Reducing Energy Consumption in Optical Access Networks Luca Valcarenghi InReTe ITU-T Green Standards Week Sep.5-9, 2011 Rome, Italy

Reducing Energy Consumption in Optical Access Networks

Luca Valcarenghi

InReTe

ITU-T Green Standards WeekSep.5-9, 2011

Rome, Italy

© 2011 Scuola Superiore Sant’Anna InReTe

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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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Fixed Broadband Access Subscriptions

Other0,6%

Fibre + LAN12,3%

Cable Modem29,4%

DSL57,6%

OECD Fixed (wired) broadband subscriptions, by technology, Dec. 2010

Total subscribers: 305.6 millionSource : OECD

Total fixed (wired) broadband subscriptions

DSL 176.139.622

Cable Modem 90.017.631

Fibre + LAN 37.732.444

Other 1.915.992

TOTAL 305.805.689

Source: OECD

DSL: DSL lines offering Internet connectivity with download speeds ≥ 256 kbit/sCable: Cable modem subscribers at download speeds ≥ 256 kbit/sFibre: 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-the-building but Ethernet to end-users.


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Energy Consumption in Communications 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

Remaining part home 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

Access=Fixed Access Network= Fiber to the Exchange (FTTE) and Fiber to the Cabinet (FTTC): fiber + xDSL; FTTH (PON)

Wired Networks


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Energy per bit of Optical Network Devices

Source: R. S. Tucker, “Energy Footprint of the Network”, OFC 2009 workshop ”Energy Footprint of ICT: Forecasts and Network Solutions”

bandwidth underutilization


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Energy per bit per technology

Per user access rate

10 Mb/s 75 Mb/s 1Gb/s

Technology

Per user power consumption [W]

Technology limit [Mb/s]

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

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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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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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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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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Power saving techniques


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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-to-

point 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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0%

10%

20%

30%

40%

50%

60%

70%

80%

Toh/Tcyc

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

% expected power saving

Ps/

Pa

ONU Energy Saving Potentials

• 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 Expected energy savings with correlation of time and power ratios

(1Gp/s TDMA PON, 16 ONUs)

% expected energy savings

Tc=cycle time Toh=overhead timeTsl=slot timePa=power consumed when ONU is activePs=power consumed when ONU is asleep

Ps Pa


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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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email: email: [email protected]:Thanks:Piero CastoldiPiero CastoldiDung Pham VanDung Pham VanIsabella CeruttiIsabella Cerutti

thank you!thank you!


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Energy Consumption per Fixed Access Technology

DSLAM

OLT

Modem

Modem

RF Combiner Node

Modem

RN

Headline access rate 10 Mb/s

Technology limit

Technology

Per userPower consumption [W]

Headline access rate

Digital Subscriber Line DSL 8 15 Mb/s

Hybrid Fiber CoaxHFC 9 100 Mb/s

Passive Optical NetworkPON 7 2.4-10 Gb/s

Fiber to the Node+VDSLFTTN+VDLS 14 50 Mb/s

Point-to-PointPtP 12 1-10 Gb/s

ONU

ONU

Ethernetswitch

OMC

OMC

DSLAM=Digital Subscriber Line Access MultiplexerRF=Radio FrequencyRN=Remote NodeOMC=Optical Media Converter

Ethernetswitch

DSLAM

Modem

Modem

copper

fiber

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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PON Evolution

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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Energy Efficient Light Bulbs and Passive Optical Networks

~20 W(~100 W traditional light bulb

tungsten filament lamps)

Energy Efficient Light bulb(Compact fluorescent bulbs)

Gigabit EthernetOptical Network Unit (ONU)

~10 W

6 hours/day → 120 Wh/day

24 hours/day → 240 Wh/day

Documents

Reducing Energy Consumption in Optical Access Networks Luca Valcarenghi InReTe ITU-T Green Standards Week Sep.5-9, 2011 Rome, Italy