conducted by the inventors of the present application. In this experiment, as in the embodiment of Figure 11, the target area for object detection was divided into a total of 32 small areas, and 12 antenna position candidates were set around the target area. However, the target area was surrounded by walls.

[0009] In the experiment whose results are shown in Fig. 12, antennas were installed at positions 5, 6, 7, and 8, and wireless communication was performed with STAs placed between small areas 16 and 17 around the target area. In the experiment whose results are shown in Fig. 13, antennas were installed at positions 1, 2, 11, and 12, and wireless communication was performed with STAs placed between small areas 16 and 17 around the target area. The straight lines connecting the STAs and each antenna indicate the paths of direct waves between the STAs and each antenna.

[0010] In each experiment, CSI was measured for each subcarrier in two adjacent small regions, and the CSI measurement results were compared between the small regions. Specifically, in the experiment shown in Fig. 12, a comparison was made between small regions 2 and 3, and between small regions 16 and 17. In the experiment shown in Fig. 13, a comparison was made between small regions 9 and 10, between small regions 2 and 3, and between small regions 16 and 17.

[0011] The experimental results shown in Fig. 12 show that in small areas 16 and 17, which are in a direction blocking the direct wave, the CSI varies greatly depending on the subcarrier, and that the change in CSI for the subcarrier differs greatly between areas 16 and 17. In contrast, in small areas 2 and 3, which are in the direction along the direct wave, the change in CSI for the subcarrier is small, and the difference in the change in CSI for the subcarrier between areas 2 and 3 is also small.

[0012] In the experiment shown in Figure 13, small areas 16 and 17 are in a direction that blocks the direct wave, while small areas 2 and 3 are in a direction along the direct wave. In small areas 16 and 17, the CSI varies greatly depending on the subcarrier, and the change in CSI for the subcarrier differs greatly between the small areas. In addition, in small areas 2 and 3, the change in CSI for the subcarrier is small, and the difference in the change in CSI for the subcarrier between the small areas is also small. Taking these experimental results together, it can be said that in object detection using direct waves, the accuracy of position estimation may be significantly degraded depending on the relationship with the path of the direct wave.

[0013] On the other hand, there are no direct waves in small areas 9 and 10 in Figure 13, and these small areas are far away from the path of the direct waves. However, not only direct waves but also radio waves reflected by the surrounding walls, i.e., reflected waves, exist within the target area. In small areas 9 and 10, the CSI varies greatly depending on the subcarrier, and the change in CSI for the subcarrier differs greatly between small areas. This is thought to be due to the influence of reflected waves present in small areas 9 and 10. The experimental results confirmed that the presence of reflected waves improves the accuracy of location estimation.

[0014] It is expected that highly accurate object detection will be possible by reflecting the knowledge obtained from the above experimental results in determining the antenna arrangement, in addition to the knowledge obtained from the experimental results reported in Non-Patent Document 1. The present disclosure aims to provide a technology that can determine, with a small load, an antenna arrangement that enables highly accurate object detection. [Means for solving the problem]

[0015] The present disclosure provides an antenna arrangement determination method for achieving the above object. The antenna arrangement determination method of the present disclosure is a method for determining an antenna arrangement in a system for detecting an object using a first wireless device having a plurality of antennas and a second wireless device that performs wireless communication with the first wireless device. The antenna arrangement determination method of the present disclosure includes the following first to sixth steps. The first step is a step of virtually dividing a target area in which object detection is performed into a plurality of small areas. The second step is a step of selecting a combination of antenna position candidates from positions where antennas can be arranged. The third step is a step of calculating a first type score for each combination of the plurality of antenna position candidates, which increases as the number of small areas on the path of a direct wave between the position of the second wireless device and the position candidates of the plurality of antennas increases. The fourth step is a step of calculating a second type score for each combination of the plurality of antenna position candidates, which increases as the number of small areas on the path of a reflected wave between the position of the second wireless device and the position candidates of the plurality of antennas increases. The fifth step is a step of calculating, using the first type score and the second type score, an evaluation index value that increases as the first type score increases and decreases as the second type score increases for each combination of the plurality of antenna position candidates. The sixth step is to select a top predetermined number of combinations from among the combinations of candidate antenna positions in order of decreasing evaluation index value, and to determine a combination of positions for placing the multiple antennas from among the selected top predetermined number of combinations.

