JP2008002888A - Wireless positioning system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a clock of a base station which cannot directly receive a radio wave for clock adjustment of a main station in a radio positioning system.
As a plurality of base stations of a radio positioning system, one main station M that transmits a clock synchronization signal to synchronize the clock of each base station S2, S3, and the main station M or another base station One or a plurality of relay stations R that receive the synchronization signal transmitted from the main station M and transmit the synchronization signal to the other base stations S2 and S3, and the base station that receives the synchronization signal transmitted from the main station M or the relay station R In the positioning server of the wireless positioning system, correction processing for adjusting the clocks of the base stations S2 and S3 to the clock of the main station M is performed based on the synchronization signal. Then, the reception time of the radio wave from the mobile terminal P is corrected, and the position of the mobile terminal P is calculated by TDOA based on the corrected time.
[Selection] Figure 1

Description

  The present invention is a wireless positioning system that determines the position of a mobile terminal using time differences of arrival (TDOA: Time Difference of Arrival) when radio waves transmitted from the mobile terminal arrive at a plurality of base stations. The present invention relates to a device that performs positioning processing by correcting information.

  FIG. 10 is a diagram illustrating the principle of TDOA. According to the principle of TDOA, the position of the mobile terminal P can be obtained by using the time difference when the radio wave transmitted from the mobile terminal P reaches the plurality of base stations B1, B2, B3. At this time, in order to obtain the difference in arrival time of radio waves transmitted from the mobile terminal P to each base station, it is necessary to set a clock (timer) between the base stations with an accuracy equal to or higher than the time accuracy required for positioning. is there. For example, in order to measure in units of 30 cm, it is necessary to set the clock with an accuracy of 1 nanosecond (ns).

  Although it is only necessary to operate the clock of each base station constituting the wireless positioning system with one clock, it is not preferable to connect each base station using a coaxial cable with a guaranteed delay because installation becomes complicated. .

  In addition, when time synchronization is performed between mobile base stations in order to know the position of the mobile phone, as in Patent Document 1, a radio wave of a global positioning system (GPS) is received and the time of the mobile base station is set to GPS. Synchronizing is done. However, it cannot be used indoors where radio waves from GPS cannot be received, and since the GPS clock accuracy is several tens of ns, the accuracy is insufficient when positioning with higher accuracy than 1 m.

  Therefore, as in Patent Document 2, in the case of the situation shown in FIG. 11, a radio wave for synchronization (synchronization signal) is transmitted from a specific base station (main station) M, and another base station (sub station) is transmitted. In S1 and S2, there is a method of receiving the synchronization signal transmitted from the main station M and correcting the clocks (timers) Ts1 and Ts2 of the local station to the clocks (Tm) of the main station M, respectively.

However, when there is an obstacle as shown in FIG. 12, or when the positioning range is wider than the reach of radio waves, the synchronization signal from the main station M can be received by all the sub stations S. Therefore, there is a problem that the clock of the substation S that cannot receive the synchronization signal cannot be corrected.
Special table 2003-513291 gazette JP 2004-101254 A

  The present invention uses a mobile terminal that transmits radio waves, a plurality of base stations whose positions for receiving radio waves from the mobile terminal are known, and a time difference in which the radio waves reach each base station from the mobile terminal. In a wireless positioning system including a positioning server that calculates the position of the mobile terminal, as the plurality of base stations, one main base station (main station) that transmits a synchronization signal for adjusting the clock of each base station; One or a plurality of relay base stations (relay stations) that receive the synchronization signal transmitted from the main station or another base station and transmit the synchronization signal to the other base station, and the main station or relay station And a base station (sub station) that receives a synchronization signal transmitted from the base station, and performs correction processing in the positioning server for adjusting the clock of each base station to the clock of the main station based on the synchronization signal Means and before Using the processing result of the correction means, characterized in that it comprises a positioning means for calculating the position of the mobile terminal.

  The correction means performs a clock adjustment correction process based on the clock of the main station for the base station that can receive the synchronization signal from the main station, and relays the base station that cannot receive the synchronization signal from the main station. A clock synchronization correction process may be performed based on the clock of the relay station that has received the synchronization signal from the station and has been corrected based on the main station.

  In addition, the correction means uses a relay station that has the smallest number of relay stations to relay between the base station and the main station for the base station that cannot receive the synchronization signal of the main station. You may make it select as a base station.

  The positioning server selects a base station that can receive radio waves transmitted by the mobile terminal, sets a group, and uses any one of the main stations or relay stations included in the group for correction processing. A combination determining means for selecting as a base station, and the correcting means for each group of base stations performing a clock adjustment correction process based on the clock of the base station selected by the combination determining means. Also good.

