CSCO-1001
`Cisco v. TQ Delta
`Page 1 of 10
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`

`
`US 8,238,412 B2
`Page 2
`
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`dated Mar. 1. 2012.
`
`Page 2 of 10
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`

`
`U.S. Patent
`
`Aug. 7, 2012
`
`2fl.01teehS
`
`US 8,238,412 B2
`
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`Page 3 of 10
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`

`
`U.S. Patent
`
`Aug. 7, 2012
`
`Sheet 2 of2
`
`US 8,238,412 B2
`
`( BEGIN )$
`S100
`
`Commence
`
`Initialization \\
`
`Select
`
`Diagnostic
`Mode
`?
`
`Enter Normal
`Steady State
`Data
`Transmission
`
`Error
`Threshold
`Exceeded
`?
`
`Transmit Initiate Diagnostic
`Mode Message
`
`Determine Diagnostic
`Link Message
`
`Re-transmit
`9
`
`For Predetermined Number Of
`
`'terati°"s S220
`
`Transmit Diagnostic Link
`
`Increase
`Transmission
`
`Page 4 of 10
`
`

`
`US 8,238,412 B2
`
`1
`ML LTICARRIER MODULATION
`MESSAGING FOR POVVER LEVEL PER
`SL BCHANNEL INFORMATION
`
`RELATED APPLICATION DATA
`
`This application is a continuation of U.S. application Ser.
`No. 12/477,742, filed Jun. 3, 2009, wl1icl1 is a continuation of
`U .S. application Ser. No. 10/619,691, filed Jul. 16, 2003, now
`U.S. Pat. No. 7,570,686, which is a divisional of U.S. appli-
`cation Ser. No. 09/755,173, filed Jan. 8, 2001, now U.S. Pat.
`No. 6,658,052, which claims the benefit of and priority under
`35 U.S.C. §119(e) to U.S. Provisional Application No.
`60/224,308, filed Aug. 10, 2000 entitled “Characterization of
`transmission lines using broadband signals in a multi—carrier
`DSL system,” and U.S. Provisional Application No. 60/174,
`865, filed Iar1. 7, 2000 entitled “Multicarrier Modulation Sys-
`tem with Remote Diagnostic Transmission Mode”, each of
`which are incorporated herein by reference in their entirety.
`FIELD OF THE IN VEN 'l'l()N
`
`This invention relates to test and diagnostic information. In
`particular,
`this invention relates to a robust system and
`method for cor11n1u11icatir1g diagnostic information.
`
`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 wl1ere 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 perfonned by dispatching a technician to
`the remote site, e.g., a truck roll, wl1ich is time consuming and
`expensive.
`In DSL technology, communications over a local sub-
`scriber loop between a central ofiice 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 fomi discrete, non—overlap—
`ping communication subcharmels oflimited 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 or1 adjacent phone lir1es, such as, for example, ADSL,
`HDSL, ISDN, '11, or the like. 'lhese 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.
`
`V
`
`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 ofvoice 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 ofiice with which it communicates. The other
`
`2
`the central ofiice and is
`modem is typically located at
`“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 office” i.e., located at the central office). 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 r11oden1 over a first set of subcharmels, 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 subchamiels, 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.
`information can include, for
`The diagnostic and test
`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 lir1e 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 specific 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 ir1 evaluat-
`ing the cause of a specific failure or problem. Alternatively,
`the diagnostic and test information can include the loop
`length and bridged tap length estimations as discussed in U.S.
`patent application Ser. No. 09/755,172, now U.S. Pat. No.
`6,865,221, filed 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 oflice (CO) trans-
`ceiver, e.g., ATU—C. Transmission of infonnation from the
`remote terminal to the central office is important since a
`typical ADSL service provider is located in the central ollice
`and would therefore benefit from the ability to determine
`
`Page 5 of 10
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`

