WO2016098635A1 - Wireless base station - Google Patents

Abstract

The wireless base stations (1) through (3) according to the present invention each include a plurality of antenna elements (4A) through (4C) and an arithmetic processing unit (5). When the antenna elements (4A) through (4C) receive signals from a wireless terminal (MP), the arithmetic processing unit (5) calculates signal arrival angles (θ₁) through (θ₃). In the case where the signal arrival angles (θ₁) through (θ₃) can be calculated, the arithmetic processing unit (5) sets, as signal arrival times (T₁) through (T₃) of the wireless base stations (1) through (3), average times of signal arrival times (ta) through (tc) from the antenna elements (4A) through (4C). In the case where the signal arrival angles (θ₁) through (θ₃) cannot be calculated, the arithmetic processing unit (5) sets, as the signal arrival times (T₁) through (T₃) of the wireless base stations (1) through (3), earliest ones of the signal arrival times (ta) through (tc) from the antenna elements (4A) through (4C).

Description

Wireless base station

The present invention relates to a radio base station used for a radio positioning system.

Generally, a wireless positioning system is known that measures the position of a wireless terminal using wireless base stations (anchors) fixed at a plurality of known positions (see, for example, Patent Documents 1 and 2). In Patent Document 1, the arrival times of signals from a wireless terminal are measured by a plurality of wireless base stations, positioning based on these arrival time differences (TDOA: Time ： Difference of Arrival), and the arrival angle of a signal from a wireless terminal ( A hybrid wireless positioning system that combines positioning based on AOA (Angle of Arrival) is disclosed. Patent Document 2 discloses a configuration in which a radio base station in a non-line-of-sight (NLOS) environment is excluded from positioning in positioning based on the arrival angle of a signal.

JP 2007-13500 A JP 2005-49199 A

By the way, in the wireless positioning system described in Patent Document 1, it is assumed that a line-of-sight (LOS) environment exists between the wireless terminal and the wireless base station. For this reason, in the non-line-of-sight environment, there is a problem that the accuracy of the arrival angle of the signal is deteriorated and the positioning accuracy is deteriorated as a result.

On the other hand, the wireless positioning system described in Patent Document 2 is configured to selectively use a wireless base station that does not interfere with the reception state of radio waves in order to avoid deterioration in accuracy of the signal arrival angle. However, in such a configuration, it is necessary to increase the number of radio base stations and arrange them closely in order to secure a radio base station in a line-of-sight environment regardless of the position of the radio terminal, which increases the cost of the entire system. There is a problem of doing.

The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a radio base station capable of improving positioning accuracy.

(1). In order to solve the above-described problem, the present invention is a radio base station used in a radio positioning system that is fixed at a plurality of known positions and measures the position of the radio terminal based on a signal arrival time from the radio terminal. When a plurality of antenna elements arranged at different positions are provided and a signal arrival direction from the radio terminal can be calculated, an average time of a plurality of signal arrival times at the plurality of antenna elements is calculated as a signal of the radio base station. If the arrival time of the signal from the wireless terminal cannot be calculated, the earliest time among the plurality of signal arrival times at the plurality of antenna elements is used as the signal arrival time of the wireless base station. Yes.

According to the present invention, when the signal arrival direction from the wireless terminal can be calculated, the average time of the plurality of signal arrival times at the plurality of antenna elements is set as the signal arrival time of the wireless base station. In this case, it is considered that the plurality of antenna elements are all in a line-of-sight environment with the wireless terminal and receive a direct wave from the wireless terminal. Therefore, for example, the position of the wireless terminal can be specified based on the center positions of the plurality of antenna elements and the signal arrival time of the wireless base station.

On the other hand, when the signal arrival direction from the wireless terminal cannot be calculated, the earliest time among the plurality of signal arrival times in the plurality of antenna elements is set as the signal arrival time of the wireless base station. In this case, it is considered that at least one of the plurality of antenna elements is in a non-line-of-sight environment with the wireless terminal and cannot receive a direct wave from the wireless terminal. For this reason, the earliest time among the plurality of signal arrival times at the plurality of antenna elements is set as the signal arrival time of the radio base station, thereby increasing the possibility of selecting the antenna element in the line-of-sight environment. As a result, since the signal arrival time in the line-of-sight environment can be used as much as possible as the signal arrival time of the radio base station, the positioning accuracy can be improved as compared with the case where the signal arrival time in the non-line-of-sight environment is used. it can.

