JP2009200926A - Position detection system, position detection server, and terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the deterioration in accuracy of position detection even against disturbance that occurs irregularly. <P>SOLUTION: A position detection server monitors a communication status between radio base stations in accordance with a communication status value, from an opposite-side base station, acquired in each radio base station. When a predetermined change or more is detected in the communication status value, an event that disturbance is caused between radio base stations where the change occurs is issued and the change amount of the corresponding communication status value is estimated. On the basis of a difference between the communication status value from the radio base station acquired by a terminal at a position just before occurrence of disturbance and the communication status value acquired this time, it is decided whether the disturbance exerts an effect on the position detection of this time. When it is decided that the disturbance affects the position detection, the change amount estimated before is used to correct the communication status value from the radio base station relating to the disturbance acquired at the terminal, and the corrected communication status value and the communication status value from the radio base station not relating to the disturbance are used to estimate the position of the terminal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a position detection system, a position detection server, and a terminal that perform position detection using communication information exchanged between a radio base station and a terminal that is a position detection target.

In a conventional position detection system, in order to store a list of radio field intensity values for each disturbance that occurs, a radio field intensity table is created by measuring in advance the radio field intensity according to disturbances from multiple radio base stations at each point. The radio wave intensity table is referenced based on the disturbance type input from another system at the time of position detection, and the combination of radio wave intensity values between the positioning target terminal and multiple radio base stations is displayed on the table. By associating with, accuracy degradation can be suppressed against disturbance.
In addition, by estimating the strength at the time of the disturbance occurrence at the measurement point specified on the map from the relationship between the map information and the location of the radio base station and the location of the disturbance, a radio field strength value table is created for each disturbance occurrence location. There has been proposed a position detection system that can save time and effort to create (see, for example, Patent Document 1).

JP 2001-128222 A (pages 9-10, FIG. 11)

  In the conventional technology, since the mechanism for detecting the occurrence of disturbance depends on other systems, the position detection system alone cannot detect the disturbance. Also, the type and location of the disturbance are specified, and it is impossible to detect disturbances that occur irregularly due to traffic of people, so that it is impossible to suppress degradation in position detection accuracy.

  The present invention has been made to solve the above-described problems, and provides a position detection system and a position detection server that can suppress deterioration in position detection accuracy even when irregular disturbances occur. is there.

  The position detection system according to the present invention acquires a communication status value from a communication target periodically transmitted by a plurality of wireless base stations at a terminal subject to position detection, and based on the acquired communication status value, In a position detection system that performs terminal position detection processing, each wireless base station acquires a communication status value from a partner station while periodically communicating with a wireless base station other than its own station. Based on the communication status value acquired at the radio base station, the communication status between the radio base stations is monitored, and when a change of a predetermined value or more is detected in the communication status value, a disturbance occurs between the radio base stations where the change has occurred. When a disturbance occurrence event is issued, the communication status from the radio base station acquired by the terminal at the position immediately before the occurrence of the disturbance is issued. Based on the difference between the value and the communication status value acquired this time, it is determined whether the disturbance affects the current position detection of the terminal. The communication status value from the radio base station related to the disturbance acquired by the terminal is corrected using the amount of change in the communication status value between the radio base stations related to the disturbance, and the corrected communication status value and disturbance The position of the terminal is estimated by using the communication status value from the radio base station that was not related to.

  According to the present invention, when the disturbance generated irregularly is detected by monitoring the communication status between the radio base stations, the radio base station in a state where there is no disturbance using the calculated amount of fluctuation of the communication status Since the distance between terminals is estimated, the accuracy of distance estimation between the target terminal and the radio base station can be improved, so even if a disturbance occurs, the accuracy of position detection is suppressed and stable position detection is possible. Enable. In addition, since the amount of change is obtained from the observed value even if the type of disturbance is not specified in advance, it is possible to reduce the preparation work such as measuring the amount of change according to the disturbance in advance.

