1627364
DC-DC converter-aware power management for battery-operated embedded systems
Most digital systems are equipped with DC-DC converters to supply various levels of voltages from batteries to logic devices. DC-DC converters maintain legal voltage ranges regardless of the load current variation as well as battery voltage drop. Although the efficiency of DC-DC converters is changed by the output voltage level and the load current, most existing power management techniques simply ignore the efficiency variation of DC-DC converters. However, without a careful consideration of the efficiency variation of DC-DC converters, finding a true optimal power management is impossible. In this work, we solve the problem of energy minimization with the consideration of the characteristics of power consumption of DC-DC converter. Specifically, the contributions of our work are: (1) We analyze the effects of the efficiency variation of DC-DC converters on a single task execution in DVS (dynamic voltage scaling) scheme, and propose a technique, called DC/spl I.bar/DVS, of DC-DC converter-aware energy-minimal DVS; (2) DC/spl I.bar/DVS is then extended to combine the effects of DC-DC converters with the procedures of general DVS techniques with multiple tasks; (3) Conversely, we propose a technique, called DC/spl I.bar/CONF, of generating a DC-DC converter that is best suited, in terms of total energy efficiency, to the intended application, and (4) finally, we complete our integrated framework DC-lp, which is based on DC/spl I.bar/DVS and DC/spl I.bar/CONF, that attempts to solve the DC-DC converter configuration selection problem and the DVS problem simultaneously. To show the effectiveness of the proposed techniques, a set of experimental results is provided. In summary, it is shown that DC-lp is able to save 16.0% /spl sim/ 22.1% of energy on the average, which otherwise was dissipated in the previous power management schemes with no consideration of DC-DC converter efficiency variation.
1609683
Web-Based Energy Exploration Tool for Embedded Systems
We describe a Web-based energy estimation tool for embedded systems. An interesting feature of this tool is that it performs real-time cycle-accurate energy measurements on a hardware prototype of the processor. The authors describe the various steps involved in using the tool and present case studies to illustrate its utility.
1746806
Identifying Expressions of Opinion in Context
While traditional information extraction systems have been built to answer questions about facts, subjective information extraction systems will answer questions about feelings and opinions. A crucial step towards this goal is identifying the words and phrases that express opinions in text. Indeed, although much previous work has relied on the identification of opinion expressions for a variety of sentiment-based NLP tasks, none has focused directly on this important supporting task. Moreover, none of the proposed methods for identification of opinion expressions has been evaluated at the task that they were designed to perform. We present an approach for identifying opinion expressions that uses conditional random fields and we evaluate the approach at the expression-level using a standard sentiment corpus. Our approach achieves expression-level performance within 5% of the human interannotator agreement.
12101738
OpinionFinder: A System for Subjectivity Analysis
OpinionFinder is a system that performs subjectivity analysis, automatically identifying when opinions, sentiments, speculations, and other private states are present in text. Specifically, OpinionFinder aims to identify subjective sentences and to mark various aspects of the subjectivity in these sentences, including the source (holder) of the subjectivity and words that are included in phrases expressing positive or negative sentiments.
14917866
Protected heap sharing for memory-constrained java environments
Multitasking is one of capabilities we often want to have in memory-constrained embedded systems. To support multiple address spaces within a small physical memory, a simple memory management frequently encounters the lack of available memory. Our paper presents an efficient heap memory management scheme that reduces memory footprints by adaptively sharing heaps among multiple tasks in JVM environments. We modified KVM from Sun Microsystems so that Java applications acquire or release heaps in a shared pool on an as-needed basis. To protect address spaces among tasks in the absence of virtual memory capabilities, we use memory protection units (MPUs) by incorporating them into our heap sharing scheme. Our experiments with J2ME MIDP applications show significant reductions by 33% on average, ranging from 6% to 50% in memory usage over the execution. The overheads of our scheme in garbage collection are kept low. The execution times in our scheme increase only by 0.2% on average.
325419
Textual compression by collapsible tries
Summary form only given. In this paper, various lossless and lossy adaptations and extensions of that paradigm are developed and tested, for the most part susceptible to simple linear time implementation. This is in contrast to the existing lossy variants of the Ziv-Lempel family of encoders, which have been traditionally built around the iterated quest for the best match within an assigned fidelity, thereby resulting in algorithms that are inherently superlinear and not easy to implement and analyze. Whereas a thorough analytical treatment of the proposed method seems hard, the basic algorithm and its main variants show good performance and latitude of practical applicability
4649924
WAF: wireless-adaptive fair scheduling for multimedia stream in time division multiplexed packet cellular systems
Cellular systems are designed to support voice service over the wireless channel but nowadays data-only networks such as cdma2000 1x EV-DO and high speed downlink packet access (HSDPA) are being deployed in the midst of evolution to the next generation wireless networks. Such systems become important because data services are essential in future wireless networks that are supposed to adopt the concept of all-IP to support integrated services. To increase the data transmission rate at downlink in cdma2000 1x EV-DO and HSDPA, the base station (BS) uses only a channel multiplexed by time division, not by code division. These systems use proportional fair scheduling to maximize throughput. While it is useful for non real time traffic, it does not provide appropriate QoS for real time services such as voice and video. Therefore we need to incorporate the multimedia QoS requirements into the design of a new scheduling algorithm. Our proposed wireless-adaptive fair scheduling (WAF) tries to allocate time slots with fair share according to the stream requirements considering the varying channel conditions to achieve good throughput. The simulation results show that our scheme can guarantee fair service and increase throughput by up to 41% compared to the purely fair (PF) scheduling scheme.