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`

`
`?§§E%‘1 1 -5 0 8-4 1
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`INTERNATIONAL SEARCH REPORT
`
`A. CJASSI FIGKTIGN
`IFC 5
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`PC1,.~;E 95/99314
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`C. DDCUMELTPS C.‘ONSlDB.I..ED TO BE ILELEVANT
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`Cihiun of dwlillmlh wllh lndluimn. vrhma Ipprupruu. at Lhc Itlcvml. pawuu
`N0,A,95 10144 (TELIA AB ;EN(-ESTROEM ED
`(SE); LARSSON ROGER (55)) 13 Apr'1'T 1995
`see the who1e document
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`US,A,5 295 138 (GREENBERG A FREDERICK ET
`AL) 15 March 1994
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`
`US,A.5 400 322 (HUNT RONALD R
`March 1995
`
`ET AL) 21
`
`see co1umn 1. Tine 31 -
`
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`
`EP.A.@ 637 181 (SIEMENS AG) 1 February
`1995
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`
`Page 525 of 1037
`
`

`
`(44)
`
`%%¥11—508417
`
`INTERNATIONAL smncu REPORT
`
`I.I:u'n- wu1Appl.|=:|:m No
`
`PCIISE 95/99314
`
`T E
`
`1-7,
`14-18,20
`
`LECTRONICS LETTERS. 27 OCT. 1994. UK,
`V01. 30. no. 22,
`ISSN G613-5194.
`pages 1831-1832, XP00049G811
`CHAN C -|( ET AL:
`‘Efficient frequency
`assignment schema for inter-modu1ation
`distortion reduction in fibre-optic
`rrn'crnce1Iular- systems"
`see the whole docuruent
`
`EP,A.0 498 539 (NORTHERN TELECDM LTD) 17
`June 1992
`see the whole document
`
`Fun Pc'rnsA;:|oq_anmnununn 51 -um mm; um um]
`
`Page 526 of 1037
`
`

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`(-4 5 )
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`Page 527 of 1037
`
`

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`
`Page 528 of 1037
`
`

`
`Intematlonal Bureau
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(51) 1nt°1‘“3ti°n31 Patent Cl35Sifi°afi°“ 7 3
`H04M 3/00
`
`(11) International Publication Number:
`_
`_
`,
`(43) International Publication Date:
`
`WO 00/64130
`
`26 October 2000 (26.10.00)
`
`(21) International Application Number:
`
`PCT/US00/10301
`
`(22) International Filing Date:
`
`17 April 2000 (17.04.00)
`
`(30) Priority Data:
`09/294,563
`
`20 April 1999 (20.04.99)
`
`US
`
`(71) Applicant: TERADYNE, INC. [US/US]; 321 Harrison Avenue,
`Boston, MA 02118 (US).
`
`(72) Inventors: RUDINSKI, Ilia, L.; 1717 W. Crystal Lane, Mount
`Prospect, IL 60056 (US). SCHMIDT, Kurt, E.; 6444 W.
`Brever Road, Burlington, WI 53105 (US).
`
`(74) Agent: WALSH, Edmund, J.; Teradyne, Inc., 321 Harrison
`Avenue, Boston, MA 02118 (US).
`
`(81) Designated States: AE. AG. AL. AM. AT. AU. AZ, BA. BB.
`BG, BR, BY, CA, CH, CN, CR, CU, CZ, DE, DK, DM,
`DZ, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL,
`IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU,
`LV, MA, MD, MG, MK, l\/DJ, MW, MX, NO, NZ, PL, PT,
`RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, TZ,
`UA, UG, UZ, VN, YU, ZA, ZW, ARIPO patent (GH, GM,
`KE, LS, MW, SD, SL, SZ, TZ, UG, ZW), Eurasian patent
`(AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), European patent
`(AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT,
`LU, MC, NL, PT, SE), OAPI patent (BF, BJ, CF, CG, CI,
`CM, GA, GN, GW, ML, MR, NE, SN, TD, TG).
`
`Published
`Without international search report and to be republished
`upon receipt of that report.
`
`(54) Title: DETERMINING THE PHYSICAL STRUCTURE OF SUBSCRIBER LINES
`
`H)
`
`(57) Abstract
`
`A method determines a structure of a subscriber line. The method includes searching a reference set for a match between the
`subscriber line and a model line of the reference set and identifying that the subscriber line has a specific physical structure. The match is
`based on electrical properties of the lines. The act of identifying is responsive to finding a match with one of the model lines that has the
`specific physical structure.
`
`Page 529 of 1037
`
`

`
`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCT on the front pages of pamphlets publishing international applications under the PCT.
