Broadband Over Power Line (BPL)
Internet access (Broadband over powerlines, BPL)
Broadband over power lines (BPL), also known as power-line internet or Powerband,
is the use of PLC technology to provide broadband Internet access through
ordinary power lines. A computer (or any other device) would need only to plug a
BPL "modem" into any outlet in an equipped building to have high-speed Internet
access.
BPL seems, at first glance, to offer benefits relative to regular cable or DSL
connections: the extensive infrastructure already available would appear to
allow people in remote locations to have access to the Internet with relatively
little equipment investment by the utility. Also, such ubiquitous availability
would make it much easier for other electronics, such as televisions or sound
systems, to hook up.
However, variations in the physical characteristics of the electricity network
and the current lack of IEEE standards mean that provisioning of the service is
far from being a standardized, repeatable process, and the amount of bandwidth a
BPL system can provide compared to cable and wireless is in question. Some
industry observers believe the prospect of BPL will motivate DSL and cable
operators to more quickly serve rural communities.
PLC modems transmit in medium and high frequency (1.6 to 80 MHz electric
carrier). The asymmetric speed in the modem is generally from 256 kbit/s to 2.7
Mbit/s. In the repeater situated in the meter room the speed is up to 45 Mbit/s
and can be connected to 256 PLC modems. In the medium voltage stations, the
speed from the head ends to the Internet is up to 135 Mbit/s. To connect to the
Internet, utilities can use optical fiber backbone or wireless link.
The system has a number of complex issues, the primary one being that power
lines are inherently a very noisy environment. Every time a device turns on or
off, it introduces a pop or click into the line. Energy-saving devices often
introduce noisy harmonics into the line. The system must be designed to deal
with these natural signaling disruptions and work around them.
Broadband over powerlines has developed faster in Europe than in the United
States due to a historical difference in power system design philosophies.
Nearly all large power grids transmit power at high voltages in order to reduce
transmission losses, then near the customer use step-down transformers to reduce
the voltage. Since BPL signals cannot readily pass through transformers — their
high inductance makes them act as low-pass filters, blocking high-frequency
signals — repeaters must be attached to the transformers. In the U.S., it is
common for a small transformer hung from a utility pole to service a single
house or a small number of houses. In Europe, it is more common for a somewhat
larger transformer to service 10 or 100 houses. For delivering power to
customers, this difference in design makes little difference with power
distribution, but it means delivering BPL over the power grid of a typical U.S.
city will require an order of magnitude more repeaters than would be required in
a comparable European city. However, since bandwidth to the transformer is
limited, this can increase the speed at which each household can connect, due to
fewer people sharing the same line. One possible alternative is to use BPL as
the backhaul for wireless communications, by for instance hanging Wi-Fi access
points or cellphone base stations on utility poles, thus allowing end-users
within a certain range to connect with equipment they already have. In the near
future, BPL might also be used as a backhaul for WiMAX networks.
Power line communication (PLC), also called power line carrier, mains
communication, power line telecom (PLT), or power line networking (PLN), are
terms describing several different systems for using electric power lines to
carry radio signals for communication purposes.
Overview
Home control (Narrowband)
Power line communications technology can use the household electrical power
wiring as a transmission medium. INSTEON and X10 are the two most popular,
defacto standards utilizing power line communications for home control. This is
a technique used in home automation for remote control of lighting and
appliances without installation of additional control wiring.
Typically home-control power line communications devices operate by modulating
in a carrier wave of between 20 and 200 kHz into the household wiring at the
transmitter. The carrier is modulated by digital signals. Each receiver in the
system has an address and can be individually commanded by the signals
transmitted over the household wiring and decoded at the receiver. These devices
may either be plugged into regular power outlets or else permanently wired in
place. Since the carrier signal may propagate to nearby homes (or apartments) on
the same distribution system, these control schemes have a "house address" that
designates the owner.
Home networking (Broadband)
Power line communications technology can also be used to interconnect (network)
home computers, peripherals or other networked consumer peripherals, although at
present there is no universal standard for this type of application. Standards
for power line home networking have been developed by a number of different
companies within the framework of the HomePlug Powerline Alliance and the
Universal Powerline Association.
