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offer upgrades via firmware downloads when the final software is complete.

IEEE 802.11g is intended to be backward compatible with 802.11b wireless
networking technology but still delivers the same transmission speeds as
802.11a ” up to 54 Mbps ” thus, effectively combining the best of both
worlds. The 802.11g products are expected to outsell a and b products in the
next few years.

IEEE 802.11g equipment offers a nice upgrade path to people who have
already invested in IEEE 802.11b equipment. The first products released carry
prices that are only marginally more expensive than plain-old IEEE 802.11b.
Tests of these products have uncovered some interoperability problems with
IEEE 802.11b equipment, but these problems are certain to be ironed out by
the time products are released on the final standard.

If you plan to do streaming video over your network, you should seriously
consider purchasing IEEE 802.11a equipment or IEEE 802.11g equipment.
Otherwise, IEEE 802.11b products should be more than adequate for your
wireless home network and are probably available at bargain prices.
However, if you™re one to hedge your bets, consider purchasing an access
point that supports multiple standards ” dual-mode, tri-standard a/b/g prod-
ucts are available. Only time and the marketplace will determine whether
IEEE 802.11a will survive or be pushed out by IEEE 802.11g. We think that
they™ll coexist. It is a virtual certainty that IEEE 802.11b™s current position as
the dominant standard will give way to one or both of the faster standards.
We predict that IEEE 802.11g will represent the majority of all wireless ship-
ments within the next few years.

The ISM bands
Here we talk about frequency bands used by the various standards in detail.
In 1985, the Federal Communication Commission (FCC) made changes to the
radio spectrum regulation and assigned three bands designated as the indus-
trial, scientific, and medical (ISM) bands. These frequency bands are

902 MHz“928 MHz: a 26 MHz bandwidth
2.4 GHz“2.4835 GHz: an 83.5 MHz bandwidth
5.15“5.35 GHz and 5.725 GHz“5.825 GHz: a 300 MHz bandwidth
Chapter 2: From a to g and b-yond

Gauging your network™s throughput
Wi-Fi standards call for different speeds, up to And that just represents the speed. The actual
11 Mbps for 802.11b and up to 54 Mbps for throughput is another, but related, matter.
802.11a and g. Radios attempt to communicate Throughput represents the actual rate at which
at the highest speed. If they encounter too many the validated data flows from one point to
errors (dropped bits), the radios will step down another. It might take some retransmissions for
to the next fastest speed, repeating the process that to occur, so your throughput will be less
until a strong connection is achieved. So although than the negotiated speed of the connection. It
we talk about 802.11g, for instance, being up to 54 might not be unusual for you to get only 20“30
Mbps in speed, the reality is that unless you™re Mbps on your 54 Mbps connection or 4“5 Mbps
very close to the AP, you™re not likely to get that on your 11 Mbps connection. In fact, that™s
maximum rate. Signal fade and interference will rather normal.
cut into your speeds, and the negotiated rate
between the two devices will drop.

The FCC also opened up some additional frequencies known as Unlicensed
National Information Infrastructure (U-NII), in the lower reaches of the five
GHz frequencies.

The purpose of the FCC change was to encourage the development and use
of wireless networking technology. The new regulation permits a user to
operate radio equipment that transmits a signal within each of these three
ISM bands without obtaining an FCC license, within certain guidelines.

Wireless networks use radio waves to send data around the network. IEEE
802.11a uses part of the U-NII frequencies, and IEEE 802.11b and g use the ISM
2.4 GHz band.

An important concept when talking about frequencies is the idea of overlap-
ping and non-overlapping channels. As we discuss in Chapter 18, signals from
other APs can cause interference and poor performance of your wireless net-
work. This specifically happens when the APs™ signals are transmitting on the
same (or sometimes nearby) channels. Recall that the standards call for a
number of channels within a specified frequency range.

