JP2005321231A - Method for measuring position of mobile terminal and server for implementing the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the position accuracy of a mobile terminal position measurement method using radio wave attenuation while increasing the calculation convergence time.
A method of measuring the position of a mobile terminal M using radio wave attenuation is determined monotonically with respect to a distance dj between each base station Bj and the mobile terminal M in a steepest descent method when determining the position of the mobile terminal M. The position correction vector Δ is calculated by applying a decreasing weighting coefficient αj to the position coordinate of the position of the mobile terminal M by loop calculation.
[Selection] Figure 3

Description

  The present invention relates to a position measuring method for a mobile terminal and a server for carrying out the method. More particularly, the present invention relates to a position measurement method for improving the accuracy by increasing the convergence time of computation in a position measurement method using three-point survey using radio wave attenuation, and a server for implementing the method.

  Conventionally, as a method for measuring the position of a mobile terminal by three-point survey using radio wave attenuation, the method of obtaining the position of the mobile terminal by the least square method, the method of obtaining the position of the mobile terminal by simultaneous equations, the position of the mobile terminal by the steepest descent method The method of calculating | requiring was used.

  FIG. 8 shows an algorithm for obtaining the position of the mobile terminal by the method of least squares. The radio field intensities from the three base stations Bj (j = 0, 1, 2) are accumulated for each sampling point Pi (i = 1, 2,...), And the radio field intensities measured by the mobile terminal M are stored for each. The measured distance dj (j = 0, 1, 2) between each base station Bj and the mobile terminal M obtained by measuring the radio field intensity in comparison with the radio field intensity at the sampling point Pi, and each base station at each sampling point Pi The sum of squares of the difference between the distance lj (j = 0, 1, 2) between Bj and the mobile terminal M is defined as an error amount f (Pi), and the sampling point with the minimum error amount f (Pi) is defined as the mobile terminal M. Is determined to be the location of

FIG. 9 shows an algorithm for obtaining the position of the mobile terminal using simultaneous equations. The position coordinates of the three base stations Bj (j = 0, 1, 2) are acquired, the initial position (x ₀ , y ₀ ) of the mobile terminal M is determined, and the mobile terminal M receives from the three base stations Bj After obtaining the measurement distance dj (j = 0, 1, 2) between each base station Bj and the mobile terminal M from the radio wave intensity, a loop calculation is performed to determine the position of the mobile terminal M. In the k-th loop, a simultaneous equation consisting of three equations is created, assuming that the position coordinate (x, y) of the mobile terminal M is on a circle with a radius dj centered on each base station Bj, and each equation is differentiated. By calculating, the position correction vector Δx in the x direction and the position correction vector Δy in the y direction are obtained, and the position correction vector (Δx, Δy) is added to the position coordinates (x, y) of the (k−1) -th loop. Calculate the position of the mobile terminal of the k-th loop. The result obtained by the loop calculation is determined as the location (x, y) of the mobile terminal M.

により算定する（ステップＳ１０４）。次に、第ｋ−１番目のループで算定された移動端末の算定位置Ｐ（ｋ−１）に上記位置修正ベクトルΔを加算して第ｋ番目のループでの移動端末の算定位置Ｐ（ｋ）を算定する（ステップＳ１０５）。ループ演算で得られた結果を移動端末Ｍの所在位置Ｐと決定する（ステップＳ１０６）。（例えば非特許文献１参照） FIG. 10 shows an algorithm for obtaining the position of the mobile terminal by the steepest descent method. The position coordinates of the three base stations Bj (j = 0, 1, 2) are acquired (step S101), then the initial position P (0) of the mobile terminal M is acquired (step S102), and then the movement The measurement distance dj (j = 0, 1, 2) between each base station Bj and the mobile terminal M is acquired from the radio field intensity received from the three base stations Bj at the terminal M (step S103). Next, a loop calculation is performed to determine the position of the mobile terminal M. In the k-th loop, the position correction vector Δ, the unit vector from the j-th base station Bj to the mobile terminal M as uj, the j-th base station Bj calculated in the k−1-th loop, The calculated distance between the mobile terminals M is lj, and the measured distance between the j-th base station Bj and the mobile terminal M obtained by the measurement of the radio field intensity is dj

(Step S104). Next, the position correction vector Δ is added to the calculated position P (k−1) of the mobile terminal calculated in the k−1 th loop, and the calculated position P (k of the mobile terminal in the k th loop is calculated. ) Is calculated (step S105). The result obtained by the loop calculation is determined as the location P of the mobile terminal M (step S106). (For example, see Non-Patent Document 1)

