Hardware Reference
In-Depth Information
Infrastructure mode is a managed mode. This topology requires one or several
devices to “manage” the network, allowing peers to connect to it (or refuse con-
nection depending on the security settings). Peers do not communicate between
themselves; instead they send their packets to the network management devices:
typically access points. Infrastructure access points often serve as access points
to other networks: typically a wired network or a connection to the Internet.
Multiple access points can be on a wired network, allowing for several zones,
or “hot spots” where peers can connect wirelessly.
Network Parameters
For a network to function, several parameters are required. Imagine an apart-
ment block—several neighbors are within close range. Each family has an
Internet connection, and each family also wants access to wireless for their
laptops, tablets, and mobile phones. Each family also wants their devices to be
private. Instead of creating one large wireless network, each family wants its
own small wireless network. It also wants it to work securely and efi ciently,
while allowing neighbors access to their wireless networks.
Channels
Wi-Fi works with two base frequencies: 2.4 GHz and 5 GHz. However, in prac-
tice, there are several frequencies; the 2.4-GHz band operates from 2.412 GHz
all the way to 2.484 GHz. This spectrum is separated into different frequen-
cies, or channels. If all wireless devices used exactly the same frequency, that
frequency would soon become saturated as small networks started competing
with other networks. Also, Wi-Fi is not the only wireless technology to use
the 2.4 GHz band. For example, Bluetooth also uses these frequencies. To help,
Wi-Fi uses channels.
A channel is a specii c frequency used by one particular wireless network.
Channels work in the same way as your television; information is received
wirelessly and picked up through the TV antenna. By selecting a particular
channel, you decide to listen to one particular frequency in the range, therefore
excluding all other channels. When you i nish watching a program, you can
switch to another channel, receiving the information on one channel at a time.
Wi-Fi channels work almost the same way except that channels can overlap each
other. Each wireless controller (an Internet modem or access point) is coni gured
to use a particular channel. Some analyze the network before initializing and
automatically choose a free channel.
Encryption
Although most people don't think much about it, Wi-Fi presents a problem. You
might be at home, shopping on your favorite Internet site. After you choose the
 
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