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Friday, May 11, 2007

Internet on the Power line?

Is broadband over power lines a failed experiment, or does the upstart technology present a real challenge to the two primary sources of residential high-speed Internet access — the cable modem and the digital subscriber line, DSL?
Rick Nicholson, vice president of research for Energy Insights of Framingham, Mass., predicted that broadband over power lines growth would be limited by, among other factors, ''a lack of utility expertise in running commercially successful consumer telecom businesses.''
PPL, which last year expanded its broadband trials to parts of Bethlehem, Upper Macungie Township and Hanover Township, Northampton County, experimented with two forms of the technology.

One allows customers to connect to the Internet anywhere in their homes by plugging a portable modem into a power outlet. The other works like the wireless hot spots common in airports, hotels and cafes: The Internet signal — sent from a transmitter attached to a medium-voltage power line outside — is carried to the computer on radio waves.
Walter Adams, vice president of new technology for COMTek, said the power outlet approach offers several advantages.

First, it can be used in neighborhoods with below-ground utilities, whereas the wireless method relies on the availability of telephone poles. Second, it eliminates the problem of interference, since it does not require a line of sight between a telephone pole-mounted transmitter and the customer's house. And lastly, it doesn't require professional installation; all the customer needs is a modem, which can be
delivered through the mail.

There have always been three major problems for powerline:
1) can you get data reliably over the (very noisy) power cables themselves
2) can you do it without using so much transmit power that it interferes
with every device in the neighbourhood
3) can you do it economically

(1) has (in most deployment scenarios) been solved by the use of advanced signal processing techniques (for example home powerline LANs now work very well - though have been completely overtaken by the even greater convenience of in-home wireless)
(2) is largely solved - better receive signal processing reduces the need for power in the transmitter
(3) remains - largely due to the architecture with which power is distributed

Power systems rely on step-down transformers located close to the consumer - each tending to serve a relatively small number of homes. It's practically impossible to get a data signal through a transformer(!) which means that data has to be passed from the core network to a head-end device on the far side of the transformer. The hardware and deployment costs of this head-end device has to be shared amongst the users of the system. Since the transformers are generally only supplying a small user base the economics demand a VERY high take-up - something that experience shows is highly unlikely, unless you are in an area of zero competition. With all the
competing options (cable, DSL, satellite) that is unlikely. While the UK trials below are clearly working, that does not imply that they are demonstrating a good commercial model. Power companies (especially in the UK and Germany) have been trying this for years, largely in attempts to see whether they can persuade a high enough density of customers to adopt the service to solve this economic problem.

Interestingly - the service described in a previous [IP] mail used wireless for the last leg to the customer - which (I think) implies that they are inverting the more usual powerline scenario, where fiber is used to the distribution box and powerline gets to the customer (as in the UK trial below). In the wireless scheme I think they are proposing to use powerline over the main distribution network to replace fiber, and then using wireless instead of powerline in the local loop. Interesting, but hardly earth-shattering.

Andrew Bale
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