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Probably the single biggest threat to your home microwave, that™s because the micro(radio)-
network is interference in the home. The Federal waves are in the same radiation band as your
Communications Commission (FCC) set aside cordless phone. Motors, refrigerators, and
certain unlicensed frequencies that could be other home consumer devices do the same
used for low-power wireless applications. In thing.
specific frequency bands, manufacturers can
So what™s the answer? The good news is that
make (and you can use) equipment that doesn™t
you can deal with almost all of these by know-
require a license from the FCC for the user to
ing what to look for and being smart about
operate. This is different from, say, buying a
where you place your equipment. If your access
50,000-watt radio transmitter and blasting it over
point is in the back office and you want to
your favorite FM radio frequency band, which
frequently work in the living room with your
would be a major no-no because those bands
laptop ” but your kitchen is in the middle ”
are licensed for certain power levels.
you might want to look at adding a second
As a result, all sorts of companies have created access point in the living room and link it with
products (including cordless phones, wireless the office via any of a number of alternative
radio frequency [RF] remote controls, wireless connections options (which we talk about in
speakers, TV set extenders, and walkie-talkies) Chapter 3) that are immune to the microwave
that make use of these frequency bands. If you problems that we mention earlier.
have a lot of wireless devices already in your
Remember these specific things to look for
home, there is a good chance that they might
when shopping. You™ll see cordless phones
use some of the same frequency bands that
operating primarily in the 900 MHz, 2.4 GHz, and
your home wireless network uses.
5 GHz frequencies. The 900 MHz phones pose
Another form of wireless interference comes no problems, but the 2.4 GHz and 5 GHz phones
from devices that emit energy in the same will interfere with your wireless network sig-
bands, such as microwave ovens. If you have nals. Just know that cordless phones and home
a cordless phone with its base station near wireless networks really don™t like each other
a microwave and you notice that the voice very much.
quality degrades every time that you use the
Chapter 4: Planning a Wireless Home Network

Factors that affect signal strength
Many variables affect whether you get an adequate signal at any given point
in your house, including the following factors:

Distance from the AP: The further away from the AP, the weaker the
signal. Wi-Fi 802.11b standards, for instance, promise a maximum operat-
ing range of 100 feet at 11 Mbps to 300 feet at 1 Mbps. Indoors, a realistic
range at 11 Mbps is about 60 feet. When 802.11a and 802.11g networks
become more prevalent, their maximum range may vary. Range differs
from vendor to vendor as well.
The power of the transmitter: Wi-Fi APs transmit at a power output of
less than 30 dBm (one watt).
The directivity or gain of the antennas attached to the AP and to
wireless network adapters: Different antennas are designed to provide
different radiation patterns. That™s a fancy way of saying that some are
designed to send radio waves in all directions equally, yet others con-
centrate their strength in certain directions. We talk more about this in
Chapter 6, but the thing to keep in mind here is that different brands and
models of access points have different kinds of antennas designed for
different applications. Check out the specifications of the ones that
you™re looking at before you buy them.
The construction materials used in the walls, floors, and ceilings:
Some construction materials are relatively transparent to radio signals,
but other materials, such as marble, brick, water, paper, bulletproof
glass, concrete, and especially metal, tend to reflect some of the signal,
thus reducing signal strength.
Your house plan: The physical layout of your house might determine
not only where it™s practical to position an AP, but it also might affect
signal strength because the position of walls, the number of floors, brick
fireplaces, basements, and so on can partially or even completely block
the wireless networks radio signal.
Client locations: Reception is affected by the distance from the AP to the
rooms in your house where someone will need wireless network access.
Stationary physical objects: Objects that are permanently installed in
your home, such as metal doors, heating ducts, and brick fireplaces can
block some or all of the signal to particular spots in your house.
Movable physical objects: Other types of objects, including furniture,
appliances, plants, and even people can also block enough of the signal
to cause the network to slow down or even to lose a good connection.
APs: Interference can also be caused by the presence of other APs. In
other words, if you™ve got a big house (too big for a single AP to cover),
you have to keep in mind that in parts of the house ” like in the area
that™s pretty much directly in between the two APs ” you™ll find that the
radio waves from each AP can interfere with the other. Check out the
following section for more information regarding this phenomenon.
74 Part II: Making Plans

You should attempt to keep a direct line between APs, residential gateways,
and the wireless devices on your network. A wall that is 1.5 feet thick, at a 45°
angle, appears to be almost 3 feet thick. At a 2° angle, it looks over 42 feet
thick. Try to make sure that the AP and wireless adapters are positioned so
that the signal will travel straight through a wall or ceiling for better reception.

