How Wi-Fi works..?

Imagine for a moment if all the wireless connections in the world were instantly replaced by cables. You’d have cables stretching through the air from every radio in every home hundreds of miles back to the transmitters. You’d have wires reaching from everycellphone to every phone mast. Radio-controlled cars would disappear too, replaced by yet more cables. You couldn’t step out of the door without tripping over cables. You couldn’t fly a plane through the sky without getting tangled up. If you peered through your window, you’d see nothing at all but a cats-cradle of wires. That, then, is the brilliance of wireless: it does away with all those cables, leaving our lives simple, uncluttered, and free! Let’s take a closer look at how it works.

Photo: A typical wireless router. This one, made by Netgear, can connect up to four different computers to the Internet at once using wired connections, because it has four ethernet sockets. Bbut—in theory—it can connect far more machines using wireless. The white bar sticking out of the back is the wireless antenna.

From wireless to radio

Wireless started out as a way of sending audio programs through the air. Pretty soon we started calling it radio and, when pictures were added to the signal, TV was born. The word “wireless” had become pretty old-fashioned by the mid-20th century, but over the last few years it’s made a comeback. Now it’s hip to be wireless once again thanks to the Internet. By 2007, approximately half of all the world’s Internet users were expected to be using some kind of wireless access—many of them in developing countries where traditional wired forms of access, based on telephone networks, are not available. Wireless Internet, commonly used in systems called Wi-Fi®, WAP, and iMode, has made the Internet more convenient than ever before. But what makes it different from ordinary Internet access?

From radio to Wi-Fi

Artwork showing how antennas transmit and receive radio waves

Radio is an invisible game of throw-and-catch. Instead of throwing a ball from one person to another, you send information, coded as a pattern of electricity andmagnetism, from a transmitter (the thrower) to a receiver (the catcher)—both of which are kinds of antennas. The transmitter is a piece of equipment that turns electrical signals (such as the sound of someone speaking, in radio, or a picture, in TV) into an oscillating electromagnetic wave that beams through the air, in a straight line, at the speed of light (300,000 km 186,000 miles per second). Thereceiver is a mirror-image piece of equipment that catches the waves and turns them back into electrical signals—so we can recreate the radio sounds or TV pictures. The more powerful the transmitter and receiver, the further apart they can be spaced. Radio stations use gigantic transmitters, and that’s why we can pick up radio signals from thousands of miles away on the opposite side of Earth. Wireless Internet is simply a way of using radio waves to send and receive Internet data instead of radio sounds or TV pictures. But, unlike radio and TV, it is typically used to send signals only over relatively short distances with low-power transmitters.

Artwork: The basic concept of radio: sending messages from a transmitter to a receiver at the speed of light using radio waves. In wireless Internet, the communication is two-way: there’s a transmitter and receiver in both your computer (or handheld device) and the piece of equipment (such as a router) that connects you to the Internet.


If you have wireless Internet access at home, you probably have a little box called a router that plugs into your telephone socket. This kind of router is a bit like a sophisticated modem: it’s a standalone computer whose job is to relay connections to and from the Internet. At home, you might use a router to connect several computers to the Internet at once (saving on the need for several separate modems). In other words, the router does two jobs: it creates a wireless computer network, linking all your computers together, and it also gives all your machines a shared gateway to the Internet.

Pie charts showing the vast growth in mobile phone and Internet access between 2000 and 2010

You can connect a router to all your different computers using ordinary network-connecting cables (for the technically minded, these are called RJ-45, Cat 5, or Ethernet cables). This creates what’s called a LAN (local area network) linking the machines together. A computer network is a very orderly affair, more like an organized committee meeting, with carefully agreed rules of behavior, than a free-for-all cocktail party. The machines on the network have to be hooked up in a standard way and they communicate in a very orderly fashion. The rules that govern the network setup and the communication are based on an international standard calledEthernet (also known as IEEE 802.3).

Netgear PCMCIA laptop wireless card

Photo: Left: If your laptop doesn’t have a built-in Wi-Fi card, you can plug in a PCMCIA adapter card like this one. They’re relatively inexpensive, especially if you get them on eBay. But beware: older PCMCIA cards may not support newer forms of wireless security such as WPA.

