Patent Publication Number: US-2021190927-A1

Title: Electronic apparatus, method, and electronic system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application of PCT Application No. PCT/JP2019/024165, filed Jun. 18, 2019, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to an electronic apparatus, a method, and an electronic system. 
     BACKGROUND 
     In recent years, it is known to measure propagation characteristics (e.g., RSSI) among a plurality of wireless machines and estimate the position where each of the plurality of wireless machines is installed. 
     However, for example, in an environment with much reflection of radio waves, a phenomenon called multipath fading, in which direct waves and reflected waves interfere with each other, occurs, and the estimation accuracy of the position of the wireless machine described above is sometimes lowered. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view for specifically explaining an example of a usage mode of an electronic apparatus according to a first embodiment. 
         FIG. 2  is a view for specifically explaining another example of a usage mode of the electronic apparatus. 
         FIG. 3  is a diagram showing an example of a hardware configuration of the electronic apparatus. 
         FIG. 4  is a block diagram showing an example of a functional configuration of the electronic apparatus. 
         FIG. 5  shows an example of a data structure of position information stored in position information storage. 
         FIG. 6  is a sequence chart showing an example of a processing procedure of the electronic apparatus and a plurality of wireless machines in a case of estimating the position where each of the plurality of wireless machines is installed. 
         FIG. 7  shows an example of a data structure of characteristic information stored in characteristic information storage. 
         FIG. 8  is a block diagram showing an example of a functional configuration of an electronic apparatus according to a second embodiment. 
         FIG. 9  is a sequence chart showing a processing procedure of the electronic apparatus and the plurality of wireless machines in a case of estimating the position where each of the plurality of wireless machines is installed. 
         FIG. 10  shows an example of the data structure of the characteristic information stored in the characteristic information storage. 
         FIG. 11  is a flowchart showing a processing procedure of secondary estimation processing. 
         FIG. 12  is a view for specifically explaining the secondary estimation processing. 
         FIG. 13  is a view for explaining an example of re-estimation processing. 
         FIG. 14  is a view for explaining another example of the re-estimation processing. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, an electronic apparatus includes a processor. The processor is configured to acquire position information indicating a plurality of installation positions including first and second installation positions of a plurality of pieces of equipment, receive characteristic information of a first piece of equipment among the plurality of pieces of equipment obtained from a first propagation characteristic in a first channel of the first piece of equipment and a second propagation characteristic in a second channel of the first piece of equipment, receive characteristic information of a second piece of equipment among the plurality of pieces of equipment obtained from a third propagation characteristic in the first channel of the second piece of equipment and a fourth propagation characteristic in the second channel of the second piece of equipment. The processor is configured to estimate a position where each of the first and second pieces of equipment is installed from among the first and second installation positions, based on the position information, the characteristic information of the first piece of equipment, and the characteristic information of the second piece of equipment. 
     Various embodiments will be described hereinafter with reference to the accompanying drawings. 
     First Embodiment 
     First, the first embodiment will be described. The electronic apparatus according to the present embodiment is used, for example, in a case where a plurality of wireless machines are installed at a plurality of predetermined installation positions, to estimate (specify) the position where each of the plurality of wireless machines is installed from among the plurality of installation positions. 
     Hereinafter, an example of the usage mode of the electronic apparatus according to the present embodiment will be specifically described with reference to  FIG. 1 . Here, a case where the electronic apparatus according to the present embodiment is used in a lighting equipment system will be described. 
       FIG. 1  shows a plurality of rooms  1   a  to  1   c  and positions P 1  to P 9  of lighting equipment arranged in the respective rooms  1   a  to  1   c . In the example shown in  FIG. 1 , the lighting equipment is arranged at each of the positions P 1  to P 3  of the room  1   a , the lighting equipment is arranged at each of the positions P 4  to P 6  of the room  1   b , and the lighting equipment is arranged at each of the positions P 7  to P 9  of the room  1   c.    
     Here, a case where in the lighting equipment system, for example, a wireless machine is installed in the lighting equipment arranged in each of the rooms  1   a  to  1   c , and the power on/off of the lighting equipment is controlled (remotely operated) via the wireless machine is assumed. Note that each wireless machine may communicate via an appropriately installed wireless master unit, or may communicate by configuring a wireless mesh network. 
     In such a case, for example, when controlling only the lighting equipment installed in the room  1   a , it is necessary to transmit a control signal to the wireless machine installed in the positions P 1  to P 3  of the room  1   a . When controlling only one of the three pieces of lighting equipment arranged in the room  1   a , it is necessary to transmit a control signal to the wireless machine installed in the one piece of lighting equipment. The wireless machine installed in each piece of lighting equipment is assigned with an identifier (hereinafter referred to as a wireless machine ID) for identifying the wireless machine. Therefore, it is possible to transmit a control signal to a specific wireless machine by using the wireless machine  1 D. 
     However, in the lighting equipment system described above, when the correspondence relationship between the wireless machine ID and the (arrangement position of) lighting equipment is unknown, it is impossible to discriminate the wireless machine that becomes the destination of the control signal when controlling a specific piece of lighting equipment. 
     In this case, it is conceivable that the correspondence relationship between the wireless machine ID and the lighting equipment is registered (set) in advance. However, considering that hundreds to thousands of pieces of lighting equipment are arranged in an office building, for example, it is very complicated for a worker to perform installation work while registering the wireless machine ID assigned to the wireless machine. It is also difficult to confirm and register the wireless machine ID assigned to a wireless machine after the wireless machine is installed. 
     Therefore, the electronic apparatus according to the present embodiment is used to estimate the position where each wireless machine is installed (i.e., the wireless machine ID assigned to the wireless machine installed at each installation position) from among the installation positions in a situation where it is known as to the position where the plurality of wireless machines are installed (hereinafter referred to as an installation position) as described above but it is unknown as to which wireless machine is installed at each of the installation positions (i.e., the correspondence relationship between the installation position and the wireless machine ID). 
     While an example in which the electronic apparatus according to the present embodiment is used in a lighting equipment system has been described here, the electronic apparatus according to the present embodiment may be used in a photovoltaic power generation system, for example. 
     Specifically, in a case where a photovoltaic power generation system includes a plurality of solar panels  2   a  to  2   l  as shown in  FIG. 2 , for example, a wireless machine is sometimes installed in each of the plurality of solar panels  2   a  to  2   l  (i.e., positions P 1  to P 12 ). According to this, it is possible to collect the power generation amount, the temperature, and the like of each of the solar panels  2   a  to  2   l  via the wireless machine, and hence it is possible to monitor the state of each of the solar panels  2   a  to  2   l  (operation status, failure, or the like) based on the power generation amount, the temperature, and the like. 
     Even in such a case, unless the positions P 1  to P 12  where the plurality of respective wireless machines are installed can be discriminated, even in a case where the power generation amount corresponding to an abnormal value, for example, is received from a specific wireless machine, a broken solar panel (i.e., solar panel in which the abnormal value is detected) cannot be specified from among the solar panels  2   a  to  2   l.    
     The electronic apparatus according to the present embodiment can also be used to estimate the position where each wireless machine is installed from among a plurality of installation positions (solar panel) in such a photovoltaic power generation system. 
     In addition to the above, the present embodiment can also be applied to a case where in an air conditioning system, a wireless machine is installed in a plurality of air conditioners, or a case where a wireless machine is installed in various facilities (air conditioner, motor, inverter, sensor, and the like) such as a train. 
     Hereinafter, the electronic apparatus according to the present embodiment will be described in detail.  FIG. 3  is a diagram showing an example of a hardware configuration of the electronic apparatus according to the present embodiment. As shown in  FIG. 3 , an electronic apparatus  10  includes a CPU  11 , a nonvolatile memory  12 , a main memory  13 , and a communication device  14 . 
     The CPU  11  is a hardware processor that controls the operation of each component in the electronic apparatus  10 . The CPU  11  executes a program loaded from the nonvolatile memory  12 , which is a storage device, to the main memory  13 . 
