Congestion status estimation device

Abstract

The purpose of the present disclosure is to provide a congestion status estimation device that is capable of reducing an estimation error when estimating a congestion status with regard to objects. A congestion status estimation device according to the present disclosure comprises a wireless station that measures the number of terminals wirelessly connected thereto and a sensor that measures a number of objects. The congestion status estimation device is configured to execute: a process for generating a first estimation result, which estimates the congestion status of the objects on the basis of the number of terminals measured by the wireless station; a process for generating a second estimation result, which estimates the congestion status of the objects on the basis of the number of objects measured by the sensor; and a process for calculating a final estimation result of the congestion status of the objects in a target area on the basis of the first estimation result and the second estimation result.

Description

Congestion situation estimation device 【0001】 The present disclosure relates to a congestion situation estimation device that estimates the congestion situation of objects such as people or things. 【0002】 In wireless LAN communication, a technique for measuring the movement of an object existing in a propagation path using CSI (Channel State Information), RSSI (Received Signal Strength Indicator), or the like is known (see, for example, Non-Patent Document 1). 【0003】 Also, in wireless LAN communication, a technique for counting a reception confirmation response transmitted from a terminal that has received pseudo VoIP packet data transmitted by an access point is disclosed (see Non-Patent Document 2). Thereby, the number of terminals connected to the access point can be measured. 【0004】 "Animal detection system using wireless LAN radio waves", NTT Technical Journal, April 2019. "Easily realize the communication quality evaluation of 1 wireless LAN access point! 3. VoIP quality estimation technology", ANSL R&D Times, No. 47, 2006. 【0005】 A technique for estimating the congestion situation of an object existing in a target area based on CSI, RSSI, or a reception confirmation response is expected. However, in the method using CSI or RSSI, there is a risk of erroneously estimating fluctuations in a wireless signal that are not caused by the movement of the object to be measured as fluctuations in the congestion situation. Further, in the method using control information from a terminal such as a reception confirmation response, an estimation error occurs because an object not carrying a terminal cannot be counted. Under such circumstances, a technique for reducing an estimation error in estimating the congestion situation is desired. 【0006】 In order to solve the above problems, an object of the present disclosure is to provide a congestion situation estimation device capable of reducing an estimation error in estimating the congestion situation of an object. 【0007】Preferably, the present disclosure is a congestion estimation device comprising: a radio station for measuring the number of terminals wirelessly connected to it; and a sensor for measuring the number of objects, wherein the device is configured to perform: a process for generating a first estimation result that estimates the congestion status of the objects based on the number of terminals measured by the radio station; a process for generating a second estimation result that estimates the congestion status of the objects based on the number of objects measured by the sensor; and a calculation process for calculating a final estimation result of the congestion status of the objects in a target area based on the first estimation result and the second estimation result. 【0008】 The congestion estimation device of this disclosure calculates a final estimation result of the congestion status of an object using a first estimation result and a second estimation result estimated by different measurement methods. Therefore, the final estimation result is not influenced by estimation errors contained in either the first or second estimation result. Accordingly, it is possible to provide a congestion estimation device that can reduce estimation errors in estimating the congestion status of an object. 【0009】 This is an example of the configuration of the congestion status estimation device according to Embodiment 1. This is a block diagram of the congestion status estimation device according to Embodiment 1. This is a diagram showing the hardware configuration of the estimation circuit according to Embodiment 1. This is a timing chart explaining the processes performed by the wireless data collection device, the wireless station, and the estimation circuit according to Embodiment 1. 【0010】 Embodiments of this disclosure will be described with reference to the drawings. The same or corresponding components will be denoted by the same reference numerals, and repetition of the description may be omitted. 【0011】 Embodiment 1 Figure 1 shows an example configuration of the congestion status estimation device 100 according to Embodiment 1. The congestion status estimation device 100 comprises an estimation circuit 130, a wireless data collection device 120, and two wireless stations 110-1 and 110-2. Here, we will describe the case where each of the wireless data collection device 120 and the two wireless stations 110-1 and 110-2 has a wireless LAN communication function that conforms to the IEEE 802.11 standard. 【0012】Furthermore, it is assumed that radio stations 110-1 and 110-2 have the same function. Hereafter, the description applies to both radio stations 110-1 and 110-2, and when there is no need to distinguish between them, they will simply be referred to as radio station 110. Only when it is necessary to distinguish between them will their respective designations be indicated. 【0013】 For convenience, the following explanation will describe the case where the target of congestion estimation is people. However, the target of estimation by the congestion estimation device 100 of this disclosure is not limited to people; it can be any object such as an animal or other object. 