EP2817954A1 - Procédé et dispositif de traitement de données dans un environnement de ligne d'abonné numérique - Google Patents

Procédé et dispositif de traitement de données dans un environnement de ligne d'abonné numérique

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Publication number
EP2817954A1
EP2817954A1 EP12705841.0A EP12705841A EP2817954A1 EP 2817954 A1 EP2817954 A1 EP 2817954A1 EP 12705841 A EP12705841 A EP 12705841A EP 2817954 A1 EP2817954 A1 EP 2817954A1
Authority
EP
European Patent Office
Prior art keywords
noise
artificial
level
snr
line
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP12705841.0A
Other languages
German (de)
English (en)
Inventor
Martin Kuipers
Thomas Ahrndt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nokia Solutions and Networks Oy
Original Assignee
Nokia Solutions and Networks Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nokia Solutions and Networks Oy filed Critical Nokia Solutions and Networks Oy
Publication of EP2817954A1 publication Critical patent/EP2817954A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M11/00—Telephonic communication systems specially adapted for combination with other electrical systems
    • H04M11/06—Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
    • H04M11/062—Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors using different frequency bands for speech and other data
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0044—Arrangements for allocating sub-channels of the transmission path allocation of payload
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0058—Allocation criteria
    • H04L5/006—Quality of the received signal, e.g. BER, SNR, water filling