[0016] The present disclosure provides an antenna arrangement determination device for achieving the above object. The antenna arrangement determination device of the present disclosure is a device for determining an antenna arrangement in a system for detecting an object using a first wireless device having a plurality of antennas and a second wireless device that performs wireless communication with the first wireless device. The antenna arrangement determination device of the present disclosure is configured to execute the following first to sixth processes. The first process is a process for virtually dividing a target area in which object detection is performed into a plurality of small areas. The second process is a process for selecting a combination of antenna position candidates from among positions where antennas can be arranged. The third process is a process for calculating a first type score for each combination of the plurality of antenna position candidates, which increases as the number of small areas on a path of a direct wave between the position of the second wireless device and the position candidates of the plurality of antennas increases. The fourth process is a process for calculating a second type score for each combination of the plurality of antenna position candidates, which increases as the number of small areas on a path of a reflected wave between the position of the second wireless device and the position candidates of the plurality of antennas increases. The fifth process is a process for calculating an evaluation index value for each combination of the plurality of antenna position candidates using the first type score and the second type score, which increases as the first type score increases and decreases as the second type score increases. The sixth process is a process of selecting a top predetermined number of combinations from among the combinations of candidate antenna positions in order of decreasing evaluation index value, and determining a combination of positions for placing the multiple antennas from among the selected top predetermined number of combinations.

[0017] The present disclosure also provides an antenna arrangement determination program for achieving the above object. The antenna arrangement determination program of the present disclosure is a program for determining the arrangement of antennas in a system that detects an object using a first wireless device having a plurality of antennas and a second wireless device that wirelessly communicates with the first wireless device. The antenna arrangement determination program of the present disclosure is configured to cause a computer to execute the first to sixth processes described above.

[0018] The present disclosure further provides an object detection system using the above antenna location determination device. The object detection system of the present disclosure is a system for detecting an object within a target area. The object detection system of the present disclosure includes a first wireless device having multiple antennas, a second wireless device that performs wireless communication with the first wireless device, and the above antenna location determination device. In the object detection system of the present disclosure, the antennas are located at positions determined by the above antenna location determination device relative to the position of the second wireless device. Effect of the Invention

[0019] In the technology disclosed herein, a top predetermined number of combinations are selected from the combinations of the position candidates of the multiple antennas in ascending order of evaluation index value, and a combination of positions for arranging the multiple antennas is determined from among them. A first type score and a second type score are used to calculate the evaluation index value. The first type score is a score that increases as the number of small areas on the path of the direct wave between the position of the second wireless device and the position candidates of each antenna increases. On the other hand, the second type score is a score that increases as the number of small areas on the path of the reflected wave between the position of the second wireless device and the position candidates of each antenna increases. The evaluation index value is calculated to be larger as the first type score increases and smaller as the second type score increases. According to this method, it is possible to determine an antenna arrangement that enables object detection with high accuracy by reducing the influence of direct waves and increasing the influence of reflected waves with a small load. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 illustrates an example of a configuration of an antenna arrangement determination device. [Diagram 2] FIG. 11 is a flow diagram showing an example of a procedure for determining an antenna arrangement. [Diagram 3] FIG. 13 is a diagram illustrating calculation of a first score. [Figure 4] FIG. 11 is a flow diagram showing a procedure for calculating a first score. [Diagram 5] FIG. 13 is a diagram illustrating calculation of a second score. [Figure 6] FIG. 11 is a flow diagram showing a procedure for calculating a second score. [Figure 7] FIG. 13 is a diagram illustrating calculation of a third score. [Figure 8] FIG. 11 is a flow chart showing a procedure for calculating a third score. [Figure 9] FIG. 13 is a diagram showing a table for calculating an evaluation index value. [Figure 10] FIG. 13 is a diagram illustrating an example of a relationship between an evaluation index value and an average error distance. [Figure 11] FIG. 1 is a diagram illustrating an example of a conventional object detection method. [Figure 12] FIG. 13 is a diagram showing experimental results regarding the relationship between a direct wave and the accuracy of position estimation. [Figure 13] 11A and 11B are diagrams illustrating experimental results regarding the relationship between reflected waves and accuracy of position estimation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] 1. Antenna layout determination device First, an example of the configuration of an antenna arrangement determination device according to an embodiment of the present disclosure will be described with reference to Fig. 1. The antenna arrangement determination device 10 constitutes an object detection system together with an access point (AP) 2 as a first wireless device and a terminal (STA) 6 as a second wireless device that performs wireless communication with the AP2. Object detection is performed, for example, based on CSI, which indicates the state of radio waves within a target area TA where object detection is performed. Multiple antennas 4 of the AP2 are arranged at positions determined by the antenna arrangement determination device 10 with respect to the position of the STA6.