RF interference
Nowadays, many devices that once required wires are now wireless, and this
is becoming more prevalent all the time. Some wireless devices use infrared
technology, but many wireless devices, including your wireless network, com-
municate by using radio frequency (RF) waves. As a consequence, the net-
work can be disrupted by RF interference from other devices sharing the
same frequencies used by your wireless network.

Among the devices most likely to interfere with IEEE 802.11b and IEEE 802.11g
networks are microwave ovens and cordless telephones that use the 2.4 GHz
band. The best way to avoid this interference is to place APs and computers
with wireless adapters at least six feet away from the microwave and the base
station of any portable phone that uses the 2.4 GHz band.

Bluetooth devices also use the 2.4 GHz band, but the hop pattern of the Blue-
tooth modulation protocol all but ensures that any interference will be short
enough in duration to be negligible.

Because there are relatively few devices that are trying to share the 5 GHz fre-
quencies used by IEEE 802.11a, your network is less likely to experience RF
interference if it™s using IEEE 802.11a.

You should also try to keep all electric motors and electrical devices that
generate RF noise through their normal operation, such as monitors, refriger-
ators, electric motors, and Universal Power Supply (UPS) units at least three
and preferably six feet away from a wireless network device.

Signal obstacles
Wireless technologies are susceptible to physical obstacles. When you
decide where best to place your AP(s), refer to Table 4-1, which lists obsta-
cles that can affect the strength of your wireless signals. The table lists
common household obstacles (although often overlooked) as well as the
degree to which the obstacle is a hindrance to your wireless network signals.
Chapter 4: Planning a Wireless Home Network

Table 4-1 Relative Attenuation of RF Obstacles
Obstruction Degree of Attenuation Example
Open space Low Backyard
Wood Low Inner wall; door; floor
Plaster Low Inner wall (older plaster is
lower than newer plaster)
Synthetic materials Low Partitions; home theater
Cinder block Low Inner wall; outer wall
Asbestos Low Ceiling (older buildings)
Glass Low Non-tinted window
Wire mesh in glass Medium Door; window
Metal tinted glass Medium Tinted window
Human body Medium Groupings of people
(dinner table)
Water Medium Damp wood; aquarium; in-
home water treatments
Bricks Medium Inner wall; outer wall; floor
Marble Medium Inner wall; outer wall; floor
Ceramic High Ceramic tile; ceiling; floor
(metal content
or backing)
Paper High Stack of paper stock, such
as newspaper piles
Concrete High Floor; outer wall; support
Bulletproof glass High Windows; door
Silvering Very high Mirror
Metal Very high Inner wall; air conditioning;
filing cabinets; reinforced
concrete walls and floors
Source: Intel (www.intel.com/network/connectivity/solutions/wireless/
deploy_site.htm); TeleChoice
76 Part II: Making Plans

