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// this tells jquery to run the function below once the DOM is ready $(document).ready(function() { // choose text for the show/hide link var showText="Show the hidden text"; var hideText="Hide the text"; // create the toggle link $("#hide_this").before("

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Showing posts with label Web:Connectivity. Show all posts

How High-speed Dial-up Works  

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How High-speed Dial-up Works

by Robert Valdes
Browse the article How High-speed Dial-up Works
Introduction to How High-speed Dial-up Works
typical phone-line modem
Typical phone-line modem
While surfing the Internet, do you find yourself going to get a cup of coffee, grab a magazine or retile your bathroom between page loads? If so, chances are you're using a dial-up connection, and a sneaking suspicion may be growing on you: Is your connection actually getting slower?
It is and it isn't. As always, the connection speed of dial-up is limited by the bandwidth of phone lines; but at the same time, the average file size for Web content is getting larger and larger. More people are using broadband connections that can handle a bigger load, so Web sites feel more comfortable bulking up their pages. It takes a lot time to squeeze all of that data through a dial-up connection.
New technology offers a solution to the slow-down that doesn't necessitate broadband. Services like NetZero andEarthLink are now offering "high-speed dial-up." According to ads for these services, you can get connection speeds that are five times faster than traditional dial-up service.
So how is this possible? In this article, HowStuffWorks examines what it takes to speed up your dial-up. First let's address what we know you're all wondering, "What is that unusual noise the modem makes when it's making a connection?"
A Very Special Handshake
When you think of dial-up Internet service, the first thing that probably comes to mind is the strange sort of "R2-D2 in a blender" type chirping that the modemmakes as it connects. This song is called the handshake protocol, and it is the first thing that bogs down the speed of dial-up Internet.
The handshake protocol, as the name implies, begins the conversation that allows data to be sent to and from your computer using the Internet. There are actually two separate handshakes that occur in this process. The first half is the modem initializing the Internet connection. We'll call that the modem handshake. The second part is the software handshake. That deals with authenticating the user's access to the ISP (Internet Service Provider). When your computer is chirping away, it is introducing itself to your ISP. High-speed dial-up providers can't do anything about the modem handshake, but they can speed up the software handshake. The standard software handshake goes something like this:
    Your machine: Hello, my name is Sparky. ISP Server: Hello, Sparky. Your machine: I am John's computer. ISP Server: John who? Your machine: John Smith. ISP Server: I know 32,422 John Smiths. Your machine: He is one of your customers. ISP Server: Does he have an account number? Your machine: Yes. ISP Server: What is that number? Your machine: 5546743897 ISP Server: Ah, yes. OK, go ahead, 5546743897. You have access.
This is a simplified explanation, of course, but you can get the idea of the back-and-forths that need to occur in the handshake protocol before information can be sent or received. High-speed dial-up providers have cut down on this back-and-forth by creating a system that allows the conversing machines to remember responses to questions. This makes for a much shorter conversation:
    Your machine: Hello, my name is Sparky. ISP Server: Ah, hello, Sparky. Aren't you John Smith's machine. Your machine: Yes, his account number is 5546743897. ISP Server: Go ahead, 5546743897. You have access.
This shorter handshake equals much faster connection times. The increase in speed varies by machine, but in some cases it can reduce the handshake byup to 50 percent. What might take 45 seconds with a "normal" dial-up service becomes maybe a 30-second process with a high-speed service.
high-speed dial-up handshake
High-speed dial-up allows your machine to establish a connection with your ISP in a fraction of the time it takes with standard dial-up.
In the next sections, we'll learn what happens to accelerate dial-up after your machine and the ISP have established a connection.
Search for Acceleration Servers at Alibaba - the world’s largest online base of suppliers and importers.
 
