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An energy-balanced task scheduling heuristic for heterogeneous wireless sensor networks 08

Proceedings of the 15th international conference on High performance computing

作者： Lee Kee Goh Bharadwaj Veeravalli Computer Networks and Distributed Systems Laboratory Department of Electrical and Computer Engineering National University of Singapore Singapore

ISBN: (纸本)9783540898931

In this paper, we propose a static scheduling algorithm forassigning tasks with precedence constraints onto a cluster of heterogeneoussensor nodes connected by a single-hop wireless network so as tomaximize the lifetime of the sensor network. The processing element oneach sensor node is equipped with dynamic voltage scaling capability. Inour algorithm, we assign the tasks to the sensor nodes so as to minimizethe energy consumption of the tasks on each sensor node while keepingthe energy consumption as balanced as possible. We also propose an algorithmto generate a second schedule that can improve the lifetime ofthe network further when it is used together with the original *** observe up to 311% lifetime improvement in our simulations whenour algorithms are compared to the baseline case where dynamic voltagescaling is not used.

关键词： dynamic voltage scaling energy-aware scheduling heterogeneous multiprocessor scheduling power management wireless sensor network

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Dynamic scheduling of imprecise-computation tasks in maximizing QoS under energy constraints for embedded systems

Dynamic scheduling of imprecise-computation tasks in maximiz...

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Asia and South Pacific Design Automation Conference

作者： Heng Yu Bharadwaj Veeravalli Yajun Ha Department of Electrical and Computer Engineering National University of Singapore Singapore Computer Networks and Distributed Systems (CNDS) Laboratory National University of Singapore Singapore

ISBN: (纸本)9781424419210

In designing energy-aware CPU scheduling algorithms for real-time embedded systems, dynamic slack reclamation techniques significantly improve system quality-of-service (QoS) and energy efficiency. However, the limited schemes in this domain either demand high complexity or can only achieve limited QoS. In this paper, we present a novel low complexity runtime scheduling algorithm for the imprecise computation (IC) modeled tasks. The target is to maximize system QoS under energy constraints. Our proposed algorithm, named gradient curve shifting (GCS), is able to decide the best allocation of slack cycles arising at runtime, with very low complexity. We study both linear and concave QoS functions associated with IC modelde tasks, on non-DVS and DVS processors. Furthermore, we apply the intra-task DVS technique to tasks and achieve as large as 18% more of the system QoS compared to the conventional "optimal" solution which is inter-task DVS based.

关键词： Dynamic scheduling Embedded system Integrated circuit modeling Voltage control Scheduling algorithm Runtime Algorithm design and analysis Real time systems Quality of service Energy efficiency

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Backbone Based GPS-Free Localization in Mobile Ad Hoc networks

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电子学报(英文版) 2007年第1期16卷 155-160页

作者： TIAN Mingjun ZHAO Dan YAN Wei Computer Networks and Distributed Systems Laboratory Peking University Beijing 100871 China

In this paper we describe a distributed, GPS-free localization algorithm called BGFL (Backbone -based GPS-free localization), which does not rely on any absolute position reference such as GPS or fixed anchor nodes. Instead, the algorithm only depends on the distances between the nodes and their neighbors. It is backbone based, in which some nodes in the network are first selected then formed into a backbone network, where every node on the backbone builds a LCS (Local coordinate system). Finally, all LCSs are merged into a global relative coordinate system. We simulate the performance of the algorithms under a variety of node densities, distance estimation errors and moving speeds. The results show that our algorithm outperforms the existing GPS-free localization algorithms in terms of accuracy, communication cost, convergence time, probability to build a global coordinate system and adaptability to the mobile environment.

关键词：移动Ad-Hoc网高速链路 GPS 定位

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Comprehensive review on blog mining under a cross-disciplinary framework

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Journal of Computational Information systems 2007年第4期3卷 1725-1730页

作者： Gao, Shengliang Yao, Conglei Lab. of Computer Networks and Distributed Systems Peking University Beijing 100871 China

Nowadays, blog has been playing a more and more important role in human life as the internet evolves dramatically. Academia has seen an research burst on blog since 2002, not only in the area of computer science like IR and web mining, but also in the area of social sciences. We present a blog-centered framework here to abstract and generalize current researches on blog mining, with the intention of providing a clear image on blog-focused research area.

关键词： Data mining

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MBF: A real matrix bloom filter representation method on dynamic set

MBF: A real matrix bloom filter representation method on dyn...

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2007 IFIP International Conference on Network and Parallel Computing Workshops, NPC 2007

作者： Jiacong, Wang Mingzhong, Xiao Yafei, Dai Computer Networks and Distributed Systems Laboratory Peking University China

ISBN: (纸本)0769529437

Bloom Filter is a simple space-efficient randomized data structure for representing a set in order to support membership queries, which uses an m-bit array to represent a data set. In order to support representing dynamic set, dynamic bloom filter (DBF) and split bloom filter (SBF) have been developed. Both DBF and SBF can support concisely representation and approximate membership queries of dynamic set instead of static set. SBF declares that it uses an s Xm bit matrix that consists of s bloom filters to represent a dynamic set, so DBF dose. But in fact, both the two bloom filters are not matrix representation method at all. They are just a set of s bloom filters whose length is m, and they have got a departure from the original idea of bloom filter: the constant query time cost. This paper points out the fact, and then introduce a truly matrix representation method of bloom filter to represent a dynamic set. We call it the Matrix Bloom Filter (MBF). Then, we will analysis the algorithm of MBF and study the average time complexity and the false positive probability. © 2007 IEEE.

关键词： Matrix algebra

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A replica-conscious load balancing strategy for large-scale multimedia storage systems

A replica-conscious load balancing strategy for large-scale ...