【0014】 <Radio Station> The radio station 110 uses one or more antennas 111 to perform wireless LAN communication with wireless terminals (hereinafter referred to as terminals). The radio station 110 is, for example, an access point for wireless LAN communication. In Figure 1, terminals are not shown, but a person (user) 50 carrying a terminal is shown. The terminal is assumed to be a mobile terminal such as a smartphone, tablet terminal, or home game console, but it may also be a fixed terminal. The terminal may also be an unmanned terminal, for example, an AGV (Automated guided vehicle) or AMR (Autonomous Mobile Robot) equipped with wireless LAN functionality. 【0015】 The radio station 110 measures the number of terminals connected to it by counting the control information contained in the radio signals notified by the terminals. The control information is a probe request that each terminal periodically broadcasts in order to find an access point. Alternatively, the control information may be an acknowledgment of receipt sent by a terminal that has received a signal broadcast from the radio station 110, or other information. 【0016】Alternatively, if the radio station 110 is a Multi-link Device (MLD) that supports IEEE 802.11be Multi-link operation, the radio station 110 establishes multiple links with terminals and uses multiple frequency bands in parallel to perform wireless communication. To prevent duplicate terminal counting for each link, the radio station 110 measures the number of terminals based on the terminal identifier included in the wireless signal from each terminal. Specifically, the radio station 110 measures the number of terminals by counting the MLD MAC addresses included in the wireless signals transmitted from terminals communicating wirelessly with it. 【0017】 If a terminal sends probe requests in multiple frequency bands, the radio station 110 receives the probe requests from the terminal in one or more frequency bands available to the radio station 110. To prevent duplicate counting of probe requests from the same terminal, the radio station 110 divides the probe request count value for each frequency band by the number of frequencies used by the radio station 110 and uses the result as the number of terminals. 【0018】 Furthermore, it is possible that a terminal may randomly select a MAC address before transmitting a wireless signal. Therefore, it is desirable for the wireless station 110 to count the MAC addresses at predetermined intervals. By recounting at predetermined intervals, duplicate counts can be prevented. 【0019】 The radio station 110 estimates the level of human congestion in the communication area based on the number of terminals measured as described above. The level of congestion is an indicator of the density of people. Each time the radio station 110 estimates the level of congestion, it notifies the estimation circuit 130 of the estimation result (first estimation result). 【0020】 While it is preferable for the congestion status to be estimated by the radio station 110 to be performed continuously, it may also be performed at arbitrary intervals. Alternatively, the estimation may be started triggered by a command notification from the estimation circuit 130. 【0021】<Radio Data Collection Device> The radio data collection device 120 continuously collects radio signals transmitted from radio station 110 (radio station 110-1 in Figure 1) using one or more antennas 121. Furthermore, the radio data collection device 120 derives propagation information from the received radio signals. The propagation information is not limited to communication quality such as RSSI, RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), or amplitude information or phase information of CSI. 【0022】 Based on the time variation of propagation information, the radio data collection device 120 measures the number of people present within the communication area. For example, the radio data collection device 120 estimates that the greater the variation in propagation information, the greater the number of people present between its own station and the radio station 110. The radio data collection device 120 can measure the number of people 50 carrying terminals and people 60 not carrying terminals. 【0023】 The wireless data collection device 120 estimates the level of human congestion in the communication area based on the measurement results. As an example of the estimation method, the wireless data collection device 120 calculates the line-of-sight level between the transmitting radio station 110 and the receiving station based on the collected propagation information. The line-of-sight level is calculated in the form of communication quality such as received power, or the amplitude or phase of CSI. Furthermore, the wireless data collection device 120 estimates the congestion level between the station and the radio station 110 based on the line-of-sight level. 【0024】 More specifically, the radio data collection device 120 estimates that the greater the fluctuation in the line-of-sight level, or the lower the line-of-sight level, the more congested the area between its own station and the radio station 110 is. Alternatively, the radio data collection device 120 stores a reference table that associates the height of the line-of-sight level with the congestion level, and determines the congestion level corresponding to the calculated line-of-sight level based on this reference table. Note that the method for estimating the congestion level is not limited to the method described here, and other methods may be used. 【0025】Furthermore, in estimating congestion levels using the radio data collection device 120, the line-of-sight level between radio station 110-1 and radio station 110-2 may be incorporated in addition to the line-of-sight level between the radio data collection device 120 and radio station 110. For example, the radio data collection device 120 will determine that the area between radio station 110-1 and radio station 110-2 is more congested the lower the line-of-sight level between them, and will incorporate this into the estimation of congestion levels in its own communication area. By incorporating congestion levels in other communication areas into the estimation of congestion levels in its own communication area, an improvement in estimation accuracy can be expected. 