CN114729985A - Communication system, base station, measurement method, and program - Google Patents

Abstract

A communication system including a terminal device and a base station connected to the terminal device so as to be capable of bidirectional communication, and estimating a position of the terminal device, the communication system comprising: a communication control unit that controls communication between the base station and the terminal device; a measurement unit that measures a signal arrival time required for a signal transmitted from the base station to reach the terminal device; and a position estimation unit configured to estimate a position of the terminal device based on the signal arrival time measured by the measurement unit.

Description

Communication system, base station, measurement method, and program

Technical Field

The invention relates to a communication system, a base station, a measurement method and a program.

The present application claims priority based on Japanese application laid-open at 2/3/2020, Japanese patent application No. 2020 and 016553, the contents of which are incorporated herein by reference.

Background

Conventionally, there are techniques as follows: a radio wave transmitted from a transmitter such as a beacon installed indoors is received, and the position of the receiver is estimated based on the intensity of the received radio wave (received radio wave intensity). For example, patent document 1 discloses the following technique: a model for obtaining the radio wave intensity distribution in a room using a predetermined radiation function is constructed from the relationship between the radio wave intensity and the position in the room measured in advance, and the position of the receiver is estimated using the constructed model.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2019-144120

Disclosure of Invention

Technical problem to be solved by the invention

However, when the technique of patent document 1 is to be applied outdoors, there is room for improvement. For example, since a building, a vehicle, or the like exists outdoors as an obstacle and the radio wave intensity distribution changes with time, it is difficult to construct a model that can accurately determine the radio wave intensity distribution. It is not realistic to measure the radio wave intensities at various outdoor locations in advance, which takes a long time.

In addition, a position detection method based on a gps (global Positioning system) signal may be used outdoors. However, power consumption is large in position detection by GPS. Therefore, in the case of a terminal that cannot be equipped with a large-capacity battery, it is difficult to use position detection by GPS.

The present invention has been made in view of such circumstances, and provides a communication system, a base station, a measurement method, and a program that can estimate the position of a mobile object without much effort by using a method of receiving radio waves transmitted from the mobile object outdoors.

Means for solving the problems

In order to achieve the above object, a communication system according to a first aspect of the present invention is a communication system including a terminal device and a base station connected to the terminal device so as to be capable of bidirectional communication, and estimating a position of the terminal device, the communication system including: a communication control unit that controls communication between the base station and the terminal device; a measurement unit that measures a signal arrival time required for a signal transmitted from a base station to reach the terminal device; and a position estimation unit configured to estimate a position of the terminal device based on the signal arrival time measured by the measurement unit.

A base station according to a second aspect of the present invention is a base station connected to a terminal device so as to be capable of bidirectional communication in a communication system for estimating a position of the terminal device, the base station including: a base station communication control unit that controls communication with the terminal device; and a measurement unit that measures a signal arrival time required for a signal transmitted from the base station to reach the terminal device, based on a transmission time of a transmission instruction signal transmitted from the base station to the terminal device and a reception time of a sub-signal received by the base station from the terminal device as a response to the transmission instruction signal.

A measurement method according to a third aspect of the present invention is a measurement method for measuring a signal arrival time required for a signal transmitted from a base station to reach a terminal device in a base station connected to the terminal device so as to be capable of bidirectional communication in a communication system for estimating a position of the terminal device, the measurement method including the steps of: controlling, by a base station communication control unit, communication with the terminal device; the measurement unit measures the signal arrival time based on a transmission time of a transmission instruction signal transmitted from the base station to the terminal device and a reception time at which the base station receives a sub-signal as a response to the transmission instruction signal from the terminal device.

A program according to a fourth aspect of the present invention is a program for measuring a signal arrival time required for a signal transmitted from a base station to reach a terminal device in a base station connected to the terminal device so as to be capable of bidirectional communication in a communication system for estimating a position of the terminal device, the program being configured to execute: a base station communication control unit that controls communication with the terminal device; a measurement unit that measures the signal arrival time based on a transmission time at which a transmission instruction signal is transmitted from the base station to the terminal device and a reception time at which the base station receives a sub-signal as a response to the transmission instruction signal from the terminal device.

Effects of the invention

According to the present invention, it is possible to estimate the position of a mobile object without trouble by using a method of receiving radio waves transmitted from the mobile object existing outdoors.

Drawings

Fig. 1 is a block diagram showing an example of the configuration of the position estimation system according to the first embodiment.

Fig. 2 is a diagram illustrating a process of estimating a position by the position estimation system according to the first embodiment.

Fig. 3 is a block diagram showing an example of the configuration of the server device according to the first embodiment.

Fig. 4 is a block diagram showing an example of the configuration of the base station according to the first embodiment.

Fig. 5 is a block diagram showing an example of the configuration of the terminal tag according to the first embodiment.

Fig. 6 is a diagram showing an example of the configuration of the transmission time information according to the first embodiment.

Fig. 7 is a diagram showing an example of the configuration of the reception time information according to the first embodiment.

Fig. 8 is a diagram showing an example of the configuration of the processing time information according to the first embodiment.

Fig. 9 is a diagram showing an example of the configuration of the retransmission number information according to the first embodiment.

Fig. 10 is a diagram showing an example of a configuration of a signal format used for position estimation in the first embodiment.

Fig. 11 is a sequence diagram showing a flow of processing performed by the position estimation system according to the first embodiment.

Fig. 12 is a block diagram showing an example of the configuration of a terminal tag according to a modification of the first embodiment.

Fig. 13 is a sequence diagram showing a flow of processing performed by the position estimation system according to the modification of the first embodiment.

Fig. 14 is a sequence diagram showing a flow of processing performed by the position estimation system according to the modification of the first embodiment.

Fig. 15 is a block diagram showing an example of the configuration of the position estimation system according to the second embodiment.

Fig. 16 is a block diagram showing an example of the configuration of the relay according to the second embodiment.

Fig. 17 is a diagram showing an example of the configuration of the first relay information according to the second embodiment.

Fig. 18 is a diagram showing an example of the configuration of the second relay information according to the second embodiment.

Fig. 19 is a sequence diagram showing a flow of processing performed by the position estimation system according to the second embodiment.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the drawings.

A first embodiment will be explained.

Fig. 1 is a block diagram showing an example of the configuration of a position estimation system 1 according to the first embodiment. The position estimation system 1 is a system for estimating the position of a terminal tag 30 which is mounted on a mobile object such as a vehicle and moves. The position estimation system 1 includes, for example, a server device 10, a plurality of base stations 20 (base stations 20-1, 20-2, and 20-3 …), and a terminal tag 30. The position inference system 1 is an example of a "communication system". The terminal tag 30 is an example of a "terminal apparatus".

The server device 10 is connected to the base station 20 so as to be able to communicate bidirectionally. The base station 20 and the terminal tag 30 are connected so as to be able to communicate bidirectionally. The position estimation system 1 may include a plurality of server devices 10, or may include a plurality of terminal tags 30. The position estimation system 1 may have only one base station 20. One of the plurality of base stations 20 may have the function of the server device 10. In this case, the plurality of base stations 20 are configured by one master base station and a plurality of other slave base stations. Each slave base station may be connected to the master base station so as to be able to communicate with the master base station.

The position estimation system 1 is a system that estimates the position of the terminal tag 30. The position inference system 1 is suitable for logistics management, for example. In this logistics management, the terminal tag 30 is attached to the article to be managed, or the terminal tag 30 is mounted on a vehicle that delivers the article. Thereby, the terminal tag 30 moves together with the article. The position estimation system 1 estimates the position of the mobile terminal tag 30, and manages the position of the product in the middle of delivery.

The terminal tag 30 is a device having various sensors and communication functions for monitoring a monitoring target. The various sensors here are, for example, a temperature sensor for measuring the temperature of the product necessary for temperature management when the monitoring target is a physical distribution, an illuminance sensor for sensing the opening of the product, and the like. The communication function provided in the terminal tag 30 performs communication between the terminal tag 30 and the base station 20.

The communication between the base station 20 and the terminal tag 30 may be any communication method as long as it can perform at least bidirectional communication. For example, as a communication method, Sigfox (registered trademark), LoRa (registered trademark), ZETA (registered trademark) and the like in the lpwa (low Power Wide area) standard are used. LPWA is characterized by suppressing the communication speed to reduce power consumption compared to conventional communication networks, for example, lte (long Term evolution) and the like. The communication distance is also characterized by being large, for example, about several tens km to 100km, as compared with short-range wireless communication such as Bluetooth (registered trademark). In order to increase the communication distance, a repeater may be disposed between the base station 20 and the terminal tag 30.

In the present embodiment, the terminal tag 30 is used only for estimation of a position. Therefore, the terminal tag 30 may have at least a communication function, and may not include a sensor. The terminal tag 30 is preferably a so-called wireless tag having a battery or the like incorporated therein, because it is attached to a product or the like and moved. The terminal tag 30 is preferably a small, thin, and lightweight tag that does not hinder the transportation of the product.

