OBJECT DETECTION DEVICE, OBJECT DETECTION METHOD, AND OBJECT DETECTION SYSTEM

Abstract

To provide an object detection system that can accurately detect an object without a device in a detection area without involving an excessive calculation load.SOLUTION: An object detector 40 detects an object in a detection area between a wireless base station 10 and a wireless terminal station 20. The object detector receives a feedback signal sent with CSI estimated by the wireless terminal station 20 for each sub carrier of a communication wave. An extraction unit 44 extracts information related to the CSI from the feedback signal. An information reduction unit 48 reduces information related to the CSI by applying a reduction condition selected as a condition that satisfies a requirement of the detection rate of an object. A determination unit 50 detects the object on the basis of a reduction impulse response for information given after the reduction processing is performed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an object detection device, an object detection method, and an object detection system, and in particular to an object detection device, an object detection method, and an object detection system that are suitable for detecting an object that does not carry a special device based on propagation channel information measured by a wireless terminal station. [Background technology]

[0002] In the field of wireless communications, efforts are being made to improve communication speeds by using a variety of technologies, such as beamforming technology, which controls the directionality of radio waves, in order to stably accommodate the ever-increasing amount of wireless traffic.

[0003] Meanwhile, services are being considered that use signal strength information of wireless signals (e.g., RSS (Received Signal Strength)) to detect wireless terminal stations within a communication area and provide location information. In such services, for example, a wireless terminal station measures the RSS of beacon signals transmitted from multiple wireless base stations, and calculates the location of the wireless terminal station from the multiple measured RSSs. This method is widely used as a positioning system in indoor environments where it is difficult to use GPS (Global Positioning System).

[0004] In addition, a device-free detection method is also known, as disclosed in the following Non-Patent Document 1. In the device-free detection method, it is possible to detect an object that does not hold a special device such as an antenna, for example, a target object such as a person.

[0005] The device-free detection method is used in an environment where a fixed wireless base station and a wireless terminal station exist within a detection area. The wireless terminal station measures propagation channel information (CSI) based on a wireless signal transmitted from the wireless base station. The CSI reflects the presence or absence of an object or the state of the object in the detection area between the wireless base station and the wireless terminal station. Then, object detection is performed based on the fluctuation characteristics appearing in the CSI. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] “WiFi Sensing with Channel State Information: A Survey”, YONGSEN MA, GANG ZHOU, and SHUANGQUAN WANG, Computer Science Department, College of William & Mary, USA, ACM Computing Surveys, Vol. 52, No. 3, Article 46. Publication date: June 2019. Summary of the Invention [Problem to be solved by the invention]

[0007] However, device-free detection methods are implemented based on small variations occurring in the propagation environment. For this reason, it is difficult to ensure detection accuracy compared to detecting an object holding a device such as an antenna. One possible method to address this issue is to perform a large amount of calculations based on a large amount of CSI acquired by wireless terminal stations. However, this solution creates a new issue of an extremely high calculation load. In addition, the high computer load may adversely affect the demand for real-time object detection.

[0008] The present disclosure has been made in light of the above-mentioned problems, and has a first objective to provide an object detection device that can detect device-free objects within a detection area with high accuracy without excessive computational load. A second object of the present disclosure is to provide an object detection method for detecting device-free objects in a detection area with high accuracy without excessive calculation load. Furthermore, a third object of the present disclosure is to provide an object detection system that can detect device-free objects within a detection area with high accuracy without excessive computational load. [Means for solving the problem]

[0009] In order to achieve the above object, a first aspect of the present disclosure is an object detection device that detects an object in a detection area between a wireless base station and a wireless terminal station, comprising: A process of receiving a feedback signal that carries information related to propagation channel information estimated for each subcarrier of a communication wave and is transmitted by the wireless terminal station; extracting information relating to the propagation channel information from the feedback signal; a reduction process for reducing information related to the propagation channel information by applying a reduction condition selected to satisfy a detection rate requirement for object detection; A process of performing the object detection based on a reduced impulse response corresponding to the information after the reduction process has been performed; Preferably, the system is configured to execute:

