<ZetaR>
DocScrutinizer05: The three receivers do not need to form a triangle enclosing the measured point. Any three will do, provided they can each measure the signal accurately, and they are sufficiently far apart. If the terrain approximates a flat surface, you can even use just two.
<DocScrutinizer05>
yes, basically you're right
<ZetaR>
Enclosing the point would give better average reception though.
<DocScrutinizer05>
but there are certzain niche cases where you can't locate anymore, afaik
<ZetaR>
I suppose, because there are cases where your vector norm does not approximate the Euclidean norm.
<ZetaR>
I think most of those cases would be in heavily populated areas, where there are probably tons of U-TDOA equipped receivers.
<DocScrutinizer05>
hmm, nope, I'm wrong. There's no mathematically impossible line or area of location outside a triangle
<DocScrutinizer05>
and yes, at last one
<DocScrutinizer05>
when the TX is outside of RX triangle, you can estimate distance only by bend of waveform
<DocScrutinizer05>
of the imaginary circly around the TX
<DocScrutinizer05>
circle*
<DocScrutinizer05>
or, by a different approach, ratio between total distance R1-T and R2-T (and R3-T) approaches 1.0 very closely, thus the positioning gets massively uncertain
<ZetaR>
It is true that it gets uncertain rapidly, but I am drawing out the problem and I don't see a significant difference between being inside and outside the imaginary circle, aside from the increasing effect of measurement error.
<ZetaR>
You still have the same type of information to calculate position in either case.
<DocScrutinizer05>
yes, no algorithmic undetermined points
<ZetaR>
Sorry, have to go AFK for a bit.
<DocScrutinizer05>
just : x . is a much better model to determine pos of x by distance to the 3 dotsm than :. x
<DocScrutinizer05>
particularly when you don't have absolute distances but only d1 = d2 + a = d3 + b
<DocScrutinizer05>
or rather you know d2=d1+M d3=d1+N. You only know M, N
<DocScrutinizer05>
you don't know d1 (or d2, d3)
<DocScrutinizer05>
for :. x d1,d2,d3 are huge compared to M,N
<DocScrutinizer05>
and M,N don't change much, no matter how far you move X away from the 3 dots
<DocScrutinizer05>
the tangens approaches 0
<DocScrutinizer05>
so it's almost impossible to tel the distance
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<R0b0t1>
DocScrutinizer05: IMEI and modem software info
<R0b0t1>
Wizzup: ^
<R0b0t1>
like could you fingerprint the device in any way besides phone number if all you had was phonenumber and some calls to it
<R0b0t1>
also,
<R0b0t1>
DocScrutinizer05: What is the bandwidth to the modems? Is it a single serial link, and what speed is it, whatever it is?
<R0b0t1>
DocScrutinizer05: Also if you happen to know the details of the memory architecture that most phones use that would be interesting
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<DocScrutinizer05>
R0b0t1: (fingerprint) the tale is that you actually could determine the type and version of modem/firmware from comparing tiny differences in signal with actual fingerprints, by just listening to the RF. IMEI is sent OTA during (re?)authentication and since we all know the crypto on GSM is weak...
<DocScrutinizer05>
and of course you can fake a BTS and force the modem to disclose all those details to that fake BTS
<DocScrutinizer05>
sorry, missed the question about bandwidth
<DocScrutinizer05>
most phones nowaday use a shared memory architecture, I'd say
<R0b0t1>
DocScrutinizer05: I mean bandwidth modem to CPU. And as to the shared memory arch, how do the two processors interact? Best guess is ok, so I have something to google that gets me somewhere.
<DocScrutinizer05>
anyway sounds like an XY problem
<DocScrutinizer05>
bandwidth from modem to CPU is not existent on shared memory architecture
<R0b0t1>
yes, DMA write speed would dictate it, but it's probably too high to be a bottleneck
<DocScrutinizer05>
often ther CPUs are not even assigned, often it's like xen/vmware
<R0b0t1>
I mean if the modem on neo900 has a serial link to the main CPU, what will the bandwidth be? max or average or min
<R0b0t1>
as it won't be DMA in the neo900 yes?
<DocScrutinizer05>
well, DMA was from radio I/Q ADC to CPU maybe
<DocScrutinizer05>
that's not data though
<R0b0t1>
could you explain xen comment?
<DocScrutinizer05>
the Neo900 bandwidth is 480MB USB highspeed maximum
<R0b0t1>
radio IQ to radio CPU to main memory I mean
<R0b0t1>
oh okay cool
<DocScrutinizer05>
(xen) your modem firmware boots the CPU and eventually loads a "virtual machine" (like xen DomU) which runs the application processes. They all share the same hw platform, incl possible multicore CPU
<R0b0t1>
aaaaah
<R0b0t1>
okay
<R0b0t1>
kind of surprising
<R0b0t1>
interesting
<DocScrutinizer05>
OMAP5 phones still use HSI a lot
<DocScrutinizer05>
so they are basically similar to N(eo)900
<DocScrutinizer05>
but this design is not "modern" anymore since it's too bulky and too expensive