共查询到20条相似文献,搜索用时 31 毫秒
1.
Mobile communications beyond 3G will integrate different (but complementary) access technologies into a common platform to deliver value-added services and multimedia content in an optimum way. However, the numerous possible configurations of mobile networks complicated the dynamic deployment of mobile applications. Therefore, research is intensely seeking a service provisioning framework that is technology-independent, supports multiple wireless network technologies, and can interwork high-level service management tasks to network management operations. This paper presents an open value chain paradigm, a model for downloadable applications and a mediating platform for service provisioning in beyond 3G mobile settings. Furthermore, we introduce mechanisms that support a coupled interaction between service deployment and network configuration operations, focusing on the dynamic provisioning of QoS state to data path devices according to the requirements of dynamically downloadable mobile value-added services (VAS). 相似文献
2.
Advances in optical technologies have enabled the deployment of wavelength division-multiplexed (WDM) transmission systems
capable of providing huge amounts of bandwidth across long distances. In this scenario, dynamic routing for direct provisioning
of optical paths at the WDM layer becomes a challenging problem. Any distributed algorithm for routing dynamic traffic demands
on optical transport infrastructures should be simple, flexible, efficient and scalable. The contribution of this paper is
a novel integrated routing and grooming scheme for setting-up bandwidth guaranteed paths on hybrid wavelength and label switched
networks. Our proposal exploits and refines the minimum interference routing idea according to an improved and re-optimized
resource and traffic-aware approach, where critical links are detected and weighted according to a low complexity all-pairs
minimum cut strategy that substantially reduce the overall number of calculations and hence the computational cost. The valuable
results achieved in the comparison against other well-known reference techniques clearly demonstrate that our algorithm is
very time-efficient while performing better in terms of blocking probability.
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3.
The use of neural networks in finance began by the end of the 1980s and by the beginning of the 1990s, it developed specific
applications related to forecasting on the failure of companies. In order to highlight the evolution of this research stream,
we have retained and analysed 30 studies in which the authors use neural networks to solve companies’ classification problems
(healthy and failing firms). This review of all these works gives us the opportunity to stress upon future trends in bankruptcy
forecasting research.
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4.
We present an enhancement towards adaptive video training for PhoneGuide, a digital museum guidance system for ordinary camera-equipped
mobile phones. It enables museum visitors to identify exhibits by capturing photos of them. In this article, a combined solution
of object recognition and pervasive tracking is extended to a client–server-system for improving data acquisition and for
supporting scale-invariant object recognition. A static as well as a dynamic training technique are presented that preprocess
the collected object data differently and apply two types of neural networks (NN) for classification. Furthermore, the system
enables a temporal adaptation for ensuring a continuous data acquisition to improve the recognition rate over time. A formal
field experiment reveals current recognition rates and indicates the practicability of both methods under realistic conditions
in a museum.
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5.
The study of interconnection networks is important because the overall performance of a distributed system is often critically
hinged on the effectiveness of its interconnection network. This paper addresses the problem of interconnection networks performance
modeling of large-scale distributed systems with emphases on heterogeneous multi-cluster computing systems. We present an
analytical model to predict message latency in multi-cluster systems in the presence of node, network and system organization
heterogeneity. The model is validated through comprehensive simulation, which demonstrates that the proposed model exhibits
a good degree of accuracy for various system organizations and under different working conditions.
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6.
The Stanford Event Heap has been shown to provide appropriate support for constructing interactive workspace applications.
Given this success it is natural to consider the Event Heap as a platform to support other classes of Ubiquitous Computing
applications. In this paper we argue that the distributed, spontaneous nature of these applications places additional demands
on the Event Heap that require extensions to both the engineering and API. Suitable extensions are described and their use
to support a typical Ubicomp application is discussed.
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7.
We present a survey of traffic models for communication networks whose key performance indicators like blocking probability
and mean delay are independent of all traffic characteristics beyond the traffic intensity. This insensitivity property, which
follows from that of the underlying queuing networks, is key to the derivation of simple and robust engineering rules like
the Erlang formula in telephone networks.
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8.
Recent advances in wireless sensor networks and positioning technologies have boosted new applications that manage moving
objects. In such applications, a dynamic index is often built to expedite evaluation of spatial queries. However, the development
of efficient indexes is a challenge due to frequent object movement. In this paper, we propose a new update-efficient index
method for moving objects in road networks. We introduce a dynamic data structure, called adaptive unit, to group neighboring objects with similar movement patterns. To reduce updates, an adaptive unit captures the movement bounds
of the objects based on a prediction method, which considers road-network constraints and the stochastic traffic behavior.
