1. Energy-Delay Tradeoffs in Smartphone Applications Moo-Ryong Ra Jeongyeup Paek, Abhishek B. Sharma Ramesh Govindan, Martin H. Krieger, Michael J. Neely University of Southern California MobiSys ’10

2. 2 2 The Urban Tomography System MotivationProblemSolutions ApproachEvaluationConclusion Video Collection 10 years ago Our way of Video Collectio n

3. 3 3 Users MotivationProblemSolutions ApproachEvaluationConclusion Transportation SecurityPost-Disaster Urban Planning Documenting Post-Katrina Reconstruction

4. 4 4 Delay-Tolerance MotivationProblemSolutions ApproachEvaluationConclusion Delay-Tolerance Many of our users are delay-tolerant Transportation Security Transportation Security Dealing with Child development Issues Dealing with Child development Issues Planning Research Planning Research But tolerance varies considerably

5. 5 5 Our Focus MotivationProblemSolutions ApproachEvaluationConclusion Transferring Large Volumes of Data Leveraging Delay Tolerance Reduce the energy cost

6. 6 6 EDGE/3GWiFi Energy (J/bit) Availability Channel Quality Trade-offs MotivationProblemSolutions ApproachEvaluationConclusion HIGH LOW HIGH LOW Time-Varying Delay transmission Adapt to wireless channel quality

7. 7 7 A Motivating Example MotivationProblemSolutions ApproachEvaluationConclusion EDGE 3G WiFi video 1 arrives video 2 arrives 40 KB/s 200 KB/s 50 KB/s 10 KB/s TIME

8. 8 8 Strawman Approaches MotivationProblemSolutions ApproachEvaluationConclusion EDGE 3G WiFi video 1 video 2 Delay Energy 246 242 95 305 50 320 J J sec Min-DelayWiFi-OnlyEnergy-Optimal Optimal can save significant energy MD ME EO MD ME EO Challenge: How to design the optimal trade-off algorithm? Challenge: How to design the optimal trade-off algorithm?

9. 9 9 Our Approach MotivationProblemSolutions ApproachEvaluationConclusion Use Lyapunov Optimization Derive Control Algorithm

10. 10 Lyapunov Optimization MotivationProblemSolutions ApproachEvaluationConclusion Sender Receiver Control Algorithm Control Algorithm Lyapunov Analysis Lyapunov Analysis 1. Queue Stability Penalty Function Penalty Function 2. Penalty Minimization Queue length will not go to the infinity

11. 11 Energy Cost Model Energy Cost Model How we use the framework MotivationProblemSolutions ApproachEvaluationConclusion Sender Receiver Control Algorithm Control Algorithm Lyapunov Analysis Lyapunov Analysis 1. Queue Stability 2. Penalty Minimization 1. Delay Bound 2. Energy Minimization

12. 12 Higher rate Derived Control Decision MotivationProblemSolutions ApproachEvaluationConclusion SALSA (Stable and Adaptive Link Selection Algorithm) AP Q Q Large Queue Backlog E E Low Energy Cost Queue Backlog Queue Backlog × −× Estimated Rate Estimated Rate Energy Cost Energy Cost V V Over Links All Links

13. 13 Importance of V Queue Backlog Queue Backlog × −× Estimated Rate Estimated Rate Energy Cost Energy Cost V V SALSA (Stable and Adaptive Link Selection Algorithm) Setting V Large Setting V Large Defer the Transmission Defer the Transmission MotivationProblemSolutions ApproachEvaluationConclusion Over Links All Links

14. 14 Tuning Delay-Tolerance MotivationProblemSolutions ApproachEvaluationConclusion No Yes TIME AP Rate No Yes V V Queueing Delay Transportation SecurityUrban Documentation Transmit?

15. 15 SALSA Summary Whether, When, Which Delayed Transmission Delayed Transmission Tunable Delay-Tolerance Tunable Delay-Tolerance SALSA MotivationProblemSolutions ApproachEvaluationConclusion

16. 16 Evaluation Methodology MotivationProblemSolutions ApproachEvaluationConclusion Trace-Driven Simulation Trace-Driven Simulation Validation with Real Implementation Validation with Real Implementation Implementation on Nokia N95 Implementation on Nokia N95 66 Link availability traces 42 Video arrival traces 2772 USCLAXMall

17. 17 Metric MotivationProblemSolutions ApproachEvaluationConclusion E(J/byte) D(Hour\byte) E(J/byte) D(Hour) dispersion Envelope in E-D Plane Dispersion Good! BAD Measured Optimal

18. 18 Comparisons MotivationProblemSolutions ApproachEvaluationConclusion Min-delay High Energy WiFi-only Unbounded delay Static-delay NOT take link quality into account NOT take link quality into account Know-WiFi NOT consider queue backlog NOT consider queue backlog

19. 19 Main Results MotivationProblemSolutions ApproachEvaluationConclusion Ignore link quality SALSAKnow-WiFiStatic-DelayWiFi-onlyMin-Delay Ignore queue backlog Since SALSA takes all factors into account, it performs closest to the optimal Since SALSA takes all factors into account, it performs closest to the optimal

20. 20 Tuning Delay-Tolerance MotivationProblemSolutions ApproachEvaluationConclusion Decay V slowest Decay V slowest Decay V fastest Decay V fastest SALSA can be tuned to different delay-tolerant requirements. SALSA can be tuned to different delay-tolerant requirements. More Delay-Tolerant Less Delay-Tolerant Like WiFi-only Like Min-Delay

21. 21 Experimental Validation MotivationProblemSolutions ApproachEvaluationConclusion GlendaleUSC Simulation Results Experiment Results Simulation Results Experiment Results Our experimental results fall within the boundary and validate the simulation Our experimental results fall within the boundary and validate the simulation

22. 22 The Bottom Line Additional Delay Gain? Loss? Save 2% ~ 80% of battery capacity Save 2% ~ 80% of battery capacity + 2 min ~ 2 hour Energy Savings Battery

23. 23 Summary of Contributions MotivationProblemSolutions ApproachEvaluationConclusion Different from prior work [Balasubramanian10], [Zaharia07], [Seth06] consider schemes similar to Static-Delay and Know-Wifi. [Rahmati07], [Armstrong06], [Agarwal07] consider link selection, but do not defer transmissions Different from prior work [Balasubramanian10], [Zaharia07], [Seth06] consider schemes similar to Static-Delay and Know-Wifi. [Rahmati07], [Armstrong06], [Agarwal07] consider link selection, but do not defer transmissions Adaptive algorithm for energy/delay tradeoff Extensive evaluation with real world scenarios Validation with real implementation Provable performance bound (in the paper) Adaptive algorithm for energy/delay tradeoff Extensive evaluation with real world scenarios Validation with real implementation Provable performance bound (in the paper)

24. 24 Thank you. Questions?

25. 25 Impact of Scanning Cost

26. 26 Instantaneous Power Measurement Transfer 1MB chunk Nokia Energy Profiler 1.1