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1.
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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2.
Data gathering is a major function of many applications in wireless sensor networks (WSNs). The most important issue in designing
a data gathering algorithm is how to save energy of sensor nodes while meeting the requirement of applications/users such
as sensing area coverage. In this paper, we propose a novel hierarchical clustering protocol (DEEG) for long-lived sensor
network. DEEG achieves a good performance in terms of lifetime by minimizing energy consumption for in-network communications
and balancing the energy load among all the nodes, the proposed protocol achieves a good performance in terms of network lifetime.
DEEG can also handle the energy hetergenous capacities and guarantee that out-network communications always occur in the subregion
with high energy reserved. Furthermore, it introduces a simple but efficient approach to cope with the area coverage problem.
We evaluate the performance of the proposed protocol using a simple temperature sensing application. Simulation results show
that our protocol significantly outperforms LEACH and PEGASIS in terms of network lifetime and the amount of data gathered.
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3.
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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4.
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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5.
Mobile ad hoc networks without centralized infrastructure change their topology rapidly because of node mobility, making multimedia
applications difficult to run across wireless networks. Moreover, video transmission over ad hoc networks causes frequent
transmission loss of video packets owing to end-to-end transmission with a number of wireless links, and requires essential
bandwidth and restricted delay to provide quality-guaranteed display. This paper presents an architecture supporting transmission
of multiple video streams in ad hoc networks by establishing multiple routing paths to provide extra video coding and transport
schemes. This study also proposes an on-demand multicast routing protocol to transport layered video streams. The multicast
routing protocol transmits layered video streaming based on a weight criterion, which is derived according to the number of
receivers, delay and expiration time of a route. A simulation is performed herein to indicate the viability and performance
of the proposed approach. The simulation results demonstrate that the proposed transport scheme is more effective than other
video transport schemes with single or multiple paths.
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6.
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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7.
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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8.
This paper describes the simulated car racing competition that was arranged as part of the 2007 IEEE Congress on Evolutionary
Computation. Both the game that was used as the domain for the competition, the controllers submitted as entries to the competition
and its results are presented. With this paper, we hope to provide some insight into the efficacy of various computational
intelligence methods on a well-defined game task, as well as an example of one way of running a competition. In the process,
we provide a set of reference results for those who wish to use the simplerace game to benchmark their own algorithms. The paper is co-authored by the organizers and participants of the competition.
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9.
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
10.
Interface toolkits in ordinary application areas let average programmers rapidly develop software resembling other standard
applications. In contrast, toolkits for novel and perhaps unfamiliar application areas enhance the creativity of these programmers.
By removing low-level implementation burdens and supplying appropriate building blocks, toolkits give people a ‘language’
to think about these new interfaces, which in turn allows them to concentrate on creative designs. This is important, for
it means that programmers can rapidly generate and test new ideas, replicate and refine ideas, and create demonstrations for
others to try. To illustrate this important link between toolkits and creativity, I describe example groupware toolkits we
have built and how people have leveraged them to create innovative interfaces.
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11.
Wireless Mesh Networks (WMNs) are an emerging technology that could revolutionize the way wireless network access is provided. The interconnection of access points using wireless links exhibits great potential in addressing the “last mile” connectivity issue. To realize this vision, it is imperative to provide efficient resource management. Resource management encompasses a number of different issues, including routing. Although a profusion of routing mechanisms has been proposed for other wireless networks, the unique characteristics of WMNs (e.g., wireless backbone) suggest that WMNs demand a specific solution. To have a clear and precise focus on future research in WMN routing, the characteristics of WMNs that have a strong impact on routing must be identified. Then a set of criteria is defined against which the existing routing protocols from ad hoc, sensor, and WMNs can be evaluated and performance metrics identified. This will serve as the basis for deriving the key design features for routing in wireless mesh networks. Thus, this paper will help to guide and refocus future works in this area. 相似文献
12.
Mobile sinks can be used to balance energy consumption for sensor nodes in Wireless Sensor Networks (WSNs). Mobile sinks are
required to inform sensor nodes about their new location information whenever necessary. However, frequent location updates
from mobile sinks can lead to both rapid energy consumption of sensor nodes and increased collisions in wireless transmissions.
We propose a new solution with adaptive location updates for mobile sinks to resolve this problem. When a sink moves, it only
needs to broadcast its location information within a local area other than among the entire network. Both theoretical analysis
and simulation studies show that this solution consumes less energy in each sensor node and also decreases collisions in wireless
transmissions, which can be used in large-scale WSNs.