A spatial index (e.g., R-tree) for the road network is then built over the adaptive unit structures. Simulation experiments,
carried on two different datasets, show that an adaptive-unit based index is efficient for both updating and querying performances.
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9.
This paper presents an analysis of the topology of transportation networks within different systems of cities. Urban entities
and their components are complex systems by their nature; there is no central force that affects their spatial structure.
Thus, we study transportation networks within different countries as complex networks. Based on the above, we consider cities
as nodes, while direct air and railways routes represent the links. We present characteristics of these networks including
their degree and clustering coefficient. Transportation networks can be used as an indicator of economic activity between
cities. Cities with strong economic relationship are characterized by high volume of connectivity. Our findings suggest that
the topology of the analyzed transportation networks can be used to classify the countries they belong to based on their economic
development.
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10.
The genetic programming bibliography aims to be the most complete reference of papers on genetic programming. In addition
to locating publications, it contains coauthor and coeditor relationships which have not previously been studied. These reveal
some similarities and differences between our field and collaborative social networks in other scientific fields.
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11.
The quality of software systems are determined in part by their optimal configurations. Optimal configurations are desired
when the software is being deployed and during its lifetime. However, initial deployment and subsequent dynamic reconfiguration
of a software system is difficult because of the interplay of many interdependent factors, including cost, time, application
state, and system resources. As the size and complexity of software systems increases, procedures (manual or automated) that
assume a static software architecture and environment are becoming untenable. We have developed a novel technique for carrying
out the deployment and reconfiguration planning processes that leverages recent advances in the field of temporal planning.
We describe a tool called Planit, which manages the deployment and reconfiguration of a software system utilizing a temporal
planner. Given a model of the structure of a software system, the network upon which the system should be hosted, and a goal
configuration, Planit will use the temporal planner to devise possible deployments of the system. Given information about
changes in the state of the system, network and a revised goal, Planit will use the temporal planner to devise possible reconfigurations
of the system. We present the results of a case study in which Planit is applied to a system consisting of various components
that communicate across an application-level overlay network.
An earlier version of this paper was presented at ICTAI’03.
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12.
A wireless sensor network (WSN) consists of a large number of small devices with computational power, wireless communication
and sensing capability. These networks have been developed for a wide range of applications, such as habitat monitoring, object
tracking, precision agriculture, building monitoring and military systems. Meanwhile, middleware systems have also been proposed
in to facilitate both the development of these applications and provide common application services. The development of middleware
for sensor networks, however, places new challenges on middleware developers due to the low availability of resources and
processing capacity of the sensor nodes. In this context, this paper presents the design and implementation of a middleware
for WSN named Mires. Mires incorporates characteristics of message-oriented middleware by allowing applications communicate
in a publish/subscribe way. In order to illustrate the proposed middleware, we have also developed an environment-monitoring
application and a data aggregation service.
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13.
Video streaming is vital for many important applications such as distance learning, digital video libraries, and movie-on-demand.
Since video streaming requires significant server and networking resources, caching has been used to reduce the demand on
these resources. In this paper, we propose a novel collaboration scheme for video caching on overlay networks, called Overlay Caching Scheme (OCS), to further minimize service delays and loads placed on an overlay network for video streaming applications. OCS is not a
centralized nor a hierarchical collaborative scheme. Despite its design simplicity, OCS effectively uses an aggregate storage
space and capability of distributed overlay nodes to cache popular videos and serve nearby clients. Moreover, OCS is light-weight
and adaptive to clients’ locations and request patterns. We also investigate other video caching techniques for overlay networks
including both collaborative and non-collaborative ones. Compared with these techniques on topologies inspired from actual
networks, OCS offers extremely low average service delays and approximately half the server load. OCS also offers smaller
network load in most cases in our study.
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14.
Ultra wideband (UWB) systems are currently an important wireless infrastructure for high performance short-range communications
and mobile applications. Indeed, forming ad-hoc networks among various UWB enabled devices is considered as an important mobile data exchange operating environment. In our
study, we explore the problem of jointly optimizing the power level and data rate used in the devices in such a UWB based
ad-hoc network. We propose a practical optimization algorithm based on judicious power control for real-time applications
and opportunistic scheduling for non-real-time applications. Simulation results indicate that our proposed techniques are
effective under various practical scenarios.
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15.
