JP2008039738A - Positioning method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the number of necessary base stations, concerning a positioning method. <P>SOLUTION: This method has a configuration including a process for transmitting a ranging radio signal from a reference station R whose position is known; a process wherein a plurality of base stations B whose positions are known measure each reception time of the ranging radio signal by each timepiece Cb in own station; a process for transmitting a response radio signal including delay time information by a timepiece Cm in own station from reception until reply after a moving terminal M receives the ranging radio signal; a process wherein the reference station R and each base station B measure each reception time of the response radio signal by each timepiece Cr, Cb in each own station; and a process for operating each distance from the reference station R and each base station B to the moving terminal M by erasing each deviation element between the timepieces Cm, Cb, Cr in each station based on each reception time of the response radio signal in the reference station R and each base station B, a transmission time of the ranging radio signal in the reference station R, the delay time information from a portable terminal, and known distance information between reference station R and each base station B. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a positioning method.

  Patent Document 1 discloses a positioning method in which a mobile terminal and a plurality of base stations whose positions are known are communicated by radio signals and the position of the mobile terminal is obtained using the arrival time of the radio signals. It has been known.

  In this conventional example, the mobile station transmits a response radio signal in response to a response request radio from the base station (reference station). The response radio signal is received by the reference station and an appropriate number of receiving apparatuses (base stations), and the reception time is measured.

Since the propagation speed of the radio wave and the distance between the reference station and the base station are known, the position of the mobile station is
|| Pt-Pj |-| Pt-P1 || = c (R _ {_ m @ j, 1}-R {t_m @ 1,1})
Where Pt is the position of the mobile station, P1 is the position of the reference station,
Pj is the position of the jth base station,
R {t_m @ 1,1}) is given as a solution in which the relational expression of the reception time at the base station and R _ {_ m @ j, 1} are simultaneous with the reception time at the jth base station.
JP 2005-117440 A

  However, since the relational expression in the above-described conventional example is given as a relative distance with respect to the distance between the reference station and the mobile station, there is a problem that a large number of base stations are required to obtain a solution. For example, the two-dimensional position of the mobile station can be obtained if the distance from at least one reference station and one base station is obtained by triangulation, but at least 1 is required to obtain the above solution. One reference station and two base stations are required.

  The present invention has been made to solve the above drawbacks, and an object of the present invention is to provide a positioning method capable of reducing the number of necessary base stations.

The distance between transmitting / receiving stations arranged at two points can be obtained by using a transmission / reception time difference at each station by reciprocating a ranging radio signal between the two stations. That is, the distance between terminals a and b is Lab, the transmission time of ranging radio signals at terminals a and b is Ta1 and Tb2, the reception time is Tb1 and Ta2, the clock offset between terminals is Toab, the speed of light is Vc, Then,
Tb1 + Toab = Ta1 + Lab / Vc
Ta2 = Tb2 + Toab + Lab / Vc
Is established, the inter-terminal distance is the Toab deleted,
Lab = Vc {(Ta2-Ta1)-(Tb2-Tb1)} / 2 (Formula 1)
Can be obtained as

  Therefore, the terminal a is a reference station R whose position is known, the terminal b is a mobile terminal M, and the response radio signal from the mobile terminal M to the ranging radio signal from the reference station R is (Tb2-Tb1), that is, the mobile terminal When the delay time until the response wireless signal is returned is included, the reference station R can determine the distance to the portable terminal.

  For example, in order to know the two-dimensional position of an arbitrary point based on the distance from the position known point, two position known points are necessary, and the above-described communication is performed between the two reference stations R and the mobile terminal M. Thus, the position of the mobile terminal M can be obtained.

  However, in this case, transmission from the mobile terminal M is required twice, and the power consumption of the mobile terminal M increases.

  In order to solve this problem, the present invention employs a distance measurement method based on reciprocal communication between two stations, and receives a distance measurement radio signal transmitted from the reference station R at the base station B. The base station B corrects the time difference between the clock and the base station B, and receives the response radio signal from the mobile terminal M by the base station B, thereby measuring the distance of the mobile terminal M.