`LS
`Lesotho
`Albania
`SI
`Slovenia
`ES
`LT
`SK
`Lithuania
`Slovakia
`Armenia
`FI
`SN
`Austria
`FR
`LU
`Senegal
`Luxembourg
`Australia
`LV
`SZ
`GA
`Latvia
`Swaziland
`TD
`Monaco
`Chad
`GB
`MC
`Azerbaijan
`MD
`TG
`GE
`Togo
`Republic of Moldova
`Bosnia and Herzegovina
`Barbados
`GH
`MG
`TJ
`Tajikistan
`Madagascar
`GN
`MK
`TM
`Turkmenistan
`The fonner Yugoslav
`Belgium
`TR
`Burkina Faso
`GR
`Turkey
`Republic of Macedonia
`TT
`HU
`Mali
`Trinidad and Tobago
`Bulgaria
`Ukraine
`IE
`UA
`Benin
`Mongolia
`Mauritania
`UG
`IL
`Brazil
`Uganda
`US
`United States of America
`Malawi
`Bclanis
`IS
`UZ
`Uzbekistan
`Canada
`IT
`Mexico
`VN
`Viet Nam
`JP
`Niger
`Central African Republic
`Netherlands
`YU
`KE
`Yugoslavia
`Congo
`Zimbabwe
`ZW
`Switzerland
`KG
`Norway
`KP
`New Zcaland
`Cote d’Ivoire
`Poland
`Cameroon
`China
`Portugal
`Cuba
`Romania
`Russian Federation
`Czech Republic
`Sudan
`Germany
`Denmark
`Sweden
`Estonia
`Singapore
`
`Spain
`Finland
`France
`Gabon
`United Kingdom
`Georgia
`Ghana
`Guinea
`Greece
`Hungary
`Ireland
`Israel
`Iceland
`Italy
`Japan
`Kenya
`Kyrgyzstan
`Democratic People's
`Republic of Korea
`Republic of Korea
`Kazakstan
`Saint Lucia
`Liechtenstein
`Sri Lanka
`Liberia
`
`ML
`MN
`MR
`MW
`MX
`NE
`NL
`NO
`NZ
`PL
`PT
`RO
`RU
`SD
`SE
`SG
`
`KR
`KZ
`LC
`LI
`LK
`LR
`
`Page 530 of 1037
`
`

`
`W0 00/64130
`
`PCT/USDO/10301
`
`DETERMINING THE PHYSICAL STRUCTURE OF SUBSCRIBER LINES
`
`This is a continuation-in—part of Application No.
`
`U.S. Application No. 09/294,563, filed April 20, 1999.
`
`
`
`This application relates generally to communications
`
`networks, and more particularly,
`
`to determining electrical
`
`properties of multi—wire communication lines.
`
`Recently,
`
`there has been an increased demand for the
`
`subscriber lines of plain old telephone services
`
`(POTS‘s)
`
`to carry high-speed digital signals.
`
`The demand has been
`
`stimulated by home access to both the Internet and distant
`
`office computers. Both types of access typically employ a
`
`POTS
`
`line as part of
`
`the path for
`
`carrying digital
`
`signals.
`POTS‘s
`
`lines were built
`
`to carry voice signals at
`
`audible frequencies and can also carry digital signals as
`
`tone signals in the near audible frequency range. Modern
`
`digital services such as
`
`ISDN and ADSL transmit data at
`
`frequencies well above the audible range. At
`
`these higher
`
`frequencies, POTS‘s lines that transmit voice signals well
`
`may transmit digital signals poorly. Nevertheless, many
`
`like to
`(TELCO‘s) would
`telephone operating companies
`offer ISDN and/or ADSL data services to their subscribers.
`
`Telephone
`
`lines
`
`between
`
`a
`
`TELCO
`
`switch
`
`and
`
`subscribers‘
`
`premises
`
`are
`
`frequent
`
`sources
`
`of
`
`poor
`
`performance at the high frequencies characteristic of ISDN
`and ADSL transmissions. Nevertheless, high cost has made
`
`an
`lines
`subscriber
`these
`of
`replacement
`widespread
`undesirable solution for providing subscribers with lines
`
`capable of
`
`supporting’
`
`ISDN and. ADSL.
`
`A less expensive
`
`Page 531 of 1037
`
`

`
`W0 00/64130
`
`PCT/US00/10301
`
`alternative would
`
`be
`
`to repair or
`
`remove only those
`
`subscriber
`
`lines
`
`that
`
`are
`
`inadequate
`
`for
`
`transmitting
`
`high—speed digital data.