Wireless sensor networks (WSN) are designed for data gathering and processing, with particular requirements: low hardware
complexity, low energy consumption, special traffic pattern support, scalability, and in some cases, real-time operation.
In this paper we present the virtual TDMA for sensors (VTS) MAC protocol, which intends to support the previous features,
focusing particularly on real-time operation. VTS adaptively creates a TDMA arrangement with a number of timeslots equal to
the actual number of nodes in range. Thus, VTS achieves an optimal throughput performance compared to TDMA protocols with
fixed size of frame. The frame is set up and maintained by a distributed procedure, which allows sensors to asynchronously
join and leave the frame. In addition, duty cycle is increased or decreased in order to keep latency constant below a given
deadline. Therefore, a major advantage of VTS is that it guarantees a bounded latency, which allows soft real-time applications.
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16.
Research on peer-to-peer (P2P) networks has attracted much attention recently. A key factor is their ability to handle dynamics
in the system in a distributed fashion, including ad hoc and dynamic join and departure of the peers and dynamic changes in
the underlying network environment. As more and more innovating P2P applications appear, the need to support intuitive communication
and synchronization among the peers in the P2P system becomes imperative. In this paper, we discuss how to build a tuple space
on top of P2P systems and use on-line games as a target application. A simple API is supported for accessing the data stored
in the tuple space and communicating between the peers. Through experiments and a demonstration game, we show that our system
can facilitate the development of network games in a fully distributed environment.
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17.
We present a study of using camera-phones and visual-tags to access mobile services. Firstly, a user-experience study is described in which participants were both observed learning to interact with a prototype mobile service and interviewed
about their experiences. Secondly, a pointing-device task is presented in which quantitative data was gathered regarding the speed and accuracy with which participants aimed and clicked
on visual-tags using camera-phones. We found that participants’ attitudes to visual-tag-based applications were broadly positive,
although they had several important reservations about camera-phone technology more generally. Data from our pointing-device
task demonstrated that novice users were able to aim and click on visual-tags quickly (well under 3 s per pointing-device
trial on average) and accurately (almost all meeting our defined speed/accuracy tradeoff of 6% error-rate). Based on our findings,
design lessons for camera-phone and visual-tag applications are presented.
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18.
Quantitative usability requirements are a critical but challenging, and hence an often neglected aspect of a usability engineering process. A case study is described where quantitative usability requirements played a key role in the development of a new user interface of a mobile phone. Within the practical constraints of the project, existing methods for determining usability requirements and evaluating the extent to which these are met, could not be applied as such, therefore tailored methods had to be developed. These methods and their applications are discussed. 相似文献
19.
MANETs are self-organizing infrastructure-less networks formed on the fly by a group of wireless nodes. The lack of central administration in these networks necessitates host auto-configuration. The proposed auto-configuration protocols to date are either not robust enough to respond efficiently to the dynamic nature of the MANETs or they are resource greedy. Also, there has been no detailed attempt made to compare the effectiveness of these protocols which is essential to judge relative merits and demerits. This paper presents a new stateful robust host auto-configuration protocol which is based on dynamically selected Address Agents (AAs) that maintain a distributed address table. The performance of the proposed protocol is comprehensively compared with a representative protocol that employs a different address table management technique. 相似文献
20.
As typical wireless sensor networks (WSNs) have resource limitations, predistribution of secret keys is possibly the most
practical approach for secure network communications. In this paper, we propose a key management scheme based on random key
predistribution for heterogeneous wireless sensor networks (HSNs). As large-scale homogeneous networks suffer from high costs
of communication, computation, and storage requirements, the HSNs are preferred because they provide better performance and
security solutions for scalable applications in dynamic environments. We consider hierarchical HSN consisting of a small number
high-end sensors and a large number of low-end sensors. To address storage overhead problem in the constraint sensor nodes,
we incorporate a key generation process, where instead of generating a large pool of random keys, a key pool is represented
by a small number of generation keys. For a given generation key and a publicly known seed value, a keyed-hash function generates
a key chain; these key chains collectively make a key pool. As dynamic network topology is native to WSNs, the proposed scheme
allows dynamic addition and removal of nodes. This paper also reports the implementation and the performance of the proposed
scheme on Crossbow’s MicaZ motes running TinyOS. The results indicate that the proposed scheme can be applied efficiently
in resource-constrained sensor networks. We evaluate the computation and storage costs of two keyed-hash algorithms for key
chain generation, HMAC-SHA1 and HMAC-MD5.
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