A wireless router is simply a router that connects to your computer (or computers) using radio waves instead of cables. It contains a very low-power radio transmitter and receiver, with a maximum range of about 90 meters or 300 ft, depending on what your walls are made of and what other electrical equipment is nearby. The router can send and receive Internet data to any computer in your home that is also equipped with wireless access (so each computer on the wireless network has to have a radio transmitter and receiver in it too). Most new laptops come with wireless cards built in. For older laptops, you can usually plug a wireless adapter card into the PCMCIA or USB socket. In effect, the router becomes an informal access pointfor the Internet, creating an invisible “cloud” of wireless connectivity all around it, known as a hotspot. Any computer inside this cloud can connect into the network, forming a wireless LAN. Just as computers connected to a wired LAN use Ethernet, machines on a wireless LAN use the wireless equivalent, which is called Wi-Fi (or, more technically, IEEE 802.11). Wireless Internet is improving all the time, so better forms of Wi-Fi are constantly evolving. You may see wireless equipment marked 802.11a, 802.11b, 802.11g or 802.11n: these are all broadly compatible variants of 802.11, with 802.11g and 802.11a somewhat faster than 802.11b. The latest standard, 802.11n, will be even faster, but is currently still in development.

Wi-Fi is where the expression Wi-Fi hotspot comes from. A Wi-Fi hotspot is simply a public place where you can connect your computer wirelessly to the Internet. The hotspots you find in airports, coffee bars, bookshops, and college campuses use one or more wireless routers to create wireless Net access over a large area. The University of Twente in the Netherlands has one of the world’s biggest hotspots. Using 650 separate access points, it has created a seamless hotspot that covers the entire 140 hectare (350 acre) campus. Cities like Philadelphia have also announced ambitious plans to turn huge areas into hotspots. Wi-Fi hotspots are now popping up all over the world. By 2007, there were estimated to be around 180,000 in the United States alone. As of October 2012, the JWire directory was listing over 793,049 hotspots in 145 countries worldwide.

Charts: Right: There’s been huge worldwide growth in cellphones (mobile phones) and wireless Internet access over the last decade, particularly in developing countries. In 2000, there were 0.7 billion cellphone subscriptions worldwide and 71 percent of them were in high-income (developed) countries. By 2010, there were 5.9 billion subscriptions and 77 percent of them were in developing countries. The implications for Internet access are obvious: more and more people are going online from wireless mobile devices, especially in the developing world. 2012 Information and Communications for Development: Maximizing Mobile, World Bank, 2012.

Wi-Fi rabbits

Karotz/Nabaztag wi-fi rabbit, picture by Violet

Made by Violet and sold under the brand name Karotz (formerly Nabaztag), electronic rabbits are compact computers with Wi-Fi wireless connections that link to the Internet through your home computer network. It’s true that they don’t look like computers, but they have input, output, storage, and memory—so computers is officially what they are. (But their input and output is a little bit unconventional, to say the least.)

They have built-in speech synthesizer chips so they can read out messages to you, their ears (operated by electric motors) can wiggle about to attract your attention, LED lights in their body flash on and off, and microphones in their chests respond to your spoken commands. They also have built-in loudspeakers so they can play MP3 music, podcasts, or other streaming media. Even when your computer is switched off, your rabbit can be online and ready to notify you of incoming emails, messages, or Web pages you’ve asked to be informed about.

In theory, because Wi-Fi rabbits are programmable, networked computers in their own right, you could use them for all kinds of different things. The manufacturers have released details of how to program them (something known as the API or Application Programming Interface), so anyone can write new applications for rabbits at any time. It’s very easy to write your own rabbit programs once you’ve mastered the API.

What can you use a rabbit for?

Your rabbit’s your personal, wireless connection to the online world when you can’t be bothered to go near you computer. There are lots of ideas on how you could use him (or her) on the Karotz website. You can also see how people are using their rabbits in interesting ways by looking at these photos on Flickr.

Are these things just gadgets? Silly, useless toys? Maybe—but they’re making a serious point too by showing us the shape of computers to come. In future, scientists expect computers to operate less like tools that we have to use laboriously and more like autonomous “agents” that we can ask to do things for us. Indeed, the World Wide Web is expected to become much more machine-friendly in future so computers can shuffle through it looking for information all by themselves (this idea is called the Semantic Web). Why sit at a desk booking a hotel room or doing your online shopping when, with a few spoken commands, you could ask your computer to do it all for you? Wi-Fi rabbits may seem frivolous today, but they could be a glimpse of the future—a taste of the computers we’ll all be using tomorrow!

Photo: A Karotz/Nabaztag wireless rabbit. Photo by courtesy of Violet.

