Reducing Energy Consumption
in Optical Access Networks
Luca Valcarenghi
ITU-T Green Standards Week
Sep.5-9, 2011
Rome, Italy
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Summary
• Energy consumption in wired access
networks
• Energy consumption in optical access
networks
• Classification of methods to reduce optical
access network energy consumption
• Standard body initiatives to reduce energy
consumption in optical access networks
• Conclusions
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© 2011 Scuola Superiore Sant’Anna
Fixed Broadband Access Subscriptions
Total fixed (wired) broadband subscriptions
DSL
176.139.622
Cable Modem
90.017.631
Fibre + LAN
37.732.444
Other
TOTAL
Source: OECD
1.915.992
305.805.689
DSL: DSL lines offering Internet connectivity with
download speeds ≥ 256 kbit/s
Cable: Cable modem subscribers at download speeds ≥
256 kbit/s
Fibre: Fibre-to-the-premises (e.g., house, apartment)
download speeds ≥ 256 kbit/s; fibre-to-the-building
subscribers (e.g., Apartment LAN) using fibre-to-thebuilding but Ethernet to end-users.
OECD Fixed (w ired) broadband subscriptions, by technology, Dec. 2010
Cable Modem
29,4%
Fibre + LAN
12,3%
DSL
57,6%
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Total subscribers: 305.6 million
Source : OECD
Other
0,6%
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© 2011 Scuola Superiore Sant’Anna
Energy Consumption in Communications
Remaining part home networks
Networks
• Except home networks, access
networks, together with mobile radio
networks, are the major contributors
to energy consumption in
communications networks
– Because of the high number of
Customer Premises Equipments (CPE)
– Because of the bandwidth
underutilization
Wired Networks
Source: C. Lange, D. Kosiankowski,
R. Weidmann, and A. Gladisch,
“Energy
Consumption
of
telecommunication
networks
and
related
improvement
options”, IEEE JSTQE, March/April,
2011
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Access=Fixed Access Network=
Fiber to the Exchange (FTTE) and
Fiber to the Cabinet (FTTC): fiber
4
+ xDSL; FTTH (PON)
© 2011 Scuola Superiore Sant’Anna
Energy per bit of Optical Network Devices
bandwidth underutilization
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Source: R. S. Tucker, “Energy Footprint of the Network”, OFC 2009
workshop ”Energy Footprint of ICT: Forecasts and Network Solutions”
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© 2011 Scuola Superiore Sant’Anna
Energy per bit per technology
Per user access rate
Technology
Per user
power
consumption Technology
[W]
limit [Mb/s]
10 Mb/s
75 Mb/s
1Gb/s
Energy per bit
[nJ/b]
Energy per bit
[nJ/b]
Energy per bit
[nJ/b]
DSL
8
15
816
NA
NA
HFC
9
100
900
120
NA
PON
7
2400
745
99
NA
FTTN
14
50
1416
NA
NA
PtP
12
1000
1201
160
12
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Source: Jayant Baliga, Robert Ayre, Kerry Hinton, and Rodney S.
Tucker, “Energy Consumption in Wired and Wireless Access
Networks”, IEEE Communications Magazine, June 2011
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© 2011 Scuola Superiore Sant’Anna
Approaches for implementing energy efficiency in
PONs
•
Physical layer solutions target physical layer of PON architectures without
modifying the upper layer protocols
– Device-oriented solutions reduce energy consumption of physical devices
– Service-oriented solutions improve the performance of the services provided by the
physical layer to enable upper layer solutions
•
Data Link solutions target the data link layer of the IEEE 802.3 architecture (i.e.,
the MAC layer) or the Transmission Convergence (TC) layer in GPON
– Based on the possibility of switching network elements to a low power mode (e.g., sleep
mode)
•
Hybrid solutions are the ones that combine physical and data link layer solutions to
reduce energy consumption.
Source: L. Valcarenghi, D. Pham
Van, P. Castoldi, “How to Save
Energy in Passive Optical
Networks”, Invited paper, ICTON
2011
Source: Shing-Wa Wong, L.
Valcarenghi, She-Hwa Yen, D.R.
Campelo, S. Yamashita, L.
