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Wireless LAN Overview:
PRO/Wireless LAN Mini PCI Adapter User's Guide
About Wireless LAN Technology
A wireless network connects computers without using network cables.
Computers use radio communications to send data between each other.
You can communicate directly with other wireless computers, or connect
to an existing network through a wireless access point. When you set up
your wireless adapter, you select the operating mode for the kind of wireless
network you want. Y
ou
can use your Intel wireless adapter to connect to other similar
wireless devices that comply with the 802.11b standard for wireless networking.
Choosing a Wireless LAN Mode
Wireless LANs can operate with or without access points, depending on the number of users in the
network. Infrastructure mode uses access points to allow wireless computers to send and receive information.
Wireless computers transmit to the access point, the access point receives the information and rebroadcasts
it to other computers. The access point can also connect to a wired network or to the Internet.
Multiple access points can work together to provide coverage over a wide area.
Peer-to-Peer mode, also called Ad Hoc mode, works without access points and allows wireless computers to send
information directly to other wireless computers. You can use Peer-to-Peer mode to
network computers in a home or small office or to set up a temporary wireless network for a meeting.
Configuring a Wireless LAN
There are three basic components that must be configured for an
802.11b wireless LAN to operate properly:
- Network Name—Each wireless network uses a unique Network Name to identify the network.
This name is called the Service Set Identifier (SSID). When you set up
your wireless adapter, you specify the SSID. If you want to connect to an existing network, you must
use the name for that network. If you are setting up your own network you can make up your own name
and use it on each computer. The name can be up to 32 characters long and contain letters and numbers.
- Profiles—When you set up your computer to access a wireless network,
In
telŪ
PROSet creates a profile for the wireless settings that you specify. If
you want to connect to another network, you can scan for existing networks
and make a temporary connection, or create a new profile for that network.
After you create profiles, your computer will automatically connect
when you change locations.
Security—The 802.11b wireless networks use encryption to help protect your data.
Wired equivalent privacy (WEP) uses a 64-bit or 128-bit shared encryption key to scramble
data. Before a computer transmits data, it scrambles the data using the
secret encryption key. The receiving computer uses this same key to unscramble
the data. If you are connecting to an existing network, use the encryption key
provided by the administrator of the wireless network. If you are setting up your own
network you can make up your own key and use it on each computer.
Identifying a Wireless Network
Depending on the size and components of a wireless LAN, there are many ways to identify a wireless LAN:
- The Network Name or Service Set Identifier (SSID)—Identifies a wireless network.
All wireless devices on the network must use the same SSID.
- Extended Service Set Identifier (ESSID)—A special case of SSID used to identify
a wireless network that includes access points.
- Independent Basic Service Set Identifier (IBSSID)—A special case of SSID
used to identify a network of wireless computers configured to communicate directly with one another
without using an access point.
- Basic Service Set Identifier (BSSID)—A unique identifier for each wireless device.
The BSSID is the Ethernet MAC address of the device.
- Broadcast SSID—An access point can respond to computers sending probe packets with
the broadcast SSID. If this feature is enabled on the access point, any wireless user can
associate with the access point by using a blank (null) SSID.
Surveying the Site of Your Wireless LAN
Conducting a site survey for your wireless LAN is
the most crucial step in the process of setting up a wireless network. It greatly
reduces the amount of troubleshooting you will have to do once you have the
wireless LAN set up and ready for connection testing. To conduct a site survey,
you will need the following tools:
- An access point (or laptop computer) that is set up to be the
transmitter. It should be mounted near and at the same height as
the designated location of your wireless LAN.
- A laptop that will act as the mobile receiver. It must contain
your site survey software.
- An area or building map, which will be used to plot the strength
of your signals.
