JP6867902B2 - Position estimator, position estimation method and computer program - Google Patents

Description

Embodiments of the present invention relate to position estimation devices, position estimation methods and computer programs.

In recent years, products in a wide range of fields have supported positioning by a satellite positioning system represented by GPS (Global Positioning System), and applications and services utilizing GPS positioning have become common. It is indispensable for GPS receivers to be able to receive ranging signals from a plurality of GPS satellites in order to perform GPS positioning. GPS positioning is possible outdoors, but GPS positioning is not possible in places where GPS radio waves do not reach, such as indoors, underground, the seabed, or extraterrestrial celestial bodies.

In order to perform positioning even in places where GPS cannot be used, it is conceivable to perform positioning using these radio waves in places where mobile communication base stations are installed. There are a method of estimating the distance using the received signal strength, an arrival time (Time of Arrival: TOA) method, or an arrival time difference (Time Difference of Arrival: TDOA) method. The method using the received signal strength requires calibration in advance, and it is difficult to make a precise measurement. In the TOA method and the TDOA method, if there is diffraction, reflection or refraction, multiple wave propagation (multipath) occurs in which a plurality of radio waves delayed in time arrive at the receiving side. When there is multilateration or noise, it is difficult to improve the measurement accuracy even if the TOA method or the TDOA method is used.

Patent No. 5632843

An embodiment of the present invention provides a position estimation device, a position estimation method, and a computer program for performing highly accurate position estimation.

The position estimation device according to the embodiment of the present invention includes a reception timing specifying unit and a position estimation unit. The reception timing specifying unit specifies the reception timing of the plurality of first signals by using the relationship between the reception signals of the plurality of first signals and the plurality of third signals based on the calculation of the predetermined second signal. To do. The position estimation unit estimates the position of the first wireless communication device, which is the source or destination of the first signal, based on the reception timing.

The figure which shows the whole of the radio positioning system which concerns on 1st Embodiment. The functional block diagram of the radio positioning system which concerns on 1st Embodiment. The figure which shows the example of the pattern signal detection in the received signal using cross-correlation. The figure which shows the example of the candidate peak extraction and peak selection of a cross-correlation signal. The figure which shows the example of the table which stored the data which shows the extracted candidate peak group. The figure which shows the positioning by the positioning server which concerns on 1st Embodiment. The figure which shows the processing flow of the radio positioning system which concerns on 1st Embodiment. The functional block diagram of the radio positioning system which concerns on 2nd Embodiment. The figure which shows the processing flow of the radio positioning system which concerns on 2nd Embodiment. The functional block diagram of the radio positioning system which concerns on 3rd Embodiment. The figure which shows the example of the interpolation processing which concerns on 3rd Embodiment. The figure which shows the processing flow of the radio positioning system which concerns on 3rd Embodiment. The functional block diagram of the radio positioning system which concerns on 4th Embodiment. The functional block diagram of the radio positioning system which concerns on 5th Embodiment. The figure which shows the positioning by the terminal which concerns on 5th Embodiment. The figure which shows the processing flow of the radio positioning system which concerns on 5th Embodiment. The functional block diagram of the radio positioning system which concerns on 6th Embodiment. The figure which shows the processing flow of the radio positioning system which concerns on 6th Embodiment. The figure which shows the whole of the radio positioning system which concerns on 7th Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Further, in the drawings, the same components are given the same number, and the description thereof will be omitted as appropriate.

(First Embodiment)
FIG. 1 is a diagram schematically showing an overall configuration of a radio positioning system according to an embodiment of the present invention. Hereinafter, an outline of the wireless positioning system will be described with reference to FIG.

The wireless positioning system of FIG. 1 includes base stations 1a, 1b, 1c, a terminal 2, and a positioning server 3 which is a position estimation device according to the present embodiment. The base stations 1a, 1b, and 1c are connected to the positioning server by the network 5. The network 5 may be an electrical medium capable of transmitting data, and may be a wired LAN (Local Area Network), a wireless LAN, other interfaces, or a combination thereof. Although three base stations are shown in FIG. 1, more base stations may be installed. Further, although the number of terminals shown in FIG. 1 is one, the number of terminals may be two or more. Although only one positioning server is shown in the figure, it is possible to prepare multiple positioning servers to improve load balancing and availability.

The base stations 1a, 1b, and 1c are, for example, a wireless LAN access point of the IEEE802.11 series or its successor standard, or a base station for mobile communication of the IEEE802.16 series or its successor standard, but other base stations such as Bluetooth. It may be by the method. The device names such as a base station and a LAN access point are examples, and a wireless communication device other than the base station or the access point can be used as a substitute. Therefore, wireless communication devices other than base stations and access points may be arranged instead of base stations 1a, 1b, and 1c. The base stations 1a, 1b, and 1c have a role as a receiver for receiving the ranging signal transmitted from the terminal 2. The ranging signal is a signal including a predetermined signal (pattern signal) described later, and is used for estimating the position of the terminal 2.

The terminal 2 is equipped with a wireless communication device capable of transmitting a ranging signal toward a base station. The wireless communication method used for transmitting and receiving data is, for example, the wireless LAN of the IEEE802.11 series or its successor standard, the mobile communication method of the IEEE802.16 series or its successor standard, but other methods such as Bluetooth are also used. Good. However, the wireless communication system used by the terminal 2 needs to be the same as or compatible with the wireless communication system supported by the base stations 1a, 1b, and 1c.

The form of the terminal 2 includes a tablet, a personal computer, a smartphone, a feature phone, a game machine, a digital camera, a video camera, a smart watch, a health band, a route guidance device, a biological information monitor, an emergency transmitter, a telemetry transmitter, and a sensor. A mounted robot, a vehicle equipped with a sensor, a drone equipped with a sensor, and the like are assumed, but other forms may also be used.

Among the ranging signals transmitted by the terminal 2, the signal s _{1 is received by the base station 1a, the signal s 2} is received by the base station 1b, _{and the signal s 3} is received by the base station 1c. The base stations 1a, 1b, and 1c _{generate cross-correlation signals 100a, 100b, and 100c from the signals s 1} , s ₂ , and s ₃ , respectively, and transmit the cross-correlation signals 100a, 100b, and 100c to the positioning server 3 via the network 5. To do. The method of generating the cross-correlation signal will be described later.

The positioning server 3 is an information processing device such as a computer that includes one or more CPUs (central processing units), a storage device, and a communication unit, and operates an OS (operating system) and an application. The positioning server 3 may be a physical computer, but may be realized by a virtual computer (VM), a container, or a combination thereof. The functions of the positioning server 3 may be shared by one or more physical computers, virtual computers, and containers. It is not excluded to use a configuration in which the number of positioning servers 3 is increased in order to improve availability and load balancing. The location of the positioning server may be near a base station, a data center at a remote site, or may be dispersed in a plurality of locations, and is not particularly limited.

FIG. 2 is a functional block diagram of the radio positioning system according to the first embodiment. Hereinafter, the components in each device constituting the wireless positioning system will be described with reference to FIG.

The base station 1a includes a wireless transmission / reception unit 10a, a time management unit 11a, a storage unit 12a, a cross-correlation calculation unit 13a, a communication unit 14a, and an antenna 6a.

The wireless transmission / reception unit 10a has a wireless communication function. When a wireless LAN such as the IEEE 802.11 series is used, the wireless transmission / reception unit 10a becomes a wireless LAN module. When mobile communication such as the IEEE 802.16 series is used, the radio transmission / reception unit 10a is composed of a baseband processor, an RF transceiver, an amplifier, a filter, and the like. These wireless communication standards are examples, and other wireless communication methods can also be used. The wireless transmission / reception unit 10a is connected to the antenna 6a and transmits / receives radio waves via the antenna 6a. The antenna 6a may be built in the wireless transmission / reception unit 10a, or may be externally attached to the wireless transmission / reception unit 10a.

The time management unit 11a provides functions such as current time management, time adjustment, and elapsed time measurement by using a clock or a timer, and further supports time synchronization in the entire wireless positioning system. The means for synchronizing the time is not particularly limited. For example, a method of referencing a master having a highly accurate time by Precision Time Protocol (PTP), a method of synchronizing time with an external server by Network Time Protocol (NTP), or a method of using the time synchronization function provided in a communication standard, etc. is there. The time management unit 11a may be realized by software, by hardware, or a combination thereof. In order to ensure the accuracy of positioning, it is necessary to suppress both the measurement error of the time management unit 11a and the error at the time of time synchronization.

The storage unit 12a can store a pattern signal, which is a predetermined signal assigned to the terminal 2 to be positioned by the wireless positioning system. When a plurality of terminals exist, the pattern signals of the terminals may be the same or different. The storage unit is composed of, for example, a non-volatile storage device such as a NAND flash memory, a NOR flash memory, an MRAM, a ReRAM, a hard disk, an optical disk, or a volatile storage device such as a DRAM, or a combination thereof.

