WO2011069552A1 - Method, arrangement and computer program product for clocking - Google Patents

Method, arrangement and computer program product for clocking Download PDF

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Publication number
WO2011069552A1
WO2011069552A1 PCT/EP2009/066858 EP2009066858W WO2011069552A1 WO 2011069552 A1 WO2011069552 A1 WO 2011069552A1 EP 2009066858 W EP2009066858 W EP 2009066858W WO 2011069552 A1 WO2011069552 A1 WO 2011069552A1
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WO
WIPO (PCT)
Prior art keywords
signal
user
time
arrival
time difference
Prior art date
Application number
PCT/EP2009/066858
Other languages
English (en)
French (fr)
Inventor
David Bevan
Simon Gale
Original Assignee
Nortel Networks Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nortel Networks Limited filed Critical Nortel Networks Limited
Priority to PCT/EP2009/066858 priority Critical patent/WO2011069552A1/en
Priority to KR1020127015791A priority patent/KR20120092156A/ko
Priority to EP10704912A priority patent/EP2510376A1/en
Priority to CN201080055565XA priority patent/CN102762999A/zh
Priority to JP2012542404A priority patent/JP2013513786A/ja
Priority to CA2782855A priority patent/CA2782855A1/en
Priority to US13/513,875 priority patent/US8818406B2/en
Priority to RU2012125038/07A priority patent/RU2510039C2/ru
Priority to BR112012013785A priority patent/BR112012013785A2/pt
Priority to PCT/EP2010/050747 priority patent/WO2011069684A1/en
Publication of WO2011069552A1 publication Critical patent/WO2011069552A1/en
Priority to US14/338,419 priority patent/US20140364142A1/en

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO 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
    • G01S5/00Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02Position-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
    • G01S5/06Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO 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
    • G01S5/00Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02Position-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
    • G01S5/0205Details
    • G01S5/021Calibration, monitoring or correction
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L7/00Arrangements for synchronising receiver with transmitter
    • H04L7/0054Detection of the synchronisation error by features other than the received signal transition
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W24/00Supervisory, monitoring or testing arrangements
    • H04W24/08Testing, supervising or monitoring using real traffic
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04WWIRELESS COMMUNICATION NETWORKS
    • H04W64/00Locating users or terminals or network equipment for network management purposes, e.g. mobility management
    • H04W64/003Locating users or terminals or network equipment for network management purposes, e.g. mobility management locating network equipment

