JP5266976B2 - Terminal position determination method, terminal position determination program, and terminal position determination apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of obtaining the arrangement of anchor terminals capable of satisfying a requirement value to position estimation accuracy when the requirement value is designated as a condition. <P>SOLUTION: The method for determining the arrangement position of an anchor terminal 200 used as a reference in estimating the position of a radio terminal 100 by using a radio signal includes: a request input step of designating a requirement value to estimation accuracy of the position of the radio terminal 100; an arrangement input step of designating the arrangement interval or arrangement number of the anchor terminals 200; and an estimation accuracy calculation step of calculating estimation accuracy by using the arrangement interval or arrangement number. The method repeatedly executes the estimation accuracy calculation step while changing the arrangement interval or arrangement number of the anchor terminals 200 until the estimation accuracy calculated in the estimation accuracy calculation step satisfies the requirement value, and determines the arrangement position of the anchor terminal 200 by the result thereof. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a technique for determining an arrangement position of an anchor terminal serving as a reference when estimating the position of a wireless terminal using a wireless signal.

  The position of the target terminal that is the target of position detection is estimated with reference to an anchor terminal whose position is known. The position estimation accuracy largely depends on the number of anchor terminals and the distance between the target terminal and the anchor terminal. Furthermore, the position estimation accuracy is also affected by the environment in which position detection is performed.

  Conventionally, with regard to position detection using radio signals, “the position of the radio transmitter is detected with high accuracy by recalculating the coefficient used for position detection of the radio transmitter according to the environment in which the radio transmitter moves. `` Providing technology that enables the position of a wireless transmitter to be detected with high accuracy even when the radio wave propagation environment of the position detection target area where the wireless transmitter moves is not uniform '' As a target technique, “a configuration in which a position detection target area is divided into a plurality of subareas and a coefficient used for position detection of a wireless transmitter is executed in units of subareas is adopted. As a result, when there is a difference in the radio wave propagation environment in the position detection target area, the position detection target area is calculated as a single area and the coefficient is calculated to calculate the position estimation. The position of the wireless transmitter can be detected with a smaller error. Is proposed (Patent Document 1).

  Non-Patent Document 1 below shows that the position estimation accuracy of the target terminal greatly depends on the distance to the nearest anchor terminal.

  Non-Patent Document 2 below shows that the position estimation accuracy of the target terminal depends on the number of anchor terminals that can transmit and receive information.

JP 2006-329688 A (summary) Daigo Tsuji, Masahiro Takashima, Kentaro Yanagihara, Junpei Takeji, Kiyoshi Fukui, Shigeru Fukunaga, Keisuke Hara, Kenichi Kitayama, “Maximum Likelihood Location Estimation Using Received Signal Power Value in Sensor Networks”, IEICE Tech. 327, pp. 409-414, Okinawa, March 2005 Masahiro Takashima, Daigo Tsuji, Kentaro Yanagihara, Kiyoshi Fukui, Shigeru Fukunaga, Keisuke Hara, Kenichi Kitayama, “Position Estimation Using Received Power and Maximum Likelihood in Sensor Networks”, The Institute of Electronics, Information and Communication Engineers (B), pp. 742-750, May 2006

An application using a position detection result may require a certain accuracy for position estimation.
However, although the technique described in Patent Document 1 has been devised to perform position estimation as accurately as possible, it is difficult to predict in advance to what extent the position can be estimated.
Therefore, even if a required value for position estimation accuracy is specified, it is difficult to determine whether or not the required value can be satisfied.

  For this reason, when a required value for position estimation accuracy is specified as a condition, a method for obtaining an arrangement of anchor terminals that can satisfy the required value has been desired.

