JP2009229393A - Radio determination system and radio determination method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the cost of the whole radio determination system by installing a base station having only a simple transmitting/receiving function on the infrastructure side and reducing the number of base stations having complicated transmitting/receiving functions. <P>SOLUTION: Radio signals R1 are asynchronously transmitted from a plurality of base stations A, B to at least one base station P and a mobile terminal M. When the base station P transmits a radio signal R2 to the mobile terminal M in response to the radio signal R1, the receiving time of receiving the radio signal R1 and the transmitting time of transmitting the radio signal R2 are included in the radio signal R2 and transmitted. The position of the mobile terminal M is determined by operation based on the receiving time of the radio signal R1 received by the mobile terminal M, the receiving time of the radio signal R2 received by the mobile terminal M, and the receiving time and transmitting time included in the radio signal R2 received by the mobile terminal M. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radio positioning system, and more particularly to a radio positioning system, a radio positioning method, a reference station, and a mobile terminal in which a mobile terminal itself specifies a position by using a propagation time of radio waves.

  As a technique for measuring the position of a mobile terminal by using the propagation time of radio waves, a TOA (Time of Arrival) method and a TDOA (Time Difference of Arrival) are known.

  FIG. 1 is a diagram for explaining a TOA type positioning system. In the TOA scheme, a plurality of base stations A, B, and C having a transmission / reception function are installed within the movement range of the mobile terminal M. The positions of the base stations A, B, C are accurately determined in advance. First, when the base station A receives the radio signal R1 transmitted from the mobile terminal M to the specific base station A, the base station A returns the radio signal R2 to the mobile terminal M. The mobile terminal M receives the radio signal R2, and measures the distance between the mobile terminal M and the base station A from the round-trip propagation time. Next, when the base station B receives a radio signal R3 emitted from the mobile terminal M toward the specific base station B, the base station B returns a radio signal R4 to the mobile terminal M. The mobile terminal M receives the radio signal R4 and measures the distance between the mobile terminal M and the base station B from the round-trip propagation time. By performing this operation sequentially for a plurality of base stations (base stations A, B, C), the mobile terminal M measures the position of the mobile terminal M based on the principle of triangulation.

  When the mobile terminal M moves in a wide range or a range with many obstacles, it is necessary to communicate with at least two base stations at the same time, and it is necessary to install a large number of base stations. In particular, if impulse radio waves are used to increase measurement accuracy, a transmitter with low power consumption and low price can be used as the transmitter of each base station. On the other hand, since the receiver requires a complicated and expensive circuit compared to the transmitter, if the transceivers are provided in all the base stations (infrastructure side), the installation cost of the base station becomes high.

  FIG. 2 is a diagram for explaining a TDOA type positioning system. In the TDOA scheme, a plurality of base stations A, B, and C are installed, but each base station A, B, and C is provided with only a transmitter and no receiver. If the transmitters of the base stations A, B, and C transmit the radio signals R1, R2, and R3 at the same time or with a known time difference, the mobile terminal M transmits the radio signal R1 from the base stations A, B, and C. , R2 and R3, the position of the mobile terminal M can be measured from the arrival time difference.

  Here, in order for each of the base stations A, B, and C to transmit the radio signals R1, R2, and R3 at the same time or with a known time difference, it is necessary to establish time synchronization between the base stations A, B, and C. There is. This time synchronization is a function that cannot be realized only by the transmitter, and each base station A, B, C needs to have a communication function for time synchronization. Therefore, if the communication function for time synchronization is provided in all the base stations, the installation cost of the base station becomes high.

  As described above, in the TOA method and the TDOA method, it is necessary to provide a receiver and communication means in all of the plurality of base stations, and accordingly, the configuration of the base station becomes complicated and the cost increases. Thus, a wireless positioning system that measures the position of a mobile terminal in a wireless network including a plurality of asynchronous base stations has been proposed (see, for example, Patent Document 1).

  FIG. 3 is a diagram for explaining the wireless positioning system disclosed in Patent Document 1. In FIG. In the wireless positioning system shown in FIG. 3, a reference station P is provided as one of base stations. The reference station P measures the time difference between the time when the reference station P receives the radio signal R1 transmitted from the base station A and the time when the reference station P receives the radio signal R2 transmitted from the base station B. Further, the reference station P measures the time difference between the time when the reference station P receives the radio signal R1 transmitted from the base station A and the time when the reference station P receives the radio signal R2 transmitted from the base station C. Then, the reference station P transmits the measured time difference to the base station A by the radio signal R4. The base station A transmits the received time difference data to the server S by radio or a wired signal R5.

  On the other hand, the mobile terminal M measures the time difference between the time when the mobile terminal M receives the radio signal R6 transmitted from the base station B and the time when the mobile terminal M receives the radio signal R7 transmitted from the base station A. . Further, the mobile terminal M measures the time difference between the time when the mobile terminal M receives the radio signal R6 transmitted from the base station B and the time when the reference station P receives the radio signal R8 transmitted from the base station C. Then, the mobile terminal M transmits the measured time difference to the base station A by the radio signal R9. The base station A transmits the received time difference data to the server S by radio or a wired signal R10.

