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A wireless broadband Netgear router

Broadband Internet

by Chris Woodford. Last updated: August 14, 2016.

If you're still using a dial-up modem to access the Internet, switching over to broadband (fast, always-on Internet access) will seem like nothing short of magic. Not only does your Internet access become many times faster, but you can use your telephone line at the same time as well (something you can never do with dialup). Broadband sweeps you from the dirt tracks to the freeway—and leaves the 21st-century information age lying at your feet! But how exactly does it get so much more Internet power from exactly the same piece of telephone cable?

Photo: A typical broadband modem made by Netgear: the piece of equipment that lets your computer make a broadband connection to the Internet. The long white bar sticking out of the back is a wireless antenna (aerial).

Telephones were never made for the Net

Before the Internet came along, the world of computing was a very different place. There were far fewer computers and they worked mostly in isolation or in small networks known as LANs (local area networks). The Internet has increased the power of people's computers many times by allowing all these machines to talk to one another and exchange information via such things as e-mail and file sharing. You might wonder where the Internet came from; it seemed to take off virtually overnight. In fact, the vital piece of infrastructure on which the Net is built was already in place and had been invented back in the 1860s. I'm referring, of course, to the telephone system.

When Alexander Graham Bell and others pioneered telephones in the 19th century, their idea was to help people talk to one another over long distances in "real-time." Although telephone equipment was designed for carrying sounds, it gradually became obvious that the technology had many other uses. During the late 20th century, for example, many people started using a technology called fax (facsimile), which transmits printed documents between two electronic machines, one at either end of a telephone line. When computer networks began to take off in the 1970s, it was perfectly natural to use the telephone system to connect them together. But this created an immediate problem: computers exchange information (data) in a number-based form known as digital, whereas the telephone system had always been designed to handle rapidly changing sound waves or analog information. How could computers and telephones be made to understand each other?

A pair of dialup modems

Photo: A pair of old-style dialup modems. The dark box on the bottom is a typical 56K dialup modem from the 1990s. On top is a 56K credit-card-sized PCMCIA modem for use in a laptop.

How dial-up Internet works

The answer turned out to be surprisingly simple. If you go on holiday to a foreign country where you can't speak the language, you have two choices. One is to shout, wave your hands around, and point excitedly. A much better option is to get yourself a translator, who can convert your words smoothly and seamlessly back and forth into the foreign language. This second approach is the one that computers use when they want to exchange information over the old-fashioned telephone network. But instead of using a translator, they use an electronic "translating" device called a modem.

A modem (which is short for modulator-demodulator) takes the digital information that your computer generates and turns it into analog information (up and down, constantly varying sound waves) that can travel along the telephone network to another computer somewhere else. At that other location, there is another modem that converts the incoming analog information back into digital data that the other computer can understand. Two computers can have a lengthy conversation over the phone, just like two people chatting away, providing there is a modem at each end of the line to translate the digital information they generate into analog signals that can travel back and forth along the telephone line. (Incidentally, if you're uncertain about the difference between analog and digital, we have a simple article about analog versus digital technology.)

When you dial into the Internet, what you are actually doing is using a modem and telephone line to make a semi-permanent connection into a much larger computer network. As your computer dials in, it sends digital information down the telephone line to a modem at your Internet service provider (ISP). Once your modem is talking to the ISPs modem, your computer can use the ISP's computer to access other computers all over the Internet. Every time you browse a web site, your computer is making a link to another computer somewhere else on the planet using your ISP's computer as a stepping stone.

How is broadband Internet different from dial-up?

Dial-up is a really inefficient way of linking to the Internet. When you dial in, your computer telephones your ISP's computer and then hogs the line for the duration of the call (in other words, for as long as you're online). No-one can call you on the phone while you're online. And even though your computer is hogging the entire line, your modem and the ISPs modem exchange information at very low speeds—at best, approximately 56Kbps (roughly 56,000 bits or binary ones and zeros) per second. If you're trying to download MP3 music tracks or digital photos, you'll know this is grindingly slow and tedious. A single music track can take half an hour or more to download.