[0010] A second aspect of the present disclosure is an object detection method for detecting an object in a detection area between a wireless base station and a wireless terminal station, comprising: a step of transmitting a radio signal to a radio terminal station by the radio base station on each of a plurality of subcarriers included in a frequency band used for communication; the wireless terminal estimating propagation channel information for each of the subcarriers; The wireless terminal station transmits a feedback signal carrying information related to the propagation channel information; extracting information related to said propagation channel profile from said feedback signal; a reduction process for reducing the extracted information related to the propagation channel information by applying a reduction condition selected as satisfying a detection rate requirement for object detection; performing the object detection based on a reduced impulse response corresponding to the information after the reduction process; It is preferable that the present invention includes the following:

[0011] A third aspect of the present disclosure is an object detection system, a wireless base station that transmits wireless signals on a plurality of subcarriers included in a frequency band used for communication; a wireless terminal station that receives the wireless signal, estimates propagation channel information for each of the subcarriers, and transmits a feedback signal carrying information related to the propagation channel information; an object detection device that detects an object in a detection area between the wireless base station and the wireless terminal station, The object detection device includes: receiving the feedback signal; extracting information relating to the propagation channel information from the feedback signal; a reduction process for reducing information related to the propagation channel information by applying a reduction condition selected to satisfy a detection rate requirement for object detection; It is preferable that the apparatus is configured to execute a process of performing the object detection based on a reduced impulse response corresponding to the information after the reduction process has been performed. Effect of the Invention

[0012] According to the present disclosure, device-free objects within a detection area can be detected with high accuracy without excessive computational load. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram for explaining a configuration of an object detection system according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is a diagram for explaining an example of a detection area targeted by the first embodiment of the present disclosure. [Diagram 3]FIG. 2 is a diagram for explaining an overview of propagation channel information acquired by a wireless terminal station in the first embodiment of the present disclosure. [Figure 4] FIG. 1 is a diagram illustrating an example of frequency characteristics appearing in CSI. [Diagram 5] FIG. 1 is a diagram illustrating an example of an impulse response obtained by performing a Fourier transform on the frequency characteristics appearing in the CSI. [Figure 6] FIG. 6 is a diagram showing a state in which a window function is applied to the impulse response shown in FIG. [Figure 7] FIG. 11 is a diagram illustrating an example of a relationship between an average object detection rate and a window function. [Figure 8] 4 is a flowchart illustrating a flow of an object detection process performed in the first embodiment of the present disclosure. [Figure 9] 11 is a flowchart illustrating the flow of an object detection process performed in the second embodiment of the present disclosure. [Figure 10] FIG. 11 is a diagram for explaining features of the Fourier transform performed in the third embodiment of the present disclosure. [Figure 11] FIG. 11 is a diagram for explaining a first modified example of a frequency band covered by the present disclosure. [Figure 12] FIG. 13 is a diagram for explaining a second modified example of a frequency band targeted by the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Embodiment 1 [Configuration of the first embodiment] 1 is a block diagram showing a configuration of an object detection system according to a first embodiment of the present disclosure. The system according to the present embodiment includes a wireless base station 10. The wireless base station 10 includes M antennas 12-1 to 12-M. Hereinafter, when there is no need to distinguish between the antennas 12-1 to 12-M, the subscripts of the reference symbols will be omitted and the antennas will be referred to as "antennas 12."

[0015] The wireless base station 10 transmits a radio signal belonging to a pre-assigned frequency band from each of the antennas 12. More specifically, this frequency band includes a plurality of subcarriers, and the antennas 12 transmit a radio signal for each of the subcarriers.

[0016] The system of this embodiment includes a wireless terminal station 20. The wireless terminal station 20 includes N antennas 22-1 to 22-N. Each of the antennas 22-1 to 22-N receives wireless signals transmitted on a plurality of subcarriers from each of the antennas 12-1 to 12-M. Hereinafter, the antennas 22-1 to 22-N will be referred to as "antenna 22" with the subscripts omitted when there is no need to distinguish between them.

[0017] 2 is a diagram for explaining an environment in which the antennas 12 of the wireless base station 10 and the antennas 22 of the wireless terminal station 20 are placed. Here, a case in which the wireless base station 10 has four antennas 12 and the wireless terminal station 20 has one antenna 22 is illustrated as an example.

[0018] In this embodiment, both the antenna 12 and the antenna 22 are fixedly disposed. A detection area is set between the antenna 12 and the antenna 22. Fig. 2 shows an example in which the detection area is divided into eight areas (1) to (8). This embodiment discloses a system that detects whether an object that does not hold a device that emits a wireless signal, such as a person, is present within the detection area, and further, in which area and at what density the object is present within the detection area.

