JP2009085780A - Mobile station positioning system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile station positioning system capable of satisfying both of keeping positioning accuracy and making a base station power-saving. <P>SOLUTION: The base station 12 which receives an electric wave transmitted by a mobile station 10, is equipped with: a first distance measuring means (RSSI acquiring section 46) for computing a distance-related value (RSSI value) which is related to a distance between a plurality of base stations 12 and respective mobile stations 10; a second distance measuring means (reception clock time measuring section 42) for computing a distance-related value (reception clock time of the electric wave) which is related to a distance between the plurality of base stations 12 and the respective mobile stations 10, by using a method different from that of the first distance measuring means; and a means (determining section 50) for switching the distance measuring means, which switches the first distance measuring means and the second distance measuring means for each of the plurality of base stations 12, based on information (switching determination value of the RSSI value) related to the distance between the base stations 12 and the mobile stations 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a mobile station positioning system in which a plurality of base stations receive radio waves transmitted from a mobile station and estimate the position of the mobile station based on the reception result, and in particular, a plurality of ranging means or The present invention relates to a technique that includes a plurality of positioning means and performs positioning by switching the plurality of distance measuring means or the plurality of positioning means.

  A mobile station positioning system has been proposed in which radio waves transmitted by a mobile station are received by a plurality of base stations, and the position of the mobile station is detected based on the reception results of the radio waves received by each of the plurality of base stations. Yes. For example, this is the technique described in Patent Document 1.

  In such a mobile station positioning system, in order to calculate the position of the mobile station, it is necessary to calculate the distances between the mobile station and a plurality of base stations, respectively. A TOA (Time of Arrival) method that is calculated based on the propagation time of a radio wave that is calculated based on the reception time of the radio wave at the base station, or when each of the plurality of base stations receives a radio wave transmitted by the mobile station. There are a TDOA (Time Difference of Arrival) method that is calculated based on a reception time difference, or an RSSI (Received Signal Strength Indicator) method that is calculated based on the strength of radio waves received at each of the plurality of base stations.

  Among these, according to the TOA method and the TDOA method, if the number of base stations required for positioning can receive radio waves transmitted from a mobile station, positioning can be performed. In the system, since it is necessary to obtain an accurate propagation time of radio waves, it is necessary for all of the mobile station and the plurality of base stations to have a clock having a common time. In the TDOA system, the plurality of base stations All of the plurality of base stations need to have a clock having a common time because it is necessary to obtain an accurate difference in radio wave reception time between the base stations. Further, in the TOA method and the TDOA method, there is a problem that, for example, the reception time of the radio wave is detected by performing synchronization detection by a correlation calculation process, so that power consumption increases due to the calculation process.

  On the other hand, according to the RSSI system, the above-mentioned clock and power consumption problems do not occur, but the accuracy of the distance measurement is increased as the radio wave reception intensity decreases, that is, the distance between the mobile station and the base station increases. There is a problem that becomes difficult.

Japanese Patent Laid-Open No. 2004-260689

  Thus, no matter which of the TOA method, the TDOA method, and the RSSI method is adopted, there is no method that dominates in all conditions. For example, firstly considering reducing power consumption, the RSSI method is considered. When using the method, as described above, the accuracy of ranging deteriorates when the distance between the mobile station and the base station increases. Therefore, accurate positioning can be performed because the mobile station performs positioning. It is limited to the case where it exists in the vicinity of the necessary number of base stations.

  The present invention has been made against the background of the above circumstances, and the object of the present invention is a mobile station positioning system having a plurality of ranging methods or a plurality of positioning methods. It is an object of the present invention to provide a mobile station positioning system that consumes less power and can widen a mobile station positioning area.

  In Patent Document 1, the difference in signal propagation distance between the mobile station and each base station is measured using the received power of the signal from the mobile station in each base station, and the mobile station is located near the base station. A technique for calculating the position of a mobile station using the propagation distance difference when it is determined that it does not exist is disclosed. However, in the technique of Patent Document 1, when the mobile station exists in the vicinity of the base station, there is no solution in the calculation of the position of the mobile station using the propagation distance difference due to a slight measurement error, and positioning can be performed. It is intended to avoid the situation of disappearance, and is not related to the object of the present invention described above.

  The gist of the invention according to claim 1 for solving this problem is that (a) a plurality of base stations receive radio waves transmitted from a mobile station, and each of the plurality of base stations receives radio waves A mobile station positioning system that estimates a position of a mobile station based on a distance between each of the plurality of base stations calculated based on a reception result and the position of the mobile station and a position of each of the plurality of base stations. (B) first distance measuring means for calculating a distance-related value related to the distance between each of the plurality of base stations and the mobile station; and (c) a method different from the first distance measuring means. A second distance measuring means for calculating a distance-related value related to the distance between each of the plurality of base stations and the mobile station, and (d) for each of the plurality of base stations, Based on information about the distance between the mobile station and the mobile station And having a distance measuring device switching means for switching between said first distance measurement means and the second distance measuring means.

  Also preferably, in the invention according to claim 2, the first distance measuring means may determine whether the base station and the mobile station are based on the radio wave intensity from the mobile station received at each of the plurality of base stations. The distance is calculated, and the second distance measuring means calculates a distance between the mobile station and the base station based on a radio wave propagation time from the mobile station to each of the plurality of base stations. It is characterized by being.

  Further preferably, in the invention according to claim 3, the distance measuring means switching means is configured such that the intensity of the received radio wave obtained by executing the first distance measuring means falls below a predetermined switching determination value. When the distance between the mobile station and the base station calculated based on the intensity of the received radio wave exceeds a predetermined value, the first distance measuring means is switched to the second distance measuring means. To do.

  Further preferably, in the invention according to claim 4, the distance measuring means switching means is a distance calculated based on the movement history information of the mobile station, the distance between each of the plurality of base stations and the mobile station. When the value exceeds a predetermined value, the first distance measuring means is switched to the second distance measuring means.

  More preferably, the invention according to claim 5 is characterized in that the first ranging means generates a ranging error according to the distance between the mobile station and the base station, and the ranging means switching means. Calculates a ranging error in the first ranging means based on information on the distance between each of the base stations and the mobile station, and if the ranging error exceeds a predetermined value, the first The distance measuring means is switched to the second distance measuring means.

  Further, the gist of the invention according to claim 6 is that: (a) a plurality of base stations receive radio waves transmitted from a mobile station, and the reception results of radio waves respectively received by the plurality of base stations; A mobile station positioning system that estimates the position of the mobile station based on the position of each of the plurality of base stations, (b) the plurality of base stations based on the strength of radio waves received by each of the plurality of base stations First positioning means for calculating a distance between each of the base stations and the mobile station, and estimating the position of the mobile station based on the calculated distance; and (c) each of the plurality of base stations receiving radio waves. Second positioning means for estimating the position of the mobile station based on either the distance calculated from the reception time of the radio wave when the radio wave is received or the time difference of the reception time of the radio wave for each base station, (d ) Of the plurality of base stations, When the number of base stations necessary for positioning the mobile station by the first positioning means exists within a predetermined distance from the mobile station, the positioning is performed by the first positioning means, and the base station does not exist Comprises positioning means switching means for performing positioning by the second positioning means.

  Preferably, in the invention according to claim 7, the positioning means switching means has predetermined strengths of radio waves received by each of the plurality of base stations obtained by executing the first positioning means. A base station that exceeds a switching determination value, or a distance between each of the plurality of base stations calculated based on the received radio wave intensity and the mobile station is lower than a predetermined switching determination value. When the number of base stations necessary for positioning the mobile station by the positioning means does not exist, the first positioning means is switched to the second positioning means.

  Preferably, the invention according to claim 8 is characterized in that the positioning means switching means is provided between the current mobile station whose position is predicted based on movement history information of the mobile station and each of the plurality of base stations. When the base station whose distance is less than the predetermined value does not exist in the number of base stations necessary for positioning the mobile station by the first positioning unit, the first positioning unit to the second positioning unit. It is characterized by switching to.

  More preferably, in the invention according to claim 9, the distance between each of the plurality of base stations calculated by the first positioning means and the mobile station is the distance between each of the plurality of base stations and the mobile station. The positioning means switching means generates the ranging error in the first positioning means based on the information about the distance between each of the base stations and the mobile station. In addition, when the distance measurement error exceeds a predetermined value, the first positioning unit is switched to the second positioning unit.

  According to the mobile station positioning system according to claim 1, the distance measurement means switching means performs the second distance measurement from the first distance measurement means to the second distance based on the information on the distance between each of the base stations and the mobile station. Therefore, the distance measuring means adapted to the information about the distance between each of the base stations and the mobile station is selected for each of the plurality of base stations.

  Further, according to the mobile station positioning system according to claim 2, the first distance measuring means is configured so that the base station and the mobile station are based on the intensity of the radio wave from the mobile station received at each of the plurality of base stations. The second distance measuring means calculates the distance between the mobile station and the base station based on the propagation time of radio waves from the mobile station to each of the plurality of base stations. Therefore, the first distance measuring means and the second distance measuring means can be switched based on the information related to the distance between the base station and the mobile station, and the same effects as those described above can be obtained.

  According to the mobile station positioning system of claim 3, the ranging means switching means uses the switching determination value in which the intensity of the received radio wave obtained by executing the first ranging means is predetermined. If the distance between the mobile station and the base station calculated below based on the received radio wave intensity exceeds a predetermined switching determination value, the first distance measuring means to the second distance measuring means. Therefore, the distance measuring means can be switched using the execution result of the first distance measuring means.

  According to the mobile station positioning system of claim 4, the ranging means switching means calculates the distance between each of the plurality of base stations and the mobile station based on the movement history information of the mobile station. When the measured distance exceeds a predetermined value, the first distance measuring means is switched to the second distance measuring means, so that the second distance measuring means performs distance measurement based on the movement history of the mobile station. When the determination is made, it is not necessary to execute the first distance measuring means.

  Further, according to the mobile station positioning system of claim 5, the distance measuring means switching means performs the distance measurement in the first distance measuring means based on the information about the distance between each of the base stations and the mobile station. When the error is calculated and the distance measurement error exceeds a predetermined value, the first distance measuring means is switched to the second distance measuring means, and therefore the distance between the base station and the mobile station increases. A first ranging means for which the accuracy of distance deteriorates, and a second ranging means for which the distance between the base station and the mobile station does not directly affect the accuracy of the ranging; The first distance measuring means can be used only when the distance measurement accuracy is within a desired range.

  According to the mobile station positioning system of claim 6, the number of base stations required for positioning at least the mobile station among the plurality of base stations is determined from the mobile station by the positioning means switching means. If the distance between the plurality of base stations is within the distance, the distance between each of the plurality of base stations and the mobile station is calculated based on the strength of radio waves received by each of the plurality of base stations. When the positioning is performed by the first positioning unit that estimates the position of the mobile station based on the number of base stations necessary for positioning the mobile station does not exist within a predetermined distance from the mobile station The position of the mobile station is determined based on either the distance calculated from the reception time of the radio wave when each of the plurality of base stations receives the radio wave, or the time difference for each base station of the reception time of the radio wave. Estimate Since positioning is performed by the second positioning means, whether or not the number of base stations necessary for positioning the mobile station by the first positioning means exists within a predetermined distance from the mobile station. The positioning means is selected accordingly.