The server S calculates the position of the mobile terminal M based on the time difference measured by the reference station P and the time difference measured by the mobile terminal M.
1 to 3, ◯ represents a base station or reference station having a transceiver, Δ represents a base station having only a transmitter, ■ represents a mobile terminal having only a receiver, and ● represents a transceiver. Represents a mobile terminal having
JP 2000-504838

  In the case of the conventional radio positioning system shown in FIG. 3, the time difference measured at the reference station P is (R1-R2) and (R1-R3), and the radio signals R1, R2, and R3 are asynchronous, resulting in a large time difference. There is. Similarly, the time differences (R6-R7) and (R6-R8) measured by the mobile terminal M may be large because the radio signals R6, R7, and R8 are asynchronous.

  When the time difference is large, the accuracy of the timer that measures the time difference becomes a problem. That is, in the conventional radio positioning system, (R1-R2) is measured by the timer of the reference station P, (R6-R7) is measured by the timer of the mobile terminal M, and if the time difference is large, the frequency of the timer An error causes an error in the measurement time, resulting in a positioning error. The positioning error due to such a timer error is, for example, an error of several meters if the position of the mobile phone is measured, and does not cause a big problem. However, for example, since the position measurement accuracy of several tens of centimeters is required for the position measurement of the indoor conveyance device, it becomes a big problem that the positioning error due to the timer error is several meters.

  Further, in the conventional wireless positioning system of FIG. 3, at least three base stations are required in addition to the reference station P in order to perform two-dimensional positioning. The reference station P is a base station equipped with a transceiver, and the installation cost of the reference station P is higher than the installation cost of the base station.

  Further, in the conventional radio positioning system of FIG. 3, the radio signal R1 from the base station A to the reference station P and the radio signal R7 from the base station A to the mobile terminal M are separated. For example, when the mobile terminal of the positioning system is a mobile cellular phone, signals are sent using individual IDs for each mobile terminal, so R1 and R7 cannot be shared. Therefore, the number of communications in the base station A increases and the power consumption in the base station A increases.

  Further, in the conventional radio positioning system of FIG. 3, since the positioning calculation is performed by the server S, in order to send time difference information to the server S, the radio signal R4 from the reference station P to the base station A and the mobile terminal M to the base station A radio signal R9 to A is required. For this reason, the frequency | count of communication is large and the probability that positioning will be impossible by a communication error etc. becomes high.

  In order to solve the above problem, a radio positioning system including a plurality of base stations having a transmission function, at least one reference station having a transmission / reception function, and a mobile terminal having a reception function, the base station comprising: Asynchronously with each other, the first radio signal is transmitted to the reference station and the mobile terminal, and the reference station transmits the second radio signal to the mobile terminal in response to the first radio signal. The reception time when the wireless signal is received and the transmission time when the second wireless signal is transmitted are included in the second wireless signal, and the mobile terminal transmits the reception time of the first wireless signal. There is provided a radio positioning system that obtains the position of the mobile terminal by calculation based on the reception time of the second radio signal and the reception time and transmission time included in the second radio signal.

  Also, a plurality of base stations asynchronously transmit a first radio signal to at least one reference station and a mobile terminal, and the reference station transmits a second radio signal in response to the first radio signal. When transmitting to the terminal, the reception time when the first radio signal was received and the transmission time when the second radio signal was transmitted were included in the second radio signal and transmitted, and the mobile terminal received A reception time of the first radio signal; a reception time of the second radio signal received by the mobile terminal; a reception time and a transmission time included in the second radio signal received by the mobile terminal; Based on the above, a radio positioning method for obtaining the position of the mobile terminal by calculation is provided.

  According to the above-described radio positioning system and radio positioning method, the base station having only a simple transmission function is installed on the infrastructure side, and the number of reference stations having a complicated transmission / reception function is reduced, thereby reducing the cost of the entire radio positioning system. Can be reduced.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 4 is a diagram showing a configuration of a wireless positioning system according to an embodiment of the present invention. The radio positioning system shown in FIG. 4 includes base stations A and B, a reference station P, and a mobile terminal M. Base stations A and B indicated by Δ are base stations having only a transmitter and no receiver. The reference station P indicated by ○ is a base station having a transceiver. The mobile terminal M indicated by (2) is a mobile terminal having only a receiver and no transmitter. FIG. 5 is a time chart showing radio signal transmission / reception timings at the base stations A and B, the reference station P, and the mobile terminal M.

  In the wireless positioning system shown in FIG. 4, the base station A asynchronously transmits a wireless signal (radio wave). The mobile terminal M and the reference station P receive the radio signal R1 transmitted from the base station A, and store the reception times Tamr and Tapr, respectively. When the reference station P receives the radio signal R1 from the base station A, the reference station P subsequently transmits the radio signal R2 and stores the transmission time Tapt of the radio signal R2. The radio signal R2 includes, as data, the time Tapr at which the radio signal R1 is received and the time Tapt at which the radio signal R2 is transmitted. When receiving the radio signal R2, the mobile terminal M stores the reception time Tapmr and reads the times Tapr and Tapt included in the radio signal as data.

