JP7375935B2 - Wireless terminal position estimation method and position estimation system - Google Patents

Description

This disclosure relates to a position estimation method and a position estimation system for a wireless terminal, and particularly relates to a position estimation method and a position estimation system suitable for estimating the position of a moving wireless terminal.

Non-Patent Document 1 discloses a method for estimating the position of a wireless terminal station using a wireless LAN system. Specifically, this document describes a method that uses the radio wave arrival time (ToA: Time of Arrival) from when a transmitting base station sends a request until a response from a receiving base station returns to the transmitting base station. Disclosed (see in particular Annex P).

Furthermore, Non-Patent Document 2 discloses a technology for estimating the position of a wireless terminal, which is intended for use in Maas (Mobility as a Service) and large-scale events. Specifically, Non-Patent Document 2 discloses a system in which a plurality of distributed antennas are connected to a wireless LAN base station via a switch. In this system, management frames can be transmitted from distributed antennas to wireless terminals belonging to the area covered by a wireless LAN base station. The wireless terminal that received the management frame returns a response confirmation signal. The wireless LAN base station measures the time from the transmission of the management frame until the reception of the response confirmation signal as ToA for each distributed antenna, and estimates the position of the wireless terminal based on the multiple measured ToAs. .

IEEE Std. 802.11-2016 Two-dimensional position estimation of wireless LAN terminals using distributed antenna access points, FIT2019 (18th Information Science and Technology Forum), Information Processing Society of Japan and Institute of Electronics, Information and Communication Engineers, 2019, Volume 4, p. 53-58

When signals are transmitted and received between a wireless base station and a wireless terminal for ToA measurement, the communication band is inevitably compressed by the amount of transmission and reception. On the other hand, if it is assumed that a wireless terminal moves, it will be necessary to measure ToA frequently in order to capture its position. Therefore, when using the conventional position estimation method described above in an environment such as MaaS or large-scale events where it is desired to target a large number of moving wireless terminals for position estimation, compression of the communication band becomes a problem that cannot be ignored.

This disclosure was made in order to solve the above-mentioned problems, and provides a method for estimating the position of a wireless terminal that can accurately capture the position of a wireless terminal that is assumed to be moving while suppressing pressure on the communication band. The primary purpose is to provide the following.
A second objective of this disclosure is to provide a position estimation system that achieves the same functions as described above.

In order to achieve the above object, a first aspect of the present disclosure is a method for estimating the position of a wireless terminal, in which each of a plurality of antennas arranged at different positions and a wireless terminal whose position is to be estimated are a step of transmitting and receiving measurement signals between the antennas; a step of estimating the position of the wireless terminal based on the plurality of measurement signals received by the plurality of antennas; and information acquiring movement information of the wireless terminal. an acquisition step, a step of estimating the moving speed of the wireless terminal based on the movement information, and a frequency setting step of setting the frequency of the signal exchange step with respect to the wireless terminal so that the frequency increases as the moving speed increases. It is desirable to include the following.

Further, a second aspect of the present disclosure is a position estimation system for a wireless terminal, which includes a plurality of antennas arranged at different positions and transmitting/receiving signals to/from the wireless terminal, and a plurality of antennas. a position estimation server that transmits and receives signals, and the position estimation server performs signal transmission and reception processing that transmits and receives measurement signals between each of the plurality of antennas and a wireless terminal that is a target of position estimation; a process of estimating the position of the wireless terminal based on the plurality of measurement signals received by a plurality of antennas; an information acquisition process of acquiring movement information of the wireless terminal; and a process of acquiring movement information of the wireless terminal based on the movement information. It is desirable to perform a process of estimating a moving speed and a frequency setting process of setting the frequency of the signal transfer process to the wireless terminal so that the frequency increases as the moving speed increases.

According to the first and second aspects, the position of the wireless terminal can be estimated based on the plurality of measurement signals exchanged between the plurality of antennas and the wireless terminal. For wireless terminals that move quickly, measurement signals can be obtained frequently, making it possible to capture their positions with high precision. On the other hand, for wireless terminals that move slowly, the frequency of generation of measurement signals can be suppressed, so pressure on the communication band can be suppressed.