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`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 ofthis
`invention will work equally well in communications from the
`central office 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 figures wherein:
`FIG. 1 is a functional block diagram illustrating an exem-
`plary coimnunications system according to this invention;
`and
`FIG. 2 is a flowchart outlining an cxcmplary mcthod for
`communicating diagnostic and test infomiation according to
`this invention.
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`For ease of illustration the following description will be
`described in relation to the CO rccciving diagnostic and test
`information from the RT. In the exemplary embodiment, the
`systems and methods of this invention complete a portion of I
`the nonnal r11ode1n initializationbefore entering i11to 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
`nomial steady state transmission mode, or the like. The tran-
`sition i11to the diagnostic link n1ode is accomplished by trans-
`mitting a message from the CO modem to the RT modem
`indicating that thc modcms arc to cntcr 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, tl1e transition signal uses ar1
`ADSL state transition to transition from a standard ADSL
`state to a diagnostic link modc 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
`prefix. Other exemplary modulation techniques include Dif-
`ferential Phase Shift Keying (DPSK) on a subset or all the
`carriers, as spccificd 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
`REVERBI signal and a bit with a value of l mapped to a
`SEGUEI signal. The REVERBI and SEGUEI signals are
`defined in the ITU and ANSI ADSL standards. The
`REVERBI signal is generated by modulating all of the car-
`riers in the multicarrier system with a known pseudo-random
`scqucncc thus generating a widcband modulated signal. The
`SEGUEI signal is generated from a carrier by 180 degree
`phase reversal of the REVERBI signal. Since both signals are
`wideband and known in advance, the receiver can easily
`
`4
`detect the REVERBI and SEGUEI signal using a simple
`matched filter in the presence of large amounts of noise and
`other disturbances.
`
`TABLE 1
`
`Exemplary Mcssagc Variablcs
`
`Data Sent in the Diag Link
`Train Type
`ADSL Standard
`Chip Type
`Vendor I )
`Code Version
`Average
`everb Received Signal
`Programmable gain amplifier (PGA) Gain - Training
`Programmable gain amplifier PGA Gain - Showtime
`Filter Present during Idle Channel Calculation
`Average dle Channel Noise
`Signal to Noise during Training
`Signal to Noise during Showtime
`
`Rccd-Solomon Coding Gain
`QAM Usagc
`Frequency Domain Equalizcr (FDQ) Cocflicicnts
`Gain Sca c
`Time domain equalizer (TDQ) Coeificients
`Digital Echo Canceller (DEC) Coefficients
`
`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 pcr tone, up to, for cxamplc, 256
`entries, dctcctcd during the ADSL Rcvcrb signal. Convcrscly,
`thc PGA Gain—Training is a single cntry, 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 ir1 the initiate diag-
`nostic mode message. The systems and methods ofthis inven-
`tion can bc tailored to contain many different diagnostic and
`test information variables. Thus, the system is fully config-
`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 thc rccciv-
`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 ofiice modem 200 and a remote terminal modem
`300. The central office modem 200 comprises, ir1 addition to
`the standard ATU-C components, a CRC checker 210, a diag-
`nostic dcvicc 220, and a diagnostic information monitoring
`device 230. The remote terminal modem 300 comprises, in
`addition to tl1e standard components associated with anATU-
`R, a message detennination device 310, a power control
`
`Page 6 of 10
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`US 8,238,412 B2
`
`~
`
`5
`device 320, a diagnostic device 330 and a diagnostic infor-
`mation storage device 340. The central office modem 200 and
`the remote terminal model 300 are also coimected, via link 5,
`to a splitter 10 for a phone switch 20, and a splitter 30 for a
`phone 40. Altematively, the ATU-R can operate without a
`splitter, e.g., splitterless, as specified in ITU standard G.992.2
`(G.lite) or with an in-li11e filter i11 series with the phone 40. In
`addition, the remote terminal modem 300, ca11 also be con-
`nected to, for example, one or more user terminals 60. Addi-
`tionally, the central ofiice 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 tl1e central office 200, it is to be
`appreciated that the various components ofthe diagnostic link
`system can be rearranged such that the diagnostic and test
`information can be forwarded from the central office 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
`the—POTS network, or other comparable telecom1m1nica-
`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 efficiency, 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 tlie system.
`The links 5 can be a wired or wireless link or any other
`known or later developed clement(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 modem 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 witl1 tl1e remote tenninal
`300 will transmit an initiate diagnostic link mode message
`from the remote terminal to the central office 200 (RT to CO).
`Altematively, the central office modem 200 can transmit an
`initiate diagnostic link mode mes sage to the remote terminal
`modem 300. If the initiate diagnostic link mode message is
`received by the central office 200, the diagnostic device 330,
`in cooperation with the message determination device 310,
`determines a diagnostic link message to be forwarded to the
`central office 200. For example, tl1e diagnostic link message
`
`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 ofthe 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 identifications, the ATU version number, the
`time domain received reverb signal. the frequency domain
`reverb signal. the amplifier settings, the CO transmitter power
`spectral density, the frequency domain received idle charmel,
`the signal to noise ratio, the bits a11d gains and the upstream
`and downstream transmission rates, or the like.
`If the initiate diagnostic link mode message is not received
`by tl1e central office 200, the initiate diagnostic link mode
`message can, for example, be re-transmitted a predetermined
`number ofiterations until a determination is made that it is not
`possible to establish a comiection.
`Assuming tl1e initiate diagnostic link mode mes sage is
`received, then, for a predetennined number of iterations, the
`diagnostic device 330, in cooperation with the remote tenni-
`nal modem 3 U0 and the diagnostic information storage device
`340,
`transmits the diagnostic link message with a cyclic
`redundancy check (CRC) to the central office 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
`ofiice 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 tlie 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 office 200 successfully.
`If for example, the CRC checker 210 is unable to deter-
`mine the correct CRC, tl1e 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 office 200. This process continues
`lmtil the correct CRC is determined by the CRC checker 210.
`The maximum power level used for transmission of the
`diagnostic link message can be specified 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).
`Altematively, as previously discussed, the central ofiice
`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 tl1e central ofiice 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.
`
`Page 7 of 10
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`