(2). In the present invention, when the signal arrival direction from the radio terminal cannot be calculated, the earliest time among the plurality of signal arrival times at the plurality of antenna elements is output as the signal arrival time of the radio base station. , Information corresponding to the position of the antenna element is output.

Thus, the position of the wireless terminal can be specified based on the signal arrival time when the earliest signal is received and information corresponding to the position of the antenna element that has received the signal. For this reason, compared with the case where it measures using another position of a wireless base station, positioning accuracy can be improved.

(3). In the present invention, when the signal arrival direction from the wireless terminal can be calculated, the signal arrival direction from the wireless terminal is output.

Thereby, since the position of the wireless terminal can be specified based on the signal arrival direction, the positioning accuracy can be improved as compared with the case of positioning based only on the signal arrival time.

It is explanatory drawing which shows the radio positioning system to which the radio base station by embodiment of this invention was applied. It is a top view which shows the wireless base station and wireless terminal in FIG. It is a flowchart which shows the preparation processing of the information for positioning by a wireless base station. It is explanatory drawing which shows the state which has all the antenna elements of a wireless base station in a line-of-sight environment. FIG. 5 is a characteristic diagram showing a change over time in signal strength of a received signal received by the antenna element in FIG. 4. It is explanatory drawing which shows the state which is a part of antenna element of a wireless base station in a line-of-sight environment. FIG. 7 is a characteristic diagram showing a time change in signal strength of a received signal received by the antenna element in FIG. 6.

Hereinafter, a radio positioning system using a radio base station according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that a radio positioning system including three radio base stations will be described as an example. However, the number of base stations is not limited to three, and three or more stations are sufficient for two-dimensional positioning. Four or more stations are sufficient to perform dimension positioning. As the number of base stations increases, the redundancy in positioning calculation increases, and the position accuracy can be improved accordingly.

1 and 2 show a radio positioning system 10 to which radio base stations 1 to 3 according to the present invention are applied. The radio positioning system 10 includes, as infrastructure equipment, three radio base stations 1 to 3, signal arrival times T ₁ to T ₃ and signal arrival angles θ ₁ to θ ₃ from the radio base stations 1 to ₃ . And a server 6 as a data processing device that calculates the estimated position of the wireless terminal MP based on the data.

It should be noted that when representing individual radio base stations, they are denoted as radio base stations 1 to 3, and when representing any radio base station, they are denoted as radio base stations n, m, and l. When the signal arrival times of the respective radio base stations 1 to 3 are expressed separately, they are described as signal arrival times T ₁ to T _3, and when any signal arrival time is expressed, they are described as signal arrival times T _n . When individually expressing the signal arrival time differences of the radio base stations 1 to 3, the signal arrival time differences ΔT ₁₂ , ΔT ₂₃ , and ΔT ₁₃ are described, and when representing the signal arrival time differences at any radio base station n, m, l, Signal arrival time differences ΔT _nm , ΔT _ml , ΔT _nl are described. When the signal arrival angles (AOA: Angle of Arrival) of each of the radio base stations 1 to 3 are represented separately, they are described as signal arrival angles θ ₁ to θ _3, and when any signal arrival angle is represented, the signal arrival angle θ _n It describes.

The wireless terminal MP to be positioned is a movable wireless mobile station, and has an antenna AT for transmitting radio waves. Although the number of wireless terminals MP is one in FIG. 1, the number of wireless terminals MP may be plural. Each wireless terminal MP has a unique identification code (hereinafter referred to as a unique ID). The wireless terminal MP transmits a wireless signal including a unique ID.

Wireless base stations 1 to 3 are all fixed at known positions. The radio base stations 1 to 3 include a plurality of (for example, three) antenna elements 4A to 4C, and an arithmetic processing unit 5 connected to the antenna elements 4A to 4C.

The antenna elements 4A to 4C are arranged in different positions along the annular shape, for example, constituting an array antenna. The antenna elements 4A to 4C each receive a signal from the radio terminal MP and output the received signal to the arithmetic processing unit 5.