High-speed Dial-up: Acceleration Servers
When you search for a Web page on the Internet, your request is routed though your ISP to the Web. After making a series of stops along the way at machines that help find the page you're looking for, your machine is connected to the computer that serves the Web page you requested. Once this connection is established, data can flow freely from the Web server to your computer. Once the information leaves the Web server and hits your dial-up connection, that's where the bottleneck begins in the typical Internet transaction.
Dial-up Presence
According to an independent study done by thePew Internet & American Life Project, in 2003 they were 147 million Internet users in the United States. Of those, 23 million had dial-up Internet service.
But high-speed dial-up providers have come up with some pretty clever ways to open up that bottleneck. By loading special software into a server, they turn it into what they call an acceleration server. And by sandwiching the acceleration server into the chain between your dial-up connection and the Web, they can speed up the process considerably.
When you search for a Web page using high-speed dial-up, your request is sent from the dial-up modem in your computer to the ISP's acceleration server. Now the acceleration server is requesting and serving pages on your behalf. The acceleration server uses a broadband connection to quickly search the Internet for the server that hosts the page you're looking for. Once it finds that server, the two machines start talking and exchanging the information you need. Your ISP's acceleration server takes that information and sends it to your machine.
high-speed dial-up data path
The high-speed dial-up data path
Acceleration servers speed up the dial-up data transfer using several techniques:
  • Compression
  • Filtering
  • Caching
Next, we'll go over how these acceleration servers drop the pedal on your dial-up.
High-speed Dial-up: File Compression
The key element of high-speed dial-up Internet is file compression. If you've read How File Compression Works, then you know that there are two types of file compression: lossy and lossless.
Text and other files that need to remain perfectly intact during the compression process use lossless compression. Once they are uncompressed, the files return to their original state.
Photos and graphics can be transmitted using lossy compression. When these files are uncompressed, they are not exactly as they were before compression: They have lost some of the original data in the process. For example, a picture that originally had 2 million colors may only have 16 thousand after lossy compression. The loss in quality may not be important to the user when weighed against the increase in speed gained through the compression process. Companies like NetZero let the user control how much compression is used on photos and certain sites.
File compression is an evolving technology, and it doesn't work on every file type yet. The chart below will help you understand what will and will not be accelerated by high-speed dial-up.
Accelerated
Not Accelerated
HTML/Java-based Web pagesStreaming media (audio or video)
TextSecure Web pages
JPG/GIF-based graphicsMusic/photos sent as e-mail attachments
E-mailDownloads
At this point, the on-the-fly file compression utilized in high-speed dial-up can't be added to the file types specified above because of the nature of the data. For instance, data on secure Web sites is encrypted. When it is transmitted, the code looks like a bunch of gibberish so that no one can read it. When this gibberish reaches the acceleration server, it can't compress the code: If the compression software were to change even one character in the encrypted transmission, that would render the data unusable.
Here is how a typical acceleration server compresses different file types:
  • For text files, including the HTML text of a Web page and the text in an e-mail message, the acceleration server compresses the text on the fly and sends it down your modem line. Typically, text will compress at least 50 percent using on-the-fly techniques.
  • For image files, including GIF and JPG images on Web pages as well as many banner ads, the acceleration server reads the image from the Web site and recompresses it to reduce its size. Typically, the image file size shrinks anywhere from 50 percent to 90 percent in the process.
  • In many other files, including video files, Zip files and MP3 music files, compression has already taken place. For example, an MP3 file is already one-tenth the size of the original track on the CD. It is not possible to compress the file any further in a quick way. In the case of secure Web pages, we already discussed why they cannot be compressed. The acceleration server will not touch these files -- it just passes them through as-is.
In the next section, we will learn how high-speed dial-up accelerators filter out useless data to increase speed.
High-speed Dial-up: Filtering and Caching