`
`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 step
`S110. In step S110, the initialization sequence is commenced.
`Next,
`in step S120. if an initialization failure is detected,
`control continues to step S170. Otherwise, control jumps to
`step S130. In step S130, a determination is made whether the
`diagnostic link mode has been selected. If the diagnostic link
`mode has been selected, control continues to step S170. oth-
`erwise, control jumps to step S140.
`In step S170, the initiate diagnostic link mode message is
`transmitted from, for example, the remote terminal to the
`central office. Next. in step S180, a determination is made
`whether the initiate diagnostic mode message has been
`received by the CO. If the initiate diagnostic mode message
`l1as been received by the CO, control jumps to step S200.
`Otherwise, control continues to step S190. In step S190, a
`determination is n1ade whether to re-transinit the initiate
`diagnostic mode message, for example, based on whether a
`predetermined number of iterations have already been com-
`pleted. If the initiate diagnostic mode message is to be re-
`transmittcd, control continucs back to step S170. Othcrwisc,
`controljumps to step S160.
`In step S200, the diagnostic link message is determined, for
`example, by assembling test and diagnostic information
`about one or more of the local loop, the modem itself, the
`telephone network at the remote terminal, or the like. Next, in
`step S210. for a predetermined number of iterations, steps
`S220-S240 are completed. In particular, in step S220 a diag-
`nostic link message comprising a CRC is transmitted to, for
`example, the CO. Next, in step S230, the CRC is determined
`Then, in step S240, a determination is made whether the CRC
`is correct. If the CRC is correct. the test and/or diagnostic
`information has been successfully communicated a11d control
`continues to step S160.
`Otherwise, if stcp S210 has completed thc predetermined
`number of iterations, control continues to step S250. In step
`S250, the transmission power is increased a11d control con-
`tinues back to step S210. Alternatively, as previously dis-
`cussed, the diagnostic link message may be transmitted a
`predetermined number of times, with our without a change in
`the transmission power.
`In step S140, the normal steady state data transmission is
`entered into between two modems, such as the remote termi-
`nal and thc ccntral officc modcms. Next,
`in step S150, a
`determina ion is made whether an error threshold during the
`normal steady state data transmission has been exceeded. If
`the error tireshold has been exceeded, control continues to
`step S170. Otherwise, control jumps to step S160. In step ,
`S160, the control sequence ends.
`As shown in FIG. 1, the diagnostic link mode system canbe
`implemen ed either on a single program general purpose
`computer, a modem, such as a DSL modem, or a separate
`program gcncral purposc computcr having a communications
`device. However, the diagnostic link system can also be
`implemen ed on a special purpose computer, a programmed
`microprocessor or microcontroller a11d peripheral integrated
`circuit element, an ASIC or other integrated circuit, a digital
`signal processor, a hardwired electronic or logic circuit such
`as a discre e element circuit, a programmed logic device such
`as a PLD, PLA, FPGA, PAL, or the like, and associated
`communications equipment. In general, any device capable
`of implementing a finite state machine that is capable of
`implemen ing the flowchart illustrated in FIG. 2 can be used
`to implement a diagnostic link system according to this inven-
`tion.
`
`8
`Furthermore, the disclosed method may be readily imple-
`mented in software using object or object-oriented software
`development environments that provide portable source code
`that can be used on a variety of computer, workstation, or
`modcm hardware platforms. Altcrnativcly,
`thc discloscd
`diagnostic link system may be implemented partially or fully
`in hardware using standard logic circuits or a VLSI design.
`Other software or hardware ca11 be used to implement the
`systems in accordance with this invention depending on the
`speed and’or efficiency requirements of the systems, the par-
`ticular function, and a particular sof