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2007 Bechtel Corporation. All rights reserved. 1
INTRODUCTION
There are two basic means of providingcommunications services: wireless or wireline.On the wireless side, the main hurdle is
scarceness of radio frequency (RF) spectrum and
the associated huge cost. In the US, spectrum is
viewed as a scarce national resource, closely
guarded by the Federal Communications
Commission (FCC). Based on the FCCs personal
communications services (PCS) auctions, the
median value of 1 MHz of spectrum per pop was
around US$1.68 [1]. Simple math shows that
a bare minimum of 10 MHz of spectrum(a pair of 5 MHz, enough for only one channel
of current frequency division duplex [FDD]
technologies such as universal mobile
telecommunications system [UMTS]) that
covers 300 million US pops could cost close to
US$5 billion! And there is the cost of deploying
the network. On top of this, there are the ongoing
site rental or lease fees, which, on a nationwide
basis, could translate to hundreds of millions
or even billions of dollars annually. These factorsmake widespread usage of wireless broadband
relatively difficult and expensive!
On the wireline side, there are currently two
means of providing broadband services: digital
subscriber line (DSL) through telephone company
telephone lines, and cable modem through cable
company coaxial cable lines. Now, with the
advent of broadband over power lines (BPL or
BoPL), a third wired option is emerging that uses
electric utility power lines. Power lines are
attractive for communications purposes because
they have an omnipresence that reaches mosthomes and businesses, even in the most rural
areas. This ubiquity implies a possible reduction
in both time and cost for broadband deployment
In this sense, power lines, like RF spectrum, can
be considered a very valuable national resource,
or even a national treasure. And, of course, there
is the inside-home power line wiring that can
literally turn every outlet plug into a broadband
communications access port.
BROADBAND OVER POWER LINES (BPL)
AbstractThe Internets proliferation has focused attention on the importance of providing widespreadaccess to broadband services. Many studies show that such access can have profound positive socioeconomicimpacts. Currently, however, broadband access is available to relatively few people worldwide. Broadbandaccess has traditionally been provided via either DSL or cable. More recently, wireless and satellite broadbandaccess has also gained significant momentum. Now, a thirdwiredoption is emerging: broadband over
power lines (BPL).
Power lines, however, were designed to deliver power, not communications, which poses three main hurdles forBPL. First, the variation in power line channel characteristics and performance over time and location must be
appropriately considered. Second, measures must be put into place to ensure that BPL does not causeinterference for the existing rightful owners of the spectrum. Third, the regulatory issues accompanying anynew technology must be addressed.
As these hurdles are overcome, as standards mature, and as inexpensive standards-based equipment becomesmore widely available, the concerns about the risks of BPL investment and deployment will gradually diminishThen, the right business and deployment models will enable BPL to capture a significant portion of the thrivingbroadband market.
Key Wordsaccess BPL, BPL, broadband over power lines, capacity, channel characteristics, coupler,extractor, FCC, injector, in-house BPL, interference, low voltage (LV) line, medium voltage (MV) line, noise,NTIA, Part 15, PLC, power line communications, repeater, Subpart G, transformer bypass
Issue Date: January 2007
Lee Lushbaugh
S. RasoulSafavian, PhD
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Bechtel Telecommunications Technical Journal2
ABBREVIATIONS, ACRONYMS, AND TERMS
AC alternating current
AMR automated meter reading
AP access point
ARRL American Radio Relay League
AWGN additive white gaussian noise
BoPL broadband over power linesBPL broadband over power lines
CALEA Communications Assistancefor Law Enforcement Act
CENELEC European Committee forElectrotechnical Standardization
CFR Code of Federal Regulations(47 CFR addressestelecommunications)
CPE consumer premises equipment
CSMA/CA carrier sensing multipleaccess/collision avoidance
DAS distributed antenna system
dBm power in decibels withreference to 1 milliwatt
DSL digital subscriber line
EHV extremely high voltage(> 300 kV)
EM electromagnetic
EMC EM compatibility
EMI EM interference
ETSI European Telecommunications
Standards InstituteFCC Federal Communications
Commission
FDD frequency division duplex
FTTH fiber to the home
GDP gross domestic product
HDTV high definition television
HF high frequency (3 to 30 MHz)
HV high voltage (36 to 300 kV)
IEEE Institute of Electrical andElectronics Engineers
ISP Internet service provider
LAN local area network
LF low frequency
LV low voltage (< 1 kV)
MAC medium access control
MO&O Memorandum ofOpinion & Order (FCC)
MTL multiconductor transmissionline
MV medium voltage (1 to 36 kV)
NEC numerical EM code
NMS network management system
NOI Notice of Inquiry
NPRM Notice of Proposed RuleMaking (FCC)
NTIA National Telecommunicationsand Information Administration
OFDM orthogonal frequency divisionmultiplexing
OPERA Open PLC European ResearchAlliance
OSS operations support system
PC personal computer
PCS personal communications
services
PL power line
PLC power line communications
POP point of presence
PSTN public switched telephonenetwork
QoS quality of service
R&D research and development
R&O Report & Order (FCC)
RF radio frequency
RMS root mean square
ROI return on investment
SCADA supervisory control and dataacquisition
SW shortwave (5.9 to 26.1 MHz)
UHF ultra high frequency
UMTS universal mobiletelecommunications system
UPA Universal PowerlineAssociation
USAC Universal Service
Administrative Company
USF Universal Service Fund
UTC United Telecom Council
VHF very high frequency(30 to 300 MHz)
VoIP voice over Internet Protocol
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Considering that broadband penetration is
currently less than 4 percent globally, the huge
growth potential for the broadband market is
obvious. BPL could provide a quick and attractive
solution. Of course, successful BPL deployment
requires not only a solid technical performance
and field trial records, but also realistic and viable
business and deployment plans.
This paper first examines the current state of
broadband access and the importance of havingthis access. Then, a quick overview of the electric
power grid and how it can be altered to allow
BPL sets the stage for a review of the current BPL
players, field trials, commercial deployments,
and standards bodies. This is followed by a brief
examination of the potential benefits of BPL to
the electric utility companies, service providers,
and end-users and a look at the main
challenges for BPL, namely harsh power line
channel characteristics and performance issues,
interference concerns, and the regulatory
activities surrounding BPL. The paper continues
with a review of the BPL business models and
economic issues before presenting conclusions
and closing remarks.
BROADBAND ACCESS
Current State of Access
Despite the widespread and spectacular growth
of broadband technologies in the last few years,
significant regions of the world, including rural
and low income areas in the US, still do not have
access to broadband services. In fact, out of the6.7 billion people who currently inhabit our
planet, roughly 3.7 billion (60 percent) have
access to electrical power services, whereas only
about 2 billion (30 percent) have access to some
type of telephony services (wireline and/or
wireless), and only roughly 250 million
(3.7 percent) have access to broadband
services [2, 3]. In the US, out of a population of
300 millionand using a relaxed definition
of broadband as only 200 kbps in at least one
direction (Internet to user [receiving or downlink]
or user to Internet [transmitting or uplink])only
roughly 50 million people currently have accessto broadband services.
A major hurdle to deploying broadband services
is the high cost of deploying the so-called last-mile
access. The last mile (also sometimes referred
to as the first mile, local loop, or access network)
is defined as the part of the network that
links users with broadband services. From a
communications perspective, power lines, due to
their omnipresence and the fact that they have
already reached electrical power users in homes
and offices, would seem to solve this access issue.
