JP5364749B2 - Wireless system and position estimator - Google Patents

Description

  Embodiments described herein relate generally to a wireless system, a relay terminal, a vehicle, and a position estimator.

  Conventionally, a wireless position estimation method is known. In this method, the transmitter first transmits a signal, and the propagation loss is calculated from the difference between this transmission power and the received power value (RSSI: Received Signal Strength Indicator) when the receiver receives it. The distance between the transceivers is measured by converting to. Then, the transmission signals are received by a plurality of receivers, the distance is obtained, a circle having a radius of the distance obtained from each receiver is drawn, and the intersection of each circle is set as the position of the transmitter.

  However, with this method, RSSI and delay time cannot be measured correctly due to shadowing where there is an obstacle between devices and radio waves are blocked, and fading where signal power fluctuates due to mixing of signals reflected by objects around the device. Sometimes.

JP 2009-76958

  As described above, the conventional wireless position estimation system has a problem that a correct propagation loss cannot be measured when shadowing due to an obstacle occurs.

  In view of this, an object of one aspect of the present invention is to improve the accuracy of position measurement when a propagation environment such as shadowing is deteriorated.

  A wireless system as one aspect of the present invention includes a transmission terminal, a first relay terminal, a measurement terminal, and a position estimator.

  The transmitting terminal transmits a first signal.

  The first relay terminal receives the first signal, calculates a first received power value, and transmits a second signal including the first received power value.

  The measurement terminal receives the first signal and calculates a second received power value, receives the second signal and calculates a third received power value, demodulates the second signal, and calculates the first signal The received power value is extracted.

  The position estimator estimates the position of the transmitting terminal based on the first received power value, the second received power value, the third received power value, and the position of the measurement terminal.

1 is a diagram showing a system configuration in a first embodiment. FIG. It is a figure which shows the system configuration example in which a relay terminal does not exist. It is a figure for demonstrating the principle of the position estimation using received power. FIG. 2 is a diagram for explaining the operation of the system of FIG. FIG. 5 is a diagram for explaining the operation following FIG. FIG. 6 is a diagram for explaining the operation following FIG. FIG. 3 is a diagram showing a configuration of a transmission terminal in the first embodiment. FIG. 3 is a diagram showing a configuration of a relay terminal in the first embodiment. It is a figure which shows the content of the received power report message. FIG. 3 is a diagram showing configurations of a measurement terminal and a position calculator in the first embodiment. 3 is a flowchart showing an operation of a transmission terminal in the first embodiment. 6 is a flowchart showing the operation of the relay terminal in the first embodiment. 3 is a flowchart showing a process of a measurement terminal in the first embodiment. It is a flowchart which shows the detail of a position computer process. FIG. 6 is a diagram showing a system configuration in a second embodiment. It is a figure which shows the structure of a new received power report message. FIG. 10 is a diagram showing a configuration of a relay terminal in the second embodiment. FIG. 10 is a diagram showing a system in a third embodiment. It is a figure which shows the specific learning algorithm in a position computer. FIG. 10 is a diagram showing a configuration of a position calculator in a third embodiment. 14 is a flowchart showing the operation of the position calculator in the third embodiment. FIG. 6 is a diagram showing an example in which the first to third embodiments are applied to a train radio system. It is a figure which shows the example which mounts the radio | wireless machine provided with the function of the transmission terminal and the relay terminal before and behind a train. FIG. 10 is a diagram showing a configuration of a position estimator in a fourth embodiment. FIG. 10 is a diagram showing a system configuration of a fifth embodiment. It is a figure which shows the example in which the position machine has a radio | wireless communication function, and the radio | wireless machine of the vehicle carrying GPS is operated as a measurement terminal. It is a figure which shows the example of a structure of the measurement terminal provided with position detection means, such as GPS.

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

(First embodiment)
FIG. 1 is a diagram showing a system configuration in the present embodiment.

  This system includes a transmission terminal (measurement target terminal) 101, a relay terminal (first relay terminal) 201, a plurality of measurement terminals 1, 2, 3 and a position calculator 401.

  The plurality of measurement terminals 1, 2, 3 and the position calculator 401 form a position estimation system 402.

  An obstacle 301 is located between the transmission terminal 101 and the measurement terminals 1 to 3.

  There are no obstacles between the transmission terminal 101 and the relay terminal 201 and between the relay terminal 201 and the measurement terminals 1 to 3.