  As a result, the positioning of the mobile terminal M can be performed by one radio wave transmission from the reference station R and the mobile terminal M. In order to measure the two-dimensional position of the mobile terminal M, it is sufficient to prepare at least one reference station R and one base station B.

  According to the present invention, the number of necessary base stations can be reduced.

  FIG. 1 shows a positioning system to which the present invention is applied. The positioning system includes one reference station R, an appropriate number of base stations B, a positioning server 2 connected to these reference stations R and base stations B via a wired LAN 1, and a mobile terminal M that is a positioning target. Configured. The positions of the reference station R and the base station B are measured in advance by appropriate means.

  As shown in FIG. 2, the reference station R has a transmitter 3r for transmitting a ranging radio signal. When receiving the positioning start command, the reference station R sets a ranging radio signal in the transmitter 3r and transmits it from the antenna. The transmission time of the ranging radio signal is measured by a clock Cr prepared in the reference station R, and the measurement result is stored in the ranging radio signal transmission time holding unit 4r.

  A receiving unit 5r receives the response wireless signal from the mobile terminal M, measures the reception time with the clock Cr, and stores the measurement result in the response wireless signal reception time holding unit 6r. The response wireless signal received by the receiving unit 5r is stored in the received data holding unit 7r.

  The base station B includes a receiving unit 5b that receives the ranging radio signal transmitted from the reference station R and the response radio signal transmitted from the mobile terminal M. When the receiving unit 5b receives any one of the above radio signals, the reception time is measured by the built-in clock Cb. When the reception signal is a distance measurement radio signal, the measurement result is obtained as the distance measurement radio signal reception time. When it is a response radio signal in the holding unit 8b, it is stored in the response radio signal reception time holding unit 6b.

  On the other hand, the mobile terminal M includes a receiving unit 5m that receives a ranging radio signal from the reference station R. When the reception unit 5m receives the distance measurement radio signal, the reception time is measured by the built-in clock Cm, and the measurement result is stored in the distance measurement radio signal reception time holding unit 8m.

  When the receiving unit 5m receives the distance measurement radio signal, the control unit (not shown) sets a response radio signal in the transmission data creating unit 9m and transmits it from the transmitting unit 3m. The response radio signal includes delay time information from when the receiving unit 5m receives the distance measurement radio signal to when the response radio signal is transmitted from the transmission unit 3m. The transmission time at the transmission unit 3m is the response radio signal. It is stored in the transmission time holding unit 10m.

  A positioning method of the mobile terminal M using the above system will be described with reference to FIG. In FIG. 1A, a broken line indicates wireless communication, a solid line indicates communication via the wired LAN 1, and lower-case Roman numerals in the figure correspond to step numbers described below.

  First, at the time of positioning, a ranging radio signal is transmitted from the reference station R (step S1), and the transmission time is transferred to the positioning server 2 (step S2). The ranging radio signal is received by the mobile terminal M and the base station B, and the reception time measured by the clock Cb of the own station measured by the base station B is transferred to the positioning server 2 (step S3).

  On the other hand, the mobile terminal M that has received the ranging radio signal holds the reception time measured by its own clock Cm in the ranging radio signal reception time holding unit 8m, and then transmits the response radio signal in the transmission data creation unit 9m. Is generated (step S4) and transmitted (step S5). As described above, the response wireless signal includes delay time information.

  The reference station R that has received the response radio signal receives the reception time measured by its own clock Cr and the delay time information transmitted from the mobile terminal M, and the base station B obtains the reception time measured by its own clock Cb. 2 (step S6).

  The positioning server 2 that has received the data transfer from the reference station R and the base station B calculates the distance between the mobile terminal M, the reference station R, and the base station B in the positioning calculation unit 11 by the following method, The position information is calculated by applying the edge survey method (step S7).

