JP2010135938A - Base station selection method, moving station localization system, moving station, and base station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a base station selection method for selecting a base station where transmission/reception of radio wave is successfully performed with a moving station, and to provide a moving station localization system for calculating a position of the moving station, and to provide the moving station and the base station. <P>SOLUTION: Radio wave whose phase is changed by a received intensity detecting part 52, according to a prescribed pattern transmitted by either the moving station 10 or a plurality of base stations 12 is received by an unselected station, and a maximum value and a minimum value of the reception intensity are detected for each base station 12. A selection part 64 selects a base station, where transmission/reception of the radio wave is performed with the base station 10, on the basis of the maximum value and the minimum value of the reception intensity detected by the received intensity detection part 52 for each of the plurality of base stations 12, so that influences, such as, interferences by a multi-path, are small, on the basis of the maximum value and the minimum value of radio waves whose phases are changed in the prescribed pattern, and the base station 12 where the interference is small, such as the interference due to the multi-path and transmission/reception of the radio waves to and from the moving station 10 is performed in a proper manner can be selected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a base station selection method, a mobile station positioning system, a mobile station, and a base station.

  A mobile station positioning system has been proposed in which radio waves transmitted from a mobile station are received by a base station capable of wireless communication with the mobile station, and the position of the mobile station is calculated based on the received intensity. For example, this is the technique described in Patent Document 1.

  In such a technique, the distance between the mobile station that transmits the radio wave and a plurality of base stations that receive the radio wave is calculated based on the received intensity of the received radio wave, and the mobile station is based on each of the calculated distances. Calculate the position.

  Here, if the relationship between the received intensity of the received radio wave and the distance between the mobile station and the base station is a relationship obtained in advance by experiment or simulation, under different conditions from the relationship, The distance calculated based on the reception strength is not necessarily accurate. Specifically, for example, when wireless communication by the mobile station and the base station is performed indoors, the reception intensity is affected by interference due to a reflected wave (multipath) from a wall surface or a floor surface. Therefore, the distance obtained by applying the relationship obtained in an environment where multipath influence does not occur to the reception intensity actually obtained in the environment where multipath influence occurs differs from the actual distance and includes an error. It will be a thing. For this reason, it is difficult to accurately calculate the position of the mobile station. The same applies when the mobile station receives radio waves transmitted from each of the plurality of base stations.

  To deal with this difficulty, Patent Document 1 has distance attenuation data based on statistical data on the relationship between the distance from a mobile station that is a radio wave transmission source and the attenuation of radio wave intensity. There has been disclosed a mobile station positioning system capable of measuring the position of a mobile station even in an environment where the propagation state of radio waves changes with time by measuring the position of the mobile station from the strength.

JP 2006-300918 A

  However, also in Patent Document 1, since the distance attenuation data is based on statistical data, the distance between the mobile station and the base station that has received the radio wave when the radio wave transmitted from the mobile station is attenuated. However, it may not be calculated accurately based on the received intensity of the received radio wave.

  The present invention has been made against the background of the above circumstances, and the object of the present invention is to receive radio waves transmitted from one of a mobile station and a plurality of base stations, and to communicate with the mobile station. To provide a base station selection method for selecting a base station that performs good radio wave transmission / reception, a mobile station positioning system that calculates the position of the mobile station based on the reception result, a mobile station, and a base station is there.

  In order to achieve this object, the present inventors have conducted various experiments and studies, and as a result, the mobile station and the base station change the phase of the radio wave transmitted by the mobile station, thereby moving the mobile station. It has been found that there is a certain relationship between fluctuations in radio wave reception intensity at the other of the station and the plurality of base stations and the magnitude of the multipath effect at the other.

  The present invention has been made based on such knowledge, and the invention according to claim 1 includes: (a) the other receives radio waves transmitted from one of the mobile station and the plurality of base stations, and A base station selection method for selecting a base station that performs good radio wave transmission / reception with a mobile station, wherein (b) the other receives a radio wave whose phase is changed by a predetermined pattern transmitted by the one. A reception strength detection step for detecting, for each base station, a maximum value and a minimum value of instantaneous reception strength corresponding to the phase changing in the predetermined pattern; and (c) the plurality of base stations by the reception strength detection step. A selection step for selecting a base station that performs good transmission and reception of radio waves with the mobile station based on the maximum value and the minimum value of the reception intensity detected for each station, and (d ) The phase of the predetermined pattern changes The phase change is such that the maximum value of the phase change amount, which is the difference between the phases before and after, is 2π radians, and there are a plurality of phase change values between 0 degree and the maximum value at substantially equal intervals. It is characterized by.

  In the invention according to claim 3, (a) the other side receives a radio wave transmitted from one of the movable mobile station and a plurality of base stations installed at known positions, and the reception result is A mobile station positioning system that calculates a position of the mobile station based on the phase change unit, wherein (b) the one side generates a transmission wave whose phase is changed according to a predetermined pattern; and (c) the phase change A transmission unit that transmits a transmission wave generated by the unit with a predetermined output, and (d) the other side receives a radio wave transmitted from the one side, and (e) is received by the reception unit. (F) a reception strength detection unit that detects an instantaneous reception strength of the received radio wave, and (f) based on a maximum value and a minimum value of the instantaneous reception strength detected for each base station by the reception strength detection unit. , A base on which radio wave transmission / reception with the mobile station is well performed A selection unit that selects a station; and (g) a positioning unit that calculates a position of the mobile station based on a reception result of a radio wave transmitted from or received by the base station selected by the selection unit; (H) In the predetermined pattern, the maximum value of the phase change amount, which is the difference between the phases before and after the phase change, is 2π radians, and the value of the phase change amount is between 0 degree and the maximum value. The pattern has a phase change such that a plurality of phases are present at substantially equal intervals.

  According to a sixth aspect of the present invention, (a) a phase changing unit that generates a transmission wave by changing a phase according to a predetermined pattern, and (b) a transmission wave generated by the phase changing unit by a predetermined output. And (c) a mobile station constituting the mobile station positioning system.

  The invention according to claim 7 includes: (a) a reception unit that receives radio waves; and (b) a reception intensity detection unit that detects instantaneous reception intensity of radio waves received by the reception unit. ) A base station constituting the mobile station positioning system.

  According to the base station selection method of claim 1, a radio wave whose phase is changed by a predetermined pattern transmitted by any one of the mobile station and the plurality of base stations by the reception intensity detection step is caused by the other. The instantaneous reception intensity that is received and detected for each base station corresponding to the phase that changes in the predetermined pattern is detected for each of the plurality of base stations by the reception intensity detection step by the selection step. Based on the maximum value and the minimum value of the intensity, a base station that performs good radio wave transmission / reception with the mobile station is selected. At this time, the predetermined pattern has a maximum phase change amount of 2π radians, which is the difference between the phases before and after the phase change, and the phase change value is between 0 degrees and the maximum value at substantially equal intervals. Since it is a pattern that causes a phase change such that there are multiple, based on the maximum and minimum values of the radio wave reception intensity whose phase is changed by the predetermined pattern, the influence of interference due to multipath is small, It is possible to select a base station that performs good transmission and reception of radio waves with the mobile station.

  Preferably, in the selection step, the base station is assumed to be a base station that performs better wireless communication with the mobile station as the difference between the maximum value and the minimum value of the instantaneous reception strength is smaller. It is characterized by selecting. In this way, even when the phase of the transmitted radio wave is changed, the base station that is less affected by multipath interference or the like is moved based on the small fluctuation in the instantaneous reception intensity value. It can be selected as a base station that performs good radio communication with a station.

  Further, according to the mobile station positioning system according to claim 3, the phase is set to a predetermined value by the phase changing unit included in any one of the movable mobile station and the plurality of base stations installed at known positions. A transmission wave changed according to a pattern is generated, the generated transmission wave is transmitted with a predetermined output by the transmission unit, and a radio wave transmitted from the one is received by the other reception unit, and the reception Based on the maximum value and the minimum value of the instantaneous reception intensity detected by the reception intensity detection unit for each base station by the selection unit by the intensity detection unit detected by the intensity detection unit. Then, a base station that performs good radio wave transmission / reception with the mobile station is selected, and the positioning unit transmits or receives power from the base station selected by the selection unit. Position of the mobile station is calculated based on the reception result. At this time, the predetermined pattern has a maximum phase change amount of 2π radians, which is the difference between the phases before and after the phase change, and the phase change value is between 0 degrees and the maximum value at substantially equal intervals. Since there are a plurality of patterns with phase changes, the influence of interference due to multipath, etc. based on the maximum and minimum values of instantaneous reception intensity of radio waves whose phases are changed by the predetermined pattern. The base station that is small and can transmit and receive radio waves to and from the mobile station can be selected, and the reception result at the base station selected to transmit and receive radio waves to and from the mobile station is used. Since the position of the mobile station is calculated, the position of the mobile station can be calculated with high accuracy.

