What
Is WiFi?
A wireless network uses
radio waves, just like cell phones, televisions and radios do. In fact, communication across a wireless network is a lot like two-way radio communication. Here's what happens:
radio waves, just like cell phones, televisions and radios do. In fact, communication across a wireless network is a lot like two-way radio communication. Here's what happens:
1.
A computer's wireless
adapter translates data into a radio signal and transmits it using an antenna.
2.
A wireless router
receives the signal and decodes it. The router sends the information to the
Internet using a physical, wired Ethernet connection.
The process also works in reverse, with the
router receiving information from the Internet, translating it into a radio
signal and sending it to the computer's wireless adapter.
The radios used for WiFi communication are
very similar to the radios used for walkie-talkies, cell phones and other
devices. They can transmit and receive radio waves, and they can convert 1s and 0s into radio waves and convert the radio waves back into 1s
and 0s. But WiFi radios have a few notable differences from other radios:
·
They transmit at
frequencies of 2.4 GHz or 5 GHz. This frequency is considerably higher than the
frequencies used for cell phones, walkie-talkies and televisions. The higher
frequency allows the signal to carry more data.
·
They use 802.11
networking standards, which come in several flavors:
·
802.11a transmits at 5 GHz and can move up to 54
megabits of data per second. It also usesorthogonal frequency-division
multiplexing (OFDM), a more efficient coding technique that splits
that radio signal into several sub-signals before they reach a receiver. This
greatly reduces interference.
·
802.11b is the slowest and least expensive
standard. For a while, its cost made it popular, but now it's becoming less
common as faster standards become less expensive. 802.11b transmits in the 2.4
GHz frequency band of the radio spectrum. It can handle up to 11 megabits of
data per second, and it usescomplementary code keying (CCK)
modulation to improve speeds.
·
802.11g transmits at 2.4 GHz like 802.11b, but
it's a lot faster -- it can handle up to 54 megabits of data per second.
802.11g is faster because it uses the same OFDM coding as 802.11a.
·
802.11n is the most widely available of the
standards and is backward compatible with a, b and g. It significantly improved
speed and range over its predecessors. For instance, although 802.11g
theoretically moves 54 megabits of data per second, it only achieves real-world
speeds of about 24 megabits of data per second because of network congestion.
802.11n, however, reportedly can achieve speeds as high as 140 megabits per second.
802.11n can transmit up to four streams of data, each at a maximum of 150
megabits per second, but most routers only allow for two or three streams.
·
802.11ac is the newest standard as of early 2013.
It has yet to be widely adopted, and is still in draft form at the Institute
of Electrical and Electronics Engineers (IEEE), but devices that support it
are already on the market. 802.11ac is backward compatible with 802.11n (and
therefore the others, too), with n on the 2.4 GHz band and ac on the 5 GHz
band. It is less prone to interference and far faster than its predecessors,
pushing a maximum of 450 megabits per second on a single stream, although
real-world speeds may be lower. Like 802.11n, it allows for transmission on
multiple spatial streams -- up to eight, optionally. It is sometimes called 5G
WiFi because of its frequency band, sometimes Gigabit WiFi because
of its potential to exceed a gigabit per second on multiple streams and
sometimes Very High Throughput (VHT) for the same reason.
·
Other 802.11 standards
focus on specific applications of wireless networks, like wide area networks
(WANs) inside vehicles or technology that lets you move from one wireless
network to another seamlessly.
·
WiFi radios can
transmit on any of three frequency bands. Or, they can "frequency
hop" rapidly between the different bands. Frequency hopping helps reduce
interference and lets multiple devices use the same wireless connection
simultaneously.
As long as they all have wireless adapters,
several devices can use one router to connect to the Internet. This connection
is convenient, virtually invisible and fairly reliable; however, if the router
fails or if too many people try to use high-bandwidth applications at the same
time, users can experience interference or lose their connections. Although
newer, faster standards like 802.11ac could help with that.
Next, we'll look at how to connect to the
Internet from a WiFi hotspot.
WiFi
Hotspots
A WiFi hotspot is simply an area with an accessible wireless network. The term is most often used to refer to wireless networks in public areas like airports and coffee shops. Some are free and some require fees for use, but in either case they can be handy when you are on the go. You can even create your own mobile hotspot using a cell phone or an external device that can connect to a cellular network. And you can always set up a WiFi network at home.
If you
want to take advantage of public WiFi hotspots or your own home-based network,
the first thing you'll need to do is make sure your computer has the right
gear. Most new laptops and many new desktop computers come
with built-in wireless transmitters, and just about all mobile devices are WiFi
enabled. If your computer isn't already equipped, you can buy a wireless adapter that plugs into the PC card slot or USB port. Desktop computers can use USB
adapters, or you can buy an adapter that plugs into the PCI slot inside the
computer's case. Many of these adapters can use more than one 802.11 standard.
Once
you've installed a wireless adapter and the drivers that allow it to operate,
your computer should be able to automatically discover existing networks. This
means that when you turn your computer on in a WiFi hotspot, the computer will
inform you that the network exists and ask whether you want to connect to it.
If you have an older computer, you may need to use a software program to detect
and connect to a wireless network.
Being
able to connect to the Internet in public hotspots is extremely convenient.
Wireless home networks are
convenient as well. They allow you to easily connect multiple computers and to
move them from place to place without disconnecting and reconnecting wires. In
the next section, we'll look at how to create a wireless network in your home.
Building a Wireless Network
1.
A port to connect to
your cable or DSL modem
2.