  In the mobile station positioning system according to claim 7, the positioning means switching means determines in advance the strength of radio waves received by each of the plurality of base stations obtained by executing the first positioning means. A base station in which the distance between each of the plurality of base stations calculated based on the received radio wave intensity or the mobile station is lower than a predetermined switching determination value, When only the number of base stations necessary for positioning the mobile station by the first positioning means does not exist, the first positioning means is switched to the second positioning means, so that the first positioning means is executed. The positioning means can be switched using the value obtained by the above.

  Further, according to the mobile station positioning system according to claim 8, the positioning means switching means includes each of the current mobile station whose position is predicted based on the movement history information of the mobile station and the plurality of base stations. If there are not as many base stations as necessary for positioning the mobile station by the first positioning means, the distance from the first positioning means to the second positioning station Since switching to the positioning means is performed, it is not necessary to execute the first positioning means when the second positioning means determines to perform positioning based on the movement history of the mobile station.

  Further, according to the mobile station positioning system according to claim 9, the positioning means switching means calculates the ranging error in the first positioning means based on information on the distance between each of the base stations and the mobile station. In addition, when the distance measurement error exceeds a predetermined value, the first positioning means is switched to the second positioning means, so that the distance between the base station and the mobile station is increased, thereby improving the positioning accuracy. Switching between the first positioning means that deteriorates and the second positioning means in which the distance between the base station and the mobile station does not directly affect the positioning accuracy is based on information about the distance between the base station and the mobile station. The first positioning means can be used only when the positioning accuracy is within a desired range.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing an example of the configuration of the mobile station position estimation system of the present invention. In FIG. 1, a movable area 5 formed of a square having a side 5 (m) is provided as an area where a mobile station 10 provided in an arbitrary shape on a plane can move. Further, the movable area 5 includes, as four base stations, a first base station 12A, a second base station 12B, and a third base station as base stations 12 having a function of performing wireless communication with a mobile station 10 described later. 12C and a fourth base station 12D are provided. As will be described later, the number of base stations 12 requires at least three base stations in order to calculate the position of the mobile station 10 moving on the plane using the radio wave propagation time. Accordingly, at any point in the movable area, the base station is arranged so that at least the mobile station can communicate with the three base stations. Note that the position of the mobile station can be calculated more accurately as the number of base stations increases. In FIG. 1, one base station 12A to 12D is arranged at each of the four corners of a square movable area 5, which satisfies this requirement. A mobile station 10 is arranged in the movable area 5 and can move in the movable area 5. In the present embodiment, the number of mobile stations 10 is one, but the number of mobile stations is not particularly limited. In addition, a positioning server 14 is provided that is communicable with the base station 12 by, for example, a wired cable 52, and the mobile station 10 transmits the mobile station 10 based on radio waves transmitted by the mobile station 10 and received by the base station 12. The position of the base station 10 in the possible area is calculated. In the present specification, the individual base stations 12A to 12D are referred to as base stations 12 unless otherwise distinguished.

  At this time, the x-axis and y-axis are defined for the movable area 5 as shown in FIG. 2 for convenience, and the coordinates of the points on the movable area 5 are defined based on these axes. That is, the first base station 12A is on the coordinates (0, 0), the second base station 12B is on the coordinates (0, 5), the third base station 12C is on the coordinates (5, 5), the fourth base The stations 12D are respectively arranged on the coordinates (5, 0).

  FIG. 3 is a functional block diagram showing an outline of the functions of the mobile station 10. The mobile station 10 includes an antenna 20, a radio communication unit 26, a signal processing unit 28, a control unit 30, a clock 31, and the like through which the mobile station transmits and receives radio waves. The mobile station 10 includes, for example, a so-called microcomputer having a CPU, a RAM, a ROM, an input / output interface, and the like, and the CPU uses a temporary storage function of the RAM to perform a signal according to a program stored in advance in the ROM. By performing the processing, processing in a signal processing unit 28, a control unit 30, and the like, which will be described later, is executed.

  The wireless communication unit 26 is mounted by, for example, an IC chip and performs wireless communication with the mobile station 10 and is a transmission unit that transmits radio waves when the mobile station 10 transmits radio waves. Specifically, the signal generated by the signal processing unit 28, which will be described later, is modulated into a format suitable for communication, and a synthesized wave synthesized with a carrier wave of a predetermined frequency is amplified by an amplifier, and is not corrected by a balun or the like. Convert a balanced line to a balanced line. The radio wave generated in this way is transmitted by the antenna 20.

  When the mobile station 10 transmits a radio wave, the signal processing unit 28 transmits information to be transmitted such as a radio wave transmission time, for example, an M-sequence code or a Gold sequence code (pseudo noise code (pseudo noise code) used also in GPS. -Noise code (PN signal))) is used to perform spread processing such as spread spectrum to generate a signal to be transmitted. Using such spread spectrum, when communication between a specific mobile station and a base station is performed using a specific spread code, other mobile stations and base stations at the same time and at the same frequency Even when the communication with is performed using another spreading code, the mutual communication is not affected.

  The clock 31 is used when the mobile station 10 determines the time of transmission of radio waves, and is used when the mobile station 10 operates at predetermined intervals, for example. In addition, the clock 31 of the mobile station 10 is clocked as necessary so that the time coincides with the time of the clock 44 of each of the base stations 12.

  The control unit 30 controls operations of the wireless communication unit 26, the signal processing unit 28, and the like. For example, when receiving a command for transmitting a radio wave to the base station 12 in order to measure the position of the mobile station 10, the radio wave is transmitted with a predetermined output. Alternatively, when a command to synchronize the time of the clock 44 of the base station 12 and the time of the clock 31 of the mobile station 10 is received from the base station 12 described later, the time of the clock 31 is set to be the designated time. To change.

  In addition, the control unit 30 switches and controls the operations of the wireless communication unit 26, the signal processing unit 28, and the like depending on whether the mobile station 10 transmits radio waves or receives radio waves. That is, when the mobile station 10 receives radio waves, the radio communication unit 26 and the signal processing unit 28 perform the following operation instead of the above-described operation. For example, the radio communication unit 26 performs demodulation processing such as digital demodulation corresponding to the communication method on the radio wave received by the antenna 20. Then, the signal processing unit 28 performs despreading processing corresponding to the diffusion processing performed at the time of transmission on the signal demodulated by the wireless communication unit 26, and extracts information contained in the received radio wave. In this way, the operation of the mobile station 10 can be controlled wirelessly.

  FIG. 4 is a functional block diagram showing an outline of the functions of the base station 12. The base station 12 includes a radio communication unit 34, a signal processing unit 36, and a control unit 38, which have the same functions as the radio communication unit 26, the signal processing unit 28, and the control unit 30 included in the mobile station 10, respectively. The base station 12 includes an RSSI acquisition unit 46, an A / D conversion unit 48, a reception time measurement unit 42, and the like in addition to the wireless communication unit 34, the signal processing unit 36, and the control unit 38. The base station 12 includes, for example, a so-called microcomputer having a CPU, a RAM, a ROM, an input / output interface, and the like. The CPU uses a temporary storage function of the RAM, and performs a signal according to a program stored in the ROM in advance. By performing processing, processing in the signal processing unit 36, the control unit 38, the RSSI acquisition unit 46, the A / D conversion unit 48, the reception time measurement unit 42, and the like of the base station 12 is executed.

  That is, the wireless communication unit 34 performs wireless communication with the base station 12 and is a receiving unit that receives radio waves when the base station 12 receives radio waves. Specifically, the radio communication unit 34 performs demodulation processing such as digital demodulation corresponding to the communication method on the radio wave received by the antenna 32.

  Further, the signal processing unit 36 performs despreading processing corresponding to the diffusion processing performed at the time of transmission on the signal demodulated by the wireless communication unit 34, and extracts information contained in the received radio wave. At this time, in the despreading process, a replica code that is the same spreading code as the spreading code used by the mobile station 10 when the received wave is generated is used.

  The RSSI acquisition unit 46 acquires a voltage value (V) corresponding to RSSI that is the intensity of the radio wave received by the antenna 32. The A / D conversion unit 48 A / D converts the RSSI acquired as analog data in the RSSI acquisition unit 46, and sets the value to a format usable in the control unit 38 or the like. The RSSI thus converted into digital data is converted into received power (dBm) expressed as a decibel value based on a relational expression or a table calculated in advance by the control unit 38 described later.

Here, the definition of the received power is expressed by the following equation (1).
P _R = −20 log (4πDf / c) + G _TA + G _RA + P _T (1)
P _R (dBm) is the received power, D (m) is the distance between the antenna that transmitted and received the radio wave, f (Hz) is the frequency of the radio wave, G _TA (dBi) is the gain of the transmitting antenna, and G _RA (dBi) represents the gain of the receiving antenna, and P _T (dBm) represents transmission power in decibels. In the present specification, the RSSI value is also referred to as an RSSI value.

That is, these values are measured in advance for the gain G _{TA of the} transmitting antenna and the gain G _RA of the receiving antenna, and the transmission power _PT is set to a predetermined transmission power when the mobile station 10 transmits radio waves. If the RSSI value can be measured at the base station 12 by controlling the value, the distance between the mobile station 10 and each base station 12 that has received the radio wave from the mobile station 10 can be calculated by the above equation (1). . Note that the distance calculated between the equation (1) and the antenna 20 of the mobile station 10 and the antenna 32 of each base station 12 that has received radio waves from the mobile station 10 are accurate. In the embodiment, this is the distance between the mobile station 10 and each base station 12 that has received radio waves from the mobile station 10.

The thus obtained, the distance D between mobile station 10 and the base station 12, those illustrated the relationship between the value of the received power P _R is FIG. Thus, the distance between the reception power P _R and the mobile station 10 and the base station 12, since the relationship of one-to-one correspondence, distance-related RSSI value related to the distance between the mobile station 10 and the base station 12 Value. Therefore, the RSSI acquisition unit 46 that measures the RSSI value corresponds to the first distance measuring means.

  The reception time measuring unit 42 measures the reception time of the radio wave received by the base station 12. Specifically, for example, the correlation value between the received wave demodulated by the wireless communication unit 34 and the replica code that is the same code as the spreading code used in the spreading process performed when transmitting the received wave Is calculated by shifting the received wave every minute time, and the time when the calculated autocorrelation value reaches its peak is defined as the time when the base station 12 receives the radio wave. Such processing is called synchronization detection. Further, the reception time measuring unit 42 is based on the information about the transmission time of the radio wave by the mobile station 10 obtained by despreading the received wave by the signal processing unit 36 and the measured reception time, for example. Is calculated. The propagation time of the radio wave and the distance between the mobile station 10 and the base station 12 have a one-to-one correspondence relationship that can be converted by multiplying the speed of the radio wave. Is a distance-related value related to the distance between the base station 12 and the base station 12. Therefore, the reception time measuring unit 42 corresponds to the second positioning means.

  The control unit 38 controls operations of the wireless communication unit 34, the signal processing unit 36, the server communication unit 40, and the like. In addition, the control unit 38 performs operations such as correcting the time so that the time of the clock 44 included in each of the plurality of base stations 12 is synchronized.

  In addition, the control unit 38 determines to switch execution of RSSI value acquisition by the RSSI acquisition unit 46 to execution of reception time measurement by the reception time measurement unit 42 according to the RSSI value obtained by the RSSI acquisition unit 46. Part 50. The determination unit 50 corresponds to a distance measuring unit switching unit.

