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1.
In recent years, we have witnessed a growing interest in the synchronous collaboration based class of applications. Several
techniques for collaborative virtual environments (CVE), haptic, audio and visual environments (C-HAVE) have been designed.
However, several challenging issues remain to be resolved before CVE and C-HAVE become a common place. In this paper, we focus
on applications that are based on closely coupled and highly synchronized haptic tasks that require a high-level of coordination
among the participants. Four main protocols have been designed to resolve the synchronization issues in such environments:
the synchronous collaboration transport protocol, the selective reliable transmission protocol, the reliable multicast transport
protocol and the scalable reliable multicast. While these four protocols have shown good performance for CVE and C-HAVE class
of applications, none of these protocols has been able to meet all of the basic CVE requirements, i.e., scalability, reliability,
synchronization, and minimum delay. In this paper, we present a hybrid protocol that is able to satisfy all of the CVE and
C-HAVE requirements and discuss its implementation and results in two tele-surgery applications.
This work is partially supported by Grants from Canada Research Chair Program, NSERC, OIT/Ontario Distinguished Researcher
Award, Early Research Award and ORNEC Research Grant. 相似文献
2.
Azzedine Boukerche Dionysios Efstathiou Sotiris Nikoletseas 《Journal of Parallel and Distributed Computing》2012
We consider sensor networks where the sensor nodes are attached on entities that move in a highly dynamic, heterogeneous manner. To capture this mobility diversity we introduce a new network parameter, the direction-aware mobility level, which measures how fast and close each mobile node is expected to get to the data destination (the sink). We then provide local, distributed data dissemination protocols that adaptively exploit the node mobility to improve performance. In particular, “high” mobility is used as a low cost replacement for data dissemination (due to the ferrying of data), while in the case of “low” mobility either (a) data propagation redundancy is increased (when highly mobile neighbors exist) or (b) long-distance data transmissions are used (when the entire neighborhood is of low mobility) to accelerate data dissemination toward the sink. An extensive performance comparison to relevant methods from the state of the art demonstrates significant improvements, i.e. latency is reduced by even four times while keeping energy dissipation and delivery success at very satisfactory levels. 相似文献
3.
Hikmat El Ajaltouni Azzedine Boukerche Abdelhamid Mammeri 《Mobile Networks and Applications》2013,18(6):814-830
One of the most challenging issues facing vehicular networks lies in the design of an efficient MAC protocol due to the mobile nature of nodes and the interference associated with the dynamic environment. Moreover delay constraints for safety applications add complexity and latency requirements to the design. Existing MAC protocols overcome some challenges however don’t provide an integrated solution. Hence, the merit if this work lies in designing an efficient MAC protocol that incorporates various VANet’s challenges in a complete end-to-end solution. In this work, we propose an efficient Multichannel QoS Cognitive MAC (MQOG). MQOG assesses the quality of channel prior to transmission employing dynamic channel allocation and negotiation algorithms to achieve significant increase in channel reliability, throughput and delay constraints while simultaneously addressing Quality of Service. The uniqueness of MQOG lies in making use of the free unlicensed bands. The proposed protocols were implemented in OMNET++ 4.1, and extensive experiments demonstrated a faster and more efficient reception of safety messages compared to existing VANet MAC Protocols. Finally, improvements in delay, packet delivery ratios and throughput were captured. 相似文献
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Recommending traveling vehicles to take a certain path towards their targeted destinations have received great interest recently. At the downtown area several paths can lead to the same located destination, this is due to the grid-layout architecture of modern downtowns. Drivers always wish to reach their destinations as fast as possible and without traveling drastically long distance or without consuming extra fuel. The best path towards any destination is determined based on the relative location of the vehicle from its destination and based on other vehicles traffic distribution on the road network. Although numerous studies have investigated this issue over the road network, the communication failures and their effects on the obtained path have been neglected in those previous studies. In this paper, we investigate these potential faults and their effects on the correctness of the selected paths. We then proposed a new protocol to tackle these potential failures while selecting the best path towards each destination over the road network, fault tolerant path recommendation protocol (FT-PR). From the experimental results, we can see that the FT-PR protocol has a higher success ratio than previous path recommendation protocols, such as ICOD. This is demonstrated by obtaining paths with shorter traveling time and shorter traveling distance. The FT-PR protocol also eliminates extra loops over the road network in each selected path. 相似文献
6.