     The communication device  14  is a device configured to execute wired or wireless communication. With this communication device  14 , the electronic apparatus  10  is communicably connected with each of the plurality of wireless machines, and can transmit and receive various information (signals). 
     Note that the present embodiment assumes that the electronic apparatus  10  is connected with each of the plurality of wireless machines so as to be capable of wireless communication. However, the electronic apparatus  10  may be connected to a wireless access point via a wired network, for example, and the wireless access point may be connected with the plurality of wireless machines so as to be capable of wireless communication by constituting a star network. Each of the wireless machines may be connected by constituting a wireless mesh network. That is, in the present embodiment, as long as the electronic apparatus  10  is communicably connected with each of the plurality of wireless machines, wired communication may be executed in a part thereof. 
     Although only the nonvolatile memory  12  and the main memory  13  are shown in  FIG. 3 , the electronic apparatus  10  may include other storage devices such as a hard disk drive (HDD) and a solid state drive (SSD). 
     Although omitted in  FIG. 3 , the electronic apparatus  10  may further include an input device such as a mouse or a keyboard, and a display device such as a display. 
       FIG. 4  is a block diagram showing an example of the functional configuration of the electronic apparatus  10 . As shown in  FIG. 4 , the electronic apparatus  10  includes a measurement instruction module  101 , characteristic information storage  102 , position information storage  103 , and an estimation module  104 . 
     Note that in the present embodiment, the electronic apparatus  10  is communicably connected with a plurality of wireless machines  20  as described above. 
     The present embodiment assumes that part or all of the measurement instruction module  101  and the estimation module  104  are implemented by causing the CPU  11  to execute a program, i.e., by software. Note that part or all of the modules  101  and  104  may be implemented by hardware such as an integrated circuit (IC), or may be implemented as a combination configuration of software and hardware. 
     The present embodiment assumes that the characteristic information storage  102  and the position information storage  103  shall be implemented by, for example, a nonvolatile memory  12  or another storage device. 
     The measurement instruction module  101  gives to each of the plurality of wireless machines  20  an instruction about a channel to be used for measuring propagation characteristics in each of the plurality of wireless machines  20 . The measurement instruction module  101  receives, from each of the plurality of wireless machines  20 , characteristic information obtained from the propagation characteristics measured by each of the plurality of wireless machines  20  using the instructed channel. 
     The characteristic information storage  102  stores the characteristic information received by the measurement instruction module  101 . 
     The position information storage  103  stores in advance position information indicating the installation position where each of the plurality of wireless machines  20  is installed. The (installation position indicated by) position information stored in the position information storage  103  may be automatically extracted from, for example, a drawing showing the positions where the plurality of wireless machines  20  are installed, or may be input by a worker or the like who installs the plurality of wireless machines  20 . 
     Based on the characteristic information stored in the characteristic information storage  102  and the position information stored in the position information storage  103 , the estimation module  104  estimates the position where each of the plurality of wireless machines  20  is installed (i.e., correspondence relationship between the installation position and the wireless machine  20 ) from among a plurality of installation positions indicated by the position information. In other words, the estimation module  104  estimates the (wireless machine ID assigned to) wireless machine installed at the installation position for each installation position indicated by the position information. 
       FIG. 5  shows an example of the data structure of position information stored in the position information storage  103  shown in  FIG. 4 . 
     As shown in  FIG. 5 , the position information includes X and Y coordinates in association with an installation position ID. The installation position ID is identification information assigned to an installation position (i.e., position where one wireless machine  20  is installed) indicated by the position information. The X coordinate is an X coordinate value of the installation position to which the associated installation position ID is assigned. The Y coordinate is a Y coordinate value of the installation position to which the associated installation position ID is assigned. In the position information, the X coordinate value and the Y coordinate value represent the position (installation position) where the wireless machine  20  is installed. Note that the position may be expressed in three-dimensional coordinates by adding a Z coordinate value. 
     In the example shown in  FIG. 5 , the position information storage  103  stores position information including the X coordinate “1” and the Y coordinate “1” in association with the installation position ID “P 1 ”. This position information indicates that one wireless machine  20  of the plurality of wireless machines  20  is installed at the installation position in which the installation position ID “P 1 ” is assigned, the X coordinate value is 1, and the Y coordinate value is 1. 
     The position information storage  103  stores position information including the X coordinate “1” and the Y coordinate “2.” in association with the installation position ID “P 2 ”. This position information indicates that one wireless machine  20  of the plurality of wireless machines  20  is installed at the installation position in which the installation position ID “P 2 ” is assigned, the X coordinate value is 1, and the Y coordinate value is 2. 
     While only the position information indicating the installation position to which the installation position IDs “P 1 ” and “P 2 ” are assigned have been described here, the same applies to other position information. 
     Note that according to the position information shown in  FIG. 5 , the installation positions (i.e., nine installation positions to which the installation position IDs “P 1 ” to “P 9 ” are assigned) where the plurality of wireless machines  20  (i.e., nine wireless machines  20 ) are installed can be discriminated, but it is not possible to discriminate as to which wireless machine  20  (wireless machine ID) is installed at each installation position. 
     With reference to the sequence chart of  FIG. 6 , an example of the processing procedure of the electronic apparatus  10  and the plurality of wireless machines  20  in a case of estimating the positions where the plurality of wireless machines  20  are installed will be described below. In  FIG. 6 , the processing of one wireless machine (hereinafter referred to as a target wireless machine)  20  of the plurality of wireless machines  20  is mainly described, but similar processing is executed also in the other wireless machines  20 . 
     First, the measurement instruction module  101  determines a channel (wireless channel) to be used for measuring propagation characteristics in each of the plurality of wireless machines  20  (step S 1 ). Note that a plurality of charnels are determined in step S 1 . 
     Next, the measurement instruction module  101  transmits, to the target wireless machine  20 , measurement instruction information including a number (hereinafter referred to as a measurement channel number) indicating each of the plurality of channels determined in step S 1  (step S 2 ). Note that the measurement instruction information is transmitted to all the wireless machines  20  by broadcast, for example. 
     Here, the measurement instruction information includes a plurality of measurement channel numbers, and the measurement channel number is only required to be one in which each of the plurality of wireless machines  20  can identify the channel determined in step S. For example, in the case of the 920 MHz band, numbers defined for channels such as  33 ,  42 ,  51 , and  60  can be used as the measurement channel numbers. The center frequency of the channel or the like may be used as the measurement channel number. 
     In addition to the measurement channel number described above, the measurement instruction information includes a period (hereinafter referred to as a measurement period) in which the propagation characteristics are measured and a number indicating the channel to be used in each of the plurality of wireless machines  20  after ending the measurement of the propagation characteristics (hereinafter, referred to as a switching destination channel number). The measurement period and the switching destination channel number may be defined in advance, for example, or may be dynamically determined by the measurement instruction module  101 . 
     The measurement period may be an identical period for a plurality of measurement channel numbers (i.e., the plurality of channels determined in step S 1 ) or may be a different period for each of the plurality of measurement channel numbers. When each of the wireless machines includes a timing module and they are synchronized with each other, the measurement period may be a period defined by, for example, the time at which the measurement of the propagation characteristics starts (hereinafter referred to as a measurement start time) and the time at which the measurement of the propagation characteristics ends (hereinafter referred to as a measurement end time). In this case, the measurement instruction information is only required to include the measurement start time and the measurement end time for each measurement channel number. 
     The switching destination channel number can be, for example, a channel before the measurement of the propagation characteristics is started, but may be another channel. For example, if the channel at the time point when the measurement of the propagation characteristics ended is continuously used, the measurement instruction information may not include the switching destination channel number. 
     In step S 2 , the measurement instruction information transmitted from the measurement instruction module  101  (electronic apparatus  10 ) is received by the target wireless machine  20 . 
     Based on a plurality of measurement channel numbers included in the received measurement instruction information, the target wireless machine  20  switches the channel on which the target wireless machine  20  executes communication (step S 3 ). 