A terminal position determination method according to the present invention is a method for determining an arrangement position of an anchor terminal serving as a reference when estimating the position of a wireless terminal using a wireless signal, and a required value for the accuracy of estimating the position of the wireless terminal A request input step for designating, an arrangement input step for designating the arrangement interval or the number of arrangements of the anchor terminal, and an estimation accuracy calculation step for calculating the estimation accuracy using the arrangement interval or the number of arrangements, Until the estimation accuracy calculated in the estimation accuracy calculation step satisfies the required value, the estimation accuracy calculation step is repeatedly executed while varying the arrangement interval or number of the anchor terminals, and the anchor terminal arrangement is determined based on the result. is intended to determine the position, the estimation accuracy calculating step, the estimated target region in the center of one of the grid delimiting a grid pattern A first step that assumes the placement of an anchor terminal, a second step that calculates a distance average from the wireless terminal to the nearest anchor terminal under the assumption, and calculates the estimation accuracy using the distance average And a third step .

According to the terminal location determination method according to the present invention, the location of anchor terminals that can satisfy the required value of location estimation accuracy is determined before the location estimation is performed, while changing the placement interval or the number of placement of anchor terminals. .
Therefore, when the position estimation of the target terminal is performed under the anchor terminal arrangement, the position estimation accuracy can be within the range of the estimation accuracy calculated in advance when the anchor terminal arrangement is determined.
Therefore, it is possible to determine in advance whether or not the request for the position estimation accuracy can be satisfied, and it is possible to meet the request of the application that requires a certain estimation accuracy.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a radio system according to Embodiment 1 of the present invention. The radio system according to the first embodiment includes target terminals 100a and 100b, anchor terminals 200a to 200f, an arrangement determination device 400, and a position estimation device 500.
The target terminals 100a and 100b and the anchor terminals 200a to 200f are arranged in the position estimation target area 300.

The target terminals 100a and 100b are wireless terminals for which position estimation is performed, and transmit and receive wireless signals. Also, the received power is measured, and the measured value is output to position estimation apparatus 500.
It is assumed that the movement range of the target terminals 100a and 100b is limited to the position estimation area 300. Although two target terminals are shown here, the number is not limited to this.

  The anchor terminals 200a to 200f are wireless terminals that have known arrangement positions and serve as a reference when estimating the positions of the target terminals 100a and 100b. Although an example in which six anchor terminals are installed is shown here, the number is not limited to this.

The arrangement determining apparatus 400 is an apparatus that determines the arrangement of the anchor terminals 200a to 200f using specified parameters.
The position estimation apparatus 500 is an apparatus that estimates the position of the target terminal using the received power values of the target terminals 100a and 100b and the position information of the anchor terminals 200a to 200f.

FIG. 2 is a functional block diagram of the arrangement determining apparatus 400.
The arrangement determining apparatus 400 includes a parameter acquisition unit 410 and a calculation unit 420.

The parameter acquisition unit 410 receives the propagation characteristics of radio signals used by the target terminals 100a to 100b and the anchor terminals 200a to 200f and the size and shape of the position estimation region 300 as environmental conditions.
Further, the parameter acquisition unit 410 is input with a required value for position estimation accuracy and a provisionally determined value of the arrangement interval or number of anchor terminals, which will be described later with reference to FIG.

  The calculation unit 420 uses the above-described parameter values input to the parameter acquisition unit 410 to determine the placement positions of the anchor terminals 200a to 200f according to the flow described in FIG. The determined arrangement position is output to the position estimation apparatus 500.

  The parameter acquisition unit 410 and the calculation unit 420 can be configured by hardware such as a circuit device that realizes these functions, or a calculation device such as a microcomputer or a CPU (Central Processing Unit) and software that defines the operation thereof. Can also be configured.

The “terminal position determination device” in the present invention corresponds to the arrangement determination device 400.
The “computer” corresponds to the case where the parameter acquisition unit 410 and the calculation unit 420 are configured by a calculation device and software.

The configuration of the wireless system according to the first embodiment has been described above.
Next, factors affecting the position estimation accuracy of the target terminal will be described.

As a method for estimating the position using the received signal power, for example, a method of estimating the distance between the three or more anchor terminals and the target terminal from the received power and estimating the position using a three-point surveying method. is there.
However, since many distances are included in the distance between terminals estimated from the received power, various methods different from the usual three-point survey are being studied.
For example, there is a method for estimating positions at all points to be position estimated by the following procedures (Step 1) to (Step 5).

