Source: http://www.google.com/patents/US6978015?ie=ISO-8859-1&dq=6437692
Timestamp: 2014-11-28 18:16:29
Document Index: 510501895

Matched Legal Cases: ['application No. 60', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 60', 'application No. 60']

Patent US6978015 - Method and apparatus for cooperative diagnosis of impairments and mitigation ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA method that sends upstream a collection of data samples measured from a DSL line....http://www.google.com/patents/US6978015?utm_source=gb-gplus-sharePatent US6978015 - Method and apparatus for cooperative diagnosis of impairments and mitigation of disturbers in communication systemsAdvanced Patent SearchPublication numberUS6978015 B1Publication typeGrantApplication numberUS 09/710,579Publication dateDec 20, 2005Filing dateNov 10, 2000Priority dateNov 11, 1999Fee statusPaidPublication number09710579, 710579, US 6978015 B1, US 6978015B1, US-B1-6978015, US6978015 B1, US6978015B1InventorsMark Alan Erickson, Ioannis Kanellakopoulos, John Josef Hench, Sunil C. Shah, James W. Waite, Michail Tsatsanis, Gurcan AralOriginal AssigneeTokyo Electron LimitedExport CitationBiBTeX, EndNote, RefManPatent Citations (41), Non-Patent Citations (41), Referenced by (20), Classifications (17), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetMethod and apparatus for cooperative diagnosis of impairments and mitigation of disturbers in communication systemsUS 6978015 B1Abstract A method that sends upstream a collection of data samples measured from a DSL line.
CLAIM OF PRIORITY This application claims the benefit of the filing date of the following Provisional U.S. patent applications:
�SPECTRAL MANAGEMENT AND OPTIMIZATION THROUGH ACCURATE IDENTIFICATION OF CROSS-TALK CHANNELS AND UNCERTAINTY�, application No. 60/164,986, filed Nov. 11, 1999; �SPECTRAL MANAGEMENT AND OPTIMIZATION THROUGH ACCURATE IDENTIFICATION OF CROSS-TALK CHANNELS AND UNCERTAINTY�, application No. 60/181,125, filed on Feb. 8, 2000; �SPECTRAL MANAGEMENT AND OPTIMIZATION THROUGH ACCURATE IDENTIFICATION OF CROSS-TALK CHANNELS AND UNCERTAINTY�, application No. 60/183,675, filed on Feb. 18, 2000; �USE OF UNCERTAINTY IN PHYSICAL LAYER SIGNAL PROCESSING IN COMMUNICATIONS�, application No. 60/165,399, filed Nov. 11, 1999; �SHARED COMPUTATIONAL RESOURCES FOR IMPROVED PERFORMANCE OF A TRANSCEIVER� application No. 60/215,159, filed on Jun. 30, 2000; and �SYSTEM LEVEL SUPPORT FOR TRANSCEIVER PERFORMANCE�, application No. 60/215,680, filed on Jun. 30, 2000. FIELD OF THE INVENTION The field of invention relates to communications generally; and more specifically, to improving the performance of a network by sharing resources or information between a network perspective and a line perspective.
Information that flows in the network 100 toward the customer (e.g., toward the direction of a CPE as seen in FIG. 1) has a �downstream� direction while information that flows in the network 100 away from the customer (e.g., away from a CPE as seen in FIG. 1) has an �upstream� direction. Thus it may be said that a transceiver within a CPE is responsible for controlling at the CPE the transmission of upstream information and the reception of downstream information.
Various DSL service schemes exist. For example, at a high level, DSL services are characterized according to the bandwidth allocated for a customer's upstream and downstream traffic. Services that reserve approximately equal amounts of bandwidth for a customer's upstream and downstream traffic are referred to as �symmetric DSL� while services that reserve approximately unequal amounts of bandwidth for a customer's upstream and downstream traffic are referred to as �asymmetric DSL�.
Symmetric DSL (SDSL), High bit rate DSL (HDSL, HDSL-2) and ISDN DSL (IDSL) are versions of symmetric DSL. Asymmetric DSL (ADSL), Rate Adaptive DSL (RADSL), Very high bit rate DSL (VDSL), and G.Lite are versions of asymmetric DSL. Any of these DSL services (as well as other potential future DSL services that are not listed above) may be referred to as �DSL�.