`
`To limit
`
`replacement or repair to inadequate lines,
`
`TELCO‘s have placed.
`
`some emphasis on developing methods
`
`for‘ predicting which subscriber
`
`lines will
`
`support data
`
`services,
`
`such as ISDN and ADSL.
`
`Some emphasis has been
`
`also placed on predicting frequency ranges at which such
`data services will be supported.
`Some methods have also
`
`been developed for
`
`finding faults
`
`in subscriber
`
`lines
`
`already supporting data services so that
`
`such faults can
`
`be repaired.
`Current methods
`
`for
`
`predicting
`
`the
`
`ability of
`
`subscriber
`
`lines
`
`to
`
`support
`
`high—speed
`
`digital
`
`transmissions
`
`are
`
`typically
`
`not
`
`automated,
`
`labor
`
`intensive,
`
`and entail
`
`test access at multiple points.
`
`Often,
`
`these methods entail using skilled interpretations
`
`to
`line parameters
`frequency measurements of
`of high
`determine data
`transmission abilities.
`At
`a
`network
`
`scale, such tests are very expensive to implement.
`
`The present
`
`invention is directed to overcoming or,
`
`at
`
`least,
`
`reducing the affects of one or more of
`
`the
`
`problems set forth above.
`
`Summary of the Invention
`
`In a first aspect,
`
`the invention provides a method of
`
`line.
`a subscriber
`determining a physical structure of
`The method includes searching a reference set for a match
`
`between the
`
`subscriber
`
`line and a model
`
`line of
`
`the’
`
`reference set and identifying that the subscriber line has
`
`a specific physical structure.
`
`The match is based on
`
`electrical
`
`properties
`
`of
`
`the
`
`lines.
`
`The
`
`act
`
`of
`
`identifying is responsive to finding a match with one of
`
`Page 532 of 1037
`
`

`
`W0 00/64130
`
`'
`
`PCT/US00/10301
`
`the model lines that has the specific physical structure.
`
`In a second aspect,
`
`the invention provides a method
`
`The
`of qualifying a subscriber line for a data service.
`method includes searching a reference set of model lines
`
`for a best match to a subscriber line by comparing sets
`
`of electrical properties and determining that the
`
`subscriber line has a specific physical structure.
`
`The
`
`act of determining is responsive to the best matching
`
`model line having the specific physical structure.
`
`The
`
`method also includes disqualifying the subscriber line
`
`for the data service,
`
`in part,
`
`in response to determining
`
`that the specific physical structure corresponds to a
`
`disqualified line.
`
`In a third aspect,
`
`the invention provides a method
`
`of providing a data service.
`
`The method includes
`
`searching for a match between electrical properties of a
`subscriber line and a model line of a reference set and
`
`determining whether the subscriber's line is qualified
`for the data service.
`The act of determining is based in
`
`part on whether the best matching model line has one of a
`
`bridged tap and a mixture of gauges.
`
`The method also
`
`includes performing a business action in response to
`
`determining that the subscriber's line is qualified.
`
`In a
`
`fourth aspect,
`
`the invention provides
`
`a data
`
`storage
`
`device
`
`that
`
`stores
`
`an
`
`executable
`
`program of
`
`instructions for causing a computer to perform one or more
`of the above—described methods.
`
`Various embodiments use test accesses, which provide
`
`data on low frequency electrical properties of subscriber
`
`lines,
`
`to
`
`make
`
`predictions
`
`about
`
`high
`
`frequency
`
`performance.
`
`Page 533 of 1037
`
`

`
`W0 00/64130
`
`PCT/US00/10301
`
`Brief Description of the Drawings
`
`Other
`
`features and advantages of
`
`the invention will
`
`be apparent
`
`from the following description taken together
`
`with the drawings in which:
`
`FIG.
`
`I
`
`shows
`
`a portion of
`
`a POTS network having a
`
`system for detecting faults in subscriber telephone lines;
`
`FIG.
`
`2A shows a first measuring setup for making one-
`
`ended electrical measurements on a
`line;
`
`subscriber
`
`telephone
`
`FIG.
`
`2B is an equivalent circuit
`
`for_ the measuring
`
`setup of FIG. 2A;
`
`FIG.
`one—ended
`
`second measuring setup. for making
`a
`2C shows
`electrical measurements
`on
`a
`subscriber
`
`telephone line;
`
`3 illustrates signal distortions produced by the
`FIG.
`test bus and standard voice test access;
`
`FIG.
`
`4 shows a split pair fault in a subscriber line;
`
`FIG.
`
`5
`
`shows how a splice error can produce a split
`
`pair fault;
`
`a phase measurement
`6A shows
`FIG.