As described above, the distance D between mobile station 10 and the base station 12, which is calculated by the equation (1), the relationship between the value of the received power P _R is expressed as in FIG. On the other hand, the RSSI value actually measured at the base station 12 is affected by fluctuations in radio waves, noise, and the like. Further, the RSSI acquired by the RSSI acquisition unit 46 needs to be A / D converted by the A / D conversion unit 48 in order to be handled by a computer, but is also affected by the resolution at the time of this A / D conversion. . Considering these effects, for example, in the case where the value of the received power P _R obtained by converting the acquired RSSI value is measured as R, it is necessary to consider the error of only the upper and lower [Delta] R. That is, when the value of the received power _{P R} was measured and R is the actual value of the received power _{P R is, R 1 (= R + ΔR} ) ≧ P R ≧ R 2 in the range of (= R-ΔR) Value. Therefore, the distance D at this time the base station 12 and the mobile station 10, the range determined by the distance _{L 2} corresponding to the distance _{L 1} corresponding to the value _{R 1} of the reception power _{P R} on the received power _P value of _{R R 2} L It becomes a value in ₂ ≧ D ≧ L ₁ . In other words, the distance measurement error when the reception power _{P R} is R, the received power _P against the distance L corresponding to the value R of _R, in a positive direction _(L 2 -L), in the negative direction (L-L ₁ ).

Incidentally, the relationship between the distance D between mobile station 10 and the base station 12 and received power P _R, as is represented by the curve of FIG. 6, as the reception power P _R is reduced, the change in the value of the received power P _R The corresponding change in the distance D increases. That is, when the value of the received power P _R obtained by converting the value of the acquired RSSI is R '(<R), the error of the received power P _R is also the same [Delta] R, the received power P _The distance measurement error corresponding to the error R ₁ ′ (= R ′ + ΔR) ≧ P _R ≧ R ₂ ′ (= R′−ΔR) of _R is the distance L ₁ ′ corresponding to the value R ₁ ′ of the received power PR. is the value of the received power P range L _{2 '≧} D ≧ L _1' determined by _'the distance L ₂ corresponding _to' the value R ₂ of the _R and, as shown in FIG. 6, the value R of the reception power P _R 'ranging error corresponding to the value R of the received power P _R' 'with respect to the positive direction (L _2' distance L corresponding to at -L '), in the negative direction (L'-L _1') There, this is the positive direction of the positioning error corresponding to the value R of the received power _{P R (L} 2 -L), as compared to the negative direction of the distance measuring error _{(L-L 1),} is larger, respectively.

Since this ranging error directly affects the positioning result of the mobile station 10 by the positioning system 8, the positioning accuracy becomes worse as the ranging error becomes larger. That is, if the ranging accuracy is further reduced, positioning with higher accuracy is possible. Conversely, when the positioning accuracy required in the positioning system 8 is determined, the maximum value that can be accepted as the ranging error is determined. Calculated. For example, as described above, when the maximum allowable value of the distance measurement error is calculated as α (m) based on the position error required for the position measurement system 8, the mobile station satisfying the maximum value of the distance measurement error. R _TH is determined as a value of the received power P _R at which the ranging error of the distance D between the 10 and the base station 12. Specifically, referring to FIG. 6, both ends of the range of values of the received power P _R when considering measurement error ± [Delta] R caused in measuring the value R _TH, R _TH of the received power P _R The values of the distance D between the mobile station 10 and the base station 12 corresponding to R _TH2 (= R _TH −ΔR) and R _TH1 (= R _TH + ΔR), respectively, are L _TH , L _TH2 , L _TH1. Then,
L _TH2 −L _TH <α
L _TH -L _TH1 <α
The value of the minimum received power P _R that satisfies any of is R _TH.

Thus, the maximum value α is set to be acceptable as the distance measurement error, R _TH, or which is the value of the minimum received power P _R capable of measuring a distance within the range of the distance measurement error The maximum L _TH value of the distance D between the mobile station 10 and the base station 12 corresponding to is calculated. Therefore, the determination unit 50, based on the distance D between the received power P value of _R or the mobile station 10 and the base station 12 corresponding thereto, obtained by converting the RSSI value acquired by the RSSI obtaining unit 46 Then, the execution of the RSSI acquisition unit 46 is switched to the execution of the reception time measurement unit 42. Receiving this, the distance-related values used by the positioning unit 56 to be described later, from the value of the received power P _R obtained by converting the RSSI value obtained by the RSSI acquisition unit 46, which is measured by the reception time measuring section 42 Corresponds to switching to time. Specifically, the determination unit 50 is determined by the maximum value α allowed as a distance measurement error value of the received power P _R obtained by converting the value of the RSSI calculated by RSSI acquisition unit 46 is set that if the received power P or below the value R _TH of _R, or the distance D between mobile station 10 and the base station 12 corresponding thereto is higher than the L _TH, the reception time from the execution of the RSSI acquisition unit 46 Switch to execution of the measurement unit 42. That is, the value R _{TH of the} received power or the maximum value L _TH of the distance D between the mobile station 10 and the base station 12 corresponding to the value R _TH corresponds to the switching determination value in the determination unit 50.

Control unit 38, the value or the mobile station 10 of the reception power P _R obtained by converting the RSSI values are calculated in the RSSI acquisition unit 46 and the reception time measuring unit 42 is performed by switching this way judging section 50 the value of the distance between the base station 12, with its value is either the value a is or distance reception power P _R obtained by converting the RSSI value information, the server communication unit 40, via the cable 52 Transmit to the positioning server 14.

In this case, the mobile station positioning system 8 having a plurality of base stations 12, in each of the plurality of base stations 12, the value of the received power P _R obtained by converting the RSSI values that are calculated by the RSSI obtaining unit 46 Alternatively, since the determination of the determination unit 50 differs depending on the distance between the mobile station 10 and the base station 12 corresponding thereto, information transmitted as a distance related value from the base station 12 to the positioning server 14 is converted from the RSSI value. may differ for each base station 12 in any of the value of the propagation time of a radio wave received power P _R value or the mobile station 10 and the base station 12 of the resulting Te.

FIG. 7 is a diagram illustrating the position of the mobile station 10 in the movable area 5 and the determination of the determination unit 50 for each base station 12. In FIG. 7, curves 6A to 6D are curves representing distances L _TH (for example, L _TH = 5 (m)) that are the switching determination values from the first base station 12A to the fourth base station 12D, respectively. , Each of which is a part of a circle having a radius L _TH (= 5 (m)) centered on the positions of the first base station 12A to the fourth base station 12D. When the mobile station 10 is inside these circles, the base station 12 located at the center of the circle is obtained by converting the RSSI value when the radio wave from the mobile station 10 is received by the determination unit 50. the value of the received power P _R, which is is a distance-related value, if outside the circle, the propagation time of the radio wave is a distance-related values. Specifically, when the mobile station 10 is at the position of point A in FIG. 7, the first base station 12A, the third base station 12C, and the fourth base station 12D receive data obtained by converting from RSSI values. is the value the distance-related value of the power P _R, in the second base station 12B propagation time of radio waves is a distance-related values. On the other hand, when the mobile station 10 is in the position of point B, the third base station 12C, the value of the received power P _R obtained by converting the RSSI value in the fourth base station 12D is a distance-related values, In the first base station 12A and the second base station 12B, the propagation time of radio waves is a distance related value.

  Returning to FIG. 4, the server communication unit 40 performs communication with a positioning server 14 (described later) connected via the wired cable 52 as necessary. For example, the reception time measured with respect to the positioning server 14 , Or a command for the base station 12 or a command for control operation to be performed wirelessly for the mobile station 10 is received from the positioning server 14.

  The clock 44 is used when the base station 12 determines the transmission time and reception time of radio waves, and is used, for example, when the operation is performed at predetermined intervals. Further, the clocks 44 included in each of the base stations 12 are set in advance so that the times coincide with each other.

  Note that the control unit 38 of the base station 12 transmits the radio wave in the same manner as the control unit 38 of the mobile station 10 switches the radio wave transmission state and reception state of the mobile station 10. The state and the state of receiving radio waves can be switched, and the operations of the wireless communication unit 34, the signal processing unit 36, and the like are switched and controlled in accordance with these states.

  That is, when the base station 12 transmits radio waves, the radio communication unit 34 and the signal processing unit 36 perform the following operation instead of the above-described operation. For example, when the base station 12 transmits a radio wave, the signal processing unit 36 transmits information to be transmitted such as a control operation command to the mobile station 10, for example, an M-sequence code or a Gold sequence code used also in GPS. Using a spread code such as a pseudo-noise code (Pseudo-Noise code; PN signal), spread processing such as spread spectrum is performed to generate a signal to be transmitted.

  The wireless communication unit 34 modulates the signal generated by the signal processing unit 36 into a format suitable for communication, amplifies a synthesized wave combined with a carrier wave of a predetermined frequency by an amplifier, and uses an unbalanced line by a balun or the like. To a balanced line. The radio wave generated in this way is transmitted by the antenna 32. In this way, the base station 12 can transmit in addition to receiving radio waves. On the other hand, since the mobile station 10 can receive and receive radio waves as described above, the base station 12 can control the operation of the mobile station 10 by radio.

  In the mobile station 10 and the base station 12 shown in FIGS. 2 and 3, functional blocks corresponding to functions not directly involved in the control operation in the present invention are omitted. For example, the mobile station 10 and the base station 12 include a power source (not shown). This power supply supplies necessary power to each of the mobile station 10, the base station, and the positioning server 14.

  FIG. 5 is a functional block diagram showing an outline of the functions of the positioning server 14. The positioning server 14 is connected to each base station 12 via a cable 52, and includes a base station communication unit 54, a positioning unit 56, a control unit 60, an output unit 62, and the like. Among these, the base station communication unit 54 communicates with the server communication unit 40 of the base station 12 connected via a wired cable (communication cable) 52, for example, transmission / reception of measurement data, and the base station 12 And a command for controlling the operation of the mobile station 10 is transmitted. The positioning server 14 includes, for example, a so-called computer having a CPU, a RAM, a ROM, an input / output interface, and the like. The CPU performs signal processing according to a program stored in the ROM in advance while using a temporary storage function of the RAM. By performing the above, processing in the positioning unit 56, the control unit 60, the output unit 62, etc. of the positioning server 14 is executed.

The positioning unit 56 that calculates the position of the mobile station 10, that is, performs positioning, performs positioning of the mobile station 10 based on the distance-related value obtained from the base station 12 via the communication cable 52 and the base station communication unit 54. . The distance-related value, as described above in the present embodiment, the radio wave measured by the value or the reception time measuring unit 42 of the reception power P _R obtained by converting the value of the RSSI calculated by RSSI acquisition unit 46 The propagation time of the radio wave calculated based on the reception time of each of the plurality of base stations 12 may be different as described above. First, the positioning unit 56, the respective distance-related value transmitted from each base station 12, or the distance related value is a value of the received power P _R obtained by converting the RSSI value or a radio wave propagation time Considering whether there is any, it is converted into the distance between the mobile station 10 and the base station 12. If it is specifically a value of the received power P _R obtained by converting the value of the distance-related value RSSI is converted from the value of the RSSI using the relationship shown in the formula (1) or FIG. 6 and calculates the distance between the mobile station 10 and the base station 12 corresponding to the value of the received power P _R obtained Te. When the distance-related value is a radio wave propagation time, the mobile station 10 and the base station 12 are multiplied by the radio wave speed c (= 2.997 × 10 ⁸ (m / s)). And the distance is calculated. In this way, the distance between each base station 12 that has received the radio wave transmitted by the mobile station 10 and the mobile station 10 is calculated.