この式（１）は連続関数についての相互相関の一例である。ｆ（ｔ）が端末のパターン信号であり、ｇ（ｔ）は無線送受信部１０ａで受信された端末からの送信信号であるとする。 The cross-correlation calculation unit 13a calculates the cross-correlation using the transmission signal from the terminal received by the wireless transmission / reception unit 10a and the pattern signal of the terminal stored in the storage unit 12a. There are various methods for calculating the cross-correlation, but as an example, it can be calculated by the following equation (1).

This equation (1) is an example of cross-correlation for a continuous function. It is assumed that f (t) is a pattern signal of the terminal and g (t) is a transmission signal from the terminal received by the wireless transmission / reception unit 10a.

The meaning of cross-correlation will be described with reference to FIG. Here, for convenience, the continuous function is taken as an example, but the following discussion is applicable even if the continuous function is replaced with discrete data. T and τ on the horizontal axis in FIG. 3 represent time. The pattern signal 90 corresponds to f (t) in the equation (1) and is a terminal pattern signal. On the other hand, the signal 92 corresponds to g (t) in the equation (1), and is a transmission signal from the terminal received by the wireless transmission / reception unit 10a.

The cross-correlation calculation unit 13a can obtain the shifted pattern signal 91 by shifting the pattern signal 90 by τ as in f (t−τ). The cross-correlation calculation unit 13a can calculate the cross-correlation 93 by multiplying the further shifted pattern signal 91 and the signal 92 and integrating them. The cross-correlation calculation unit 13a can calculate the cross-correlation 93 for a plurality of values τ, but when the pattern signal 90 is _{shifted by τ 1} as shown in FIG. 3, the shifted pattern signal 91 becomes a signal. It can be seen that it matches the pattern signal portion of 92. Since the pattern signals match best when τ = τ ₁ , the cross-correlation 93 also peaks when _{τ = τ 1.}

In order to extract the received signal as data, it is necessary to periodically sample the signal with an A / D converter or the like, so that the signal 92 corresponding to g (t) is discrete. Therefore, although the pattern signal 90, the shifted pattern signal 91, the signal 92, and the cross-correlation 93 are all drawn as continuous functions in FIG. 3, they are treated as discrete data in the actual processing of the cross-correlation calculation unit 13a. Will be.

In this way, when the data to be calculated is discrete, the cross-correlation equation in the discrete system of the following equation (2) can be used instead of the cross-correlation of the continuous function of the equation (1).

For discrete data, it is necessary to obtain the cross-correlation I (τ) for a plurality of τ using the above equation (2). Here, τ represents the amount of shifting f (t) corresponding to the pattern signal 90. Since the amount of shift τ also takes a discrete value according to the period in which g (t) corresponding to the signal 92 is sampled, f (t−τ) corresponding to the shifted pattern signal 91 is also distributed discretely. As a result, the calculated cross-correlation I (τ) becomes discrete data (sample) depending on the sampling period of the signal g (t). That is, it is a sample group including the time at regular time intervals and the cross-correlation value (intensity value). Such discrete cross-correlation data will be referred to hereinafter as cross-correlation signals.

式（３）を用いることにより受信信号の強度に依存した相互相関の計算値の変動を抑制することができる。このように相互相関には種々の計算法や変形が存在するが、信号ｇ（ｔ）中のパターン信号ｆ（ｔ）の検出が可能であれば、そのいずれを用いてもよい。複数の相互相関の計算式による計測を繰り返し、最も誤検出が少なく正確なピーク検出ができる計算式を選択する処理を行ってもよい。 In order to improve the calculation accuracy of the cross-correlation, the discrete data is divided into a plurality of calculation areas, subtracted by the average value for each calculation area, and divided by the standard deviation. (Normalized cross correlation: NCC) can also be used.

By using the equation (3), it is possible to suppress the fluctuation of the calculated value of the cross-correlation depending on the strength of the received signal. As described above, there are various calculation methods and variations in the cross-correlation, and any of them may be used as long as the pattern signal f (t) in the signal g (t) can be detected. The measurement by a plurality of cross-correlation calculation formulas may be repeated, and a process of selecting a calculation formula capable of performing accurate peak detection with the least false detection may be performed.

The cross-correlation calculation unit 13a shall be realized by hardware such as a microprocessor, ASIC, FPGA, PLD, software running on the hardware, or a combination thereof. The cross-correlation calculation unit 13a may further include a buffer for calculating the cross-correlation signal or holding the calculation result. The buffer is composed of, for example, a non-volatile storage device such as a NAND flash memory, a NOR flash memory, an MRAM, a ReRAM, a hard disk, an optical disk, or a volatile storage device such as a DRAM, or a combination thereof.

The communication unit 14a has a function of transmitting and receiving signals including data. Although not shown in FIG. 2, the base station 1a may include a plurality of communication units in order to ensure redundancy. The physical interface may be a wired Ethernet standardized by the IEEE802.3 series, or an interface using wireless communication such as a wireless LAN. In this case, the hardware related to the wireless transmission / reception unit 10a and the hardware of the communication unit 14a can be shared.

Although the components and functions of the base station 1a have been described so far, it is assumed that the configurations and functions of the base station 1b and the base station 1c are the same as those of the base station 1a.

The terminal 2 includes a wireless transmission / reception unit 20, a time management unit 21, and a storage unit 22.

The wireless transmission / reception unit 20 has a function of transmitting / receiving signals wirelessly. When a wireless LAN such as the IEEE 802.11 series is used, the wireless transmission / reception unit 20 becomes a wireless LAN module. When mobile communication such as the IEEE 802.16 series is used, the radio transmission / reception unit 20 is composed of a baseband processor, an RF transceiver, an amplifier, a filter, and the like. These wireless communication standards are examples, and other wireless communication methods can also be used. However, it is necessary to use a method that is the same as or compatible with the wireless communication method supported by the wireless transmitter / receiver provided in each base station.

The wireless transmission / reception unit 20 is connected to the antenna 7 and transmits / receives radio waves via the antenna 7. The antenna 7 may be built in the wireless transmission / reception unit 20 or may be externally attached to the wireless transmission / reception unit 20.

The time management unit 21 provides functions such as current time management, time adjustment, and elapsed time measurement by using a clock or a timer, and further supports time synchronization in the entire positioning system. The means for synchronizing the time is not particularly limited. For example, a method of referencing a master having a highly accurate time by Precision Time Protocol (PTP), a method of synchronizing time with an external server by Network Time Protocol (NTP), or a method of using the time synchronization function provided in a communication standard, etc. is there. The time management unit 21 may be realized by software, by hardware, or a combination thereof. In order to ensure the accuracy of positioning, it is necessary to suppress both the measurement error of the time management unit 21 and the error at the time of time synchronization.

A pattern signal, which is a predetermined signal, is stored in the storage unit 22. The type of the pattern signal is not particularly limited as long as the pattern signal is commonly recognized by each base station. The pattern signal may be a pilot signal used for channel estimation (propagation path estimation) as in other embodiments described later. The storage unit 22 is composed of, for example, a non-volatile storage device such as a NAND flash memory, a NOR flash memory, an MRAM, a ReRAM, a hard disk, an optical disk, or a volatile storage device such as a DRAM, or a combination thereof.

The network 5 connects the base station 1a, the base station 1b, the base station 1c, and the positioning server 3. The physical interface may be wired Ethernet or may be another method such as wireless LAN. The communication protocol used for data communication is assumed to be TCP / IP, but other protocols or a combination thereof may be used. Although not shown in FIG. 2, there may be network devices such as switches, routers, and load balancers in the middle of the network 5. Teaming and port trunking may be performed to make the communication path redundant.

The positioning server 3 includes a communication unit 30, a reception timing specifying unit 31, a position estimation unit 32, and a storage unit 33. When the network 5 is a wireless network, the positioning server 3 also includes an antenna.

The communication unit 30 has a function of transmitting and receiving signals including data. Although not shown in FIG. 2, the positioning server 3 may include a plurality of communication units in order to ensure redundancy. The physical interface may be a wired Ethernet standardized by the IEEE802.3 series or a module using wireless communication such as a wireless LAN. Further, the communication unit 30 may be made redundant.

The reception timing specifying unit 31 identifies the peak time τ of the cross-correlation signal, and determines this time as the timing at which the corresponding base station receives the ranging signal. Here, the processing performed by the reception timing specifying unit 31 will be described with reference to FIG.

First, the reception timing specifying unit 31 receives the cross-correlation signal to which the base station identifier is assigned from the communication unit 30. By referring to this identifier, it is possible to grasp which base station the cross-correlation signal is generated from. Here, as shown in FIG. 4, the cross-correlation signal 100a obtained by the base station 1a from _{the distance measurement signal s 1,} the cross-correlation signal 100b obtained by the base station 1b from _{the distance measurement signal s 2 , and the distance measurement signal s 3} The cross-correlation signals 100c obtained by the base station 1c can be obtained.