`resistive imbalance on a subscriber line;
`
`signature of
`
`a
`
`FIG.
`
`6B shows
`
`a phase measurement
`
`signature of
`
`a
`
`split pair fault on a subscriber line;
`
`FIG.
`
`7
`
`is
`
`a
`
`flow chart
`
`illustrating a method of
`
`detecting faults on subscriber
`
`lines with the system of
`
`FIGS. 1, 4, and 5:
`
`FIG.
`
`8
`
`is
`
`a
`
`flow chart
`
`illustrating a method of
`
`qualifying subscriber lines with the method of FIG. 7;
`
`FIG.
`
`9
`
`shows
`
`a method of providing high speed data
`
`services using the methods of FIGs.
`
`7 and 8;
`
`FIG.
`
`1OA—lOE show exemplary subscriber
`
`lines having
`
`different gauge mixes;
`
`FIG.
`
`11 shows a subscriber line with a bridged tap;
`
`Page 534 of 1037
`
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`FIG.
`
`12A—12E shows exemplary structures of subscriber
`
`lines having one bridged tap;
`FIG.
`13 is a flow chart for a method of determining
`
`the specific physical structure of a subscriber line from
`a reference set;
`
`FIG.
`
`14
`
`is a
`
`flow chart
`
`for
`
`a method of
`
`finding a
`
`best match between a subscriber and model lines;
`
`FIG.
`
`15 is a
`
`flow chart
`
`for a method of qualifying
`
`subscriber lines; and
`
`FIG.
`
`16
`
`is a
`
`flow chart
`
`for
`
`a business method of
`
`providing high—speed data services to subscribers.
`FIG.
`17
`is a
`flow chart
`for
`a
`stacked method of
`
`detecting bridged taps using auxiliary variables;
`FIG.
`18A
`shows
`predicted
`and
`actual
`
`attenuations of nominal subscriber lines;
`
`actual
`and
`predicted
`shows
`18B
`FIG.
`attenuations of non—nominal subscriber lines;
`
`signal
`
`signal
`
`FIG.
`
`18C shows predicted,
`
`shifted predicted,
`
`and
`
`signal
`actual
`subscriber line;
`
`attenuations
`
`for
`
`an
`
`exemplary
`
`nominal
`
`FIG. 19 shows an exemplary decision tree;
`
`FIG.
`
`20 illustrates the action of
`
`the rules of
`
`the
`
`decision tree of FIG. 19 on a set of subscriber lines;
`
`FIG.
`
`21
`
`is a
`
`flow chart
`
`illustrating a method of
`
`creating the decision trees with machine learning methods;
`and
`
`FIG. 22 is a
`
`flow chart for a method of determining
`
`the branching rules of
`FIGs. 19-20.
`
`the decision tree illustrated in
`
`Description of the Preferred Embodiments
`MEASUREMENT AND TEST APPARATUS
`
`FIG.
`
`1 shows a portion of a POTS network 10 that has
`
`a system 11 for detecting faults in subscriber
`
`lines 12-
`
`Page 535 of 1037
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`14.
`
`The subscriber
`
`lines 12-14 connect subscriber units
`
`telephony
`to a
`telephones,
`and/or
`i.e., modems
`16-18,
`switch 15.
`The switch 15 connects the subscriber
`lines
`
`12-14 to the remainder of
`
`the telephone network 10.
`
`The
`
`switch 15 may be a POTS switch or another device, e.g.,
`
`a
`
`digital subscriber loop access multiplexer (DSLAM).
`Each subscriber
`line 12-14 consists of
`a
`
`standard
`
`twisted
`
`two-wire
`
`telephone
`
`line
`
`adapted
`
`to
`
`voice
`
`transmissions.
`
`The two wires are generally referred to as
`
`the ring AR@ and tip AT@ wires.
`
`line 12-14
`each subscriber
`A large portion of
`housed in one or more standard telephone cables 22.
`
`is
`The.
`
`cable 22 carries many subscriber lines 12-14, e.g., more
`
`than a dozen,
`
`in a closely packed configuration.
`
`The
`
`close
`
`packing
`
`creates
`
`an electrical
`
`environment
`
`that
`
`transmission
`changes
`subscriber lines 12-14.
`
`properties
`
`of
`
`the
`
`individual
`
`Electrical measurements for detecting line faults are
`
`various
`In
`,
`40.
`unit
`a measurement
`by
`performed
`embodiments,
`the measurement unit 40 includes one or both
`devices 41 and 43.
`Each device 41,
`43 performs one-ended
`
`electrical measurements
`
`on
`
`selected lines
`
`12-14.