The positioning unit 56 calculates the position of the mobile station 10 based on the calculated distance between each base station 12 and the mobile station 10 and each known position of the base station 12. FIG. 8 is a diagram for explaining the outline of calculation of this position. In FIG. 8, the first base station 12A, the second base station 12B, and the third base station 12C, which are the three base stations, receive radio waves from the mobile station 10, and the RSSI values of the radio waves received at each base station 12 Alternatively, the distance between the first base station 12A and the mobile station 10 is r _{1 ′} and the distance between the second base station 12B and the mobile station 10 is r ₂ ′ based on the propagation time of the radio wave received at each base station 12. The distance between the third base station 12C and the mobile station 10 is calculated as r ₃ '. Further, the position of each base station 12 is known, and the coordinates indicating the position are (x ₁ , y ₁ ) for the first base station 12A, (x ₂ , y ₂ ) for the second base station 12B, The three base stations 12C are (x ₃ , y ₃ ). At this time, if the coordinates indicating the position of the mobile station 10 that is the object of positioning are (x, y), the relationship of the following equation (2) is established.
^{_{(X-x 1) 2 +}} (y-y 1) 2 = r 1 '2,
(X−x ₂ ) ² + (y−y ₂ ) ² = r ₂ ′ ² , (2)
(X−x ₃ ) ² + (y−y ₃ ) ² = r ₃ ′ ²
The positioning unit 56 can obtain the position (x, y) of the mobile station 10 by solving the equation (2). Note that if an error occurs during RSSI acquisition by the RSSI acquisition unit 46, the equation (2) may not be solved, but a term corresponding to the error is provided in the equation (2). An approximate solution can be calculated using a square method or the like.

  The control unit 60 controls operations of the base station communication unit 54, the positioning unit 56, and the like. The output unit 62 outputs information about the position of the mobile station 10 calculated by the positioning unit 56 by a predetermined method, for example, by displaying the information on a display device provided as an output device (not shown). The mobile station location storage unit 92 and the mobile station location estimation unit 94 are used in another embodiment to be described later.

  FIG. 9 is a flowchart for explaining the outline of the control operation of the mobile station positioning system 8 in the present embodiment. First, in step (hereinafter, “step” is omitted) SA0, the clock 44 of each base station 12 and the clock 31 of the mobile station 10 are timed. This is to measure the time required for the radio wave emitted from the mobile station 10 to reach each base station 12 in SA9 to SA11 described later, and based on the propagation time of this radio wave, the mobile station 10 and the base station 12 This is because the distance 31 may be calculated. At this time, in order to accurately calculate the propagation time of the radio wave, the clock 31 of the mobile station 10 and the clock 44 of the base station 12 need to match. The time adjustment in this step is performed as follows, for example. The mobile station 10 moves to a known predetermined position, transmits a radio wave to the base station 12, measures the propagation time of the radio wave, and calculates from the distance between the mobile station 10 and the base station 12 at the predetermined position. Calculate the theoretical value of the propagation time of the radio wave. Then, the theoretical value of the propagation time of the radio wave is compared with the actual propagation time, and any of these clocks is corrected by regarding the difference between the clock 31 of the mobile station 10 and the clock 44 of the base station 12. And synchronize the time of these clocks.

Subsequently, in SA 1, a command for measuring the RSSI value is issued from the positioning server 14 to each base station 12 via the communication cable 52. On the other hand, each base station 12 waits for a command from the positioning server 14 in SA2.

  Subsequent SA 3 to SA 6 correspond to the RSSI acquisition unit 46. First, in SA3, a command for transmitting a radio wave for measuring the RSSI value to the mobile station 10 is wirelessly transmitted to the mobile station 10 by any one of the base stations 12 that received the command from the positioning server 14 in SA2. Called. In addition, in each base station 12 that has received a command to measure the RSSI value from the positioning server 14, preparation for RSSI value measurement, that is, preparation for reception of radio waves transmitted from the mobile station 10 is performed.

In SA4, a radio wave transmission command transmitted from one of the base stations 12 in SA3 is received, and a radio wave is transmitted from the mobile station 10 with a predetermined output. On the other hand, each base station 12 receives a radio wave transmitted from the mobile station 10 at SA4 in SA5, and measures an RSSI value, which is the strength of the radio wave from the mobile station 10 received at SA5, at SA6. . The measured RSSI value is then made that processing such as A / D conversion, using pre-calculated relationship and relationships such as a table, is converted into a value of the received power P _R, which is expressed in decibels The

Subsequent SA7 and SA8 correspond to the determination unit 50. First, in SA7, for example, based on the α is the maximum allowable amount of the positioning error is determined from the accuracy of the positioning system 8, the error ΔR of the reception power P _R caused by the measurement error of the RSSI, the RSSI value switching threshold value R _TH of the received power P _R obtained by conversion is calculated. In Subsequently SA8, whether exceeds the switching threshold value R _TH calculated in the value of the received power P _R obtained by converting the measured RSSI values SA7 in SA6 or not. When the value of the received power P _R obtained by converting the RSSI value is above the switching threshold value R _TH is affirmative determination at this step, in SA13, converts the RSSI value measured in SA6 the value of the received power P _R obtained is adopted as the distance related value. On the other hand, the determination at this step is negative if the value of the received power P _R obtained by converting the RSSI value is below the switching threshold value R _TH is equal or switching threshold value R _TH, RSSI measured at SA6 the value of the received power P _R obtained by converting from a value not used as distance-related value for the distance measurement error is large, another distance measuring means, i.e. SA9 subsequent steps are executed.

SA9 to SA12 correspond to the reception time measuring unit 42. First, in SA9, a command for transmitting a radio wave for measuring the reception time is given from any of the plurality of base stations 12 to the mobile station 10, and the determination in SA8 is denied, that is, SA6. base station 12 the value of the received power P _R obtained by converting the measured RSSI value is below the switching threshold value R _TH is equal or switching threshold value R _TH in for signal reception from the mobile station 10 It is made to wait.

  In SA10, the mobile station 10 having received the radio wave transmission command performed in SA9 transmits a radio wave for reception time measurement. The radio wave transmitted at this time includes, for example, information related to the transmission time, and the base station 12 that has received the radio wave can know the transmission time of the radio wave.

  In SA11, the radio wave transmitted from the mobile station 10 in SA10 is received by the base station 12 in which the determination in SA8 is denied. Then, the reception time is calculated by detecting the synchronization between the spread code and the replica code included in the received radio wave. Further, information on the transmission time included in the received wave is extracted, and from the calculated reception time and the transmission time extracted from the received wave until the radio wave is transmitted by the mobile station 10 and received by the base station 12. The required propagation time is calculated as a distance related value.

In SA12, the distance-related values measured via the communication cable 52 are transmitted from each base station 12 to the positioning server 14. At this time, distance-related values to be transmitted, the base station 12 determines the SA8 is negative, the value of the received power P _R obtained by converting the measured RSSI values in SA6, also, the SA8 In the base station for which the determination is affirmed, the propagation time of the radio wave calculated in SA13.

In SA14 corresponding to the positioning unit 56 of the positioning server 14, positioning of the mobile station 10 is performed based on the distance-related value transmitted from each base station 12 in SA12 and information on the position of each base station 12. Specifically, the mobile station 10 and the base station 12 by the relationship of the equation (1) or Figure 6 for the transmitted distance-related value as a value of the received power P _R obtained by converting the RSSI value in SA12 The distance-related value that is converted into the distance and transmitted as the radio wave propagation time is converted into the distance between the mobile station 10 and the base station 12 by multiplying by the radio wave velocity c. Based on the converted distance between the mobile station 10 and each base station 12 and the coordinates representing the position of each base station, the equation (2) is solved to obtain the position of the mobile station 10 as a solution.

According to the embodiment, the distance measuring means by judging unit 50 corresponding to the switching means, the received power P _R obtained by converting the RSSI value is information relating to the distance between the respectively mobile station 10 of base station 12 Since each of the plurality of base stations 12 is switched from the RSSI acquisition unit 46 corresponding to the first ranging means to the reception time measuring unit 42 corresponding to the second ranging means based on the value, the plurality of base stations For every twelve, ranging means adapted to information about the distance between each of the base stations 12 and the mobile station 10 is selected.

  In addition, according to the above-described embodiment, the RSSI acquisition unit 46 corresponding to the first distance measuring unit is connected to the base station 12 based on the radio wave intensity from the mobile station 10 received at each of the plurality of base stations 12. The reception time measuring unit 42 corresponding to the second distance measuring means moves based on the propagation time of the radio wave from the mobile station 10 to each of the plurality of base stations 12. Since the distance between the station 10 and the base station 12 is calculated, the first distance measuring means and the second distance measuring means can be switched based on the information on the distance between the base station 12 and the mobile station 10. it can. In addition, the second distance measuring means that consumes more power than the first distance measuring means in terms of performing synchronization detection is executed only when switched by the determination unit 50 corresponding to the distance measuring means switching means. Therefore, the power consumption of the base station 12 can be suppressed.

Further, according to the above-described embodiment, the determination unit 50 corresponding to the distance measurement unit switching unit is obtained by converting from the received radio wave intensity obtained by the RSSI acquisition unit 46 corresponding to the first distance measurement unit. If less than the received power P value of _R is predetermined switching threshold value R _TH is the reception time measuring unit 42 corresponding to the second distance measuring means from the RSSI obtaining unit 46 corresponding to the first distance measuring means since switching, the values of the received power P _R, which is expressed in decibels obtained by converting the signal intensity (voltage) of the received radio wave as the RSSI values obtained in the RSSI acquisition unit 46 is a first distance measuring means The distance measuring means can be switched using this.

Further, according to the above-described embodiment, the first distance measuring unit based on the RSSI value that is information on the distance between each of the base stations 12 and the mobile station 10 by the determination unit 50 corresponding to the distance measuring unit switching unit. A distance measurement error ((L-L ₁ ) and (L ₂ -L) in FIG. 6) associated with an RSSI value acquisition error in the RSSI acquisition unit 46 is calculated, and the distance measurement error exceeds a predetermined value α. Is switched from the RSSI acquisition unit 46, which is the first distance measuring means, to the reception time measuring unit 42, which is the second distance measuring means, so that the distance between the base station 12 and the mobile station 10 is increased. The RSSI acquisition unit 46, which is the first ranging means whose accuracy deteriorates, and the receiving, which is the second ranging means, in which the distance between the base station 12 and the mobile station 10 does not directly affect the accuracy of the ranging. The time measuring unit 42 is connected to the base station 12 and the mobile station 10. Convert from RSSI value is information relating to the distance can be switched based on the value of the received power P _R obtained, it is the first distance measuring means only when the distance measurement accuracy is within the desired range The RSSI acquisition unit 46 can be used.

  Next, another embodiment of the present invention will be described with reference to FIGS. In the following description, portions common to the embodiments are denoted by the same reference numerals and description thereof is omitted.

  In the present embodiment, the positioning server 14 further includes a mobile station position storage unit 92 and a mobile station position estimation unit 94 as shown in FIG. When the mobile station positioning system 8 repeatedly performs positioning of the mobile station 10, the mobile station position storage unit 92 stores information on the results of positioning performed by the positioning unit 56 in the past, that is, movement history information of the mobile station 10. To do.

