US008238412B2
`
`(12) United States Patent
`Krinsky et al.
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`US 8,238,412 B2
`*Aug. 7, 2012
`
`(54)
`
`(75)
`
`MULTICARRIER MODULATION
`MESSAGING FOR POWER LEVEL PER
`SUBCHANNEL INFORMATION
`
`Inventors: David M. Krinsky, Acton, MA (US);
`Robert Edmund Pizzano, Stoneham,
`MA (US)
`
`(73)
`
`Assignee: Aware, Inc., Bedford, MA (US)
`
`(*)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`USC 154(b) by 194 days.
`This patent is subject to a terminal dis
`claimer.
`
`(21)
`
`(22)
`
`(65)
`
`(60)
`
`(60)
`
`(51)
`
`(52)
`(58)
`
`Appl. N0.: 12/779,660
`
`Filed:
`
`May 13, 2010
`
`Prior Publication Data
`
`US 2010/0226418 A1
`
`Sep. 9,2010
`
`Related US. Application Data
`
`Continuation of application No. 12/477,742, ?led on
`Jun. 3, 2009, noW Pat. No. 7,835,430, Which is a
`continuation of application No. 10/619,691, ?led on
`Jul. 16, 2003, noW Pat. No. 7,570,686, Which is a
`division ofapplication No. 09/755,173, ?led on Jan. 8,
`2001, noW Pat. No. 6,658,052.
`Provisional application No. 60/224,308, ?led on Aug.
`10, 2000, provisional application No. 60/ 174,865,
`?led on Jan. 7, 2000.
`
`Int. Cl.
`(2006.01)
`H04B 1/38
`US. Cl. .................................... ..
`
`375/219
`
`Field of Classi?cation Search ................ .. 375/222,
`375/224e225, 227, 220, 284; 370/241, 252,
`370/282; 379/22.02, 22.04, 27.01, 27.03
`See application ?le for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`4,385,384 A
`5/1983 Rosbury et 31.
`4,566,100 A
`1/1986 MiZuno et a1.
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`(Continued)
`
`EP
`
`FOREIGN PATENT DOCUMENTS
`0889615
`1/1999
`(Continued)
`
`OTHER PUBLICATIONS
`
`U.S. Appl. No. 13/004,254, ?led Jan. 11, 2011, Krinsky et a1.
`(Continued)
`
`Primary Examiner * Khanh C Tran
`(74) Attorney, Agent, or Firm *Jason H. Vick; Sheridan
`Ross, PC
`
`ABSTRACT
`(57)
`Upon detection of a trigger, such as the exceeding of an error
`threshold or the direction of a user, a diagnostic link system
`enters a diagnostic information transmission mode. This
`diagnostic information transmission mode alloWs for tWo
`modems to exchange diagnostic and/or test information that
`may not otherwise be exchangeable during normal commu
`nication. The diagnostic information transmission mode is
`initiated by transmitting an initiate diagnostic link mode mes
`sage to a receiving modem accompanied by a cyclic redun
`dancy check (CRC). The receiving modem determines, based
`on the CRC, if a robust communications channel is present. If
`a robust communications channel is present, the tWo modems
`can initiate exchange of the diagnostic and/or test informa
`tion. Otherwise, the transmission poWer of the transmitting
`modem is increased and the initiate diagnostic link mode
`message re-transmitted to the receiving modem until the CRC
`is determined to be correct.
`
`21 Claims, 2 Drawing Sheets
`
`5
`?/ 5O
`?/
`
`Central Of?ce
`
`200
`M
`
`230
`
`210
`
`CRC
`Checker
`
`(ATU-C)
`Diagnostic
`Information
`Monitoring
`Device
`
`5
`m
`220
`/M
`Diagnostic
`Device
`
`20
`
`POTS-C
`/M
`
`Phone
`Switch
`
`Remote Terminal
`310
`A/
`
`V
`
`(ATU_R)
`
`33o
`
`300
`?/
`
`Message
`Determination
`Device
`
`30
`
`_
`/V I
`Diagnostic
`eVlCe
`
`10
`
`5
`
`I Splitter
`
`'
`
`sphtterl
`
`320
`?/
`Power
`Control
`-
`Device
`
`340
`/i/
`Diagnostic
`Information
`Storage
`, Deivce
`
`6O
`i
`
`User
`
`Terminal
`
`POTS-R
`
`40
`
`W
`
`

`
`US 8,238,412 B2
`Page 2
`
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`8/2009 Krinsky et al.
