(12) United States Patent
`Vogel et al.
`
`USOO64.98924B2
`(10) Patent No.:
`US 6,498,924 B2
`(45) Date of Patent:
`*Dec. 24, 2002
`
`(54) APPARATUS FOR MEASURING THE
`DISTANCE BETWEEN A MOBILE STATION
`AND A BASE STATION IN A MOBILE
`RADIOCOMMUNICATIONS SYSTEM
`as
`AA
`(75) Inventors; Hélène Vogel, Meylan (FR), Michel
`Galligo, Paris (FR)
`
`(73) Assignee: Alcatel, Paris (FR)
`(*) Notice:
`This patent issued on a continued pros-
`ecution application filed under 37 CFR
`1.53(d), and is subject to the twenty year
`patent term provisions of 35 U.S.C.
`154(a)(2).
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/179,389
`(22) Filed:
`Oct. 27, 1998
`(65)
`Prior Publication Data
`US 2002/0155814A1 Oct. 24, 2002
`Foreign Application Priority Data
`(30)
`Oct. 27, 1997
`(FR) ............................................ 97 13434
`(51) Int. Cl." ................................................. H04M 7/20
`(52) U.S. Cl. ....................................... 455/67.1; 455/115
`(58) Field of Search ............................... 455/67.1, 67.6,
`455/63, 65, 33.1, 440, 422, 575, 562, 456,
`423, 424, 67.3, 504-506, 272, 278.1, 296,
`553, 458, 457, 463, 115,324; 542/463,
`149, 189, 152, 34, 417, 442,386, 363,
`450, 457, 464, 465
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`5,075.863 A * 12/1991 Nagamune et al. ......... 364/561
`5,184,135 A 2/1993 Paradise
`5,271,034 A 12/1993 Abaunza ........................ 375/1
`
`2/1994 Leonard et al. ................ 375/1
`5,285,472 A
`5.488.662 A * 1/1996 Fox et al. ..................... 380/34
`RE : is: R tal
`364/561
`2
`agamune C al. . . . . . . . . .
`5,670.964 A 9/1997 Dent
`5,748,677 A
`5/1998 Kumar ....................... 375/285
`5,926,133 A * 7/1999 Green, Jr. ................... 342/363
`5,926,768 A * 7/1999 Lewiner et al. ............. 455/562
`5,953,370 A * 9/1999 Durrant et al. ............. 375/208
`5,966,401. A * 10/1999 Kumar ....................... 375/200
`5.999,124. A * 12/1999 Sheynblat ....... ... 342/357.09
`6,031,490 A
`2/2000 Forssen et al. ............. 342/457
`6,035,202 A * 2/2000 Camp, Jr. ................... 455/456
`6,052,605 A * 4/2000 Meredith et al. ........... 455/561
`6,055.281 A * 4/2000 Hendrickson et al. ...... 375/329
`FOREIGN PATENT DOCUMENTS
`
`EP
`
`O 600 796 A1
`
`6/1994
`
`* cited by examiner
`
`Primary Examiner Daniel Hunter
`ASSistant Examiner Pablo Tran
`(74) Attorney, Agent, or Firm Sughrue Mion, PLLC
`(57)
`ABSTRACT
`Apparatus for measuring the distance between a mobile
`Station and a base Station in a mobile radio-communications
`System, the apparatus including a device for determining the
`reception instant at which the mobile Station receives pre
`determined data transmitted by the base Station, the circuit
`including a correlator for correlating an in-phase component
`and a quadrature component of a modulated Signal received
`by the mobile Station respectively with an in-phase compo
`nent and a quadrature component of a reference Signal
`generated in the mobile Station and corresponding to the
`predetermined data, correlator delivering real components
`and imaginary components of correlation coefficients, and
`the apparatus being characterized in that it further includes
`a processor for using the real components and the imaginary
`components of the correlation coefficients to determine a
`complex magnitude whose phase varies continuously as a
`function of the reception instant.
`
`8 Claims, 3 Drawing Sheets
`
`
`
`FREQUENCY
`CONVERTER
`
`ANTENNA
`
`
`
`
`
`MEMORY
`
`1
`
`LG 1024
`
`

`

`U.S. Patent
`US. Patent
`
`Dec. 24, 2002
`
`Sheet 1 0f 3
`
`US 6,498,924 B2
`US 6,498,924 B2
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`U.S. Patent
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`Dec. 24, 2002
`
`Sheet 2 of 3
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`US 6,498,924 B2
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`U.S. Patent
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`Dec. 24, 2002
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`Sheet 3 of 3
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`US 6,498,924 B2
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`

`1
`APPARATUS FOR MEASURING THE
`DISTANCE BETWEEN A MOBILE STATION
`AND A BASE STATION IN A MOBILE
`RADIOCOMMUNICATIONS SYSTEM
`
`BACKGROUND OF THE INVENTION
`The present invention relates generally to mobile radio
`communications Systems.