(Step 1) Assuming the position of the target terminal, the distance between each anchor terminal and the target terminal is obtained.
(Step 2) From the obtained distance to the anchor terminal and the actually measured value of the received power, the probability of obtaining the actually measured received power value at the assumed target terminal position is calculated.
(Step 3) The above (Step 2) is executed for all anchor terminals.
(Step 4) Multiply all the results of (Step 3) above.
(Step 5) The point with the highest probability obtained in (Step 4) is set as the estimated position.

  In the above procedure, items such as the following (influence item 1) to (influence item 5) are considered to affect the position estimation accuracy.

(Influence item 1) Size of position estimation area 300 (Influence item 2) Radio signal propagation characteristics in position estimation area 300 (Influence item 3) Number of anchor terminals arranged in position estimation area 300 (Influence item 4) Position estimation area Position of anchor terminal placed at 300 (influence item 5) Difference in installation height between anchor terminal and target terminal

Of the above (influence item 1) to (influence item 5), (influence item 1) and (influence item 2) are known items, and therefore can be input items for the position estimation procedure.
Since (influence item 3) and (influence item 4) are target values to be calculated in the present invention, they cannot be determined and input in advance.
(Influence item 5) will be described later.

The factors affecting the position estimation accuracy of the target terminal have been described above.
Next, a procedure for obtaining an arrangement of anchor terminals that can satisfy a required value for position estimation accuracy will be described. First, the preconditions for obtaining the optimal anchor terminal arrangement position will be described in the following (1) to (3), and the specific procedure will be described with reference to FIG.

(1) Basic procedure for determining the placement position of an anchor terminal When the position of a target terminal is estimated, the position of the anchor terminal that serves as a reference for estimation needs to be known. However, when trying to obtain the optimum anchor terminal position, the anchor terminal position cannot be determined in advance as described above.
Therefore, when calculating the position estimation accuracy, the position of the anchor terminal is provisionally determined and then the process of calculating the position estimation accuracy is repeated, and the anchor terminal arrangement satisfying the required value of the position estimation accuracy is determined in an exploratory manner. become.

  Even if the position of the anchor terminal is provisionally determined, the position estimation accuracy varies greatly depending on the position of the target terminal.

  In the following description, it is assumed that the request for the position estimation accuracy is given as a request for the average estimation error in the entire position estimation region 300.

  It should be noted that, when a plurality of anchor terminal arrangement candidates are obtained, what arrangement is most preferable depends on the case, but it is generally considered that the smallest number of anchor terminals is desirable. This is also assumed in the following description.

(2) Items to be considered when determining the placement position of an anchor terminal As shown in Non-Patent Document 1 described above, the position estimation accuracy of a target terminal largely depends on the distance to the nearest anchor terminal. That is, the position estimation accuracy is improved when the distance to the anchor terminal is as small as possible.
Further, as shown in Non-Patent Document 2 described above, the position estimation accuracy of the target terminal also depends on the number of anchor terminals that can transmit and receive information.

  In view of the above, it is desirable that the position of the anchor terminal is determined so as to optimize the distance between the target terminal and the anchor terminal while varying the number of anchor terminals.

Therefore, in the present invention, using any one of the following (Expression 1) to (Expression 7), the distance between the target terminal and the anchor terminal, the number of anchor terminals, or both of these are used as variables, and the position estimation accuracy is increased. Represent.

The meaning of each variable is as follows.
A to G: Constants obtained experimentally β: Attenuation coefficient among radio signal propagation characteristics L: Average distance from target terminal to nearest anchor terminal i: Transmit / receive information within position estimation region 300 Number of anchor terminals that can be used-R: Position estimation accuracy-F: Constant value that depends on the difference in installation height between the anchor terminal and the target terminal

  The attenuation coefficient β represents a coefficient when the received signal power at the receiver is proportional to the β power of the distance from the transmitter to the receiver.

The above (influence item 5) is considered by appropriately setting the value of the constant value F.
In addition, said (Formula 1)-(Formula 7) are illustrations, and arithmetic expressions other than these can also be used.

