Wireless Home Networking - Index of

Chapter 2: From a to n and b-yond
adopted in 1997, specified two wireless networking protocols that can transmit
at either 1 or 2 megabits per second (Mbps) using the 2.4 GHz radio
frequency band, broken into fourteen 5 MHz channels (eleven in the United
States). IEEE 802.11b-1999 is a supplement to IEEE 802.11 that added subsections
to IEEE 802.11 that specify the protocol used by Wi-Fi certified wireless
networking devices.
The 802.11b protocol is backward compatible with the IEEE 802.11 protocols
adopted in 1997, using the same 2.4 GHz band and channels as the slower
protocol. The primary improvement of the IEEE 802.11b protocol was a technique
that enabled data transmission at either 5.5 Mbps or 11 Mbps.
802.11b is an old standard. Most vendors no longer sell 802.11b equipment
(or they sell one single line of products for customers who want to replace
old gear). 802.11g, which we discuss in a moment, is compatible with 802.11b,
but is much faster and not a penny more expensive. It has pretty much
replaced 802.11b, particularly in the home networking market.
IEEE adopted 802.11a at the same time it adopted 802.11b. 802.11a specifies a
wireless protocol that operates at higher frequencies than the 802.11b protocol
and uses a variety of techniques to provide data transmission rates of 6,
9, 12, 18, 24, 36, 48, and 54 Mbps. 802.11a has twelve nonoverlapping channels
in the United States and Canada, but most deployed products use only
eight of these channels.
Because it uses a different set of frequencies, 802.11a offers the following
advantages over IEEE 802.11b:
� Capacity: 802.11a has about four times as many available channels,
resulting in about eight times the network capacity: that is, the number
of wireless stations that can be connected to the AP at one time and still
be able to communicate. This isn’t a significant advantage for a wireless
home network because you almost certainly will never use all the network
capacity available with a single access point (approximately 30
stations simultaneously).
� Less competition: Portable phones, Bluetooth, and residential microwave
ovens use portions of the same 2.4 GHz radio frequency band used by
802.11b, which sometimes results in interference. By contrast, few
devices other than IEEE 802.11a devices use the 5 GHz radio frequency
band. Note: A growing number of cordless phones are starting to use
this same frequency range, so the relative uncrowdedness of the 5 GHz
spectrum isn’t likely to last forever.
� Improved throughput: Tests show as much as four to five times the data
link rate and throughput of 802.11b in a typical office environment.
Throughput is the amount of data that can be transferred over the
connection in a given period. (See the nearby sidebar, “Gauging your
network’s throughput.”)
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