18051966
Design and analysis of adaptive strategies for locating internet-based servers in MANETs
A critical problem in providing Internet access to Mobile Ad Hoc Networks (MANETs) is how the mobile hosts can locate Internet-based servers efficiently in a dynamic, unstructured network. This paper studies adaptive strategies that combine both proactive advertising by the servers and on-demand discovery by the mobile hosts. The adaptive strategies determine the relative rate of proactive advertising and on-demand discovery according to system characteristics such as host mobility level and offered load. Our simulation study reveals that, compared to the previous proactive strategies and reactive strategies, the adaptive strategies reduce network traffic by several times when the network has a moderate offered load and a low or high level of host mobility.
16906364
Scalable and Robust Aggregation Techniques for Extracting Statistical Information in Sensor Networks
Wireless sensor networks have stringent constraints on system resources and data aggregation techniques are critically important. However, accurate data aggregation is difficult due to the variation of sensor readings and due to the frequent communication failures. To address these difficulties, we propose a scalable and robust data aggregation algorithm. The novelty of our work includes two aspects. First, our algorithm exploits the mixture model and the Expectation Maximization (EM) algorithm for parameter estimation. Hence, it captures the effects of aggregation over different scales while keeping the communication cost low. Second, our algorithm exploits loss-tolerant multi-path routing schemes. Hence, it obtains accurate statistical information even in the presence of high link and node failure rates. We demonstrate that our techniques reduce communication cost while retaining the precious statistical information otherwise neglected by other aggregation techniques. Our evaluation shows the proposed techniques are robust against link and node failures, and perform consistently well.
6280246
A dynamic load balancing scheme for I/O-intensive applications in distributed systems
In this paper, a new I/O-aware load-balancing scheme is presented to improve overall performance of a distributed system with a general and practical workload including I/O activities. The proposed scheme dynamically detects I/O load imbalance on nodes of a distributed system and determines whether to migrate the I/O requests of some jobs from overloaded nodes to other less- or under-loaded nodes, depending on data migration cost and remote I/O access overhead. Besides balancing I/O load, the scheme judiciously takes into account both CPU and memory load sharing in distributed systems, thereby maintaining the same level of performance as the existing schemes when I/O load is low or well balanced. Results from a trace-driven simulation study show that, compared with the existing schemes that only consider CPU and memory, the proposed scheme reduces the mean slowdown by up to 54.5% (with an average of 39.9%). On the other hand, when compared to the existing approaches that only consider I/O, the proposed scheme reduces the mean slowdown by up to 57.2% (with an average of 31.6%). More importantly, the new scheme improves over a very recent algorithm found in the literature that considers all the three resources by up to 49.6% (with an average of up to 41.9%).
18986466
Modeling parallel applications performance on heterogeneous systems
The current technologies have made it possible to execute parallel applications across heterogeneous platforms. However, the performance models available do not provide adequate methods to calculate, compare and predict the applications performance on these platforms. In this paper, we discuss an enhanced performance evaluation model for parallel applications on heterogeneous systems. In our analysis, we include machines of different architectures, specifications and operating environments. We also discuss the enabling technologies that facilitate such heterogeneous applications. The model is then validated through experimental measurements using an agent-based parallel Java system, which facilitates simultaneous utilization of heterogeneous systems for parallel applications. The model provides good evaluation metrics that allow developers to assess and compare the parallel heterogeneous applications performances.
20921565
Dynamical Process of Excitation Fusion in Polymers
Due to the confinement effect in the nondegenerate polymers and the electron-lattice interaction, the electron-hole pair forms a self-trapped single excitation. It is shown that two single excitations in one chain can fuse into one double excitation, and the relaxation time of the fusion process is about 160 fs.
21605308
Impact of priority-based ATM switch design on system performance
We investigate the performance impact of a Banyan type MIN ATM switch with priority-based design and its impact on system performance. The switch design consists of static buffer splitting, adaptive buffer splitting, as well as the priority-based selection strategies for solving cell contentions. A new analytical model is developed for the favorite load traffic pattern which can reflect some typical ATM applications and also include the uniform load as its special case. System performance comparisons are conducted for a number of different priority-based ATM switch designs.<<ETX>>
2360073
Performance properties of combined heterogeneous networks
We study the performance properties of combined multiple heterogeneous networks. We consider two nodes: node1 and node2, with multiple heterogeneous physical networks connecting them. Each network has some properties such as bandwidth, latency, and packet loss ratio. We develop an analytical model to find the peak performance, or upper bound, of combined networks for the transfer of a message of a given size in parallel. The model is based on the existence of an optimal load balancing mechanism for parallel transfer that fully utilizes the existing networks. The paper provides a framework to find the peak performance parameters of message transfer over combined heterogenous networks as well as to measure the actual utilization and efficiency of parallel message transfer implementations.