  FIG. 2 shows a system configuration example in which no relay terminal exists for comparison with the configuration of FIG. In this example, the signal transmitted from the transmission terminal 101a causes attenuation called shadowing due to the obstacle 301a between the transmission terminal 101a and the measurement terminals 1a, 2a, and 3a. For this reason, the reception power of the signal from the transmission terminal 101a is measured low at the measurement terminals 1a to 3a. As a result, the position calculator 401a erroneously determines that a large attenuation has occurred due to the large propagation distance, and erroneously recognizes that the transmitting terminal 101a is located far away. Therefore, this system cannot correctly estimate the position.

  Here, the principle of position estimation using received power will be described with reference to FIG. As an example, an example is shown in which the measurement terminals 1 to 3 estimate the position of the transmission terminal 101 based on the RSSI (RSSI1, RSSI2, RSSI3) of the signal received from the transmission terminal 101. It is assumed that the transmission power of the transmission terminal 101 is known (the same applies hereinafter).

  At the measurement terminals 1 to 3 whose positions are known, first, received powers RSSI1 to RSSI3 are obtained and converted into distances, respectively. The relationship between RSSI and distance is given by the following equation, for example.

RSSI = β-αlog distance And the position is estimated using the principle of triangulation. Circles that are separated from the measurement terminals 1 to 3 are drawn, and the intersection of each circle is the position of the transmission terminal 101. However, if distances measured by a plurality of measuring terminals 1 to 3 are used, as shown in the figure, there may be a plurality of intersections instead of one intersection (in the example shown, three intersections I1, I2, I3 ).

  Therefore, we will intentionally adjust the distances obtained by each so that they meet at one point. For example, if adjustment is performed so that the sum of the squares of the respective adjustment amounts is minimized, position estimation is performed based on the least square error criterion, and the steepest descent method can be used for such position estimation. That is, the position where the sum of squares of the difference between the three distances d1, d2, and d3 is minimized is obtained. Thus, the position of the transmission terminal is specified as one point (point I4 in the drawing).

  Note that the intersection of the circles corresponds to an intermediate value in the middle of the calculation, and in the actual calculation, it is possible to use a calculation formula that calculates the position of the transmitting terminal directly from the position information of each measuring terminal and RSSI information It is. In this case, the calculation for obtaining the intersection of the circles is not necessary.

  The operation of the system shown in FIG. 1 will be described with reference to FIGS.

  FIG. 4 is a diagram showing an initial operation of the system of FIG. In the first step, the transmitting terminal 101 transmits a signal. A signal transmitted from the transmission terminal 101 is referred to as a transmission terminal signal (first signal). It is assumed that the transmission terminal signal is received from the relay terminal 201 and each of the three measurement terminals 1 to 3. Here, RSSIs measured by the measurement terminals 1 to 3 are respectively RSSI [1] -1, RSSI [1] -2, and RSSI [1] -3. Also, RSSI received and measured by the relay terminal 201 is RSSI [2].

  RSSI [2] measured by relay terminal 201 corresponds to the first received power value. RSSI [1] -1, RSSI [1] -2, and RSSI [1] -3 measured by the measurement terminals 1 to 3 correspond to the second received power value.

  FIG. 5 is a diagram showing the next operation of the system of FIG. The relay terminal 201 transmits a signal including RSSI [2] measured by receiving it to the measurement terminals 1 to 3. A signal transmitted by the relay terminal 201 is referred to as a relay terminal signal (second signal).

  The measurement terminals 1 to 3 receive and demodulate the relay terminal signal to obtain RSSI [2] (first received power value) information.

  Further, each of the measurement terminals 1 to 3 measures the RSSI of the relay terminal signal. The RSSIs measured by the measurement terminals 1 to 3 are respectively RSSI [3] -1, RSSI [3] -2, and RSSI [3] -3. RSSI [3] -1, RSSI [3] -2, RSSI [3] -3 correspond to the third received power value.

  Then, position calculator 401 specifies the position of the relay terminal using RSSI [3] -1, RSSI [3] -2, RSSI [3] -3 (third received power value). As a specific specifying method, a method similar to that shown in FIG. 3 may be used. For example, calculate the intersection of the circles drawn for each of the measurement terminals 1 to 3, or if the number of intersections is not one, calculate the position that minimizes the sum of squares of the distance difference. Determine the position. Since it is assumed that there is no obstacle between the relay terminal 201 and the measurement terminals 1 to 3, shadowing does not occur. For this reason, it is possible to estimate the position of the relay terminal 201 relatively accurately.

