08/10/10 – This is a research paper I wrote in the Fall of 2007 for a Villa Julie College ‘High Speed Broadband Networks’ class. It is the final version to be turned in.
BPL stands for Broadband over Power Lines. Simply put, it is a technology in which broadband internet access made available through ordinary medium-voltage power lines. BPL can be used for many things such as providing wireless internet access to homes and companies, alternative solution to DSL and cable, high speed data transmission to remote areas, and utility applications. The speed of BPL is between 500kb/s and 3mb/s per second which is equivalent to DSL and cable) BPL is seen by some as a viable alternative to cable and DSL. The broadband market is a duopoly, in that 2 technologies control the market. Competition exists between broadband companies and not technologies. This paper will describe how BPL works, the pros and cons of BPL, interference issues, and the future of BPL.
How it works
Starting with the regular ISP backbone lines such as fiber or wireless, the signals run to the medium voltage lines and their couplers at the point of entry onto the power grid. Data signals travel across medium voltage power lines until they reach transformers. The data travels at a higher frequency than the power so the two signals to not interfere. BPL loses signal strength through transformers. To compensate for the loss of signal strength, the line needs to be boosted with a power injector. Repeaters are placed strategically along the power line route to ensure optimal signal strength. The final step in the delivery of BPL is having the data go across low-voltage lines into buildings with BPL modems or across a wireless link. For the later method, the user plugs a BPL modem, provided by the BPL provider, into any power outlet in their home, and then connects the modem to their PC/router via an Ethernet cable. The diagram to the left illustrates how this works. The modem is the size of a normal power brick/block and is capable of handling the various electrical noise generated by the BPL signal. This is different than power-line networking which simply makes use of the power lines within your home to share a network connection. Merging these two technologies will be great. Imagine not having to run CAT5 cable throughout a building, and rather, relying on pre-existing electrical wire to form the network. This conglomeration of technology is being developed. The former method uses a wireless transmitter/receiver on a nearby pole to provide the last-link to the customers’ building. This method is not as prevalent for the delivery of BPL. However, it is used in the upload of data from the building TO the pole.
An issue that arises with the deliverance of BPL is what is used as the backhaul device for uploads. We understand that data gets into the building by utilizing existing power lines. But when you want to upload something, how does it get back? It cannot use the same line, can it? One of my group members spoke with a BPL technician (Walt Adams) from the Manassas, VA based company COMTek which specializes in BPL and he briefly explained how data gets sent from the house to the ISP. Outside every building with BPL where your typical power meter is, the ISP places a gateway and repeater in order to re-inject your upload data back onto the power lines to the substation. The substation is connected to the ISP via fiber optic cabling and routes internet traffic like any cable or DSL ISP would.
An alternative method of backhaul is making use of a wireless access point located on telephone poles around an ISP’s distribution area. This wireless technology can also be used as the last-step communication between power lines and building. A coupler/modulator would convert BPL signals into an understandable stream that a typical wireless access point can understand and broadcast. This method would prevent the need for a gateway and repeater to be placed on each building receiving BPL. Enough WAP’s would need to be placed around an area to provide sufficient bandwidth, signal strength, and signal coverage to an ISP’s customers. The wireless signal would also need to be secured and remain secured at all times.
Another option for BPL backhaul is the use of shorter distance fiber optic cable runs. Instead of the data being sent the entire distance of the power lines back to the main distribution centers, the signal would travel over power lines to various substations. Each substation would be connected to the main distribution center via fiber optic cable. The image to the above-left demonstrates this method. In addition, substations could be connected to one another and then a single fiber run to the distribution center. This could be considered a passive optical network in that it is not a single point-to-point network. This would also reduce the amount of fiber cable need and reduce the need for multiple networks of expensive equipment. A foreseeable issue that may arise would be the lack of redundancy. In the former network setup each substation would directly connect. Should a fiber line go down, this would limit the number of affected customers. Running these fiber lines from substations to distribution centers would put fiber optic cable closer to customer’s buildings and provide for future fiber-only broadband internet access. But that is just a side-thought/benefit for now.
BPL operates on medium and high frequencies from 1.8MHz to 80 MHz. This varies depending on the system and equipment being used. Below is a chart showing the frequencies used today. The blacked out areas indicate the range of frequencies that BPL either uses or interferes with.
As you can see, this covers a HUGE portion of Federally licensed frequencies that have been in place for years. It is not right for a new technology to completely trample on current legal frequencies and render them useless.
Interference is the most prevalent issue when discussing BPL. The United States government began licensing Amateur Radio operators in 1912. There is no denying the fact that a BPL signal seriously interferes with the operation of Federally Licensed radio operators through Electro Magnetic Interference (EMI). The American Radio Relay League (ARRL), formed in the 1890’s, has been fighting the FCC in court about BPL interference.
Who has joined the AARL?
- The Association for Maximum Service Television (MSTV)
- National Association of Broadcasters (NAB)
- National short-wave listener associations
- Short-wave broadcasters
- NTIA (National Telecommunications and Information Administration)
Members of the IEEE working group for BPL
- Texas Instruments
- Conexant Systems.
The ARRL takes the stance that BPL must restrict signal strength and certain frequencies. They do not want to abolish the technology they just want to improve it so it does not interfere with other devices. The FCC states that they have, “struck the right balance between encouraging unlicensed BPL deployment and protecting existing licensed devices–including those run by public safety workers, TV broadcasters and amateur radio operators–from harmful interference on those airwaves” and “didn’t find ample evidence that BPL posed real potential for “harmful” interference”. Many ham radio operators would beg to differ.
The FCC is pushing BPL. In its October 14, 2004 Report and Order in this proceeding, the Commission recognized the significant benefits that BPL technology offers to the American public in extending broadband access to homes and businesses and introducing additional competition to existing broadband services, such as cable modem and Digital Subscriber Line (DSL) services.
