WO2018163440A1 - Position estimation apparatus - Google Patents

Position estimation apparatus Download PDF

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Publication number
WO2018163440A1
WO2018163440A1 PCT/JP2017/010816 JP2017010816W WO2018163440A1 WO 2018163440 A1 WO2018163440 A1 WO 2018163440A1 JP 2017010816 W JP2017010816 W JP 2017010816W WO 2018163440 A1 WO2018163440 A1 WO 2018163440A1
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WIPO (PCT)
Prior art keywords
mobile communication
communication device
base station
base stations
received signal
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PCT/JP2017/010816
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French (fr)
Inventor
Xiao Peng
Naoto Ishii
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Nec Corporation
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Priority to PCT/JP2017/010816 priority Critical patent/WO2018163440A1/en
Publication of WO2018163440A1 publication Critical patent/WO2018163440A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/04—Position of source determined by a plurality of spaced direction-finders
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/12—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial

Definitions

  • the present invention relates to a position estimation apparatus, a computer-implemented position estimation method, and a computer readable storage medium, and more particularly to a position estimation apparatus which detects the position of a mobile communication device, i.e. , a mobile station (MS), based on wireless signals received by a base station.
  • a mobile communication device i.e. , a mobile station (MS)
  • MS mobile station
  • LBS Location based services
  • GPS global positioning systems
  • time based positioning In cellular systems, both time based positioning and angle based positioning are possible methods.
  • the accuracy of time based methods is limited by the smallest unit of time, and synchronization in the network, e.g. , in the current 4G cellular system the smallest unit of time is 32ns resulting in an uncertainty of about 10m as described in NPL 1 .
  • OTDOA methods need special measurements, which require frequency resources and cost time. Namely, OTDOA methods influence the efficiency of ordinary communication.
  • angle based positioning especially angle of arrival (AoA) or direction of arrival (DoA) based positioning which uses only the communication signals themselves, accuracy is not limited by the smallest unit of time and synchronization, but by the angle detection accuracy.
  • 5G cellular systems will provide much higher throughput by adopting a much higher frequency band than the current 4G cellular system. Since the intervals between the antennas deployed in a cellular system are inversely proportional to the frequency, it is possible to integrate more antennas into devices using the 5G cellular system. As a result, in order to guarantee communication quality at sufficient range, both the base stations and the mobile communication devices in the 5G cellular system will employ many more antennas than before. For example, 256 antennas for base stations and 8 antennas for mobile communication devices are being considered, as described in NPL 2, by the standardization organization, 3rd Generation Partnership Project (3GPP). The larger antenna number of 5G systems makes it possible to detect a more accurate AoA.
  • 3GPP 3rd Generation Partnership Project
  • angles between a mobile communication device and two base stations can be used to determine the position of the mobile communication device in a two dimensional plane.
  • Fig. 1 shows the basic process of AoA based positioning.
  • Base stations BS1 and BS2 receive the wireless signals from a mobile communication device, and calculate the AoAs, a1 and a2 (corresponding to base stations BS1 and BS2 respectively) using a conventional algorithm , such as the multiple signal classification (MUSIC) algorithm .
  • MUSIC multiple signal classification
  • the AoAs are perfectly calculated , and corresponding lines l t and the line l 2 are obtained .
  • the intersection of the line l and the line l 2 is the estimated position of the MS.
  • the AoA calculation has uncertainty.
  • a valid estimation of the line l t is between l and ⁇ '
  • a valid estimation of the line l 2 is between 1 2 ' and l 2 .
  • valid estimated positions are within the intersection area marked in gray.
  • the AoA based positioning would be affected by what is known as dilution of precision (DoP) in some situations.
  • DoP dilution of precision
  • N PL 3 discusses DoP in terms of a G PS system .
  • Such a problem similarly applies to AoA positioning using a cellular system .
  • Fig. 2 shows the basic concept of the DoP in AoA positioning.
  • the intersection area becomes narrow and long, which is shown in the gray area in Fig.2.
  • the AoA calculation uncertainty remains the same as the situation shown in Fig. 1 , it is possible that the distance between the estimated position and the actual position of a mobile communication device is much larger than the distance in Fig. 1 .
  • This phenomenon in which the positioning error is very large is the DoP in AoA positioning.
  • the conventional solution to DoP in AoA positioning is introducing additional base stations for calibration.
  • the AoA calculation from another base station BS3 can be used as calibration for the DoP.
  • Fig. 3 shows the calibration process with an additional base station BS3.
  • the line i 3 and l' restrict the intersection area into a much smaller area than the situation in Fig. 2.
  • the possible estimated position is restricted to a smaller intersection area, and the positioning error is reduced.
  • the conventional calibration method for DoP requires that there are at least three base stations and additional base stations BS are deployed in proper positions.
  • the location of deployment of the base stations BS depends on many factors, including the coverage of the communication area, communication quality, setup difficulty, operation costs, and the like. That is to say, positioning is not the most important factor in deploying the base stations, which requires that the positioning technology using a cellular system can deal with various situations according to actual base station deployment.
  • this requirement cannot always be satisfied, and conventional calibration methods do not always work well.
  • Fig. 4 shows a problematic situation in which the conventional calibration method is used.
  • the mobile communication device is near the base stations BS1 and BS2, and the base station BS3 is very far away. Since base station BS3 is far away, the range of line 1 3 ' and l 3 covers the entirety of the intersection area. Because of this, it cannot provide a calibration effect. That is to say, although there are 3 base stations, only two base stations are available for detecting the position of mobile communication device.
  • Fig. 5 shows another problematic situation in which the conventional calibration method is used.
  • the base station BS3 is not far away, but the base stations BS1 , BS2, and BS3 are mounted on street lamps in a line, for example, along a street. If the mobile communication device is in the intersection area marked in gray, the AoA al , a2 calculation from the base station BS3 cannot be used for calibration, since the range of line i 3 and l 3 covers the entirety of the intersection area.
  • the base stations BS1 , BS2, and BS3 are mounted on street lamps in a line, for example, along a street.
  • the common feature is that only two base stations are available and additional base stations cannot provide calibration.
  • a calibration method with only two base stations is needed for these base station deployments under a cellular system.
  • the two base stations receive a wireless signal from a mobile communication device.
  • the received signal strength (RSS) and AoA a1 , a2 are used to generate the position candidate for each base station.
  • the final estimated position is produced using the position candidates.