Next, the reception timing specifying unit 31 performs extraction processing of candidate peaks (set of time and intensity value) for each of the cross-correlation signals 100a, 100b, and 100c. Candidate peaks correspond to candidate samples. When multiple wave propagation (multipath) occurs, multiple peaks may occur in the cross-correlation signal. In this case, these peaks may include peaks generated by propagation paths other than direct waves and noise. Here, for each cross-correlation signal, a plurality of candidate peaks that are candidates for peaks caused by direct waves are extracted.

When the extraction process of the candidate peaks is completed, a table summarizing the data related to the candidate peaks extracted for each base station is obtained. The individual data includes the time, receiver ID, terminal ID and cross-correlation value (intensity value). An example of the obtained table is shown in FIG. One horizontal line is the data. For example, the data 112 has a time of 000000433 nanoseconds, a receiver ID of s3, a terminal ID of XXXXX, and a cross-correlation value (intensity value) of 0.90. Table 111 in FIG. 5 corresponds to the extracted candidate peak group 110 in FIG. Hereinafter, description will be given with reference to FIG.

The receiver ID is an identifier of a base station indicating which base station received the ranging signal for which the cross-correlation is calculated. The receiver ID may be any value as long as the base station can be identified. As an example, the receiver ID may be a MAC address or an identifier defined in the communication standard to be used (in the case of IEEE802.11, an association ID or the like). In the figure, for convenience, the receiver ID is represented by using the same pattern signals s1, s2, and s3 as the distance measuring signal.

The terminal ID is an identifier of the terminal that has transmitted the distance measurement signal for which the cross-correlation is calculated. As an example, the terminal ID may be a MAC address or an identifier defined in the communication standard to be used (in the case of IEEE802.11, an association ID or the like). In the example of Table 111, the terminal IDs are all XXX for convenience, but the identifier of the terminal is actually entered.

In the next candidate cluster generation process, peaks (sets of time and cross-correlation values) are selected from a plurality of candidate peaks for each base station (receiver) based on Table 111 to form a set. That is, in Table 111, one data is selected for each _{of the receiver IDs s 1} , s ₂ and s _{3 to form a set.} Here, the combination of candidate peaks selected for each base station (receiver) is called a cluster. The candidate cluster group 110 selected in FIG. 4 schematically shows the candidate cluster group selected by this peak selection process.

The selection of candidate clusters from each candidate peak group is based on analyzing the relationship between the peaks of each candidate cluster. As a specific example, as shown in FIG. 4, a combination of candidate peaks is generated so that one candidate peak corresponding to each receiver ID is included. Clusters (here, clusters 110A, 110B, 110C) are generated, comparison is performed for each cluster, and one cluster is selected. In the example of clusters 110A, 110B, and 110C, candidate peaks having the closest time and different receiver IDs are grouped as a cluster. Here, it is assumed that the same candidate peak does not belong to a plurality of clusters, but a case where the same candidate peak belongs to a plurality of clusters may be allowed. The reason for forming a cluster in this way is that it is generally presumed that data whose times are close to each other correspond to similar propagation paths. For example, a distance measurement signal that has been received by different base stations but has undergone multiple reflections and has followed a propagation path longer than the direct wave has an arrival time later than the distance measurement signal of the direct wave.

As another example of the selection method of the candidate cluster, there is a method of combining samples (set of time and intensity value) whose cross-correlation value (intensity value) is equal to or higher than the threshold value among the cross-correlation signals as a candidate cluster. .. The threshold value may be a fixed value or one whose value fluctuates according to the input cross-correlation signal. For example, when using unnormalized cross-correlation, it is expected that the peak height will fluctuate depending on the input cross-correlation signal. Therefore, as an example, the average value of the input cross-correlation signals is used. It can be used as a threshold value.

As another example of the method of selecting candidate clusters, narrowing down by time may be performed. For example, there are a method of selecting and combining peaks in order from the earliest time, and a method of selecting and combining only peaks before a certain time. By excluding the peak whose time is relatively late in this way from the selection, it is possible to remove the peak generated from the other propagation path which is a longer path than the direct wave.

Further, there is also a method of comparing the distances on the time axis, which is the time difference between peaks, and excluding peaks that are more than the threshold value but farther than other peaks from the selection as candidate peaks to be combined. By using this method, it is possible to exclude not only propagation paths other than direct waves but also peaks caused by noise.

Another method is to perform time integration within a certain time range including peaks (for example, a range in the vicinity that does not include adjacent samples), and exclude peaks with relatively small integrated values from the options for combining. Since the cross-correlation signal is discrete data in the first embodiment, for example, the time integral is approximately calculated by using the segmental quadrature method. This method also makes it possible to remove peaks accidentally generated by noise.

If multiple peaks are still dense (for example, within a certain short distance) after the above processing, only the peak with the largest cross-correlation value is selected from the dense samples. May be combined.

In the cluster selection process used for the next final position estimation, one cluster is finally selected from the generated candidate clusters. That is, in the table 111, one data is selected for each _{of the receiver IDs s 1} , s ₂ and s _3. The selected cluster 120 in FIG. 4 schematically shows the peak group selected by the cluster selection process. The peak group included in the selected cluster 120 is the peak used for the positioning of the terminal 2. That is, using these peaks, the position estimation unit 32 measures the distance between each base station and the terminal and estimates the position of the terminal 2.

The cluster selection used for the final position estimation from each candidate cluster group is based on analyzing the relationship between the peak groups in each candidate cluster group.

When a cluster is generated, candidate peaks that are far apart (for example, separated by a certain distance or more) may occur in the cluster as compared with the other two candidate peaks. For example, in the cluster, the candidate peak of receiver ID_s3 may be isolated and exist at the latest time. It is presumed that such a candidate peak has more reflections than the ranging signals received from other base stations and follows a long propagation path. Therefore, clusters containing such candidate peaks may be excluded from the selection.

Several criteria can be used for cluster-by-cluster comparisons. One is to select the cluster with the largest average value, minimum value, or maximum value of the cross-correlation values of the candidate peaks in the cluster. It is based on the speculation that the cluster with the highest mean, minimum or maximum is likely to correspond to the direct wave. It is known that when an electromagnetic wave hits a substance, a part of it is absorbed by the substance, a part of it passes through the substance, and the rest is reflected. Since the reflected wave of radio waves, which is a type of electromagnetic wave, has a lower energy than the incident wave even when the reflectance is high, it is presumed that clusters with a small mutual correlation value are likely to correspond to the reflected wave. To. When applying this criterion, cluster 110B is selected in FIG.

The second method is to exclude the cluster having the smaller average value, minimum value, or maximum value of the cross-correlation value in the cluster from the selection. For example, there is a process of excluding only the cluster having the smallest average value from the selection. Another method is to find the average value of the cross-correlation values of all clusters in addition to the average value of the cross-correlation values in each cluster, and exclude the clusters whose former value is less than the latter value from the selection target. is there. If the average cross-correlation value is lower than in other clusters, false positives may have occurred. By using this method, erroneously detected peaks can be removed. When applying this criterion, for example, cluster 110C in FIG. 4 is excluded from selection.

The third method is to select the cluster with the earliest or latest time, or the earliest time, or the average time, and select it as a representative data row. For example, identify the earliest time of data contained in a cluster, compare the earliest times between clusters, and select the cluster with the earliest earliest time. Since the reflected wave has a longer propagation path than the direct wave, this criterion can be applied when it can be inferred that the cluster with an earlier time corresponds to the direct wave. When applying this criterion, cluster 110A is selected in FIG.

The fourth method is to make a selection based on the time difference of the samples in the cluster. Specifically, the time difference between adjacent candidate peaks on the time axis in each cluster is obtained, and the process of selecting the cluster in which the average value, the minimum value, or the maximum value of these time differences is the minimum or maximum is performed. For example, select the cluster with the smallest average time difference. If the installation locations of the base stations 1a, 1b, and 1c are close to each other, but the terminal 2 is far away from any of the base stations, the distance between the base station 1a and the terminal 2 and the distance between the base station 1b and the terminal If it can be assumed that the distance between the two is approximately equal to the distance between the base station 1c and the terminal 2, the correct peak may be selected by making this selection. For example, when selecting the cluster having the smallest average time difference, the cluster 110C is selected in FIG.

One of the criteria described above can be applied alone, but a plurality of criteria may be applied in combination. For example, it is possible to first apply the second criterion, remove the cluster having a small cross-correlation value, then apply the third criterion, and execute the process of extracting the cluster with the earlier time. Implementation may be performed in which the applicable standard can be switched depending on the setting of the positioning server. The setting may be switched either by the operation of the maintenance staff or by the diagnosis result when the positioning server diagnoses the installation environment of the positioning system.

By combining candidate peaks between different base stations (receivers) to generate multiple clusters in this way and selecting clusters that are presumed to reflect the direct wave between the terminal and the base station. It is possible to reduce the possibility of erroneously selecting a peak generated from a propagation path other than a direct wave or a ranging signal of another terminal.