  Preferably, the selection unit determines that the base station is a base station that performs better wireless communication with the mobile station as the difference between the maximum value and the minimum value of the instantaneous reception strength is smaller. It is characterized by selecting. In this way, even if the received intensity value changes the phase of the transmitted radio wave, the influence of multipath interference and the like is affected on the basis of small fluctuations in the received intensity value. A small base station can be selected as a base station in which radio communication with a mobile station is favorably performed.

  Preferably, the positioning unit has a maximum value of the instantaneous reception intensity detected by the reception intensity detection unit for radio waves transmitted from the base station selected by the selection unit or received by the base station. The position of the mobile station is calculated as an average of the minimum value and a reception result related to the base station. In this way, since the value obtained by reducing the influence of interference due to multipath, etc. is used as the reception result, the position of the mobile station can be accurately calculated by the positioning unit.

  According to the mobile station of claim 6, the phase change unit generates a transmission wave whose phase is changed according to a predetermined pattern, and the transmission unit transmits the generated transmission wave with a predetermined output. Therefore, it can be suitably used in the above-described mobile station positioning system.

  According to the base station of claim 7, since the radio wave is received by the reception unit, and the instantaneous reception intensity of the radio wave received by the reception unit is detected by the reception intensity detection unit, It can be suitably used in a station positioning system.

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

  FIG. 1 is a diagram for explaining an outline of the configuration of a mobile station positioning system 8 according to an embodiment of the present invention. In FIG. 1, a mobile station positioning system 8 includes, for example, a mobile station 10 that can move in a plane parallel to the figure, and a plurality of base stations whose positions are known. The base station 12B, the third base station 12C, the fourth base station 12D (hereinafter referred to as “base station 12” if they are not distinguished from each other), and these base stations 12 are connected by, for example, a communication cable 18. For example, the server 14 is configured to be capable of information communication. In the mobile station positioning system 8, the number of base stations 12 exceeding the minimum number necessary for positioning the mobile station 10 is included. In the mobile station positioning system 8, for example, coordinates as shown in FIG. 1 are defined so that the positions of the mobile station 10 and the base station 12 can be represented. In the following description, the coordinates of the mobile station 10 are (x, y), the coordinates of the first base station 12A are (xa, ya), the coordinates of the second base station 12B are (xb, yb), and the third base station. The coordinates of 12C are represented as (xc, yc), and the coordinates of the fourth base station 12D are represented as (xd, yd).

  As shown in FIG. 1, the mobile station 10 and the base station 12 constituting the mobile station positioning system 8 are provided in a space surrounded by a wall 20 that reflects radio waves. Therefore, for example, when the base station 12 receives a radio wave transmitted from the mobile station 10, the direct wave that directly reaches the mobile station 10 that has transmitted the radio wave without being reflected by the wall 20 or the like is reflected by the wall 20 or the like. Both of the reflected waves reaching the base station 12 are received.

  The mobile station 10 and the base station 12 can wirelessly communicate with each other. Similarly, each of the plurality of base stations 12 can wirelessly communicate with each other. For example, when the radio wave is received by an identification code (ID) or a unique spreading code included in the radio wave transmitted by each of the mobile station 10 and the base station 12, it is transmitted by the mobile station 10 or any of the base stations 12. It is possible to identify whether it is a radio wave. Further, by having a common encoding and decoding procedure, information can be exchanged between the mobile station 10 and the base station 12 and between the plurality of base stations 12.

  FIG. 2 is a functional block diagram for explaining a main part of the functions of the mobile station 10. As shown in FIG. 2, the mobile station 10 has an antenna 22 for transmitting / receiving radio waves, a radio unit 23 having a function for transmitting / receiving radio waves, and a control unit 26 for controlling the radio unit 23. And functionally. The wireless unit 23 includes a phase change unit 28 that changes the phase of a radio wave to be transmitted and an amplification unit 27 that amplifies the output from the phase change unit 28. It comprises a transmission / reception switching unit 29 that switches between transmission and reception of radio waves.

  Here, in the base station 12 that receives the radio wave transmitted from the mobile station 10, the base station 12 that is at an equal distance from the mobile station 10 receives the radio wave with the same reception intensity regardless of the direction from the mobile station 10. Therefore, the antenna 22 is preferably an antenna having no directivity.

  The radio unit 23 performs transmission / reception of radio waves in the mobile station 10 and is switched between a transmission state and a reception state by a control unit 26 described later. That is, the wireless unit 23 switches and connects a transmitting unit 25 for transmitting radio waves, a receiving unit 24 for receiving radio waves, and an antenna 22 to either the transmitting unit 25 or the receiving unit 24. A transmission / reception switching unit 29 is functionally provided.

  The transmission unit 25 transmits radio waves by the antenna 22 according to the control content instructed by the control unit 26, that is, the content of the signal wave, the frequency of the carrier wave, the transmission output and the like. The transmission unit 25 includes a carrier wave generation unit 32, a phase change unit 28 including modulation units 36 and 38, and an amplification unit 27 including a transmission amplifier. The carrier generation unit 32 is a carrier generation circuit such as an oscillator. The modulators 36 and 38 are, for example, modulators such as multipliers. The phase changing unit 28 generates a transmission wave while changing the phase according to a predetermined pattern. The amplifying unit 27 amplifies the radio wave generated by the phase changing unit 28 to a predetermined transmission output. At this time, the transmission / reception switching unit 29 performs switching so that the antenna 22 and the transmission unit 25 can transmit, and the radio wave amplified by the amplification unit 27 is transmitted from the antenna 22. The configuration of the phase change unit 28 will be described later.

  The receiving unit 24 amplifies the radio wave received by the antenna 22 and extracts a signal wave by performing predetermined demodulation processing or the like. At this time, the transmission / reception switching unit 29 performs switching so that the antenna 22 and the receiving unit 24 can transmit, and the radio wave received by the antenna 22 is transmitted to the receiving unit 24. Thus, the receiving unit 24 includes a receiving amplifier, a demodulator, and the like.

  As described above, the transmission / reception switching unit 29 switches between a state in which the antenna 22 and the reception unit 24 can transmit and a state in which the antenna 22 and the transmission unit 25 can transmit. The operation is controlled by 26.

  The phase changing unit 28 changes the phase of the radio wave for positioning transmitted by the wireless unit 23. FIG. 3 is a diagram illustrating an example of the configuration of the phase changing unit 28. The phase change unit 28 includes a transmission signal generation unit 30, an oscillation unit 32, a phase shift unit 34, multiplication units 36 and 38, and an addition unit 40. The transmission signal generator 30 receives an instruction to transmit a radio wave for positioning from the control unit 26, and generates an IQ signal that determines the phase of the radio wave for positioning. The adder 40 is a so-called adder and outputs a sum of a plurality of inputs. This IQ signal is composed of an I signal and a Q signal, and controls the magnitudes of the I component and the Q component in the output of the adder 40 described later. That is, in the present embodiment, the phase change unit 28 performs IQ modulation.

  The oscillation unit 32 generates a carrier wave having a predetermined frequency and supplies the carrier wave to the I-phase multiplication unit 36 and the phase shift unit 34 which are multiplication units for the I-phase component. The phase shifter 34 shifts (for example, advances) the phase of the carrier wave generated by the oscillator 32 by 90 degrees (π / 4). The I-phase multiplication unit 36 multiplies the I signal generated by the transmission signal generation unit 30 and the carrier wave generated by the oscillation unit 32. A Q-phase multiplier 38, which is a multiplier for the Q-phase component, multiplies the Q signal generated by the transmission signal generator 30 and the carrier wave whose phase is shifted by the phase shifter 34. Further, the adder 40 adds the output of the I-phase multiplier 36 and the output of the Q-phase multiplier 38 and outputs the sum. This output is used as a transmission signal, amplified by the amplifying unit 27, and then transmitted wirelessly.

FIG. 4 is a diagram for explaining the relationship between the IQ signal generated by the transmission signal generator 30 and the output of the adder 40, that is, the output of the phase change unit 28. For example, when the I signal generated by the transmission signal generator 30 is 1 and the Q signal is 0, the output of the phase change unit 28 is as shown in FIG. When the I signal is 0 and the Q signal is 1, the output of the phase change unit 28 is as shown in (2) of FIG. When the normalized magnitudes of the I signal and the Q signal generated by the transmission signal generating unit 30 are both 1 / √2, the output of the phase changing unit 28 is as shown in (3) of FIG. become. As described above, by changing the I signal and the Q signal generated by the transmission signal generating unit 30, the phase of the output of the phase changing unit 28 can be changed. For example, the phase angle φi is
φi = π / M * ((i + 1) * i) / 2) (i = 0, 1, 2,...)
In this way, the phase change amount Δφi = φi−φi−1 can be changed by π / M. Here, the natural number M is called the step number. Further, the phase of the output of the phase changing unit 28 is represented as an angle φ formed by the axis representing the I phase and the vector representing the output in FIG.

