Signal-to-Noise Ratio

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Zipper A Digital FDM for DMT VDSL
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VDSL ?? ? ?? ??

• VDSL Alliance(DMT-based VDSL) 48??
• Alcatel, Aware, Ericsson, ETRI, Globespan, IBM
  Research, NEC, Nortel, Samsung,
  STMicroelectronics, Stanford University, Telia
  Research AB, Texas Instruments, etc.
• http//www.vdslalliance.com
• VDSL Coalition(QAM-based VDSL) 39??
• ADI, Broadcom, Globespan, Infineon(Siemens),
  Lucent, Metalink, Orckit, Rockwell, Samsung
  Electronics, etc.
• http//www.vdsl.org

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VDSL Chipset ?? ??

• ?? ?
• Broadcom BCM6010, BCM6020 (QAM)
• Infineon/Savan Tech POTSWIRE (QAM)
• Lucent MBA Chipsets (CAP/QPSK)
• ETRI SMC Chipsets (CAP/QPSK)
• ?? ?? ?
• Alcatel FDD DMT VDSL(w/TI)
• TI VDSL AFE chip, TDD SDMT ???(w/NEC)
• Telia/STMicroelectronics Zipper-DMT prototype,
  12-bit VDSL ADC, 2000? ??? ?? ?
• ETRI DAVIC QAM, 4-band QAM PDSL, DMT VDSL

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VDSL Chipset ?? ?? ??
?? ???? ?? ?? ???
???? ??? 1996-2000 TDD-DMT ?? VDSL simulator ??, VDSL alliance member, FDD-DMT ??? VDSL ??? ?? ( ITU ? T1 )
ETRI 1997-1998 DAVIC ?? CAP/QPSK VDSL ??? ?? ?(3?) ?? ?? ??? 2?, ??? ??? 1?
ETRI 1999-2000 4-band QAM ?? ITU-T ?? ?? VDSL ??? ?? ? ?? ??/???? ?? ??? 1? ?? ?? ?
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Zipper Digital Duplexing
John Cioffi, Stanford Mikael R. Isaksson, Telia
Research AB, VDSL Performance Improvement by
Aversion of Frequency Guard Bands, ETSI TM6
TD13, Sept 20-24,1999.
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DMT for ADSL and VDSL
ADSL VDSL (default)
(I)FFT Size 512 8192 (4096)
of sub-carriers 256 4096 (2048)
Cyclic extension L v 40 L 640 gt v D
Sampling rate 2.208 MHz 35.328 (17.664) MHz
Bandwidth 1.104 MHz 17.664 (8.832) MHz
Duplexing Analog FDM(filters) Digital FDM(Zipper)
Tone width 4.3125 kHz 4.3125 kHz
Excess bandwidth 86 kHz (prefix) 7.8 40 kHz (filters) 3.6 1.3 MHz (650 kHz) 7.4 (3.7) (no filters)
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Duplexing Methods
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What is Zipper-DMT ?

• Zipper is a digital FDM method with no guard
  bands
• Different sub-carriers are used in up and
  downstream directions

• To make it work Zipper needs
• ???? FFT ?? ??(DataNEXT/Echo)? alignment? ??
• A cyclic suffix is used to compensate for
  propagation delay

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DMT Transmission System

• Dashed lines(---) are control channels between
  transmitter and receiver

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Basic DMT at Transmitter

• DMT transmitter? IFFT
• ? QAM ??? IFFT?? ????, ??? ??? ??
• ? ??? ???.
• Sampling rate( (NL) / T )
• 1/T 4000 Hz, L cyclic extension
• ADSL (NL) x 4000 (51240) x 4000 2,208 MHz
• VDSL (NL) x 4000 (8192640) x 4000 35.328
  MHz

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At Receiver

• FFT
• ???? FFT? ??? ?? ??? ????? ??? ??.
• ??, FFT? m???? ?? ?????, FFT ???
• ???, ? ?? packet? DMT ??? ???? ? packet?
  disturbance? ???. ?? ? packet?? m?? ??? ?????.
  ??? FFT ???
• ? ?? ?? ??? ??? ??. Synchronization
  patterns ??.

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Symbol Alignment ??