The position estimation unit 32 estimates the position of the terminal using the peak group 120 selected by the reception timing identification unit 31. As an example, the position estimation in the case of the TOA method is shown. Since each base station and the terminal are time-synchronized, the transmission time at which the terminal transmits the ranging signal is known in advance. This time may be notified to the positioning server 3 by each base station, or may be known in advance by the positioning server 3. Further, the reception time at which the ranging signal is received at each base station is the peak time corresponding to each base station included in the peak group 120. Therefore, based on the difference between the reception time and the transmission time, the time required from the transmission of the ranging signal from the terminal to the reception at each base station can be known. By multiplying this required time by the speed of light c, the distance between the terminal and each base station can be obtained. Various calculations can be performed by the program on the positioning server 3 using computational resources such as a CPU and a storage area, but dedicated hardware or the like may be used to speed up the processing.

By using the distance between each base station and the terminal and the position information of each base station, it is possible to calculate the position of the terminal. For example, when a circle is drawn with the position of each base station as the center and the distance to the terminal obtained by each base station as the radius, the point where all the circles intersect can be estimated as the terminal position. In the two-dimensional TOA system, three base stations need to receive distance measurement signals from terminals for position estimation, but in this embodiment, there are three base stations, base stations 1a, 1b, and 1c. The position of the terminal 2 can be estimated. When there are four or more base stations, three or more base stations capable of wireless communication with the terminal 2 may be used. When there are two base stations, the position of the terminal 2 can be narrowed down to two candidates (two points where two circles intersect). This embodiment is also effective for narrowing down the position of the terminal to two candidates when there are two base stations.

When the base station and the terminal are installed in an environment where there are no large undulations or steps such as one room, it is considered that it is often sufficient to perform two-dimensional position estimation. However, in an environment with a plurality of floors or a large undulation or step, it may be necessary to estimate the position three-dimensionally including the height difference. In such a case, in the TOA method, if a sphere model is used instead of the circle model, the height of the terminal can be estimated. For example, in this case, when it is desired to estimate the position using the TOA method, the position of the terminal can be estimated to one position by using four or more base stations.

It is also possible to estimate the position of the terminal by the TDOA method. When using the TDOA method, a pair of two base stations is generated, a hyperbola that focuses on the positions of the two base stations is drawn for each pair, and the intersection of the hyperbolas is based on the difference in arrival time of the peaks of each base station. The position of the terminal can be estimated from the inside. When performing two-dimensional position estimation, it is necessary for four or more base stations to receive distance measurement signals in order to obtain a theoretical solution. When estimating the position in three dimensions, it is necessary to draw a hyperboloid instead of a hyperbola, and five base stations that receive the ranging signal are required.

In the case of the two-dimensional TDOA system, when the number of base stations receiving the ranging signal from the terminal is more than four, a plurality of combinations of four or more base stations are generated from these base stations, and each of them is generated. The accuracy of the position estimation may be verified by using the position estimation result for each combination of the above, and the position estimation with high accuracy may be realized. Moreover, you may use all the base stations which can communicate.

For example, when five base stations receive a distance measurement signal from a certain terminal and perform position estimation by the TOA method using information from the three base stations, the combination of base stations is ₅ C ₃ = 10. There is a street. In this way, position estimation may be performed for a plurality of combinations to verify whether stable position estimation can be realized. Alternatively, a plurality of position estimation results may be compared and combinations deviating from other calculation results may be excluded. Alternatively, the average value of the results of a plurality of position estimations can be used. Further, three or more receivers may be used. What has been said here applies to both the TOA method and the TDOA method.

The TOA method and the TDOA method are examples, and if there is another method that can be used for position estimation, it may be used.

The storage unit 33 stores the position information of the terminal calculated by the position estimation unit 32. The location information of the terminal shall be stored in a format that can be referenced by a program running on the positioning server 3 or other computer. The type and use of the program are not particularly limited. The storage format may be arbitrary, and may be XML, JSON, CSV, or any other format.

The position estimation unit 32 may generate a terminal position map including the estimated position information of the terminal. FIG. 6 shows an example of the terminal position map 330. The terminal position map visually represents the estimated terminal position. The movement history of the terminal may be displayed by estimating the position of the terminal in a short cycle and updating the terminal position map 330 in real time. The position estimation may be executed periodically, may be executed in response to a user's command, or may be executed when the occurrence of a predetermined event is detected. The terminal position 330a in FIG. 6 represents the position of the terminal 2.

The storage unit 33 is composed of, for example, a non-volatile storage device such as a NAND flash memory, a NOR flash memory, an MRAM, a ReRAM, a hard disk, an optical disk, or a volatile storage device such as a DRAM, or a combination thereof. Although the storage unit 33 is arranged inside the positioning server 3 in FIG. 2, the storage unit 33 does not have to be inside the server 3. For example, it is possible to use various storage areas such as an external storage device, a storage server connected to the server 3 via a network, and cloud storage in an external data center.

So far, as an example, a case where position estimation is performed using _{the ranging signals s 1} , s ₂ , and s ₃ transmitted by the terminal 2 has been described. However, the wireless positioning system according to the embodiment of the present invention can perform position estimation in parallel not only for one terminal but also for a plurality of terminals.

FIG. 7 is a flowchart showing the processing of the entire wireless positioning system according to the first embodiment. As a premise of this process, it is assumed that some times in the wireless positioning system are synchronized. For example, when the position of a terminal is specified as one by the position estimation of the two-dimensional TOA method, it is necessary that the times of at least three base stations and the terminal are synchronized. Therefore, the distance to the terminal can be obtained based on the reception time of the distance measurement signal from the terminal 2 and the transmission time of the distance measurement signal from the terminal 2 in each of the base stations 1a, 1b, and 1c. Further, in the case of three-dimensional TOA position estimation, it is necessary that the times of at least four base stations and terminals are synchronized. When the position of the terminal is specified as one by the two-dimensional TDOA method position estimation, at least four base stations must be used, and at least the base stations to be paired for TDOA acquisition must be synchronized with each other. There is. In the case of three-dimensional TDOA method position estimation, at least five base stations must be used, and at least the base stations to be paired for TDOA acquisition need to be time-synchronized with each other.

In addition, the pattern signal of the terminal is shared with each base station in advance. The pattern signal of the terminal may be defined in advance by the wireless communication standard to be used, or the pattern signal to be used for the terminal may be determined in cooperation between the base stations. Alternatively, the terminal may determine the pattern signal and notify each base station. In this case, in order to ensure security, the pattern signal information may be encrypted and transmitted by the terminal and decrypted by each base station. The encryption method is not particularly limited. Each base station holds the pattern signal of the terminal to be the target of position estimation in the storage unit.

In step S101, the terminal 2 to be the target of position estimation transmits a ranging signal including a pattern signal to each base station (1a to 1c). The pattern signal can be transmitted by arranging it in the preamble or header of the frame, for example.

In step S102, each base station receives the distance measurement signal from the terminal 2 and performs a cross-correlation calculation based on the distance measurement signal and the pattern signal previously held in the storage unit to obtain a cross-correlation signal. To get. The details of the calculation of the cross-correlation are as described in the explanation of the cross-correlation calculation unit 13a.

In step S103, each base station adds the identifier of the terminal 2 to the cross-correlation signal and transmits it to the positioning server 3. In addition to the identifier of the terminal 2, information indicating the transmission time at which the terminal 2 transmitted the distance measurement signal may be added. The transmission time may be known in advance by each base station, or the transmission time may be added to the ranging signal transmitted by the terminal 2. The distance measuring server 3 may know the transmission time in advance.

In step S104, the positioning server 3 extracts a candidate peak group from each of the cross-correlation signals received from each base station. The number of candidate peaks to be extracted may be predetermined. The specific processing executed in step S104 is as described in the description of the reception timing specifying unit 31 of the positioning server 3.

In step S105, the positioning server compares the candidate peak group between the base stations to generate a candidate cluster group, and selects one cluster to be used for positioning from the candidate cluster group. As an example, candidate peaks are combined between base stations to generate a plurality of combinations (clusters) of candidate peaks, and finally one combination is selected from the combinations (clusters). The specific processing executed in step S105 is as described in the description of the reception timing specifying unit 31 of the positioning server 3.

In step S106, the positioning server 3 obtains the position information of the terminal 2 by performing the positioning (position estimation) of the terminal. The positioning server 3 stores the obtained position information of the terminal 2 in the storage unit 33. The specific processing of the positioning of the terminal 2 is as described in the description relating to the processing of the position estimation unit 32 of the positioning server 3.

(Second Embodiment)
In the first embodiment, the pattern signal is used to generate a cross-correlation signal, and the cross-correlation signal is used to estimate the position of the terminal. In the second embodiment, a pilot signal is used as the pattern signal, and an impulse response obtained by performing inverse Fourier transform (IFFT) on the frequency characteristics of the channel obtained by performing channel estimation (channel estimation) is used. , Estimate the position of the terminal. Since the inverse Fourier transform is performed at high speed, the inverse Fourier transform to be executed may be an inverse discrete Fourier transform (the same applies hereinafter).

FIG. 8 is a functional block diagram of the radio positioning system according to the second embodiment. Hereinafter, FIG. 8 will be described with reference to the functional block diagram of FIG. 2 according to the first embodiment.