The receiver 201 includes an equalizer 202 and a symbol detection unit 203 (which may also be referred to as a symbol detector 203). The equalizer 202 adjusts the transfer function of the receive channel such that the frequency components of the received waveform rx(t) 221 that are associated with the signal (i.e., the frequency components of the received waveform rx(t) 221 that are associated with the downstream information sent from the service provider to the transceiver 208) are enhanced with respect to the frequency components of the waveform rx(t) 221 that are not associated with the signal (i.e., the frequency components of the waveform's �noise�). For example, the signal components alone may be amplified, the noise components alone may be suppressed or a combination of both.
SUMMARY OF INVENTION A method that sends upstream a collection of data samples measured from a network line.
Thus, for example, disturber d1(t) may correspond to a waveform on a first line, d2(t) may correspond to a waveform on a second line, and d3(t) may correspond to a waveform on a third line. Each disturber d1(t), d2(t), d3(t) passes through and is processed by its corresponding co-channel h1(t), h2(t), and h3(t). Each co-channel h1(t), h2(t), and h3(t) represents the impulse response of the electromagnetic coupling that exists between lines that �cross-talk� with one another.
FIG. 3 b shows another perspective of a DSL network that may be referred to as a network perspective. A network perspective is an understanding of cross-talk (or other interference) as developed through the correlation of information obtained from events observed on the lines within a network. As seen in FIG. 3 b, note that a network perspective may be developed by a DSL network's NMA 318. The NMA 318 �keeps track of� events such as changes in the performance and/or configuration of each line in the DSL network that the NMA 318 exhibits control over.
That is, to the extent possible, the output of the signal removal unit 404 corresponds to pure �noise�. The disturber receiver 407 includes a disturber equalizer 405 and a disturber symbol detection unit 406. The disturber equalizer 407 attempts to �undo� the activity of the equalizer 203. That is, recall from the discussion in the background that an equalizer (such as equalizer 203 of FIG. 2 or equalizer 403 of FIG. 4) suppresses a channel's noise and/or amplifies it's signal.
In so doing, the equalizer 203 attempts to �whiten� the noise so that it possesses an approximately constant power spectral density over the frequency range of interest. As a result, particularly strong disturber noise frequency components (e.g., a 20�392 KHz band for a symetric DSL service on a neighboring line) will be individually and disproportionately attenuated by the equalizer 203 (as compared to other noise frequency components). The disturber equalizer 405 attempts to reverse this disproportionate attenuation so that the pure spectral components of the disturber noise, as they appear on the line 420 prior to processing by the equalizer 402, are recaptured.
FIG. 5 shows an exemplary embodiment of a Discrete Multi Tone�Asymmetric Digital Subscriber Line (DMT-ADSL) receiver 501 that conforms to the processing approach just described with respect to FIG. 4. The DMT-ADSL receiver 501 of FIG. 5 includes an equalizer 502 (which corresponds to the equalizer 402 of FIG. 4), a DMT signal removal unit 504 (which corresponds to the signal removal unit 404 of FIG. 4), a disturber receiver 507 (which corresponds to the disturber receiver 407 of FIG. 4), a disturber removal unit 508 (which corresponds to the disturber removal unit 408 of FIG. 4) and a symbol detection unit 503 (which corresponds to the symbol detection unit 403 of FIG. 4).
During a sequence referred to as �line training�, the equalizer 502 searches for the signal based upon the type and/or speed of service that is to be received. When the signal is found, the equalizer 502 adjusts an impulse response function profile associated with a time domain equalizer (TEQ) 509. This impulse response function, when convoluted with the received signal rx(t), produces an efficient representation of the received signal rx(t) at the TEQ output 509. Furthermore, the TEQ convolution may also provide (as an ancillary benefit) some degree of noise suppression.
The DMT signal removal unit 504 corresponds to the signal removal unit 404 of FIG. 4. As such the output 510 of the DMT signal removal unit 504 corresponds to, to the extent possible, pure �noise�. As seen in FIG. 5, a slicer unit 521 detects (within the frequency domain) the DMT signal.
DMT is a modulation scheme that uses a plurality of quadrature amplitude modulated (QAM) sinusoids to transmit digital information. The frequency of each sinusoid is centered within a frequency �bin� (e.g., a frequency band of 4.3125 KHz reserved for its transmission. According to QAM modulation, the phase and amplitude of a sinusoid are modulated to represent the different possible states of the digital bits being transmitted. The number of bits that are transmitted on a line increases with the number of sinusoids that are transmitted and/or the number of different phase and amplitude positions (i.e., bit states) implemented per sinusoid.
As discussed with respect to the disturber equalizer 405 of FIG. 4, the DEQ 505 attempts to �undo� any noise suppression provided by the equalizer 502. That is, with respect to the design approach of FIG. 5, the DEQ 505 attempts to undo any noise suppression provided by the TEQ 509. Noise suppression from the TEQ may be undone by effectively inversely compensating for the adjustments made by the TEQ (during line training as discussed above) to the TEQ impulse response function profile.