Definitions

  • the present invention relates to wireless mobile networks or access points of a wireless local network having mobile user location functions, associated methods and computer program products.
  • the difference in time it takes for the signal to reach each tower of a base station can be used to triangulate the position of the mobile unit.
  • TDOA systems do not need any specialized antennas and as such the infrastructure is kept simple.
  • the arrival time of the target mobile signal is recorded by a TDOA location measuring unit at each base station or access point which is able to receive the signal. Since the mobile's signal travels at a constant speed (the speed of light), comparison of the arrival time of the signal for any two sides allows a
  • the method according to the present invention exploits the fact that base stations of a wireless mobile network or access points of a wireless local network are located at known positions and thus are situated in a fixed positional relationship. This allows to calculate signal propagation delays of beacon signals transmitted amongst those stations and received individually. These are calculated based on the known signal propagation speed and the respective distance between the stations.
  • determining the time difference of arrival allows determination of the relation of local clocks of two individual receiving stations to each other and requires no absolute values.
  • a relative clock behavior of pairs of individual receiving stations can be modeled and exploited together with the absolute known time difference of arrival to calculate a correction value for a signal received from a mobile device of a user by the respective base stations or wireless access points to correct the corresponding time difference of arrival for the user signal. Consequently, the method according to the present invention solves the problem of the present invention with using no additional hardware only by relating suitable calculations of suitable measurements at the access points respectively base stations.
  • the signals are transmitted wirelessly over the air, which advantageously allows for a very simple infrastructure as no cables and wires need to be deployed.
  • the signal is embodied as a beacon signal, because this allows using normal wireless access points or base stations which already transmit beacon signals to be used in the context of the present invention.
  • a signal is a frame, as frames by nature provide the advantage to possess a unique identification property in their frame number and thus further ease the implementation of the method of the present invention in presently used transmission systems.
  • the frame can be embodied as a frame according to a local area network protocol such as the IEEE 802.1 1 standard, as in this manner standards can be easily adapted by the present invention and commonly used transmission standards are suitable for incorporation in the method according to the present invention.
  • a local area network protocol such as the IEEE 802.1 1 standard
  • a polynomial with least squares may be used because such a polynomial is simple in its mathematical structure while at the same time satisfying the descriptive needs of the dependency of two clocks according to the method of the present invention without sacrificing any accuracy in the modeling process.
  • At least one signal is being transmitted before the arbitrary point in time and one is being transmitted after the arbitrary point in time in order to improve the accuracy of the clocking at the arbitrary point in time according to the method of the present invention.
  • the timing difference of arrival at a different pair of receiving stations is used to be able to accurately determine the location of a mobile station by a method of time difference of arrival based location determination. This allows the determination of two hyperbolas and their corresponding intersection point as the location of the mobile device.
  • the present invention provides an arrangement for clocking comprising:
  • the first device having transmitting means for transmitting at least a first and a second signal with a unique identification
  • the second and third devices having receiving means and a clock for receiving the at least first and second signals and processing means for associating a respective measured second and third local clock at the reception time of the respective signal to it, leading to at least two value pairs of local clocks of the second and third device;
  • the second and third device further being adapted to receiving at an arbitrary point in time a user signal from a user device at the second and third device and associating a reception time measured by the respective second and third local clock of the second and third device to the user signal upon its reception, leading to a user value pair of local clocks of the second and third device,
  • - processing means for calculating a reference time difference of arrival RTDOA for a signal from the first device received at the second and third device from the fixed positional relationship, based on the respective distance between the first and the second device and the first and the third device and the known signal propagation speed; and for calculating a user time difference of arrival UTDOA from the user value pair;
  • processing means is adapted to relate the RTDOA and DTDOA to determine a current correction factor
  • the arrangement according to the present invention comprises a minimum number of receiving devices to achieve the clocking according to the present invention which provides a simple infrastructure in a competitive manner capable to solve the problem of the present invention.
  • a further development of the arrangement according to the present invention allows employing a server for the computational intensive tasks that need to be performed, which on the other hand allows a further simplification of the receiving stations, and only requires corresponding communications of the respective identification of the received signals together with their associated time information to the computation server for calculating a location of the mobile device.
  • the computer program product of the invention provides a simple means to implement the method of the present invention at respective base stations and access points by providing a means of storage and transport.
  • Fig. 1 shows a simple transmitter and receiver arrangement according to an embodiment of the present invention
  • Fig. 2 gives an example of a relative clock behaviour of two receiving stations
  • Fig. 3 shows an example of signal transmission according to an embodiment of the present invention
  • Fig. 4 shows a flow-chart explaining the estimation of a user location based on a time difference of arrival according to an embodiment of the present invention
