802.11

[Ronnie Gauthier]

While its rate is slower "b" will give greater penetration ability
(than "g") through walls or surrounding steel structures

Ronnie

On Thu, 05 Jan 2006 09:21:57 +0100
Roger Oberholtzer <roger at opq.se> wrote:

> On Wed, 2006-01-04 at 19:54 -0500, David Bandel wrote:
> > On 1/4/06, Man-wai CHANG <mwchang at i-cable.com> wrote:
> > >
> > > Why are they "a", "g" and "n"?
> > 
> > 802.11a:  5GHz (actually 4.9GHz to 6.1GHz) usually OFDM, but can be DSSS, 54Mb+
> > 802.11b:  2.4GHz (DSSS or FHSS) -- old, slow, 11Mb
> > 802.11g:  2.4GHz (OFDM) faster -- 54Mb+
> > 
> > OFDM: orthagonic frequency division and multiplexing (means the signal
> > can take multiple paths and the signal can be recombined by the signal
> > processor in the radio to get signal where there are obstructions to
> > lines of sight -- note that this means reflected signal as found in
> > other than the 1st fresnal zone -- also note that rocks, buildings
> > made of concrete, glass, and/or metal, roads, deserts, water, are
> > reflective surfaces, but trees are not.)
> > 
> > The + means that many systems can basically do channel bonding and go
> > into "turbo" mode where they actually get 108Mb.
> > 
> > Throughput is another story.  But my 802.11a networks see 12Mb+
> > throughput on a 36Mb connection.  This slow throughput is actually a
> > function more of the slow ack times required for the distances
> > involved (I have 20+ mile links -- several).  Throughput also suffers
> > as number of radio connections increases.
> > 
> > You can calculate the radius of your fresnel zone (required
> > object-free area) for any line-of-sight shot at my web page
> > (http://www.pananix.com), look for the RF calculations link.
> 
> Interesting page. Not that I knew what to enter. I live in an old
> building (>100 years), and some walls are very thick (>1 foot) with
> stone and brick. I have a wireless access point (11g) that I simply
> cannot reach from some surprising places. So I have been looking at
> newer hardware that claim to address these issues. Like 11pre-n. A
> friend that works for Swedish telecom (Televerket) said that a main
> reason pre-n and other higher-availability devices have not been
> finalized (pre-n -> n) is that to provide greater availability they up
> the power, which is not considered a good thing to do in home
> appliances. The real odd thing is that I can sometimes connect to a
> neighbor's access point better than my own - even when I am in the same
> room with mine. And the neighbor's AP is behind a number of these walls.
> Odd.
> 
> -- 
> Roger Oberholtzer
> OPQ Systems AB
> 
> 
> _______________________________________________
> Linux-users mailing list ( Linux-users at linux-sxs.org )
> Unsub/Password/Etc: http://mail.linux-sxs.org/cgi-bin/mailman/listinfo/linux-users
> 
> Need to chat further on this subject? Check out #linux-users on irc.linux-sxs.org !