Re: can somebody explains OFDM in FreeBSD?

From: Etienne Robillard <erob_at_gthcfoundation.org>
Date: Sun, 06 Mar 2011 10:59:00 -0500
.
> https://gthc.org/investigations/OFDM/72_armstrong_ofdm.pdf
>
> That paper is a basic paper. COFDM is being used just about everywhere now.
> OFDM was used in the Telebit modems of years gone by. To this day
> (last I checked) it is superiour to the v32.bis format used today on
> third world phone lines, because of its ability to ignore dead spots
> in the frequency spectrums used.
>
> ...
>   
Reference(s) please?
>> I'm worried from a amateur computer scientist point-of-view about the
>> harmfulness
>> of EMF fields; in particular the ELF/VLF frequencies as defined in OFDM,
>> for operating WLAN devices as 'ethernet-class subcarriers'..
>>     
> I personally would not worry about DSL and ethernet. The fields are 
> self cancelling due to the twisted pair. It's a transmission line.
> I do worry much more about cell phone and wifi signals. I advise others
> not to use cellphones for long periods of time without a remote earpiece.
> (And of course, do likewise). Cell phone towers provided they are up high
> enough do not bother me. Keep in mind the inverse square law here. 
> I would also suggest you look for the papers on double blind studies of
> so-called RF sensitive individuals. (ES) I am very sceptical personally
> of the effects. That said, I would not want to be within the near field
> of any high power transmitter. This is why broadcast stations have
> fences around their antennas and warning signs. The high power stuff
> is dangerous.  
>
>   
Its not phone lines who are the main issue, rather the radiation levels
of OFDM
ethernet class devices (including USB devices and routers) using ELF/VLF
frequencies below 30khz
as per the newer 802.11(ng) drafts... ;-)


-- 
Etienne Robillard

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Received on Sun Mar 06 2011 - 14:59:24 UTC

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