Introduction Approaches Experiments/Results Conclusions




                      Power Saving in Wireless VoIP

         ...
Introduction Approaches Experiments/Results Conclusions

 Outline




             Problem
             Related Work
     ...
Introduction Approaches Experiments/Results Conclusions

 Problem


      Where does power get consumed on WiFi phones dur...
Introduction Approaches Experiments/Results Conclusions

 Power Consumption
      Understanding where power is consumed


...
Introduction Approaches Experiments/Results Conclusions

 Projections of VoWiFi




      Figure: Harden,
      http://ntr...
Introduction Approaches Experiments/Results Conclusions

 Approaches



             802.11 MAC, Power Save Mode (PSM), Un...
Introduction Approaches Experiments/Results Conclusions

 802.11 Frame/Packet Format




      Figure: more than 150 vs. 1...
Introduction Approaches Experiments/Results Conclusions

 Header Compression/MAC Protocols Experiment




             Mea...
Introduction Approaches Experiments/Results Conclusions

 IP Header Compression


      Emulation of IP Header Compression...
Introduction Approaches Experiments/Results Conclusions

 802.11a/b/g Power Consumption



               PHY             ...
Introduction Approaches Experiments/Results Conclusions

 802.11 Power Save Mode
             Power Saving bit based




 ...
Introduction Approaches Experiments/Results Conclusions

 802.11 Power Save Mode


             UPSD (Unscheduled Power Sa...
Introduction Approaches Experiments/Results Conclusions

 Power Save Comparison Experiment




             Measurement to...
Introduction Approaches Experiments/Results Conclusions

 PSM Power Consumption

        Setting                          ...
Introduction Approaches Experiments/Results Conclusions

 PSM Experiment Conclusion




      Conclusion
         Legacy P...
Introduction Approaches Experiments/Results Conclusions

 Codec Comparison




                        Figure: http://www....
Introduction Approaches Experiments/Results Conclusions

 Codec Complexity




          Figure: Krishna, Signal Processin...
Introduction Approaches Experiments/Results Conclusions

 Codec Power Consumption Setup




             Measurement tool:...
Introduction Approaches Experiments/Results Conclusions

 Codec Power Consumption
      Codecs




      Conclusion
      ...
Introduction Approaches Experiments/Results Conclusions

 Guidelines for Power Savings on WiFi VoIP




             Our d...
Introduction Approaches Experiments/Results Conclusions

 Lessons Learned
             Very difficult to measure power.



...
Introduction Approaches Experiments/Results Conclusions

 Lessons Learned




             iwconfig power save mode does n...
Introduction Approaches Experiments/Results Conclusions

 Thank You




                                          Please A...
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Power Saving in Wireless VoIP

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Power Saving in Wireless VoIP