     Here, as described above, the measurement instruction information includes a plurality of measurement channel numbers, and in the measurement of propagation characteristics, it is necessary to transmit and receive signals between the plurality of wireless machines  20  as described later. Therefore, within the identical measurement period, the channel used (on which communication is performed) by each of the plurality of wireless machines  20  is unified. In this case, in each of the plurality of wireless machines  20 , the channels indicated by each of the plurality of measurement channel numbers included in the measurement instruction information shall be used in a predetermined order. The order in which the channels indicated by each of the plurality of measurement channel numbers are used may be in ascending order of the measurement channel numbers or the like, or may be specified by the electronic apparatus  10  (measurement instruction module  101 ) side. In the case where the order in which the channels are used is specified by the electronic apparatus  10  side, the specified order is only required to be included in the measurement instruction information. 
     When the channels are switched based on the order described above in step S 3 , each of the plurality of wireless machines  20  becomes capable of transmitting and receiving signals using the identical channel among the plurality of channels indicated by each of the plurality of measurement channel numbers. 
     Hereinafter, the channel switched in step S 3  (i.e., channel on which the target wireless machine  20  executes communication) will be referred to as a target channel. 
     Next, the target wireless machine  20  starts measurement of the propagation characteristics (step S 4 ). The processing of step S 4  may be executed immediately after the processing of step S 3  is executed, or, if the measurement instruction information received by the wireless machine  20  includes the measurement start time, it may be executed upon reaching the measurement start time. 
     When the measurement of the propagation characteristics is started in step S 4 , the target wireless machine  20  transmits, by broadcast, a signal for measuring the propagation characteristics (hereinafter referred to as a measurement signal) to the plurality of other wireless machines  20  at random timing (step S 5 ). In this case, the measurement signal is transmitted using the target channel. The measurement signal includes a wireless machine ID (i.e., wireless machine ID of the transmission source of the measurement signal) assigned to the target wireless machine  20 . Note that it is also possible to determine the timing, the order, and the like in which the target wireless machine  20  transmits the measurement signals, and in this case, the measurement signals are only required to be transmitted in accordance with the determined timing, order, and the like. 
     Here, the measurement signal is similarly transmitted by broadcast also from each of the plurality of wireless machines  20  other than the target wireless machine  20 . Therefore, the target wireless machine  20  receives the measurement signals transmitted from each of the other wireless machines  20 . When the target wireless machine  20  receives the measurement signal, the target wireless machine  20  measures the propagation characteristics in the target channel of the target wireless machine  20  based on the measurement signal (step S 6 ). Note that the propagation characteristics in the present embodiment are only required to represent characteristics related to the wireless communication environment between the target wireless machine  20  and the other wireless machine  20 . Specifically, for example, a received signal strength indicator (RSSI) is measured as propagation characteristics. 
     Note that the target wireless machine  20  receives the measurement signal transmitted from each of the other wireless machines  20  (measurement signal including the wireless machine ID assigned to the other wireless machine  20 ), and in step S 6 , based on the measurement signal received by the target wireless machine  20 , the propagation characteristics between the target wireless machine  20  and the other wireless machines  20  to which the wireless machine ID included in the measurement signal is assigned are measured. That is, the target wireless machine  20  measures the propagation characteristics for each of the other wireless machines  20  based on the measurement signal transmitted from each of the other wireless machines  20 . 
     The propagation characteristics (propagation characteristics measured for each of the other wireless machines  20 ) measured based on the measurement information in step S 6  are held inside the target wireless machine  20  together with the wireless machine ID included in the measurement information (wireless machine IDs assigned to the other wireless machines  20 ). 
     Note that the processing of steps S 5  and S 6  described above may be executed a plurality of times after the processing of step S 4  is executed and before the processing of step S 7  to be described later is executed. Thus, for example, when a plurality of measurement signals are received from one of the other wireless machines  20 , at least one of the mean value, Maximum value, median value, mode value, and standard deviation of the propagation characteristics (e.g., RSSI) measured based on each of the plurality of measurement signals can be used as the propagation characteristics between the target wireless machine  20  and the other wireless machine  20 . 
     Although  FIG. 6  shows that the processing of step S 6  is executed after the processing of step S 5  is executed for convenience, the processing of steps S 5  and S 6  may be replaced as appropriate. 
     Next, the target wireless machine  20  ends the measurement of the propagation characteristics (step S 7 ). The processing of step S 7  is executed at the time point when the measurement period measured after the execution of step S 4  has elapsed. Note that in a case where the measurement instruction information includes the measurement end time, the processing of step S 7  may be executed at the time point when the measurement end time has elapsed. 
     The measurement of the measurement period described above shall be carried out by using, for example, a timing module (not illustrated) operating synchronously among the plurality of wireless machines  20 . The timing module may be incorporated in the target wireless machine  20  such as a TSF timer of IEEE 802.11 for communication control, or may be implemented in the target wireless machine  20  as an application program synchronized by IEEE 1588. 
     When the processing of step S 7  is executed, it is determined whether or not the processing of steps S 3  to S 7  described above has been executed for all the channels indicated by each of the plurality of measurement channel numbers included in the measurement instruction information (step S 8 ). 
     If it is determined that the processing has not been executed for all the channels (NO in step S 8 ), the process returns to step S 3  and the processing is repeated. In this case, a process of discriminating the channel to be used next based on the order of using the channel described above among the plurality of channels indicated by the plurality of measurement channel numbers included in the measurement instruction information and switching the target channel to the discriminated channel is executed in step S 3 . 
     Due to this, in the present embodiment, the propagation characteristics are measured in all the channels instructed by the measurement instruction module  101  (i.e., all the channels indicated by the plurality of measurement channel numbers included in the measurement instruction information). 
     On the other hand, if it is determined that the processing has been executed for all the channels (YES in step S 8 ), the propagation characteristics of each of the other wireless machines  20  measured in each of the plurality of channels indicated by the plurality of measurement channel numbers are held in the target wireless machine  20 . In this case, the target wireless machine  20  extracts the feature amount of the propagation characteristics for each of the other wireless machines  20  (step S 9 ). 
     The feature amount of the propagation characteristics extracted in step S 9  can be obtained as, for example, at least one of the mean value, maximum value, median value, mode value, and standard deviation of the propagation characteristics (RSSI) measured in each of the plurality of channels indicated by the plurality of measurement channel numbers, but may be another feature amount. 
     When the processing of step S 9  is executed, the target wireless machine  20  switches the channel on which the target wireless machine  20  executes communication based on the switching destination channel number included in the measurement instruction information (step S 10 ). Note that if the measurement instruction information does not include the switching destination channel number, the processing of step S 10  is not executed, and the current channel (channel switched in step S 3 ) is continuously used in the target wireless machine  20 . If all the wireless machines  20  have been notified in advance of that a channel used before starting measurement, for example, is to be used as a specific channel, the channel is used. 
     When the processing of step S 10  is executed, the target wireless machine  20  transmits, to the electronic apparatus  10 , characteristic information including the feature amount of the propagation characteristics extracted for each of the other wireless machines  20  (wireless machine ID) in step S 9  (step S 11 ). This characteristic information is transmitted to the electronic apparatus  10  together with the wireless machine ID assigned to the target wireless machine  20  so that the electronic apparatus  10  can specify the wireless machine  20  that has transmitted the characteristic information. The processing of step S 11  may be executed at the timing when the processing of step S 10  is executed, or may be executed in response to an instruction from the electronic apparatus  10  (e.g., measurement instruction module  101 ). 
     Here, the processing of steps S 3  to S 11  described above is executed in each of the plurality of wireless machines  20 . Therefore, when the processing of step S 11  is executed in each of the plurality of wireless machines  20 , the electronic apparatus  10  receives the characteristic information transmitted from each of the plurality of wireless machines  20 . 
     The characteristic information received by the electronic apparatus  10  is stored in the characteristic information storage  102  together with the wireless machine ID assigned to the wireless machine  20  that has transmitted the characteristic information (step S 12 ). 