  • a position estimation apparatus is provided which is included in a wireless communication system having a mobile communication device configured to communicate with first and second base stations configured to calculate a received signal strength and an angle of arrival of a wireless signal from the mobile communication device, including: a position estimation unit configured to determine a calibrated position of the mobile communication device by using the received signal strength and the angle of arrival at each of the first and second base stations.
  • position candidates are calculated when angles of deviation of the wireless signal from the mobile communication device are less than a predefined threshold, and the position candidates are used to determine the calibrated position of the mobile communication device.
  • an imaginary circle is centered at each of the first and second base stations, the respective radius of each imaginary circle are calculated based on the received signal strengths of the first and second base stations and a distance between the first and second base stations, and the imaginary circles are used to determine position candidates of the mobile communication device.
  • the position candidates are on the respective imaginary circles of the first and second base stations at the respective angles of arrival from each of the first and second base stations.
  • the calibrated position of the mobile communication device is determined as a point between the position candidates calculated according to a ratio of the received signal strengths from the first and second base stations.
  • an imaginary circle is used to determine position candidates of the mobile communication device, the imaginary circle being defined so that a first distance between any point on the imaginary circle and the first base station, and a second distance between the point on the imaginary circle and the second base station, are in accordance with the ratio between the received signal strengths of the first and second base stations.
  • the first base station has a received signal strength that is greater than the received signal strength of the second base station, and one of the position candidates is on the imaginary circle and in the direction of the angle of arrival at the first base station.
  • the second base station has a received signal strength that is less than the received signal strength of the first base station, two points on the imaginary circle are in the direction of the angle of arrival from the second base station, and one of the position candidates for the calibrated position is determined to be one of the two points that has an angle from the first base station that is closer to the angle of arrival at the first base station.
  • a computer-implemented position estimation method for a wireless communication system having a mobile communication device configured to communicate with first and second base stations configured to calculate a received signal strength and an angle of arrival of a wireless signal from the mobile communication device, including: determining a calibrated position of the mobile communication device from the received signal strength and the angle of arrival.
  • position candidates are calculated when angles of deviation of the wireless signal from the mobile communication device are less than a predefined threshold, and the position candidates are used to determine the calibrated position of the mobile communication device
  • an imaginary circle is centered at each of the first and second base stations, the respective radius of each imaginary circle are calculated based on the received signal strengths of the first and second base stations and a distance between the first and second base stations, and the imaginary circles are used to determine position candidates of the mobile communication device.
  • the position candidates are on the respective imaginary circles of the first and second base stations at the respective angles of arrival from each of the first and second base stations
  • the calibrated position of the mobile communication device is determined as a point between the position candidates calculated according to a ratio of the received signal strengths from the first and second base stations.
  • an imaginary circle is used to determine position candidates of the mobile communication device, the imaginary circle being defined so that a first distance between any point on the imaginary circle and the first base station, and a second distance between the point on the imaginary circle and the second base station, are in accordance with the ratio between the received signal strengths of the first and second base stations.
  • the first base station has a received signal strength that is greater than the received signal strength of the second base station, and one of the position candidates is on the imaginary circle and in the direction of the angle of arrival at the first base station.
  • the second base station has a received signal strength that is less than the received signal strength of the first base station, two points on the imaginary circle are in the direction of the angle of arrival from the second base station, and one of the position candidates for the calibrated position is determined to be one of the two points that has an angle from the first base station that is closer to the angle of arrival at the first base station.
  • a non-transitory computer readable storage medium containing instructions to make a computer perform a position estimation method for a wireless communication system having a mobile communication device configured to communicate with first and second base stations configured to calculate a received signal strength and an angle of arrival of a wireless signal from the mobile communication device, including: determining a calibrated position of the mobile communication device from the received signal strength and the angle of arrival.
  • the present invention provides a position estimation apparatus included in a wireless communication system in which the accuracy of estimating a position of the mobile communication device is improved, even when estimating using only two base stations.
  • Fig. 1 illustrates a conventional method for position estimation using AoA positioning.
  • Fig. 2 illustrates the concept of DoP in AoA positioning.
  • Fig. 3 illustrates the conventional solution to DoP.
  • Fig. 4 illustrates a first problematic situation for the conventional technique.
  • Fig. 5 illustrates a second problematic situation for the conventional technique.
  • Fig. 6 is a block diagram of a first example embodiment
  • Fig. 7 is a process flow chart of the first example embodiment
  • Fig. 8 illustrates a calibration example of the first example embodiment
  • Fig. 9 illustrates a calibration example of a second example embodiment
  • Fig. 10 is a block diagram of a third example embodiment
  • Fig. 11 is a process flow chart of the first example embodiment in the first example embodiment.
  • Fig. 12 is an alternative process flow chart for determining a calibrated position in the first example embodiment.
  • Fig. 13 is another alternative process flow chart for determining a calibrated position in the first example embodiment.
  • Fig. 14 is a process flow chart for the third example embodiment.
  • Fig. 15 is an alternate process flow chart for the third example embodiment.
  • Fig. 16 is another alternate process flow chart for the third example embodiment.
  • Fig. 17 is a graph showing the results of a simulation of the first embodiment.
  • Fig. 18 is a graph showing a comparison of simulated results between the first embodiment and the conventional method.
  • Fig. 6 shows the block diagram of the proposed apparatus for estimating the position of a mobile communication device MS.
  • the base stations BS1 , BS2 have the same structure, each of which contains a first communication unit 130a, an angle calculation unit 142, and a second communication unit 130b.
  • the first communication unit 130a is used to communicate with the mobile communication device MS through wireless signals.
  • the angle calculation unit 142 is used to calculate the AoA a1 , a2 of wireless signals from the mobile communication device MS.
  • the RSS detection unit 144 is used to detect the RSS of the wireless signals from the mobile communication device MS.
  • the second communication unit 130b is used to communicate with a position calculation unit 146.
  • a position calculation entity is tasked with determining the position of the mobile communication device MS.
  • the position calculation entity PCE includes the position calculation unit 146, a calibration determination unit 148, and a calibration calculation unit 149.
  • the position calculation unit 146 is used to calculate the position of the mobile communication device MS based on information from the base stations.
  • the calibration determination unit 148 is used to determine whether or not to perform calibration.
  • the calibration calculation unit 149 is used to complete the calibration calculation.