  FIG. 5 illustrates the phase at the output of the phase changing unit 28 when the number of steps M is M = 4, and the I and Q signals generated by the transmission signal generating unit 30 when outputting the phase. FIG. As shown in FIG. 5, the change in phase at the output of the phase change unit 28 is achieved by changing the I signal and the Q signal to -1, -1 / √2, 0, 1 / √2, 1 respectively. The phase change amount Δφi can be changed between 0 and 2π radians so as to increase by π / 4. In other words, eight phase change amounts can be arranged at an equal interval of π / 4 between 0 and 2π radians (assuming that 0 and 2π are the same because they are the same). FIG. 6 shows an example of the output of the phase change unit 28 at this time, that is, the time change of the output of the phase change unit 28 in which the phase change amount Δφi increases by π / 4 at every constant time T. It is a thing.

  Returning to FIG. 2, the control unit 26 controls the operation of the mobile station 10. Specifically, the control unit 26 processes information received by the radio unit 23, operates the radio unit 23, and more specifically. Specifically, control of transmission output and transmission frequency, generation of a signal wave transmitted wirelessly, and the like are performed. The control unit 26 is implemented by, for example, a known microcomputer. The wireless unit 23 and the control unit 26 have a function as a transmitter.

  FIG. 7 is a functional block diagram for explaining a main part of the functions of the base station 12. As shown in FIG. 7, the base station 12 has an antenna 42 for transmitting and receiving radio waves. The base station 12 includes a radio unit 44 that transmits and receives radio waves via the antenna 42, a control unit 46, a signal detection unit 50, a reception intensity detection unit 52, a clock 54, a communication interface 56, and the like. . 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 to perform a signal according to a program stored in the ROM in advance. By performing processing, these functions are performed.

  Similar to the antenna 22 of the mobile station 10 described above, the antenna 42 is used for transmission / reception of radio waves, and an antenna having no directivity is preferably used. The radio unit 44 transmits and receives radio waves in the base station 12 in the same manner as the radio unit 23 of the mobile station 10 described above, and is switched between a transmission state and a reception state by a control unit 46 described later. At the time of transmitting the radio wave, the radio unit 44 transmits the radio wave by the antenna 42 corresponding to each of the radio units 44 according to the control content instructed by the control unit 46, that is, the content of the signal wave, the frequency of the carrier wave, the transmission output, and the like. As described above, the radio unit 44 includes a carrier wave generation circuit, a modulator, a transmission amplifier, and the like. The radio unit 44 amplifies the radio wave received by the antenna 42 when receiving the radio wave, and extracts a signal wave by performing a predetermined demodulation process or the like. That is, the radio unit 44 includes a reception amplifier, a demodulator, and the like. The wireless unit 44 corresponds to a receiving unit.

  The control unit 46 controls the operation of the base station 12. Specifically, the control unit 46 processes a signal extracted by the radio unit 44, processes information obtained from the server 14 described later, The operation of the base station 12 is changed. The operation of the wireless unit 44, more specifically, control of transmission output and transmission frequency, generation of a signal wave transmitted wirelessly, and the like are performed. The control unit 46 is implemented by, for example, a known microcomputer.

  The signal detection unit 50 is a circuit composed of a diode, an operational amplifier, a resistor, and a capacitor, and performs processing for extracting a signal addressed to itself from the radio wave received by the radio unit 44.

  The reception intensity detection unit 52 detects the reception intensity of a received radio wave that is one of reception results when the radio unit 44 receives a radio wave for positioning transmitted from the mobile station 10. This reception intensity is an instantaneous reception intensity detected as an instantaneous value, and is detected corresponding to a change in phase, that is, for each state of the changing phase. This received intensity is used by the positioning unit 66 of the server 14 described later for calculating the position of the mobile station 10 and the like. In the present embodiment, for example, an RSSI (Receive Signal Strength Indicator) that is an index obtained by quantifying the intensity of the received radio wave is used as the reception intensity.

  The clock 54 supplies time information to the reception time detection unit 48, the control unit 46, and the like. The control unit 46 records the time variation of the reception intensity based on the reception intensity value sequentially detected by the reception time detection unit 52 and the time information supplied from the clock 54, and a communication interface described later. 56 to the server 14.

  Incidentally, as described above, in the present embodiment, the positioning radio wave transmitted from the mobile station 10 is transmitted with the phase changed by the phase changing unit 28. On the other hand, in the present embodiment, as described above, the radio wave transmitted from the mobile station 10 reaches the base station indirectly after being directly reflected by the direct wave that reaches the base station 12 and the wall or floor surface. Each becomes a reflected wave and is received at the base station 12. Since the propagation distance of the reflected wave is longer than that of the direct wave, the reflected wave is received by the base station 12 later than the direct wave. Therefore, although the phase change in the radio wave for positioning is expressed in both the direct wave and the reflected wave, the phase change in the reflected wave is detected by the base station 12 later than the phase change in the direct wave. The

FIG. 8 is a conceptual diagram showing the time change of the reception intensity of the radio wave for positioning received at the base station 12 separated into a direct wave component and a reflected wave component. As shown in FIG. 8, the phase change in the radio wave for positioning transmitted from the mobile station 10 is detected in the direct wave at times Tc1, Tc2, and Tc3, respectively. On the other hand, in the reflected wave, the phase change is detected at times Tc1 ′, Tc2 ′, and Tc3 ′, respectively. Tc1 and Tc1 ′, Tc2 and Tc2 ′, Tc3 and Tc3 ′ are separated from each other by time t _diff . This time t _diff is the difference in propagation time between the two based on the difference in propagation distance between the direct wave and the indirect wave.

FIG. 9 shows the predetermined pattern, the change in the phase of the direct wave and the reflected wave in the base station 12, when the phase in the radio wave for positioning transmitted from the mobile station 10 is changed along the predetermined pattern. FIG. 5 is a diagram expressing the phase difference between the phase of the direct wave and the phase of the reflected wave on the same time axis. As shown in the upper part of FIG. 9, in the mobile station 10, the number of steps M of the phase change unit 28 is set to M = 4, and the phase change amount Δφi can be increased in units of π / 4. . Then, the radio wave for positioning transmitted from the mobile station 10 has a phase that is initially set to 0 by a phase change amount Δφi every predetermined time interval ts from the time Ts1 by the phase change unit 28. 4, 3π / 4, 6π / 4, 10π / 4, 15π / 4, 21π / 4, 28π / 4, 36π / 4, and so on. That is, the predetermined pattern in the present embodiment refers to the phase of a radio wave for positioning to be transmitted at every predetermined time ts by π / 4, 2π / 4, 3π / 4, 4π / 4, 5π / 4, 6π / 4, 7π / 4, and 8π / 4 are respectively advanced. Note that the value of the time interval ts is set so that the difference in propagation time between a direct wave and a reflected wave, which will be described later, is larger than t _diff .

On the other hand, the positioning radio wave transmitted from the mobile station 10 is calculated by the linear distance (direct wave propagation distance) between the mobile station 10 and the base station 12 that receives the positioning radio wave and the speed of the radio wave. The direct wave arrives at the base station 12 and is received after the elapse of the direct wave propagation time t _tran . For example, in FIG. 9, the radio wave transmitted at time Ts1 is received by the base station 12 at time Tc1 after the elapse of time t _tran . In addition, if the difference in propagation time between the direct wave and the reflected wave, which is calculated by the distance difference between the direct wave and the reflected wave and the velocity of the radio wave, is t _diff , the direct wave is received by the base station 12. Later, after the elapse of time t _diff , the reflected wave is received by the base station 12. For example, in FIG. 9, the reflected wave corresponding to the radio wave received by the base station 12 as a direct wave at time Tc1 is received by the base station 12 at time Tc1 ′ after the elapse of time t _diff from time Tc1. That is, Tc1′−Tc1 = t _diff and Tc1′−Ts1 = t _diff + t _tran . The phase change in the radio wave for positioning transmitted from the mobile station 10 is also detected as a change in the phase of the direct wave at the base station 12 after the elapse of time t _tran from the phase change in the mobile station 10, and further, the time t _diff , I.e., after the time t _tran + t _diff elapses from the phase change in the mobile station 10, the base station 12 detects the phase change of the reflected wave.

  The lower part of FIG. 9 represents the change in the phase of the direct wave and the change in the phase of the reflected wave received by the base station 12, and the change in the phase difference between the phase of the direct wave and the phase of the reflected wave. In the lower part of FIG. 9, the phase of the radio wave received as a direct wave by the mobile station 10 before the change of the phase of the radio wave for positioning transmitted from the mobile station 10, that is, before the time Tc1, is set as a reference (= 0). ) For convenience, it may be different from the phase of the radio wave for positioning transmitted by the mobile station 10 in the upper part of FIG.

  Here, attention is focused on the phase difference between the phase of the direct wave and the phase of the reflected wave. First, the phase of the direct wave received by the base station 12 is set to 0 before the phase of the radio wave for positioning transmitted from the mobile station 10 is changed, that is, before the time Tc1. At this time, if the phase of the reflected wave is ψ, which is a value determined by the difference between the propagation distance of the direct wave and the propagation distance of the reflected wave and the wavelength of the radio wave, the phase difference between the two is ψ.