  In addition, the mobile station position estimation unit 94 estimates the current position of the mobile station 10 based on the movement history information of the mobile station 10 stored in the mobile station position storage unit 92. The position of the mobile station is estimated by, for example, calculating the movement speed of the mobile station 10 based on the past predetermined number of positioning results and the positioning execution interval, and the movement speed and movement at the time of the last positioning. This can be done by calculating based on the position of the station 10 and the time elapsed since this last positioning. If the interval at which positioning is repeatedly performed is short, the positioning result in the previous positioning may be estimated as the current position of the current mobile station 10 as it is. The mobile station position estimation unit 94 transmits the estimated current position of the mobile station 10 to the determination unit 50 of each base station 12.

In addition to the operation in the first embodiment, the determination unit 50 performs the following operation in the second embodiment. That is, the determination unit 50 estimates the current mobile station 10 and the base station 12 based on the estimated position of the current mobile station 10 estimated by the mobile station position estimation unit 94 and the position of its own base station 12. Calculate the distance. Then, as in the first embodiment, the RSSI switching determination value R _TH is calculated based on the maximum allowable amount α of the distance measurement error performed based on the RSSI value calculated by the RSSI acquisition unit 46. . Further, a switching determination value L _TH for the distance between the mobile station 10 and the base station 12 corresponding to the switching determination value R _TH is calculated based on the equation (1) or the relationship shown in FIG. Then, based on the calculated estimated distance and the distance switching determination value L _TH , it is determined whether the RSSI acquisition unit 46 acquires the RSSI value or the reception time measurement unit 42 measures the reception time. While Specifically, the of acquiring an RSSI value by RSSI obtaining unit 46 if the estimated distance is less than the switching threshold value L _TH, obtain the value of the received power P _R and converts the acquired RSSI value, the If the estimated distance exceeds the switching threshold value L _TH is equal or the switching threshold value L _TH is to measure the reception time by the reception time measuring section 42.

  Other points such as the configuration of the mobile station positioning system 8 shown in FIGS. 1 and 2 and the functions of the mobile station 10 shown in FIG.

  FIG. 10 is a flowchart for explaining the outline of the control operation of this embodiment, and is executed in combination with the flowchart of FIG. Specifically, the flowchart of FIG. 10 is executed prior to FIG. 9, and thereafter, the flowchart of FIG. 9 is executed from the step indicated by the flowchart of FIG.

  First, in SB 1 corresponding to the mobile station position estimation unit 94, the current position of the mobile station 10 is estimated based on the movement history information of the mobile station 10 stored in the mobile station position storage unit 92. Then, the estimated current position of the mobile station is transmitted to each base station 12.

Subsequent SB2 and SB3 correspond to the determination unit 50. First, in SB2, in each base station 12, the estimated distance between its own base station 12 and the estimated position of the current mobile station 10 is based on the estimated position of the current mobile station 10 estimated in SB1. Calculated. Then, in SB3, either with switching threshold value _{L TH} of the distance corresponding to the switching threshold value _{R TH} of the RSSI value is calculated, the estimated distance calculated in SB2 is below the switching threshold value _{L TH} distance not Is judged. When the estimated distance is less than the switching threshold value L _TH distance, the determination at this step is affirmative, on the basis of the value of the received power P _R obtained by converting the RSSI value acquired by the RSSI acquisition unit 46 Assuming that there is a high possibility that the positioning error in the distance measurement to be performed is smaller than the allowable maximum value, for the base station, SA1 and subsequent steps in the flowchart of FIG. 9 are executed so that the RSSI acquisition unit 46 acquires the RSSI value. Is done. On the other hand, when the estimated distance exceeds the distance switching threshold value L _TH equal to or distance switching threshold value L _TH, the determination at this step is negative, by converting the RSSI value calculated by the RSSI obtaining unit 46 to obtain as a likely exceed the maximum positioning error is allowed in the distance measurement is performed based on the value of the received power P _R, which is, for the base station, receiving without performing acquisition of the RSSI by the RSSI acquisition unit 46 As the reception time is measured by the time measurement unit 42, SA9 and subsequent steps in the flowchart of FIG. 9 are executed for the base station.

  In the second embodiment, when executing the flowchart of FIG. 9, SA14 corresponds to the positioning unit 56 and the mobile station position storage unit 92, and the mobile station is similar to SA14 in the first embodiment. 10 is measured, and the measured position of the mobile station 10 is stored in a storage means (not shown) of the positioning server 14.

According to the above-described embodiment, the determination unit 50 corresponding to the ranging unit switching unit includes the distance between each of the plurality of base stations 12 and the mobile station 10 of the mobile station 10 stored in the mobile station position storage unit 92. measuring the RSSI acquisition unit 46 is the first distance measuring means when the estimated distance calculated by the mobile station position estimation unit 94 exceeds the switching threshold value L _TH of the distance of the second based on the movement history information Since switching is made to the reception time measuring unit 42 which is a distance means, if the reception time measuring unit 42 which is the second distance measuring means determines to perform distance measurement based on the movement history of the mobile station 10, There is no need to execute the RSSI acquisition unit 46 which is one distance measuring means.

  FIG. 11 is a functional block diagram showing an outline of the functions of the base station 12 in this embodiment, and corresponds to FIG. 4 in the above-described embodiment. Comparing FIG. 4 with FIG. 11, the base station 12 in the present embodiment shown in FIG. 11 is different in that it does not have the determination unit 50. That is, in the first and second embodiments described above, the control unit 38 has the determination unit 50, and switches between execution of the RSSI acquisition unit 46 and execution of the reception time measurement unit 42 based on the determination in the determination unit 50. It was. On the other hand, in the present embodiment, the control unit 38 acquires the RSSI value by the RSSI acquisition unit 46 and the reception time in accordance with the switching of the positioning method by the positioning method switching unit 72 included in the positioning unit 56 of the positioning server 14 described later. Switching between measurement of radio wave reception time by the measuring unit 42 is performed.

  In other respects, the function of the base station 12 is the same as that of the base station 12 of the previous embodiment shown in FIG.

  FIG. 12 is a functional block diagram showing an outline of functions of the positioning server 14 in the present embodiment, and corresponds to FIG. 5 in the above-described embodiment. 5 and FIG. 12, the positioning unit 56 is different in that it includes an RSSI positioning unit 68, a positioning method switching unit 72, and at least one of the TDOA positioning unit 70 or the TOA positioning unit 71.

As described above, the positioning unit 56 that performs positioning of the mobile station 10 based on the information transmitted from each of the base stations 12 via the communication cable 52 includes the RSSI positioning unit 68, the positioning method switching unit 72, and the TDOA. At least one of the positioning unit 70 or the TOA positioning unit 71. Among, RSSI measurement unit 68 based on the value of the received power _{P R} obtained by converting the RSSI value obtained by the RSSI acquisition unit 46 of each base station 12 performs positioning of the mobile station 10. Specifically, for each value of the received power P _R obtained by converting the RSSI value obtained by the RSSI acquisition unit 46 of each base station 12, based on the relationship shown in the formula (1) or FIG. 6 The distance between the corresponding mobile station 10 and each base station 12 is converted. Then, Equation (2) is solved using the distance between the mobile station 10 and each base station 12 obtained by the conversion, and coordinates representing the position of the mobile station 10 are obtained as the solution. That is, the RSSI positioning unit 68 corresponds to the first positioning means.

  When the TDOA positioning unit 70 receives radio waves transmitted from the mobile station 10 by the plurality of base stations 12, the TDOA positioning unit 70 receives a reception time difference that is a difference in reception time measured by the reception time measurement unit 42 in each base station 12. Based on the position of the base station 12, the mobile station 10 is positioned.

  Specifically, first, as a premise, the time of the clock 44 of each base station 12 is synchronized, and the time difference between the clock 44 of each synchronized base station 12 and the clock 31 of the mobile station 10 is synchronized. Is Δt, that is, the time of the clock 44 of the base station 12 is advanced by Δt with respect to the time of the clock 31 of the mobile station 10. However, the value of Δt is an unknown value. Then, when the radio wave transmitted by the mobile station 10 is received by each base station 12, for example, the transmission time information of the mobile station 10 included in the radio wave and the reception time measurement unit 42 of the base station 12 perform synchronization detection. A radio wave propagation time is calculated based on the measured reception time.

を例えばニュートンラプソン法などにより解くことで、移動局１０の位置（ｘ，ｙ）が算出される。なお、前記式（３）が式（４）のように変形されると、移動局１０による電波の発信時刻ｔ_０および移動局１０の時計３１と基地局１２の時計４４の時刻ずれΔｔに伴う距離ｓは式（４）から消去されている。すなわち、移動局１０による電波の発信時刻ｔ_０は基地局１２からＴＤＯＡ測位部７０に送信される必要がなく、また、未知の値である時刻ずれΔｔに伴う距離ｓも考慮しなくてよい。 For example, in FIG. 8, a radio wave is transmitted from the mobile station 10 at time t ₀ , and the reception time measuring unit 42 at each of the three base stations, the first base station 12A, the second base station 12B, and the third base station 12C. Assume that radio waves from mobile stations are received at t ₁ , t ₂ , and t ₃ . At this time, the actual propagation time of the radio wave is equal to the difference between the reception time measured by the clock 44 of the base station 12 and the transmission time measured by the clock 31 of the mobile station 10. The time difference Δt with respect to the ten clocks 31 is taken into consideration. Specifically, the propagation time of the radio wave from the mobile station 10 to the first base station 12A is (t ₁ −t ₀ + Δt), and the propagation time of the radio wave from the mobile station 10 to the second base station 12B is (t ₂ − t ₀ + Δt), the propagation time of the radio wave from the mobile station 10 to the third base station 12C is (t ₃ −t ₀ + Δt). As described above, the position of each base station 12 in FIG. 8 is known, and the coordinates indicating the position are (x ₁ , y ₁ ) for the first base station 12A and (x _{2 for} the second base station 12B). , Y ₂ ) and the third base station 12C is (x ₃ , y ₃ ), and the coordinates indicating the position of the mobile station 10 that is the object of positioning are (x, y), the velocity of the radio wave is c (m / S),
(X−x ₁ ) ² + (y−y ₁ ) ² = (c × (t ₁ −t ₀ ) + s) ² ,
(X−x ₂ ) ² + (y−y ₂ ) ² = (c × (t ₂ −t ₀ ) + s) ² , (3)
(X−x ₃ ) ² + (y−y ₃ ) ² = (c × (t ₃ −t ₀ ) + s) ²
It becomes. However, s = Δt × c. In addition, r ₁ ′, r ₂ ′, and r ₃ ′ in FIG. 8 are r ₁ ′ = c × (t ₁ −t ₀ ), r ₂ ′ = c × (t ₂ −t ₀ ), and r ₃ ′, respectively. = C × (t ₃ −t ₀ ). Here, an equation derived by taking the square roots of both sides of the second and third formulas of the formula (3) and further subtracting the square root of both sides of the first formula from both sides,

For example, the position (x, y) of the mobile station 10 is calculated by solving Newton-Raphson method. When equation (3) is transformed into equation (4), it accompanies transmission time t ₀ of radio waves by mobile station 10 and time difference Δt between clock 31 of mobile station 10 and clock 44 of base station 12. The distance s is eliminated from the equation (4). That is, the radio wave transmission time t ₀ by the mobile station 10 does not need to be transmitted from the base station 12 to the TDOA positioning unit 70, and the distance s associated with the time shift Δt, which is an unknown value, need not be considered.