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`JP A-Hei10(1998)-513622
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`ITU-T Recommendation G.992.2, “Splitterless asymmetric digital
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`ITU-T Recommendation G.994.1, “Handshake procedures for digi
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`Notice of Acceptance for Australian Patent Application No.
`2004203321, dated Aug. 7, 2008.
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`2009222537, dated Mar. 21, 2011.
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`2009222537, dated May 27, 2011.
`Communication Under Rule 71(3) EPC for European Patent Appli
`cation No. EP 06022008, dated Apr. 4, 2011.
`Of?cial Action (including translation) for Japanese Patent Applica
`tion No. 2001-552611, mailed Mar. 28,2011.
`
`Notice of Allowance for Japanese Patent Application No. 2008
`190051, mailed Mar. 14,2011.
`Of?cial Action for US. Appl. No. 09/755,173, mailed Jun. 20, 2002.
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`US. Appl. No. 12/779,708, ?led May 13, 2010, Krinsky et al.
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`Project, Amati Communications Corporation, Dec. 1, 1992, pp. 1-14.
`Lewis L. et al. “Extending Trouble Ticket System to Fault Diagnos
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`Examiner’s First Report for Australian Patent Application No.
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`Examiner’s First Report for Australian Patent Application No.
`2008203520, mailed Mar. 9, 2009.
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`2008203520, mailed Jul. 9, 2009.
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`Of?cial Action for European Patent Application No. 019018084,
`mailed Dec. 1, 2004.
`Of?cial Action for European Patent Application No. 019018084,
`mailed Sep. 14, 2005.
`Communication about intention to grant a European patent for Euro
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`European Search Report for European Patent Application No. EP
`06022008 completed Jan. 8, 2007.
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`mailed Apr. 23, 2010.
`Noti?cation of Reasons (including translation) for Refusal for Japa
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`2009222537, dated Aug. 25, 2011.
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`Jun. 30, 2011.
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`G.992.1,Jun.1999,pp.91-117,125,126,131,132.
`Notice of Allowance for Canadian Patent Application No. 2,394,491,
`dated Jul. 16,2010.
`Of?cial Action for European Patent Application No. EP 06022008,
`mailed Jul. 7, 2010.
`Of?cial Action (including translation) for Japanese Patent Applica
`tion No. 2001-552611, mailed Aug. 2, 2010.
`Of?cial Action (including translation) for Japanese Patent Applica
`tion No. 2008-191051, mailed Jul. 26,2010.
`Of?cial Action for US. Appl. No. 12/477,742, mailed Aug. 16,2010.
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`2010.
`Notice of Allowance for Canadian Patent Application No. 2,726,826,
`dated Mar. 1, 2012.
`
`

`
`U.S. Patent
`
`Aug. 7, 2012
`
`Sheet 1 of2
`
`US 8,238,412 B2
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`
`US. Patent
`
`Aug. 7, 2012
`
`Sheet 2 M2
`
`US 8,238,412 B2
`
`BEGIN x
`8100
`
`Commence
`Initialization \
`S110
`
`Diagnostic
`Mode
`?
`
`Fig. 2
`
`Y
`“
`
`S170
`A/
`,
`‘ Transmit Initiate Diagnostic
`7
`<—]
`Mode Message
`Yes
`
`Re'transmit
`?
`
`Determine Diagnostic
`Link Message
`I
`For Predetermined Number Of
`t
`era "m8 3220
`?/
`
`Transmit Diagnostic Link
`Message With CRC
`
`8210
`
`->
`
`8230
`|
`Determine ?/
`CRC
`
`N°
`
`8140
`M
`Enter Normal
`Steady State
`Data
`-
`-
`Transm'ss'm
`
`Yes
`
`Error
`Threshold
`Exceeded
`?