  When the time Tc1 elapses, the phase of the direct wave is advanced by π / 4 at the time Ts1 at the mobile station 10, and thus is further advanced by π / 4 than before, that is, π / 4. On the other hand, since the reflected wave arrives at the mobile station 10 before time Ts1, that is, before the phase is advanced, the phase of the reflected wave continues to be ψ. Therefore, the phase difference defined by the difference between the phase of the reflected wave and the phase of the direct wave is ψ−π / 4.

When the time Tc1 ′, that is, after the elapse of the time t _diff from the time Tc, the phase of the direct wave continues to be π / 4, while the phase of the reflected wave is also advanced by π / 4 at the time Ts1 in the mobile station. Therefore, it is advanced by π / 4, that is, ψ + π / 4. Therefore, the phase difference between them is ψ.

  When the time Tc2 elapses, the phase of the direct wave is further advanced by 2π / 4 at the time Ts2 at the mobile station 10, so that the phase is advanced by 3π / 4 before the phase is advanced, that is, before the time Ts1. That is, 3π / 4. On the other hand, since the reflected wave arrives at the mobile station 10 before time Ts2, that is, before the phase is further advanced by 2π / 4, the phase of the reflected wave continues to be ψ + π / 4. Therefore, the phase difference between the two becomes ψ-2π / 4.

As described above, in the time section Tci <t ≦ Tc (i + 1) (i = 1, 2,...) In FIG. 9, reception is performed by the base station 12 in the time section Tci <t ≦ Tci ′ (= Tci + t _diff ). The direct wave to be performed is after the phase change performed at the time Tsi in the mobile station 10, while the reflected wave is the one before the phase change performed at the time Tsi in the mobile station 10. The phase difference between the two is ψ−iπ / 4.

  In the time interval Tci ′ <t ≦ Tc (i + 1), both the direct wave and the reflected wave received at the base station 12 are after the phase change performed at the time Tsi in the mobile station 10. The phase difference between them is ψ.

  Thus, each time the phase of the radio wave for positioning transmitted by the mobile station 10 is changed according to the predetermined pattern, the phase difference between the phase of the direct wave and the phase of the reflected wave increases by π / 4. To change. Therefore, the phase difference can be changed by 2π by changing the phase of the radio wave for positioning eight times.

  When a plurality of radio waves interfere with each other, the result of the interference varies greatly depending on the phase of each radio wave. That is, if the two are in phase, the received intensity is strengthened, and if the two are in reverse, they are weakened. Also in the present embodiment, the direct wave and the reflected wave received at the base station 12 interfere with each other. On the other hand, the phase difference between the phase of the direct wave and the phase of the reflected wave changes with a change in the phase of the radio wave for positioning as described above with reference to FIG. Since the reception intensity of the radio wave detected by the reception intensity detection unit 52 of the base station 12 is actually the reception intensity when the direct wave and the reflected wave are received together, the order of the direct wave and the reflected wave is low. The interference that changes with the change in phase difference also appears as this received intensity.

  In the time interval Tci <t ≦ Tci ′ in FIG. 9, the phase difference between the phase of the direct wave and the phase of the reflected wave corresponds to the phase change amount Δφi. Therefore, by setting a plurality of (eight in this case) phase change amounts Δφi between 0 and 2π at equal intervals such as π / 4, the phase change amount Δφi is directly set regardless of the value of the phase ψ of the reflected wave. There is always a time interval in which the phase difference between the wave phase and the reflected wave phase is approximately zero and a time interval in which the phase difference is approximately π. For example, if ψ is π / 2, in the time interval Tc2 <t ≦ Tc2 ′, the phase difference between the phase of the direct wave and the phase of the reflected wave is almost 0, the reception strength is strengthened, and the reception strength is maximized, In the time interval Tc6 <t ≦ Tc6 ′, the phase difference between the phase of the direct wave and the phase of the reflected wave is approximately π, the reception strength is weakened, and the reception strength is minimized.

FIG. 10 illustrates an example of the reception intensity detected by the reception intensity detector 52 of the base station 12 when the phase of the radio wave for positioning transmitted from the mobile station 10 changes as shown in FIG. It is a figure to do. The horizontal axis in FIG. 10 represents time t and corresponds to the time in FIG. As shown in FIG. 10, when the phase difference between the phase of the direct wave and the phase of the reflected wave is ψ, the received intensity is P0, while the time interval Tci <t ≦ Tci ′ (= Tci + t _diff ) (i = 1, 2,... 8), the reception intensity is in accordance with the phase difference ψ-iπ / 4 between the phase of the direct wave and the phase of the reflected wave. That is, the reception intensity corresponds to a phase that changes as shown in FIG. 5 which is a predetermined pattern. In the following description, the time period _{Tci <t ≦ Tci '(=} Tci + t diff) (i = 1,2, ... 8) the time interval (i) (i = 1,2, ... 8) also referred to. As will be described later with reference to FIG. 11, a time interval Tci <t ≦ Tci ′ (= Tci + t _diff ) (i) in which a reception intensity corresponding to the phase difference ψ−iπ / 4 between the phase of the direct wave and the phase of the reflected wave is obtained. = 1, 2,... 8), the reception intensity detector 52 needs to receive the value of this time interval, that is, the time interval Tci that is the reception intensity corresponding to the phase change point of the phase that changes in a predetermined pattern. Only the reception intensity of <t ≦ Tci ′ (= Tci + t _diff ) (i = 1, 2,..., 8) may be output as the detection result.

  As shown in FIG. 10, when the phase of the radio wave for positioning transmitted from the mobile station 10 is changed, the received radio wave detected by the reception intensity detecting unit 52 of each base station 12 is associated with this change. The reception strength also changes. This change in reception intensity differs for each base station based on the difference in propagation distance between the direct wave and the reflected wave. FIG. 11 is a table showing changes in reception intensity detected by the reception intensity detection unit 52 in each of the first base station 12A to the fourth base station 12D. In FIG. 11, the receiving section (i) (i = 1, 2,... 8) corresponds to that of FIG. The length of the reception section (i) is defined by the difference between the propagation time of the direct wave and the propagation time of the reflected wave. The propagation path and propagation distance of the reflected wave are different for each base station 12, and Since the distance between the mobile station 10 and the base station 12, that is, the propagation distance of the direct wave is also different for each base station 12, the length of the reception interval (i) is different for each base station 12. Each reception intensity in FIG. 10 indicates reception of radio waves received with a time interval in which the phase difference between the direct wave phase and the reflected wave phase corresponding to the reception interval (i) is ψ−iπ / 4 as the reception time interval. It means strength and is not related to the length of the reception section (i) for each base station 12. The reception intensity in the reception section (i) is, for example, the detection of the reception intensity value by the reception intensity detection unit 52 a plurality of times in the reception section (i), and the average of the reception intensity values in the plurality of times. Used. That is, according to this, reception intensity corresponding to a phase that changes in a predetermined pattern can be obtained even with an average of a plurality of times.

  Returning to FIG. 7, the communication interface 56 transmits and receives information from the base station 12 to the server 14 and other base stations 12 via the communication cable 18. For example, from each base station 12 to the server 14, information on the reception time of the radio wave for positioning detected by the reception time detection unit 48 and the time change of the reception intensity of the radio wave detected by the reception intensity detection unit 52. Information or the like is transmitted via the communication interface 56. In addition, commands relating to the operation of the base station 12 and the mobile station 10 are transmitted from the server 14 to the base station 12 and received via the communication interface 56.

  FIG. 12 is a functional block diagram for explaining a main part of the functions of the server 14. As shown in FIG. 12, the server 14 is configured to functionally include a selection unit 64, a positioning unit 66, a communication interface 62, and the like. The server 14 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 signals according to a program stored in the ROM in advance. By performing the processing, necessary operations and the like are executed.

  The communication interface 62 transmits / receives information via the communication cable 18 in the same manner as the communication interface 56 of the base station 12 described above. Specifically, the server 14 transmits / receives information to / from the base station 12. Do. For example, a command for controlling the operation is transmitted to the base station 12, a radio wave reception time for positioning detected by the reception time detection unit 48 of the base station 12, or a reception intensity detection unit 52 is detected. Information about the received intensity of the received radio wave is received from the base station 12.

  The selection unit 64 transmits and receives radio waves to and from the mobile station 10 based on the maximum value and the minimum value of the reception intensity detected by the reception intensity detection unit 52 for the radio waves for positioning received at each base station 12. The base stations 12 are ranked in the order in which they are performed well. Further, the selection unit 64 selects the base station 12 used for calculating the position of the mobile station 10 in the positioning unit 66 to be described later, based on the ranking made for each base station 12.