FIG. 2 is a diagram for explaining features of Embodiment 1 of the present disclosure. FIG. 1 is a block diagram for explaining the configuration of a position estimation system according to Embodiment 1 of the present disclosure. It is a flowchart which shows the procedure of the process which a position estimation server performs in Embodiment 1 of this indication. FIG. 2 is a block diagram for explaining the configuration of a position estimation system according to Embodiment 2 of the present disclosure. It is a flowchart which shows the procedure of the process which a position estimation server performs in Embodiment 2 of this indication.

Embodiment 1.
[Features of Embodiment 1]
FIG. 1 is a diagram for explaining features of a wireless terminal position estimation system 10 according to Embodiment 1 of the present disclosure. The position estimation system 10 of this embodiment includes a position estimation server 12, as shown in FIG. A plurality of wireless base stations 14 located at different positions are connected to the position estimation server 12. The wireless base stations 14 are each equipped with an antenna and can establish wireless communication with wireless terminals.

FIG. 1 shows that two wireless terminals 16 and 18 exist within the communication area of the wireless base station 14. The wireless base station 14 can transmit management frames to the wireless terminals 16 and 18, respectively. The wireless terminals 16 and 18 that have received the management frame send back response confirmation signals. The radio base station 14 measures the time from transmitting the management frame to receiving the response confirmation signal as ToA (Time on Arrival). In this embodiment, the management frame and response confirmation signal exchanged to measure ToA are referred to as "measurement signals."

ToA has a correlation with the distance between each radio base station 14 and a radio terminal that sends and receives measurement signals. Therefore, the position estimation server 12 can estimate the positions of the wireless terminals 16 and 18 using a well-known method based on the ToA measured by each of the plurality of wireless base stations 14.

Both wireless terminals 16 and 18 may move. In order to continue to accurately capture the positions of the wireless terminals 16 and 18 while they are moving, it is necessary to continue measuring ToA at a high frequency. However, as the ToA measurement frequency increases, the communication band that can be used by the wireless base station 14 is compressed. Moreover, this tendency becomes more pronounced as the number of wireless terminals belonging to the wireless base station 14 increases.

FIG. 1 illustrates a state in which wireless terminal 16 is moving at high speed, while wireless terminal 18 is substantially stationary. In this case, for the wireless terminal 18 that moves slowly, the accuracy of position acquisition can be maintained even if the ToA measurement frequency is lowered. By reducing the ToA measurement frequency in this way, it is possible to suppress pressure on the communication band that can be used by the wireless base station 14.

Therefore, in this embodiment, the frequency of ToA measurement for a wireless terminal is adjusted according to the moving speed of the wireless terminal. More specifically, the ToA measurement frequency was set to be high for wireless terminals that move at high speeds, and the ToA measurement frequency was set to be low for wireless terminals that move at low speeds. According to such a setting, even when a large number of wireless terminals belong to the wireless base station 14, it is possible to effectively suppress pressure on the communication band and continue to accurately capture the positions of the large number of wireless terminals. can.

[Configuration of Embodiment 1]
FIG. 2 is a block diagram for explaining the configuration of the position estimation server 12. The position estimation server 12 is composed of various types of hardware including a processor, memory, and interface, as well as software necessary to realize the functions described below. Each block shown in FIG. 2 can be configured by dedicated hardware or a combination of dedicated hardware and software. Alternatively, each block may be configured by implementing dedicated software on mutually common hardware.

As shown in FIG. 2, the position estimation server 12 includes a measurement signal generation section 20. The measurement signal generation unit 20 generates a measurement signal for ToA measurement, specifically, a management frame addressed to the MAC address of the wireless terminal to be measured. The measurement signal generated by the measurement signal generation section 20 is provided to the switching section 22.

