than using GPS and network location server. Wifi routers are used in a different way in this method, disclosed in US Patent 8,886,221. Complementary to GPS and network location server. Faster and much more power efficient, while usually less accurate than GPS. Can be used as the first-line location estimating method, before trying others such as GPS. Potentially useful in most, if not all, applications where geographic location of a mobile device is relevant. Most helpful to those where continuous (24/7) location tracking is needed.

1. Get Location
Quicker and For Less

2. Mobile
devices
are
mobile

3. Location is or will be
essential for many apps
Credits: company websites

5. GPS is great

6. when there is a clear
view of the sky

7. Location server helps
too. It needs network
connection,
a little luck, and lots
of trust.

8. How about when
a device got
none of those?

9. If a location
fix is requested
then, the device
usually keeps
GPS unit
working...

10. until battery is drained

11. or time is up

12. “Not working?”

13. Not good...

14. Need white knight...
Credit: D Miller

15. Here they are,
Wi-Fi Routers

16. They are everywhere
Credit: wigle.net; google map

17. More than 161 millions
of them in wigle
database alone
Credit: wigle.net

18. Many are
stationary

19. Some are mobile
Credit: startribune, coloradodot, giga.de

20. Techniques described below are

21. Observation:
when a device can
detect a stationary
Wi-Fi router, they
are close...

22. so close that the
router's location
can be used to infer
the device's location,

23. and vice versa.

24. On the device,
not on a server

25. When the device
detects a Wi-Fi
router for the first time,
it infers the router's
location based on its
own location and
stores router's location
on the device.

26. When the device detects
the same router again,
the router's location
stored on the device
can be used to infer
the device's location
then.

27. Sounds good...
except
How to tell
mobile
WiFi router?

28. Solution 1:
track the
probability
that a router
is mobile.

29. Solution 2:
Stay humble, ask GPS or
location server for help
once a while even it does
not have to.

31. Faster location fix
When it
works,
it works in
a few seconds.

32. Medium Accuracy
In the range
of 30~300
meters, or
90~900 feet

33. Lower power
consumption
It uses less power
during fixing process.
Also less chance
for GPS to waste
power searching
for elusive signals...

34. Most importantly, it
may work where GPS
and location server fail.

35. “Smooth”

36. See it in action!
State Days app
in Google Play Store
tracks location
continuously
with low battery
impact.

37. Technical Details:
US Patent 8,886,221
Contact:
Jian Zou
XG Network
xgnetworkllc@gmail.com