Embodiment 1 FIG.
1 is a block diagram showing a configuration of a position detection system according to Embodiment 1 of the present invention.
Each of the radio base stations 1 to 4 is connected to each other via the network 100. The terminal 106 is a terminal that is a position detection target (hereinafter referred to as “target terminal”), and communicates with the wireless base stations 1 to 4 by a wireless function. The position detection server 101 is a server that performs calculation for position detection, and is connected to the radio base stations 1 to 4 via the network 100. In the example of the first embodiment, it is assumed that the wireless base stations 1 to 4 and the target terminal 106 comply with the wireless LAN standard IEEE802.11b / g, but the present invention complies with other standards and systems. This includes cases where equipment is used. In the first embodiment, the case where there are four radio base stations in a specific range is described as an example. However, similar processing can be performed even when four or more radio base stations are used. . Further, the range of position detection is not limited. It is assumed that the target terminal is moved by a person.

Next, the basic principle of position detection will be described.
The terminal 106 estimates the distance d between the terminal and the radio base station by the processing of equation (1) using the radio wave intensity value included in the communication information from each radio base station.
d = (f (−20 / N)) ^* (10 (L + 28−Lf (n)) / N) (1)
Where N is the attenuation coefficient, f is the frequency (MHz), L is the received RSSI (Received Signal Strength Indicator) value (dB), Lf (n) is the loss due to the passage of n walls, and the symbol * is an arithmetic operation. Let it be a child.
Here, a space close to a commercial space such as a station premises is assumed. Therefore, N is set to 30 which is an attenuation coefficient close to that of the office environment (see Revised 802.11 high-speed wireless LAN textbook Impress p256 Table 11-2). Since the environment is IEEE801.11b / g, it is assumed that f = 2450 and Lf (n) = 14n. Here, if the number of walls is zero for easy understanding, Lf (0) = 0.

  The beacon information is periodically transmitted from the radio base stations 1 to 4 to notify that there is an available radio base station. Therefore, the target terminal 106 receives this beacon information and establishes communication connection. The radio field intensity values from a plurality of radio base stations 1 to 4 that are not yet acquired are acquired. Each time the beacon information is received, the target terminal 106 generates radio wave intensity information having a data structure in which the terminal ID, each radio base station ID, and each acquired radio wave intensity value are associated with each other as shown in FIG. 101 is transmitted to the network 101 via the network 100. The terminal ID is previously registered in the position detection server 101, and the same program is used on the terminal 106 side. Both the terminal ID and the wireless base station ID use the MAC address that is the unique ID of the communication device included in the communication information, so that information from which terminal and which wireless base station can be obtained without any special device. Can be associated.

  The position detection server 101 holds map information including arrangement information of wireless base stations as shown in FIG. In the position detection server 101, based on the radio field strength value for each radio base station in the radio field intensity information received from the target terminal 106, the distances d1 to d4 between each radio base station and the target terminal 106 are calculated according to the equation (1). calculate. Then, as shown in FIG. 4, the position detection server 101 estimates that the target terminal 106 is located at a point where circles having the radii of the distances d1 to d4 intersect with each wireless base station as the center. When this estimation result is superimposed on the map information of FIG. 3, the current position of the target terminal 106 is as shown in FIG. The estimation result obtained in this manner is transmitted from the position detection server 101 in response to requests from various devices including the target terminal 106, but the processing capability of the position detection server 101 is sufficient May be immediately returned as a response to the radio wave intensity information received from the target terminal 106.

  Each of the circles with radii d1 to d4 centering on each radio base station should ideally meet at one point as shown in FIG. However, since there are many cases that are actually affected by noise, they rarely intersect at a single point, and the way of intersection is as shown in FIG. For this reason, the position detection server 101 calculates the center of gravity of a region (a portion indicated by hatching in FIG. 6) where all the circles overlap with each other to obtain an estimated position. The above is the basic principle of position detection and is a general method.

