Wireless Home Networking - Index of

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Part I: Wireless Networking Fundamentals
Figure 3-2:
A Bluetooth
scatternet
is composed
of several
piconets.
Master
Slave
As mentioned, Bluetooth isn’t nearly as fast as Wi-Fi — many Bluetooth
devices reach a maximum data rate of 723 Kbps (compare that to 248 Mbps
for 802.11n), but that’s not usually important because Bluetooth is typically
not used for transferring huge files and the like. The newest version of
Bluetooth (Bluetooth 2.1) includes something called EDR (Enhanced Data
Rate) that allows data transfers at speeds of up to 2.1 Mbps. (The raw speed
is 3 Mbps; 2.1 is the actual data throughput rate.)
To maintain the security of the data you send over a Bluetooth link, the Bluetooth
standard includes several layers of security. First, the two Bluetooth
devices that are connecting use authentication to identify each other. After
the authentication process (sometimes called pairing in the Bluetooth world),
the devices can begin sharing information. 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 802.11b, g, and n versions) and Bluetooth use the 2.4 GHz
frequency radio band, but note the significant differences in how these technologies
use the band. Bluetooth radios transmit a signal strength that complies
with transmission regulations in most countries and is designed to
connect at distances from 10 centimeters to 10 meters through walls and
other obstacles — although like any radio wave, Bluetooth transmissions c
an 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 compatible
devices, which is fine for the applications for which Bluetooth is
intended, such as replacing short-run cables.