`The present invention relates more particularly to appa
`ratus for measuring the distance, or the propagation time,
`between a mobile Station and a base Station in Such a System.
`Such knowledge of distance or of propagation time can be
`used for various purposes, Such as the following, given by
`way of example:
`in a mobile radiocommunications System of the Time
`Division Multiple Access (TDMA) type, such as in
`particular the Global System for Mobile communica
`tions (GSM), such knowledge can be used for the
`purpose of determining the timing advance to be
`applied to information from the mobile Station So as to
`enable said information to be received at the base
`Station in that one of the time channels which has been
`allocated to Said mobile Station, regardless of the
`propagation time between said mobile Station and Said
`base Station; and
`in a mobile radiocommunications System of the cellular
`type (also such as the above-mentioned GSM), such
`knowledge can be used for the purpose of controlling
`the transmission power of the mobile Station as a
`function of the distance between it and the base Station
`So as to reduce the Overall interference level in the
`System, or else So as to locate the mobile Station, e.g. by
`combining the result of Such a measurement of the
`distance between the mobile Station and a base Station
`with the results of measurements of the distances
`between said mobile Station and other base Stations.
`To determine the propagation time, or the distance,
`between a mobile Station and a base Station in a mobile
`radiocommunications System, it is known to be possible to
`determine the reception instant at which predetermined data
`transmitted by the base station is received by the mobile
`Station, Such predetermined data being, in particular, a
`“training sequence' (used in known manner to estimate the
`transmission channel prior to equalizing the Signals received
`over said transmission channel). Once said reception instant
`has been determined, the base Station can be informed of it,
`and, by comparing it with the transmission instant at which
`Said data was transmitted, and also given that the mobile
`Station is Synchronized continuously on the base Station, Said
`base Station can deduce the propagation time, i.e. the looked
`for distance.
`To determine Such a reception instant at which the mobile
`Station receives predetermined data, it is also known to be
`possible to correlate the modulated Signal as received by the
`mobile Station with a reference Signal generated in the
`mobile Station and corresponding to Said predetermined
`data. In known manner, Such correlation is performed on
`Signals that have been Sampled and digitized, and it involves
`performing Similarity measurements on the two signals for
`various positions in time of one Signal relative to the other,
`the positions being obtained by Shifting the reference Signal
`relative to the received signal by one Sampling period each
`time. That one of the positions for which the similarity
`between the two signals is the greatest is thus representative
`of the reception instant at which the mobile Station receives
`Said predetermined data.
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`Using known methods, the accuracy of an instantaneous
`measurement of the propagation time cannot be better than
`the sampling period (or the accuracy of an instantaneous
`measurement of distance cannot be better than the product of
`the Sampling period multiplied by the propagation Speed of
`the signals). By way of example, for a mobile radiocom
`munications System Such as the above-mentioned GSM, the
`accuracy of Such a distance measurement is thus about one
`kilometer.
`
`SUMMARY OF THE INVENTION
`An object of the present invention is to improve that
`accuracy.
`The present invention provides apparatus for measuring
`the distance between a mobile Station and a base Station in
`a mobile radiocommunications System, Said apparatus
`including means for determining the reception instant at
`which the mobile Station receives predetermined data trans
`mitted by the base Station, which means themselves include
`correlation means for correlating an in-phase component and
`a quadrature component of a modulated Signal received by
`the mobile Station respectively with an in-phase component
`and with a quadrature component of a reference Signal
`generated in the mobile Station and corresponding to Said
`predetermined data, Said correlation means delivering real
`components and imaginary components of correlation
`coefficients, and Said apparatus being characterized in that it
`further includes means for using the real components and the
`imaginary components of the correlation coefficients to
`determine a complex magnitude whose phase varies con
`tinuously as a function of Said reception instant.
