Successive interference cancellation (SIC) is an effective way of multipacket reception (MPR) to combat interference in wireless networks. To understand the potential MPR advantages, we study link scheduling in an ad ...
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ISBN:
(纸本)9781424499199
Successive interference cancellation (SIC) is an effective way of multipacket reception (MPR) to combat interference in wireless networks. To understand the potential MPR advantages, we study link scheduling in an ad hoc network with SIC at the physical layer. The fact that the links detected sequentially by SIC are correlated at the receiver poses key technical challenges. We characterize the link dependence and propose simultaneity graph (SG) to capture the effect of SIC. Then interference number is defined to measure the interference of a link. We show that scheduling over SG is NP-hard and the maximum interference number bounds the performance of maximal greedy schemes. An independent set based greedy scheme is explored to efficiently construct a maximal feasible schedule. Moreover, with careful selection of link ordering, we present a scheduling scheme that improves the bound. The performance is evaluated by both simulations and measurements in testbed. The throughput gain is on average 40% and up to 120% over IEEE 802.11. The complexity of SG is comparable with that of conflict graph, especially when the network size is not large.
The widening gap between processor and memory speeds makes cache an important issue in the computer system design. Compared with work set of programs, cache resource is often rare. Therefore, it is very important for ...
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The widening gap between processor and memory speeds makes cache an important issue in the computer system design. Compared with work set of programs, cache resource is often rare. Therefore, it is very important for a computer system to use cache efficiently. Toward a dynamically reconfigurable cache proposed recently, DOOC （Data- Object Oriented Cache）, this paper proposes a quantitative framework for analyzing the cache requirement of data-objects, which includes cache capacity, block size, associativity and coherence protocol. And a kind of graph coloring algorithm dealing with the competition between data-objects in the DOOC is proposed as well. Finally, we apply our approaches to the compiler management of DOOC. We test our approaches on both a single-core platform and a four-core platform. Compared with the traditional caches, the DOOC in both platforms achieves an average reduction of 44.98% and 49.69% in miss rate respectively. And its performance is very close to the ideal optimal cache.
A hierarchical diagnosis approach, namely Magnifier, was proposed, which models the execution path graph of a user request as component layer, module layer and function layer, and detects anomalies from higher layer t...
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A hierarchical diagnosis approach, namely Magnifier, was proposed, which models the execution path graph of a user request as component layer, module layer and function layer, and detects anomalies from higher layer to lower layer separately. Extensive experiments were conducted on the Alibaba cloud computing platform. The results indicate that, under the conditions of large volume of data and high complexity of execution paths, Magnifier can accurately and efficiently locate the prime causes of performance degradation.
Graph isomorphism problem has always been mathematics and engineering technology community concern, the reason mainly from two aspects: First, in theory, is generally believed that the problem is NP-complete problem; ...
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Graph isomorphism problem has always been mathematics and engineering technology community concern, the reason mainly from two aspects: First, in theory, is generally believed that the problem is NP-complete problem; Second, the graph isomorphism the problem with good prospects, in chemistry, operations research, computer science, electronics, network theory has applications in many fields, but the exponential complexity of the algorithm and the algorithm itself makes the limitations applicable to the object involved with complex graphics the application of structure is difficult to determine the start. In this paper, class tree is proposed based on the node to delete the exact graph isomorphism problem, you can quickly determine the graph isomorphism problem, and theoretical analysis and experiments show that the algorithm can determine the class in polynomial time tree isomorphism problem.
As the energy consumption of embedded multiprocessor systems becomes increasingly prominent, the real-time energy-efficient scheduling in multiprocessor systems becomes an urgent problem to reduce the system energy co...
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As the energy consumption of embedded multiprocessor systems becomes increasingly prominent, the real-time energy-efficient scheduling in multiprocessor systems becomes an urgent problem to reduce the system energy consumption while meeting real-time constraints. For a multiprocessor with independent DVFS and DPM at each processor, this paper proposes an energy-efficient real-time scheduling algorithm named LRE-DVFS-EACH, based on LRE-TL which is an optimal real-time scheduling algorithm for sporadic tasks. LRE-DVFS-EACH utilizes the concept of TL plane and the idea of fluid scheduling to dynamically scale the voltage and frequency of processors at the initial time of each TL plane as well as the release time of a sporadic task in each TL plane. Consequently, LRE-DVFS-EACH can obtain a reasonable tradeoff between the real-time constraints and the energy saving. LRE-DVFS-EACH is also adaptive to the change of workload caused by the dynamic release of sporadic tasks, which can obtain more energy savings. The experimental results show that compared with existing algorithms, LRE-DVFS-EACH can not only guarantee the optimal feasibility of sporadic tasks, but also achieve more energy savings in all cases, especially in the case of high workloads.