“Indoor positioning system using wireless communication network” Teruaki Kitasuka et al., Transactions of Information Processing Society of Japan: Computing System Vol. 44, no. 10, P131-140, July 2003

  However, the algorithm for determining the position of the mobile terminal by the least square method requires a large number of sampling points in order to improve the measurement accuracy, and the comparison is made at each sampling point. . In addition, the algorithm for finding the position of a mobile terminal using simultaneous equations has a problem that the calculation speed is slow and the position accuracy is poor because the calculation is complicated, and the problem that the solution cannot be obtained when the circle has no intersection. there were. In addition, the algorithm for obtaining the position of the mobile terminal by the steepest descent method is relatively simple, so the convergence time for obtaining the position is considerably shortened, but there is still a problem that the error amount is still large.

  It is an object of the present invention to improve the position accuracy of a mobile terminal position measurement method using radio wave attenuation while increasing the calculation convergence time. Moreover, it aims at providing the server which performs control for implementing this position measuring method.

  In order to solve the above problem, the mobile terminal position measurement method according to claim 1 acquires the positions of at least three base stations Bj (j = 0, 1, 2) as shown in FIG. A step (step S001), a step of obtaining the initial position P (0) of the mobile terminal M (step S002), and a step of obtaining the measurement distance dj between each base station Bj and the mobile terminal M from the measurement of received radio waves ( Step S003), a step of calculating a weighting coefficient αj that monotonously decreases with respect to the measurement distance dj (Step S004), a step of calculating the calculation position P of the mobile terminal M by a loop calculation, and a loop calculation A step of determining the calculation position P as the location of the mobile terminal M (step S007), and the step of calculating by the loop calculation includes the measurement distance dj in the k-th loop. A step of calculating the position correction vector Δ using the attaching coefficient αj (step S005), and a vector s proportional to the position correction vector Δ at the calculated position P (k−1) calculated in the k−1 th loop. A step of calculating the calculation position P (k) in the k-th loop by adding xΔ (step S006).

  Here, s is a parameter related to the speed of convergence and accuracy. The smaller s, the slower the convergence, but the higher the accuracy. If comprised in this way, about the position measuring method of the mobile terminal using electromagnetic wave attenuation, convergence of a loop calculation can be made quick, and position accuracy can be improved greatly.

を用いて算定され、位置修正ベクトルΔに比例するベクトルは、収束の早さと精度に係るパラメータｓを前記位置修正ベクトルΔに乗じて算定される。なお、本請求項における位置修正ベクトルΔは第ｋ番目のループにおける位置修正ベクトルである。このように構成すると、位置修正ベクトルΔを重み付け係数を用いて表現でき、移動端末Ｍの算定位置を所在位置に効率よく収束できる。 Further, according to a second aspect of the present invention, in the mobile terminal position measuring method according to the first aspect, for example, as shown in FIG. 2, the position correction vector Δ is transmitted from the j-th base station Bj to the mobile terminal M. Uj for the unit vector in the direction, αj for the weighting coefficient for the jth unit vector, lj for the calculated distance between the jth base station Bj and the mobile terminal M calculated in the (k−1) th loop, When the measurement distance between the j-th base station Bj and the mobile terminal M obtained from the measurement of the received radio wave is dj and the number of base stations is n,

A vector proportional to the position correction vector Δ is calculated by multiplying the position correction vector Δ by a parameter s related to the speed and accuracy of convergence. The position correction vector Δ in this claim is a position correction vector in the k-th loop. If comprised in this way, the position correction vector (DELTA) can be expressed using a weighting coefficient, and the calculation position of the mobile terminal M can be efficiently converged to a location.

  A program according to a third aspect is a server-readable program for causing a server to execute the position measuring method according to the second or second aspect.

  Further, the server according to claim 4 is a server S that can communicate with each base station Bj, for example, as shown in FIG. 1, and includes the positions of at least three base stations Bj and the initial position P ( 0) and calculating means 5 for calculating the calculated position P of the mobile terminal M by loop calculation and determining the calculated position P calculated by the loop calculation as the location of the mobile terminal M, The calculation means 5 acquires the measurement distance dj between each base station Bj and the mobile terminal M from the measurement of the received radio wave, calculates a weighting coefficient αj that monotonously decreases with respect to the measurement distance dj, and calculates the k-th loop. In the calculation, the position correction vector Δ is calculated using the measured distance dj and the weighting coefficient αj, and the calculated position Pi (k−1) calculated in the k−1 th loop is a vector proportional to the position correction vector Δ. Add s × Δ And to calculate the estimated position P (k) at the k-th loop.

