current code and TeX. code fine?!?!?!
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tex/bare_conf.tex
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tex/bare_conf.tex
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@@ -81,6 +81,8 @@
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%\usepackage{ulem}
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%\setcounter{figure}{0}
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%\renewcommand{\thefigure}{A\arabic{section}.\arabic{figure}}
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% replacement for the SI package
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tex/chapters/abstract.tex
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tex/chapters/abstract.tex
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tex/chapters/conclusion.tex
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tex/chapters/conclusion.tex
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tex/chapters/experiments.tex
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tex/chapters/experiments.tex
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@@ -41,13 +41,13 @@
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\centering
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\input{gfx/all_fingerprints.tex}
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}
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\label{fig:referenceMeasurements}
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\caption{
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Locations of the 121 reference measurements.
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The size of each square denotes the number of permanently installed \docAPshort{}s
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that are visible at this location,
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and ranges between 2 and 22 with an average of 9.
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}
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\label{fig:referenceMeasurements}
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\end{figure}
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% visible APs:
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@@ -56,12 +56,12 @@
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\begin{figure}[b]
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\centering
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\input{gfx/compare-wifi-in-out.tex}
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\label{fig:wifiIndoorOutdoor}
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\caption{
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Measurable signal strengths of a testing \docAPshort{} (black dot).
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While the signal diminishes slowly along the corridor (upper rectangle)
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the metallised windows (dashed outline) attenuate the signal by over \SI{30}{\decibel} (lower rectangle).
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}
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\label{fig:wifiIndoorOutdoor}
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\end{figure}
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Figure \ref{fig:wifiIndoorOutdoor} depicts the to-be-expected issues by examining the signal strength
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@@ -105,11 +105,11 @@
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\begin{figure}
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\input{gfx/wifi_model_error_0_95.tex}
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%\input{gfx/wifi_model_error_95_100.tex}
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\label{fig:wifiModelError}
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\caption{
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Comparison between different optimization strategies by examining the error (in \decibel) at each reference measurement.
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The higher the number of variable parameters, the better the model resembles real world conditions.
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}
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\label{fig:wifiModelError}
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\end{figure}
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% statds:
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@@ -135,30 +135,77 @@
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As we try to minimize the system's setup time as much as possible, we need to determine
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the amount of necessary reference measurements for the optimization to produce viable model parameters.
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Depending on the number of to-be-optimized model parameters, more measurements are required.
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This especially holds true for {\em \optPerRegion{}} where each region needs at least some measurements
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to determine transmitter positions and parameters.
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Depending on the chosen model and thus the number of to-be-optimized parameters, more measurements are required.
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While there was almost no difference between using 121 or 30 reference measurements for
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{\em \optParamsAllAP{}} and {\em \optParamsEachAP{}}
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(average \SIrange{5.3}{5.4}{\decibel} and \SIrange{4.5}{5.0}{\decibel}),
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{\em \optPerRegion{}} is highly affected
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(average \SIrange{2.0}{6.2}{\decibel}), as it needs at least a certain number of measurements for each
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of its regions for the optimization to converge.
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\begin{figure}[b]
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\input{gfx/wifi_model_error_num_fingerprints_method_5_0_90.tex}
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\input{gfx/wifi_model_error_num_fingerprints_method_5_90_100.tex}
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\label{fig:wifiNumFingerprints}%
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\caption{%
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number of fingerprints
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Impact of reducing the number of reference measurements during optimization on {\em \optPerRegion{}}.
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The model's cumulative error distribution is determined by comparing the its signal strength prediction against all 121 measurements.
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While using only \SI{50}{\percent} of the 121 scans has barely an impact on the error,
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30 measurements (\SI{25}{\percent}) are clearly insufficient.
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}%
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\label{fig:wifiNumFingerprints}%
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\end{figure}
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Figure \ref{fig:wifiNumFingerprints} depicts the impact of reducing the number of fingerprints
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for the {\em \optPerRegion{}} strategy. Only using 60 of the 121 fingerprints yields only a slightly
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increasing model error and still provides good results. While using only \SI{25}{\percent} of the reference
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measurements increases the error rapidly, \SI{75}{\percent} of all considered errors are still better
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than using just empiric values without any reference measurements.
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Figure \ref{fig:wifiNumFingerprints} depicts the impact of reducing the number of reference measurements
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during the optimization process for the {\em \optPerRegion{}} strategy.
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The error is determined by using the (absolute) difference between expected signal strength and
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the optimized model's corresponding prediction for all of the 121 reference measurements.
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%
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Considering only 60 of the 121 scans (\SI{50}{\percent}) yields a slightly increasing model error and still provides good results.
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While using only \SI{25}{\percent} of the reference measurements increases the error rapidly,
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for \SI{75}{\percent} of the 121 considered cases the estimation is still better than using just empiric values without optimization.