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13.
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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14.
Thermal functional circuits are an interesting group of the MEMS elements with high a potential. A practical realisation is
called Quadratic Transfer Characteristics (QTC) element of which driving principle is the Seebeck effect. Such devices can
be applied e.g. as RMS meters. In this paper we are dealing with the analyses of a QTC element from different perspectives.
A family of compact models is presented. These models are suitable to use in network simulation programs. To investigate the
detailed behaviour of the device, we measured a few secondary properties of the structure, such as temperature dependence,
cut-off frequency and non-quadratic error.
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15.
Awareness systems have attracted significant research interest for their potential to support interpersonal relationships.
Investigations of awareness systems for the domestic environment have suggested that such systems can help individuals stay
in touch with dear friends or family and provide affective benefits to their users. Our research provides empirical evidence
to refine and substantiate such suggestions. We report our experience with designing and evaluating the ASTRA awareness system,
for connecting households and mobile family members. We introduce the concept of connectedness and its measurement through
the Affective Benefits and Costs of communication questionnaire (ABC-Q). We inform results that testify the benefits of sharing
experiences at the moment they happen without interrupting potential receivers. Finally, we document the role that lightweight,
picture-based communication can play in the range of communication media available.
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16.
The complexity of group dynamics occurring in small group interactions often hinders the performance of teams. The availability
of rich multimodal information about what is going on during the meeting makes it possible to explore the possibility of providing
support to dysfunctional teams from facilitation to training sessions addressing both the individuals and the group as a whole.
A necessary step in this direction is that of capturing and understanding group dynamics. In this paper, we discuss a particular
scenario, in which meeting participants receive multimedia feedback on their relational behaviour, as a first step towards
increasing self-awareness. We describe the background and the motivation for a coding scheme for annotating meeting recordings
partially inspired by the Bales’ Interaction Process Analysis. This coding scheme was aimed at identifying suitable observable
behavioural sequences. The study is complemented with an experimental investigation on the acceptability of such a service.
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17.
A number of mobile applications have emerged that allow users to locate one another. However, people have expressed concerns
about the privacy implications associated with this class of software, suggesting that broad adoption may only happen to the
extent that these concerns are adequately addressed. In this article, we report on our work on P eopleF inder, an application that enables cell phone and laptop users to selectively share their locations with others (e.g. friends,
family, and colleagues). The objective of our work has been to better understand people’s attitudes and behaviors towards
privacy as they interact with such an application, and to explore technologies that empower users to more effectively and
efficiently specify their privacy preferences (or “policies”). These technologies include user interfaces for specifying rules
and auditing disclosures, as well as machine learning techniques to refine user policies based on their feedback. We present
evaluations of these technologies in the context of one laboratory study and three field studies.
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18.
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
19.
Listening to music on personal, digital devices whilst mobile is an enjoyable, everyday activity. We explore a scheme for
exploiting this practice to immerse listeners in navigation cues. Our prototype, ONTRACK, continuously adapts audio, modifying
the spatial balance and volume to lead listeners to their target destination. First we report on an initial lab-based evaluation
that demonstrated the approach’s efficacy: users were able to complete tasks within a reasonable time and their subjective
feedback was positive. Encouraged by these results we constructed a handheld prototype. Here, we discuss this implementation
and the results of field-trials. These indicate that even with a low-fidelity realisation of the concept, users can quite
effectively navigate complicated routes.
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20.
The growing need for ubiquitous access to video on demand (VoD) applications by large audiences has driven researches to build
new scalable VoD systems that can guarantee Quality of Service (QoS) over wireless networks. In this paper, we propose and
evaluate a novel system-level design that guarantees QoS by eliminating the service latency for short videos over IEEE 802.11
networks. Furthermore, our VoD system attains scalable performance by employing collocated access points (APs) coupled with
an efficient association management of clients to the APs using a generic least-loaded-first heuristic on non-overlapping
channels. Simulated results of our VoD system demonstrated that it achieved scalable performance due to its effective use
of available bandwidth of the APs while supporting a low blockage rate for short videos up to 360 s. These results suggest
that our VoD system can be an attractive solution for several classes of scalable VoD applications that require QoS guarantee
such as movie trailers, news, video clips, and commercials.
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