The issue will be height. Remember, the longer the link, the taller the
freznel zone height requirement will be at the middle of the link.
Tom DeReggi
RapidDSL Wireless, Inc
IntAirNet- Fixed Wireless Broadband
- Original Message -
From: Fred Goldstein fgoldst...@ionary.com
To: WISPA General List wireless@wispa.org
Sent: Monday, November 15, 2010 11:14 AM
Subject: Re: [WISPA] 90-mile path (was Wireless Digest, Vol 35, Issue 21)
At 11/15/2010 04:06 AM, Akinlolu Ajay-Obe wrote:
I need to move 155MB internet traffic over 90miles. Fiber will take
too long and cost too much. Anybody have a solution that will work.
Power is an issue where repeaters are used. Solar would be the
preferred option. I also need to manage and distribute bandwidth. Any
ideas?
The obvious answer is to build a microwave link; the trick is to find the
path.
An old rule of thumb is that microwave links in the 6 GHz range are
good for about 30 miles per hop. This is based on needing very high
reliability (telephone company backbone links) even with
weather-related fade. But it is not a hard limit.
You could theoretically go 90 miles on one hop. The physics are
favorable if the path is direct (mountain to mountain) and doesn't
have extraordinary loss, like rain or trees, or a tropo-ducting event
going on. It takes a large antenna, of course. A 4-foot dish at 5.8
GHz has a lot of gain! One watt TPO is a lot of ERP. Orthogon, now
part of Motorola, did some moby links that way, including a 100-mile
or so high-speed link in Central America. It beats not being on line
at all, even if it fails 1% of the time (not that it's that
bad). But it's not at all likely to give you 99.99% reliability.
Since you're in Nigeria, the climate varies quite a bit and what
works in the dryer areas might not works so well in the wetter
ones. But the main trick is to find a path. If you could find a
mountain or tower with real line-of-sight that let you do two 50-mile
paths, and you could put up big dishes, there are radios that can
pump 155 Mbps. Three hops might be easier. But you should spend some
time with a path calculator.
--
Fred Goldsteink1io fgoldstein at ionary.com
ionary Consulting http://www.ionary.com/
+1 617 795 2701
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