A router
3.
An Ethernet hub
4.
A firewall
5.
A wireless access
point
A wireless router allows you to use wireless
signals or Ethernet cables to connect your computers and mobile devices to one
another, to a printer and to the Internet. Most routers provide coverage for about 100 feet (30.5 meters)
in all directions, although walls and doors can block the signal. If your home
is very large, you can buy inexpensive range extenders or repeaters to increase
your router's range.
As with wireless adapters, many routers can
use more than one 802.11 standard. Normally, 802.11b routers are slightly less
expensive than others, but because the standard is older, they're also slower
than 802.11a, 802.11g, 802.11n and 802.11ac routers. 802.11n routers are the
most common.
·
The
name of the network, known as its service set identifier (SSID) -- The default setting is usually the
manufacturer's name.
·
The
channel that the router uses -- Most routers use channel 6 by default. If you live in
an apartment and your neighbors are also using channel 6, you may experience
interference. Switching to a different channel should eliminate the problem.
·
Your
router's security options --
Many routers use a standard, publicly available sign-on, so it's a good idea to
set your own username and password.
Security is an important part of a home
wireless network, as well as public WiFi hotspots. If you set your router to
create an open hotspot, anyone who has a wireless card will be able to use your
signal. Most people would rather keep strangers out of their network, though.
Doing so requires you to take a few security precautions.
It's also important to make sure your security
precautions are current. The Wired Equivalency Privacy (WEP) security measure
was once the standard for WAN security. The idea behind WEP was to create a
wireless security platform that would make any wireless network as secure as a
traditional wired network. But hackers discovered vulnerabilities in the WEP
approach, and today it's easy to find applications and programs that can
compromise a WAN running WEP security. It was succeeded by the first version of
WiFi Protected Access (WPA), which uses Temporal Key Integrity Protocol (TKIP)
encryption and is a step up from WEP, but is also no longer considered secure.
To keep your network private, you can use one
or both of the following methods:
·
WiFi
Protected Access version 2 (WPA2)
is the successor to WEP and WPA, and is now the recommended security standard
for WiFi networks. It uses either TKIP or Advanced Encryption Standard (AES)
encryption, depending upon what you choose at setup. AES is considered the most
secure. As with WEP and the initial WPA, WPA2 security involves signing on with
a password. Public hotspots are either open or use any of the available
security protocols, including WEP, so use caution when connecting away from
home. WiFi Protected Setup (WPS), a feature that ties a hard-coded PIN to the
router and makes setup easier, apparently creates a vulnerability that can be
exploited by hackers, so you may want to turn off WPS if possible, or look into
routers that do not have the feature.
·
Media
Access Control (MAC) address
filtering is a little different from WEP, WPA or WPA2. It doesn't use a
password to authenticate users -- it uses a computer's physical hardware. Each
computer has its own unique MAC address. MAC address filtering allows only
machines with specific MAC addresses to access the network. You must specify
which addresses are allowed when you set up your router. If you buy a new
computer or if visitors to your home want to use your network, you'll need to
add the new machines' MAC addresses to the list of approved addresses. The
system isn't foolproof. A clever hacker can spoof a MAC
address -- that is, copy a known MAC address to fool the network that the computer
he or she is using belongs on the network.
You can also change other router settings to
improve security. For instance, you can set it to block WAN requests to keep
the router from responding to IP requests from remote users, set a limit to the
number of devices that can connect to your router and even disable remote
administration so that only computers plugged directly into your router can
change your network settings. You should also change the Service Set Identifier
(SSID), which is your network name, to something other than the default so that
hackers can't immediately tell what router you are using. And selecting a
strong password never hurts.
Wireless networks are easy and inexpensive to
set up, and most routers' Web interfaces are virtually self-explanatory. For
more information on setting up and using a wireless network,
Lots
More Information
Author's Note: How WiFi Works -- Bernadette
Johnson
I worked on an update to the
content of this article, and I think it's amazing that in a few scant years
we've gone from mostly wired to mostly wireless data transfer, via WiFi in our
homes and public places, as well as cell phones. Of course, a lot of the
infrastructure still uses wires, but the fact that we can communicate via both
radio waves and electricity traveling through wires is pretty incredible. A big
thanks to the inventors of the telegraph and every communication innovation
that came after.
I remember the days when most mere mortals didn't have modems
and couldn't get on the net, even if they had computers. Perhaps I'm projecting
my experiences onto everyone else, but when I was a kid, our computer was this
tool we used in isolation, save for the times friends would come over to play
video games. My computer programmer aunt was the only person I knew who had a
modem. It was the type where you put your phone directly onto a cradle and some
crazy analog communication went on.
When modems became widespread, they were still these clunky
external things that we hooked up to our computers to noisily and slowly dial
up to a larval Internet. They tied up the phone line, so you couldn't keep them
connected indefinitely, and if you didn't want to run up an astronomical phone
bill you had to make sure you were using a phone number for a local access
point. Modems went internal and got a bit faster, but now dial-up is going the
way of the dodo bird due to the ubiquity of affordable broadband services in
the home like DSL and cable.
With an astounding jump in bandwidth, and the ability of our
computers to connect wirelessly, many of us are online all the time, and free
to compute all over the house or even away from home. I've surfed the net,
streamed shows and downloaded books while on vacation via hotel, airport and
other hotspots. And I fall asleep nightly streaming Netflix on my WiFi-only
tablet at home. Which is great, aside from the fact that I really should be
resting. But insomnia and information overload are topics for another time.
Related Articles
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