[e2e] VJCC vs. Keshav

Jon Crowcroft Jon.Crowcroft at cl.cam.ac.uk
Thu Apr 18 08:18:29 PDT 2013

yes, actually we can simulate that - 
in fact i was on the committee of a very smart PhD student (Gregor Gaertner)in Trinity College
Dublin who did a bunch of empirical studies  of wifi propagation in the streets
and then built exactly the hybrid matlab+ns2 simulation I am describing
[note wifi is wideband radio in a sense so this is notionally harder than a single narrow band

yes, it has to do something like the spatial resolution of the 1/2 wavelength of the radio
and temporal resolution of the movement of people/devices over that space (actually it turns out it doesnt for
various interesting reasons) - the simulator and measurements matched well...

no humour involved at all

In missive <51700BB6.2080606 at web.de>, Detlef Bosau typed:

 >>Am 18.04.2013 14:53, schrieb Jon Crowcroft:
 >>> In missive <516FE1DA.9050708 at web.de>, Detlef Bosau typed:
 >>>   >>Yes. And being short and frankly: When it comes to mobile networks, I
 >>>   >>don't believe a word of the packet-pair and packet-train stuff.
 >>>   >>Even for the radio interface, it simply doesn't make sense to talk about
 >>>   >>an "average bit rate" in this case, when this is associated with both, a
 >>>   >>reasonable hight throughput and a reasonably low block corruption rate.
 >>> this depends on the model and simulator - if you model the signal
 >>> propagation and do it with fine grain enough discrete event rate, then
 >>Jon, I once attended a talk where the speaker proposes to do ray traicing...
 >>And please keep in mind the GEOMETRIC "period" of minima and maxima in 
 >>IIRC: Rule of thumb: half of the bearer frequencies wavelength. I.e. 
 >>with GSM, round abouht 1 GHz, wavelength round about 30 centimetres.
 >>I.e. 15 centimetres between two points of maximum receiving power.
 >>It was exactly that moment, where I stopped giggling about the persons 
 >>who I've seen "mobile phone callisthenics" by shifting around their 
 >>phones 5 cm to the left or 10 cm to the right in order to increase their 
 >>WWW browsers throughput.
 >>And you want to simulate that, perhaps with ray tracing and perhaps a 
 >>temporal resolution of say 1 ms and a geometric resolution of say 1 cm?
 >>Sorry, I cannot take this seriously.
 >>Detlef Bosau
 >>Galileistraße 30
 >>70565 Stuttgart                            Tel.:   +49 711 5208031
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 >>                                            skype:     detlef.bosau
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 >>detlef.bosau at web.de                     http://www.detlef-bosau.de



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