In the bidirectional communication between the base station 20 and the terminal tag 30, one communication method and the other communication method may be the same communication method or different communication methods. For example, the communication method in the direction in which the terminal tag 30 transmits to the base station 20 may be a communication method to which the LPWA standard is applied, and the communication method in the direction in which the terminal tag 30 receives from the base station 20 may be a communication method in a standard different from the LPWA standard. When the ZETA is applied, multichannel communication using an ultra Narrow band (un b) in which a communication band is divided into a plurality of bands is performed. In this case, the frequency band of the channel used for communication may be fixed to the same frequency band each time, or may be operated to change without being fixed.

The base station 20 may communicate with the terminal tag 30, and collect sensor information such as temperature and illuminance measured by a sensor of the terminal tag 30.

The base station 20 of the present embodiment communicates with the terminal tag 30, and measures the signal arrival time of a signal used for communication. The signal arrival time is a time until the signal transmitted from the base station 20 reaches the terminal tag 30. The base station 20 communicates with the server apparatus 10 and notifies the server apparatus 10 of the measured signal arrival time. The method for measuring the signal arrival time by the base station 20 will be described in detail later.

The server apparatus 10 communicates with the base station 20. The server device 10 estimates the position of the terminal tag 30 from the signal arrival time measured by each base station 20. The position of the terminal tag 30 is inferred by applying the principle of triangulation to the signal arrival time (refer to fig. 2).

The server device 10 notifies the estimated position of the terminal tag 30 to an external device such as a position search application server not shown. In this case, the server device 10 is connected to the location search application server via a communication network such as the internet. The location search application server is an application program that provides a service for searching for the location of a product being distributed. The location search application server receives a request for searching for the location of a product from a user terminal in which the application is installed, for example. The position search application server causes the position estimation system 1 to estimate the position of the terminal tag 30 attached to the search target product based on a request from the user terminal. The location search application server also notifies the user terminal of the location estimated by the location estimation system 1 as a search result.

A method of estimating the position of the terminal tag 30 by the server device 10 will be described with reference to fig. 2. Fig. 2 is a diagram illustrating a process of estimating a position by the position estimation system 1 according to the first embodiment. The server apparatus 10 (not shown in fig. 2) communicates the base stations 20 with the same terminal tag 30 at substantially the same time, for example, and measures the arrival times of the signals. The server device 10 extracts candidates of the position of the terminal tag 30 based on the signal arrival times of the base stations 20.

For example, the server device 10 calculates the signal arrival distance from the relationship with the signal speed (light speed) based on the signal arrival time of each base station 20. The signal arrival distance is a distance that a signal transmitted from the base station 20 travels to reach the terminal tag 30, and is synonymous with the distance from the base station 20 to the terminal tag 30. The server apparatus 10 sets, as candidates for the position of the terminal tag 30, positions on a circle having the respective signal arrival distances as radii, with respect to the respective base stations 20 as centers.

In the example of fig. 2, the signal arrival time measured by the base station 20-1 is 0.2 seconds, and the position on the circle R1 is a candidate for the position of the terminal tag 30. The signal arrival time measured by the base station 20-2 is 0.1 second, and the position on the circle R2 is a candidate for the position of the terminal tag 30. The signal arrival time measured by the base station 20-3 is 0.5 seconds, and the position on the circle R3 is a candidate for the position of the terminal tag 30.

The server device 10 estimates the position of the terminal tag 30 as the position where the candidate of the position of the terminal tag 30 extracted based on the signal arrival distances measured by the plurality of base stations 20 intersects. In this example, the points where circles R1-R3 intersect are the inferred positions of terminal tags 30.

In the above description, the case where the server apparatus 10 estimates the position of the terminal tag 30 based on the signal arrival times measured by the three base stations 20 has been described as an example. However, the present invention is not limited thereto.

The server device 10 may estimate the position of the terminal tag 30 based on the signal arrival times measured by the four or more base stations 20. The server device 10 may also infer the location of the terminal tag 30 based on one or both signal arrival times. In this case, for example, the server device 10 superimposes the candidate of the position of the terminal tag 30 extracted based on the signal arrival distance measured by the base station 20 on the road map around the candidate position. The server device 10 estimates the position of the terminal tag 30 as a point at which the candidate of the position of the terminal tag 30 extracted based on the signal arrival distance intersects with the travel route of the vehicle or the like on which the terminal tag 30 is mounted.

When the position of the terminal tag 30 is estimated based on the arrival time of one signal, the server device 10 may be omitted. In this case, the function of the position estimating unit 13 described later provided in the server device 10 may be provided in the base station 20.

In the position estimation system 1, it is assumed that the times used in the respective devices of the base station 20 are synchronized with each other (time synchronization). Hereinafter, a case will be described as an example in which the server apparatus 10 notifies each base station 20 of a signal (time information) for synchronizing time, and the base stations 20 synchronize time. However, the present invention is not limited to this, and any method may be used as long as the base stations 20 are synchronized with each other in time. For example, each base station 20 may receive a gps (global Positioning system) signal or a radio wave of a radio wave clock to synchronize the time.

The measurement accuracy of the time in the base station 20 may be determined arbitrarily according to the accuracy of the estimated position of the terminal tag 30, the processing capability of the base station 20, and the like.

For example, when the position is estimated on the order of Km (kilometers), the time is measured on the order of milliseconds. Alternatively, when it is desired to estimate the position on the order of m (meters), the time is designed to be measurable on the order of nanoseconds. When it is difficult to measure the time on the order of nanoseconds due to the processing capability of the base station 20, the accuracy of the estimated position is lowered within an allowable range, and the time is measured on the order of magnitude (for example, on the order of 100 nanoseconds) that the base station 20 can process.

Fig. 3 is a block diagram showing an example of the configuration of the server device 10 according to the first embodiment. The server device 10 includes, for example, a communication unit 11, a signal arrival time acquisition unit 12, a position estimation unit 13, a GPS information acquisition unit 14, a time synchronization unit 15, a control unit 17, and a storage unit 18.

The communication unit 11 communicates with each base station 20 and receives information indicating the arrival time of the signal.

The signal arrival time acquisition unit 12 acquires information indicating the signal arrival time measured by each base station 20 via the communication unit 11.

The position estimation unit 13 estimates the position of the terminal tag 30 based on the signal arrival time acquired by the signal arrival time acquisition unit 12.

The GPS information acquisition unit 14 is, for example, a GPS receiving module, and acquires information of time transmitted by GPS (hereinafter, GPS time information).

The time synchronization unit 15 synchronizes the time in the server device 10 with the GPS time information by using the GPS time information acquired by the GPS information acquisition unit 14. The time synchronization unit 15 generates time information using the GPS time information acquired by the GPS information acquisition unit 14. The time information is information for time synchronization of the base stations 20. The time synchronization unit 15 notifies the generated time information to each base station 20 via the communication unit 11.

The control unit 17 controls the server devices 10 collectively. For example, the control unit 17 causes the signal arrival time acquisition unit 12 to output the signal arrival time received by the communication unit 11.

The Processing performed by the signal arrival time acquisition unit 12, the position estimation unit 13, the GPS information acquisition unit 14, the time synchronization unit 15, and the control unit 17 is realized by, for example, causing a cpu (central Processing unit) provided as hardware of the server device 10 to execute a program.

The storage unit 18 is configured by a storage medium, for example, an hdd (hard Disk drive), a flash Memory, an eeprom (electrically Erasable Programmable Read Only Memory), a RAM (Random Access Read/write Memory), a rom (Read Only Memory), or any combination of these storage media. The storage unit 18 stores programs for executing various processes of the server device 10 and temporary data used when performing various processes.

Fig. 4 is a block diagram showing an example of the configuration of the base station 20 according to the first embodiment. The base station 20 includes, for example, a communication unit 21, a base station communication control unit 22, a storage control unit 23, a signal arrival time calculation unit 24, a time information acquisition unit 25, a time synchronization unit 26, and a control unit 27. The base station 20 may further include a storage unit 28. The signal arrival time calculation unit 24 is an example of a "measurement unit".

The communication unit 21 communicates with the server device 10 and the terminal tag 30. The communication unit 21 receives time information from the server device 10. The communication unit 21 receives a signal notified from the terminal tag 30. The communication unit 21 transmits a signal notified from the terminal tag 30 to the server device 10.

The base station communication control unit 22 controls communication between the base station 20 and the terminal tag 30. The base station communication control unit 22 controls to notify the terminal tag 30 of the transmission instruction signal at a predetermined timing. The transmission instruction signal is a signal for instructing transmission of a signal to the terminal tag 30. The predetermined time is, for example, a time instructed from the server device 10. In this case, the server apparatus 10 synchronizes the time of each base station 20 and instructs the same terminal tag 30 to notify the transmission instruction signal at the same time. Thus, even if the terminal tag 30 is moving, each base station 20 can receive the sub-signal (response to the transmission instruction signal) from the terminal tag 30 located at substantially the same position. Therefore, the signal arrival times of the terminal tags 30 and the base stations 20 located at substantially the same positions can be measured, and the positions of the terminal tags 30 can be specified.

