We study how knowledge of a moving object's path can be used to select sensors in a network that maximize the coverage of its path. We propose a mobility model that combines the shortest path between two points wi...
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ISBN:
(纸本)9781538654705
We study how knowledge of a moving object's path can be used to select sensors in a network that maximize the coverage of its path. We propose a mobility model that combines the shortest path between two points with random movement. Given the mobility model, we have different knowledge levels in terms of knowing nothing, the start, destination, movement model, and the whole path. We present a framework to assign weights to points on the movement grid based on the knowledge level and to greedily select sensors to maximize weighted coverage of the grid. We show in simulations of random movement that knowing more information generally has better performance, but for certain levels of knowledge, this decreases as the randomness increases. We also find that it is possible to obtain the maximum coverage by assuming the target follows the shortest path when the randomness is below a certain threshold. We verified these results on real human mobility traces.
the paper presents a distributedcomputing environment for embedded control systems with time-triggered and event-triggered distributed processing. We have already presented a time-triggered distributed object model a...
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ISBN:
(纸本)9780769533490
the paper presents a distributedcomputing environment for embedded control systems with time-triggered and event-triggered distributed processing. We have already presented a time-triggered distributed object model and a time-triggered distributedcomputing environment for embedded control systems. However there are many embedded control systems with time-triggered and event-triggered processing. In this paper we present two kinds of event-triggered distributed object models, a pure event-triggered distributed object model and a data-triggered distributed object model, in addition to the time-triggered distributed object model. We also present a distributed object computing environment based on a time-division scheduling for the mixed architecture with time-triggered and event-triggered distributed processing. the time division scheduling divides an execution cycle into a time-triggered processing segment and a non-time-triggered processing segment. the time-triggered distributed processing is executed in the former segment, and the event-triggered distributed processing is executed in the latter segment. the distributed object computing environment consists of a real-time operating system withthe time division scheduling and distributedcomputing middleware to support the three kinds of distributed object models. We provide a development environment that generates stubs and configuration data to build distributed control systems.
the paper develops a generalized model to capture the interactions between the ordering of messages exchanged across various entities of a distributed application and the consistency requirements on a shared data acro...
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ISBN:
(纸本)0818658401
the paper develops a generalized model to capture the interactions between the ordering of messages exchanged across various entities of a distributed application and the consistency requirements on a shared data across these entities. the model is based on causal broadcasting of data access messages that allows messages to be ordered at all entities as per the constraints specified by the application. this allows each entity to change its local data copy based on the messages processed and still be in agreement with other entities at selected points of message exchanges that are meaningful to the application, which we refer to as stable points in the underlying execution. Since the causal relationships among messages depict an invariant property of the application and stable points are reproducible across different execution instances, application-specific consistency of the data can be enforced in many cases without explicit protocols to reach agreement. the model of integrating causality with data consistency allows more flexibility in the implementation of data access protocols for distributed services and offers potential for increased performance of the protocols.
Storage applications are in urgent need of multi-erasure codes. But there is no consensus on the best coding technique. Hafner has presented a class of multi-erasure codes named HoVer codes[1]. this kind of codes has ...
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ISBN:
(纸本)9780769534343
Storage applications are in urgent need of multi-erasure codes. But there is no consensus on the best coding technique. Hafner has presented a class of multi-erasure codes named HoVer codes[1]. this kind of codes has a unique data/parity layout which provides a range of implementation options that cover a large portion of the performance/efficiency trade-off space. thus it can be applied to many scenarios by simple tuning. In this paper, we give a combinatorial representation of a family of double-erasure HoVer codes - create a mapping between this family of codes and Latin squares. We also present two families of double-erasure HoVer codes respectively based on the column-Hamiltonian Latin squares (of odd order) and a family of Latin squares of even order. Compared withthe double-erasure HoVer codes presented in [1], the new codes enable greater flexibility in performance and efficiency trade-off.
this paper deals withthe studies of the distributed object computing environments. We have developed several client/server systems to compare key aspects of the distributed object computing. We will present the devel...
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distributed shared memory (DSM) allows multi-computer systems with no physically shared memory to be programmed using a shared memory paradigm. However, as the number of nodes in a system increases the probability of ...