[0019] 1 again. Radio units 24-1 to 24-N are connected to antennas 22-1 to 22-N, respectively, of wireless terminal station 20. Hereinafter, when there is no need to distinguish between radio units 24-1 to 24-N, the subscripts of the reference numerals will also be omitted and they will be referred to as "radio unit 24."

[0020] The radio unit 24 converts the radio signal received by the antenna 22 into a format that enables estimation of propagation channel information (CSI). The signal converted by the radio unit 24 is provided to a CSI estimation unit 26. Here, CSI refers to amplitude information, phase information, and information on relative values ​​between antennas for each subcarrier of OFDM (Orthogonal Frequency Division Multiplexing) in the propagation path.

[0021] M types of radio signals emitted from antennas 12-1 to 12-M of radio base station 10 arrive at antenna 22-1 of radio terminal station 20. The same applies to other antennas 22-2 to 22-N. Since radio units 24-1 to 24-N each receive M types of radio signals, M×N types of signals are provided to CSI estimation unit 26. Each of these M×N types of signals includes a frequency element for each subcarrier.

[0022] Fig. 3 is a diagram for explaining an overview of the CSI estimated by the CSI estimation unit 26. Fig. 3 shows how an M×N CSI matrix is ​​defined for each subcarrier. As shown in Fig. 3, the CSI estimation unit 26 estimates the CSI in the form of an M×N matrix arranged in the frequency direction.

[0023] 1, the CSI estimated by the CSI estimation unit 26 is provided to a conversion unit 28. The conversion unit 28 converts the M×N CSI matrix into a right singular matrix by singular value decomposition according to standard techniques for wireless communication. The converted right singular matrix is ​​provided to a compression unit 30.

[0024] Compression unit 30 compresses the information of the right singular matrix using a known method defined by standardization technology. The compressed information is converted into a radio signal by radio unit 32 and transmitted as a feedback signal from antennas 22-1 to 22-N.

[0025] The system of this embodiment includes an object detection device 40 in addition to a wireless base station 10 and a wireless terminal station 20. A CSI feedback signal emitted from the wireless terminal station 20 is received by the wireless base station 10 and also by an antenna 42 of the object detection device 40. The signal received by the antenna 42 is provided to an extraction unit 44.

[0026] The extraction unit 44 extracts compressed CSI information from the signal provided by the antenna 42. The extracted compressed information is provided from the extraction unit 44 to the decompression unit 46. The decompression unit 46 restores a right singular matrix from the extracted information using a decompression method defined by standardization. This restores a right singular matrix for each subcarrier, that is, a right singular matrix arranged in the frequency direction.

[0027] Fig. 4 shows the result of extracting specific elements of a right singular matrix and arranging them in the frequency direction. Each element of the right singular matrix generated for each subcarrier can be expressed as a frequency characteristic as shown in Fig. 4.

[0028] The information of the right singular matrices restored by the decompression unit 46 is provided to the information reduction unit 48, as shown in Fig. 1. The information reduction unit 48 first performs an inverse Fourier transform on the right singular matrices arranged in the frequency domain. This converts the information in the frequency domain into information in the time domain. As a result, information on the impulse response represented in a time series is generated.

[0029] An example of an impulse response generated by the above process is shown in Figure 5. The impulse response generated in this way contains information that is essentially meaningless from the viewpoint of object detection, such as periodic noise called aliases.

[0030] After generating an impulse response, the information reduction unit 48 shown in FIG. 1 applies an appropriate window function to the impulse response.

[0031] 6 shows an example of an impulse response after a window function is applied to reduce meaningless information. In this embodiment, the amount of information to be applied to object detection processing is reduced in this manner.

[0032] 1, the information processed by the information reduction unit 48 is provided to the determination unit 50. The determination unit 50 performs object detection processing using a known method based on the impulse response provided in this manner. More specifically, the determination unit 50 applies machine learning to the impulse response to perform object detection using a known method.

[0033] Figure 7 shows the results of object detection simulations performed with different window functions. In the figure, the bar on the far left is the result of object detection performed using all information (64 points). The "T / 4" bar is the result when a window function that limits the amount of information to 1 / 4 (16 points) is used. Similarly, the "T / 8" and "T / 16" bars are the results when window functions that limit the amount of information to 1 / 8 (8 points) and 1 / 16 (4 points), respectively. In this example, we see that the average detection rate improves as the "window" is narrowed.