It should be noted that the number of antenna elements 4A to 4C is not limited to three, and may be a plurality of two or more. The arrangement and arrangement of the antenna elements 4A to 4C are not limited to an annular arrangement, and may be a linear or square arrangement, or any other arrangement or arrangement. Further, when the antenna elements are separately represented, they are described as antenna elements 4A to 4C, and when any antenna element is represented, they are described as antenna elements 4.

The arithmetic processing unit 5 is constituted by, for example, a microcomputer and executes a positioning information creation process shown in FIG. The arithmetic processing unit 5 measures received signal strength indicators SSa to SSc (RSSI: Received Signal Strength Indicators) and signal arrival times ta to tc based on signals from the radio terminal MP received by the antenna elements 4A to 4C. . The arithmetic processing unit 5 calculates the signal arrival times T _n and signal arrival angles θ _n of the respective radio base stations 1 to 3 based on the signal strengths SSa to SSc and signal arrival times ta to tc of the antenna elements 4A to 4C. . The arithmetic processing unit 5 creates positioning information IF ₁ to IF ₃ for each of the radio base stations 1 to 3 based on the signal arrival time T _n and the signal arrival angle θ _n , and the positioning information IF ₁ to IF _3. Is output to the server 6. When the positioning information output from each of the radio base stations 1 to 3 is expressed individually, it is described as positioning information IF ₁ to IF _3, and when any positioning information is expressed, it is described as positioning information IF _n. To do.

The server 6 constitutes a real-time location information system (RTLS: Real-Time Location System) and specifies the current location of the wireless terminal MP. At this time, the radio base stations 1 to 3 are time-synchronized. In order to perform various communications including time synchronization, the server 6 and each of the radio base stations 1 to 3 are connected via a cable 7. This connection may be a wireless connection instead of a wired connection using the physical cable 7. Server 6 on the basis of the positioning information IF ₁ ~ IF ₃ from the radio base station 1-3, performs for example the signal arrival time difference positioning, the arithmetic processing by one or both of the signal arrival angle positioning, the wireless terminal MP Specify the position of.

Next, with reference to FIG. 3 to FIG. 7, the positioning information creation processing by the arithmetic processing unit 5 will be described.

In step 1, the arithmetic processing unit 5 measures signal arrival times ta to tc when signals from the radio terminal MP reach the antenna elements 4A to 4C. Specifically, the arithmetic processing unit 5 receives the first signal peak when each antenna element 4A to 4C receives a predetermined signal from the radio terminal MP, that is, the arrival of the first incoming wave. The time is measured as signal arrival times ta to tc.

In step 2, the arithmetic processing unit 5 calculates the signal arrival angle θ _n from the wireless terminal MP. Specifically, the arithmetic processing unit 5 uses the antenna elements 4A to 4C when the signal strengths SSa to SSc of the first arrival waves of the received signals received by the antenna elements 4A to 4C are substantially the same. The signal arrival angle θ _n which is the arrival direction of the radio signal is calculated based on the difference between the signal arrival times ta to tc of the first arrival wave or the phase difference of the first arrival wave.

As shown in FIG. 4, for example, in a line-of-sight environment, the distance between the wireless terminal MP and the antenna element 4A is the shortest, the distance between the wireless terminal MP and the antenna element 4C is the longest, and the distance between the wireless terminal MP and the antenna element 4B. Is the middle of the antenna elements 4A and 4C. In this case, as shown in FIG. 5, the signal arrival time ta is the earliest, the signal arrival time tc is the latest, and the signal arrival time tb is an intermediate time between the signal arrival times ta and tc. Therefore, based on the time differences Δtab, Δtbc, Δtac of the signal arrival times ta, tb, tc and the positions Pa, Pb, Pc of the antenna elements 4A, 4B, 4C, the signal arrival angle θ which is the arrival direction of the radio signal _n can be calculated.