WAP and i-mode

Browsing a cellphone with WAP

HSDPA mobile broadband modem or dongle made by ZTE

Wi-Fi isn’t the only way to access the Internet wirelessly. If you have a reasonably new “smartphone” (an advanced kind of cellphone), such as an iPhone or an Android, it’ll have a miniature Web browser that works in exactly the same way as the one you’d find on a laptop (albeit using a much smaller screen). In the late 1990s and early 2000s, some cellphones had very crude built-in web browsers that could haul up simplified, text-versions of web pages using a system called WAP (technically known as Wireless Application Protocol, though no-one ever called it that). WAP was very slow to take off and has now been rendered largely obsolete by faster cellphone networks and smartphones.

While Europe and North America were struggling with WAP, Japan’s cellphone users already had a much better version of cellphone Internet called i-mode that offered fast access to web pages and emails. i-mode was always more popular than WAP and was gradually exported to a number of other countries. However, it too has now been superseded by better technologies based on faster 3G (third-generation) cellphone networks. Effectively, mobile and desktop Internet have now converged: thanks to wireless, it’s almost as easy to do things on your cellphone or tablet computer as it is on your desktop PC.

Photo: Left Mobile broadband with a USB modem is an increasingly popular form of wireless Internet.

Photo: Right: State-of-the-art Web browsing c.2002 on an old-fashioned cellphone! This phone is using WAP to browse breaking news on a website called Ananova. Note the crude, monochrome text-only screen. What you can’t see here is the grindingly slow speed, which was about 5 times slower even than old-fashioned, dialup Internet access.

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.

How to secure a home wireless network

Ethernet networking cable in close-up

If you’ve set up your home wireless network, you’ve probably noticed something: your neighbors have all got them too! Not only that, you could quite easily connect to someone else’s network if it weren’t secured properly—and by the same token, they could connect to your network too. So how do you secure a network? We suggest:

  • Make sure you secure your network (with what’s called a pre-shared key or PSK). Use the strongest form of security your hardware supports: use WPA2 rather than WPA and use WPA in preference to WEP.
  • Choose a nontrivial password (and certainly not something your neighbors could easily guess, like your surname). At the very least, if you’re going to use an easy-to-remember password, put a special character ($, %, and so on) at the beginning or the end of it—you’ll make it vastly more secure.
  • Set up your network to use an access control list (ACL). This is a list of specific, trusted computers that will be allowed to connect to your network. For each computer on the list, you’ll need to specify what’s called its MAC address (or LAN MAC address). You’ll find the MAC address written on the bottom of a laptop computer, round the back of a desktop, or on the bottom of a plug-in PCMCIA network card.
  • If you have only one computer and it never moves from your desktop, which is reasonably close to your router, don’t use wireless at all. Connect with an Ethernet cable instead and use your network in wired mode. It’ll be faster as well as more secure.
  • You could make your network a “hidden” one (in other words, so the network name (SSID) is not broadcast). Only people who know the network name can connect by typing in the correct SSID and password. Hidden networks can sometimes be a bit erratic if you use Windows XP and Microsoft’s default networking software, but they work fine with most other systems. Opinions vary on whether hidden networks do anything for security. Some people claim they are more secure; others say they have security risks.

A brief history of wireless

Guglielmo Marconi.

  • 1888: German physicist Heinrich Hertz(1857–1894) makes the first electromagnetic radio waves in his lab.
  • 1894: British physicist Sir Oliver Lodge (1851–1940) sends the first message using radio waves in Oxford, England.
  • 1899: Italian inventor Guglielmo Marconi (1874–1937) sends radio waves across the English Channel. By 1901. Marconi has sent radio waves across the Atlantic, from Cornwall in England to Newfoundland.
  • 1940s: Taxi firms begin using two-way radios.
  • 1970s: First analog cellphones appear, developed in Chicago by Illinois Bell and AT&T.
  • 1980s: GSM (Global System for Mobile communications) digital cellphones appears in Europe, followed by PCS (Personal Communications Services) phones in the United States.
  • 1994: Nokia, Finnish cellphone maker, sends data over a cellphone network.
  • 1994: develops WAP in the United States.
  • 1997: Wi-Fi standard (IEEE 802.11) is agreed internationally.
  • 1999: Japanese telecommunications company NTT DoCoMo develops i-mode.
  • 2007: Apple Computer releases its iPhone—tilting the balance of power from desktop PCs and wired Internet to mobile devices and wireless Internet.

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Jeffry is a Mechanical Engineer by education and an aspiring writer and blogger. After working hard for around 12 hours a day on his core job, he spends his remaining time in blogging and reading articles online. And he loves to make poor jokes, so be prepared.

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