  FIG. 6 is a diagram showing a final operation of the system of FIG. By the operation so far, the position of relay terminal 201, RSSI [2] (first received power value) that is RSSI measured by relay terminal 201, and RSSI [3] -1 that is RSSI measured by each measurement terminal , RSSI [3] -2, RSSI [3] -3 (second received power value) are obtained. The positions of the measurement terminals 1 to 3 are assumed to be known.

  The position calculator 401 estimates the position of the transmission terminal 101 from the position information of these four devices (relay terminal and three measurement terminals) and RSSI information. As a specific estimation method, the same method as in FIG. 3 can be used. A circle drawn from the position of the relay terminal and the RSSI of the signal received by the relay terminal from the transmitting terminal, and each circle drawn from the position of each measuring terminal 101 and the signal received by each measuring terminal 101 from the transmitting terminal Then, the intersection of these circles or the position where the sum of squares of the distance difference is minimized is determined as the position of the transmitting terminal.

  In the actual calculation, the position of the transmitting terminal may be obtained directly from the position information of the four devices (relay terminal and three measuring terminals) and the RSSI information. That is, it is not necessary to calculate the intersection of the circles, and it is possible to directly calculate the position of the transmitting terminal without obtaining the position of the relay terminal (that is, without obtaining the position of the relay terminal as an intermediate value) , Using a formula that directly calculates the location of the sending terminal).

  The system configuration shown in FIG. 2 has a drawback that the transmitting terminal appears far away due to the influence of an obstacle. In contrast, in the present embodiment, by using the relay terminal 201, the error is averaged by increasing the number of measurement locations, and the relay terminal 201 that may not be affected by shadowing is used. By doing so, the position measurement accuracy of the transmission terminal 101 can be improved.

  FIG. 7 is a diagram showing a configuration of transmitting terminal 101 in the present embodiment.

  The transmission terminal 101 includes a transmission control unit 111, a transmission unit 112, and a transmission antenna 113. For example, the transmission control unit 111 instructs the transmission unit 112 to transmit a signal at regular intervals. The transmission unit 112 generates a transmission signal and transmits it from the transmission antenna 113 as a transmission terminal signal.

  FIG. 8 is a diagram showing the configuration of the relay terminal 201.

  The relay terminal 201 includes a relay reception antenna 211, a relay reception power measurement unit 212, a relay control unit 213, a relay transmission unit 214, and a relay transmission antenna 215.

  The relay reception antenna 201 receives a transmission terminal signal from the transmission terminal 101 and sends a signal to the relay reception power measurement unit 212. Relay reception power measuring section 212 measures the RSSI of the received signal and sends it to relay control section 213. The relay control unit 213 creates a received power report message based on the RSSI received from the relay received power measuring unit 212. Then, the received power report message is sent to the relay transmission unit 214, and the relay transmission unit 214 transmits it from the relay transmission antenna 215 as a relay terminal signal.

  FIG. 9 shows the content of the received power report message.

  The received power report message is a message for reporting received RSSI information, and consists of three fields. The first field is a wireless transmission unit address, and an address indicating the transmission source of the received signal is entered. The second field is the received power measuring unit address, which contains the address of the device that received the signal and measured RSSI. The third field is a received power value field.

  When the relay terminal 201 receives the transmission terminal signal, the address of the transmission terminal is entered in the first radio transmission unit address field. The address of relay terminal 201 is entered in the second received power measuring unit address field. The measured RSSI is entered in the received power value field.

  As described above, the received power report message is transmitted from the relay terminal 201 and received by the measurement terminals 1 to 3, or when the measurement terminal receives a signal from the transmission terminal 101 or the relay terminal 201 as described later. Is also created.

  FIG. 10 shows the configuration of the measurement terminals 1 to 3 and the position calculator 401.

  The measurement terminal 1 to the measurement terminal 3 have the same configuration, and include measurement terminal reception antennas 11, 21, 31, reception units 12, 22, 32, and reception power measurement units 13, 23, 33.

  The measurement terminal reception antennas 11 to 31 receive the radio signals transmitted from the relay terminal 201 and the transmission terminal 101 and send them to the reception units 12 to 32 and the reception power measurement units 13 to 33.