The storage controller 23 causes the storage unit 28 to store information for measuring the signal arrival time. The information for measuring the signal arrival time is the transmission time and the reception time. The transmission time is a time when the base station 20 transmits the transmission instruction signal to the terminal tag 30. The reception time is a time when the sub-signal (response to the transmission instruction signal transmitted at the transmission time) is received from the terminal tag 30.

When the transmission instruction signal is transmitted through the communication unit 21, the storage control unit 23 sets the time as the transmission time and stores the transmission time information 280 in the storage unit 28. The transmission time information 280 is information in which identification information of the transmission instruction signal is associated with the transmission time. When the sub-signal (response to the transmission instruction signal transmitted at the transmission time) is received from the terminal tag 30, the storage control unit 23 sets the transmission time as the reception time, and stores the reception time information 281 in the storage unit 28. The reception time information 281 is information in which identification information of the sub-signal is associated with the reception time.

The base station communication control unit 22 and the memory control unit 23 of the base station 20 are configured to control communication between the terminal tag 30 and the base station 20, and may be referred to as "communication control units", respectively.

The signal arrival time calculation section 24 calculates a signal arrival time. The signal arrival time calculation unit 24 calculates a signal arrival time using the transmission time information 280, the reception time information 281, and the processing time information 282. The processing time information 282 is information in which the signal processing performed in the terminal tag 30 is associated with the time required for the processing. The signal arrival time calculation unit 24 extracts the transmission time of the specific transmission instruction signal from the transmission time information 280. The signal arrival time calculation unit 24 extracts the reception time of the sub-signal corresponding to the response of the transmission instruction signal extracted from the transmission time information 280. The signal arrival time calculation unit 24 calculates the difference between the extracted transmission time and reception time, and sets the time of the calculated difference as the signal round trip processing time.

The signal round-trip processing time includes not only the time required for round-trip of the signal but also the time required for various kinds of signal processing.

The time required for round trip of the signal is the sum of the time required for transmitting the instruction signal from the base station 20 to the terminal tag 30 and the time required for the sub-signal from the terminal tag 30 to reach the base station 20. 1/2, the time required for the signal to make a round trip, corresponds to the signal arrival time.

The time required for various signal processing is the sum of the time required for processing for demodulating the transmission instruction signal, processing for determining a response based on the result of the demodulation, processing for generating a response signal, processing for modulating the generated signal, and the like. In the present embodiment, the time required for various signal processing in the terminal tag 30 is associated with the signal processing and stored in the storage unit 28 as the processing time information 282.

The signal arrival time calculation unit 24 calculates the time required for round trip of the signal by subtracting the time required for such signal processing from the signal round trip processing time. The signal arrival time calculation unit 24 calculates the signal arrival time by multiplying 1/2 by the time required for the round trip of the signal.

The time information acquisition unit 25 acquires the time information notified from the server device 10 via the communication unit 21. The time information is a signal for time-synchronizing the base stations 20. The time information acquiring unit 25 outputs the acquired time information to the time synchronizing unit 26. The time synchronization unit 26 adjusts the time of a timer operating inside the base station 20 based on the time information so as to be synchronized with the time indicated by the time information.

The control unit 27 collectively controls the base station 20. The control unit 27 outputs the time information received by the communication unit 21 to the time information acquisition unit 25. When the sub-signal received by the communication unit 21 includes sensor information, the control unit 27 extracts the sensor information and stores the sensor information in the storage unit 28.

The processing of each of the base station communication control unit 22, the storage control unit 23, the signal arrival time calculation unit 24, the time information acquisition unit 25, the time synchronization unit 26, and the control unit 27 is realized by causing a CPU provided as hardware of the base station 20 to execute a program.

The storage unit 28 is configured by a storage medium, such as an HDD, a flash memory, an EEPROM, a RAM, a ROM, or any combination of these storage media. The storage unit 28 stores programs for executing various processes of the base station 20 and temporary data used when performing various processes. The storage unit 28 stores transmission time information 280, reception time information 281, and processing time information 282. When the sub-signal includes sensor information, the storage unit 28 stores the sensor information.

Fig. 5 is a block diagram showing an example of the configuration of the terminal tag 30 according to the first embodiment. The terminal tag 30 includes, for example, a sensor unit 300 and a communication module 310. The sensor unit 300 is various sensors such as a temperature sensor and an illuminance sensor. In addition, when only the position estimation based on the terminal tag 30 is executed, the terminal tag 30 may not include the sensor unit 300. The communication module 310 includes a communication unit 31, a terminal communication control unit 32, a sensor information acquisition unit 33, a transmission signal generation unit 34, a control unit 37, and a storage unit 38.

The communication unit 31 communicates with the base station 20. The communication unit 31 transmits the sub-signal to the base station 20. The communication unit 31 receives a transmission instruction signal from the base station 20.

The terminal communication control unit 32 controls communication between the terminal tag 30 and the base station 20. The terminal communication control unit 32 controls to transmit the sub-signal to the base station 20. The sub-signal is a signal indicating a response to the transmission instruction signal notified from the base station 20. The terminal communication control unit 32 of the terminal tag 30 is configured to control communication between the terminal tag 30 and the base station 20, and may be referred to as an example of a "communication control unit".

The terminal communication control unit 32 determines whether or not the transmission of the signal to the base station 20 is successful. The terminal communication control unit 32 determines that transmission is successful when ACK (Answer) for a signal transmitted to the base station 20 is returned (received) from the base station 20 of the notification destination. When ACK for a signal transmitted to the base station 20 is not returned from the base station 20 of the notification destination within a certain period, the terminal communication control unit 32 determines that transmission has failed.

When transmission fails, the terminal communication control unit 32 controls retransmission of the failed signal to the base station 20 that is the source of notification. When the signal is retransmitted, the terminal communication control unit 32 stores the number of times of retransmitting the signal (retransmission number) as retransmission number information 380 in the storage unit 38. The retransmission number information 380 is information in which the number of retransmissions is associated with identification information of a retransmitted signal.

The sensor information acquiring unit 33 is, for example, an IO (input output) port connected to the sensor unit 300, and is connected to the sensor unit 300 via the IO port to acquire information (sensor information) measured by the sensor unit 300. The sensor information acquisition unit 33 stores the acquired sensor information in the storage unit 38.

The transmission signal generating unit 34 generates a signal to be transmitted to the base station 20. The signal transmitted to the base station is, for example, a sub-signal in response to the transmission instruction signal, a signal notifying sensor information, or the like. When generating the sub-signal, the transmission signal generating unit 34 generates the sub-signal by including information necessary for calculating the signal arrival time. The information required for calculating the signal arrival time is, for example, signal type information indicating that the sub-signal is a response to the transmission instruction signal, identification information of the corresponding transmission instruction signal, retransmission number information 380, and the like.

The transmission signal generating unit 34 generates a signal for notifying the sensor information by including the sensor information stored in the storage unit 38. The transmission signal generating unit 34 may generate a signal for notifying the sensor information each time the sensor information is acquired, or may generate one signal (signal for notifying the sensor information) for notifying the sensor information acquired in a fixed period.

The transmission signal generating unit 34 may generate the sub-signal including the sensor information, or may generate the sub-signal without including the sensor information. By generating the sub-signal including the sensor information, it is possible to collectively notify the response to the transmission instruction and the sensor information, and it is possible to perform efficient communication. By generating the sub-signal without including the sensor information, the volume of data used for each communication can be suppressed, and the communication volume can be reduced.

The control unit 37 controls the terminal tags 30 collectively. The control unit 37 outputs the signal generated by the transmission signal generating unit 34 to the communication unit 31.

The processes performed by the terminal communication control unit 32, the sensor information acquisition unit 33, the transmission signal generation unit 34, and the control unit 37 are realized by causing a CPU provided as hardware of the terminal tag 30 to execute a program.

The storage unit 38 is configured by a storage medium, such as an HDD, a flash memory, an EEPROM, a RAM, a ROM, or any combination of these storage media. The storage unit 38 stores programs for executing various processes of the terminal tag 30 and temporary data used when performing various processes. The storage unit 38 stores retransmission number information 380. The storage unit 38 may store sensor information and the like.

Fig. 6 is a diagram showing an example of the configuration of the transmission time information 280 according to the first embodiment. The transmission time information 280 includes items such as a signal ID, a communication destination terminal ID, a signal type, a transmission date, and a transmission time.

The signal ID is identification information that uniquely identifies a signal transmitted by the base station 20. The communication destination terminal ID is identification information of a device to be notified of a signal specified by the signal ID. The signal type is the type of signal determined by the signal ID. The transmission date is the date on which the signal specified by the signal ID is transmitted. The transmission time is the time at which the signal specified by the signal ID is transmitted. In this example, the signal specified by the signal ID (Tx0001) indicates that the notification destination is the terminal tag 30, the signal type is the transmission instruction signal, and the transmission date is yy year mm month dd day.

Fig. 7 is a diagram showing an example of the configuration of reception time information 281 according to the first embodiment. The reception time information 281 includes items such as a signal ID, a transmission source terminal ID, a signal type, a reception day, a reception time, a response source signal ID, and the number of retransmissions.

