WO1999048219A1 - METHOD AND APPARATUS FOR CLOCK TIMING RECOVERY IN ψDSL, PARTICULARLY VDSL MODEMS - Google Patents
METHOD AND APPARATUS FOR CLOCK TIMING RECOVERY IN ψDSL, PARTICULARLY VDSL MODEMS Download PDFInfo
- Publication number
- WO1999048219A1 WO1999048219A1 PCT/IL1999/000154 IL9900154W WO9948219A1 WO 1999048219 A1 WO1999048219 A1 WO 1999048219A1 IL 9900154 W IL9900154 W IL 9900154W WO 9948219 A1 WO9948219 A1 WO 9948219A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- circuitry
- modem
- data
- dac
- value
- Prior art date
Links
- 238000000034 method Methods 0.000 title claims abstract description 35
- 238000011084 recovery Methods 0.000 title claims abstract description 28
- 238000005070 sampling Methods 0.000 claims description 18
- 230000005540 biological transmission Effects 0.000 claims description 16
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- 230000003595 spectral effect Effects 0.000 claims description 16
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 15
- 238000004891 communication Methods 0.000 claims description 15
- 239000013598 vector Substances 0.000 claims description 15
- 229910052802 copper Inorganic materials 0.000 claims description 12
- 239000010949 copper Substances 0.000 claims description 12
- 238000001914 filtration Methods 0.000 claims description 9
- 230000001360 synchronised effect Effects 0.000 claims description 6
- 238000009825 accumulation Methods 0.000 claims description 3
- 239000013078 crystal Substances 0.000 claims description 3
- GNFTZDOKVXKIBK-UHFFFAOYSA-N 3-(2-methoxyethoxy)benzohydrazide Chemical compound COCCOC1=CC=CC(C(=O)NN)=C1 GNFTZDOKVXKIBK-UHFFFAOYSA-N 0.000 claims description 2
- 230000007423 decrease Effects 0.000 claims description 2
- 230000003247 decreasing effect Effects 0.000 abstract 1
- 238000010586 diagram Methods 0.000 description 7
- 238000012546 transfer Methods 0.000 description 6
- 230000007246 mechanism Effects 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M1/00—Analogue/digital conversion; Digital/analogue conversion
- H03M1/66—Digital/analogue converters
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L27/38—Demodulator circuits; Receiver circuits
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/02—Speed or phase control by the received code signals, the signals containing no special synchronisation information
- H04L7/027—Speed or phase control by the received code signals, the signals containing no special synchronisation information extracting the synchronising or clock signal from the received signal spectrum, e.g. by using a resonant or bandpass circuit
Definitions
- the present invention relates to digital data communication between two locations over
- the invention relates to the use of Very High
- VDSL Digital Subscriber Loop
- Such users may be home Personal
- PCs Computers
- office desktop workstations office desktop workstations
- cable television broadcasting services
- LANs Local Area Networks
- others are connected to
- modems modulator-demodulator which encode the digital data to be
- DSLs Digital Subscriber Loops
- ADSLs Asymmetric Digital Subscriber Loops (ADSLs), High speed Digital Subscriber Loops
- HDSLs High speed Digital Subscriber Loops
- NDSLs Very High speed Digital Subscriber Loops
- DSL DSL family of DSLs
- data should be transmitted in very fast rates, usually up to 12.96 Mb/Sec
- leased copper lines between two locations can reach higher data rates, up to 64 Kb/s or
- transmission medium interferes with the transmitted data by adding noise, by
- LANs are very intensively used to connect users, usually in the range of a single
- copper lines for example, 107100-Base-T coaxial cables and fiber-optic lines.
- VDSL modems which are commonly called in the art, VDSL modems.
- FDD Frequency Division Duplex
- QAM Quadrature Amplitude Modulation
- a one kilometer twisted pair line has a propagation delay (impulse response time) in the range of about 12 ⁇ Sec,
- each symbol duration is 0.463 ⁇ Sec in the above case.
- the effective duration of the line impulse response is about 25 symbols. This long duration of the impulse response of the line leads to a severe Inter symbol Interference (ISI) which may result in a large errors at the receiving modem if cannot canceled, and practically limits the data rate.