`
`$250
`'
`I
`ncrease
`Transmission W
`Power
`_—J
`
`Yes
`
`8160
`
`4
`
`

`
`US 8,238,412 B2
`
`1
`MULTICARRIER MODULATION
`MESSAGING FOR POWER LEVEL PER
`SUBCHANNEL INFORMATION
`
`RELATED APPLICATION DATA
`
`This application is a continuation of Us. application Ser.
`No. 12/477,742, ?led Jun. 3, 2009, Which is a continuation of
`Us. application Ser. No. 10/619,691, ?led Jul. 16, 2003, noW
`U.S. Pat. No. 7,570,686, Which is a divisional ofU.S. appli
`cation Ser. No. 09/755,173, ?led Jan. 8, 2001, noW U.S. Pat.
`No. 6,658,052, Which claims the bene?t of and priority under
`35 U.S.C. §119(e) to Us. Provisional Application No.
`60/224,308, ?led Aug. 10, 2000 entitled “Characterization of
`transmission lines using broadband signals in a multi-carrier
`DSL system,” and Us. Provisional Application No. 60/ 174,
`865, ?led Jan. 7, 2000 entitled “Multicarrier Modulation Sys
`tem With Remote Diagnostic Transmission Mode”, each of
`Which are incorporated herein by reference in their entirety.
`
`20
`
`FIELD OF THE INVENTION
`
`This invention relates to test and diagnostic information. In
`particular, this invention relates to a robust system and
`method for communicating diagnostic information.
`
`25
`
`BACKGROUND OF THE INVENTION
`
`The exchange of diagnostic and test information betWeen
`transceivers in a telecommunications environment is an
`important part of a telecommunications, such as an ADSL,
`deployment. In cases Where the transceiver connection is not
`performing as expected, for example, Where the data rate is
`loW, Where there are many bit errors, or the like, it is necessary
`to collect diagnostic and test information from the remote
`transceiver. This is performed by dispatching a technician to
`the remote site, e. g., a truck roll, Which is time consuming and
`expensive.
`In DSL technology, communications over a local sub
`scriber loop betWeen a central of?ce and a subscriber pre
`mises is accomplished by modulating the data to be transmit
`ted onto a multiplicity of discrete frequency carriers Which
`are summed together and then transmitted over the subscriber
`loop. Individually, the carriers form discrete, non-overlap
`ping communication subchannels of limited bandWidth. Col
`lectively, the carriers form What is effectively a broadband
`communications channel. At the receiver end, the carriers are
`demodulated and the data recovered.
`DSL systems experience disturbances from other data ser
`vices on adjacent phone lines, such as, for example, ADSL,
`HDSL, ISDN, T1, or the like. These disturbances may com
`mence after the subj ect ADSL service is already initiated and,
`since DSL for internet access is envisioned as an alWays-on
`service, the effect of these disturbances must be ameliorated
`by the subject ADSL transceiver.
`
`SUMMARY OF THE INVENTION
`
`The systems and methods of this invention are directed
`toWard reliably exchanging diagnostic and test information
`betWeen transceivers over a digital subscriber line in the
`presence of voice communications and/ or other disturbances.
`For simplicity of reference, the systems and methods of the
`invention Will hereafter refer to the transceivers generically as
`modems. One such modem is typically located at a customer
`premises such as a home or business and is “doWnstream”
`from a central of?ce With Which it communicates. The other
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`modem is typically located at the central of?ce and is
`“upstream” from the customer premises. Consistent With
`industry practice, the modems are often referred to as “ATU
`R” (“ADSL transceiver unit, remote,” i.e., located at the cus
`tomer premises) and “ATU-C” (“ADSL transceiver unit, cen
`tral of?ce” i.e., located at the central of?ce). Each modem
`includes a transmitter section for transmitting data and a
`receiver section for receiving data, and is of the discrete
`multitone type, i.e., the modem transmits data over a multi
`plicity of subchannels of limited bandWidth. Typically, the
`upstream or ATU-C modem transmits data to the doWnstream
`or ATU-R modem over a ?rst set of subchannels, Which are
`usually the higher-frequency subchannels, and receives data
`from the doWnstream or ATU-R modem over a second, usu
`ally smaller, set of subchannels, commonly the loWer-fre
`quency subchannels. By establishing a diagnostic link mode
`betWeen the tWo modems, the systems and methods of this
`invention are able to exchange diagnostic and test informa
`tion in a simple and robust manner.
