But critics have a problem with this. For starters, it may not necessarily be economically viable (or cheaper) because of the cost of the technology of “transformer bypassing.” And, the interference from the power lines could inhibit other radio frequency (RF) communications.
How power lines and broadband work together
BPL uses the existing power grid infrastructure and inside wire, so power lines have two purposes that have to coexist without interference. Basically, customers plug a BPL modem into any electrical wall socket and send data over a city’s electrical wires to substations that are connected to the Internet by city-owned fiber-optic cables. Because the data travels at higher frequencies than electrical current, the two do not interfere with each other. But that doesn’t mean Internet traffic doesn’t interfere with other signals. BPL faces continuing criticism that transmitting data over unshielded power lines can interfere with both ham radio broadcasts and police and fire radios.
BPL uses power line communication (PLC) technology on existing power distribution lines that now has the challenge of also using those power lines for communications purposes. Power lines weren’t designed to also carry data because the problems of attenuation (loss or any reduction in the signal) at high frequencies and noise (EMI/RFI) have led to errors in that physical layer. The power lines are unshielded (not insulated) and can act as aerials and can then pick up noise and transmit it further along the lines. This means that any reasonably strong source of noise can cause a problem—just like interference caused from radio stations, wireless intercom systems, TVs, vacuum cleaners, etc. Some of the RF energy “leakage” could cause interference if not carefully managed. Licensed users on the same frequency bands as local access BPL signals could possibly receive harmful interference from this signal leakage if adequate precautions aren’t taken, and BPL operators are required to investigate and mitigate any instances of harmful interference.
Two types of BPL
There are two types of BPL: access and in-house. Access BPL uses certain elements of the existing electrical power grid as a sort of local loop for delivery of broadband services. It uses BPL modems and couplers (like a modem to connect to a network) to take advantage of medium-voltage power lines in a power utilities’ distribution network.
Those medium-voltage power lines are on the electric utility poles beside the roadways where there is no underground electric service. At the utility substation, the high-voltage lines are stepped down to medium for the distribution network. Repeaters are used to regenerate the signal as it travels from the utility substation toward the customer premises. Signals are removed from the power lines by extractors placed just ahead of the transformers, which typically serve a number of households. The transformers serve to step the voltage down from the several thousand volts of the distribution lines to the 110/220-volt level used within the premises.
Problems start when BPL signals reach a transformer, as the signal must get through or bypass it. A typical solution is to bypass the transformer in order to couple the BPL signal directly between the medium-voltage distribution cable and the low-voltage line. In this case, couple means the transfer of desirable energy from one medium (wire or fiber) to another medium.
Current Communications, working with Ohio-based utility company Cinergy, has a “bypass” unit that touches the electric wires, allowing the signal to travel along the power line into the house.
That transformer location can also double as a central communications hub where signals must be upstream and need to be multiplexed onto the distribution line and downstream signals demultiplexed to the premises. Routing and security also take place here. BPL security could be enhanced with VPNs and SSL encryption.
In-house BPL is a home-networking technology that uses the transmission standards developed by the HomePlug Powerline Alliance. Products for in-home networking using the electric outlets in your home (or office) are available in stores now. In-house BPL products can comply relatively easily with the radiated emissions limits in Part 15 of the Federal Communication Commission (FCC) rules, because the products connect directly with the low-voltage electric lines inside your home or office. The challenge is how to get broadband Internet access over “the last mile” to the home.
How IEEE got involved
Early on, the Institute of Electrical and Electronics Engineers (IEEE) was asked to get involved because the United Power Line Council (UPLC), a subsidiary of the United Telecom Council (UTC) of Washington, D.C., wanted the organization to look at standards for BPL. The responsibility fell to its power-engineering people.
This started in January 2004—manufacturers discussed what standards would be needed and hardware was suggested. Eventually a project authorization request (PAR) was approved.
Now, the IEEE has three projects going that are involved with broadband over power lines. They will be the ones to tell people what the hardware has to look like and how it has to test out.
The installation standard will tell users “how to install it properly to protect the distribution line.” IEEE wants 1) to protect the public by showing the utilities how to have a well-designed distribution system, and 2) to come up with a “universal” model that service providers can sell to users or install in a building.
Trials are going on now
In the Cincinnati area, you can find high-speed Internet access being offered by the Ohio-based utility Cinergy along with Current Technologies, using Current’s broadband over power line service. It is referred to as Current Broadband. And according to Current, the company recently received communication from the American Radio Relay League (ARRL) that it has tested Current’s service and found no interference. The ARRL recommends all companies implement BPL the way Current has.
Current has definitely seen renewed interest in BPL. Utilities get something out of it because they can purchase features BPL uses that give the utility a more reliable distribution network (with monitoring, preventive maintenance, etc.), and the regulators like the competition.
Manassas, Va., has recently been covered with BPL, by a network operated by Communication Technologies (COMTek). This Washington, D.C., suburb has 37,000 people. It’s the first citywide commercial deployment of BPL technology in the United States.
- The service is always on and it can provide fast speeds—up to 75 times faster than dial-up. No more slow sending of graphic files, pictures or video files. The service can also be affordable with a choice of plans that depend on the type of performance the customer wants.
- Symmetrical services, such as Current’s, mean the upload and download speeds on the Internet are the same.
- More than one person can be on the line at once. Just as we think of cable or DSL service, same as BPL. You can have as many computers as you want using the service at the same time. Most importantly, BPL has a plug-and-play feature. (Note that BPL doesn’t handle phone service so phone lines are left to do what they were meant to do.)
- Methods of delivering data or high-speed Internet access vary and it is important to know how it is done in your case. Transmitting data over power lines for extended distances can lead to degradation of the signals; consequently, data is typically transmitted over fiber optic cables for the length of the high-voltage lines, before being converted to electrical signals and being added to the medium-voltage or low-voltage lines. On medium- and low-voltage lines, boosters are required at regular intervals (as with most other technologies) for reamplification to prevent signal loss.
- BPL has serious bandwidth and radio interference issues. It also has stiff competition from the incumbent DSL and cable networks. In the home, it could be looked as a competitor to other Internet access devices/services.
- Not all BPL providers use the same bypass method.
Some markets are terminating trials with this technology. In October 2005, Philadelphia Power and Light, in eastern Pennsylvania, ended its two-year-old marketplace trial of the technology. They said their market trials showed that the BPL technology was promising, but combining competition with the need for a large-scale deployment, led them to decide not to proceed as a retail communications service provider.
Despite the challenges, forecasts kept appearing for growth starting in 2005. Even some stock market watchers feel that the BPL industry may become a leader in growth. They believe BPL is here to stay and feel that the industry will experience unprecedented growth in 2006.
To see if this will become a solid market in the United States, keep watching it to see whether it is going to be trouble free, devices become interoperable and providers design their equipment not to interfere with radio frequencies used by amateur ratio operators.
Three things will be important: that utilities work with consumer telecom businesses so they can improve their track record and successfully deliver BPL to the home or business, that no RF interference is created by BPL, and that hardware delivering BPL to the home follow IEEE standards as well as the HomePlug spec.
Regarding customers, it will be important that they know how the process offered to them works along with electrical service, that it has been tested successfully, how BPL comes down into their home/building, that EMI/RFI is controlled, and then which devices or customer premises equipment are built to standard and certified to be interoperable with the other hardware that will be on the market. EC
MICHELSON, president of Jackson, Calif.-based Business Communication Services and publisher of the BCS Reports, is an expert in TIA/EIA performance standards. Contact her at www.bcsreports.com or firstname.lastname@example.org.