VDSL FOR TRIPLE PLAY

VDSL for Triple Play
Copyright 2010 Fernando Ramirez-Mireles
ramirezm@ieee.org, framirez@itam.mx
1
Fernando Ramirez-Mireles, Ph.D.
VDSL for
Triple Play

2
• This presentation is being given for
academic purposes only.
• This talk provides information that is of
public nature and can be found in the
references and the WWW. We are not
describing the capabilities of any
commercial system in particular.
• The presentation does not endorse the
products of any company. We are not
making any forward looking statement.
Disclaimer

3
• A definition for VDSL (What?)
• Penetration of VDSL (Who?)
• VDSL for Triple-Play (Why?)
• Anatomy of a VDSL system (How?)
• The VDSL standard (How?)
• Deployment of VDSL (How?)
• Some VDSL-based applications (Where?)
• The future …
Overview

4
(modified from source: www.webopedia.com)
• VDSL: Very High Speed DSL, transmits data in the 13-100 Mbps
range over short distances, usually between 300 and 4500 feet (100
- 1500 meters), of twisted pair copper wire. The shorter the
distance, the faster the connection rate.
• DSL: Digital Subscriber Line, technology using sophisticated
modulation schemes to pack data onto copper wires. They are
sometimes referred to as last-mile technologies because they are
used only for connections from a telephone switching station to a
home or office, not between switching stations.
• xDSL: Refers collectively to all types of DSL (VDSL, ADSL, SDSL,
SHDSL, HDSL, ISDN)
A dictionary definition
for VDSL

5
The shorter the distance,
the faster the connection rate
Modified from source : “DSL”, Chapter 15 in Internetworking Technology Overview,
100

6
Modified from source: “Very-High-Speed Digital Subscriber Lines”, Cioffi etal., IEEE Commun. Magazine,
The larger the bandwidth,
the faster the connection rate
VDSL PSD Mask

7
Penetration of VDSL

8
Broadband Acces Technologies
Modified from source: OIDA NEWS, Vol. 12, Issue 3,

9
Penetration of DSL
Source: "DSL Anywhere" - Issue 2, DSL Forum

10
VDSL in Korea

11
VDSL for Triple-Play

12
Full Service Access Network:
FSAN initiative based on VDSL
Data
Television
Telephone
4 Services
4 Neworks
4 Services
1 Nework
Radio
FSAN
Voice Data
Video Audio
Today: Tomorrow:
A T M
3
3
3
Video
Yesterday: Tomorrow:
data
Networks Networks
VDSL

13
SOHO scenario for Triple-Play
Dad
• Medical doctor with
private practice at
home
• One HDTV monitor
for telemedicine
• One HDTV for
waiting room
• Database consulting
with the hospital
• Two telephone lines
Mom
• Engineer
telecommuting at
home
• Teleconferencing
• Database consulting
with the office
• One telephone line
Kid
• 15 years old
Entrepreneur
• Peer to peer on line
gaming
• Web surfing
• One telephone line
• One interactive
HDTV for
entertainment
Baby
• Crib with “DTV on
board”
• Monitoring from
day care

14
Sample Requirements for Triple Play
Applications Central office to
premises
(Downstream)
Premises to
central office
(Upstream)
Delay
sensitivity
3 HDTV Channels
(MPEG2 12 Mbps each)
1 DTV channel
(4 Mbps)
40 Mbps 1 Mbps Low
Data (VPN, internet) 10 Mbps 10 Mbps Low
Videoconferencing 4 Mbps 4 Mbps High
Online games 2 Mbps 2 Mbps High
VoIP (4 lines) 0.4 Mbps 0.4 Mbps High
Total 56.4 Mbps 17.4 Mbps

