Open Communication
the need for transceivers that comply
with all three standards (a/b/g). If you
truly want mobility and the ability to
connect to anything available, you
need an adapter that handles all of
them and switches automatically. An
example of a chipset that does all
three is Agere', as shown in Figure 3.
But that's not all. The IEEE just
recently approved a study group to
develop the next version of the standard. Tentatively designated 802.11n,
this new standard which won't be
available for a few years promises
data rates from 108 to 320 Mbps.
im solution called the Wi-Fi Protected
Access (WPA). Both of these are
included in most transceivers.
The IEEE has also developed new
security techniques under its 802.11i
standard for encryption and 802.11x
for authentication. If that is not
enough, many companies have implemented virtual private networks
(VPNs), a popular technique for
securing the transmission of data over
the Internet, to handle their wireless
networks. So, while security is an
issue, there are many solutions for
those who want and need to send sensitive data over their WLAN.
Critical Issue
If WLANs are so great, why isn't
everyone using them? The answer to
that question is usually one word:
security. Almost anyone can pick up a
wireless signal. With a sensitive
receiver and a directional antenna,
you can easily eavesdrop on almost
any WLAN. If you are transmitting
sensitive information, this is not
something you want to take a chance
on. There have been numerous examples of hackers sitting in a parking lot
of a major retailer stealing credit card
numbers from the 802.11b-based
cash registers and credit card
scanners.
The creators of the 802.11 standard anticipated the security problem
and provided for encryption. Known
as Wireless Equivalent Protocol
(WEP), this capability is built into
every Wi-Fi chipset. It does provide a
minimum data encryption process
that can protect most information.
WEP is not turned on automatically,
meaning the user has to enable it.
For that reason, most users don't use
it. It is rarely used in home networks
or at hot spots. Many companies do
not enable it despite their need for
security.
WEP has also proven to be vulnerable to hacking. Some Wi-Fi
vendors, like Cisco, have come up
with their own security/encryption
measures like the Temporal Key
Integrity Protocol (TKIP). The Wi-Fi
Alliance developed an improved inter-
FEBRUARY 2004
Antennas: The Key
to a Successful
WLAN
While the reliability of a wireless
connection depends on a variety of
factors, many of them are beyond
your control. Transmitter power is
one. With most units you get the maximum allowable power, usually 100
m W. Next is AP location. You can control this to some extent. You should
place your AP high and in the clear so
it sees as many of the remote nodes
as possible. If possible, experiment
with the location of the access point
for best overall results. In some cases,
you may find that you need more than
one access point. This is especially
true in large companies with lots of
employees and space to cover.
A real help for those installing
multiple APs is the IEEE’s newly
approved 802.3af standard, also
called Power over Ethernet (PoE).
This standard provides a way to send
a DC voltage over the standard CAT5
or CAT6 twisted pair Ethernet cable.
In this way, the AP does not need a
separate AC or DC power source
which can be a problem in placing an
AP in an optimum location. Most of
the newer access points now come
with PoE capability.
One thing you do have control
over in your AP is your antennas.
While all access points and wireless
adapters come with an antenna,
sometimes you have a choice. Select
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