[0022] The antenna arrangement determination device 10 is a computer including an input / output interface 11, a processor 12, a program memory 13, and an information memory 15. The number of each of the processor 12, the program memory 13, and the information memory 15 may be plural.

[0023] The processor 12 may be a CPU, RISC, DSP, FPGA, ASIC, PLD, or another processing unit, or may be a combination of two or more thereof, or may be a dedicated processor for the antenna placement determination apparatus 10. The processor 12 may also be communicatively coupled to a program memory 13 and an information memory 15, or may include the program memory 13 and the information memory 15.

[0024] The program memory 13 stores a plurality of instructions 14 executable by the processor 12. A program consisting of the plurality of instructions 14 may be stored in a computer-readable non-transitory storage medium, or may be provided via a network. The instructions 14 constituting the antenna arrangement determination program are executed by the processor 12, causing the antenna arrangement determination device 10 to implement the antenna arrangement determination method. The information memory 15 stores various information required to implement the antenna arrangement determination method.

[0025] Conditions for determining antenna placement are input to the input / output interface 11. The conditions to be input include the shape of the target area TA and the number of divisions into small areas, the number of antennas 4 of the AP2, positions where the antennas 4 can be placed, and the placement positions of the STA6. In the example shown in Fig. 1, the target area TA is virtually divided into 32 small areas numbered 1 to 32. The number of antennas 4 of the AP2 is four, and 12 position candidates for the antennas 4, numbered 1 to 12, indicated by circled numbers, are set. The STA6 is placed between the small areas numbered 16 and 17 around the target area TA.

[0026] The instructions 14 cause the processor 12 to execute processing for determining an antenna arrangement based on the conditions input to the input / output interface 11. The antenna arrangement determination method implemented by the antenna arrangement determination device 10 will now be described in detail.

[0027] 2. Antenna placement decision method 2-1. Procedure for determining antenna placement Fig. 2 is a flow diagram showing an example of a procedure for determining an antenna arrangement. The antenna arrangement determination device 10 executes the antenna arrangement determination method according to the procedure shown in Fig. 2. One feature of the antenna arrangement determination method according to this embodiment is that two types of scores are calculated for each combination of position candidates for the antenna 4 (also referred to as a placement pattern of the antenna 4), and an evaluation index value S for evaluating the placement pattern is calculated based on the two types of scores. The calculation of the evaluation index value S is performed for each combination of position candidates for the antenna 4.

[0028] The two types of scores are a first type score and a second type score. The first type score is a score that reflects the influence of the direct wave between the STA6 and each antenna 4. More specifically, the first type score is a score that increases as the number of small areas on the path of the direct wave increases. The first type score includes a first score S1 and a second score S2a. In the antenna arrangement determination method according to this embodiment, the number of small areas on the path of the direct wave between the STA6 and each antenna 4 is calculated as the first score S1 (step S101). In addition, the total number of small areas on the path counted for each path of the direct wave between the STA6 and each antenna 4 is calculated as the second score S2a (step S102). Details of the first score S1 and the second score S2a and the calculation procedure will be described later.

[0029] On the other hand, the second type of score is a score that reflects the influence of the reflected wave between the STA 6 and each antenna 4. More specifically, the second type of score is a score that increases as the number of small areas on the path of the reflected wave increases. The second type of score includes a third score S2b. In the antenna arrangement determination method according to this embodiment, the total number of small areas on the path counted for each path of the reflected wave between the STA 6 and each antenna 4 is calculated as the third score S2b (step S103). Details of the third score S2b and the calculation procedure will be described later. Note that the order of calculation of the first score S1, the second score S2a, and the third score S2b is not limited to the order shown in the flow diagram. They may be calculated in an order different from that shown in the flow diagram, or may be calculated in parallel.

