1. SDTW
Xuehan Ye

2. SDTW Offline
1. Problem 1 For the same path, the length of RSS sequence is quite different. Example: s1:t1 t2 t3 t4 t5 t6 t7 t8 s2:t1 t2 t3 t4 After t4 for s2, the phone cannot detect one RSS any more.

3. SDTW Offline
1. Problem 1 Reason: (1) Maybe I have connected to one wifi. I should forget the wifi and try again. For some conditions, it is helpful. (2) Maybe it depends on the mobilephone.

4. SDTW Offline
1. Problem 1 Solution: In the training phase, we should train one path for several times. Then, we compare their lengths, remove noisy paths and calculate the mean of left data. In the offline locating phase, we should pick the path with suitable length.

5. SDTW Offline
1. Problem 2 There are too many unreliable wifi. Reason: (1) Hulu problem. In TsingHua, I detect many DIVIs, whose MAC addresses are very similar. They occupy a large proportion in the wifi list. (2) Some wifi are unreliable, e.g. 360 free wifi. (3) Too little wifi.

6. SDTW Offline
1. Problem 2 Solution: (1) The problem deeply depends on the specific environment. We have to analyze wifi environment in advance, and just remain reliable wifi, which guarantee the best accuracy in preliminary tests. If the best accuracy is not satisfactory, it is attributed to too little wifi.

7. SDTW Offline
1. Problem 2 Solution: (2) We have to pick efficient wifi by our hands. For example, remove DIVI/Hulu and remove 360 free wifi.

8. SDTW Online
1. Problem 1 Too many missing value for the online moving window. In many cases, collaborative filter cannot fill boundary values. Example: [] [] [] [] [] [] [] Solution: We can apply CF in the longer period of time, which is stitched by many moving windows...???

9. SDTW Online
1. Problem 2 The accuracy of online locating is much lower than offline. ???

10. Thank you!
Xuehan Ye