War Walking vs. War War Walking vs. War DrivingDriving

Trying to find the reasons why war Trying to find the reasons why war walking radio map performs betterwalking radio map performs better

War Walking Radio-map Performs War Walking Radio-map Performs BetterBetter

Major Possible Origin of ErrorMajor Possible Origin of Error

Bias on war-driving ground truthsBias on war-driving ground truths Quality of collected WiFi signal patternsQuality of collected WiFi signal patterns

Signal strength and varianceSignal strength and variance Amount of dataAmount of data

GPS as War Driving Ground TruthGPS as War Driving Ground Truth GPS itself suppose to have a 15m errorGPS itself suppose to have a 15m error GPS and WiFi reading does not synchronized in our GPS and WiFi reading does not synchronized in our

experimentexperiment

GPS Lags

Uniformly Shift GPS ReadingsUniformly Shift GPS Readings

Driving Testing TraceDriving Testing Trace Intuition: same manner for training and testing Intuition: same manner for training and testing

leads better resultleads better result

Not in our testsNot in our tests

If “resemblance” does not account for If “resemblance” does not account for difference in war walking and war difference in war walking and war driving, what does?driving, what does?

Signal strengthSignal strength Variance of signalsVariance of signals ……??

Signal StrengthSignal Strength Intuition: Lower strength in radio map Intuition: Lower strength in radio map larger errors larger errors

somewhatsomewhat

Variance of signalsVariance of signals Intuition: Higher variance in signals is better for Intuition: Higher variance in signals is better for

differentiation, so lowering the variance differentiation, so lowering the variance larger errors larger errors

somewhatsomewhat

Number of Access Points in RadiomapNumber of Access Points in Radiomap

Intuition: war walking tend to receive more APs Intuition: war walking tend to receive more APs and those may be criticaland those may be critical

In bothIn both

Only in war walkingOnly in war walkingWar War walking:walking:

Only in war drivingOnly in war drivingWar driving:War driving:

Walking Walking reduced:reduced:

Driving plus:Driving plus:

Signal as recv’d Signal as recv’d by walkingby walking

War driving onlyWar driving only

Signal as recv’d Signal as recv’d by drivingby driving

Signal as recv’d Signal as recv’d by walkingby walking

Signal as recv’d Signal as recv’d by drivingby driving War walking onlyWar walking only

Only in war walkingOnly in war walking

Number of Access Points in RadiomapNumber of Access Points in Radiomap

Intuition: war walking tend to receive more APs Intuition: war walking tend to receive more APs and those may be criticaland those may be critical

The additional APs seems to be redundantThe additional APs seems to be redundant

Number of SamplesNumber of Samples Intuition: war walking tends to receive more samples and Intuition: war walking tends to receive more samples and

it’s criticalit’s critical

it’s not criticalit’s not critical

RecapRecap

Signal quality (strength, variance)Signal quality (strength, variance)

Amount of dataAmount of data