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Lecture: 7 Energy Efficiency in Optical Networks


Title: Titel Author: MDMC Last modified by: AJMAL MUHAMMAD Created Date: 11/12/2012 3:03:48 PM Document presentation format: On-screen Show (4:3) Other titles – PowerPoint PPT presentation

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Title: Lecture: 7 Energy Efficiency in Optical Networks

Lecture 7 Energy Efficiency in Optical Networks
Ajmal Muhammad, Robert Forchheimer Information
Coding Group ISY Department
  • Introduction to Energy Issue
  • Network Devices Power Profile
  • Access, metro core networks
  • Approaches to low Energy Networking
  • Energy Saving Strategies
  • Core, metro access networks

  • Two main factors that drive the quest for Green
  • (1) Reduction of CO2 emission
  • The ICT (Information and Communications
    Technology) sector is responsible for 2.0 of the
    global greenhouse emissions, estimated by ITU
    (International Telecommunication Union).

(2) Reduction of operational cost Power
consumption of the ICT (Information and
Communications Technology) accounted for the 4
of the global energy consumption
BAU Business-As-Usual ECO Eco Sustainable
  • 50 of CO2 emission is due to the
  • production stage
  • 45 due to the usage stage
  • 5 due to recycling/disposal stage

For European Telecom network infrastructures
Terminal versus Network Power Consumption
  • Typical current mobile terminal power consumption
    is 0.83Wh per day (including battery charger and
  • The corresponding network power consumption is
  • The ratio is 1501 and therefore the network
    power consumption is the main contributor to CO2
    and effort has to be directed at the network
  • Significant research effort has gone into
    extending the mobile terminal battery life by
    optimizing and reducing its power utilization
    from 32Wh per day in 1990 to 0.83Wh per day in
    2008, a factor of 38.
  • In comparison the network power consumption has
    received little attention to date.

Power Consumption of Access Networks
Mobile access is becoming dominant access
technology Any where, any time, any
service Mobile is least energy efficient 25
W/user _at_ 10 Mb/s PON is most efficient 7 W/user
PON Passive optical Network HFC Hybrid fiber
coaxial PtP Point to point FTTN Fiber to the
node or neighborhood
Network Segmentation
Key Components
  • Customer home terminal
  • ADSL modem, ONU.
  • Access network field equipment
  • PON splitter, DSLAM, RF amps
  • Central office equipment
  • OLT, gateway, switch, base station,

Access Network
Metro Network
Key Components Core Network
  • Core routers switched
  • Number of router hops
  • Long haul submarine optical WDM transport
  • EDFAs, Raman Amps, transmit receive units, etc.
  • TDM and WDM cross connects OADM

Photonic Versus Electronic Switching
  • Photonic switching has much lower energy
    consumption compared to electronic switching.
  • It has been shown that the power needed per bit
    for switching is 100 to 1000 times higher in an
    electronic semiconductor switch as compared to a
    photonic switch.

Data Centers and Content Servers
Access, Metro, Core Power Consumption
  • PON based access network - power consumption
    estimates are 10W for optical network units (ONU)
    and 100W for optical line terminal (OLT) which
    resides in an edge node.
  • Edge router in the metro, for example Cisco
    12816, with capacity 160Gb/s consumes 4.21 kW.
    Efficiency 26.5nJ/bit
  • Core router, such as Cisco CRS-1 with 640 Gb/s
    capacity consumes 1020 kW. Efficiency 17nJ/bit
  • WDM systems connecting the edge nodes to the core
    node consume 1.5 kW for every 64 wavelengths.
  • Typically one multi-wavelength amplifier is
    required per fibre, consuming around 6W.
  • The WDM terminal systems connecting core nodes
    consume 811 W for every 176 channels, while each
    intermediate line amplifier consumes 622 W for
    every 176 channels.