In this sense, they may be considered as a
possible third set of broadband wires reaching
homes or businesses (the other two being
DSL and cable modem). Of course, last-mile
broadband access could also be provided
wirelessly via fixed wireless, cellular, or
satellite systems.The wiring inside a home or office can also be
used to provide a local area network (LAN)
connecting computers, printers, and smart
appliances and basically turning every outlet into
an Internet connection. This is sometimes referred
to as last-inch access or connectivity.
It is worth noting that while industrialized
countries typically have severalalbeit
sometimes prohibitively priceytelephony and
broadband options, less developed countries may
have access only to power line services and
frequently lack well-established conventionaltelecommunications infrastructure. It is here that
power line communications can be particularly
useful and effective. Households connected to
power lines may be quickly provided with
telephony via voice over Internet Protocol (VoIP)
and broadband Internet services, with minimal
need for a new major infrastructure and its
associated huge financial investment. For many
of those underserved communities, this would be
their first access to telephony, Internet, and
related services.
Importance of Access
Numerous studies have shown a direct
relationship between the availability and
penetration rate of broadband and an
improvement in productivity, quality of
education, quality of health care, generation of
new high-paying jobs, and facilitation of new
channels for commerce. These, in turn, can all
lead directly to national economic growth (with a
direct impact on gross domestic product [GDP])
and even enhanced national security. According
to Thomas L. Friedman, the frequently quoted
op-ed commentator on globalization:Jobs, knowledge use and economic growthwill gravitate to those societies that are themost connected, with the most networks andthe broadest amount of bandwidthbecausethese countries find it easiest to amass,deploy and share knowledge in order todesign, invent, manufacture, sell, provideservices, communicate, educate and enter-tain. Connectivity is now productivity. [4]
January 2007 Volume 5, Number 1 3
Considering that
broadband
penetration is
currently less than
4 percent globally,
the huge growth
potential for the
broadband market
is obvious.
BPL could provide
a quick and
attractive solution.
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Bechtel Telecommunications Technical Journal4
Unfortunately, both nationally and globally, a
large digital divide, or gap, separates those
with regular and effective access to digital
technologies and those without. More
specifically, a gap exists between people who
have effective high-speed Internet access (the
information haves) and those who do not (the
information have-nots). Realizing the importance
of broadband, US President George W. Bush, on
April 26, 2004, called for providing universal andaffordable broadband access in every part of
America by 2007 as part of his initiative to create
A New Generation of American Innovation [5].
With respect to the presidents broadband
initiative, BPL could play an important role
by offering:
Affordability: With no need for new wiring
or major infrastructure deployment, BPL
creates an alternative broadband solution
that could lead to lower prices for broadband
consumers.
Universality: BPL could facilitate and speed
up connecting the rural and low income
parts of America to broadband services,
thereby helping to bridge the digital divide.
Thus, power lines could perform double duty by
delivering electrical power services and
providing broadband information services. BPL
deployment, in turn, holds the promise of
providing both telephony (via VoIP) and
broadband services to all 3.7 billion people on
our planet who have access to power lines!
It is also worth mentioning that power line
communications (PLC) is not a new subject, but
one that has been around for decades. Several
power companies around the globe have been
using power lines for low-speed applications
(a few kbps in the low frequency [LF] portion of
the spectrum), such as power line meteringand control. The recent renewed interest in
using power lines for communications revolves
specifically around providing BPL applications.
The main idea is to use specialized equipment
to slightly modify the existing power grid to
allow it to also carry high speed data over a
broad spectrum range (high frequency [HF], the
lower portion of very high frequency [VHF],
and potentially beyond) without causing
unreasonable interference to the rightful
incumbent users of those RF bands. Furthermore,
this has to be done in an economically and
financially viable manner.
ELECTRIC POWER GRID
Overview of Grid Structure and Topology
While the details of electric power grid structures
and topologies differ from country to country,
High VoltageTransmission Lines
Medium VoltageTransmission Lines
PowerSubstation
Power Plant
PowerSubstation
Low VoltageTransmission Lines
Low VoltageTransmission Lines
Medium VoltageTransmission Lines
High Voltage Transmission(69 kV and Above)
Primary Distribution Medium Voltage(2.4 to 35 kV)
Secondary Distribution Low Voltage(Up to 600 V)
Figure 1. Typical Electric Power Grid
US President
George W. Bush,
in April 2004,
called for providing
universal and
affordable
broadband access
in every part of
America by 2007
as part of his
initiative to create
A New Generation
of American
Innovation.
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January 2007 Volume 5, Number 1 5
a power grid basically consists of power
plants or generators, transmission substations,
transmission lines, power substations with
transformers to change voltage levels, and
distribution lines that collectively generate
and carry the electricity from power plants all
the way to wall plugs. See Figure 1.
Power plants are basically spinning electricity
generators. Spinning can be performed by a
steam turbine, and steam can be created by
burning fossil fuel or from a nuclear reactor.
A generators output is three-phase alternating
current (AC) power at voltage levels in the
thousands. The three single phases are
synchronized and offset by 120 degrees.
Three-phase current is chosen because single-
phase AC goes through a full cycle (from zero
to peak to zero to other peak and back to
zero) at the line rate, which is 60 timesper second in the US and 50 in the other parts
of the world. With three synchronized phases, on
the other hand, one of the three phases is nearing
a peak at any given instant. More phases could be
used, but this implies more wires and higher cost;
three seems to be a good compromise between
cost and performance.
Power P, transferred over lines and delivered to
customers, is equal to the product of voltage V
and current I (P = IV). Power loss in the line
grows with the square of the current, that is,
Ploss = Rline I2, where Rline is the line resistance
and depends on the line material and increases
with the length of the line. For a given generated
P and a given Rline , to reduce Ploss , current Imust
be made as small as possible. This means that
the line voltage must be made as large as possible,
especially for long-distance transmissions.
Transmission substations located next to power
plants use large transformers to step up generator
output from thousands of volts to hundreds of
thousands of volts (typically between 155,000 and
765,000 volts), thus allowing megawatts of power
transmission over distances of 300 miles or more.
At power substations, voltages are stepped down
and lines are branched out to cover larger areas.
This is performed successively, transforming and
branching out from extremely high voltage (EHV,
typically 155 to 765 kV) to high voltage (HV,
typically 45 to 155 kV), and then from HV to
medium voltage (MV, typically 2 to 45 kV), and
finally from MV to low voltage (LV, typically
100 to 600 V) for delivery to homes or businesses.
The result is a tree-structured power distribution
hierarchy. Basically, EHV and HV are used to
transmit AC electric power, and MV and LV are
used to distribute it. See Figure 2.
The structures needed to support EHV and HV
lines are typically tall, massive towers. MV and
LV lines, on the other hand, are typicallymounted on street poles. In the US, street poles
are typically 10 meters high, located 50 meters
apart, and support three wires that carry the
three separate phases, plus a neutral (possibly
grounded) wire. A network of MV lines is usually
referred to as the primary distribution; a network
of LV lines is the secondary distribution.
In the US, at the primary distribution level, most
power lines are aerial or overhead. At the
secondary distribution level, particularly in
newer urban areas, most lines run underground.
Overhead lines are more susceptible thanunderground lines to producing radiation
interference and to picking up interference. But
underground lines are used less due to the
prohibitive cost of burying cables. In the US,
MV lines typically run between 15 and 50 km.