  • the position calculation entity PCE can be deployed in the base stations BS1 , BS2 or in an independent server.
  • Fig. 7 shows the processing flow of proposed calibration method.
  • the base stations BS1 , BS2 calculate the AoAs a1 , a2 and angles of deviation (AoDs) ⁇ ⁇ , ⁇ 2.
  • the AoD ⁇ , ⁇ 2 is an angle between the estimated line /- ⁇ , I2 from the base station and the line between the base stations B1 , B2. Since the positions of the base stations B1 , B2 are fixed, the angle between the base stations B1 , B2 and the exact distance between the base stations is known in advance. Such information with respect to the angle/distance of surrounding base stations may be stored in, for example, the base stations themselves or in a server.
  • the calibration process is conducted. Otherwise, the position calculation entity PCE determines the position of mobile communication device MS without calibration . In the calibration process, each of the base stations BS1 , BS2 detect the RSS. The position calculation entity PCE uses the RSS data for calibration calculation.
  • the calibration calculation process is illustrated in Fig. 8.
  • the angle between the estimated line l from the base station BS 1 and the line connecting the base stations BS 1 , BS2 is denoted as ⁇ 1 .
  • the angle between the estimated line l 2 from BS2 and the line connecting the base stations BS 1 , BS2 is denoted as ⁇ 2 . If both ⁇ 1 and ⁇ 2 are less than the predefined threshold , e.g. , 5 degrees, the calibration process is conducted .
  • the calibration process firstly defines two imaginary circles to be used for calculation.
  • the base station BS 1 is the center of a first imaginary circle C1
  • the base station BS2 is the center of a second imaginary circle C2.
  • the radiuses r and r 2 of the two circles C1 and C2, respectively, are calculated using the equations of Math. 1 and Math . 2.
  • d in the above equations (Math. 2 and 3) represents the distance between the base stations BS1 , BS2.
  • the purpose of defining the two imaginary circles C1 , C2 is to find the possible range of the mobile communication device MS with the RSS data.
  • position candidate P1 The intersection of the circle C1 and the estimated line l x is denoted as position candidate P1 .
  • position candidate P2 The intersection of the circle C1 and the estimated line l 2 is denoted as position candidate P2.
  • the position candidates P1 , P2 are regarded as the candidates for the calibrated position.
  • the most straight-forward method is simply selecting the position candidate P1 or the position candidate P2 according to the RSS data based on the consideration that a larger RSS value provides better reliability. If the RSS of the base station B2 is larger than that of the base station BS1 , the position candidate P2 is selected as the calibrated position, and vice versa.
  • a process flow chart for this method of determining the final calibrated position is shown in Fig. 11 .
  • S1 The distance between the position candidate P1 and the calibrated position
  • S2 the distance between position candidate P2 and the calibrated position
  • FIG. 13 A process flow chart for this method of determining the final calibrated position is shown in Fig. 13.
  • the second example embodiment is similar to the first example embodiment in configuration of the system and the internal configuration of each apparatus, the following description will be made with a focus on the difference between the first and second example embodiments.
  • the two position candidates P1 , P2 are determined as the intersection of the lines l l t l 2 and two circles C1 , C2.
  • the two position candidates P1 , P2 of a calibrated position are determined by a different procedure.
  • Fig. 9 shows the calibration process in the second example embodiment.
  • the calibration process first defines a circle C3.
  • the distance between the point of on the circle and the base station BS1 is denoted as e1 .
  • the distance between the point of on the circle and the base station BS1 is denoted as e2.
  • e1 and e2 satisfy the following equation (math. 5).
  • the intersections of the circle C3 and the line ⁇ and line l 2 are regarded as the position candidates.
  • An additional candidate selection process is needed in this example embodiment.
  • the mobile communication device MS is at a position which is in closer proximity to the base station BS1 , and therefore the received signal strength RSS1 is larger than the received signal strength RSS2.
  • the base station BS1 is within the circle C3, and the base station BS2 is outside of the circle C3.
  • the line l and the circle have one intersection, which is denoted as position candidate P1 .
  • the line l 2 and the circle C3 have two intersections, which are denoted as position candidates P2, P2'.
  • the candidate selection process is used to determine which one is selected as the candidate.
  • the angle of the intersection, i.e. , position candidate P2, with the line of the base stations BS1 , BS2 is denoted as ⁇ 1 '.
  • the angle of the intersection, i.e., position candidate P2', with the line of the base stations BS1 , BS2 is denoted as ⁇ 1 ".
  • ⁇ 1 ' is closer to the ⁇ 1 than the ⁇ 1 ", and therefore, P2 is selected as the candidate.
  • the final calibrated position can be obtained similarly to the three methods described in the first example embodiment.
  • Process flow charts for the second embodiment are shown in Figs. 14 - 16 for each final calibrated position selection method.
  • the mobile communication device MS is, typically but not necessarily, a large object with multiple antennas and sufficient computation capability, such as a device mounted on a car, a drone, or the like.
  • the third example embodiment is similar to the first example embodiment and the second example embodiment in the respective internal configurations of each apparatus and in the calibration calculation method, the following description will be made with a focus on the differences of the third example embodiment.
  • Fig.10 shows the block diagram of the third example embodiment.
  • the base stations BS1 , BS2 contain the communication unit 130 which is used to communicate with the mobile communication device MS through wireless signals.
  • the mobile communication device MS contains a communication unit 130 which is used to communicate with the base stations through wireless signals.
  • the angle calculation unit 142 is used to calculate the AoA a1 , a2 of wireless signals from the BSs.
  • the RSS detection unit is used to detect the received signal strength of the wireless signals from the base stations.
  • the position calculation unit 146 is used to calculate the position of the mobile communication device MS based on the information from angle calculation unit 142.
  • the calibration determination unit 148 is used to determine whether to provide calibration or not.
  • the calibration calculation unit 149 is used to finish the calibration calculation.
  • the calibration processing is completed in the mobile communication device MS.
  • the benefit is that the base station can use conventional base stations, and only the mobile communication device MS needs the corresponding hardware or software.
  • Fig. 17 and Fig. 18 are used to demonstrate that the proposed method is valid through simulation.
  • the locations of two base stations were fixed, and the location of a mobile communication device MS was changed randomly.
  • Fig. 17 shows the locations of the two base stations, which are denoted as circles, and the location distribution of the mobile station is shown as inverted triangles.
  • the y-axis is the y coordinate in the plane, and the x-axis is the x coordinate in the plane.