  If comprised in this way, it is a server which performs the control for implementing the position measuring method of the mobile terminal using electromagnetic wave attenuation, Comprising: Loop convergence can be made quick, and position accuracy can be improved dramatically. Server that can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, about the position measuring method of the mobile terminal using radio wave attenuation, while making the convergence time of a calculation quick, a positional accuracy can be improved. Moreover, the server which performs control for implementing this position measuring method can be provided.

  A first embodiment of the present invention will be described below with reference to the drawings. The first embodiment is an example in which the mobile terminal M measures the radio wave transmitted by each base station Bj.

  FIG. 1 shows a configuration example of a mobile terminal position measurement system according to an embodiment of the present invention. In addition, the thing which shows the same function as FIGS. 8-10 uses the same code | symbol, and abbreviate | omits description. The mobile terminal position measurement system A is a control for performing mobile terminal position measurement with the mobile terminal M to be measured and three or more base stations Bj (j = 0, 1, 2,..., N−1). It is comprised from the server S which performs. As a result of communication between the mobile station M and the base station Bj, the communication unit CM that performs communication via the base station Bj, the radio wave measurement unit 1 that receives the radio wave transmitted from the base station Bj and measures the received radio wave, and the base station Bj Each base station Bj has a radio wave transmitting unit 3j (j = 0, 1, 2,..., N−1) for transmitting radio waves, and a mobile terminal. M, a server S, and a communication unit Cj that communicates with other base stations Bj. The server S communicates with the base station Bj and data about each base station Bj and the mobile terminal M (mobile Data acquisition unit 4 that acquires received radio wave data measured by terminal M from each base station Bj via communication unit CS, and each base station Bj of mobile terminal M from the received radio wave data acquired from mobile terminal M Calculate the distance from the position of the mobile terminal M from the distance data Calculation is performed by the calculation unit 5 that performs calculation such as calculation of the mark, the memory unit 6 that records the acquired data and the calculated data, and the information acquired as a result of communication with the base station Bj and the calculation unit 5 And a display unit 2S for displaying the results.

  FIG. 2 shows the positional relationship between each base station and mobile terminal according to the present embodiment. FIG. 2 shows a case where the base station Bj is three stations (j = 0, 1, 2). The mobile terminal M measures the received power Pr (j) received from each base station Bj (j = 0, 1, 2) at the location P. The received power Pr (j) data received by the mobile terminal M is distinguished from the received power data from other base stations, transmitted from the mobile terminal M to the base station Bj, and transmitted by each base station Bj. The data is transmitted from each base station Bj to the server S together with the Pt (j) data. The server S calculates the measured distance dj between each base station Bj and the mobile terminal M from the ratio of the transmission power Pt (j) transmitted by each base station Bj and the received power Pr (j) received by the mobile terminal M.

  FIG. 3 shows a processing flow example of the position measurement method according to the present embodiment. This embodiment can be said to be a position measurement method in which the weighting coefficient αj is combined with the steepest descent method.

  First, the server S acquires the position coordinates of each base station Bj by the data acquisition unit 2 through communication with each base station Bj or the like, and records it in the memory unit 6 (step S001). When these base stations Bj are fixed stations, the position coordinates are known. In the case of a mobile station, position coordinates at the time of radio wave transmission for measuring the measurement distance dj are adopted, but it is necessary to determine the position coordinates before acquisition.

  Next, the initial position P (0) of the mobile terminal is acquired and recorded in the memory unit 6 (step S002). As the initial position P (0), for example, the center of gravity of three or more base station coordinates related to mobile terminal position measurement may be used, or the convergence position of the mobile terminal M at the previous time may be used.

により算定される。なお、ａ，ｂは電波環境、送信アンテナ、受信アンテナのゲインなどによるパラメータである。パラメータａ，ｂは位置計測に先立って２地点での電波減衰を利用した計測を行い決定されるのが好ましい。 Next, the measurement distance dj between each base station Bj and the mobile terminal M is acquired from the measurement of the received radio wave (step S003). Each base station Bj transmits a radio wave from the radio wave transmission unit 3j, and the mobile terminal M receives a radio wave from each base station Bj by the radio wave measurement unit 1, and measures the received power Pr (j). The measurement data is transmitted from the mobile terminal M to the server S together with the transmission power Pt (j) data from each base station Bj via each base station Bj, and the measurement distance dj is calculated by the calculation unit 5 of the server S. The result is recorded in the memory unit 6. When each base station Bj transmits a radio wave of transmission power Pt (j), the measured distance dj between the base station Bj and the mobile terminal M is

Calculated by Here, a and b are parameters based on the radio wave environment, the gain of the transmission antenna, the reception antenna, and the like. The parameters a and b are preferably determined by measurement using radio wave attenuation at two points prior to position measurement.