Diagram showing how ADSL broadband and dialup compare in how they send data down a telephone line.

Broadband works a completely different way. Instead of treating your phone line as a single, narrow pipe between your computer and the ISP's computer, like a dialup connection, it divides the line into many different channels. Information can travel in parallel streams down these channels. It's like dividing a highway into several lanes: lots more traffic can go down it in parallel than down a single-lane road. This is why broadband is so much faster than dialup. Even a slowish broadband line, working at 512Kbps, is about nine times faster than the best dialup connection, while a moderately fast broadband line, working at around 8MBps (megabits per second), can be over 100 times quicker!

Most people download far more information than they upload (browsing web pages is almost exclusively downloading—because most of the data is flowing into your computer from the Net), so broadband allocates more channels to downloading than to uploading. This is why broadband computers download several times faster than they upload. In other words, downloading and uploading are not equivalent or "symmetrical" processes: they are asymmetric. That's why the technical name for this type of broadband is Asymmetric Digital Subscriber Line or ADSL. Another type of broadband called DSL allows uploading and downloading at the same speed.

If most people are just downloading, why doesn't broadband Internet scrap the uploading channels altogether and make browsing even faster? Any type of web browsing involves a certain amount of two-way traffic between your computer (which is called a client) and the remote computers (servers) that host the pages you're looking at. Even though most of the data is flowing into your computer, a certain amount still has to flow in the opposite direction each time your computer requests a new page. In other words, even when all you're apparently doing is downloading, there's some uploading going on in the background to make that happen.

That just leaves one more question: how can you talk on the phone while your computer is simultaneously sending and receiving data? Simple. Some of the channels on the line are reserved for phone calls. People's voices use relatively low-frequency sounds, compared to the higher-frequency signals that computer modems use, so it's relatively easy to keep the phone signals separate from the computer data.

Artwork: Dialup and broadband use the same phone line, but broadband uses it much more efficiently. Where dialup sends only one voice or data signal down one channel, broadband divides the line into multiple channels, each of which can send data in parallel. Most channels (red) are used for downloading; a few are reserved for uploading (blue). You can also have a phone conversation at the same time (using the green channel).

What is fiber-optic broadband... and is it the future?

Simulated image showing light emerging from a fiber-optic cable

Photo: Fiber optics involves sending digital signals encoded in light beams down strands of glass or plastic. (Simulated image.)

Telephone lines were never designed to carry computer data. The history of the Internet is, in part, a struggle to shake off obsolete telephone technology.

There's obviously a limit to how fast your broadband Internet connection can be if it's still largely based on copper-wire technology dating back to the 19th century! If you're lucky enough to live in an urban area where telephone calls and TV programs flow along fiber-optic cables, you'll probably find cable broadband is the fastest form of Internet you can get—and many times faster than landline broadband.

Fiber-optic broadband cabinet.

In some countries, telephone operators are now gradually rolling out what's called fiber-optic broadband, which promises much faster connections than traditional broadband but still essentially over the ordinary public telephone network: "much faster" means download speeds of up to 40Mbps (typically 10–20 times faster) and upload speeds of 1–10Mbps (2–20 times faster). But it's still a compromise. For most people, what they'll actually be using is a system called Fiber To The Cabinet (FTTC) (sometimes called Fiber to the Curb), which means there's a fiber-optic connection all the way from the local exchange to a "cabinet" (switching box) somewhere in your street or neighborhood (usually within 0.5km or so of your home)—but the connection from the cabinet to your home is still (you guessed it) that slow old copper cable! Only if you have a Fiber To The Building (FTTB) or Fiber To The Home (FTTH) connection, with fiber-optic cable running all the way, will you truly experience the benefits of mega-fast Internet.

So will we all enjoy fast fiber-optic broadband access in future? Possibly not. Now that cellphone networks can compete effectively with wired telephone networks, it's much more cost-effective to deliver mobile broadband to people in remote areas than to refit the entire, antiquated, public telephone network; that's why people in developing countries are enjoying growing Internet access through cellphones rather than through ordinary landline telephones (which they never had and probably never will have). As cellphone networks become ever more sophisticated and computers and phones continue to converge, it's likely many people will abandon wired landlines and wired broadband altogether in favor of increasingly sophisticated wireless Internet.