Regarding the base station 1a, the storage unit 12a and the cross-correlation calculation unit 13a in FIG. 2 are replaced with the storage unit 15a, the channel estimation unit 16a, and the IFFT unit 17a in FIG. The components of the base stations 1b and 1c are similarly replaced.

Looking at the terminal 2, the storage unit 22 in FIG. 2 is replaced with the storage unit 23 that stores the pilot signal in FIG. There is no change in the components of the positioning server 3.

The storage unit 15a stores a pilot signal including a bit string or a symbol string of a predetermined pattern. The pattern of the pilot signal is shared in advance between the terminal and the base station. The pilot signal may be defined by the wireless communication standard to be used. The storage unit 15a is composed of, for example, a non-volatile storage device such as a NAND flash memory, a NOR flash memory, an MRAM, a ReRAM, a hard disk, an optical disk, or a volatile storage device such as a DRAM, or a combination thereof.

The channel estimation unit 16a compares the pilot signal included in the reception signal from the terminal with the known pilot signal stored in the storage unit 15a, and estimates the propagation path between the terminal and the base station. As a result, the frequency characteristics of the propagation path including information on the fluctuation of the amplitude and the phase for each of a plurality of frequencies are obtained. Interpolation in the frequency domain may be performed in order to perform position estimation with high accuracy. Interpolation in the frequency domain includes linear interpolation and interpolation using an FIR filter, but the interpolation method is not particularly limited.

The IFFT unit 17a derives an impulse response by performing an inverse Fourier transform on the frequency characteristics of the propagation path. The derived impulse response includes time axis delay, signal attenuation and phase rotation information. The impulse response is a function that peaks at the time of arrival. Therefore, the impulse response can be used instead of the cross-correlation signal of the first embodiment. The inverse Fourier transform may be performed using various fast Fourier transform algorithms. When performing the inverse Fourier transform, the resolution may be increased by increasing the number of IFFT points. The impulse response is configured as a sequence of a plurality of amplitude values (intensity values) arranged at time intervals according to the resolution.

The estimation of the propagation path corresponds to an example of calculation in which the pilot signal included in the received signal is calculated with a known pilot signal stored in the storage unit 15a. Further, the signal of the frequency characteristic of the impulse response or the propagation path corresponds to an example of the signal obtained by the calculation.

The pilot signal pattern is stored in the storage unit 23 of the terminal 2. The storage unit 23 is composed of, for example, a non-volatile storage device such as a NAND flash memory, a NOR flash memory, an MRAM, a ReRAM, a hard disk, or an optical disk, or a volatile storage device such as a DRAM, or a combination thereof.

The reception timing specifying unit 31 of the positioning server 3 extracts a candidate peak group from the impulse response received from each base station. The positioning server 3 selects a peak (a set of time and a cross-correlation value) for each base station (receiver) from the extracted candidate peak group to form a group (candidate cluster). The selection of the candidate cluster from each candidate peak group may be performed based on the analysis of the relationship between the candidate peak groups of each receiver. This process is the same as that described above in the description of the reception timing specifying unit 31 of the positioning server 3 according to the first embodiment.

The reception timing specifying unit 31 selects one cluster to be used for positioning from each candidate cluster group. This process is the same as that described above in the description of the reception timing specifying unit 31 of the positioning server 3 according to the first embodiment.

FIG. 9 is a flowchart showing the processing of the entire wireless positioning system according to the second embodiment. Hereinafter, FIG. 9 will be described with reference to the flowchart of FIG. 7 according to the first embodiment. The same description as in FIG. 7 will be omitted as appropriate.

In step S201, the terminal 2 transmits a ranging signal including a pilot signal to each base station (1a to 1c). The pilot signal may be included in the header or preamble of the frame, for example, or the pilot signal may be dispersed in the data symbol such as the scattered pilot symbol, and the method is not particularly limited.

In step S202, each base station estimates the propagation path (channel estimation) using the pilot signal included in the received signal and the pattern of the pilot signal stored in the storage units (15a to 15c) in advance. Obtain the frequency characteristics of the propagation path from the terminal 2 to each base station. The details of the channel estimation process are as described above in the description of the channel estimation unit 16a.

In step S203, each base station derives an impulse response by performing an inverse Fourier transform on the frequency characteristics obtained in step S202. The details of the process performed in step S203 are as described in the description of the Fourier unit 17a.

In step S204, each base station adds the identifier of the terminal 2 to the impulse response signal and transmits it to the positioning server 3.

In step S205, the positioning server 3 extracts a candidate peak group from the impulse response received from each base station.

The positioning server 3 compares the candidate peak groups between the base stations, compares the candidate peak groups between the base stations to generate a candidate cluster group, and selects one cluster to be used for positioning from each candidate cluster group. The process executed in step S205 is the same as that described above in the description of the reception timing specifying unit 31 of the positioning server 3 according to the first embodiment.

In the positioning server 3, when the Fourier is performed with a low resolution, the obtained impulse response may be subjected to interpolation processing such as quadratic interpolation and polynomial interpolation. As a result, it is possible to improve the resolution in the extraction processing and peak selection processing of candidate peaks. Further, when the peak selection is performed by using the time integration for the candidate peak described in the first embodiment, the candidate peak group is interpolated, and the interpolated peak is used to integrate the candidate peak. The value may be calculated. This interpolation process may be performed after the candidate cluster is generated.

In step S206, the position estimation unit 32 of the positioning server 3 performs positioning (position estimation) of the terminal and acquires the position information of the terminal. The positioning server 3 stores the position information of the terminal in the storage unit 33.

The position estimation of the second embodiment can also be executed as an alternative process when a clear peak cannot be extracted even if a peak is erroneously detected in the first embodiment or the measurement test is repeated. .. Further, the position estimation of the second embodiment may be executed first, and when a clear peak cannot be extracted by the impulse response, the position estimation of the first embodiment may be executed as an alternative process. It is also possible to let maintenance personnel select a process that can estimate the position with less error according to the installation environment of the wireless positioning system.

The channel estimation function is provided in many wireless communication devices including wireless LAN and mobile communication. Further, for high-speed transmission, an example of adopting OFDM (Orthogonal Frequency Division Multiplexing) as a modulation method as a wireless communication method is increasing, and Fourier transform and inverse Fourier transform are performed in many wireless communication devices. In particular, the physical layer circuit (OFDM transmission circuit) of the wireless LAN has a function of performing an inverse Fourier transform. In the case of wireless LAN or mobile communication, the position of the second embodiment can be estimated with a minimum of customization by utilizing the functions of the existing wireless communication chip or the like.

(Third Embodiment)
In the first embodiment, the sample interval of the cross-correlation signal is determined by the sampling period of the distance measuring signal. That is, the sample interval of the cross-correlation signal depends on the performance of the A / D converter mounted on the apparatus.

For example, when the sampling frequency of the A / D converter is 160 MHz, the sample interval is 6.25 nanoseconds, and there is a possibility that a measurement error of about 1.9 m may occur at the maximum. In this way, even if an A / D converter having a high sampling frequency is used, a measurement error corresponding to the sampling frequency will occur.

In the third embodiment, in order to reduce the influence of such measurement error, the cross-correlation signal is interpolated to increase the time resolution of the cross-correlation signal.

FIG. 10 is a functional block diagram of the radio positioning system according to the third embodiment.

The configuration of the radio positioning system according to the third embodiment is the same as that of the first embodiment shown in FIG. 2, except that the interpolation unit 31a is added to the reception timing specifying unit 31 of the positioning server 3. It is the same as the wireless positioning system.

The interpolation unit 31a performs the cross-correlation signal interpolation processing received from each base station before the candidate cluster generation processing in the reception timing specifying unit 31 is executed. The range in which the interpolation processing is performed may be the entire cross-correlation signal or only the periphery of the sample in which the cross-correlation value is equal to or higher than the threshold value. FIG. 11 shows an example of interpolation. Samples 72 and 72 are added by interpolating only around the sample 71 above the threshold value (the area between the adjacent samples). By performing interpolation, a sample having an intensity value larger than that of the sample may be interpolated. The processing load can be reduced by limiting the range or sample to be interpolated. Interpolation methods include interpolation using a quadratic function, interpolation using a polynomial, spline interpolation, and the like, but other interpolation may be performed.

The interpolation unit 31a may perform the interpolation processing after the candidate cluster generation processing and before the cluster selection processing finally used for the position estimation. That is, for each base station, interpolation may be performed on the entire candidate peak group or around the candidate peaks that satisfy specific conditions. An example of a candidate peak that satisfies a specific condition is a candidate peak whose intensity value is less than or equal to the threshold value. In addition, there is a candidate peak having an intensity value above or below the average of the candidate peak group. By performing interpolation, a sample having an intensity value larger than that of the originally existing sample (set of time and intensity value) may be interpolated.

By interpolating the cross-correlation signal or the candidate peak group in this way, it can be expected that the peak detection accuracy will be further improved.

FIG. 12 is a flowchart showing the processing of the entire radio positioning system according to the third embodiment. Here, the case of interpolating the cross-correlation signal will be described as an example.