- ISI Inter symbol Interference
- the communication between two tDSL modems is carried out while one modem is the transmitter (master) and the other is the receiver (slave).
- Data directed to the slave modem are termed "downstream” while the data directed to the master modem are termed "upstream”.
- Communication between the two modems requires synchronization between their timing clocks.
- Proper operation of tDSL systems requires almost perfect synchronization between master and slave clocks, which means that they must work at the same frequency. Any constant frequency offset leads to a constant growing phase error which may lead to mismatch between the number of transmitted and received symbols per time unit, which is unacceptable.
- Different clocks always have somewhat different frequencies due to manufacturing tolerances, aging (changes in then- component characteristics versus time), temperature variations, power supply tolerances, random noise deviations, etc. Therefore, synchronization means are required in the slave modem to recover the master clock frequency (timing) from the transmitted symbols, together with a correction apparatus to lock the slave clock frequency to the master clock frequency.
- BTR Blind Timing Recovery
- unshielded copper or the like wiring for example connecting LANs.
- the invention is directed to a method for fast timing recovery of transmitted data
- SI ⁇ (0.5 ⁇ W) ...,0,1,0,-1,...
- PLL phase-locked loop
- the timing oscillator of the receiving modem may be a Voltage-Controlled Crystal
- VXO Volt Control Oscillator
- blind timing recovery is
- DAC Digital to Analog Converter
- circuitry is utilized to correct the input word to the DAC to attenuate frequency jitter
- step d) Comparing the result of step d) above with half the value of the DAC's Least
- the output value is smaller than half the value of the DAC's LSB
- Fig. 1 schematically illustrates a full duplex data communication channel
- Fig. 2A is a graph of typical frequency bands occupied by VDSL transmission; -11- Fig. 2B is a graph of the attenuation of a typical copper wire communication
- Fig. 3 is a graph of the Impulse-Response (IR) of the communication line of
- Fig. 4 illustrates a 16 QAM generation and the resulting 16 state constellation
- Fig. 5 A is a block diagram of the demodulator of the slave modem
- Fig. 5B is a block diagram of a first order low-pass filter of Fig. 5 A;
- Fig. 6 schematically illustrates the output decisions of the slicer of Fig. 5 A
- Fig. 7 is a block diagram of the controller of Fig. 5 A.
- Fig. 8 schematically illustrates the phase shift of a 16 QAM constellation
- Fig. 1 illustrates a full duplex data communication channel between master and slave
- SDH Digital Hierarchy
- the slave modem is driven by another clock 5,
- the frequency spectrum of an -# SL channel utilizes two separated frequency bands
- the second band 7 occupies the range from 4 to 7.9 MHz and is used for up-stream
- Fig. 2B shows the attenuation of typical copper lines for common diameters (0.35, 0.4,
- the attenuation of the line is smaller at the downstream band. Therefore, the BTR
- downstream data is encoded with 64-state
- Fig. 3 is a graph of the Impulse-Response (IR) of a 1 Km long line.
- the IR of a system is a graph of the Impulse-Response (IR) of a 1 Km long line. The IR of a system
- Fig. 4 illustrates a 16 QAM generation and the resulting state constellation.
- Quadrature channel (Q-channel) respectively, are modulated by two information signals
- respective modulated carriers provide 16 different vectors (symbols), representing 16
- Fig. 5A is a block diagram of the demodulator of the slave modem. Symbols are
- A/D Analog to Digital
- the samples are fed into two multipliers 11 and 12, which are phase-shifted by 90°,
- I and Q channels are filtered by Low Pass Filters
- the filtered I and Q channels are fed into a complex Linear Equalizer (LEQ) 5, which
- LEQ 5 is able to
- LEQ 5 feeds both I and Q
- Equalizer (DFE) 17 via the adder 16, into the slicer 18.
- the DFE provides an additional
- Fig. 6 illustrates the output of the slicer 18.
- the slicer 18 slices the I-Q complex plain to
- a Timing Recovery Loop (TRL) 40 samples the information of
- VXO Voltage Controlled Crystal Oscillator
- This sampling rate should follow the incoming symbol rate
- PLL Phase-Locked Loop
- TRL 40 may function in two possible modes.
