JP2018142767A - Mobile terminal, method and mobile communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow for update of the reference position even in the opportunity other than communication with a fixed node.SOLUTION: A mobile terminal includes a positional information acquisition unit for acquiring the positional information of the mobile terminal calculated by accumulating the variation in the position of the mobile terminal to a reference position, a confidence coefficient acquisition unit for acquiring the confidence coefficient information of the positional information of the mobile terminal based on the lapsed time after update of the reference position, an other terminal information acquisition unit for acquiring the positional information of other mobile terminal and the confidence coefficient information of the positional information of other mobile terminal therefrom, and a control unit for controlling update of the reference position using the positional information of other mobile terminal, based on the relationship of the confidence coefficient information of the positional information of the mobile terminal, and the confidence coefficient information of the positional information of other mobile terminal.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a mobile terminal, a method, and a mobile communication system.

  Recently, techniques for estimating the position of a user of a mobile terminal have been actively used. As a position estimation technique, for example, a technique called PDR (Pedestrian Dead Reckoning) is known. PDR is a technique for estimating the position of a user by accumulating the rotation angle calculated from the angular velocity sensor and the movement distance calculated from the acceleration sensor. In this regard, Patent Document 1 discloses a car navigation device that estimates the current position of a vehicle.

  In the above-described PDR, errors in position estimation are also accumulated, so it is useful to correct (update) the reference position using, for example, the coordinates of a fixed node.

JP 2012-112691 A

  However, there are location and cost limitations in installing fixed nodes. If the fixed node installation density is insufficient, it is difficult for the mobile terminal to perform position estimation with sufficient accuracy.

  Therefore, the present invention has been made in view of the above-mentioned problems, and the object of the present invention is a new and improved technique capable of updating the reference position even at an opportunity other than communication with a fixed node. To provide a mobile terminal, a method, and a mobile communication system.

  In order to solve the above-described problem, according to an aspect of the present invention, a mobile terminal is configured to acquire position information of the mobile terminal calculated by accumulating a change amount of the position of the mobile terminal in a reference position. A position information acquisition unit, a reliability acquisition unit that acquires reliability information of the position information of the mobile terminal based on an elapsed time from the update of the reference position, and a position of the other mobile terminal from another mobile terminal Information, and another terminal information acquisition unit that acquires reliability information of the position information of the other mobile terminal, reliability information of the position information of the mobile terminal, and reliability information of the position information of the other mobile terminal And a control unit that controls updating of the reference position using the position information of the other mobile terminal based on the above relationship.

  The reliability acquisition unit may acquire the reliability information based on a total of a set time set when the reference position is updated and an elapsed time since the update of the reference position.

  The said control part may set the said setting time using the reliability information of the positional information on the said other mobile terminal together with the update of the said reference position.

  The mobile terminal further includes a fixed node information acquisition unit that acquires position information of the fixed node from a fixed node, and the control unit updates the reference position using the position information of the fixed node, and the setting The time may be set to a predetermined value.

  The control unit determines whether or not the reception strength of the signal received from the other mobile terminal exceeds a threshold, and based on the reception strength of the signal received from the other mobile terminal exceeds the threshold, The updating of the reference position using the position information of the other mobile terminal may be controlled.

  The control unit is configured based on the fact that the reliability indicated by the reliability information of the location information of the other mobile terminal is higher than the reliability indicated by the reliability information of the location information of the mobile terminal. The updating of the reference position using the position information may be controlled.

  The reliability acquisition unit may acquire the reliability information further based on a change history of a traveling direction of a user carrying the mobile terminal.

  The reliability acquisition unit may acquire reliability information indicating lower reliability as the change angle in the traveling direction and the number of changes in the traveling direction are larger.

  In order to solve the above-described problem, according to another aspect of the present invention, there is provided a method executed by a mobile terminal, wherein the change amount of the position of the mobile terminal is calculated and accumulated in a reference position. Acquiring position information of the mobile terminal, acquiring reliability information of the position information of the mobile terminal based on an elapsed time from the update of the reference position, and from the other mobile terminal to the other mobile terminal And the reliability information of the location information of the other mobile terminal, and the reliability information of the location information of the other mobile terminal and the reliability information of the location information of the other mobile terminal And controlling the update of the reference position using the position information of the other mobile terminal.