  • the distance between BS1 and BS2 was 500 meters.
  • the locations of the mobile station were such that the AoDs were less than 5 degrees.
  • Fig. 18 shows the summary of the simulation results, which are cumulative distribution function (CDF) curves of the 1000 rounds of simulation.
  • the y-axis is the probability that the position estimation error is less than the value on the x-axis after 1000 rounds of simulation.
  • the x axis is the position estimation error between the estimated position and the actual position with base 10 logarithm.
  • the solid line is the position estimation error of the estimation with calibration.
  • the dashed line is the position estimation error of the estimation without calibration. As the figure shows, in 90% of the rounds of simulation, the estimation achieves about 20m position estimation error with the proposed calibration method, while the position estimation error is about 300m without calibration.
  • the pre-defined threshold (of the AoDs) used to determine whether or not to calculate position candidates for a calibrated position was described as being 5 degrees, but should not be considered as limited thereto and may be higher or lower depending on design requirements or the like.
  • MS mobile station mobile communication device

Abstract

A position estimation apparatus included in a wireless communication system having a mobile communication device configured to communicate with first and second base stations configured to calculate a received signal strength and an angle of arrival of a wireless signal from the mobile communication device comprises a position estimation unit configured to determine a calibrated position of the mobile communication device by using the received signal strength and the angle of arrival at each of the first and second base stations.

Description

,
DESCRIPTION
TITLE OF INVENTION
POSITION ESTIMATION APPARATUS
TECHNICAL FIELD
[0001 ]
The present invention relates to a position estimation apparatus, a computer-implemented position estimation method, and a computer readable storage medium, and more particularly to a position estimation apparatus which detects the position of a mobile communication device, i.e. , a mobile station (MS), based on wireless signals received by a base station.
BACKGROUND ART
[0002]
Location based services (LBS) have become popular in our daily life, such as global positioning systems (GPS) in vehicles or mobile phones. The current trend in the development of LBS technology is to achieve a high positioning accuracy in which the error of a positioning estimation is within a few meters or even centimeters and also to achieve full coverage such that the positioning estimation will work in both indoor and outdoor environments.
[0003] Existing systems encounter difficulties in providing full coverage for position estimation. GPS does not work well for indoor environments since it is difficult for a mobile device to receive satellite signals while in a building, underground, in a tunnel, or the like. On the other hand, WiFi or Bluetooth based systems are limited to small areas. Positioning technology utilizing cellular systems is a promising solution to providing full coverage due to the widespread deployment of base stations and mobile communication devices that can communicate with base stations almost anywhere.
[0004]
In cellular systems, both time based positioning and angle based positioning are possible methods. The accuracy of time based methods, especially observed time difference of arrival (OTDOA) methods, is limited by the smallest unit of time, and synchronization in the network, e.g. , in the current 4G cellular system the smallest unit of time is 32ns resulting in an uncertainty of about 10m as described in NPL 1 . Moreover, OTDOA methods need special measurements, which require frequency resources and cost time. Namely, OTDOA methods influence the efficiency of ordinary communication. On the other hand, in angle based positioning, especially angle of arrival (AoA) or direction of arrival (DoA) based positioning which uses only the communication signals themselves, accuracy is not limited by the smallest unit of time and synchronization, but by the angle detection accuracy.
[0005] Modern cellular systems are evolving towards the fifth generation known as the 5G cellular system. 5G cellular systems will provide much higher throughput by adopting a much higher frequency band than the current 4G cellular system. Since the intervals between the antennas deployed in a cellular system are inversely proportional to the frequency, it is possible to integrate more antennas into devices using the 5G cellular system. As a result, in order to guarantee communication quality at sufficient range, both the base stations and the mobile communication devices in the 5G cellular system will employ many more antennas than before. For example, 256 antennas for base stations and 8 antennas for mobile communication devices are being considered, as described in NPL 2, by the standardization organization, 3rd Generation Partnership Project (3GPP). The larger antenna number of 5G systems makes it possible to detect a more accurate AoA.
[0006]
Generally, in AoA based positioning, the angles between a mobile communication device and two base stations can be used to determine the position of the mobile communication device in a two dimensional plane.
[0007]
Fig. 1 shows the basic process of AoA based positioning. Base stations BS1 and BS2 receive the wireless signals from a mobile communication device, and calculate the AoAs, a1 and a2 (corresponding to base stations BS1 and BS2 respectively) using a conventional algorithm , such as the multiple signal classification (MUSIC) algorithm . Ideally, the AoAs are perfectly calculated , and corresponding lines lt and the line l2 are obtained . The intersection of the line l and the line l2 is the estimated position of the MS. However, in real world applications, the AoA calculation has uncertainty. That is to say, a valid estimation of the line lt is between l and Ιΐ' , and a valid estimation of the line l2 is between 12' and l2 . As a result, valid estimated positions are within the intersection area marked in gray.
[0008]
The AoA based positioning would be affected by what is known as dilution of precision (DoP) in some situations.
[0009]
N PL 3 discusses DoP in terms of a G PS system . Such a problem similarly applies to AoA positioning using a cellular system . Fig. 2 shows the basic concept of the DoP in AoA positioning. When the mobile communication device is near the line connecting the two base stations, the intersection area becomes narrow and long, which is shown in the gray area in Fig.2. In this situation, although the AoA calculation uncertainty remains the same as the situation shown in Fig. 1 , it is possible that the distance between the estimated position and the actual position of a mobile communication device is much larger than the distance in Fig. 1 . This phenomenon in which the positioning error is very large is the DoP in AoA positioning.
[001 0] The conventional solution to DoP in AoA positioning is introducing additional base stations for calibration. For example, the AoA calculation from another base station BS3 can be used as calibration for the DoP. Fig. 3 shows the calibration process with an additional base station BS3. With the AoA calculation from BS3, the line i3 and l' restrict the intersection area into a much smaller area than the situation in Fig. 2. Thus, the possible estimated position is restricted to a smaller intersection area, and the positioning error is reduced.
[0011 ]
Conventional techniques, such as those described in PL1 and PL2, have been used to estimate the position of a mobile device. However, these techniques do not recognize the problem that arises in certain situations where dilution of precision is an issue. Therefore, a technique that addresses such a problem has been needed.