`
`In
`
`are
`the electrical measurements
`preferred embodiments,
`one—ended.
`The device 41 performs measurements on tip and
`
`ring wires of a selected subscriber line 12-14 in a common
`mode
`configuration
`and
`produces
`results
`useful
`for
`
`detecting split pairs.
`
`The
`
`device
`
`43
`
`can measure.
`
`admittances of the tip and ring wires of a selected line
`
`12-14 either
`
`separately or
`
`together
`
`and produces data
`
`useful
`
`for
`
`determining
`
`the
`
`specific
`
`physical
`
`line
`
`structure.
`
`The measurement unit 40 may also house other
`
`devices
`
`(not
`
`shown)
`
`for
`
`performing
`
`other
`
`types
`
`of
`
`electrical measurements,
`
`i.e.,
`
`one-ended
`
`or
`
`two-ended
`
`measurements.
`
`The measurement unit
`
`40
`
`couples
`
`to the
`
`Page 536 of 1037
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`
`switch 15 via a test bus 42.
`
`The devices 41,
`
`43 connect
`
`to the switch 15 through
`
`the test bus 42 and a standard voice test access 44.
`
`voice test
`
`access
`
`44 electrically connects either
`
`The
`
`the
`
`device
`
`41 or device
`
`43
`
`to the subscriber
`
`lines
`
`12-14
`
`selected for testing.
`
`The voice test access 44 generally
`
`transmits electrical signals with low frequencies between
`
`(KHZ).
`and 20 kilo Hz
`about 100 Hertz (Hz)
`access
`44 may
`transmit
`signals at higher
`
`the test
`But,
`frequencies,
`
`in some switches 15.
`e.g., up to 100 to 300 KHZ,
`The measurement unit 40 is controlled by computer 46,
`
`the
`which selects the types of measurements performed,
`device 41,
`43 used,
`and the subscriber
`lines 12-14 to
`
`test.
`
`The
`
`computer
`
`46
`
`sends
`
`control
`
`signals
`
`to the
`
`measurement unit
`
`40 via a connection 48, e.g.,
`
`a
`
`line,
`
`network,
`
`or dedicated wire,
`
`and
`
`receives measurement
`
`from the measurement
`results
`connection 48.
`
`unit
`
`40 Via
`
`the
`
`same
`
`The
`
`computer
`
`46
`
`contains
`
`a
`
`software program for
`
`controlling line testing by the measurement unit
`
`40 and
`
`for detecting line conditions or faults with results from
`the measurement unit 40.
`The software program is stored,
`
`a
`in a data storage device 49, e.g.,
`in executable form,
`hard drive or random access memory (RAM).
`The program may
`also be encoded on a readable storage medium 50,
`such as
`
`an optical or magnetic disk,
`executed.
`
`from which the program can be
`
`40 signals
`the measurement unit
`test,
`To perform a
`the voice test access 44 to connect
`the line 12-14 to be
`
`tested to wires of
`
`the bus 42 for connecting to internal
`
`devices 41, 43.
`
`Then, one or both of the internal devices
`
`43 performs electrical. measurements on the selected
`41,
`line 12-14. After
`the measurements are completed,
`the
`
`measurement unit
`
`40 signals the switch 15 to disconnect
`
`Page 537 of 1037
`
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`
`the line 12-14 from the wires of the bus 42.
`
`The
`
`computer
`
`46
`
`can classify selected subscriber
`
`lines 12-14 prior to fully connecting the lines 12-14 for
`
`data services.
`
`The range of possible classes to which a
`
`line 12-14 can. be assigned will depend on the business
`
`needs of
`
`a TELCO.
`
`A simple, but very useful
`
`set of
`
`classes is "qualified" and "disqualified" to provide data
`
`services.
`
`Qualification is based on ‘determining, with
`
`high certainty,
`
`that a selected line 12-14 will support a
`
`specified data
`
`service.
`
`Disqualification is based on
`
`determining, with high certainty,
`
`that
`
`the selected line
`
`12-14 will not support the specified data service.
`FIG.
`2A shows
`a first
`setup 52
`for -performing one
`
`type of one—ended electrical measurements with the device
`41.
`The measurements are used to detect faults such as
`
`split pairs in the subscriber lines 12-14 of FIG. 1.
`The device 41 has a variable frequency voltage source
`
`54
`
`for driving the
`
`tip and
`
`ring wires
`
`T,
`
`R of
`
`the
`
`subscriber
`
`line 12-14 under
`
`test.
