Shivajit Mohapatra

Integrated power management for video streaming to mobile handheld devices

Optimizing user experience for streaming video applications on handheld devices is a significant research challenge. In this paper, we propose an integrated power management approach that unifies low level architectural optimizations (CPU, memory, register), OS power-saving mechanisms (Dynamic Voltage Scaling) and adaptive middleware techniques (admission control, optimal transcoding, network traffic regulation). Specifically, we identify interaction parameters between the different levels and optimize them to significantly reduce power consumption. With knowledge of device configurations, dynamic device parameters and changing system conditions, the middleware layer selects an appropriate video quality and fine tunes the architecture for optimized delivery of video. Our performance results indicate that architectural optimizations that are cognizant of user level parameters(e.g. transcoded video quality) can provide energy gains as high as 57.5% for the CPU and memory. Middleware adaptations to changing network noise levels can save as much as 70% of energy consumed by the wireless network interface. Furthermore, we demonstrate how such an integrated framework, that supports tight coupling of inter-level parameters can enhance user experience on a handheld substantially.

Dynamic backlight adaptation for low-power handheld devices

Backlight power minimization can effectively extend battery life for mobile handheld devices. This article proposes an adaptive middleware-based approach to optimize backlight power consumption when playing streaming video. The technique simultaneously minimizes the negative impact on perceived video quality.

PARM : power aware reconfigurable middleware

In distributed environments, generic middleware services (e.g. caching, location management etc.) are widely used to satisfy application needs in a cost-effective manner. Such middleware services consume system resources such as storage, computation and communication and can be sources of significant power overheads when executed on low-power devices. We present a distributed middleware framework (PARM), that is inherently power-aware and reconfigures itself to adapt to diminishing power levels of low-power devices. In this paper, we i) determine whether a reconfigurable component-based middleware framework can be utilized to achieve energy gains in low-power devices, while preserving the semantics of the middleware services, ii) present and evaluate a graph theoretic approach for dynamically determining middleware component reconfigurations and ascertaining the optimal frequency at which the restructuring should occur, for maximal energy gains at the device. We use extensive profiling to chart the energy usage patterns of middleware components and applications, and use the profiled data to drive our reconfiguration decisions. Our simulation results demonstrate that our framework is able to save 5% to 35% of energy depending on the nature and class of applications and middleware components used.

A cross-layer approach for power-performance optimization in distributed mobile systems

The next generation of mobile systems with multimedia processing capabilities and wireless connectivity will be increasingly deployed in highly dynamic and distributed environments for multimedia playback and delivery (e.g. video streaming, multimedia conferencing). The challenge is to meet the heavy resource demands of multimedia applications under the stringent energy, computational, and bandwidth constraints of mobile systems, while constantly adapting to the global state changes of the distributed environment. In this paper, we present our initiatives under the FORGE framework to address the issue of delivering high quality multimedia content in mobile environments. In order to cope with the resource intensive nature of multimedia applications and dynamically changing global state (e.g. node mobility, network congestion), an end-to-end approach to QoS aware power optimization is required. We present a framework for coordinating energy optimizing strategies across various layers of system implementation and functionality and discuss techniques that can be employed to achieve energy gains for mobile multimedia systems.

Design and implementation of a composable reflective middleware framework

With the evolution of the global information infrastructure, service providers will need to provide effective and adaptive resource management mechanisms that can serve more concurrent clients and deal with applications that exhibit quality-of-service (QoS) requirements. Flexible, scalable and customizable middleware can be used as an enabling technology for next-generation systems that adhere to the QoS requirements of applications that execute in highly dynamic distributed environments. To enable application-aware resource management, we are developing a customizable and composable middleware framework called CompOSE|Q (Composable Open Software Environment with QoS), based on a reflective meta-model. In this paper, we describe the architecture and runtime environment for CompOSE|Q and briefly assess the performance overhead of the additional flexibility. We also illustrate how flexible communication mechanisms can be supported efficiently in the CompOSE|Q framework.

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.

