A strong point of Bluetooth is that the hardware does all of the work. Once
any two devices find each other, they negotiate between them for all of the
technical details of the conversation: things like exchanging electronic
addresses, selecting the best protocol for data, and setting in motion a timing
sequence for frequency hopping (which I explain in a moment).The conversation between devices determines if one or the other device
needs something from the other, or if one unit needs to control the other.
Once they’ve established an electronic handshake, they establish a personal-
area network, also called a piconet.One way in which Bluetooth devices avoid interference is by working at a
very low power level. The standard calls for transmitting at 1 milliwatt, which
is one-thousandth of a watt; by comparison, a typical cell phone uses one to
three watts (one thousand to three-thousandths as much power) to commu-
nicate with the nearest tower.Of course, using lower power limits their range; in a typical home or office a
Bluetooth unit works no more than about 32 feet, although some manufactur-
ers claim a range of about 50 percent more. That works fine across a room,
and the signal will penetrate most walls, but it’s still a limited area.A key element of the technology behind Bluetooth is spread-spectrum frequency
hopping. It’s pretty much all in the name: The devices in a piconet continually
change the exact frequency, using any one of 79 tiny slices of the radio pie
and hopping randomly to another 1,600 times per second. What this does is
make it extremely unlikely that there will be any sustained period of interfer-
ence between Bluetooth devices. Even if by chance two units end up on the
same frequency for the moment, they bounce to a different randomly selected
one almost immediately. Bluetooth includes the ability to reject (or ask for a
resend) any time there is corruption in a tiny packet of data it receives.Adding Bluetooth to your laptop .....................................................
Bluetooth technology is already being used in some cell phones, PDAs, cord-
less computer accessories (including mice, headsets, and keyboards), and
home appliances (including stereo systems and universal remote controls
that can send signals through walls and floors).You’ll be hard-pressed to find any standard laptops that come equipped with
Bluetooth technology, but it is very easy to add: Purchase a USB Bluetooth
adapter and plug it in to your laptop. You may have to add a driver (supplied
on CD with the adapter or downloaded over the Internet). Software supplied
with the adapters adds a Bluetooth icon to the system tray that opens to a
connection wizard for modems and a synchronization page to facilitate com-
munication between a pair of Bluetooth devices.222 Part IV: Failing to Communicate