Hereinafter, the position detection process for dealing with the occurrence of disturbance according to the present invention will be described. FIG. 9 is a flowchart showing a processing procedure in the position detection server 101.
In wireless communication, it is known to change communication conditions such as communication quality according to surrounding conditions. In particular, the radio wave intensity value is attenuated when a shielding object enters between the radio base station and the terminal. By the way, it is possible to know that a fixed shielding object (such as a wall) is a value in which the radio field intensity value is attenuated by knowing that the shielding object is present at that position in advance. However, the present invention is not a countermeasure against the above-mentioned fixed shielding object, but a radio wave shielding that is dynamically generated at an arbitrary timing, specifically, shielding by entering or passing a train in a station premises, traffic of people, etc. On the other hand, increasing the accuracy of position detection is handled.

  Taking the radio base station 1 as an example, the radio base station 1 exchanges beacon information transmitted between the other radio base stations 2 to 4 wirelessly. Here, when confirming the beacon information, processing is performed in a time-sharing manner so as not to hinder communication with the target terminal 106. The radio base station 1 receives beacon information from radio base stations 2 to 4 other than its own station, acquires radio field intensity values from the respective radio base stations, and identifies which radio base station the radio field intensity value from. As shown in FIG. 7, radio wave intensity information associated with a radio base station ID (assuming use of a MAC address) is generated. The position detection server 101 receives the radio wave intensity information acquired at each wireless base station via the network 100 (step ST1).

  The position detection server 101 monitors whether there is a disturbance between the current wireless base station 1 and the other wireless base stations 2 to 4 based on the radio wave intensity information received from the wireless base station 1 (step ST2). ). In this case, statistical values such as an average value, median value, and standard deviation of radio field intensity values from a specific radio base station (for example, the radio base station 4) are calculated based on the data received several times in the past, and received this time. Monitor whether the disturbance is occurring by checking if the data is within the range of those statistics. For example, when the data of the radio field intensity values of the past several times is an average A and a standard deviation B, the radio field intensity value indicated by the currently received data is G. Statistically, since about 97% of the data is in the range up to twice the average A ± standard deviation B, it can be considered that a disturbance has occurred when the radio wave intensity value G is not within this range. . When the average ± standard deviation is set, about 67% of data is included in this value range, but this value or another index may be used. When a disturbance is detected by such a processing method, the position detection server 101 issues a disturbance occurrence event (step ST3) and estimates the amount of change in the radio wave intensity value (step ST4).

  As a method for estimating the amount of change in the radio wave intensity value, a method of simply using the difference from the average value of the most recent records as the amount of change is used. In the first embodiment, when the average of the radio field intensity values of the most recent records is A, the change amount D of the radio field intensity value can be calculated as D = A−G. The calculated change amount D of the radio wave intensity value is stored in association with the disturbance occurrence event. It should be noted that the disturbance occurrence event is stored as additional information together with data indicating which radio base station has occurred.

Next, an estimation process for determining whether a disturbance generated between radio base stations affects the position detection of the target terminal 106 will be described.
As shown in FIG. 8, it is assumed that a disturbance has occurred at a location between the radio base station 1 and the radio base station 4. Since it is possible to estimate the movable range of the terminal position from the immediately preceding position, it is determined whether this disturbance can affect the next position detection of the target terminal 106 (step ST5). For example, when the target terminal 106 is located at position A, there is a high possibility that the disturbance between the radio base stations 1 and 4 is not directly related, so the disturbance occurrence event can be ignored. However, when the target terminal 106 is at the position A, there is a strong possibility that the disturbance between the radio base stations 1 and 4 has an influence. In this case, the position detection server 101 uses the radio wave intensity values from the respective radio base stations periodically acquired by the target terminal 106 for use in the above-described position detection, as shown in FIG. Since it is received as information, it is determined whether the target terminal 106 is affected by disturbance using this information. The position detection server 101 compares the radio wave intensity value from the radio base station 4 at the position immediately before the occurrence of the disturbance between each radio base station and the terminal 106 and the radio wave intensity value from the base station acquired this time. Do. Assuming that the reception interval is sufficiently short (assuming that it is less than 1 second), the amount of change in the radio wave intensity value according to the moving distance of the target terminal 106 does not increase or decrease rapidly when communication is performed normally. It can be judged that there is no relationship. On the other hand, when the amount of change in the radio field intensity value is extremely increased or decreased, it can be considered to be related to disturbance. If the radio field intensity value from the radio base station 4 is extremely reduced, it can be estimated that this is highly likely to be an influence of disturbance. Assuming that a disturbance is occurring between the radio base stations 1 and 4, the radio field intensity value from the radio base station 4 is affected by the disturbance when estimated from the position a immediately before the target terminal 106. Can be estimated.

