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Realizing the Full Potential of PSM using Proxying

Realizing the Full Potential of PSM using Proxying. Clay Shepard Lin Zhong. Dimitrios Koutsonikolas. Ning Ding Abhinav Pathak Y. Charlie Hu. Smartphone is Energy Constrained. Battery capacity only doubles in last 15 years. 3G/4G. GPS. CPU. Screen. WiFi. Camera.

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Realizing the Full Potential of PSM using Proxying

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  1. Realizing the Full Potential of PSM using Proxying Clay Shepard Lin Zhong DimitriosKoutsonikolas Ning Ding AbhinavPathak Y. Charlie Hu

  2. Smartphone is Energy Constrained Battery capacity only doubles in last 15 years 3G/4G GPS CPU Screen WiFi Camera

  3. WiFi Energy Consumption Data AP … … Phone Data Idle Even in idle, WNIC drains out battery in 6-10 hrs! Send WiFi NIC Power (mW) Recv 1000mW Idle Listen 765mW 650mW Time (ms)

  4. Modes of WiFi NIC • Constant Awake Mode (CAM) • Send, Recv, Idle Listen • High power • Power Saving Mode (PSM) • Cannot send/recv/idle listen • Very little power

  5. WiFi: Power Saving Mode Beacon Beacon Beacon Beacon AP 100ms Beacon 100ms 100ms Phone WiFi NIC Power (mW) Time (ms)

  6. WiFi: Power Saving Mode (cont’d) Server Data PSM Wake-up Delay PSM does not come for free! Beacon AP Phone WNIC switch to CAM WNIC in PSM, cannot recv WiFi NIC Power (mW) Time (ms)

  7. PSM • Energy - performance trade off • Two implementations of PSM • Static PSM • Dynamic PSM

  8. Static PSM Server Data SYNACK Wake-up Delay Wake-up Delay Wake-up Delay ACK SYNACK AP Beacon Req SYN Phone Static PSM Flow Time: 300ms Energy: 3 μAh WiFi NIC Power (mW) Already in PSM Time (ms)

  9. Dynamic PSM Server Data SYN ACK ACK AP Beacon Req SYN Phone PSM Timeout Static PSM Flow Time: 300ms Energy: 3 μAh Dynamic PSM Flow Time: 90ms Energy: 10 μAh WiFi NIC Power (mW) Time (ms)

  10. Motivation Can we make it ?

  11. Understand Dynamic PSM Server AP Phone RTT PSM Timeout Key: PSM Timeout > RTT

  12. Percy: Design 1. AP Split-TCP Proxy AP 2. PSM Timeout 200ms/95ms PSM Timeout 30ms

  13. Percy: Short Flows Data Server Data SYN SYN ACK Req ACK Req AP+Proxy Beacon SYN Phone Static PSM Flow Time: 300ms Energy: 3 μAh Percy Flow Time: 110ms Energy: 4 μAh Dynamic PSM Flow Time: 90ms Energy: 10 μAh WiFi NIC Power (mW) Time (ms)

  14. Percy: Long Flows Data SYN Req SYN ACK ACK SYN Beacon Req Periodical Flush WiFi NIC Power (mW) Time (ms)

  15. Evaluation • Trace-driven experiment • 10-phone 1-week trace • 38,069 HTTP flows • PSM configurations • Percy • Static PSM • Dynamic PSM: Nokia N900 HTC Nexus One iPhone 4

  16. Result – Energy Consumption 67% 44% Total energy consumption for different PSM schemes

  17. Result – Network Performance Time (ms) CDF of flow time difference compared to Android PSM configuration

  18. Conclusion • Existing PSMs have inherent problems • A simple system: Percy • improve the energy savings • maintain good performance • Percy saves 44-67% energy while incur minimal flow time elongation

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