  The TOA positioning unit 71 is transmitted from the mobile station 10 when the time of radio wave propagation is accurately calculated by synchronizing the time of the clock 31 of the mobile station 10 and the time of the clock 44 of the base station 12. When radio waves are received by a plurality of base stations 12, the propagation time of the radio waves is calculated based on the transmission time by the mobile station 10 and the reception time of the radio waves at each base station, and the mobile station 10 is further based on the propagation times. The distance between each mobile station 10 and each base station 12 is calculated, and positioning of the mobile station 10 is performed based on the calculated distance between the mobile station 10 and each base station 12 and the position of the base station 12.

  Specifically, the signal processing unit 36 of the base station 12 extracts information on the transmission time included in the radio wave transmitted from the mobile station 10 and received by the base station 12 by despreading processing and the like. The time measuring unit 42 measures the reception time of the radio wave by the synchronization detection. The TOA positioning unit 71 calculates the radio wave propagation time based on the radio wave transmission time and reception time obtained from the base station 12 in this way.

  That is, the TOA positioning unit 71 calculates the position of the mobile station 10 by solving an equation in which the clock deviation Δt is Δt = 0, that is, s = 0 in Equation (3). This equation is the same as the above equation (2). As described above, an error may occur in the reception time and the solution may not occur. However, a term corresponding to the error is provided, and this is reduced to a minimum of 2. An approximate solution can be obtained by solving so as to minimize by multiplication. As described above, the TDOA positioning unit 70 and the TOA positioning unit 71 correspond to second positioning means that performs positioning of the mobile station 10 based on either the reception time of the radio wave or the reception time difference.

  By the way, when the positioning by the RSSI positioning unit 68 and the positioning by the TDOA positioning unit 70 or the TOA positioning unit 71 are compared, the positioning by the TDOA positioning unit 70 or the TOA positioning unit 71 is based on the reception time measuring unit 42 of the base station 12. It is necessary to calculate the reception time of radio waves at the station 12. Since the calculation of the reception time is performed by the synchronization detection process, specifically, for example, by a delay circuit and a matched filter, when positioning is performed by the TDOA positioning unit 70 or the TOA positioning unit 71, positioning is performed by the RSSI positioning unit 68. Compared to the case, the power consumption in the base station 12 is increased. That is, when positioning is possible by the RSSI positioning unit 68, positioning by the RSSI positioning unit 68 is required for positioning of the base station 12 compared to when positioning is performed by the TDOA positioning unit 70 or the TOA positioning unit 71. It becomes possible to reduce electric power.

When performing positioning of the mobile station 10 by the RSSI measurement unit 68, RSSI measurement unit 68, corresponds to the value of the received power _{P R} obtained by converting the RSSI value calculated by the RSSI acquisition unit 46 of the base station 12 It is converted into the distance to be used. However, as described above, when the distance between the mobile station 10 that is the transmission point of the radio wave and the base station 12 that is the reception point is calculated based on the RSSI value of the received radio wave, the reception obtained by converting the RSSI value. mobile station due to the influence of such resolution in power P as the value of _R is small, or the mobile station 10 and the base station 12 and the distance is longer becomes higher radio wave fluctuation or noise, RSSI value of the acquired error or a / D converter 48, The error that occurs in the distance between 10 and the base station 12 increases. When the RSSI measurement unit 68 using the value of the received power P _R obtained by converting the RSSI value produced a large error in the distance to perform positioning, which may include a large error positioning results. In other words, when the positioning accuracy required in the positioning system 8 is determined, the maximum value allowable as an error occurring in the distance between the mobile station 10 and the base station 12 is calculated.

For example, when the maximum value allowable as the distance measurement error is calculated as α (m) based on the position error required for the position measurement system 8, as described in the first embodiment, the maximum value of the distance measurement error. R _TH as the minimum value of the received power P _R which satisfies α is calculated, and the value of the maximum of L _TH of the distance D between mobile station 10 and the base station 12 corresponding thereto is calculated. Therefore, returning to FIG. 12, the positioning method switching unit 72, the value of the received power P _R obtained by converting the value of the RSSI obtained by the RSSI acquisition unit 46 satisfies the maximum value α of the distance measuring error exceeds the value R _TH of minimum received power P _R, or the distance D between mobile station 10 and the base station 12 is a base station 12 below the maximum L _TH which satisfies the maximum value α of the distance measurement error corresponding thereto Based on the number, the execution of the RSSI positioning unit 68 is switched to the execution of the TDOA positioning unit 70 or the TOA positioning unit 71. That is, the positioning method switching unit 72 corresponds to the positioning means switching means.

Specifically, the positioning method switching unit 72 is allowed as a distance measurement error value of the received power P _R obtained by converting the value of the acquired RSSI by RSSI acquisition unit 46 of the base station 12 is set or exceeds the value R _TH of the received power P _R, which is determined by the maximum value alpha, or number RSSI positioning of the base station the distance D is below the L _TH of the mobile station 10 and the base station 12 corresponding thereto When the number of base stations necessary for positioning by the unit 68 does not exist, the execution of the RSSI positioning unit 68 is switched to the execution of the TDOA positioning unit 70 or the TOA positioning unit 71. In addition, when the movable area 5 in which the mobile station 10 can move is set as a two-dimensional plane, three equations are necessary to uniquely find the solution of the equation (2), so the RSSI positioning unit The number of base stations required for positioning by 68 is three. Similarly, when the mobile station 10 moves in a three-dimensional space, the number of base stations necessary for positioning by the RSSI positioning unit 68 is four.

For example, in the example of FIG. 7 described above, when the mobile station 10 is at the position of the curve point A, the RSSI value is converted in the first base station 12A, the third base station 12C, and the fourth base station 12D. while the value of the received power P _R obtained Te is larger than the switching determination value R _TH, than the received power P value of _R switching determination value R _TH obtained by converting the RSSI value in the second base station 12B Get smaller. That is, since the number of base stations exceeds the RSSI value _{R TH} is present only three stations required to perform positioning by RSSI positioning unit 68, the positioning by the RSSI measurement unit 68 is performed. On the other hand, when the mobile station 10 is in the position of point B, the third base station 12C, the value is switched decision value of the received power P _R obtained by converting the RSSI value in the fourth base station 12D R while larger than _TH, the first base station 12A, the value of the received power _{P R} obtained by converting the RSSI value in the second base station 12B is smaller than the switching determination value _{R TH.} That is, since the number of base stations exceeding the RSSI value R _TH is not more than three stations necessary for positioning by the RSSI positioning unit 68, the positioning method switching unit 72 changes the RSSI positioning unit 68 to the TDOA positioning unit 70 or Switching to the positioning by the TOA positioning unit 71 is performed.

  In other respects, the positioning server 14 has the same function as the positioning server 14 of the previous embodiment shown in FIG. Other points such as the configuration of the mobile station positioning system 8 shown in FIGS. 1 and 2 and the functions of the mobile station 10 shown in FIG.

  FIG. 13 is a flowchart illustrating an outline of the control operation of the mobile station positioning system 8 according to the second embodiment. First, in step (hereinafter, “step” is omitted) SC <b> 1, an instruction to acquire an RSSI value is issued from the positioning server 14 to each base station 12 via the communication cable 52. On the other hand, each base station 12 waits for a command from the positioning server 14 in SC2.

  Subsequent SC3 to SC6 correspond to the RSSI acquisition unit 46, the A / D conversion unit 48, the control unit 38, and the like. First, in SC3, a command for transmitting a radio wave for acquiring the RSSI value to the mobile station 10 is transmitted wirelessly to the mobile station 10 by any one of the base stations 12 receiving the command from the positioning server 14 in SC2. Called. In addition, in each base station 12 that has received a command to acquire an RSSI value from the positioning server 14, preparation for acquiring the RSSI value, that is, preparation for receiving a radio wave transmitted from the mobile station 10 is performed.

In SC4, a radio wave transmission command transmitted from one of the base stations 12 in SC3 is received, and a radio wave is transmitted from the mobile station 10 with a predetermined output. On the other hand, each base station 12 receives a radio wave transmitted from the mobile station 10 at SC4 in SC5, and acquires an RSSI value which is the radio wave intensity from the mobile station 10 received at SC5 at SC6. converting the acquired RSSI value to the value of the received power P _R with the value of the converted reception power P _R is transmitted to the server 14, respectively.

Subsequent SC7 to SC9 correspond to the positioning method switching unit 72. First, in the SC7, the values of the received power _{P R} obtained by converting the value of the RSSI obtained by the RSSI acquisition unit 46 of each base station 12 is received by the server 14. In the subsequent SC8, for example, based on the α is the maximum allowable amount of the positioning error is determined from the accuracy of the positioning system 8, the error ΔR of the reception power P _R caused by the measurement error of the RSSI, the reception power P _R switching threshold value _{R TH} is calculated for. In Subsequently SC9, the number of base stations 12 that the value of the received power P _R obtained by converting the RSSI values received to the positioning server 14 is above the switching threshold value R _TH calculated in SC8 in SC7 The RSSI positioning unit 68 determines whether or not there are more than the number necessary for positioning, that is, three or more. When the base station 12 that the value of the received power P _R obtained by converting the RSSI value is greater than the switching threshold value R _TH is present more than two converts the RSSI values received at SC7 the value of the received power _{P R} obtained passes to SC19 as performs positioning by RSSI positioning unit 68 with reference to. On the other hand, when the value of the received power _{P R} obtained by converting the RSSI value is below the switching threshold value _{R TH} is equal or switching threshold value _{R TH} is, the RSSI value by the RSSI measuring means 68 received in SC7 the positioning using the value of the received power P _R, which is obtained by converting the not executed, another positioning means, namely SC10 subsequent steps are executed.

  SC10 to SC15 correspond to the reception time measuring unit 42. First, in SC10, the positioning server 14 instructs each base station 12 to measure the reception time of radio waves transmitted from the mobile station 10. In SC11, each base station 12 waits to receive the command transmitted from the positioning server 14 in SC10. Then, when the instruction transmitted from the positioning server 14 is received in SC10, the subsequent SC12 is executed. In SC12, the time of the clock of each base station 12 is determined when positioning by the TDOA positioning unit 70 is performed in SC18 described later, and the positioning of the mobile station 10 is performed when positioning by the TOA positioning unit 71 is performed in SC18. The time of the clock 31 and the time of the clock 44 of the base station 12 are synchronized. In addition, in each base station 12, when the command from the positioning server 14 is not received within a predetermined time, the determination in the SC9 is affirmed and it is determined that the positioning by the RSSI positioning unit 68 is performed. The control operation of the base station 12 is terminated.

  In SC13, a command to transmit a radio wave for measuring the reception time is transmitted from any of the plurality of base stations 12 to the mobile station 10, and each base station 12 transmits a radio wave from the mobile station 10 to the mobile station 10. Waited for reception.

  In SC14, the mobile station 10 having received the radio wave transmission command performed in SC13 transmits a radio wave for reception time measurement. In addition, when the positioning by the TOA positioning unit 71 is performed in the SC 18, the radio wave transmitted in this step is assumed to include, for example, information regarding the transmission time, and the base station 12 that has received this radio wave It will be possible to know the time of transmission of radio waves.