Next, a process for correcting the radio field intensity value from the radio base station 4 related to the disturbance of the target terminal 106 and estimating the position of the terminal will be described.
The position detection server 101 uses the change amount of the radio wave intensity value between the wireless base stations related to the disturbance, which is calculated when the disturbance occurrence event is issued, so that the wireless base station 4 near the position i in FIG. Estimate the attenuation of the radio field intensity value from. For example, since the change amount D of the radio wave intensity value is a change amount between the radio base stations 1 and 4, this is associated with the change amount at the position immediately before the target terminal 106. That is, a value obtained by adding the change amount D to the radio wave intensity value measured by the target terminal 106 from the radio base station 4 is used as the radio wave intensity value at that position when no disturbance occurs (step ST6). Next, the distance between the target terminal 106 and the radio base station 4 is calculated based on the corrected radio wave intensity value. Further, the distance from the remaining radio base stations 1 to 3 not related to the occurrence of disturbance is also normally calculated, and the detection position of the target terminal 106 is estimated by using the distances by the method described in FIG. (Step ST7). Therefore, since the influence due to disturbance can be corrected, the accuracy of distance estimation between the target terminal 106 and the radio base stations 1 to 4 is improved, and stable position detection is possible.

  By the way, when considering the arrangement of the radio base stations, the disturbance detection accuracy can be improved by installing the radio base station at a height at which the disturbance can occur. For example, when traffic of people becomes a major disturbance, the disturbance can be detected by installing a radio base station about 1 to 1.5 m above the floor. In addition, if there is something that can be a major disturbance such as a train in a station, if the accuracy is improved, the difference between the disturbance of the train and the disturbance caused by the traffic of people can be achieved by making a difference in the height of the arrangement of the radio base stations. It is also possible to detect both. For example, the main radio base station of the communication channel is placed in a place with a high visibility of 2 to 3 meters, and the radio base station that also serves to detect disturbance due to traffic is placed at the same height as the home. This makes it easy to detect disturbances between radio base stations installed at high altitudes and radio base stations installed at low altitudes, so both disturbances caused by trains and disturbances caused by traffic of people can be detected. Therefore, it is possible to suppress the deterioration of the position detection accuracy even for a plurality of disturbances.

  As described above, according to the first embodiment, each radio base station acquires a communication status value from beacon information from a radio base station other than its own station, and the position detection server 101 determines each radio base station. The communication status between wireless base stations is monitored based on the radio field strength value (communication status value) from the other base station acquired in step 1, and if a change of more than a predetermined value is detected in the radio field strength value, the change occurs. An event that a disturbance has occurred between the wireless base stations is issued, and the amount of change in the corresponding radio wave intensity value is estimated. When a disturbance occurrence event is issued, the target terminal 106 is acquired at a position immediately before the occurrence of the disturbance. Based on the difference between the radio field strength value (communication status value) from the received radio base station and the radio field intensity value acquired this time, it is determined whether the disturbance affects the current position detection of the target terminal 106, and the current position Determined to affect detection In the case where the signal is received, the communication status value from the radio base station related to the disturbance acquired by the target terminal 106 using the change amount of the radio field intensity value between the radio base stations related to the disturbance estimated previously. , And the position of the target terminal 106 is estimated using the corrected radio wave intensity value and the radio wave intensity value from the radio base station that was not related to the disturbance. Therefore, since the accuracy of estimating the distance between the target terminal and the radio base station can be improved, even if a disturbance occurs, it is possible to suppress deterioration in accuracy of position detection and perform stable position detection. Further, since the amount of change is obtained from the observed value without prescribing the disturbance type in advance, it is possible to reduce the time and effort of preparing in advance such as measuring the amount of change according to the disturbance.