On the other hand, as shown in FIG. 6, for example, a case is considered in which some of the antenna elements 4B and 4C among the antenna elements 4A to 4C are in a non-line-of-sight environment. In this case, as shown in FIG. 7, the signal arrival times tb and tc are greatly delayed compared to the signal arrival time ta. For this reason, since the time differences Δtab and Δtac are much larger than the time difference Δtbc, if the signal arrival angle θ _n is obtained from the time differences Δtab, Δtbc, Δtac, a contradiction occurs in the signal arrival angle θ _n . For this reason, the signal arrival angle θ _n that is the arrival direction of the radio signal cannot be calculated.

Step 3 shows a specific example of the signal arrival angle calculation determination unit. In step 3, it is determined whether or not the signal arrival angle θ _n can be calculated. Specifically, the signal strengths SSa to SSc of the first arrival waves of the received signals received by the antenna elements 4A to 4C are substantially the same, and the signals of the first arrival waves at the antenna elements 4A to 4C are the same. It is determined whether or not the signal arrival angle θ _n can be calculated without contradiction based on the difference between arrival times ta to tc or the phase difference of the first arrival wave. When it is determined as “YES” in Step 3, a reasonable signal arrival angle θ _n has been calculated, and the process proceeds to Step 4.

Step 4 shows a specific example of the LOS signal arrival time calculation unit. In step 4, the processing unit 5, the antenna elements 4A ~ 4C largest wave signal arrival time ta of, tb, based on tc, calculates the signal arrival time T _n of the radio base station 1-3. Specifically, the arithmetic processing unit 5 calculates the average time of the peak wave signal arrival times ta, tb, tc received by the antenna elements 4A to 4C, and uses this average time as the first wave arrival at the radio base station n. The wave signal arrival time T _{n is} assumed.

In step 5, the processing unit 5, a signal arrival time T _n of the radio base station n, and the unique ID of the wireless terminal MP that transmitted the radio signal, the positioning information IF _n including the signal arrival angle theta _n The positioning information IF _n is created and transmitted to the server 6. At this time, as an option, the signal strengths SSa to SSc of the first incoming wave can be transmitted together.

On the other hand, when it is determined as “NO” in step 3, a reasonable signal arrival angle θ _n cannot be calculated. Specifically, when the signal strengths SSa to SSc of the leading incoming waves of the received signals received by the antenna elements 4A to 4C are different among the antenna elements 4A to 4C, and / or the top of each antenna element 4A to 4C. The signal arrival angle θ _n cannot be calculated from the incoming wave. In this case, the process proceeds to step 6.

Step 6 shows a specific example of the NLOS signal arrival time calculation unit. In step 6, the arithmetic processing unit 5 selects the earliest signal arrival time ta to tc of the first arrival wave of each antenna element 4 A to 4 C as the signal arrival time T _n of the first arrival wave in the radio base station 2. And

In step 7, the processing unit 5 includes a signal arrival time T _n of the radio base station n, and the unique ID of the wireless terminal MP that transmitted the radio signal, the identification information of the antenna elements 4A ~ 4C that receives the largest incoming waves Alternatively, positioning information IF _n including information indicating the positions Pa to Pc of the antenna elements 4A to 4C is created, and the positioning information IF _n is transmitted to the server 6.

Here, the information indicating the positions Pa to Pc of the antenna elements 4A to 4C is, for example, the relative positions of the antenna elements 4A to 4C with respect to the center position O of the plurality of antenna elements 4A to 4C of the radio base station n. is there.

The radio base stations 1 to 3 according to the present embodiment output the positioning information IF _n created by the above processing to the server 6, and then the radio positioning system including the positioning processing in the server 6 The operation of 10 will be described.

When the radio terminal MP transmits a radio signal including the unique ID, each radio base station n receives a signal from the radio terminal MP at each of the antenna elements 4A to 4C, and based on this signal, positioning information IF _n Create

A radio signal from the radio terminal MP is received by each antenna element 4A to 4C of the radio base station n. The arithmetic processing unit 5 of the radio base station n compares the signal strengths SSa to SSc of the first incoming wave of the received signals received by the antenna elements 4A to 4C. In addition to this, the arithmetic processing unit 5 calculates the signal arrival angle θ _n from the difference or phase difference between the signal arrival times ta to tc of the leading arrival waves at the antenna elements 4A to 4C.