  The selection unit 64 ranks the base stations 12 as follows. First, the selection unit 64 extracts, for each base station 12, the maximum value and the minimum value in the time change of the reception intensity detected by the reception intensity detection unit 52 of each base station 12, and the reception intensity that is the difference between the two values. Calculate the difference. Here, the time change of the reception intensity is detected at the time when the phase difference between the phase of the direct wave and the phase of the reflected wave changes by at least 2π, as shown in FIG. 9 or FIG.

  The selection unit 64 ranks the base stations 12 on the assumption that radio wave transmission / reception with the mobile station 10 is favorably performed in the order of the small reception intensity difference for each base station 12 calculated. This is because the greater the fluctuation of the reception intensity at the base station 12, the greater the influence of the reflected wave, that is, the multipath.

  In addition, the selection unit 64 determines that the number of base stations 12 required for the calculation of the position of the mobile station 10 in the positioning unit 66 is favorably transmitted and received with the mobile station 10 by the ranking. The base station 12 is selected from the base stations 12 included in the mobile station positioning system 8 in order. The number of base stations 12 required for calculating the position of the mobile station 10 in the positioning unit 66 is defined in advance in the mobile station positioning system 8 depending on the range in which the mobile station 10 moves.

  The ranking of the base stations 12 by the selection unit 64 will be specifically described with reference to FIG. When the reception intensity at each base station 12 is obtained as shown in FIG. 11, the selection unit 64 extracts the maximum value and the minimum value of the reception intensity at each base station 12 and calculates the difference in reception intensity. In the example of FIG. 11, the maximum value of the reception strength of the first base station 12A is 20, the minimum value is 0, and the reception strength difference is 20. Similarly, the maximum value of the reception strength of the second base station 12B is 15, the minimum value is 5, and the reception strength difference is 10. The maximum value of the reception strength of the third base station 12C is 25, the minimum value is −5, The strength difference is 30, the maximum value of the reception strength of the fourth base station 12D is 13, the minimum value is 7, and the reception strength difference is 6. As a result, the fourth base station 12D having the smallest reception intensity difference is the base station that performs the best transmission / reception of radio waves with the mobile station 10, followed by the second base station 12B, the first base station 12A, In the order of 3 base stations 12C, ranking is performed when radio wave transmission / reception with the mobile station 10 is successfully performed. Furthermore, assuming that the mobile station 10 moves on the plane and the base station necessary for calculating the position of the mobile station 10 is three stations in the positioning unit 66, Three base stations 12 are selected in the order in which radio wave transmission / reception is performed satisfactorily. That is, the three base stations 12 of the fourth base station 12D, the second base station 12B, and the first base station 12A are selected as base stations used for calculating the position of the mobile station 10 in the positioning unit 66.

  As described above, the mobile station positioning system 8 according to the present invention selects the base station selection system 9 that selects the base station 12 that transmits and receives radio waves satisfactorily from a plurality of base stations 12 that have received radio waves transmitted from the mobile station 10. Is substantially comprised. Selection of the base station 12 in this base station selection system 9 is performed based on the base station selection method of the present invention. The operation of the reception intensity detection unit 52 corresponds to the reception intensity detection process, and the operation of the selection unit 64 corresponds to the selection process.

  Returning to FIG. 12, the positioning unit 66 calculates the position of the mobile station 10 using the base station 12 selected by the selection unit 64. Specifically, the positioning unit 66 calculates the position of the mobile station 10 based on the reception strength of the radio wave for positioning detected by the reception strength detection unit 52 in the base station 12 selected by the selection unit 64. To do. That is, the reception intensity of the radio wave for positioning corresponds to the reception result.

  The positioning unit 66 includes a reception intensity calculation unit 68 that calculates the reception intensity of radio waves for positioning based on the time change of the reception intensity of radio waves for positioning measured at each base station 12. The reception intensity calculation unit 68 obtains the average of the maximum value and the minimum value in the time change of the reception intensity of the radio wave for positioning obtained at each base station 12 as shown in FIG. Calculated as the radio wave reception strength for. In this way, it is possible to calculate a more accurate received intensity value considering the influence of the reflected wave (multipath).

FIG. 13 is a diagram for explaining the reception intensity calculation operation by the reception intensity calculator 68. As described above, the reception intensity calculation unit 68 calculates the average P _AV (= (Pmax + Pmin) / 2) between the maximum value Pmax and the minimum value Pmin of the radio wave reception intensity measured at the base station 12. The reception strength value for positioning is used. This value is represented by a broken line in FIG. On the other hand, unlike the present embodiment, when the phase of the radio wave for positioning transmitted from the mobile station 10 is not changed, the reception intensity of the radio wave for positioning transmitted from the mobile station 10 in the base station 12 is: For example, it becomes a constant value of P _DEF in FIG. The value of the reception intensity P _DEF is the reception intensity when receiving both the direct wave and the reflected wave, and includes a multipath effect. Thus, by calculating the reception intensity of the radio wave for positioning by the reception intensity calculation unit 68, it is possible to calculate a more accurate reception intensity value in consideration of the influence of the reflected wave (multipath). Specifically, taking FIG. 11 as an example, the reception intensity of the radio wave for positioning in the first base station 12A is calculated as an average value PAV = 10 of the maximum value Pmax = 20 and the minimum value Pmin = 0. The Similarly, the reception intensity of the radio wave for positioning at the second base station 12B is the average value PAV = 10 of the maximum value Pmax = 15 and the minimum value Pmin = 5, and the radio wave intensity for positioning at the third base station 12C. The reception intensity is an average value PAV = 15 between the maximum value Pmax = 25 and the minimum value Pmin = −5, and the reception intensity of radio waves for positioning in the fourth base station 12D is the maximum value Pmax = 13 and the minimum value Pmin =. 7 and an average value PAV = 10, respectively.

  Subsequently, the positioning unit 66 determines the position of the mobile station 10 for each of the base stations 12 selected by the selection unit 64 based on the value of the reception intensity of the radio wave for positioning calculated by the reception intensity calculation unit 68. Is calculated. The reception intensity when a radio wave transmitted with a predetermined output is received and the radio wave propagation distance D, that is, the distance between the mobile station 10 and the base station 12 are in a one-to-one relationship as shown in FIG. . Therefore, the relationship shown in FIG. 14 is stored in advance in a storage device or the like (not shown) of the server 14, and the radio wave reception intensity for each base station 12 is determined based on this relationship between the base station 12 and the mobile station 10. Can be converted into a distance. In this way, the positioning unit 66 calculates the distance between each base station 12 and the mobile station 10.

  The positioning unit 66 continues to know the distance between each of the base stations 12 selected by the selection unit 64 and the mobile station 10 and the base station 12 stored in a storage device or the like of the server 14 (not shown). The position of the mobile station 10 is calculated based on the information on the position of the mobile station 10. The process in which the positioning unit 66 calculates the position of the mobile station 10 using the first base station 12A, the second base station 12B, and the third base station 12C, which are examples of the base station selected by the selection unit 64, is shown in FIG. 15 will be described.

FIG. 15 is a diagram for explaining the principle of calculation of the position of the mobile station 10 by the positioning unit 66. The coordinates representing the position of the mobile station 10 are (x, y), the coordinates representing the position of the first base station 12A, which is the base station selected by the selection unit 64, are (xa, ya), and the second base station 12B If the coordinates representing the position are (xb, yb) and the coordinates representing the position of the third base station 12C are (xc, yc), these relationships are obtained by the following equation (1). Note that the arrangement of base stations 12 in FIG. 15 is different from that in FIG. 1 for the sake of simplicity.
(xa-x) ² + (ya-y) ² = r1 ²
(xb-x) ² + (yb-y) ² = r2 ² (1)
(xc-x) ² + (yc-y) ² = r3 ²
Here, r1, r2, and r3 (m) are distances from the first base station 12A, the second base station 12B, and the third base station 12C to the mobile station 10, respectively, as described above. It is a value obtained from the reception intensity of radio waves for positioning at each base station 12 calculated by the reception intensity calculation unit 68 and the relationship shown in FIG. 14, for example. Then, the positioning unit 66 calculates the position (x, y) of the mobile station 10 by solving the equation (1). As described above, when calculating the position of the mobile station 10 based on the position of the base station 12 and the distance between the base station 12 and the mobile station 10, if there are three or more expressions as the expression (1), the movement The position of the station 10 can be calculated as a solution. That is, it is only necessary that at least three or more base stations 12 can receive positioning radio waves transmitted from the mobile station 10. Therefore, in this embodiment, the selection unit 64 selects three base stations.

  16 to 18 are flowcharts for explaining an example of the control operation in the mobile station positioning system 8 of the present invention, and are flowcharts for explaining the operations of the server 14, the base station 12, and the mobile station 10, respectively. The flowcharts of FIGS. 16 to 18 are executed in cooperation with each other as described later.