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The extremely large outlier depicted in the lower half of figure \ref{fig:wifiNumFingerprints} (red line) relates to one
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sub-model with only one assigned reference measurement, where the optimized result is unable to predict values
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for the rest of the sub-model's region. \todo{versteht man das?}
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Additionally we examined the impact of skipping reference measurements for difficult locations
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like aforementioned staircases, surrounded by concrete. While this slightly decreases the
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estimation error for all other positions, the error within those locations is dramatically
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like staircases, surrounded by steel-enforced concrete. While this slightly decreases the
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estimation error for all other positions (hallway, etc) as expected, the error within the skipped locations is dramatically
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increasing (see lower half of figure \ref{fig:wifiNumFingerprints}). It is thus highly recommended
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to include such locations.
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to also perform reference measurements for locations, that are expected to strongly deviate (signal strength)
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from their surroundings.
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%leaving out fingerprints for model 1
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% 25%: cnt(1128) min(0.007439) max(27.804710) range(27.797272) med(4.404236) avg(5.449720) stdDev(4.470373)
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% 50%: cnt(1128) min(0.006027) max(27.732193) range(27.726166) med(4.367859) avg(5.437861) stdDev(4.475426)
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% 100%: cnt(1128) min(0.000282) max(27.705376) range(27.705093) med(4.272881) avg(5.411202) stdDev(4.493495)
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% noStair%: cnt(1128) min(0.000801) max(27.209221) range(27.208420) med(4.333328) avg(5.459918) stdDev(4.459484)
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%leaving out fingerprints for model 2
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% 25%: cnt(1128) min(0.000320) max(29.752560) range(29.752239) med(3.837357) avg(5.027578) stdDev(4.617191)
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% 50%: cnt(1128) min(0.015305) max(34.152130) range(34.136826) med(3.627090) avg(4.635868) stdDev(4.135866)
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% 100%: cnt(1128) min(0.000488) max(25.687740) range(25.687252) med(3.319756) avg(4.441193) stdDev(3.912525)
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% noStair%: cnt(1128) min(0.017693) max(25.687740) range(25.670048) med(3.304321) avg(4.507620) stdDev(3.957071)
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%leaving out fingerprints for model 3
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% 25%: cnt(1128) min(0.003242) max(39.470978) range(39.467735) med(3.371758) avg(4.977330) stdDev(5.213937)
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% 50%: cnt(1128) min(0.002808) max(30.113415) range(30.110607) med(2.941238) avg(4.015042) stdDev(3.696969)
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% 100%: cnt(1128) min(0.000557) max(16.813850) range(16.813293) med(3.056915) avg(3.813013) stdDev(3.062580)
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% noStair%: cnt(1128) min(0.002518) max(30.370636) range(30.368118) med(3.016884) avg(3.983101) stdDev(3.508327)
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%leaving out fingerprints for model 4
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% 25%: cnt(1128) min(0.000000) max(62.233345) range(62.233345) med(2.502831) avg(5.432897) stdDev(8.664582)
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% 50%: cnt(1128) min(0.000000) max(56.843803) range(56.843803) med(1.543137) avg(2.937506) stdDev(4.417061)
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% 100%: cnt(1128) min(0.000046) max(33.175812) range(33.175766) med(1.537933) avg(2.441976) stdDev(2.793499)
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% noStair%: cnt(1128) min(0.000000) max(62.233345) range(62.233345) med(1.493668) avg(2.744918) stdDev(4.428092)
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%leaving out fingerprints for model 5
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% 25%: cnt(1128) min(0.000000) max(62.620842) range(62.620842) med(2.140709) avg(6.257105) stdDev(11.638572)
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% 50%: cnt(1128) min(0.000000) max(57.371948) range(57.371948) med(1.357452) avg(2.982217) stdDev(5.877471)
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% 100%: cnt(1128) min(0.000000) max(14.837151) range(14.837151) med(1.251358) avg(1.989277) stdDev(2.189072)
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% noStair%: cnt(1128) min(0.000000) max(62.233345) range(62.233345) med(1.143669) avg(2.316189) stdDev(4.164822)
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@@ -198,8 +245,8 @@
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at location $\mPosVec$ returned from the to-be-examined prediction model.
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For all comparisons we use a constant uncertainty $\sigma = $\SI{8}{\decibel}.
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The quality of the estimated location is determined by comparing the estimation
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$\mPosVec^*$ with the pedestrian's ground truth position at the time the scan $\mRssiVec$
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The quality of the estimated location is determined by using the Euclidean distance between estimation
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$\mPosVec^*$ and the pedestrian's ground truth position at the time the scan $\mRssiVec$
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has been received.
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@@ -226,18 +273,20 @@
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\begin{figure}[b]
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\input{gfx/modelPerformance_meter.tex}
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\label{fig:modelPerformance}
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\caption{
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Error between ground truth and estimation using \refeq{eq:bestWiFiPos} depending
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on the underlying signal strength prediction model
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on the underlying signal strength prediction model.
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Extremely high errors between the \SIrange{90}{100}{\percent} quartile are related to bad \docWIFI{}
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coverage within outdoor areas (see figure \ref{fig:wifiIndoorOutdoor}).
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}
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\label{fig:modelPerformance}
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\end{figure}
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%To estimate the overall performance of the prediction models, we compare the position estimation
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%for each \docWIFI{} measurement within the recorded paths (3756 \docAPshort{} scans in total)
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%against the corresponding ground-truth, which indicates the absolute 3D error in meter.
