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

2. © 2011 Scuola Superiore SantAnna InReTe 2 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

3. © 2011 Scuola Superiore SantAnna InReTe 3 Fixed Broadband Access Subscriptions 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-the- building but Ethernet to end-users.

4. © 2011 Scuola Superiore SantAnna InReTe 4 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

5. © 2011 Scuola Superiore SantAnna InReTe 5 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

6. © 2011 Scuola Superiore SantAnna InReTe 6 Energy per bit per technology Per user access rate 10 Mb/s75 Mb/s1Gb/s Technology Per user power consumption [W] Technology limit [Mb/s] Energy per bit [nJ/b] DSL815816NA HFC9100900120NA PON7240074599NA FTTN14501416NA PtP121000120116012 Source: Jayant Baliga, Robert Ayre, Kerry Hinton, and Rodney S. Tucker, Energy Consumption in Wired and Wireless Access Networks, IEEE Communications Magazine, June 2011

7. © 2011 Scuola Superiore SantAnna InReTe 7 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

8. © 2011 Scuola Superiore SantAnna InReTe 8 Evolution of energy saving in PONs in the Standards ITU-T G.Sup45 GPON power conservation IEEE 802.3az Energy Efficient Ethernet

9. © 2011 Scuola Superiore SantAnna InReTe 9 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

10. © 2011 Scuola Superiore SantAnna InReTe 10 Power saving techniques

11. © 2011 Scuola Superiore SantAnna InReTe 11 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

12. © 2011 Scuola Superiore SantAnna InReTe 12 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 (T oh /T c ) –decreasing the power ratio (P s /P a ) 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 T c =cycle time T oh =overhead time T sl =slot time P a =power consumed when ONU is active P s =power consumed when ONU is asleep PsPs PaPa

13. © 2011 Scuola Superiore SantAnna InReTe 13 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 SantAnna 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)

14. © 2011 Scuola Superiore SantAnna InReTe 14 email: luca.valcarenghi@sssup.it luca.valcarenghi@sssup.it Thanks: Piero Castoldi Dung Pham Van Isabella Cerutti thank you!

15. © 2011 Scuola Superiore SantAnna InReTe 15 Energy Consumption per Fixed Access Technology DSLAM OLT Modem RF Combiner Node Modem RN Headline access rate 10 Mb/s Technology limit Technology Per user Power consumption [W] Headline access rate Digital Subscriber Line DSL815 Mb/s Hybrid Fiber Coax HFC9100 Mb/s Passive Optical Network PON72.4-10 Gb/s Fiber to the Node+VDSL FTTN+VDLS1450 Mb/s Point-to-Point PtP121-10 Gb/s ONU Ethernet switch OMC DSLAM=Digital Subscriber Line Access Multiplexer RF=Radio Frequency RN=Remote Node OMC=Optical Media Converter Ethernet switch DSLAM 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

16. © 2011 Scuola Superiore SantAnna InReTe 16 PON Evolution Source: Yukio Akiyama, R&D toward Access Networks–\Building Trust, Connecting People, NTT Technical Review, vol. 9, no. 5, May 2011

17. © 2011 Scuola Superiore SantAnna InReTe 17 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 Ethernet Optical Network Unit (ONU) ~10 W 6 hours/day 120 Wh/day 24 hours/day 240 Wh/day