`In the diagnostic link mode, the diagnostic and test infor
`mation is communicated using a signaling mechanism that
`has a very high immunity to noise and/ or other disturbances
`and can therefore operate effectively even in the case Where
`the modems could not actually establish an acceptable con
`nection in their normal operational mode.
`For example, if the ATU-C and/or ATU-R modem fail to
`complete an initialiZation sequence, and are thus unable to
`enter a normal steady state communications mode, Where the
`diagnostic and test information Would normally be
`exchanged, the modems according to the systems and meth
`ods of this invention enter a robust diagnostic link mode.
`Alternatively, the diagnostic link mode can be entered auto
`matically or manually, for example, at the direction of a user.
`In the robust diagnostic link mode, the modems exchange the
`diagnostic and test information that is, for example, used by a
`technician to determine the cause of a failure Without the
`technician having to physically visit, i.e., a truckroll to, the
`remote site to collect data.
`The diagnostic and test information can include, for
`example, but is not limited to, signal to noise ratio informa
`tion, equalizer information, programmable gain setting infor
`mation, bit allocation information, transmitted and received
`poWer information, margin information, status and rate infor
`mation, telephone line condition information, such as the
`length of the line, the number and location of bridged taps, a
`Wire gauge, or the like, or any other knoWn or later developed
`diagnostic or test information that may be appropriate for the
`particular communications environment. For example, the
`exchanged diagnostic and test information can be directed
`toWard speci?c limitations of the modems, to information
`relating to the modem installation and deployment environ
`ment, or to other diagnostic and test information that can, for
`example, be determined as needed Which may aid in evaluat
`ing the cause of a speci?c failure or problem. Alternatively,
`the diagnostic and test information can include the loop
`length and bridged tap length estimations as discussed in Us.
`patent application Ser. No. 09/755,172, noW U.S. Pat. No.
`6,865,221, ?led hereWith and incorporated herein by refer
`ence in its entirety.
`For example, an exemplary embodiment of the invention
`illustrates the use of the diagnostic link mode in the commu
`nication of diagnostic information from the remote terminal
`(RT) transceiver, e. g., ATU-R, to the central of?ce (CO) trans
`ceiver, e.g., ATU-C. Transmission of information from the
`remote terminal to the central of?ce is important since a
`typical ADSL service provider is located in the central of?ce
`and Would therefore bene?t from the ability to determine
`
`

`
`US 8,238,412 B2
`
`3
`problems at the remote terminal without a truckroll. However,
`it is to be appreciated, that the systems and the methods of this
`invention will work equally well in communications from the
`central of?ce to the remote terminal.
`These and other features and advantages of this invention
`are described in or are apparent from the following detailed
`description of the embodiments.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The embodiments of the invention will be described in
`detail, with reference to the following ?gures wherein:
`FIG. 1 is a functional block diagram illustrating an exem
`plary communications system according to this invention;
`and
`FIG. 2 is a ?owchart outlining an exemplary method for
`communicating diagnostic and test information according to
`this invention.
