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FrankE
2017-05-06 21:33:58 +02:00
parent edd41293c1
commit ea887af537
8 changed files with 69 additions and 53 deletions
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tex/chapters/work.tex
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@@ -51,7 +51,7 @@
to also serve for indoor purposes.
%
It predicts an \docAP{}'s signal strength
for an arbitrary location
for an arbitrary location,
%$\mPosVec{}$
given the distance $d$ between both and two environmental parameters:
The \docAPshort{}'s signal strength \mTXP{} measurable at a known distance $d_0$ (usually \SI{1}{\meter}) and
@@ -97,7 +97,7 @@
\mTXP{}, \mPLE{} and \mWAF{}.
While it is possible to use empiric values for those environmental parameters \cite{Ebner-15}, the positions are mandatory.
For many buildings, there should be floorplans that include the locations of all installed transmitters.
For many buildings there should be floorplans that include the locations of all installed transmitters.
If so, a model setup takes only several minutes to (vaguely) position the \docAPshort{}s within a virtual
map and assign some fixed, empirically chosen parameters for \mTXP{}, \mPLE{} and \mWAF{}.
Depending on the building's architecture this might already provide enough accuracy for some use-cases,
@@ -261,7 +261,7 @@
Evaluations within previous works showed, that there are many situations where the overall \docWIFI{} location estimation
is highly erroneous. Either when the signal strength prediction model does not match real-world
conditions or the received measurements are ambiguous and there is more than one location
conditions, or the received measurements are ambiguous and there is more than one location
within the building that matches those readings. Both cases can occur e.g. in areas surrounded by
concrete walls, where the model does not match the real-world conditions as those walls are not considered,
and the smartphone barely receives \docAPshort{}s due to the high attenuation.
@@ -307,12 +307,12 @@
due to environmental conditions like temperature, humidity, open/closed doors and RF interference.
Fast variations can be addressed by averaging several consecutive measurements at the expense
of a delay in time.
To prevent this delay we use the fact, that many buildings use so called virtual access points
To prevent this delay, we use the fact, that many buildings use so called virtual access points
where one physical hardware \docAP{} provides more than one virtual network to connect to.
They can usually be identified, as only the last digit of the MAC address is altered among the virtual networks.
%
As those normally share the same frequency, they are unable to transmit at the same instant in time.
When scanning for \docAPshort{}s one will thus receive several responses from the same hardware, all with
When scanning for \docAPshort{}s, one will thus receive several responses from the same hardware, all with
a very small delay (micro- to milliseconds). Such measurements may be grouped using some aggregate
function like average, median or maximum instead of using each single measurement.