The signal ID is identification information that uniquely identifies a signal received by the base station 20. The transmission meta terminal ID is identification information of a device that becomes a notification source of the signal specified by the signal ID. The signal type is the type of signal determined by the signal ID. The reception date is the date on which the signal specified by the signal ID is received. The reception time is the time when the signal specified by the signal ID is received. The response source signal ID is identification information of a signal that becomes a source of the response when the signal specified by the signal ID is a response signal. The number of retransmissions is the number of times the signal is retransmitted, which is determined by the signal ID.

In this example, the signal determined by the signal ID (Rx0001) represents the following case: the source of notification is the terminal tag 30, the signal type is a sub-signal, the reception day is yy year mm month dd, the response to the transmission instruction signal specified by the signal ID (Tx0001), and the number of retransmissions is 0 (zero).

Fig. 8 is a diagram showing an example of the configuration of the processing time information 282 according to the first embodiment. The processing time information 282 includes items such as a processing ID, a processing terminal ID, a processing type, a signal processing time, and details.

The process ID is identification information that uniquely identifies the process. The process terminal ID is identification information for identifying a device that performs the process specified by the process ID. The process type is a type of process determined by the process ID. The details are details of the process specified by the process ID, and include, for example, a process item and a process time. The processing items are items of processing performed for the response. The processing time is a time required for processing the item representation.

In this example, the time required for the demodulation processing and/or the modulation processing in the case where the terminal tag 30 performs the response based on the sub-signal of the sensorless information is shown. In addition, the time required for the process of acquiring the sensor information when the terminal tag 30 responds based on the sub-signal having the sensor information is shown. In addition, the time required for the process of determining whether to retransmit is shown in the case where the terminal tag 30 retransmits the sub-signal.

Fig. 9 is a diagram showing an example of the configuration of retransmission number information 380 according to the first embodiment. The retransmission count information 380 includes items such as a signal ID, a communication destination device ID, a signal type, and the number of retransmissions.

The signal ID is identification information that uniquely identifies the signal transmitted by the terminal tag 30. The communication destination device ID is identification information of a device to be a transmission destination of the signal specified by the signal ID. The signal type is the type of signal determined by the signal ID. The number of retransmissions is the number of retransmissions of the signal determined by the signal ID to the device of the transmission destination.

In this example, the sub-signal determined by the signal ID (Tx1001) is shown as being transmitted to the base station 20-1 0 (zero) times the number of retransmissions. The sub-signal determined by the signal ID (Tx1002) is shown as being transmitted to the base station 20-2 the number of retransmissions 2 times.

Fig. 10 is a diagram showing an example of a configuration of a format of signal SG used for communication in position estimation system 1 according to the first embodiment. The signal SG is, for example, a transmission instruction signal, a sub-signal of no sensor information, a sub-signal of sensor information, a signal for notifying of sensor information, and the like.

The signal SG is composed of, for example, a header HD, a data section DA, and a trailer FT.

The header HD is information added to the head of the signal SG, and is composed of, for example, a notification source ID, a notification destination ID, a signal type, and the like. The notification source ID is identification information of a device that becomes a notification source. The notification destination ID is identification information of a device to be notified.

The data portion DA is information indicating the content of the notification, and in the example of fig. 10, information in which information is combined so as to be modularized for each predetermined data length from the notification content 1 to the notification content K.

The tail FT is information added to the end of the signal, and is, for example, a cyclic Redundancy code (crc) for error detection.

For example, when the signal SG is a transmission instruction signal, the header HD indicates information indicating that the notification source is the base station 20, the notification destination is the terminal tag 30, and the signal type is the transmission instruction signal. The data section DA shows: the content indicating that the sub-signal is returned as a response, or information indicating whether or not the sensor information or the like is included in the sub-signal. The trailer FT shows, for example, CRC bits generated from a bit string of the data section DA.

For example, when the signal SG is a sub-signal, the header HD shows information indicating that the notification source is the terminal tag 30, the notification destination is the base station 20, and the signal type is a sub-signal. The data section DA shows, for example, in the blocks of the notification content 1: information indicating whether the signal is a sub-signal in response to any of the transmission instructions or whether the signal includes sensor information or the like. When the sensor information is included, the sensor information is shown in a block located behind the notification content 1. The trailer FT indicates, for example, CRC bits generated from a bit string of the data section DA.

When the sensor information is not included, the data section DA is configured only by the module of the notification content 1. When the sensor information is included, the data unit DA links the modules after the notification content 1. That is, the amount of information in the entire signal differs between the case where the sensor information is not included and the case where the sensor information is included, and the amount of information can be reduced in the case where the sensor information is not included as compared to the case where the sensor information is not included.

Fig. 11 is a sequence diagram showing a flow of processing performed by the position estimation system 1 according to the first embodiment. Here, as the processing performed by the position estimation system 1, the flow of each processing will be described with respect to the processing for performing time synchronization (reference numeral S100) and the processing for estimating a position (reference numeral S200). The respective processes may be performed at respective timings or may be performed in a linked manner.

First, a process of performing time synchronization (reference numeral S100) will be described.

The server apparatus 10 receives the GPS information (step S10). The server device 10 receives, for example, a signal transmitted from a GPS satellite as GPS information. The GPS information may be any signal that can synchronize time. The GPS information may be a signal indicating the time transmitted from a radio-controlled clock, or may be a signal indicating the periodic timing output from a crystal oscillator or the like. The server device 10 generates time information based on the received GPS signal, and notifies the base station 20 of the generated time information.

The base station 20 adjusts the time used in the base station 20 based on the time information received from the server apparatus 10, and performs time synchronization (step S11).

Next, a process of estimating the position (reference numeral S200) will be described.

The base station 20 notifies the terminal tag 30 of the transmission instruction signal at a predetermined timing (step S20). The base station 20 stores the transmission time at which the transmission instruction signal was transmitted (step S21).

Upon receiving the transmission instruction signal from the base station 20, the terminal tag 30 generates a sub-signal in response thereto (step S22). The terminal tag 30 transmits the generated sub-signal to the base station 20 (step S23).

When receiving the sub-signal from the terminal tag 30, the base station 20 stores the reception time when the sub-signal was received (step S24). The base station 20 calculates a signal arrival time using the transmission time stored in step S21 and the reception time stored in step S24 (step S25).

The base station 20 notifies the server device 10 of the calculated signal arrival time. The server apparatus 10 estimates the position of the terminal tag 30 using the arrival time of the signal received from the base station 20 (step S26).

As described above, the position estimation system 1 ("an example of a communication system") according to the first embodiment is a system including the terminal tag 30 ("an example of a terminal device") and the base station 20. The position estimation system 1 includes a terminal communication control unit 32 (an example of a "communication control unit") and a base station communication control unit 22 (an example of a "communication control unit"), a signal arrival time calculation unit 24 (an example of a "measurement unit"), and a position estimation unit 13. The terminal communication control unit 32 and the base station communication control unit 22 control communication between the base station 20 and the terminal tag 30. The signal arrival time calculation unit 24 measures the signal arrival time required until the signal transmitted from the base station 20 is received by the terminal tag 30. The position estimating unit 13 estimates the position of the terminal tag 30 based on the signal arrival time measured by the signal arrival time calculating unit 24.

Thus, the position estimation system 1 according to the first embodiment can estimate the position of the terminal tag 30 by calculating the signal arrival distance from the relationship between the signal speed and the signal arrival time using the method of receiving the signal transmitted from the base station 20 by an outdoor mobile object (terminal tag 30). Therefore, the position of the moving object can be estimated with high accuracy without taking the trouble of measuring the received radio wave intensity in the space in advance.

In the position estimation system 1 according to the first embodiment, the communication control unit may include the base station communication control unit 22, the terminal communication control unit 32, and the storage control unit 23. The base station communication control unit 22 transmits a transmission instruction signal from the base station 20 to the terminal tag 30. The terminal communication control unit 32 transmits a sub-signal in response to the transmission instruction signal from the terminal tag 30 that has received the transmission instruction signal to the base station 20. The storage control unit 23 stores, in the storage unit 28, a transmission time at which the base station 20 transmits the transmission instruction signal to the terminal tag 30 and a reception time at which the base station 20 receives the sub-signal from the terminal tag 30.

The signal arrival time calculation unit 24 (an example of the "measurement unit") may calculate the signal arrival time using the transmission time and the reception time stored in the storage unit 28.

Thus, the position estimation system 1 according to the first embodiment can calculate the signal arrival time based on the time until the base station 20 transmits a signal and the base station 20 receives a response to the transmitted signal. In this way, the terminal tag 30 can calculate the signal arrival time only by the base station 20 without measuring the reception time. Therefore, it is not necessary to perform time synchronization with high accuracy with respect to the terminal tag 30.

In the position estimation system 1 according to the first embodiment, the sub-signal (an example of the "signal transmitted from the terminal tag 30 to the base station 20") may be either a sub-signal not including sensor information (an example of "small data") or a sub-signal including sensor information (arbitrary measurement information measured by the terminal device).