The switching section 22 is connected to a plurality of radio base stations 14 and provides the measurement signal from the measurement signal generation section 20 to the plurality of radio base stations 14 by switching the connection destination. Further, the switching unit 22 transmits the measurement signals received by the plurality of wireless base stations 14 from the respective wireless terminals, specifically, a response confirmation signal to the management frame described above, to the response signal receiving unit 24.

The response signal receiving unit 24 receives the measurement signal transmitted from the switching unit 22 while distinguishing which wireless base station 14 has received the measurement signal. The above-mentioned timing ts at which the measurement signal generation section 20 transmitted the measurement signal and timing tr at which the response signal reception section 24 received the measurement signal are provided to the round trip time measurement section 26.

The round trip time measurement unit 26 measures the time from the transmission timing ts of the measurement signal to the reception timing tr as ToA. The ToA measured by the round trip time measuring section 26 is provided to the terminal position estimating section 28.

The terminal position estimating unit 28 estimates the position of the wireless terminal based on the plurality of ToAs measured for each wireless base station 14. The estimated position information is stored in the position history storage unit 30 along with the identification number and time of the wireless terminal, and is provided to the moving speed estimation unit 32.

When the moving speed estimating unit 32 receives the position information of the wireless terminal from the terminal position estimating unit 28, it reads out the history of the position of the wireless terminal from the position history storage unit 30. Then, the moving speed SPD of the wireless terminal is estimated based on the latest position, the history of read positions, and the difference in time when both were measured. The moving speed SPD is estimated for all wireless terminals communicating with the wireless base station 14. Hereinafter, the number of wireless terminals in communication is represented by n, and the moving speed of the i-th wireless terminal is represented by SPDi. The estimated moving speed SPDi (i=1 to n) is provided to the measurement frequency control section 34.

The position estimation server 12 includes a traffic monitoring section 36. The traffic monitoring unit 36 monitors the total amount of communication traffic of each of the plurality of wireless base stations 14 via the switching unit 22. The monitoring results are provided to the measurement total number control section 38.

The total number of measurements control unit 38 performs the following processing for each wireless base station 14.
1. Calculate the available bandwidth where ToA can be measured.
2. The total number Msum of ToA measurements that can be performed per unit time is calculated based on the free bandwidth.
The total number Msum of ToA measurements calculated by the above processing is provided to the measurement frequency control unit 34.

The measurement frequency control unit 34 adjusts the ToA measurement frequency for each wireless terminal based on its moving speed SPD. Specifically, the total number Msum of ToA measurements that can be performed by the wireless base station 14 is distributed to all wireless terminals i (i=1 to n) according to the moving speed SPD. The number of ToA measurements Mi allocated to the wireless terminal i is calculated, for example, using the following formula.
Mi=Msum×SPDi/ΣSPD...(1)
However, ΣSPD is the sum of the moving speeds SPD of all wireless terminals.

The number of ToA measurements Mi calculated by the measurement frequency control section 34 is supplied to the measurement signal generation section 20. The measurement signal generation unit 20 updates the transmission timing ts of the measurement signal to the wireless terminal i based on Mi.

[Flow of processing in Embodiment 1]
FIG. 3 is a flowchart for explaining the flow of processing executed by the position estimation server 12 in this embodiment.
In the routine shown in FIG. 3, first, the number i of the wireless terminal whose position is to be estimated is updated (step 100).

Next, it is determined whether the timing for measuring ToA for wireless terminal i has arrived (step 102). If it is determined that the measurement timing has not arrived, the process of step 100 is executed again.

In step 102, if it is determined that the measurement timing has arrived, a process of transmitting a measurement signal from one wireless base station 14 toward the wireless terminal i, and a measurement signal returned from the wireless terminal i. A process of receiving the received information via the wireless base station 14 is executed (step 104).

Next, it is determined whether transmission and reception of measurement signals has been completed for all wireless base stations 14 communicating with wireless terminal i (step 106). As a result, if it is determined that there is a radio base station 14 that has not yet completed signal exchange, the control target is switched to that radio base station and the process of step 104 is executed again.