Citation List
[0012]
[Non Patent Literature]
[NPL 1 ]
S. Fischer, "Observed time difference of arrival (OTDOA) positioning in 3GPP LTE," Qualcomm White Pap, vol. 1 , no. 1 , pp. 1-62, Jun 2014. [NPL 2]
3GPP, "Study on New Radio (NR) Access Technology Physical Layer Aspects," 3GPP, TR 38802, Oct 2016. [NPL 3]
Richard B. Langley, "Dilution of Precision", GPS World, pp. 52-59, May 1999
[Patent Literature]
[0013]
[PL1 ]
European Patent EP1330136A1 , "Method of Cell Initial Search in
CDMA Digital Mobile Telecommunication System" He et al.
[PL2]
US Patent Application 2009/0176507A, "Systems and Methods for Location Positioning Within Radio Access Systems" Wu et al.
DISCLOSURE OF INVENTION
Problem to be Solved by the Invention
[0014]
The conventional calibration method for DoP requires that there are at least three base stations and additional base stations BS are deployed in proper positions. In the actual deployment of cellular systems, the location of deployment of the base stations BS depends on many factors, including the coverage of the communication area, communication quality, setup difficulty, operation costs, and the like. That is to say, positioning is not the most important factor in deploying the base stations, which requires that the positioning technology using a cellular system can deal with various situations according to actual base station deployment. However, in real-world deployment, this requirement cannot always be satisfied, and conventional calibration methods do not always work well.
[0015]
Fig. 4 shows a problematic situation in which the conventional calibration method is used. In this case, the mobile communication device is near the base stations BS1 and BS2, and the base station BS3 is very far away. Since base station BS3 is far away, the range of line 13' and l3 covers the entirety of the intersection area. Because of this, it cannot provide a calibration effect. That is to say, although there are 3 base stations, only two base stations are available for detecting the position of mobile communication device.
[0016]
Fig. 5 shows another problematic situation in which the conventional calibration method is used. In this case, the base station BS3 is not far away, but the base stations BS1 , BS2, and BS3 are mounted on street lamps in a line, for example, along a street. If the mobile communication device is in the intersection area marked in gray, the AoA al , a2 calculation from the base station BS3 cannot be used for calibration, since the range of line i3 and l3 covers the entirety of the intersection area. In particular, although there are three base stations, only two base stations are available for detecting the position of the mobile communication device when the mobile communication device is at particular positions.
[0017]
In the above mentioned cases, the common feature is that only two base stations are available and additional base stations cannot provide calibration. Thus, a calibration method with only two base stations is needed for these base station deployments under a cellular system.
Means for Solving the Problem
[0018]
In the case of two base stations, the two base stations receive a wireless signal from a mobile communication device. The received signal strength (RSS) and AoA a1 , a2 are used to generate the position candidate for each base station. The final estimated position is produced using the position candidates.
[0019]
As a first aspect of the present invention, a position estimation apparatus is provided which is included in a wireless communication system having a mobile communication device configured to communicate with first and second base stations configured to calculate a received signal strength and an angle of arrival of a wireless signal from the mobile communication device, including: a position estimation unit configured to determine a calibrated position of the mobile communication device by using the received signal strength and the angle of arrival at each of the first and second base stations.
In a second aspect of the present invention in accordance with the first aspect, position candidates are calculated when angles of deviation of the wireless signal from the mobile communication device are less than a predefined threshold, and the position candidates are used to determine the calibrated position of the mobile communication device.
In a third aspect of the present invention in accordance with the first aspect, an imaginary circle is centered at each of the first and second base stations, the respective radius of each imaginary circle are calculated based on the received signal strengths of the first and second base stations and a distance between the first and second base stations, and the imaginary circles are used to determine position candidates of the mobile communication device.
In a fourth aspect of the present invention in accordance with the third aspect, the position candidates are on the respective imaginary circles of the first and second base stations at the respective angles of arrival from each of the first and second base stations.
In a fifth aspect of the present invention in accordance with the third aspect, the calibrated position of the mobile communication device is determined as a point between the position candidates calculated according to a ratio of the received signal strengths from the first and second base stations.
In a sixth aspect of the present invention in accordance with the first aspect, an imaginary circle is used to determine position candidates of the mobile communication device, the imaginary circle being defined so that a first distance between any point on the imaginary circle and the first base station, and a second distance between the point on the imaginary circle and the second base station, are in accordance with the ratio between the received signal strengths of the first and second base stations.
In a seventh aspect of the present invention in accordance with the sixth aspect, the first base station has a received signal strength that is greater than the received signal strength of the second base station, and one of the position candidates is on the imaginary circle and in the direction of the angle of arrival at the first base station.
In an eighth aspect of the present invention in accordance with the sixth aspect, the second base station has a received signal strength that is less than the received signal strength of the first base station, two points on the imaginary circle are in the direction of the angle of arrival from the second base station, and one of the position candidates for the calibrated position is determined to be one of the two points that has an angle from the first base station that is closer to the angle of arrival at the first base station.
As a ninth aspect of the present invention, a computer-implemented position estimation method is provided for a wireless communication system having a mobile communication device configured to communicate with first and second base stations configured to calculate a received signal strength and an angle of arrival of a wireless signal from the mobile communication device, including: determining a calibrated position of the mobile communication device from the received signal strength and the angle of arrival.
In an tenth aspect of the present invention in accordance with the ninth aspect, position candidates are calculated when angles of deviation of the wireless signal from the mobile communication device are less than a predefined threshold, and the position candidates are used to determine the calibrated position of the mobile communication device
In an eleventh aspect of the present invention in accordance with the ninth aspect, an imaginary circle is centered at each of the first and second base stations, the respective radius of each imaginary circle are calculated based on the received signal strengths of the first and second base stations and a distance between the first and second base stations, and the imaginary circles are used to determine position candidates of the mobile communication device.
In a twelfth aspect of the present invention in accordance with the eleventh aspect, the position candidates are on the respective imaginary circles of the first and second base stations at the respective angles of arrival from each of the first and second base stations
In a thirteenth aspect of the present invention in accordance with the eleventh aspect, the calibrated position of the mobile communication device is determined as a point between the position candidates calculated according to a ratio of the received signal strengths from the first and second base stations.
In a fourteenth aspect of the present invention in accordance with the ninth aspect, an imaginary circle is used to determine position candidates of the mobile communication device, the imaginary circle being defined so that a first distance between any point on the imaginary circle and the first base station, and a second distance between the point on the imaginary circle and the second base station, are in accordance with the ratio between the received signal strengths of the first and second base stations.