Definitions

  • the invention relates to a method and to a device for data processing in a digital subscriber line environment.
  • the invention also suggests a communication system comprising at least one such device.
  • DSL or xDSL is a family of technologies that provide digital data transmission over the wires of a local telephone network.
  • High speed Internet access is gaining importance and is often realized via xDSL services using existing copper lines.
  • other applications emerge that require broadband transmission services, e.g., triple play offers comprising subscriber access to Internet, TV and voice data transmission.
  • a bandwidth consuming application is the transmission of TV data via xDSL, wherein one HDTV channel requires a data rate amounting to 12 Mbit/s.
  • Fig.l shows a schematic diagram comprising a power of a noise 101, a margin 102 and user data 103 over time.
  • An impulse noise during a time period 104 affects the user data thereby leading to CRC errors, which may be visible to a user's IPTV application.
  • Additional noise from the DSL during a time period 105 results in a retraining of the modem adjusting its user data/margin differently starting at a time 106.
  • the retraining leads to an outage of the user data 103 and thus of the IPTV service, which will continue at said time 106 at a reduced data rate .
  • Fig.2 shows a schematic diagram visualizing several portions of a reception power in a logarithmic scale over a frequency for illustration purposes comprising a flat noise margin 203, a floor 201 of a receiver and a crosstalk noise 202 on top of this noise floor 201.
  • the flat noise margin 203 is applied on top of both, the noise floor 201 and the crosstalk noise 202.
  • An area beyond the noise margin 203 corresponds to the portion of a received signal power to be available for data transmission 204, i.e. is proportional to an attainable data rate.
  • the crosstalk noise 202 increases beyond the noise margin, a retraining of the modem will become necessary and the noise margin will be adjusted at the cost of a reduced attainable data rate.
  • Fig.2 shows an operational case of signals received at an xDSL modem in case a connection between a DSLAM and a CPE has been established.
  • xDSL with DMT modulation can be used according to, e.g., ADSL G.992.1, ADSL2 G992.3,
  • the received signal power 204 declines at higher frequencies due to an attenuation of the channel.
  • the amount of data that can be transported at a certain subcarrier frequency is roughly proportional to a signal- to-noise ratio (SNR) .
  • SNR signal- to-noise ratio
  • the achievable data rate may be substantially proportional to the area between the receiver noise floor 201 and the received signal power at the receiver.
  • Crosstalk noise 202 from other lines and services limit the achievable data throughput.
  • a moderate increase of the crosstalk noise 202 can be compensated as the signal-to-noise ratio is not fully exploited for data transmission.
  • the noise margin 203 is provided for safety reasons .
  • the SNR margin may represent an acceptable increase of noise received (in dB) such that the system still meets a target bit error rate (BER) amounting to 10 ⁇ 7 .
  • BER target bit error rate
  • a large target noise margin can be utilized by the modem during initialization.
  • the high noise margin protects the system against an increasing noise level, but allows only a reduced suboptimal data rate. Such high noise margin stabilizes the system in case the noise increases . If however the increased noise due to additional operating DSL services is dependent on the frequency, the maximum noise level will be different for different frequencies .
  • Fig.3 shows a schematic diagram visualizing a huge noise margin 303.
  • a power e.g., in a logarithmic scale
  • the flat noise margin 303 is applied on top of both, the noise floor 201 and the crosstalk noise 202 according to Fig.2 and shows how the high crosstalk noise 302 can be tolerated by a large flat margin 303.
  • An area beyond the noise margin 303 corresponds to a received signal power to be available for data transmission 304, i.e. is proportional to an attainable data rate.
  • the data rate corresponding to the received signal power is significantly reduced in case the modem is initialized using this high noise margin 303 in a situation where the external noise from other lines is already on a high level.
  • This high noise level leads to a reduced data rate and the large noise margin further reduces the data rate based on the fact that the target noise margin is applied on top of the measured external noise independent of its absolute level.
  • Such kind of noise margin is however not required in case the DSL is
  • breakpoints can be used to set frequency-dependent noise levels . This is an improvement over the flat noise margin and allows for higher data rates. This beneficial effect is also referred to as shaping gain.
  • ADSL G.992.1
  • ADSL2 G.992.3
  • ADSL2plus G.992.5
  • An approach to solve this issue is by using an Artificial Noise (see, e.g., EP 1 641 173 Al ) .
  • Artificial Noise works similar to Virtual Noise, but injects real noise into the loop, whereas Virtual Noise is a numerical correction term in the SNR computation.
  • the level of the Artificial Noise as well as the level of the Virtual Noise are set to the expected maximum noise level.
  • Fig . 4 shows a degradation of the SNR based on Artificial Noise.
  • a curve 402 shows a SNR at a receiver comprising external noise and Artificial Noise.
  • a curve 403 depicts a SNR at a receiver based on the Virtual Noise approach explained above.
  • a curve 401 shows a SNR at a receiver without external noise (with only Artificial Noise being present ) .
  • the level of SNR degradation depends on the noise level of the line and the level of the Artificial Noise. The situation is worst in case the Artificial Noise and the external noise reach the same level. This is indicated in Fig.4 as a SNR degradation amounting to 3 dB, which corresponds to a significant loss with regard to an achievable data rate.
  • An ADSL2plus system may use up to 506 tones in downstream direction while an SNR degradation of 3 dB corresponds to a reduction of about 1 bit per tone. This may sum up to a downstream rate loss of up to 2 Mbit/s.
  • the problem to be solved is to overcome the disadvantages described above and in particular to prevent or reduce a SNR reduction in case Artificial Noise is used on digital subscriber lines .
  • a noise level of a line is determined
  • an Artificial Noise is adapted based on the noise level determined.
  • Artificial Noise can be applied like Virtual Noise.
  • Artificial Noise can be set to a predefined level, e.g., a maximum expected loop noise level, to avoid undesired effects .
  • the Artificial Noise can be switched off in case the external noise is above the predefined level of Artificial Noise. In case the external noise is below the predefined level of Artificial Noise, it will be set in a way that the sum of both results in the desired level of noise.
  • loop noise is in particular referred to as noise that could be determined (in particular measured) on the line, comprising in particular artificial noise.
  • noise could be regarded as noise without any artificial noise, e.g., thermal noise, crosstalk, RFI, etc.
  • the Artificial Noise is adapted to the noise level of the line. In another embodiment, the Artificial Noise is switched off in case the noise level of the line reaches or exceeds a predefined threshold, in particular a predefined level of Artificial Noise .
  • the switching off is preferably done for single carriers (also referred to as subcarriers) .
  • the Artificial Noise is received with a damped due to attenuating effects of the line or along the line.
  • the predefined threshold may be used to compare the damped Artificial Noise obtained at the receiver.
  • the Artificial Noise in case the noise level does not reach or does not exceed the predefined threshold, the Artificial Noise will be set such that the sum of the noise level and the Artificial Noise reaches or equals the predefined threshold.
  • the noise level is determined during initialization, training or showtime state of a terminal .
  • the terminal can be regarded as a DSL terminal device, e.g., a CPE.
  • the terminal can be connected to a CO or DSLAM.
  • ADSL2 G.992.3 or ADSL2plus G.992.5 each provides measurement of the loop noise during