  In order to solve the above problem, according to another aspect of the present invention, there is provided a mobile communication system including a plurality of mobile terminals, each of the plurality of mobile terminals being a change amount of a position of the mobile terminal. A position information acquisition unit that acquires position information of the mobile terminal calculated by accumulating the reference position and a reliability information of the position information of the mobile terminal is acquired based on an elapsed time since the update of the reference position A reliability level acquisition unit, a location information of the other mobile terminal, a location information of the location of the other mobile terminal, and a location information of the mobile terminal. A control unit that controls updating of the reference position using the position information of the other mobile terminal based on the relationship between the reliability information of the other mobile terminal and the reliability information of the position information of the other mobile terminal. A mobile communication system is provided

  As described above, according to the present invention, it is possible to update the position information at an opportunity other than communication with the fixed node.

It is explanatory drawing which shows the structure of the mobile communication system by embodiment of this invention. It is explanatory drawing which shows the structure of the mobile terminal by this embodiment. The structural example of a beacon is shown. It is explanatory drawing which shows the change with progress of time of a probability density function. 3 is a flowchart illustrating an operation of a mobile terminal according to an embodiment of the present invention. It is explanatory drawing which shows the specific example of communication between mobile terminals. It is explanatory drawing which shows the specific example of communication between mobile terminals. It is explanatory drawing which shows the specific example of communication between mobile terminals. It is explanatory drawing which shows typically the relationship between the change angle of the advancing direction, and the amount of error to generate | occur | produce. It is explanatory drawing which showed the hardware constitutions of the mobile terminal.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  In the present specification and drawings, a plurality of components having substantially the same functional configuration may be distinguished by adding different alphabets after the same reference numeral. For example, a plurality of configurations having substantially the same functional configuration or logical significance are distinguished as the mobile terminals 20A, 20B, and 20C as necessary. However, when it is not necessary to particularly distinguish each of a plurality of constituent elements having substantially the same functional configuration, only the same reference numeral is given to each of the plurality of constituent elements. For example, when there is no need to particularly distinguish the mobile terminals 20A, 20B, and 20C, each mobile terminal is simply referred to as the mobile terminal 20.

<1. Configuration of mobile communication system>
FIG. 1 is an explanatory diagram showing a configuration of a mobile communication system according to an embodiment of the present invention. As shown in FIG. 1, the mobile communication system according to the embodiment of the present invention includes a plurality of mobile terminals 20A to 20C and a plurality of fixed nodes 30A and 30B.

  The fixed node 30 is a node installed at a fixed position, and holds position information indicating its own installation position. The fixed node 30 has a wireless communication function and periodically transmits a beacon including its own position information, for example. Such a fixed node 30 may be a public wireless LAN (Local Area Network) access point.

  The mobile terminal 20 is an information processing device carried by a user. For example, in the example shown in FIG. 1, the user UA carries the mobile terminal 20A, the user UB carries the mobile terminal 20B, and the user UC carries the mobile terminal 20C. The mobile terminal 20 may be a portable information processing device such as a smartphone, a mobile phone, a PHS (Personal Handyphone System), a portable music playback device, a portable video processing device, a portable game device, and a wearable terminal. .

  The mobile terminal 20 has a wireless communication function for communicating with the fixed node 30 and other mobile terminals 20. The mobile terminal 20 according to the present embodiment has a PDR function that estimates the current position by accumulating the amount of position change with respect to the reference position. Since errors are accumulated in the position estimation by the PDR function, when the beacon is received from the fixed node 30, the mobile terminal 20 updates the reference position using the position information included in the beacon, and the updated reference The amount of change in position is accumulated with respect to the position.

  However, the installation of the fixed node 30 is limited in terms of location and cost. If the fixed density of the fixed nodes 30 is insufficient, the method for updating the reference position based only on the beacon from the fixed node 30 will increase the time interval for updating the reference position and increase the accumulated amount of error. There was concern.

  The present inventor has come up with an embodiment of the present invention by focusing on the above circumstances. According to the embodiment of the present invention, it is possible to update the position information at an opportunity other than communication with the fixed node 30. As a result, it is possible to improve the estimation accuracy of the current position. Hereinafter, the configuration and operation of the embodiment of the present invention will be sequentially described in detail.

<2. Configuration of mobile terminal>
FIG. 2 is an explanatory diagram showing the configuration of the mobile terminal 20 according to the present embodiment. As shown in FIG. 2, the mobile terminal 20 according to the present embodiment includes a sensor unit 220, a change amount calculation unit 230, a reference information management unit 240, a position estimation unit 250, an accuracy specification unit 260, and a transmission unit. 272, a receiving unit 274, a display unit 276, and a battery 278.