`The present invention further provides a mobile station
`including Such means for measuring the reception instant at
`which the mobile Station receives predetermined data trans
`mitted by a base Station in a mobile radiocommunications
`System.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`Other objects and characteristics of the present invention
`appear on reading the following description of an embodi
`ment given with reference to the accompanying drawings, in
`which:
`FIG. 1 is a block diagram Serving to recall the type of
`means to be provided in a mobile Station in order to measure
`the distance between the mobile Station and a base Station in
`the prior art;
`FIGS. 2a, 2b, and 2C are diagrams Serving to recall the
`principle of Such distance measurement in the prior art,
`FIG. 3 is a block diagram serving to show the type of
`means to be provided in a mobile Station in order to measure
`the distance between the mobile Station and a base Station in
`the invention; and
`FIGS. 4a and 4b are diagrams Serving to explain the
`principle of Such distance measurement in the invention.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`The block diagram shown in FIG. 1 includes the
`following, in Succession:
`an antenna 1,
`a frequency conversion Stage 2 delivering, in known
`manner, two components, namely an in-phase compo
`nent I and a quadrature component Q, of a modulated
`Signal received by the mobile Station via the antenna 1,
`
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`US 6,498,924 B2
`
`4
`correlation coefficients h(i) in question, said complex mag
`nitude then being written as follows:
`
`3
`an analog-to-digital converter 3 delivering components I'
`and Q' corresponding respectively to the components I
`and Q, and
`a correlator 4 receiving the components I" and Q' corre
`sponding to the modulated Signal received by the
`mobile Station, and also receiving an in-phase compo
`nent I, and a quadrature component Q, corresponding
`to a reference Signal generated in the mobile Station and
`corresponding to predetermined data transmitted by the
`base Station, the components I, and Q, being delivered
`by a memory 5 in this example.
`The correlator 4 performs correlation on the in-phase
`components and correlation on the quadrature components,
`and it thus delivers two sets of coefficients, one of which is
`referenced Re(h(i)), the other one being referenced Im(h(i)),
`where i varies in the range 1 to k (where k designates the
`number of respective time positions considered of the
`received signal and of the reference signal), and Re(h(i)) and
`Im(h(i)) respectively designate the real component and the
`imaginary component of the correlation coefficient h(i).
`The apparatus recalled in FIG. 1 further includes means 6
`for determining which of the correlation coefficients h(i) is
`of greatest amplitude, the instant at which the coefficient is
`obtained thus being representative of the reception instant at
`which the mobile Station receives said predetermined data.
`The base Station can be informed of Said reception instant,
`and, by comparing it with the transmission instant at which
`the data was transmitted, and also given that the mobile
`Station is Synchronized continuously on the base Station, Said
`base Station can deduce the propagation time, i.e. the looked
`for distance.
`FIG.2b shows an example of correlation coefficients h(i)
`obtained as a function of time t, the correlation coefficient of
`greatest amplitude (coefficient ha in this example) being
`obtained, in this example, at an instant t corresponding to
`a mobile Station Situated, as shown in FIG. 2a, at a point A.
`FIG.2c shows another example of correlation coefficients
`h(i) obtained as a function of time, the correlation coefficient
`of greatest amplitude (also coefficient ha in this example)
`being obtained, in this example, at an instant to correspond
`ing to a mobile Station situated, as shown in FIG. 2a, at a
`point C distant from point A by a distance corresponding to
`a propagation time difference equal to T (where T designates
`the sampling period).
`In the prior art thus recalled, it is not possible to have
`access to a reception instant corresponding to a mobile
`Station Situated, as shown in FIG. 4a, at a point B distant
`from point A by a distance corresponding to a propagation
`time difference equal to CT (where 0<C.<1), where T des
`ignates the Sampling period.
`With the present invention, it becomes possible to have
`access to Such reception instants.
`As shown in FIG. 3, the apparatus of the invention differs
`from the apparatus shown in FIG. 1 in that, instead of
`including the means 6, it includes means 7 for using the real
`components and the imaginary components of correlation
`coefficients h(i) to determine a complex magnitude whose
`phase varies continuously as a function of Said reception
`instant. The correlation coefficients taken into account by the
`means 7 may be either all of the coefficients, or only the
`more significant components if Some of them are of too
`Small an amplitude.
`By way of example, the real component of Said complex
`magnitude may be equal to the Sum of the real components
`of the correlation coefficients h(i) in question, and the
`imaginary component of Said complex magnitude may be
`equal to the Sum of the imaginary components of the
`
`In another example, Said complex magnitude may also be
`equal to the Sum of the moduli of the complex coefficients
`h(i) in question, each multiplied by the complex value
`exp(i.i.at/2), said complex magnitude then being written as
`follows:
`
`X|Rethi) + j Imchi): exp(-i)
`
`In another example applicable to both of the above
`examples, Said Sums could also be weighted Sums. In other
`examples, functions other than Sums or weighted Sums can
`be used provided that the phase of the resulting complex
`magnitude varies continuously as a function of Said recep
`tion instant. The variation in Said complex magnitude may
`take place in compliance with a function that is affine or
`linear.