When you type a URL (like www.AnyWebSite.com) into the address bar of your browser, you are sending a request for a specific page. If that page uses pop-up advertising, there are pop-up parameters hiding in its programming code. When the information is sent back to your machine, the hidden code executes a program that launches the advertisement. In order for the pop-up to pop, that hidden code must display parameters that tells your machine what size the ad is, where on the screen it should appear, and other details about the ad. These ads take up valuable bandwidth, slowing down the transmission of data to your machine.
high-speed filtering image
To combat this drag, high-speed dial-up providers have bundled a pop-up blocker into the software they send to subscribers. This pop-up blocker is programmed to recognize those lines of code that spell out the ad parameters. When it sees those tell-tale lines of code, it rejects the ad's request to be displayed. What this amounts to is less information being sent across the phone line to your machine. The less data that is sent, the faster the load time.
Caching
The first time your browser loads a Web page, it has to load the entire thing, along with all of the images it displays. If the browser saves the images and text, then the second time it loads the same page it can check for duplicates. If an image has not changed, there is no need to download it again. This process of saving a file in the hopes of reusing it in the future is called caching. For a complete explanation of the caching process, see How Caching Works.
High-speed dial-up uses a similar system for commonly requested Web pages. Instead of constantly requesting the same page, the acceleration server takes note of which Web pages are being commonly asked for by all subscribers. So instead of asking the HowStuffWorks server thousands of times a day if it can see the homepage of HowStuffWorks.com, it just asks once. Then it stores the page in its memory, and every time another subscriber asks to see HowStuffWorks, it simply transmits the page out of its memory to the user. This is called server-side caching, and it saves time by eliminating redundant requests.
There is a second side to caching -- client-side caching. Internet browsers like Explorer or Netscape are made to cache frequently viewed pages to cut down on load times.
client-side caching image
Client-side caching
The browser stores the cached pages on your computer's hard disk. High-speed dial-up software enhances this feature. In addition to storing frequently viewed pages, it also looks for elements in those pages that remain constant. For instance, instead of caching the entire HowStuffWorks homepage, most of which changes every day, it looks for things that don't change. On our homepage, the logo, the header, the navigation, and the search bar stay the same every day. The software makes note of that consistency, saves those elements, and then only loads what has changed every time you come to the HowStuffWorks homepage.
You can see how caching saves time by avoiding unnecessary data transmission. The most amazing thing about this tool is that with the combination of server-side caching and client-side caching, the system learns about your surfing habits. It uses what it learns to streamline your connection process as much as possible. So the more you use it, the faster it gets.
Compression, filtering and caching are the three key steps in dial-up acceleration. But what actually happens when you put all three techniques together? Does performance really improve? And is the improvement enough to be noticeable?
The answer is yes, and in the next section we will try out NetZero to see how well it actually works with real-world Web pages.
High-speed Dial-up: The Bottom Line
Now that you understand how it works, let's take a moment to look at how well it works. We decided to try out one of the more popular high-speed dial-up providers, NetZero, to see how much the service sped up a dial-up connection.
After signing up for the service and choosing the "out of the box" settings, HowStuffWorks tooled around the Web with both normal and high-speed dial-up connections to test the difference in speed.
After log-in, we surfed repeatedly to some of the most popular sites on the Web. The results varied by site, but as an example, HowStuffWorks came up three times faster with high-speed dial-up. For the complete results, see the chart below.
With Dial-Up
With High Speed Dial-Up
Web Page
Original Load Time (seconds)
Web Page
Original Load Time (seconds)
Cached Load Time (seconds)
Amazon.com
49.29
Amazon.com
39.05
14.05
CNN.com
72.4
CNN.com
32.57
9.32
Ebay.com
57.68
Ebay.com
40.38
34.2
Google.com
8.08
Google.com
3.15
1.65
Google search (100 results)
10.45
Google search (100 results)
9
7.42
HowStuffWorks.com
92.3
HowStuffWorks.com
31.78
18.7
NetZero.com
33.26
NetZero.com
16.29
10.53
Yahoo.com
26.81
Yahoo.com
12.51
7.1
It would seem that a clever combination of fairly straightforward technologies has helped to overcome some of the speed bumps of dial-up Internet. These advances serve to prolong the life of dial-up Internet and provide an alternative for those who are tired of standard dial-up but not quite ready for the leap tobroadband. If these advances continue, dial-up may be here to stay for quite a while.

