With the fast increases in the size of the scientific data, the visualization technique has been widely adopted to transform the information into an easy-to-understand representation. Since the security clearance and ...
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Cloud computing provides a platform for new software applications that run across a large collection of physically separate computers and free computation from the computer in front of a user. distributedcomputing is...
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ISBN:
(纸本)9783642119699
Cloud computing provides a platform for new software applications that run across a large collection of physically separate computers and free computation from the computer in front of a user. distributedcomputing is not new, but the commodification of its hardware platform along with ubiquitous networking;powerful mobile devices;and inexpensive, embeddable, networkable computers-heralds a revolution comparable to the PC. Software development for the cloud offers many new (and some old challenges) that are central to research in programming models, languages, and tools. The language and tools community should embrace this new world as fertile source of new challenges and opportunities to advance the state of the art.
A new algorithm named QRNA (Quasi Regular Node Activation) is proposed in this paper, which employ equilateral triangular structure to control topology distribution of active nodes. In QRNA, sufficient and necessary c...
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Parallel computing is increasingly exposed to the development and challenges of distributed systems, such as asynchrony, long latencies, network partitions, failures, disconnected operations, heterogeneity and protoco...
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As the notion of Green computing becomes more popular in the IT world, new power saving features start to appear in both computer hardware and software. The difficulty of leveraging existing means of power management ...
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Cognitive radio is an emerging technique to improve the utilization of the scarce radio frequency spectrum, which is characterized by the dynamic spectrum access of the secondary users coexisting with the primary user...
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ISBN:
(纸本)9781424437092
Cognitive radio is an emerging technique to improve the utilization of the scarce radio frequency spectrum, which is characterized by the dynamic spectrum access of the secondary users coexisting with the primary users. In cognitive radio network, secondary users strive for temporally unused spectrum access opportunities offered by primary services;as a result, the opportunistic nature of the spectrum utilization among secondary users leads to great threats to primary users. Considering the fact that the cognitive ability of secondary users in cognitive radio network are similar to the intelligent behaviors of ant colonies in biological environment. Therefore, in this paper, the dynamic spectrum access problem is modeled as an adaptive task assignment in ant colonies. Furthermore, we propose to use the ACO algorithm to assign a set of secondary users to a given number of available spectrum bands owned by a special primary service subject to minimal cost constraint. So the basic idea of the ACO algorithm is to let each secondary user distributively select a spectrum band with a good enough quality and without interfering with the primary users, meanwhile minimize spectrum cost of the primary service. Performance evaluation has also been conducted and the results recorded after 100 runs have shown the optimal spectrum assignment.
This paper proposes an OFDM based transmission scheme for asynchronous amplify-and-forward cooperative systems with two relay nodes over frequency-selective channels. To combat the inter-symbol interference from multi...
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ISBN:
(纸本)9781424437092
This paper proposes an OFDM based transmission scheme for asynchronous amplify-and-forward cooperative systems with two relay nodes over frequency-selective channels. To combat the inter-symbol interference from multi-path fading and timing errors, the cyclic prefix (CP) is used at both the source node and relay nodes. Unlike [7] using IDFT and DFT modulation for two consecutive OFDM blocks respectively, all data blocks are modulated by IDFT at the source node and demodulated by DFT at the destination node in the proposed scheme. A subcarrier basis symbol-by-symbol ML decoding can be employed by exploiting the Alamouti code structure of two consecutive OFDM blocks at the destination node. Simulation results show that the proposed scheme can achieve diversity order 2 over frequency-selective channels in the presence of asynchronism between nodes. Moreover, we prove that the proposed scheme over frequency selective fading channel has the identical BER performance with the case of flat fading. Extension to more relay nodes is straightforward and the proposed scheme can achieve diversity order equal to the number of relay nodes.
For designing a wireless network, field test is mostly preferred for researchers to test and evaluate the system performance. However, it is expensive for field constructions and thus it is not affordable for most res...
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This work proposes a novel two-stage scheme for constructing an effective multicast tree. The first stage applies a priority-based algorithm to find suitable multicast points and construct effective multicast subtrees...
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Establishing efficient and scalable operations of the CMS distributedcomputing system critically relies on the proper integration, commissioning and scale testing of the data and workload management tools, the variou...
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Establishing efficient and scalable operations of the CMS distributedcomputing system critically relies on the proper integration, commissioning and scale testing of the data and workload management tools, the various computing workflows and the underlying computing infrastructure, located at more than 50 computing centres worldwide and interconnected by the Worldwide LHC computing Grid. computing challenges periodically undertaken by CMS in the past years with increasing scale and complexity have revealed the need for a sustained effort on computing integration and commissioning activities. The Processing and Data Access ( PADA) Task Force was established at the beginning of 2008 within the CMS computing Program with the mandate of validating the infrastructure for organized processing and user analysis including the sites and the workload and data management tools, validating the distributed production system by performing functionality, reliability and scale tests, helping sites to commission, configure and optimize the networking and storage through scale testing data transfers and data processing, and improving the efficiency of accessing data across the CMS computing system from global transfers to local access. This contribution reports on the tools and procedures developed by CMS for computing commissioning and scale testing as well as the improvements accomplished towards efficient, reliable and scalable computing operations. The activities include the development and operation of load generators for job submission and data transfers with the aim of stressing the experiment and Grid data management and workload management systems, site commissioning procedures and tools to monitor and improve site availability and reliability, as well as activities targeted to the commissioning of the distributed production, user analysis and monitoring systems.
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