As mentioned, levels and structures of branching,
network architectures, and voltage levels vary
from country to country. For instance, in the US,
TransformerGeneration
MV
EHV HV MV
MV
MV
MVHV
HV
Transformer
Transmission Distribution
LV
LV LV
LV
LV
LVLV
LV
LV
Consumption
Figure 2. From Generation to Consumption: Power Grid Hierarchies
A power grid
basically consists
of power plants
or generators,
transmission
substations,
transmission lines,
power substations
with transformers
to change
voltage levels, and
distribution lines
that collectively
generate and
carry the electricity
from power plants
all the way
to wall plugs.
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Bechtel Telecommunications Technical Journal6
typically fewer than a dozen homes are served
by a single MV/LV transformer, whereas in
Japan this number is about 30 and in Europe it
is several hundred. This affects not only the
communications characteristics, but also the
economic viability of a BPL system. (BPL business
models are examined later in this paper.)
Altering the Power Grid To Allow BPL
EHV and HV lines are usually too noisy totransmit broadband communications signals;
only MV and LV lines are used for BPL. MV
lines are usually less branched than LV lines,
making point-to-point connections possible.
MV networks allow communication over
longer distances because of their weaker signal
attenuation and lower noise level.
To use power lines for broadband communi-
cations, the broadband signal must be injected
into and extracted from the lines through
couplers. LV couplers may be capacitive or
inductive, depending on distribution systemtopology, performance requirements, and cost. In
capacitive coupling, a capacitor is responsible for
the actual coupling, and the signal is modulated
onto the networks voltage waveform. In
inductive coupling, an inductor is used to couple
the signal onto the networks current waveform.
Inductive couplers are known to be rather lossy,
but since they require no physical connection to
the network, they are safer to install on energized
lines than capacitive couplers. MV couplers are
typically inductive. It is important that couplers
be easy-to-install passive devices with low failurerates that can be used outdoors and installed on
energized lines.
Line noise, limitations on the amount of signal
power that can be injected into power lines
without causing unacceptable interference for
other spectrum users, and signal attenuation as
the signal traverses the line make it necessary to
regenerate or repeat the signal periodically. This
can be done by using MV couplers to couple the
broadband signal off of the MV line so that it can
be regenerated if necessary and amplified before
being fed back onto the MV line through another
coupler. Repeaters, on the other hand, could add
latency (especially if the signal is regenerated)
MobileNetwork
PSTN
BackhaulBox
Power Substation
Backhaul Network
Internet
Access BPL In-House BPL
Power Generator
MVLines
MV Coupler
MVLines
HVTransmission Lines
RepeaterBox
TransferBypass
Box
MVCoupler
LV CouplerMV
Coupler
LV Lines
PC
VoIPPhone
MVLines
LV Lines toHomes/Businesses
MVLine
MVCoupler
LVCoupler
LV Line toHome/Business
TransferBypass
Box
Transformer
LVLine
Coax
Figure 3. Typical BPL Architecture
Couplers should be
easy-to-install
passive devices
with low failure
rates that
can be used
outdoors and
installed on
energized lines.
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January 2007 Volume 5, Number 1 7
and could also create single points of failure,
because a single bad repeater can bring down an
entire communications line.
The distribution transformers that changevoltage levels between MV and LV lines are
particularly harsh on the weak broadband signal.
Transformers, which are intended to pass low
frequencies near 50 or 60 Hz, appear as open
circuits for the passage of higher frequency
signals and typically attenuate and distort the
weak broadband signal beyond reconstruction
and usability. This implies that BPL signals
going between MV and LV lines need to bypass
the transformers. Typically, the bypass box can
also have built-in repeating functionality at a
small incremental cost. The recent capability to
effectively and safely bypass transformers hasbeen instrumental to the success and deployment
of BPL.
A point-of-presence (POP) is needed to connect
the BPL network to a backhaul network such
as the Internet, a public switched telephone
network (PSTN), or a mobile network. The
connection is made through a backhaul network
box coupled to an MV distribution line, typically
next to a power substation where multiple
MV lines are connected. The backhaul network
box is typically a bidirectional device that
converts data formats, aggregates andconcentrates uplink data streams, provides
routing functionality, helps allocate bandwidth
and resources, generates billing and charging
data, and provides various backhaul Ethernet
interfaces to fiber optic or wireless connections.
Figure 3 illustrates a typical BPL architecture.
A BPL network, like any other communications
network, also requires a network management
system (NMS) or operations support system
(OSS) to observe and manage network resources
and perform billing and other back-end tasks.
BPL Deployment Options
The MV and LV line portions of the BPL are
usually referred to as the access BPL, while the
portion inside a home or office using the inside
wiring is called the in-house BPL. BPL can be
deployed either as end-to-end BPL or as hybrid
BPL, using one of the three options illustrated
in Figure 4.
An end-to-end BPL system uses both access
BPL and in-house BPL, i.e., power lines are used
all the way from the power substation to
the end user. Two of the three BPL deployment
options involve the access BPL portion of an
end-to-end system: the BPL signal can either
(1) bypass the MV/LV transformer (as does
CURRENT Technologies equipment) or (2) go
through the transformer (as does MainNet
Communications equipment).
The third BPL deployment option is hybrid BPL.
In this option, typically only the MV lines are
used, and a fixed wireless network replaces the
LV lines and in-house BPL (Amperion takes
this approach). In hybrid BPL, the bypass box
does not couple the broadband signal to/from
the LV line but converts it to/from a wirelessformat and delivers it to the wireless access point
(AP) also located on the pole.
These different deployment options have their
associated performance and cost tradeoffs. For
end-to-end BPL, bypass boxes and LV couplers
must be installed on all LV lines, and in-house
BPL modems are required. For hybrid BPL,
bypass boxes with wireless conversion boards,
The MV and LV line
portions of the BPL
are usually
referred to as
theaccessBPL,
while the portion
inside a home or
office using the
inside wiringis called the
in-houseBPL.
BPL can be
deployed either
as end-to-end BPL
or as hybrid BPL .
Substationwith Modem
Injector
Option 1Transformer
Bypass System
Option 3Wireless Connection
Option 2
ThroughTransformer
Repeater
Extractor
Coupler
Coupler
Router
WirelessTransmitter
with AntennaWireless Receiver
with Antenna
Figure 4. BPL Deployment Options
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Bechtel Telecommunications Technical Journal8
wireless APs, and existing standard wireless
user modems are required, but LV transformer
bypasses and LV couplers are not. Also
associated with hybrid BPL are the usual
existing issues regarding wireless performance
in unlicensed spectrum and the current state
of wireless quality of service (QoS), security,
and so forth.
INDUSTRY PLAYERS, FIELD TRIALS,
COMMERCIAL DEPLOYMENTS, AND
STANDARDS BODIES
Industry Players, Field Trials, and
Commercial Deployments
Globally, the number of BPL players (electric
utility companies, equipment manufacturers,
investors, etc.), field trials, and commercial
deployments has been growing steadily in the
last few years. In the US alone, there have been
more than 39 trial deployments [6]. CURRENT
Technologies is currently offering commercialBPL services with Duke Energy in Cincinnati,
Ohio, with plans to expand elsewhere within
Dukes 1.5-million-customer service territory in
Ohio, Indiana, and Kentucky. CURRENT
Technologies is also planning to deploy BPL
services to potentially 2 million residents of
Dallas, Texas, using TXU Electric delivery. The
City of Manassas, Virginia, has been offering
citywide BPL services using MainNet equipment
since 2005. Progress Energy and EarthLink plan
to provide BPL services in North Carolina using
Amperion equipment.