- the first mode is a blind mode which
- PLLs operate as Frequency Modulation (FM) demodulators.
- FM Frequency Modulation
- a PLL is used to lock the frequency of the timing clock of the
- the VCXO to change its frequency to the new frequency.
- the VCXO which is the plant of the control
- loop can be mathematically represented as an integrator, because its phase is -16- proportional to the integral of the frequency and the control voltage of the VCXO
- Vvcxo(t) sin[2 ⁇ Kvcxo ⁇ c(t)dt ] [Eq. 1]
- c(t) is the VCXO control voltage
- v vcxo (t) is the VCXO output voltage
- the critical parameter of the VCXO is its instantaneous phase, which is given by:
- phase error is small and the approximation sinx « x may be used. Hence, the
- phase error is given by e(t) » ⁇ in (t) - ⁇ (t) and both the VCXO 30 and the error signal
- controller 29 may also be LTI.
- Fig. 7 is a block diagram of the controller, comprising two functional blocks: an LPF
- controller 51 which provides a correction voltage proportional to the frequency offset
- an integrative controller smoothes the transition of the TRL from
- ⁇ 0 is the loop cutoff frequency (the maximum frequency error that the loop is
- r is the loop damping factor (an indication of the loop reaction
- the denominator (known as the characteristic polynomial) of the loop transfer function
- this cubic polynomial has one real root and two complex conjugate roots, which
- r is chosen to be r
- ⁇ 0 is chosen to satisfy the condition
- H(s) H,(s) H 2 (s), or
- K vco is chosen to be K vco
- ⁇ 0 is chosen to be:
- Ki and K 2 are given by:
- u[k] u[k-l] +a - (e[k]-u[k-l]) where e[k] and u[k] are the input and output signals of
- u[k] is the output signal from the LPF
- y[k] is the state variable of the
- DAC Analog Converter
- x[k] accumulates the error c [k] . If x[k] becomes larger than 0.5b, b is added to c[k]
- This signal has bandwidth from -0.5(1 + ⁇ )f b to 0.5(1 + ⁇ )f b , where f b is the symbol
- spectral lines can be recovered -22- by multiplying the demodulated complex signal z[n] by exp(J ⁇ f b t) and e ⁇ p(-j ⁇ f b t).
- the sampling rate in blind mode is the sampling rate in blind mode
- Equalization which is utilized for reducing the line amplitude and delay
- the band-edge components can be
- the lower band edge component is given by:
- the upper band edge component is given by:
- phase of the spectral line vector is given by:
- phase error of the timing loop is proportional to v,[ «].
- the proportionality factor is a function of the signal amplitude
- AGC Automatic Gain Control
- blind equalization is accomplished in less than
- All the LPFs of TRL 40 are first-order Infinite Impulse Response (IIR) filters.
- IIR Infinite Impulse Response
- each LPF may be realized with no need for any
- a reduced constellation is
- the slave modem switches to the well known DDTR mode, as
- phase error is generated, shifting the phase of any symbol
- phase shifts are detected by measuring the deviations of pre-detected
- these clusters are relatively small, and the DDTR mode is utilized to
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/623,952 US6922436B1 (en) | 1998-03-19 | 1999-03-18 | Method and apparatus for clock timing recovery in χDSL particularly VDSL modems |
AU29541/99A AU2954199A (en) | 1998-03-19 | 1999-03-18 | Method and apparatus for clock timing recovery in chiDSL particularly VDSL modems |
EP99910642A EP1060571A4 (en) | 1998-03-19 | 1999-03-18 | METHOD AND APPARATUS FOR CLOCK TIMING RECOVERY IN $g(x)DSL, PARTICULARLY VDSL MODEMS |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IL12373998A IL123739A (en) | 1998-03-19 | 1998-03-19 | Method and apparatus for clock timing recovery in xdsl, particularly vdsl modems |