• ? ?? ??? ?? ??? ??? ??.
• ? ??? ??(LT-gtNT), ?? ??? ??(NT-gtLT)? ??, NT???
  ???? ??? ????? echo ??? ?? ?? ????? ??? ????. ???
  alignment ?? ?? ??.
• ??? ?? echo ??? ??? ? ????

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Symbol Alignment with CS
D ??? ?? ?? ?? ?? n ??? ?? Pulse-Spread CP(Cyc
lic Prefix) ?? Pulse-Spread? ?? ISI ??, CP gt n
, ADSL? ?? CS(Cyclic Suffix) ?? ?? ?? ??? ?? ??
VDSL???? ??? ?? ??
??, CS gt D
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Cyclic Suffix? ?? ??

• N10, v2, ?3, CP2, CS0? ?
• LT??? DMT ??? ???? ??.
• ??? NT??? DMT ??? ???? ?? ??.
• NT?? DS ???? FFT ??? ????? 5 14????.

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Zipper-DMT (4)
Cyclic Suffix? ??? ??

• Cyclic suffix (CS 2? 6 samples)
• LT??? DS? US? ???? ??.
• NT??? 514????? DS? ??? ?? ??????, US? ??? ??
  ???????
• NT ???? 514??? ?? FFT? ????, US? DS?? ?? ???
  ????.

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CS? ??? ??
CS? ??? ??

• Timing Advance at LT( CS ? 3 samples)
• LT? DS ??? timing advance(3)? ?? 211?????? ???
  ???? ????.
• ??? Timing advance? ??? cyclic suffix ??? ???.

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Zipper-DMT (5)
CS? ??? ?? NEXT? ??
NEXT source
FEXT
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Near End Crosstalks (NEXT)
Near End Crosstalks (NEXT)

• Crosstalk from neighboring VDSL circuits
• Synchronization of VDSL lines
• Easy to handle.
• ?? NEXT ??? ??? sampling clock? ???
  orthogonality? ??? tone?? ??? ??.
• Asynchronous VDSL lines
• Tx windowing, Rx windowing -gt side lobe? power?
  ??? ?? ??? tone ?? ??? ?? ?? ? ??.
• ??? tone ?? ??? adaptive NEXT canceller? ?? ????.

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Magnitude of windowed sinusoid
Magnitude of windowed sinusoid

• A single DMT tone
• with rectangular window
• -13 dB, side lobe

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Tx windowing side lobe ??
Tx windowing side lobe ??

• ? ??? ???? ??? PSD? side lobe ??? ??? ????? ??.
  ?? ??, extra extension ????? smoothing window
  (ex. raised-cosine window)? ????.
• Rectangular window
• Raised cosine function(time-domain window)

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Raised Cosine Window
Raised Cosine Window

• ???? window
• ? ??? ?? roll-off? ???.
• Overlapped Transmitter windows
• Bit-rate ??? ??? ??, pulse-shaped ??? overlap??
  ????? ??.

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Windowing? ??
Windowing? ??
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Rx windowing? ??? ??
Rx windowing? ??? ??

• 24AWG, 1,000m

40 tones ???? AWGN ??
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Adaptive NEXT Canceller
Adaptive NEXT Canceller

• Windowing ??? ???? ?? NEXT? ??? ? ?? tone?????
  ???? adaptive NEXT canceller? ?? ??? ? ??.

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Telia/STMicro VDSL Chip(1999.11)
CP/CS ?? ??
Digital FDM ??? Zipper DMT, 0.25 um, 9.5 million
Trs, 1.5 W, 10 Mbps C-gtR(IFFT)
pre-processing2K IFFT, R-gtC(FFT) 2K
FFTpost-processing Mixed-radix Cooley-Tukey
Algorithm, ??? ???(2001??)
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DMT based Zipper VDSL
Denis J. G. Mestdagh, STMicroelectronics, Mikael
R. Isaksson, Telia Research AB, Per Odling, Lund
Institute of Technology, Zipper VDSL A
solution for robust duplex communication over
telephone lines, IEEE Comm. Mag., Vol. 38, No.
5, pp. 90-96, May 2000.
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? ?
Zipper is a digital duplexing without guard
frequency and has been proposed for a DMT VDSL