In wireless ad hoc networks, the flooding operation is an important utility function. To solve the broadcast storm problem, some efficient flooding schemes have been proposed. However, there also exist many problems i...
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In wireless ad hoc networks, the flooding operation is an important utility function. To solve the broadcast storm problem, some efficient flooding schemes have been proposed. However, there also exist many problems in these schemes, such as signal collision. In this paper, we propose an efficient flooding algorithm called EFDA based on the algorithm proposed in [1] (we reference the algorithm as EF1). Through theoretical analysis, our algorithm doesn't affect the local optimality gained by EF1. We have implemented our algorithm in ns-2 simulator, and the results show that exploiting directional antenna can reduce the number of signal collisions and our algorithm achieves better performance than pure flooding and EF1 due to smaller number of signal collisions.
In this paper, according to the resource management problems brought by a large number of replicas, a multi-replica clustering management method based on limited-coding is proposed. In this method, according to the pr...
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In this paper, according to the resource management problems brought by a large number of replicas, a multi-replica clustering management method based on limited-coding is proposed. In this method, according to the process of creating new replicas from existent single replica, replicas are partitioned into different hierarchies and clusters. Then replicas are coded and managed based on the user-defined limited-coding rule consisting of replica hierarchy and replica sequence, which can also dispose the alteration of clusters caused by dynamic adjustments on replicas (replica addition or replica removal) effectively. After that, a management model of centralization in local and peer to peer in wide area is adopted to organize replicas, and the cost of reconciling consistency can be greatly depressed combining with defined minimal-time of update propagation. The relevance between the coding rule and the number of replicas, and the solutions to replica failure and replica recover are discussed. The results of the performance evaluation show that the clustering method is an efficient way to manage a large number of replicas, achieving good scalability, not sensitive to moderate node failure, and adapting well to applications with frequent updates.
In open Internet environment, it is inevitable that multiple ontologies coexist. Centralized service discovery mechanism becomes the bottleneck of SOC (service oriented computing), which results in poor scalability of...
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In open Internet environment, it is inevitable that multiple ontologies coexist. Centralized service discovery mechanism becomes the bottleneck of SOC (service oriented computing), which results in poor scalability of system. Aiming at solving these problems, a two layered P2P based model for semantic service discovery is proposed in this paper. The model is based on ontology community and integrates iVCE (Internet-based virtual computing environment) core concepts into a P2P model. Based on this model, a service discovery algorithm composed of two stages and three steps is proposed. It matches services across communities as well as within community. Within a community, algorithm locates registers holding service information with a high probability of satisfying a request firstly. Then it captures semantic matching between service advertisements and service requests by logical reasoning. Service discovery across communities occurs according to some policies. The model is suitable for opening environment with coexistent multiple ontologies. Experimental results show that given an appropriate setting, the model can make a tradeoff between recall and responding time. In addition, the model will release the mean load of registers efficiently while holding recall.
Resources over Internet have such intrinsic characteristics as growth, autonomy and diversity, which have brought many challenges to the efficient sharing and comprehensive utilization of these resources. This paper p...
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Resources over Internet have such intrinsic characteristics as growth, autonomy and diversity, which have brought many challenges to the efficient sharing and comprehensive utilization of these resources. This paper presents a novel approach for the construction of the Internet-based Virtual Computing Environment （iVCE）, whose sig- nificant mechanisms are on-demand aggregation and autonomic collaboration. The iVCE is built on the open infrastructure of the Internet and provides harmonious, transparent and integrated services for end-users and applications. The concept of iVCE is presented and its architectural framework is described by introducing three core concepts, i.e., autonomic element, virtual commonwealth and virtual executor. Then the connotations, functions and related key technologies of each components of the architecture are deeply analyzed with a case study, iVCE for Memory.
Data replication introduces well-known consistency issues. This paper puts forward the question about data dependence in data consistency, which embodies pseudo-conflict updates and update dependency. According to tha...
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Program mode is a regular trajectory of the execution of a program that is determined by the values of its input variables. By exploiting program modes we may make Worst Case Execution Time (WCET) analysis more precis...
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ISBN:
(纸本)1595934081
Program mode is a regular trajectory of the execution of a program that is determined by the values of its input variables. By exploiting program modes we may make Worst Case Execution Time (WCET) analysis more precise. This paper presents a novel method to automatically find program modes and calculate the WCET of programs. It consists of two phases. In phase one, we firstly automatically find the modes of a program by mode-relevant program slicing;then we compute the precondition for each mode using a path-wise test data generation method;after that, we can either conclude that it is an infeasible path, or get its precondition. In phase two, we calculate the WCET estimate of each given mode for modern RISC processors with caches and pipelines. The experiments are demonstrated to show the effectiveness of the method. Copyright 2006 ACM.
Memory-intensive applications often suffer from the poor performance of disk swapping when memory is inadequate. Remote memory sharing schemes, which provide a remote memory that is faster than the local hard disk, ar...
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Meteorology Grid Computing aims to provide scientist with seamless, reliable, secure and inexpensive access to meteorological resources. In this paper, we presented a semantic-based meteorology grid service registry, ...
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