(3) Method of making distance average L as small as possible In order to improve position estimation accuracy, it is desirable to make distance average L as small as possible among the above variables.
A method of making the distance average L the smallest is to divide the position estimation region 300 into i rectangular regions that are as close to a square as possible, and place an anchor terminal at the center of each rectangular region.
Therefore, in order to obtain an anchor terminal arrangement that satisfies the required value for position estimation accuracy with the smallest possible number of anchor terminals, the anchor terminal is arranged by dividing the position estimation region 300 into a substantially square lattice. It is possible to search repeatedly for the optimum arrangement by repeatedly executing the arrangement interval and the number of arrangements.

In the above, the premise matter when calculating | requiring the optimal arrangement position of an anchor terminal was demonstrated.
To summarize the above, it can be seen that in order to obtain an anchor terminal arrangement that satisfies the required value for position estimation accuracy, the following matters described in (Premise 1) to (Premise 3) may be followed.

(Premise 1) The process of temporarily determining the position and number of anchor terminals to temporarily calculate the position estimation accuracy is repeatedly executed to determine the optimal anchor terminal layout in a search manner.

(Premise 2) In each iteration, the position estimation accuracy R is calculated using arithmetic expressions as exemplified in the above (Expression 1) to (Expression 7).

(Assumption 3) In each iteration, it is assumed that the position estimation region 300 is divided into a substantially square lattice and an anchor terminal is arranged at the center of each divided region.
When changing the arrangement position and number of anchor terminals, the distance between the anchor terminals is kept as small as possible while maintaining the distance average L satisfying the required value (the distance average L is kept as small as possible). Make sure to keep the interval as large as possible.

  FIG. 3 is a flow showing a procedure for obtaining the arrangement of anchor terminals that satisfy the required value for position estimation accuracy. Hereinafter, each step of FIG. 3 will be described.

(S301)
The user designates the anchor terminal arrangement interval I or the arrangement number X. Instead of being specified by the user, for example, based on the size of the position estimation region 300 given in advance, the calculation unit 420 may set an appropriate initial value. The same applies to the following embodiments.
The parameter acquisition unit 410 of the arrangement determination device 400 acquires the arrangement interval I or the arrangement number X and outputs the acquired arrangement interval I or the arrangement number X to the calculation unit 420.
Note that the size of the position estimation region 300 is assumed to be given to the calculation unit 420 in advance via the parameter acquisition unit 420.

(S302)
The calculation unit 420 tentatively determines the anchor terminal arrangement in the position estimation area 300 using the arrangement interval I or the arrangement number X. At this time, the anchor terminal number i is provisionally determined.
When the position estimation area 300 is sufficiently smaller than the reach range of the radio signal (when the radio signal reaches every corner of the position estimation area 300), the arrangement number X is equal to i. When the position estimation region 300 is larger, the calculation unit 420 recalculates i using the area where the radio signal reaches and the arrangement interval I, and temporarily determines the anchor terminal arrangement again.
When this step is completed, the temporary position of the anchor terminal is determined.

(S303)
The calculation unit 420 calculates the average distance L between the target terminal and the anchor terminal for the entire position estimation region 300.
For example, when the position estimation region 300 is divided into a grid pattern, the distances from all grid points to the nearest anchor terminal are obtained and averaged, the distance average L is obtained.

(S304)
The calculation unit 420 calculates the position estimation accuracy R by applying the distance average L obtained in step S303 to the calculation formulas exemplified in the above (formula 1) to (formula 7).

(S305)
The calculation unit 420 determines whether or not the position estimation accuracy R calculated in step S304 satisfies the required value. If the request value is satisfied, this flow is terminated. If the request value is not satisfied, the process returns to step S301 and the same processing is repeated.
Alternatively, even when R satisfies the required value, the arrangement interval I is increased to return to step S301 again in order to reduce the number of anchor terminals as much as possible while maintaining the distance average L small so as to satisfy the required value. The process may be repeated.

FIG. 4 is a specific example of step S302 in FIG. FIG. 4A shows an example of the arrangement number X = 4, and FIG. 4B shows an example of the arrangement number X = 6.
4 (a) and 4 (b), in order to make the distance average L as small as possible, the position estimation area 300 is divided into a substantially square lattice (area drawn with a dotted line in each figure), and an anchor terminal is located at the center of each division. Is arranged.