15
Technology
(bandwidth)
DS/US Data Rate Reach Applications
VDSL2
(up to 30 MHz)
50-100/50-100 Mbps 300 ft Symmetric: EFM, LRE
VDSL1
(12 MHz)
50-100/20-30 Mbps
50/20 Mbps
54/13 Mbps
26/26 Mbps
22/13 Mbps
13/13 Mbps
10/10 Mbps
6/6 Mbps
16/1 Mbps
300 ft
1000 ft
3000 ft
4500 ft
6000 ft
Asymmetric: multiple simultaneous
HDTV’s and/or DTV’s, internet, audio,
games, with POTS (plain old telephone
service)
Others: High quality Video-conference,
Tele-commuting, Tele-medicine, Distance-
learning, Home-shopping.
ADSL2+
(up to 2.2 MHz)
20/0.8 Mbps
10/0.8 Mbps
7200 ft
14400 ft
Asymmetric: one HDTV or two
simultaneous DTV’s, internet, audio,
games, with POTS
ADSL2
(1.1 MHz)
10/0.8 Mbps
3.5/3.5 Mbps
14400 ft
10000 ft
Asymmetric: one DTV, internet, audio,
games, with POTS
VDSL and ADSL

16
Technology DS/US Data Rate Reach Applications
SHDSL 2.3/2.3 Mbps 16000 ft Symmetric: One or more T1/E1,
data, remote LAN, with POTS
HDSL-2 1.544/1.544 Mbps
2.044/2.044 Mbps
9600 ft Symmetric: T1/E1 over one pair
with no repeaters, no POTS
ISDN 144/144 Kbps 14400 ft Symmetric: Digital voice plus
data
T1/E1 over
twisted pair
(not a DSL)
1.544/1.544 Mbps
2.044/2.044 Mbps
14400 ft or
12800 ft
Symmetric: Data, no POTS
(leased line), uses two pairs
with repeaters every 1500
meters
Other xDSL technologies

17
Anatomy of a
VDSL SYSTEM

18
Network topology for VDSL and POTS
VDSL
MODEM
Phone
Switch
Internet DSLAM
Splitter Splitter
WAN
PSTN
Twisted Pair
"Last Mile"
"First Mile"
backbone
backbone
packet
or cell
based
circuit
based
CO: Central
Office
CPE: Customer's
Premises Equipment
POTS
POTS
DS: Downstream
US: Upstream
VDSL VDSL
Voice Voice
VDSL + POTS
POTS: Analog Voice
(filter) (filter)
Two networks

19
VDSL Transmission
Environment
Z_2
Z_1
voltaje
diferencial
impedancias
con respecto
a tierra

20
Transmission Environment
CO VDSL
MODEM Channel
Loss
(dB)
Frequency (MHZ)
Channel: Insertion Loss
CPE VDSL
MODEM
+
+
DS1 US1 DS2 US2
Signal
PSD
(dBm/Hz)
Frequency (MHZ)
FDD: Freq. Division Duplexing
TX DS
DS1 US1 DS2 US2
Signal
PSD
(dBm/Hz)
Frequency (MHZ)
FDD: Freq. Division Duplexing
TX US
RX
PSD
(dBm/Hz)
Frequency (MHZ)
Impairments: Noise and Interference
POTS
POTS

21
Transmission environment
• Crosstalk:
– Next (f1.5)
– Fext (|H(f)|2 d f2)
• RFI Ingress:
– HAM Radio
– AM Radio
• Impulse Noise.
Regulation &
requirements
• Spectrum
compatibility.
– Legacy systems
• RFI Egress.
– HAM Radio
• Upstream Power
Back-off
Noise
Impairments
Channel
Impairments
• Insertion Loss
• Bridge taps (BT)

22
Channel
Impairments
• Attenuation
is a
function of:
– Length
– Gauge
– Frequency
– Bridge
taps
Bridge Tap
CO

23
• Crosstalk:
– Next (f1.5)
– Fext (|H(f)|2 d f2)
• RFI Ingress:
– HAM Radio
– AM Radio
• Impulse Noise.
Noise
Impairments
Channel
Impairments
• Insertion Loss
Regulation &
requirements
• Spectrum
compatibility.
– Legacy systems
• RFI Egress.
– HAM Radio
• Upstream Power
Back-off

24
Crosstalk
Transmitter
Receiver
CO
Modem
Receiver
Transmitter
CPE/RT
Modem
Transmitter
Receiver
CO
Modem
Noise Received from
Near Transmitter
Noise Received from
Far Transmitter
NEXT: Near End Xtalk FEXT: Far End Xtalk
10's, 100's, 1000's feets
Cable with several
Twisted pairs

25
Crosstalk (from a duplexing perspective)
CO
Modem
CPE/RT
Modem
CO
Modem
CPE/RT
Modem
US
DS
US
DS
US
DS
US
DS
CO
Modem
CPE/RT
Modem
US
DS
US
DS
NEXT into US FEXT into US
FEXT into DS
NEXT into DS
STRONG FEXT into US
Distance