  When the received signal is a relay terminal signal, the receiving units 12 to 32 demodulate the received signal and obtain a received power report message. The obtained received power report message is sent to the position calculator 401.

  The received power measuring units 13 to 33 measure RSSI both when the received signal is a transmission terminal signal and when it is a relay terminal signal. Then, the address of the signal transmission source is specified, a reception power report message is created, and the message is sent to the position calculator 401.

  The position calculator 401 includes a position estimation unit 411 and an estimation control unit 412. The position estimation unit 411 estimates the position of the transmission terminal based on a plurality of received power report messages sent from the measurement terminals 1 to 3. Further, the estimation control unit 412 monitors whether or not necessary reception power messages are collected, determines whether to perform position estimation or wait for a while, and sends an instruction to the position estimation unit 411.

  FIG. 11 is a flowchart showing the operation of the transmission terminal 101.

  When the transmission terminal process is started, the transmission terminal 101 transmits a transmission terminal signal (S101), thereby ending the transmission terminal process.

  FIG. 12 is a flowchart showing the operation of the relay terminal 201.

  When the relay terminal process is started, it first waits until a transmission terminal signal is received (S201).

  When the transmitting terminal signal is received, first, the transmitting unit address of the transmitting terminal that has transmitted the transmitting terminal signal is specified by demodulating the received signal (S202). Then, the RSSI of the signal is measured (S203). The processing so far is performed in the relay reception power measurement unit 212 shown in FIG.

  Subsequently, a reception power report message is created in the relay control unit 213 (S204).

  Finally, the relay terminal signal including the received power report message is transmitted by the relay transmission unit 214 via the relay transmission antenna 215 (S205). Thus, the relay terminal process ends.

  FIG. 13 is a flowchart showing the processing of the measurement terminals 1 to 3.

  When the measurement terminal process is started, both the process of waiting for reception of a transmission terminal signal (S301) and the process of waiting for reception of a relay terminal signal (S311) start operation.

When the transmitting terminal signal is received, the transmitting unit address of the transmitting terminal that subsequently transmitted the transmitting terminal signal is specified (S302). Then, the RSSI of the transmitting terminal signal is measured (S303). Then, a received power report message is created (S304) and sent to the position calculator (S305). The above processing is performed by the received power measuring units 13, 23 and 33 in FIG.
This process is repeated until the transmission terminal signals of all the transmission terminals are received or until a sufficient number of transmission terminal signals are received to estimate the positions of the transmission terminals (S306). Since there is usually one transmitting terminal, the process ends when a transmitting terminal signal is received once. The timing at which the measurement terminal first receives the transmission terminal signal or the timing determined in advance by the measurement terminal may be used as a reference, and when a predetermined time has elapsed from this reference timing, the process may be terminated as a timeout ( S306).

  When the relay terminal signal is received, first, the transmission unit address of the relay terminal that has transmitted the relay terminal signal is specified (S312), and the RSSI of the relay terminal signal is measured (S313). Then, a reception power report message is created and notified to the position calculator (S314, S315). The processing so far is performed in the reception power measuring units 13, 23, and 33.

  Further, the receiving terminal 12, 22, 32 demodulates the relay terminal signal (S316), and extracts a received power report message related to RSSI (RSSI of the signal received from the transmitting terminal by the relay terminal) sent from the relay terminal (S317). . Then, this message is notified to the position calculator (S318).

  The above processing related to the relay terminal signal is repeated until the relay terminal signals of all the relay terminals are received or until a sufficient number of relay terminal signals are received to estimate the positions of the relay terminals (S319). In the former case, the number of relay terminals is defined as the specified number. In the latter case, a number sufficient to estimate the position of the relay terminal is defined as the specified number, and processing is performed when the number of received relay terminal signals exceeds the specified number. Shall be terminated. Further, the timing may be terminated when a predetermined time elapses from the reference timing based on the timing at which the first relay terminal signal is received or the timing determined in advance by the measurement terminal (S319).

  Thus, the measurement terminal process ends.

  FIG. 14 is a flowchart showing details of the position computer processing.

  When the position calculator process is started, first, a total received power report message is received (S401). Then, the position of the relay terminal is estimated (S402), the position of the transmitting terminal is further estimated (S403), and the position calculator process ends.