Aggregation/disaggregation is a method for implementing multi-resolution simulations within a High Level Architecture (HLA)
federation. HLA is a U.S. Department of Defense (DoD) developed standard to facilitate linking different types of simulations,
in various locations, to form an or interactive, full-scale simulation, called a federation. Data Distribution Management
(DDM) is a High Level Architecture/Run-time Infrastructure (HLA/RTI) service that manages the distribution of state updates
and interaction information and controls the volume of data exchanged, in large-scale distributed simulations. The purpose
of HLA is to promote interoperability and reuse among heterogenous simulations, including those simulations that offer varied
levels of resolution, to provide practical training to military personnel of different ranks. The purpose of Aggregation/disaggregation
is to ensure consistency in state updates between federates simulating objects at various levels of resolution. This paper
focuses on the scalability of aggregation/disaggregation with different DDM implementations and examines the effects, on performance
of large-scale simulations. We implement a federate-based aggregation/disaggregation scheme, originally introduced in [TAN01],
with a tank dogfight scenario, aggregating five tanks into one tank battalion and disaggregating the battalion back into five
individual entities (tanks). The DDM methods we analyze consist of the Fixed Grid-Based method, the Dynamic Grid-Based method
and the Region-Based method. In [TAN01], testing of this federate-based aggregation/disaggregation was limited to a dual federation
and a single DDM scheme. In an effort to determine the scalability of aggregation/disaggregation, with three methods of DDM,
we measure the communication overhead and analyze performance during a federation execution. We present the results of extensive
testing, varying the number of aggregation/disaggregation requests, the number of multi-resolution federates participating
in the federation, the number of objects, the number/size of the grids and report on the performance evlauation of our protocols
using an extensive set of simulation experiments.
This work was partially supported by Grants from NSERC, Canada Research Chairs Program, Canada Foundation for Innovation,
OIT/Distinguished Researcher Award. 相似文献
7.
Boukerche A. Sungbum Hong Jacob T. 《Parallel and Distributed Systems, IEEE Transactions on》2002,13(9):911-923
Recent advances in mobile computing and distributed multimedia systems allow mobile hosts (clients) to access wireless multimedia systems anywhere and at anytime, but not without creating a new set of issues and trade-offs. To the best of our knowledge, there has been very little research in dealing with the synchronization problem in wireless and mobile multimedia systems. In this paper, we propose an efficient distributed synchronization algorithm using quasi-sink for wireless and mobile multimedia systems to ensure and facilitate mobile client access to multimedia objects. We discuss the algorithm and provide its proof of correctness. We also present a set of simulation experiments to evaluate the performance of our scheme using message complexity and buffer usage at each frame arrival time. Our results indicate that our scheme exhibits a significant low message complexity and no underflow and overflow within the bounded delivery time. 相似文献
8.
Emerson de Araujo Macedo Alba Cristina Magalhaes Alves de Melo Gerson Henrique Pfitscher Azzedine Boukerche 《The Journal of supercomputing》2013,63(3):740-756
Multiple Sequence Alignment (MSA) is an important problem in Bioinformatics that aims to align more than two sequences in order to emphasize similarity regions. This problem is known to be NP-Hard, so heuristic methods are used to solve it. DIALIGN-TX is an iterative heuristic method for MSA that generates alignments by concatenating ungapped regions with high similarity. Usually, the first phase of MSA algorithms is parallelized by distributing several independent tasks among the nodes. Even though heterogeneous multicore clusters are becoming very common nowadays, very few task allocation policies were proposed for this type of architecture. This paper proposes an MPI/OpenMP master/slave parallel strategy to run DIALIGN-TX in heterogeneous multicore clusters, with several allocation policies. We show that an appropriate choice of the master node has great impact on the overall system performance. Also, the results obtained in a heterogeneous multicore cluster composed of 4 nodes (30 cores), with real sequence sets show that the execution time can be drastically reduced when the appropriate allocation policy is used. 相似文献
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Performance analysis of a novel hybrid push–pull algorithm with QoS adaptations in wireless networks
In this paper, we present a novel hybrid push–pull algorithm which combines broadcasting of push data items, with dissemination upon request of pull items in asymmetric communication environments. These environments are made up only of one database server and many clients. Requests made by the clients are queued up for the pull items. The (pull) item with the number of pending requests is the one selected to be pulled. We present a performance analysis of our scheme, and determine the individual response time for each item disseminated and the overall time for the pull queue to be flushed. Next, we extend our algorithm by incorporating quality of service (QoS) factors, and then, study its performance analytically. 相似文献