【0026】 The wireless data collection device 120 notifies the estimation circuit 130 of the estimation result (second estimation result) each time it estimates the congestion status. 【0027】 While it is preferable for the wireless data collection device 120 to continuously estimate the congestion status, it may be performed at arbitrary intervals. Alternatively, the estimation may be triggered by a command notification from the estimation circuit 130. Furthermore, the timing of starting the congestion status estimation may be synchronized between the wireless data collection device 120 and the wireless station 110. 【0028】 <Estimation Circuit> The estimation circuit 130 acquires a first estimation result from the radio station 110 and a second estimation result from the radio data collection device 120. Furthermore, the estimation circuit 130 performs a calculation process to calculate a final estimation result of the human congestion status in the target area based on the first and second estimation results. 【0029】 The target area is an area that includes at least one of the communication area of ​​the radio station 110 and the communication area of ​​the radio data collection device 120, or an area near the communication area of ​​the radio station 110 and the communication area of ​​the radio data collection device 120, but is not particularly limited to that area. 【0030】 As an example of a method for calculating the final estimation result, the estimation circuit 130 uses the lower of the first estimation result and the second estimation result, the higher of the two, or the midpoint between the first and second estimation results as the final estimation result. 【0031】Furthermore, the estimation circuit 130 outputs a new final estimation result based on the first and second estimation results if the congestion fluctuations estimated by the radio station 110 and the congestion fluctuations estimated by the radio data collection device 120 are within a predetermined time difference. Alternatively, the estimation circuit 130 outputs a new final estimation result if the difference between the congestion fluctuations estimated by the radio station 110 and the congestion fluctuations estimated by the radio data collection device 120 is within a predetermined difference. 【0032】 In this way, by calculating the final estimated result of congestion using the first and second estimated results obtained by different measurement methods, the final estimated result is not influenced by either the estimation error contained in the first or second estimated result. This reduces the estimation error. 【0033】 Furthermore, the estimation circuit 130 can correct the number of terminals measured by the radio station 110 and update the first estimation result notified by the radio station 110 based on the corrected number of terminals. The estimation circuit 130 is capable of acquiring environmental information of the communication area of ​​the radio station 110. The first estimation result notified to the estimation circuit 130 from the radio station 110 includes the measurement result of the number of terminals that served as the basis for the estimation. The estimation circuit 130 corrects the measurement result of the number of terminals using the terminal connection ratio to the radio station 110, which is determined based on the environmental information of the communication area of ​​the radio station 110. 【0034】 For example, if the communication area of ​​radio station 110 is a public environment, it can be assumed that the connection rate of terminals in the communication area to radio station 110 is less than 1, that is, not all terminals are connected to radio station 110. Therefore, the estimation circuit 130 corrects the number of terminals by dividing the measured number of terminals by the connection rate of terminals to radio station 110. For example, if the connection rate is expected to be 0.2, the number of terminals is corrected by 5 times by dividing the measured number of terminals by 0.2. Furthermore, the estimation circuit 130 updates the first estimation result using the corrected number of terminals. The estimation circuit 130 then incorporates the updated first estimation result into the calculation of the final estimation result. 【0035】On the other hand, if the communication area of ​​the radio station 110 is a factory environment, it can be assumed that all terminals present in the communication area are connected to the radio station 110. In this case, the estimation circuit 130 incorporates the first estimation result notified by the radio station 110 into the calculation of the final estimation result without updating it. This is essentially the same as dividing the number of measured terminals by a connection ratio of 1. 【0036】 Furthermore, the connection ratio used to correct the number of terminals may be updated based on the second estimation result from the wireless data collection device 120. For example, the estimation circuit 130 approaches the connection ratio closer to 1 when the first estimation result and the second estimation result can be considered equal, and approaches the connection ratio closer to 0 as the difference between the first and second estimation results widens. Alternatively, the estimation circuit 130 stores a reference table that associates the amount of congestion fluctuation estimated by the wireless data collection device 120 with the connection ratio, and determines the corresponding connection ratio based on the reference table each time a new second estimation result is notified. 【0037】 By correcting the number of terminals according to the environment of the communication area of ​​the radio station 110 in this way, the estimation accuracy in the final estimation result can be further improved. 【0038】 Furthermore, the estimation circuit 130 incorporates area information obtained using the internet or the like into the calculation of the final estimation result. Area information refers to information that may affect the congestion status of the target area, and may include, for example, events in or near the target area (date and time, location, content, number of participants, etc.), or intent-related information such as weather (heavy rain, typhoon, heavy snow, sunny), and temperature. 