  As described above, according to the present embodiment, it is possible to improve the measurement accuracy of the position of the transmitting terminal by using the relay terminal to increase the reception power measurement points and average the errors. Specifically, the accuracy of measurement can be improved by first obtaining the position of the relay terminal that may be highly accurate, and obtaining the position of the transmitting terminal using the information.

(Second embodiment)
FIG. 15 is a diagram illustrating a system configuration according to the second embodiment.

  In the second embodiment, the transmission terminal of the first embodiment is changed to the relay terminal (second relay terminal) 202, and the new transmission terminal 131 is located in a range where signals can reach the relay terminals 201 and 202. It is the structure to do. Elements equivalent to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  In this system configuration, the relay terminal 202 receives the transmission signal (first signal) of the transmission terminal 131 and measures RSSI [4] -2 (fourth received power value). The relay terminal 202 transmits a relay terminal signal (third signal) including the received power report message. This received power report message is received by the relay terminal 201 and the measurement terminals 1 to 3.

  The measurement terminals 1 to 3 receive the message signal and measure RSSI, which are RSSI [1] -1, [1] -2, and [1] -3, respectively. RSSI [1] -1, [1] -2, [1] -3 correspond to the sixth received power value. In addition, the signal is demodulated to extract RSSI [4] -2 (fourth received power value).

  The relay terminal 201 receives the transmission signal (first signal) of the transmission terminal 131, measures RSSI [4] -1 (first reception power value), and transmits a reception power report message. However, the relay terminal 201 also receives the relay terminal signal (third signal) transmitted from the relay terminal 202 and measures RSSI [2] (fifth received power value). Furthermore, RSSI [4] -2 (fourth received power value) sent on the relay terminal signal is also demodulated.

Relay terminal 201 receives a new reception including RSSI [4] -2 (fourth received power value), RSSI [2] (fifth received power value), and RSSI [4] -1 (first received power value). A power report message is created, and the created message is transmitted on the relay terminal signal (second signal).
This relay terminal signal is received by the measurement terminals 1 to 3. The structure of this new received power report message is shown in FIG. Although RSSI [4] -2, RSSI [2], and RSSI [4] -1 are included in one frame and transmitted here, they may be transmitted separately in separate frames.

  RSSI [4] -2 (fourth received power value) is notified from each of relay terminal 202 and relay terminal 201 to measurement terminals 1 to 3, but acquired from one of measurement terminals 1 to 3 May be used. RSSI [4] -2 (fourth received power value) is notified to the measurement terminal only from relay terminal 202, and RSSI [4] -2 (fourth received power value) is sent to the signal transmitted from relay terminal 201. It is also possible not to include.

  First, the position calculator 401 estimates the position of the relay terminal 201 using the positions of the measurement terminals 1 to 3 and RSSI [3] -1, [3] -2, [3] -3.

  Subsequently, using the estimated position of the relay terminal, the positions of the measurement terminals 1 to 3, and RSSI [2] and RSSI [1] -1, [1] -2, [1] -3, Estimate the position. The position of the transmission terminal 131 is estimated using the estimated positions of the relay terminal 201 and the relay terminal 202 and RSSI [4] -1 and RSSI [4] -2.

  FIG. 17 is a diagram showing the configuration of relay terminals 201 and 202 in the second embodiment.

  The relay terminal in the second embodiment has a relay receiving unit 216 added to the relay terminal in the first embodiment shown in FIG.

  When the relay terminal receives the transmission terminal signal transmitted from the transmission terminal 131, the relay terminal operates in the same manner as in the first embodiment and creates a reception power report message.

  When a relay terminal signal transmitted from another relay terminal is received, the RSSI is measured by the relay reception power measurement unit 212, and a reception power report message is created in the same manner as when the transmission terminal signal is received. Further, the relay terminal signal is demodulated by the relay receiving unit 216, and the received received power report message is extracted.

  A total of three received power report messages created or extracted by the above processing are concatenated and transmitted as new relay terminal signals by the relay transmission unit 214 and the relay transmission antenna 215.

(Third embodiment)
FIG. 18 shows a system according to the third embodiment. The system according to the present embodiment is characterized in that a learning operation is performed after the last operation (the operation shown in FIG. 6) of the first embodiment or the second embodiment. This learning operation makes it possible to accurately estimate the transmission terminal position even after the relay terminal has disappeared. This operation is performed in the position calculator. Elements having the same names as those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

  In the present embodiment, RSSI [3] − is obtained by performing learning by a position estimation algorithm using an accurate position of a transmission terminal obtained using RSSI of a transmission terminal signal transferred from a relay terminal as a teacher signal. This is to correct the received power distortion of 1, [3] -2, [3] -3.