[0030] After the first score S1, the second score S2a, and the third score S2b are calculated, the evaluation index value S is calculated using them. According to the flow diagram, first, the score difference S2 between the second score S2a and the third score S2b is calculated (step S104). Then, the numerical value obtained by multiplying the first score S1 by the score difference S2 is calculated as the evaluation index value S (step S105). According to such a calculation, the larger the second score S2a, the larger the evaluation index value S, and the larger the third score S2b, the smaller the evaluation index value S. Furthermore, when the first score S1 is large, the second score S2a is also large, so that the score difference S2 is likely to be a positive value. When the score difference S2 is a positive value, the larger the first score S1, the larger the evaluation index value S. Thus, in the antenna arrangement determination method according to this embodiment, the evaluation index value S is calculated to be larger as the first type score is larger, and smaller as the second type score is larger.

[0031] When the evaluation index value S has been calculated for all the arrangement patterns of the antenna 4, a top predetermined number (here, M) of arrangement patterns are selected from all the arrangement patterns of the antenna 4 in ascending order of evaluation index value S (step S106). Then, from the selected top M arrangement patterns, the arrangement pattern with the highest object detection accuracy is adopted as the pattern in which the antenna 4 is actually arranged (step S107). If the top M arrangement patterns are one, the selected arrangement pattern is adopted as the optimal arrangement pattern as is. If the top M arrangement patterns are more than one, for example, a simulation or experiment such as ray tracing is performed for each of the selected M arrangement patterns, and the optimal arrangement pattern is determined based on the results of the simulation or experiment.

[0032] According to the above-described method, by reducing the influence of direct waves and increasing the influence of reflected waves, it is possible to determine an arrangement pattern of antennas 4 that enables highly accurate object detection with a small load.

[0033] 2-2. Calculation of the first score 3 is a diagram for explaining the calculation of the first score S1 performed in step S101 of the procedure for determining the antenna placement. In the example shown in Fig. 3, the antenna 4 is placed at the position candidates No. 5 to No. 8.

[0034] In the calculation of the first score S1, the number of small areas through which the direct wave of the radio wave between the antenna 4 and the STA 6 has passed is counted. Specifically, each antenna 4 and the STA 6 are connected by a straight line, and the number of small areas through which the straight line passes is counted. In the example shown in FIG. 3, the small areas with the number "0" are areas through which the direct wave does not pass, and the small areas with the number "1" are areas through which the direct wave passes. The sum of the numerical values ​​of all the small areas constituting the target area is calculated as the first score S1 of the arrangement pattern of the corresponding antenna 4. In the example shown in FIG. 3, the first score S1 of the arrangement patterns of No. 5, No. 6, No. 7, and No. 8 is 22 points. This calculation is performed for all 495 arrangement patterns.

[0035] Fig. 4 is a flow diagram showing the procedure for calculating the first score S1. The antenna arrangement determination device 10 executes the calculation according to this flow diagram. In the flow diagram, Narea indicates the number of small areas, and Np indicates the number of arrangement patterns of the antenna 4. In the example shown in Fig. 3, Narea = 32, and Np = 495.

[0036] Step S201 is a repetitive process including steps S202 to S203. The processes from step S202 to S203 are repeatedly executed for each of the arrangement patterns of the antennas 4 from No. 1 to No. Np.

[0037] In step S202, all antennas 4 and STAs 6 are connected by straight lines.

[0038] Step S203 is a repetitive process including steps S204 to S205. The processes from step S204 to S205 are repeatedly executed for each of the small areas No. 1 to No. Narea.

[0039] In step S204, it is determined whether or not a straight line passes through the small region focused on in step S203. If a straight line does not pass through the small region, the process of step S205 is skipped, and if a straight line passes through the small region, the process of step S205 is executed.

[0040] In step S205, a value of 1 is added to the first score S1(i). The first score S1(i) means the first score of the i-th arrangement pattern among the 1st to Npth arrangement patterns. The initial value of the first score S1(i) is zero. The determination in step S204 is performed for all antennas 4 from the 1st to the Nantth arrangement patterns and for all small regions from the 1st to the Nareath arrangement patterns, and the accumulated value of the positive determination results is output as the first score S1(i) of the i-th arrangement pattern.

[0041] When the first score S1 has been calculated for all the arrangement patterns, the condition of step S201 is met, and step S101 of the procedure for determining the antenna arrangement is completed.

[0042] 2-3. Calculation of the second score 5 is a diagram for explaining the calculation of the second score S2a performed in step S102 of the procedure for determining the antenna placement. In the example shown in Fig. 5, the antenna 4 is placed at the position candidates No. 5 to No. 8.