  In SC15, the radio wave transmitted from mobile station 10 in SC14 is received in each base station 12. In SC16, the reception time is calculated by detecting the synchronization between the spread code and the replica code included in the radio wave received in SC15. Further, when information regarding the transmission time is included in the radio wave transmitted from the mobile station 10 in SC14, the information included in the received wave is extracted by performing, for example, despreading processing, and the transmission time of the radio wave is obtained. . Then, the radio wave transmission time and reception time obtained in this way are transmitted to the positioning server 14.

  SC17 and SC18 correspond to the TDOA positioning unit 70 or the TOA positioning unit 71. First, in SC17, the reception time and transmission time of radio waves at the base stations 12 are received from the number of base stations 12 required for positioning by the TDOA positioning unit 70 or the TOA positioning unit 71 executed in the subsequent SC18. Is done. Here, in the present embodiment, since the movable area 5 of the mobile station 10 is provided as a plane, the mobile station 10 is placed on standby so as to receive reception times from at least three base stations 12. In the positioning performed by the TDOA positioning unit 70 or the TOA positioning unit 71, the number of formulas corresponding to the formula (3), that is, the number of base stations 12 that have obtained the reception time of radio waves from the mobile station 10 is large. Since accurate positioning becomes possible, the SC 18 that follows when the reception times are obtained from at least three base stations 12 in this step is not executed, but a large number of base stations 12 are waiting by waiting for a predetermined time. You may make it obtain reception time from.

  In SC18, positioning of the mobile station 10 is performed based on the information on the reception time and transmission time of the radio wave received in each base station 12 received in SC17. That is, the equation (3) or (4) is solved based on the radio wave reception time and radio wave transmission time at each base station 12 and the coordinates representing the position of each base station 12, and the position of the mobile station 10 is taken as a solution. Obtain (TDOA method). If the time of the clock 31 of the mobile station 10 is synchronized with the time of the clock 31 of each base station 12 when the time is synchronized in the SC 12, the radio wave measured by the clock 31 of the mobile station 10 is also synchronized. The propagation time of the radio wave calculated from the transmission time of the radio wave and the reception time of the radio wave measured by the clock of the clock 44 of each base station 12 is accurate, and a solution can be obtained as s = 0 in equation (3). Yes (TOA method).

According to the above-described embodiment, the positioning method switching unit 72 corresponding to the positioning means switching means uses the three base stations 12 that are the number necessary for positioning at least the mobile station 10 among the plurality of base stations 12. Is present within a predetermined distance L _TH from the mobile station 10, based on the strength of the radio waves received by each of the plurality of base stations 12, and between each of the plurality of base stations 12 and the mobile station 10 In order to perform positioning by the RSSI positioning unit 68 corresponding to the first positioning means that calculates the distances and estimates the position of the mobile station 10 based on the calculated distances. If the required number of base stations 12 do not exist within a predetermined distance from the mobile station 10, the distance calculated from the reception time of radio waves when each of the plurality of base stations 12 receives radio waves, or Is determined by the TDOA positioning unit 70 or the TOA positioning unit 71 corresponding to the second positioning means for estimating the position of the mobile station 10 based on one of the time differences between the base stations 12 of the reception time of the radio wave. Therefore, whether or not the number of base stations 12 necessary for positioning the mobile station 10 by the RSSI positioning unit 68 serving as the first positioning means exists within a predetermined distance from the mobile station 10 is determined. The positioning means is selected accordingly.

Further, according to the above-described embodiment, the positioning means switching unit 72 corresponding to the positioning method switching means is configured such that each of the plurality of base stations obtained by executing the RSSI positioning unit 68 serving as the first positioning means the value of the received power P _R obtained by converting the RSSI value is the intensity of the received radio wave exceeds a predetermined switching threshold value R _TH, or said plurality of calculated based on the intensity of the radio wave thus received base station 12 in which the distance between the mobile station 10 and respective base stations 12 is below a predetermined switching threshold value L _TH is, for performing positioning of the mobile station 10 by the RSSI measurement unit 68 is a first positioning means When there are not three or more base stations necessary for the operation, the RSSI positioning unit 68 serving as the first positioning unit to the TDOA positioning unit 70 or the TOA positioning unit 71 serving as the second positioning unit. Since switching may utilize the values of the received power P _R obtained by converting the RSSI values obtained by the execution of the RSSI measurement unit 68 is a first positioning means for switching the positioning means.

Further, according to the above-described embodiment, the positioning means switching unit 72 corresponding to the positioning method switching means is the RSSI that is the first positioning means based on the information about the distance between each of the base stations 12 and the mobile station 10. It calculates a distance measurement error in the positioning unit 68, TDOA positioning unit that the distance measurement error is the second positioning means from the RSSI measurement unit 68 which is the first positioning means in the case above a predetermined value R _TH 70 or the TOA positioning unit 71, the RSSI positioning unit 68, which is the first positioning means whose positioning accuracy deteriorates as the distance between the base station 12 and the mobile station 10 increases, the base station and the mobile station The TDOA positioning unit 70 or the TOA 71, which is the second positioning means that does not directly affect the positioning accuracy, is based on information on the distance between the base station 12 and the mobile station 10. The RSSI positioning unit 68 as the first positioning means can be used only when the positioning accuracy is within a desired range.

  In the present embodiment, the positioning server 14 further includes a mobile station position storage unit 92 and a mobile station position estimation unit 94 as in the second embodiment. When the mobile station positioning system 8 repeatedly performs positioning of the mobile station 10, the mobile station position storage unit 92 stores information on the results of positioning performed by the positioning unit 56 in the past, that is, movement history information of the mobile station 10. To do.

  In addition, the mobile station position estimation unit 94 estimates the current position of the mobile station 10 based on the movement history information of the mobile station 10 stored in the mobile station position storage unit 92. The position of the mobile station is estimated by, for example, calculating the movement speed of the mobile station 10 based on the past predetermined number of positioning results and the positioning execution interval, and the movement speed and movement at the time of the last positioning. This can be done by calculating based on the position of the station 10 and the time elapsed since this last positioning. If the interval at which positioning is repeatedly performed is short, the positioning result in the previous positioning may be estimated as the current position of the current mobile station 10 as it is. The mobile station position estimation unit 94 transmits the estimated current position of the mobile station 10 to the positioning method switching unit 72 of the positioning server 14.

  The positioning method switching unit 72 performs the following operation in the fourth embodiment in addition to the operation in the third embodiment. That is, the positioning method switching unit 72 determines whether the current mobile station 10, each base station 12, or the current mobile station 10 based on the current estimated position of the mobile station 10 and the position of each base station 12 estimated by the mobile station position estimation unit 94. Are estimated distances Dp.

Further, the positioning method switching unit 72, as in the above first embodiment, the distance measurement of the distance measurement is performed based on the value of the received power P _R obtained by converting the RSSI value calculated by the RSSI obtaining unit 46 calculating the switching threshold value R _TH of the received power P _R based on the maximum allowable amount of error alpha. Further, a switching determination value L _TH for the distance between the mobile station 10 and the base station 12 corresponding to the switching determination value R _TH is calculated based on the equation (1) or the relationship shown in FIG. Then, the estimated distance Dp calculated for each base station 12 compares the distance switching threshold value L _TH, for each base station 12, or the estimated distance Dp is greater than the switching threshold value L _TH not Based on this determination, switching is performed between the positioning of the mobile station 10 by the RSSI positioning unit 68 and the positioning by the TDOA positioning unit 70 or the TOA positioning unit 71. Specifically, it is determined whether or not the number of base stations 12 for which the estimated distance Dp is less than the switching determination value L _TH is greater than the number necessary for positioning by the RSSI positioning unit 68, and the estimated distance Dp is If the number of base stations 12 that are lower than the switching determination value L _TH is more than the number necessary for positioning by the RSSI positioning unit 68, positioning by the RSSI positioning unit 68 is performed. Switching to the positioning by the TDOA positioning unit 70 or the TOA positioning unit 71 is executed.

  Other points such as the configuration of the mobile station positioning system 8 shown in FIGS. 1 and 2 and the functions of the mobile station 10 shown in FIG.

  FIG. 14 is a flowchart for explaining the outline of the control operation of this embodiment, and is executed in combination with the flowchart of FIG. Specifically, the flowchart of FIG. 14 is executed prior to FIG. 13, and thereafter, the flowchart of FIG. 13 is executed from the step indicated by the flowchart of FIG.

  First, in SD1 corresponding to the mobile station position estimation unit 94, the current position of the mobile station 10 is estimated based on the movement history information of the mobile station 10 stored in the mobile station position storage unit 92. Then, the estimated current position of the mobile station is transmitted to each base station 12.

The subsequent SD2 and SD3 correspond to the positioning method switching unit 72. First, in SD2, in each base station 12, the estimated distance Dp between its own base station 12 and the estimated position of the current mobile station 10 based on the estimated position of the current mobile station 10 transmitted in SD1. Is calculated. Then, in SD3, with switching threshold value _{L TH} of the distance corresponding to the switching threshold value _{R TH} values of the received power _{P R,} which is obtained by converting the RSSI value is calculated, for each base station 12 at SD2 calculated estimated distance Dp whether below the switching threshold value L _TH distance is determined to. If the number of base stations whose estimated distance Dp is less than the distance switching determination value L _TH is more than the number necessary for positioning by the RSSI positioning unit 68, that is, three or more base stations, the determination of this step is affirmative. When the mobile station 10 is positioned by the RSSI positioning unit 68, it is highly possible that the ranging can be performed within the range of the desired positioning error. get RSSI value by the RSSI acquisition unit 46 of the base station 12, and SC1 subsequent flowchart of FIG. 13 to convert from the acquired RSSI value to the received power _{P R} is performed is executed. On the other hand, the base station estimated distance Dp is below the switching threshold value L _TH distances, or number required to perform positioning by RSSI positioning unit 68, in the absence i.e. three or more, the determination of this step is negative Since the error may increase in the distance measurement by the RSSI positioning unit 68, the reception time measuring unit 42 is set so that the positioning is performed by the TDOA positioning unit 70 or the TOA positioning unit 71 without performing the positioning by the RSSI positioning unit 68. As the measurement of the reception time according to, SC10 and subsequent steps in the flowchart of FIG. 13 are executed for the base station.

  In the fourth embodiment, when the flowchart of FIG. 13 is executed, SC18 and SC19 correspond to the positioning unit 56, and the position of the mobile station 10 is the same as SC18 and SC19 in the first embodiment. And the measured position of the mobile station 10 is stored in a storage means (not shown) of the positioning server 14.

According to the above-described embodiment, the positioning method switching unit 72 corresponding to the positioning unit switching unit is operated by the mobile station position estimation unit 94 based on the movement history information of the mobile station 10 stored in the mobile station position storage unit 92. The base station in which the estimated distance Dp between the current position of the mobile station 10 and the plurality of base stations 12 that are predicted to be less than a predetermined value L _TH is detected by the RSSI positioning unit 68 serving as the first positioning means. When there are not only three base stations necessary for performing the positioning, the RSSI positioning unit 68 serving as the first positioning unit is transferred to the TDOA positioning unit 70 or the TOA positioning unit 71 serving as the second positioning unit. Since the switching is performed, if the TDOA positioning unit 70 or the TOA positioning unit 71, which is the second positioning means, determines to perform positioning based on the movement history of the mobile station 10, the first positioning hand There is no need to execute the stage RSSI positioning unit 68.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this invention is applied also in another aspect.