  FIG. 19 shows a specific learning algorithm in the position calculator 401.

  As a learning method of the position calculator, conventionally known adaptive filters such as RLS (Recursive least squares) and LMS (Least mean squares) can be used, and neural networks and support vector machines known as learning algorithms are used. You can also The input of this learning algorithm is the RSSI of the transmitting terminal signal measured by the measuring terminals 1 to 3, and the RSSI measured by the relay terminal is not input. The output of the learning algorithm is the estimated position of the transmitting terminal.

  During learning, the learning algorithm uses the accurate transmission terminal position estimated using the RSSI measured by the relay terminal as teacher information, and updates the operation parameters of the algorithm. In the case of RLS or LMS, instead of teacher information, the difference between the estimated position of the transmission terminal output by the algorithm and the estimated position of the accurate transmission terminal given as the teacher signal is given to the algorithm as error information.

  After the relay terminal disappears, an accurate transmitting terminal position is not given as a teacher signal, but the operating parameter is updated through learning, so that only the RSSI measured by the measuring terminal and the above algorithm are used to determine the transmitting terminal position. Can be estimated with high accuracy.

  FIG. 20 shows the configuration of the position calculator in the present embodiment.

  The received power measurement message input from the measurement terminal is input to the first position estimation unit 421 and the second position estimation unit 422. Here, it is assumed that the received power report message input from the measurement terminal includes the received power report message received from the relay terminal in addition to the received power report message related to RSSI measured by the measurement terminal itself.

  When the received power report message from the relay terminal can be used, first position estimating section 421 estimates the transmitting terminal position with high accuracy by the same method as in the first embodiment. If the received power report message from the relay terminal cannot be used, the first position estimating unit 421 outputs nothing.

  The second position estimation unit 422 uses only the received power report message based on RSSI measured by the measurement terminal. When the transmitting terminal position is obtained from the first position estimating unit 421, it is output as it is, and parameter learning is performed by the method described with reference to FIG. When there is no output from the first position estimation unit 421, the transmission terminal position is estimated based on the RSSI measured by the measurement terminal using the learned parameters and output.

  FIG. 21 is a flowchart showing the operation of the position calculator in the present embodiment.

  When the position calculator process is started, first, all received power report messages are received (S411). Whether the message from the relay terminal is included in the received power report message is checked (S412), and if included, based on the operating principle of the first embodiment, the first position estimating unit 421 relays it The position of the terminal is estimated (S413), and the position of the transmitting terminal is estimated (S414). Then, the second position estimating unit 413 performs learning using the position of the transmitting terminal estimated by the first position estimating unit 412 (S415). When the message from the relay terminal is not included in the received power report message, the second position estimation unit 422 determines the position of the transmitting terminal according to the learned parameter based on the RSSI of the transmitting terminal signal measured by the measuring terminal. Is estimated (S416).

  As described above, according to the present embodiment, even when the relay terminal cannot be used, highly accurate estimation is maintained by using the model updated by learning.

(Fourth embodiment)
The fourth embodiment relates to position measurement of a moving body such as a train. As a means for measuring the position of a train traveling on a track, for example, a position detection device called a transponder is arranged along the railway line, and a method of grasping the position by detecting when the train passes on the train is a method. Are known. Furthermore, by using together with the moving distance obtained from the rotational speed of the wheel, the integrated value of the speed, etc., it is possible to detect an arbitrary position. However, the method based on the integration of the rotation speed and speed of the wheel may be disabled due to a failure or the like. Therefore, wireless position detection is considered as an alternative means.

  FIG. 22 shows an example in which the first to third embodiments are applied to a train radio system.

  The train is equipped with radios 501 and 502 that have both the functions of a transmission terminal and a relay terminal, and radios 1, 2, and 3 that have the function of a measurement terminal are installed along the railway. To do. The wireless devices 1 to 3 along the line are connected to a single server 601, and the server has a function as a position calculator.

  For example, a certain train transmits a transmission terminal signal from a wireless device (for example, the wireless device 501) as in the first embodiment. Then, the wireless devices 1 to 3 along the line that have received this and the wireless devices 502 of the surrounding train operate as a measurement terminal and a relay terminal, respectively, and in the same principle as in the first embodiment, the server 601 and the transmission terminal The position of the train, that is, the position of the train is specified.