[0043] In the calculation of the second score S2a, the total number of small areas on the path counted for each path of the direct wave between the antenna 4 and the STA6 is calculated. Specifically, each antenna 4 and the STA6 are connected by a straight line, and the total number of small areas through which the straight line passes is calculated. In the example shown in FIG. 5, the small areas with the number "0" are areas where the direct wave does not pass. The small areas with the number "1" are areas where one direct wave passes, and the small areas with the number "2" are areas where two direct waves pass. The total value of the numerical values ​​of all the small areas constituting the target area is calculated as the second score S2a of the combination of the position candidates of the corresponding antenna 4, that is, the arrangement pattern of the antenna 4. In the example shown in FIG. 5, the second score S2a of the arrangement patterns of No. 5, No. 6, No. 7, and No. 8 is 34 points. Such calculation is performed for all 495 arrangement patterns.

[0044] Fig. 6 is a flow diagram showing the procedure for calculating the second score S2a. The antenna arrangement determination device 10 executes the calculation according to this flow diagram. In the flow diagram, Narea indicates the number of small regions, Np indicates the number of arrangement patterns of the antennas 4, and Nant indicates the number of antennas 4. In the example shown in Fig. 5, Narea = 32, Np = 495, and Nant = 4.

[0045] Step S301 is a repetitive process for repeating the process of step S302. The process of step S302 is repeatedly executed for each of the arrangement patterns of the antennas 4 from No. 1 to No. Np.

[0046] Step S302 is a repetitive process including the processes from step S303 to step S304. The processes from step S303 to step S304 are repeatedly executed for each of antennas 4 from No. 1 to No. Nant.

[0047] In step S303, the j-th antenna 4 among the antennas 1 to Nant is connected to the STA 6 by a straight line.

[0048] Step S304 is a repetitive process including steps S305 to S306. The process from step S305 to step S306 is repeated for each of the small areas No. 1 to No. Narea.

[0049] In step S305, the number of straight lines passing through the small area focused on in step S304 is counted.

[0050] In step S306, the count number obtained in step S305 is added to the second score S2a(i). The second score S2a(i) means the second score of the i-th arrangement pattern among the 1st to the Npth arrangement pattern. The initial value of the second score S2a(i) is zero. The counting in step S305 is performed for all antennas 4 from the 1st to the Nantth arrangement pattern and for all small regions from the 1st to the Nareath arrangement pattern, and the integrated value of the count number is output as the second score S2a(i) of the i-th arrangement pattern.

[0051] When the second scores S2a are calculated for all the arrangement patterns, the condition of step S301 is met, and step S102 of the procedure for determining the antenna arrangement is completed.

[0052] 2-4. Calculation of the third score Fig. 7 is a diagram for explaining the calculation of the third score S2b performed in step S103 of the procedure for determining the antenna placement. Here, assuming a maximum of two reflections, a method for determining the area through which the radio wave passes by the imaging method in each case of a direct wave (n=0), a wave reflected once (n=1), and a wave reflected twice (n=2) is described. In the example shown in Fig. 7, the antenna 4 is placed at position candidates 5 to 8. However, for simplicity, in the example shown in Fig. 7, the target area is virtually divided into four small areas, 1 to 4.

[0053] In the imaging method, target areas for single reflected waves are drawn to the left and right of the central target area for direct waves. At this time, the arrangement of the small areas (arrangement of the small area numbers) is reversed left and right. In addition, target areas for single reflected waves are drawn above and below the central target area for direct waves. At this time, the arrangement of the small areas is reversed up and down. Next, a target area for double reflected waves is drawn to the right or left of the target area for single reflected waves. In this case, the arrangement of the small areas is further reversed left and right. In addition, a target area for double reflected waves is drawn above or below the target area for single reflected waves. In this case, the arrangement of the small areas is further reversed up and down. Then, a STA6 corresponding to each target area is drawn, and straight lines are drawn to connect the position candidates for antenna 4 set in the central target area to the STA6 of each target area.

[0054] As an example, in Fig. 7, a straight line (dotted line) is drawn connecting antenna 4 in position candidate No. 6 and STA6 in the target area for double-reflected waves, which is two areas to the left of the central target area. This dotted line shows one of the double-reflected waves (the double-reflected wave shown by the broken line in the central target area for direct waves) heading from antenna 4 in position candidate No. 6 to STA6.