Thus, in the position estimation system 1 according to the first embodiment, depending on the application of the system, the communication load can be suppressed by giving importance to the data transfer efficiency and by suppressing the data capacity per one time.

In the position estimation system 1 according to the first embodiment, the position estimation unit 13 may estimate the position of the terminal tag 30 based on the signal arrival times of at least three or more base stations 20.

Thus, in the position estimation system 1 according to the first embodiment, the position of the terminal tag 30 can be estimated with high accuracy using the principle of triangulation.

The position estimation system 1 according to the first embodiment may further include a terminal communication control unit 32 (communication control unit), and the terminal communication control unit 32 may determine whether or not transmission of a sub-signal (an example of a "signal transmitted from the terminal tag 30 to the base station 20") has failed, and store retransmission number information 380 indicating the number of times of retransmission, in which information indicating the number of times of retransmission is included in the retransmitted sub-signal, and retransmit the sub-signal, when transmission of the sub-signal has failed.

Thus, in the position estimation system 1 according to the first embodiment, even when a sub-signal is retransmitted, the signal arrival time can be calculated in consideration of the time required for the retransmission processing.

(modification 1 of the first embodiment)

Modification 1 of the first embodiment will be described. The present modification differs from the first embodiment described above in that the base station 20 and the terminal tag 30 are synchronized in time. In the present modification, the base station 20 notifies the terminal tag 30 of the time information. The time information is the same as the time information notified to the base station 20 by the server device 10 in the first embodiment. The terminal tag 30 synchronizes the time used for the process in the device of the terminal tag 30 with the time indicated by the time information, based on the time information received from the base station 20.

Fig. 12 is a block diagram showing an example of the configuration of the terminal tag 30 according to modification 1 of the first embodiment. The terminal tag 30 of the present modification includes, for example, a time information acquisition unit 35 and a time synchronization unit 36. The time information acquisition unit 35 acquires the time information notified from the base station 20 via the communication unit 31. The time information acquiring unit 35 and the time synchronizing unit 36 have the same functions as the time information acquiring unit 25 and the time synchronizing unit 26, and therefore, the description thereof is omitted.

Fig. 13 is a sequence diagram showing a flow of processing performed by the position estimation system 1 according to modification 1 of the first embodiment. Here, as the processing performed by the position estimation system 1, the flow of each processing will be described with respect to the processing (reference numeral S100#) for performing time synchronization and the processing (reference numeral S300) for estimating the position. Each process may be performed at a separate timing or may be performed in a linked manner.

First, a process (reference numeral S100#) of performing time synchronization is described.

The processing shown in steps S10 and S11 is the same as the processing shown in steps S10 and S11 in fig. 11, and therefore, the description thereof is omitted. The base station 20 generates time information based on the GPS information received from the server device 10, and notifies the terminal tag 30 of the generated time information. The terminal tag 30 adjusts the time used in the terminal tag 30 based on the time information received from the base station 20, and performs time synchronization (step S12).

Next, a process of estimating a position (reference numeral S300) will be described.

Base station 20 instructs terminal tag 30 of a transmission scheduled time at which terminal tag 30 transmits the sub-signal (step S30).

The terminal tag 30 generates a sub-signal at an arbitrary timing (step S32). The terminal tag 30 transmits the generated sub-signal to the base station 20 at the instructed timing (step S33).

When receiving the sub-signal from the terminal tag 30, the base station 20 stores the reception time when the sub-signal was received (step S34). The base station 20 calculates a signal arrival time using the transmission scheduled time indicated in step S30 and the reception time stored in step S34 (step S35).

The processing shown in step S36 is the same as step S26 of fig. 11.

Fig. 14 is a sequence diagram showing a flow of processing performed by the position estimation system 1 according to the modification of the first embodiment. Here, as the processing performed by the position estimation system 1, the flow of the processing will be described with respect to the processing (reference numeral S400) for estimating the position. The processing for performing time synchronization (reference numeral S100#) is the same as the processing shown in fig. 13 (reference numeral S100#), and therefore, the description thereof is omitted. Each process may be performed at a separate timing or may be performed in a linked manner.

The base station 20 notifies the terminal tag 30 of the transmission instruction signal (step S40).

The terminal tag 30 generates a sub-signal as a response to the transmission instruction signal (step S42). Here, the terminal tag 30 generates a sub-signal including information indicating the transmission time. The terminal tag 30 transmits the sub-signal at the transmission timing indicated by the sub-signal (step S43).

The processing shown in steps S44 to S46 is the same as steps S34 to S36 in fig. 13.

In the above description, the case where the base station 20 notifies the terminal tag 30 of a signal (time information) for synchronizing time and the base station 20 and the terminal tag 30 are time-synchronized has been described as an example, but the present invention is not limited to this. In the present modification, the base station 20 and the terminal tag 30 may be time-synchronized with each other by any method. For example, the time synchronization may be performed by adding a sensor for receiving a radio wave of a radio wave clock to each of the base station 20 and the terminal tag 30.

As described above in the modification 1 of the first embodiment, the position estimation system 1 may include the time synchronization unit 26 and the time synchronization unit 36 for synchronizing the time of the terminal tag 30 with the time of the base station 20, and the time synchronization unit 26 and the time synchronization unit 36 may synchronize the time of the terminal tag 30 with the time of the base station 20.

The communication control unit may include the terminal communication control unit 32 and the storage control unit 23. The terminal communication control unit 32 transmits the sub-signal from the terminal tag 30 to the base station 20 at a predetermined transmission timing (an example of "predetermined first timing") instructed from the base station 20. The storage control unit 23 stores the reception time of the sub-signal from the terminal tag 30 in the storage unit 28 via the base station 20.

The signal arrival time calculation unit 24 (an example of the "measurement unit") may calculate the signal arrival time using the scheduled transmission time and the reception time stored in the storage unit 28.

As described above, in the position estimation system 1 according to modification 1 of the first embodiment, the terminal tag 30 transmits the sub-signal to the base station 20 at the predetermined first time. That is, the time from the scheduled transmission time (first time) to the reception time does not include the time required for signal processing such as sub-signal generation. Therefore, the signal arrival time calculation section 24 can easily calculate the signal arrival time.

As described in modification 1 of the first embodiment, the position estimation system 1 may further include a time synchronization unit 26 and a time synchronization unit 36 for synchronizing the terminal tag 30 with the time of the base station 20. The time synchronizer 26 and the time synchronizer 36 synchronize the time of the terminal tag 30 with the time of the base station 20.

The communication control unit may include the terminal communication control unit 32 and the storage control unit 23. The terminal communication control unit 32 transmits a sub-signal including information indicating the transmission time (an example of the "second time") from the terminal tag 30 to the base station 20. The storage control unit 23 stores the reception time of the sub-signal from the terminal tag 30 in the storage unit 28 via the base station 20.

The signal arrival time calculation unit 24 (an example of the "measurement unit") may calculate the signal arrival time using the transmission time indicated by the sub-signal and the reception time stored in the storage unit 28.

As described above, in the position estimation system 1 according to the modification 1 of the first embodiment, the sub-signal includes the second time as the transmission time from the terminal tag 30 to the base station 20. That is, the time from the transmission time (second time) to the reception time does not include the time required for signal processing for generating the sub-signal and the like. Thus, the same effects as those described above are obtained. In addition, the position of the terminal tag 30 can be estimated at any timing when the terminal tag 30 notifies the base station 20 of the signal.

(modification 2 of the first embodiment)

Modification 2 of the first embodiment will be described. The present modification differs from the first embodiment in that the position estimation system 1 estimates the position of the terminal tag 30 using both the signal arrival time and the received radio wave intensity.

In the present modification, each base station 20 includes a functional unit (referred to as a received radio wave intensity measurement unit) for measuring the intensity of a received radio wave. The received radio wave intensity measurement unit measures the received radio wave intensity of the signal notified from the terminal tag 30. The received radio wave intensity measuring unit measures the received radio wave intensity, for example, based on the magnitude of the amplitude of the radio wave received by the receiving antenna of the base station 20. The received radio wave intensity measuring unit transmits the measured received radio wave intensity to the server device 10.

The position estimating unit 13 of the server device 10 estimates the distance from the base station 20 to the terminal tag 30 using the received radio wave intensity obtained from the received radio wave intensity measuring unit. The position estimating unit 13 refers to a table or the like stored in advance, for example, based on the acquired intensity of the received radio wave, and estimates the distance to the terminal tag 30. The table here is information indicating the correspondence between the received radio wave intensity and the distance.

The position estimating unit 13 calculates the distance from each base station 20 to the terminal tag 30 using the received radio wave intensity acquired from each base station 20. The position estimating unit 13 estimates the position of the terminal tag 30 based on the calculated distance from each base station 20 to the terminal tag 30.

The position estimating unit 13 determines the position of the terminal tag 30 using the position of the terminal tag 30 estimated based on the signal arrival time (hereinafter referred to as a first estimated position) and the position of the terminal tag 30 estimated based on the received radio wave intensity (hereinafter referred to as a second estimated position). The position estimating unit 13 sets, for example, a representative value of the first estimated position and the second estimated position as the position of the terminal tag 30. The representative value is a value calculated using the first estimated position and the second estimated position, and is, for example, a simple addition average value, a weighted average value, a maximum value, a minimum value, or the like.

