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MobiSys ’10. 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. The Urban Tomography System. Video Collection 10 years ago.
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MobiSys’10 Energy-Delay Tradeoffs in Smartphone Applications Moo-Ryong Ra JeongyeupPaek, Abhishek B. Sharma RameshGovindan, Martin H. Krieger, Michael J. Neely University of Southern California
The Urban Tomography System • Video Collection 10 years ago • Our way of Video Collection
Documenting • Post-Katrina • Reconstruction Users • Transportation Security • Post-Disaster Urban Planning
Delay-Tolerance • Many of our users are delay-tolerant • But tolerance varies considerably Planning Research Transportation Security Delay-Tolerance Dealing with Child development Issues
Our Focus Transferring Large Volumes of Data Leveraging Delay Tolerance Reduce the energy cost
Trade-offs • Delay transmission • Adapt to wireless • channel quality HIGH HIGH Time-Varying LOW LOW Time-Varying
A Motivating Example EDGE 3G WiFi 200 KB/s video 2 arrives 50 KB/s video 1 arrives 10 KB/s 40 KB/s TIME
Strawman Approaches EDGE 3G WiFi • Energy-Optimal • WiFi-Only • Min-Delay Optimal can save significant energy Challenge: How to design the optimal trade-off algorithm? video 2 video 1 TIME Delay Energy 246 320 305 sec 242 J 95 50 MD ME EO MD ME EO
Our Approach Use Lyapunov Optimization Derive Control Algorithm
Lyapunov Optimization • 1. Queue Stability • 2. Penalty Minimization Sender Receiver Queue length will not go to the infinity Lyapunov Analysis Control Algorithm Penalty Function
How we use the framework • 1. Queue Stability • 2. Penalty Minimization • 1. Delay Bound • 2. Energy Minimization Sender Receiver Lyapunov Analysis Control Algorithm Energy Cost Model
Derived Control Decision SALSA(Stable and Adaptive Link Selection Algorithm) Queue Backlog Estimated Rate V Energy Cost MAX − × × Over All Links AP Higher rate Q Large Queue Backlog E Low Energy Cost
Importance of V SALSA(Stable and Adaptive Link Selection Algorithm) Queue Backlog Estimated Rate V Energy Cost MAX − × × Over All Links Setting V Large Defer the Transmission
Tuning Delay-Tolerance • Transportation Security • Urban Documentation AP Rate TIME Transmit? No No Yes No No Yes V Queueing Delay
SALSA Summary • SALSA Whether, When, Which Tunable Delay-Tolerance Delayed Transmission
Evaluation Methodology • USC • LAX • Mall Trace-Driven Simulation 2772 66 Link availability traces 42 Video arrival traces Implementation on Nokia N95 Validation with Real Implementation
Metric • Envelope in E-D Plane • Dispersion BAD Measured D(Hour) D(Hour\byte) dispersion E(J/byte) E(J/byte) Good! Optimal
Comparisons Min-delay WiFi-only NOT take link quality into account NOT consider queue backlog Unbounded delay High Energy Static-delay Know-WiFi
Main Results Ignore queue backlog Since SALSA takes all factors into account, it performs closest to the optimal Ignore link quality Min-Delay WiFi-only Static-Delay Know-WiFi SALSA
Tuning Delay-Tolerance Like WiFi-only Like Min-Delay Decay V slowest Decay V fastest SALSA can be tuned to different delay-tolerant requirements. More Delay-Tolerant Less Delay-Tolerant
Experimental Validation • Glendale • USC Simulation Results Experiment Results Our experimental results fall within the boundary and validate the simulation
The Bottom Line • Additional Delay • Energy Savings Save 2% ~ 80% of battery capacity • Loss? • Gain? + 2 min ~ 2 hour • Battery
Summary of Contributions • Adaptive algorithm for energy/delay tradeoff • Extensive evaluation with real world scenarios • Validation with real implementation • Provable performance bound (in the paper) • 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