How Internet Radio Works  

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How Internet Radio Works

by Debra Beller
Browse the article How Internet Radio Works
Introduction to How Internet Radio Works
A college student in Wisconsin listens to a disc jockey in Jamaica play the latest rapso (calypso rap) music. A children’s advocacy group unites its geographically diverse members via private broadcast. A radio listener hears an ad for a computer printer and places an order immediately using the same medium on which he heard the ad. All of this is possible with Internet radio, the latest technological innovation in radio broadcasting since the business began in the early 1920s.
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Internet radio has been around since the late 1990s. Traditional radio broadcasters have used the Internet to simulcast their programming. But, Internet radio is undergoing a revolution that will expand its reach from your desktop computer to access broadcasts anywhere, anytime , and expand its programming from traditional broadcasters to individuals, organizations and government.
In this article, we’ll explore the Internet radio revolution in terms of equipment, transmission, programming and the alterations in the listener/broadcaster relationship.
Freedom of the Airwaves
Radio broadcasting began in the early ‘20s, but it wasn’t until the introduction of the transistor radio in 1954 that radio became available in mobile situations. Internet radio is in much the same place. Until the 21st century, the only way to obtain radio broadcasts over the Internet was through your PC. That will soon change, as wireless connectivity will feed Internet broadcasts to car radios, PDAs and cell phones. The next generation of wireless devices will greatly expand the reach and convenience of Internet radio.
Uses and Advantages
Traditional radio station broadcasts are limited by two factors:
  • the power of the station’s transmitter (typically 100 miles)
  • the available broadcast spectrum (you might get a couple of dozen radio stations locally)
Internet radio has no geographic limitations, so a broadcaster in Kuala Lumpur can be heard in Kansas on the Internet. The potential for Internet radio is as vast as cyberspace itself (for example, Live365 offers more than 30,000 Internet radio broadcasts).
In comparison to traditional radio, Internet radio is not limited to audio. An Internet radio broadcast can be accompanied by photos or graphics, text and links, as well as interactivity, such as message boards and chat rooms. This advancement allows a listener to do more than listen. In the example at the beginning of this article, a listener who hears an ad for a computer printer ordered that printer through a link on the Internet radio broadcast Web site. The relationship between advertisers and consumers becomes more interactive and intimate on Internet radio broadcasts. This expanded media capability could also be used in other ways. For example, with Internet radio, you could conduct training or education and provide links to documents and payment options. You could also have interactivity with the trainer or educator and other information on the Internet radio broadcast site.
Internet radio programming offers a wide spectrum of broadcast genres, particularly in music. Broadcast radio is increasingly controlled by smaller numbers of media conglomerates (such as Cox, Jefferson-Pilot and Bonneville). In some ways, this has led to more mainstreaming of the programming on broadcast radio, as stations often try to reach the largest possible audience in order to charge the highest possible rates to advertisers. Internet radio, on the other hand, offers the opportunity to expand the types of available programming. The cost of getting “on the air” is less for an Internet broadcaster (see the next section, "Creating an Internet Radio Station"), and Internet radio can appeal to “micro-communities” of listeners focused on special music or interests.
Creating an Internet Radio Station
What do you need to set up an Internet radio station?
  • CD player
  • Ripper software (copies audio tracks from a CD onto a computer’s hard drive)
  • Assorted recording and editing software
  • Microphones
  • Audio mixer
  • Outboard audio gear (equalizer, compressor, etc.)
  • Digital audio card
  • Dedicated computer with encoder software
  • Streaming media server
Getting audio over the Internet is pretty simple:
  1. The audio enters the Internet broadcaster’s encoding computer through a sound card.
  2. The encoder system translates the audio from the sound card into streaming format. The encoder samples the incoming audio and compresses the information so it can be sent over the Internet.
  3. The compressed audio is sent to the server, which has a high bandwidth connection to the Internet.
  4. The server sends the audio data stream over the Internet to the player software or plug-in on the listener’s computer. The plug-in translates the audio data stream from the server and translates it into the sound heard by the listener.
There are two ways to deliver audio over the Internet: downloads or streaming media. In downloads, an audio file is stored on the user’s computer. Compressed formats like MP3 are the most popular form of audio downloads, but any type of audio file can be delivered through a Web or FTP site.Streaming audio is not stored, but only played. It is a continuous broadcast that works through three software packages: the encoder, the server and the player. The encoder converts audio content into a streaming format, the server makes it available over the Internet and the player retrieves the content. For a live broadcast, the encoder and streamer work together in real-time. An audio feed runs to the sound card of a computer running the encoder software at the broadcast location and the stream is uploaded to the streaming server. Since that requires a large amount of computing resources, the streaming server must be a dedicated server.

How does a T1 line work?  

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How does a T1 line work?

Browse the article How does a T1 line work?
Introduction to How does a T1 Line Work?
Most of us are familiar with a normal business or residential line from the phone company. A normal phone line like this is delivered on a pair of copper wires that transmit your voice as an analog signal. When you use a normal modem on a line like this, it can transmit data at perhaps 30 kilobits per second (30,000 bits per second).
Wires on the machinery in the Network Operating Center, from which broadband access is distributed to customers in the borough of Kutztown, Pa.
Scott J. Ferrell/Congressional Quarterly/Getty Images
If your office has a T1 line, it means that the phone company has brought a fiber optic line into your office that can carry data at a rate of 1.544 megabits per second.

The phone company moves nearly all voice traffic as digital rather than analog signals. Your analog line gets converted to a digital signal by sampling it 8,000 times per second at 8-bit resolution (64,000 bits per second). Nearly all digital data now flows over fiber optic lines, and the phone company uses different designations to talk about the capacity of a fiber optic line.
If your office has a T1 line, it means that the phone company has brought a fiber optic line into your office (a T1 line might also come in on copper). A T1 line can carry 24 digitized voice channels, or it can carry data at a rate of 1.544 megabits per second. If the T1 line is being used for telephone conversations, it plugs into the office's phone system. If it is carrying data it plugs into the network's router.
A T1 line can carry about 192,000 bytes per second -- roughly 60 times more data than a normal residential modem. It is also extremely reliable -- much more reliable than an analog modem. Depending on what they are doing, a T1 line can generally handle quite a few people. For general browsing, hundreds of users are easily able to share a T1 line comfortably. If they are all downloading MP3 files or video files simultaneously it would be a problem, but that still isn't extremely common.
A T1 line might cost between $1,000 and $1,500 per month depending on who provides it and where it goes. The other end of the T1 line needs to be connected to a web server, and the total cost is a combination of the fee the phone company charges and the fee the ISP charges.
A large company needs something more than a T1 line. The following list shows some of the common line designations:
  • DS0 - 64 kilobits per second
  • ISDN - Two DS0 lines plus signaling (16 kilobytes per second), or 128 kilobits per second
  • T1 - 1.544 megabits per second (24 DS0 lines)
  • T3 - 43.232 megabits per second (28 T1s)
  • OC3 - 155 megabits per second (84 T1s)
  • OC12 - 622 megabits per second (4 OC3s)
  • OC48 - 2.5 gigabits per seconds (4 OC12s)
  • OC192 - 9.6 gigabits per second (4 OC48s)