That is, the difference between the clock Cm and Cb of the mobile terminal M and the base station B with respect to the clock Cr of the reference station R is Tom, Toa, Tob (hereinafter, the alphabetic subscripts attached to the variables indicate the station type and the numerical subscripts). The letter indicates the signal type, "r" for the reference station R, "a", "b" for the two base stations B, and "m" for the mobile terminal M. Also, the numeral " 1 "indicates a ranging radio signal, subscript" 2 "indicates a response radio signal), and distance L (according to the subscript assignment rule described above, the distance between the reference station R and the mobile terminal M is Lmr, one base The distance between the station B and the mobile terminal M is Lam, the distance between the other base station B and the mobile terminal M is Lbm, the distance between the reference station R and the base station B is Lar, Lbr), and the transmission / reception time T (the distance measurement radio of the reference station R) The signal transmission time is Tr1, the distance measurement radio signal is received by the mobile terminal M, the base station B is Tm1, Ta1, Tb1, the response radio signal transmission time of the mobile terminal M is Tm2, and the response radio signal If the reference stations R, the reception time in the base station B Tr2, Ta2, Tb2) that,
From the relationship between the transmission / reception path length and the radio wave arrival time in step S1,
Tm1 + Tom = Tr1 + Lmr / Vc
Ta1 + Toa = Tr1 + Lar / Vc
Tb1 + Tob = Tr1 + Lbr / Vc
(Expression 2) is established. Vc is the speed of light.

In addition, from the relationship between the transmission / reception path length and the radio wave arrival time in step S5,
Tr2 = Tm2 + Tom + Lmr / Vc
Ta2 + Toa = Tm2 + Tom + Lam / Vc
Tb2 + Tob = Tm2 + Tom + Lbm / Vc
Is established.

Since the positions of the base station R and the two base stations B are known, Lar and Lbr are known, and the unknowns of the above six formulas are Lmr, Lam, Lbm, Tom, Toa and Tob, and Lmr, Lam and Lbm are expressions that delete Tom, Toa, and Tob.
Lmr = Vc {(Tr2-Tr1)-(Tm2-Tm1)} / 2
Lam = Lar + Vc (Ta2-Ta1)-Vc {(Tr2-Tr1) + (Tm2-Tm1)} / 2
Lbm = Lbr + Vc (Tb2-Tb1)-Vc {(Tr2-Tr1) + (Tm2-Tm1)} / 2
Given in.

As a result, if the two-dimensional coordinates (Xm, Ym) of the mobile terminal M are (Xr, Yr), (Xa, Ya), (Xb, Yb), the coordinates of the base station R and the base station B are
{(Xm-Xr) ² + (Ym-Yr) ² } ^1/2 = Lmr
{(Xm-Xa) ² + (Ym-Ya) ² } ^1/2 = Lam
{(Xm-Xb) ² + (Ym-Yb) ² } ^1/2 = Lbm
Is required.

  In the final formula, since there are three formulas for the unknowns Xm and Ym, the formulas are redundant. Therefore, Xm and Ym are obtained as a least squares solution of the above three formulas.

  In the above embodiment, in order to accurately measure the reception time, an impulse radio wave can be used for the ranging radio signal and the response radio signal. In this case, the transmission data format is shown in FIG. The apparatus configuration of R is shown in FIG.

  Referring to FIG. 3, transmission data is time-hopped (TH) with an 8-value Reed-Solomon RS sequence, which is a kind of PN sequence, and further data-modulated with pulse position modulation. In the case of one chip of 100 ns, if 576421 is used as the RS sequence, the first pulse is time-hopped to the position of 500 ns and the next pulse is time-hopped to the position of 700 ns in the pulse section of 1 μs. The unmodulated preamble portion for data synchronization is 7 pulses 7 μs, followed by the data portion. The data portion is also time-hopped with the same RS sequence, but when the data is 1, pulse position modulation (PPM) is performed in which the position of one chip pulse is shifted.

  For example, in the case of 0110 data, the 5763... RS sequence is modulated as 5873..., And pulses are hopped at 500 ns, 800 ns, 700 ns, and 300 ns positions.