As described above, the received radio wave intensity measuring unit (an example of the "measuring unit") measures the radio wave intensity of the signal received by the base station 20, and the position estimating unit 13 may estimate the position of the terminal tag 30 (terminal device) based on the signal arrival time and the radio wave intensity measured by the measuring unit.

Thus, in modification 2 of the position estimation system 1, the position estimation unit 13 estimates the position of the terminal tag 30 using both the signal arrival time and the received radio wave intensity. Therefore, in modification 2 of the position estimation system 1, the position of the terminal tag 30 can be estimated with high accuracy by using the received radio wave intensity together with the signal arrival time alone, as compared with the case where only the signal arrival time is used.

As a modification, the position estimation system 1 may include an estimated position verification unit in the server device 10 (or the base station 20) communicably connected to the base station 20.

The estimated position checking section checks the accuracy of the position estimation of the terminal tag 30 (the position of the terminal tag 30 estimated by the position estimating section 13). For example, the estimated position verification unit holds information indicating the estimated position of the nearest terminal tag 30 (hereinafter referred to as estimated position information), information relating to the mobile object (vehicle, freight train, motorcycle, or the like) on which the terminal tag 30 is mounted (hereinafter referred to as mobile object information), and estimated arrival distance information for each mobile object.

The estimated arrival distance information is information indicating a distance estimated to be reached by the mobile object at a predetermined time. The estimated arrival distance information is calculated based on, for example, the average speed of the moving object, the latest estimated position information, and the elapsed time. The elapsed time is a time difference between the time when the closest estimated position information is acquired and the time when the estimated distance is acquired. The estimated arrival distance information corresponds to the radius of a circular area indicating the moving range of the moving object and the terminal tag 30 mounted on the moving object.

When calculating the latest estimated position information of the terminal tag 30, the estimated position checking unit checks the accuracy of the position estimation based on the estimated arrival distance information and the latest estimated position information.

When the difference between the movement distance calculated based on the estimated latest position of the terminal tag 30 and the distance based on the estimated arrival distance information is larger than a predetermined threshold value, the estimated position verification unit determines that the possibility of erroneous estimation is high, that is, the position estimation by the position estimation unit 13 is unreliable and the possibility of error is high. On the other hand, when the difference between the movement distance of the terminal tag 30 and the distance based on the estimated arrival distance information is smaller than the predetermined threshold value, the estimated position verification unit determines that the estimation is not an error, that is, the position estimation by the position estimation unit 13 is reliable.

The estimated position checking unit may estimate the position again, for example, when it is determined that the position estimation by the position estimating unit 13 is erroneous. Further, when it is determined that the position estimation by the position estimation unit 13 is erroneous, the estimated position verification unit may repeat the position estimation until the accuracy of the position estimation reaches a predetermined reference, for example.

When the position estimation is performed again, the server apparatus 10 (or the base station 20) may transmit an instruction to the terminal tag 30 immediately after determining that the position estimation has an error, or may transmit an instruction after a predetermined time has elapsed. In this case, it is considered that the terminal tag 30 moves within a predetermined time. Therefore, the server apparatus 10 (or the base station 20) may change the communication environment with the terminal tag 30 by sending the transmission instruction again after a predetermined time has elapsed, thereby increasing the probability of performing normal communication.

(second embodiment)

A second embodiment will be explained. The present embodiment is different from the first embodiment described above in that it is considered that communication between the base station 20 and the terminal tag 30 is performed via a relay.

Fig. 15 is a diagram showing an example of the configuration of the position estimation system 1 according to the second embodiment. The position estimation system 1 includes a relay 40. The repeater 40 relays communication between the base station 20 and the terminal tag 30. The repeater 40 is disposed between the base station 20 and the terminal tag 30, for example. The repeater 40 receives a signal transmitted from the base station 20 to the terminal tag 30 and transmits the received signal to the terminal tag 30. The repeater 40 receives the signal transmitted from the terminal tag 30 to the base station 20 and transmits the received signal to the base station 20.

Fig. 16 is a block diagram showing an example of the configuration of the relay according to the second embodiment. The relay 40 includes, for example, a relay communication unit 41, a relay storage unit 42, and a relay control unit 43. The repeater communication unit 41 communicates with the base station 20 and the terminal tag 30. The relay storage unit 42 is configured by a storage medium, for example, an HDD, a flash memory, an EEPROM, a RAM, a ROM, or any combination of these storage media. The repeater storage unit stores programs for executing various processes of the repeater and temporary data used when performing the various processes. The relay storage unit 42 stores the first relay information 420 and the second relay information 421.

Fig. 17 is a diagram showing an example of the configuration of the first relay information according to the second embodiment. As shown in fig. 17, the first relay information 420 includes items such as a relay ID, a signal type, a relay flag, and a relay transmission time. The repeater ID is identification information that uniquely identifies a repeater that has repeated a transmission instruction signal. The relay flag is information indicating whether or not the transmission instruction signal is transmitted (relayed) by the relay. For example, if the relay flag is "1", it is information indicating that the transmission instruction signal has been relayed, and if the relay flag is "0 (zero)", it is information indicating that the transmission instruction signal has not been relayed. The relay transmission time is information indicating the time at which the relay transmits the transmission instruction signal to the terminal tag 30.

Fig. 18 is a diagram showing an example of the configuration of the second relay information according to the second embodiment. The second relay information 421 includes items such as a relay ID, a signal type, a relay flag, and a relay reception time. The relay ID and the relay flag are the same as those in the first relay information. The repeater reception time is information indicating the time at which the sub-signal is received by the repeater.

Returning to fig. 16, the relay controller 43 controls the relay 40. The process performed by the relay control unit 43 is realized by causing the relay 40 to execute a program by a CPU provided as hardware.

The relay controller 43 receives the transmission instruction signal transmitted from the base station 20 via the relay communication unit. The repeater control unit 43 adds the first relay information 420 to the received transmission instruction signal. For example, the relay controller 43 adds the first relay information 420 to the data section DA in the format of the signal SG shown in fig. 10. The relay controller 43 transmits the transmission instruction signal to which the first relay information 420 is added to the terminal tag 30.

The terminal tag 30 receives the transmission instruction signal to which the first relay information 420 is added. In this case, the terminal tag 30 adds the first relay information 420 to the sub-signal that is a response to the transmission instruction signal. The terminal tag 30 transmits the sub-signal to which the first relay information is added to the base station 20.

The repeater control section 43 receives the sub-signal transmitted by the terminal tag 30 via the repeater communication section 41. The relay controller 43 generates the second relay information 421, and stores the time when the sub-signal is received in the relay storage 42 as the relay reception time of the second relay information 421.

The repeater control unit 43 adds the second relay information 421 to the received sub-signal. The relay controller 43 acquires the second relay information 421, for example, with reference to the relay storage unit 42. The relay control unit 43 adds second relay information 421 to the data unit DA in the format of the signal SG shown in fig. 10, for example. The relay device 40 transmits the sub-signal to which the second relay information 421 is added to the base station 20.

The base station 20 receives the sub-signals. The base station 20 determines whether or not relay information (at least either the first relay information 420 or the second relay information 421) is added to the received sub-signal. When relay information is added to the sub-signal, the base station 20 does not calculate the round trip processing time of the signal using the transmission time information 280 and the reception time information 281.

When relay information is added to the sub-signal, the notification indicates that at least one of the transmission instruction signal and the sub-signal is notified via the relay. In this case, at least one of the transmission instruction signal and the sub-signal is transmitted via the repeater. Therefore, the base station 20 does not calculate the round trip processing time of the signal using the transmission time information 280 and the reception time information 281 on the premise that the transmission instruction signal or the sub-signal is directly transmitted.

When relay information is added to the sub-signal, the base station 20 calculates a signal round-trip processing time based on the added relay information. In this case, the relay information may take the following details.

(1) Includes a first relay message 420 and a second relay message 421.

(2) The first relay information 420 and the second relay information 421 are included in different numbers.

In the case of (1), it is indicated in the relay information that the transmission instruction signal is relayed by one relay and the sub-signal is relayed by one relay. In this case, the base station 20 determines whether or not the relay that has relayed the transmission instruction signal (hereinafter, referred to as a first transmission signal relay) and the relay that has relayed the sub-signal (hereinafter, referred to as a first reception signal relay) are the same relay. When the relay ID included in the first relay information 420 matches the relay ID included in the second relay information 421, the base station 20 determines that the first transmission signal relay and the first reception signal relay are the same relay. When the first transmission signal repeater and the first reception signal repeater are the same repeater, the base station 20 calculates a time required for signal transmission between the repeater and the terminal tag 30 as a signal round trip processing time. The base station 20 calculates the signal round trip processing time using the relay transmission time indicated by the first relay information 420 as the transmission time information 280 and the relay reception time indicated by the second relay information 421 as the reception time information 281, in the same manner as in the first embodiment.