Once you have the tools you need, you are ready to survey the
inside of the building. Launch the site survey software on the mobile
receiver laptop and carry it around in the intended wireless LAN area
to test the signal strength. Be sure to also check the signal strength
of each intended access point location. If you encounter problems
while surveying the site, make sure your transmitter laptop is not
located on a wall containing metal, such as an air-conditioning duct,
which will interfere with the range of your signal. Simply move the
transmitter and test the signal strength again. For users to have
seamless coverage when moving from access point to access point, the
signal levels at each point must overlap. There is software available
that will seamlessly hand off changing signal levels from one access
point to another. Y
our building's infrastructure can sometimes interfere with the
microwave signal, but finding the location and cause of the
interference will allow you to figure out the best place to mount your
access points for optimal area coverage. Microwave signals travel in
all directions, which means there is one access point for a
multi-floor building. However, the range is highly dependent on the
material used to construct the flooring, especially metal materials.
Once your signal strength is strong inside the building, you are ready
to check the strength outside the building. To do so, simply carry the
mobile receiver laptop as far down the street or around the building
as you can go without losing significant signal strength.
If possible, you should be aware of the types of networks being
used by the companies on the floors above and below you, so that you
can work together in harmony. With wireless networks, security is very
important and if you communicate with those around you, you are better
prepared to select the right channels, as well as the best location
for access points.
Factors Affecting Range
Although access points can transmit signals up to 60 feet away in an area with
many walled barriers or as much as 500 feet away in a large open area, the
range is affected by the following factors:
- Building materials, such as steel and drywall, can shorten the range of
the radio signals.
- Physical layout of the area can interfere with the signals and cause them
to be dropped.
- Electronic noise from cell phones, microwave ovens, or other devices on
the same frequency can interfere with the transmission of the signals.
- Range is inversely proportional to data rate, so the faster that the signals
are sent, the less distance they will travel.
Taking these factors into consideration when you survey the site for your WLAN
is key to providing all of your users with undisturbed mobile connectivity.
Using multiple access points will, of course, reduce the impact of these factors
if your area has dividing walls throughout.
What is a Site Survey?
A site survey is an in-depth examination and analysis of a proposed wireless LAN
site. The purpose of a site survey is to determine the number of access points
needed, the types of antennas needed, and the best placement for those access points and antennas. Although the goal of a site survey is simple, the means of arriving at that
goal are not. Some of the steps involve taking measurements, but most
involve experience, trial and error, and a little guesswork rather than
numbers and figures.
When to Perform a Site Survey
Intel® recommends that you perform a site survey prior to installing a
wireless LAN. Site surveys are especially important when:
- You are installing a new site — Evaluate the placement of the
access points and antennas throughout the proposed site.
- You are changing an existing site — When modifying or extending
an existing network structure, re-evaluate the placement of the access points
and antennas. If you need a different level of coverage in some areas, you
may need to move, replace, or supplement access points and antennas.
- You are physically changing the site — Remodeling may introduce
new sources of interference, such as motors and metal structures within the
coverage area of the access point, even if it does not directly effect the
sites where the access points are located.
Elements of an Effective Site Survey
An effective site survey requires three elements. Failure to commit the appropriate
time, money, and energy to accomplish a proper site survey in advance may result
in greater expenditures of money and time later, when problems arise that require
repeated adjustments to the wireless configuration. The three elements of an
effective site survey are:
- Examine the network usage problems solved by the wireless LAN.
How many clients need a wireless LAN connection? What areas of the site require
wireless LAN connectivity? How many hours each day is wireless LAN connectivity
required? Which locations are likely to generate the largest amount of data
traffic? Where is future network expansion most likely?
- Study blueprints of the proposed wireless LAN site.
A site blueprint provides a map of the site as well as the location of objects,
such as walls, partitions, and anything else that could affect the performance
of a wireless LAN. Examining the site blueprint prior to conducting the physical
walk-through helps you identify areas in which wireless equipment is likely
to perform well and areas where it is not. Many obstructions are not readily
visible and, in some cases, a room originally built for a specific purpose,
such as a radiology lab, might have been converted into something completely
different, such as a conference room. The blueprint may also show areas proposed
for future building expansion. To prepare for the next step of the site survey,
mark possible wireless device locations on the blueprint and refer to the
marked blueprint during the physical walk-through and inventory.
- Conduct a physical walk-through and inventory.
The primary purpose of the physical walk-through is to document any items
or materials near a proposed device location that may interfere with reception
or transmission and affect network performance. Document stock and inventory
levels, current environmental conditions and any materials that may interfere
with the wireless LAN.
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