  The combination determining means may select the relay station having the maximum number of base stations in the group that can receive the synchronization signal transmitted from the relay station when selecting the relay station from the group. Good.

  FIG. 1 is a diagram showing the principle of the present invention.

  In the present invention, as shown in FIG. 1, as a base station constituting a wireless positioning system, a synchronization signal is transmitted between a main station M that transmits a synchronization signal for clock adjustment and a base station that receives radio waves from the main station M. A relay station R1 is provided. Then, the sub-station (distant station) S3, which is another base station from which the radio wave from the relay station R1 does not reach the radio wave of the main station M, is set to the clock (timer) Tr1 of the relay station R1. Since the relay station R1 receives radio waves from the main station M, the timer Tr1 of the relay station R1 can be corrected in accordance with the timer Tm of the main station. Therefore, after converting the timer Ts3 of the remote station S3 to the timer Tr1 of the relay station R1, it is converted again to the timer Tm of the main station M.

  Also, as shown in FIG. 2, the positioning area can be expanded as much as possible by providing a plurality of relay stations R as base stations in the wireless positioning system and re-relaying the synchronization signal of the main station M to the sub-stations. Can do.

  However, the accuracy of clock adjustment deteriorates every time the sync signal is relayed. In order to calculate the positioning of a mobile terminal, it is only necessary that the clocks are synchronized between base stations within the range where radio waves can reach from the mobile terminal, and the clocks of all base stations in the wireless positioning system are not necessarily synchronized. There is no. Therefore, the clock is adjusted only between base stations that receive radio waves from mobile terminals. For this purpose, the base stations that receive radio waves from one mobile terminal are set as much as possible by synchronizing signals from one relay station R (including the main station M) as much as possible.

  For example, at the position of the mobile terminal P1 in FIG. 2, the radio wave from the mobile terminal P1 reaches the relay station R2, the relay station R3, the substations S3, S4, and S5. On the other hand, the sub-stations S3 and S4 receive both the synchronization signal from the relay station R1 and the synchronization signal from the relay station R2. In such a case, when the position of the mobile terminal P1 is calculated, the sub-stations S3 and S4 do not set the clock to the relay station R1, but set the clock to the relay station R2. Similarly, the sub-station S5 receives both the synchronization signal from the relay station R2 and the synchronization signal from the relay station R3. However, the sub-station S5 does not set the clock to the relay station R3, but the clock to the relay station R2. Try to match.

  By selecting the synchronization signal to be used in this way, all the base stations R2, R3, S3, S4, and S5 that receive the radio wave from the mobile terminal P1 can set the clock to the relay station R2. Further, at the position of the mobile terminal P2, the radio wave from the mobile terminal P2 reaches the relay station R3, the substations S5, S6, and S7. In this case, the sub station S5 does not set the clock to the relay station R2, but sets the clock to the relay station R3. As described above, it is a feature of the present invention that the relay station used for clock adjustment changes depending on the position of the mobile terminal P even when the same sub-station S5 is clock-adjusted.

  Furthermore, as shown in FIG. 3, there are cases where positioning cannot be performed with only a synchronization signal from one relay station R. At the position of the mobile terminal P1, the radio wave from the mobile terminal P1 reaches the relay station R3, the substations S4, S5, and S6. However, these base stations cannot receive a synchronization signal from one relay station. Specifically, the substations S5 and S6 can receive the synchronization signal from the relay station R3, but cannot receive only the synchronization signal from the relay stations R1 and R2. The sub station S4 can receive only the synchronization signal from the relay stations R1 and R2, and cannot receive the synchronization signal from the relay station R3. Therefore, only the sub station S4 is set to the clock of the relay station R2 once, and further, since the synchronization signal of the relay station R3 arrives at the relay station R2, it is further converted into the clock of the relay station R3. The substation S4 can be matched to the relay station R1, then to the relay station R2, and further to the relay station R3. However, since this increases the number of re-conversion processes, first the relay station Match to R2.

  According to the present invention, even if a synchronization signal does not reach all base stations from one main station in a wireless positioning system, it passes through a relay station that can receive radio waves from the main station. It is possible to realize clock adjustment between necessary base stations.

  In addition, since the clock can be set with higher accuracy without using GPS radio waves, high-accuracy positioning in units of 30 cm can be realized indoors.

  Therefore, it is possible to realize a high-accuracy indoor radio positioning system in which there are complicated obstacles or the positions of the obstacles change.

  Several examples will be described below as the best mode of the present invention.

  The wireless positioning system of the present invention includes a positioning server 1 and a plurality of base stations 2 whose position information is known.

