energy smart apps - location-aware algorithms to save energy on mobile devices

1. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE Location-aware algorithms that save energy on mobile devices

2. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE U.S. Patent # 8,036,679 Optimizing performance of location-aware applications using state machines. IEEE Pervasive Computing, vol. 10, no. 3, pp. 58-67, July-Sept. 2011. 2011 IEEE Proceedings of IEEE UBICOMM 2008 The Second International Conference on Mobile Ubiquitous Computing, Systems, Services, and Technologies, Valencia, Spain, September 29 October 4, 2008. 2008 IEEE The Journal of Navigation, volume 64, issue 03, pp. 381-399. July 2011. 2011 The Royal Institute of Navigation. 2

3. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE GPS Auto-Sleep 3 GPS Auto-Sleep Critical Point Algorithm Location Data Signing Adaptive Location Buffering Location Data Encryption SessionManagement Legend Real-time Phone-Generated Location Data Flow Control Signals Application Data Flow UDP HTTP(S) TCP Location Data Flow Control Device Platform Software LAISYC Communications Management LAISYC Positioning Systems Management Server Location API Persistent Storage API I/O API Virtual Machine Java ME / Android LAISYC Comm. APILAISYC Positioning API Location-Aware Application (Device-side)

4. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE GPS Tracking High-definition view of travel Frequent sampling allows us to determine: Path, distance traveled Origin-Destination pairs Avg. speeds Enables high-accuracy real- time, historical LBS Challenges: Battery life Amount of data 4

5. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE GPS Tracking Infrequent tracking solves energy, data problems BUT, doesnt give us the data we want: Path, distance traveled Origin-Destination pairs Avg. speeds 5

6. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE Purpose to save battery energy & reduce data transfer to server by dynamically adjusting the GPS sampling interval based on user movement Change states based on speed/distance/time thresholds GPS-Auto Sleep ASLEEPAWAKE State [0] State [1] State [n 1] State [n] Move directly to state[0] when current_speed > high_speed_threshold. GPS Sampling Interval = 4 sec. GPS Sampling Interval = 8 sec. GPS Sampling Interval = 128 sec. GPS Sampling Interval = 256 sec. After leaving state[0], gradually move towards state[n] when ((current_speed < low_speed value) AND (distance_between_fixes < moved_distance_threshold)) OR if a GPS fix cant be acquired. Gradually move towards state[0] when (low_speed_threshold < current_speed < high_speed_threshold) OR (distance_between_fixes > moved_distance_threshold). 6

7. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE State [0] State [1] State [n 1] State [n] Move directly to state[0] when current_speed > high_speed_threshold. GPS Sampling Interval = 4 sec. GPS Sampling Interval = 8 sec. GPS Sampling Interval = 128 sec. GPS Sampling Interval = 256 sec. After leaving state[0], gradually move towards state[n] when ((current_speed < low_speed value) AND (distance_between_fixes < moved_distance_threshold)) OR if a GPS fix cant be acquired. Gradually move towards state[0] when (low_speed_threshold < current_speed < high_speed_threshold) OR (distance_between_fixes > moved_distance_threshold). ASLEEPAWAKE 7

8. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE 8 8.04 10.71 13.01 14.20 15.68 18.77 41.94 0 5 10 15 20 25 30 35 40 45 4 8 15 30 60 150 300 BatteryLife(hours) Interval Between GPS Fixes (s) Impact of Interval Between GPS Fixes on Battery Life Sanyo Pro 200 Sprint CDMA EV-DO Rev. A network

9. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE 9 0 50 100 150 200 250 300 1 23 45 67 89 111 133 155 177 199 221 243 265 287 309 331 353 375 397 419 441 463 485 507 529 551 573 595 617 639 661 683 705 727 749 771 793 815 837 859 881 903 925 947 969 991 1013 1035 IntervalBetweenGPSFixes(seconds) GPS Auto-Sleep Transitions - Awake to Asleep Sanyo Pro 200 Sprint CDMA EV-DO Rev. A network Asleep Awake State errors No GPS signal

10. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE 10 0.51% 29.10% 11.60% 10.54% 15.67% 23.97% 7.37% 0.00% 5.00% 10.00% 15.00% 20.00% 25.00% 30.00% 35.00% Min Max Mean 50th 68th 95th STD DEV GPS Auto-Sleep - State ErrorPercentage Approx. 88% mean accuracy in state tracking Avg. doubling of battery life (based on TRAC-IT tests) n = 30

11. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE U.S. Patent # 8,249,807 Method for Determining Critical Points in Location Data Generated by Location-Based Applications IEEE Pervasive Computing, vol. 10, no. 3, pp. 58-67, July-Sept. 2011, doi:10.1109/MPRV.2010.48 2011 IEEE The Journal of Navigation, volume 64, issue 03, pp. 381-399. July 2011. 2011 The Royal Institute of Navigation. Proceedings of IEEE UBICOMM 2008 The Second International Conference on Mobile Ubiquitous Computing, Systems, Services, and Technologies, Valencia, Spain, September 29 October 4, 2008. 2008 IEEE 11

12. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE Critical Point Algorithm 12 Critical Point Algorithm Location Data Signing GPS Auto-Sleep Adaptive Location Buffering Location Data Encryption SessionManagement Legend Real-time Phone-Generated Location Data Flow Control Signals Application Data Flow UDP HTTP(S) TCP Location Data Flow Control Device Platform Software LAISYC Communications Management LAISYC Positioning Systems Management Server Location API Persistent Storage API I/O API Virtual Machine Java ME / Android LAISYC Comm. APILAISYC Positioning API Location-Aware Application (Device-side)

13. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE 13 Critical Point Algorithm 13 Purpose to reduce battery energy expenditures and amount of data transferred by eliminating non-essential GPS data Pre-filters real-time GPS data on mobile device before it is wirelessly transmitted

14. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE Critical Point Algorithm 14 changeInDirection() = |Angle2 Angle1| NORTH Last Critical Point Current Point Last Trigger Point (Under Evaluation) Angle1 Angle2 = Mobile Device Path = Location Points

15. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE 15 START (Input = currentLocation) TransportationMode= WALKING TransportationMode= VEHICLE First Point? lastCriticalPoint= currentLocation lastCriticalPoint=lastTriggerPoint YES NO YES NO YES NO (Since currentLocation is first point in sequence, it is saved as both the lastCriticalPoint and LastValidPoint) (lastTriggerPoint is a CriticalPoint, and is stored as lastCriticalPoint for future executions of CP algorithm and returned to application) (No Critical Points were found) NO YES Return currentLocation lastTriggerPoint= currentLocation lastTriggerPoint=currentLocation (Optional) Reset Conditional Evaluation Variables (for Real-time Applications) Return lastCriticaPointReturn null Speed > max_walk_speed (Optional) Conditional Evaluations = TRUE? (for Real-time Applications) (changeInDirection() > angle_threshold) AND (currentSpeed > min_speed_threshold)? changeInDirection() Uses angle threshold Changed per speed min_speed() If currentSpeed > min_speed, device is moving Real-time Conditional Evaluations (Optional) timerExpired()? distanceCounterExceeded? receivedServerProbe? Critical Point Algorithm

16. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE 16 Sanyo 7050 Sprint CDMA 1xRTT Network UDP Effect of Wireless Transmission Interval on Battery Life

17. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE Critical Point Algorithm Uses several thresholds for filtering points, based on observed data: min_speed_threshold max_walk_speed Used to determine angle_threshold angle_threshold Increasing angle threshold results in fewer points Tradeoff of reduced data vs. line accuracy Example shown in following slides 17

18. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE Angle 1 18

30. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE Avg. GPS reduction of 77% per trip Avg. 18.8kB saved per trip Average distance error percentage under 10% On avg., as Tx interval doubles battery life doubles Critical Point Algorithm 30 Min Max Avg. 5th percentile 25th percentile 50th percentile 68th percentile 95th percentile Total Critical Point Count 2 322 35 3 13 27 38 97 Total GPS Fix Count 20 3,710 193 31 74 130 188 511 % Savings 20.83% 99.40% 77.43% 47.97% 69.49% 80.00% 86.83% 95.84% Bytes Saved* 595 403,172 18,883 2,380 6,426 12,138 17,493 54,788 Distance Critical Points (m) 0.00 1,043,805.50 7,437.09 328.14 1,162.37 2,675.00 4,049.37 22,815.61 Total Distance (m) 2.36 1,087,043.20 7,878.02 380.79 1,252.55 2,913.39 4,345.91 24,231.34 Distance Error Percentage 0.00% 100.00% 8.90% 1.94% 3.98% 6.20% 8.70% 24.11% * Based on 119 bytes per UDP payload

31. CONFIDENTIAL - Protected under U.S. Patent #8036679,#8,249,807 Other Patents Pending USF 2012. 2012 USF, Sean J. Barbeau, IEEE Questions? 31 Principal Mobile Software Architect for R&D Center for Urban Transportation Research & Department of Computer Science & Engineering University of South Florida (813) 974-7208 USF Location-Aware Information Systems Lab: http://www.locationaware.usf.edu/ Sean J. Barbeau, Ph.D.

energy smart apps - location-aware algorithms to save energy on mobile devices

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