`
`The voltage source
`
`drives
`
`both wires
`
`together,
`
`i.e.,
`
`in a
`
`common mode
`
`configuration,
`
`at
`
`a
`
`frequency
`
`controlled
`
`by
`
`the
`
`measurement unit 40.
`
`The tip and ring wires T, R of the
`
`line 12-14 under test are connected to the device 41 via
`
`the voice test access 44.
`
`The voltage
`
`source
`
`54
`
`connects
`
`to one
`
`side
`
`of
`
`resistors Ri and R2.
`
`The second side of resistors R1 and R2
`
`the
`to the respective tip and ring wires T, R of
`connect
`subscriber
`line 12-14 under
`test.
`Thus,
`the voltage
`source 54 drives the tip and ring wires T,
`R in common
`
`mode through the corresponding resistors R1 and Rp
`
`The resistors R1 and R2 have equal resistances so that
`
`the voltage source 54 induces equal voltages V1, V2 between
`each resistor R1,
`R2
`and ground if the currents
`IT,
`IR
`
`therein are
`
`also equal.
`
`Differences
`
`in
`
`the
`
`input
`
`Page 538 of 1037
`
`

`
`WO 00/64130
`
`PCT/US00/1030]
`
`impedances ZT,
`
`ZR of the tip and ring wires T,
`
`R make the
`
`voltages Vb
`
`V2 differ
`
`in amplitude and/or phase.
`
`For
`
`example, mutual
`
`inductance effects produced by a split
`
`ZR unequal.
`impedances ZT,
`pair can make the input
`Voltmeters VM1 and VM2 measure amplitudes and phases
`
`From measurements of
`respectively.
`of voltages V1 and V2,
`the voltmeters VM1 and VM2,
`the computer 46 can obtain the
`
`phase difference between V1 and V;
`
`FIG.
`
`2B
`
`shows
`
`an
`
`equivalent circuit
`
`55
`
`for
`
`the
`
`measurement
`
`setup 52 of
`
`FIG.
`
`4.
`
`In the common mode
`
`configuration,
`
`the :ip and ring wires T, R act as elements
`
`the voltage
`that connect
`57
`independent circuits 56,
`of
`source 54
`to a
`common ground 58.
`The
`tip wire T
`is
`
`equivalent
`
`to an impedance ZT
`
`in the circuit 56,
`
`and the
`
`ring wire R is equivalent to an impedance ZR in the circuit
`57.
`
`The
`
`input
`
`impedances
`
`ZT
`
`and ZR may ‘have different
`
`amplitudes and/or phases due to the presence of a fault on
`
`either the tip or ring wires T, R. Different values for ZT
`
`and Zn produce different currents IT and IR in the circuits
`56 and 57 and different measured voltages V; and V2.
`The
`
`phase of the voltage difference V1 — V2
`
`is proportional
`
`to
`
`the phase difference between the input
`
`impedances of
`
`the
`
`tip and ring wires T, R.
`
`In the phase of the difference V1
`
`— V2,
`
`termination effects associated with the attached
`
`subscriber unit 16 can largely be ignored.
`
`for performing
`Ineasuring setup 60
`a
`2C shows
`FIG.
`one—ended electrical measurements on a selected subscriber
`
`line 12-14 with the device 43 shown in FIG 1.
`
`The device
`
`43 measures electrical properties, which can be used to
`
`determine the specific physical structure of the lines 12-
`14
`and to determine line conditions
`and‘ faults
`as
`is
`
`described below.
`
`Some methods
`
`for detecting line faults
`
`and conditions with the device 43 have been described in
`
`Page 539 of 1037
`
`

`
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`
`U.S. Application No. 09/294,563
`
`(‘563),
`
`filed April 20,
`
`1999.
`
`The
`
`‘563 application is incorporated. herein,
`
`by
`
`reference,
`
`in its entirety.
`
`The device
`
`43
`
`is
`
`adapted to measure
`
`admittances
`
`between the tip wire T,
`
`ring wire R,
`
`and ground G for a
`
`subscriber
`
`line 12-14 being tested.
`
`The"
`
`tip and ring
`
`wires T,
`
`R of
`
`the
`
`line 12—14 being tested couple
`
`to
`
`driving voltages V1’ and V2’
`
`through known conductances Gt
`
`and Gr.
`
`The
`
`tip and ring wires T,
`
`R also connect
`
`to
`
`voltmeters V; and VI. The Vt and V, voltmeters
`
`read the
`
`voltage between the tip wire T and ground G and between
`
`The readings
`respectively.
`the ring wire R and ground G,
`from the voltmeters Vt and Vr enable the computer
`46 to
`
`determine three admittances Yw, Ytn
`
`and Yng between the
`
`respectively.