Note that the association of particular portions of the disturber noise presented by the DEQ 505 with specific types of �nearby� services is an aspect of the line level perspective (discussed with respect to FIG. 3 a) held by the receiver 501. An exemplary embodiment of how this understanding/perspective is developed is provided in more detail below. The Viterbi detector 506 of FIG. 5 employs Maximum Likelihood Sequence Estimation (MLSE) to reconstruct, from its line level perspective, the particular disturber signal on the cross coupled line.
FIG. 6 shows a methodology that may be used to develop the line perspective discussed just above. The development of a line perspective (and/or any disturber noise compensation that results) may be referred to as mitigation of disturbers. The development of a line perspective may occur during line training. Line training is a period of time prior to the actual use of the line to transmit a customer's information (referred to as �showtime�). During line training the CPE transceiver responsible for controlling the transmission/reception of upstream/downstream traffic �learns� about the operating environment of the line.
Referring to FIG. 6, a disturber signal may be identified or otherwise characterized through its type of service 601. Said another way, with foresight of the types of services that may cause disturber noise (e.g., T1 or PAM-SDSL on a DMT-ADSL line), certain frequency ranges may be �focused upon� to see if disturber noise exists.
That is, for example, it is known that a T1 signal has a fundamental frequency of approximately 1.5 MHz. By searching across a frequency range centered at 1.5 MHz, the existence (or lack thereof of disturber noise resulting from a cross-coupled T1 line may be confirmed and its exact frequency may be determined. Such a frequency range may be referred to as a �service specific� frequency range.
If disturber noise power (e.g., above a critical threshold to warrant further analysis) is detected for a particular service type, the corresponding frequency range may be further analyzed 602 to see how many disturber signals (i.e., how many cross coupled lines) exist for this type of service. For example, by �refocusing� in the service specific frequency range with a finer resolution bandwidth, each discovered �peak� may be assumed to be caused by a different line (owing to differences in crystal oscillator frequencies used to form the disturber signals). Note that identification of the frequency at which a particular peak occurs corresponds to a further refinement of the line level perspective. That is, not only has the service type for a source of disturbance been identified but also its particular frequency has been identified.
Once the number of disturbers of a particular service type is determined, a model of the spectral content of an ideal disturber signal for each discovered disturber is generated. This ideal disturber signal model may be compared against what is actually observed on the line (i.e., the disturber signal's corresponding disturber noise) to generate 603 an estimation of the disturber signal's co-channel. That is, the co-channel is responsible for (and may be characterized by) the �distortion� that occurs to the disturber signal as it is converted from a disturber signal to disturber noise.
The line level perspective is then built 620 into the design of the transceiver. First, because the amount of disturber noise that will be removed is understood, the transceiver can estimate its expected improved SNR and determine 606 an appropriate line speed (or data rate) for the line. Second, the disturber equalizer (e.g., disturber equalizers 405, 505 of FIGS. 4 and 5) is configured 607 to �undo� the equalization of the equalizer (e.g., equalizer 402, 502 of FIGS. 4 and 5) based upon the parameters that setup the equalizer.
For examples of the methodologies and apparati discussed just above, see co-pending patent applications entitled �Method and Apparatus for Characterization of Disturbers in Communication Systems�, �Method and Apparatus for Mitigation of Disturbers in Communication Systems�, �Design & Architecture of an Impairment Diagnosis System for Use in Communication Systems�, �Method and Apparatus for Impairment Diagnosis in Communication Systems�, �Method and Apparatus for Prediction & Optimization in Impaired Communication Systems� all assigned to the present assignee and filed on an even date herewith.
FIG. 7 shows a depiction of event notification flows that may be used to develop a network perspective. Development of a network perspective (and/or any network improvement that results) may be referred to as diagnosis of impairments. Recall from the discussion of FIG. 3 b that a network perspective is an understanding of cross-talk (or other interference) as developed through the correlation of events observed on the lines within a network. The cross-talk understanding may be embodied in the form of a �chart� that identifies: 1) which lines are cross coupled with one another; and 2) for each cross coupling that is identified, how strong the particular cross coupling is.
In an embodiment, event notifications are sent to and collected by the NMA 718. The NMA �keeps track of� these events and attempts to correlate them with other network events that the NMA is aware of. For example, if the NMA 718 collects event notifications from lines 720, 721 and 722 that each has experienced a drop in SNR just after an increase in the service speed on line 724 was allowed, the NMA 718 can assume that line 724 is the source of disturber noise on lines 720, 721 and 722.