       FIG. 7  shows an example of the data structure of characteristic information stored in the characteristic information storage  102 . In the example shown in  FIG. 7 , the plurality of wireless machines  20  are wireless machines D 1  to D 9 , and the characteristic information storage  102  stores characteristic information  102   a  to  102   i  (characteristic information of wireless machines D 1  to D 9 ) transmitted from the respective wireless machines D 1  to D 9 . Note that “D 1 ” to “D 9 ” shown in  FIG. 7  correspond to the wireless machine IDs assigned to the wireless machines D 1  to D 9 , respectively. 
     The characteristic information  102   a  is characteristic information transmitted from the wireless machine D 1 . The characteristic information  102   a  includes a feature amount (here, RSSI) of the propagation characteristics measured in the wireless machine D 1  based on the measurement signal transmitted from the other wireless machines D 2  to D 9  in association with the wireless machines ID assigned to the wireless machine D 1  and the wireless machine IDs assigned to the respective other wireless machines D 2  to D 9 . 
     Specifically, the characteristic information  102   a  indicates that the feature amount of the propagation characteristics between the wireless machine D 1  and the wireless machine D 2  is “−50”. Note that this “−50” is, for example, a mean value (i.e., feature amount) of the propagation characteristics between the wireless machine D 1  and the wireless machine D 2  measured in each of the plurality of channels. 
     The characteristic information  102   a  indicates that the feature amount of the propagation characteristics between the wireless machine D 1  and the wireless machine D 3  is “−55”. Note that this “−55” is, for example, a mean value (i.e., feature amount) of the propagation characteristics between the wireless machines D 1  and D 3  measured in each of the plurality of channels. 
     Although detailed description is omitted, the same applies to the feature amounts of the propagation characteristics between the wireless machine D 1  and each of the other wireless machines D 4  to D 9  included in the characteristic information  102   a . Since the other characteristic information  102   b  to  102   i  are the same as the characteristic information  102   a , detailed description thereof is omitted here. 
     Note that, for example, the (feature amount of) propagation characteristics measured in the wireless machine D 1  based on the measurement signal transmitted from the wireless machine D 2  and the (feature amount of) propagation characteristics measured in the wireless machine D 2  based on the measurement signal transmitted from the wireless machine D 1  both correspond to the propagation characteristics between the wireless machine D 1  and the wireless machine D 2 , and often become substantially the same values. The same applies to the propagation characteristics between two wireless machines other than the wireless machine D 1  and the wireless machine D 2  among the plurality of wireless machines D 1  to D 9 . Therefore, the (characteristic information including) propagation characteristics between two of the plurality of wireless machines D 1  to D 19  may be measured by only one of the wireless machines and stored in the characteristic information storage  102  without distinction between the transmission side wireless machines and the reception side wireless machines. In this case, it becomes possible to reduce the information amount (data amount) stored in the characteristic information storage  102  shown in  FIG. 7 , for example. 
     Returning to  FIG. 6  again, the estimation module  104  acquires the position information stored in the position information storage  103  (step S 13 ). 
     Next, based on the characteristic information stored in the characteristic information storage  102  in step S 12  and the position information acquired in step S 13 , the estimation module  104  estimates the position (i.e., correspondence relationship between each of the plurality of installation positions and each of the plurality of wireless machines  20 ) where each of the plurality of wireless machines  20  is installed from among the plurality of installation positions indicated by the position information (step  314 ). 
     To specifically explain the processing in step S 14 , first, the estimation module  104  generates a plurality of hypotheses of combination of, for example, each installation position indicated by position information with (the wireless machine ID assigned to) each of the plurality of wireless machines  20 . 
     Assuming that the installation positions are P 1  to P 9  and the plurality of wireless machines  20  are the wireless machines D 1  to D 9  as described above, the combination of each of the installation positions P 1  to P 9  and each of the wireless machines D 1  to D 9  includes various combinations such as “P 1 -D 1 , P 2 -D 2 , P 3 -D 3 , P 4 -D 4 , P 5 -D 5 , P 6 -D 6 , P 7 -D 7 , P 8 -D 8 , P 9 -D 9 ”, “P 1 -D 9 , P 2 -DA, P 3 -D 7 , P 4 -D 6 , P 5 -D 5 , P 6 -D 4 , P 7 -D 3 , P 8 -D 2 , P 9 -D 1 ”, and “P 1 -D 2 , P 2 -D 3 , P 3 -D 4 , P 4 -D 5 , P 5 -D 6 , P 6 -D 7 , P 7 -D 8 , P 8 -D 9 , P 9 -D 1 ”. 
     Next, the estimation module  104  calculates evaluation values for various combinations of each of the installation positions and each of the wireless machines  20  described above, and estimates the position where each of the wireless machines  20  is installed based on the combination for which the highest evaluation value has been calculated. Specifically, if the highest evaluation value is calculated for the combination of, for example, “P 1 -D 2 , P 2 -D 3 , P 3 -D 4 , P 4 -D 5 , P 5 -D 6 , P 6 -D 7 , P 7 -D 8 , P 8 -D 9 , P 9 -D 1 ”, it is estimated that the wireless machine D 2  is installed at the installation position P 1 , the wireless machine D 3  is installed at the installation position P 2 , the wireless machine D 4  is installed at the installation position P 3 , the wireless machine D 5  is installed at the installation position P 4 , the wireless machine D 6  is installed at the installation position P 5 , the wireless machine D 17  is installed at the installation position P 6 , the wireless machine D 8  is installed at the installation position P 7 , the wireless machine D 9  is installed at the installation position P 8 , and the wireless machine D 1  is installed at the installation position P 9 . 
     The evaluation value is calculated based on the correlation relationship between the distance between the installation positions indicated by the position information and the propagation characteristics among the wireless machines  20 , for example. When RSSI has been measured as the propagation characteristics as described above, a combination in which the RSSI decreases as the distance between the installation positions increases is searched. In the present embodiment, since the RSSI decreases (attenuates) as the distance increases, the combination in which the correlation coefficient, which is an index representing the correlation relationship described above, is closest to −1 is used as the estimation result. 
     Note that the estimation processing in step S 14  may be executed for all combinations in each of the plurality of installation positions and each of the plurality of wireless machines  20 , or may be executed for a limited combination using, for example, a genetic algorithm in order to reduce the processing load. Furthermore, this estimation processing may be executed by using artificial intelligence based on machine learning, for example. The estimation method using the correlation coefficient is disclosed in JP 2017-227600 A, for example. 
     When the processing of  FIG. 6  described above is executed, the position where each of the plurality of wireless machines  20  is installed (i.e., correspondence relationship between each of the plurality of installation positions and each of the plurality of wireless machines  20 ) can be obtained as an estimation result, and the estimation result can be used in various systems, for example. 
     Specifically, for example, a case in which the correspondence relationship between the positions P 1  to P 9  and the wireless machines D 1  to D 9  in the lighting equipment system described in  FIG. 1  is estimated is assumed. In this case, assuming that the correspondence relationship (i.e., estimation result) between the positions P 1  to P 9  and the wireless machines D 1  to D 9  is, for example, “P 1 -D 2 , P 2 -D 3 , P 3 -D 4 , P 4 -D 5 , P 5 -D 6 , P 6 -D 7 , P 7 -D 8 , P 8 -D 9 , P 9 -D 1 ”, in the case of performing control such as turning on only the lighting equipment arranged in the room  1   a , for example, it is only required to transmit a control signal to the wireless machines D 2 , D 3 , and D 4 . Thus, when the correspondence relationship between the positions P 1  to P 9  and the wireless machines D 1  to D 9  is estimated in the lighting equipment system, the lighting equipment can be appropriately controlled using the estimation result. 
     It is assumed that the correspondence relationship between the positions P 1  to P 12  and the wireless machines D 1  to D 12  in the photovoltaic power generation system described in  FIG. 2 , for example, is estimated. In this case, assuming that the correspondence relationship (i.e., estimation result) between the positions P 1  to P 12  and the wireless machines D 1  to D 12  is, for example, “P 1 -D 12 , P 2 -D 11 , P 3 -D 10 , P 4 -D 9 , P 5 -D 8 , P 6 -D 7 , P 7 -D 6 , P 8 -D 5 , P 9 -D 4 , P 10 -D 3 , P 11 -D 2 , P 12 -D 1 ”, by receiving the power generation amount corresponding to an abnormal value from the wireless machine D 8 , for example, it is possible to specify that an abnormality has occurred in the solar panel  2   e  arranged at the position P 5  where the wireless machine D 8  is installed. In the case where the correspondence relationship between the positions P 1  to P 12  and the wireless machines D 1  to D 12  is estimated thus in the photovoltaic power generation system, the state of the solar panel can be appropriately monitored using the estimation result. 