  The positioning server 1 acquires the reception time of positioning radio waves (positioning signals) from each base station 2 and calculates the position of the mobile terminal P by TDOA. In addition, the clocks of the respective base stations are set based on the transmission time and reception time of the radio waves for synchronization (synchronization signals) transmitted and received between the respective base stations 2. The positioning server 1 acquires the information on the transmission / reception time of the synchronization signal from each base station 2 using a wired or wireless line. In the present embodiment, the positioning server 1 and each base station 2 are connected via a network such as Ethernet (registered trademark).

  The base station 2 receives the positioning signal transmitted by the mobile terminal P, and transmits the received identification information of the mobile terminal P and the reception time of the positioning signal to the positioning server 1. The base station 2 is configured as a main station M, a relay station R, and a sub station S that is a base station other than these.

The main station M is a base station that can transmit a synchronization signal for clock adjustment of each base station 2. The relay station R is a base station that can receive a synchronization signal from the main station M or another relay station R and can transmit the synchronization signal to another base station 2. The sub station is a base station that receives a synchronization signal from the main station M and the relay station R.
[First embodiment]
In the first embodiment, all the clocks of the base stations constituting the wireless positioning system are finally set to the clocks of the main station M. The clock of the sub station S that does not receive radio waves from the main station M is set to the main station M via the relay station R.

  With reference to FIG. 2, the clock adjustment processing of each base station in the first embodiment will be described more specifically. The sub-stations S1 and S2 and the relay station R1 that receive the synchronization signal from the main station M are set to the main station M. The relay station R2, the sub-stations S3 and S4 are adjusted to the relay station R1, and further to the main station M using the correction of the relay station R1. The relay station R3 and the substation S5 are matched with the relay station R2, further matched with the relay station R1, and then matched with the main station M. The sub-stations S6 and S7 are matched with the relay station R3, further matched with the relay station R2, further matched with the relay station R1, and matched with the main station M. The substation S5 can be adjusted to the relay station R3 and then routed to the relay stations R2 and R1. However, the accuracy of clock adjustment deteriorates when the number of relay stations that relay to the main station M is small. Therefore, it is adjusted to the relay station R2 without going through the relay station R3. Similarly, the sub-stations S3 and S4 are adjusted not to the relay station R2 but to the relay station R1.

  FIG. 4 shows a configuration example of the wireless positioning system in the first embodiment.

  The main station M includes a synchronization signal generation unit 21, a transmission unit 22, a synchronization transmission time holding unit 23, a reception unit 24, and a terminal reception time holding unit 26. The main station M generates a synchronization signal by the synchronization signal generation unit 21, transmits it from the antenna via the transmission unit 22, and holds the time (synchronization transmission time) at which the synchronization signal is transmitted in the synchronization transmission time holding unit 23. . Further, the positioning signal transmitted by the mobile terminal P is received by the receiving unit 24, and the time when the positioning signal is received (terminal reception time) is held in the terminal reception time holding unit 26. The synchronous transmission time held in the synchronous transmission time holding unit 23 and the terminal reception time of the mobile terminal P held in the terminal reception time holding unit 26 are transmitted to the positioning server 1.

  The relay stations R1,..., Rn include a synchronization signal generation unit 31, a transmission unit 32, a synchronization transmission time holding unit 33, a reception unit 24, a synchronization reception time holding unit 35, and a terminal reception time holding unit 36. The relay stations R1,..., Rn generate a synchronization signal by the synchronization signal generation unit 31 and transmit the synchronization signal from the antenna via the transmission unit 32, and also transmit the synchronization signal transmission time (synchronization transmission time) to the synchronization transmission time holding unit 33. The synchronization signal transmitted from the main station M or another relay station R is received by the reception unit 34, and the time when the synchronization signal is received (synchronous reception time) is held by the synchronization reception time holding unit 35. Further, the terminal reception time holding unit 36 holds the time when the positioning signal is received from the mobile terminal P (terminal reception time). The synchronous transmission time held in the synchronous transmission time holding unit 33, the synchronous reception time held in the synchronous reception time holding unit 35, and the terminal reception time of the mobile terminal P held in the terminal reception time holding unit 36 are: It is transmitted to the positioning server 1.

  The sub stations S1,..., Sn include a receiving unit 44, a synchronous reception time holding unit 45, and a terminal reception time holding unit 46. The sub stations S1,..., Sn receive the synchronization signal from the main station M and the relay stations R1,..., Rn by the receiving unit 44, and the time at which the synchronization signal is received (synchronous reception time) is the synchronous reception time holding unit 45. Hold on. Further, the terminal reception time holding unit 46 holds the time at which the positioning signal is received from the mobile terminal P (terminal reception time). Then, the synchronization reception time held in the synchronization reception time holding unit 45 and the terminal reception time of the mobile terminal P held in the terminal reception time holding unit 46 are transmitted to the positioning server 1.

  The positioning server 1 includes a correction coefficient creation unit 11, a terminal reception time correction unit 12, and a positioning calculation unit 13.

