Re: Long wireless point-to-point connection with 802.11n

Godigo <Godigo.31uhg5@no-mx.wirelessforums.org> hath wroth:

>I'm new in this jkind of technology,

Welcome.

>so I question if despite 802.11n
>being still in the third draft, it is possible to create directional
>long point-to-point connections with 802.11n... I wanted to do a
>backbone with higher throughput than possible with 802.11g for 2 miles
>(3km) connections.

No, you cannot do a long range link with Pre-802.11n Draft 2.
No, you cannot do 2 miles at speeds faster than 802.11g (i.e. faster
than 54Mbit/sec).

The long range Pre-802.11n Draft 2 link will be impossible for the
simple reason that you'll need 3 external antennas at each end. Also,
external antennas suitable for MIMO are not commonly available. Most
Pre-802.11n Draft 2 routers do NOT have removable antennas.

The long range on faster than 54Mbits/sec is a simple matter of fade
margin. At 54Mbits/sec, you'll need an impossibly strong signal to
get such speeds at 2miles. It can be done, but you won't like the
price or size of the antennas. I can grind the numbers (later) if you
want to see them.

>Since 802.11n uses MIMO smart antenna technologies and consequently two
>or more antennas to transmit using the multipath for transmission
>enhancement, the fact of using multiple directional antennas pointing to
>the same destiny will work??

Close. The Airgo spatial mux mutation of Pre-802.11n Draft 2 spatial
multiplexing requires that the various streams to have slightly
different path lengths to work. If they're all the same, the
interleaved carriers will "collide", and you won't get very much
thruput. It's possible to derrange the multiple antennas to insure
different path lengths, but that becomes ugly with larger arrays.

>Do you know any recommended equipment?

Nope.

Some light reading, which might explain a few things:
<http://www.veriwave.com/gurus/index.asp>
<http://www.intel.com/technology/itj/2003/volume07issue03/art05_air/vol7iss3_art05.pdf>
(A bit old, from 2003, but still useful).

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558