  First, FIG. 16 for explaining the control operation of the server 14 will be described. In FIG. 16 (hereinafter, “step” is omitted) SA1, the server 14 transmits a positioning instruction signal for instructing the base station 12 to execute the calculation (positioning) of the position of the mobile station 10. Is done. This positioning instruction signal is (1) a command for causing the mobile station 10 to transmit a radio wave for positioning to any one of the plurality of base stations 12 (hereinafter referred to as “representative base station”). A command to be transmitted from the radio unit 44 of the station 12 to the mobile station 10, and (2) a positioning radio wave transmitted from the mobile station 10 to each of the plurality of base stations 12, and a received intensity detecting unit 52 And a command for detecting the reception intensity of the radio wave for the positioning. Among these, the command (1) is such that the server 14 does not have a function for transmission / reception of radio waves for wireless communication, so the command from the server 14 to the mobile station 10 is any base station 12. The representative base station that is any one of the base stations 12 is, for example, a base station 12 that is arbitrarily selected. In the base station 12 that has received the command in this step, the determination in step SB2 in the flowchart of FIG.

  In SA2, reception of information about the reception intensity of radio waves for positioning detected in each base station 12 that has received the command transmitted in SA1 is started. That is, as will be described later, each base station 12 detects the reception intensity of radio waves for positioning, and the detected reception result is transmitted to the server 14, and is transmitted from each base station 12. Reception of information on received reception strength is started. The information about the reception strength includes information for identifying the base station 12, information about the time and information about the reception strength at that time, and the like.

  In SA3, it is determined whether or not information on the reception intensity is received from any of the base stations 12 in the reception started in SA2. When information about the reception strength at any of the base stations 12 is received, the determination at this step is affirmed and SC4 is executed. On the other hand, if no information about the reception intensity at any base station 12 is received, the determination at this step is denied and reception is continued.

  In SA4, information on the reception intensity at any of the base stations 12 received in SA3 is recorded. This recording is performed, for example, as shown in FIG. 11 as the time change of the reception intensity at each base station 12.

  In SA5, it is determined whether or not the information about the reception intensity has been received for all the base stations 12 included in the mobile station positioning system 8. When the information about the reception intensity is received for all the base stations 12, the determination in this step is affirmed and SA6 and subsequent steps are executed. On the other hand, if there is a base station 12 that has not received the information about the reception strength, the determination at this step is denied, and SA3 and the subsequent steps are executed again to receive the information about the reception strength transmitted from the base station 12. It is.

  In SA6, which is executed when the determination of SA5 is affirmed, reception of information on the reception intensity of radio waves for positioning detected in each base station 12 is terminated.

  In SA7 corresponding to the selection unit 64, based on the reception intensity of the radio wave for positioning in each base station 12 recorded in SA4, the base station 12 used for calculating the position of the mobile station 10 in SA9 to be described later. A selection is made. Specifically, in this step, the difference between the maximum value and the minimum value in the time change of the reception intensity of the radio wave for positioning at each base station 12 recorded in SA4 is calculated, and the difference moves in ascending order. Ranking is performed on the assumption that radio waves are successfully transmitted to and received from the station 10. Then, based on the ranking, the number of base stations 12 used for calculating the position of the mobile station 10 is selected in SA9 in the order in which radio waves are transmitted and received with the mobile station 10 in a favorable manner.

In SA8 corresponding to the reception intensity calculation unit 68, the reception intensity of the radio wave for positioning at each base station is determined based on the time change of the radio wave reception intensity for positioning at each base station 12 recorded in SA4. A value is calculated. Specifically, in this step, the average P _AV of the maximum value Pmax and a minimum value Pmin is calculated in the time variation of the radio wave reception intensity for positioning in each base station 12 recorded in SA4, the calculated The average _PAV value is the value of the radio wave reception intensity for positioning at the base station 12.

In SA9 corresponding to the positioning unit 66, the value of the radio wave reception intensity for positioning calculated in SA8 for the base station selected to be used for calculating the position of the mobile station 10 in SA7 is known in advance. Information on the position of each base station 12 and each pre-stored base station and the base station 12 when receiving a radio wave transmitted with a predetermined output from the mobile station 10 as shown in FIG. The position of the mobile station 10 is calculated on the basis of the reception intensity and the propagation distance of the radio wave, that is, the relationship between the mobile station 10 and the base station 12. Specifically, the value of the reception intensity P _AV of the radio waves for positioning calculated in SA8, and a relationship of the propagation distance of the reception intensity radio wave, and the mobile station 10 and each of the base stations 12 Distance ri (i = 1, 2, 3,...) Is calculated. The calculated distance ri and the position (xn, yn) (n = a, b, c,...) Of each base station 12 that is known in advance are represented by the relational expression shown in the above equation (1). By solving this, the position (x, y) of the mobile station 10 is calculated.

  FIG. 17 is a flowchart for explaining the control operation in the base station 12 and is executed for each base station 12 included in the mobile station positioning system 8. First, in step (hereinafter, “step” is omitted) SB1, reception of a positioning instruction signal, which is a signal instructing execution of positioning, transmitted from server 14 in SA1 of FIG. 16 is started.

  In SB2, it is determined whether or not a positioning instruction signal from the server 14 has been received. When a positioning instruction signal from the server 14 is received, the determination at this step is affirmed, and SB3 and subsequent steps are executed. If the positioning instruction signal from the server 14 has not been received, the determination at this step is denied, SB2 is subsequently executed, and the positioning instruction signal from the server 14 is received.

  SB3 is a step executed when the determination of SB2 is affirmed, and is a radio wave for positioning to the mobile station 10 based on the positioning instruction signal transmitted from the server 14 at SA1 in FIG. 16 and received at SB2. This is executed when a command for transmitting the command from the radio unit 44 to the mobile station 10 is included. In SB 3, a command for transmitting a radio wave for positioning to the mobile station 10 is transmitted from the radio unit 44. That is, the base station 12 on which this step SB3 is executed corresponds to the representative base station.

  In SB4, reception of radio waves for positioning transmitted from the mobile station 10 is started. That is, as will be described later with reference to the flowchart of FIG. 18, a radio wave for positioning is transmitted from the mobile station 10 based on a command transmitted from the representative base station by SB3. Specifically, for example, the operation state of the wireless unit 44 is controlled by the control unit 46, and the wireless unit 44 is caused to function as a receiving unit that receives radio waves.

  In SB5, it is determined whether a radio wave for positioning transmitted from the mobile station 10 is received. If a positioning radio wave transmitted from the mobile station 10 is received, the determination in this step is affirmed and SB6 and subsequent steps are executed. When the positioning radio wave transmitted from the mobile station 10 has not been received, the determination in this step is denied, SB5 is executed again, and the positioning radio wave received from the mobile station 10 is received. Is done.

  In SB6 corresponding to the reception intensity detection unit 52, the reception intensity of the radio wave for positioning received in SB5 is detected. For example, reception intensity detection is repeatedly performed at predetermined sampling times.

  In SB7, information about the reception strength including the reception strength for positioning detected in SB6 is transmitted to the server. At this time, the information on the reception strength may include, for example, information on the detection time in addition to the reception strength detected in SB6.

  In SB8, the value of the reception time, which is the elapsed time since the reception of the radio wave for positioning is started, that is, the determination of SB5 is affirmed, is 2 * M * ts, which is a predetermined time. It is determined whether or not the number has been exceeded. As will be described later, the value of the length of time 2 * M * ts is the time required for the mobile station 10 to change until the phase difference between the phase of the direct wave and the phase of the reflected wave is different by 2π, that is, to be described later. This is the time required for SC4 to SC12 to be executed in the flowchart of FIG.

  In SB9, reception of radio waves for positioning transmitted from the mobile station 10 is terminated.

  FIG. 18 is a flowchart for explaining the outline of the control operation in the mobile station 10. First, in step (hereinafter, “step” is omitted) SC1, the positioning instruction signal transmitted from the representative base station is received in SB3 of FIG.

SC2 and SC3 correspond to the transmission signal generating unit 30 of the phase changing unit 28. First, in SC2, which is executed when a positioning instruction signal is received in SC1, a variable i indicating the number of phase changes and a variable θ ₀ for determining the I value and the Q value are initialized, respectively. The value is set to 0.

In SC3, the value of the I and Q signals, based on the value of theta ₀ set in SC2, respectively, are calculated as _{I = cosθ 0, Q = sinθ} 0.

In the phase change unit 28 and the radio unit 23 set in the transmission state by the control unit 26, that is, in SC4 corresponding to the transmission unit 25, the values of the I signal and the Q signal are set to the values calculated in SC3. That is, by performing modulation based on the set I signal and Q signal, a radio wave for positioning with a phase angle θ ₀ is generated and transmitted wirelessly with a predetermined output. In addition, the value of the variable t representing the radio wave transmission time is initialized, and the value is set to zero.

  In SC5, it is determined whether or not the value of the variable t representing the radio wave transmission time exceeds a predetermined time interval ts. If the value of the variable t exceeds the time interval ts, the determination at this step is affirmed and SC6 is executed. When the value of the variable t does not exceed the predetermined time interval ts, the radio wave for positioning the phase being transmitted is continuously transmitted, and the determination of SC5 is performed again.

