Re: Long-Distance Wi-Fi

[David Farber <dave () farber net>]

________________________________________
From: Lars Poulsen [lars () beagle-ears com]
Sent: Tuesday, March 25, 2008 1:25 AM
To: David Farber
Subject: Re: [IP] Re:   Long-Distance Wi-Fi

From: Brett Glass [brett () lariat net]
> What the article fails to mention is that this technology would not be legal to use in the United States due to the 
> FCC's restrictions on effective isotropic radiated power. Our wireless ISP has long advocated that the FCC allow 
> broadband providers to use additional power to reach outlying areas, subject to the use of spectrum etiquettes to 
> avoid interference.

What the article describes should be feasible under FCC's ISM rules for
the 2.4GHz band. You may have overlooked the rule that allows an
increase in EIRP for point-to-point links with directional antennas
at both ends.

With 24dBi antennas at both ends and 20dBm transmit power, you
can get 69 miles at -90 dBm sensitivity. (Try the RF link budget
calculator at http://www.afar.net/rf-link-budget-calculator/ ).

My company routinely provides equipment for the provisioning
of such links, albeit at lower data rates (2.75 Mbps raw link
speed and below) for scientific and industrial data collection
applications.

As pointed out in the cited article, WiFi protocol is not suited
for this. Our equipment, like the system described in the article,
uses strictly controlled time slots to accomplish this, as well
as to synchronize multiple links on the same tower to avoid
mutual interference.

/ Lars Poulsen
  Afar Communications Inc

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