In a fifteenth aspect of the present invention in accordance with the eleventh aspect, the first base station has a received signal strength that is greater than the received signal strength of the second base station, and one of the position candidates is on the imaginary circle and in the direction of the angle of arrival at the first base station.
In a sixteenth aspect of the present invention in accordance with the eleventh aspect, the second base station has a received signal strength that is less than the received signal strength of the first base station, two points on the imaginary circle are in the direction of the angle of arrival from the second base station, and one of the position candidates for the calibrated position is determined to be one of the two points that has an angle from the first base station that is closer to the angle of arrival at the first base station.
As a seventeenth aspect of the present invention, a non-transitory computer readable storage medium containing instructions to make a computer perform a position estimation method for a wireless communication system having a mobile communication device configured to communicate with first and second base stations configured to calculate a received signal strength and an angle of arrival of a wireless signal from the mobile communication device, including: determining a calibrated position of the mobile communication device from the received signal strength and the angle of arrival.
Advantageous Effects of the Invention
The present invention provides a position estimation apparatus included in a wireless communication system in which the accuracy of estimating a position of the mobile communication device is improved, even when estimating using only two base stations.
BRIEF DESCRIPTION OF DRAWINGS
[0020]
Fig. 1 illustrates a conventional method for position estimation using AoA positioning.
Fig. 2 illustrates the concept of DoP in AoA positioning.
Fig. 3 illustrates the conventional solution to DoP.
Fig. 4 illustrates a first problematic situation for the conventional technique.
Fig. 5 illustrates a second problematic situation for the conventional technique.
Fig. 6 is a block diagram of a first example embodiment Fig. 7 is a process flow chart of the first example embodiment Fig. 8 illustrates a calibration example of the first example embodiment
Fig. 9 illustrates a calibration example of a second example embodiment
Fig. 10 is a block diagram of a third example embodiment
Fig. 11 is a process flow chart of the first example embodiment in the first example embodiment.
Fig. 12 is an alternative process flow chart for determining a calibrated position in the first example embodiment.
Fig. 13 is another alternative process flow chart for determining a calibrated position in the first example embodiment.
Fig. 14 is a process flow chart for the third example embodiment.
Fig. 15 is an alternate process flow chart for the third example embodiment.
Fig. 16 is another alternate process flow chart for the third example embodiment.
Fig. 17 is a graph showing the results of a simulation of the first embodiment.
Fig. 18 is a graph showing a comparison of simulated results between the first embodiment and the conventional method.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
[0021 ] <First example embodiment
A first example embodiment of the present invention will be described in detail below with reference to the drawings.
[0022]
Fig. 6 shows the block diagram of the proposed apparatus for estimating the position of a mobile communication device MS. The base stations BS1 , BS2 have the same structure, each of which contains a first communication unit 130a, an angle calculation unit 142, and a second communication unit 130b.
[0023]
The first communication unit 130a is used to communicate with the mobile communication device MS through wireless signals. The angle calculation unit 142 is used to calculate the AoA a1 , a2 of wireless signals from the mobile communication device MS. The RSS detection unit 144 is used to detect the RSS of the wireless signals from the mobile communication device MS. The second communication unit 130b is used to communicate with a position calculation unit 146.
[0024]
A position calculation entity is tasked with determining the position of the mobile communication device MS. The position calculation entity PCE includes the position calculation unit 146, a calibration determination unit 148, and a calibration calculation unit 149. The position calculation unit 146 is used to calculate the position of the mobile communication device MS based on information from the base stations. The calibration determination unit 148 is used to determine whether or not to perform calibration. The calibration calculation unit 149 is used to complete the calibration calculation. The position calculation entity PCE can be deployed in the base stations BS1 , BS2 or in an independent server.
[0025]
Fig. 7 shows the processing flow of proposed calibration method. After receiving the wireless signals from the mobile communication device MS, the base stations BS1 , BS2 calculate the AoAs a1 , a2 and angles of deviation (AoDs) β ΐ , β2. The AoD βΐ , β2 is an angle between the estimated line /-ι , I2 from the base station and the line between the base stations B1 , B2. Since the positions of the base stations B1 , B2 are fixed, the angle between the base stations B1 , B2 and the exact distance between the base stations is known in advance. Such information with respect to the angle/distance of surrounding base stations may be stored in, for example, the base stations themselves or in a server. If the value of the AoDs β ΐ, β2 are less than a predefined threshold, the calibration process is conducted. Otherwise, the position calculation entity PCE determines the position of mobile communication device MS without calibration . In the calibration process, each of the base stations BS1 , BS2 detect the RSS. The position calculation entity PCE uses the RSS data for calibration calculation.
[0026]
The calibration calculation process is illustrated in Fig. 8. The angle between the estimated line l from the base station BS 1 and the line connecting the base stations BS 1 , BS2 is denoted as β1. The angle between the estimated line l2 from BS2 and the line connecting the base stations BS 1 , BS2 is denoted as β2. If both β1 and β2 are less than the predefined threshold , e.g. , 5 degrees, the calibration process is conducted . The calibration process firstly defines two imaginary circles to be used for calculation. The base station BS 1 is the center of a first imaginary circle C1 , and the base station BS2 is the center of a second imaginary circle C2. The radiuses r and r2 of the two circles C1 and C2, respectively, are calculated using the equations of Math. 1 and Math . 2.
[0027]
Figure imgf000018_0001
[Math. 2] r + r2
Figure imgf000018_0002
[0028]
d in the above equations (Math. 2 and 3) represents the distance between the base stations BS1 , BS2. The purpose of defining the two imaginary circles C1 , C2 is to find the possible range of the mobile communication device MS with the RSS data.
[0029]
The intersection of the circle C1 and the estimated line lx is denoted as position candidate P1 . The intersection of the circle C1 and the estimated line l2 is denoted as position candidate P2. The position candidates P1 , P2 are regarded as the candidates for the calibrated position.
[0030]
There are a various methods to determine the final calibrated position. The most straight-forward method is simply selecting the position candidate P1 or the position candidate P2 according to the RSS data based on the consideration that a larger RSS value provides better reliability. If the RSS of the base station B2 is larger than that of the base station BS1 , the position candidate P2 is selected as the calibrated position, and vice versa. A process flow chart for this method of determining the final calibrated position is shown in Fig. 11 .