In the case of (2), it is indicated in the relay information that the transmission instruction signal is relayed by one or more relays, and the sub-signal is relayed by one or more relays.

In this case, the base station 20 specifies a relay (hereinafter, referred to as a second transmission signal relay) that has directly transmitted the transmission instruction signal to the terminal tag 30. When one piece of first relay information is included in the sub-signal, the base station 20 sets a relay corresponding to the relay ID indicated by the first relay information as a second transmission signal relay. When the plurality of first relay information are included in the sub-signal, the base station 20 extracts the first relay information whose relay transmission time is the latest time among the plurality of first relay information. The base station 20 sets the relay corresponding to the relay ID indicated by the extracted first relay information as the second transmission signal relay.

The base station 20 determines a repeater (hereinafter, referred to as a second received signal repeater) that has directly received the sub signal from the terminal tag 30. When one piece of second relay information is included in the sub-signal, the base station 20 sets the relay corresponding to the relay ID indicated by the second relay information as the second received signal relay. When the plurality of second relay information are included in the sub-signal, the base station 20 extracts the second relay information whose relay reception time is the earliest time among the plurality of second relay information. The base station 20 sets the relay corresponding to the relay ID indicated by the extracted second relay information as the second received signal relay.

The base station 20 determines whether the second transmission signal repeater and the second reception signal repeater are the same repeater. When the relay ID corresponding to the second transmission signal relay matches the relay ID corresponding to the second reception signal relay, the base station 20 determines that the second transmission signal relay and the second reception signal relay are the same relay. When the second transmission signal repeater and the second reception signal repeater are the same repeater, the base station 20 calculates a time required for signal transmission between the repeater and the terminal tag 30 as a round trip processing time. The base station 20 calculates the round trip signal processing time using the relay transmission time indicated by the first relay information 420 as the transmission time information 280 and the relay reception time indicated by the second relay information 421 as the reception time information 281, in the same manner as in the first embodiment. Here, the first relay information 420 is first relay information associated with the second transmission signal repeater. The second relay information here is second relay information corresponding to the second received signal repeater.

In the case of (1), when the first transmission signal repeater and the first reception signal repeater are not the same repeater, the calculation of the signal round trip processing time is not performed. In the case of (2), when the second transmission signal repeater and the second reception signal repeater are not the same repeater, the calculation of the round trip processing time of the signal is not performed. This is because the signal transmission path for transmitting the instruction signal is different from that for its sub-signals.

When calculating the signal round-trip processing time, the base station 20 calculates a signal arrival time based on the signal round-trip processing time. When notifying the server apparatus 10 of the calculated signal arrival time, the base station 20 collectively notifies the server apparatus 10 of information indicating which relay 40 has passed through, for example, the relay ID of the relay 40 that has relayed the signal.

Fig. 19 is a sequence diagram showing a flow of processing performed by the position estimation system 1 according to the second embodiment.

The base station 20 notifies the transmission instruction signal (step S50). The base station 20 stores the transmission time at which the transmission instruction signal was transmitted (step S51).

Upon receiving the transmission instruction signal from the base station 20, the relay unit 40 adds the first relay information 420 to the received transmission instruction signal (step S52). The relay 40 transmits the transmission instruction signal to which the first relay information 420 is added to the terminal tag 30 (step S53).

Upon receiving the transmission instruction signal, the terminal tag 30 generates a sub-signal in response thereto (step S54). In this case, the terminal tag 30 attaches the first relay information 420 attached to the transmission instruction signal to the sub signal. The terminal tag 30 transmits the generated sub-signal to the base station 20 (step S55).

When receiving the sub-signal from the terminal tag 30, the repeater 40 adds the second relay information 421 to the received sub-signal (step S56). The repeater 40 transmits the sub-signal to the base station 20 (step S57). In this case, the first relay information 420 and the second relay information 421 are added to the sub signal transmitted from the relay 40 to the base station 20.

When receiving the sub-signal from the relay device 40, the base station 20 stores the reception time when the sub-signal is received (step S58). The base station 20 calculates a signal arrival time (step S59). The base station 20 calculates the signal arrival time using the relay transmission time added to the first relay information 420 and the relay reception time added to the second relay information 421. The base station 20 transmits the calculated signal arrival time to the server device 10.

As described above, the position estimation system 1 according to the second embodiment further includes the relay 40. The repeater 40 relays communication between the base station 20 and the terminal tag 30. The relay device 40 includes a relay device communication unit 41 and a relay device control unit 43. The repeater communication unit 41 communicates with the base station 20 and the terminal tag 30. Upon receiving the transmission instruction signal, the relay controller 43 transmits a signal (first signal) obtained by adding the first relay information 420 to the received transmission instruction signal, to the terminal tag 30. The first relay information 420 is information including a relay transmission time indicating a time at which the transmission instruction signal is transmitted from the relay 40. When the transmission instruction signal includes the first relay information 420, the terminal tag 30 transmits the sub-signal to which the first relay information 420 is added to the base station 20. When receiving the sub-signal, the relay controller 43 stores relay reception time indicating the time at which the sub-signal was received in the relay storage 42. The relay controller 43 transmits a signal (second signal) obtained by adding the second relay information 421 to the sub-signal to the base station 20. The second relay information 421 is information including a relay reception time indicating a time at which the relay 40 receives the sub signal. When receiving the sub-signal (second signal), the base station 20 determines whether or not the first relay information 420 and the second relay information 421 are added to the received sub-signal (second signal). When the first relay information 420 and the second relay information 421 are added to the sub-signal (second signal), the base station 20 calculates a time required for the terminal tag 30 and the relay device 40 to make a signal round-trip using the relay device transmission time indicated by the first relay information 420 and the relay device reception time indicated by the second relay information 421, as a signal round-trip processing time.

Thus, in the position estimation system 1 according to the second embodiment, when a signal (transmission instruction signal and sub-signal) is relayed, relay information is added. Therefore, it is possible to determine whether or not the signal is relayed by the relay 40, and to change the method of calculating the round trip processing time of the signal according to whether or not the signal is relayed by the relay 40. Therefore, even when the repeater 40 is relayed, the signal round-trip processing time can be calculated with high accuracy.

(modification of the second embodiment)

A modified example of the second embodiment will be described. The present modification differs from the second embodiment described above in that the server device 10 includes a determination unit. The determination unit determines whether or not the signal arrival time calculated while passing through the repeater 40 is used for estimating the position of the terminal tag 30.

The base station 20 calculates the signal arrival time by the signal arrival time calculation unit 24, and notifies the server device 10 of the calculated signal arrival time. In this case, the base station 20 adds route information to the information indicating the arrival time of the signal. The route information is information indicating a transmission path (route) of a signal corresponding to the signal arrival time. The signal corresponding to the signal arrival time is a transmission instruction signal and a sub-signal (hereinafter, referred to as a sub-signal or the like) that is a response thereto. The route information is information indicating that the sub-signal or the like is directly transmitted or passes through the repeater 40. When the relay information is not included in the sub-signal, the base station 20 sets information indicating that the relay information is directly transmitted to the route information. When the relay information is included in the sub-signal, the base station 20 sets information indicating that the relay 40 has been passed through in the route information. When the information indicating the relay 40 has passed through is set in the route information, the base station 20 notifies the server apparatus 10 of information indicating which relay 40 has passed through, for example, the relay ID of the relay 40 that has relayed the signal.

The determination unit of the server device 10 determines whether or not the signal arrival time is used as information for estimating the position of the terminal tag 30 based on the route information. For example, when the route information indicates that the terminal tag is directly transmitted, the determination unit of the server device 10 determines that the signal arrival time is used as the information for estimating the position of the terminal tag 30. On the other hand, when the route information indicates that the route information is transmitted via the relay 40, the determination unit of the server device 10 determines not to use the signal arrival time as the information for estimating the position of the terminal tag 30.

The determination unit of the server device 10 determines whether or not the signal transmitted through the relay 40 is used for estimating the position, for example, based on the accuracy required for estimating the position of the terminal tag 30. When the signal passes through the repeater 40, a time lag occurs due to a processing time required for signal processing or the like in the repeater 40, and an error included in a signal arrival time may increase. In this case, when the signal transmitted through the repeater 40 is used to estimate the position of the terminal tag 30, the estimation accuracy may be reduced. Therefore, the determination unit of the server device 10 determines whether or not to use the signal arrival time as information for estimating the position of the terminal tag 30 based on the route information. This enables selection of a signal for position estimation according to whether or not the relay 40 is passed. Therefore, when the server device 10 estimates the position of the terminal tag 30, the accuracy of the estimation can be controlled.