`tip—ring, and ring—ground,
`pairs tip—ground,
`The device 43 can measure the admittances at preselected
`
`frequencies
`
`in the
`
`range
`
`supported by the voice test
`
`access 44.
`
`The ‘563 application has described methods for
`
`performing such measurements.
`
`Referring to FIG. 3,
`
`the computer 46 may compensate
`
`42
`test bus
`the
`introduced by
`signal distortions
`for
`and/or the voice test access 44.
`To perform compensation,
`
`the computer 46 treats the two lines of the combined bus
`42 and test access 44 as a linear two port systems.
`Then,
`
`the currents
`and voltages
`IT‘,
`VT’
`and IR‘, Va’
`at
`the
`output
`terminals of the measurement device 40 are related
`to the currents and voltages IT, VT and IR, VR on the output
`
`terminals of the tip and ring wires T, R by the following
`
`2x2 matrix equations:
`
`[In VT] = A<f>
`
`[IT', vmt and [IT] VT] = A'<f> [L9, VR']t-
`
`The
`
`frequency dependent matrices A(f)
`
`and A'(f)
`
`are
`
`42 and voice test
`determined experimentally for each bus
`access
`44.
`Then,
`the
`computer
`46
`calculates
`the
`
`impedances or admittances of
`
`the tip and ring wires T,
`
`R
`
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`
`with the currents and voltages IT,
`
`VT and IR, Va obtained
`
`from the above equations.
`
`The measurement unit
`
`40
`
`and computer 46 can detect
`
`faults such as split pairs, resistive imbalances, metallic
`
`faults,
`
`load coils, bridged taps, gauge mixtures, and high
`
`signal attenuations.
`O9/285,954
`('954),
`
`Co—pending U.S. Patent Application
`filed April
`2,
`1999, describes
`the
`
`detection. of
`
`some of
`
`these faults
`
`and is incorporated
`
`herein by reference in its entirety;
`
`SPLIT PAIRS
`
`Referring again to
`
`FIG.
`
`1,
`
`close proximity can
`
`inductively produce
`
`cross
`
`talk between
`
`the
`
`subscriber
`
`lines 12-14.
`
`Cross
`
`talk is frequently caused by large
`
`noise or ringing signals on one of the lines 12-14.
`
`The
`
`large signal
`
`inductively produces signals on nearby lines
`
`12-14.
`
`To reduce cross talk,
`
`the tip and ring wires T, R
`
`of each subscriber line 12-14 are either tightly twisted
`
`together or kept
`
`in close proximity in the cable 22.
`
`this way,
`
`stray signals affect both wires of
`
`a pair
`
`In
`
`so
`
`that
`
`induced signals do not
`
`impact
`
`the difference signal
`
`between the tip and ring wires.
`
`Referring to FIG. 4,
`
`the tip and ring wires T‘, R‘ of
`
`a subscriber line 24 are separated spatially in a portion
`
`the subscriber
`The portion of
`of cable 25.
`which
`the
`tip and
`ring wires T’,
`R‘
`are
`
`in
`line 24
`spatially
`
`separated is referred to as
`
`a split pair.
`
`A split pair
`
`talk other
`a high risk of picking up cross
`T’, R‘ has
`lines 28-29 in the same cable 26 or external noise sources
`
`such as power lines (not shown).
`
`Split pairs also introduce impedance discontinuities
`into subscriber
`lines, because the split pair creates a
`
`localized and
`
`abrupt
`
`impedance variation.
`
`Impedance
`
`discontinuities
`
`can
`
`cause
`
`signal
`
`reflections
`
`and high
`
`Page 541 of 1037
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`signal attenuations for high—speed digital transmissions.
`FIG.
`5
`illustrates one type of split pair,
`i.e.,
`
`a
`
`The splice error
`split pair caused by a splice error.
`occurred when two portions of a subscriber line 32, which
`
`are located in two different cables 33, 34, were joined.
`
`The splice 35 has joined tip and ring wires T1, R2
`
`from two
`
`different twisted pair lines 36,
`
`37 in the cable 33 to tip-
`
`and ring wires T3,
`
`R3 of a single twisted pair 38 in the
`
`adjacent cable 34.
`
`The tip and ring wires T1,
`
`R2 of
`
`the
`
`portion of the subscriber line 32 are widely separated in
`
`a substantial portion of the cable 33.
`
`Thus,
`
`the tip and
`
`ring wires T1, R2 form a split pair.