     Note that  FIG. 6  illustrates that a plurality of channels are determined in step S 1 , but the plurality of channels can be determined sequentially. In this case, the processing of steps S 1  to S 7  is only required to be repeatedly executed for each channel for which propagation characteristics are to be measured. 
     Although  FIG. 6  illustrates that the feature amount is extracted on the wireless machine (target wireless machine)  20  side, the propagation characteristics (characteristic information) measured on each of the plurality of channels may be transmitted from the wireless machine  20  to the electronic apparatus  10 , and the processing of extracting the feature amount of the propagation characteristics may be executed on the electronic apparatus  10  side. 
       FIG. 6  illustrates that after the processing in step S 12  is executed, the processing in step S 13  is executed (i.e., position information is acquired), but the processing in step S 13  (processing of acquiring position information) may be executed at any timing after the processing shown in  FIG. 6  is started before the processing in step S 14  is executed. 
     As described above, in the present embodiment, the characteristic information of the first wireless machine  20  obtained from the first propagation characteristics in the first channel of the first wireless machine  20  and the second propagation characteristics in the second channel of the first wireless machine  20 , and the characteristic information of the second wireless machine  20  obtained from the third propagation characteristics in the first channel of the second wireless machine  20  and the fourth propagation characteristics in the second channel of the second wireless machine  20  are received, and based on the position information stored in the position information storage  103 , the characteristic information of the first wireless machine  20 , and the characteristic information of the second wireless machine  20 , the position where the first and second wireless machines  20  are installed is estimated from the first and second installation positions indicated by the position information (i.e., correspondence relationship between each of the plurality of installation positions and each of the plurality of wireless machines  20 ). Note that in the present embodiment, the positions where the first and second wireless machines  20  are installed correspond to the installation positions of various pieces of equipment where the first and second wireless machines  20  are installed, including the lighting equipment shown in  FIG. 1  and the solar panel shown in  FIG. 2  described above. 
     Here, assuming that the position where each of the plurality of wireless machines  20  is installed is estimated based on the RSSI (propagation characteristic) in one channel, for example, in an environment with much reflection of radio waves, a phenomenon called multipath fading, in which direct waves and reflected waves interfere with each other, occurs, and even if the distance between the two wireless machines  20  is the same, the RSSI sometimes drops greatly depending on the installation position (environment) of the two wireless machines  20 . When the position where each of the plurality of wireless machines  20  is installed is estimated based on such RSSI, the estimation accuracy of the position is lowered. 
     However, even if the RSSI drops due to multipath fading in a specific channel, the RSSI can sometimes be measured without being affected by multipath fading in other channels having different wavelengths. 
     Therefore, in the present embodiment, the influence of multipath fading can be mitigated by using RSSI measured in a plurality of channels, and the estimation accuracy can be improved by enhancing the correlation between the distance between installation positions and RSSI (propagation characteristics). 
     Note that in the present embodiment, it has been mainly described that the RSSI is used as the propagation characteristics measured by the first and second wireless machines  20 , but, for example, packet error rate (PER) or the like may be used as the propagation characteristics. 
     Furthermore, in the present embodiment, the propagation characteristics in each of the plurality of channels are measured in each of the first and second wireless machines  20 , and the feature amounts of the propagation characteristics in the plurality of channels (i.e., feature amount extracted from the propagation characteristics in each of the plurality of channels) are transmitted from the first and second wireless machines  20  to the electronic apparatus  10 . With such a configuration, it is not necessary to transmit all of the propagation characteristics in each of the plurality of channels to the electronic apparatus  10 , and hence the communication amount from the first and second wireless machines  20  to the electronic apparatus  10  can be reduced, and the electronic apparatus  10  can collect (receive) measurement results in a shorter time. 
     On the other hand, the propagation characteristics measured in each of the plurality of channels may be transmitted from each of the first and second wireless machines  20  to the electronic apparatus  10 , and the feature values of the propagation characteristics measured in the plurality of channels may be extracted (calculated) on the electronic apparatus  10  side. In general, since the electronic apparatus  10  has a higher hardware performance than that of the first and second wireless machines in most cases, such a configuration can more efficiently extract the feature amounts of the propagation characteristics measured in the plurality of channels. 
     For example, at least one of the mean value, maximum value, median value, mode value, and standard deviation of the propagation characteristics measured in each of the plurality of channels can be used as the feature amount of the propagation characteristics. 
     In the present embodiment, the instructions about the measurement period (time) of the propagation characteristics of the first and second wireless machines  20  and the third channel (switching destination channel) are given to each of the first and second wireless machines  20 . In this case, each of the first wireless machines  20  measures the first and second propagation characteristics based on the instructed measurement period, and switches the channel on which the first wireless machines execute communication to the third channel after the measurement ends. Similarly, each of the second wireless machines  20  measures the third and fourth propagation characteristics based on the instructed measurement period, and switches the channel on which the second wireless machines execute communication to the third channel after the measurement ends. Such a configuration makes it possible to measure the propagation characteristics in each channel of the first and second wireless machines  20  at the identical timing, and to continuously execute communication in the third channel after the measurement ends. The instruction about measurement start time and the measurement end time may be given as the measurement period. 
     Note that it has been described that in the present embodiment, each of the plurality of wireless machines  20  measures the propagation characteristics with the other wireless machines  20 , but for example, the electronic apparatus  10  may measure the propagation characteristics with the wireless machines  20  by receiving a measurement signal from each of the plurality of wireless machines  20 , and may estimate the position where each wireless machine  20  is installed based on the measured propagation characteristics. 
     Furthermore, in the present embodiment, it has been described that the parts  101  to  104  shown in  FIG. 4  are included in one device, but the parts  101  to  104  may be arranged in a plurality of devices. That is, the electronic apparatus  10  according to the present embodiment may be implemented by a plurality of devices. Furthermore, for example, the position information storage  103  may be provided in an external server device or the like outside the electronic apparatus  10 . In this case, in step S 13  shown in  FIG. 6  described above, the position information may be acquired (received) from the external server device. 
     Second Embodiment 
     Next, the second embodiment will be described. Note that in the present embodiment, parts similar to those in the drawings used in the description of the first embodiment described earlier are given the identical reference numerals for description. Since the usage mode and hardware configuration of the electronic apparatus according to the present embodiment are similar to those of the first embodiment described above, a detailed description thereof will be omitted here. In the following description, parts different from those of the first embodiment described above will be mainly described. 
       FIG. 8  is a block diagram showing an example of the functional configuration of an electronic apparatus  10  according to the present embodiment. The present embodiment is different from the above-described first embodiment in that the estimation module  104  includes a primary estimation module  104   a  and a secondary estimation module  104   b.    
     In the above-described first embodiment, the characteristic information including the feature amounts of the propagation characteristics measured in the plurality of channels is transmitted from each of the plurality of wireless machines  20 , but in the present embodiment, it is assumed that not the characteristic information including the feature amounts but the characteristic information for each channel obtained from the propagation characteristics measured in each of the plurality of channels is transmitted from each of the plurality of wireless machines  20 . That is, in the present embodiment, the characteristic information storage  102  stores the characteristic information for each channel. 
     Based on the characteristic information stored in the characteristic information storage  102  for each channel and the position information stored in the position information storage  103 , the primary estimation module  104   a  estimates, for each channel, the position (i.e., the correspondence relationship between the installation position and the wireless machine  20 ) at which each of the plurality of wireless machines  20  is installed from among the plurality of installation positions indicated by the position information. 