There are also commercial deployments in Spain,
Germany, Korea, Chile, Brazil, and the UK.
In Spain, Endesa began service in 2003
in Saragossa and Barcelona; Iberdrola initiated
service in Madrid and Valencia in the same year.
Power Plus Communications has started offering
services in Germany, as has Scottish Southern
Electric in the UK.
Standards Bodies
Standardization is of paramount importance
to the success of any new technology
such as BPL. To this end, the Open PLCEuropean Research Alliance (OPERA), European
Telecommunications Standards Institute (ETSI),
Institute of Electrical and Electronics Engineers
(IEEE), Universal Powerline Association (UPA),
European Committee for Electrotechnical
Standardization (CENELEC), and HomePlug
Powerline Alliance have been leading the
activities and creating their own standards.
OPERAa consortium of currently 37
organizations, including electric utility
companies, PLC equipment manufacturers, and
universitiesis a research and development
(R&D) project with funding from the European
Commission to create and promote open global
specifications for low-cost, high-performance,
high-speed power line communications. Its
first specification documents were released on
February 21, 2006. These specifications will bepromoted through international standardization
organizations, including IEEE and ETSI [7].
The IEEE BPL study group drove the creation
of the BPL-related Pxxxx working groups.
The IEEE P1675 Standard for Broadband
over Power Line Hardware Working Group
is chartered to develop standards for
power line hardware installation and safety.
The IEEE P1775 Powerline Communication
Equipment Electromagnetic Compatibility
(EMC) Requirements Testing and Measurement
Methods Working Group is focused on
PLC equipment, electromagnetic compatibility
requirements, and testing and measurement
methods. The IEEE P1901 Draft Standard
for Broadband over Power Line Networks:
Medium Access Control and Physical Layer
Specifications Working Group is responsible for
defining the medium access control (MAC) and
physical layers for high speed (greater than
100 Mbps at the physical layer) for both
in-house and access BPL. The standard will focus
on transmission frequencies below 100 MHz.
The specifications of these working groups are
scheduled for release in 2007 [8].The UPA has also released a number of
specifications related to different aspects of
power line technology. Three main specifications
are the UPA coexistence specification, released in
June 2005; the UPA access BPL specification,
endorsed by OPERA and released in
February 2006; and the UPA in-house BPL
specification, called Digital Home Standard v1.0
and also released in February 2006. The UPA
also works with and through international
standardization bodies such as IEEE and ETSI to
promote its standards [9].
The HomePlug Powerline Alliance was founded
in 2000 and currently has over 65 member
companies. The alliances standards (HomePlug
1.0 and AV) are for home networking over
power lines (in-house BPL). The HomePlug 1.0
specification allows for speeds up to 14 Mbps.
The current HomePlug AV specification allows
for speeds greater than 100 Mbps (suitable for
Globally,
the number of
BPL players (electric
utility companies,
equipment
manufacturers,
investors, etc.),
field trials, and
commercialdeployments
has been growing
steadily in
the last few years.
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January 2007 Volume 5, Number 1 9
high definition television [HDTV] and VoIP) and
is compatible with HomePlug 1.0. In 2004, to
provide a harmonized end-to-end BPL standard,
the HomePlug Powerline Alliance started looking
into creating an access BPL standard planned for
completion by early 2007 [10].
POTENTIAL BENEFITS
Benefits to Service Providers
From a service providers point of view, BPL
could provide large cost savings. The first, and by
far the most important, factor is that the
transmission medium, i.e., the power lines, is
already in place. There is no need to purchase
spectrum or to hang, dig, or lay new wires,
because most of the required infrastructure
already exists. There is also no need for the
difficult, expensive, and time-consuming site
acquisition, permitting, and licensing tasks
needed for a typical deployment. Given the
omnipresence of power lines, BPL also holds thepromise of being able to provide genuinely
ubiquitous coverage. These factors imply
potential cost and time savings that could level
the BPL deployment playing field a bit more
compared with DSL and cable, both of which
have significant deployment head starts.
Benefits to Electric Utilities
For the electric utility companies, BPLs benefits
are twofold: (1) It can create new sources of
revenue from an existing investment, and
(2) it can help create a smart grid for the utilitycompanies that would enable enhanced utility
applications [11, 12] such as:
System monitoring from any point on the
electric grid
Load shifting and balancing
Optimized asset utilization and management
Performance of preventive maintenance and
improvement of service reliability and
customer satisfaction by avoiding power
outages and emergencies
Advanced supervisory control and data
acquisition (SCADA)
Fault detection, fault analysis, and adaptive
self-healing
Automatic outage detection, restoration
detection, and verification
BPL-enabled electricity meters that enable
time-of-day and real-time pricing through
automated meter reading (AMR) with
remote disconnect (and reconnect) and
theft detection
Real-time video surveillance of the sensitive
national power infrastructure (e.g., grid
and substations)
Benefits to End Users
End users can benefit from BPL deployment
because:
BPL could create competition and thus help
reduce end-user service prices.
BPL could provide high user throughputs,
as discussed later in this paper.
In some places, BPL may be the only viable
choice (e.g., in rural areas), although satellite-
based service may also be of interest in
these areas.
BPL could be used for smart appliances,
connected and controlled through a PC andremotely. While these devices could possibly
be controlled through a DSL or a cable
modem connection, BPL may provide a more
integrated (neater) solution.
BPL may provide a more ubiquitous and
reliable service coverage area.
The explosive growth of the Internet and the
recent deregulation of telecommunications in the
US and Europe have led to the renewed interest
in BPL. Extensive research on BPL channel
modeling [1320] and a considerable amount of
interference analysis [2125] have taken place.Concurrently, there have been a large number
of field trials and measurements to validate
various models [2131], along with advances in
signal processing such as the newer adaptive
modulation and coding techniques [28] and
faster, cheaper processors and electronics.
Nonetheless, despite its renewed attractiveness,
BPL must overcome implementation challenges
as well as regulatory concerns before it can
become a viable avenue of broadband access. The
next sections of this paper examine in more
detail the key implementation challenges and
regulatory concerns facing BPL.
IMPLEMENTATION CHALLENGES
The Nature of the Power Grid
The most obvious challenges to implementing
BPL arise from the fact that power line grids were
originally developed to transmit electrical power
The explosive
growth of the
Internet and
the recent
deregulation of
telecommunications
in the US and
Europe have led to
the renewedinterest in BPL .
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(high voltage AC at low frequencies of 50 or 60 Hz)
from a small number of sources (the generators)
to a large number of sinks (the end customers).
Power grids were neither designed nor devised
for communications purposes. Even though the
interest in using power lines for communications
is not new, their early use for data transmission
was mainly for simple, low-data-rate (a few
kilobits per second) remote monitoring and meter
reading applications at a low frequency (typicallyonly up to a few hundred kilohertz).
The main challenges to BPL arising from the
nature of the power grid have been the extremely
harsh, unpredictable, time-and-location-variable
characteristics of the power line channel,
and potential interference concerns (in both
directions) [1325]. Because power lines are not
twisted and have no shielding, they can produce
electromagnetic radiation that is easily detected
by radio receivers. For the same reasons, power
lines can also easily pick up nearby radio
frequency signals. Thus, addressing mutual
interference is not only a challenge, but becomes
a valid regulatory concern.