  The correction coefficient creation unit 11 acquires the synchronous transmission time and the synchronous reception time from each of the base stations 2 (main station M, relay stations R1,..., Rn, substations S1,..., Sn). Then, using the transmission time (synchronous transmission time) of the synchronization signal held in the synchronous transmission time holding unit 23 and the synchronous reception time holding unit 35 and the reception time (synchronous reception time), a correction coefficient for clock adjustment is obtained. It is created by the correction coefficient creation unit 11.

  The terminal reception time correction unit 12 corrects the terminal reception times held by the terminal reception time holding units 26, 36, and 46 of each base station 2 using the correction coefficient calculated by the correction coefficient creation unit 11.

  The positioning calculation unit 13 calculates the position of each mobile terminal P using the result corrected by the terminal reception time correction unit 12.

  In this embodiment, an impulse radio wave is used as the synchronization signal. As a result, the reception time can be accurately obtained. FIG. 5 shows a block configuration example of the base station 2 in this case, and FIG. 6 shows a transmission data format example.

  As shown in FIG. 5, each base station 2 has basically the same configuration, and includes a transmission block 100, a plurality of reception blocks 200, a timer 300, a bandpass filter unit (BPF) 400, and a power amplifier unit (PA). 410, an antenna unit 420, a low noise amplifier unit (LNA) 430, a pulse detection unit 440, and an MPU 500.

  The transmission block 100 includes a synchronization PN sequence generation unit 101, a PPM data modulation unit 103, an impulse generation unit 105, and a transmission time holding unit 107. The reception block 200 includes a correlator 201, a PN sequence generation unit 203, a PPM data demodulation unit 205, and a reception time holding unit 207.

  Since the main station M does not receive the synchronization signal from the other base station 2, it is not necessary to include the reception block 200 for receiving the synchronization signal, and a plurality of positioning signals from the plurality of mobile terminals P1,. Reception blocks 200-1,..., 200-L.

  The relay station R has one reception block 200-1 for receiving a synchronization signal from the main station M or another relay station 2, and a plurality of reception blocks 200-2 for receiving positioning signals from a plurality of mobile terminals P. ,..., 200-L.

  Since the sub-station S does not transmit a synchronization signal, there is no need to provide the transmission block 100, and one reception block 200-1 for synchronization signal and a plurality of reception blocks 200- that receive positioning signals from the mobile terminal P are received. 2, ..., 200-L.

  As shown in FIG. 6, the 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. When one chip is 100 ns and “5763421” 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 1 μs pulse section. The data unmodulated preamble part for synchronization is 7 pulses 7 μs, and the data part comes after that. The data part is also time-hopped by 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 RS sequence of “5763...” Is modulated as “5873...”, And pulses are hopped at positions of 500 ns, 800 ns, 700 ns, and 300 ns.

  In the case of the configuration shown in FIG. 5, the base station 2 on the transmission side generates an RS sequence by the synchronization PN sequence generation unit 101. The PPM data modulation unit 103 performs PPM data modulation according to transmission data 1 and 0 passed from the MPU 500, and sends a pulse to the impulse generation unit 105. The impulse generator 105 generates a very thin impulse at the rising edge of the pulse by the step recovery diode. Although the generated impulse has a very wide band, for example, unnecessary 3.1 GHz or less by passing through the BPF 400 that performs band-pass filtering of 3.1 GHz to 5 GHz so as to conform to the radio law mask. And 5 GHz or higher components are removed. The impulse radio wave is amplified by the PA 410 after passing through the BPF 400 and radiated by the antenna 420. In the transmission time holding unit 107, the time at which the first pulse after the preamble is generated during data transmission is stored as the synchronous transmission time.

  On the other hand, in the base station 2 on the receiving side, the impulse radio wave received from the antenna 420 is amplified by the LNA 430 after unnecessary frequency components are removed by the BPF 400, and the presence or absence of a pulse is detected by the pulse detection unit 440. The pulse detection unit 440 is 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 generation unit 203 in the correlator 201 using a digital matched filter. If the preamble is detected by the correlator 201, the PPM data demodulating unit 205 demodulates the PPM of the subsequent data unit and generates received data, assuming that synchronization is established. Further, when the reception time holding unit 207 detects the first pulse of the data portion, the reception time holding unit 207 holds that time as the synchronous reception time.

  FIG. 7 shows a device configuration example of the mobile terminal P. The mobile terminal P includes an MPU 610, a positioning PN sequence generation unit 621, a PPM data modulation unit 623, an impulse generation unit 625, a bandpass filter unit (BPF) 630, a power amplifier unit (PA) 640, and an antenna unit 650. The mobile terminal P has only a transmission function, and generates and transmits an impulse radio wave by TH / PPM, similarly to the transmission block 100 of the base station 2.

