Wireless Home Networking - Index of

Chapter 15: Using a Bluetooth Network
� Bluetooth operates in the 2.4 GHz frequency spectrum. It uses the
same general chunk of the airwaves as do 802.11g and 802.11n. (This
means that interference between the two technologies is indeed a
possibility, though 802.11n draft 2.0 is designed to sense Bluetooth
transmissions and switch to different channels so they don’t interfere.)
� The Bluetooth specification allows a maximum data connection speed
of 723 Kbps. A few of the most recent Bluetooth specifications can
go much faster (2.1 Mbps for Bluetooth 2.0 and 3.0 Mbps for Bluetooth
2.1, with a proposed Bluetooth 3.0 that can go up to 480 Mbps), but
many Bluetooth devices still use the slower speed specification — and
Bluetooth 3.0 won’t exist for a few more years. Compare this with the
248 Mbps of 802.11n. Bluetooth is much slower than wireless LAN
technologies for now.
� Bluetooth uses much lower power levels than do wireless LAN technologies
(802.11). Thus, Bluetooth devices have a much smaller effect,
power-wise, than 802.11 devices. This is a huge deal for some of the small
electronic devices because Bluetooth eats up a whole lot less battery
life than 802.11 systems. The proposed Wibree specification of Bluetooth
will use even less power than the current version; it’s designed to be
used in wireless-enabled watches and will increase the battery life of
your cell phone Bluetooth headset five times what it is today.
Because Bluetooth uses a lower power level than 802.11, it can’t beam
its radio waves as far as 802.11 does. Thus, the range of Bluetooth is
considerably less than that of a wireless LAN. Theoretically, you can get
up to 100 meters (these are called Class 1 devices), but most Bluetooth
systems use less than the maximum allowable power ratings, and you
typically see ranges of 30 feet or less with most Bluetooth gear — which
means that you can reach across the room (or into the next room), but
not all the way across the house.
� Bluetooth uses a peer-to-peer networking model. This means that you
don’t have to connect devices back through a central network hub like
an access point (AP). Devices can connect directly to each other using
Bluetooth’s wireless link. The Bluetooth networking process is highly
automated; Bluetooth devices actively seek out other Bluetooth devices
to see whether they can connect and share information.
� Bluetooth doesn’t require line of sight between any connected
devices. Bluetooth uses radio signals that can pass through walls,
doors, furniture, and other objects. So you don’t need to have a direct
line of sight like you do with infrared systems.
� Bluetooth can also connect multiple devices in a point-to-multipoint
fashion. One master device (often a laptop computer or a PDA) can connect
with as many as seven slave devices simultaneously in this manner.
(Slave devices are usually things such as keyboards and printers.)
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