[e2e] Congestion control as a hot topic in IETF
detlef.bosau at web.de
Fri Mar 8 11:30:18 PST 2013
Am 08.03.2013 16:54, schrieb Jon Crowcroft:
> In missive <513A04BE.4060505 at web.de>, Detlef Bosau typed:
> >>> btw, path loss is very real (and not at the antennae)
> >>Or can you tell me where the waves have gone? Where the energy has gone?
> this is physics #101 - if you transmit with some power level, and spread that over a distance, guess what, at a
> distance with a signal that is spreading out over a surface, the power level is lower
Good answer :-)
I see, you understood why the power level depends on the distance via a
And that means what?
Merely nothing. When I move around my laptop in my apartment, I use WLAN
to access my DSL router, the power level will change.
However: Hardly that much that the packet corruption level is affected.
Unfortunately, in my appartment I see up to 8 (eight) WLANs.
So, what do you think affects my data rate notebook - router? Me moving
around in the apartment or my neighbours surfing the Internet?
In addition, the SNR sinks continuously when moving around. The packet
corruption ratio doesn't.
It is a theoretical game with numbers.
> 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.
> 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.
I don't think I misread Dave Reed - to the contrary, in some particular
respects I share his anger.
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