(Sensor part)
The sensor unit 220 detects information related to the movement and movement of the mobile terminal 20. The sensor unit 220 may include an acceleration sensor 222, an angular velocity sensor 224, and a geomagnetic sensor 226, for example, as shown in FIG. The acceleration sensor 222 acquires information regarding acceleration, the angular velocity sensor 224 acquires information regarding angular velocity, and the geomagnetic sensor 226 acquires information regarding orientation.

(Change amount calculation part)
The change amount calculation unit 230 periodically calculates the change amount of the position of the mobile terminal 20 using the sensor information supplied from the sensor unit 220. Here, the amount of change in the position is the amount of change in the position of the mobile terminal 20 between the time when the change amount calculation unit 230 calculates the amount of change in position last time and the next time the amount of change in position is calculated. It is.

(Standard Information Management Department)
The reference information management unit 240 manages reference information used for position estimation by the position estimation unit 250. Specifically, the reference information management unit 240 includes a reference information storage unit 242 and an update determination unit 244 as illustrated in FIG.

  The reference information storage unit 242 stores reference position information indicating the reference position and reference accuracy information indicating the reference accuracy as the reference information. The update determination unit 244 is an example of a control unit that determines whether or not to update the reference information and controls the update of the reference information according to the determination result.

  For example, when the beacon is received from the fixed node 30 with the received power exceeding the threshold, the update determination unit 244 updates the reference position information with the position information included in the beacon. Since the distance between the fixed node 30 and the mobile terminal 20 is smaller as the received power is higher, the reliability of the reference position information is improved by updating the reference position information with the position information of the fixed node 30 when the received power exceeds the threshold. can do. That is, the received power threshold value is set to a received power value when the positional deviation due to the distance between the mobile terminal 20 and another mobile terminal 20 is close enough to cause no practical problem. In the following, the update of the reference position information using the position information of the fixed node 30 may be referred to as a first update.

  The reference accuracy information is information indicating the reliability of the reference position information. The update determination unit 244 sets the reference accuracy information to a predetermined value together with the first update.

  Furthermore, the update determination unit 244 according to the present embodiment also determines whether or not to update the reference information based on beacons received from other mobile terminals 20. The update of reference information based on beacons received from other mobile terminals 20 will be described later in detail.

(Position estimation part)
The position estimation unit 250 is a position information acquisition unit that acquires position information of the mobile terminal 20 by accumulating the amount of change in the position of the mobile terminal 20 in the reference position. Specifically, the position estimation unit 250 accumulates the change amount of the position calculated by the change amount calculation unit 230 in the reference position information stored in the reference information storage unit 242, so that the current position of the mobile terminal 20 can be obtained. Estimate the position.

(Accuracy specifying part)
The accuracy specifying unit 260 is an example of a reliability acquisition unit that specifies accuracy information (reliability information) of position information estimated by the position estimation unit 250. As described above, in position estimation using the PDR function, errors accumulate as time passes. For this reason, the accuracy specifying unit 260 may estimate the accuracy information based on the elapsed time since the previous update of the reference position information.

(Transmitter)
The transmission unit 272 transmits a signal to another mobile terminal 20 or the fixed node 30. In particular, the transmission unit 272 according to the present embodiment transmits a beacon including the location information of the mobile terminal 20 estimated by the location estimation unit 250 and the accuracy information specified by the accuracy specification unit 260.

  FIG. 3 shows a configuration example of a beacon. As shown in FIG. 3, the beacon includes a header and a payload. The header stores a preamble, control information, and the like. The payload includes location information and accuracy information of the mobile terminal 20. The beacon is transmitted at a timing determined according to the communication method.

(Receiver)
The receiving unit 274 receives a signal transmitted from another mobile terminal 20 or the fixed node 30. For example, the reception unit 274 includes a fixed node information acquisition unit that receives a beacon including the position information of the fixed node 30 from the fixed node 30, and the position information and accuracy information of the other mobile terminal 20 from the other mobile terminals 20. It has a function as an other terminal information acquisition part which receives a beacon.

(Display section)
The display unit 276 displays various information. For example, the display unit 276 may display the position information of the mobile terminal 20 estimated by the position estimation unit 250. The user of the mobile terminal 20 can grasp the current position by viewing the display unit 276.

(Battery)
The battery 278 is a general-purpose secondary battery. The mobile terminal 20 operates based on the electric power stored in the battery 278.

<3. About accuracy of position estimation>
The configuration of the mobile terminal 20 according to the present embodiment has been described above. Subsequently, the accuracy of the position information of the mobile terminal 20 estimated by the position estimation unit 250 will be described.

