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Parallel and Distributed Systems, IEEE Transactions on

Issue 11 • Date Nov. 2004

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Displaying Results 1 - 13 of 13
  • [Front cover]

    Publication Year: 2004 , Page(s): c1
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  • [Inside front cover]

    Publication Year: 2004 , Page(s): c2
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  • Localization from connectivity in sensor networks

    Publication Year: 2004 , Page(s): 961 - 974
    Cited by:  Papers (154)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2312 KB) |  | HTML iconHTML  

    We propose an approach that uses connectivity information - who is within communications range of whom - to derive the locations of nodes in a network. The approach can take advantage of additional information, such as estimated distances between neighbors or known positions for certain anchor nodes, if it is available. It is based on multidimensional scaling (MDS), an efficient data analysis technique that takes O(n3) time for a network of n nodes. Unlike previous approaches, MDS takes full advantage of connectivity or distance information between nodes that have yet to be localized. Two methods are presented: a simple method that builds a global map using MDS and a more complicated one that builds small local maps and then patches them together to form a global map. Furthermore, least-squares optimization can be incorporated into the methods to further improve the solutions at the expense of additional computation. Through simulation studies on uniform as well as irregular networks, we show that the methods achieve more accurate solutions than previous methods, especially when there are few anchor nodes. They can even yield good relative maps when no anchor nodes are available. View full abstract»

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  • Scalable and efficient parallel algorithms for Euclidean distance transform on the LARPBS model

    Publication Year: 2004 , Page(s): 975 - 982
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (768 KB) |  | HTML iconHTML  

    A parallel algorithm for Euclidean distance transform (EDT) on linear array with reconfigurable pipeline bus system (LARPBS) is presented. For an image with n×n pixels, the algorithm can complete EDT transform in O(n log n/c(n) log d(n)) time using n·d(n)·c(n) processors, where c(n) and d(n) are parameters satisfying 1≤c(n)≤n, and 1ε, the algorithm can be completed in O(1) time using n2+ε processors. To the best of our knowledge, this is the most efficient constant-time EDT algorithm on LARPBS. View full abstract»

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  • A Scalable Asynchronous Cache Consistency Scheme (SACCS) for mobile environments

    Publication Year: 2004 , Page(s): 983 - 995
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1656 KB) |  | HTML iconHTML  

    In the literature, there exit two types of cache consistency maintenance algorithms for mobile computing environments: stateless and stateful. In a stateless approach, the server is unaware of the cache contents at a mobile user (MU). Even though stateless approaches employ simple database management schemes, they lack scalability and ability to support user disconnectedness and mobility. On the other hand, a stateful approach is scalable for large database systems at the cost of nontrivial overhead due to server database management. We propose a novel algorithm, called Scalable Asynchronous Cache Consistency Scheme (SACCS), which inherits the positive features of both stateless and stateful approaches. SACCS provides a weak cache consistency for unreliable communication (e.g., wireless mobile) environments with small stale cache hit probability. It is also a highly scalable algorithm with minimum database management overhead. The properties are accomplished through the use of flag bits at the server cache (SC) and MU cache (MUC), an identifier (ID) in MUC for each entry after its invalidation, and estimated time-to-live (TTL) for each cached entry, as well as rendering of all valid entries of MUC to uncertain state when an MU wakes up. The stale cache hit probability is analyzed and also simulated under the Rayleigh fading model of error-prone wireless channels. Comprehensive simulation results show that the performance of SACCS is superior to those of other existing stateful and stateless algorithms in both single and multicell mobile environments. View full abstract»

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  • Quasidynamic layout optimizations for improving data locality

    Publication Year: 2004 , Page(s): 996 - 1011
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1272 KB) |  | HTML iconHTML  

    Compiler-directed locality optimization techniques are effective in reducing the number of cycles spent in off-chip memory accesses. Recently, methods have been developed that transform memory layouts of data structures at compile-time to improve spatial locality of nested loops beyond current control-centric (loop nest-based) optimizations. Most of these data-centric transformations use a single static (program-wide) memory layout for each array. A disadvantage of these static layout-based locality enhancement strategies is that they might fail to optimize codes that manipulate arrays, which demand different layouts in different parts of the code. We introduce a new approach, which extends current static layout optimization techniques by associating different memory layouts with the same array in different parts of the code. We call this strategy "quasidynamic layout optimization." In this strategy, the compiler determines memory layouts (for different parts of the code) at compile time, but layout conversions occur at runtime. We show that the possibility of dynamically changing memory layouts during the course of execution adds a new dimension to the data locality optimization problem. Our strategy employs a static layout optimizer module as a building block and, by repeatedly invoking it for different parts of the code, it checks whether runtime layout modifications bring additional benefits beyond static optimization. Our experiments indicate significant improvements in execution time over static layout-based locality enhancing techniques. View full abstract»

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  • Optimal scheduling algorithms in WDM optical interconnects with limited range wavelength conversion capability

    Publication Year: 2004 , Page(s): 1012 - 1026
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1328 KB) |  | HTML iconHTML  