[0055] In calculating the third score S2b, the number of small areas through which each straight line passes is counted. In the example shown in Fig. 7, the double reflected wave shown by the dotted line passes through a total of five small areas, number 4, number 4, number 2, number 1, and number 1. Therefore, in the example shown in Fig. 7, the number of small areas through which the double reflected wave shown by the dotted line passes is counted as "5".

[0056] The above calculation is also performed for the line connecting antenna 4 in position candidate number 6 and STA 6 in another target area. Furthermore, a similar calculation is performed for the other three position candidates for antenna 4, and the third score S2b for the arrangement pattern of antenna 4 shown in Fig. 7 is calculated. Then, such calculation is performed for all 495 arrangement patterns.

[0057] As a modification of the calculation of the third score S2b, when counting the number of small areas through which the radio wave passes, a coefficient A according to the number of reflections is calculated. nThe count number may be multiplied by A0. Specifically, when the number of reflections is zero, it is multiplied by coefficient A0. The value of coefficient A0 may be 1. When the number of reflections is one, it is multiplied by coefficient A1 which is smaller than coefficient A0, and when the number of reflections is two, it is multiplied by coefficient A2 which is smaller than coefficient A1. In the example shown in FIG. 7, the number of small areas through which radio waves that have been reflected zero times pass is one, the number of small areas through which radio waves that have been reflected once pass is three, and the number of small areas through which radio waves that have been reflected two times pass is one. Therefore, the count number calculated by 1×A0+3×A1+1×A2 may be calculated as the score corresponding to the two-reflected waves shown in FIG. 7. Note that when coefficient A n The value of may be determined according to the material of the wall, for example. The same value may be used for the top, bottom, left, and right sides, or different values ​​may be used when the materials of the walls on the top, bottom, left, and right sides are different.

[0058] Furthermore, when the same reflected wave passes through the same area multiple times, it may be counted as one instead of being counted twice. In that case, the number of small areas through which the twice-reflected wave passes, as shown by the dotted line in Fig. 7, is counted as "3." Note that, although the example shown in Fig. 7 considers the once-reflected wave and the twice-reflected wave, it is also possible to consider only the once-reflected wave, or to consider more reflected waves including the three-reflected wave.

[0059] 8 is a flow diagram showing the procedure for calculating the third score S2b. The antenna arrangement determination device 10 executes the calculation according to this flow diagram. In the flow diagram, Narea indicates the number of small areas, Np indicates the number of arrangement patterns of the antennas 4, Nant indicates the number of antennas 4, and N indicates the maximum number of reflections to be considered.

[0060] Step S401 is a repetitive process for repeating the process of step S402. The process of step S402 is repeatedly executed for each of the arrangement patterns of the antennas 4 from No. 1 to No. Np.

[0061] Step S402 is a repetitive process for repeating the process of step S403. The process of step S403 is repeatedly executed for each of antennas 4 from No. 1 to No. Nant.

[0062] Step S403 is a repetitive process including steps S404 to S405. The process from step S404 to step S405 is repeated N times.

[0063] In step S404, the j-th antenna 4 among the antennas 1 to Nant and the STA 6 are connected by a straight line representing the radio waves reflected n times by the wall.

[0064] Step S405 is a repetitive process for repeating the process of step S406. The process of step S406 is repeatedly executed for each of the J straight lines drawn in step S404.

[0065] Step S406 is a repetitive process including steps S407 to S408. The processes from step S407 to S408 are repeatedly executed for each of the small areas No. 1 to No. Narea.

[0066] In step S407, the number of straight lines passing through the small area focused on in step S406 is counted.

[0067] In step S408, the count number obtained in step S407 is added to the third score S2b(i). The third score S2b(i) means the third score of the i-th arrangement pattern among the 1st to the Npth arrangement pattern. The initial value of the third score S2b(i) is zero. The count in step S407 is performed for all antennas 4 from the 1st to the Nantth arrangement pattern, for all small areas from the 1st to the Nareath arrangement pattern, and for the reflected waves for all reflections from one reflection to Nth reflections, and the integrated value of the count number is output as the third score S2b(i) of the i-th arrangement pattern.

[0068] When the third score S2b has been calculated for all the arrangement patterns, the condition of step S401 is met, and step S103 of the procedure for determining the antenna arrangement is completed.