26
Sample Crosstalk PSD
Crosstalk a function of:
• Disturber’s PSD (Self: VDSL, Alien: ADSL, SHDSL, etc)
• Frequency location and cable length
• Cable type (wrapping and insulation inside the bundle)
and gauge

27
Radio Frequency Interference (RFI)
RFI Ingress
(from AM & HAM)
RFI Egress
(to HAM)
AM
Radio
HAM
Radio

28
Electromagnetic Coupling of RFI
Z_2
Z_1
voltaje
diferencial
impedancias
con respecto
a tierra
Differential
voltage
Unbalance in
Impedances with
respect to ground

29
Impulse Noise
Nature Domestic Industrial
Sources of Impulse Noise

30
Impulse Noise

31
(frequency, time and location dependant)
Summary for Transmission Medium:

32
• Crosstalk:
– Next (f1.5)
– Fext (|H(f)|2 d f2)
• RFI Ingress:
– HAM Radio
– AM Radio
• Impulse Noise.
Noise
Impairments
Channel
Impairments
• Insertion Loss
Regulation &
requirements
• Spectrum
compatibility.
– Legacy systems
• RFI Egress.
– HAM Radio
• Upstream Power
Back-off

33
Regulation in Medium Interface:
• TX PSD: Conforms to a band plan:
– FSAN 997,998, ITU FX (depends on standard and
deployment)
– Proprietary
– Symmetric or asymmetric
(VDSL1)

34
Regulation in the transmission environment
DS1 US1
DS2 US2
Signal PSD (dBm/Hz)
Frequency (MHZ)
Limit PSD Mask
freq.
1
freq.
2
freq.
3
freq.
4
freq.
5
RFI NOTCHES
Agregate
Power
In-Band Signal PSD dictated by band Plan
US1 US2
Signal PSD (dBm/Hz)
Frequency (MHZ)
PSDa
Fa Fb Fc Fd
SIDELOBES
Out-of-Band Signal PSD mandated by standard
PSDb
In-band
Mask
Out-of-band
Mask

35
Requirements in the Medium Interface:
• Upstream power back-off at CPE/RT: alleviates
near-far problem
– Frequency dependant
– Band plan, crosstalk composition, wire gauge and
cable type of bundling.
CO
Modem
CPE/RT
Modem
CO
Modem
CPE/RT
Modem
US
DS
US
DS
US
DS
US
DS
NEXT into US FEXT into US
STRONG FEXT into US
Other CO modems

36
The VDSL standard

37
ANSI ETSI ITU IEEE
Working groups and industry associations
ANSI T1E1.4 ETSI TM6 ITU Study
Group 15
IEEE EFM
Task Force
802.3.ah
VDSL Alliance
(DMT)
VDSL
Coalition
(SCM)
ADSL Forum
ATM Forum
FSAN
Standards bodies

38
• ANSI T1.E1
– Finalized in 2003, based on DMT “Discrete Multi Tone”
• IEEE EFM 802.3ah
– Finalized in 2003, based on DMT
• ETSI TS 101 270-1&2
– Finalized in 2003, based on both DMT and SCM “Single
Carrier Modulation”
• ITU G993.1-2004
– VDSL1 finalized in 2004, based en DMT (SCM in annex)
• ITU G993.2-2005
– VDSL2 specifications finalized in 2005, based on DMT
VDSL standards

39
System Architecture in
the VDSL Standard

40
System Architecture
• TPS-TC: Transport
Protocol-Specific
Transmission
Convergence
• OAM: Operation
And Maintenance
• PMS-TC: Physical
Medium-Specific
Transmission
Convergence
• FEC: Forward
Error Correction
• PMD: Physical
Medium
Dependant
• UPBO: Upstream
Power Back-off
TPS-TC:
OAM, Multiplexing
asynchronous and
synchrounous channels
Transmission Medium:
Loop, Noise
PMS-TC:
Framing,
Scarmbling
FEC, Interleaving,
PMD:
Data Encoding,
Modulation
Duplexing
Transport :
Data flow,
synchronization flow,
control flow, OAM flow
TPS-TC:
OAM, Demultiplexing
asynchronous and
synchronous channels
PMS-TC:
Frame synchronization
De-Interleaving,FEC Decoder,
De-Scrambling,De-Framing
PMD:
Synchronization,Equalization,
Demodulation, Data Decoding
De-Duplexing
Transport :
Data flow,
synchronization flow,
control flow, OAM flow
Transmitter Receiver
Medium Interface:
TX PSD
UPBO
Electrical requirements
Medium Interface:
AGC
Electrical requirements
Depends
on
Line Code
DMT
or
SCM
VDSL
Standard
Scrambling