In the first embodiment, the above-described series of position detection processing is performed by the position detection server. However, the position detection system is configured by providing the function of the position detection processing to the target terminal itself. The same effect can be expected even without the position detection server.
The radio base station also separates communication status acquisition means for acquiring a communication status value with a radio base station other than its own station and transmitting it to the position detection server, and communication processing means for performing normal communication processing in its own station. May be prepared, and each processing may be executed in parallel. By doing in this way, it becomes possible to acquire a communication status value with a radio base station other than its own station without dropping a communication response.
In the first embodiment, the suppression of accuracy deterioration in the form of correction has been described. However, there may be a case where the correction cannot be sufficiently performed depending on the content of the disturbance. In that case, if the position priority calculation is performed using only reliable information by lowering or not using the calculation priority of the radio field strength value from the radio base station related to the occurrence of disturbance. It is also possible to suppress deterioration in accuracy.
In the first embodiment, an example of attenuation is described. However, the present invention can also be applied to a case where a reflected wave is generated due to the influence of a train or the like and the radio wave intensity is amplified.

Embodiment 2. FIG.
In Embodiment 1 described above, an example in which the amount of change in radio wave intensity occurring between radio base stations at the time of a disturbance has been estimated from the most recent state is described. In Embodiment 2, a steady-state observation time zone, An example will be described in which disturbance detection can be performed with higher accuracy and accuracy degradation can be suppressed by monitoring the communication status between radio base stations divided into two time zones for disturbance detection.
The position detection server 101 is provided with means capable of setting the steady state observation time. Time other than the steady state observation time can be considered as a disturbance detection time zone. For example, the user selects and sets a time zone in which the occurrence frequency of disturbances such as night falls extremely as the steady state observation time. In addition, by specifying the day of the week instead of only the time of the day, a specific date and time such as a nighttime on Sunday that causes almost no disturbance may be selected as the steady state observation time.

  The position detection server 101 acquires radio wave intensity information from wireless base stations other than its own, which are periodically acquired by each wireless base station during the steady state observation time. At this time, state accumulation is performed without detecting disturbance. Accumulation of the state improves the statistical reliability of the radio field intensity. By comparing the statistical information of the steady-state radio field intensity values obtained from this accumulated data with the radio field intensity values obtained from the radio base stations other than the own station obtained by each radio base station obtained in the disturbance detection time zone, Is detected and the amount of change is calculated. The difference from the first embodiment is that the statistical values acquired in advance in the steady state observation time are used instead of using the information of the last few records.

  As described above, according to the second embodiment, since the time zone for monitoring the communication status is divided into the steady state observation time zone and the disturbance detection time zone, the steady state statistical communication status is stabilized. Therefore, the fluctuation amount can be obtained with high reliability from this information, the disturbance can be reliably detected, and the deterioration of accuracy in the case of the disturbance can be suppressed. Therefore, even when an environmental change caused by a layout change or the like occurs, the steady state is automatically grasped and accuracy deterioration can be suppressed.