  Base station B transmits radio signal R3 asynchronously. The mobile terminal M and the reference station P receive the radio signal R3 transmitted from the base station B, and store the reception times Tbmr and Tbpr. When receiving the radio signal R3 from the base station B, the reference station P subsequently transmits the radio signal R4 to the mobile terminal M and stores the transmission time Tbpt. The radio signal R4 includes a time Tbpr when the radio signal R3 is received and a time Tbpt when the radio signal R4 is transmitted. When receiving the radio signal R4, the mobile terminal M stores the reception time Tbpmr and reads the times Tbpr and Tbpt included in the radio signal R4 as data.

  Next, the mobile terminal M receives the measured radio signals R1, R2, R3, R4, the transmission / reception times of the radio signals R1, R2, R3, R4 sent as data from the reference station P, and the base station A. , B and the known coordinate values of the reference station P, the position of the mobile terminal M itself is obtained by calculation. That is, the mobile terminal M determines the position using the principle of TDOA based on the reception time difference between the radio signal R1 and the radio signal R2 and the reception time difference between the radio signal R3 and the radio signal R4. However, since the radio signal R1 and the radio signal R2 are not transmitted simultaneously, they cannot be compared as they are. Thus, the transmission of the radio signal R2 is performed using the delay time for the radio signal R1 to reach the reference station P from the base station A and the delay time from the reception of the radio signal R1 to the transmission of the radio signal R2 by the reference station P. Correct the time. Thereby, it can convert as radio signal R1 and radio signal R2 were transmitted simultaneously. The radio signals R3 and R4 are also corrected in the same manner as the radio signals R1 and R2, and the transmission time of the radio signal R4 is corrected.

  Here, a calculation method for determining the position of the mobile terminal M from the transmission / reception times of the radio signals R1, R2, R3, and R4 will be described.

  The time Tat when the base station A transmits the radio signal R1, the time when the mobile terminal M receives the radio signal R1 is Tamr, and the distance between the base station A and the mobile terminal M is Lam. Further, since the timers of the mobile terminal M and the base station A are not synchronized, an offset error has occurred. If the offset error is Tamo and the speed of light is Vc, the following relationship is established.

同様に基準局Pが無線信号Ｒ２を送信した時刻をＴａｐｔ、移動端末Ｍが無線信号Ｒ２を受信した時刻をＴａｐｍｒ、基準局Pと移動端末Ｍとの間の距離をＬｐｍ、移動端末Ｍのタイマと基準局Ｐのタイマとのオフセット誤差をＴｐｍｏとすると、以下の関係が成り立つ。

Similarly, the time when the reference station P transmits the radio signal R2 is Tapt, the time when the mobile terminal M receives the radio signal R2 is Tapmr, the distance between the reference station P and the mobile terminal M is Lpm, the timer of the mobile terminal M and the reference station When the offset error with respect to the timer of P is Tpmo, the following relationship is established.

また、同様に基準局Pが無線信号Ｒ１を受信した時刻をＴａｐｒ、基地局Ａと基準局Ｐとの間の距離をＬａｐ、基準局Ｐのタイマと基地局Ａのタイマとのオフセット誤差をＴａｐｏとすると、以下の関係が成り立つ。

Similarly, when the time when the reference station P receives the radio signal R1 is Tapr, the distance between the base station A and the reference station P is Lap, and the offset error between the timer of the reference station P and the timer of the base station A is Tapo. The following relationship holds.

また、タイマオフセットは、

The timer offset is

となるため、式（１）〜（４）から、以下の関係が求められる。

Therefore, the following relationship is obtained from the equations (1) to (4).

基地局Bについても同様に以下の関係が求められる。

The following relationship is similarly required for the base station B.

一方、基地局Ａの座標（Ｘａ，Ｙａ）、基地局Ｂの座標（Ｘｂ，Ｙｂ）、基準局Ｐの座標Ｘｐ，Ｙｐ）は既知であり、移動端末Mの座標（ｘ，ｙ)は未知であるが、これらの座標には以下の関係がある。

On the other hand, the coordinates (Xa, Ya) of the base station A, the coordinates (Xb, Yb) of the base station B, the coordinates Xp, Yp) of the reference station P are known, and the coordinates (x, y) of the mobile terminal M are unknown. However, these coordinates have the following relationship:

したがって、式（７）を式（５）、（６）に代入することで以下の関係が求められる。

Therefore, the following relationship is obtained by substituting equation (7) into equations (5) and (6).

以上の式（８）を未知数ｘ，yについて解くことにより移動端末Mの位置が求められる。

The position of the mobile terminal M is obtained by solving the above equation (8) for the unknowns x and y.

  Next, the configurations of the base stations A and B, the reference station P, and the mobile terminal M shown in FIG. 4 will be described in detail.

  Base station A and base station B have the same configuration, and base station A will be described here. FIG. 6 is a block diagram showing the configuration of the base station A. In this embodiment, the reception time is accurately obtained by using an impulse radio wave for the radio signal.