41
PMD layer for DMT
• Actions in PMD’s Transmitter:
– Data Encoding: Mapping bits to symbols
– Modulation: Multicarrier QAM with bit loading
– Duplexing: FDD
• Actions in PMD’s Receiver:
– Synchronization: Sampling frequency and symbol
time
– Equalization: TDQ in time and FEQ in frequency
– Demodulation: QAM slicer
– Data decoding:De-mapping symbol to bits
– “De-Duplexing”: Digital de-duplexing using FFT

42
DSP in PMS-TC + PMD + Medium Interface for DMT-VDSL
IFFT Cyclic
Extension
TX
Windowing LPF
Line
Driver
Hybrid
tip
ring
symbol
mapper
Bit Extraction
with
Tone Ordering
DAC
Framing CRC Scrambling FEC Interleaving
Framing CRC Scrambling FEC
slow
fast
fast
slow
FFT
Remove
Cyclic
Extension
RX
Windowing ADC
LPF
Hybrid
tip
ring
Slicer
symbol
demapper
FEQ TEQ
bit insertion
with
tone ordering
de-
Framing
CRC
checksum
de-
Scrambling
FEC
decoder
de-
Interleaving
de-
Framing
CRC
checksum
de-
Scrambling
FEC
decoder
slow
fast
fast
slow
Near Transmitter
Far Receiver

43
Training of the VDSL modem
• Flexibility during training
• Training signals allows training the modem
– Synchronization, Equalization, Bit Loading
• Training signals communicate parameters to
allow configuration of modem during training
– What frequency bands to use for US and DS
– What PSD to use in each frequency band
– Some parameters for system optimization
(performance optimization, overhead reduction)
– Enable optional features

44
Training signals in DMT-VDSL
• VDSL training signals and FSM allow
configuration of features during training
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 . . . . . . . . . . . . . (N/2)-1
Tone
Amplitude
Tone Index q
Pilot
tone
Data
carrier
Tone amplitudes at the receiver

45
VDSL
line codes
Discrete Multi-Tone (DMT):
All international standards for ADSL, ADSL2, ADSL2+,
VDSL1 and VDSL2 are based on DMT
Single Carrier Modulation:
Two international standards for VDSL1 include SCM

46
DMT and SCM
Signal PSD (dBm/Hz)
Frequenc
y
(MHZ)
freq.
1
freq.
2
freq.
3
freq.
4
freq.
5
US1 DS1 US2 DS2 US3
Signal PSD (dBm/Hz)
Frequenc
y
(MHZ)
freq.
1
freq.
2
freq.
3
freq.
4
freq.
5
US1 DS1 US2 DS2 US3
DISCRETE MULTI TONE (Divide and Conquer) SINGLE CARRIER MODULATION
Mr. FEC

47
DMT Processing

48
SCM Processing

49
Comparing DMT and SCM
Issues Deleterious
effects
DMT solution SCM solution Advantages of
DMT over
SCM
Channel
Time
Dispersion
Signal
Smearing
Equalization: Two simple
equalizers, one in time
domain and one in
frequency domain
Equalization:
One complicated
equalizer in time
domain
Simplicity in
design and
implementation
Frequency
dependent
Noise
Frequency
dependent
signal-to-
noise ratio
(SNR)
Bit loading: Transmit
more bits in frequency
bands where there is less
noise and less bits in
frequency bands where
there is more noise
No bit loading:
Transmit the
same average
number of bits in
every frequency
band regardless
of amount of
noise in each
frequency band
Bandwidth
efficiency and
higher throughput
FDD full
duplex
operation in
multi-band
spectrum
plans
Interference
between
upstream
and
downstream
signals
Signal separation: Use no
filtering, utilize Fourier
Transform orthogonality
properties
Signal
separation: Use
one complicated
filter per
transmission
band
Higher spectrum
utilization, higher
throughput and
flexible
implementation of
different band
plans

