RE: [CUWiN] WiMax Vs Wi-Fi RF Issues

Re: WiMax Article Response


First of all, I would avoid any criticism regarding RF exposure with
WiMax since it is obvious to me that you are shooting from the hip.

Many of the cellular towers that are used for cellular telephony use 20
watts output into a 10 db gain antenna for 200 EIRP or more. The North
America cellular phones operate in both the 800 MHz and 1800 MHz
spectrum. The 1800 MHz band is close to the 2400 MHz for 802.11b/g.

The cellular handsets operate at 0.6 watt power output with the antenna
often next to you ear or eye.  This compares to an AP or PCMCIA card at
0.1 watt. While the AP antenna may have a 6 dB gain for an EIRP 0f .4
watts, it is rarely located next to your ear or eye.  (There are issues
regarding measurements based on a dipole or Isotropic radiator with a 2+
dB difference but this is not significant to this discussion).

Further, Public safety personnel, Police and Fire plus utility companies
and Municipalities use 800 MHz radios with handheld power outputs of 2
watts or more --often 4 watts. These radios are used with their antennas
near the users ear or eye. The Base Station radios again are like the
cellular radios with outputs of 40 watts and more into high gain
antennas. The FCC has RF exposure limits and today's handheld RF devices
comply with those regulations. However, there is some controversy and
there are new studies made yearly that are critical of the US standards.

Finally, WiMax HANDHELD radios will not have 30 watts output power. The
battery would be to heavy to carry to support that much power for
several hours of use.  The power output for the handhelds will likely be
similar to today's cellular telephones. The base station radios
---located outside on 100 foot towers/poles--- will likely be at 30
watts output power into high gain antennas--not too dissimilar to
today's cellular infrastructure network.

Carl Kolenda
BSEE
NW8Z





-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Illustrious
niteshad
Sent: Tuesday, September 14, 2004 5:46 PM
To: Sascha Meinrath; Paul Smith
Cc: [email protected]
Subject: Re: [CUWiN] Slate on community wireless networks



> On Tue, 14 Sep 2004, Paul Smith wrote:
> 
> > http://slate.msn.com/id/2106657/
> >
> > I'm composing a response to Paul emphasizing emerging spectrum 
> > management methods that mitigate interference.
> 
> This is a pretty shoddy piece of work.  I wonder how much of it was 
> written in consultation with Ron Resnick of the WiMax Forum and where 
> they're getting their information on Wi-Fi capabilities (since they
are 
> clearly incorrect -- CUWiN has multiple links that are way over 300
feet 
> and can make solid links through trees of several hundred meters
before 
> things become marginal).  I do agree that city-wide WiFi systems won't
be 
> "free", but they'll be "free to the end-users" if they're municipally 
> supported (thus helping to eliminate the digital divide and allowing
_all_ 
> users to get online, not just the priviledged few who can afford it).
> 

First, we must define "municipally supported."  To my mind, municipal
has a much more organized connotation associated with it than does
"community."  "Municipal" implies that the city government will be
involved, as is the case in Philiadelphia.  If the city is absorbing the
cost of building and supporting the network, as well as the cost of
providing bandwidth to the Internet from the network, then it is
decidedly _not_ free; the citizens are paying for this service through
the various municipal taxes they pay.  In my experience, a concerned
group of citizens is capable of acting far more quickly and efficiently
than the government ever could.  Therefore, I very much favor the
community co-op model in terms of paying the costs associated with the
network, since I believe that this will lead to a lower total cost to
the end-users of the network.  That said, I also have no problem with
subsidizing the service for those who can't otherwise afford it.  

Paul Boutin's article oozes FUD (Fear, Uncertainty & Doubt), which
shouldn't surprise any of us, since it was published on MSN Slanted...I
mean, Slate ;)  What surprised and shocked me was that they are talking
about power outputs (from sector or omnidirectional antennas) of 30
Watts for the licensed users.  In the physics lab, I've personally
(accidentally) had my head in the side-band of a 10 Watt microwave beam
(can't recall if it was 2.4 GHz  or 10 GHz); a very brief exposure gave
me a splitting headache that lasted all afternoon.  This shouldn't be
surprising, since my brain was basically being cooked.  The microwave
spectrum, long-wards of 2 GHz is semi-permeable; if the signal is
powerful enough to permeate a wall, it's powerful enough to permeate a
person.  Some of that radiation will be absorbed by the person, and the
effects of long-term, low doses of radiation are poorly understood at
this time.  I don't know much about WiMax, but I'm wondering if all of
the proper
  health physics studies have been done regarding its deployment.

best regards,

Mark Lenigan
Director of Research and Development
Detroit Wireless Project



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