How Powerline Broadband Functions

A new and emerging technology might soon take the lead in the competitive broadband Internet sector. It provides speedy access to your home via an unexpected route: the ordinary electrical outlet.

With Broadband Over Power Lines, or BPL, you can plug your computer into any household electrical outlet and immediately enjoy high-speed Internet. By merging the technologies of radio, wireless networking, and modems, engineers have figured out a way to transmit data through power lines, offering speeds ranging from 500 kilobits to 3 megabits per second (comparable to DSL and cable).

BPL is currently being tested in various cities across the United States and the United Kingdom. In this article, Mytour explores this innovative service, how it works, and its potential impact on everyday electrical devices. We will also dive into the debate surrounding BPL.

If you’re impressed by broadband, click here to discover how wireless mesh networks function.

What’s the Big Idea?

Even though broadband technology has expanded significantly in recent years, vast regions of the world still lack access to high-speed Internet. Given the high cost of laying cables and building infrastructure to provide DSL or cable in rural areas, it’s often not worth it for Internet providers, considering the relatively small number of customers they would serve. However, if broadband could be delivered through power lines, no new infrastructure would be required. As long as there is electricity, broadband could be available anywhere.

By making small adjustments to the existing power grids with specialized technology, BPL developers could collaborate with utility companies and Internet providers to bring broadband to anyone with access to electricity.

Currently, the proposal suggests two forms of BPL service:

By transmitting high-speed data through the electrical outlets in a home, it becomes possible to link various household devices. Imagine if your coffee maker, alarm clock, and light switches could communicate with one another—your mornings might be completely transformed.

In the upcoming sections, we'll explore the technology behind both In-House and Access BPL in more detail.

The Old Way

If you've read How Internet Infrastructure Works, you know that the Internet is essentially a vast network of interconnected networks, made up of cables, computers, and both wired and wireless devices spread across the globe.

In most cases, large ISPs rent fiber-optic lines from telecom companies to transfer data across the Internet, ultimately sending it through other mediums like phone, DSL, or cable lines into your home. Trillions of bytes are transmitted daily over fiber-optic lines, as they offer a reliable method of data transfer without causing interference with other signals.

The concept of using AC (alternating current) power for data transmission is not a new one. By sending radio-frequency (RF) energy alongside electrical current on the same wire, data can be transmitted without needing a separate line. Since the electric current and RF operate at distinct frequencies, they don’t disrupt each other. Electric companies have utilized this method for years to monitor power grid performance. There are even existing networking solutions that send data using the electrical wiring in homes and businesses, though the data transmitted is basic, and the transmission speed is relatively slow.

BPL technology developers Current Communications Group and Enikia are collaborating with power companies like Ameren and EPRI to bring BPL into operation. There are multiple strategies being explored to tackle the challenges of transmitting data over power lines, but the specifics of these approaches remain closely guarded as the companies compete for the FCC's and IEEE's approval to establish their method as the industry standard for BPL deployment.

The next section will introduce you to the fundamental concepts of the various approaches.

Power to the People

Similar to phone companies, power companies have extensive networks of lines spanning the globe. The key difference is that power lines are far more widespread than fiber optics, making them an obvious option for providing Internet access to areas that fiber optics have yet to reach.

Power lines are just one part of the electrical grid used by utility companies. Alongside the lines, power grids include generators, substations, transformers, and other distribution components that carry electricity from the power plant all the way to your home. When power is generated, it first reaches a transmission substation before being sent through high-voltage transmission lines. These high-voltage lines present the first challenge when transmitting broadband.

The electricity flowing through high-voltage lines ranges from 155,000 to 765,000 volts, which is far too much for data transmission. The signal is too "noisy" to carry cleanly.

As mentioned earlier, both electricity and the RF signals used for data transfer operate at specific frequencies. For data to travel smoothly from one point to another, it requires a designated band within the radio spectrum to vibrate without interference from other sources.