`Thus, in the complex plane shown in FIG. 4b, the vector
`H, corresponding to the complex magnitude obtained for a
`mobile Station located at point A forms an angle (p, with the
`axis Re of the real values, the vector H, corresponding to the
`complex magnitude obtained for a mobile Station located at
`point B forms an angle (p, with the axis of the real values,
`and the vector H. corresponding to the complex magnitude
`obtained for a mobile Station located at point C forms an
`angle (p, with the axis of the real values, the angle (p (cp., (p.
`(b) being, for example, a linear function of the reception
`instant.
`It is thus possible to have access to a reception instant
`corresponding to a mobile Station Situated, as shown in FIG.
`4a, at a point B distant from point A by a distance corre
`sponding to a propagation time difference is equal to C.T
`(where 0<C.<1), where T designates the sampling period.
`The present invention thus makes it possible to obtain
`accuracy better than the Sampling period for measuring Said
`reception instant at which the mobile Station receives pre
`determined data, and thus for measuring the propagation
`time (or the distance) between the mobile station and the
`base Station, this accuracy then being limited only by the
`quality of the received signals.
`What is claimed is:
`1. A method for measuring the distance between a mobile
`Station and a base Station in a mobile radio communications
`System, comprising:
`receiving a modulated Signal at Said mobile Station having
`in-phase components I and quadrature components Q,
`converting Said modulated Signal to a received digital
`Signal having received signal components including
`respective in-phase components I" and respective
`quadrature components Q',
`obtaining predetermined components including in-phase
`reference components Ir and predetermined quadrature
`reference components Qr,
`correlating Said received signal components with Said
`predetermined components to provide correlation coef
`ficients h(i), where i varies in a range of 1 to k, and k
`designates a number of respective time positions with
`respect to Said received digital Signal;
`determining from Said correlation coefficients h(i) two
`Sets of coefficients, including a Set of real components
`Re(h(i)) and a set of imaginary components Im(h(i));
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`identifying one of Said correlation coefficients h(i) having
`a greatest correlation;
`determining a first distance value based on Said one of
`Said correlation coefficients h(i) having said greatest
`correlation;
`defining a complex plane with real and imaginary axes,
`defining a vector Ha corresponding to a complex magni
`tude with respect to Said one of Said correlation coef
`ficients h(i) having said greatest correlation;
`defining a vector Hb corresponding to a complex magni
`tude with respect to a mobile Station;
`determining an angle (pa of Said vector Ha with respect to
`Said real axis,
`determining an angle pb of Said vector Hb with respect to
`Said real axis as a function of Said real components
`Re(h(i)) and said imaginary components (Im(h(i));
`determining a distance increment relating to the difference
`between (pa and (pb; and
`combining Said distance increment with Said first distance
`value to provide a final distance value representing Said
`distance between Said mobile Station and Said base
`Station.
`2. A method for measuring a distance between a mobile
`Station and a base Station in a mobile radio-communications
`System, comprising:
`converting a received modulated Signal, having in-phase
`components I and quadrature components Q, to a
`received digital Signal having received signal compo
`nents including respective in-phase components I" and
`respective quadrature components Q',
`obtaining predetermined components including in-phase
`reference components Ir and quadrature reference com
`ponents Qr;
`35
`correlating I and Q with Ir and Qr to provide correlation
`coefficients h(i), where i varies in a range of 1 to k, and
`k designates a number of respective time positions with
`respect to Said received digital Signal;
`determining from h(i) a set of real components Re(h(i))
`and a set of imaginary components Im(h(i));
`determining a first distance value based on one of h(i)
`having a greatest correlation;
`defining a vector Ha corresponding to a complex magni
`tude with respect to said one of h(i) having said greatest
`correlation, with an angle (pa with respect to a real axis
`in a complex plane;
`defining a vector Hb corresponding to a complex magni
`tude with respect to a mobile Station, with an angle (pb,
`with respect to said real axis, as a function of Re(h(i))
`and Im(h(i));
`modifying the first distance value based on a difference
`between (pa and pb to provide a final distance value
`representing Said distance between Said mobile Station
`and Said base Station.