[0034] In this embodiment, a window function that realizes a high average detection rate is selected in advance based on the results shown in Fig. 7. Therefore, only information that is meaningless or unimportant in terms of object detection is deleted in the information reduction unit 48, and only a small amount of information that is significant is provided to the determination unit 50. As a result, the system of this embodiment realizes highly accurate object detection without an excessive calculation load.

[0035] [Processing flow in object detection device] Fig. 8 is a flowchart for explaining the flow of processing executed by the object detection device 40 in this embodiment. In this embodiment, the object detection device 40 may include a calculation processing unit and a memory that stores a program. The processing shown in Fig. 8 may be realized by the calculation processing unit executing the program stored in the memory.

[0036] In the routine shown in FIG. 8, first, a CSI feedback signal transmitted from the wireless terminal station 20 is received (step 100).

[0037] Next, the compressed CSI information is extracted from the received signal (step 102), thereby implementing the function of the extraction unit 44 shown in FIG.

[0038] Next, the right singular matrix is ​​restored from the compressed information by a default decompression process (step 104), thereby realizing the function of the decompression unit 46 shown in FIG.

[0039] The object detection device 40 then reduces information from the restored right singular matrix (step 106). Specifically, first, an inverse Fourier transform is performed on the right singular matrix arranged in the frequency direction. Then, an appropriate window function set in advance is applied to the resulting impulse response to reduce information. By executing the process of step 106, the function of the information reduction unit 48 shown in FIG. 1 is realized.

[0040] Finally, object detection processing is executed based on the impulse response after the information has been reduced (step 108). The processing of step 108 realizes the function of the determination unit 50 shown in FIG.

[0041] As described above, the system of the present embodiment can perform object detection calculations while deleting information that is meaningless or unimportant from the viewpoint of object detection. Therefore, the system can achieve highly accurate object detection without excessive computational load.

[0042] Embodiment 2 Next, a second embodiment of the present disclosure will be described with reference to Fig. 9 together with Fig. 1. The object detection system of the present embodiment can be realized by the configuration shown in Fig. 1, similar to the first embodiment. More specifically, the object detection system of the present embodiment can be realized by causing object detection device 40 to execute a routine shown in Fig. 9, which will be described later, instead of the routine shown in Fig. 8 above.

[0043] In the above-described first embodiment, the object detection device 40 executes the routine shown in Fig. 8 on the premise that a window function used to reduce information is set in advance. The routine shown in Fig. 9 executed in this embodiment includes a process of selecting an appropriate window function. The object detection system of this embodiment is characterized in that the routine shown in Fig. 9 is used to provide the object detection device 40 with a function of selecting an appropriate window function.

[0044] Fig. 9 shows a flowchart of a routine executed by the object detection device 40 in this embodiment. In Fig. 9, steps similar to those shown in Fig. 8 are denoted by the same reference numerals, and their description will be omitted or simplified.

[0045] 9, in step 106, information of the impulse response based on the right singular matrix is ​​reduced using an appropriate window function, as in the case of embodiment 1. Then, in step 108, object detection is performed based on the reduced information.

[0046] In the routine shown in Fig. 9, following the above process, it is determined whether or not the search for window functions has been completed (step 110). In the object detection device 40, candidates for window functions for information reduction are determined in advance. Here, it is determined whether or not the processes of steps 106 and 108 have been performed for all of the candidates. If it is determined that these processes have not been performed for all of the candidates, the determination of the end of the search is denied.

[0047] If the determination of the end of the search is negative in step 110, the window function is changed to an unused one (step 112). Thereafter, the processes of steps 106 and 108 are carried out again using the changed window function.

[0048] On the other hand, if the search end determination is affirmative in step 110, a threshold value for the detection rate of object detection is set (step 114). More specifically, the allowable amount of deterioration of the detection rate with respect to the maximum detection rate is set as the threshold value.

[0049] Next, based on the object detection result obtained in step 108, a window function that clears the above threshold is extracted (step 116). Specifically, an average detection rate is calculated for each window function. Then, a window function whose average detection rate clears the above threshold is extracted as pass data.