A related challenge facing BPL centers around
data sensitivity. To prevent interception of
sensitive data by unintended and unauthorized
receivers, data encryption is a must.
The fact that the power line grid is a shared
medium and BPL is a contention-based system
creates additional challenges. Because all users
share the available channel capacity or
bandwidth, as the number of users goes up,
per-user throughput goes down. In the US, thereare typically 50 homes per substation. An average
available throughput of 50 Mbps implies roughly
an average of 1 Mbps per user, a speed on par
with the current average speeds delivered by DSL
or cable modem. However, BPL is thought to be
distance limited, similar to DSL. Thus, the
distance between the customers home and the
supplying substation is a factor in the
bit rate available to the user.
Channel Characteristics and Capacity
Power Line NoiseIn general, a power line channel is a very
harsh and noisy transmission medium. The noise
on the line is typically time, location, and
frequency dependent.
Time-variable behavior is due mainly to the
dynamically changing nature of the load
connected to the power lines. Line branching, the
number and types of branches, the lengths of line
segments, the types of power line equipment
connected (such as capacitor banks and
transformers), and the kinds of loads connected
all affect channel characteristics. Furthermore,
impedance mismatches caused by unterminated
stubs and line branches cause signal reflections
and create a frequency-dependent fading
channel, much like the multipaths typically seen
in mobile wireless communication channels.
MV and LV lines have very different noisecharacteristics. The MV grid is usually less
branched than the LV grid, and LV lines are
typically terminated at time-varying consumer
electrical appliances. Noise on the LV grid is
typically the sum of background noise, impulsive
noise, and synchronous/nonsynchronous (with
the power line frequency) colored noise,
generated primarily by electrical appliances; this
noise is certainly not an additive white gaussian
noise (AWGN). On the MV grid, the on/off
switching of the capacitor banks used to correct
the power factor typically causes high noise
peaks [14]. At the same time, background noise
and narrow-band noise are dominant on MV
lines. The background noise is environmental
noise that is highly dependent on weather,
location, and elevation. The narrow-band noise
is caused by RF interferers such as amateur or
shortwave (SW) radios and varies randomly
across location and time. Noise levels on
MV lines are typically as much as 20 to 30 dB
higher than on LV lines in the frequency range
of 1 to 20 MHz [21].
Channel Attenuation
Power lines have been modeled in the literatureby using either statistical approaches based
on extensive measurements or deterministic
approaches based on multiconductor trans-
mission line (MTL) theory and numerical
analysis. Carsons earlier MTL model [17]
allowed for ground impedance but did not
include ground admittance, which cannot be
ignored in higher frequencies and/or under
poor conductive ground plane conditions.
The subsequent MTL models in [18, 19] include
ground admittance.
A simple matched uniform MV line segment withno connected device or junctions could have as
little as 1 dB/km ohmic absorption or attenuation
loss. For a complex overhead MV network, on the
other hand, the amplitude of the channel
frequency response (or, equivalently, the channel
attenuation) in the frequency range of 10 kHz to
100 MHz shows highly frequency-dependent
attenuations of as high as 40 dB/km caused by
reflections from abrupt discontinuities and
The main challenges
to BPL arising from
the nature of
the power grid
have been
the extremely harsh,
unpredictable,
time-and-
location-variablecharacteristics of
the power line
channel,
and potential
interference
concerns (in both
directions).
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mismatched impedances [23]. LV network losses
are typically higher than MV network losses and
could be as high as 100 dB/km [14].
Performance Improvements
Conditioning the grid can improve power
line performance by minimizing impedance
mismatches, terminating stubs, filtering noise,
etc. These options, however, may deteriorate or
diminish the advantages of power line grids. A
better approach is to use modulation and codingschemes robust enough to work in the hostile
power line channel environment. Currently, most
BPL products use orthogonal frequency division
multiplexing (OFDM), well known for its
excellent robustness against channel distortions
such as multipath and impulsive noise and for its
good spectral efficiency, reasonable cost, and
ability to avoid certain bands.
In BPL systems, multiple user modems are
connected in a bus or star topology. Some type
of MAC must be implemented to provide
communications through shared bandwidth onpower lines. To provide the necessary QoS
for applications that require bandwidth
and performance guarantees, such as video
streaming, the carrier sensing multiple
access/collision avoidance (CSMA/CA) protocol
may be used. This widely used scalable
protocol, also used in the wireless fidelity
(IEEE 802.11) MAC layer, is suitable for power
line channel characteristics.
Capacity and Spectral Efficiency
Depending on the bandwidth used on the powerlines (typically a frequency range between 2 and
100 MHz), on the BPL injection power level
(typically 1 to 30 dBm), and on load and channel
conditions, throughputs in the range of tens, or
even hundreds, of megabits per second and
spectral efficiencies in the range of 1 to 20 bps/Hz
can be achieved [20]. Theoretical and field trials
have also claimed throughputs of the same order
of magnitude, and even in the gigabit-per-second
range if larger frequency bandwidths in
the upper VHF/ultra high frequency (UHF)
spectrum and higher input signal powers are
used. In the US, however, this may not be a viableoption, considering that licensed spectrum in the
VHF and UHF bands is heavily occupied.
A system developed by Corridor Systems, Inc., in
the US uses MV power lines in frequency ranges
from VHF through microwave as distributed
antenna systems (DASs) to extend existing
cellular network coverage [29]. The cellular
network RF signal is picked up by the Corridor
equipment, converted into a proprietary BPL
format, and injected into and transported down
the MV lines. At cellular dead zones, the Corridor
equipment converts the signal back to its original
format for re-radiation by local antennas. Thus,
MV lines are used to carry cellular signals to areas
too difficult or expensive to reach by cellular
networks, conventional repeaters, or DASs.
Interference Concerns and Regulatory IssuesUnlike the twisted wires of telephone companies
and the shielded cables of cable companies, long
unshielded, untwisted, overhead power lines can
act as large antennas and be natural sources and
targets of electromagnetic interference (EMI). In
addition, BPL signals tend to radiate from the
injectors and repeaters spaced along the power
lines. This raises concerns about interfering
with the rightful owners of the radio spectrum in
the BPL range of operation [30]. The most
concerned and vocal opponents of BPL in the
US are amateur radio operators, through the
American Radio Relay League (ARRL), andgovernment agencies.
The US FCC started examining the use of power
lines for broadband communications services by
issuing a Notice of Inquiry (NOI) on April 23,
2003. The NOI sought information on potential
interference from BPL systems and associated
changes that may be needed to accommodate BPL
systems in Part 15 of the FCCs rules published
in the Telecommunications Code of Federal
Regulations (47 CFR).
Part 15 addresses RF devices. Part 15, Subpart A,addresses general issues. Section 15.3 defines
terms used in the FCCs rules. Subpart B
addresses unintentional radiators, with Section
15.109 defining the radiated emission limits.
Subpart C deals with intentional radiators, with
Section 15.209 defining the corresponding general
requirements and radiated emission limits.
Section 15.3 (f) defines a carrier current system as
a system, or part of a system, that transmits RF
energy by conduction over electric power lines.