  1. 1. Introduction Approaches Experiments/Results Conclusions Power Saving in Wireless VoIP Wei Wu, Sung Hyuck Lee, Kwan Hong Lee 6.829 Final Project December 7, 2006 Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  2. 2. Introduction Approaches Experiments/Results Conclusions Outline Problem Related Work Approach Experiment/Analysis Guidelines/Conclusions Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  3. 3. Introduction Approaches Experiments/Results Conclusions Problem Where does power get consumed on WiFi phones during VoIP session? Figure: Chen, Power Management for VoIP over IEEE 802.11 WLAN Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  4. 4. Introduction Approaches Experiments/Results Conclusions Power Consumption Understanding where power is consumed Figure: Pering, CoolSpots: reducing the power consumption of wireless mobile devices with multiple radio interfaces Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  5. 5. Introduction Approaches Experiments/Results Conclusions Projections of VoWiFi Figure: Harden, http://ntrg.cs.tcd.ie/undergrad/4ba2.05/group9/index.html Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  6. 6. Introduction Approaches Experiments/Results Conclusions Approaches 802.11 MAC, Power Save Mode (PSM), Unscheduled Power Save Delivery (UPSD) Silence Detection, Voice Codec Header Compression Current Status A lot has been done to save power on VoWiFi!! Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  7. 7. Introduction Approaches Experiments/Results Conclusions 802.11 Frame/Packet Format Figure: more than 150 vs. 160/40/20, TI, Low Power Advantage of 802.11a/g vs. 802.11b Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  8. 8. Introduction Approaches Experiments/Results Conclusions Header Compression/MAC Protocols Experiment Measurement tool: ACPI(Advanced Configuration and Power Interface) battery information, Kismet WLAN cards: Intel PRO/Wireless 2200 Network Connection/Mad-WiFi(Atheros) Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  9. 9. Introduction Approaches Experiments/Results Conclusions IP Header Compression Emulation of IP Header Compression (ROHC) (Packet Size vs. Power Consumption) Setting (payload size) ∆ power (mW/min) 4 35 40 37 Conclusion 5% of energy saved by compressing header Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  10. 10. Introduction Approaches Experiments/Results Conclusions 802.11a/b/g Power Consumption PHY ∆ power (mW/min) Header Size (µsec) 802.11a 40 20 802.11g 39 20 802.11b 45 96, 192 Conclusion 802.11b’s larger header size and greater time for transmitting (smaller rate), it consumes more power Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  11. 11. Introduction Approaches Experiments/Results Conclusions 802.11 Power Save Mode Power Saving bit based Power Saving poll based Figure: Chen, Power Management for VoIP over IEEE 802.11 WLAN Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  12. 12. Introduction Approaches Experiments/Results Conclusions 802.11 Power Save Mode UPSD (Unscheduled Power Saving Delivery), part of 802.11e standard Figure: Chen, Power Management for VoIP over IEEE 802.11 WLAN Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  13. 13. Introduction Approaches Experiments/Results Conclusions Power Save Comparison Experiment Measurement tool: ACPI(Advanced Configuration and Power Interface) battery information, Kismet WLAN cards: Intel PRO/Wireless 2200 Network Connection/Mad-WiFi(Atheros) Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  14. 14. Introduction Approaches Experiments/Results Conclusions PSM Power Consumption Setting Total (mW/min) ∆ power NIC off (base) 202 NIC on, no traffic, PSM off 236 34 NIC on, no traffic, PSM on 218 16 NIC on, VoIP traffic, PSM off 244 42 NIC on, VoIP traffic, PSM on, level 1 243 41 NIC on, VoIP traffic, PSM on, level 3 242 40 NIC on, VoIP traffic, PSM on, level 5 238 36 Intel card. PSM level 1: timeout 350ms, period 400ms Intel card. PSM level 3: timeout 75ms, period 1000ms Intel card. PSM level 5: timeout 25ms, period 1000ms Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  15. 15. Introduction Approaches Experiments/Results Conclusions PSM Experiment Conclusion Conclusion Legacy PSM does not help much because of bidirectional (every 20 ms) traffic. UPSD is beneficial for VoWiFi Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  16. 16. Introduction Approaches Experiments/Results Conclusions Codec Comparison Figure: http://www.oreillynet.com/lpt/a/6373 Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  17. 17. Introduction Approaches Experiments/Results Conclusions Codec Complexity Figure: Krishna, Signal Processing for Packet Voice Telephony Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  18. 18. Introduction Approaches Experiments/Results Conclusions Codec Power Consumption Setup Measurement tool: ACPI(Advanced Configuration and Power Interface) battery information, Kismet WLAN cards: Intel PRO/Wireless 2200 Network Connection/Mad-WiFi (Atheros) Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  19. 19. Introduction Approaches Experiments/Results Conclusions Codec Power Consumption Codecs Conclusion Computation does not matter because of CPU on laptop, packet size dominates. Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  20. 20. Introduction Approaches Experiments/Results Conclusions Guidelines for Power Savings on WiFi VoIP Our design principles for Power Savings Talk less (Send Less) codecs, MAC protocol (11g), header compression, slience detection Be lazy (Sleep More) codecs, PSM(timeout/period) < UPSD, slience detection Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  21. 21. Introduction Approaches Experiments/Results Conclusions Lessons Learned Very difficult to measure power. Figure: Raghunathan, Experience with a low power wireless mobile computing platform Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  22. 22. Introduction Approaches Experiments/Results Conclusions Lessons Learned iwconfig power save mode does not work. Don’t use it! use iwpriv, iwlist Please use 802.11e (QoS) enabled access points. Further study: Transmit Power, AP topologies Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
  23. 23. Introduction Approaches Experiments/Results Conclusions Thank You Please Applaud! Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP

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