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IEEE GLOBECOM 2006 - 2006 Global Telecommunications Conference

作者： Zeng Veeravalli, Bharadwaj Computer Networks and Distributed Systems Laboratory National University of Singapore Singapore 117576 Singapore

ISBN: (纸本)142440357X

In distributed multimedia storage systems where client requests for different multimedia objects may have different demands, placement and replication of the objects is an important factor, as it may result in an imbalance in server loading across the system. Replica management and load balancing is all the more a crucial issue for large-scale multimedia systems. We design and analyze a heuristic static strategy to determine the placement, number of replicas of the objects, and balance the client requests among the servers, to minimize the average waiting time (AWT) of the requests. Our strategy exploits clever virtual routing technique to strike a balance among the servers for load balancing. We validate the performance via rigorous simulations with respect to several influencing factors and compare with a system that uses hashing function only for load balancing. © 2006 IEEE.

关键词： Resource allocation

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An analytical flow control scheme for real-time traffic in wireless mesh network: From theoretic model to practical mechanism 07

An analytical flow control scheme for real-time traffic in w...

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4th International Conference on Mobile Technology, Applications and systems, Mobility 2007, Incorporating the 1st International Symposium on computer Human Interaction in Mobile Technology, IS-CHI 2007

作者： Liu, Yongqiang Zhao, Tong Liu, Zhongyi Yan, Wei Li, Xiaoming Computer Networks and Distributed Systems Lab. School of EECS Peking University 100871 China

ISBN: (纸本)9781595938190

The link interference and multi-hop characters make Wireless Mesh Network (WMN) performance can not be tuned well by local information. We propose an analytical flow control scheme (AFCS) based on the optimal bandwidth allocation model that is specifically designed for the unique characteristics of WMN. The original contribution incorporated in a flow contention model of WMN based on maximal link interference region. With the contention constraint, the optimality of bandwidth allocation can be achieved by maximizing the aggregated utility across all flows. We then deduce a practical equation for adjusting sending rate from the bandwidth allocation model. Based on the simplified analytical equation and the congestion notification message mechanism, we propose an equation-based flow control framework for real-time traffic in WMN. Simulation results have shown the AFCS can improve the capacity of the WMN by 40% and alleviate the unfairness and delay jitter greatly. The fast response, fairness and steadiness characters of the AFCS are helpful for rigorous real-time traffic and dynamic wireless network. Copyright 2007 ACM.

关键词： Flow control

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A Comprehensive Worst-Case Calculus for Wireless Sensor networks with In-Network Processing

A Comprehensive Worst-Case Calculus for Wireless Sensor Netw...

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Real-Time systems Symposium (RTSS)

作者： Jens B. Schmitt Frank A. Zdarsky Lothar Thiele Distributed Computer Systems Laboratory University of Kaiserslautern Germany Computer Engineering and Networks Laboratory Swiss Federal Institute of Technology Switzerland

Today's wireless sensor networks (WSN) focus on energy-efficiency as the main metric to optimize. However, an increasing number of scenarios where sensor networks are considered for time-critical purposes in application scenarios like intrusion detection, industrial monitoring, or health care systems demands for an explicit support of performance guarantees in WSNs and, thus, in turn for a respective mathematical framework. In (J. Schmitt and U. Roedig, 2005) , a sensor network calculus was introduced in order to accommodate a worst-case analysis of WSNs. This sensor network calculus focused on the communication aspect in WSNs, but had not yet a possibility to treat in-network processing in WSNs. In this work, we now incorporate in-network processing features as they are typical for WSNs by taking into account computational resources on the sensor nodes. Furthermore, we propose a simple, yet effective priority queue management discipline which achieves a good balance of response times across sensor nodes in the field.

关键词： Calculus Wireless sensor networks Energy efficiency Sensor systems and applications Time factors Intrusion detection Monitoring Medical services Sensor phenomena and characterization Delay

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Resource Unaware Computing - A distributed Strategy for Divisible Load Processing on Linear Daisy Chain networks

Resource Unaware Computing - A Distributed Strategy for Divi...

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IEEE International Conference on networks

作者： Jingxi Jia Bharadwaj Veeravalli Computer Networks and Distributed Systems Laboratory (CNDS) Department of Electrical and Computer Engineering National University of Singapore Singapore

ISBN: (纸本)0780397460

In this paper we present a novel load distribution strategy for scheduling divisible loads on linear networks, when the speeds of the computing nodes and the speeds of the communication links are unknown. This practical assumption is captured in our problem formulation and we present a novel strategy, referred to as early start strategy (ESS), to generate a load distribution. Our strategy estimates the speed parameters and takes distinct advantage in utilizing a processor that responds earliest in the computation and including other fast processors in a progressive manner in phases to minimize the overall processing time. We analyze the strategy under several influencing parameters such as, load size, network size, and probe load size. We present simulation studies to validate all the theoretical findings and quantify the performance of our strategy

关键词： computer networks distributed computing Processor scheduling Electronic switching systems Probes Delay effects Laboratories Drives Distribution strategy Parameter estimation

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Peking university at the TREC 2006 terabyte track

Peking university at the TREC 2006 terabyte track

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15th Text REtrieval Conference, TREC 2006

作者： Jingjing, Li Hongfei, Yan Networks and Distributed Systems Laboratory School of Electronic Engineering and Computer Science Peking University Beijing 100871 China

This paper details the experiments carried out at TREC 2006 Terabyte Track using Indri Search Engine. There were three tasks in the Terabyte track of TREC 2006, i.e. efficiency task, ad hoc task and named page finding task. We participated in two tasks, and submitted 5 runs for ad hoc task and 3 runs for named page task respectively. In ad hoc task, we looked at the importance of term proximity. In named page finding task, we cared more about the information of document structure and document prior.

关键词： Search engines

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