[0069] 2-5. Calculation of evaluation index value Fig. 9 is a diagram for explaining the calculation of the evaluation index value S performed in steps S104 and S105 of the procedure for determining the antenna arrangement. A table shown in Fig. 9 is created in the information memory 15 of the antenna arrangement determination device 10. This table has cells for the first score S1, the second score S2a, the third score S2b, the score difference S2, and the evaluation index value S for each arrangement pattern of the antenna 4. In the table shown in Fig. 9, there are a total of 495 arrangement patterns of the antenna 4.

[0070] The cells of the table for the first score S1, the second score S2a, and the third score S2b are filled with the numerical values ​​obtained by the calculations in steps S101, S102, and S103. For the arrangement patterns in which the cells of the first score S1, the second score S2a, and the third score S2b have been filled, the score difference S2 and the evaluation index value S are then calculated. First, the difference between the second score S2a and the third score S2b is entered into the cell of the score difference S2. Then, the numerical value obtained by multiplying the first score S1 by the score difference S2 is entered into the cell of the evaluation index value S. In this manner, the cells of the evaluation index value S are filled for all 495 arrangement patterns.

[0071] When the cells of the evaluation index value S are filled in for all the arrangement patterns, the antenna arrangement determination device 10 sorts the table in ascending order of the evaluation index value S. In the sorted table, the arrangement patterns of the antennas 4 are arranged in ascending order of the evaluation index value S.

[0072] 2-6. Determining antenna placement Fig. 10 is a diagram for explaining the determination of antenna arrangement performed in steps S106 and S107 of the procedure for determining antenna arrangement. There is a relationship between the evaluation index value S and the average error distance in object detection as shown in the graph in Fig. 10. The horizontal axis of the graph represents the antenna arrangement patterns after sorting for the evaluation index value S. Therefore, the evaluation index value S decreases from right to left on the graph. The average error distance is the result of an actual experiment performed in the target area TA shown in Fig. 1.

[0073] From the graph shown in Fig. 10, it can be seen that, overall, the smaller the evaluation index value S, the smaller the average error distance tends to be. In other words, there is a correlation between the evaluation index value S and the average error distance, as shown by the arrow line in Fig. 10. Based on such correlation, the top M antenna arrangement patterns with the smallest evaluation index values ​​S are selected as candidates for the pattern in which the antenna 4 is actually arranged.

[0074] In Fig. 10, the top 10 antenna arrangement patterns with the smallest evaluation index value S are extracted in a separate graph. As can be seen from the graph, there is a difference in the average error distance even among the top 10 antenna arrangement patterns with the smallest evaluation index value S. The reason for performing simulations such as ray tracing or experiments on the selected top M antenna arrangement patterns is to ensure that the antenna arrangement pattern with the smallest average error distance is selected.

[0075] According to the above antenna arrangement determination method, it is possible to determine an antenna arrangement that enables highly accurate object detection with a smaller load than when simulations and experiments are performed for all antenna arrangement patterns.

[0076] If the top M are counted as 1, the antenna arrangement pattern with the smallest evaluation index value S is adopted as the pattern for actually arranging the antennas 4. Since the smaller the evaluation index value S, the smaller the average error distance tends to be, there is little possibility that the object detection accuracy will decrease even if such an antenna arrangement pattern is selected. On the other hand, since there is no need to perform simulations or experiments, it is possible to determine an antenna arrangement that can detect objects with high accuracy with very little load.

[0077] 3. Other embodiments The first score S1 is not necessarily required in the calculation of the evaluation index value S. The score difference S2, which is the difference between the second score S2 and the third score S2b, may be used as the evaluation index value S. In that case, only the second score S2 is the first type of score. [Explanation of symbols]

[0078] 2 AP (first wireless device) 4 Antennas 6 STA (Secondary Wireless Device) 10 Antenna layout determination device

Claims

1. 1. An antenna arrangement determination method for determining an arrangement of a plurality of antennas in a system for detecting an object using a first wireless device having a plurality of antennas and a second wireless device that performs wireless communication with the first wireless device, comprising: virtually dividing a target area in which the object is to be detected into a plurality of small areas; selecting a combination of candidate positions for the plurality of antennas from among positions where the plurality of antennas can be arranged; calculating a first score for each combination of the plurality of antenna position candidates, the first score increasing as the number of small areas on a direct wave path between the position of the second wireless device and the plurality of antenna position candidates increases; calculating a second score for each combination of the plurality of antenna position candidates, the second score increasing as the number of small areas on a path of a reflected wave between the position of the second wireless device and the plurality of antenna position candidates increases; calculating, for each combination of the plurality of antenna position candidates, an evaluation index value that is larger as the first score is larger and that is smaller as the second score is larger, using the first score and the second score; selecting a top predetermined number of combinations in ascending order of the evaluation index value from among the combinations of the candidate positions of the plurality of antennas, and determining a combination of positions for arranging the plurality of antennas from among the top predetermined number of combinations selected.

