1. Supervisor: Paul Gardner-Stephen Student: Alexander Kotov Master Thesis 19.09.2011

2.  What is GPS? How does it work?  What is A-GPS?  Why? Serval Project and A-GPS  Plan and deliverables  How to measure success? 2

3. GPS enabled mobile phone GPS satellites GPS require: Almanac data Ephemeris data Problem: The data rate of the satellite signal is only 50 b/s !!! 3

4. GPS Assisted GPS Server Internet GPRS, EDGE, 3G, WiFi Base station GPS enabled mobile phone GPS satellites 4

5. Serval creates a WiFi mesh network of mobile phones that doesn’t require infrastructure and enables mobile communications regardless what your circumstance:  in the face of disaster,  in the face of poverty,  in the face of isolation,  in the face of civil unrest,  in the face of network black-spots. Source based on data from The Serval Project, www.servalproject.org, 2011 5

6.  Knowing location is quite important in case of disastrous situation,  Quicker location fix means less battery usage,  Serval Project use location for other services (e.g. mapping),  It is good to know where you are! 6

7. GPS satellites No or limited: Internet connection Cell phone towers Mobile phone with assistance data Assistance information 7

8. GPS satellites  Extract A-GPS data from one phone  Transmit it over Serval network  Inject into another phone 8

9. GPS satellites  Extract A-GPS data from one phone  Pretend to be A-GPS assistance server  Transmit assistance data to another phone 9

10.  Wipe out any assistance data from mobile phone  Measure TTFF  Repeat it several times  Do the same process with Serval A-GPS assistance  Compare TTFF 10

11. Conclusion 11  A-GPS can give a faster TTFF  A-GPS is not available in Serval network  There are some ways to share assisted data in Serval network

12. Thank you! Any questions? 12