  Referring to FIG. 4, the RS sequence is generated by PN sequence generation unit 12, PPM data modulation unit 13 performs PPM data modulation according to transmission data 1 and 0, and sends a pulse to impulse generation unit 14. It is done. The impulse generator 14 generates a very thin impulse at the rising edge of the pulse by the step recovery diode.

  The generated impulse has a very wide band, but, for example, an unnecessary component of 3.1 GHz or less is passed through a bandpass filter (BPF) of 3.1 GHz to 5 GHz so as to conform to the mask of the Radio Law. And remove components above 5GHz. After passing through the band pass filter (BPF), it is amplified by a power amplifier (PA), and radio waves are radiated from the antenna. When transmitting data, the time for generating the first pulse after the preamble is stored in the distance measurement radio transmission time holding unit 4r.

  On the other hand, on the receiving side, the impulse radio wave received by the antenna is amplified by a low noise amplifier (LNA) after unnecessary frequency components are removed by a band pass filter (BPF), and the presence or absence of a pulse is detected. The pulse detection unit 15 can be realized by a known diode envelope detection circuit and a comparator. The detected pulse is compared with the RS sequence generated by the PN sequence generator 12 by the correlator 16 using a digital matched filter.

  When the preamble part is detected by the correlator 16, it is assumed that synchronization has been established, and the PPM data demodulator 17 demodulates the PPM of the next data part to generate received data. If the first pulse of the data part is detected, the time is held in the response wireless signal reception time holding part 6r.

  Although FIG. 3 shows the apparatus configuration of the reference station R, each base station B is omitted from the apparatus configuration of the reference station R because the transmitter 3r is excluded from the apparatus configuration of the reference station R. Further, since the device configuration of the mobile terminal M is the device configuration of the reference station R excluding the wired LAN interface, the illustration is omitted.

  Furthermore, in the above-described embodiment, the case where the data from the reference station R and the base station B is accumulated in the positioning server 2 via the wired LAN 1 and is calculated by the positioning calculation unit 11 is shown in FIGS. As shown, the positioning calculator 11 can be placed in the reference station R. In this case, steps S2 and S3 in FIG. 1 are removed, and in step S6, each base station B transmits a response radio signal to the reference station R as a base station radio signal after receiving the response radio signal.

  As a result, all the information for obtaining the above-mentioned Lmr, Lam, and Lbm is collected in the reference station R, and a necessary calculation is performed in the positioning calculation unit 11.

  Referring to FIG. 6, the base station B creates a base station radio signal by the transmission data creation unit 9b from the distance measurement radio signal reception time and the response radio signal reception time, and transmits data to the reference station R from the transmission unit 3b. . In the following description, components that are substantially the same as those of the above-described embodiment are denoted by the same reference numerals in the drawings, and description thereof is omitted.

  With this configuration, it is not necessary to install the wired LAN 1 between the base station B and the reference station R, and the configuration is simplified.

FIG. 7 shows a second embodiment of the present invention. This embodiment provides an effective means for eliminating an error (scale error) in how the built-in clocks Cm, Cb, Cr progress due to the frequency difference of the clocks for each station.
For example, when a distance measurement radio signal and a response radio signal are reciprocated between the reference station R and the mobile terminal M and an attempt is made to perform distance measurement based on the equation (1), if (Tam2-Tam1) becomes longer, a scale error will occur. Cannot be ignored. In this example, when there is a clock frequency difference of 10 ppm, if (Tam2-Tam1) = 1 ms, 1 ms × 10 ⁻⁵ / 2 = 5 ns =, which is an error of 1.5 m in terms of distance. Therefore, when it takes a long time to reply, as shown in FIG. 7, a radio signal for clock error detection is further transmitted from the reference station R (hereinafter, a variable related to this signal is given a subscript “3”). (Step S1 ′).

  Since the ratio between the transmission time interval of the distance measurement radio signal and the clock error detection radio signal at the reference station R and the reception time interval at the mobile terminal M and the base station B is a frequency difference, the frequency difference is obtained and corrected. be able to.