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The position estimation for each \docWIFI{} measurement within the recorded walks (3756 \docAPshort{} scans in total)
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is compared against its corresponding ground-truth, indicating the absolute 3D error.
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The position estimation for each \docWIFI{} measurement within the recorded walks (3756 scans in total)
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is compared against its corresponding ground-truth, indicating the 3D error.
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The resulting cumulative error distribution can be seen in figure \ref{fig:modelPerformance}.
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The quality of the location estimation directly scales with the quality of the signal strength prediction model.
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However, as discussed earlier, the maximal estimation error might increase for some setups.
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@@ -252,13 +301,13 @@
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\begin{figure}[t]
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\input{gfx/wifiMultimodality.tex}
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\label{fig:wifiMultimodality}
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\caption{
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Location probability \refeq{eq:bestWiFiPos} for three scans. Higher color intensities are more likely.
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Ideally, places near the ground truth (black) are highly highly probable (green).
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Often, other locations are just as likely as the ground truth (blue),
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or the location with the highest probability does not match at all (red).
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}
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\label{fig:wifiMultimodality}
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\end{figure}
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Figure \ref{fig:wifiMultimodality} depicts aforementioned issues of multimodal (blue) or wrong (red) location
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@@ -318,13 +367,13 @@
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\begin{figure}
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\input{gfx/wifiCompare_normalVsExp_cross.tex}
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\input{gfx/wifiCompare_normalVsExp_meter.tex}
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\label{fig:normalVsExponential}
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\caption{
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Comparison between normal- (black) and exponential-distribution (red) for \refeq{eq:wifiProb}.
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While misclassifications are slightly reduced (upper chart),
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the median error between ground-truth and estimation (lower chart) increases by
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about \SI{1}{\meter}.
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}
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\label{fig:normalVsExponential}
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\end{figure}
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tex/chapters/interoduction.tex
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tex/chapters/interoduction.tex
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tex/chapters/introduction.tex
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tex/chapters/introduction.tex
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tex/chapters/relatedwork.tex
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tex/chapters/relatedwork.tex
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tex/chapters/system.tex
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tex/chapters/system.tex
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tex/chapters/work.tex
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tex/chapters/work.tex
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@@ -100,12 +100,12 @@
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\begin{figure}[t!]
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\input{gfx/wifiop_show_optfunc_params}
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\label{fig:wifiOptFuncTXPEXP}
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\caption{
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The average error (in \SI{}{\decibel}) between all reference measurements and corresponding model predictions
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for one \docAPshort{} dependent on \docTXP{} \mTXP{} and \docEXP{} \mPLE{}
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[known position $\mPosAPVec{}$, fixed \mWAF{}] denotes a convex function.
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}
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\label{fig:wifiOptFuncTXPEXP}
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\end{figure}
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For systems that demand a higher accuracy, one can choose a compromise between fingerprinting and
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@@ -138,12 +138,12 @@
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\begin{figure}[t!]
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\input{gfx/wifiop_show_optfunc_pos_yz}
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\label{fig:wifiOptFuncPosYZ}
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\caption{
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The average error (in \SI{}{\decibel}) between reference measurements and model predictions
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for one \docAPshort{} dependent on $y$- and $z$-position [fixed $x$, \mTXP{}, \mPLE{} and \mWAF{}]
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usually denotes a non-convex function with multiple [here: two] local minima.
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}
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\label{fig:wifiOptFuncPosYZ}
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\end{figure}
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Such functions demand for optimization algorithms, that are able to deal with non-convex functions,
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@@ -186,6 +186,9 @@
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axis-aligned bounding box. This approach allows a distinction between in- and outdoor-regions
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or locations that are expected to highly differ from their surroundings.
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\todo{AP wird in einer region nur dann beruecksichtigt, wenn mindestanzahl an messungen vorhanden ist!}
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\todo{das heißt aber, dass an unterschiedlichen stellen unterschiedlich viele APs verglichen werden. das geht ned. deshalb feste -100}
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\subsection{\docWIFI{} quality factor}
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@@ -243,8 +246,11 @@
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When scanning for \docAPshort{}s one will thus receive several responses from the same hardware, all with
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a very small delay (micro- to milliseconds). Such measurements may be grouped using some aggregate
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function like average, median or maximum.
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Furthermore, VAP grouping can be used to suppress unlikely observations: If a physical hardware is known
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to provide six virtual networks, it is unlikely to only see one of those networks. This is likely due to
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temporal effects and/or multipath signal propagation and the received signal strength will often be far from
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the normal average. It thus makes sense to just omit such unlikely observations, focusing on the remaining, stable ones.
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tex/egbib.bib
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tex/egbib.bib
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tex/gfx/build.sh
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tex/gfx/build.sh
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for file in *.gp
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do
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gnuplot $file;
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gnuplot "$file";
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done
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tex/make.sh
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tex/make.sh
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tex/misc/functions.tex
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tex/misc/functions.tex
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tex/misc/keywords.tex
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tex/misc/keywords.tex
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