At this time, the arithmetic processing unit 5 of the radio base station n determines whether or not the signal arrival angle θ _n can be calculated. The signal strengths SSa to SSc of the first arrival wave of the received signal are substantially the same, and the difference Δtab, Δtbc, Δtac or the phase difference of the signal arrival times ta to tc of the first arrival wave at each of the antenna elements 4A to 4C. If the signal arrival angle θ _n can be calculated without contradiction, the arithmetic processing unit 5 determines that the signal arrival angle θ _n can be calculated.

In this case, the arithmetic processing unit 5 of the radio base station n uses the average time of the peak wave arrival times ta to tc of the antenna elements 4A to 4C as the signal arrival time T _{n of the} peak wave arrival at the radio base station n. And At this time, the arithmetic processing unit 5 creates positioning information IF _n including the signal arrival time T _n , the unique ID of the wireless terminal MP, and the signal arrival angle θ _n , and this positioning information IF _n is stored in the server 6. Send to.

On the other hand, when the signal strengths SSa to SSc of the first arrival wave of the received signal are different between the antenna elements 4A to 4C and / or the signal arrival angle θ _{n of the} radio signal is calculated from the first arrival wave of each antenna element 4A to 4C. If not, the arithmetic processing unit 5 determines that the signal arrival angle θ _n cannot be calculated.

In this case, the arithmetic processing unit 5 of the radio base station n uses the earliest signal arrival time ta to tc of each of the antenna elements 4A to 4C as the earliest signal arrival of the signal at the radio base station 1. and time T _n. At this time, the arithmetic processing unit 5 of the radio base station 1 determines the signal arrival time T _n , the unique ID of the radio terminal MP, the identification information of the antenna element 4 (for example, the antenna element 4A) that has received the first incoming wave, and the like. The positioning information IF _n including is generated, and the positioning information IF _n is transmitted to the server 6.

FIG. 6 shows that the signal strength SSa to SSc of the first arrival wave of the received signal is different between the antenna elements 4A to 4C and / or the signal arrival angle θ of the radio signal from the first arrival wave of each antenna element 4A to 4C. An example when _n cannot be calculated is shown.

As shown in FIG. 6, the obstacle OB is partially shielded between the wireless terminal MP and the wireless base station n. At this time, since the antenna element 4A of the radio base station n is in a line-of-sight environment, the signal from the antenna AT of the radio terminal MP is in a state where the direct wave DW reaches, and the antenna AT and the antenna element 4A It propagates on the path | route 21 which connects between. On the other hand, since the other antenna elements 4B and 4C are in an out-of-sight environment, the signal from the antenna AT of the wireless terminal MP is in a state where only the reflected wave RW from the reflector 20 reaches, It propagates along a path 22 bent in an L shape by reflection of the reflector 20.

Note that the reflected wave RW also arrives at the antenna element 4A. For this reason, the delay profile of the received signal at each of the antenna elements 4A to 4C of the radio base station n has a value as shown in FIG. 7, for example.

That is, the direct wave DW from the path 21 arrives at the antenna element 4A at the time t1, and the other antenna elements 4B and 4C have no incoming wave near the time t1. On the other hand, in the vicinity of time t2, which is delayed from time t1, the incoming wave due to the reflected wave RW reaches all the antenna elements 4A to 4C after attenuation. In such a state, the direct wave DW signal has arrived only at some antenna elements 4A. For this reason, near the time t1, the signal strength of the reception signal of the antenna element 4A increases, whereas the signal strength of the reception signals of the antenna elements 4B and 4C becomes a value near zero and decreases. Thus, near the time t1, the signal arrival angle θ _n cannot be calculated because the signal strength of the received signal is significantly different between the antenna elements 4A to 4C. Therefore, in this case, the arithmetic processing unit 5 of the radio base station n specifies the unique ID of the radio terminal MP, the signal arrival time T _n corresponding to the time t1, and the information for identifying the antenna element 4A that has received the signal earliest. Or positioning information IF _n including information indicating the position Pa of the antenna element 4A is generated, and the positioning information IF _n is transmitted to the server 6.