  The base station A transmits a radio signal asynchronously with other radio stations (for example, the base station B) at a predetermined cycle. The MPU 11 generates transmission data (digital signal) to be included in the radio signal R1 and sends the transmission data to the PPM data modulation unit 12. PPM means (Pulse Position Modulation). The PPM data modulation unit 12 is supplied with a pseudo random number (PN) sequence from the PN sequence generation unit 13. The PPM data modulation unit 12 performs PPM data modulation according to transmission data “1” and “0” using the supplied pseudo-random numbers, and outputs a pulse train to the impulse generation unit 14. The impulse generator 13 uses a step recovery diode or the like to generate a very thin impulse at the rising edge of the pulse. The generated impulse has a very wide band. Therefore, for example, an unnecessary component of 3.4 GHz or less and a component of 4.8 GHz or more can be obtained by passing a 3.4 GHz to 4.8 GHz pan-pass filter (BPF) 15 so as to conform to a radio law mask. Remove. The impulse signal that has passed through the BPF 15 is amplified by the power amplifier A (PA) 16 and radiated from the antenna 17 as a radio signal (radio wave) R1.

  FIG. 7 is a block diagram showing the configuration of the reference station P. The reference station P includes a transmission unit having substantially the same configuration as that of the base station A, and also includes a reception unit that is not included in the base station A. 7, parts that are the same as the parts shown in FIG. 6 are given the same reference numerals, and descriptions thereof will be omitted.

  When receiving a radio signal (impulse radio wave) from the antenna 22, the reference station P removes unnecessary frequency components by a band pass filter (BPF) 23. Thereafter, the radio signal is amplified by a low noise amplifier (LNA) 24 and sent to a pulse detector 25. The pulse detector 25 is a circuit including, for example, an envelope detection circuit using a diode, a comparator, and the like, and detects a pulse in the radio signal. The detected pulse is compared with a pseudo random number (PN) sequence supplied from the PN sequence generator 13 in a correlator 26 using a digital matched filter. When the correlator 26 detects the preamble part, it is determined that synchronization is established, and the PPM data demodulator 27 demodulates the PPM of the next data part to generate received data. When the first pulse of the data part is detected, the time is held in the reception time holding part 28.

  Further, when the reference station P receives the radio wave (radio signal R1) from the base station A, the MPU 21 generates transmission data and transmits the radio wave (radio signal R2) to the mobile terminal M. The configuration of the transmission unit is the same as that of the base station A, except that the transmission time holding unit 29 holds the transmission time of the first pulse position of the data unit during transmission. The reception time and transmission time held in the reception time holding unit 28 and the transmission time holding unit 29 are transmitted to the mobile terminal M as transmission data via the MPU 21. The reception time holding unit 28 and the transmission time holding unit 29 are supplied with time data (clock signal) from the timer 30, and the reception time holding unit 28 and the transmission time holding unit 29 refer to the supplied time data. Thus, the reception time and transmission time are determined, and the time data is held.

  FIG. 8 is a flowchart of the operation of the reference station P. When receiving the radio signal R1 from the base station A, the reference station P holds the reception time Tapr in the reception time holding unit 28 (step S1). Subsequently, the reference station P starts transmission of the radio signal R2 to the mobile terminal M, and holds the transmission time Tapt at which transmission is started in the transmission time holding unit 29 (step S2). Then, the reference station P transmits the data part of the radio signal R2 including the reception time Tarp of the radio signal R1 and the transmission time Tapt of the radio signal R2 (step S3).

  Thereafter, the reference station P waits for transmission of the radio signal R3 from the base station B, and when receiving the radio signal R3, holds the reception time Tbpr in the reception time holding unit 28 (step S4). Subsequently, the reference station P starts transmitting the radio signal R4 to the mobile terminal M, and holds the transmission time Tbpt at which the transmission is started in the transmission time holding unit 29 (step S5). Then, the reference station P transmits the data part of the radio signal R4 including the reception time Tarp of the radio signal R3 and the transmission time Tapt of the radio signal R4 (step S6).

  As described above, the reference station P transmits to the mobile terminal M the reception time of the wireless signal transmitted from each of the base stations A and B and the transmission time of the wireless signal to be returned included in the data portion of the wireless signal. To do. Each of the base stations A and B only periodically transmits a radio signal to the reference station, and does not transmit signals synchronously.

  Next, the configuration of the mobile terminal M will be described. FIG. 9 is a diagram showing a configuration of the mobile terminal M. In FIG. 9, parts that are the same as the parts shown in FIG. 7 are given the same reference numerals in the first digit, and descriptions thereof are omitted. In this embodiment, the mobile terminal M has only a receiving unit, and no transmitter is provided. FIG. 10 is a flowchart of the operation of the mobile terminal M.