Electricity carrying hundreds of thousands of volts doesn't vibrate at a steady frequency. Instead, it fluctuates wildly across the spectrum, creating a host of interference. If it spikes at the same frequency as the RF used for data transmission, it can cancel out the signal, causing the data transfer to be disrupted or damaged along the way.

BPL solves this issue by avoiding high-voltage power lines altogether. Instead, it transfers the data from traditional fiber-optic lines onto the more manageable 7,200 volts of medium-voltage power lines further down the line.

Once the data is transferred to the medium-voltage lines, it can only travel a certain distance before it begins to degrade. To address this, specialized devices are placed along the lines to function as repeaters. These devices capture the data and re-transmit it, boosting the signal for the next segment of the journey.

In the BPL model by Current Communications Group, two additional devices are placed on power poles to help distribute the Internet traffic. The CT Coupler enables the data to bypass transformers.

Transformers reduce the 7,200 volts to the 240 volts typically used for household electrical service. Since low-power data signals cannot pass through a transformer, a coupler is required to provide a data path around it. The coupler ensures that the data can smoothly travel from the 7,200-volt line to the 240-volt line and into the home without losing quality.

In the upcoming section, we'll explore how data moves once it arrives at your home.

The Last Mile

The 'last mile' refers to the final leg of the journey, where Internet service reaches the subscriber's home or office.

In various last-mile solutions for BPL, some companies transmit the signal over power lines, while others install wireless links on power poles to send data into homes wirelessly. The CT Bridge is versatile, capable of supporting both methods.

The CT Bridge is also capable of the following:

The signal is received by a powerline modem, which plugs into the wall. This modem then transmits the signal to your computer. Let's take a closer look at these modems.

BPL Modems

BPL modems are equipped with silicon chipsets that are specifically designed to manage the task of extracting data from an electrical current. With advanced modulation techniques and adaptive algorithms, these modems can effectively manage powerline noise across a broad spectrum.

A BPL modem is plug and play, roughly the size of a standard power adapter. It plugs directly into a wall socket, with an Ethernet cable connecting to your computer to complete the setup. Wireless versions are also offered.

While the promise of this new technology is exciting, not everyone shares the enthusiasm. The next section will explore some of the challenges that are hindering the widespread adoption of BPL.

Challenges

On April 23, 2003, the FCC released a Notice of Inquiry, encouraging public input on the potential of BPL technology and aiming to establish standards for its implementation. This move was met with immediate opposition from both the American Radio Relay League (ARRL) and the Federal Emergency Management Agency (FEMA), both of which argue that BPL could lead to significant interference problems.

A BPL modem is classified as an unlicensed device, similar to a cordless phone or a garage door opener. These unlicensed devices are regulated under the FCC's Part 15 rules, which stipulate that all electronic devices sold in the U.S. must comply with FCC radio-frequency emissions limits. These regulations are in place to prevent interference with critical communications, including CB radios, air-traffic control, and government channels. Both ARRL and FEMA are concerned about the potential interference from BPL signals transmitted over unshielded medium-voltage power lines.

Cable TV providers avoid interference issues by using shielding around their cables. The coaxial cable used by cable companies, for example, features a metal braid that shields the signal wire. Telephone lines also employ shielding. Power lines, however, are not shielded, and in many instances, they are either bare wires or wires covered in plastic. The absence of shielding is the root of the interference concerns with BPL.

Depending on how the FCC allocates bandwidth for BPL, interference with other radio services could become problematic. Currently, the frequency allocation for various services is as follows:

While FEMA is open to the idea of allowing the FCC to explore a potential compromise, the ARRL insists that such a compromise is unfeasible, as the bandwidth required for BPL will inevitably interfere with ham radio and short-wave radio signals. BPL developers argue that these interference problems have already been addressed. Only time and further testing will provide clarity. In the meantime, the progress of BPL continues at a slow pace as it awaits the finalization of standards and logistical considerations from regulatory authorities.