  • the noise level is derived or estimated based on a signal-to-noise ratio.
  • the SNR can be used to determine or derive the actual noise level.
  • Updated measurements of the SNR(i) per subcarrier can be requested from ADSL2 G.992.3 or ADSL2plus G.992.5 during showtime, where (i) is the subcarrier index and is equivalent to a point in frequency f (i) .
  • the noise level is based on an iterative mechanism utilizing the signal-to-noise ratio, in particular according to
  • AN new (i) VN(i) + AN M (i) - P(l)
  • SNR(i) is a signal-to-noise ratio per
  • AN r is a new value for the Artificial
  • AN is an old value of the Artificial
  • P(i) denotes a frequency dependent transmit power spectral density
  • VN (i) is the desired level of an equivalent
  • the value for the new Artificial Noise AN new (i) may become negative in case the loop noise of the line exceeds the desired Virtual Noise level. In such case, the
  • the signal-to-noise ratio is determined according to
  • b(i) is the number of bits that can be
  • SNRGAP is an additional factor that is used to achieve the desired level of BER for a given modulation scheme
  • SNRM is the signal-to-noise-ratio margin
  • SNR(i) is a signal-to-noise ratio per
  • the Artificial Noise is used as a replacement for transmitter-referred Virtual Noise in downstream direction.
  • H(i) is the magnitude of a channel transfer function
  • LN(i) is the loop noise
  • (i) corresponds to the subcarrier index and is equivalent to a point in frequency f ( i ) ;
  • VN(i) is the desired level of an equivalent
  • AN ( i ) is the Artificial Noise.
  • One way of retrieving the loop noise LN(i) is to set the system into a loop diagnostic mode prior to an
  • the test parameters Quiet line noise PSD per subcarrier provides the data required.
  • the loop diagnostic mode also provides
  • the Artificial Noise is initially set to a predefined value and adapted later, in particular during showtime of the digital subscriber line.
  • the noise margin can (e.g., gradually) be set to its normal range.
  • seamless rate adaptation SRA can be used after the start-up.
  • a device for data processing in a digital subscriber line environment comprising or being associated with a processing unit that is arranged
  • the device may be associated with a CPE or a DSLAM/CO.
  • processing unit can comprise at least one, in particular several means that are arranged to execute the steps of the method described herein.
  • the means may be logically or physically separated; in
  • Said processing unit may comprise at least one of the following: a processor, a microcontroller, a hard-wired circuit, an ASIC, an FPGA, a logic device.
  • the solution provided herein further comprises a computer program product directly loadable into a memory of a digital computer, comprising software code portions for performing the steps of the method as described herein.
  • a computer-readable medium e.g., storage of any kind, having computer-executable instructions adapted to cause a computer system to perform the method as described herein.
  • Fig.5 shows a schematic flow chart comprising steps of how to use Artificial Noise in an efficient manner.
  • Artificial Noise can be applied like Virtual Noise.
  • Artificial Noise can be set to a predefined level, e.g., a maximum expected loop noise level, to avoid the undesired effects as explained in the introductory portion, e.g., retraining, loss of connection, etc.
  • the Artificial Noise can be switched off in case the external noise is above the predefined level of Artificial Noise. In case the external noise is below the predefined level of Artificial Noise, it will be set in a way that the sum of both results in the desired level of noise.
  • this approach avoids or reduces SNR degradation and loss in data rate.
  • the actual noise level can be determined at the time of or during initialization and showtime at the CPE. For example, ADSL2 G.992.3 or
  • ADSL2plus G.992.5 each provides measurement of the loop noise during initialization.
  • the SNR can be used to determine or derive the actual noise level.
  • Updated measurements of the SNR(i) per subcarrier can be requested from ADSL2 G.992.3 or ADSL2plus G.992.5 during showtime, where (i) is the subcarrier index and is equivalent to a point in frequency f (i) ⁇
  • the SNR(i) can be estimated using the calculations shown below.
  • P(i) denotes a frequency dependent transmit power spectral density (PSD) and may include fine gains;
  • H(i) is the magnitude of a channel transfer
  • LN(i) is the loop noise
  • (i) corresponds to the subcarrier index and is equivalent to a point in frequency f(i);
  • VN(i) is the desired level of an equivalent
  • AN ( i ) is the Artificial Noise.
  • MIB management information base
  • the desired noise level amounts to:
  • AN(i) VN(i) - ⁇ - ( 5 )
  • One way of retrieving the loop noise LN(i) is to set the system into a loop diagnostic mode prior to an
  • the loop diagnostic mode also provides
  • the loop noise may vary. This may requires an adaptation of the loop noise during showtime. If measurements of the loop noise LN(i) cannot be done during showtime, an indirect approach using measurements of the SNR(i) per subcarrier is conducted. For example, an iterative scheme employing only measured SNR(i) values can be used. It is assumed that SNR(i) was measured during a time when an Artificial Noise AN old (i) was applied. The new value for the Artificial Noise AN new (i) can thus be determined as follows:
  • This scheme has the advantage that it does not require measurements of the channel or the loop noise. Furthermore, due to its iterative nature, any bias error in the application of Artificial Noise or measurement of the channel transfer function can be reduced or eliminated.
  • the value for the new Artificial Noise AN new (i) may become negative in case the loop noise of the line exceeds the desired Virtual Noise level. In such case, the
  • Updated SNR(i) values per subcarrier can be retrieved during showtime from ADSL2 G.992.3 or ADSL2plus G.992.5. It is not necessary to request an update of the test parameter frequently. For example, bitswap activities and/or changes in SNR margin (SNRM) may trigger an update of the test parameter.
  • the SNR margin is the maximum increase (scalar gain, in dB) of the reference noise PSD (at all relevant frequencies), such that the BER of each bearer channel does not exceed 10 ⁇ 7 .
  • the Artificial Noise is higher during initialization which results in a lower data rate . This can be compensated or avoided according to the following approaches :
  • the noise margin can (e.g.,
  • a number of bits b(i) that can be transported on a subcarrier can be estimated, e.g.: where
  • b(i) is the number of bits that can be
  • SNRGAP is an additional factor (e.g. 4.79) that is used to achieve the desired level of BER for a given modulation scheme and implementation ;
  • SNRM is the signal-to-noise-ratio margin
  • S(i) is a received signal power on the subcarrier i (content information);
  • N(i) is a received noise power on the subcarrier i (unwanted signal) .
  • S(i)/N(i) may be replaced by the signal to-noise ratio SNR.
  • Equations (7) and (8) can be re-formulated to obtain an estimate of the SNR:
  • Fig.5 shows a schematic flow chart comprising steps of how to use Artificial Noise in an efficient manner.
  • an actual external noise level (which could also be perceived as loop noise level) is determined and in a step
  • the Artificial Noise is set or adapted based on such external noise level determined.
  • the step 501 may consider at least one of steps 503 to 505:
  • the noise level of the line is determined during initialization, training or showtime of a terminal.
  • external noise level is determined or estimated based on a SNR.
  • the estimated external noise level can be adapted, e.g., during showtime.
  • the step 502 may comprise a step 506 and/or a step 507.
  • Artificial Noise may be switched off in case the external noise level of the line reaches or exceeds a predefined threshold (e.g., a predefined level of
  • the Artificial Noise in case the external noise level does not reach or does not exceed the predefined threshold, the Artificial Noise can be set such that the sum of the external noise level and the Artificial Noise reaches or equals the predefined threshold.
  • VDSL Very High Speed Digital Subscriber Line xDSL Any of the various types of Digital Subscriber

