Broadband over power lines
01 January 2010 |
Broadband over power lines (BPL) is a way of transmitting data over a standard electricity network, where high-frequency radio waves are modulated with the digital signals from the internet. Data is sent over the same power line as the AC current, with both able to coexist as they use different frequency bands.
What’s it all about?
A BPL subscriber installs a modem that plugs into a standard wall socket in the home or business, and pays for the service by subscription fee on a similar basis to other types of broadband. No phone line, cable or satellite link is needed.
One of the key benefits that BPL offers is that the base infrastructure is already universally available, requiring only small modifications by the utility provider to enable transmission of broadband traffic over existing copper wiring. This suits it to connect remote locations to the internet with relatively little investment.
BPL technology has been around for several years now but it has not yet achieved widespread usage thanks partly to a lack of buy-in from utility companies, perhaps unwilling to risk head-on competition with specialist broadband players. But there are other issues with the technology which could be holding it back.
How does BPL stack up against rival broadband options?
The speed at which BPL can transmit data is an issue, say the technology’s watchers: “Some current live deployments only offer speeds of between 256Kbps and 1Mbps,” says Manoj Solanki, technical director with broadband comparison web site Seekbroadband. “By today’s standards and expectations, that is a difficult proposition, particularly in suburban areas with a high proliferation of fixed-line services, which are also cheaper. It is more attractive to rural areas that cannot get any other form of broadband service.”
At its current best, BPL can deliver download speeds of 5Mbps, according to Vince Vittore, principal analyst with Yankee Group. He says: “That’s not too bad as it stands, but is BPL stuck with that download speed for the foreseeable future? If so it won’t compete in a world of 100Mbps symmetrical. There’s talk of chips out there that can help it do better, but how far can it be squeezed?”
Are there other drawbacks?
“Electricity cables present a hostile ‘noise’ environment,” argues David Thorne, chief broadband and access strategist for BT Group. “Clever transmission methods have been tested but in reality it results in low reach and low bit rate, or you have to up the power which increases the noise which again slows the bit rate. Increasing power can also affect other services.”
There is a huge variance in transmission timing which makes BPL unsuitable for mobile traffic, he says: “Also electricity distribution varies from country to country, and so this makes common standards difficult which leads to market segmentation.”
There is also a degree of controversy that surrounds the whole principle of BPL. “There’s a question over whether it can be right for a municipally-controlled, tax-funded utility to compete with the commercial sector,” says Vittore. “The commercial sector doesn’t want competition that is not fair, and the tax payer doesn’t want to pay up to fix it when it breaks."
So what are the positives?
BPL got a boost in the US in February 2009 with the economic stimulus bill signed into law by President Obama.
One of Obama’s election pledges was the delivery of broadband internet services to rural and other underserved areas of the country. Now some powerful forces are gearing up to ride the stimulus wave and push broadband into some of these digital backwaters with BPL. In late 2008, IBM signed a contract with International Broadband Electric Communications (IBEC) to jointly deploy the technology in rural areas of the US.
The need for standards to unify the technology on a global basis is also being partially addressed by an IEEE working group, currently polishing up proposals that deal with more than 400 functional and technical BPL requirements.
Between them, these two breakthroughs may quite possibly have the side effect of stimulating DSL and cable operators to move more quickly to serve the rural communities that they have hitherto had on the back burner.
So what is the likely future for BPL?
Analysts think BPL is unlikely to take a place as a mainstream technology. “Ultimately this is a fill-in technology for areas where other broadband is lacking,” says Yankee Group’s Vittore. “Pilots are springing up in certain places. It is proving quite popular in developing markets in Latin America and Asia. Where it competes with satellite, it stacks up. With other options, less so.”
Many regard the technology as potentially complementary to Wimax, as it could provide a solution to the difficulty of the “middle mile”, and could also help to backhaul wireless traffic from remote areas to central locations.
This model could work by hanging Wifi or Wimax access points or even cellular base stations from utility poles. This would then allow end users within a certain range to connect to them, the data traffic then shifted by BPL to major network nodes.