  • Fig. 5 gives an example of a computer program product according to the present invention.
  • Fig. 6 gives an example of a device of an arrangement according to the present invention. Description of the illustrative embodiments
  • a basic configuration to embody the method of the present invention comprises or consists of three access points AP1 , AP2 and AP4.
  • these access points can be any stations that are capable of transmitting respectively receiving signals, e.g. wireless signals.
  • the potential to be a transceiver, i.e. as well a transmitter as a receiver has certain advantages in terms of not having to have separate transmitting and receiving stations and thus providing an optimum use of resources.
  • the access points may be access points of a wireless LAN, e.g. according to the IEEE Standard 802.1 1.
  • the access points may be stations that are capable of transmitting respectively receiving a signal, respectively a number of signals, especially wireless signals which can be provided with a unique identifier or at least an element that enables a signal to be identifiable as a unique signal. It is for instance conceivable that each signal has a different format and thus the unique identifier of the signal to be a unique signal is the format.
  • the station AP4 transmits a unique signal, respectively a sequence of unique signals that is/are received by stations AP2 and AP1 .
  • the respective stations AP1 and AP2 associate the unique signal with a time measured by their local clock that has been measured at the time of reception of the unique signal.
  • such an association may be performed for one, two or a plurality of unique signals in order to protocol a dependency of the local clocks of the stations AP2 and AP1 in association to a joint reception of the same individual unique signal from the station AP4.
  • these clocks are subject to a temperature drift to a clock inaccuracy drift, e.g. to a phase drift, and/or to a frequency drift of the clock, which imposes a certain inaccuracy of the clocking of the individual stations AP1 to AP4.
  • the absolute offsets and rate differences of the various clocks of the stations AP1 to AP4 may be quantified in microseconds of drift per second, or equivalently, parts per million PPM. These offsets can be accumulated or built up and maintained over long periods of many seconds or minutes when they are measured. This provides accurate measurement.
  • the accumulated offsets or any related value thereto can be stored, e.g. in an optional location engine.
  • the location engine may be implemented in the form of a server performing the calculation of the time difference of arrival at the various stations.
  • a time difference of the signal flight times between a user device (not shown), which may be implemented as a mobile device, and two or more receiving stations, for instance AP2, AP1 , and AP4 may be calculated.
  • hyperbolas marked from 2.410 to 2.480 indicate lines of constant delay differences between AP2 and AP4 whereas hyperbolas marked from 1.410 to 1 .480 mark lines of constant delay difference between stations AP1 and AP4.
  • 1 10 in the given example the user's position should be somewhere on hyperbola 120.
  • the user's position should also be somewhere on the hyperbola marked by reference sign 130. Therefore, at the intersection of hyperbolas 1 10 and 130 the user's position also indicated by reference sign 140, respectively the position of the mobile device of the user, can be identified.
  • the embodiment of the present invention exploits the fact, that the distances between the known stations AP1 to AP4 are known, as they are in a fixed positional relationship and that based on the separation distances of the stations between each other, an accurate propagation time of a correspondingly transmitted signal can be calculated by taking the distance and the propagation speed.
  • an accurate propagation time of a correspondingly transmitted signal can be calculated by taking the distance and the propagation speed.
  • the system is able to compute a correction value and thus to derive an accurate time difference of arrival at an arbitrary point in time regarding these two receiving stations. For instance, this can be achieved by relating the correct values at an arbitrary point in time to the modeled value at this point in time to calculate the current correction value.
  • Mathematical operations in this context are preferably division to relate the values and multiplication to calculate the corrected time difference of arrival for a signal received from a user device with the current correction value.
  • Such a process may be performed for any two receiving stations that are part of the configuration shown in the embodiment of Fig. 1 .
  • Fig. 2 gives an example of a clock behavior at two stations AP1 and AP2 indicated by reference sign 290.
  • the local time of the clock at station AP2 is marked by 275 and on the horizontal axis the time at station AP1 is marked by 265.
  • the triangles in the diagram indicated by reference signs 215, 220, 230, 235, 240, 245 and 255 represent the reception times of unique signals at the station AP1 respectively AP2. If the clocks at AP1 and AP2 were performing correctly and very accurately, there would be no curve connecting the triangles and they would all lie on a straight line.
  • the known propagation time of the signal based on a calculation of the signal propagation speed and the distance between respectively AP4 and AP2 and AP4 and AP1 have been subtracted from the reception times of the signal, which may be a beacon signal from AP4.
  • the locations of the station are known such a calculation can be easily performed by a skilled person.
  • the curve represented by reference sign 210 connecting the various triangles can be modeled by any suitable regression or interpolation method, e.g. by a simple polynomial.
  • other suitable modeling techniques are conceivable like value approximation by a neural network trained with the value pairs of measured local clocks.
  • Reference sign 250 indicates the time as an arbitrary point in time at which a signal from a mobile device of a user is received at the respective stations AP1 and AP2.
  • a smooth curve between measurements can be obtained by polynomial curve fit which yields a time difference between AP1 and AP2 at a user observation time.
  • a dependency of the inaccurate local clocks is for instance further explained in the configuration shown in Fig. 3.
  • a local clock of station AP2 referenced by 321 and a local clock of station AP1 referenced by 31 1 is shown.
  • a signal propagation time between AP4 and AP2 marked by reference sign T p4,2 is known based on a calculation of the distance and the propagation speed, which also holds true for the propagation time of a signal transmitted between AP4 and AP1 indicated by T p4j1 .