In the example of FIG. 6, since the radio base station n has a plurality of antenna elements 4A to 4C, the direct wave DW that may have been missed by a single antenna can be received as the first incoming wave. . The situation illustrated in FIG. 6 is a relatively simple example in which the direct wave DW reaches a part of the antenna elements 4A, but the actual environment is often more complicated. Even in such a state, for example, even when all the antenna elements 4A to 4C are in a non-line-of-sight environment and the surrounding environment is in a complex scattered wave environment, the radio base station n has a plurality of antenna elements. If 4A to 4C are provided, the possibility of receiving the first incoming wave that reaches an earlier time is higher than when only one antenna element 4 is provided.

The information indicating the signal arrival time T _n , the signal arrival angle θ _n , the unique ID of the wireless terminal MP, and the positions of the antenna elements 4A to 4C is transmitted to the server 6 via the cable 7 or the like as positioning information IF _n. Is done. Since the radio base stations 1 to 3 are synchronized, the server 6 determines the difference in signal arrival time of radio signals between the radio base stations 1 to 3 from the signal arrival times T ₁ to T ₃ of the radio base stations 1 to 3. ΔT ₁₂ , ΔT ₂₃ , ΔT ₁₃ are calculated. Since the positions of the radio base stations 1 to 3 are known, the position of the radio terminal MP can be calculated from the positions of the radio base stations 1 to 3 and the arrival time difference ΔT _nm of the radio signals.

For example, when the signal arrival angle θ ₂ is calculated in the radio base station 2, the server 6 places the position of the radio terminal MP on a straight line in the direction of the signal arrival angle θ ₂ with the radio base station 2 as a base point. Can be limited. Further, when the signal arrival angles (for example, signal arrival angles θ ₂ , θ ₃ ) are calculated by two or more radio base stations (for example, radio base stations ₂ and ₃ ), the server 6 The position of the radio terminal MP can also be calculated from the position of the station (for example, the radio base stations 2 and 3) and the signal arrival angles (for example, the signal arrival angles θ ₂ and θ ₃ ).

Here, if all of the radio base stations 1 to 3 are in the line-of-sight environment with respect to the radio terminal MP, the positions of the radio terminals MP calculated from these plural procedures are substantially the same within an error range. . Therefore, the position of the wireless terminal MP can be determined with high accuracy.

In an actual environment, it is rare that all the radio base stations 1 to 3 become a line-of-sight environment, and there are cases where the radio base stations 1 to 3 and the radio terminal MP become a line-of-sight environment. When the radio base stations 1 to 3 and the radio terminal MP are in an out-of-sight environment, the radio wave propagation path between the radio base stations 1 to 3 and the radio terminal MP is based on the reflected wave RW, and the reflected wave RW is When there are a plurality, a so-called multipath propagation path is formed. Of these, the radio wave that reaches the radio base stations 1 to 3 at the earliest time is the first incoming wave. When the first incoming wave is a reflected wave RW, the following error factors are caused for positioning.

First, the first, for positioning using the signal incoming time difference [Delta] T _nm, the signal arrival times T ₁ ~ T ₃ in the radio base station 1-3 as the signal arrival time difference [Delta] T _nm of the original, the propagation path length by the reflection path By extending, it becomes a time later than the arrival time originally obtained in the line-of-sight environment. This becomes an error factor in positioning due to the signal arrival time difference ΔT _nm . In order to reduce the error, it is indispensable to supplement the arrival time of a signal that reaches a time as early as possible even in an unforeseen environment.

Secondly, as for the signal arrival angle θ _n , the radio base station n may not be able to obtain the signal arrival angle θ _n without any contradiction. Further, even when the signal arrival angle θ _n is obtained consistently at the radio base station n, the signal arrival angle θ _n is calculated not in the direction where the radio terminal MP is originally present but in the direction where the reflector 20 is present due to the reflected wave. May be.

For example, in the example of FIG. 6, when the space between the wireless terminal MP and the wireless base station n is completely shielded by the obstacle OB, all the antenna elements 4A to 4C of the wireless base station n are not completely in the line-of-sight environment (line of sight Think of outside environment). In this case, since there is no signal propagation path (path) of the direct wave DW, the radio base station n detects the reflected wave RW from the reflector 20 as the first incoming wave. For this reason, the radio base station n calculates the signal arrival angle θ _n on the assumption that the radio wave of the radio terminal MP comes from the direction of the reflector 20. Such a case becomes an error factor in positioning based on the signal arrival angle θ _n .

