On Wed, 17 Oct 2007 14:14:43 -0500, "P.Schuman"
<pschuman_NO_SPAM_ME@interserv.com> wrote:
>
>"Jeff Liebermann" <jeffl@cruzio.com> wrote in message >
>> Note that this is a steerable antenna system which works on point to
>> point rules instead of point to multipoint. That means they can belch
>> up to 28 watts EIRP instead of the usual 4 watts EIRP. See some
>> detail at bottom of:
>> <http://www.skypilot.com/technology/sectorswitch.php>
>> In my never humble opinion, this sucks as it creates an alligator (big
>> mouth, small ears) which is an access point that has much more
>> transmit range than receive range.
>It was interesting reading thru the various product pages.
>Wonder if anyone else is using the cellular antenna "sector" concept for WiFi ?
>We have it here for our Motorola Canopy wireless W-ISP system.
Please read the articles again. Skypilot is NOT a sector approach.
Sectors systems, such as Canopy, assume one radio per sector. Skypilot
uses a *steerable* antenna system, where one radio can select a
variety of antennas, pointed around the compass circle. That's quite
different in the bloodshot eyes of the FCC. Sectors to no in
themselves reduce interference with other users. Steerable antenna
systems will reduce interference as they can simultaneously increase
gain in the desired directions, while inserting nulls and holes in the
directions of interference.
Sure. One mutation of the proposed 802.11n standard is to have
steerable antennas, which somehow equates to being MIMO. Ruckus
Wireless is the major chipset vendor, which is used in all manner of
home wireless access points.
<http://www.ruckuswireless.com/technology/beamflex.php>
>The 28w EIRP is for the backhaul in the 4.9-5.4 range...
>so the "A" band would be impacted.
>http://www.skypilot.com/pdf/ds_skyextender.pdf
That's just one of their models. These days, all the mesh vendors are
going after the Homeland Security money, and building mesh radios that
include the 4.9GHz band. The 5.4 to 5.7Ghz 802.11a band is more in
line with what a WISP might be using.
>Noticed that receiver is mentioned as -90dbm @ 6mbps
>How does that compare to what I remember as something like
>20db quieting @ .4uv sensitivity.
Argh. Forget everything you know about ham and commercial land mobile
FM measurement techniques. You can't compare analog and digital
senstivity measurements. 20dB quieting is miserable reference for
digital data because there's no audio output to measure. Instead, we
measure BER (bit error rate) or PER (packet error rate). There are
standards for measurement in the 802.11/b/g specs. The usual
reference levels are 1*10^-5 BER, 1*10^-6 BER, 8% PER, or 10% PER
depending on speed and regulatory authority. I made a graph of the
some published and measured specifications. Note that everyone lies:
<http://802.11junk.com/jeffl/rx-sens/receiver%20sensitivity.htm>
Details if you want, but methinks some reading on digital radio
preformance measurements might be in order first.
--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
jeffl@comix.santa-cruz.ca.us
#
http://802.11junk.com jeffl@cruzio.com
#
http://www.LearnByDestroying.com AE6KS
muni WiFi antenna on lightpole 
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