50
Deployment of VDSL

51
Deployment options
Network topology Deployment architecture
•VDSL and POTS
•Integrated Telephony
•Multi-Services Platform
•Direct deployment
•Fiber extensions

52
Network topology for VDSL and POTS
VDSL
MODEM
Phone
Switch
Internet DSLAM
Splitter Splitter
WAN
PSTN
Twisted Pair
"Last Mile"
"First Mile"
backbone
backbone
packet
or cell
based
circuit
based
CO: Central
Office
CPE: Customer's
Premises Equipment
POTS
POTS
DS: Downstream
US: Upstream
VDSL VDSL
Voice Voice
VDSL + POTS
POTS: Analog Voice
(filter) (filter)
Two networks

53
Network topology for integrated telephony
VDSL
LIM
ONT
CO/Exchange/cabinet
CPE
VDSL VDSL
VOICE VOICE
VDSL + POTS
backbone
splitter splitter

54
Network topology for multi-services over VDSL
“Multi-service” platform
(DSL, voice, video, data)
VDSL modem
Gateway
Twisted pair
internet
PSTN
Video
WAN
fiber

55
• Direct deployment
– Distance < 4500 ft
• CO/RT: Central Office/Remote Terminal
• Fiber extensions
• FTTEx: Fiber to the Exchange
• FTTCab: Fiber to the Cabinet
• FTTCurb: Fiber to the Curb
• FTTB: Fiber to the Building
– MxUs: Multi-Tenant/Dwelling units
Deployment Architectures

56
Deployment with Fiber Extensions
Modified from source: ITU-T FS-VDSL FGTS Technical Specification, "Part 1: Operator requirements,“ Version 1.0.0 5 June 2002
ONU: Optical Network Unit
OLT: Optical Line Termination
< 4.5 Kft
< 4.5 Kft
< 900 ft
< 100 ft
(1000 lines)
(10-100 lines)
(10 lines)
(10 lines)

57
VDSL and POTS:
CO/RT D < 4500 ft; DS/US = 13/13 to 54/13 Mbps
VDSL
MODEM
Internet DSLAM
Splitter Splitter
WAN
phone
switch
Bundle of
Twisted Pairs
backbone
packet
or cell
based
CABINET RT
POTS
VDSL VDSL
Voice Voice
VDSL + POTS
Bundle
of
Twisted
Pairs
100's, 1000's ft
phone
switch
CO
< 4500 ft
D

58
VDSL and POTS:
FTTX
FTTCab
FTTCurb
D < 4500 ft; DS/US = 13/13 to 54/13 Mbps
D < 4500 ft; DS/US = 13/13 to 54/13 Mbps
D < 900 ft; DS/US = 50/20 to 100/30 Mbps
ONU
cpe
Exchange/Cabinet/ONU
D
VDSL VDSL
VOICE VOICE
VDSL+VOICE

59
•DS/US = 100/50 Mbps for VDSL1
VDSL and POTS:
FTTB D < 100 ft;
ONU
< 100 ft
CPE
VDSL + POTS
Individual
Twisted
pairs
D
VDSL VDSL
VOICE VOICE

60
CO/RT
Integrated Telephony:
FTTX
FTTCab
FTTCurb
D < 4500 ft; DS/US = 13/13 to 54/13 Mbps
D < 4500 ft; DS/US = 13/13 to 54/13 Mbps
D < 900 ft; DS/US = 50/20 to 100/30 Mbps
ONU
< 900 ft
cpe
Exchange/Cabinet/ONU
D
VOICE VOICE
VDSL VDSL
VDSL + POTS

61
CO/RT
VDSL
LIM
ONT
fiber
ONU
< 100 ft
Individual
Twisted
pairs
CPE
Integrated Telephony:
FTTB D < 100 ft;
D
VDSL VDSL
VOICE VOICE
VDSL + VOICE

62
Multi-services platform
FTTCurb •DS/US = 50/20 to 100/30 Mbps
D < 900 ft;
Gateway
< 900 ft
Data
Video
Voice
Premises
D
Multi-services platform
(DSL, voice, video, data)