As described above, in the non-line-of-sight environment, there are error factors in positioning in both the signal arrival time difference ΔT _nm and the signal arrival angle θ _n . However, by comparing the information of both the signal arrival time difference ΔT _nm and the signal arrival angle θ _n , the server 6 determines whether the line-of-sight environment exists between the wireless terminal MP and each of the wireless base stations 1 to 3. It is possible to guess whether the environment is out of sight.

For example, if there is a discrepancy between the position of the radio terminal MP by the signal arrival time difference positioning and the direction from the radio base station n by the signal arrival angle θ _n , the server 6 may have the radio base station n in a non-line-of-sight environment. Can be estimated. Also, when the signal arrival time T _n of a certain radio base station _n is significantly later than the position information estimated from the signal arrival angle θ _n or the signal arrival time difference ΔT _{ml of the} other radio base stations m and l. In addition, there is a high possibility that the delay is caused by reflection, and the server 6 can estimate that the radio base station n is highly likely to be in an out-of-sight environment.

Further, if the server 6 receives the transmission of the optional signal strength values SSa to SSc, the server 6 receives the signal strength values SSa to SSc received by the wireless base stations 1 to 3, the positioning position, and the wireless base stations. By considering the ratio with the distance between 1 and 3, it can be used as further information when estimating a radio base station that is in an out-of-sight environment. That is, the reflected wave RW is attenuated by reflection in addition to the distance attenuation due to the propagation path length (path length) becoming longer. Therefore, for example, when the radio base station 1 is in the non-line-of-sight environment and the radio base stations 2 and 3 are in the line-of-sight environment, the values of the signal strengths SSa to SSc of the radio base station 1 that is in the non-line-of-sight environment are Is smaller than the values of the signal strengths SSa to SSc of the radio base stations 2 and 3. Therefore, the values of the signal strengths SSa to SSc are information for estimating whether the radio base station n is in the line-of-sight environment or in the non-line-of-sight environment.

As described above, the server 6 uses the signal arrival time difference ΔT _nm , the signal arrival angle θ _n , and optionally the signal strengths SSa to SSc of the received signals, thereby causing the unintended environment of the radio base stations 1 to 3. It is possible to guess things. In addition, using information on both the signal arrival time T _n and the signal arrival angle θ _n as positioning information increases the amount of information, which increases redundancy in positioning calculation. That is, a plurality of positioning position candidates appear. In addition, if the number of radio base stations n that can be used for positioning is increased, the redundancy is further increased and positioning position candidates are increased.

The server 6 performs the following signal processing in order to reduce positioning errors. That is, firstly, for example, when the radio base station n is estimated to be an out-of-sight environment, the information on the signal arrival angle θ _n is not used. Secondly, the signal arrival time T _n of the radio base station n estimated to be a non-line-of-sight environment is treated as having a delay due to reflection, and delay correction is performed when calculating the signal arrival time difference ΔT _nm . In the calculation of the signal arrival time differences ΔT _nm and ΔT _{nl including} the delay correction, the maximum likelihood estimation is performed between the positioning position when the assumed delay amount is swept and a plurality of positioning position candidates having the above redundancy. By doing so, the final positioning position is determined.

Thus, in the embodiment, when the signal arrival angle θ _n from the radio terminal MP can be calculated, the radio base station n that has calculated the signal arrival angle θ _n receives a plurality of signal arrivals at the plurality of antenna elements 4A to 4C. the average time of the time ta ~ tc the signal arrival time T _n of the radio base station n. In this case, the plurality of antenna elements 4A to 4C are all in a line-of-sight environment with the wireless terminal MP, and are considered to receive direct waves from the wireless terminal MP. Thus, for example, based on the signal arrival time T _n of the center position O and the radio base station n of a plurality of antenna elements 4A ~ 4C, it is possible to specify the position of the wireless terminal MP.