【0039】 For example, if the area information is such as the opening of a new store or the holding of an event that suggests congestion is likely to occur in the target area, the estimation circuit 130 adopts the higher of the first estimation result and the second estimation result as the final estimation result. 【0040】 Alternatively, the estimation circuit 130 decides, based on the acquired area information, whether to adopt the first estimation result or the second estimation result as the final estimation result, or to give greater weight to each result when calculating the final estimation result. 【0041】For example, in the case of information on an event held in an area with narrow area information or an event predicted to have low human mobility, the radio station 110 that estimates the congestion situation using control information or the like because the variation in propagation information becomes small is expected to have higher estimation accuracy than the radio collection device 120. Therefore, the estimation circuit 130 adopts the first estimation result by the radio station 110, or calculates the final estimation result after giving a weight larger than the second estimation result to the first estimation result. By incorporating area information, it becomes possible to estimate the congestion situation according to the cause of congestion, and a further improvement in estimation accuracy is expected. 【0042】 Further, when the acquired area information is event information, the estimation circuit 130 outputs a new final estimation result from the first estimation result and the second estimation result in the time zone of the event. 【0043】 Alternatively, the estimation circuit 130 outputs a command notification for starting estimation in accordance with the occurrence of an event, thereby causing the radio station 110 and the radio collection device 120 to estimate the congestion situation in the time zone of the event. Further, the estimation circuit 130 calculates the final estimation result of the congestion situation accompanying the occurrence of the event based on the first estimation result from the radio station 110 and the second estimation result from the radio collection device 120. By using the area information as a trigger for starting estimation in this way, a useful estimation result is expected. 【0044】 Also, the area information may be collected from posts on an SNS (Social Networking Service) such as a short text posting site. More preferably, for example, the estimation circuit 130 may monitor the number of posts on the SNS regarding the information of the target area or its vicinity, or may monitor the presence or absence of posts. The estimation circuit 130 outputs a new final estimation result from the first estimation result and the second estimation result in the time zone when the number of posts has changed. Since it is expected that the congestion also changes in the time zone when the number of posts has changed, a useful estimation result is expected. 【0045】 As described above, the estimation circuit 130 of the present disclosure incorporates area information into the calculation of the final estimation result. 【0046】<Modification Example 1> In FIG. 1, it has been described that the radio station 110 and the radio collection device 120 perform wireless LAN communication. However, the wireless communication method is not necessarily limited to wireless LAN communication, and cellular communication may also be used. For example, by using Open Air Interface (OAI), which is known as OSS (Open Source Software) in LTE / 5G, the radio collection device 120 can collect wireless signals and derive propagation information. Note that the wireless communication methods of the radio station 110 and the radio collection device 120 do not necessarily have to be the same. 【0047】 <Modification Example 2> In FIG. 1, it has been described that the congestion situation estimation device 100 includes two radio stations 110-1 and 110-2. However, the number of radio stations 110 does not necessarily have to be plural, and even one radio station may be used. 【0048】 FIG. 2 is a block diagram of the congestion situation estimation device 100 according to Embodiment 1. 【0049】 First, the radio station 110 will be described. The antenna 111 transmits and receives wireless signals to and from the terminal. The measurement circuit 112 measures the number of terminals connected to its own station based on the control information, MAC address, or terminal identifier such as the MLD MAC address included in the wireless signal from the terminal. The estimation circuit 113 estimates the congestion situation in the communication area based on the number of terminals measured by the measurement circuit 112. The communication device 114 notifies the estimation circuit 130 of the estimation result (the first estimation result) of the congestion situation. 【0050】 Next, the radio collection device 120 will be described. The measurement circuit 122 collects wireless signals from the radio station 110 using the antenna 121. Further, the measurement circuit 122 calculates propagation information based on the collected wireless signals. The radio collection device 120 may calculate, as the propagation information, the amplitude information or phase information of the CSI, or the communication quality such as RSSI, RSRP, or RSRQ. 【0051】Furthermore, the measurement circuit 122 measures the number of people present in the communication area based on the time variation of the propagated information. The estimation circuit 123 estimates the congestion status in the communication area based on the measurement results from the measurement circuit 122. The communication device 124 notifies the estimation circuit 130 of the congestion status estimation result (second estimation result). 【0052】 Next, the estimation circuit 130 will be described. The communication device 101 acquires a first estimation result from the radio station 110 and a second estimation result from the radio data collection device 120. The communication device 101 is also connected to the internet via the core network 140. The information collection circuit 102 uses the communication device 101 to access applications (apps) or websites (homepages) on the internet and collect area information. 