Yao Liu @ George Mason UniversityFei Li @ George Mason University

Lei Guo @ MicrosoftYang Guo @ Bell Labs

Songqing Chen @ George Mason University

BlueStreaming: Towards Power-Efficient Internet P2P Streaming to Mobile Devices

Internet streaming• Internet video streaming is gaining increased

popularity in practice– 90% of Internet traffic will be video by 2014

• Internet peer-to-peer (P2P) streaming is also popular

– P2P TV has generated 6% of total Internet traffic today

Internet streaming to mobile devices• Mobile devices are pervasively used today to

access streaming services

More than 66% of mobile network traffic will be video by 2015

Streaming to mobile devices is challenging

• Heterogeneity among devices– Software: different mobile operating systems, supported

audio/video codecs…– Hardware: different screen sizes…– Connection: 3G, WiFi, WiMAX, …

• Less reliable wireless connections• Slower CPUs• …• Limited battery power supply• Major power drainage sources:– CPU– Display– Wireless network interface card (WNIC)

How to save the power consumed by Wireless Network Interface?

30% ~ 40%

Power saving for P2P streaming to mobile devices is even more challenging

• In addition to downloading, a peer is expected to upload an equivalent amount to other peers in order to get service– Tit-for-tat

• In order to upload and download, a peer has to frequently exchange control packets with neighbors– Buffermaps– Fine-grained data requests

• Streaming data is downloaded from multiple and dynamically changing neighbors

Our contribution• Through Internet measurements, we confirm the

uploading traffic, control traffic significantly prevent the WiFi interface from switching to sleep mode

• We propose to leverage Bluetooth to transmit highly frequent and low throughput control traffic in P2P streaming for mobile devices

• We design and implement BlueStreaming, which trades Bluetooth’s power consumption for greater power saving from WiFi via intelligent traffic shaping

Outline

• Introduction• Internet Measurement• Design of BlueStreaming• Evaluation• Conclusion

P2P streaming consumes more energy than C/S based streaming on iTouch

Architecture Encoding Rate (Kbps)

Sleep Time (%)

TVUPlayer P2P 281 26Justin.tv C/S 281 83

iPod Touch

• Experiments on iPod Touch– Use Pwr Mgt flag to determine the sleep time

P2P streaming consumes more energy than C/S based streaming on laptop

Architecture Encoding Rate (Kbps)

Sleep Time (%)

Avg. # of Neighbors

PPTV P2P 400 4.42 12PPS P2P 396 0.09 20SopCast P2P 530 0.99 3QQLive P2P 500 7.12 4Justin.tv C/S 433 21.44 n/a

Laptop Windows 7

• Experiments on Laptop running Windows 7:– With maximum WiFi Power Saving Enabled

60-75% total transmitted packets are control packets

SopCast (530 Kbps) QQLive (500 Kbps)

PPTV (400 Kbps) PPS (396 Kbps)

Significantly reduces inter-packet delay

Results in less sleep time, and more power

consumption

Smaller than streaming data

packets

Up to 2 times more than streaming data traffic

SopCast (530 Kbps) QQLive (500 Kbps)

Control traffic throughput is low

PPTV (400 Kbps) PPS (396 Kbps)

Throughput is generally less than 100 Kbps

Smaller compared to the streaming rate of

400 - 530 Kbps

Uploading traffic varies

SopCast (530 Kbps) QQLive (500 Kbps)

PPTV (400 Kbps) PPS (396 Kbps)

Throughput of uploading traffic varies between 10 Kbps to 1.5 Mbps

MAX MIN

PPTV 4.42% 0.08%

PPS 0.09% 0.00%

SopCast 0.99% 0.22%

QQLive 7.12% 4.33%

Summary

• Control packets are delay-sensitive, highly frequent, but their throughput is low

• Uploading traffic changes dynamically, and could reach a very high throughput

• # of neighbors directly affect the control traffic and uploading traffic amount, the response time variance further shortens inter-packet delay

Outline

• Problem Statement and Proposal• Internet Measurement• Design of BlueStreaming• Evaluation• Conclusion

• Let the media traffic arrive in a predicable pattern:– Periodic bursts– WiFi can work / sleep correspondingly– Allows the WiFi interface to exploit more sleep

opportunities

Traffic shaping

Time

Sleeping

Time

How about direct traffic shaping?