  When the mobile terminal M receives the radio signal R1 from the base station A with the antenna 42, the mobile terminal M extracts the reception time Tamr through the BPF 43, the LNA 44, the pulse detection unit 45, and the correlator 46, and holds it in the reception time holding unit 48 (step). S11). The reception time Tamr is sent to the MPU 41. Further, when the mobile terminal M receives the radio signal R2 from the reference station P, the mobile terminal M similarly holds the reception time Tapmr in the reception time holding unit 48 (step S12). The reception time Tapmr is sent to the MPU 41. Further, since the radio signal R2 from the reference station P includes time data generated as data at the reference station P as received data, the received data is demodulated by the PPM data demodulator 47. The demodulated received data is also sent to the MPU 41.

  Similarly, when the mobile terminal M receives the radio signal R3 from the base station B by the antenna 42, the mobile terminal M holds the reception time Tbmr in the reception time holding unit 48 (step S13). The reception time Tbmr is sent to the MPU 41. Moreover, when the mobile terminal M receives the radio signal R4 from the reference station P, the mobile terminal M similarly holds the reception time Tbpmr in the reception time holding unit 48 (step S14). The reception time Tbpmr is sent to the MPU 41. Further, since the radio signal R4 from the reference station P includes time data generated as data at the reference station P as received data, the received data is demodulated by the PPM data demodulator 47. The demodulated received data is also sent to the MPU 41.

  The MPU 41 calculates the position coordinate of the mobile terminal M itself by solving the above equation (8) from the transmission / reception times obtained in steps S11 to S14 and the position coordinates of the base stations A and B and the reference station P (step). S15). In this way, the mobile terminal M can determine the position of the mobile terminal M itself by calculation by receiving the radio signals from the two base stations A and B and the single reference station P.

  Since the base stations A and B only need a transmission function, low-cost transmitters can be used as the base stations A and B. For this reason, the installation cost of the whole base station can be reduced. In addition, the mobile terminal M only needs a reception function for position measurement, and the cost of the mobile terminal M can be reduced by not providing a transmitter.

  In addition, since it is not necessary to transmit radio signals from the mobile terminal M to the base stations A and B and the reference station P, and communication between the base stations A and B is unnecessary, the number of communication is small. The probability that a communication error will occur is reduced. Thereby, reliable position measurement can be achieved without being influenced by communication conditions and environments.

  Further, even when there are a large number of mobile terminals M, there is no need to transmit different signals for each mobile terminal M. Therefore, the amount of communication is constant even when the number of mobile terminals M increases, and the occurrence of congestion and response due to the increase in mobile terminals M Deterioration does not occur.

  Note that the number of base stations, the number of reference stations, and the number of mobile terminals are not limited to the example shown in FIG. 4 and can be any number.

  As described above, the wireless positioning system according to the present embodiment includes a plurality of base stations A and B having a transmission function, at least one reference station P having a transmission / reception function, and a mobile terminal M having a reception function. Then, the base stations A and B transmit the first radio signal R1 to the reference station P and the mobile terminal M asynchronously with each other. When transmitting the second radio signal R2 to the mobile terminal M in response to the first radio signal R1, the reference station P transmits the reception time Tapr at which the first radio signal R1 is received and the second radio signal R2. The transmitted time Tapt is included in the second radio signal R2 and transmitted. The mobile terminal M is based on the reception time Tamr of the first radio signal R1, the reception time Tapmr of the second radio signal R2, and the reception time Tapr and transmission time Tapt included in the second radio signal R2. The position of the mobile terminal M is obtained by calculation.

  FIG. 11 is a diagram showing a wireless positioning system in which a large number of base stations are installed. In the example shown in FIG. 11, base stations C and D are installed in addition to base stations A and B. Any number of base stations can be used as long as it is two or more. For example, when the mobile terminal M moves in a wide range or a range with many obstacles, communication with the base station may be disabled depending on the position of the mobile terminal M. However, if the mobile terminal M can communicate with two base stations and the reference station P among many base stations, the mobile terminal M can be positioned. The mobile terminal M may appropriately select only two base stations that can communicate for positioning from the communicable base stations.

  Here, when only one reference station P is installed, if the radio waves from the reference station P cannot be received for some reason, the mobile terminal M cannot perform positioning no matter how many radio waves can be received from the base stations. End up. Therefore, as shown in FIG. 12, this problem can be solved by installing a plurality of reference stations in the movement range of the mobile terminal M.

  FIG. 13 is a time chart of radio signal transmission / reception in the radio positioning system shown in FIG. When receiving the radio signal R1 from the base station A, the reference stations P1 and P2 transmit radio signals R2-1 and R2-2 to the mobile terminal, respectively. Here, if both the reference stations P1 and P2 receive radio waves and immediately transmit the radio signals R2-1 and R2-2, the radio signals from both the reference stations P1 and P2 will interfere. Therefore, as shown in FIG. 13, for each reference station, the time from when the radio wave is received from the base station to when the radio signal is transmitted to the mobile terminal M is set to a different time in advance. In the example shown in FIG. 13, the reference station P1 transmits the radio signal R2-1 as soon as possible after receiving the radio signal R1 from the base station A. On the other hand, the reference station P2 transmits the radio signal R2-2 after waiting for the maximum packet length Lmax of the radio signal R2-2 from the start of transmission of the reference station P1. Similarly, the reference station P1 transmits the radio signal R4-1 as soon as possible after receiving the radio signal R3 from the base station B, and the reference station P2 receives the maximum packet of the radio signal R4-1 from the transmission start of the reference station P1. The wireless signal R4-2 is transmitted after waiting for the length Lmax. Thereby, even if there are a plurality of reference stations, interference can be avoided.