  Next, the clock setting process of each base station will be described in more detail.

  For example, in FIG. 2, the clock of the sub station S1 is set to the clock of the main station M. The clock Ts1 of the sub station S1 is corrected by the following primary equation (1) because the offset (time origin) and scale (clock advancement, clock clock frequency) are shifted from the main station M.

Tms1 = Ams1 ・ Ts1 + Bms1 (1)
The time when the main station M transmits the synchronization signal is Tm, the propagation delay time of the radio wave from the main station M to the substation S1 is Dms1, and the time when the substation S1 viewed from the clock of the main station M receives the synchronization signal is Tms1. , When the reception time of the synchronization signal as seen on the clock of the sub station S1 is Ts1,
Tm + Dms1 = Tms1 = Ams1 · Ts1 + Bms1 (2)
It becomes. And from equation (2),
Tm = Ams1, Ts1 + Bms1-Dms1 (3)
Assuming that the propagation delay time Dms1 is known, the unknowns are two in the equation (3), Ams1 and Bms1, and therefore, Ams1 and Bms1 can be solved by two synchronization signals. Actually, since an error is included, the accuracy of the correction coefficient is improved by, for example, obtaining from the continuous q number of synchronization signals by the least square method. That is, a synchronization signal is transmitted from the main station M at times Tm ⁽¹⁾ , Tm ⁽²⁾ ,..., Tm ^(q) , and Ts1 ⁽¹⁾ , Ts1 ⁽²⁾ , ..., assuming that a synchronization signal is received at Ts1 ^(q) ,
Tm ⁽¹⁾ = Ams1 · Ts1 ⁽¹⁾ + Bms1-Dms1,
Tm ⁽²⁾ = Ams1 · Ts1 ⁽²⁾ + Bms1-Dms1,
…,
Tm ^(q) = Ams1 · Ts1 ^(q) + Bms1-Dms1 (4)
It becomes. Therefore, by the least square method, the correction coefficient is
Ams1 = (ΣTs1 ^(k) ΣTm ^(k) −qΣTm ^(k) Ts1 ^(k) ) /
((ΣTs1 ^(k) ) ² −qΣTs1 ^{(k) 2} )
Bms1 = (ΣTs1 ^(k) ΣTm ^(k) Ts1 ^(k) −ΣTm ^(k) ΣTs1 ^{(k) 2} ) /
((ΣTs1 ^(k) ) ² −qΣTs1 ^{(k) 2} ) + Dms1 (5)
It becomes. In addition, the correction coefficient is first obtained with q synchronization signals. Next, every time one synchronization signal comes, the latest q values are sequentially updated.

In the same way, the clock Tr1 of the relay station R1 uses the correction coefficients Amr1 and Bmr1,
Tmr1 = Amr1 ・ Tr1 + Bmr1 (6)
On the other hand, the sub station S3 first matches the relay station R1,
Tr1s1 = Ar1s3 · Ts3 + Br1s3 (7)
From Equation (6) and Equation (7),
Tms3 = Amr1, Ar1s3, Ts3 + Amr1, Br1s3 + Bmr1 (8)
Can be set to the clock of the main station M. In the same manner, the clocks of all base stations 2 can be set to the clock of the main station M.

  Here, the timepiece is corrected by the primary expression, but the present invention is not limited to this, and it may be corrected by a secondary expression or a higher order expression.

  Next, positioning calculation is shown.

  The positioning signal transmitted from the mobile terminal P1 is received by the n base stations 2. The positioning server 1 obtains the position of the mobile terminal P1 by the TDOA method using the time difference at which the radio waves reach each base station.

The reception time of the positioning signal of the mobile terminal P received at each base station 2 is time-corrected by the positioning server 1 and adjusted to the clock of the main station M. When the unknown coordinates of the mobile terminal P are (X, Y) and the known coordinates of each base station 2 are (X ₁ , X ₂ ), ..., (X _n , Y _n ), the i-th base station and If the reception time difference at the j-th base station is Tij and the speed of light is C,

Therefore, the above simultaneous equations should be solved for X and Y.

  In general, the least squares method is used for the iterative calculation by Newton's method.

  If the estimated initial value of the position of the mobile terminal P is (X0, Y0), a residual matrix consisting of the difference between the measured reception time difference and the reception time difference obtained based on the estimated terminal coordinates is

Therefore, the initial correction term is

The estimated values are corrected by adding ΔX and ΔY to the estimated values X0 and Y0 until the correction terms ΔX and ΔY are equal to or less than the predetermined values, and the equations (10) and (11) are repeated.
[Second Embodiment]
Next, a second embodiment is shown. In the first embodiment, the clocks of all the base stations 2 are set to the main station M. In the second embodiment, a plurality of base stations 2 that can receive radio waves from the mobile terminal P are set as one group. As much as possible, the base station 2 is clocked to one relay station R (including the main station M). In the first embodiment, since the accuracy of clock adjustment deteriorates every time the synchronization signal is relayed, the clocks of all the base stations 2 are not set to one, but the clock is set locally for each group. is there.