A carrier current system can be designed so that
the RF signals are received by conduction directly
from the connection to the electric power lines
(unintentional radiator) or so that the signals are
received as over-the-air radiation from the
electric power lines (intentional radiator). Carrier
current systems operate on an unlicensed basis
under Part 15. As a general condition of
operation, Part 15 devices may not cause harmful
interference to authorized radio services and
must accept any interference they receive.
Unlike the
twisted wires of
telephone
companies and
the shielded cables
of cable companies,
long unshielded,
untwisted, overhead
power lines can actas large antennas
and be
natural sources
and targets of EMI.
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The FCC amended the existing Section 15.3 to
include Sections 15.3 (ff) for access BPL and
15.3 (gg) for in-house BPL, as follows:
Section 15.3 (ff) Access BPL: A carriercurrent system installed and operated on anelectric utility service as an unintentionalradiator that sends radio frequency energyon frequencies between 1.705 MHz and80 MHz over medium voltage lines or overlow voltage lines to provide broadband
communications and is located on thesupply side of the utility services points ofinterconnection with customer premises.
Section 15.3 (gg) In-House BPL: A carriercurrent system, operating as an unintentionalradiator, that sends radio frequency energyby conduction over electric power lines thatare not owned, operated or controlled by anelectric service provider. The electric powerlines may be aerial (overhead), underground,or inside the walls, floors or ceilings ofuser premises. In-House BPL devices mayestablish closed networks within a userspremises or provide connections to AccessBPL networks, or both.
In its response to the FCCs NOI, the
National Telecommunications and Information
Administration (NTIA) of the US Department
of Commerce described the federal governments
usage of the 1.7 to 80 MHz spectrum, identified
associated interference concerns, and outlined the
studies it planned to conduct to address those
concerns. In April 2004, the NTIA published
its Phase 1 Study technical report, NTIA
Report 04-413, Potential Interference from
Broadband over Power Line (BPL) Systems to
Federal Government Radiocommunications at1.7 80 MHz [31]. In this report, the NTIA
defined interference risks to radio reception in the
immediate vicinity of overhead power lines
used by an access BPL system. The radio systems
to be considered in interference analyses included
a land vehicular receiver, a ship-borne receiver,
a receiver using a rooftop antenna (e.g., a base
or fixed-service station), and an aircraft receiver
in flight. The study included various
measurement campaigns and the use of
numerical electromagnetic code (NEC) software
to characterize BPL signal radiation and
propagation and to evaluate interference risks.
The report also suggested means for reducing
interference risks and identified techniques for
mitigating local interference should it occur.
The Phase 1 Study focused on simple BPL
deployment models. The Phase 2 Study is
focusing on evaluating the effectiveness of the
NTIAs Phase 1 recommendations and on the
results of a study of potential interference via
ionospheric propagation of BPL emissions
resulting from the mature large-scale deployment
of BPL networks. As of the date of this paper, the
Phase 2 Study report had not yet been released.
Some of the NTIAs Phase 1 Study highlights
include:
In the 1.7 to 80 MHz spectrum, the dominant
propagation modes are ground waves, space
waves, and sky waves. Ground waves consistof direct waves, ground-reflected waves, and
surface waves. Direct waves decay at a rate
proportional to the square of their distance
from their source. Ground-reflected waves
(along with direct waves) decay at the rate of
distance raised to the power of four. Ground-
reflected waves may be of no major concern if
the radiator is relatively far from ground.
Surface waves propagate close to the ground
and have a substantially higher rate of
attenuation than direct waves. Ground wave
propagation is pertinent on BPL signal paths
below the power line horizon. Space wavesinvolve only direct waves and occur over
elevated signal paths, e.g., signal paths above
the power line horizon. Sky waves are
particularly important in the HF band (for
BPL, 1.7 to 30 MHz) and have temporal and
spatial variability. Here, signal paths are
represented as rays reflected and refracted by
the ionosphere. Sky waves can extend the
signals reach to several kilometers.
The space around a radiator is typically
divided into three regions: reactive near-
field, radiating near-field, and far-field.These regions are typically defined as:
where ris the distance from the radiator, D is
the largest linear dimension of the radiator,
and is wavelength. For BPL systems, the
victim receiver is typically in the radiating
near-fields, although far-fields are important
because of sky waves and at distances seen
by aircraft receivers.
D3
r< 0.62
D3
0.62 < r< 2
D2
r> 2
D2
Reactive Near-Field
Radiating Near-Field
Far-Field
The FCC amended
the existing
Section 15.3
to include
Sections 15.3 (ff)
for access BPL
and 15.3 (gg)
for in-house BPL .
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The NTIA also provided some recommendations
and suggested some interference mitigation
techniques; these include:
Mandatory registration of certain parameters
of planned and deployed BPL systems
A requirement for BPL devices to be
frequency agile (i.e., to have notching and
retuning capabilities) and to have remote
power reduction and shutdown capabilitiesto eliminate interference if any is reported
Use of minimal required power
Avoidance of locally used radio frequencies
Use of symmetry and differential mode
signal injection to minimize radiation [31, 23].
Symmetry is defined in terms of impedance
between conductors and ground. If, for a
two-wire line, the impedance between each
conductor and ground is equal, the line is
symmetrical or balanced. Balanced lines are
necessary for differential mode transmission,in which the currents are equal in magnitude
and flow in opposite directions on the
conductors. The fields radiating from these
conductors tend to cancel each other.
Subsequent to the above activities, the FCC
released its Notice of Public Rule Making
(NPRM) in February 2004, and received more
than a thousand comments and replies from
many concerned parties [32]. The FCC eventually
finalized its decision by adopting its Report &
Order (R&O) FCC 04-245 on October 14, 2004
(published in the Federal Register on January 7,
2005) [33]. The FCC considered various petitions
to reconsider the R&O and subsequently
amended the Part 15 rules to modify some of the
previous specified exclusion zones and add a few
new exclusion zones. However, the FCC denied
other petitions to reconsider other aspects and
published the final Memorandum Opinion &
Order (MO&O) on August 7, 2006, and the new
amended rules in 47 CFR.
The FCC basically decided to keep BPL under
existing Part 15 unlicensed device rules and
added Subpart G for access BPL. More
specifically, Sections 15.601, 15.607, 15.611, and15.613 of this new Subpart include the following
new rules:
Exclusion Bands: These are certain bands
of frequencies within which access BPL
operations are not permitted.
Exclusion Zones: These are certain
geographic areas within which access
BPL operations are not allowed.
Consultation: A consultation is to be held
between an entity operating access BPL and a
licensed public safety or other designated
point of contact, for the purpose of avoiding
potential harmful interference.
Equipment Authorization: Because BPL is a
new technology, the FCC has required that
all BPL-related equipment be certified.
Certification is an equipment authorization by
the FCC or its designated entities, as opposedto verification, which is a manufacturers self-
approval procedure. The rules adopted in the
R&O require that all access BPL devices
manufactured, imported, marketed, or
installed 18 months or later after the Federal
Register publication of the R&O (i.e., after
July 7, 2006) must comply with the
newly adopted requirements of Subpart G
of Part 15 for BPL devices, including
certification of the equipment.
Databases: Publicly available databases are
to be created and maintained by an industry-sponsored entity recognized by the FCC and
the NTIA. They are to contain information
regarding existing and planned access BPL
systems. Each database should be available
within 30 days before initiation of the specific
systems service and should include the
following information:
The name of the access BPL provider
The frequency of the access BPL
operation
The postal ZIP codes served by the
specific access BPL operation
The manufacturer and type of access
BPL equipment and its associated
FCC identification, etc.