  The actual position of the mobile terminal 20 does not necessarily match the position estimated by the position estimation unit 250. That is, there is a probability that the mobile terminal 20 actually exists at a position (x, y) in the vicinity of the position (x ′, y ′) estimated by the position estimation unit 250. The probability that the mobile terminal 20 exists at the position (x, y) is the probability density of the standard bivariate normal distribution shown in the following Equation 1 using the position (x ′, y ′) estimated by the position estimation unit 250. Expressed as a function. Although Equation 1 shows the probability density function at the x and y coordinates, a three-dimensional probability density function to which the height direction is added may be applied.

  In Equation 1, σx is the standard deviation of error in the x coordinate, and σy is the standard deviation of error in the y coordinate. As described above, in the position estimation using the PDR function, errors accumulate as time elapses. Therefore, the standard deviations σx and σy are arbitrary functions fx (t) whose values increase with the elapse of time since the update of the reference position information. , Fy (t).

  For example, the standard deviations σx and σy may be a linear function of time t (elapsed time from the first update) as shown in Equation 2 below, or time as shown in Equation 3 below. It may be a quadratic function of t. In the following mathematical formula, a to f are proportional constants. The specific function can be designed experimentally based on the performance of the sensor.

  FIG. 4 is an explanatory diagram showing a change of the probability density function p (x, y) with the passage of time. As described above, since the standard deviations σx and σy increase with the passage of time since the update of the reference position information, the peak of the probability density function p (x, y) decreases with the passage of time, and the probability distribution is entirely To disperse. The probability density function p (x, y) can be said to be an index indicating the reliability and accuracy of the position information estimated by the position estimation unit 250.

  As described above, the accuracy specifying unit 260 specifies the peak value of the probability density function p (x, y) or the probability density function p (x, y) as the accuracy information of the position information estimated by the position estimation unit 250. Also good.

  Alternatively, since the peak values of the probability density function p (x, y) and the probability density function p (x, y) depend on the standard deviations σx and σy, the accuracy specifying unit 260 uses the standard deviations σx and σy as accuracy information. May be specified. Furthermore, since the standard deviations σx and σy depend on the elapsed time from the first update, the accuracy specifying unit 260 may specify the elapsed time from the first update as accuracy information. When the elapsed time from the update of the reference position information is used as the accuracy information, the amount of accuracy information is small, so the traffic volume for communication of accuracy information is suppressed. As described above, the accuracy information specified by the accuracy specifying unit 260 is transmitted from the transmission unit 272 together with the position information.

<4. Reference position information update determination>
The update determination unit 244 determines whether to update the reference position information using the position information included in the beacons received from the other mobile terminals 20 based on the accuracy information included in the beacons. Specifically, when the accuracy information received from the other mobile terminal 20 indicates higher accuracy than the accuracy information specified by the accuracy specifying unit 260, the update determination unit 244 It is determined that the reference position information is updated (overwritten) with the position information included in the received beacon. In addition, the update of the reference | standard position information using the positional information contained in the beacon received from the other mobile terminal 20 may be called a 2nd update below.

  For example, when the elapsed time from the first update is used as the accuracy information, the update determination unit 244 is specified by the elapsed time included in the beacon received from the other mobile terminal 20 and the accuracy specifying unit 260. Compare with elapsed time. The update determination unit 244 is received from the other mobile terminal 20 when the elapsed time included in the beacon received from the other mobile terminal 20 is shorter than the elapsed time specified by the accuracy specifying unit 260. The reference position information is updated with the position information included in the beacon.

  Here, the position information received from other mobile terminals 20 also includes an error. Therefore, after the reference position information is updated with the position information received from another mobile terminal 20, the position estimation unit 250 estimates the position of the mobile terminal 20 using the updated reference position information. This includes the sum of errors included in the reference position information and errors generated after the update of the reference position information.

  Therefore, the update determination unit 244 sets the elapsed time included in the beacons received from the other mobile terminals 20 in the reference accuracy information during the second update. Thereafter, the accuracy specifying unit 260 specifies the total time of the elapsed time from the second update and the time (set time) indicated by the reference accuracy information as accuracy information. Here, the time indicated by the reference accuracy information is a time from when the first update is performed in another mobile terminal 20 to when the second update is performed by the mobile terminal 20. Therefore, the total time corresponds to the elapsed time from the timing when the first update is performed in the other mobile terminal 20 to the current time point. By specifying the total time as accuracy information by the accuracy specifying unit 260, it is possible to reflect both the error included in the reference position information and the error generated after the update of the reference position information in the accuracy information. Become. In the present specification, the above total time may be referred to as an elapsed time from the first update for convenience.