  In FIG. 2, relay stations R2, R3, substations S3, S4, and S5 that are within a range where radio waves reach from the mobile terminal P1 are set as one group. Then, the clock of each base station 2 in the group is set to the relay station R2. On the other hand, the relay station R3 and the substations S5, S6, and S7 within the range where radio waves reach from the mobile terminal P2 are made into one group, and the clock of each base station 2 is set to the relay station R3. The relay station R3 and the substation S5 are set to different groups, that is, to the clocks of different relay stations R, when the positioning calculation of the mobile terminal P1 is performed and when the positioning calculation of the mobile terminal P2 is performed.

  Further, as shown in FIG. 3, the relay station R3 and the substations S4, S5, and S6 that are within the range where radio waves reach from the mobile terminal P1 are set as one group, but the clock cannot always be set to one relay station R. Therefore, the substations S5 and S6 to which the radio waves of the relay station R3 reach are set to the relay station R3, and the substation S4 is set to the relay station R2 once and further to the relay station R3. The method for setting the clock via a plurality of relay stations R is the same as the processing in the first embodiment.

  FIG. 8 shows an example of a system configuration in the second embodiment. In the second embodiment, since the main station M and the relay station R are handled in the same manner, the following description will be made as the relay station R.

  The relay station R and the substation S are configured in the same manner as in the first embodiment. The relay station R holds the time when the synchronization signal is transmitted (synchronization transmission time) and the time when the synchronization signal from the other base station 2 is received (synchronization reception time). The sub station holds the time when the synchronization signal is received.

  The positioning server 1 adds a function for determining a group in addition to the configuration in the first embodiment, and includes a correction coefficient creating unit 11, a terminal reception time correcting unit 12, a positioning calculating unit 13, a correction table creating unit 15, a correction table. 16 and the combination determination part 17 are provided.

  Prior to positioning, the correction table creation unit 15 obtains the base station 2 to which radio waves reach from each relay station R, and creates the correction table 16. The correction table 16 is created according to a predetermined period or trigger.

  FIG. 9 shows an example of the correction table. Each row of the correction table 16 indicates each base station, and each column indicates the relay station R. When the base station in the row can receive radio waves from the relay station R in the column, “reception is possible (◯)” is set in the matrix position.

  For example, the correction table 16 in FIG. 9A shows base stations that can receive radio waves from each relay station R in FIG. In FIG. 9A, the main station M may receive radio waves from the main station M to the base stations 2 of the main station M (including itself), the relay station R1, and the sub stations S1 and S2 by looking at the M column. I understand. It can be seen from the relay station R1 that the radio wave reaches the main station M, the relay stations R1, R2, and the sub stations S2, S3, S4 by looking at the R1 column. Also, it can be seen that the sub station S3 can receive the synchronization signals from the relay stations R1 and R2 by looking at the row S3.

  Then, the correction count generation unit 11 calculates a correction coefficient for setting the clock of the base station 2 at the position where “reception ready (◯)” is set in the correction table 16 by the synchronization signal from the relay station R. And stored in the correction table 16. The method for obtaining the correction coefficient and the correction formula are the same as in the first embodiment.

  Next, when the positioning calculation is performed, radio waves arrive from the mobile terminal P1 to the relay stations R2, R3, the substations S3, S4, and S5. Therefore, the combination determination unit 17 sets the column of the mobile terminal P1 in the correction table 16. Create and set a flag (/) at the position of the row of the base station where the radio wave reaches. At this time, a search is made for a column in which the flag (/) position of the column of the mobile terminal P1 and the position of “reception ready (◯)” are more consistent. Here, it can be seen that the columns of the relay station R2 match. Therefore, when the positioning calculation of the mobile terminal P1 is performed, it is determined to match the clock of the relay station R2. Similarly, in the positioning calculation of the mobile terminal P2, since the flag (/) in the column of the mobile terminal P2 is included in “Receivable (O)” in the column of the relay station R3, it is determined to match the clock of the relay station R3. Is done.