• With traffic shaping:– Control packets, streaming data packets, and

uploading packets are scheduled together periodically

– Delayed control packets caused:• Playback freezing, distortion• 10% more streaming packets are received

QQLive500 Kbps

Total # of Streaming Packets

WiFi Sleep Time (%)

Distortion/Freeze Time (%)

Adaptive PSM 109,800 5.24 0

WiFi with traffic shaping 121,598 26.89 38

Control traffic is delay-sensitive!!

Re-requests

How about using Bluetooth directly?

• Using Bluetooth to access P2P streaming:– Bluetooth also has lower data rate, and cannot

afford the streaming rate– Only 34% streaming data packets were received

QQLive500 Kbps

Total # of Streaming Packets

WiFi Sleep Time (%)

Distortion/Freeze Time (%)

Adaptive PSM 109,800 5.24 0

WiFi with traffic shaping 121,598 26.89 38

Bluetooth only 37,228 n/a 96

BlueStreaming overview

• Traffic Classifier at AP and client:– Decouples control traffic from streaming data

traffic, and uses Bluetooth to transmit

• Traffic Shaper at the client:– Intelligently shapes streaming data downloading

traffic, and allows WiFi to save more power

• Uploading Scheduler at the client:– Handles the uploading traffic with minimized extra

power consumption

• Decouple control traffic from uploading traffic and streaming data traffic

• How can control traffic be decoupled from streaming data traffic transparently?

Traffic classifier: diverting control traffic to Bluetooth

WiFi

Time

• Control packets are identified empirically based on packet sizes

• Bluetooth is always on to transmit delay-sensitive control packets

Traffic classifier: diverting control traffic to Bluetooth

Bluetooth

WiFi

Time

• Buffers streaming data packets at Access Point• Applies client-centric traffic shaping, and

schedules transmission in a burst periodically• How should the burst interval be set?

Traffic shaper: shaping ingress streaming traffic intelligently

??

TimeBluetooth

WiFi

SleepingSleeping

• How should the burst interval be set?–P2P streaming applications have a re-request

timer to determine if a chunk should be re-requested.• Application-specific

–Packets should be transmitted before re-request timer times out:

Traffic shaper: shaping ingress streaming traffic intelligently

• How can a client perform uploading with minimized battery power consumption?

• Priority-based Bluetooth Uploading

Uploading scheduler: scheduling uploading wisely

TimeBluetooth

WiFi

Sleeping Sleeping

• How can a client perform uploading with minimized battery power consumption?

• Opportunistic WiFi Uploading:– Allows WiFi to upload with a minimum consumption of

extra battery power– Works seamlessly with the PSM mechanism

Uploading scheduler: scheduling uploading wisely

TimeBluetooth

WiFi

Sleeping Sleeping

Infrastructure Mode• A dedicated AP with both

WiFi and Bluetooth• A BlueStreaming client

connects to the AP directly

Hybrid Mode• WiFi AP does not need to

support Bluetooth• An intermediate node relays

the control traffic to WiFi AP

Deployment issue

Outline

• Problem Statement and Proposal• Internet Measurement• Design of BlueStreaming• Evaluation• Conclusion

Implementation of BlueStreaming

• Prototype systems on Windows and Mac• Why laptop instead of mobile devices?– Desktop OS has more complete Bluetooth profiles

including Personal Area Network (PAN)– More P2P streaming applications are available on

Windows

Experimental setup

• Use our Windows prototype running on one laptop as BlueStreaming client to access:– PPTV, PPS, SopCast, QQLive

• Use one MacBook with Bluetooth and WiFi (802.11n at 2.4GHz) as the BlueStreaming Access Point

• In hybrid mode:– Another laptop is used to relay the control traffic

between BlueStreaming client and access point

Infrastructure mode: PPTV results

Sleep Time (%) Consumed Energy (J)

PSM-A 0.56 2005Classifier only 25.82 1745

PSM-A Classifier only

Infrastructure mode: PPTV results

Sleep Time (%) Consumed Energy (J)

PSM-A 0.56 2005Classifier only 25.82 1745BlueStreaming 60.50 1090

PSM-A Classifier only BlueStreaming

Energy consumption comparisons

PPS has very small re-request timeout

BlueStreaming effectively saves energy consumption for PPTV,

SopCast, QQLive

Conclusion

• A mobile client in P2P streaming consumes excessive power because of – extra control traffic– extra uploading traffic– dynamics of neighboring peers.

• BlueStreaming trades Bluetooth’s power consumption for greater power saving on WiFi interface via intelligent traffic shaping– Saves up to 46% battery power consumption

Thank you!