63
• ATM/PTM over DSL
(Symmetric/Asymmetric)
– PTM less overhead than ATM for IP
• EFM: Ethernet in the first mile (10BT)
• LRFE: Long reach fast Ethernet (100BT)
Applications

64
ATM/PTM over VDSL
TPS-TC:
ATM-TC OR PTM-TC
(fast and slow)
Transmission Medium:
PMS-TC
PMD
Transport:
ATM or PTM
TPS-TC:
ATM-TC OR PTM-TC
(fast and slow)
PMS-TC
PMD
Transport:
ATM or PTM
Transmitter Receiver
Medium Interface Medium Interface
Exchange CPE/RT
VDSL PHY
CPE

65
Ethernet over VDSL
PTM-TC
PMS-TC
PMD
MII
Medium
Interface
Transmission Medium (Twisted pair)
PTM-TC
PMS-TC
PMD
MII
Medium
Interface
Ethernet MAC
MII
Ethernet
Phy
Transmission Medium (LAN)
Ethernet
port
Ethernet MAC
MII
Ethernet
Phy
Transmission Medium
Ethernet
Core
Network
VDSL
PHY
CPE/RT
CO
Exchange CPE

66
The future …
• Data rate for VDSL
• VDSL.n?
– Better coding techniques
– Interference mitigation










MARGIN
GAIN
GAP
LOOP
Loop
VDSL
Noise
Code
SNR
SNR
B
R 1
log2

67
FERNANDO RAMIREZ-MIRELES
ramirezm@ieee.org

68
Abstract of the presentation
• VDSL is the most powerful member of the xDSL family, capable to
provide up to 100 Mbps on a single telephone wire. It provides
unmatched flexibility in rate, reach and symmetry to satisfy the increasing
demand for high-speed services such as corporate communications, fast
internet access and high quality digital audio and video delivery.
• This presentation will provide and introduction to the VDSL technology
and its applications.
• It will give an overview of a VDSL system, describing channel conditions,
system architecture, and VDSL performance in terms of rate-reach-
symmetry objectives.
• It will cover the basic principles of VDSL, explaining why VDSL is not just
an upgrade of ADSL in terms of higher transmission speed, and
summarizing the features in the current VDSL standard that allow
customization and on-the-fly configuration of the modems.
• In particular, it will study a general block diagram of a DMT based VDSL
modem, describing some of the signal processing techniques that enable
this high performance operation and flexibility.
• Finally, it will describe some of the applications for VDSL such as ATM
over DSL and Ethernet over DSL.

69
References
• VDSL Standards, documents by ANSI, ETSI and ITU.
• J. M. Cioffi et al., “Very-High-Speed Digital Subscriber Lines”, in IEEE Commun. Magazine.
• P. Vetter et al., "Systems Aspects of APON/VDSL Deployment," IEEE Commun. Mag.
• M Diaz Nava et. al., “A Short Overview of the VDSL System Requirements”, in IEEE Commun.
Magazine.
• Rich Wagner, “Broadband Access Network Options,” Corning Incorporated.
• “Very-High_Data-Rate Digital Subscriber Line (VDSL)’, White paper, International Engineering
Consortium, available at www.iec.org/online/tutorials/vdsl
• “A VDSL Tutorial”, F. Sjöberg, Luleå Tekniska Universitet., available at
http://epubl.luth.se/1402-1528/2000/02/LTU-FR-0002-SE.pdf
• F. Ramirez-Mireles et. al., “The Benefits of Discrete Multi-Tone (DMT) Modulation for VDSL
Systems”, White paper, www.analogzone.com
• S. Hass, “Choose Wisely Between QAM and DMT for VDSL”,in Communications System
Design.
• “ADSL2 and ADSL+, The New Standards”, white paper, Aware Inc.
• K. S. Jacobsen, “xDSL Technology and Applications: Removing the Telephone Line
Bottleneck”, white paper, Texas Instruments, available at
www.ewh.ieee.org/r6/scv/comsoc/9909.pdf

70
About the author
Fernando has over 10 years of experience in
R&D in VDSL, UWB and speech processing.
He has worked in the DSL field as a systems
and algorithms engineer. He is currently a
professor in the engineering division at ITAM in
Mexico City. He has authored more than
twenty technical articles and has one patent
granted and two more pending. He is a senior
member of the IEEE. He can be reached at
ramirezm@ieee.org.

VDSL FOR TRIPLE PLAY

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