[0050] After the extraction of the acceptable data is completed, the window function that realizes the largest reduction rate is selected from the extracted window functions (step 118). In this way, a window function that can realize the desired detection rate and achieve a large reduction rate is selected.

[0051] Next, it is determined whether the selected window function satisfies the processing time condition (step 120). More specifically, it is determined whether the object detection processing performed based on the information reduced using the window function fits within a specified processing time. The specified processing time is determined in advance according to, for example, a requirement for real-time performance regarding object detection.

[0052] In this embodiment, priority is given to real-time requirements over object detection accuracy, so if the time condition is not met in step 120, the process returns to step 114 and the detection rate threshold is reviewed.

[0053] On the other hand, if it is determined in step 120 that the time condition is met, the window function selected at that time is finally determined as the window function for information reduction (step 122).

[0054] As described above, the routine shown in Fig. 9 makes it possible to appropriately select a window function that realizes both a desired detection rate and a desired real-time property. Therefore, the object detector detection system of this embodiment can realize a function of detecting an object with high accuracy without excessive calculation load.

[0055] In the above-described second embodiment, one of the requirements for selecting a window function is to satisfy a time condition, but the present disclosure is not limited to this. In an environment in which the time condition is not important, the condition may be removed and the window function may be selected based only on the detection rate.

[0056] Embodiment 3 Next, a third embodiment of the present disclosure will be described with reference to Fig. 10 together with Fig. 1 and Fig. 8. The object detection system of this embodiment can be realized by the configuration shown in Fig. 1, similarly to the first and second embodiments.

[0057] In the above-mentioned first and second embodiments, the frequency domain information is converted into time domain information, and then the window function is used to reduce the information. However, the method of reducing the information is not limited to this. Specifically, the information reduction of the right singular matrix may be performed at the stage of frequency characteristics before performing the inverse Fourier transform to convert into the time domain impulse response.

[0058] Fig. 10 is a diagram for explaining the timing at which the object detection device 40 performs information reduction in this embodiment. In Fig. 10, the upper left region shows how specific elements of a right singular matrix are arranged in the frequency direction. Here, each of the dots constituting the dashed line and each of the circles shown at intervals of 4Δf represent data of a specific element.

[0059] The lower left area of ​​Fig. 10 shows the result of extracting data corresponding to circles from the data shown in the upper left area. Specifically, the number of data points is reduced to 1 / 4 by extracting data at intervals of 4Δf.

[0060] The right area of ​​Figure 10 shows the result of performing an inverse Fourier transform on the frequency domain information reduced by 1 / 4. This result is equivalent to the result shown in Figure 6, which was obtained by applying a window function to the impulse response shown in Figure 5. In this way, the technique of extracting data at regular intervals from the frequency domain information can achieve information reduction similar to that achieved by applying a window function to the time domain information.

[0061] In this embodiment, object detection device 40 performs object detection processing in accordance with the flowchart shown in Fig. 8, similarly to the first embodiment. However, in this embodiment, in step 106, information reduction is performed in the following procedure. 1. Generate a frequency characteristic (see the upper left region of Figure 4 or Figure 10) based on the restored right singular matrix. 2. Extract information from the above frequency characteristics at regular intervals to generate a reduced frequency characteristic. 3. An inverse Fourier transform is applied to the extracted reduced frequency characteristic to obtain an impulse response with reduced information.

[0062] Thereafter, in step 108, object detection processing is performed based on the impulse response after the information reduction, as in the case of embodiment 1. Therefore, the system of this embodiment can also achieve highly accurate object detection without an excessive calculation load, as in the case of embodiment 1.

[0063] [Modification of the third embodiment] Incidentally, in the above-described third embodiment, the object detection device 40 proceeds with the object detection process according to the flowchart shown in Fig. 8, as in the first embodiment. However, the present disclosure is not limited to this. That is, the method of reducing information at the frequency domain stage may be combined with the process according to the flowchart shown in Fig. 9.

[0064] [Modifications common to the first to third embodiments] In addition, in the above-described first to third embodiments, it is assumed that only one frequency band having multiple subcarriers is used. However, the present disclosure is not limited to this, and the object detection system may handle multiple frequency bands.

[0065] Fig. 11 shows a state where a plurality of frequency bands are arranged adjacent to frequency band 52 used in the first to third embodiments. The object detection device of the present disclosure can also perform object detection after performing information reduction using a plurality of frequency bands as shown in Fig. 11. In this case, since a more detailed impulse response can be acquired, it is expected that the accuracy of the detection rate will be improved.