Except for the fact that the positioning server interpolates the cross-correlation signal in step S304 and then executes the extraction process of the candidate peak group, the flowchart of FIG. 12 is the same as the flowchart of FIG. 7 showing the process according to the first embodiment. The process is similar.

By interpolating the cross-correlation signals before generating candidate clusters and selecting clusters in this way, it becomes possible to specify more accurate peak times and improve the accuracy of position estimation. be able to. This makes it possible to reduce the influence of measurement error due to the sampling interval of the A / D converter.

In FIG. 10, the interpolation unit 31a is arranged on the positioning server 3, but instead, each base station may interpolate the cross-correlation signal and transmit the interpolated signal to the positioning server 3.

(Fourth Embodiment)
In the first embodiment and the third embodiment, each base station calculates the cross-correlation signal, transmits the cross-correlation signal to the positioning server, and the positioning server performs processing using the cross-correlation signal. In the fourth embodiment, a part of the processing of each base station is integrated on the positioning server side.

Specifically, each base station transfers the ranging signal received from the terminal as it is to the positioning server. On the positioning server side, processing from calculation of cross-correlation signal, interpolation, extraction / selection of peak to calculation of terminal position is executed.

FIG. 13 is a functional block diagram of the radio positioning system according to the fourth embodiment. Hereinafter, the difference from the block diagram of FIG. 10 according to the third embodiment will be mainly described.

In the radio positioning system according to the fourth embodiment, the base stations 1a, 1b, and 1c do not have a cross-correlation calculation unit.

The base stations 1a, 1b, and 1c of FIG. 13 assign a receiver ID that identifies their own station to the distance measurement signal received from the terminal, and transfer the signal to the positioning server 3.

A storage unit 34 and a cross-correlation calculation unit 35 are added to the positioning server 3 according to the fourth embodiment.

The storage unit 34 stores the pattern signal of the terminal. Specifically, the pattern signal is associated with the identifier of the terminal and stored. When the pattern signal is common to all terminals, it is not necessary to associate the terminal identifier with the pattern signal.

The subsequent processing flow is the same as that of the radio positioning system according to the third embodiment.

By consolidating a part of the processing of each base station on the positioning server side in this way, it is expected that the processing speed can be increased by effectively utilizing the computing resources such as the CPU time and the storage area of the positioning server 3. Further, since the cross-correlation calculation unit 35, the interpolation unit 31a, the reception timing identification unit 31, and the position estimation unit 32 are all integrated in the positioning server 3, the burden of maintenance of each base station can be reduced, and the overall system Easy maintenance. For example, when these functions are realized by a program on the server 3, modifications and changes in processing can be handled only by modifying the program on the positioning server 3.

In the fourth embodiment, the positioning using the cross-correlation signal has been described as an example, but in the case of the positioning using the impulse response described in the second embodiment, a part of the processing of the base station is similarly performed. It can be aggregated on the positioning server side. For example, it is possible to have the positioning server 3 perform a part of the processing such as channel estimation, interpolation, and inverse Fourier transform performed in the base station.

(Fifth Embodiment)
In the first to fourth embodiments described so far, the terminal transmits a ranging signal to each base station, and the positioning server side estimates the position of the terminal. On the contrary, in the fifth embodiment, the distance measurement signal is transmitted from each base station to the terminal, and the position of the own terminal is estimated on the terminal side.

FIG. 14 is a functional block diagram of the radio positioning system according to the fifth embodiment.

The radio positioning system according to the fifth embodiment includes a base station 1a, a base station 1b, a base station 1c, a terminal 2, and a management server 4. By transmitting distance measurement signals from the three base stations, the terminal 2 estimates the position of the own terminal. That is, the terminal according to the present embodiment is equipped with a position estimation device that estimates the position of the own terminal.

It is assumed that the TOA method two-dimensional position estimation is performed. When performing three-dimensional position estimation by the TOA method, it is necessary to transmit distance measurement signals from at least four base stations. In that case, the shortage of base stations may be added. The number of base stations may be four or five or more. If the number of base stations is larger than this, all the base stations, or some of them, can also transmit the ranging signal to the terminal. Alternatively, when performing three-dimensional position estimation by the TDOA method, it is necessary to transmit distance measurement signals from at least five base stations, and in that case as well, an insufficient number of base stations may be added.

It is also possible to transmit ranging signals from more base stations to terminals than the number required for each method. For example, when two-dimensional position estimation is performed by the TOA method, when distance measurement signals are transmitted from five base stations to terminals, the base stations when only three base stations are used for position estimation. There are ₅ C ₃ = 10 combinations of. Position estimation may be performed for a plurality of combinations, verification of the position estimation result, identification of a combination having a significant deviation from other estimation results, calculation of the average value of all estimation results, and the like. This also applies to the case where the TDOA method is used. Further, the information of all the base stations that can communicate with each other may be used without limiting the number of base stations.

Although one terminal is shown in FIG. 14, there may be two or more terminals.

In FIG. 14, the management server 4 is installed in place of the positioning server 3 that existed in the first to fourth embodiments. The management server 4 is connected to the base stations 1a, 1b, and 1c by the network 5. The network 5 may be a wired network such as Ethernet, or may be composed of other means such as a wireless LAN or a combination thereof.

The management server 4 includes a communication unit 40 and a base station control unit 41. The base station control unit 41 receives the position estimation processing start command transmitted from the terminal, and generates a distance measurement signal transmission command for each base station when the command is received. The communication unit 40 transmits the generated transmission command to each base station. If the management server 4 can specify the distance measurement signal transmission time of each base station, the time may be notified to the terminal in advance. The management server 4 may transmit a transmission command without receiving a position estimation process start command from the terminal. For example, the management server 4 may transmit the transmission command when the predetermined conditions are satisfied. In this case, the management server 4 does not need to be able to communicate with the terminal 2. As a predetermined condition, the transmission command may be transmitted every time a certain time elapses.

Further, when the position is estimated by the TDOA method, each base station may synchronize the time with each other without waiting for the transmission command from the management server 4. If a plurality of base stations are time-synchronized, the distance measurement signal can be transmitted at the same time, so that the terminal can obtain the TDOA from the time difference at which the signals are received. If the base station can start the time synchronization and the transmission of the distance measurement signal in response to the position estimation process start command, the base station can also serve as the management server 4. Four or more base stations are required for two-dimensional position estimation by the TDOA method, and five or more base stations are required for three-dimensional position estimation.

The management server 4 controls the transmission timing of each base station so that the transmission times of the distance measurement signals from each base station do not overlap. However, if the terminal 2 is capable of multiplex communication with the base stations 1a to 1c, the base stations 1a to 1c may be configured to transmit the ranging signal at the same time. The method of multiplex communication may be spatial division multiplexing, time division multiplexing, frequency division multiplexing, or a combination thereof.

The management server 4 is equipped with a CPU and a storage device, and is assumed to be an information processing device such as a computer on which an OS (operating system) and an application are operated, but even if it is realized by other configurations such as a VM and a container. Good.

When the wireless transmission / reception units 10a to 10c of each base station receive the distance measurement signal transmission command of the management server 4, the radio transmission / reception units 10a to 10c transmit the distance measurement signal to the terminal 2 as a trigger. The ranging signal includes a predetermined pattern signal. This pattern signal is stored in the storage units 12a to 12c of each base station, and the wireless transmission / reception units 10a to 10c of each base station generate a distance measurement signal by reading the pattern signal from the storage units 12a to 12c. To do.

The terminal 2 includes a wireless transmission / reception unit 20, a time management unit 21, a storage unit 22, a cross-correlation calculation unit 24, a reception timing identification unit 25, a position estimation unit 26, and a storage unit 27. The position estimation device according to the present embodiment is configured by all or a part of these elements (for example, the reception timing specifying unit 25 and the position estimation unit 26).

The functions and configurations of the wireless transmission / reception unit 20 and the time management unit 21 are the same as those of the terminals according to the conventional embodiments. The storage unit 22 stores predetermined pattern signals for each of the base stations 1a to 1c. These pattern signals are the same as the pattern signals stored in the storage units 12a to 12c of the base stations 1a to 1c. The pattern signal may be the same or different for each base station.

The cross-correlation calculation unit 24 calculates the cross-correlation in the same manner as the cross-correlation calculation unit of the base station according to the first embodiment. More specifically, the cross-correlation calculation unit 24 identifies the source base station of the ranging signal, and calculates the cross-correlation signal for the ranging signal by using the pattern signal corresponding to the identified base station. .. The cross-correlation calculation unit 24 sends the calculated cross-correlation signal to the reception timing specifying unit 25. The function of the cross-correlation calculation unit 24 may be realized by hardware such as an A / D converter, a program running on a CPU, or a combination thereof.

The reception timing specifying unit 25 executes candidate cluster generation and finally cluster selection processing used for position estimation from extraction of candidate peaks, as in the reception timing specifying unit 31 of the positioning server 3 of the previous embodiments. To do. Before performing the candidate cluster generation process or the final cluster selection process, the same interpolation as that of the interpolation unit 31a according to the third embodiment may be performed. In this case, the function of the interpolation unit may be added to the reception timing specifying unit 25.