As described above, according to the first embodiment, when a required value for position estimation accuracy is specified, an anchor terminal arrangement that can satisfy the required value can be determined in an exploratory manner.
Thereby, when the position estimation of the target terminal is performed under the anchor terminal arrangement determined by the arrangement determining apparatus 400, the position estimation accuracy can be within the range of the estimation accuracy calculated in advance.

  Moreover, according to this Embodiment 1, since the number of anchor terminals which can satisfy | fill a request value can be estimated before arrangement | positioning, the cost which builds a radio | wireless system can be held down.

Further, in the first embodiment, each step of FIG. 3 is performed while the input to the parameter acquisition unit 410 is varied so as to make the arrangement interval I as large as possible while keeping the distance average L small so as to satisfy the required value. It can be repeated.
Thereby, the number of anchor terminals satisfying the required value can be minimized, and the cost for constructing the wireless system can be further suppressed.

Embodiment 2. FIG.
In Embodiment 1, it is assumed that the arrangement of all anchor terminals is undecided, but depending on the environment of position estimation region 300, the arrangement of some anchor terminals may be determined.
For example, when anchor terminals are installed in a building, some anchor terminals may be connected to a power source and positioned within a range where a power cord can reach.

  Therefore, in Embodiment 2 of the present invention, a method for determining the arrangement of an anchor terminal whose position has not been determined will be described in response to such a case.

  In the second embodiment, steps S301 to S302 in FIG. 3 are changed to the following S301a to S302a.

(S301a)
The user designates the number X of anchor terminal arrangements. The parameter acquisition unit 410 of the arrangement determining apparatus 400 acquires the arrangement number X and outputs it to the calculation unit 420. The number of arrangements X designated at this time excludes the number of anchor terminals whose arrangement has been determined in advance.
Further, the user designates the number Y of anchor terminals whose positions have been determined and their positions. These are similarly output to the calculation unit 420.
The size of the position estimation area 300 is the same as that in step S301.

(S302a)
The calculation unit 420 tentatively determines the arrangement positions of the X anchor terminals so as to be as evenly spaced as possible including the anchor terminals whose arrangement has been determined in advance.
For example, the calculation unit 420 divides the entire position estimation area 300 into X + Y rectangular areas in a grid pattern, and prevents a plurality of position-fixed anchor terminals from entering each rectangular area. Next, an anchor terminal whose position has not been determined is arranged at the center of each rectangular area where no fixed anchor terminal has been installed.

  Other processes are the same as those in FIG. 3 described in the first embodiment.

  As described above, according to the second embodiment, the anchor terminal arrangement that can satisfy the required value for the position estimation accuracy is determined even in an environment in which the arrangement positions of some anchor terminals have been determined in advance. be able to.

Embodiment 3 FIG.
In the first and second embodiments, it is assumed that the required value for the position estimation accuracy is uniform over the entire area of the position estimation area 300.
However, depending on the environment of the position estimation area 300, the required value for the position estimation accuracy may not be uniform over the entire area of the position estimation area 300, and the required value may be different in some areas.
Therefore, in the third embodiment of the present invention, a method for determining the placement of anchor terminals in an environment where the requirement system for position estimation accuracy is not uniform will be described in response to such a case.

  In the third embodiment, the following step S300 is added before step S301 in FIG.

(S300)
The user designates a required value for each partial area in the position estimation area 300 that has a different required value for position estimation accuracy.
In addition, the user selects any partial area in the position estimation area 300. For example, a region having a large area or a region having a high required value for position estimation accuracy is selected.
Instead of specifying or selecting these by the user, the calculation unit 420 may specify or select an appropriate initial region.
The following steps are executed assuming that the other regions are regions in which the placement of anchor terminals has been determined, which has been described in the second embodiment.

  The subsequent processing is the same as in FIG. 3 described in the first embodiment.

  As described above, according to the third embodiment, it is possible to determine an anchor terminal arrangement that can satisfy the required value for position estimation accuracy even in an environment where the required value for position estimation accuracy is not uniform.