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`20
`
`25
`
`30
`
`35
`
`40
`
`For ease of illustration the following description will be
`described in relation to the CO receiving diagnostic and test
`information from the RT. In the exemplary embodiment, the
`systems and methods of this invention complete a portion of
`the normal modem initialiZation before entering into the diag
`nostic link mode. The systems and methods of this invention
`can enter the diagnostic link mode manually, for example, at
`the direction of a technician or a user after completing a
`portion of initialiZation. Alternatively, the systems and meth
`ods of this invention can enter the diagnostic link mode auto
`matically based on, for example, a bit rate failure, a forward
`error correction or a CRC error during showtime, e.g., the
`normal steady state transmission mode, or the like. The tran
`sition into the diagnostic link mode is accomplished by trans
`mitting a message from the CO modem to the RT modem
`indicating that the modems are to enter into the diagnostic
`link mode, as opposed to transitioning into the normal steady
`state data transmission mode. Alternatively, the transition into
`the diagnostic link mode is accomplished by transmitting a
`message from the RT modem to the CO modem indicating
`that the modems are to enter into the diagnostic link mode as
`opposed to transitioning into the normal steady state data
`transmission mode. For example, the transition signal uses an
`ADSL state transition to transition from a standard ADSL
`45
`state to a diagnostic link mode state.
`In the diagnostic link mode, the RT modem sends diagnos
`tic and test information in the form of a collection of infor
`mation bits to the CO modem that are, for example, modu
`lated by using one bit per DTM symbol modulation, as is used
`in the C-Ratesl message in the ITU and ANSI ADSL stan
`dards, where the symbol may or may not include a cyclic
`pre?x. Other exemplary modulation techniques include Dif
`ferential Phase Shift Keying (DPSK) on a subset or all the
`carriers, as speci?ed in, for example, ITU standard G.994.l,
`higher order QAM modulation (>1 bit per carrier), or the like.
`In the one bit per DMT symbol modulation message
`encoding scheme, a bit with value 0 is mapped to the
`REVERBl signal and a bit with a value of l mapped to a
`SEGUEl signal. The REVERBl and SEGUEl signals are
`de?ned in the ITU and ANSI ADSL standards. The
`REVERBl signal is generated by modulating all of the car
`riers in the multicarrier system with a known pseudo -random
`sequence thus generating a wideband modulated signal. The
`SEGUEl signal is generated from a carrier by 180 degree
`phase reversal of the REVERBl signal. Since both signals are
`wideband and known in advance, the receiver can easily
`
`50
`
`55
`
`60
`
`65
`
`4
`detect the REVERBl and SEGUEl signal using a simple
`matched ?lter in the presence of large amounts of noise and
`other disturbances.
`
`TABLE 1
`
`Exemplary Message Variables
`
`Data Sent in the Diag Link
`Train Type
`ADSL Standard
`Chip Type
`Vendor ID
`Code Version
`Average Reverb Received Signal
`Programmable gain ampli?er (PGA) Gain — Training
`Programmable gain ampli?er PGA Gain — Showtime
`Filter Present during Idle Channel Calculation
`Average Idle Channel Noise
`Signal to Noise during Training
`Signal to Noise during Showtime
`Bits and Gains
`Data Rate
`Framing Mode
`Margin
`Reed-Solomon Coding Gain
`QAM Usage
`Frequency Domain Equalizer (FDQ) Coei?cients
`Gain Scale
`Time domain equalizer (TDQ) Coef?cients
`Digital Echo Canceller (DEC) Coef?cients
`
`Table 1 shows an example of a data message that can be
`sent by the RT to the CO during the diagnostic link mode. In
`this example, the RT modem sends 23 different data variables
`to the CO. Each data variable contains different items of
`diagnostic and test information that are used to analyZe the
`condition of the link. The variables may contain more than
`one item of data. For example, the Average Reverb Signal
`contains the power levels per tone, up to, for example, 256
`entries, detected during the ADSL Reverb signal. Conversely,
`the PGA GainiTraining is a single entry, denoting the gain
`in dB at the receiver during the ADSL training.
`Many variables that represent the type of diagnostic and
`test information that are used to analyZe the condition of the
`link are sent from the RT modem to the CO modem. These
`variables can be, for example, arrays with different lengths
`depending on, for example, information in the initiate diag
`nostic mode message. The systems and methods of this inven
`tion can be tailored to contain many different diagnostic and
`test information variables. Thus, the system is fully con?g
`urable, allowing subsets of data to be sent and additional data
`variables to be added in the future. Therefore, the message
`length can be increased or decreased, and diagnostic and test
`information customiZed, to support more or less variables as,
`for example, hardware, the environment and/ or the telecom
`munications equipment dictates.