    Optical communication is a promising candidate for many emerging networking and parallel/distributed computing applications because of its huge bandwidth. Wavelength division multiplexing (WDM) is a technique that can better utilize the optical bandwidth by dividing the bandwidth of a fiber into multiple wavelength channels. In this paper, we study optimal scheduling algorithms to resolve output contentions in bufferless time slotted WDM optical interconnects with wavelength conversion ability. We consider the general case of limited range wavelength conversion with arbitrary conversion capability, as limited range wavelength conversion is easier to implement and more cost effective than full range wavelength conversion, and it also includes full range wavelength conversion as a special case. We first consider the conversion scheme in which each wavelength can be converted to multiple wavelengths in an interval of wavelengths and the intervals for different wavelengths are "ordered". We show that the problem of maximizing network throughput can be formalized as finding a maximum matching in a bipartite graph. We then give an optimal scheduling algorithm called the first available algorithm that runs in O(k) time, where k is the number of wavelengths per fiber. We also study the case where the connection requests have different priorities. We formalize the problem as finding an optimal matching in a weighted bipartite graph and give a scheduling algorithm called the downwards expanding algorithm that runs in O(kD + Nklog(Nk)) time where N is the number of input fibers of the interconnect and D is the conversion degree. Finally, we consider the circular symmetrical wavelength conversion scheme and give optimal scheduling algorithms for nonprioritized scheduling in O(Dk) time and prioritized scheduling in O(k2+Nklog(Nk)) time. View full abstract»

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  • Performance analysis of broadcast protocols in ad hoc networks based on self-pruning

    Publication Year: 2004 , Page(s): 1027 - 1040
    Cited by:  Papers (25)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1344 KB) |  | HTML iconHTML  

    Self-pruning is an effective scheme for efficient broadcasting in ad hoc wireless networks. In a self-pruning broadcast protocol, a node may not forward a broadcast packet if a certain self-pruning condition is satisfied based on the neighborhood information. In a static network with an ideal MAC layer, only a subset of nodes forward the broadcast packet and still guarantee the complete network delivery. Various protocols have been proposed with different self-pruning conditions. Recently, a generic self-pruning protocol was proposed by Wu and Dai (2003), which combines the strength of previous conditions and is more effective. In this paper, we first propose an enhanced version of the generic protocol, which is more elegant in interpreting existing protocols and has a simpler correctness proof. Then, we evaluate the performance of the family of self-pruning protocols under various network situations with ns2. The objective is to observe the efficiency and reliability of these protocols as a function of network density, congestion, and mobility, and provide a guideline of implementation in the "real world". Our performance analysis reveals that the protocol reliability is barely affected by packet collision. However, most self-pruning protocols suffer from low delivery ratio in highly mobile networks. We further explore various techniques that improve the delivery ratio and show that both high efficiency and reliability can be achieved in highly mobile networks. View full abstract»

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  • Voice and video transmissions with global data parameter control for the IEEE 802.11e enhance distributed channel access

    Publication Year: 2004 , Page(s): 1041 - 1053
    Cited by:  Papers (39)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1784 KB) |  | HTML iconHTML  

    Best-effort data control and admission control are vital to guarantee quality of service for real-time (voice and video) transmissions in the IEEE 802.11e wireless LANs. In this paper, we propose and study a global data parameter control scheme integrated with a measurement-based admission control scheme for the IEEE 802.11e enhanced distributed channel access. In the proposed global data control scheme, the access point dynamically controls best-effort data parameters of stations globally based on traffic condition. Such a global/centralized data parameter control mechanism provides the best fairness for data transmissions among stations. In the proposed centrally-assisted distributed admission control scheme for voice and video transmissions, stations listen to available budgets from the access point to make decisions on acceptance or rejection of a voice or video stream. Such a scheme provides good differentiation among different access categories and provides good fairness among real-time streams within the same access category. The proposed mechanisms are evaluated via extensive simulations. Studies show that, with the proposed global data control scheme and the admission control scheme, quality of service can be greatly improved while maintaining a good utilization. View full abstract»

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  • Comments and corrections to "Dominating sets and neighbor elimination-based broadcasting algorithms in wireless networks"

    Publication Year: 2004 , Page(s): 1054 - 1055
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (61 KB) |  | HTML iconHTML  

    The paper by I. Stojmenovic et al. (2002) generated a lot of interest among researchers in ad hoc networks. A number of researchers questioned, through their articles, or directly to the first author, the correctness of the described procedure, and the correctness of the claim that the procedure does not need any communication exchange between nodes, in addition to "hello" messages needed to learn information about neighboring nodes. This correspondence completes the article by providing the actual dominating set definitions used in the procedure (from which zero communication overhead follows easily), the correct procedure (the published one has few misprints at key places), and the proof that the new definitions and procedure indeed define connected dominating sets. View full abstract»

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  • Call for Papers for Special Issue on Localized Communication and Topology Protocols for Ad Hoc Network

    Publication Year: 2004 , Page(s): 1056
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  • TPDS Information for authors

    Publication Year: 2004 , Page(s): c3
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  • [Back cover]

    Publication Year: 2004 , Page(s): c4
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Aims & Scope

IEEE Transactions on Parallel and Distributed Systems (TPDS) is published monthly. It publishes a range of papers, comments on previously published papers, and survey articles that deal with the parallel and distributed systems research areas of current importance to our readers.

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Meet Our Editors

Editor-in-Chief
David Bader
College of Computing
Georgia Institute of Technology