Next, the weighting coefficient is calculated as αj = 1 / dj ^C (step S004). By using the weighting coefficient αj that monotonously decreases with respect to the measurement distance dj, the influence of information from the short-range base station Bj is increased, and as a result, the measurement accuracy can be improved. The calculation is performed by the calculation unit 5, and the calculation result is recorded in the memory unit 6. Increasing the parameter c increases the influence from the short-range base station Bj.

  Next, the location P of the mobile terminal M is obtained by loop calculation. The loop calculation is performed to converge the position of the mobile terminal M and improve the position accuracy.

により算定される（図２参照）。 First, the position correction vector Δ is calculated using the measured distance dj and the weighting coefficient αj (step S005). In the k-th loop, the position correction vector Δ is a weighting coefficient αj, a unit vector from the j-th base station Bj to the mobile terminal M, uj, and the j-th loop calculated in the (k−1) -th loop. If the calculated distance between the base station Bj and the mobile terminal M is lj, and the measurement distance between the jth base station Bj and the mobile terminal M obtained by measuring the received radio wave, that is, measuring the radio wave attenuation, is dj,

(See Fig. 2).

  Next, a vector s × Δ proportional to the position correction vector Δ is added to the calculated position Pi (k−1) of the mobile terminal M calculated in the k−1th loop to move in the kth loop. The calculation position P (k) of the terminal M is calculated (step S006). That is, the calculation position P (k) of the mobile terminal M is calculated as P (k) = P (k−1) + s × Δ. Here, s is a parameter relating to the speed and accuracy of convergence. The smaller s, the slower the convergence, but the higher the accuracy. The parameter s may be set to 1.

  Steps S005 to S006 are repeated to perform a loop calculation. The calculated position P calculated by the loop calculation is determined as the location of the mobile terminal M (step S007). The loop calculation is performed by the calculation unit 5 using the position coordinates of the base station Bj stored in the memory unit 6, the initial position P (0), the weighting coefficient αj, the measurement distance dj, and the calculation distance lj. The calculation result is recorded in the memory unit 6 again. The loop calculation is repeated, and the calculated position P (N−1) obtained in the final loop is set as the location position P of the mobile terminal M. The location position P is one of the base stations Bj related to the location measurement of the mobile terminal M from the server S. Is transmitted to the mobile terminal M via (for example, B0) and displayed on the display unit 2M of the mobile terminal M. Further, the location P may be displayed on the display unit 2M of the server S.

  FIG. 4 shows an arrangement example of the base station Bj and the mobile terminal M when the error simulation is performed. FIG. 4 shows a case where the number of base stations is three. The position coordinates of the base stations B0, B1, B2 are (0, 0), (10, 0), (10, 10), respectively, in m units, and the position coordinates of the mobile terminal M are (1, 1). The temporary error is set as error 1 to error 3 in FIG. In FIG. 6A, the magnitude of the error is shown in units of m from the base station Bj to the mobile terminal M. The error in FIG. 4 is indicated by βj (j = 0, 1, 2) corresponding to the base station Bj.

  FIG. 5 shows the relationship between the weighting coefficient, the loop operation repetition count N, and the position correction vector Δ when the position measurement method according to the present embodiment is used. The graph is shown when the horizontal axis indicates the number of repetitions N, the vertical axis indicates the position correction vector Δ (m), and the parameters c = 1, 2, and 3. As shown in FIG. 5, the magnitude of the position correction vector Δ depends on the weighting coefficient and the number of iterations N of the loop operation, and the loop iteration number N can vary depending on conditions, so that the number of loops is sufficient. It is preferable to make the calculated position converge by increasing it. For example, it is preferable that the position correction vector Δ is continued for a predetermined number of times until it becomes smaller than a predetermined threshold. In this example, when c = 1 to 3 and N ≧ 3000, the position correction vector Δ converges to about 5 cm or less, and when N ≧ 10000, Δ converges to about 1 cm or less.

