master and Master
at least one
The three types of Bluetooth connections are
Data-only: When communicating data, a master can manage connections
with up to seven slaves.
Voice-only: When the Bluetooth piconet is used for voice communica-
tion (for example, a wireless phone connection), the master can handle
no more than three slaves.
Data and voice: A piconet transmitting both data and voice can exist
between only two Bluetooth devices at a time.
Each Bluetooth device can, in full compliance with the Bluetooth standard,
join more than one piconet at a time. A group of more than one piconet with
one or more devices in common is a scatternet. Figure 3-2 depicts a scatternet
made up of several piconets.
The amount of information sent in each packet over a Bluetooth connection
and the type of error correction used determine the data rate that a connec-
tion can deliver. Bluetooth devices can send data over a piconet by using 16
different types of packets. Sending more information in each packet (that is,
sending longer packets) causes a faster data rate. Conversely, more robust
error correction causes a slower data rate. Any application that uses a
Bluetooth connection will determine the type of packet used and, therefore,
the data rate.
52 Part I: Wireless Networking Fundamentals
In order to maintain the security of the data that you send over a Bluetooth
link, the Bluetooth standard includes several layers of security. First, the two
Bluetooth devices that are connecting use a process called authentication to
identify each other. After the authentication process is done (sometimes
called pairing in the Bluetooth world), the devices can begin sharing informa-
tion. The data being sent across the radio link is encrypted (scrambled) so
that only other authenticated devices have the key that can decrypt
(unscramble) the data.
Both Wi-Fi (the IEEE 802.11b and g versions) and Bluetooth use the 2.4 GHz
frequency radio band, but note the significant differences in how these tech-
nologies use the band. Bluetooth radios transmit a signal strength that com-
plies with transmission regulations in most countries and is designed to
connect at distances from 10 centimeters to 10 meters through walls and
other obstacles â€” although like any radio wave, Bluetooth transmissions can
be weakened by certain kinds of construction material, such as steel or
heavy concrete. Although Bluetooth devices can employ a transmission
power that produces a range in excess of 100 meters, you can assume that
most Bluetooth devices are designed for use within 10 meters of other com-
patible devices, which is fine for the applications for which Bluetooth is
intended, such as replacing short run cables.
Chapter 3: Bluetooth, HPNA, and HomePlug
To make full use of the 2.4 GHz frequency radio band and to reduce the likeli-
hood of interference, Bluetooth uses a transmission protocol that hops 1,600
times per second between 79 discrete 1 MHz-wide channels from 2.402 GHz to
2.484 GHz. Each piconet establishes its own random hopping pattern so that
you can have many piconets in the same vicinity without mutual interference.
If interference does occur, each piconet switches to a different channel and
tries again. Even though Wi-Fi (IEEE 802.11b/g) and Bluetooth both use the
2.4 GHz band, both protocols use hopping schemes that should result in
little, if any, mutual interference.
Integrating Bluetooth in
Your Wireless Network
Products that are the first to take advantage of Bluetooth technology include
Bluetooth adapters for PCs
Bluetooth hands-free car kits
You can get a great idea of all the various ways that Bluetooth can be used in
your network by going to the official Bluetooth products Web site at www.
bluetooth.com/tech/products.asp. We also go into great detail about
some of the more common ways that youâ€™ll use Bluetooth in Chapter 15.
One of the more interesting and promising applications of Bluetooth technol-
ogy is for cell phones. Bring your Bluetooth-enabled phone home and dock it
in a power station near your PC, and it will instantly log onto your home wire-
less network via a Bluetooth connection to a nearby PC or Bluetooth access
54 Part I: Wireless Networking Fundamentals
point. Phones that function as PDAs can update their address books and sync
data from the PC. All your events, to-do lists, grocery lists, and birthday
reminders can be kept current just by bringing your Bluetooth-enabled prod-
uct in range. There are even Bluetooth headsets for your Bluetooth phones â€”
getting rid of that wireless headset hassle.
Bluetooth technology is advancing into the arena of autos, too. The Bluetooth
SIG formed the Car Profile Working Group in December 1999, in response to
interest by the automotive industry. This working group has defined how
Bluetooth wireless technology will enable hands-free use of mobile phones in
automobiles. Microsoft is using Bluetooth-driven products in car dashboards
to enable the car to access your cell phone service for downloading digital
music and live traffic updates.
The Microsoft Pocket PC 2002 operating system supports both Bluetooth and
IEEE 802.11b through add-on adapters. The initial release of Windows XP
offered native driver support for IEEE 801.11b but not Bluetooth. Microsoft
cited the lack of commercially available Bluetooth devices as the main reason
for not including the necessary Host Controller Interface (HCI) device drivers
out of the box. Subsequently, Microsoft has added Bluetooth support to
Windows XP through a software update. Mac OS v. 10.2 (Jaguar) also has
integrated support for Bluetooth.
Wirelessly synching your PDAs
Bluetooth is onboard inside PDAs, like the HP iPAQ Pocket PC H5450 (www.
hp.com; $699) that has both 802.11b and Bluetooth inside. Now thatâ€™s really
cool. (We wonâ€™t mention that the H5450 also has a thermal biometric finger-
print reader that authenticates the ownerâ€™s unique fingerprint, allowing
access with a simple fingerprint swipe. That would probably be too cool
for you to handle.)