     Based on the result estimated for each channel by the primary estimation module  104   a , the secondary estimation module  104   b  estimates the position where each of the plurality of wireless machines  20  is installed from among the plurality of installation positions indicated by the position information stored in the position information storage  103 . 
     With reference to the sequence chart of  FIG. 9 , an example of the processing procedure of the electronic apparatus  10  and the plurality of wireless machines  20  when the position where each of the plurality of wireless machines  20  is installed is estimated will be described below.  FIG. 9  mainly describes the processing of one wireless machine (hereinafter referred to as a target wireless machine)  20  of the plurality of wireless machines  20 , but similar processing is executed also in the other wireless machines  20 . 
     First, the processing of steps S 21  to S 29  is executed, which corresponds to the processing of steps S 1  to S 8  and step S 10  shown in  FIG. 6  described earlier. 
     Note that in the above-described first embodiment, when it is determined in step S 8  that the processing has been executed for all the channels, the feature amount of the propagation characteristics for each of the other wireless machines  20  is extracted by executing the processing of step S 9 . However, in the present embodiment, processing corresponding to the processing in step S 9  is not executed. 
     When the processing of step S 29  is executed, the target wireless machine  20  transmits, to the electronic apparatus  10 , characteristic information (i.e., the characteristic information for each channel) obtained from the propagation characteristics of each of the other wireless machines  20  measured in each of the plurality of channels indicated by the plurality of measurement channel numbers held in the target wireless machine  20  (step S 30 ). This characteristic information is transmitted to the electronic apparatus  10  together with the wireless machine ID assigned to the target wireless machine  20 . The measurement channel number may also be transmitted. The processing of step S 30  may be executed at the timing when the processing of step S 29  is executed, or may be executed in response to an instruction from the electronic apparatus  10  (e.g., measurement instruction module  101 ). 
     Note that the processing of step S 30  may be executed each time the measurement of the propagation characteristics in one of the plurality of channels indicated by the plurality of measurement channel numbers included in the measurement instruction information ends (i.e., processing of step S 27  is executed). 
     Similarly to the processing of steps S 5  and S 6  shown in  FIG. 6 , when the processing of steps S 25  and S 26  are executed a plurality of times, at least one of the mean value, maximum value, median value, mode value, standard deviation, and the like of the propagation characteristics measured based on each of the plurality of measurement signals received from one of the other wireless machines  20  can be obtained as characteristic information between the target wireless machine  20  and the other wireless machine  20 . 
     Here, the processing of steps S 23  to S 30  described above is executed in each of the plurality of wireless machines  20 . Therefore, when the processing of step S 30  is executed in each of the plurality of wireless machines  20 , the electronic apparatus  10  receives the characteristic information for each channel (measurement channel number) transmitted from each of the plurality of wireless machines  20 . 
     The characteristic information for each channel received by the electronic apparatus  10  is stored in the characteristic information storage  102  together with the wireless machine ID assigned to the wireless machine  20  having transmitted the characteristic information and the measurement channel number indicating the channel (step S 31 ). 
       FIG. 10  shows an example of the data structure of the characteristic information stored in the characteristic information storage  102 . In the example shown in  FIG. 10 , the plurality of wireless machines  20  are wireless machines D 1  to D 9 , and the characteristic information storage  102  stores characteristic information transmitted from the respective wireless machines D 1  to D 9 . 
     In the present embodiment, the characteristic information storage  102  stores characteristic information for each channel for which the propagation characteristics are measured.  FIG. 10  shows the characteristic information obtained from the propagation characteristics of the wireless machines D 1  to D 9  in the channel indicated by a measurement channel number  1  and the characteristic information obtained from the propagation characteristics of the wireless machines D 1  to D 9  in the channel indicated by a measurement channel number  2 . Note that although omitted in  FIG. 10 , characteristic information is similarly stored for channels other than the channels indicated by the measurement channel number  1  and the measurement channel number  2 . 
     Note that the data structure of the characteristic information stored in the characteristic information storage  102  is the same as that described above with reference to  FIG. 7  except that the characteristic information is stored for each channel, and hence a detailed description thereof is omitted here. 
     Returning to  FIG. 9  again, the processing of step S 32  corresponding to the processing of step S 13  shown in  FIG. 6  described above is executed. 
     Next, the primary estimation module  104   a  executes primary estimation processing based on the characteristic information for each channel stored in the characteristic information storage  102  in step S 31  and the position information acquired in step S 32  (step S 33 ). This primary estimation processing is similar processing to the processing (estimation processing) executed by the estimation module  104  in the above-described first embodiment, but in the primary estimation processing, the position where each of the plurality of wireless machines  20  is installed is estimated for each channel. 
     When the processing of step S 33  is executed, the secondary estimation module  104   b  acquires the result of the primary estimation processing for each channel in step S 33 , and executes the secondary estimation processing (step S 34 ). When the secondary estimation processing is executed, the position where each of the plurality of wireless machines  20  is installed is estimated from among the plurality of installation positions indicated by the position information acquired in step S 32 , but in the present embodiment, the estimation result (i.e., secondary estimation result) obtained by executing this secondary estimation processing will be used by the various systems described in the above-described first embodiment. 
     Next, the processing procedure of the secondary estimation processing will be described in detail with reference to the flowchart of  FIG. 11 . The secondary estimation processing shown in  FIG. 11  is executed by the secondary estimation module  104   b  as described above. 
     Note that when the processing of step S 33  shown in  FIG. 9  is executed, the secondary estimation module  104   b  acquires the result of the primary estimation processing for each channel (hereinafter referred to as a primary estimation result) from the primary estimation module  104   a . This primary estimation result includes the correspondence relationship (i.e., position where each of the wireless machines  20  is estimated to be installed from among the plurality of installation positions) between each of the plurality of installation positions indicated by the position information described above and (the wireless machine ID assigned to) each of the plurality of wireless machines  20 . 
     In this case, the secondary estimation module  104   b  executes the following processing of steps S 41  and S 42  for each of the plurality of installation positions indicated by the position information. Note that in the following description, the installation positions to be subjected to the processing of steps S 41  and S 42  will be referred to as target installation positions for convenience. 
     First, the secondary estimation module  104   b  determines whether or not a wireless machine (hereinafter referred to as a corresponding wireless machine)  20  estimated to be installed at the target installation position in accordance with the primary estimation results, the number of which is equal to or more than a predetermined number, of the primary estimation results for each channel exists (step S 41 ). 
     If it is determined that the corresponding wireless machine  20  exists (YES in step S 41 ), the secondary estimation module  104   b  estimates that the corresponding wireless machine  20  is installed at the target installation position (step S 42 ). 
     On the other hand, if it is determined that the corresponding wireless machine  20  does not exist (NO in step S 41 ), the processing of step S 42  is not executed. 
     Next, it is determined whether or not the processing of steps S 41  and S 42  has been executed for all the installation positions indicated by the position information (step S 43 ). 
     If it is determined that the processing has not been executed for all the installation positions (NO in step S 43 ), the process returns to step S 41  and the processing is repeated. In this case, the processing of steps S 41  and S 42  is executed with the installation position where the processing has not been executed as the target installation position. 
     On the other hand, if it is determined that the processing has been executed for all the installation positions (YES in step S 43 ), the secondary estimation module  104   b  determines whether or not there is an installation position where the corresponding wireless machine  20  is determined not to exist (i.e., it is not estimated that a specific wireless machine  20  from among the plurality of wireless machines  20  is installed) (step S 44 ). 
     If it is determined that there is no installation position where the corresponding wireless machine  20  is determined not to exist (NO in step S 44 ), the wireless machine  20  installed at each installation position is specified (estimated), and hence the processing of  FIG. 11  is ended. 
     On the other hand, if it is determined that, there is an installation position where the corresponding wireless machine  20  is determined not to exist (YES in step S 44 ), re-estimation processing is executed for the installation position (step  345 ). Note that the details of the re-estimation processing will be described later. 