An energy-efficient middleware for supporting multimedia services in mobile grid environments

In this paper, we present techniques for exploiting intermittently available resources in grid infrastructures to support QoS-based multimedia applications on mobile devices. Specifically, we integrate power aware admission control, grid resource discovery, dynamic load-balancing and energy adaptation techniques to enable power deficient devices such as PDAs to run distributed multimedia applications. Our integrated solution adapts to dynamic changes in device energy consumption and unpredictable grid resource availabilities without compromising application quality of service (QoS). Our simulation results indicate that our power-aware grid-based approaches, not only improve QoS of mobile multimedia services, but also efficiently load-balance the grid resources.

Energy-aware system design for wireless multimedia

In this paper, we present various challenges that arise in the delivery and exchange of multimedia information to mobile devices. Specifically, we focus on techniques for maintaining QoS to end-user multimedia applications (e.g. video streaming, multimedia conferencing) while maximizing device lifetimes. In order to cope with the resource intensive nature of multimedia applications (in terms of computation, bandwidth and consequently power) and dynamic congestion levels in wireless networks, an end-to-end approach to QoS-aware power optimization is required. We discuss the trend towards such an integrated approach that couples the architectural, OS, middleware and application layers to achieve both user experience and device energy gains. We conclude with a discussion of tools for integrated system design and testing that will aid in rapid deployment of wireless multimedia.

A backlight optimization scheme for video playback on mobile devices

For a typical portable 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 an adaptive 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. I. INTRODUCTION With the widespread availability of 3G cellular networks, mobile hand-held devices are increasingly being designed to support stream- ing video content. These devices have stringent power constraints because they use batteries with finite lifetime. On the other hand, multimedia services are known to be very resource intensive and tend to exhaust battery resources quickly. Therefore, conserving power to prolong battery life is an important research problem that needs to be addressed, specifically for video streaming applications on mobile handheld devices. Most hand-held devices are equipped with a TFT (Thin-Film Transistor) LCD (Liquid Crystal Display). For these devices, the display unit is driven by the illumination of backlight. The backlight consumes a considerable percentage of the total energy usage of the handheld device; it consumes 20%-40% of the total system power (for Compaq iPAQ) (?). Dynamically dimming the backlight is considered an effective method to save energy (?), (?), (?) with scaling up of the pixel luminance to compensate for the reduced fidelity. The luminance scaling, however, tends to saturate the bright part of the picture, thereby affecting the fidelity of the video quality. In (?), a dynamic backlight luminance scaling (DLS) scheme is proposed. Based on different scenarios, three compensation strategies are discussed, i.e., brightness compensation, image enhancement, and context processing. However, their calculation of the distortion does not consider the fact that the clipped pixel values do not contribute equally to the quality distortion. In (?), a similar method, named concurrent brightness and contrast scaling (CBCS), is proposed. CBCS aims at conserving power by reducing the backlight illumi- nation while retaining the image fidelity through preservation of the image contrast. Their distortion definition and proposed compensation technique may be good for static image based applications, such as the graphic user interface (GUI) and maps, but might not be suitable for streaming video scenarios, because their contrast compensation further compromises the fidelity of the images. In addition, neither (?) nor (?) solves the problem associated with frequent backlight switching which can be quite distracting to the end user. In this paper, we explicitly incorporate video quality into the backlight switching strategy and propose a quality adaptive back- light scaling (QABS) scheme. The backlight dimming affects the brightness of the video. Therefore, we only consider the luminance compensation such that the lost brightness can be restored. The lumi- nance compensation, however, inevitably results in quality distortion. For the video streaming application, the quality is normally defined as the resemblance between the original and processed video. Hence, for the sake of simplicity and without loss of generality, we define the quality distortion function as the mean square error (MSE)(see Equation (1)) and the quality function as the peak signal to noise ratio (PSNR)(see Equation (2)), both of which are well accepted objective video quality measurements.

Quality adapted backlight scaling (QABS) for video streaming to mobile handheld devices

For a typical portable 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 an adaptive 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.