【0053】 The calculation circuit 103 calculates the final estimated result of the crowding situation in the target area based on the first and second estimation results. Area information collected by the information gathering circuit 102 is incorporated into the calculation of the final estimated result. 【0054】 In Figure 2, the case in which the information gathering circuit 102 is built into the estimation circuit 130 is explained. However, the information gathering circuit 102 may be located outside the estimation circuit 130 as a server or cloud server, etc. 【0055】 Figure 3 shows the hardware configuration of the estimation circuit 130 according to Embodiment 1. The processing performed by the estimation circuit 130 may be executed by a program using a computer equipped with a CPU and memory, in which a congestion status estimation program is stored. Alternatively, it may be executed by a program using an integrated circuit such as an FPGA (Field Programmable Gate Array). The congestion status estimation program may be provided by recording it on a storage medium or by providing it via a network. 【0056】The estimation circuit 130 has an input unit 40, an output unit 41, a communication unit 42, a CPU (Central Processing Unit, also called a processor) 43, a memory 44, and an HDD (Hard Disk Drive) 45 connected via a bus 46, and functions as a computer. The estimation circuit 130 is also configured to input and output data to and from a storage medium 47 that can be read by a computer. 【0057】 The input unit 40 is, for example, a keyboard and mouse. The output unit 41 is, for example, a display device such as a display. 【0058】 The communication unit 42 is a communication interface that communicates with, for example, the radio station 110 and the radio data collection device 120. 【0059】 Memory 44 refers to volatile or non-volatile semiconductor memory such as RAM, ROM, and flash memory, or magnetic disks, flexible disks, optical disks, and DVDs. 【0060】 The CPU 43 controls each part that constitutes the estimation circuit 130 and performs predetermined processing. The memory 44 and HDD 45 are storage devices that store, for example, a congestion status estimation program, a reference table, a first estimation result, a second estimation result, a final estimation result, and data of collected area information. 【0061】 The storage medium 47 is capable of storing a congestion status estimation program, etc., which is used to execute the functions of the estimation circuit 130. The storage medium 47 is a USB (Universal Serial Bus) memory, a CD-ROM (Compact Disc Read Only Memory), etc. 【0062】 Note that the architecture of the estimation circuit 130 is not limited to the example shown in Figure 3. 【0063】Figure 4 is a timing chart illustrating the processes performed by the wireless data collection device 120, the radio station 110, and the estimation circuit 130 according to Embodiment 1. The estimation circuit 130 continuously collects area information from the information collection circuit 102 (step S01). The estimation circuit 130 then outputs a command notification to the wireless data collection device 120 to start estimation (step S02). The estimation circuit 130 then outputs a command notification to the radio station 110 to start estimation (step S03). The wireless data collection device 120, which has estimated the congestion status in response to the command from the estimation circuit 130, then notifies the estimation circuit 130 of the second estimation result (step S04). The radio station 110, which has estimated the congestion status in response to the command from the estimation circuit 130, then notifies the estimation circuit 130 of the first estimation result (step S05). The estimation circuit 130 then calculates the final estimation result of the human congestion status in the target area based on the first estimation result and the second estimation result (step S06). 【0064】 The above set, including steps S02 to S06, is repeated at predetermined timings or triggered by area information. 【0065】 As described above, this disclosure provides a congestion estimation device 100 that can reduce estimation errors in estimating the congestion status of objects. 【0066】 <Modification 3> In the above description, it was stated that the radio station 110 generates a first estimation result for estimating the congestion status, and the radio collection device 120 generates a second estimation result for estimating the congestion status. However, the first and second estimation results may also be generated in the estimation circuit 130. In this case as well, the same effects as in Embodiment 1 can be obtained. 【0067】 <Modification 4> The congestion status estimation device 100 is modified by replacing the wireless collection device 120 with a camera, a sound sensor, and CO2. ２ Sensors, weight sensors, infrared sensors, etc., may be used to estimate the congestion status of objects and generate a second estimation result. In this case as well, the same effects as in Embodiment 1 can be obtained. 【0068】This disclosure is not limited to the embodiments described above, and various modifications can be made during implementation without departing from its essence. Furthermore, each embodiment and its modifications may be combined as appropriate, and in that case, the combined effects can be obtained. 【0069】 <Correspondence with terms used in the claims> In this disclosure, the terms used are wireless collection device 120, camera, voice sensor, CO ２ Sensors include weight sensors, infrared sensors, and the like. 【0070】 40: Input unit, 41: Output unit, 42: Communication unit, 43: CPU, 44: Memory, 45: HDD, 46: Bus, 47: Storage medium, 50: Person (user), 60: Person, 100: Congestion status estimation device, 101: Communication device, 102: Information collection circuit, 103: Calculation circuit, 110: Radio station, 110-1: Radio station, 110-2: Radio station, 111: Antenna, 112: Measurement circuit, 113: Estimation circuit, 114: Communication device, 120: Wireless collection device, 121: Antenna, 122: Measurement circuit, 123: Estimation circuit, 124: Communication device, 130: Estimation circuit, 140: Core network

