At 11:15 PM 10/3/2009, Lawrence wrote:
>All things being equal (which they often aren't) 802.11b will give 
>you a higher S/N and C/I than 802.11g, because in almost all cases 
>and especially at higher speeds. 802.11g has to lower the PA power 
>because of the PAPR of OFDM and meeting the 802.11g EVM spec.

Given, and considering OFDM modulation vice CCK, there are a couple 
things to note.  With G, and the faster data rates, client 
transactions are over faster and tend to give the AP back sooner, 
especially if the operator elects to transmit the PLCP header with a 
short (56 bit) preamble.  This is true for at least 90% of the 
traffic on my network which is very bursty activity.  Get 'em out of 
the way faster!  Additionally, OFDM survives in a multi-path 
environment much better.  In my environment, water towers, barns, 
machine sheds, silos all seem to reflect the signal around.

>Having said all that we didn't use 802.11b at all because it's data 
>rates are too low for video.

There are some links which, because of a lower signal to noise, where 
B just works much better.  But, while they are "on" are using the 
resources of the sector much longer than their G counterparts.

>Also while we supported 2.4 GHz, we mostly deployed at 5.8 GHz ISM 
>because of the increased power available there and the pollution was 
>much less, but that maybe different now.

In my environment neither is saturated.  2.4 works better because of 
the variability in terrain.  Signals arriving over corn fields also 
work better than signals arriving over bean fields.  :-)

>There is no substitute for link margin, you can never really have enough.
I like to do installs this time of year.  Foliage is at maximum 
growth for the year.  Crops are mature and waving in the breeze. The 
leaves are drying but still on the trees.  Rain water collects in 
those trees.  If it works now, and I have sufficient fade margin, it 
will only get better this winter as the leaves drop.

>Tne of the down sides of fitting a 5 or 10 MHz channel in a sweet 
>spot is that it can change at any time.

This is true of any "public" frequency, but the effects on a half or 
quarter channel are less pronounced, and the fractional channels give 
an immediate boost in the SI over a 20 MHz channel size.

I think there is room for ANY lively discussions on this list; 
administrative, technical or otherwise.  Long live wireless and free 


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