  FIG. 14 is a flowchart of the operation of the reference station P2 in FIG. The reference station P2 is set to transmit a radio signal to the mobile terminal later than the reference station P1.

  When the base station P2 receives the radio signal R1 from the base station A, the reference station P2 holds the reception time Tapr in the reception time holding unit 28 (step S21). Subsequently, the reference station P2 waits for a preset time Lmax (step S22). This waiting time Lmax is the maximum time taken for the reference station P1 to transmit the radio signal R2-1 to the mobile terminal M. That is, the reference station P1 finishes transmitting the radio signal R2-1 to the mobile terminal M during this waiting time Lmax. Therefore, when the time Lmax has passed, the reference station P2 starts transmitting the radio signal R2-2 to the mobile terminal M, and holds the transmission time Tapt at which the transmission is started in the transmission time holding unit 29 (step S23). Then, the reference station P2 transmits the data part of the radio signal R2-2 including the reception time Tarp of the radio signal R1 and the transmission time Tapt of the radio signal R2-2 (step S24).

  Thereafter, similarly, when receiving the radio signal R3 from the base station B, the reference station P2 holds the reception time Tbpr in the reception time holding unit 28 (step S25). Subsequently, the reference station P2 waits for a preset packet transmission time Lmax (step S26). This waiting time Lmax is the maximum time taken for the reference station P1 to transmit the radio signal R4-1 to the mobile terminal M. That is, during this waiting time Lmax, the reference station P1 finishes transmitting the radio signal R4-1 to the mobile terminal M. Therefore, when the time Lmax has passed, the reference station P2 starts transmitting the radio signal R4-2 to the mobile terminal M, and holds the transmission time Tbpt at which the transmission is started in the transmission time holding unit 29 (step S27). Then, the reference station P2 transmits the data portion of the radio signal R4-2 including the reception time Tbrp of the radio signal R4-2 and the transmission time Tbpt of the radio signal R4-2 (step S28).

  As described above, in the wireless positioning system according to the present embodiment, a plurality of reference stations P1, P2,. Then, the transmission times Tapt, Tapt2,... Of the second radio signals R2-1, R2-2,... Transmitted by each of the plurality of reference stations P1, P2,. The two radio signals R2-1, R2-2,... Are sequentially delayed so as to be after the transmission.

  In the above-described embodiment, the radio signals from the base stations A and B may be short packets that only represent the base station ID and the like. On the other hand, the radio signal from the reference station P has a longer packet because the transmission / reception time is included as data. If the timers of the mobile terminal M and the reference station P are different in how the timers advance (clock frequency), for example when the reference station P2 responds for a long time as in the example shown in FIG. . For example, with a clock accuracy of 10 ppm, an error of 1 nsec occurs in a packet time of 100 μsec. This time error corresponds to a position error of 30 cm in terms of distance, and becomes a problem when performing high-accuracy positioning.

  Therefore, the second radio signal R2 transmitted from the reference stations P1 and P2 is divided into a radio signal (front signal) consisting of a short distance measuring packet without data and a long data packet (rear signal) including transmission / reception time data. ) And separated. Then, after first transmitting a radio signal (front signal) consisting of a short distance measurement packet without data, and after measuring the time using these packets, a long data packet (rear part) including transmission / reception time data Signal). In this way, a clock shift caused by a long data packet is not a problem.

  FIG. 15 is a time chart showing data transmission / reception timing when transmission / reception time data is transmitted in a long packet after a short distance measurement packet is transmitted.

  When the reference station P1 receives the radio signal R1 from the base station A, it immediately transmits the radio signal R2-1 to the mobile terminal M. At this time, the radio signal R2-1 is only a short distance measuring packet, and the data signal transmission is not performed while the reception time Tapr of the radio signal R1 and the transmission time Tapt of the radio signal R2-1 are held. When the transmission time of the radio signal R2-1 by the reference station P1 ends, the reference station P2 immediately transmits the radio signal R2-2 to the mobile terminal M. At this time, the radio signal R2-2 is only a short distance measuring packet, and the data signal transmission is not performed while the reception time Tapr of the radio signal R1 and the transmission time Tapt of the radio signal R2-2 are held.

  After the transmission of the radio signal R2-2 by the reference station P2, the reference station P1 transmits the radio signal D1 to the mobile terminal M. The radio signal D1 includes a reception time Tapr of the radio signal R1 and a transmission time Tapt of the radio signal R2-1. When the transmission of the radio signal D1 by the reference station P1 is completed, the reference station P2 transmits the radio signal D2 to the mobile terminal M. The radio signal D2 includes a reception time Tapr of the radio signal R1 and a transmission time Tapt of the radio signal R2-2.

