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FrankE
2017-05-08 14:38:14 +02:00
parent ea887af537
commit 7021034e6d
8 changed files with 107 additions and 43 deletions
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tex/chapters/work.tex
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@@ -17,7 +17,7 @@
\label{eq:wifiObs}
\end{equation}
where matching a single signal strength observation against the reference is given by
\noindent where matching a single signal strength observation against the reference is given by
\begin{equation}
p(\mRssi_i \mid \mPosVec) =
@@ -127,6 +127,8 @@
The target function \refeq{eq:optTarget} optimizes the model-parameters for one \docAP{} by reducing the squared error between
reference measurements $s_{\mPosVec} \in \vec{s}$ with well-known location $\mPosVec$ and corresponding
model predictions $\mu_{\mPosVec}$.
The number of floors between $\mPosVec$ and the transmitter's location $\mPosAPVec$ is
$\text{floors}(\mPosVec,\mPosAPVec)$.
\begin{equation}
\epsilon^* =
@@ -189,7 +191,7 @@
%\end{figure}
Such functions demand for optimization algorithms, that are able to deal with non-convex functions.
We thus used a genetic algorithm to perform this task.
We thus used a genetic algorithm to perform this task \cite{goldberg89}.
However, initial tests indicated that while being superior to simplex
and similar algorithms, the results were not yet satisfying as the optimization often did not converge.
@@ -198,9 +200,11 @@
genetic algorithm: The initial population is now uniformly sampled from the known range. During each iteration,
the best \SI{25}{\percent} of the population are kept and the remaining entries are
re-created by modifying the best entries with uniform random values within
$\pm$\SI{10}{\percent} of the known range. The result is stabilized by narrowing the allowed modification range
$\pm$\SI{10}{\percent} of the known range.
Inspired by {\em cooling} known from simulated annealing \cite{Kirkpatrick83optimizationby},
the result is stabilized by narrowing the allowed modification range
%(starting at \SI{10}{\percent})
over time, often referred to as {\em cooling} \cite{Kirkpatrick83optimizationby}.
over time.
\subsection{Modified Signal Strength Model}
@@ -300,7 +304,7 @@
\label{eq:wifiQuality}
\end{equation}
\subsection {Virtual \docAP{}s}
\subsection {Virtual \docAP{}s (VAP)}
\label{sec:vap}
Assuming normal conditions, the received signal strength at one location will also (strongly) vary over time