  FIG. 23 shows an example in which radios having functions of a transmission terminal and a relay terminal are mounted before and after a train.

  The transmission terminal signal transmitted from the radio device 501 of a certain train is received by the radio devices 502 and 503 before and after the other train. The received two wireless devices 502 and 503 operate as relay terminals, and transmit a received power report message to the measurement terminals 1 to 3. Thereafter, the position of the transmission terminal, that is, the position of the train is estimated in the same manner as in the first embodiment.

  However, here, the distance between the two radios 502 and 503 mounted on the front and rear of the train is almost unchanged except for a slight extension of the connecting part. It can be assumed that the number of vehicles to be known is known.

  Therefore, when these radio devices 502 and 503 operate as relay terminals, the position calculator 601 gives the distance difference between them as the train length, and is used as a constraint condition in estimating the relay terminal position and the transmission terminal position. Accuracy can be improved.

  The principle will be described in more detail. If relay terminal 502 and relay terminal 503 in FIG. 23 are regarded as transmitting terminal 101 and relay terminal 201 in FIG. 1, in the above embodiments, the distance between the two is measured by the relay terminal (RSSI measurement). Has been measured.

  However, in this embodiment, the distance between the two is given by the train length, and a more accurate value with less error can be obtained. Therefore, the position calculator 601 uses this accurate value to improve the accuracy of position estimation.

  FIG. 24 is a diagram showing a configuration of the position estimator 601 in the present embodiment.

  The position estimator 601 includes a position estimation unit 611, an estimation control unit 612, and a train length setting unit 613. The position estimation unit 611 and the estimation control unit 612 are the same as the position estimation unit 411 and the estimation control unit 412 shown in the figure, and here a train length setting unit 613 is added. The train length setting unit 613 sets, for the position estimation unit 611, an interval between relay terminals mounted on the train or a train length according to the interval.

  In this embodiment, both are installed on the train as relay terminals, but one may be a transmission terminal (measurement target terminal), or both may be transmission terminals (measurement target terminals). Also good.

(Fifth embodiment)
FIG. 25 illustrates a system configuration according to the fifth embodiment.

  The fifth embodiment is an example in which the first to third embodiments are applied to vehicle-to-vehicle / road-vehicle communication. It is assumed that adjacent vehicles are wirelessly connected to each other, and wireless devices 1 to 3 are installed on the road side so that they can communicate with the vehicle. The positions of the roadside radio devices 1 to 3 are assumed to be known.

  In this case, the wireless device 701 mounted on one of the traveling vehicles serves as the transmission terminal of the first to third embodiments, and can communicate with this vehicle and also with the roadside wireless devices 1, 2, and 3. Since the wireless device 702 becomes a relay terminal, the position of the vehicle equipped with the wireless device 701 corresponding to the transmitting terminal can be specified.

  FIG. 26 shows a case where the position calculator has a wireless communication function and can communicate with a vehicle. Further, instead of the roadside measurement terminal in FIG. 25, an example in which a vehicle wireless device equipped with GPS operates as a measurement terminal. Indicates.

  Vehicles equipped with measurement terminals 1, 2, and 3 can obtain their position by GPS 1b, 2b, and 3b, notify the position information to position computer 704 in advance by wireless communication, and receive power created from the received signal By transmitting the report message wirelessly to the position calculator 704, it is possible to operate in the same manner as the measurement terminal in the first to third embodiments.

  According to the above method, it is possible to specify the position by wireless communication even if the vehicle is not equipped with GPS or even if it is equipped with a vehicle that cannot be located because it is in the tunnel or under the roof. It becomes. In other words, by using a vehicle whose position can be accurately known by GPS or the like as a measurement terminal, the position of a vehicle not equipped with GPS or a vehicle located indoors can be estimated.

  FIG. 27 shows an example of the configuration of a measurement terminal provided with position detection means such as GPS.

  The configuration of the measurement terminal includes a measurement terminal reception antenna 41, a reception unit 42, a reception power measurement unit 43, a position detection unit 44, a measurement terminal transmission unit 45, and a measurement terminal transmission antenna 46. In addition to the configuration of the measurement terminal shown in FIG. 10, a position detection unit 44, a measurement terminal transmission unit 45, and a measurement terminal transmission antenna 46 are added, and the measurement terminal reception antenna 41, the reception unit 42, and the reception power measurement unit 43 are It has the same function as the element of the same name in FIG.