  Thereafter, when the reference station P1 receives the radio signal R3 from the base station B, it immediately transmits the radio signal R4-1 to the mobile terminal M. At this time, the radio signal R4-1 is only a short distance measuring packet, and the data signal transmission is not performed while the reception time Tbpr of the radio signal R3 and the transmission time Tbpt of the radio signal R4-1 are held. When the transmission time of the radio signal R4-1 by the reference station P1 ends, the reference station P2 immediately transmits the radio signal R4-2 to the mobile terminal M. At this time, the radio signal R4-2 is only a short distance measuring packet, and the data signal transmission is not performed while the reception time Tbpr of the radio signal R3 and the transmission time Tbpt of the radio signal R4-2 are held.

  After the transmission of the radio signal R4-2 by the reference station P2, the reference station P1 transmits the radio signal D3 to the mobile terminal M. The radio signal D3 includes the reception time Tbpr of the radio signal R3 and the transmission time Tbpt of the radio signal R4-1. When the transmission of the radio signal D3 by the reference station P1 is completed, the reference station P2 transmits the radio signal D4 to the mobile terminal M. The radio signal D4 includes the reception time Tbpr of the radio signal R3 and the transmission time Tbpt of the radio signal R4-2.

  As described above, since the reference stations P1 and P2 transmit a short distance measurement packet and then transmit data including the transmission / reception time to the mobile terminal M, the distance measurement communication time is shortened. The position error due to the timer error can be minimized.

  As described above, in the present embodiment, the second radio signal R2 includes the front signal R2 that does not include the reception time Tapr at which the first radio signal R1 is received and the transmission time Tapt at which the second radio signal R2 is transmitted. -1 and a rear signal D1 including a reception time Tapr at which the first radio signal R1 is received and a transmission time Tapt at which the second radio signal R2-1 is transmitted. Then, the reference stations P1, P2,... Sequentially transmit the front signals R2-1, R2-2,... Of the second radio signal R2 after all the reference stations P1, P2,. The rear signals D1, D2,... Of the second radio signal R2 are sequentially transmitted.

  As shown in FIG. 16, the reference station P1 may collectively transmit the radio signals D1 and D3 related to the base stations A and B later, and similarly, the reference station P2 transmits the radio signals related to the base stations A and B. You may transmit D2 and D4 collectively later.

  That is, for example, the reference station P1 transmits the second radio signal R2 to the front signal R2-1 that does not include the reception time Tapr at which the first radio signal R1 is received and the transmission time Tapt at which the second radio signal R2 is transmitted. And a rear signal D1 including a reception time Tapr when the first radio signal R1 is received and a transmission time Tapt when the second radio signal R2-1 is transmitted. Further, the reference station P1 transmits the second radio signal R4 to the front signal R4-1 that does not include the reception time Tbpr at which the first radio signal R3 is received and the transmission time Tbpt at which the second radio signal R4 is transmitted. The rear signal D3 including the reception time Tbpr at which the first radio signal R3 is received and the transmission time Tbpt at which the second radio signal R4 is transmitted is separated. .., And R4-1, R4, the front signals R2-1, R2-2,..., R4-1, R4 of the second radio signals R2, R4,. -2,... Are sequentially transmitted, and then a plurality of second radio signals R2, R2, R2,... Corresponding to the first radio signals R1, R3,. The latter half (D1 + D3 +...) Of R4,. In this way, the entire data packet for transmitting the transmission / reception time data can be shortened, and the entire communication time can be shortened.

  As described above, according to the above-described embodiment, the base station having only a simple transmission function is installed on the infrastructure side, and the number of reference stations having a complicated transmission / reception function is reduced, thereby reducing the cost of the entire wireless positioning system. it can. When impulse radio waves are used, the infrastructure base station can be driven by, for example, only a button battery as a low power consumption circuit, and can be easily installed on a wall in a building, for example. For this reason, the installation cost of a base station can be reduced. For example, it is assumed that the cost ratio is 1 for the transmitter, 9 for the receiver, and 10 for the transceiver, and 10 base stations are installed on the infrastructure side. In this case, the cost of the conventional wireless positioning system shown in FIG. 1 is 110, whereas in the present embodiment, eight transmitters and two reference stations may be installed on the infrastructure side, resulting in a cost of 37. The overall cost can be reduced to 1/3.

It is a figure for demonstrating the positioning system of a TOA system. It is a figure for demonstrating the positioning system of a TDOA system. It is a figure for demonstrating an example of the conventional wireless positioning system. It is a figure which shows the structure of the radio positioning system by 1st Embodiment. It is a time chart which shows the transmission / reception timing of the radio signal in a base station, a reference station, and a mobile terminal. It is a block diagram which shows the structure of a base station. It is a block diagram which shows the structure of a reference station. It is a flowchart of operation | movement of a reference station. It is a figure which shows the structure of a mobile terminal. It is a flowchart of operation | movement of a mobile terminal. It is a figure which shows the structure of the radio positioning system which installed many base stations. It is a figure which shows the structure of the radio positioning system which installed many base stations and several reference stations. It is a time chart of transmission / reception of the radio signal in the radio positioning system shown in FIG. 13 is a flowchart of the operation of the reference station in FIG. It is a time chart which shows the data transmission / reception timing at the time of transmitting transmission / reception time data by a long packet after transmitting the short packet for ranging. It is a time chart which shows the data transmission / reception timing at the time of transmitting transmission / reception time data collectively.

