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Technology
Service Providers Go
Green With Fiber
Reducing energy usage is a critical goal for network builders. But what’s the
right way to measure energy efficiency?
By Masha Zager ■ Broadband Properties
A
s energy costs consume ever
higher proportions of telecom
budgets – as much as 50 percent
in some cases – operators are looking
for new ways to operate more energyefficiently. For example, Verizon now
uses fuel cells to power equipment in the
field and it is experimenting with geothermal heating and cooling facilities to
test the value of tapping the earth’s constant temperature.
More significantly, Verizon mandated that all network equipment purchased after January 1, 2009, must be at
least 20 percent more efficient than prior
technologies. Verizon uses tracking software to calculate consumption and carbon equivalents for the energy that the
new equipment saves. In the past few
years, power-saving requirements have
become standard features of RFPs issued by most large telecom providers.
Watts per What?
When network operators issue RFPs
requesting energy-efficient equipment,
they typically define efficiency in terms
of energy consumption per port. Some
equipment vendors argue this measure is
too simplistic. Jeff Baher, senior director
of product marketing at Ericsson, compares per-port consumption to a car’s gas
mileage. A Prius may get more miles to
the gallon than a minivan, but a carpooling parent taking six children to school
will use less gas with the minivan.
Ericsson is promoting alternative
metrics, such as energy consumption
per circuit and per subscriber, which
measure how efficiently network equip-
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Large telecom operators are making energy
efficiency an important criterion in their
selection of new equipment – and driving
the development of a new generation of
low-power network components.
ment can provide subscriber services.
The company says the new metrics are
more closely related to the way service
providers monetize their business and
plan infrastructure investments.
Since the 2008 launch of its ambitious five-year program to reduce carbon
emissions, Ericsson has focused its efforts primarily on its IP edge and metro
Ethernet platforms. Baher says, “The
edge of the network is typically where
packets are aligned from the subscriber
perspective. Operators monetize traffic
at the edge of the network. … Capacity planning at the edge is based on the
number of subscribers and the services
delivered. The business assumptions and
network assumptions are predicated on
subscribers and services, so we represent
our platforms in those terms.”
Measured in terms of power consumption required to support 256,000
subscribers, Ericsson’s new equipment
models perform impressively in comparison with competitive offerings, based
on independent testing – although one
competitor, Alcatel-Lucent, says the
comparisons made incorrect assumptions about its equipment.
Glen Hunt, principal analyst at Current Analysis, calls Ericsson’s metrics
“more relevant and practical,” and says
he anticipates traction from the carrier
community and standards bodies.
One such standards body, the Alliance for Telecommunications Industry
Solutions (ATIS), has taken an approach
similar to Ericsson’s in developing its
standards for telecommunication equipment energy efficiency. ATIS’ standards
introduce the Telecommunications Energy Efficiency Ratio (TEER) as a measure of network-element efficiency. The
standards, which are specific to equipment type, network location and classification, quantify a network compo-
About the Author
Masha Zager is the editor of Broadband Properties. You can reach her at masha@
broadbandproperties.com.
| BROADBAND PROPERTIES | www.broadbandproper ties.com | September 2009
Technology
nent’s ratio of work performed to energy
consumed.
The Role of Network
Architecture
Other vendors, such as ADVA Optical
Networking, argue that the energy efficiency of specific equipment – however
it is measured – should not be the operator’s primary concern. Because the efficiency of a component depends on how
the network is set up, predicting its realworld performance is not always possible. Jim Theodoras, director of technical
marketing for ADVA, says that answering RFPs for energy-efficient equipment
can be difficult without an understanding of the network design.
According to Theodoras, changing
the network architecture can be more
effective than changing specific pieces
of equipment when it comes to reducing
power consumption. “You may have power-hungry boxes, but if you need fewer
of them, you can do better,” he points
out. For this reason, longer-distance
technologies on fiber optic long-haul
links save power.
Operators can also save power in
transport networks by reducing the
number of conversions from optical to
electrical signals and back again. “The
most power-intensive task at any node
is conversion,” Theodoras says. So nodes
with wavelength-selective switching reconfigurable optical add-drop multiplexers (WSS-ROADMs), which pass most
optical signals through without converting them, consume far less energy than
nodes with routers, cross-connect modules or other types of equipment that
convert all the signals passing through.
PON Saves Power
In the access network, reducing the number of aggregation layers saves power because every layer requires power-hungry
equipment. A passive optical network
(PON), which does not require powered
equipment in the field, uses less power
than a fiber-to-the-curb network even
though it may provide more bandwidth
to subscribers.
Chuck Graff, Verizon’s director of
corporate and network technology, says
Verizon’s fiber-to-the-home network is
responsible for enormous energy sav-
But even low-power network components
won’t save enough energy to meet future
demands. To deliver more bandwidth without
using more energy, operators must rethink
their network architectures.
ings. Verizon’s GPON equipment consumes only 38 percent of the electric
power that access equipment for copper
networks consumes, according to Graff. Other network operators transitioning to PON have also identified energy
savings. In our July/August issue, Tom
Anderson of Alloptic wrote about an Alloptic client that upgraded a section of its
hybrid fiber/cable (HFC) network to all
fiber, using RFoG technology, and reduced its power purchases by more than
95 percent as a result.
Part of this savings was simply a
transfer of costs to retail customers, who
had to pay for the electricity that powered the micronodes at their premises.
However, Anderson’s colleague Julian
Thomas calculated that, even taking
customers’ expenditures into account,
fiber to the premises saves power in
comparison with HFC networks that
serve fewer than 500 to 750 customers
per node. (HFC networks must reduce
the number of customers per node to
well below 500 in order to deliver advanced services such as high-definition
video channels and high-bandwidth Internet access.)
WDM-PON – An Efficient
Network Architecture
The more aggregation layers are eliminated, the greater the power savings. The
ultimate layer compression will probably
come from wavelength-division-multiplexing PON (WDM-PON). WDMPON eliminates more layers than
GPON because the function that the
optical line terminal performs in GPON
is no longer required in a WDM-PON
architecture; in effect, local exchanges
can be eliminated altogether.
WDM-PON collapses networks
even further by permitting business,
residential and backhaul networks to
be merged into a single network. Rather
than operating three separate networks
for three different functions, carriers
can operate a single infrastructure. “If
you use an Ethernet demarcation that
lets you tag packets, you can combine
everything, and you know where it came
from so you can account for billing. It
saves you more power than having different infrastructures,” Theodoras says.
In general, Theodoras adds, processing is more energy-efficient at lower
network layers. Layer 3 (IP and similar
protocols) has more overhead than Layer
2 (Ethernet and similar protocols). To
continue expanding subscriber bandwidth without running out of power,
operators should drive more processing
to Layer 2 equipment. Contrary to the
received wisdom of only a few years
ago, operators should avoid using IP in
the first mile and at the edge and use it
only at the point where Internet access
is needed. “Most phone calls and server
backups don’t have to touch the cloud,”
Theodoras says. “So you can concentrate
most of the Layer 3 cloud in efficient
data centers using hydroelectric power.”
Of course, transitioning to energyefficient network architectures is even
more difficult than transitioning to
energy-efficient network components.
Carriers building all-new networks can
choose efficient network architectures,
but in overbuilds their range of options
is typically limited. Some operators are
making the effort, however; according
to Theodoras, one European carrier has
set a goal of eliminating 85 percent of
its local exchanges. But it won't happen
overnight. “It will be a slow process to
gradually migrate to more efficient architectures,” he says. BBP
September 2009 | www.broadbandproper ties.com | BROADBAND PROPERTIES |
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