  On the other hand, the correction table 16 in FIG. 9B shows base stations that can receive radio waves from each relay station R in FIG. In FIG. 9B, at the position of the mobile terminal P1, flags (/) are set in the rows of the relay stations R2, R3, sub stations S4, S5, S6. There is no column in the correction table 16 that matches. Therefore, when a matching column is searched for more, it becomes the column of the relay station R3. However, since there is no “Receivable (O)” in the row of the sub station S4, it can be seen that the sub station S4 does not receive the synchronization signal of the relay station R3. Further, looking at the row of the sub-station S4, there is “Receivable (O)” in the columns of the relay stations R1 and R2. Thus, looking at the rows of the relay stations R1 and R2, it can be seen that the relay station R2 can be synchronized with the relay station R3 because the row of the relay station R2 has “Receivable (O)” in the column of the relay station R3. That is, it is determined that the sub station S4 is matched with the relay station R2 and further matched with the relay station R3. Thus, the combination determination part 17 determines the above combination. According to this determination, a correction coefficient is obtained from the correction table 16, and the terminal reception time is corrected to perform positioning calculation. The time correction method and the positioning calculation method are the same as in the first embodiment.

  As another processing example of the second embodiment, among base stations 2 of a group used for positioning calculation, a base station 2 that does not receive radio waves from one relay station R is not used for positioning calculation. You can also. For example, in FIG. 9B, the sub station S4 does not receive the radio wave from the relay station R3. However, in the case of positioning calculation in two dimensions, positioning calculation can be performed if radio waves reach at least three base stations 2. In this mobile terminal P1, radio waves reach five base stations 2 and two are redundant in positioning calculation. Therefore, positioning calculation may be performed without using the substation S4.

  Furthermore, as another processing example, the sub station S4 is not used at all for the positioning calculation as in the above processing example, but the base station is weighted in the positioning calculation, and the weight to the sub station S4 is reduced to perform positioning. It can also be used for calculations. For the base station 2 in which radio waves do not reach from one relay station R by the least square method of Equation (11), the weight is set to 1 / w of the other base station, and Equation (11) is set to the least weighted minimum 2 It may be modified as the multiplication formula (12).

  While the present invention has been described above with reference to the embodiments, it is obvious that the present invention can be variously modified within the scope of the gist thereof.

  Although the present invention has been described as being implemented as a processing program that is read and executed by a computer, the processing program that implements the present invention includes a portable medium memory, a semiconductor memory, a hard disk, and the like that can be read by a computer. It can be stored in an appropriate recording medium, provided by being recorded on these recording media, or provided by transmission / reception using various communication networks via a communication interface.

  The features of the embodiments and examples of the present invention are listed as follows.

(Appendix 1)
A mobile terminal that transmits radio waves, a plurality of base stations whose positions for receiving radio waves from the mobile terminal are known, and a time difference in which the radio waves reach each base station from the mobile terminal In a wireless positioning system comprising a positioning server for calculating a position,
As the plurality of base stations,
One main base station that transmits a clock synchronization signal to set the clock of each base station;
One or a plurality of relay base stations that receive the synchronization signal transmitted from the main base station or another base station and transmit the synchronization signal to the other base station;
A base station that receives the synchronization signal transmitted from the main base station or the relay base station;
The positioning server includes a correction unit that performs a correction process for adjusting the clock of each base station to the clock of the main base station based on the synchronization signal;
A wireless positioning system comprising: positioning means for calculating the position of the mobile terminal using the processing result of the correcting means.

(Appendix 2)
The correction means performs a clock adjustment correction process on the base station capable of receiving a synchronization signal from the main base station based on the clock of the main base station, and outputs the synchronization signal from the main base station. For a base station that cannot be received, a synchronization signal from the relay base station is received, and the clock is set based on the clock of the relay base station that has been corrected based on the main base station. The wireless positioning system according to appendix 1, wherein correction processing is performed.

(Appendix 3)
The correction means includes a relay base that minimizes the number of relay base stations that relay between the base station and the main base station for a base station that cannot receive the synchronization signal of the main base station. The radio positioning system according to claim 2, wherein a station is selected as a relay base station used for the correction processing.

(Appendix 4)
The positioning server selects a base station that can receive radio waves transmitted by the mobile terminal, sets a group, and selects any one of a main base station and a relay base station included in the group as the base station. A combination determining means for selecting a base station to be used for the correction process;
The wireless positioning system according to claim 1, wherein the correction unit performs a clock adjustment correction process on the base stations of each group based on a clock of the base station selected by the combination determination unit. .

(Appendix 5)
When the combination determining means selects a base station for relaying from the group, the combination determining means is used for relaying that has the maximum number of base stations in the group that can receive the synchronization signal transmitted by the base station for relaying. The base station is selected. The wireless positioning system according to appendix 4, wherein the base station is selected.

(Appendix 6)
The correction means uses a clock of the selected relay base station for a base station that cannot receive the synchronization signal transmitted by the selected relay base station in the group. 5. The wireless positioning system according to appendix 4, wherein a clock adjustment correction process is performed based on a clock of another relay base station that has been performed.