If it is determined that the transmission and reception of measurement signals has been completed for all wireless base stations 14 communicating with wireless terminal i, next, for each wireless base station 14, the transmission timing ts and reception timing tr of the measurement signal are determined. Based on this, ToA is calculated (step 108).

Next, the position of wireless terminal i is estimated based on the plurality of calculated ToAs (step 110). The estimated position is stored in the position history storage unit 30 together with the identification number of the wireless terminal i and the measurement time of ToA.

Next, the location history of the wireless terminal i is read from the location history storage unit 30 (step 112). Specifically, the previously calculated position of wireless terminal i and the time at which the position was estimated are read.

Next, the difference between the latest position estimated this time and the position history read out in step 112 is calculated as the movement information of wireless terminal i. Furthermore, the moving speed SPDi of wireless terminal i is estimated based on the movement information and the difference in time when both are obtained (step 114). The moving speed SPDi is stored in a memory included in the position estimation server 12.

When the above processing is completed, next, the total number Msum of ToA measurements that can be performed per unit time is calculated for each radio base station 14 (step 116). The position estimation server 12 monitors the total amount of traffic being communicated with respect to all the wireless base stations 14 under its management by a process different from this routine. In this step, the amount obtained by subtracting the total sum from the communication capacity of the wireless base station 14 is calculated as the communication capacity. Furthermore, the above-mentioned total number Msum is calculated by dividing the communication margin by the communication amount required for one ToA measurement.

After the above process is completed, the ToA measurement frequency for wireless terminal i is set based on the moving speed SPDi and the total number Msum (step 118). Specifically, here, the number of ToA measurements Mi to be allocated to the wireless terminal i out of the total executable number Msum is calculated according to the above equation (1).

When the number of ToA measurements Mi is calculated through the above process, the next timing for measuring ToA for wireless terminal i is updated based on Mi (step 120). Thereafter, in step 102, it is determined whether the timing updated in step 120 has arrived.

According to the above process, among the n wireless terminals i (i=1 to n) communicating with the wireless base station 14, for a wireless terminal that is moving at high speed, ToA measurement can be repeated with high frequency. can. Therefore, according to the system of this embodiment, it is possible to continue to accurately capture the position of a wireless terminal that moves at high speed. Furthermore, among the communicating wireless terminals i (i=1 to n), the frequency of ToA measurement can be reduced for wireless terminals that are moving at low speed or are hardly moving. In this case, pressure on the communication band of the wireless base station 14 can be suppressed without deteriorating the acquisition accuracy of the wireless terminal. Therefore, according to the system of this embodiment, even in situations where there are a large number of wireless terminals whose location is to be estimated, such as during Maas or large-scale events, it is possible to secure a sufficient communication speed and to accurately estimate a large number of wireless terminals. The location of wireless terminals can be continuously captured.

[Modification of Embodiment 1]
By the way, in the first embodiment described above, the management frame transmitted by the wireless base station 14 and the response confirmation signal returned by the wireless terminal are used as measurement signals, and the position of the wireless terminal is estimated based on the ToA. However, the method of estimating the position of a wireless terminal is not limited to this. For example, the wireless base station 14 may measure the reception strength of a response confirmation signal emitted from the wireless terminal, and the position estimation server 12 may estimate the position of the wireless terminal based on the reception strength measured for each wireless base station 14. You can also use it as In this case, the response confirmation signal emitted by the wireless terminal becomes the "measurement signal." Alternatively, the position estimation server 12 may estimate the position of the wireless terminal using both ToA and reception strength.

Furthermore, in the first embodiment described above, it is assumed that each radio base station 14 has a configuration in which one or more antennas are provided at positions that are not spatially far apart. However, the configuration is not limited to this. For example, each radio base station may manage a plurality of distributed antennas located at widely separated locations.