IL123739 | 1998-03-19 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1999048219A1 true WO1999048219A1 (en) | 1999-09-23 |
Family
ID=11071352
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IL1999/000154 WO1999048219A1 (en) | 1998-03-19 | 1999-03-18 | METHOD AND APPARATUS FOR CLOCK TIMING RECOVERY IN ψDSL, PARTICULARLY VDSL MODEMS |
Country Status (6)
Country | Link |
---|---|
US (1) | US6922436B1 (en) |
EP (1) | EP1060571A4 (en) |
KR (1) | KR100417238B1 (en) |
AU (1) | AU2954199A (en) |
IL (1) | IL123739A (en) |
WO (1) | WO1999048219A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7415090B2 (en) | 2004-02-02 | 2008-08-19 | Samsung Electronics Co., Ltd. | Method and device for loop timing recovery based on maximum constellation signal |
EP1976214A1 (en) | 2007-03-30 | 2008-10-01 | Dragonwave, Inc. | Communication signal symbol timing error detection and recovery |
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US7822154B2 (en) | 2001-04-27 | 2010-10-26 | The Directv Group, Inc. | Signal, interference and noise power measurement |
US8005035B2 (en) | 2001-04-27 | 2011-08-23 | The Directv Group, Inc. | Online output multiplexer filter measurement |
US7209524B2 (en) * | 2001-04-27 | 2007-04-24 | The Directv Group, Inc. | Layered modulation for digital signals |
US7423987B2 (en) | 2001-04-27 | 2008-09-09 | The Directv Group, Inc. | Feeder link configurations to support layered modulation for digital signals |
US7471735B2 (en) | 2001-04-27 | 2008-12-30 | The Directv Group, Inc. | Maximizing power and spectral efficiencies for layered and conventional modulations |
US7483505B2 (en) * | 2001-04-27 | 2009-01-27 | The Directv Group, Inc. | Unblind equalizer architecture for digital communication systems |
US7583728B2 (en) | 2002-10-25 | 2009-09-01 | The Directv Group, Inc. | Equalizers for layered modulated and other signals |
US7778365B2 (en) * | 2001-04-27 | 2010-08-17 | The Directv Group, Inc. | Satellite TWTA on-line non-linearity measurement |
AU2003280499A1 (en) * | 2002-07-01 | 2004-01-19 | The Directv Group, Inc. | Improving hierarchical 8psk performance |
ES2604453T3 (en) | 2002-07-03 | 2017-03-07 | The Directv Group, Inc. | Method and apparatus for layered modulation |
DE10231648B4 (en) * | 2002-07-12 | 2007-05-03 | Infineon Technologies Ag | Method and device for stuffing control |
CA2503530C (en) | 2002-10-25 | 2009-12-22 | The Directv Group, Inc. | Lower complexity layered modulation signal processor |
EP1559009A4 (en) * | 2002-10-25 | 2010-03-31 | Grand Virtual Inc | Fixed client identification system for positive identification of client to server |
US7463676B2 (en) * | 2002-10-25 | 2008-12-09 | The Directv Group, Inc. | On-line phase noise measurement for layered modulation |
US7729464B2 (en) * | 2006-12-22 | 2010-06-01 | Teranetics, Inc. | Aiding synchronization between master and slave transceivers |
US8457191B2 (en) * | 2007-08-24 | 2013-06-04 | Comtech Ef Data Corp. | Adaptive equalizer and related methods |
JP2009088793A (en) * | 2007-09-28 | 2009-04-23 | Fujitsu Ltd | Synchronizing system, synchronizing signal transmitting apparatus, clock supplying apparatus, and synchronizing method |
IN2014CN03997A (en) * | 2011-10-28 | 2015-09-04 | Koninkl Philips Nv | |
US9166832B1 (en) * | 2013-10-04 | 2015-10-20 | Altera Corporation | Methods and apparatus for decision feedback equalization adaptation |
US9634694B2 (en) * | 2013-11-26 | 2017-04-25 | Avago Technologies General Ip (Singapore) Pte. Ltd. | Transmitter with a reduced complexity digital up-converter |
CN106209342B (en) * | 2016-08-25 | 2022-10-18 | 四川灵通电讯有限公司 | System for realizing low-frequency clock transmission in xDSL transmission system |
US10305495B2 (en) * | 2016-10-06 | 2019-05-28 | Analog Devices, Inc. | Phase control of clock signal based on feedback |