Take 802.11b, for example: Its frequency range is between 2.4 GHz and 2.4835
GHz, and it™s broken up into 14 equally sized channels (although only 11 can
be used in the United States ” any equipment sold for use here will only allow
you to access these 11 channels). The problem is that these are defined in a
way such that many of the channels overlap with one another ” and with
802.11b, there are only three non-overlapping channels. Thus, you wouldn™t
46 Part I: Wireless Networking Fundamentals

want to have channels 10 and 11 operating side by side because you™d get
signal degradation. You want non-interfering, non-overlapping channels. So
you find that people tend to use Channels 1, 6, and 11, or something similar.
802.11a doesn™t have this problem because its eight channels, in the 5 GHz fre-
quency band, don™t overlap; therefore, you can use contiguous channels. As
with 802.11b and g, however, you don™t want to be on the same channel.
Chapter 3
Bluetooth, HPNA, and HomePlug
In This Chapter
Understanding the Bluetooth standard
Data networking with HPNA
Plugging in with HomePlug

G etting the most from computer technology is all about selecting the
best and most dominant technology standards. The most dominant
technology for home wireless networks today clearly is the Wireless Fidelity
(Wi-Fi) family of technologies defined by the IEEE 802.11a, 802.11b, and
802.11g standards (which we describe in Chapter 2).

But Wi-Fi isn™t the only game in town. You™ll run into other home networking
standards when you buy and install your Wi-Fi gear ” standards that will
make it easier to get Wi-Fi where you want it.

This chapter briefly describes the Bluetooth wireless technology that either
complements or competes with Wi-Fi, depending on your application. Even if
you intend to purchase and use only Wi-Fi wireless networking equipment,
you should still be aware of Bluetooth. Who knows? ” it might even come in
handy for you.

We also talk about two key wired home networking standards (oops, did we
say a dreaded word . . . wired?): Home Phone Networking Alliance (HPNA),
the standard for networking over your installed phone wiring in your home;
and HomePlug, the standard for networking over your electrical power cables
in your home. As surprising as it might seem, you can actually connect your
computers, access points, and other devices together over these in-wall cables.
What™s more, many APs come with these interfaces onboard to make it easier
for you to install that AP wherever you want it. Isn™t that nice? You betcha.
48 Part I: Wireless Networking Fundamentals

Who or What Is Bluetooth?
One of the most often talked about wireless standards, besides Wi-Fi, is
Bluetooth. The Bluetooth wireless technology, named for the tenth-century
Danish King Harald Blatand “Bluetooth,” was invented by the L.M. Ericsson
company of Sweden in 1994. King Harald helped unite his part of the world
during a conflict around 960 AD. Ericsson intended for Bluetooth technology
to unite the mobile world. In 1998, Ericsson, IBM, Intel, Nokia, and Toshiba
founded the Bluetooth Special Interest Group (SIG), Inc. to develop an open
specification for always-on, short-range wireless connectivity based on
Ericsson™s Bluetooth technology. Their specification was publicly released on
July 26, 1999. The Bluetooth SIG now includes 3Com, Agere, Ericsson, IBM,
Intel, Microsoft, Motorola, Nokia, Toshiba, and nearly 2,000 other companies.
Dozens of Bluetooth-enabled products are already on the market, with many
more on the way.

Sometimes a network of devices communicating via Bluetooth is described as
a personal area network (PAN) to distinguish it from a network of computers
often called a local area network (LAN). In March 2002, the Institute for
Electrical and Electronics Engineers (IEEE) approved IEEE 802.15.1, a stan-
dard for wireless PANs (WPANs), which was adapted from portions of the
Bluetooth wireless specification. IEEE 802.15.1 is fully compliant with the
Bluetooth v1.1 specification. As IEEE worked toward the 802.15 standard, the
Bluetooth SIG simultaneously has been working on Bluetooth Version 3.0.
Any new Bluetooth standard will likely also become an updated IEEE 802.15
standard. (Read more at the Bluetooth Web site at www.bluetooth.com.)

The following is a small sampling of existing Bluetooth products:

Microsoft Wireless IntelliMouse Explorer for Bluetooth (a wireless mouse)
Microsoft Wireless Optical Desktop for Bluetooth (wireless multimedia
center keyboard and mouse)
Sony digital video camera recorder
HP Deskjet 995c printer
HP iPAQ H5450 Pocket PC with Bluetooth (and Wi-Fi) onboard
Ericsson Bluetooth Phone Adapter
Motorola Bluetooth Handsfree Car Kit
Belkin Bluetooth Universal Serial Bus (USB) Adapter
Chapter 3: Bluetooth, HPNA, and HomePlug

Although originally intended as a wireless replacement for cables, Bluetooth
is being applied to make it possible for a wide range of devices to communi-
cate with each other wirelessly with minimal user intervention. The technol-
ogy is designed to be low-cost and low-power to appeal to a broad audience
and to conserve a device™s battery life.