[0031 ]
An alternative to simply choosing either position candidate P1 or position candidate P2 as the estimated position of the mobile communication device MS is to set the midpoint of the position candidates P1 , P2 as the calibrated position, in order to utilize information from both base stations in the calibrated position. A process flow chart for this method of determining the final calibrated position is shown in Fig. 12.
[0032]
Another possible alternative is to calculate the calibrated position at a line between the position candidates P1 , P2. The distance between the position candidate P1 and the calibrated position is denoted as S1 in the following equation, and the distance between position candidate P2 and the calibrated position is denoted as S2. Based on the consideration that a larger RSS provides better reliability, S1 and S2 satisfy the equation (Math. 4).
[0033]
[ 1Math. 4] J-S2 = ^ RS½S1
A process flow chart for this method of determining the final calibrated position is shown in Fig. 13.
[0034]
It is noteworthy that the positioning in a 2-dimensional plane is discussed in the above description. Actually, the proposed calibration method can be easily extended to the positioning in a 3-dimensional space.
[0035]
<Second example embodiment
A second example embodiment will be described in detail.
Since the second example embodiment is similar to the first example embodiment in configuration of the system and the internal configuration of each apparatus, the following description will be made with a focus on the difference between the first and second example embodiments.
[0036]
In the first example embodiment, the two position candidates P1 , P2 are determined as the intersection of the lines ll t l2 and two circles C1 , C2. In the second example embodiment, the two position candidates P1 , P2 of a calibrated position are determined by a different procedure.
[0037]
Fig. 9 shows the calibration process in the second example embodiment. The calibration process first defines a circle C3. The distance between the point of on the circle and the base station BS1 is denoted as e1 . The distance between the point of on the circle and the base station BS1 is denoted as e2. e1 and e2 satisfy the following equation (math. 5).
[0038]
[Math. 5] = ^
Hereinafter, assuming a two dimensional space configured by x- and y-coordinates by denoting the coordinates of any point on the circle C3 as (x, y), the coordinates of base station BS1 and base station BS2 as (xi , y-i ) and (X2 , i), respectively, and introducing a constant k=RSS2IRSS Math. 5 is derived to Math. 6.
[Math. 6] ( Xl yi = k
Further, deriving Math. 6 will yield a standard circle representation in Math 7.
[Math. 7] (x - ¾ )2 + (y - ¾ )2 = ^- ^-y^2)
[0039]
The intersections of the circle C3 and the line ^ and line l2 are regarded as the position candidates. An additional candidate selection process is needed in this example embodiment. In the example shown in Fig. 9, the mobile communication device MS is at a position which is in closer proximity to the base station BS1 , and therefore the received signal strength RSS1 is larger than the received signal strength RSS2. The base station BS1 is within the circle C3, and the base station BS2 is outside of the circle C3. The line l and the circle have one intersection, which is denoted as position candidate P1 . The line l2 and the circle C3 have two intersections, which are denoted as position candidates P2, P2'. The candidate selection process is used to determine which one is selected as the candidate.
[0040]
The angle of the intersection, i.e. , position candidate P2, with the line of the base stations BS1 , BS2 is denoted as β1 '. The angle of the intersection, i.e., position candidate P2', with the line of the base stations BS1 , BS2 is denoted as β1 ". β1 ' is closer to the β1 than the β1 ", and therefore, P2 is selected as the candidate.
[0041 ]
After the calibrated position candidates P1 , P2 are calculated, the final calibrated position can be obtained similarly to the three methods described in the first example embodiment. Process flow charts for the second embodiment are shown in Figs. 14 - 16 for each final calibrated position selection method.
[0042]
It is noteworthy that the positioning in a 2-dimensional plane is discussed in the above description. However, the proposed calibration method can be easily extended to positioning in a 3-dimensional space, and should not be considered as being limited to a 2-dimensional plane.
[0043]
<Third example embodiment
This example embodiment is based on the consideration that the mobile communication device MS is, typically but not necessarily, a large object with multiple antennas and sufficient computation capability, such as a device mounted on a car, a drone, or the like.
[0044]
The third example embodiment will be described in detail.
Since the third example embodiment is similar to the first example embodiment and the second example embodiment in the respective internal configurations of each apparatus and in the calibration calculation method, the following description will be made with a focus on the differences of the third example embodiment.
Fig.10 shows the block diagram of the third example embodiment. The base stations BS1 , BS2 contain the communication unit 130 which is used to communicate with the mobile communication device MS through wireless signals.
[0045]
The mobile communication device MS contains a communication unit 130 which is used to communicate with the base stations through wireless signals.
The angle calculation unit 142 is used to calculate the AoA a1 , a2 of wireless signals from the BSs. [0046]
The RSS detection unit is used to detect the received signal strength of the wireless signals from the base stations.
[0047]
The position calculation unit 146 is used to calculate the position of the mobile communication device MS based on the information from angle calculation unit 142. The calibration determination unit 148 is used to determine whether to provide calibration or not. The calibration calculation unit 149 is used to finish the calibration calculation.
[0048]
Compared with the first example embodiment, the calibration processing is completed in the mobile communication device MS. The benefit is that the base station can use conventional base stations, and only the mobile communication device MS needs the corresponding hardware or software.
[0049]
Fig. 17 and Fig. 18 are used to demonstrate that the proposed method is valid through simulation. In 1000 rounds of simulation, the locations of two base stations were fixed, and the location of a mobile communication device MS was changed randomly. Fig. 17 shows the locations of the two base stations, which are denoted as circles, and the location distribution of the mobile station is shown as inverted triangles. The y-axis is the y coordinate in the plane, and the x-axis is the x coordinate in the plane. The distance between BS1 and BS2 was 500 meters. The locations of the mobile station were such that the AoDs were less than 5 degrees.
Fig. 18 shows the summary of the simulation results, which are cumulative distribution function (CDF) curves of the 1000 rounds of simulation. The y-axis is the probability that the position estimation error is less than the value on the x-axis after 1000 rounds of simulation. The x axis is the position estimation error between the estimated position and the actual position with base 10 logarithm. The solid line is the position estimation error of the estimation with calibration. The dashed line is the position estimation error of the estimation without calibration. As the figure shows, in 90% of the rounds of simulation, the estimation achieves about 20m position estimation error with the proposed calibration method, while the position estimation error is about 300m without calibration.