The position estimation unit 26 performs the same position estimation as the position estimation unit 32 of the positioning server 3 of the first embodiment. Either the TOA method or the TDOA method may be used for the position estimation. In order to estimate the position, the terminal 2 needs to obtain the position information of each base station in advance. For example, when the terminal 2 is initially connected to each base station, or in an arbitrary process thereafter, the position information of each base station may be acquired, and the acquired position information may be stored in the storage unit 27 or the storage unit 22. Alternatively, the position information of each base station may be included in the ranging signal. In this case, the terminal may read the position information from the received ranging signal. Alternatively, the terminal 2 may acquire the location information of each base station from the management server 4.

The position estimation unit 26 stores the estimated position information of the terminal 2 in the storage unit 27. The storage format may be XML, JSON, CSV, or any other format. The storage unit 27 is composed of, for example, a non-volatile storage device such as a NAND flash memory, a NOR flash memory, an MRAM, a ReRAM, a hard disk, an optical disk, or a volatile storage device such as a DRAM, or a combination thereof.

The functions of the reception timing specifying unit 25 and the position estimation unit 26 may be realized by mounting by a program running on the CPU or by mounting by dedicated hardware.

FIG. 15 is a diagram schematically showing the overall configuration of the positioning system according to the fifth embodiment. Ranging from the base station 1a signal U ₁ is transmitted and received by the terminal 2. _{The ranging signal U 2} is transmitted from the base station 1b and received by the terminal 2. Ranging signal U ₃ from the base station 1c are transmitted and received by the terminal 2.

The terminal 2 estimates the position of its own terminal based on the ranging signals received from the base stations 1a to 1c. The position estimation unit 26 may create a terminal position map (see FIG. 6 described above) to which the estimated position information of the terminal is added. The terminal position map may be displayed on the screen of the terminal 2 by various programs such as a map application for displaying the current position of the terminal, a route guidance application, and a game.

FIG. 16 is a flowchart showing the processing of the entire radio positioning system according to the fifth embodiment.

In step S311 each base station transmits a ranging signal including a predetermined pattern signal to the terminal 2.

In step S312, the terminal 2 calculates the cross-correlation for each base station based on the distance measurement signal received from each base station and the pattern signal for each base station held in advance. The method for calculating the cross-correlation is the same as the process described in the description of the cross-correlation calculation unit 13a of the first embodiment.

In step S313, the terminal 2 extracts a candidate peak group from the cross-correlation signal for each base station. When the cross-correlation signal is interpolated as in the third embodiment, the interpolation may be performed after the candidate peak group is extracted and before the candidate cluster is generated. Alternatively, it is possible to perform interpolation after generating candidate clusters and before selecting the final cluster. The candidate peak extraction process is the same as that described in the description of the first embodiment.

In step S314, the terminal 2 compares the candidate peak groups acquired for each base station with each other, and selects one peak to be used for positioning from each candidate peak group. The process performed here is the same as the peak selection process of the first embodiment.

In step S315, the terminal 2 positions the position of the own terminal based on the selected peak, and stores the estimated position information of the own terminal in the storage unit 27. The details of the positioning process are as described in the description of the position estimation unit 26.

In the fifth embodiment, since the position information of the own terminal can be obtained on the terminal side, the terminal can call the API for acquiring the position information by the mobile application and update the position information in real time. Thereby, for example, route guidance can be performed in an environment where GPS cannot be used.

In the first to fourth embodiments, since the position information of the terminal is obtained on the server side, the position information of the terminal can be utilized in a system for managing, monitoring, and tracking the terminal, or in a server-side application. Not only the distance measurement signal but also the measurement information of the sensor mounted on the terminal may be transmitted from the terminal to the server. This makes it possible to provide, for example, a service on the server side that displays information (temperature, humidity, etc.) measured at a point indicated by the position information of the terminal in association with the point. By using the position information and measurement information of a plurality of terminals, it is possible to display a map that visualizes the measurement information at each point in a wide area.

(Sixth Embodiment)
In the sixth embodiment, positioning is performed on the terminal side as in the fifth embodiment. In the fifth embodiment, positioning and position estimation are performed using a cross-correlation signal, but in the sixth embodiment, positioning and position estimation are performed using an impulse response obtained by inverse Fourier transforming the frequency characteristics.

In the present embodiment, a positioning signal including a pilot signal is transmitted from each base station to a terminal, channel estimation and inverse Fourier transform are performed at the terminal that receives the positioning signal, and then candidate peak extraction, peak selection, and position are further performed. Estimates are made. Each process is common to the second embodiment.

FIG. 17 is a functional block diagram of the radio positioning system according to the sixth embodiment. FIG. 17 will be described with reference to the block diagram according to the fifth embodiment of FIG.

Although three base stations are shown in FIG. 17, it is the same as in the fifth embodiment that there may be more base stations.

The base station 1a according to the sixth embodiment has a storage unit 15a for storing a pilot signal instead of the storage unit 12a in FIG. The pattern of the pilot signal is stored in the storage unit 15a. Specific examples of the storage device used for the storage unit 15a may be the same as those in the third embodiment. The functions and configurations of the base stations 1b and 1c are the same as those of the base station 1a. The pattern of the pilot signal may be common to a plurality of base stations 1a to 1c, or may be different for each base station.

The terminal 2 according to the sixth embodiment includes a storage unit 23 for storing pilot signals of each base station, a channel estimation unit 28, and an IFFT unit 29, instead of the storage unit 22 and the cross-correlation calculation unit 24 of FIG.

The storage unit 23 stores the pilot signal pattern of each base station. If the pilot signals of each base station are the same, one common pilot signal may be stored. Specific examples of the storage device used by the storage unit 23 may be the same as those in the third embodiment.

The channel estimation unit 28 compares the pilot signal included in the received signal from each base station with the pattern of the pilot signal stored in the storage unit 23, and estimates the propagation path to determine the frequency characteristics of the propagation path. Ask. The process is the same as that of the channel estimation unit 16a according to the second embodiment.

The IFFT unit 29 performs an inverse Fourier transform on the frequency characteristics of the propagation path to obtain an impulse response which is time series data. This process is the same as that of the IFFT unit 17a according to the second embodiment.

The channel estimation unit 28 and the IFFT unit 29 are realized by dedicated hardware or a combination of a processor and software. Similar to the second embodiment, a function such as a wireless communication chip originally provided in the terminal may be used.

The implementation of the reception timing specifying unit 25, the position estimation unit 26, and the storage unit 27 is the same as in the fifth embodiment.

FIG. 18 is a flowchart showing the processing of the entire radio positioning system according to the sixth embodiment.

In step S401, each base station transmits a ranging signal including a pilot signal to the terminal. The pilot signal may be transmitted by including the pattern signal in the preamble or header of the frame, or may be dispersed in the data like the scattered pilot symbol, and the method is not particularly limited.

In step S402, the terminal estimates the channel using the ranging signals received from each base station. The processing of channel estimation is the same as that performed by the base station according to the second embodiment.

In step S403, the terminal obtains an impulse response corresponding to the propagation path to and from each base station by performing an inverse Fourier transform on the frequency characteristics obtained by channel estimation. This process is the same as that performed by the base station according to the second embodiment.

In step S404, the terminal extracts a candidate peak group from the impulse response of each base station and compares each candidate peak group to select one peak from each candidate peak group. This process corresponds to the candidate peak extraction process and the peak selection process performed by the positioning server 3 according to the second embodiment.

In step S405, the terminal estimates the position of its own terminal by positioning the position of its own terminal using each selected peak (that is, the time corresponding to the peak). The terminal stores the position information indicating the estimated position of the own terminal. This process is the same as the process of step S305 according to the fifth embodiment.

According to the sixth embodiment, the position information of the terminal can be obtained on the terminal side as in the fifth embodiment.

(7th Embodiment)
In the first to sixth embodiments, the positioning server 3 or the management server 4 exists independently of the base stations and is connected to each base station by a network. In the seventh embodiment, the functions of the positioning server 3 or the management server 4 are integrated with the base station.

FIG. 19 is a diagram showing the entire radio positioning system according to the seventh embodiment.

The radio positioning system according to the seventh embodiment includes a terminal 2, a base station 1b, a base station 1c, and a base station 300 with a server function. In FIG. 19, there are two base stations, one terminal, and one base station with a server function, but the number of each device may be larger than this. In particular, when there are two or more base stations having a positioning function as a server function, the positioning function can be made redundant. It may be operated as a mere base station without using the positioning function of the base station with a server function.

It is assumed that the configuration of the base station 300 with a server function is a combination of the positioning server 3 and the base station, or a combination of the management server 4 and the base station. In the former case, the base station is equipped with the position estimation device according to the present embodiment.

The base station 300 with a server function can perform wireless communication with other base stations 1b and 1c.

In the radio positioning system of the seventh embodiment, the position of the terminal may be estimated using the cross-correlation signal, or the position of the terminal may be estimated using the impulse response.