4. A method for determining an antenna arrangement comprising:

2. 2. The antenna arrangement determination method according to claim 1, Calculating the first score includes calculating a total number of small areas on a path counted for each path of a direct wave between the location of the second wireless device and the candidate locations of the plurality of antennas.

4. A method for determining an antenna arrangement comprising:

3. 2. The antenna arrangement determination method according to claim 1, Calculating the second type of score includes calculating a total number of small areas on a path counted for each path of a reflected wave between the location of the second wireless device and the candidate locations of the plurality of antennas.

4. A method for determining an antenna arrangement comprising:

4. 2. The antenna arrangement determination method according to claim 1, Calculating the first score comprises: Calculating the number of small areas on a direct wave path between the location of the second wireless device and the candidate locations of the plurality of antennas as a first score; and calculating, as a second score, a total number of small areas counted for each path of a direct wave between the position of the second wireless device and the candidate positions of the plurality of antennas; calculating the second type of score includes calculating, as a third score, a total number of small areas counted for each path of a reflected wave between the position of the second wireless device and the candidate positions of the plurality of antennas; Calculating the evaluation index value includes multiplying a difference between the second score and the third score by the first score.

4. A method for determining an antenna arrangement comprising:

5. 1. An antenna arrangement determination device for determining an arrangement of a plurality of antennas in a system for detecting an object using a first wireless device having a plurality of antennas and a second wireless device that wirelessly communicates with the first wireless device, comprising: A process of virtually dividing a target area in which the object is to be detected into a plurality of small areas; A process of selecting a combination of candidate positions of the plurality of antennas from among positions where the plurality of antennas can be arranged; a process of calculating a first score for each combination of the plurality of antenna position candidates, the first score increasing as the number of small areas on a direct wave path between the position of the second wireless device and the plurality of antenna position candidates increases; a process of calculating a second type score for each combination of the plurality of antenna position candidates, the second type score increasing as the number of small areas on a path of a reflected wave between the position of the second wireless device and the plurality of antenna position candidates increases; a process of calculating, for each combination of the plurality of antenna position candidates, an evaluation index value that is larger as the first type score is larger and that is smaller as the second type score is larger, using the first type score and the second type score; and selecting a top predetermined number of combinations from among the combinations of the plurality of antenna position candidates in ascending order of the evaluation index value, and determining a combination of positions for arranging the plurality of antennas from among the selected top predetermined number of combinations.

4. An antenna arrangement determination device comprising:

6. 1. A program for determining an arrangement of a plurality of antennas in a system for detecting an object using a first wireless device having a plurality of antennas and a second wireless device that wirelessly communicates with the first wireless device, the program comprising: A process of virtually dividing a target area in which the object is to be detected into a plurality of small areas; A process of selecting a combination of candidate positions of the plurality of antennas from among positions where the plurality of antennas can be arranged; a process of calculating a first score for each combination of the plurality of antenna position candidates, the first score increasing as the number of small areas on a direct wave path between the position of the second wireless device and the plurality of antenna position candidates increases; a process of calculating a second type score for each combination of the plurality of antenna position candidates, the second type score increasing as the number of small areas on a path of a reflected wave between the position of the second wireless device and the plurality of antenna position candidates increases; a process of calculating, for each combination of the plurality of antenna position candidates, an evaluation index value that is larger as the first type score is larger and that is smaller as the second type score is larger, using the first type score and the second type score; and selecting a top predetermined number of combinations in ascending order of the evaluation index value from among the combinations of the plurality of antenna position candidates, and determining a combination of positions for arranging the plurality of antennas from among the selected top predetermined number of combinations.

4. An antenna arrangement determination program comprising:

7. 1. An object detection system for detecting an object within a region of interest, comprising: a first wireless device having a plurality of antennas; a second wireless device that wirelessly communicates with the first wireless device; The antenna arrangement determination device according to claim 5, the plurality of antennas are arranged at positions determined by the antenna arrangement determination device relative to the position of the second wireless device; 1. An object detection system comprising:

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