Assuming that the scales of the clocks Cm, Cb, and Cr of the mobile terminal M and the base station B with respect to the reference station R are Sm, Sa, and Sb, Equation (2) is
Sm (Tm1 + Tom) = Tr1 + Lmr / Vc
Sm (Tm3 + Tom) = Tr3 + Lmr / Vc
Tr2 = Sm (Tm2 + Tom) + Lmr / Vc
Sa (Ta1 + Toa) = Tr1 + Lar / Vc
Sa (Ta3 + Toa) = Tr3 + Lar / Vc
Sb (Tb1 + Tob) = Tr1 + Lbr / Vc
Sb (Tb3 + Tob) = Tr3 + Lbr / Vc
Sa (Ta2 + Toa) = Sm (Tm2 + Tom) + Lam / Vc
Sb (Tb2 + Tob) = Sm (Tm2 + Tom) + Lbm / Vc
(Formula 3)
And can be transformed. When the unknown numbers Lmr, Lam, Lbm, Tom, Toa, Tob, Sm, Sa, and Sb are obtained in the simultaneous equations of (Expression 3).

Lmr = Vc {(Tr2-Tr1)-(Tr3-Tr1) (Tm2-Tm1) / (Tm3-Tm1)} / 2
Lam = Lar + Vc (Ta2-Ta1) (Tr3-Tr1) / (Ta3-Ta1)-Vc {(Tr2-Tr1) + (Tm2-Tm1) (Tr3-Tr1) / (Tm3-Tm1)} / 2
Lbm = Lbr + Vc (Tb2-Tb1) (Tr3-Tr1) / (Tb3-Tb1)-Vc {(Tr2-Tr1) + (Tm2-Tm1) (Tr3-Tr1) / (Tm3-Tm1)} / 2
(Formula 4)
It becomes.

  In this embodiment, since the difference between the clocks Cm, Cb, and Cr is expressed by a primary expression (frequency difference and offset), it is sufficient that at least two radio waves are transmitted from the reference station R. In some cases or statistically, a plurality of clock error detection radio signals may be transmitted from the reference station R.

  FIG. 8 shows a third embodiment of the present invention. This embodiment provides an efficient positioning method when there are a plurality of mobile terminals M, and the reference station R obtains at least unknowns (scale error, distance) due to the addition of the mobile terminal M. The distance measurement radio signal and the clock error detection radio signal are transmitted over the number of times that the simultaneous equations more than the necessary number can be established.

  In this embodiment for positioning two mobile terminals M, as shown in FIG. 8 (b), the mobile terminals Ma and base stations Ba and Bb receive radio waves A, B and C from the reference station R. The mobile terminal Ma responds to the radio wave C with the radio wave D, and the radio wave D at this time is received by the reference station R and the base stations Ba and Bb. On the other hand, the radio waves B and C from the reference station R are also received by the mobile terminal Mb. The mobile terminal Mb responds to the radio wave E from the reference station R with the radio wave F. At this time, the radio wave F is received by the reference station R and the base stations Ba and Bb.