  In SC6, the value of the variable i representing the number of phase changes is increased by one.

  In SC7 corresponding to the transmission signal generating unit 30 of the phase changing unit 28, the amount of change Δθ of the radio wave phase for positioning is calculated according to a predetermined pattern. Specifically, the phase change amount Δθ is calculated as Δθ = π * i / M using a predetermined number of steps M and a variable i representing the number of phase changes.

  In SC8, it is determined whether or not the phase change amount Δθ calculated in SC7 exceeds 2π. This phase change amount Δθ is obtained when the direct wave is the one after the phase change when the positioning radio wave is received by the base station 12, while the reflected wave is the one before the phase change. The phase difference between the phase of the direct wave and the phase of the reflected wave, and the phase difference between the phase of the direct wave and the phase of the reflected wave when both the direct wave and the reflected wave are before or after the phase change. It corresponds to the difference. Therefore, when the value of the phase change amount Δθ exceeds 2π, it is generated for all aspects of the phase difference between the direct wave phase and the reflected wave phase under the condition of the number of steps M. Therefore, when the value of the phase change amount Δθ exceeds 2π, the determination in this step is affirmed, and the transmission of the radio wave for positioning for changing the phase according to the predetermined pattern is completed, and the SC 12 is executed. . On the other hand, when the value of the phase change amount Δθ does not exceed 2π, SC9 is executed.

SC9 to SC10 correspond to the transmission signal generation unit 30 of the phase change unit 28. First, in SC9, the phase angle value θ _i after the change of the radio wave for positioning is calculated based on the phase change amount Δθ calculated in SC7. Specifically, the phase angle value θ _i after the change is obtained by using the phase angle value θ _i−1 before the change and the phase change amount Δθ calculated in SC7, using θ _i = θ _i−1 + Δθ. It is calculated as follows.

In SC10, the value of the I and Q signals for realizing the phase angle theta _i calculated in SC9 is, I = cos [theta] _i, is calculated as Q = sin [theta _i.

In the phase change unit 28 and the radio unit 23 set in the transmission state by the control unit 26, that is, the SC 11 corresponding to the transmission unit 25, the values of the I signal and the Q signal are set to the values calculated by the SC10. That is, by performing modulation based on the set I signal and Q signal, a radio wave for positioning with a phase angle θ _i is generated and transmitted wirelessly with a predetermined output. Further, the value of the variable t representing the radio wave transmission time is reset, and after the value is set to 0, the transmission time is measured again.

  In SC12 executed when the determination in SC8 is affirmed, transmission of radio waves for positioning is terminated assuming that transmission of radio waves for positioning that changes the phase according to the predetermined pattern is completed.

  According to the above-described embodiment, the reception intensity detection unit 52 receives a radio wave whose phase is changed by a predetermined pattern transmitted by one of the mobile station 10 and the plurality of base stations 12, and receives the other. The maximum value Pmax and the minimum value Pmin of the intensity are detected for each base station 12, and the maximum value Pmax and the minimum value Pmin of the received intensity detected by the selection unit 64 for each of the plurality of base stations 12 by the reception intensity detection unit 52. Based on the above, the base station 12 that performs good radio wave transmission / reception with the mobile station 10 is selected, so that the maximum value Pmax and the minimum value Pmin of the radio wave reception intensity whose phase is changed by a predetermined pattern are selected. Based on this, it is possible to select a base station 12 that is less affected by interference due to multipath and that performs good radio wave transmission / reception with the mobile station 10.

  Further, according to the above-described embodiment, the selection unit 64 is the base station 12 that performs better wireless communication with the mobile station 10 as the difference between the maximum value Pmax and the minimum value Pmin of the reception strength is smaller. Since the base station 12 is selected, even if the phase of the transmitted radio wave is changed, the base station is less affected by multipath interference or the like based on the small variation in the value of the received intensity. 12 can be selected as the base station 12 in which radio communication with the mobile station 10 is satisfactorily performed.

  Further, according to the above-described embodiment, in the mobile station positioning system 8, a transmission wave whose phase is changed in a predetermined pattern is generated by the phase changing unit 28 of the movable mobile station 10, and the transmitting unit 25 The generated transmission wave is transmitted with a predetermined output, and radio waves transmitted from the mobile station 10 are received by the radio unit 44 as the reception unit of the plurality of base stations 12 installed at known positions, and the reception intensity The detection unit 52 detects the reception intensity of the received radio wave, and the selection unit 64 of the server 14 further detects the maximum value Pmax and the minimum value Pmin of the reception intensity detected by the reception intensity detection unit 52 for each base station 12. Based on the above, the base station 12 that performs good transmission and reception of radio waves with the mobile station 10 is selected, and the base station 1 selected by the selection unit 64 by the positioning unit 66 is selected. Since the position of the mobile station 10 is calculated based on the reception intensity (RSSI) that is the reception result of the radio wave received by, the maximum value Pmax and the minimum value Pmin of the radio wave reception intensity whose phase is changed by a predetermined pattern Based on the above, it is possible to select the base station 12 that is less affected by interference due to multipath and the like, and that allows good transmission / reception of radio waves to / from the mobile station 10. Since the position of the mobile station 10 is calculated using the reception intensity at the base station 12 selected to be performed, the position of the mobile station 10 can be calculated with high accuracy.

  Further, according to the above-described embodiment, the selection unit 64 is the base station 12 that performs better wireless communication with the mobile station 10 as the difference between the maximum value Pmax and the minimum value Pmin of the reception strength is smaller. Since the base station 12 is selected, even if the phase of the transmitted radio wave is changed, the base station is less affected by multipath interference or the like based on the small variation in the value of the received intensity. 12 can be selected as the base station 12 in which radio communication with the mobile station 10 is satisfactorily performed.

Further, according to the above-described embodiment, the positioning unit 66 includes the reception intensity calculation unit 68, and the reception intensity calculation unit 68 detects reception intensity for radio waves received by the base station 12 selected by the selection unit 64. the average _{P AV} of the maximum value Pmax and a minimum value Pmin of reception intensity detected by section 52, is calculated as a reception result relating to the base station 12. In addition, since the positioning unit 66 calculates the position of the mobile station 10 using the reception strength calculated by the reception strength calculation unit 68, a value obtained by reducing the influence of multipath interference or the like is used as the reception result. The positioning unit 66 can calculate the position of the mobile station 10 with high accuracy.

  Further, according to the above-described embodiment, the mobile station 10 includes the phase change unit 28 and the radio unit 23 as the transmission unit 25. The phase change unit 28 generates a transmission wave whose phase is changed according to a predetermined pattern. Since the transmission unit 25 transmits the generated transmission wave with a predetermined output, it can be suitably used in the mobile station positioning system 8.

  Further, according to the above-described embodiment, the base station 12 includes the radio unit 44 and the reception intensity detection unit 52 as a reception unit, the radio unit 44 receives radio waves, and the reception intensity detection unit 52 is received by the radio unit 44. Therefore, the mobile station positioning system 8 can be suitably used.

  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 the above-described embodiment, the mobile station 10 moves on a plane. However, the mobile station 10 is not limited to this mode, and may move in space (three dimensions). In this case, an expression corresponding to the expression (1) may be derived by using the coordinates (x, y, z) representing the position of the mobile station 10 as unknowns.

  Further, in the above-described embodiment, the positioning unit 66 determines whether each of the base stations 12 and the mobile station 10 are based on the radio wave reception strength for positioning at each base station 12 selected by the selection unit 64. A distance ri (i = 1, 2,...) Was calculated, and the position of the mobile station 10 was calculated from this distance and information about the position of each base station 12 that was previously known. Here, the distance ri between each base station 12 and the mobile station 10 is not limited to being calculated based on the reception intensity of radio waves for positioning. Specifically, for example, the radio wave propagation time for positioning calculated from the transmission time of the radio wave for positioning at the mobile station 10 and the reception time at each base station 12 is multiplied by a known radio wave speed. (TOA (time of arrival) method). Further, the position of the mobile station 10 can also be calculated based on the reception time difference of radio waves at the plurality of base stations 12 (TDOA (time difference of arrival) method). In these cases, preferably, a radio wave for positioning transmitted by the mobile station 10 includes a spreading code such as a PN (Pseudo Noise) code. Since the PN code generates a sharp peak in the correlation, the base station 12 on the receiving side uses a known matched filter or the like to extract the PN code extracted from the received radio wave, and the PN code stored in advance. Correlation values with replica codes that are the same code are sequentially calculated, and synchronization detection can be performed based on the fact that the correlation value has a peak. In other words, the time at which the correlation value is peaked is detected as a synchronization time with reference to the clock 54 of the base station 12, for example, and is used as the reception time of the radio wave transmitted from the mobile station 10, so that the accurate reception time Can be detected.

  In the above-described embodiment, the selection unit 64, the positioning unit 66, the reception intensity calculation unit 68, and the like are functions that the server 14 has, but are not limited thereto. For example, it is possible to use these functions as one of the base stations 12. In this way, it is not necessary to provide the server 14.