As in the first to fourth embodiments, the terminal transmits a distance measurement signal to the base stations 300, 1b, 1c, and the base station 300 with a server function transmits information based on the distance measurement signal from the other base stations 1b, 1c. The position of the terminal may be estimated by acquiring. Further, as in the fifth and sixth embodiments, the distance measurement signals may be transmitted from the plurality of base stations 300, 1b, 1c to the terminal 2, and the terminal 2 may estimate the position of the own terminal. ..

According to this embodiment, by integrating the server function into the base station, it is not necessary to construct a network connecting the server and each base station, or to prepare a separate machine for the server. Positioning of terminals can be performed even in an environment where there is no information infrastructure accessible from the base station nearby.

The present invention is not limited to each of the above embodiments as it is, and at the implementation stage, the components can be modified and embodied within a range that does not deviate from the gist thereof. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in each of the above embodiments. Further, for example, a configuration in which some components are deleted from all the components shown in each embodiment can be considered. Furthermore, the components described in different embodiments may be combined as appropriate.

1a, 1b, 1c Base station 2 Terminal 3 Positioning server 4 Management server 5 LAN
10a, 10b, 10c, 20 Wireless transmitter / receiver 11a, 11b, 11c, 21 Time management unit 12a, 12b, 12c, 22, 34 Storage unit 13a, 13b, 13c, 24, 35 Cross-correlation calculation unit 14a, 14b, 14c Communication Units 15a, 15b, 15c, 23 Storage units 16a, 16b, 16c, 28 Channel estimation units 17a, 17b, 17c, 29 IFFT units 25, 31 Reception timing identification units 26, 32 Position estimation units 27, 33 Storage units 30 Communication units 31a Interpolator 90 Pattern signal 91 Shifted pattern signal 92 Signal 93 100 Cross-correlation 100a, 100b, 100c Cross-correlation signal 110 Selected candidate clusters 110A, 110B, 110C Cluster 111 Table 112 Data 120 Selected cluster 260 terminals Location map 330a Terminal location 300 Base station with server function

Claims (19)

Based and reception signals of a plurality of first signals, the calculation of the second signal to obtain a first set and a second set of samples for intensity values at a plurality of times,
A plurality of first candidate samples are selected based on the integral of the intensity values in the first time range from the first set to the samples.
A plurality of second candidate samples are selected based on the integral of the intensity values in the second time range with respect to the samples from the second set.
Between the first set and the second set, one or more of the plurality of first candidate samples and one or more of the second candidate samples are combined, and the first set is included in a combination selected from a plurality of combinations. The reception timing of the plurality of first signals is specified based on the time corresponding to one of the candidate samples and one of the second candidate samples.
Reception timing identification part and
A position estimation device including a position estimation unit that estimates the position of a first wireless communication device that is a source or reception destination of the first signal based on the reception timing. Based on the calculation of the received signals of the plurality of first signals and the second signal, the first set and the second set of samples for the intensity values at a plurality of times are acquired.
Combining the samples between the first set and the second set based on the time proximity of the samples.
The reception timing of the plurality of first signals is specified based on the time corresponding to the plurality of the samples included in the combination selected from the plurality of combinations.
Reception timing identification part and
With a position estimation unit that estimates the position of the first wireless communication device that is the source or destination of the first signal based on the reception timing.
Position estimation device equipped with. Based on the calculation of the received signals of the plurality of first signals and the second signal, the first set and the second set of samples for the intensity values at a plurality of times are acquired.
Combining the sample between the first set and the second set,
One combination is selected by comparing a value based on the intensity value of the sample, a value based on the time of the sample, or a value based on the time difference of the sample among a plurality of combinations.
The reception timing of the plurality of first signals is specified based on the time corresponding to the plurality of samples included in the selected combination.
Reception timing identification part and
With a position estimation unit that estimates the position of the first wireless communication device that is the source or destination of the first signal based on the reception timing.
Position estimation device equipped with. The operation, the position estimation device according to any one of claims 1 to 3 is to calculate the cross correlation between the received signal and the second signal of the first signal. The operation, the frequency characteristic of the propagation path is calculated by channel estimation on the basis of said received signal and said second signal of the first signal, one of the claims 1 to 3 is to inverse Fourier transform The position estimation device according to one item. The reception timing specifying unit, the size of the intensity values of further said sample from said first set, and based on at least one of time corresponding to the sample, according to claim 1 for selecting the plurality of first candidate sample The position estimation device described in 1. The position estimation device according to any one of claims 1 to 6 , further comprising an interpolation unit that increases the number of samples by performing interpolation processing on the first set and the second set. Wherein the plurality of candidate samples by performing an interpolation process, the position estimation device according to claim 1, further comprising an interpolation unit to increase the number of candidates samples. The first wireless communication device is a source of the plurality of first signals, and is
The position estimation device according to any one of claims 1 to 8 , wherein the reception destination of the plurality of first signals is a plurality of second wireless communication devices different from the first wireless communication device. The position estimation device according to claim 9 , further comprising a communication unit that communicates with the plurality of second wireless communication devices and acquires the first set and the second set. The position estimation device according to claim 10 , wherein the position estimation device is mounted on one of the plurality of second wireless communication devices. The sources of the plurality of first signals are a plurality of second wireless communication devices.
The position estimation device according to any one of claims 1 to 8 , wherein the first wireless communication device is a receiving destination of the plurality of first signals. The position estimation device according to claim 12 , wherein the position estimation device is mounted on the first wireless communication device. Based and reception signals of a plurality of first signals, the calculation of the second signal to obtain a first set and a second set of samples for intensity values at a plurality of times,
A plurality of first candidate samples are selected based on the integral of the intensity values in the first time range from the first set to the samples.
A plurality of second candidate samples are selected based on the integral of the intensity values in the second time range with respect to the sample from the second set.
Between the first set and the second set, one or more of the plurality of first candidate samples and one or more of the second candidate samples are combined, and the first set is included in a combination selected from a plurality of combinations. Based on the time corresponding to one of the candidate samples and one of the second candidate samples, the reception timings of the plurality of first signals are specified.
Based on the reception timing, the position of the first wireless communication device, which is the source or destination of the first signal, is estimated.
Position estimation method. Based on the calculation of the received signals of the plurality of first signals and the second signal, the first set and the second set of samples for the intensity values at a plurality of times are acquired.
Combining the samples between the first set and the second set based on the time proximity of the samples.
The reception timing of the plurality of first signals is specified based on the time corresponding to the plurality of the samples included in the combination selected from the plurality of combinations.
Based on the reception timing, the position of the first wireless communication device, which is the source or destination of the first signal, is estimated.
Position estimation method. Based on the calculation of the received signals of the plurality of first signals and the second signal, the first set and the second set of samples for the intensity values at a plurality of times are acquired.
Combining the sample between the first set and the second set,
One combination is selected by comparing a value based on the intensity value of the sample, a value based on the time of the sample, or a value based on the time difference of the sample among a plurality of combinations.
The reception timing of the plurality of first signals is specified based on the time corresponding to the plurality of samples included in the selected combination.
Based on the reception timing, the position of the first wireless communication device, which is the source or destination of the first signal, is estimated.
Position estimation method. The received signal of the plurality of first signals, based on the operation on the second signal, obtaining a first set and a second set of samples for intensity values at a plurality of times,
A step of selecting a plurality of first candidate samples based on the integral of the intensity values in the first time range from the first set to the samples,
A step of selecting a plurality of second candidate samples based on the integral of the intensity values in the second time range from the second set to the samples,
Between the first set and the second set, one or more of the plurality of first candidate samples and one or more of the second candidate samples are combined, and the first set is included in a combination selected from a plurality of combinations. A step of specifying the reception timing of the plurality of first signals based on the time corresponding to one of the candidate samples and one of the second candidate samples, and
A step of estimating the position of the first wireless communication device, which is the source or destination of the first signal, based on the reception timing, and
A computer program that lets a computer run. A step of acquiring the first set and the second set of samples for the intensity values at a plurality of times based on the calculation of the received signals of the plurality of first signals and the second signal.
A step of combining the samples between the first set and the second set based on the time proximity of the samples.
A step of specifying the reception timing of the plurality of first signals based on the time corresponding to the plurality of samples included in the combination selected from the plurality of combinations, and
A step of estimating the position of the first wireless communication device, which is the source or destination of the first signal, based on the reception timing, and
A computer program that lets a computer run. A step of acquiring the first set and the second set of samples for the intensity values at a plurality of times based on the calculation of the received signals of the plurality of first signals and the second signal.
A step of combining the samples between the first set and the second set,
A step of selecting one combination by comparing a value based on the intensity value of the sample, a value based on the time of the sample, or a value based on the time difference of the sample among a plurality of combinations.
A step of specifying the reception timing of the plurality of first signals based on the time corresponding to the plurality of samples included in the selected combination, and
A step of estimating the position of the first wireless communication device, which is the source or destination of the first signal, based on the reception timing, and
A computer program that lets a computer run.

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