802.11b occupies 83.5 MHz (for North America) from 2.4000 GHz to
802.11a occupies 300 MHz in three different bandwidths of 100 MHz
- 5.150 to 5.250 GHz (U-NII lower band)
- 5.250 to 5.350 GHz (U-NII middle band)
- 5.725 to 5.825 GHz (U-NII upper band)
802.11b provides 11 channels (for North America), each channel being
22 MHz in width, and each channel centered at 5 MHz intervals (beginning
at 2.412 GHz and ending at 2.462 GHz). This means that there are only 3
channels which do NOT overlap (channels 1, 6, 11).
802.11a provides 12 channels, each channel being 20 MHz wide, and
each centered at 20 MHz intervals (beginning at 5.180 GHz and ending at
5.320 GHz for the lower and middle U-NII bands, beginning at 5.745 GHz
and ending at 5.805 GHz for the upper U-NII band). It is important to
note that NONE of these channels overlap.
- IEEE standards
pages, to download IEEE 802.x standard documents.
3G and Wi-Fi: Will they Ever Get Together?, 802.11 Planet
- Host AP driver for Intersil
evaluation: "802.11b tests averaged 4.5 Mbps throughput, with a
range of 3.4 to 5.8. 802.11g averaged 18.9 Mbps, with a range of 16.6
to 21.3. 802.11a averaged 14.7 Mbps with a range of 7.4 to 20.3. The
7.4 Mbps probably indicates a defective PC card - excluding it, the
average is 18.4."
LAN resources for Linux
- Linux and wireless
- RF lighting
- 802.11b networking news
- Cantenna: cheap antenna in a can
in the Wireless City, NY Times, November 24, 2002.
on Wireless: A New Class of 802.11 Devices Go the Distance,
Network Computing, March 22, 1999; reviews DS and FH cards.
faults in access control
- Brief introduction to
- Tutorial (1997!)
- Wireless LAN Alliance
- Sonic.net: DSL
provider lets users provide wireless access
802.11, includes tutorial (1996)
from Prof. Jim Kurose's lectures
- WaveLAN: 915 MHz and 2.4 Gb/s
direct-sequence spread spectrum, 2 Mb/s data rate, supports 802.1d
bridging; supports Linux
driver, with documentation
- Voice and 802.11:
The 900 MHz band is subject to channel etiquette. To comply with the
FCC rules, they must not transmit at more than 1W, and they must not use
the same frequency for more than 0.4s out of every 20 seconds, which is
why they hop around in a pseudo-random order between 162 different
channels in that frequency range. As well as allowing them to comply
with the FCC rules, this channel hopping makes the radios relatively
immune to interference -- if there is interference on one channel, they
automatically switch to another one.
Internet Technical Notes and Resources
by Henning Schulzrinne