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Subject: Re: Simulate Radio wave interference
To:     Johannes Berg <johannes@sipsolutions.net>
Cc:     linux-wireless@vger.kernel.org
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From:   Masashi Honma <masashi.honma@gmail.com>
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Date:   Sun, 22 Mar 2020 09:34:31 +0900
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On 2020/03/17 0:42, Johannes Berg wrote:
 > I don't see this - the signal strength is just taken as is, and
 > overwritten, so there's no accumulation going on?

Right. The signal strength is not accumulated. The commit log is wrong.
The interference model is accumulating frame duration to calculate
probabilities. About accumulation of signal strength, it could be
calculated as vector. I wrote about it in response to realistic
simulation.

I think I should explain the concept of this interference model.
The interference model assumes signals which strength is under CCA
threshold are interference signal. The model accumulates the duration
of such signals. The model assumes (accumulated duration / time slot)
is probability of occurrence of interference. When interference occurs,
the model reduce the max signal strength of interfering STA from
transmitting STA's signal strength.

Though the implementation is not among the concept of the model. The
signal strength from node A to B was calculated and wrongly accumulated
to interference duration of "A to all".

I fixed it to "A to B" and sent a Pull Request to wmediumd.
https://github.com/bcopeland/wmediumd/pull/22

 > I guess my question really is how what's actually implemented is meant
 > to map to the physical world?

To get closer to real world, it is necessary to consider the phase of
radio wave. A radio wave could be weakened by radio waves which has
opposite phase.

Calculation of radio wave phase of multi signals could be described by
electric field created by mesh node antenna. By using this electric
field model, we could accumulate some interference signals as vector.

I have an idea of implementation. Though I need some more time to
implement this.

Regards,
Masashi Honma.