[0050]
While the preferred example embodiments of the present invention have been described, it is to be understood that the present invention is not limited to the example embodiments above and that further modifications, replacements, and adjustments may be added without departing from the basic technical concept of the present invention.
For example, the pre-defined threshold (of the AoDs) used to determine whether or not to calculate position candidates for a calibrated position was described as being 5 degrees, but should not be considered as limited thereto and may be higher or lower depending on design requirements or the like.
[0051 ]
The cited references given above are hereby incorporated by reference into this specification. The example embodiments may be changed and adjusted while remaining within the scope of the entire disclosure (including claims) of the present invention and based on the basic technological concept. In the scope of the claims of the present invention, various disclosed elements may be combined and selected in a variety of ways. That is, it is to be understood that modifications and changes that may be made by those skilled in the art within the scope of the present invention are included.
Reference Symbols List
[0052]
RSS received signal strength
AoA angle of arrival
BS1 , BS2 base station
MS mobile station (mobile communication device)
I, Γ, I", I2, I2', I2" line
130 communication unit
130a first communication unit
130b second communication unit
142 angle calculation unit
144 RSS detection unit PCE position calculation entity
146 position calculation unit
148 calibration determination unit
149 calibration calculation unit
C1 first imaginary circle
C2 second imaginary
C3 third imaginary circle
r1 , r2 radius
P1 , P2 position candidate
S1 distance between position candidate P1 and the calibrated position
S2 distance between position candidate P2 and the calibrated position
C3 third imaginary circle
e1 distance between a point of on the circle C3 and the base station BS1
e2 distance between a point of on the circle C3 and the base station BS2

Claims

[Claim 1 ]
A position estimation apparatus included in a wireless communication system having a mobile communication device configured to communicate with first and second base stations configured to calculate a received signal strength and an angle of arrival of a wireless signal from the mobile communication device, comprising: a position estimation unit configured to determine a calibrated position of the mobile communication device by using the received signal strength and the angle of arrival at each of the first and second base stations.
[Claim 2]
The position estimation apparatus of Claim 1 , wherein
position candidates are calculated when angles of deviation of the wireless signal from the mobile communication device are less than a predefined threshold, and
the position candidates are used to determine the calibrated position of the mobile communication device.
[Claim 3]
The position estimation apparatus of Claim 1 , wherein
an imaginary circle is centered at each of the first and second base stations,
the respective radius of each imaginary circle are calculated based on the received signal strengths of the first and second base stations and a distance between the first and second base stations, and
the imaginary circles are used to determine position candidates of the mobile communication device.
[Claim 4]
The position estimation apparatus of Claim 3, wherein
the position candidates are on the respective imaginary circles of the first and second base stations at the respective angles of arrival from each of the first and second base stations.
[Claim 5]
The position estimation apparatus of Claim 3, wherein
the calibrated position of the mobile communication device is determined as a point between the position candidates calculated according to a ratio of the received signal strengths from the first and second base stations.
[Claim 6]
The position estimation apparatus of Claim 1 , wherein
an imaginary circle is used to determine position candidates of the mobile communication device, the imaginary circle being defined so that a first distance between any point on the imaginary circle and the first base station, and a second distance between the point on the imaginary circle and the second base station, are in accordance with the ratio between the received signal strengths of the first and second base stations.
[Claim 7]
The position estimation apparatus of Claim 6, wherein
the first base station has a received signal strength that is greater than the received signal strength of the second base station, and
one of the position candidates is on the imaginary circle and in the direction of the angle of arrival at the first base station.
[Claim 8]
The position estimation apparatus according to claim 6, wherein
the second base station has a received signal strength that is less than the received signal strength of the first base station,
two points on the imaginary circle are in the direction of the angle of arrival from the second base station, and
one of the position candidates for the calibrated position is determined to be one of the two points that has an angle from the first base station that is closer to the angle of arrival at the first base station.
[Claim 9]
A computer-implemented position estimation method for a wireless communication system having a mobile communication device configured to communicate with first and second base stations configured to calculate a received signal strength and an angle of arrival of a wireless signal from the mobile communication device, comprising:
determining a calibrated position of the mobile communication device from the received signal strength and the angle of arrival.
[Claim 10]
The computer-implemented position estimation method of Claim 9, wherein
position candidates are calculated when angles of deviation of the wireless signal from the mobile communication device are less than a predefined threshold, and
the position candidates are used to determine the calibrated position of the mobile communication device
[Claim 11 ]
The computer-implemented position estimation method of Claim 9, wherein
an imaginary circle is centered at each of the first and second base stations,
the respective radius of each imaginary circle are calculated based on the received signal strengths of the first and second base stations and a distance between the first and second base stations, and
the imaginary circles are used to determine position candidates of the mobile communication device.
[Claim 12]
The computer-implemented position estimation method of Claim 11 , wherein
the position candidates are on the respective imaginary circles of the first and second base stations at the respective angles of arrival from each of the first and second base stations
[Claim 13]
The computer-implemented position estimation method of Claim 11 , wherein
the calibrated position of the mobile communication device is determined as a point between the position candidates calculated according to a ratio of the received signal strengths from the first and second base stations.
[Claim 14]
The computer-implemented position estimation method of Claim 9, wherein
an imaginary circle is used to determine position candidates of the mobile communication device, the imaginary circle being defined so that a first distance between any point on the imaginary circle and the first base station, and a second distance between the point on the imaginary circle and the second base station, are in accordance with the ratio between the received signal strengths of the first and second base stations.
[Claim 15]
The computer-implemented position estimation method of Claim 11 , wherein
the first base station has a received signal strength that is greater than the received signal strength of the second base station, and
one of the position candidates is on the imaginary circle and in the direction of the angle of arrival at the first base station. [Claim 16]
The computer-implemented position estimation method of Claim 11 , wherein
the second base station has a received signal strength that is less than the received signal strength of the first base station,
two points on the imaginary circle are in the direction of the angle of arrival from the second base station, and
one of the position candidates for the calibrated position is determined to be one of the two points that has an angle from the first base station that is closer to the angle of arrival at the first base station. [Claim 17]
A non-transitory computer readable storage medium containing instructions to make a computer perform a position estimation method for a wireless communication system having a mobile communication device configured to communicate with first and second base stations configured to calculate a received signal strength and an angle of arrival of a wireless signal from the mobile communication device, comprising:
determining a calibrated position of the mobile communication device from the received signal strength and the angle of arrival.
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