On the other hand, when the signal arrival angle θ _n from the radio terminal MP cannot be calculated, the radio base station n that cannot calculate the signal arrival angle θ _n has a plurality of signal arrival times ta to tc at the plurality of antenna elements 4A to 4C. among the earliest time that the signal arrival time T _n of the radio base station n. In this case, at least one antenna element (for example, the antenna elements 4B and 4C) among the plurality of antenna elements 4A to 4C is in a non-line-of-sight environment with the wireless terminal MP, and a direct wave from the wireless terminal MP is present. Is considered unreceivable. Therefore, by the signal arrival time T _n of the earliest time the radio base station n from a plurality of signal arrival time ta ~ tc in a plurality of antenna elements 4A ~ 4C, the antenna elements of sight environment (e.g., the antenna element The possibility of selecting 4A) increases. As a result, as the signal arrival time T _n of the radio base station n, as much as possible signal arrival time at the sight environment (e.g., signal arrival time ta) from can be used, the signal arrival time at the sight environment (e.g., signal The positioning accuracy can be improved as compared with the case of using the arrival times tb, tc).

When the signal arrival angle θ _n from the radio terminal MP cannot be calculated, in addition to the signal arrival time T _n of the radio base station MP, information corresponding to the position of the antenna element 4 that received the earliest signal Is output. Specifically, as shown in FIG. 6, when the antenna element 4A is in the line-of-sight environment and the antenna elements 4B and 4C are in the non-line-of-sight environment, the signal arrival angle θ _n from the wireless terminal MP cannot be calculated. At this time, the radio base station n outputs information corresponding to the position Pa of the antenna element 4A that received the earliest signal in addition to the signal arrival time T _n of the radio base station MP. As a result, the server 6 identifies the position of the wireless terminal MP based on the signal arrival time ta when the earliest signal is received and the information corresponding to the position Pa of the antenna element 4A that has received the signal. can do. For this reason, positioning accuracy can be improved compared with the case where the position of radio | wireless terminal MP is specified using the other position of the radio base station n like the center position O of the radio base station n, for example.

Further, when the signal arrival angle θ _n from the radio terminal MP can be calculated, the radio base station n outputs the signal arrival angle θ _n from the radio terminal MP. At this time, since the radio base station n is considered as a line-of-sight environment with respect to the radio terminal MP, the positioning accuracy can be improved by using the signal arrival angle θ _n . That is, since the server 6 can specify the position of the wireless terminal MP based on the signal arrival angle θ _n , the positioning accuracy can be improved as compared with the case where the positioning is performed only with the signal arrival time T _n .

Further, even when the radio base station n is in a non-line-of-sight environment, by using the signal arrival time T _n , the number of radio base stations can be increased without using the signal arrival angle θ _n alone, In addition, by capturing the earliest incoming wave between the antenna elements 4A to 4C, the possibility of supplementing the first incoming wave at an earlier time is increased, and the positioning accuracy can be improved.

In the above embodiment, it is determined whether or not the signal arrival angle θ _n can be calculated using both the signal strengths SSa to SSc and the signal arrival times ta to tc. However, the present invention is not limited to this, and it may be determined whether the signal arrival angle θ _n can be calculated using, for example, one of the signal strengths SSa to SSc and the signal arrival times ta to tc. Good.

1 to 3 Radio base stations 4A to 4C Antenna element 5 Arithmetic processing device 6 Server 7 Cable 10 Wireless positioning system MP Wireless terminal AT Antenna

Claims (3)

A radio base station used in a radio positioning system that is fixed at a plurality of known positions and measures the position of the radio terminal based on signal arrival times from the radio terminal,
A plurality of antenna elements arranged at different positions from each other,
When the signal arrival direction from the wireless terminal can be calculated, the average time of the plurality of signal arrival times in the plurality of antenna elements is the signal arrival time of the wireless base station,
The radio base station characterized in that when the signal arrival direction from the radio terminal cannot be calculated, the earliest time among the plurality of signal arrival times at the plurality of antenna elements is the signal arrival time of the radio base station. . When the signal arrival direction from the wireless terminal cannot be calculated, in addition to outputting the earliest time among the plurality of signal arrival times at the plurality of antenna elements as the signal arrival time of the wireless base station, the antenna element The radio base station according to claim 1, which outputs information according to the position of the radio base station. The radio base station according to claim 1, wherein when the signal arrival direction from the radio terminal can be calculated, the signal arrival direction from the radio terminal is output.

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