Wireless protos- 11a 11b 11g ....11x?

[Bill Freeman]

Jeff Kinz writes:
 > I just got asked what the differences are between the various wireless 
 > protoccols and I'm realizing I don't have a good summary available.  Does
 > anyone know of a website or document that explains what is special about
 > "11n" (possibly vs 11g)?

	If you're an IEEE member you can get PDF's of the specs free.
Otherwise they charge.

	There are lots of other letters two, but these are the (current)
ones that deal with the connectivity (as opposed to security, etc.).

	802.11b is an 11Mbps (max, with fall baxk) scheme using "channels"
around 2.4GHz.  There are, I believe, 14 channels, where almost no country
allows the use of all of them.  The US authorizes 11 of them.

	802.11g uses the same spectrum as b, but uses wider bandwidth
signals to allow 54Mbps (max).  The wider bandwidth means that these
signals don't fit in a 802.11b channel: each g uses several of the b
channels, allowing only 3 channels of g in the "band".

	802.11a uses a separate band around 5GHz, where more spectrum is
available, allowing a more reasonable number of 54Mbps channels (I don't
remember exactly, but I think that it's on the order of 10 of them).

	I believe that these are all spread spectrum schemes.  I don't
know if a and g are similar modulation schemes that are just on
different frequencies.  Because the RF stuff is compatible between b
and g, most g designs allow communication in b as well, with
essentially no extra hardware.

	The g stuff came in at the same time as it became comfortable
to produce somewhat software defined radios.  The channel set and more
is determined by software controls, and these radios are capable of
operating well outside the allowed (in any given country) frequency
ranges, etc.  The manufacturer's lawyers have told them that folks
like the FCC will hold them accountable if they make it too easy for
users to set them up to operate illegally, which is the main reason
that they won't give sufficient hardware info for Linux folks to write
device drivers.

	I hope that this helps, and I hope that it isn't too
inaccurate.

							Bill