Lots of toolboxes of accelerating MatLab using GPU are available now[1], but, users are confused by which toolbox is best suitable for a particular task. Three toolboxes-Jacket, GPUmat, and parallel Computing Toolbox ...
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P2P application is one of the most popular applications in the Internet, but its performance is badly influenced by the churn character-the nodes continuous arrival and departure. On the basis of introducing the origi...
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P2P application is one of the most popular applications in the Internet, but its performance is badly influenced by the churn character-the nodes continuous arrival and departure. On the basis of introducing the origin of the churn, the definition of it and its influences to the P2P system performance, we minutely describe the research on the statistical properties, and discover some dynamic law including nodes' session time generally obey the heavy-tailed distribution. Then we detail the measurement methods. For passive monitoring, active monitoring, sample and so on, we present the advantages and disadvantages of each method, and explain the corresponding improving method to enhance the accuracy of the measurement. After that we elaborate the resilience strategies to the churn. Towards the neighbor selection, failure recovery, replica maintenance, link lifetime maintenance and so on, we present also the advantage and disadvantage of each strategy, and present our view to each of aspects. Finally, the summary and prospect of the future research are given.
It is an important issue to preserve the consistent delivering order of messages at each site in distributed Virtual Environments(DVEs). Currently, the violations of message delivery order are inclined to happen in th...
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It is an important issue to preserve the consistent delivering order of messages at each site in distributed Virtual Environments(DVEs). Currently, the violations of message delivery order are inclined to happen in the large-scale and frequently interactive DVEs running on Wide Area Network(WAN). The inconsistent anomalies are characterized as unpredictable, unrepeatable and uncontrollable, which results in the severe problem for the development of the consistency control approaches. Meanwhile, it is also highly expensive to directly verify the proposed approaches on WAN. Therefore, in this paper, we design and establish an original multi-layered emulation platform in LAN, which can emulate the network latency of WAN and repeat the scenarios of violations. On the platform, the designers of consistency approaches don't have to spend efforts to realize the fundamental functions of the verification, but could pay more attention to the development and optimization of the control algorithms, which is very beneficial for the improvement of message ordering approaches.
Graph isomorphism problem has applications in many fields, such as chemistry, computer science, electronics, and network theory. But the exponential complexity of the algorithm makes the testing is time consuming. In ...
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Graph isomorphism problem has applications in many fields, such as chemistry, computer science, electronics, and network theory. But the exponential complexity of the algorithm makes the testing is time consuming. In this paper, a new algorithm named Unique Vertex Delete (UVD for short) is presented to speed up the process of isomorphic testing. The main idea of UVD algorithm is deleting vertex continuously to reduce the scale of the problem, and new field is added for each vertex to indicate the information of deleted neighbor vertices. Theoretical analysis and experiments show that the UVD algorithm consistently and significantly outperforms existing state-of-the-art approaches.
Building distributed applications is difficult mostly because of concurrency management. Existing approaches primarily include events and threads. Researchers and developers have been debating for decades to prove whi...
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Building distributed applications is difficult mostly because of concurrency management. Existing approaches primarily include events and threads. Researchers and developers have been debating for decades to prove which is superior. Although the conclusion is far from obvious, this long debate clearly shows that neither of them is perfect. One of the problems is that they are both complex and error-prone. Both events and threads need the programmers to explicitly manage concurrencies, and we believe it is just the source of difficulties. In this paper, we propose a novel approach—superscalar communication, in which concurrencies are automatically managed by the runtime system. It dynamically analyzes the programs to discover potential concurrency opportunities; and it dynamically schedules the communication and the computation tasks, resulting in automatic concurrent execution. This approach is inspired by the idea of superscalar technology in modern microprocessors, which dynamically exploits instruction-level parallelism. However, hardware superscalar algorithms do not fit software in many aspects, thus we have to design a new scheme completely from scratch. Superscalar communication is a runtime extension with no modification to the language, compiler or byte code, so it is good at backward compatibility. Superscalar communication is likely to begin a brand new research area in systems software, which is characterized by dynamic optimization for networking programs.
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