  FIG. 6 shows an error comparison example when the position measurement method according to the present embodiment and the conventional example is used. FIG. 6A shows a table, and FIG. 6B shows a bar graph. When the least squares method (mesh pattern), simultaneous equations (downward stripe pattern), steepest descent method (upward right stripe pattern), and this embodiment (plain) are compared, the convergence time is It can be seen that the form converges much faster than others (7 ms), and the error is extremely small in this embodiment. FIG. 6A shows the set values of error 1 to error 3 and the measured distance dj between the mobile terminal M and each base station Bj.

  FIG. 7 shows a configuration example of a mobile terminal position measurement system according to the second embodiment of the present invention. In addition, the same code | symbol is used for what exhibits the same function as FIG. 1, and description is abbreviate | omitted. The second embodiment is an example in which radio waves transmitted from the mobile terminal M are measured at each base station Bj.

  In FIG. 1, instead of the mobile terminal M having the radio wave measurement unit 1 and each base station Bj having the radio wave transmission unit 3j, in FIG. 7, each base station Bj has the radio wave measurement unit 1′j and moving The terminal M has a radio wave transmission unit 3 ′. Other configurations are the same as those in FIG. The positional relationship between each base station and mobile terminal in FIG. 2 can be applied as it is if the direction of the arrow indicating the flow of radio waves is reversed, but the content of the description changes as follows. The mobile terminal M transmits radio waves at the location P, and each base station Bj (j = 0, 1, 2) measures the received power Pr (j) received from the mobile terminal M. The received power Pr (j) data received by each base station Bj is transmitted from the base station Bj to the mobile terminal M, and passes through, for example, one base station B0 together with the transmission power Pt (j) data transmitted by the mobile terminal M. Are collectively transmitted to the server S. The server S calculates the measured distance dj between each base station Bj and the mobile terminal M from the ratio between the transmission power Pt (j) transmitted by the mobile terminal M and the received power Pr (j) received by each base station Bj.

  The processing flow example of the position measurement method of FIG. 3 can also be applied as it is. Only step S003 in which the content of the processing flow is changed will be described. In step S003, the mobile terminal M transmits a radio wave from the radio wave transmission unit 3 ′, and each base station Bj receives the radio wave from the mobile terminal M by the radio wave measurement unit 1′j and measures the received power Pr (j). . The measurement data is transmitted from each base station Bj to the mobile terminal M, and transmitted from the mobile terminal M together with the transmission power Pt (j) data to the server S via, for example, one base station B0. The calculation distance 5 is calculated by the calculation unit 5 and the calculation result is recorded in the memory unit 6. Other steps are the same as those in the first embodiment. The explanation about the errors and the like in FIGS. 4 to 6 is the same as that in the first embodiment.

  The present invention can also be realized as a server-readable program for causing the server S to execute the position measurement method described above. The program may be recorded and used in the program unit built in the server S, recorded in an external recording device or CDROM, read out and used by the program unit, or downloaded from the Internet to the program unit. May be used.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it is obvious that various modifications can be made to the embodiments.

  For example, the example of measuring the power of the received radio wave in the step of acquiring the measurement distance between each base station and the mobile terminal from the measurement of the received radio wave has been shown, but the electric field of the received radio wave may be measured. In this embodiment, an example in which a measurement distance or loop calculation is performed by a server has been described. However, these calculations may be performed by a mobile terminal, and these calculations may be performed by a computer installed in any base station. You can do it.

  In the first embodiment, the received power Pr data received by the mobile terminal M is transmitted from the mobile terminal M to each base station Bj, and transmitted from each base station Bj together with the transmission power Pt data transmitted by each base station Bj. Although the example transmitted to the server S has been described, the received power Pr data received by the mobile terminal M is transmitted from the mobile terminal M to a predetermined base station B0, for example, and transmitted to the server S together by the base station B0. May be. Further, in the second embodiment, the received power Pr data received by each base station Bj is transmitted from each base station Bj to the mobile terminal M, and one base station B0 together with the transmission power Pt data transmitted by the mobile terminal M. In the above description, the base station Bj acquires the transmission power Pt data when measuring the reception power Pr, and moves the reception power Pr data and the transmission power Pt data. It may be transmitted directly to the server S without going through the terminal M, or may be transmitted to the server S collectively via one base station B0.