  • the measurements taken for a signal transmitted from station AP4 and the associated timing can for instance be transmitted to a server indicated by reference sign 380 performing the required calculations as well as a suitable modeling function such as a regression analysis of which a polynomial curve fit is one example whereas the transmission is exemplified by an arrow marked by reference sign 350.
  • a relative clock behavior may be obtained by over air measurements.
  • a propagation time correction may be performed in the following manner. It may be assumed, that there are two receiving stations AP1 and AP2 at known locations. The clocks of AP1 and AP2 are ticking in nano seconds and are not
  • AP1 time stamps a frame received from AP4 with the reading of 629, 154,927 ns
  • AP2 time stamps the same frame received from AP4 with the reading of 402,549,572 ns.
  • the fitting of a regression curve such as a polynomial curve to an observed relative AP clock behavior may be performed in the following manner.
  • a relative clock behavior is monitored over a segment of time containing n observations that span the instant when a relative timing of a user observation needs to be established.
  • n observation times which eventually need to be corrected for known propagation times of the same beacon transmissions, are indicated by T AP1J and T AP2 ,i
  • a polynomial curve may be fitted to the observed data which is, for example, a least squares fit to the observed data, e.g. in form of
  • TAP2 ao + ai TAPI + 32 (TAPI ) 2 ⁇
  • a (X T X) "1 X T Y
  • a is a column vector consisting of a 0 , a-i , and a 2
  • Y is a column vector of the n AP2 observations of T A p2,i to T A p2,n
  • X is an n x 3 matrix formed from the AP1 observations e.g.:
  • a 0 represents a fixed time offset; represents a fixed frequency offset and a 2 represents a linear frequency drift with time.
  • a second order solution is likely to be good enough giving the shape of the curve shown in Fig. 2 which is not a complicated curve.
  • Fig. 4 shows an example of a position determination process in a flow-chart according to an embodiment of the present invention.
  • each station measures its inaccurate signal arrival time against its own clock for every signal it receives.
  • the stations send the observations meaning the arrival time of the individual signal and the associated signal identification for instance to a location server which may be employed to calculate a location.
  • the server stores all measurements over a period of time, for instance for the period of some 10 th 's of a second.
  • each station receiving a suitable signal e.g. a user frame, measures the arrival time of each particular user frame, representative of a user signal using its local clock and at 430 sends the observed user signal measurement and the associated identification as well as time to the location server.
  • the server retrieves the values stored for signal transmission between the wireless stations corresponding to the wireless stations that have received the user signal and at 440 corrects the observation regarding the retrieved communication between the wireless station by subtracting the known propagation delays based on propagation speed and positional relationship, respectively known distances. Subsequently at 440 a regression analysis such as fitting a polynomial is carried out on the corrected value pairs for each pair of wireless stations which received the common intercommunication between the wireless stations. At 450 the server, for instance, uses the polynomials to estimate the clock offsets of the wireless stations at times corresponding to the time where the user signal was received.
  • a time difference of arrival for the user signal is calculated and corrected for the factor determined on the basis of the stored values from the corresponding pair of wireless stations and the calculated polynomial estimate of the clock offset.
  • the corrected time difference of arrivals information are transmitted to the location algorithm and at 470 the estimated user location is calculated by intersecting the two hyperbolas as shown in Fig. 1 but marked by reference sign 120 and 130 to determine the user location indicated by arrow 140 which is retrieved at 495. Marked by 475 such a process may be repeated to determine various user locations.
  • Fig. 5 shows an example of a computer program product according to the present invention.
  • Reference sign 500 indicates a data carrier which comprises a program code 520 representative of any of the method steps according to the present invention.
  • Such a computer program product constitutes a simple entity to transport the method of the present invention and to implement it on the transmitting and receiving stations AP1 to AP4 of the present invention in case they are equipped with a network interface or a corresponding data reader.
  • the data carrier of the present invention may be a suitable data carrier such as a magnetic- or optical medium or a hardware storage medium such as a flash storage. It may also be represented by a signal that is transmitted on a network according to a certain network protocol implemented on a wired network or on a wireless network for downloading the program code from one computer to another computer.
  • Fig. 6 shows an example of a station that may be employed in an arrangement according to the present invention.
  • Reference sign 600 indicates a wireless station e.g. an access point or any other wireless or wire bound device capable of transmitting and/ or receiving unique signals preferably identifiable by a unique identifier such as e.g. a frame number. It has an input/ output interface 610 of any kind be it mechanical electrical or user specific for data entry and display. Further the station contains a receiver 615 and a transmitter 620 for instance capable of emitting and receiving in the GSM, Bluetooth or WLAN range of frequencies, or to handle standard packet communication over wire or optical media.
  • a controller or processor 625 is capable to control the functions of the station 600 and has the power to perform the required computations.
  • a memory 630 is present which may be any optical semiconductor or magnetic device for storing communication and operation data.
  • Reference sign 635 indicates a power supply which may be a battery or a transformer connected to a wall outlet. All the internal components are connected by a suitable system bus 650 ensuring the proper operation of the station 600.
  • a computation server 380 may be equipped with one or all of the components 610, 615, 620, 625, 630 and 650 dimensioned in a corresponding manner to perform a location determination of a user device and the required communication.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Position Fixing By Use Of Radio Waves (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Electric Clocks (AREA)
PCT/EP2009/066858 2009-12-10 2009-12-10 Method, arrangement and computer program product for clocking WO2011069552A1 (en)