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Telephonic Communication Services (AREA)

Abstract

La présente invention concerne un procédé et un dispositif de traitement de données dans un environnement de ligne d'abonné numérique. Selon l'invention, un niveau de bruit d'une ligne est déterminé et un bruit artificiel est adapté sur la base du niveau de bruit déterminé. L'invention concerne en outre un système de communication comprenant au moins un tel dispositif.
EP12705841.0A 2012-02-20 2012-02-20 Procédé et dispositif de traitement de données dans un environnement de ligne d'abonné numérique Withdrawn EP2817954A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2012/052855 WO2013123964A1 (fr) 2012-02-20 2012-02-20 Procédé et dispositif de traitement de données dans un environnement de ligne d'abonné numérique

Publications (1)

Publication Number Publication Date
EP2817954A1 true EP2817954A1 (fr) 2014-12-31

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EP12705841.0A Withdrawn EP2817954A1 (fr) 2012-02-20 2012-02-20 Procédé et dispositif de traitement de données dans un environnement de ligne d'abonné numérique

Country Status (2)

Country Link
EP (1) EP2817954A1 (fr)
WO (1) WO2013123964A1 (fr)

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7184467B2 (en) * 2001-12-27 2007-02-27 Texas Instruments Incorporated Method to mitigate effects of ISDN off/on transitions in ADSL
US20050254562A1 (en) * 2004-05-17 2005-11-17 Texas Instruments Incorporated System and method to reduce noise estimation error during a digital subscriber line communication session and digital subscriber line modem incorporating the same
PL1641173T3 (pl) 2004-09-23 2008-12-31 Alcatel Lucent Nadajnik modemu z wieloma nośnymi, z kontrolowaną degradacją jakości sygnału transmitowanego dla poprawienia stabilności pracy
US8238450B2 (en) * 2009-01-30 2012-08-07 Futurewei Technologies Inc. Dynamic transmitter noise level adjustment for digital subscriber line systems

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2013123964A1 *

Also Published As

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WO2013123964A1 (fr) 2013-08-29

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