`
`Detection of
`
`split pair
`
`faults
`
`is difficult
`
`for
`
`several reasons. First, split pairs do not produce easily
`
`detected effects
`
`such as metallic faults,
`
`i.e.,
`
`broken
`
`wires or shorted wires, or impedance imbalances.
`
`Second,
`
`split pairs produce cross talk that produce intermittent
`
`faults depending on the signals on nearby lines, e.g.,
`
`The
`ringing signals.
`intermittent
`such faults difficult to recognize.
`
`intermittency makes
`
`Conventional
`
`tests have not been very successful
`
`in
`
`detecting split pairs.
`
`Nevertheless,
`
`split pairs
`
`can«
`
`degrade the quality of a subscriber
`data services.
`
`line for high—speed
`
`FIG.
`
`6A and 6B provide graphs 68,
`
`69 of the phase of
`
`the voltage difference V1
`
`— V2 between resistors R1 and R2
`
`while testing two exemplary subscriber
`
`lines 12-14 with
`
`the measurement
`
`setup 52 of FIG. 4.
`
`The graphs 68,
`
`69
`
`provide frequency sweeps of
`
`the phase difference, which
`
`show signatures of faults that can interfere with high—
`
`speed data services, e.g.,
`
`ISDN or ADSL.
`
`the graph 68 shows a signature
`6A,
`Referring to FIG.
`for a resistive imbalance fault on the tested subscriber
`
`line 12-14.
`
`The signature for a resistive imbalance is a
`
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`
`pronounced peak in the phase of the voltage difference V1 -
`
`V2.
`
`The
`
`peak appears
`
`in the phase difference between
`
`a
`The peak has
`the tip and ring wires.
`impedances of
`narrow width that is typically not more than a few hundred
`
`to about
`
`2 KHz.
`
`Typically,
`
`the phase has
`
`a height of
`
`greater than about 53
`Referring to FIG.
`
`6B,
`
`the graph 69 shows a signature
`
`for a split pair fault on the tested subscriber line 12-
`
`14. The
`
`signature is a
`
`flat
`
`and substantially’ constant
`
`phase for V1
`
`— Vg,
`
`i.e.,
`
`a substantially constant non—zero
`
`phase difference between the input
`
`impedances ZT,
`
`ZR of the
`
`the phase has a value of between
`Typically,
`wires T, R.
`about
`.5° and l.5°.i The nonzero and flat phase extends
`
`over a
`
`region of
`
`frequencies having a width of at
`
`least
`
`5,000 kilo Hz.
`
`The phase of Zr and ZR may remain flat,
`
`nonzero, and peakless from about 100 Hz to about 20,000 Hz
`if a split pair is present, i.e., over the frequency range
`measurable through the voice test access 44,
`shown in FIG.
`
`1.
`
`A nonzero and substantially frequency independent
`
`phase difference between the input
`
`impedances ZT,
`
`ZR of the
`
`tip and ring wires is a signature for a split pair on the
`subscriber line 12-14 being tested.
`
`FIG.
`
`7
`
`is a flow chart
`
`illustrating a method 70 of
`
`detecting a fault
`
`in the subscriber lines 12-14 with the
`
`selects
`46
`computer
`The
`1.
`FIG.
`system 11 .of
`subscriber line 12-14 to test for faults (step 72).
`
`the
`The
`
`measurement unit 40 electrically connects to the selected
`
`line 12-14 via the voice test access
`
`44 of
`
`the TELCO
`
`switch
`
`15
`
`(step
`
`74).
`
`The
`
`connection
`
`produces
`
`the
`
`measurement setup 52 illustrated in FIGS.
`
`4 and 5.
`
`The measurement unit 40 performs one—ended electrical
`
`measurements
`
`to determine a
`
`signal proportional
`
`to the
`
`phase difference of the input
`
`impedances ZT,
`
`ZR of the tip
`
`Page 543 of 1037
`
`

`
`WO 00/64130
`
`PCT/US00/10301
`
`and ring wires of
`
`the selected line 12-14
`
`(step 76). The
`
`— V2, which
`quantity actually measured is the phase of V1
`is proportional
`to the phase of
`the difference of
`the
`input
`impedances ZT,
`ZR. The device 41 measures the phase
`
`by driving the tip and ring wires
`
`in the common mode
`
`The driving frequencies
`configuration shown in FIG. 4.
`are between about 100 Hz
`to 20,000 kilo Hz and accessible
`
`via the voice test access 44.
`
`Such frequencies are very
`
`to transmission frequencies of high—speed
`low compared
`data services such as ISDN and ADSL.
`
`The
`
`computer
`
`46
`
`analyzes
`
`the measurements of
`
`the
`
`phase as a function of
`
`frequency to determine wheth