International Symposium on Low Power Electronics and Design

A Cloud-Based Energy-Saving Service for Mobile Streaming Applications

Cheng-Kang Hsieh, Chun-Han Lin, Pi-Cheng Hsiu

Research Center for Information Technology Innovation Academia Sinica, Taiwan

• Introduction

• A Dynamic Backlight Scaling Service

• Real-World Case Studies

• Conclusion

2

Outline

• Mobile applications and services are having a profound effect on people's lifestyles.

• The energy consumption of mobile devices is a major challenge in sustaining the applications and services.

3

Motivation

• The concept would be realized as a value-added service offered by ISPs, like AT&T.

• AT&T helps mobile devices to save energy when they access Internet applications.

• The services must be easy to use & transparent to the users.

4

Cloud-based Energy-Saving Services

• The screen backlight consumes most of the energy for mobile streaming applications.

• Dynamic backlight scaling is deemed a promising technical solution.

• When to dim the backlight to which level? Our ISPLED’11 paper has the answer!

5

Power Consumption when

browsing YouTube on iPad

CPU, 17.21%

WIFI, 4.32%

Backlight, 60.49%

LCD Screen, 17.98%

Dynamic Backlight Scaling

A Dynamic Backlight Scaling Service

6

System Architecture

Video Stream

Backlight File Backlight Server

Streaming Server

Mobile Device

• Responsible for generating backlight files

7

The Cloud Side

Phase 1 • Analyze the video to decide the critical backlight

levels (i.e., the dimmest backlight level with respect to the tolerable video distortion)

Phase 2 • Determine an optimal backlight assignment for the

video based on the device’s power model and capability

Backlight File

Download the requested video from YouTube

Critical backlight levels of the video

8

The Device Side

• Measure power models • Develop mobile application programs

iPad’s display subsystem Power Monitors

9

System Deployment

• The dynamic backlight scaling service has been deployed on Chunghwa Telecom’s hicloud.

• The mobile application program for Android is going to be released in the Android Market for free.

Backlight File

• Process Time & Transmission Delay

• Video Perceptual Quality (Demo)

10

Approach Validation

Video Download Phase I Phase II

124 seconds 1020 seconds 2.1 seconds

Transmission Delay

335 milliseconds

Cloud Side

Device Side

11

Performance Evaluation

Experimental Results Case Studies

12

Conclusion

• We raise the concept of cloud-based energy-saving services. – The dynamic backlight scaling service has been deployed on

CHT hicloud as a prototype service. – Two mobile application programs were developed for Google’s

Android and Apple’s iOS. – With the service applied, HTC Desire and Apple iPad achieved

energy savings of 11-20% and 31-41% when browsing videos on YouTube.

• We will release the mobile application programs to

seek the feedback on the performance and identify the issues that require further investigation.

13

We are the Research Center for IT Innovation