Reducing Energy Consumption in Optical Access Networks

1. Reducing Energy Consumption in Optical Access Networks Luca Valcarenghi ITU-T Green Standards Week Sep.5-9, 2011 Rome, Italy 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. 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. Energy Consumption in Communications Networks Remaining part home 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 Access=Fixed Access Network= Fiber to the Exchange (FTTE) and Fiber to the Cabinet (FTTC): fiber + xDSL; FTTH (PON)

5. Energy per bit of Optical Network Devices bandwidth underutilization Source: R. S. Tucker, “Energy Footprint of the Network”, OFC 2009 workshop ”Energy Footprint of ICT: Forecasts and Network Solutions”

6. Energy per bit per technology 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. 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. Evolution of energy saving in PONs in the Standards • ITU-T G.Sup45 “GPON power conservation” • IEEE 802.3az “Energy Efficient Ethernet”

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. Power saving techniques

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. 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 • Tc=cycle time • Toh=overhead time • Tsl=slot time • Pa=power consumed when ONU is active • Ps=power consumed when ONU is asleep % expected energy savings Pa Ps Expected energy savings with correlation of time and power ratios(1Gp/s TDMA PON, 16 ONUs)

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 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)

14. thank you! email: luca.valcarenghi@sssup.it Thanks: Piero Castoldi Dung Pham Van Isabella Cerutti

15. Energy Consumption per Fixed Access Technology DSLAM=Digital Subscriber Line Access Multiplexer RF=Radio Frequency RN=Remote Node OMC=Optical Media Converter copper Modem DSLAM Modem RF Combiner Node Modem fiber ONU OLT RN ONU Modem Ethernet switch DSLAM Modem OMC Ethernet switch Source: Jayant Baliga, Robert Ayre, Kerry Hinton, and Rodney S. Tucker, “Energy Consumption in Wired and Wireless Access Networks”, IEEE Communications Magazine, June 2011 OMC

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. Energy Efficient Light Bulbs and Passive Optical Networks Energy Efficient Light bulb (Compact fluorescent bulbs) Gigabit Ethernet Optical Network Unit (ONU) ~20 W (~100 W traditional light bulb tungsten filament lamps) ~10 W 24 hours/day → 240 Wh/day 6 hours/day → 120 Wh/day