Complete contact information for a
person at the BPL operators company
in charge of resolving any interference
complaints
The proposed or actual date of access
BPL operation
Interference Mitigation and Avoidance:
Access BPL systems are basically required toadhere to the NTIA recommendations for
interference mitigation and avoidance
mentioned above.
Field Limits: Access BPL systems that
operate in the 1.705-to-30-MHz band over
MV lines must comply with the radiation
limits for intentional radiators provided in
Section 15.209. Systems operating in the
Because BPL is
a new technology,
the FCC has
required that
all BPL-related
equipment
be certified.
Certificationis
an equipmentauthorization
by the FCC or its
designated entities,
as opposed to
verification, which is
a manufacturers
self-approval
procedure.
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30-to-80-MHz band over MV lines mustcomply with the radiation limits for
unintentional radiators provided in Section
15.109 (b). Systems operating over LV lines
must comply with the Section 15.109 (a) and
(e) limits. Radiation emission limits for access
BPL equipment are summarized in Table 1.
The FCC also decided to eliminate conducted
emission limits and testing for BPL systems
because of the danger and inconvenience
associated with measuring power line
conducted emissions.
Measurement Procedure and Guidelines:
The FCC requires that access BPL system
emissions be measured in situ to demonstrate
compliance with the new Part 15 rules.
Measurements are to be made at a minimum
of three overhead and three underground
representative points and according to the
measurement guidelines outlined in
Appendix C of the NPRM. For access BPL
systems installed on overhead power lines, to
take into account the effect of line length, the
received measurement antenna will be
moved down-line parallel to the power line,starting from the access BPL signal injection
equipment location, to find the maximum
emissions at each frequency within the
frequency range of the access BPL device.
The distance from the measurement antenna
to power line is the slant distance or range,
as shown in Figure 5.
Because the distances rspecified in the guidelines
may coincide with unsafe locations (e.g., the
middle of a highway), the guidelines also specify
how to extrapolate a distance correction factor
from measurements made at distances other thanas specified in the rules. For frequencies below
30 MHz, the measured values are reduced by
40 log(10) (30/r); for frequencies at or above
30 MHz, the measured value is increased by
20 log(10) (r/10). The guidelines also specify the
type of measurement antenna (loop or linear)
and the type of detector (peak, quasi-peak, or root
mean square [RMS]).
It is worth mentioning again that the FCC
recognized the interference potential of BPL
systems. That is why the FCC decided that, even
though access BPL systems remain under thenewly added Subpart G of Part 15 for unlicensed
device rules, their operations cannot cause
harmful interference and the systems must accept
any outside interference. Furthermore, any BPL
resultant interference must be corrected and
resolved by the BPL operator immediately,
without ceasing broadband service to the public.
On November 3, 2006, the FCC also decided to
classify BPL-enabled Internet access services as
information services. By virtue of being considered
information services, BPL services become free
from many, if not all, common carrier regulationsand associated fees and taxes. Specifically,
the FCCs Order finds that the transmission
The FCC recognized
the interference
potential of
BPL systems.
That is why the
FCC decided that,
even though access
BPL systems remain
under the newlyadded Subpart G
of Part 15
for unlicensed
device rules,
their operations
cannot cause
harmful interference
and the systems
must accept
any outsideinterference.
Power Line
Type
Frequency
(MHz)
Field Strength
Limits (V/m)Measurement
Distance (m)
LV or MV 1.70530 30 30
LV 3080 100 3
MV 3080 90 10
Table 1. Radiation Limits
RingAnten na
Antenn a Hei ght
Distance Specified in Rule (e.g., 30 m for
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component underlying BPL-enabled access
services is telecommunications and that
providing this telecommunications transmission
component as part of a functionally integrated,
finished BPL-enabled Internet access service
offering is an information service. The FCCs
decision was based on its desire to regulate
similar services in a similar manner. The FCCs
Order places BPL-enabled Internet access services
on an equal regulatory footing with otherbroadband services such as DSL or cable modem
Internet access services [34].
The FCC may, however, still decide to require
BPL operators who provide VoIP services to
contribute to the Universal Service Fund (USF),
based on a percentage of their gross revenues.
The USF was created by the FCC in 1997,
following enactment of the Telecommunications
Act of 1996, primarily to ensure that rural
and low-income customers receive levels of
telecommunications service similar to those in
nonrural areas. All telecommunications carriers
that provide service internationally and
between states are required to contribute to the
USF. The Universal Service Administrative
Company (USAC) submits fund size and
administrative cost projections for each quarter
in accordance with FCC rules.
The FCC also released a new R&O in May 2006
regarding law enforcement and emergency
services [35]. More specifically, the FCC resolved
a second R&O in the Communications Assistance
for Law Enforcement Act (CALEA) and
Broadband Access Services proceedings. As a
result of this FCC Order, VoIP- and facilities-based broadband access providers, such as
BPL operators who provide VoIP services,
must bring their networks into compliance
with wiretap, surveillance, and other official
law enforcement and emergency services
requirements by May 14, 2007.
BUSINESS MODELS AND ECONOMIC ISSUES
Depending on their particular businessand financial objectives, electric utilitycompanies can choose one of three businessmodels with respect to their BPL deployment. As
presented below, each model has successively
more associated risks and rewards:
The Landlord or Retail Model: In this
model, the electric utility company leases
its facilities to another company (preferably
one with prior communications experience)
that builds and operates the BPL system.
End users interface only with this company
for all customer care, billing, and support.
The electric utility company only collects
leases on its facilities, and may also receive
smart-grid services from the same
BPL service builder/provider. This model
requires the lowest investment from the
electric company and provides it with a new
source of income along with its existing
investments. This is the lowest risk, if any,model for the electric company.
The Wholesale Model: In this model,
the electric company builds out the BPL
network and leases it to another company,
which wholesales the bandwidth to
communications service providers or
Internet service providers (ISPs) that operate
the network and interface with customers.
This is a medium risk option, and the BPL
network can be used to provide smart-grid
services for the electric company.
The Service Provider Model: This is themost aggressive model. The electric utility
company builds and operates the BPL
network and interfaces directly with the
customers. Here, the electric company needs
to acquire the communications expertise
required to build, operate, and maintain
the BPL network. Of course, the electric
company must also market the broadband
services. This model carries the most risk,
but offers the greatest potential return on
investment (ROI).
Currently, precise data regarding BPLdeployment costs is not publicly available.
Various estimates show that BPL costs per home
passed could range from $50 to $300, depending
on the electric grids architecture, the need for
repeaters, the number of homes connected to the
substation, and similar factors. This cost includes
not only the cost of equipment and installation,
but also the cost over time of maintenance,
equipment replacement, and upgrades.
Consumer premises equipment (CPE) costs
currently range from $50 to $200. Assuming a
conservative initial deployment with a subscriber
penetration rate of 10 percent (blended over rural,suburban, and urban areas), which is typical
of current initial deployment results, and a
$100-per-home-passed deployment cost and a
$100 CPE cost, the initial BPL deployment cost
becomes about $1,100 per subscriber. This
number is in line with numbers published in
the final BPL report from United Telecom
Council (UTC) Research and The Shpigler Group,
In November 2006,
the FCC decided
to classify
BPL-enabled
Internet access
services as
information
services.
