Bluetooth Basics

The technology of Bluetooth wireless is a short
range communications method intended to replace
the cables that connect portable or fixed devices
while maintaining the highest levels of security.

The key features offered by Bluetooth include
low power and low cost. The specification in
Bluetooth defines a uniform structure for a wide
range of devices to communicate and connect with
one another.

The technology behind Bluetooth has achieved
global satisfaction such as enabled devices, almost
everywhere in the world. Bluetooth devices will
connect and communicate without wires through
short range and networks known as piconets.

Each device will simultaneously communicate with
up to seven other devices within a single piconet,
meaning that each device can also belong to
several piconets simultaneously. The piconets
are dynamically established as Bluetooth enabled
devices enter and leave the proximity of radio.

A fundamental to Bluetooth strength is the
ability to handle both data and voice transmissions
simultaneously. This will enable users to enjoy
varieties of innovative solutions such as hands
free talking, printing and fax capabilities,
and other applications.

Specifications
Unlike other standards of wireless, the Bluetooth
specification gives product developers both a
link layer and application layer definitions,
which will help support data and voice applications.

Spectrum
The Bluetooth technology operates in the industrial
and scientific band at 2.4 to 2.485 GHz, using a
spread spectrum, frequency hopping signal.

Interference
The adaptive frequency hopping of Bluetooth
technology was designed to reduce interference
between wireless technologies that share the 2.4
GHz spectrum. Adaptive frequency hopping (AFH)
works well within the spectrum to take full
advantage of the frequency available.

AFH hopping allows for more efficient transmission
within the spectrum, which provides users with
greater performance even if they are using other
technologies along with Bluetooth.

Bluetooth In Action

In the United States, Bluetooth gets absolutely no
respect. It is however, becoming more and more
common in notebooks, PDAs, and especially cell
phones. Bluetooth will provide wireless users a
way to transmit small amounts of data over short
distances.

Now, Bluetooth is facing stiff competition from
new wireless technology. Referred to as UWB or
Ultra Wideband, it promises data transfer of up
to 480 MB a second - while most current Bluetooth
devices transfer data up to 721 KB a second.

For the time being, Bluetooth devices are surely
cropping up. Below, we will look at some of
the accessories offered with Bluetooth technology.

Talking to the dashboard
When pairing it with a cell phone, the CCM Blue
Warrior car kit becomes a great speaker phone that
plugs into the power adapter of your vehicle. The
noise cancelling microphone will reduce background
noise efficiently, with the large buttons making
adjusting the speaker volume a snap. Although
the Blue Warrior is far from sexy or sleek, it's
very practical.

Tiny tuning box
Part MP3 player and part hands free phone, the
compact and lightweight Sony HBM-30 is an attractive
gadget that lets you accept calls with minimal
interruption of your tunes. When you get an incoming
call it will automatically pause your music, then
you speak into the built in microphone that you
can wear around your neck or clip to your clothes.

The pen
With Nokia's SU-1B digital pen, you can doodle and
make hand written notes in ink on a special pad
then transmit them from the pad to your Bluetooth
phone. Being an alternative to typing on a cell
phone keypad, the pen is very handy, although a
pricey tool from MMS fans.

Snapshots
If you want to make slide shows with your camera
photos, the Nokia SU-2 image viewer will let you
disply your pictures on a TV or projector. Simply
hook this square gray device to your TV's input
with the built in cable, then beam the pictures
to the SU-2 from your Bluetooth enabled phone and
the photo fest will begin.

This device is a snap to set up and use, although
it displays resolutions of up to 640 by 480. If
you have a newer phone that takes high resolution
photos, you won't be able to use the Nokia SU-2
image viewer.

Keep in mind, the 640 by 480 pixel photos will
appear blocky on TV screens, no matter what you
do. If your phone can send batches of photos, you
can create a slide show - although Nokia claims
you can use sequentially beamed shots as well.

Bluetooth Operation

The networking standards of Bluetooth will transmit
data via low power radio frequency. Bluetooth
communicates on a 2.45 GHz frequency. This very
band of frequency has been set aside by international
agreement for the use of industrial and medical
devices.

Many devices that you already known and use take
advantage of this frequency band. Garage door
openers, baby monitors, and the next generation of
mobile phones all use this frequency within the ISM
band. Ensuring that Bluetooth and the other
devices don't interfere with each other is a crucial
part of the design process.

One of the ways Bluetooth will avoid interfering
with other electronic devices is by sending out
weak signals of around 1 mw. In comparison, even
the most powerful of cell phones can transmit a
signal of 3 watts.

The low power signals will limit the range of a
Bluetooth device to around 32 feet, which cut the
chances of interference between your computer and
other electronic devices. Even though it has low
power, Bluetooth doesn't require a line of sight
between the communicating devices. The walls in
your home won't stop the signal, making it great
for rooms throughout the house.

Bluetooth can connect 8 devices at the same time.
With each of those devices on the same radius,
you may think they would interfere with each
other, although it's very unlikely. Bluetooth
utilizes a technique known as low frequency
hopping, which makes it harder for more than
one device to transmit on the same frequency
at the same time.

With this technique, a device will use 79
individual, randomly chosen frequencies within
a designated range, which change from one another
on a regular basis.

In the case of Bluetooth, the transmitters will
change frequency 1,600 times or more every
second, meaning that more devices can make full
use of the radio spectrum. Since every
transmitter of Bluetooth will use spread spectrum
automatically, it's very unlikely that two
transmitters will be on the same frequency at the
exact same time.

When the Bluetooth devices come within close range
of each other, an electronic conversation will
occur to determine whether or not they have
data to share or whether one needs to take total
control. The user doesn't have any buttons to
press or commands to give - as the conversation
will occur automatically.

Once the conversation has occured, the devices
will form a network. Bluetooth devices will
create a PAN (Personal Area Network) or piconet
that may fill a room. Once the piconet has been
established, the devices will randomly hop in
frequencies.