  Moreover, although the server and the mobile terminal showed the example which communicates via a base station in the said embodiment, the server may serve as a base station and may communicate directly with a mobile terminal. Further, the base station is not limited to a fixed station, and may be a mobile station. The number of base stations involved in the measurement may be three or more, and the measurement accuracy improves as the number of base stations increases. The parameter c and the number of repetitions N are not fixed and can be changed according to the situation. When the data attenuation is extremely low, such as when the propagation attenuation is higher than a predetermined threshold value or when the propagation attenuation is suddenly changed, the weighting coefficient αj is set to 0, the calculated value based on the measurement data is set to 0, and the position measurement is performed. You may make it not reflect.

  The present invention is used for position measurement of a mobile terminal.

It is a figure which shows the structural example of the mobile terminal position measurement system by the 1st Embodiment of this invention. It is a figure which shows the positional relationship of the base station and mobile terminal by 1st Embodiment. It is a figure which shows the example of a processing flow of the position measuring method by 1st Embodiment. It is a figure which shows the example of arrangement | positioning of base station Bj and the mobile terminal M in the case of performing error simulation. It is a figure which shows the relationship between the weighting coefficient, the repetition frequency N of loop calculation, and the position correction vector (DELTA). It is a figure which shows the comparative example of the error at the time of using the position measuring method by 1st Embodiment and a prior art example. It is a figure which shows the structural example of the mobile terminal position measurement system by the 2nd Embodiment of this invention. It is a figure which shows the algorithm which calculates | requires the position of a mobile terminal by the least squares method. It is a figure which shows the algorithm which calculates | requires the position of a mobile terminal by simultaneous equations. It is a figure which shows the algorithm which calculates | requires the position of a mobile terminal by the steepest descent method.

Explanation of symbols

1, 1′j radio wave measuring unit 2M, 2S display unit 3j, 3 ′ radio wave transmission unit 4 data acquisition unit 5 calculation unit 6 memory unit 7 display unit A mobile terminal position measurement system a, b, c Parameter Bj Base station Cj, CM, CS communication unit dj Measured distance lj between base station Bj and mobile terminal M measured from radio wave attenuation Mj Calculated distance between base station Bj and mobile terminal M Mobile terminal N Number of repetitions n Number of base stations P of mobile terminal M Location position P (0) Initial position P (k) of mobile terminal M Calculated position Pi of mobile terminal M in the k-th loop Sampling position Pr (j) Received power Pt () received from base station Bj by mobile terminal M j) Transmission power S server s transmitted from base station Bj Parameter uj Unit vector αj from base station Bj to mobile terminal M direction Weighting coefficient βj Error Δ for base station Bj Δ Position correction vector

Claims (4)

Obtaining the positions of at least three base stations;
Obtaining an initial position of the mobile terminal;
Obtaining a measurement distance between each base station and the mobile terminal from measurement of received radio waves;
Calculating a weighting factor that decreases monotonously with respect to the measured distance;
Calculating a calculation position of the mobile terminal by a loop calculation;
Determining a calculated position calculated by the loop calculation as a location of the mobile terminal;
The step of calculating by the loop calculation is performed in the k-th loop,
Calculating a position correction vector using the measured distance and the weighting factor;
Calculating a calculated position in the k-th loop by adding a vector proportional to the position correction vector to the calculated position calculated in the k-th loop;
A method for measuring the position of a mobile terminal. The position correction vector Δ is represented by uj as a unit vector from the jth base station toward the mobile terminal, αj as a weighting coefficient related to the jth unit vector, and jth calculated in the (k−1) th loop. If the calculated distance between the th-th base station and the mobile terminal is lj, the measured distance between the j-th base station and the mobile terminal obtained from the measurement of the received radio wave is dj, and the number of base stations is n,

Is calculated using
A vector proportional to the position correction vector is calculated by multiplying the position correction vector by a parameter relating to the speed and accuracy of convergence;
The position measuring method of the mobile terminal according to claim 1.   A server-readable program for causing a server to execute the position measurement method according to claim 1. A server capable of communicating with each base station;
Obtaining means for obtaining the position of at least three base stations and the initial position of the mobile terminal;
Calculating means for calculating a moving position of the mobile terminal by a loop calculation and determining a calculated position calculated by the loop calculation as a location of the mobile terminal;
The calculation means obtains a measurement distance between each base station and the mobile terminal from measurement of received radio waves, calculates a weighting factor that monotonously decreases with respect to the measurement distance, and calculates the k-th loop. Then, a position correction vector is calculated using the measured distance and the weighting coefficient, and a vector proportional to the position correction vector is added to the calculated position calculated in the (k−1) th loop, to obtain a kth loop. To calculate the position at
server.

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