Embodiment 3 FIG.
In the first and second embodiments, the radio base station is configured to have a function of acquiring a communication status value with a radio base station other than the own station for disturbance detection. A disturbance detection communication status acquisition apparatus having the same function is assumed to be a position detection system that is arranged at the same position as a radio base station or at a position where a disturbance is expected to occur.
The communication status acquisition device placed at the same position as the wireless base station or a position where disturbance is expected to receive receives the beacon information transmitted from each wireless base station and acquires the radio field intensity value from each wireless base station Then, the radio wave intensity information is transmitted to the position detection server (or the target terminal if the target terminal has a position detection processing function). The position detection server performs the same process as the position detection server 101 of the first embodiment on the basis of the radio wave intensity value from the radio base station acquired by the communication status acquisition device, and performs the position detection process of the symmetrical terminal.
Therefore, it is possible to detect disturbance without providing a special mechanism to the radio base station, and it is possible to suppress degradation in accuracy of position detection caused by the disturbance as in the first and second embodiments.

It is a block diagram which shows the structure of the position detection system by Embodiment 1 of this invention. It is explanatory drawing which shows the data structure of the information of the electromagnetic wave intensity value from each radio base station of the object terminal which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the example of the content of the map information which the position detection server which concerns on the same Embodiment 1 holds. 6 is an explanatory diagram showing a method for estimating the position of a target terminal from the distance between the plurality of radio base stations and the target terminal according to Embodiment 1. FIG. It is explanatory drawing which shows the position on the map information of the target terminal which concerns on the same Embodiment 1. FIG. It is explanatory drawing which shows the method of estimating the position of the object terminal when the circle which drew the calculation distance between a wireless base station and an object terminal as a radius according to Embodiment 1 does not cross at one point. 7 is an explanatory diagram illustrating a data configuration of information representing a radio field intensity value from another radio base station according to the first embodiment. FIG. It is explanatory drawing which shows the condition where the disturbance which concerns on the same Embodiment 1 generate | occur | produced in the location between a wireless base station and a wireless base station. It is a flowchart which shows the process sequence in the position detection server which concerns on the same Embodiment 1. FIG.

Explanation of symbols

  1, 2, 3, 4 Wireless base station, 100 network, 101 position detection server, 106 terminals.

Claims (9)

