self-tuning wireless network power management
DESCRIPTION
Explores strategies to design and implement an intelligent power management module that adapts to the usage pattern and the characteristics of the network interface card. Anand, Manish, Edmund B. Nightingale, and Jason Flinn. "Self-Tuning Wireless Network Power Management." Wireless Networks 11.4 (2005): 451-69. Print.TRANSCRIPT
![Page 1: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/1.jpg)
Self-Tuning Wireless Network Power
Management
CSC 547 - Fall 2013, University of ArizonaSumin Byeon
![Page 2: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/2.jpg)
Problems
• Wireless card shortens battery life
• Obvious solution: turn it off!
• Power management can degrade performance
• Critical for latency sensitive applications
• No one-fits-to-all solution
![Page 3: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/3.jpg)
Previous Work
• Power Saving Mode (PSM) in 802.11
• Will refer this as “PSM-static”
• Does not adapt to power characteristics of the network and mobile devices
• Does not adapt to usage patterns
![Page 4: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/4.jpg)
Solution
• Self-tuning power management module that adapts to
• Usage patterns
• Network interface characteristics
• System (i.e., hardware)
![Page 5: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/5.jpg)
Design Principles
• Know application intent
• Be proactive
• Respect the critical path
• Embrace the performance/energy tradeoff
• Adapt to the operating environment
![Page 6: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/6.jpg)
Know Application Intent
• Not knowing intent of applications - Leads to either too conservative or too extravagant power management
• Allow applications to disclose “hints” - STPM can work more efficiently
![Page 7: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/7.jpg)
Be Proactive
• Reactive strategy - Cost of transition between modes must be low
• Transition time 200-600ms; exceeds perception threshold (50-200ms)
• STPM performs cost-benefit analysis based on hints
• Not always possible
![Page 8: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/8.jpg)
Respect the Critical Path
• Perception threshold - generally 50-200ms
• Foreground transfer - latency sensitive, interactive, synchronous
• Background transfer - latency tolerable, asynchronous
![Page 9: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/9.jpg)
Performance-Energy Tradeoff
• Inherent tradeoff between performance and energy conservation
• Static threshold won’t work
• STPM provides mechanism to adjust priorities
• Is performance your priority? Or energy conservation?
![Page 10: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/10.jpg)
Adapt to Environment
• Global optimization
• Excessive power saving on network interface may lead to inefficient energy usage on other components
• Consider base power usage
![Page 11: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/11.jpg)
Implementation
• Implemented as Linux kernel module
• Inputs:
• Base power and current tradeoff between energy conservation and performance
• Device-specific power usage characteristics and transition costs
![Page 12: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/12.jpg)
API
![Page 13: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/13.jpg)
Power Cost Analysis
1. Base power
2. Power usage for each mode
3. Translation cost between modes
4. Power usage for data transfer in each mode
![Page 14: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/14.jpg)
Algorithm
• Assume network card only supports two modes: CAM and PSM
![Page 15: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/15.jpg)
Transition to CAM
• Delay tolerance is less than the maximum latency of PSM (i.e., beacon interval)
• Forthcoming transfer will be large enough
• Forthcoming transfer will be large enough, and STPM expects that there will be enough subsequent short transfers
![Page 16: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/16.jpg)
Transition to PSM
• No transfers in progress
• No application specified delay tolerance
• Network card will be idle long enough
![Page 17: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/17.jpg)
General Model
• Some network cards support more than two modes
• Number of possible strategies proportional to square of number of modes
• Calculates the lowest cost policy that transitions to each mode
• Calculates the lowest cost hybrid policies then make a further transition at some later time
![Page 18: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/18.jpg)
Evaluation
• Question: How much did STPM improve the power efficiency? What was the impact on the performance?
![Page 19: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/19.jpg)
Experiments
• Coda (distributed file system)
• NFS (Network File System)
• Xmms (audio streaming)
• Thin client using remote X
![Page 20: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/20.jpg)
Coda
![Page 21: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/21.jpg)
NFS
![Page 22: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/22.jpg)
Xmms
![Page 23: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/23.jpg)
Remote X
![Page 24: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/24.jpg)
Effect of Think Time
![Page 25: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/25.jpg)
Potential Weakness
• In their experiments, they made modifications on applications to emit hints
• Unrealistic to modify every single application in the world
• How would have STPM behaved if applications were not modified? (i.e., no hints)
![Page 26: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/26.jpg)
Conclusion
• Power management may degrade performance, and even increase total energy consumption
• Power management must be tuned to reflect application intent and characteristics of network interface card
• Can’t expect users to manually tune power management algorithm
![Page 27: Self-Tuning Wireless Network Power Management](https://reader033.vdocuments.net/reader033/viewer/2022052622/5590480c1a28ab492c8b4646/html5/thumbnails/27.jpg)
Conclusion (cont.)
• Results show that STPM improves both performance and energy conservation
• Future work: adapt STPM to other network cards and different system components (e.g., disks)