1 is a configuration diagram of a radio system according to Embodiment 1. FIG. 3 is a functional block diagram of an arrangement determining apparatus 400. FIG. It is a flow which shows the procedure which calculates | requires arrangement | positioning of the anchor terminal which satisfy | fills the required value with respect to position estimation precision. It is a specific example of step S302 of FIG.

Explanation of symbols

  100a to 100b Target terminal, 200a to 200f Anchor terminal, 300 position estimation region, 400 arrangement determination device, 410 parameter acquisition unit, 420 calculation unit, 500 position estimation device.

Claims (11)

A method of determining an arrangement position of an anchor terminal serving as a reference when estimating a position of a wireless terminal using a wireless signal,
A request input step for specifying a required value for the estimation accuracy of the position of the wireless terminal;
An arrangement input step for designating an arrangement interval or the number of arrangements of the anchor terminals;
An estimation accuracy calculation step of calculating the estimation accuracy using the arrangement interval or the number of arrangements;
Have
Until the estimated accuracy calculated in the estimated accuracy calculation step satisfies the required value,
Repeatedly executing the estimation accuracy calculation step while varying the arrangement interval or the number of arrangement of the anchor terminal,
The position of the anchor terminal is determined based on the result,
The estimated accuracy calculation step includes:
A first step assuming that the estimation target region is divided into a grid and the anchor terminal is arranged at the center of any grid;
A second step of calculating an average distance from the wireless terminal to the nearest anchor terminal under the assumption;
A third step of calculating the estimation accuracy using the distance average;
End end position determination how to, comprising a. A method of determining an arrangement position of an anchor terminal serving as a reference when estimating a position of a wireless terminal using a wireless signal,
A request input step for specifying a required value for the estimation accuracy of the position of the wireless terminal;
An arrangement input step for designating an arrangement interval or the number of arrangements of the anchor terminals;
An estimation accuracy calculation step of calculating the estimation accuracy using the arrangement interval or the number of arrangements;
Have
Until the estimated accuracy calculated in the estimated accuracy calculation step satisfies the required value,
Repeatedly executing the estimation accuracy calculation step while varying the arrangement interval or the number of arrangement of the anchor terminal,
The position of the anchor terminal is determined based on the result,
A second arrangement input step of designating an arrangement position of the anchor terminal whose position is fixed;
For the other anchor terminals,
The request input step, the arrangement input step, and the end-terminal position determination how to, characterized in that running estimation accuracy calculation step to determine the position of the anchor terminal. While repeatedly performing the estimated accuracy calculation step,
The terminal location determination method according to claim 1 or 2, wherein an arrangement position that maximizes an arrangement interval of the anchor terminals while satisfying the required value is searched. In the estimated accuracy calculation step,
The terminal position determination method according to any one of claims 1 to 3, wherein the estimation accuracy is calculated using a radio signal characteristic in an area where the radio terminal is arranged. In the estimated accuracy calculation step,
The terminal location determination method according to claim 4, wherein an attenuation coefficient of the radio signal is used as the radio signal characteristic. In the estimation accuracy calculation step, as the wireless signal characteristics,
The terminal position determination method according to claim 4 or 5, wherein at least one of a logarithmic value and a power value of an attenuation coefficient of the radio signal is used. In the estimated accuracy calculation step,
The terminal position determination method according to any one of claims 1 to 6, wherein the estimation accuracy is calculated using the number of the anchor terminals that can transmit and receive information. In the estimated accuracy calculation step,
The terminal location determination method according to any one of claims 1 to 7, wherein the estimation accuracy is calculated using a logarithmic value of the number of the anchor terminals that can transmit and receive information. For each partial area of the target area for estimating the position of the wireless terminal,
Performing the request input step, the arrangement input step, and the estimated accuracy calculation step;
The terminal location determination method according to any one of claims 1 to 8 , wherein, in the request input step, the request value is designated for each partial area. A terminal location determination program that causes a computer to execute the terminal location determination method according to any one of claims 1 to 9 . A terminal position determination apparatus comprising: a computer that executes the terminal position determination program according to claim 10 .

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