Explanation of symbols

11, 21, 41 MPU
12 PPM data modulation unit 13 PN sequence generation unit 14 Impulse generation unit 15, 23, 43 Band pass filter (BPF)
16 Power amplifier (PA)
17, 22, 42 Antenna 24, 44 Low noise amplifier (LNA)
25, 45 Pulse detection unit 26, 46 Correlator 27, 47 PPM data demodulation unit 28, 48 Reception time holding unit 29 Transmission time holding unit 30, 50 Timer A, B, C, D Base station P, P1, P2 Base station M Mobile terminal

Claims (10)

A plurality of base stations having a transmission function;
At least one reference station having transmission and reception functions;
A wireless positioning system having a mobile terminal having a receiving function,
The base station transmits a first radio signal asynchronously to the reference station and the mobile terminal,
When the reference station transmits a second radio signal to the mobile terminal in response to the first radio signal, a reception time when the first radio signal is received and a transmission that transmits the second radio signal The time is included in the second radio signal and transmitted,
The mobile terminal, based on the reception time of the first radio signal, the reception time of the second radio signal, and the reception time and transmission time included in the second radio signal, Wireless positioning system that finds the position of a computer by calculation. The wireless positioning system according to claim 1,
A plurality of the reference stations are installed, and the transmission time of the second radio signal transmitted by each of the plurality of reference stations is sequentially delayed so that the transmission time of the second radio signal by another reference station ends. Wireless positioning system. The wireless positioning system according to claim 2, wherein
The second radio signal includes a front signal that does not include a reception time when the first radio signal is received and a transmission time when the second radio signal is transmitted, and a reception that receives the first radio signal. The second signal is separated into a rear signal including a transmission time at which the second radio signal is transmitted, and all the reference stations sequentially transmit the front signal of the second radio signal, and then the second signal is transmitted. A wireless positioning system that sequentially transmits the rear signal of a wireless signal. The wireless positioning system according to claim 2, wherein
The second radio signal includes a front signal that does not include a reception time when the first radio signal is received and a transmission time when the second radio signal is transmitted, and a reception that receives the first radio signal. Separating into a rear signal including a time and a transmission time at which the second radio signal was transmitted;
Each of the reference stations transmits a plurality of the second radio signals corresponding to the first radio signals from a plurality of the base stations after all the reference stations sequentially transmit the front signal of the second radio signal. A wireless positioning system that collectively transmits the latter half of the wireless signal. A plurality of base stations transmitting first radio signals asynchronously with each other to at least one reference station and a mobile terminal;
When the reference station transmits a second radio signal to the mobile terminal in response to the first radio signal, a reception time when the first radio signal is received and a transmission time when the second radio signal is transmitted And included in the second radio signal,
Included in the reception time of the first radio signal received by the mobile terminal, the reception time of the second radio signal received by the mobile terminal, and the second radio signal received by the mobile terminal A radio positioning method for calculating a position of the mobile terminal based on a reception time and a transmission time. The wireless positioning method according to claim 5, wherein
A plurality of the reference stations are installed, and the transmission time of the second radio signal transmitted by each of the plurality of reference stations is sequentially delayed so as to be after the transmission of the second radio signal by another reference station is completed. Wireless positioning method. The wireless positioning method according to claim 6, comprising:
The second radio signal includes a front signal that does not include a reception time when the first radio signal is received and a transmission time when the second radio signal is transmitted, and a reception that receives the first radio signal. Separating into a rear signal including a time and a transmission time at which the second radio signal was transmitted;
A radio positioning method in which all of the reference stations sequentially transmit the front signal of the second radio signal, and then sequentially transmit the rear signal of the second radio signal. The wireless positioning method according to claim 6, comprising:
The second radio signal includes a front signal that does not include a reception time when the first radio signal is received and a transmission time when the second radio signal is transmitted, and a reception that receives the first radio signal. Separating into a rear signal including a time and a transmission time at which the second radio signal was transmitted;
Each of the reference stations transmits a plurality of the second radio signals corresponding to the first radio signals from a plurality of the base stations after all the reference stations sequentially transmit the front signal of the second radio signal. A wireless positioning method in which the latter half of the wireless signal is collectively transmitted. A reference station having a transmission / reception function,
When the second radio signal is transmitted to the mobile terminal in response to the first radio signal transmitted from the base station, the reception time when the first radio signal is received and the transmission that transmits the second radio signal A reference station that transmits the time included in the second radio signal. A mobile terminal having a receiving function,
The reception time of the first radio signal transmitted from the base station, the reception time of the second radio signal transmitted from the reference station, and the first radio by the base station included in the second radio signal A mobile terminal that obtains the position of the mobile terminal by calculation based on a signal reception time and a transmission time of the second radio signal by the base station included in the second radio signal.

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