Further, in the first embodiment described above, the position estimation server 12 directly detects the total amount of communication traffic of the wireless base station 14, but the detection method is not limited to this. . The total amount of traffic of the wireless base station 14 may be detected, for example, by the following method.
1. Traffic is detected for every wireless terminal communicating with the wireless base station 14.
2. The communication bit rate is detected for each wireless terminal.
3. The estimated communication time for each wireless terminal is calculated by dividing the traffic for each wireless terminal by the communication bit rate for each wireless terminal.
4. The sum of estimated communication times of all wireless terminals is calculated as a substitute value for the total amount of communication traffic of the wireless base station 14.
Note that the above communication bit rate used in this substitution method may be replaced with a value representing communication quality, such as an MCS (Modulation and Coding Scheme) index or a CQI (Channel Quality Indicator).

Furthermore, in the first embodiment described above, the total number Msum of ToA measurements that can be performed by the wireless base station 14 is proportionally distributed to each wireless terminal based on the moving speed SPD. However, the allocation method is not limited to this. For example, the moving speed SPD may be classified into a plurality of groups using one or more threshold values, and the number of times Mi of ToA measurements may be determined for each classification.

Embodiment 2.
Next, a second embodiment of the present disclosure will be described with reference to FIGS. 4 and 5. The position estimation system of this embodiment can be realized by replacing the position estimation server 12 with the position estimation server 40 shown in FIG. 4 in the hardware configuration shown in FIG.

FIG. 4 is a block diagram of the position estimation server 40 used in this embodiment. Incidentally, in FIG. 4, the same elements as those shown in FIG. 2 are given the same reference numerals, and the explanation thereof will be omitted or simplified.

The position estimation server 40 shown in FIG. 4 performs the following processing as in the first embodiment.
1. Estimation of position of wireless terminal 2. Estimation of moving speed SPD of wireless terminal 3. Set the ToA measurement frequency for each wireless terminal based on the moving speed SPD of each wireless terminal.

The position estimation server 40 of this embodiment executes the processes 1 and 3 above in the same way as the position estimation server 12 of the first embodiment. The position estimation server 40 of this embodiment is characterized in that the above-mentioned process 2 is executed using a method different from that of the first embodiment.

As shown in FIG. 4, the position estimation server 40 includes a sensor information receiving section 44. The sensor information receiving section 44 can acquire the output of a motion detection sensor built into the wireless terminal via the switching section 42 and the wireless base station 14. More specifically, in this embodiment, the position estimation server 40 requests the wireless terminal communicating with the wireless base station 14 to transmit the output of the motion detection sensor at each predetermined timing.

A wireless terminal has a built-in motion detection sensor, such as an acceleration sensor or a gyro sensor, that detects the movement of the wireless terminal. The wireless terminal that receives the above request transmits the output of the motion detection sensor to the wireless base station 14. The sensor information receiving unit 44 receives the output transmitted in this manner as sensor information.

The sensor information received by the sensor information receiving section 44 is provided to the moving speed estimating section 46. The moving speed estimation unit 46 calculates the moving speed SPD of the wireless terminal that has issued the output based on the output of the motion detection sensor. The moving speed SPD thus calculated is provided to the total number of measurements control section 38. Then, the total number of measurements control unit 38 calculates the total number of ToA measurements Msum wo for each wireless terminal based on the moving speed SPD, as in the first embodiment.

[Processing flow in Embodiment 2]
FIG. 5 is a flowchart for explaining the flow of processing executed by the position estimation server 40 in this embodiment. Note that in FIG. 5, steps that are the same as those shown in FIG.

In the routine shown in FIG. 5, when the process of step 110 is completed, sensor information of wireless terminal i is next acquired as movement information of wireless terminal i (step 122). Specifically, here, a request is issued to wireless terminal i to provide the output of the motion detection sensor. Sensor information emitted from the wireless terminal i is then taken into the position estimation server 40 via the wireless base station 14.

Next, the moving speed SPDi of wireless terminal i is estimated based on the acquired sensor information (step 124). In this embodiment, it is assumed that the output of a triaxial acceleration sensor and the output of a gyro sensor are provided as sensor information. In this step, the moving speed SPDi of wireless terminal i is calculated based on these outputs.