`Therefore, it is to be appreciated, that in general the vari
`ables transmitted from the modem being tested to the receiv
`ing modem can be any combination of variables which allow
`for transmission of test and/ or diagnostic information.
`FIG. 1 illustrates an exemplary embodiment of the addi
`tional modem components associated with the diagnostic link
`mode. In particular, the diagnostic link system 100 comprises
`a central of?ce modem 200 and a remote terminal modem
`300. The central of?ce modem 200 comprises, in addition to
`the standard ATU-C components, a CRC checker 210, a diag
`nostic device 220, and a diagnostic information monitoring
`device 230. The remote terminal modem 300 comprises, in
`addition to the standard components associated with anATU
`R, a message determination device 310, a power control
`
`

`
`US 8,238,412 B2
`
`5
`device 320, a diagnostic device 330 and a diagnostic infor
`mation storage device 340. The central of?ce modem 200 and
`the remote terminal model 300 are also connected, via link 5,
`to a splitter 10 for a phone sWitch 20, and a splitter 30 for a
`phone 40. Alternatively, the ATU-R can operate Without a
`splitter, e.g., splitterless, as speci?ed in ITU standard G.992.2
`(G.lite) or With an in-line ?lter in series With the phone 40. In
`addition, the remote terminal modem 300, can also be con
`nected to, for example, one or more user terminals 60. Addi
`tionally, the central of?ce modem 200 can be connected to
`one or more distributed netWorks 50, via link 5, Which may or
`may not also be connected to one or more other distributed
`netWorks.
`While the exemplary embodiment illustrated in FIG. 1
`shoWs the diagnostic link system 100 for an embodiment in
`Which the remote terminal modem 300 is communicating test
`and diagnostic information to the central of?ce 200, it is to be
`appreciated that the various components of the diagnostic link
`system can be rearranged such that the diagnostic and test
`information can be forWarded from the central of?ce 200 to
`the remote terminal modem 300, or, alternatively, such that
`both modems can send and receive diagnostic and/or test
`information. Furthermore, it is to be appreciated, that the
`components of the diagnostic link system 100 can be located
`at various locations Within a distributed netWork, such as
`theiPOTS netWork, or other comparable telecommunica
`tions netWork. Thus, it should be appreciated that the com
`ponents of the diagnostic link system 100 can be combined
`into one device for respectively transmitting, receiving, or
`transmitting and receiving diagnostic and/ or test information.
`As Will be appreciated from the folloWing description, and for
`reasons of computational ef?ciency, the components of the
`diagnostic link system 100 can be arranged at any location
`Within a telecommunications netWork and/or modem Without
`affecting the operation of the system.
`The links 5 can be a Wired or Wireless link or any other
`knoWn or later developed element(s) that is capable of sup
`plying and communicating electronic data to and from the
`connected elements. Additionally, the user terminal 60 can
`be, for example, a personal computer or other device alloWing
`a user to interface With and communicate over a modem, such
`as a DSL modem. Furthermore, the systems and method of
`this invention Will Work equally Well With splitterless and
`loW-pass mulitcarrier modern technologies.
`In operation, the remote terminal 300, commences its nor
`mal initialiZation sequence. The diagnostic device 330 moni
`tors the initialiZation sequence for a failure. If there is a
`failure, the diagnostic device 330 initiates the diagnostic link
`mode. Alternatively, a user or, for example, a technician at the
`CO, can specify that the remote terminal 300 enter into the
`diagnostic link mode after completing a portion of an initial
`iZation. Alternatively still, the diagnostic device 330 can
`monitor the normal steady state data transmission of the
`remote terminal, and upon, for example, an error threshold
`being exceeded, the diagnostic device 330 Will initiate the
`diagnostic link mode.
