5 research outputs found
Quality-Based Backlight Optimization for Video Playback on Handheld Devices
For a typical handheld device, the backlight accounts for a significant percentage of the total energy consumption (e.g., around 30% for a Compaq iPAQ 3650). Substantial energy savings can be achieved by dynamically adapting backlight intensity levels on such low-power portable devices. In this paper, we analyze the characteristics of video streaming services and propose a cross-layer optimization scheme called quality adapted backlight scaling (QABS) to achieve backlight energy savings for video playback applications on handheld devices. Specifically, we present a fast algorithm to optimize backlight dimming while keeping the degradation in image quality to a minimum so that the overall service quality is close to a specified threshold. Additionally, we propose two effective techniques to prevent frequent backlight switching, which negatively affects user perception of video. Our initial experimental results indicate that the energy used for backlight is significantly reduced, while the desired quality is satisfied. The proposed algorithms can be realized in real time
Adaptive display power management for mobile games
Ministry of Education, Singapore under its Academic Research Funding Tier
Energy-aware adaptive solutions for multimedia delivery to wireless devices
The functionality of smart mobile devices is improving rapidly but these devices are limited
in terms of practical use because of battery-life. This situation cannot be remedied by simply
installing batteries with higher capacities in the devices. There are strict limitations in the
design of a smartphone, in terms of physical space, that prohibit this “quick-fix” from being
possible. The solution instead lies with the creation of an intelligent, dynamic mechanism for
utilizing the hardware components on a device in an energy-efficient manner, while also
maintaining the Quality of Service (QoS) requirements of the applications running on the
device.
This thesis proposes the following Energy-aware Adaptive Solutions (EASE):
1. BaSe-AMy: the Battery and Stream-aware Adaptive Multimedia Delivery (BaSe-AMy)
algorithm assesses battery-life, network characteristics, video-stream properties and
device hardware information, in order to dynamically reduce the power consumption of
the device while streaming video. The algorithm computes the most efficient strategy for
altering the characteristics of the stream, the playback of the video, and the hardware
utilization of the device, dynamically, while meeting application’s QoS requirements.
2. PowerHop: an algorithm which assesses network conditions, device power consumption,
neighboring node devices and QoS requirements to decide whether to adapt the
transmission power or the number of hops that a device uses for communication.
PowerHop’s ability to dynamically reduce the transmission power of the device’s
Wireless Network Interface Card (WNIC) provides scope for reducing the power
consumption of the device. In this case shorter transmission distances with multiple hops
can be utilized to maintain network range.
3. A comprehensive survey of adaptive energy optimizations in multimedia-centric wireless
devices is also provided.
Additional contributions:
1. A custom video comparison tool was developed to facilitate objective assessment of
streamed videos.
2. A new solution for high-accuracy mobile power logging was designed and implemented
Energy Accounting and Optimization for Mobile Systems
Energy accounting determines how much a software process contributes
to the total system energy consumption. It is the foundation for
evaluating software and has been widely used by operating system based
energy management. While various energy accounting policies have been
tried, there is no known way to evaluate them directly simply because
it is hard to track every hardware use by software in a heterogeneous
multicore system like modern smartphones and tablets. This work
provides the ground truth for energy accounting based on multi-player
game theory and offers the first evaluation of existing energy
accounting policies, revealing their important flaws. The proposed
ground truth is based on Shapley value, a single value solution to
multi-player games of which four axiomatic properties are natural and
self-evident to energy accounting.
This work further provides a utility optimization formulation of
energy management and shows, surprisingly, that energy accounting does
not matter for existing energy management solutions that control the
energy use of a process by giving it an energy budget, or budget based
energy management (BEM). This work shows an optimal energy management
(OEM) framework can always outperform BEM. While OEM does not require
any form of energy accounting, it is related to Shapley value in that
both require the system energy consumption for all possible
combination of processes under question.
This work reports a prototype implementation of both Shapley
value-based energy accounting and OEM based scheduling. Using this
prototype and smartphone workload, this work experimentally
demonstrates how erroneous existing energy accounting policies can be,
show that existing BEM solutions are unnecessarily complicated yet
underperforming by 20% compared to OEM