Thus, the total radio waves transmitted from the reference station R can be reduced by combining the radio waves B and C with the mobile terminals Ma and Mb. In particular, when two or more radio waves from the reference station R are used as in the present embodiment, the effect becomes remarkable. The same applies to the case where there are three or more mobile terminals M. By doing so, the time required for positioning does not increase much even if there are many mobile terminals M.
(Appendix 1)
Transmitting a ranging radio signal from a reference station having a known position;
A step of measuring a reception time of a radio signal for ranging by a base station having a plurality of known positions with a clock of the own station;
After the mobile terminal receives the ranging radio signal, a step of transmitting a response radio signal including delay time information by the clock of the own station from reception to reply;
Measuring the reception time of the response radio signal by the reference station and the base station with its own clock;
Based on the reception time of the response radio signal at the reference station and the base station, the transmission time of the distance measurement radio signal at the reference station, the delay time information from the mobile terminal, and the known distance information between the reference station and the base station, Calculating the distance between the base station and each base station and the mobile terminal by eliminating the clock deviation element;
Positioning method including.
(Appendix 2)
The base station transmits a clock error detection radio signal at a time different from the transmission time of the distance measurement radio signal, and at each base station, the reception time is measured by its own clock,
The positioning method according to supplementary note 1, wherein the frequency difference of the clock of each base station with respect to the reference station is corrected based on the arrival time difference between the ranging radio signal and the clock error detecting radio signal.
(Appendix 3)
The positioning method according to supplementary note 2, wherein the clock error detection radio signal is shared by a plurality of mobile terminals during positioning operation.
(Appendix 4)
4. The positioning method according to appendix 1, 2, or 3, wherein an impulse radio signal is used as a distance measurement radio signal and a reply radio signal.
(Appendix 5)
The acquired data in each base station is transmitted to the positioning server by radio,
The positioning method according to any one of supplementary notes 1 to 4, wherein the calculation process is executed by the positioning server.
(Appendix 6)
Transmits a ranging radio signal to the mobile terminal and receives a response radio signal transmitted from the mobile terminal that has received the ranging radio signal and including delay time information from the local station's clock from reception to transmission at the mobile terminal A reference station whose position is known,
An appropriate number of base stations whose positions for receiving communication between the mobile terminal and the reference station are known;
Based on the reception time of the response radio signal at the reference station and the base station, the transmission time of the distance measurement radio signal at the reference station, the delay time information from the mobile terminal, and the known distance information between the reference station and the base station, A positioning server that calculates the position of the mobile terminal by calculating the distance between the mobile terminal and the base station and each base station by eliminating the clock deviation element;
Positioning system with.
(Appendix 7)
In the base station, the number of transmission / reception paths is such that the distance between the reference station and the base station and the mobile terminal, and the time difference between the base station and the mobile terminal with respect to the reference station are unknown, and the number is excessive with respect to the number of unknowns. The number of radio wave arrival time relational expressions that can be derived is prepared,
The positioning system according to appendix 6, wherein a distance from the mobile terminal is obtained as a least squares solution of the simultaneous equations.

It is a figure which shows this invention, (a) is a figure which shows the positioning method, (b) is a figure which shows a procedure. It is a system configuration figure of a positioning system. It is a figure which shows the apparatus structure of a reference station. It is a figure which shows the data format of transmission / reception data. It is a figure which shows the modification of FIG. It is a device block diagram of FIG. It is a figure which shows the 2nd Embodiment of this invention. It is a figure which shows the 3rd Embodiment of this invention.

Explanation of symbols

R Base station Cr clock B Base station Cb clock M Mobile terminal Cm clock

Claims (5)

Transmitting a ranging radio signal from a reference station having a known position;
A step of measuring a reception time of a radio signal for ranging by a base station having a plurality of known positions with a clock of the own station;
After the mobile terminal receives the ranging radio signal, a step of transmitting a response radio signal including delay time information by the clock of the own station from reception to reply;
Measuring the reception time of the response radio signal by the reference station and the base station with its own clock;
Based on the reception time of the response radio signal at the reference station and the base station, the transmission time of the distance measurement radio signal at the reference station, the delay time information from the mobile terminal, and the known distance information between the reference station and the base station, Calculating the distance between the base station and each base station and the mobile terminal by eliminating the clock deviation element;
Positioning method including. The base station transmits a clock error detection radio signal at a time different from the transmission time of the distance measurement radio signal, and at each base station, the reception time is measured by its own clock,
2. The positioning method according to claim 1, wherein the frequency difference of the clock of each base station with respect to the reference station is corrected based on the arrival time difference between the distance measurement radio signal and the clock error detection radio signal.   3. The positioning method according to claim 2, wherein the clock error detection radio signal is shared by a plurality of mobile terminals that are performing a positioning operation.   The positioning method according to claim 1, 2, or 3, wherein an impulse radio signal is used for the distance measurement radio signal and the reply radio signal. The acquired data in each base station is transmitted to the reference station by radio,
The positioning method according to claim 1, wherein the calculation step is executed at the reference station.

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