Kazovsky, “Sleep Mode for Energy
Saving PONs: Advantages and
Drawbacks”, GrennComm2, IEEE
Globecom 2009 Workshops
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© 2011 Scuola Superiore Sant’Anna
Evolution of energy saving in PONs in the
Standards
• ITU-T G.Sup45 “GPON power conservation”
• IEEE 802.3az “Energy Efficient Ethernet”
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© 2011 Scuola Superiore Sant’Anna
ITU-T G.Sup45 (05/2009)
• Solution to improve power conservation through
reduced power consumption and other
techniques within optical access networks
• First priorities: quality of service, availability and
interface variety
• Second priority: energy savings during emergency
(mains outage) and normal (mains powered)
operations
• Results are expected to be applicable to G-PON,
GE-PON, and to NG-PON
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© 2011 Scuola Superiore Sant’Anna
Power saving techniques
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© 2011 Scuola Superiore Sant’Anna
IEEE 802.3-2008 and IEEE 802.3av
• In 802.3-2008 (1GE-PON)
– Energy saving is not mentioned
• In 802.3av (10G-EPON)
– Energy saving is not mentioned
• Energy Efficient Ethernet (EEE)
– Specified in IEEE 802.3az (October 2010) for point-topoint links
• Amendment 5: Media Access Control Parameters, Physical
Layers, and Management Paramenters for Energy-Efficient
Ethernet
• EEE combines the IEEE 802.3 Media Access Control (MAC)
Sublayer with a family of Physical Layers defined to support
operation in the Low Power Idle (LPI) mode
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© 2011 Scuola Superiore Sant’Anna
ONU Energy Saving Potentials
Tc=cycle time
Toh=overhead time
Tsl=slot time
Pa=power consumed when ONU is active
Ps=power consumed when ONU is asleep
0.9
0.8
% expected
saving
% expected
energy power
savings
0.7
10%
Ps
Pa
Ps/Pa
0.6
20%
0.5
0%
30%
0.4
40%
0.3
•
The energy consumption of an ONU
can be reduced by
–
–
•
minimizing the recovery time of
CDR circuit for decreasing the
time ratio (Toh/Tc)
decreasing the power ratio (Ps/Pa)
Only by decreasing both the power
consumed during sleep mode and
the overhead time high energy
savings can be obtained
50%
60%
0.2
70%
0.1
80%
0.0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.9
1.0
Toh/Tcyc
Expected energy savings with correlation of time and power ratios
(1Gp/s TDMA PON, 16 ONUs)
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0.8
12
© 2011 Scuola Superiore Sant’Anna
Conclusions
• Moving from DSL to PON
– For decreasing energy per bit
• Reducing optical access network energy
consumption
– Combining physical layer ad data link layer approaches for
PON
– EEE for PtP architectures
• Current research ongoing at Scuola Superiore
Sant’Anna TeCIP
– Development of advanced scheduling for improving the
efficiency of sleep mode energy savings in TDM PONs
– Green PON testbed
– “Green labeling” (i.e., characterization) of energy efficient
PONs
– Energy efficiency studies in NG-PON2 (e.g., CDM, OFDM,
WDM)
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© 2011 Scuola Superiore Sant’Anna
thank you!
email:
luca.valcarenghi@sssup.it
Thanks:
Piero Castoldi
Dung Pham Van
Isabella Cerutti
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© 2011 Scuola Superiore Sant’Anna
Energy Consumption per Fixed Access
Technology
copper
Modem
DSLAM
Modem
RF Combiner
Technology
Node
15 Mb/s
Hybrid Fiber Coax
HFC
9
100 Mb/s
Passive Optical
Network
PON
7
2.4-10 Gb/s
Modem
Fiber to the
Node+VDSL
FTTN+VDLS
14
50 Mb/s
OMC
Point-to-Point
PtP
12
1-10 Gb/s
ONU
RN
ONU
Ethernet
switch
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Headline
access rate
8
fiber
Ethernet
switch
Per user
Power
consumption [W]
Digital Subscriber
Line DSL
Modem
OLT
DSLAM=Digital Subscriber Line Access Multiplexer
RF=Radio Frequency
RN=Remote Node
OMC=Optical Media Converter
Headline access rate
Technology
10 Mb/s
limit
Modem
DSLAM
OMC
Source: Jayant Baliga, Robert Ayre, Kerry Hinton, and Rodney S.
Tucker, “Energy Consumption in Wired and Wireless Access
15
Networks”, IEEE Communications Magazine, June 2011
© 2011 Scuola Superiore Sant’Anna
PON Evolution
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Source: Yukio Akiyama, R&D toward “Access Networks–\Building Trust, Connecting
People”, NTT Technical Review, vol. 9, no. 5, May 2011
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© 2011 Scuola Superiore Sant’Anna
Energy Efficient Light Bulbs and
Passive Optical Networks
Energy Efficient Light bulb
Gigabit Ethernet
(Compact fluorescent bulbs) Optical Network Unit (ONU)
~20 W
(~100 W traditional light bulb
tungsten filament lamps)
6 hours/day →
120 Wh/day
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~10 W
24 hours/day →
240 Wh/day
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© 2011 Scuola Superiore Sant’Anna