`3. The method for measuring the distance between the
`mobile Station and the base Station as Set forth in claim 2,
`wherein the modifying of the first distance value is per
`formed as a function of the difference between (pa and pb, the
`function being linear or affine.
`4. A mobile Station for a mobile radio communications
`System, comprising:
`a signal analyzer for:
`converting a received modulated Signal, having
`in-phase components I and quadrature components
`Q, to a received digital Signal having received Signal
`
`6
`components including respective in-phase compo
`nents I" and respective quadrature components Q',
`and
`obtaining predetermined components including
`in-phase reference components Ir and quadrature
`reference components Qr;
`a correlator for:
`correlating I and Q with Irand Qr to provide correlation
`coefficients h(i), where i varies in a range of 1 to k,
`and k designates a number of respective time posi
`tions with respect to Said received digital Signal; and
`determining from h(i) a set of real components Re(h(i))
`and a set of imaginary components Im(h(i)); and
`a coefficient processor for:
`determining a first distance value based on one of h(i)
`having a greatest correlation,
`defining a vector Ha corresponding to a complex mag
`nitude with respect to said one of h(i) having Said
`greatest correlation, with an angle (pa with respect to
`a real axis in a complex plane,
`defining a vector Hb corresponding to a complex
`magnitude with respect to a mobile Station, with an
`angle (pb, with respect to Said real axis, as a function
`of Re(h(i)) and Im(h(i)), and
`modifying the first distance value based on a difference
`between to provide a final distance value represent
`ing Said distance between Said mobile Station and
`Said base Station.
`5. The mobile station for a mobile radio communications
`System as Set forth in claim 4, wherein the coefficient
`processor modifies the first distance value as a function of
`the difference between (pa and (pb, the function being linear
`or affine.
`6. A mobile Station for a mobile radio communications
`System, comprising:
`Signal analysis means for:
`converting a received modulated Signal, having
`in-phase components I and quadrature components
`Q, to a received digital Signal having received Signal
`components including respective in-phase compo
`nents I" and respective quadrature components Q',
`and
`obtaining predetermined components including
`in-phase reference components Ir and quadrature
`reference components Qr;
`correlation means for:
`correlating I and Q with Irand Qr to provide correlation
`coefficients h(i), where i varies in a range of 1 to k,
`and k designates a number of respective time posi
`tions with respect to Said received digital Signal, and
`determining from h(i) a set of real components Re(h(i))
`and a set of imaginary components Im(h(i)); and
`coefficient processing means for:
`determining a first distance value based on one of h(i)
`having a greatest correlation,
`defining a vector Ha corresponding to a complex mag
`nitude with respect to said one of h(i) having Said
`greatest correlation, with an angle (pa with respect to
`a real axis in a complex plane,
`defining a vector Hb corresponding to a complex
`magnitude with respect to a mobile Station, with an
`angle (pb, with respect to Said real axis, as a function
`of Re(h(i)) and Im(h(i)), and
`modifying the first distance value based on a difference
`between to provide a final distance value represent
`ing Said distance between Said mobile Station and
`Said base Station.
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`7
`7. The mobile station for a mobile radio communications
`System as Set forth in claim 6, wherein the coefficient
`processor modifies the first distance value as a function of
`the difference between (pa and (pb, the function being linear
`or affine.
`8. A method for measuring the distance between a mobile
`Station and a base Station in a mobile radio communications
`System, comprising:
`converting a received modulated Signal to a received
`digital signal having received signal components,
`including respective in-phase components and respec
`tive quadrature components,
`obtaining predetermined reference components including
`in-phase reference components and predetermined
`quadrature reference components,
`correlating Said received signal and Said predetermined
`reference components to provide correlation coeffi
`cients,
`determining, from Said correlation coefficients, a set of
`real components and a Set of imaginary components,
`determining a first distance value based on one of Said
`correlation coefficients having a greatest correlation;
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`using the Set of real components and the Set of imaginary
`components to determine a complex magnitude, includ
`ing:
`determining an angle of a first vector corresponding to
`a complex magnitude with respect to Said one of Said
`correlation coefficients having Said greatest
`correlation, with respect to a real axis of a complex
`plane;
`defining an angle of a Second vector corresponding to
`a complex magnitude with respect to a mobile
`Station, with respect to Said real axis, as a function of
`Said Sets of real and imaginary components,
`determining a distance increment relating to the differ
`ence between Said angles of Said first and Second
`vectors, and
`combining Said distance increment with Said first dis
`tance value to provide a final distance value repre
`Senting Said distance between Said mobile Station and
`Said base Station.
`
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