Priority Applications (11)

Application Number Priority Date Filing Date Title
PCT/EP2009/066858 WO2011069552A1 (en) 2009-12-10 2009-12-10 Method, arrangement and computer program product for clocking
CA2782855A CA2782855A1 (en) 2009-12-10 2010-01-22 Tdoa based positioning with calculation of correction factors for compensating the clock offsets of unsynchronized network stations
EP10704912A EP2510376A1 (en) 2009-12-10 2010-01-22 Tdoa based positioning with calculation of correction factors for compensating the clock offsets of unsynchronized network stations
CN201080055565XA CN102762999A (zh) 2009-12-10 2010-01-22 通过计算用于补偿未同步网络站时钟偏移的校正因数的基于tdoa的定位
JP2012542404A JP2013513786A (ja) 2009-12-10 2010-01-22 非同期ネットワーク局のクロックのずれを補正するための補正因子の計算を用いたtdoaに基づく位置測定方法
KR1020127015791A KR20120092156A (ko) 2009-12-10 2010-01-22 비동기 네트워크 국들의 클럭 오프셋들을 보상하기 위한 교정 팩터들의 계산에 의한 tdoa 기반 위치 결정
US13/513,875 US8818406B2 (en) 2009-12-10 2010-01-22 TDOA based positioning with calculation of correction factors for compensating the clock offsets of unsynchronized network stations
RU2012125038/07A RU2510039C2 (ru) 2009-12-10 2010-01-22 Основанное на разности времен прихода определение местоположения с вычислением корректирующих коэффициентов для компенсации смещений часов несинхронизированных сетевых станций
BR112012013785A BR112012013785A2 (pt) 2009-12-10 2010-01-22 posicionamento com base em diferença de tempo de chegada com cálculo de fatores de correção para compensar os desvios de relógio de estações de rede não sincronizadas
PCT/EP2010/050747 WO2011069684A1 (en) 2009-12-10 2010-01-22 Tdoa based positioning with calculation of correction factors for compensating the clock offsets of unsynchronized network stations
US14/338,419 US20140364142A1 (en) 2009-12-10 2014-07-23 Tdoa based positioning with calculation of correction factors for compensating the clock offsets of unsynchronized network stations