Photo: Fiber To The Cabinet (FTTC) means you get fiber cabling as far as your local curbside telephone cabinet. This is mine! The rest of the distance to your home is handled by more conventional cabling.

What's involved in switching from dial-up to broadband?

If you're currently a dialup Internet user and you want to switch to broadband instead, you'll need some slightly different equipment. First, you'll need to have your telephone line tested and upgraded to broadband. This is a simple process that your ISP will arrange when you order broadband for the first time.

An ADSL microfilter

Next, you'll need a new ADSL modem or router to connect your computer to your ISP's broadband system. An ADSL modem looks much like a dialup modem and simply allows one computer to make one broadband connection. Think of it as a translator plugged into your computer, just like a dialup modem. A router is slightly different. It looks similar to a modem, but it's a self-contained little computer whose job is to act as a go-between: it links your home network to the outside world. Most routers let you plug several different computers (and other things like printers) into them. So if you have five PCs at home that all need Internet access, you can use one router instead of five separate modems. You can connect a computer to a router in two ways, either by plugging it in with a cable or by making a wireless (Wi-Fi) connection. To make a wireless connection, both your router and your computer need to be capable of wireless networking (they must have wireless networking cards, aerials, and so on).

If you intend to use your telephone at the same time as your broadband Net connection, you'll need some little plastic boxes called microfilters. As their name suggests, they filter out the broadband traffic so you don't hear it screeching away in your ear when you're making a phone call. How do they work? Remember up above where we were talking about the separate broadband channels? Broadband data channels use higher frequencies than human voice channels, so it's relatively easy to separate the two with electronic filters that allow only certain frequencies through. Microfilters simply block the high-frequency sounds that carry your Internet data and stop it from getting through to your telephone.

Photo: An ADSL microfilter splits the incoming phone line into two parts, one for broadband Internet and the other for your phone. The incoming phone line plugs into the left side. The outgoing ADSL modem and telephone lines plug into the right side.

Who invented broadband Internet?

Search for that question online and you'll find a plethora of suggestions, ranging from Alexander Graham Bell (developer of the telephone) and Claude Shannon (father of information theory) to Robert Metcalfe (the inventor of Ethernet) and Tim Berners-Lee (pioneer of the World Wide Web). In fact, as with other notable technologies such as cars and computers, it's almost impossible to credit broadband to a single inventor: I'd suggest it was a collective effort. If you trawl through records of inventions at the US Patent and Trademark Office, you'll find a whole series of patents covering simultaneous use of telephone lines for voice and data (the essence of broadband). Among the earliest were patents filed by Teltone's John D. Foulkes and Stephen Brolin et al of Bell Labs. DSL, the concept we'd recognize as broadband today—defined as "the transmission of high-speed digital signals between a telephone central office and the customer premises"—dates from 1986 and was formally patented in 1990 by Richard D. Gitlin et al of AT&T (currently Distinguished University Professor of Electrical Engineering at the University of South Florida).

What's mobile broadband?

If you want to find out more about high-speed mobile, wireless broadband (broadband Internet access using a USB modem to connect to a cellphone network), please see our separate article on mobile broadband.

Bar chart comparing maximum fixed-line broadband speeds in 20 different countries.

Chart: Broadband speed varies dramatically both within countries and between them. Here are typical, maximum, fixed-line broadband speeds for 20 representative countries around the world, from Ireland (100 Mbit/s) to Vanuatu (256 kbps). Source: Drawn using 2014 data from Table 4.1 of the Executive Summary of Measuring the Information Society 2015, International Telecommunication Union (ITU).

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Text copyright © Chris Woodford 2006, 2016. All rights reserved. Full copyright notice and terms of use.

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Woodford, Chris. (2006) Broadband Internet. Retrieved from http://www.explainthatstuff.com/howbroadbandworks.html. [Accessed (Insert date here)]

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