  As a result, after the mobile terminal 20A updates the reference position information with the position information received from the mobile terminal 20B, the mobile terminal 20C updates the reference position information with the position information received from the mobile terminal 20A. It is possible to appropriately realize the update of the chained reference position information. Note that the update determination unit 244 may update the reference accuracy information to a predetermined value (for example, 0) during the first update.

  As a modification, the accuracy information estimated by the position estimation unit 250 and the accuracy information received from the other mobile terminals 20 by the reception unit 274 are the peak value of the probability density function p (x, y), or the standard deviation σx and It may be σy or the like. Even in this case, it is desirable that the elapsed time from the first update is added to the accuracy information. With this configuration, after the update determination unit 244 performs the second update, the accuracy specifying unit 260 adds the elapsed time added to the accuracy information received from the other mobile terminals 20 at the time of the second update, Based on the total time with the elapsed time from the second update, it is possible to specify the standard deviations σx and σy, the peak value of the probability density function p (x, y), and the like.

<5. Operation>
The configuration of the mobile terminal 20 according to the embodiment of the present invention has been described above. Subsequently, referring to FIG. 5, the operation of the mobile terminal 20 according to the embodiment of the present invention is organized.

  FIG. 5 is a flowchart showing an operation of the mobile terminal 20 according to the embodiment of the present invention. As shown in FIG. 5, first, when the reference information storage unit 242 stores the reference information (S304 / Yes), the position estimation unit 250 adds the reference position information stored in the reference information storage unit 242 to the reference position information. Then, the position information of the mobile terminal 20 is estimated by accumulating the position change amount calculated by the change amount calculation unit 230 (S308). Further, the accuracy specifying unit 260 specifies the accuracy information of the position information estimated by the position estimating unit 250 (S312). Then, the transmission unit 272 transmits a beacon including the location information of the mobile terminal 20 estimated by the location estimation unit 250 and the accuracy information specified by the accuracy specification unit 260 (S316).

  Thereafter, when a beacon is received (S320 / Yes), the update determination unit 244 determines whether or not the received power of the beacon exceeds a threshold value (S324). When the received power of the beacon is equal to or less than the threshold (S324 / No), the processing from S308 is repeated. On the other hand, when the received power of the beacon exceeds the threshold (S324 / Yes), the update determination unit 244 performs different processing depending on whether the beacon transmission source is the fixed node 30 or the other mobile terminal 20.

  Specifically, when the beacon transmission source is the fixed node 30 (S328 / fixed node), the update determination unit 244 updates the reference position information in the reference information storage unit 242 with the position information included in the beacon (S332). ), A predetermined value is set in the reference accuracy information (S336).

  On the other hand, when the transmission source of the beacon is another mobile terminal 20 (S328 / mobile terminal), the update determination unit 244 specifies the accuracy information received from the other mobile terminal 20 by the accuracy specifying unit 260. It is determined whether or not the accuracy information is higher than the accuracy information (S340). When the accuracy information received from the other mobile terminal 20 indicates higher accuracy than the accuracy information specified by the accuracy specifying unit 260 (S340 / Yes), the update determining unit 244 receives from the other mobile terminal 20 The reference position information is updated with the position information included in the received beacon (S344). Furthermore, the update determination unit 244 sets reference accuracy information using accuracy information included in beacons received from other mobile terminals 20 (S348). When the accuracy information received from the other mobile terminals 20 indicates lower accuracy than the accuracy information specified by the accuracy specifying unit 260 (S340 / No), the update determining unit 244 determines the reference position information and the reference accuracy information. Will not be updated. Thereafter, the processing from S308 is repeated. Here, if the arrival direction and the relative distance of the radio wave having received the accuracy information can be estimated, the position information may be corrected by shifting the received position information by the relative distance in the arrival direction. For example, if an array antenna is used, the direction of arrival of radio waves can be estimated from the difference in reception time. The relative distance can be estimated based on the received power value by determining the transmission power in advance and storing the relationship between the distance and the received power intensity in a table.

  When the reference information storage unit 242 does not store the reference information in S304 (S304 / No), the mobile terminal 20 waits until a beacon is received from another mobile terminal 20 or the fixed node 30 (S352 / No). When a beacon is received from another mobile terminal 20 or the fixed node 30, the processes after S324 are advanced.

