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<div class="moz-cite-prefix">Am 09.03.2013 11:28, schrieb Jon
Crowcroft:<br>
</div>
<blockquote cite="mid:E1UEH0X-0003SN-V1@mta0.cl.cam.ac.uk"
type="cite">
<pre wrap="">
no, its a basis for sound system design.
</pre>
</blockquote>
<br>
Up to now, and I'm looking for this for a decade now and asked many,
many researchers, I don't know a formula which derives the possible
throughput over a wireless channel depending on the SNR. <br>
<br>
And no, Shannon-Hartley doesn't.<br>
<blockquote cite="mid:E1UEH0X-0003SN-V1@mta0.cl.cam.ac.uk"
type="cite">
<pre wrap="">
>>> eventually the signal (to background noise) is too low level to carry any info in any way distinguishable
>>>
>>> >>Data corruption is a phenomenon which occurs at the receiver. The
>>> >>problem is that the receiver cannot successfully rebuild a packet from
>>> >>what he received. The air interface has no idea of which waves are
>>> >>travelling along and whether they make any sense at all.
>>>
>>> you're confusing interference with other sources and misreading the honorably Dave Reed
>>
>>I'm quite sure that I'm not misreading Dave Reed.
>>
you are conflating two (or three) completely different facets of
wireless nets...</pre>
</blockquote>
<br>
Just the opposite is true.<br>
<br>
The problem is that we often observe <u>one</u> phenomenon, e.g.
packets are not ACKed in time, which can be the consequence of<br>
- collision, i.e. a MAC problem,<br>
- corruption, caused by noise, shading, interference etc.,<br>
- congestion,<br>
and believe that there is <u>the one single reason</u> for the
observed phenomenon and afterwards identify this by an educated
guess or divine inspiration.<br>
<br>
This is sometimes called "ratio ex post" and is one of the two most
often made mistakes in science.<br>
(The other one is to mistake coincidence for correlation and even
more causal relation. Take this and "ratio ex post" - and I'm
convinced you can falsify the vast majority of medical studies
currently being published.) <br>
<br>
When I understand Dave correctly, this is what Dave sometimes calls
"confirmation bias". <br>
<br>
<blockquote cite="mid:E1UEH0X-0003SN-V1@mta0.cl.cam.ac.uk"
type="cite">
<pre wrap="">
>>> secondly, you are ignoring absorption (e.g. by water vapour which gets a little bit hotter)
>>> and also _self_ interferance (aka Ricean fading) and scattering (rayleigh fading)
>>>
>>
>>So, a model which correctly describes wireless channels is that flexible
>>that it fits anything - and has no use at all.
incorrect - it is a sound basis for design. </pre>
</blockquote>
<br>
No. A model with dozens of variables, hardly any of which can be
estimated in a sound way doesn't prove anything.<br>
<br>
A typical example is the loss differentiation debate.<br>
<br>
There are literally hundreds of papers around which try to determine
whether a packet loss is due to corruption or congestion.<br>
<br>
Take any of them - and look for "ratio ex post" - I don't know at
least one single paper which holds.<br>
<br>
<br>
<pre class="moz-signature" cols="72">--
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