[Hidden-tech] WiredWest fiberoptic broadband

[ussailis at shaysnet.com]

Absorption by leaves is what is reported by several sources.  The issue is
how this is measured. Typically an experiment is set up where a source
(transmitter and antenna) sends energy thru the forest, and the energy on
the other side is measured with a receiver and antenna.

Unfortunately this measurement does not measure the energy reflected by the
leaves, which is typically back-scattered. And, by conversation of energy,
what doesn't go into the forest isn't measured on the other side.

I made several observations of this and came to the conclusion that at 700
MHz and 2900 MHz that back-scatter was dominant, which explained the
multipath that I measured.

Since my last email, a client found ad for a gadget in the WiFi band that
claimed to have built-in multipath reduction. It claimed to use
'post-priori' processing information.

There was no accompanying patent number, so I remain a skeptic. 

Yes, propagation gets more directional as frequency goes up. There is some
'bending' around sharp edges, but the sharpness of the edge is inversely
related to frequency, so for our purposes, as we say "RF don't go thru
rock."

BTW, this is the drive to go from the 2.45 GHz band to 700 MHz. The other
drive ad nothing to do with technology...The FCC netted 19.8 B$ from the
"sale" of the frequencies that were freed-up from the move to digital TV.
Guess who eventually pays for that? 

And the bandwidth of fiber is the bandwidth of light. Astronomically more
than what can be achieved even with millimeter transmission. The tradeoff
is between lots of "wiring" vs some wiring plus towers and access points.
Politically I think fiber wins here.

Cost-wise? I am not so sure.


Jim Ussailis
jim at nationalwireless.com



Original Message:
-----------------
From: Robert Heller heller at deepsoft.com
Date: Sat, 17 Apr 2010 13:39:03 -0400
To: ussailis at shaysnet.com, reva at revareck.com,
hidden-discuss at mm01.tnrnet.com, heller at deepsoft.com
Subject: Re: [Hidden-tech] WiredWest fiberoptic broadband


At Fri, 16 Apr 2010 22:49:23 -0400 ussailis at shaysnet.com wrote:

> 
>    ** Be sure to fill out the survey/skills inventory in the member's
area.
>    ** If you did, we all thank you.
> 
> 
> The issue with trees, etc is known as "multipath." It represents signals
> arriving from many directions into your antenna. The many directions are
> caused by reflections from leaves, trees, hills, etc.

I also understand that the leaves also tend to absorb the higher
frequencies, esp. those edging up into microwaves.  That is, some of the
radio signal is being turned into sugars (not a lot or particularly
efficiently). 

> 
> Multipath gets worse as frequency increases. 
> 
> Everyone who drives and listens to an FM radio has experienced it: You are
> listing to a interesting program say you stop at a light. The signal is
> distorted, & garbled. That is a multipath null (where the sum of the
> various signal directions results in a very reduced, or null, signal
> level). You inch forward a wee, the signal & interesting program is back.
> You moved out from the multipath null.

Of course, the FM broadcast band is between 88 and 108mhz and broadcast
FM transmitters are far more powerful (in the kilowatt and 10s of
kilowatt range) then any sort of digital wireless transmitters (which
are about 1/4 watt). The long-distance wireless are 700mhz and 900mhz. 
WiFi (802.11) is in the 2.4Ghz band.  The higher the freq., the worse
the foliage affects it (absorption / reflection, plus the more
line-of-sight the signal needs to be (this is where the hills come in).
 

> 
> One problem with wireless broadband is the antennas are fixed, while the
> mutipath null moves about because the trees, etc move about. This results
> in the null moving about. Since you can't easily move the antenna, you
> can't control it.
> 
> Wireless broadband in the clear works well. Thru the trees doesn't work so
> well. Thru rocks (ie hills) it doesn't work at all. 

One should also note: it won't work well though a "shielded box".  Some
building walls behave like a "shielded box" (metal studs or rebar).  Of
course concrete is mostly rock...

> 
> This is another problem we face here in W.MA. Many "access points" would
be
> required to service few customers because of the hills. Each of these
> access points would require a transmitter / receiver and antenna on a
> tower. Some folks don't like that because they think (wrongly) that it
> lowers their property value. This is the NIMBY aspect of it all. In some
> ways the politics are more difficult to overcome than the engineering. 
> 

In some places, politics aside, the number of "access points" would be
so high, that it might be cheaper to just run fiber optic.

Another very important point is that ANY wireless technology is doomed
to becoming obsolescent fairly quickly -- the equipment is very
specialized (as to frequency and signaling methods) and any improvement
in the technology would require wholesale replacement.  Fiber optic, is
pretty much 'future proofed': the bare fiber optic has more bandwidth
capability than the *electronics* currently available to drive it.  As
the technology advances, all that needs to be updated/replaced are the
interface points -- the fiber (on the poles or buried in the ground)
would still be usable as is.

One other thing: wireless technology is bandwidth limited.  

> 
> 
> Jim Ussailis
> 
> jim at nationalwireless.com
> 
> 
> 
> 
> Original Message:
> -----------------
> From: Reva Reck reva at revareck.com
> Date: Wed, 14 Apr 2010 12:17:24 -0400
> To: Hidden-discuss at lists.hidden-tech.net
> Subject: Re: [Hidden-tech] WiredWest fiberoptic broadband
> 
> 
>    ** Be sure to fill out the survey/skills inventory in the member's
area.
>    ** If you did, we all thank you.
> 
> 
> 
> 
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-- 
Robert Heller             -- 978-544-6933
Deepwoods Software        -- Download the Model Railroad System
http://www.deepsoft.com/  -- Binaries for Linux and MS-Windows
heller at deepsoft.com       -- http://www.deepsoft.com/ModelRailroadSystem/
                                                                            
                                              


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