[160883] in North American Network Operators' Group
Re: 10 Mbit/s problem in your network
daemon@ATHENA.MIT.EDU (Owen DeLong)
Mon Feb 18 04:45:44 2013
From: Owen DeLong <owen@delong.com>
In-Reply-To: <alpine.DEB.2.00.1302180606130.32644@uplift.swm.pp.se>
Date: Mon, 18 Feb 2013 01:42:04 -0800
To: Mikael Abrahamsson <swmike@swm.pp.se>
Cc: NANOG <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Feb 17, 2013, at 21:12 , Mikael Abrahamsson <swmike@swm.pp.se> wrote:
> On Sun, 17 Feb 2013, Owen DeLong wrote:
>=20
>> Greater attenuation is an oversimplification. 5Ghz penetrates things =
like stucco and concrete better than 2.4. OTOH, 2.4 gets through trees
>=20
> My empirical experience with 5GHz says it penetrates concrete a lot =
less than 2.4. For instance, in one building I was in, 5GHz didn't =
penetrate the floor so it was only available on the same floor as the =
AP, but 2.4 GHz worked well both on the floor above and below the AP. =
This was in a building with quite thick concrete floor, a 3 story town =
house with the AP placed on the middle.
The floor isn't just concrete. Many industrial floors include solid =
steel plating in the floor. 5 Ghz will not penetrate that and neither =
will 2.4 (at least not very well).
A town house is also likely to have some form of metal plating (or at =
least a very high concentration of rebar) in the concrete between floors =
as well, so, I suspect your issue was the metal, not the concrete.
2.4Ghz probably found a path around the outside of the building and back =
in. 5Ghz once it starts in a direction tends to continue in that =
direction. It doesn't bounce or curve well at all. 2.4Ghz tends to do =
better at that, creating the illusion of lesser attenuation.
As I said, attenuation is an oversimplification. RF path identification =
and multipath can get very complex very quickly.
>=20
> In my current apartment, I moved my AP out of the clothes closet =
(fairly thin "light concrete" (don't know what it's called) and put it =
on the wall in my hallway, this increased performance on 5GHz =
substantially.
>=20
> So I'd like to know where you got your information from because I'd =
like to read up more because my experience says exactly the opposite.
Without knowing the details of the makeup of the walls in your closet, I =
have to say that seems a bit odd to me. Perhaps there is another =
explanation.
The reason 5Ghz penetrates stucco better, for example is that the 23cm =
wavelength is more than 4x the size of the openings in most of the =
chicken wire used to adhere stucco to walls. The 12cm wavelength of =
5Ghz, OTOH, goes through quite nicely.
Owen