  Here, the operation of the mobile terminal 20 according to the present embodiment will be described more specifically with reference to FIGS.

  6 to 8 are explanatory diagrams illustrating specific examples of communication between the mobile terminals 20. 6 to 8 show an example in which the elapsed time (minutes) from the update of the reference position information using the position information of the fixed node 30 is used as the accuracy information.

  In the example illustrated in FIG. 6, the mobile terminal 20 </ b> A updates the reference position information based on the beacon received from the fixed node 30 at 11:00. For this reason, the accuracy information of the mobile terminal 20A becomes 0 (minutes) at 11:00. It is assumed that the accuracy information of the mobile terminal 20B is 8 (minutes) and the accuracy information of the mobile terminal 20C is 15 (minutes) at 11:00.

  Then, as shown in FIG. 7, at 11:05, the mobile terminal 20A and the mobile terminal 20B approach each other, and the mobile terminal 20A and the mobile terminal 20B transmit and receive each other's beacons. At this time, the accuracy information of the mobile terminal 20A is 5 (minutes), the accuracy information of the mobile terminal 20B is 13 (minutes), and the accuracy information of the mobile terminal 20A is higher than the accuracy information of the mobile terminal 20B. For this reason, the mobile terminal 20B updates the reference position information using the position information included in the beacon received from the mobile terminal 20A. Also, the mobile terminal 20B sets 5 (minutes), which is the accuracy information of the mobile terminal 20A, as the reference accuracy information.

  Further, as shown in FIG. 8, at 11:10, the mobile terminal 20B and the mobile terminal 20C approach each other, and the mobile terminal 20B and the mobile terminal 20C transmit and receive each other's beacons. At this time, the accuracy information of the mobile terminal 20B is 10 (minutes), the accuracy information of the mobile terminal 20C is 25 (minutes), and the accuracy information of the mobile terminal 20B is higher than the accuracy information of the mobile terminal 20C. For this reason, the mobile terminal 20C updates the reference position information using the position information included in the beacon received from the mobile terminal 20B. Also, the mobile terminal 20C sets 10 (minutes), which is the accuracy information of the mobile terminal 20B, as the reference accuracy information.

  In this way, each mobile terminal 20 can update the reference position information using more likely position information received from other mobile terminals 20. Therefore, according to the present embodiment, since the opportunity to update the reference position information is increased, the position estimation accuracy by the mobile terminal 20 can be improved.

<6. Application example>
The embodiments of the present invention have been described above. Various applications can be applied to the above-described embodiments of the present invention. Hereinafter, an example of application applicable to the embodiment of the present invention will be described.

  The position estimation unit 250 can calculate the travel distance of the user based on information obtained from the acceleration sensor 222 and can calculate the travel direction of the user based on information obtained from the angular velocity sensor 224. It has been experimentally found that the travel distance error and the travel direction error can be approximated by a normal distribution.

  The position estimation unit 250 can estimate the position (x ′, y ′) of the mobile terminal 20 using the travel distance D and the travel direction E according to the following mathematical formula.

  According to Equation 4, the accuracy of position estimation by the position estimation unit 250 depends on the accuracy of the travel distance D and the travel direction E. Here, the degree of accuracy decrease in the travel distance D and the travel direction E also varies depending on the movement history of the user. For example, the information on the angular velocity detected by the angular velocity sensor 224 is more likely to have an error as the change in the angular velocity is larger.

  FIG. 9 is an explanatory diagram schematically showing the relationship between the change angle in the traveling direction and the amount of error that occurs. As shown in FIG. 9, as the absolute value of the change angle in the traveling direction increases, the amount of error that occurs increases, for example, in a quadratic function. For this reason, when the user changes the traveling direction, an error is more likely to be added than when the user is walking straight. The same applies to the moving speed, and it is considered that the higher the moving speed, the easier the error is added.

  Therefore, the accuracy specifying unit 260 according to the application example specifies the accuracy information based on the movement history such as the change history of the user's traveling direction and the movement speed in addition to the elapsed time from the first update. For example, the accuracy specifying unit 260 may specify, as accuracy information, a standard deviation expressed by a mathematical formula in which a term calculated based on a user's movement history is added to the right side of Formula 2 or Formula 3.

  The term is desirably a term that shows a larger value as the change angle in the traveling direction and the number of changes in the traveling direction are larger. For example, the term may be a multiplication of the number of times that the change angle of the user's traveling direction exceeds a threshold value and a predetermined count. Since the corner is often 90 degrees in a building, the threshold may be 90 degrees from the viewpoint of using the number of times the user has bent the corner, and the user may bend the corner slowly. In consideration of this, the threshold value may be set to less than 90 degrees, for example, 80 degrees. Or the said term may show the cumulative value of the weight according to the change angle of the advancing direction.