Claims

1. A congestion estimation device comprising: a radio station for measuring the number of terminals wirelessly connected to it; and a sensor for measuring the number of objects, configured to perform: a process for generating a first estimation result that estimates the congestion status of the objects based on the number of terminals measured by the radio station; a process for generating a second estimation result that estimates the congestion status of the objects based on the number of objects measured by the sensor; and a calculation process for calculating a final estimation result of the congestion status of the objects in a target area based on the first estimation result and the second estimation result.

2. The congestion status estimation device according to claim 1, wherein the calculation process is a process in which the lower of the first estimation result and the second estimation result, the higher of the two estimation results, or the midpoint between the first estimation result and the second estimation result is used as the final estimation result.

3. The congestion status estimation device according to claim 1, wherein the calculation process is a process of calculating the final estimation result based on the first estimation result and the second estimation result, when the fluctuation in congestion status estimated by the radio station and the fluctuation in congestion status estimated by the sensor are within a predetermined time difference, or when the difference between the fluctuation in congestion status estimated by the radio station and the fluctuation in congestion status estimated by the sensor is within a predetermined difference.

4. A congestion status estimation device according to any one of claims 1 to 3, further comprising: a process for acquiring area information which is information that may affect the congestion status of the target area; and in the calculation process, the final estimation result is calculated based on the area information.

5. The congestion status estimation device according to claim 4, wherein the calculation process includes a process of determining, based on the area information, which of the first estimation result and the second estimation result to adopt as the final estimation result, or which to give greater weight to when calculating the final estimation result.

6. The congestion status estimation device according to claim 4, wherein, when the area information is event information, the calculation process is a process of calculating a final estimation result from the first estimation result and the second estimation result during the time period of the event.

7. A congestion status estimation device according to any one of claims 1 to 3, comprising: a process of acquiring environmental information of the communication area of ​​the radio station before the process of generating the first estimation result; and a process of correcting the number of terminals measured by the radio station based on the terminal connection rate to the radio station determined based on the environmental information.

8. The congestion estimation device according to any one of claims 1 to 3, wherein the sensor is configured to perform the following: a process of collecting a radio signal transmitted from the radio station; and a process of measuring the number of objects present in the path between the sensor and the radio station based on at least one of channel state information and communication quality contained in the radio signal.

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