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2009/066858 WO2011069552A1 (en) 2009-12-10 2009-12-10 Method, arrangement and computer program product for clocking

Publications (1)

Publication Number Publication Date
WO2011069552A1 true WO2011069552A1 (en) 2011-06-16

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Family Applications (2)

Application Number Title Priority Date Filing Date
PCT/EP2009/066858 WO2011069552A1 (en) 2009-12-10 2009-12-10 Method, arrangement and computer program product for clocking
PCT/EP2010/050747 WO2011069684A1 (en) 2009-12-10 2010-01-22 Tdoa based positioning with calculation of correction factors for compensating the clock offsets of unsynchronized network stations

Family Applications After (1)

Application Number Title Priority Date Filing Date
PCT/EP2010/050747 WO2011069684A1 (en) 2009-12-10 2010-01-22 Tdoa based positioning with calculation of correction factors for compensating the clock offsets of unsynchronized network stations

Country Status (8)

Country Link
US (2) US8818406B2 (ru)
JP (1) JP2013513786A (ru)
KR (1) KR20120092156A (ru)
CN (1) CN102762999A (ru)
BR (1) BR112012013785A2 (ru)
CA (1) CA2782855A1 (ru)
RU (1) RU2510039C2 (ru)
WO (2) WO2011069552A1 (ru)

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US20210153156A1 (en) * 2014-03-24 2021-05-20 Imagination Technologies Limited High definition timing synchronisation function

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WO2011069552A1 (en) * 2009-12-10 2011-06-16 Nortel Networks Limited Method, arrangement and computer program product for clocking
EP2420855A1 (en) * 2010-08-20 2012-02-22 EPFL Ecole Polytechnique Fédérale de Lausanne Location system and corresponding calibration method
EP3078222A4 (en) * 2013-12-03 2017-08-23 Red Point Positioning Corporation Method and system to estimate the location of a receiving device
CN103713277B (zh) * 2013-12-19 2016-02-10 中国航天科工集团八五一一研究所 一种基于位置信息场的辐射源定位方法
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US9172424B2 (en) 2014-03-04 2015-10-27 Qualcomm Incorporated Network self-synchronization using ultra wide band (UWB) impulse radio (IR) pulse train with unique repetition rates
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FR3023964B1 (fr) 2014-07-21 2016-08-05 Legrand France Ensemble de finition pour interrupteur electrique et interrupteur electrique avec un tel ensemble de finition
WO2016011601A1 (zh) * 2014-07-22 2016-01-28 华为技术有限公司 接入点、终端及无线保真WiFi室内定位方法
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TWI715237B (zh) * 2018-11-20 2021-01-01 慧波科技有限公司 無線定位方法
CN110174641A (zh) * 2019-06-14 2019-08-27 中国科学院自动化研究所 基于时间校正的tdoa定位方法、系统、装置
US10820170B1 (en) * 2019-09-25 2020-10-27 Mapsted Corp. Time offset based synchronization in mobile device localization
US10915137B1 (en) 2019-10-11 2021-02-09 Scientific Innovations, Inc. Estimation of clock synchronization errors using time difference of arrival
KR102359205B1 (ko) 2020-06-04 2022-02-07 최옥재 TDoA기반 측위 시스템
CN113038364B (zh) * 2021-02-25 2024-05-03 王学慧 一种基于uwb技术的tdoa与ds_twr结合的井下二维定位方法
CN113311392B (zh) * 2021-06-03 2024-01-23 苏州触达信息技术有限公司 非同步网下声波定位的误差补偿方法
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CN115499907A (zh) * 2022-07-19 2022-12-20 浙江赛思电子科技有限公司 一种基于5g空口的双向高精度时间同步控制方法

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US20130137452A1 (en) 2013-05-30
RU2510039C2 (ru) 2014-03-20
BR112012013785A2 (pt) 2016-05-03
US20140364142A1 (en) 2014-12-11
US8818406B2 (en) 2014-08-26
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CA2782855A1 (en) 2011-06-16
CN102762999A (zh) 2012-10-31

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