  In the above-described embodiment, the value of the reception intensity in each reception section (i) (i = 1, 2,...) Detected by the reception intensity detection unit 52 is the average value of detections performed a plurality of times in the reception section. However, the present invention is not limited to this, and may be a value obtained by one detection.

  In the above-described embodiment, the radio wave for positioning is transmitted from the mobile station 10 and received by each base station 12, but the present invention is not limited to such a mode. That is, the mobile station 10 has a reception intensity detection unit 52, each base station 12 has a phase change unit 28, the radio unit 23 of the mobile station 10 is a reception unit, and the radio unit 44 of each base station 12 is a transmission unit. It is also possible to receive radio waves for positioning transmitted from the respective base stations 12 by the radio unit 23 of the mobile station 10 and detect the received intensity of the received radio waves. .

  In the above-described embodiment, the selection unit 64 determines the order of the order in which radio communication with the mobile station 10 is satisfactorily performed for all the base stations 12 necessary for calculating the position of the mobile station 10 in the positioning unit 66. Although the selection is made based on the attachment, the present invention is not limited to such a mode. For example, when the base station 12 that is always used when the positioning unit 66 calculates the position of the mobile station 10 is set in advance, the base station used by the positioning unit 66 to calculate the position of the mobile station 10 Of these, a base station other than the base station 12 that is always used may be selected.

  In the above-described embodiment, the mobile station positioning system 8 includes the reception strength calculation unit 68, and the positioning unit 66 determines the position of the mobile station 10 based on the reception strength calculated by the reception strength calculation unit 68. Although the calculation is performed, the present invention is not limited to such a mode. For example, for the positioning radio wave transmitted from the mobile station 10, the position of the mobile station 10 can be calculated based on the value of the received intensity detected at a predetermined time, for example, before the phase change. . Thus, even if the mobile station positioning system 8 does not include the reception intensity calculation unit 68, a certain effect can be obtained.

  In the above-described embodiment, the mobile station positioning system 8 is disposed so as to be surrounded by the wall 20 and a reflected wave is generated. However, this is an example of the case where there is an influence of the reflected wave. It is not limited to situations where waves are generated. For example, it can also occur on the floor.

  Further, in the above-described embodiment, the number of steps M is set as M = 4, and the predetermined pattern regarding the change in the phase of the radio wave for positioning transmitted from the mobile station 10 was initially set to 0. The phase is π * i such as π / 4, 3π / 4, 6π / 4, 10π / 4, 15π / 4, 21π / 4, 28π / 4, 36π / 4,... At predetermined time intervals ts. Although it was increased by / M, it is not limited to such a mode. Specifically, for example, the value of the number of steps M is not limited to 4, and the initial phase angle value is not limited to 0. That is, the phase difference between the phase of the direct wave and the phase of the reflected wave only needs to change in accordance with the change in phase.

  In the above-described embodiment, the control unit 46 of the base station 12 receives a radio wave for positioning the phase angle and transmits information about the reception strength to the server 14 every time the reception strength is detected. However, the present invention is not limited to this mode. For example, the control unit 46 of the base station 12 receives radio waves for positioning of all types of phase angles, and after detecting the reception strength thereof, collects information on the reception strengths in a batch by the server 14. May be sent to. Alternatively, the information about the value of the reception intensity detected by the reception intensity detection unit 52 may be sequentially transmitted to the server 14 so that the server 14 generates information about the temporal change in the reception intensity.

  In addition, although not illustrated one by one, the present invention is implemented with various modifications within a range not departing from the gist thereof.

It is a figure explaining the outline | summary of the mobile station positioning system which is one Example of this invention. It is a figure explaining the principal part of the function which the mobile station which comprises the mobile station positioning system of FIG. 1 has. It is a figure explaining the function of the phase change part which the mobile station of FIG. 2 has further in detail. It is a figure explaining the phase angle changed by the phase change part of FIG. It is a figure explaining the phase angle changed by the phase change part of FIG. 3, and the I signal and Q signal corresponding to each phase. It is a figure showing the example of the output from which a phase is changed by the phase change part of FIG. It is a figure explaining the principal part of the function which the base station which comprises the mobile station positioning system of FIG. 1 has. It is the conceptual diagram which isolate | separated the time change of the receiving intensity of the electromagnetic wave for the positioning received in a base station into the direct wave component and the reflected wave component. A predetermined pattern, a change in the phase of a direct wave and a reflected wave in a base station, and a phase of the direct wave when the phase in a radio wave for positioning transmitted from a mobile station is changed along a predetermined pattern; It is the figure which expressed the phase difference with the phase of a reflected wave on the same time axis. It is a figure explaining the example of the time change of the reception strength detected by the reception strength detection part of a base station when the phase of the electromagnetic wave for positioning is changed along a predetermined pattern. It is a figure explaining the example of the time change of the reception strength in a some base station, Comprising: It is a figure corresponding to FIG. It is a figure explaining the principal part of the function which the server which comprises the mobile station positioning system of FIG. 1 has. It is a figure explaining the calculation operation | movement of the receiving strength by the receiving strength calculation part of FIG. It is a figure explaining the relationship between the reception intensity in the base station which received the electromagnetic wave transmitted by the predetermined output from the mobile station, and the distance of a base station and a mobile station. It is a figure explaining calculation of the position of the mobile station by the positioning part of FIG. It is a flowchart explaining the outline | summary of the control action of the server in one Example of the mobile station positioning system of this invention. It is a flowchart explaining the outline | summary of the control action of the base station in one Example of the mobile station positioning system of this invention. It is a flowchart explaining the outline | summary of the control action of the mobile station in one Example of the mobile station positioning system of this invention.

Explanation of symbols

10: Mobile station 12: Base station 8: Mobile station positioning system 28: Phase changing unit 25: Transmitting unit 44: Radio unit (receiving unit) of base station
52: Reception strength detection unit 64: Selection unit 66: Positioning unit

Claims (7)

A base station selection method for selecting a base station in which radio waves transmitted from either one of a mobile station and a plurality of base stations are received by the other and radio waves are successfully transmitted / received to / from the mobile station. ,
A reception intensity detection step of detecting, for each base station, an instantaneous reception intensity corresponding to a phase that is changed in phase by the predetermined pattern, wherein the other receives a radio wave whose phase is changed by a predetermined pattern transmitted by the one;
In order to select a base station that can satisfactorily transmit and receive radio waves with the mobile station based on the maximum and minimum values of the instantaneous reception strength detected for each of the plurality of base stations by the reception strength detection step. And a selection process of
The predetermined pattern has a maximum phase change amount of 2π radians, which is a phase difference before and after the phase change, and a plurality of phase change values exist at substantially equal intervals between 0 degree and the maximum value. A pattern that results in a phase change,
A base station selection method characterized by the above. The selecting step selects the base station as a base station that performs better wireless communication with the mobile station as the magnitude of the difference between the maximum value and the minimum value of the instantaneous reception strength is smaller;
The base station selection method according to claim 1. Mobile station positioning in which the other receives a radio wave transmitted from one of a movable mobile station and a plurality of base stations installed at a known position, and calculates the position of the mobile station based on the reception result A system,
The one side generates a transmission wave whose phase is changed according to a predetermined pattern; and
A transmission unit that transmits the transmission wave generated by the phase change unit with a predetermined output;
The other is a receiving unit that receives radio waves transmitted from the one;
A reception intensity detection unit that detects an instantaneous reception intensity of the radio wave received by the reception unit;
A selection unit that selects a base station that performs good radio wave transmission and reception with the mobile station based on the maximum and minimum values of instantaneous reception strength detected for each base station by the reception strength detection unit; ,
A positioning unit that calculates the position of the mobile station based on a reception result of radio waves transmitted from the base station selected by the selection unit or received by the base station;
The predetermined pattern has a maximum phase change amount of 2π radians, which is a phase difference before and after the phase change, and a plurality of phase change values exist at substantially equal intervals between 0 degree and the maximum value. A pattern that results in a phase change,
A mobile station positioning system. The selection unit selects the base station as a base station that performs better wireless communication with the mobile station as the magnitude of the difference between the maximum value and the minimum value of the instantaneous reception strength is smaller;
The radio station selection system according to claim 3. The positioning unit is an average of the maximum value and the minimum value of the instantaneous reception intensity detected by the reception intensity detection unit for radio waves transmitted from the base station selected by the selection unit or received by the base station. The mobile station positioning system according to claim 3, wherein the position of the mobile station is calculated as a reception result related to the base station. A phase change unit that generates a transmission wave by changing the phase according to a predetermined pattern;
A transmission unit that transmits the transmission wave generated by the phase change unit with a predetermined output;
A mobile station constituting the mobile station positioning system according to any one of claims 3 to 5. A receiver for receiving radio waves;
A reception intensity detection unit that detects an instantaneous reception intensity of the radio wave received by the reception unit;
The base station which comprises the mobile station positioning system of any one of Claim 3 thru | or 5.

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