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US5163044A (en) * | 1991-01-02 | 1992-11-10 | At&T Bell Laboratories | Use of a fractionally spaced equalizer to perform echo cancellation in a full-duplex modem |
US5222077A (en) * | 1991-04-09 | 1993-06-22 | Racal-Datacom, Inc. | Radix mapping with variable number of symbols in mapping period |
US5331670A (en) * | 1992-01-31 | 1994-07-19 | At&T Bell Laboratories | Synchronization scheme for a digital communications system |
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EP0413875B1 (en) * | 1989-08-21 | 1994-06-01 | International Business Machines Corporation | Timing control for modem receivers |
US5388127A (en) * | 1993-02-09 | 1995-02-07 | Hitachi America, Ltd. | Digital timing recovery circuit |
US5504785A (en) * | 1993-05-28 | 1996-04-02 | Tv/Com Technologies, Inc. | Digital receiver for variable symbol rate communications |
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US6526101B1 (en) * | 1994-06-28 | 2003-02-25 | Samsung Electronics Co., Ltd. | Receiver for QAM digital television signals |
US5793821A (en) * | 1995-06-07 | 1998-08-11 | 3Com Corporation | Timing Recovery using group delay compensation |
US5872815A (en) * | 1996-02-16 | 1999-02-16 | Sarnoff Corporation | Apparatus for generating timing signals for a digital television signal receiver |
US5987069A (en) * | 1996-12-24 | 1999-11-16 | Gte Government Systems Corporation | Method and apparatus for variably allocating upstream and downstream communication spectra |
US6249557B1 (en) * | 1997-03-04 | 2001-06-19 | Level One Communications, Inc. | Apparatus and method for performing timing recovery |
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US6449325B1 (en) * | 1998-03-13 | 2002-09-10 | Samsung Electronics Co., Ltd. | Circuitry operative on selected symbol slicing results for synchronizing data fields in a digital television receiver |
-
1998
- 1998-03-19 IL IL12373998A patent/IL123739A/en unknown
-
1999
- 1999-03-18 WO PCT/IL1999/000154 patent/WO1999048219A1/en active IP Right Grant
- 1999-03-18 KR KR10-2000-7010277A patent/KR100417238B1/en not_active IP Right Cessation
- 1999-03-18 EP EP99910642A patent/EP1060571A4/en not_active Withdrawn
- 1999-03-18 US US09/623,952 patent/US6922436B1/en not_active Expired - Fee Related
- 1999-03-18 AU AU29541/99A patent/AU2954199A/en not_active Abandoned
Patent Citations (3)
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US5163044A (en) * | 1991-01-02 | 1992-11-10 | At&T Bell Laboratories | Use of a fractionally spaced equalizer to perform echo cancellation in a full-duplex modem |
US5222077A (en) * | 1991-04-09 | 1993-06-22 | Racal-Datacom, Inc. | Radix mapping with variable number of symbols in mapping period |
US5331670A (en) * | 1992-01-31 | 1994-07-19 | At&T Bell Laboratories | Synchronization scheme for a digital communications system |
Non-Patent Citations (1)
Title |
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7415090B2 (en) | 2004-02-02 | 2008-08-19 | Samsung Electronics Co., Ltd. | Method and device for loop timing recovery based on maximum constellation signal |
EP1976214A1 (en) | 2007-03-30 | 2008-10-01 | Dragonwave, Inc. | Communication signal symbol timing error detection and recovery |
US8036332B2 (en) | 2007-03-30 | 2011-10-11 | 4472314 Canada Inc. | Communication signal symbol timing error detection and recovery |
Also Published As
Publication number | Publication date |
---|---|
EP1060571A1 (en) | 2000-12-20 |
US6922436B1 (en) | 2005-07-26 |
KR20010052213A (en) | 2001-06-25 |
KR100417238B1 (en) | 2004-02-05 |
IL123739A (en) | 2001-11-25 |
AU2954199A (en) | 1999-10-11 |
EP1060571A4 (en) | 2005-12-21 |
IL123739A0 (en) | 1998-10-30 |
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