Re: 40 GBit @ 240 GHz across 1 km LoS

[Warren Bailey <wbailey () satelliteintelligencegroup com>]

I disagree.

It's not the near field stuff that is an issue.. It's the far field stuff
further down the road that is going to murder the link.. Look at his Fig 1
and Fig 2. 

Fig 1 is saying that he is getting killed at 50mm/h of rain at 60 gig and
at 175 gig. Fig 2 is saying that everything works well until you exceed
.1km - where real life kicks back in. His clear sky is normal for anything
wireless, but look at what happens at distances exceeding his comfort
zone. From .1km to 1km he's taking 30-50dB of loss on his link. I don't
know what kind of transmitter he has, but *IF* he were to encounter rain I
sure as hell hope he has a form of transmit power control. I also noticed
that they're using OOK, which is much better than FSK but runs the risk of
being clobbered by a relatively small amount of noise.

So yes, this is awesome for running huge data rates across the street.
Down the road, you may have a few bad days.

On 5/17/13 8:22 AM, "Carsten Bormann" <cabo () tzi org> wrote:

> On May 17, 2013, at 16:30, Warren Bailey
> <wbailey () satelliteintelligencegroup com> wrote:
>
> > By not working. At those frequencies you're talking a light moisture
> > pocket taking the entire link down.
>
> Not quite as bad:
>
> http://www.uni-stuttgart.de/int/institut/MA_Publikationen/reichart/COMCAS_
> 25G_link.pdf
>
> The ~ 50 mm/h rain they seem to budget for is not yet quite an "end of
> the world" torrent, but it's not like you sneeze and the link goes down.
> (And if you have more than 50 mm/h sustained, you've got a much, much
> bigger problem :-)
>
> Grüße, Carsten