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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
Introduction Approaches Experiments/Results Conclusions
Outline
ProblemRelated WorkApproachExperiment/AnalysisGuidelines/Conclusions
Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
Introduction Approaches Experiments/Results Conclusions
Problem
Where does power get consumed on WiFi phones during VoIPsession?
Figure: Chen, Power Management for VoIP over IEEE 802.11 WLAN
Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
Introduction Approaches Experiments/Results Conclusions
Power Consumption
Understanding where power is consumed
Figure: Pering, CoolSpots: reducing the power consumption ofwireless mobile devices with multiple radio interfaces
Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
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
Introduction Approaches Experiments/Results Conclusions
Approaches
802.11 MAC, Power Save Mode (PSM), UnscheduledPower Save Delivery (UPSD)Silence Detection, Voice CodecHeader Compression
Current StatusA lot has been done to save power on VoWiFi!!
Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
Introduction Approaches Experiments/Results Conclusions
802.11 Frame/Packet Format
Figure: more than 150 vs. 160/40/20, TI, Low Power Advantage of802.11a/g vs. 802.11b
Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
Introduction Approaches Experiments/Results Conclusions
Header Compression/MAC Protocols Experiment
Measurement tool: ACPI(Advanced Configuration andPower Interface) battery information, KismetWLAN cards: Intel PRO/Wireless 2200 NetworkConnection/Mad-WiFi(Atheros)
Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
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 3540 37
Conclusion5% of energy saved by compressing header
Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
Introduction Approaches Experiments/Results Conclusions
802.11a/b/g Power Consumption
PHY ∆ power (mW/min) Header Size (µsec)802.11a 40 20802.11g 39 20802.11b 45 96, 192
Conclusion802.11b’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
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
Introduction Approaches Experiments/Results Conclusions
802.11 Power Save Mode
UPSD (Unscheduled Power Saving Delivery), part of802.11e 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
Introduction Approaches Experiments/Results Conclusions
Power Save Comparison Experiment
Measurement tool: ACPI(Advanced Configuration andPower Interface) battery information, KismetWLAN cards: Intel PRO/Wireless 2200 NetworkConnection/Mad-WiFi(Atheros)
Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
Introduction Approaches Experiments/Results Conclusions
PSM Power Consumption
Setting Total (mW/min) ∆ powerNIC off (base) 202NIC on, no traffic, PSM off 236 34NIC on, no traffic, PSM on 218 16NIC on, VoIP traffic, PSM off 244 42NIC on, VoIP traffic, PSM on, level 1 243 41NIC on, VoIP traffic, PSM on, level 3 242 40NIC on, VoIP traffic, PSM on, level 5 238 36
Intel card. PSM level 1: timeout 350ms, period 400msIntel card. PSM level 3: timeout 75ms, period 1000msIntel card. PSM level 5: timeout 25ms, period 1000ms
Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
Introduction Approaches Experiments/Results Conclusions
PSM Experiment Conclusion
ConclusionLegacy 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
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
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
Introduction Approaches Experiments/Results Conclusions
Codec Power Consumption Setup
Measurement tool: ACPI(Advanced Configuration andPower Interface) battery information, KismetWLAN cards: Intel PRO/Wireless 2200 NetworkConnection/Mad-WiFi (Atheros)
Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
Introduction Approaches Experiments/Results Conclusions
Codec Power Consumption
Codecs
ConclusionComputation does not matter because of CPU on laptop,packet size dominates.
Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
Introduction Approaches Experiments/Results Conclusions
Guidelines for Power Savings on WiFi VoIP
Our design principles for Power SavingsTalk less (Send Less)
codecs, MAC protocol (11g), header compression, sliencedetection
Be lazy (Sleep More)codecs, PSM(timeout/period) < UPSD, slience detection
Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
Introduction Approaches Experiments/Results Conclusions
Lessons Learned
Very difficult to measure power.
Figure: Raghunathan, Experience with a low power wireless mobilecomputing platform
Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP
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
Introduction Approaches Experiments/Results Conclusions
Thank You
Please Applaud!
Wei Wu, Sung Hyuck Lee, Kwan Hong Lee Power Saving in Wireless VoIP