(Appendix 7)
The positioning means, when calculating the position of the mobile terminal based on the base station of the group, a base station that cannot receive the synchronization signal transmitted by the selected relay base station in the group The wireless positioning system according to Appendix 4, wherein the position of the mobile terminal is calculated based on the remaining base stations.

(Appendix 8)
When the positioning means calculates the position of the mobile terminal based on the base station of the group, in the calculation of the position of the mobile terminal, the base station for relay selected in the group transmits the position The wireless positioning system according to claim 4, wherein the calculation is performed by a calculation formula in which a weight for a base station that cannot receive a synchronization signal is lighter than a weight for another base station.

(Appendix 9)
The correction means receives a synchronization signal transmitted from the main base station or the relay base station a plurality of times when performing clock adjustment of the base station, and transmits and receives the synchronization signal, and The wireless positioning system according to any one of Supplementary Note 1 to Supplementary Note 8, wherein correction processing for clock adjustment of the base stations is performed based on a propagation delay time between the base stations.

(Appendix 10)
The correction means sequentially performs correction processing using the latest predetermined number of synchronization signals among a plurality of synchronization signals received from the main base station or the relay base station. The wireless positioning system according to Appendix 9.

(Appendix 11)
The wireless positioning system according to claim 9, wherein the correction unit performs processing using a linear correction formula in the correction processing.

(Appendix 12)
The radio positioning system according to any one of Supplementary Note 1 to Supplementary Note 11, wherein the radio wave and the synchronization signal transmitted from the mobile terminal are impulse radio waves.

It is a figure which shows the principle of this invention. It is a figure for demonstrating the process in case there exist several relay stations. It is a figure for demonstrating the process when clock adjustment cannot be performed in one relay station. It is a figure which shows the wireless positioning system structural example in 1st Example. It is a figure which shows the block structural example of a base station. It is a figure which shows the example of a format of transmission data. It is a figure which shows the apparatus structural example of the mobile terminal P. FIG. It is a figure which shows the system configuration example in a 2nd Example. It is a figure which shows the example of a correction table. It is a figure which shows the principle of TDOA. It is a figure for demonstrating the process of the conventional time synchronization. It is a figure for demonstrating the subject by a conventional method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positioning server 11 Correction coefficient preparation part 12 Terminal reception time correction part 13 Positioning calculation part 15 Correction table preparation part 16 Correction table 17 Combination determination part M Main station R1, ..., Rn Relay station S1, ..., Sn Sub station P Mobile terminal 21, 31 Synchronization signal generation unit 22, 32, Transmission unit 23, 33, Synchronization transmission time holding unit 24, 34, 44 Reception unit 35, 45, Synchronization reception time holding unit 26, 36, 46 Terminal reception time holding unit

Claims (5)

A mobile terminal that transmits radio waves, a plurality of base stations whose positions for receiving radio waves from the mobile terminal are known, and a time difference in which the radio waves reach each base station from the mobile terminal In a wireless positioning system comprising a positioning server for calculating a position,
As the plurality of base stations,
One main base station that transmits a clock synchronization signal to set the clock of each base station;
One or a plurality of relay base stations that receive the synchronization signal transmitted from the main base station or another base station and transmit the synchronization signal to the other base station;
A base station that receives the synchronization signal transmitted from the main base station or the relay base station;
The positioning server includes a correction unit that performs a correction process for adjusting the clock of each base station to the clock of the main base station based on the synchronization signal;
A wireless positioning system comprising: positioning means for calculating the position of the mobile terminal using the processing result of the correcting means. The correction means performs a clock adjustment correction process on the base station capable of receiving a synchronization signal from the main base station based on the clock of the main base station, and outputs the synchronization signal from the main base station. For a base station that cannot be received, a synchronization signal from the relay base station is received, and the clock is set based on the clock of the relay base station that has been corrected based on the main base station. The wireless positioning system according to claim 1, wherein correction processing is performed. The correction means includes a relay base that minimizes the number of relay base stations that relay between the base station and the main base station for a base station that cannot receive the synchronization signal of the main base station. The radio positioning system according to claim 2, wherein a station is selected as a relay base station used for the correction processing. The positioning server selects a base station that can receive radio waves transmitted by the mobile terminal, sets a group, and selects any one of a main base station and a relay base station included in the group as the base station. A combination determining means for selecting a base station to be used for the correction process;
2. The radio positioning system according to claim 1, wherein the correction unit performs a clock adjustment correction process on the base stations of each group based on a clock of the base station selected by the combination determination unit. 3. . When the combination determining means selects a base station for relaying from the group, the combination determining means is used for relaying that has the maximum number of base stations in the group that can receive the synchronization signal transmitted by the base station for relaying. The base station is selected. The wireless positioning system according to claim 4, wherein the base station is selected.

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