The projected growth plans for Bluetooth are phenomenal. It is expected that
the number of devices enabled with Bluetooth will jump from near nothing in
2000 to nearly 1.4 billion units (yup, billion with a b) in 2005, according to
industry analyst firm In-Stat/MDR.

Wi-Fi versus Bluetooth
Wi-Fi and Bluetooth are designed to coexist in the network, and although
they certainly have overlapping applications, each has its distinct zones of

The biggest differences between Wi-Fi and Bluetooth are

Distance: Bluetooth is lower powered, which means its signal can only
go short distances (up to 30 feet). 802.11 technologies can cover your
home, and in some cases more, depending on the antenna that you use.
Note: New software for Bluetooth devices is enabling the creation of
mesh networks in the home, where interconnected Bluetooth devices
can create a large mesh network that can be interconnected to the
Internet ” thereby creating a network similar to an 802.11b network in
the home, for instance.
Application: Bluetooth is designed as a replacement of cables: that is,
trying to get rid of that huge tangle of cables that link your mouse,
printer, monitor, scanner, and other devices on your desk and around
your home. In fact, the first Bluetooth device was a Bluetooth headset,
eliminating that annoying cable to the telephone that got in the way of
typing. New cars are also becoming outfitted with Bluetooth so that you
can use your cell phone in your car, with your car™s stereo speakers and
an onboard microphone serving as your hands-free capability. Pretty
neat, huh?

Wi-Fi (IEEE 802.11a, 802.11b, and 802.11g) and Bluetooth are similar in certain
respects: They both enable wireless communication between electronic
devices but are more complementary than direct competitors. Wi-Fi technol-
ogy is most often used to create a wireless network of personal computers
that can be located anywhere in a home or business. Bluetooth devices usu-
ally communicate with other Bluetooth devices in relatively close proximity.
50 Part I: Wireless Networking Fundamentals

The easiest way to distinguish Wi-Fi from Bluetooth is to focus on what each

Wi-Fi is wireless Ethernet. Wi-Fi is a wireless version of the Ethernet
communication protocol and is intended to replace networking cable
that would otherwise be run through walls and ceilings to connect com-
puters in multiple rooms or even multiple floors of a building.
Bluetooth replaces peripheral cables. Bluetooth wireless technology
operates at short distances ” usually about 10 meters ” most often
replaces cables that connect peripheral devices, such as a printer, key-
board, mouse, or personal digital assistant (PDA) to your computer.
Bluetooth replaces IrDA. Bluetooth can also be used to replace
another wireless technology ” Infrared Data Association (IrDA) wireless
technology ” that™s already found in most laptop computers, PDAs, and
even many printers. Although IR signals are very secure and aren™t both-
ered with radio frequency (RF) interference, IrDA™s usefulness is hin-
dered by infrared™s requirement for line-of-sight proximity of devices.
Just like how your TV™s remote control must be pointed directly at your
TV to work, the infrared ports on two PDAs must be lined up to trade
data, and your laptop has to be “pointing” at the printer to print over
the infrared connection. Because Bluetooth uses radio waves rather
than light waves, line-of-sight proximity is not required.

Like Wi-Fi, Bluetooth offers wireless access to LANs, including Internet
access. Bluetooth devices can potentially access the Public Switched
Telephone Network (PSTN: you know, the phone system) and mobile tele-
phone networks. Bluetooth should be able to thrive alongside Wi-Fi by
making possible such innovative solutions as a hands-free mobile phone
headset, print-to-fax, and automatic PDA, laptop, and cell phone/address
book synchronization.

Piconets, Masters, and Slaves
Communication between Bluetooth devices is similar in concept to the ad
hoc mode of Wi-Fi wireless networks (which we describe in Chapter 2). A
Bluetooth device automatically and spontaneously forms informal WPANs,
called piconets, with from one to seven other Bluetooth devices that have the
same Bluetooth profile. Piconets get their name from merging the prefix pico
(probably from the Italian word piccolo [small]) and network. A capability
called unconscious connectivity enables these devices to connect and discon-
nect almost without any user intervention.
Chapter 3: Bluetooth, HPNA, and HomePlug

A particular Bluetooth device can be a member of any number of piconets at
any moment in time (see Figure 3-1). Each piconet has one master, the device
that first initiates the connection. Other participants in a piconet are slaves.


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