5.7/5.8 GHz 802.11n dual polarity MIMO through office building glass, 1.5 km distance

Wed Dec 29 13:27:25 UTC 2010

On 12/28/2010 11:48 PM, Anonymous List User wrote:
> For architectural and building management reasons we cannot mount our
> antennas in a rooftop or outdoor location at either end.  The distance
> between two buildings is 1.5 km, and the fresnel zone is clear.  Antennas
> need to be located indoors at both ends and will be placed on small speaker
> stand tripod pointing at windows.  This has been done successfully before
> with 2.4 GHz 802.11g equipment and a link from an office in the Westin to a
> nearby apartment building, but I am unsure of what effect glass will have on
> 5 GHz.  Has anyone tried this?
>    
Low-E glass is brutal on radio waves.  If the windows are tinted, 
multi-layer, or have metalic particles success may be difficult.  You 
may want to test with some 802.11a network cards in ad-hoc mode to see 
if you can actually communicate over the 1500m path.   We have had to 
deal with a condo association to get approval to mount some panels 
outside at one site.  It can usually be discussed when presented with 
the facts and some photo-shop edits to show what visual impact it will 
have.  However, be prepared for a significant delay in some cases and 
success is never a sure thing.

Another item of concern is you are looking at IC/FCC unlicensed bands.  
Ten years ago 5.8 was fairly clean, but more recently we have found a 
lot more consumer devices invading the spectrum.  We had a 1km path with 
a $15K microwave system knocked out by a consumer $50 cordless phone 
that was 1/2 block away.  (We purchased a DECT6 phone for them and 
'solved' the immediate issue... until we could obtain a license/path and 
the equipment to install something that wouldn't be interfered with.)

-- 
Shane Allan Godmere
Senior Telecommunications Engineer II
Michigan Technological University
1400 Townsend Dr.  EERC-B31
Houghton, MI 49931