1. War Walking vs. War Driving Trying to find the reasons why war walking radio map performs better

2. War Walking Radio-map Performs Better

3. Major Possible Origin of Error  Bias on war-driving ground truths  Quality of collected WiFi signal patterns Signal strength and variance Signal strength and variance Amount of data Amount of data

4. GPS as War Driving Ground Truth  GPS itself suppose to have a 15m error  GPS and WiFi reading does not synchronized in our experiment GPS Lags

5. Uniformly Shift GPS Readings

6. Driving Testing Trace  Intuition: same manner for training and testing leads better result  Not in our tests

7.  If “resemblance” does not account for difference in war walking and war driving, what does?  Signal strength  Variance of signals  …?

8. Signal Strength  Intuition: Lower strength in radio map  larger errors  somewhat

9. Variance of signals  Intuition: Higher variance in signals is better for differentiation, so lowering the variance  larger errors  somewhat

10. Number of Access Points in Radiomap  Intuition: war walking tend to receive more APs and those may be critical In both Only in war walking War walking: Only in war driving War driving: Walking reduced: Driving plus: Signal as recv’d by walking Signal as recv’d by walking War driving only Signal as recv’d by driving Signal as recv’d by driving Signal as recv’d by walking Signal as recv’d by walking Signal as recv’d by driving Signal as recv’d by driving War walking only Only in war walking

11. Number of Access Points in Radiomap  Intuition: war walking tend to receive more APs and those may be critical   The additional APs seems to be redundant

12. Number of Samples  Intuition: war walking tends to receive more samples and it’s critical  it’s not critical

13. Recap  Signal quality (strength, variance)  Amount of data