With broadband over power lines, or BPL, you can plug your computer into any electrical outlet in your home and instantly have access to high-speed Internet. By combining the technological principles of radio, wireless networking, and modems, developers have created a way to send data over power lines and into homes at speeds between 500 kilobits and 3 megabits per second (equivalent to DSL and cable).
BPL is already being tested in several cities around the United States and the United Kingdom. In this article, HowStuffWorks takes a look at this new service, how it's possible, and what it could mean for the common electrical appliance. We'll also learn about the controversy surrounding BPL.
What's the Big Idea?
Despite the proliferation of broadband technology in the last few years, there are still huge parts of the world that don't have access to high-speed Internet. When weighed against the relatively small number of customers Internet providers would gain, the cost of laying cable and building the necessary infrastructure to provide DSL or cable in rural areas is too great. But if broadband could be served through power lines, there would be no need to build a new infrastructure. Anywhere there is electricity there could be broadband.
By slightly modifying the current power grids with specialized equipment, the BPL developers could partner with power companies and Internet service providers to bring broadband to everyone with access to electricity.
At this point, the proposal is for two types of BPL service:
In-House BPL will network machines within a building.
Access BPL will carry broadband Internet using power lines and allow power companies to electronically monitor power systems.
By providing high-speed data transmission between all of the electrical plugs in a house, there is the potential to network all kinds of common appliances in a household. If your alarm clock, light switch and coffee maker could talk each other via a high-speed connection, mornings might look a lot different.
The Old Way
If you've read How Internet Infrastructure Works, then you understand that the Internet is physically a huge network of networks that are connected through cables, computers, and wired and wireless devices worldwide.
Typically, large ISPs lease fiber-optic lines from the phone company to carry the data around the Internet and eventually to another medium (phone, DSL or cable line) and into your home. Trillions of bytes of data a day are transferred on fiber-optic lines because they are a stable way to transmit data without interfering with other types of transmissions.
The idea of using AC (alternating current) power to transfer data is not new. By bundling radio-frequency (RF) energy on the same line with an electric current, data can be transmitted without the need for a separate data line. Because the electric current and RF vibrate at different frequencies, the two don't interfere with each other. Electric companies have used this technology for years to monitor the performance of power grids. There are even networking solutions available today that transfer data using the electrical wiring in a home or business. But this data is fairly simple and the transmission speed is relatively slow.
BPL technology developers Current Communications Group and Enikia are working with power companies like Ameren and EPRI to get BPL off the ground. There are several different approaches to overcoming the hurdles presented when transmitting data through power lines. The details of these approaches are still pretty closely guarded secrets as both companies vie for the FCC's and IEEE's blessing for having their method adopted as the standard way to deploy BPL.
Power to the People
Like phone companies, power companies also have lines strung all over the world. The difference is that they have power lines in a lot more places than phone companies have fiber optics. This makes power lines an obvious vehicle for providing Internet to places where fiber optics haven't reached.
These power lines are just one component of electric companies' power grids. In addition to lines, power grids use generators, substations, transformers and other distributors that carry electricity from the power plant all the way to a plug in the wall. When power leaves the power plant, it hits a transmission substation and is then distributed to high-voltage transmission lines. When transmitting broadband, these high-voltage lines are the first obstacle.
The power flowing down high-voltage lines is between 155,000 to 765,000 volts. That amount of power is unsuitable for data transmission. It's too "noisy."
As stated before, both electricity and the RF used to transmit data vibrate at certain frequencies. In order for data to transmit cleanly from point to point, it must have a dedicated band of the radio spectrum at which to vibrate without interference from other sources.
Hundreds of thousands of volts of electricity don't vibrate at a consistent frequency. That amount of power jumps all over the spectrum. As it spikes and hums along, it creates all kinds of interference. If it spikes at a frequency that is the same as the RF used to transmit data, then it will cancel out that signal and the data transmission will be dropped or damaged en route.
BPL bypasses this problem by avoiding high-voltage power lines all together. The system drops the data off of traditional fiber-optic lines downstream, onto the much more manageable 7,200 volts of medium-voltage power lines.
Once dropped on the medium-voltage lines, the data can only travel so far before it degrades. To counter this, special devices are installed on the lines to act as repeaters. The repeaters take in the data and repeat it in a new transmission, amplifying it for the next leg of the journey.
In Current Communications Group's model of BPL, two other devices ride power poles to distribute Internet traffic. The CT Coupler allows the data on the line to bypass transformers.
The transformer's job is to reduce the 7,200 volts down to the 240-volt standard that makes up normal household electrical service. There is no way for low-power data signals to pass through a transformer, so you need a coupler to provide a data path around the transformer. With the coupler, data can move easily from the 7,200-volt line to the 240-volt line and into the house without any degradation.
In the various approaches to last-mile solutions for BPL, some companies carry the signal in with the electricity on the power line, while others put wireless links on the poles and send the data wirelessly into homes. The CT Bridge is capable of both.
The CT Bridge can also:
Manage symmetric data transmission to all the electrical outlets in the customer's home or office ("Symmetric" means that uploads and downloads are transmitted at the same speed.)
Support WiFi hot spots
Handle data routing
Manage subscriber information
Employ Dynamic Host Configuration Protocol (DHCP - The protocol that allows the management and assignment of IP addresses on a network)
Support security encryption of all transmissions
The signal is received by a powerline modem that plugs into the wall. The modem sends the signal to your computer.
Really very Interesting and a sound technology to emerge
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