However, it also recognized that those substantial benefits might not be realized if BPL devices were to cause interference to licensed services and other important radio operations. Accordingly, the Commission established technical standards, operating restrictions and measurement procedures for Access BPL to minimize instances of interference and to facilitate resolution of such interference where it might occur. Potential revenue, an FCC that is very pro-big business lobbyist friendly and technically lacking, a high demand for broadband from a starving public, and the classic promises of broadband and hype are driving BPL.
The FCC’s definition of harmful interference is “Any emission, radiation or induction that endangers the functioning of a radio navigation service or of other safety services or seriously degrades, obstructs or repeatedly interrupts a radio communications service” The FCC believes that “if the they [the FCC] restricts the strength of the signal on BPL lines, others using spectrum will not notice differenc e.” BPL regulation will reduce benefits of BPL. It will also raise costs to the public because the BPL operators would need to provide a fix for the interference. “If real-world evidence of harmful interference arises, the regulators have voiced willingness to reconsider their rules” One would wonder if the FCC is oblivious to the proof of interference that has been posted on many websites and online radio communities or if they just chose to disregard. The image above is a group of men who set up their car to be a mobile Ham radio receiver to document the interference BPL has on the transmission of radio signals. Many people have done this.
Part 15 Title 47 of the Code of Federal Regulations says that “To comply with FCC: (1) this device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.” Operation shall not resume until the condition causing the harmful interference has been corrected. This would clearly end the life of BPL if this rule was followed to the T.
The higher frequencies radiate from the power line so much (causing interference to radio and TV) that repeaters are needed at 3/4-mile intervals, and customers around here live farther apart than that. The article reports on the status of delivering broadband over power lines in the U.S. The idea of delivering Internet service over power lines has arrived in the U.S. For instance, IBM Corp. and CenterPoint Energy Inc. announced a pilot broadband-over-power-line (BPL) project in Houston, Texas. The potential of BPL for monitoring and controlling its own power networks is emphasized. Also testing the service are Google Inc., which has invested in the technology, and Intel Corp. and Cisco Systems Inc., which have joined in writing standards.
FEMA says, “This interference will severely impair FEMA’s mission-essential HF radio operations in areas serviced by BPL technology.” HAM radio operators were some of the first responders in the wake of Hurricane Katrina. They provided valuable communication to emergency personnel when all other lines of communication were down. A interesting thought regarding BPL’s interference with emergency communication is that if those emergency lines ar e down, than the power lines would most likely be down in which case BPL interference would be non-existent and not preventing HAM radio operation.
Up front investment must be made in BPL head-end/feed point equipment and repeaters. Significant recurring costs in backhauling the IP traffic from the numerous BPL feed points serving an area. Neither DSL nor Cable has this recurring cost or need for multiple network origination points. These costs unique to BPL make it even less attractive for deployment in rural areas because there would be less potential for customers. BPL would most likely have an initial rollout in metropolitan areas to pay for rural deployments, meaning the first customers may be paying a premium just for BPL can further develop and spread beyond the city.
BPL signals cannot easily pass through transformers. Many transformers in the U.S. serve a select few homes. This is why BPL technology is advancing more rapidly in Europe. There are less transformers per neighborhood. There is a need for repeaters to be installed at every transformer to boost the signal to the next transformer or power junction. This is not a cost effective technology in rural areas. It relies on densely populated areas (the city and suburbs) to get any appreciable return on investment. However, it also allows for more bandwidth for the customers since only a few homes would be sharing the line.
The future of BPL
The future of BPL relies on the reduction of skepticism on the part of power companies that investment in the technology will pay off. Equipment (power injectors, couplers, gateways, wireless access points, bridges, etc) are an expensive investment. Companies are questioning the return? Rural homeowners/businesses need internet access. Cable/DSL can only go so far. WIFI, WiMAX, and directed antennas can only go so far. Satellite is way too expensive. Really, it is a cable and telephone duopoly. (Only two producers exist in one market). BPL technology would also benefit the power company because they would be able to use their own BPL infrastructure to manage the power grid, automate meter reading from a central office, and remote connect/disconnect of service, and other overall grid management.
Some industry observers believe the prospect of BPL will motivate DSL and cable operators to more quickly serve rural communities. It could drive down costs of cable/DSL service. BPL could be the third option. Power lines are typically untwisted and unshielded, they are essentially large antennas, and will broadcast large amounts of radio energy. Because of their lack of shielding, the BPL systems are also at risk of being interfered with by outside radio signals as previously mentioned.
Besides cable and DSL, the alternatives for BPL are quite slim. Satellite internet, which provides internet anywhere, is extremely expensive and requires expensive hardware. Wireless technologies are becoming very prevalent around metropolitan areas. Wireless is even being used to provide internet to locations untouched by cable and DSL, but not too far that the signal cannot reach.
Every year is supposed to be “the year” for BPL. BPL is a great idea and an excellent benefit to many families, businesses, and non-profits. If a building already has power lines, wouldn’t it be great to tap into those lines to deliver your internet? In theory, the answer would be a resounding “YES”. However, the issues of interference, cost, and reliability are slowing down the development of BPL technology. Even with mega-companies such as Google volleying for a share in the BPL market, development is slow. It is a serious investment and many companies are not convinced that their returns would be worth the risk. As 2008 rapidly approaches, it will be interesting to see how BPL proponents will push. Will politicians include BPL in their telecommunications platform in the upcoming election year? I believe 2008 may be a major milestone in the advancement of BPL.
Sources of information
Broadband Over Power Line and Amateur Radio. Ed Hare, PowerPoint Presentation.