As another example, with respect to DSLAM 702, consider an instance where each line card 706, 707, 708 reports an event that was correlated to each of the line card's lines. If the DSLAM control unit 704 further determines that each of these reports are correlated (e.g., the timestamp of the event reported by each line card 706, 707, 708 are approximately the same), the DSLAM control unit 704 may conclude that a �significant� event has occurred that has affected every line coupled to the DSLAM 702.
For example, if an existing customer desires to increase the speed of his or her service, the service provider can send a higher speed test signal over the line. Depending on the SNR changes to other lines that are caused by the increase in speed, the service provider may permit or deny the increased service. Furthermore, the service provider may continuously run tests during a network's �quiet time� (e.g., in the early morning when the customer population is mostly asleep). By continually running tests (e.g., adjustments in speed and/or power to one or more lines) and continually collecting the events that follow, the NMA 718 can build upon and improve its understanding of the cross-talk that exists between the lines on its network.
For examples of improving an understanding through continued monitoring and analysis of the lines see patent applications entitled �Design and Architecture of an Impairment Diagnosis System for Use in Communication Systems� and �Method and Apparatus for Impairment Diagnosis in Communication Systems� assigned to the present assignee and filed on an even data herewith.
That is, the aforementioned �chart� (that identifies: 1) which lines are cross coupled with one another; and 2) for each cross coupling that is identified, the strength of the particular cross coupling) is continuously refined and improved as to its accuracy. Note that so far the network perspective has been limited to �in domain� lines. In domain lines are lines that the NMA 718 has control over (in terms of being able to adjust their speed or power) and can receive event notifications from.
The NMA 718 may also be able to build an understanding of �out of domain� disturbers (i.e., disturbers that the NMA 718 does not have control over and does not receive event reports from). For example, if a local AM radio station reduces its transmitted power every day after sunset, those in-domain lines that are cross coupled with the AM radio station will report an increase in SNR every day after sunset. The NMA 718 can therefore add to the �chart� the existence of an AM radio station that affects the lines that indicate cross coupling. Various other processes may also be used to identify at least the presence of disturbers originating from lines that are controlled by other service providers.
First, the NMA 718 may develop a more accurate �chart� of lines that are cross coupled. That is, recall that the disturber information gathered during a line perspective development phase (as discussed with respect to FIG. 6) includes: 1) description of the service that the disturber signal corresponds to; 2) the actual frequency of the disturber signal; and 3) an estimate of the co-channel between the line and the cross coupled line carrying the disturber signal.
By sending such a description of one or more disturbers upstream to the NMA 818, the NMA 818 can more readily and with more confidence develop its chart. For example, if the NMA 818 believes (as a result of the event reporting described above with respect to FIG. 7) that a particular line (e.g., line 724 in FIG. 7) causes disturber noise on particular lines (e.g., lines 720, 721, and 722), this belief may be �confirmed� if the victim lines (e.g., lines 720, 721, and 722) each report identical disturber information that match the configuration of the disturber line (e.g., line 724).
Note that disturber information 801 sent upstream to the NMA may also describe �out-of domain� disturbers. Thus, whereas the event reporting scheme may be limited to realizing only the existence of an �out of domain� disturber, the sending of out of domain disturber information to the NMA 818 allows the NMA 818 to gain a deeper understanding of the out of domain disturber. Specifically, the type of service, the service speed and the co-channel of the out of domain disturber may be understood.
Also, if the NMA 818 notices a change in the disturber profile (i.e., if a significant loss in SNR is reported by various lines), the NMA 818 may request any line to �re-develop� its line level understanding. When the subsequent disturber information 801 gathered from the new line understanding is forwarded to the NMA 818, the NMA 818 can search for the cause of the change (e.g., such as a newly introduced out of domain disturber).
As an alternate cooperative enhancement, note that the NMA's development of a more detailed and accurate analysis of the spectral content of the line may be used to �pinpoint� to the CPE transceiver precisely where important disturbers are to be found. That is, for example, the disturber information 902 directed to the CPE may be used by the CPE to execute its own (i.e., �local�) transceiver training and design routines (e.g., as discussed with respect to FIG. 6). Because the NMA has informed the CPE transceiver �where to look�, the CPE transceiver can immediately focus upon one or more disturbers, rather than scan a wide frequency range. More efficient use of training time results (e.g., via improved disturber and co-channel models and/or reduced time spent during training the training period).
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