Yao Liu @ George Mason University Fei Li @ George Mason University Lei Guo @ Microsoft Y ang Guo @ Bell Labs Son

1. BlueStreaming: Towards Power-Efficient Internet P2P Streaming to Mobile Devices Yao Liu @ George Mason University Fei Li @ George Mason University Lei Guo @ Microsoft Yang Guo @ Bell Labs SongqingChen @ George Mason University

2. 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 totalInternet traffic today

3. 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

4. Streaming to mobile devices is challenging • Heterogeneityamong 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%

5. Power saving forP2P streamingtomobile devicesiseven morechallenging • 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

6. 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

7. Outline • Introduction • Internet Measurement • Design of BlueStreaming • Evaluation • Conclusion

8. P2P streaming consumes more energy than C/S based streaming on iTouch • Experiments on iPod Touch • Use PwrMgtflag to determine the sleep time iPod Touch

9. P2P streaming consumes more energy than C/S based streaming on laptop • Experiments on Laptop running Windows 7: • With maximum WiFi Power Saving Enabled Laptop Windows 7

10. 60-75% total transmitted packets are control packets Smaller than streaming data packets Up to 2 times more than streaming data traffic SopCast (530 Kbps) QQLive (500 Kbps) PPS (396 Kbps) PPTV (400 Kbps) Significantly reduces inter-packet delay Results in less sleep time, and more power consumption

11. Control traffic throughput is low Throughput is generally less than 100 Kbps Smaller compared to the streaming rate of 400 - 530 Kbps SopCast (530 Kbps) QQLive (500 Kbps) PPS (396 Kbps) PPTV (400 Kbps)

12. Uploading traffic varies Throughput of uploading traffic varies between 10 Kbps to 1.5 Mbps PPS (396 Kbps) PPTV (400 Kbps) SopCast (530 Kbps) QQLive (500 Kbps)

13. 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

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

15. Traffic shaping • 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 Time Time Sleeping

16. How about direct traffic shaping? • With traffic shaping: • Control packets, streaming data packets, and uploading packets are scheduled togetherperiodically • Delayed control packets caused: • Playback freezing, distortion • 10% more streaming packets are received Control traffic is delay-sensitive!! Re-requests

17. 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

18. 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

19. Traffic classifier: diverting control traffic to Bluetooth • Decouple control traffic from uploading traffic and streaming data traffic • How can control traffic be decoupled from streaming data traffic transparently? WiFi Time

20. Traffic classifier: diverting control traffic to Bluetooth • Control packets are identified empirically based on packet sizes • Bluetooth is always on to transmit delay-sensitive control packets WiFi Time Bluetooth

21. Traffic shaper: shaping ingress streaming traffic intelligently • Buffers streaming data packets at Access Point • Applies client-centric traffic shaping, and schedules transmission in a burstperiodically • How should the burst interval be set?  ??  WiFi     Time Bluetooth Sleeping Sleeping

22. Traffic shaper: shaping ingress streaming traffic intelligently • 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 beforere-request timer times out:

23. Uploading scheduler: scheduling uploading wisely • How can a client perform uploading with minimized battery power consumption? • Priority-based Bluetooth Uploading WiFi     Time Bluetooth Sleeping Sleeping

24. Uploading scheduler: scheduling uploading wisely • 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 WiFi     Time Bluetooth Sleeping Sleeping

25. Deployment issue Infrastructure Mode Hybrid Mode WiFi AP does not need to support Bluetooth An intermediate node relays the control traffic to WiFi AP • A dedicated AP with both WiFi and Bluetooth • A BlueStreaming client connects to the AP directly

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

27. 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

28. 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

29. Infrastructure mode: PPTV results PSM-A Classifier only

30. Infrastructure mode: PPTV results PSM-A Classifier only BlueStreaming

31. Energy consumption comparisons PPS has very small re-request timeout BlueStreaming effectively saves energy consumption for PPTV, SopCast, QQLive

32. 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

33. Thank you!