As described above, in the position estimation system 1 according to the modification of the second embodiment, the server device 10 further includes the determination unit. The base station 20 transmits information indicating the arrival time of the signal to which the route information is added to the server apparatus 10. The route information is information indicating a transmission path of the sub-signal corresponding to the signal arrival time. The route information is, for example, information indicating whether the route information is directly transferred between the base station 20 and the terminal tag 30 without passing through the repeater 40 or is transferred through the repeater 40. The determination unit of the server device 10 determines whether or not to use the signal arrival time as information for estimating the position of the terminal tag 30 based on the route information. Thus, in the position estimation system 1 according to the modification of the second embodiment, the signal arrival time can be selected with the required accuracy. For example, in a case where it is desired to improve the accuracy of the position estimation, only the signal directly transferred from the base station 20 to the terminal tag 30 without via the repeater 40 may be used. On the other hand, in the case where accuracy is not so required, it can be used separately in such a manner that the position is estimated using the signal via the repeater 40.

In the first and second embodiments described above, the case where the base station 20 calculates the signal arrival time by the signal arrival time calculation unit 24 is exemplified and explained. However, the present invention is not limited thereto. The server device 10 may calculate the signal arrival time. In this case, each base station 20 transmits information used for calculating the signal arrival time, for example, the time when the transmission instruction signal was transmitted, the time when the sub-signal was received, and the like, to the server apparatus 10. The server device 10 includes a functional unit that performs processing equivalent to the signal arrival time calculation unit 24. The functional section calculates a signal arrival time based on information received from each base station 20. The server apparatus 10 calculates the signal arrival time, and can reduce the processing load in the base station 20 as compared with the case where the signal arrival time is calculated in each base station 20. Thus, higher performance is no longer required for the base station 20, and therefore, the equipment of the base station 20 can be simplified.

A program for realizing all or a part of the functions of the position estimation system 1 in at least one of the above-described embodiments may be recorded in a computer-readable recording medium, and the program recorded in the recording medium may be read and executed by a computer system to perform processing. The "computer system" referred to herein includes hardware such as an OS and peripheral devices.

In addition, the "computer system" also includes a WWW system having a homepage providing environment (or a display environment). The "computer-readable recording medium" refers to a storage device such as a flexible disk, a magneto-optical disk, a removable medium such as a ROM or a CD-ROM, or a hard disk incorporated in a computer system. The "computer-readable recording medium" also includes a medium that holds a program for a certain period of time, such as a volatile memory (RAM) in a computer system serving as a client or a server when the program is transmitted via a network such as the internet or a communication line such as a telephone line.

The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the "transmission medium" to which the program is transmitted refers to a medium having a function of transmitting information, such as a network (communication network) such as the internet or a communication line (communication line) such as a telephone line. The program may be a program for realizing a part of the above-described functions. Further, the above-described functions may be realized by a combination with a program already recorded in a computer system, so-called differential file (differential program).

While the embodiments of the present invention have been described in detail with reference to the drawings, the specific configurations are not limited to the embodiments, and the present invention also includes designs and the like that do not depart from the scope of the present invention.

Description of the reference numerals

1 … position inference system (communication system)

10 … server device

11 … communication part

12 … signal arrival time acquiring unit

13 … position estimation unit

14 … GPS information acquisition unit

15 … time synchronization unit

17 … control unit

18 … storage part

20 … base station

21 … communication part

22 … base station communication control part (communication control part)

23 … storage control part

24 … Signal arrival time calculating part (measuring part)

25 … time information acquisition unit

26 … time synchronization unit

27 … control part

28 … storage part

280 … sending time information

281 … receiving time information

282 … processing time information

30 … terminal label (terminal device)

31 … communication part

32 … terminal communication control unit (communication control unit)

33 … sensor information acquisition unit

34 … sending signal generating part

35 … time information acquisition unit

36 … time synchronization unit

37 … control part

38 … storage part

Claims (13)

1. A communication system comprising a terminal device and a base station connected to the terminal device so as to be capable of two-way communication, and estimating a position of the terminal device,

the communication system includes:

a communication control unit that controls communication between the base station and the terminal device;

a measurement unit configured to measure a signal arrival time required for a signal transmitted from the base station to reach the terminal device; and

and a position estimation unit configured to estimate a position of the terminal device based on the signal arrival time measured by the measurement unit.

2. The communication system as set forth in claim 1,

the communication control unit includes:

a base station communication control unit configured to transmit a transmission instruction signal from the base station to the terminal apparatus;

a terminal communication control unit that transmits a sub-signal in response to the transmission instruction signal from the terminal device that received the transmission instruction signal to the base station; and

a storage control unit that causes a storage unit to store a transmission time at which the transmission instruction signal is transmitted from the base station to the terminal device, and a reception time at which the sub-signal from the terminal device is received by the base station,

the measurement unit calculates the signal arrival time using the transmission time and the reception time stored in the storage unit.

3. The communication system as set forth in claim 1,

further comprising a time synchronization unit for synchronizing the terminal device with the time of the base station,

the communication control unit includes:

a terminal communication control unit that transmits a sub-signal from the terminal device to the base station at a predetermined first time; and

a storage control unit for causing a storage unit to store reception time at which the sub-signal from the terminal device is received by the base station,

the measurement unit calculates the signal arrival time using the first time and the reception time stored in the storage unit.

4. The communication system as set forth in claim 1,

further comprising a time synchronization unit for synchronizing the terminal device with the time of the base station,

the communication control unit includes:

a terminal communication control unit that causes the base station to transmit a sub-signal transmitted from the terminal device, the sub-signal including information indicating a second time that is a time at which the sub-signal is transmitted from the terminal device; and

a storage control unit for causing a storage unit to store reception time at which the sub-signal from the terminal device is received by the base station,

the measurement unit calculates the signal arrival time using the information indicating the second time included in the sub-signal and the reception time stored in the storage unit.

5. The communication system according to any one of claims 1 to 4,

the position estimation unit estimates the position of the terminal device based on the signal arrival time of each of at least three or more base stations including the base station.

6. The communication system according to any one of claims 1 to 5,

the measuring unit measures the radio wave intensity of the signal received by the base station,

the position estimating unit estimates the position of the terminal device based on the signal arrival time and the radio wave intensity measured by the measuring unit.

7. The communication system according to any one of claims 1 to 6,

further comprising a server device communicatively connected to the base station,

the server device includes the position estimation unit.

8. The communication system according to any one of claims 1 to 7,

the communication control unit includes a terminal communication control unit that determines whether or not transmission of a signal transmitted from the terminal device to the base station has failed, performs control to retransmit the signal when the transmission of the signal has failed, and stores retransmission number information indicating the number of times of retransmission of the signal,

the retransmitted signal includes information indicating the number of retransmissions.

9. The communication system according to claim 2, wherein,

further comprising a relay for relaying communication between the base station and the terminal device,

the relay device is provided with:

a repeater communication unit that receives the transmission instruction signal and the sub-signal; and

a relay controller that transmits a first signal obtained by adding first relay information to the transmission instruction signal received by the relay communication unit to the terminal device, and transmits a second signal obtained by adding second relay information to the sub-signal received by the relay communication unit to the base station,

the first relay information includes a relay transmission time indicating a time at which the relay transmits the first signal to the terminal device,

the second relay information includes a relay reception time indicating a time at which the sub-signal is received by the relay,

the terminal device, when receiving the transmission instruction signal and when adding the first relay information to the received transmission instruction signal, generates the sub-signal to which the first relay information is added as the sub-signal corresponding to the transmission instruction signal and transmits the generated sub-signal to the base station,

when the received second signal includes the first relay information and the second relay information, the measurement unit calculates, as the signal arrival time, a time required for a signal transmitted from the relay to reach the terminal device, using the relay transmission time indicated by the first relay information and the relay reception time indicated by the second relay information.

10. The communication system as set forth in claim 9,

further comprising a determination unit for determining whether or not to use the signal arrival time when estimating the position of the terminal device, based on route information of the signal arrival time measured by the measurement unit,

the route information is information indicating a transmission path of a signal corresponding to the signal arrival time.

11. A base station connected to a terminal device so as to be capable of bidirectional communication in a communication system for estimating the position of the terminal device,

the base station is provided with:

a base station communication control unit that controls communication with the terminal device; and

and a measuring unit configured to measure a signal arrival time required for a signal transmitted from the base station to reach the terminal device, based on a transmission time of a transmission instruction signal transmitted from the base station to the terminal device and a reception time of a sub-signal, which is a response of the transmission instruction signal received by the base station from the terminal device.

12. A measurement method for measuring a signal arrival time required for a signal transmitted from a base station to reach a terminal device in the base station connected to the terminal device so as to be capable of bidirectional communication in a communication system for estimating a position of the terminal device, the measurement method comprising:

controlling, by a base station communication control unit, communication with the terminal device;

the measurement unit measures the signal arrival time based on a transmission time of a transmission instruction signal transmitted from the base station to the terminal device and a reception time of a sub-signal that is a response of the transmission instruction signal received by the base station from the terminal device.

13. A program for measuring a signal arrival time required for a signal transmitted from a base station to reach a terminal device in a base station connected to the terminal device so as to be capable of bidirectional communication in a communication system for estimating a position of the terminal device,

the program is for executing:

a base station communication control unit that controls communication with the terminal device; and

and a measurement unit configured to measure the signal arrival time based on a transmission time of a transmission instruction signal transmitted from the base station to the terminal device and a reception time of a sub-signal that is a response of the transmission instruction signal received by the base station from the terminal device.

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