     Note that in steps S 41  and S 42 , it has been described that the wireless machine  20  estimated to be installed at the target installation position in accordance with the primary estimation results, the number of which is equal to or more than a predetermined number, of the primary estimation results for each channel is assumed to be installed at the target installation position, but in steps S 41  and S 42 , it may be estimated that the wireless machine  20  estimated most frequently to be installed at the target installation position in the primary estimation result for each channel is installed at the target installation position, for example. 
     The secondary estimation processing shown in  FIG. 11  will be specifically described below with reference to  FIG. 12 . Here, it is assumed that the plurality of installation positions indicated by the position information are installation positions P 1  to P 6 , and the plurality of wireless machines  20  are wireless machines D 1  to D 6 . It is also assumed that the propagation characteristics have been measured in the channels indicated by each of the measurement channel numbers  1  to  3 , and the primary estimation result for each channel has been acquired. 
     As shown in  FIG. 12 , in the primary estimation result (measurement channel number  1 ), the installation positions P 1  to P 6  are associated with the (wireless machine IDs assigned to the) wireless machines D 1 , D 2 , D 3 , D 4 , D 5 , and D 6 , respectively. The primary estimation result (measurement channel number  1 ) indicates that in the primary estimation processing in the channel indicated by the measurement channel number  1 , it has been estimated that the wireless machine D 1  is installed at the installation position P 1 , the wireless machine D 2  is installed at the installation position P 2 , the wireless machine D 3  is installed at the installation position P 3 , the wireless machine D 4  is installed at the installation position P 4 , the wireless machine D 5  is installed at the installation position P 5 , and the wireless machine D 6  is installed at the installation position P 6 . 
     In the primary estimation result (measurement channel number  2 ), the installation positions P 1  to P 6  are associated with the (wireless machine IDs assigned to the) wireless machines D 1 , D 2 , D 6 , D 3 , D 4 , and D 5 , respectively. The primary estimation result (measurement channel number  2 ) indicates that in the primary estimation processing in the channel indicated by the measurement channel number  2 , it has been estimated that the wireless machine D 1  is installed at the installation position P 1 , the wireless machine D 2  is installed at the installation position P 2 , the wireless machine D 6  is installed at the installation position P 3 , the wireless machine D 3  is installed at the installation position P 4 , the wireless machine D 4  is installed at the installation position P 5 , and the wireless machine D 5  is installed at the installation position P 6 . 
     In the primary estimation result (measurement channel number  3 ), the installation positions P 1  to P 6  are associated with the (wireless machine IDs assigned to the) wireless machines D 1 , D 5 , D 3 , D 2 , D 6 , and D 4 , respectively. The primary estimation result (measurement channel number  3 ) indicates that in the primary estimation processing in the channel indicated by the measurement channel number  3 , it has been estimated that the wireless machine D 1  is installed at the installation position P 1 , the wireless machine D 5  is installed at the installation position P 2 , the wireless machine D 3  is installed at the installation position P 3 , the wireless machine D 2  is installed at the installation position P 4 , the wireless machine D 6  is installed at the installation position P 5 , and the wireless machine D 4  is installed at the installation position P 6 . 
     Here, in the secondary estimation processing described above, with the installation position P 1  as the target installation position, it is determined whether or not there is a wireless machine (corresponding wireless machine) estimated to be installed at the installation position P 1  in accordance with the primary estimation results, the number of which is equal to or more than a predetermined number, of the three primary estimation results (measurement channel numbers  1  to  3 ). 
     Assuming that the predetermined number described above is, for example, 2, it is estimated that the wireless machine D 1  is installed at the installation position P 1  in all of the three primary estimation results, and hence the secondary estimation module  104   b  estimates that the wireless machine D 1  corresponds to the corresponding wireless machine, and that the wireless machine D 1  is installed at the installation position P 1  as the secondary estimation result. 
     Similarly, with the installation position P 2  as the target installation position, it is determined whether or not there is a wireless machine (corresponding wireless machine) estimated to be installed at the installation position P 2  in accordance with the primary estimation results, the number of which is equal to or more than a predetermined number, of the three primary estimation results (measurement channel numbers  1  to  3 ). 
     Assuming that the predetermined number is, for example, 2 as described above, it is estimated that the wireless machine D 2  is installed at the installation position P 2  in two primary estimation results (measurement channel numbers  1  and  2 ) of the three primary estimation results, and hence the secondary estimation module  104   b  estimates that the wireless machine D 2  corresponds to the corresponding wireless machine, and that the wireless machine D 2  is installed at the installation position P 2  as the secondary estimation result. 
     Furthermore, with the installation position P 3  as the target installation position, it is determined whether or not there is a wireless machine (corresponding wireless machine) estimated to be installed at the installation position P 3  in accordance with the primary estimation results, the number of which is equal to or more than a predetermined number, of the three primary estimation results (measurement channel numbers  1  to  3 ). 
     Assuming that the predetermined number is, for example, 2 as described above, it is estimated that the wireless machine D 3  is installed at the installation position P 3  in two primary estimation results (measurement channel numbers  1  and  3 ) of the three primary estimation results, and hence the secondary estimation module  104   b  estimates that the wireless machine D 3  corresponds to the corresponding wireless machine, and that the wireless machine D 3  is installed at the installation position P 3  as the secondary estimation result. 
     Next, with the installation position P 4  as the target installation position, it is determined whether or not there is a wireless machine (corresponding wireless machine) estimated to be installed at the installation position P 4  in accordance with the primary estimation results, the number of which is equal to or more than a predetermined number, of the three primary estimation results (measurement channel numbers  1  to  3 ). 
     In this case, as shown in  FIG. 12 , the wireless machines estimated to be installed at the installation position P 4  in the three primary estimation results are the wireless machines D 4 , D 3 , and D 2 , respectively, and it is determined that there is no wireless machine estimated to be installed at the installation position P 4  in the primary estimation results equal to or more than a predetermined number (here, 2). Note that it is determined that the corresponding wireless machine does not exist at the installation positions P 5  and P 6  similarly. 
     If it is determined that the corresponding wireless machine does not exist at the installation positions P 4  to P 6  as described above in the secondary estimation processing, the re-estimation processing is executed in step S 45  shown in  FIG. 11 . 
     An example of the re-estimation processing will be described below with reference to  FIG. 13 . Note that the upper part of  FIG. 13  shows the processing result of the secondary estimation processing before the re-estimation processing described in  FIG. 12  is executed. That is, it is assumed a case where as a result of executing the secondary estimation processing (processing of steps S 41  to S 44  shown in  FIG. 11 ) after the primary estimation result (measurement channel numbers  1  to  3 ) has been acquired, it is estimated that the wireless machines D 1  to D 3  are installed in the installation positions P 1  to P 3 , respectively, and it is determined that the corresponding wireless machine does not exist in the installation positions P 4  to P 6 . 
     In the re-estimation processing, the primary estimation processing is executed again for each channel in consideration of the fact that the wireless machines D 1  to D 3  are estimated to be installed in the installation positions P 1  to P 3 , respectively, as described above. 
     Specifically, in the primary estimation processing, evaluation values are calculated for various combinations (hypotheses) of each of the installation positions P 1  to P 6  and each of the wireless machines D 1  to D 6  as described in the above-described first embodiment, and the positions where the wireless machines D 1  to D 6  are installed are estimated based on the combination for which the highest evaluation value has been calculated, but in the primary estimation processing executed again in the re-estimation processing, the position where each of the wireless machines D 1  to D 6  is installed is estimated based on the combination for which the highest evaluation value has been calculated from among the combinations satisfying the correspondence relationships (P 1 -D 1 , P 2 -D 2 , and P 3 -D 3 ) between the installation positions P 1  to P 3  and the wireless machines D 1  to D 3  having been already estimated in the secondary estimation processing. 
     Note that the primary estimation processing may not be executed again for the channel indicated by the measurement channel number  1  having already satisfied the correspondence relationship between the installation positions P 1  to P 3  and the wireless machines D 1  to D 3  having been already estimated in the secondary estimation processing. 
     Here, the lower part of  FIG. 13  shows an example of a result (primary estimation result) of the primary estimation processing being executed again in the re-estimation processing. 