If you have a PDA, you can get clip-on devices, like the BlueM from TDK
Systems Europe (www.tdksys.com/products/intro.asp?id=2). Use the
BlueM with your Palm handheld to communicate with other Bluetooth-
enabled devices, including PCs, notebooks, printers, and other handhelds
that are within range. This one-ounce device has a thin, sled design and
slides onto the back of the Palm m500, m505, and m125 handhelds, as well as
IBM C500 devices, connecting via the docking port on the bottom of the PDA.
For example, if you have your Bluetooth-enabled PDA in your pocket and
walk into the room where your Bluetooth-enabled PC is located, the two will
automatically synchronize your calendar, your e-mail, and your to-do list â€”
with no intervention on your part. Or, if your cell phone is Bluetooth enabled,
Chapter 3: Bluetooth, HPNA, and HomePlug
you can transfer your contact list wirelessly from your Bluetooth-enabled PC
to the phoneâ€™s address list. (Thatâ€™d cut down on those expensive directory
assistance calls, wouldnâ€™t it?)
Also now available are Bluetooth Compact Flash card adapters that can be
used in Pocket PC-driven PDAs to add Bluetooth capability (see Figure 3-3).
Toshiba and other manufacturers have released Bluetooth PC Cards that add
the Bluetooth wireless technology to any PC with a PC Card slot. Other
adapters are available that plug into a USB port, making it possible to easily
add Bluetooth capability to any desktop or laptop PC (see Figure 3-4). Prices
for these adapters range widely â€” from as low as about $50 to as much as
Use a USB
a desktop or
56 Part I: Wireless Networking Fundamentals
Ultra-cool Ultra Wideband (UWB) is coming
With all the innovation happening in the Wi-Fi the propagation phenomenon that results in sig-
and Bluetooth area, more neat stuff is on the nals reaching the receiving antenna by two or
way. Ultra Wideband (UWB) is a revolutionary more paths, usually because of reflections of
wireless technology for transmitting digital data the transmitted signal off walls or mirrors or the
over a wide spectrum of frequency bands with like. Because UWB has the ability to time-gate
very low power. It can transmit data at very high (that is, prescribe the precise time when it is
rates (for wireless LAN applications in the supposed to receive the data), the receiver
home). Within the power limit allowed under allows it to ignore signals arriving outside a pre-
current FCC regulations, Ultra Wideband also scribed time interval, such as signals caused by
has the ability to carry signals through doors multipath reflections.
and other obstacles that tend to reflect signals
UWB is still in the early stages, but it is coming
at more limited bandwidths and a higher power.
on strong. UWB is simpler, cheaper, less power-
At higher power levels, UWB signals can travel
hungry, and 100 times faster than Bluetooth.
to significantly greater ranges.
What more could you want? UWB communica-
Ultra wideband radiobroadcasts digital pulses tion devices could be used to wirelessly distrib-
(instead of traditional sine waves) that are timed ute services such as phone, cable, and computer
very precisely on a signal across a very wide networking throughout a building or home. For
spectrum at the same time. Transmitter and now, itâ€™s still on the drawing boards, so just know
receiver are coordinated to send and receive that more cool stuff is on the horizon.
pulses with an accuracy of trillionths of a
You can find out more about UWB at the official
second! Not only does UWB enable high data
UWB Working Group Web site: www.uwb.org.
rates, but it also does so without suffering the
effects of multipath interference. Multipath is
Wireless printing and data transfer
Hewlett-Packard and other printer companies manufacture printers that have
built-in Bluetooth wireless capability, enabling a computer that also has
Bluetooth wireless capability to print sans printer cables. Other examples are
a wireless keyboard and a wireless mouse from Microsoft that both use
Bluetooth technology to replace their traditional cables.
Another great use of Bluetooth wireless technology is to wirelessly transfer
your digital photographs from your Bluetooth-enabled digital camera to your
Bluetooth-enabled PC or Bluetooth-enabled printer . . . or even directly to
your Bluetooth-enabled PDA. The newest wave of PDAs from several manu-
facturers includes wireless-enhanced models that include both Bluetooth and
Wi-Fi built in. Wouldnâ€™t it be cool to carry your family photo album around on
your Palm or iPAQ to show off at the office?
Chapter 3: Bluetooth, HPNA, and HomePlug
You might run into products that have the environment. Over time, Wi-Fi moved into the
HomeRF logo. The HomeRF standard, which consumer space faster and with more success
was sponsored by the Home Radio Frequency than ever envisioned, ultimately pulling the
Working Group (HomeRF WG), was launched in market from the HomeRF products. If you run
March 1998, and died at the end of 2002, largely into a HomeRF product, recognize that these are
because of the widespread popularity of Wi-Fi. mostly gone from the shelves, and we donâ€™t rec-
HomeRF was designed to be a wireless stan- ommend that you buy them because of Wi-Fi
dard optimized for the consumer markets. Wi-Fi interoperability reasons.
was initially used primarily in the corporate