  The outputs of the reception unit 42 and the reception power measurement unit 43 are sent to the measurement terminal transmission unit 45, and are sent to the position calculator 704 using the radio through the measurement terminal transmission antenna 46. At this time, for example, the position of the measurement terminal itself detected by the position detection unit 44 configured by GPS is also sent to the measurement terminal transmission unit 45, and wirelessly through the measurement terminal transmission unit 45 and the measurement terminal transmission antenna 46. It is sent to the position calculator 704. The position calculator 704 estimates the positions of the transmission terminal 701 and the relay terminal 702 by receiving radio signals transmitted from the measurement terminals 1021, 1022, and 1023 and obtaining information, as in the previous embodiment.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

Claims (7)

A wireless system including a transmission terminal, a first relay terminal, at least three measurement terminals, and a position estimator,
The transmitting terminal transmits a first signal;
The first relay terminal receives the first signal, calculates a first received power value, transmits a second signal including the first received power value,
The measurement terminal receives the first signal and calculates a second received power value, receives the second signal and calculates a third received power value, demodulates the second signal, and calculates the first signal Extract the received power value,
The position estimator, when the second signal is obtained from the first relay terminal at the measurement terminal, the first received power value, the second received power value obtained at the measurement terminal, the third The position of the transmitting terminal is estimated based on the received power value and the position of the measurement terminal, and the second received power value is calculated based on the second received power value and the estimated position of the transmitting terminal. Update the parameters of the model for estimating the position of the transmitting terminal from
A radio system for estimating a position of the transmitting terminal from the second received power value and the model when the second signal cannot be obtained from the first relay terminal at the measuring terminal . The position estimator estimates the position of the first relay terminal using the third received power value,
The position of the transmitting terminal is estimated based on the estimated position of the first relay terminal, the first received power value, the second received power value, and the position of the measurement terminal. The wireless system according to 1. A second relay terminal,
The second relay terminal receives the first signal, calculates a fourth received power value, and transmits a third signal including the fourth received power value;
The first relay terminal receives the third signal, measures a fifth received power value, transmits the second signal further including the fifth received power value,
The measurement terminal receives the third signal, calculates a sixth received power value, demodulates the third signal to extract the fourth received power value, receives the second signal, and demodulates the second signal And extracting the fifth received power value,
Wherein the position estimator, the fourth received power value, the a fifth received power value, further using said sixth received power value, claim 1, wherein the estimating the position of the transmitting terminal Or the radio system according to 2 . The first relay terminal and the second relay terminal are mounted on a moving body with a predetermined distance therebetween, and the position estimator further uses the predetermined distance between the first and second relay terminals. 4. The wireless system according to claim 3 , wherein a position of the transmitting terminal is estimated. The first relay terminal demodulates the third signal, extracts the fourth received power value, includes the fourth received power value in the second signal to be transmitted,
The measurement terminal, the radio system according to claim 3 or 4, characterized in that extracting the fourth reception power value by demodulating the second signal. The measurement terminal includes a position measurement unit that measures the position of the measurement terminal,
The measurement terminal, the radio system according to any one of claims 1 to 5, characterized in that the position of the measuring terminal acquired by the measuring terminal, notifies the position estimator. A position estimator that performs position estimation of the transmission terminal using at least three measurement terminals that communicate with each of the transmission terminal and the relay terminal,
The first received power value at the relay terminal of the first signal transmitted by the transmitting terminal is acquired via the measuring terminal, and the second received power value at the measuring terminal of the first signal transmitted by the transmitting terminal. Is obtained from the measurement terminal, the third control unit obtains a third received power value at the measurement terminal of the second signal transmitted by the relay terminal, and
When the second signal is obtained from the relay terminal at the measurement terminal, the first received power value, the second received power value, the third received power value acquired by the estimation control unit, and the measuring terminal based on the position, as well as estimates the position of the transmitting terminal, the second received power value, based on the position of the transmitting terminal that the estimated, estimates the position of the transmission terminal from the second received power value Update the model parameters
When the second signal cannot be obtained from the relay terminal by the measuring terminal, a position estimator comprising: a position estimating unit that estimates the position of the transmitting terminal from the second received power value and the model .

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