Thereafter, as in the case of Embodiment 1, the processes from step 116 onward are executed, so that a high ToA measurement frequency is set for a wireless terminal with a high moving speed, and a low ToA measurement frequency is set for a wireless terminal with a low moving speed. ToA measurement frequency is set. Therefore, similarly to the case of Embodiment 1, the system of this embodiment can realize highly accurate location acquisition for a large number of wireless terminals while effectively suppressing pressure on the communication band.

Incidentally, in the second embodiment described above, the output of the motion detection sensor is transmitted from the wireless terminal starting from the position estimation server 40 issuing a request, but the method is limited to this. isn't it. For example, the wireless terminal may be provided with a motion detection sensor output providing function, and the wireless terminal may determine the timing of providing the sensor information.

10 Position estimation system 12, 40 Position estimation server 14 Wireless base station 16, 18 Wireless terminal 20 Measurement signal generation unit 24 Response signal reception unit 26 Round trip time measurement unit 28 Terminal position estimation unit 30 Position history storage unit 32 Traveling speed estimation unit 34 Measurement frequency control unit 36 Traffic monitoring unit 38 Total number of measurements control unit

Claims (6)

a signal exchange step of transmitting and receiving measurement signals between each of the plurality of antennas arranged at different positions and a wireless terminal that is a target of position estimation;
a position estimation server estimating the position of the wireless terminal based on the plurality of measurement signals received by the plurality of antennas;
an information acquisition step in which the position estimation server acquires movement information of the wireless terminal;
the position estimation server estimating a moving speed of the wireless terminal based on the movement information;
a frequency setting step in which the position estimation server sets the frequency of the signal exchange step with respect to the wireless terminal so that the frequency increases as the moving speed increases;
The position estimation server calculates a communication margin of the wireless base station based on the communication capacity of the wireless base station that manages the antenna and the total traffic amount of the wireless base station;
The position estimation server calculates a total frequency of the signal exchange step that is permissible in the wireless base station based on the communication margin,
The frequency setting step is a wireless terminal position estimating method, wherein the frequency setting step is performed such that the total frequency is distributed to each of all wireless terminals belonging to the wireless base station according to their respective moving speeds. The information acquisition step includes:
storing the estimated location of the wireless terminal in a location history storage unit;
reading the location history of the wireless terminal from the location history storage unit;
generating a difference between the read history and the estimated position as the movement information;
The position estimation method according to claim 1, comprising: The information acquisition step includes:
acquiring from the wireless terminal the output of a motion detection sensor built into the wireless terminal;
generating the movement information based on the output;
The position estimation method according to claim 1 or 2, comprising: multiple antennas placed at different locations and transmitting and receiving signals to and from wireless terminals;
a position estimation server that sends and receives signals to and from the plurality of antennas,
The location estimation server is
signal exchange processing for transmitting and receiving measurement signals between each of the plurality of antennas and a wireless terminal that is a target of position estimation;
a process of estimating the position of the wireless terminal based on the plurality of measurement signals received by the plurality of antennas;
information acquisition processing for acquiring movement information of the wireless terminal;
a process of estimating a moving speed of the wireless terminal based on the movement information;
a frequency setting process of setting the frequency of the signal transfer process to the wireless terminal so that the frequency increases as the moving speed increases;
A process of calculating a communication margin of the wireless base station based on a communication capacity of the wireless base station that manages the antenna and a total traffic amount of the wireless base station;
and calculating a total frequency of the signal exchange processing that is permissible in the radio base station based on the communication margin,
In the wireless terminal position estimation system, the frequency setting process is executed such that the total frequency is distributed to each of all wireless terminals belonging to the wireless base station according to their respective moving speeds. The position estimation server includes a position history storage unit that stores the estimated position of the wireless terminal,
The information acquisition process includes:
a process of reading the location history of the wireless terminal from the location history storage unit;
a process of generating a difference between the read history and the estimated position as the movement information;
The position estimation system according to claim 4, comprising: The information acquisition process includes:
a process of acquiring, from the wireless terminal, an output of a motion detection sensor built into the wireless terminal;
a process of generating the movement information based on the output;
The position estimation system according to claim 4 or 5, comprising:

Images