Router Power Consumption
  • Dominated by router forwarding engines

Power driver IP look-up/forward engine I/O-
optical transport is lower in power Consumption
than switch fabric
  • Introduction to Energy Issue
  • Network Devices Power Profiles
  • Access, metro, core network components
  • Approaches to Low Energy Networking
  • Energy Saving Strategies
  • Core, metro, access networks

Approaches to low Energy Networking
Modulate capacities of processing engines and of
network interfaces, to meet actual traffic loads
and requirements
  • Introduce and design
  • More energy efficient elements for network
  • Optimize the internal organization of devices
  • Reduce devices intrinsic complexity levels

Smartly and selectively drive unused
network/device portions to low standby mode
Network Domain Utilization
Internet traffic profile Networks are
provisioned with resources for worse case
Energy Saving in Core Networks
  • Approaches
  • Selectively turn down network elements
  • - Energy efficient protocols
  • Energy efficient network architecture
  • Energy efficient routing
  • Green routing

Energy Efficient Protocols
  • Sleep standby states
  • Network devices enter low power state when
    not in use
  • Can apply to systems and sub-systems
    Need to ensure network presence is retained
    use network connection proxy with sleep
  • Need to account for state transition energy
    and time
  • May have multiple lower energy states
  • IEEE Energy Efficient Ethernet (802.3az)
  • Low power idle mode when no packets are
    being sent
  • Approved Sept. 2010 Currently
    applies to copper interface only not optical

Example Exploiting Sleep Mode
off not used
must be active to support working lightpath
can be set to sleep
Dynamic Rate Adaptation
  • Modify capacity of network devices in response to
    traffic demands
  • Change clock frequency, processor voltage
  • Power C x Voltage2 frequency
  • Slower speed to reduce power consumption
  • 100 Mb/s uses 10-20 W less than 10GE, 4 W
    less than 1GE
  • Need to allow transition time between rates
  • Dynamic rate adaptation and standby states
    can be combined

Sleep Mode for Dynamic Networks
  • Some nodes are selected to go to sleep according
    to the traffic flow and their location in the
    network topology
  • When nodes go to sleep, they can still transmit
    and receive traffic but they cannot route traffic

A node which is the only neighbour for another
node cannot go to sleep Some traffic flows will
have to take longer routes, i.e., energy is
saved at the expense of QoS If the network
blocking probability exceeds the acceptable
(service) blocking probability threshold,
the most recent node to sleep wake up
Energy Efficient Network Architecture
  • Architectures that reduce the number of router
  • Optical bypass
  • Layer 2 rather than Layer 3 where possible
  • Without optical bypass
  • All traffic goes to IP layer for processing
  • 10nJ per bit
  • Allow aggregation of incoming traffic flow
  • Statistical multiplexing

Layer 3 Layer 2
Architecture Bypass Option
  • With bypass
  • TDM Layer
  • Some traffic streams processed at TDM layer
  • 1nJ per bit
  • WDM Layer
  • Some traffic streams processed at WDM layer
  • lt 0.1nJ per bit
  • Switching wavelengths

Energy Efficient Routing Network with Dedicated
Path Protection
Energy-unaware Routing
Energy-aware Routing
Energy Efficient Routing Network with Shared Path
Energy-unaware Routing
Energy-aware Routing
Green Routing

Energy Saving in Metro Networks
  • Reduce Regeneration

PIC Peripheral Interface Controller WSS
Wavelength Selective Switch ROADM Reconfigurable
Optical Add Drop Multiplexer
Energy Efficient Traffic Grooming
  • DXC Digital cross-connect
  • OXC Optical cross-connect

FG First Generation SH Single-hop MH Multi-hop
Energy Efficiency in Access Networks
Remove Layers
British Telecom network architecture today More
Future Plan
Less power
Network simplification
From PON to Long Reach-PON

The Ring-and-Spur LR-PON

Two dimensional coverage for failure
protection Reusing the existing metro
rings Cost-effective extended coverage
integrated system less active sites low
CapEx and OpEx
(No Transcript)
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