[0066] Fig. 12 shows a state in which a plurality of frequency bands are arranged at intervals to the right of frequency band 52 used in embodiments 1 to 3. The object detection system of the present disclosure can also handle a plurality of frequency bands arranged in a so-called gapped state, as shown in Fig. 12. [Explanation of symbols]

[0067] 10 Radio base station 20 Wireless terminal station 40 Object detection device 48 Information Reduction Department

Claims

1. An object detection device that detects an object in a detection area between a wireless base station and a wireless terminal station, A process of receiving a feedback signal that carries information related to propagation channel information estimated for each subcarrier of a communication wave and is transmitted by the wireless terminal station; extracting information relating to the propagation channel information from the feedback signal; a reduction process for reducing information related to the propagation channel information by applying a reduction condition selected to satisfy a detection rate requirement for object detection; A process of performing the object detection based on a reduced impulse response corresponding to the information after the reduction process is performed; The reduction condition is a condition that a detection rate of the object detection clears a pass threshold, An object detection device in which the detection rate is an average detection rate of object detection performed by applying the results of machine learning that uses the reduced impulse response as input.

2. the reduction condition is a condition for a window function to be applied to the impulse response, The reduction process includes: performing an inverse Fourier transform on frequency domain information relating to the propagation channel information to generate the impulse response; The object detection apparatus according to claim 1 , further comprising: a process of applying the window function to the impulse response to generate the reduced impulse response.

3. the reduction condition is a condition for an extraction process of extracting frequency domain information related to the propagation channel information at a certain frequency interval; The reduction process includes: performing the extraction process on frequency domain information related to the propagation channel information; The object detection device according to claim 1 , further comprising a process of performing an inverse Fourier transform on the frequency domain information after the extraction process to generate the reduced impulse response.

4. In order to select the reduction conditions, calculating a detection rate of the object detection for each of the available reduction conditions; A process of extracting a reduction condition that satisfies the pass condition as the pass condition, selecting an optimal condition that achieves a maximum information reduction rate from among the pass conditions; a selection process for selecting the optimal condition as the reduction condition; 4. The object detection device according to claim 1 , further configured to:

5. In order to select the reduction conditions, a process of determining whether a processing time for object detection based on the reduced impulse response generated by applying the optimal condition satisfies a time condition; If it is determined that the processing time does not satisfy the time condition, a process of relaxing the judgment condition of the pass condition is further executed; The object detection device according to claim 4 , wherein the selection process includes a process of selecting the optimum condition determined to satisfy the time condition as the reduction condition.

6. 1. An object detection method for detecting an object in a detection area between a wireless base station and a wireless terminal station, comprising: a step of transmitting a radio signal to a radio terminal station by the radio base station on each of a plurality of subcarriers included in a frequency band used for communication; the wireless terminal estimating propagation channel information for each of the subcarriers; The wireless terminal station transmits a feedback signal carrying information related to the propagation channel information; extracting information related to said propagation channel profile from said feedback signal; a reduction step of reducing the extracted information related to the propagation channel information by applying a reduction condition selected as meeting a requirement of a detection rate of object detection; performing the object detection based on a reduced impulse response corresponding to information after the reduction step has been performed; The reduction condition is a condition that a detection rate of the object detection clears a pass threshold, An object detection device in which the detection rate is an average detection rate of object detection performed by applying the results of machine learning that uses the reduced impulse response as input.

7. a wireless base station that transmits wireless signals on a plurality of subcarriers included in a frequency band used for communication; a wireless terminal station that receives the wireless signal, estimates propagation channel information for each of the subcarriers, and transmits a feedback signal carrying information related to the propagation channel information; an object detection device that detects an object in a detection area between the wireless base station and the wireless terminal station, The object detection device includes: receiving the feedback signal; extracting information relating to the propagation channel information from the feedback signal; a reduction process for reducing information related to the propagation channel information by applying a reduction condition selected to satisfy a detection rate requirement for object detection; A process of performing the object detection based on a reduced impulse response corresponding to the information after the reduction process is performed; The reduction condition is a condition that a detection rate of the object detection clears a pass threshold, An object detection system in which the detection rate is an average detection rate of object detection performed by applying the results of machine learning using the reduced impulse response as input.

Images