By virtue ofbeing considered
information
services, BPL
services become
free from many,
if not all,
common carrier
regulations and
associated fees
and taxes.
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which compares deployment costs for various
broadband technologies [36, 37]. See Figure 6.
It is also interesting to note that, even though
deploying BPL in rural areas could be less
expensive than deploying DSL, cable, or fiber, it
may still be prohibitively expensive per capita.
With this in mind, BPL operators may choose,
instead, to compete with DSL, cable, and other
service providers in suburban and urban areas
where some sort of broadband services already
exists. Ironically, this would defeat the main
reason that the FCC adopted BPL: to accelerate
the availability of broadband services in
underserved areas. Furthermore, prior experience
and research have shown that BPL service
needs to be either significantly better (e.g., have
higher user throughputs), cheaper, or both, to
be able to convince subscribers to change
existing services to BPL or to attract new
subscribers to this new technology.
With this in mind, BPL service penetration PBPLwould typically be some function of BPL service
cost CBPL , including CPE, installation and setup,
and a monthly service fee; the service costs of
existing broadband services Cexisting ; the available
data throughput of BPL RBPL ; and the data
throughput of existing services Rexisting [38]. Asimple formulation could be:
where is a weighting factor (e.g., 10 or 20)
that reflects the importance of performance
versus cost.
In this formulation, PBPL becomes null if its cost
and data rates are the same as those of existing
broadband services. Of course, this formulation
does not take into account the value that BPL
offers by providing smart-grid services.
(Assessing the potential revenue and savings
from BPL smart grid services would be the
subject of another study.)
CONCLUSIONS
Even though the importance and directsocioeconomic impact of access to broadbandservices are well understood, currently only
4 percent of the Earths population has access
to some type of broadband services, typically
via DSL or cable modem. BPL offers a new,
potentially powerful alternative means of
providing high-speed Internet services, VoIP, and
other broadband services to homes and
businesses by using existing MV and LV power
lines. Because roughly 60 percent of Earths
inhabitants have access to power lines, BPL couldplay a significant role in bridging the existing
digital divide. But the success of BPL, like
that of any new technology in its infancy,
depends on more than strong theoretical
results or successful field testing. It also depends
greatly on the appropriate business models and
deployment plans.
As the regulatory uncertainties and interference
issues surrounding BPL dissipate, and with the
success of many field trials and early commercial
deployments, the release of various standards,
and the growing availability of reasonably pricedstandardized and reliable equipment, the road
to BPL is becoming increasingly well paved
and broadband over power lines seems to be
well energized. Indeed, BPLs future looks
very bright!
ACKNOWLEDGMENTS
One of the authors, S. Rasoul Safavian, wouldlike to express his gratitude for usefuldiscussions with Professor Mohsen Kavehrad of
the Electrical Engineering Department at thePennsylvania State University, several staff
members of the Federal Communications
Commission, and David Shpigler of The
Shpigler Group.
AccessMethod
Wireless
DSL
Cable Modem
BPL
Satellite
FTTH
Deployment Cost per Subscriber ($)
$1,825
$1,408
$1,007
$900
$828
$800
0 400 800 1,200 1,600 2,000
Figure 6. Deployment Costs for
Different Access Technologies
PBPL = Min{100, Max{0, [(CexistingCBPL)
+[log2(RBPL) log2( Rexisting)]]}}
As the regulatory
uncertainties and
interference issues
surrounding
BPL dissipate, and
with the success of
many field trials and
early commercial
deployments,the release of
various standards,
and the growing
availability of
reasonably priced
standardized and
reliable equipment,
the road to BPL
is becoming
increasinglywell paved.
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January 2007 Volume 5, Number 1 17
TRADEMARKS
Amperion is a trademark of Amperion, Inc.
CURRENT Technologies is a registered
trademark of CURRENT Communications
Group, LLC.
EarthLink is a registered trademark of EarthLink,
Inc.
HomePlug is a registered trademark of the
HomePlug Powerline Alliance.
P1675 is a trademark of the IEEE.
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Bechtel Telecommunications Technical Journal18
[26] W. Liu, H. Widmer, and P. Raffin, BroadbandPLC Access Systems and Field Deploymentin European Power Line Networks,IEEE Communications Magazine, Vol. 41, No. 5,May 2003, pp. 114118.
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BIOGRAPHIES
Lee Lushbaugh, principal vicepresident, Bechtel Corporation,and general manager, Tele-
communications, Americas,provides day-to-day oversightfor both business developmentand operational activitiesin the region. During 2006,the regional staff reachedapproximately 1,500 employees
working in 35 markets across the continental UnitedStates. Previously, Lee has served as director ofengineering and as the program director of severalnationwide wireless programs and a fiber deploymentprogram. He joined Bechtel Telecommunications in1996 as vice president/manager of engineering and wasthe initial developer of its engineering department.
Lee joined Bechtel Corporation in 1974 and, before
joining Bechtel Telecommunications, held bothfunctional and operational roles in the fossil power andnuclear business lines, including the plant design, civil,and mechanical engineering disciplines.
Lee received a BS in Mechanical Engineering fromthe University of Maryland. He is a RegisteredProfessional Engineer in various states, a member of theAmerican Society of Mechanical Engineers, and a SixSigma Champion.
Rasoul Safavian brings morethan 15 years of experiencein the wired and wirelesscommunications industry tohis position as BechtelTelecommunications vice
president of Technology,Americas Regional BusinessUnit. He is charged withestablishing and maintaining
the overall technical vision for Bechtels Americanmarkets and providing guidance and direction toits specific technological activities. In fulfillingthis responsibility, he is well served by hisbackground in cellular/PCS, fixed microwave, satellitecommunications, wireless local loops, and fixednetworks; his working experience with major 2G, 2.5G,3G, and 4G technologies; his exposure to the leadingfacets of technology development as well as itsfinancial, business, and risk factors; and his extensiveacademic, teaching, and research experience.
Before joining Bechtel in June 2005, Dr. Safavian
oversaw advanced technology research anddevelopment activities, first as vice president of theAdvanced Technology Group at Wireless Facilities, Inc.,then as chief technical officer and vice president ofengineering at GCB Services. Earlier, over an 8-yearperiod at LCC International, Inc., he progressedthrough several positions. Initially, as principalengineer at LCCs Wireless Institute, he was in chargeof CDMA-related programs and activities. Next, aslead systems engineer/senior principal engineer,
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January 2007 Volume 5, Number 1 19
he provided nationwide technical guidance for LCCsXM satellite radio project. Then, as senior technicalmanager/senior consultant, he assisted key clients withthe design, deployment, optimization, and operation of3G wireless networks.
Dr. Safavian has spoken at numerous conferencesand industry events and has been publishedextensively, including technical papers in theprevious three issues of the Bechtel TelecommunicationsTechnical Journal.
Dr. Safavian is quite familiar with the Electrical
Engineering departments of four universities: TheGeorge Washington University, where he has been anadjunct professor for several years; The PennsylvaniaState University, where he is an affiliated facultymember; Purdue University, where he received hisPhD in Electrical Engineering, was a graduate researchassistant, and was later a member of the visiting faculty;and the University of Kansas, where he received bothhis BS and MS degrees in Electrical Engineering andwas a teaching and a research assistant. He is a seniormember of the IEEE and a past official reviewer ofvarious transactions and journals.
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