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ISBN:
(纸本)0818658401
distributed shared memory (DSM) allows multi-computer systems with no physically shared memory to be programmed using a shared memory paradigm. However, as the number of nodes in a system increases the probability of a failure that can corrupt the DSM increases. this paper presents a fault-tolerant DSM (FTDSM) algorithm that can tolerate single node failures. Each page in the DSM is assigned a snooper that keeps a backup copy of the page and can take over if the page owner fails. the snooper is dynamic because the responsibility for snooping a page can migrate from node to node. the FTDSM presented in this paper is an improvement over other FTDSMs because it is scalable, is based on the efficient dynamic distributed manager (DDM) DSM algorithm, does not require the repair of a failed processor to access the DSM, and does not query all nodes to rebuild the state of the DSM. It is shown that any single node failure can be tolerated because either the owner or the snooper of a page can always be found.
this paper argues that simply applying a multiple-tree scheme does not provide sufficient fairness for applications in an Internet-scale distributed system, in terms of performance. Motivated from the observation of t...
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ISBN:
(纸本)0780390377
this paper argues that simply applying a multiple-tree scheme does not provide sufficient fairness for applications in an Internet-scale distributed system, in terms of performance. Motivated from the observation of the tax and donation systems in our society, we believe that a better way to define fairness, for performance's sake, is to factor in nodes' proportional contributions because it provides the opportunity to support many simultaneous multicasting sessions. this paper then presents a protocol, called FairOM (Fair Overlay Multicast), to enforce proportional contribution among peers in an Internet-scale distributed system.
the objective of ODP is according to ITU-T Recommendation X.901 stated as follows: "the objective of ODP standardization is the development of standards that allow the benefits of distributing information process...
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ISBN:
(纸本)9780769541648
the objective of ODP is according to ITU-T Recommendation X.901 stated as follows: "the objective of ODP standardization is the development of standards that allow the benefits of distributing information processing services to be realized in an environment of heterogeneous IT resources and multiple organizational domains. these standards address constraints on system specification and the provision of a system infrastructure that accommodate difficulties inherent in the design and programming of distributedsystems." this objective seems to cover planning and interworking of IT systems within an organization, such as a telecom operator. therefore, we in this paper discuss the needs of an Overall IT Plan, and discuss the use of ODP for specifying the solution. We indicate that the current ODP may be too abstract for the purpose, and indicate how to adapt ODP to fit the purpose.
With an ever-increasing number of services being moved to cloud computing platforms, it is essential for data centre operators to quickly identify any problems in their network in order to ensure optimal performance a...
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ISBN:
(纸本)9780769547497
With an ever-increasing number of services being moved to cloud computing platforms, it is essential for data centre operators to quickly identify any problems in their network in order to ensure optimal performance and provide guidance for when actions such as migration of computing instances are required. this paper introduces a distributed measurement infrastructure using low-cost in-line link measurements to reveal the true traffic-perceived service quality in short timescales. In-line measurement is highly relevant for data centres as it allows an accurate measure of important network services without the problem of injecting artificial traffic into a network with high contention for resources. the infrastructure presented allows real-time monitoring and visualisation of the state of the network, which can be used to inform virtual machine migration/instantiation events. We show that the in-line measurements used by the infrastructure have negligible impact on network traffic and the hosts conducting the measurements. the low overhead of in-line measurements potentially enables the infrastructure to function as an always-on measurement and management platform.
In a mobile computing system, mobile hosts may move around cells, resulting in a considerable cost for locating and retrieving the recovery information, which is necessary for fault tolerance. To speed up the recovery...
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ISBN:
(纸本)9780769534343
In a mobile computing system, mobile hosts may move around cells, resulting in a considerable cost for locating and retrieving the recovery information, which is necessary for fault tolerance. To speed up the recovery, traditionally, recovery information is migrated according to the location of the mobile host. In this paper, a scheme for efficiently handling the recovery information is proposed. When a mobile host moves out of a certain range, only partial recovery information of the mobile host needs to be migrated to mobile support stations. It can avoid the unnecessary migration of recovery information. Moreover, the performance of the proposed scheme is evaluated and compared withthe traditional movement based scheme.
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