  According to such an application example, the accuracy specifying unit 260 can specify the accuracy information more appropriately, so that the update determination unit 244 can also make the determination regarding the update of the reference position information more appropriately. Become. Similarly, as the moving distance per unit time is larger as the moving distance is increased, the accuracy specifying unit 260 may specify the accuracy information based on the moving distance history.

<7. Hardware configuration>
The embodiments of the present invention have been described above. Information processing such as position estimation and update determination described above is realized by cooperation of software and hardware of the mobile terminal 20 described below.

  FIG. 10 is an explanatory diagram showing a hardware configuration of the mobile terminal 20. As illustrated in FIG. 10, the mobile terminal 20 includes a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, a RAM (Random Access Memory) 203, an input device 208, an output device 210, A storage device 211 and a communication device 215 are provided.

  The CPU 201 functions as an arithmetic processing device and a control device, and controls the overall operation in the mobile terminal 20 according to various programs. Further, the CPU 201 may be a microprocessor. The ROM 202 stores programs used by the CPU 201, calculation parameters, and the like. The RAM 203 temporarily stores programs used in the execution of the CPU 201, parameters that change as appropriate during the execution, and the like. These are connected to each other by a host bus including a CPU bus. Functions such as a change amount calculation unit 230, a reference information management unit 240, a position estimation unit 250, and an accuracy specifying unit can be realized by cooperation of the CPU 201, the ROM 202, the RAM 203, and the software.

  The input device 208 includes input means for a user to input information, such as a mouse, keyboard, touch panel, button, microphone, switch, and lever, and an input control circuit that generates an input signal based on the input by the user and outputs the input signal to the CPU 201. Etc. The user of the mobile terminal 20 can input various data and instruct processing operations to the mobile terminal 20 by operating the input device 208.

  The output device 210 includes a display device such as a liquid crystal display (LCD) device, an OLED (Organic Light Emitting Diode) device, and a lamp. Furthermore, the output device 210 includes an audio output device such as a speaker and headphones. For example, the display device displays a captured image or a generated image. On the other hand, the audio output device converts audio data or the like into audio and outputs it.

  The storage apparatus 211 is a data storage apparatus configured as an example of a storage unit of the mobile terminal 20 according to the present embodiment. The storage device 211 may include a storage medium, a recording device that records data on the storage medium, a reading device that reads data from the storage medium, a deletion device that deletes data recorded on the storage medium, and the like. The storage device 211 stores programs executed by the CPU 201 and various data.

  The communication device 215 is a communication interface configured with a communication device or the like for communicating with other devices. The communication device 215 may be a wireless LAN (Local Area Network) compatible communication device, an LTE (Long Term Evolution) compatible communication device, or a wire communication device that performs wired communication.

<8. Conclusion>
As described above, the mobile terminal 20 according to the embodiment of the present invention can update the reference position information using more likely position information received from other mobile terminals 20. Therefore, according to the present embodiment, since the opportunity to update the reference position information is increased, the position estimation accuracy by the mobile terminal 20 can be improved.

  Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

  For example, in the above embodiment, the example in which the mobile terminal 20 has the position estimation function has been described, but the mobile terminal 20 may not have the position estimation function. In this case, the mobile terminal 20 transmits the information obtained by the sensor unit 220 to the fixed node 30, the fixed node 30 estimates the position information of the mobile terminal 20 based on the information received from the mobile terminal 20, and the fixed node 30 However, the position information may be notified to the mobile terminal 20 by, for example, a beacon.

  In addition to the beacon transmission unit that transmits a beacon, the fixed node 30 may include a reception unit that receives the location information of the mobile terminal 20 from the mobile terminal 20 and a display unit that displays the location information of the mobile terminal 20. Good.

  In addition, when each mobile terminal 20 transmits a probability density function as accuracy information, each mobile terminal 20 performs a statistical process using the probability density function received from a plurality of other mobile terminals 20 to perform a process of the mobile terminal 20. It is also possible to estimate the position. For example, maximum likelihood estimation is given as a statistical process, and according to maximum likelihood estimation, the current likely position of the mobile terminal 20 can be estimated from a plurality of probability density functions.