     According to the example shown in the lower part of  FIG. 13 , in the primary estimation result (measurement channel number  1 ), the installation positions P 1  to P 6  are associated with the wireless machines D 1 , D 2 , D 3 , D 4 , D 5 , and D 6 , respectively. In the primary estimation result (measurement channel number  2 ), the installation positions P 1  to P 6  are associated with the wireless machines D 1 , D 2 , D 3 , D 5 , D 4 , and D 6 , respectively. In the primary estimation result (measurement channel number  3 ), the installation positions P 1  to P 6  are associated with the wireless machines D 1 , D 2 , D 3 , D 4 , D, and D 6 , respectively. 
     In the re-estimation processing, the above-described secondary estimation processing (processing shown in  FIG. 11 ) is executed again based on the result of the primary estimation processing having been executed again. 
     According to this secondary estimation processing having been executed again, as shown in the lower part of  FIG. 13 , it can be estimated that the wireless machine D 4  is installed at the installation position P 4 , the wireless machine D 5  is installed at the installation position P 5 , and the wireless machine D 6  is installed at the installation position P 6 . 
     In a case where it is impossible to estimate the wireless machines installed at all the installation positions even if the secondary estimation processing is executed again in the re-estimation processing described above, the re-estimation processing may be executed again. 
     Note that in the re-estimation processing, it has been described that the secondary estimation processing is executed again after the primary estimation processing is executed again, but the secondary estimation processing may not be executed again. 
     Specifically, the evaluation value (e.g., correlation coefficient) is calculated in the primary estimation processing, but it may be configured that the primary estimation result having the highest evaluation value among the primary estimation results for each channel acquired by executing the primary estimation processing again in the re-estimation processing is selected (adopted), and the position where each of the wireless machines D 1  to D 6  is installed is estimated based on the selected primary estimation result. 
     In the case of such a configuration, as shown in  FIG. 14 , for example, even in a case where the wireless machine installed in the installation positions P 4  to P 5  cannot be estimated even if the secondary estimation processing is executed again based on the result of the primary estimation processing executed again in the re-estimation processing, it is possible to estimate that the wireless machine D 4  is installed at the installation position P 4 , the wireless machine D 5  is installed at the installation position P 3 , and the wireless machine D 6  is installed at the installation position P 6 , based on the primary estimation result (measurement channel number  1 ) having a high evaluation value. 
     Note that in the re-estimation processing described above, the primary estimation processing is executed again using all of the characteristic information stored in the characteristic information storage  102  (propagation characteristics between the wireless machines D 1  to D 6 ), but for example, in a case where it has been estimated that the wireless machines D 1  to D 3  have been installed in the installation positions P 1  to P 3  before the re-estimation processing is executed, the primary estimation processing in each channel may be executed using only the position information indicating the installation positions P 4  to P 6  and the characteristic information including the propagation characteristics between the wireless machines D 4  to D 6  for which the installation positions have not been estimated. In other words, in this primary estimation processing, processing of estimating the position where each of the wireless machines D 4  to D 6  is installed from among the installation positions P 4  to P 6  is executed. Even in the case of such a configuration, the estimation result as described in  FIG. 13 , for example, can be obtained. 
     As described above, in the present embodiment, based on the position information stored in the position information storage  103 , first characteristic information obtained from first propagation characteristics in the first channel of the first wireless machine  20 , and third characteristic information obtained from third propagation characteristics in the first channel of the second wireless machine  20 , the first estimation result (primary estimation result in the first channel) of the position where each of the first and second wireless machines  20  is installed is acquired, and based on the position information, second characteristic information obtained from second propagation characteristics in the second channel of the first wireless machine  20 , and fourth characteristic information obtained from fourth propagation characteristics in the second channel of the second wireless machine  20 , the second estimation; result (primary estimation result in the second channel) of the position where each of the first and second wireless machines  20  is installed is acquired. In the present embodiment, based on the above-described first and second estimation results, the position where each of the first and second wireless machines  20  is installed is estimated. 
     Note in the embodiments, such an expression as “acquiring an estimation result” may mean, for example that a position where each of the first and second wireless machines is installed is estimated and acquired or that (information on) the estimation result is acquired from another module or the like. The estimation result is data based on position information and characteristic information, but may be acquired based on the position information and the characteristic information. 
     In this case, in a case where it is estimated that an identical wireless machine  20  from among the plurality of wireless machines  20  is installed at an identical position from the first and second installation positions in accordance with the first and second estimation results, the number of which is equal to or more than a predetermined number, it is estimated that the wireless machine  20  is installed at the position. Note that it may be estimated that a specific wireless machine  20  from among the plurality of wireless machines  20  most frequently estimated to be installed at the first installation position in the first and second estimation results is installed at the first installation position, and it may be estimated that a specific wireless machine  20  from among the plurality of wireless machines  20  most frequently estimated to be installed at the second installation position in the first and second estimation results is installed at the second installation position. 
     In the present embodiment, since, by the configuration described above, the position where each of the first and second wireless machines  20  is installed is estimated in consideration of each of the first estimation result in the first channel and the second estimation result in the second channel, it can be expected that the estimation is less affected by an outlier of the propagation characteristics and the estimation accuracy is improved compared with the case where the position is estimated using the feature amount of the propagation characteristics measured in each of the plurality of channels as in the first embodiment described above. 
     Furthermore, in the present embodiment, in a case where based on the first and second estimation results, the first and second wireless machines  20  installed at the first and second installation positions from among the plurality of installation positions are estimated and third and fourth wireless machines  20  installed at third and fourth installation positions among the plurality of installation positions cannot be estimated, re-estimation processing of estimating again the position where each of the third and fourth wireless machines  20  is installed from among the third and fourth installation positions is executed. 
     Specifically, in the re-estimation processing, based on the position information stored in the position information storage  103 , the first characteristic information obtained from the first propagation characteristics of the first wireless machine  20 , the third characteristic information obtained from the third propagation characteristics of the second wireless machine  20 , and the first and second wireless machines  20  estimated to be installed at the first and second installation positions, the third estimation result (primary estimation result in the first channel) of the position where each of the third and fourth wireless machines  20  is installed among the third and fourth installation positions is acquired, and based on the position information, the second characteristic information obtained from the second propagation characteristics of the first wireless machine  20 , the fourth characteristic information obtained from the fourth propagation characteristics of the second wireless machine  20 , and the first and second wireless machines  20  estimated to be installed at the first and second installation positions, the fourth estimation result (primary estimation result in the second channel) of the position where each of the third and fourth wireless machines  20  is installed among the third and fourth installation positions is acquired. In the re-estimation processing, the position where each of the third and fourth wireless machines  20  is installed is estimated again from among the third and fourth installation positions based on the thus acquired third and fourth estimation results. 
     According to such a configuration, even if the wireless machines  20  installed at all the installation positions cannot be estimated in the secondary estimation processing (estimation processing based on the first and second estimation results), it becomes possible, by repeatedly executing the re-estimation processing (primary estimation processing and secondary estimation processing), to estimate the wireless machines  20  installed at all the installation positions. 
     In the re-estimation processing, the positions where the third and fourth wireless machines  20  are installed from the third and fourth installation positions may be estimated again based on the third or fourth estimation result selected based on the first evaluation value for the third estimation result and the second evaluation value for the fourth estimation result. According to such a configuration, since it is not necessary to execute the secondary estimation processing again in the re-estimation processing, the processing load in the electronic apparatus  10  can be reduced. 
     Furthermore, in the re-estimation processing, based on the position information indicating each of the third and fourth installation positions and the characteristic information of the third and fourth wireless machines  20  other than the first and second wireless machines  20  estimated to be installed at the first and second installation positions, the position where the wireless machine  20  is installed is estimated again from the third and fourth installation positions. According to such a configuration, since it is not necessary to execute the re-estimation processing using all the characteristic information stored in the characteristic information storage  102 , the processing load in the electronic apparatus  10  can be reduced. 
     In at least one of the embodiments described above, it is possible to provide an electronic apparatus and a method capable of highly accurately estimating the position where the wireless machine  20  is installed. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.