The RF doughnut
The shape of the radio signal that will be trans- Draw a circle with a 60-foot radius on your
mitted to the rooms in your home is determined house plan, using the trial AP location as the
by the type of antenna that you™ve attached to center of the circle. If your entire house falls
the AP. The standard antenna on any AP is an inside the circle, one AP will probably do the
omnidirectional antenna, which broadcasts its job. Conversely, if some portion of the house is
signal in a spherical shape. The signal pattern outside the circle, coverage might be weaker in
that radiates from a typical omnidirectional that area. You™ll need to experiment to deter-
dipole antenna is shaped like a fat doughnut mine whether you get an adequate signal there.
with a tiny hole in the middle. The hole is directly
If you determine that one AP will not cover your
above and below the antenna.
house, you need to decide how best to place
The signal goes from the antenna to the floor two APs (or even three, as necessary). The
above and the floor below, as well as to the floor design of your house will determine the best
on which the AP is located. If your house has placement. For a one-level design, start at one
multiple floors, try the second floor first. Most end of the house and determine the best loca-
AP manufacturers claim a range of 100 feet tion for a 60-foot radius circle that will cover all
indoors (at 11 Mbps for IEEE 802.11b or at 54 the way to the walls. The center of this circle
Mbps for IEEE 802.11a and IEEE 802.11g). To be is the location of the first AP. Then move toward
conservative, assume a range of 60 feet later- the other end of the house, drawing 60-foot
ally and one floor above or below the AP. Keep radius circles until the house is covered. The
in mind that the signal at the edges of the center of each circle will be a trial location of an
“doughnut” and on the floors below or above AP. If possible, don™t leave any area in the house
the AP will be weaker than the signal nearer the uncovered. And especially don™t forget your
center and on the same floor as the AP. garage; before long, you™ll be synchronizing your
wireless network with your car, including send-
Because of this signal pattern, you should try to
ing digital movies and MP3 files. (See Chapter 14
place the AP as close to the very center of your
for more about connecting to your car.)
house as is practically possible. Use a drawing of
your house plan to locate the center of the house.
This spot will be your first trial AP location.

You might want to consider reading Chapter 18 on troubleshooting before
you finish your planning. There are some good tips in that chapter about set-
ting up and tweaking your network.

Adding printers
In addition to your computer(s), you might also want to connect your
printer(s) to the network. Next to sharing an Internet connection, printer
sharing is perhaps the biggest cost-savings reason for building a network of
Chapter 4: Planning a Wireless Home Network

home computers. Rather than buying a printer for every PC, everyone in the
house can share one printer. Or maybe you have one color ink jet printer and
one black-and-white laser printer. If both printers are connected to the net-
work, all computers on the network can potentially print to either printer. Or
perhaps you just want to sit by the pool with your wireless laptop and still be
able to print to the printer up in your bedroom; it™s easy with a network-
attached printer.

You can also share other peripherals, such as network-aware scanners and
fax machines. Leading manufacturers of digital imaging equipment (like
Hewlett-Packard) offer feature-rich, multiple-function peripherals that com-
bine an ink jet or laser printer with a scanner, copier, telephone, answering
machine, and fax machine all-in-one device. If you want to share such a
device over your network, make sure that you buy one that comes with net-
work server software.

Here are two ways to share printers over a wired or wireless network:

Connect to a computer: The easiest and cheapest way to connect a
printer to the network is to connect a printer to one of the computers on
the network. Windows enables you to share any printer connected to
any Windows computer on the network. (For more on this, read Chap-
ter 11.) The computer to which the printer is connected has to be run-
ning for any other computers on the network to use the printer.
Similarly, if you™re using Apple computers, any computer connected to
the network can print to a printer that™s connected to one of the comput-
ers on the network.
Print server: Another way to add a printer is through a print server.
Several hardware manufacturers produce print server devices that
enable you to connect one or more printers directly to the network.
Some of these devices connect via a network cable, and others are wire-
less. Many high-end printers even have print server options that install
inside the printer cabinet. For home use, standalone network print
servers are a bit pricey. Surprisingly, some manufacturers bundle a print
server with their cable/DSL router at little or no additional cost. If you
shop around, you can probably find a wireless AP, cable/DSL router, and
print server bundled in one device for less than the cost of some stand-
alone print servers.

You should be able to get your home network printer connections for free.
Obviously, it won™t cost anything to connect a printer to a computer that™s
already connected to the network. Several manufacturers also include a print
server for free with other network devices. If you don™t need one of those
devices, just connect the printer that you want to share to one of the comput-
ers on your home network.
78 Part II: Making Plans

Figure 4-3 depicts a home network with one printer connected to one of the
PCs on the network and another printer connected to a wireless Internet gate-


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