  In the above description, the fixed node 30 is described as an example of an apparatus that provides accurate position information. However, an apparatus that provides accurate position information is not limited to the fixed node 30. For example, a device having a GPS function, a device having a function of estimating its own position based on reception intensity of radio waves received from a plurality of devices whose positions are known, and the like, as devices that provide accurate position information It is also possible to apply to the embodiment of the present invention.

  In addition, each step in the processing of the mobile terminal 20 in this specification does not necessarily have to be processed in time series in the order described as a sequence diagram or a flowchart. For example, each step in the processing of the mobile terminal 20 may be processed in an order different from the order described as the flowchart, or may be processed in parallel.

  In addition, it is possible to create a computer program for causing hardware such as the CPU 201, the ROM 202, and the RAM 203 built in the mobile terminal 20 to perform the same functions as the components of the mobile terminal 20 described above. A storage medium storing the computer program is also provided.

20 mobile terminal 30 fixed node 220 sensor unit 222 acceleration sensor 224 angular velocity sensor 226 geomagnetic sensor 230 variation calculation unit 240 reference information management unit 242 reference information storage unit 244 update determination unit 250 position estimation unit 260 accuracy identification unit 272 transmission unit 274 reception Unit 276 display unit 278 battery

Claims (10)

A mobile terminal,
A position information acquisition unit that acquires position information of the mobile terminal calculated by accumulating the amount of change in the position of the mobile terminal in a reference position;
A reliability acquisition unit that acquires reliability information of the position information of the mobile terminal based on an elapsed time from the update of the reference position;
An other terminal information acquisition unit for acquiring position information of the other mobile terminal and reliability information of the position information of the other mobile terminal from another mobile terminal;
Control for controlling updating of the reference position using the position information of the other mobile terminal based on the relationship between the reliability information of the position information of the mobile terminal and the reliability information of the position information of the other mobile terminal And
A mobile terminal comprising:   The movement according to claim 1, wherein the reliability acquisition unit acquires the reliability information based on a total of a set time set when the reference position is updated and an elapsed time since the update of the reference position. Terminal.   The said control part is a mobile terminal of Claim 2 which sets the said setting time using the reliability information of the positional information on the said other mobile terminal together with the update of the said reference position. The mobile terminal
A fixed node information acquisition unit for acquiring position information of the fixed node from the fixed node;
The mobile terminal according to claim 2, wherein the control unit updates the reference position using position information of the fixed node and sets the set time to a predetermined value.   The control unit determines whether or not the reception strength of the signal received from the other mobile terminal exceeds a threshold, and based on the reception strength of the signal received from the other mobile terminal exceeds the threshold, The mobile terminal as described in any one of Claims 1-4 which controls the update of the said reference position using the positional information on the said other mobile terminal.   The control unit is configured based on the fact that the reliability indicated by the reliability information of the location information of the other mobile terminal is higher than the reliability indicated by the reliability information of the location information of the mobile terminal. The mobile terminal according to claim 1, wherein the update of the reference position using the position information is controlled.   The mobile terminal according to any one of claims 1 to 6, wherein the reliability acquisition unit acquires the reliability information further based on a change history of a traveling direction of a user carrying the mobile terminal.   The mobile terminal according to claim 7, wherein the reliability acquisition unit acquires reliability information indicating a lower reliability as the change angle in the traveling direction and the number of changes in the traveling direction are larger. A method performed by a mobile terminal,
Obtaining position information of the mobile terminal calculated by accumulating the amount of change in the position of the mobile terminal in a reference position;
Obtaining reliability information of position information of the mobile terminal based on an elapsed time from the update of the reference position;
Obtaining position information of the other mobile terminal and reliability information of the position information of the other mobile terminal from another mobile terminal;
Controlling updating of the reference position using the position information of the other mobile terminal based on the relationship between the reliability information of the position information of the mobile terminal and the reliability information of the position information of the other mobile terminal. When,
Including a method. A mobile communication system comprising a plurality of mobile terminals,
Each of the plurality of mobile terminals is
A position information acquisition unit that acquires position information of the mobile terminal calculated by accumulating the amount of change in the position of the mobile terminal in a reference position;
A reliability acquisition unit that acquires reliability information of the position information of the mobile terminal based on an elapsed time from the update of the reference position;
An other terminal information acquisition unit for acquiring position information of the other mobile terminal and reliability information of the position information of the other mobile terminal from another mobile terminal;
Control for controlling updating of the reference position using the position information of the other mobile terminal based on the relationship between the reliability information of the position information of the mobile terminal and the reliability information of the position information of the other mobile terminal And
A mobile communication system.

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