How Broadband Over Powerlines Works  

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How Broadband Over Powerlines Works

by Robert Valdes
Browse the article How Broadband Over Powerlines Works
Introduction to How Powerline Broadband Works

Photo courtesy Morguefile
An emerging technology may be the newest heavy hitter in the competitive world of broadband Internet service. It offers high-speed access to your home through the most unlikely path: a common electrical outlet.
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, andmodems, 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.

If you think broadband is amazing, then click here to learn how wireless mesh networks work.
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.
In the next sections, we'll learn about the technology behind both In-House and Access BPL.
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 orcable 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.
In the next section, you'll learn the basics about the different approaches.
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.
BPL Retailers
For a complete list of third party products that support BPL, seeHomePlug-certified Products. 
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 next section, we will see how the data moves around once it reaches the house.
The Last Mile
The last mile is the final step that carries Internet into the subscriber's home or office.

Available Now
Current Technologies is offering BPL service in Cincinnati, Ohio, and Rockville, Maryland. 
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. Let's take a look at these modems.
BPL Modems
BPL modems use silicon chipsets specially designed to handle the work load of pulling data out of an electric current. Using specially developed modulation techniques and adaptive algorithms, BPL modems are capable of handling powerline noise on a wide spectrum.

The BPL modem simply plugs into the wall and then into your computer. These modems are capable of speeds comparable to DSL or cable modems.
A BPL modem is plug and play and is roughly the size of a common power adapter. It plugs into a common wall socket, and an Ethernet cable running to your computer finishes the connection. Wireless versions are also available.
While the potential of this new technology is exciting, not everyone is excited about it. In the next section, we'll discuss some of the challenges confronting the implementation of BPL.
Challenges
On April 23, 2003, the FCC put forth a Notice of Inquiry to the public supporting the potential of the BPL technology and seeking to set standards in practice for its implementation. Immediate opposition came from the American Radio Relay League (ARRL) and the Federal Emergency Management Agency (FEMA). Both entities claim that BPL will cause serious interference issues.
A BPL modem is considered an unlicensed device, like a cordless phone or garage door opener. All unlicensed devices are governed by the FCC's Part 15rules. Part 15 mandates that all electronic devices sold in the United States must meet FCC radio-frequency emissions limits. These limits are in place to secure against interference with important transmissions like CB communications, air-traffic control and government channels. ARRL and FEMA are concerned about the interference caused by BPL signals transmitted on exposed medium-voltage power lines.
Cable TV operators get around the interference problem by shielding all of their cables. "Coaxial cable" used by cable TV operators has a braided metal shield that surrounds the signal wire. Telephone cables are also shielded. Power lines, on the other hand, have no shielding. In many cases, a power line is a bare wire, or a wire coated in plastic. The lack of shielding is where the interference concern comes from.
Depending on the bandwidth the FCC allots for BPL, interference with other radio services may be a problem. Currently, the frequency band breaks down as follows:

  • AM radio - 535 kilohertz to 1.7 megahertz
  • Short-wave radio - 5.9 megahertz to 26.1 megahertz
  • Citizens-band (CB) radio - 26.96 megahertz to 27.41 megahertz
  • Television stations - 54 to 88 megahertz for channels 2 through 6
  • FM radio - 88 megahertz to 108 megahertz
  • Television stations - 174 to 220 megahertz for channels 7 through 13
While FEMA is wiling to allow the FCC to seek a compromise, the ARRL claims that compromise is not possible because the bandwidth needed for BPL will directly interfere with ham radio and short-wave radio transmissions. Developers of BPL say that these interference issues have been solved. Only tests and time will tell. Until then, the advancement of BPL moves forward slowly as it waits for standards and logistics to be decided by regulating bodies.

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