  For example, in SA3, SA10 in FIG. 9 or SC3, SC13 in FIG. 13, one of the base stations 12 has issued a command for radio wave transmission to the mobile station 10, but this is not a limitation. . That is, the server 14 may specify which base station 12 performs.

In Examples 1 and 3 above, respectively determination unit 50 and the positioning method switching unit 72 performs the determination based on the switching determination value R _TH values of the received power P _R obtained by converting the RSSI value, also, In the above-described second and fourth embodiments, the determination unit 50 and the positioning method switching unit 72 perform the determination based on the switching determination value L _TH for the distance between the mobile station 10 and each base station 12, respectively. It is not restricted to a certain aspect. That is, since the RSSI value and the distance between the mobile station 10 and each base station 12 are in a one-to-one correspondence as shown in the above equation (1) or FIG. 6, by converting these, the RSSI it can be determined using any value or the mobile station 10 of the reception power P _R obtained by converting the value of the distance between each base station 12.

The determination unit 50 and the positioning method switching section 72 was determined based on the previously calculated reception power obtained by converting the RSSI P switching determination of the values of _R R _TH or distance switching determination value L _TH . That is, in the above-described embodiment, when the maximum value α allowable as the distance measurement error is calculated, the maximum distance L satisfying this or the RSSI value R corresponding to the maximum distance α is calculated, and the distance switching determination value is calculated. L _TH or RSSI switching determination value R _TH is used, and by comparing these switching determination values with the actual RSSI value or the distance between the mobile station 10 and the base station 12, the determination by the determination unit 50 and the positioning method Switching by the switching unit 72 was performed. However, switching by the determination and positioning method switching unit 72 by the determination unit 50 is not limited to such embodiments, for example, the actual value or the mobile station 10 of the reception power P _R obtained by converting the RSSI value and the base station 12 May be determined based on whether or not the calculated distance measurement error is less than the maximum value α allowable for the distance measurement error.

  Further, in the above-described embodiment, each base station 12 and the positioning server 14 are connected by the wired cable 52, and exchange of data and delivery of commands are performed. However, the present invention is not limited to this. For example, infrared rays, radio waves, Communication may be performed using ultrasonic waves or the like. That is, each base station 12 and positioning server 14 need only be connected so as to communicate with each other by any means, and the connection may be wireless.

In the foregoing embodiments, switching threshold value R _TH values of the received power P _R obtained by converting the RSSI value _or the switching threshold value L _TH distance corresponding thereto may be calculated each time, advance It may be determined. The calculation of the switching determination value is performed by the determination unit 50 of the base station 12 in the first and second embodiments, and by the positioning method switching unit 72 of the positioning server 14 in the third and fourth embodiments. However, it is not limited to such a mode. That is, it may be calculated in the positioning server 14 in the above-described first and second embodiments, or may be calculated in any of the base stations 12 in the third and fourth embodiments.

In the foregoing embodiment, whether or not the value of the received power P _R obtained by converting the RSSI value is below the switching threshold value R _TH determines the distance between the mobile station 10 and the base station 12 is switching threshold value The RSSI value and the distance between the mobile station 10 and the base station 12 may be determined based on whether or not _LTH is exceeded, based on the relationship of the formula (1) or the relationship of FIG. However, the conversion may be performed in consideration of other corrections and errors.

  In the above-described third and fourth embodiments, the positioning unit 56 of the positioning server 14 includes the TDOA positioning unit 70 and the TOA positioning unit 71 corresponding to the second positioning means, and the positioning method switching unit 72 performs the first operation. By switching to the RSSI positioning unit 68 corresponding to the positioning means, positioning is performed by either the TDOA positioning unit 70 or the TOA positioning unit 71. At this time, which one is used can be arbitrarily determined. For example, when the time of the clock 31 of the mobile station 10 and the time of the clock 44 of the base station 12 can be synchronized in the SC 12 of FIG. 13, the positioning is performed by the TOA positioning unit 71 and cannot be synchronized. In such a case, positioning by the TDOA positioning unit 70 may be performed. In addition, the positioning unit 56 of the positioning server 14 does not necessarily include both the TDOA positioning unit 70 and the TOA positioning unit 71, and may include at least one of them.

In the above-described third and fourth embodiments, in the movable area 5 of the mobile station, the distance from at least three base stations is shorter than the distance switching determination value L _TH , for example, in the example of FIG. If there is no hatched area, the effect is not produced. Conversely, it can be said that it is a requirement of the present invention to arrange the base station 12 so as to satisfy this requirement.

In the third and fourth embodiments described above, when the positioning of the mobile station 10 cannot be performed by the RSSI positioning unit 68, that is, when the determination of SC9 is denied, the positioning by the TDOA positioning unit 70 is performed. However, the present invention is not limited to this (after SC10), and when the positioning of the mobile station 10 cannot be performed by the RSSI positioning unit 68 (when the determination of SC9 is negative), the first and second embodiments described above are performed. It is also possible to execute (after SA8 in FIG. 9). In this way, when at least two or less base stations 12 exist at a position within the distance switching determination value L _TH from the mobile station 10, the base stations 12 for the base stations 12 are based on the RSSI value. And the base station 12 can be calculated.

  In the above-described embodiment, the mobile station 10 moves in a movable area provided as a plane. However, the present invention is not limited to this, and the mobile station 10 moves in a movable area provided as a space. Even in this case, the same applies.

It is a figure explaining an example of a structure of the mobile station positioning system of this invention. It is a figure explaining the coordinate system set to the movable area | region in the mobile station positioning system of this invention. It is a functional block diagram explaining the outline | summary of the function of the mobile station of this invention. It is a functional block diagram explaining the outline | summary of the function of the base station of this invention. It is a functional block diagram explaining the outline | summary of the function of the positioning server of this invention. It is a figure explaining the relationship between the value of RSSI, and the distance of a mobile station and a base station. It is a figure explaining an example of the relationship between the position of a mobile station, and the determination of a determination part. It is a figure explaining the principle which performs positioning of a mobile station based on the distance of a mobile station and each base station. It is a flowchart explaining the control operation | movement of the positioning of the mobile station by the mobile station positioning system of this invention. FIG. 10 is a flowchart for explaining a mobile station positioning control operation by the mobile station positioning system according to another embodiment of the present invention, which is used in combination with the flowchart of FIG. 9. It is a functional block diagram explaining the outline | summary of the function of the base station in another Example of this invention, Comprising: It is a figure corresponding to FIG. It is a functional block diagram explaining the outline | summary of the function of the positioning server in another Example of this invention, Comprising: It is a figure corresponding to FIG. It is a flowchart explaining the control operation | movement of the positioning of the mobile station by the mobile station positioning system in another Example of this invention, Comprising: It is a figure corresponding to FIG. It is a flowchart explaining the control operation | movement of the positioning of the mobile station by the mobile station positioning system in another Example of this invention, Comprising: It is a figure used in combination with the flowchart of FIG.

Explanation of symbols

8: Mobile station positioning system 10: Mobile station 12: Base station 14: Positioning server 46: RSSI acquisition unit (first ranging means)
42: Reception time measuring unit (second distance measuring means)
50: Determination unit (ranging means switching means)
68: RSSI positioning unit (first positioning means)
70: TDOA positioning unit (second ranging means)
71: TOA positioning unit (second ranging means)
72: Positioning method switching unit (positioning method switching means)

Claims (9)

A plurality of base stations receive radio waves transmitted from a mobile station, and the distance between each of the plurality of base stations and the mobile station calculated based on reception results of radio waves received by the plurality of base stations, respectively A mobile station positioning system that estimates the position of the mobile station based on the position of each of the plurality of base stations,
First distance measuring means for calculating a distance related value related to the distance between each of the plurality of base stations and the mobile station;
Second distance measuring means for calculating a distance-related value related to the distance between each of the plurality of base stations and the mobile station in a method different from the first distance measuring means;
For each of the plurality of base stations, ranging means switching means for switching from the first ranging means to the second ranging means based on information on the distance between each of the base stations and the mobile station; A mobile station positioning system comprising: The first ranging means calculates the distance between the base station and the mobile station based on the radio wave intensity from the mobile station received at each of the plurality of base stations,
The second distance measuring unit is configured to calculate a distance between the mobile station and the base station based on a propagation time of a radio wave from the mobile station to each of the plurality of base stations. Item 4. The mobile station positioning system according to Item 1. The ranging means switching means is configured to calculate the received radio wave intensity obtained by executing the first ranging means below a predetermined switching determination value or based on the received radio wave intensity. The switching from the first distance measuring means to the second distance measuring means when the distance between the mobile station and the base station exceeds a predetermined switching determination value. Mobile station positioning system. The distance measuring means switching means, when the distance calculated based on the movement history information of each of the plurality of base stations and the mobile station exceeds a predetermined switching determination value The mobile station positioning system according to claim 1 or 2, wherein the first ranging means is switched to the second ranging means. The first ranging means generates a ranging error according to the distance between the mobile station and the base station,
The ranging means switching means calculates a ranging error in the first ranging means based on information on the distance between each of the base stations and the mobile station, and the ranging error exceeds a predetermined value. In this case, the mobile station positioning system according to any one of claims 1 to 4, wherein the first ranging means is switched to the second ranging means. A plurality of base stations receive radio waves transmitted from the mobile station, and the positions of the mobile stations are determined based on reception results of the radio waves respectively received by the plurality of base stations and positions of the plurality of base stations. A mobile station positioning system to estimate,
The distance between each of the plurality of base stations and the mobile station is calculated based on the strength of radio waves received by each of the plurality of base stations, and the position of the mobile station is estimated based on the calculated distance. A first positioning means;
The position of the mobile station is estimated based on either the distance calculated from the reception time of the radio wave when each of the plurality of base stations receives the radio wave or the time difference for each base station of the reception time of the radio wave A second positioning means for
Of the plurality of base stations, when the number of base stations necessary for positioning the mobile station by the first positioning means is within a predetermined distance from the mobile station, the first positioning means And a positioning means switching means for performing positioning by the second positioning means when there is no position, and a mobile station positioning system. The positioning means switching means is configured such that the intensity of radio waves received by each of the plurality of base stations obtained by executing the first positioning means exceeds a predetermined switching determination value or the intensity of the received radio waves Necessary for positioning the mobile station by the first positioning means such that the distance between each of the plurality of base stations calculated based on the mobile station and the mobile station is less than a predetermined switching determination value 7. The mobile station positioning system according to claim 6, wherein when there are only a small number of base stations, switching is performed from the first positioning means to the second positioning means. The positioning means switching means is configured such that a base station whose distance between the current mobile station whose position is predicted based on movement history information of the mobile station and each of the plurality of base stations is less than a predetermined value is the first base station. The switching from the first positioning means to the second positioning means when there are not as many base stations as necessary to perform positioning of the mobile station by the positioning means. Mobile station positioning system. The distance between each of the plurality of base stations calculated by the first positioning means and the mobile station causes a ranging error corresponding to the distance between each of the plurality of base stations and the mobile station. Yes,
The positioning means switching means calculates a ranging error in the first positioning means based on information on the distance between each of the base stations and the mobile station, and when the ranging error exceeds a predetermined value 7. The mobile station positioning system according to claim 6, wherein the switching from the first positioning means to the second positioning means is performed.

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