From communication information periodically transmitted by a plurality of radio base stations, a communication status value from the radio base station is acquired by a terminal that is a target for position detection, and the position detection server determines the communication status value of the terminal based on the acquired communication status value. In a position detection system that performs position detection processing,
Each radio base station acquires the communication status value from the partner station while periodically communicating with a radio base station other than its own station,
The position detection server is
Monitor the communication status between radio base stations based on the communication status values acquired at each radio base station,
When a change of a predetermined value or more is detected in the communication status value, an event that a disturbance has occurred between the radio base stations in which the change has occurred and an amount of change in the corresponding communication status value is estimated,
When a disturbance occurrence event is issued, based on the difference between the communication status value from the radio base station acquired by the terminal at the position immediately before the occurrence of the disturbance and the communication status value acquired this time, the disturbance is To determine whether it affects the position detection of
If it is determined that the current position detection will be affected, the radio related to the disturbance acquired by the terminal using the amount of change in the communication status value between the radio base stations related to the previously estimated disturbance Correct the communication status value from the base station,
A position detection system that estimates the position of the terminal using the corrected communication status value and the communication status value from a radio base station that was not related to disturbance.   The position detection system according to claim 1, wherein the terminal performs a position detection process performed by the position detection server instead of the position detection server.   The position detection system according to claim 1 or 2, wherein the communication status value used for position detection and disturbance detection is a radio wave intensity value.   The position detection system according to any one of claims 1 to 3, wherein the radio base stations are arranged with a difference in height in consideration of a disturbance generation source.   The time period for monitoring the communication status between radio base stations is divided into a steady state observation time in which the occurrence frequency of disturbance events is extremely low and a disturbance detection time excluding this time period. Communication status values from wireless base stations other than the base station acquired by the wireless base station are stored without performing disturbance detection, while other than the local station acquired by each wireless base station obtained in the disturbance detection time zone The disturbance is detected by comparing the communication status value from the wireless base station with the statistical information of the steady state based on the stored communication status value. The position detection system according to any one of the above.   The wireless base station is characterized in that when acquiring a communication status value from a radio base station other than its own, the communication status value acquisition and normal communication processing are performed in a time-sharing manner. Item 6. The position detection system according to any one of Items 5 to 5. From communication information periodically transmitted by a plurality of radio base stations, a communication status value from the radio base station is acquired by a terminal that is a target for position detection, and the position detection server determines the communication status value of the terminal based on the acquired communication status value. In a position detection system that performs position detection processing,
A communication status acquisition device that is arranged at the same position as a radio base station or a location where disturbance is expected to occur, receives communication information transmitted by each radio base station, and acquires a communication status value from each radio base station Prepared,
The position detection server
Monitor the communication status between the radio base station and the communication status acquisition device based on the communication status value acquired by each communication status acquisition device,
When a change of a predetermined value or more is detected in the communication status value, an event that a disturbance has occurred between the radio base station where the change has occurred and the communication status acquisition device is issued, and the corresponding communication status value change amount Estimate
When a disturbance occurrence event is issued, based on the difference between the communication status value from the radio base station acquired by the terminal at the position immediately before the occurrence of the disturbance and the communication status value acquired this time, the disturbance is To determine whether it affects the position detection of
If it is determined that it will affect the current position detection, the disturbance acquired by the terminal using the amount of change in the communication status value between the radio base station and the communication status acquisition device related to the previously estimated disturbance Correct the communication status value from the related radio base station,
A position detection system that estimates the position of the terminal using the corrected communication status value and the communication status value from a radio base station that was not related to disturbance. From the communication information periodically transmitted by a plurality of radio base stations, the communication status value from the radio base station is acquired by the terminal that is the target of position detection, and the position detection processing of the terminal is performed based on the acquired communication status value. In the position detection server to perform,
The position detection server is
Monitor the communication status between the radio base stations based on the communication status value obtained from the partner station while periodically communicating with the radio base station other than its own in each radio base station,
When a change of a predetermined value or more is detected in the communication status value, an event that a disturbance has occurred between the radio base stations in which the change has occurred and an amount of change in the corresponding communication status value is estimated,
When a disturbance occurrence event is issued, based on the difference between the communication status value from the radio base station acquired by the terminal at the position immediately before the occurrence of the disturbance and the communication status value acquired this time, the disturbance is To determine whether it affects the position detection of
If it is determined that the current position detection will be affected, the radio related to the disturbance acquired by the terminal using the amount of change in the communication status value between the radio base stations related to the previously estimated disturbance Correct the communication status value from the base station,
A position detection server that estimates the position of the terminal using the corrected communication status value and the communication status value from a radio base station that was not related to disturbance. From the communication information periodically transmitted by a plurality of radio base stations, to obtain the communication status value from each radio base station, in the terminal that performs its own location detection processing based on the acquired communication status value,
Monitor the communication status between the radio base stations based on the communication status value obtained from the partner station while periodically communicating with the radio base station other than its own in each radio base station,
When a change of a predetermined value or more is detected in the communication status value, an event that a disturbance has occurred between the radio base stations in which the change has occurred and an amount of change in the corresponding communication status value is estimated,
When a disturbance occurrence event is issued, based on the difference between the communication status value from the radio base station acquired by the terminal at the position immediately before the occurrence of the disturbance and the communication status value acquired this time, the disturbance is To determine whether it affects the position detection of
If it is determined that the current position detection will be affected, the radio related to the disturbance acquired by the terminal itself using the change amount of the communication status value between the radio base stations related to the estimated disturbance. Correct the communication status value from the base station,
A terminal characterized by estimating the position of its own terminal using the corrected communication status value and a communication status value from a radio base station that was not related to disturbance.

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