`Upon initialiZation of the diagnostic link mode, the diag
`nostic device 330, in cooperation With the remote terminal
`300 Will transmit an initiate diagnostic link mode message
`from the remote terminal to the central of?ce 200 (RT to CO).
`Alternatively, the central of?ce modem 200 can transmit an
`initiate diagnostic link mode message to the remote terminal
`modem 300. If the initiate diagnostic link mode message is
`received by the central of?ce 200, the diagnostic device 330,
`in cooperation With the message determination device 310,
`determines a diagnostic link message to be forWarded to the
`central of?ce 200. For example, the diagnostic link message
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6
`can include test information that has been assembled during,
`for example, the normal ADSL initialiZation procedure. The
`diagnostic and/or test information can include, but is not
`limited to, the version number of the diagnostic link mode, the
`length of the diagnostic and/ or test information, the commu
`nications standard, such as the ADSL standard, the chipset
`type, the vendor identi?cations, the ATU version number, the
`time domain received reverb signal, the frequency domain
`reverb signal, the ampli?er settings, the CO transmitter poWer
`spectral density, the frequency domain received idle channel,
`the signal to noise ratio, the bits and gains and the upstream
`and doWnstream transmission rates, or the like.
`If the initiate diagnostic link mode message is not received
`by the central of?ce 200, the initiate diagnostic link mode
`message can, for example, be re-transmitted a predetermined
`number of iterations until a determination is made that it is not
`possible to establish a connection.
`Assuming the initiate diagnostic link mode message is
`received, then, for a predetermined number of iterations, the
`diagnostic device 330, in cooperation With the remote termi
`nal modem 3 00 and the diagnostic information storage device
`340, transmits the diagnostic link message With a cyclic
`redundancy check (CRC) to the central of?ce modem 200.
`HoWever, it is to be appreciated that in general, any error
`detection scheme, such as bit error detection, can be used
`Without affecting the operation of the system. The central
`o?ice 200, in cooperation With the CRC checker 210, deter
`mines if the CRC is correct. If the CRC is correct, the diag
`nostic information stored in the diagnostic information stor
`age device 340 has been, With the cooperation of the
`diagnostic device 330, and the remote terminal modem 300,
`forWarded to the central of?ce 200 successfully.
`If, for example, the CRC checker 210 is unable to deter
`mine the correct CRC, the diagnostic device 330, in coopera
`tion With poWer control device 320, increases the transmis
`sion poWer of the remote terminal 300 and repeats the
`transmission of the diagnostic link message from the remote
`terminal 300 to the central of?ce 200. This process continues
`until the correct CRC is determined by the CRC checker 210.
`The maximum poWer level used for transmission of the
`diagnostic link message can be speci?ed by, for example, the
`user or the ADSL service operator. If the CRC checker 210
`does not determine a correct CRC at the maximum poWer
`level and the diagnostic link mode can not be initiated then
`other methods for determining diagnostic information are
`utiliZed, such as dispatching a technician to the remote site, or
`the like.
`Alternatively, the remote terminal 300, With or Without an
`increase in the poWer level, can transmit the diagnostic link
`message several times, for example, 4 times. By transmitting
`the diagnostic link message several times, the CO modem 200
`can use, for example, a diversity combining scheme to
`improve the probability of obtaining a correct CRC from the
`received diagnostic link message(s).
`Alternatively, as previously discussed, the central of?ce
`200 comprises a diagnostic information monitoring device
`230. The remote terminal 300 can also include a diagnostic
`information monitoring device. One or more of these diag
`nostic information monitoring devices can monitor the nor
`mal steady state data transmission betWeen the remote termi
`nal 300 and the central of?ce 200. Upon, for example, the
`normal steady state data transmission exceeded a predeter
`mined error threshold, the diagnostic information monitoring
`device can initiate the diagnostic link mode With the coopera
`tion of the diagnostic device 300 and/or the diagnostic device
`220.
`
`

`
`US 8,238,412 B2
`
`7
`FIG. 2 illustrates an exemplary method for entering a diag
`nostic link mode in accordance with this invention. In par
`ticular, control begins in step S100 and continues to