Wireless sensor networks are comprised of a vast number of ultra-small autonomous computing, communication and sensing devices, with restricted energy and computing capabilities, that co-operate to accomplish a large ...
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Wireless sensor networks are comprised of a vast number of ultra-small autonomous computing, communication and sensing devices, with restricted energy and computing capabilities, that co-operate to accomplish a large sensing task. Such networks can be very useful in practice, e.g. in the local monitoring of ambient conditions and reporting them to a control center. In this paper we propose a distributed group key establishment protocol that uses mobile agents (software) and is particularly suitable for energy constrained, dynamically evolving ad-hoc networks. Our approach totally avoids the construction and the maintenance of a distributed structure that reflects the topology of the network. Moreover, it trades-off complex message exchanges by performing some amount of additional local computations in order to be applicable at dense and dynamic sensor networks. The extra computations are simple for the devices to implement and are evenly distributed across the participants of the network leading to good energy balance. We evaluate the performance of our protocol in a simulated environment and compare our results with existing group key establishment protocols. The security of the protocol is based on the Diffie-Hellman problem and we used in our experiments its elliptic curve analog. Our findings basically indicate the feasibility of implementing our protocol in real sensor network devices and highlight the advantages and disadvantages of each approach given the available technology and the corresponding efficiency (energy, time) criteria.
Electroencephalograph (EEG) recordings during the right and the left hand motor imagery can be used to move a cursor to a target on a computer screen. Such an EEG-based brain-computer interface (BCI) can provide a new...
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ISBN:
(纸本)4907764278
Electroencephalograph (EEG) recordings during the right and the left hand motor imagery can be used to move a cursor to a target on a computer screen. Such an EEG-based brain-computer interface (BCI) can provide a new communication channel to replace an impaired motor function. It can be used by e.g., handicap users with amyotrophic lateral sclerosis (ALS). The conventional method purposes the recognition of the right hand and the left hand motor imagery. In this sturdy, feature extraction based on Directed Information analysis is introduced to discriminate the EEG signals recorded during the right hand, the left hand and the right foot motor imagery. The effectiveness of our method is confirmed through the experimental studies.
This paper proposes a business model for the successful operation of the currently developing broadband metropolitan area networks in Greece. Having recorded and examined relevant international practices, we describe ...
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This paper proposes a business model for the successful operation of the currently developing broadband metropolitan area networks in Greece. Having recorded and examined relevant international practices, we describe in detail the way that these networks should be managed, operated, maintained and expanded. Taking into consideration that these infrastructures will alter the broadband map of Greece widely, that Greece currently has one of the lowest broadband penetration percentages in Europe and that the proper exploitation of the networks to be deployed could boost the demand for broadband connections and applications, the proposition of the business model appears to be of vital importance. We present the proposed business model in detail including information regarding network management and network expansion of the broadband metropolitan networks and viability issues regarding the authority which will manage the broadband metropolitan networks.
This paper treats the output feedback H 2 control with H ∞ norm constraint (mixed H 2 /H ∞ control problem). In general, this problem is a BMI problem which is difficult to be solved theoretically. The purpose of...
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This paper treats the output feedback H 2 control with H ∞ norm constraint (mixed H 2 /H ∞ control problem). In general, this problem is a BMI problem which is difficult to be solved theoretically. The purpose of this paper is to propose an iterative method for obtaining a sub-optimal solution of the mixed H 2 /H ∞ control problem. The key idea of this paper is to employ a full-order observer-based controller. The proposed method produces a sequence of controllers which approaches to the unconstrained globally optimal H 2 controller while it satisfies the H ∞ norm constraint. A numerical example shows the effectiveness of our method.
In this study we tested the average delay and packet loss performance of access networks under variable bit rate (VBR) video traffic. We used ns-2 simulator to perform the simulations, and actual as well as synthetica...
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In this study we tested the average delay and packet loss performance of access networks under variable bit rate (VBR) video traffic. We used ns-2 simulator to perform the simulations, and actual as well as synthetically generated ON/OFF sources with ON and OFF times taken from exponential or Pareto distributions are used as inputs to the simulated networks. To make sure that the synthetic sources have VBR-video like characteristics we chose the parameters of these sources such that their Hurst parameter is as close to 1 as possible. We then tested the performance of a network when data produced by these sources is applied as input. The results show that both actual and synthetic sources produce similar results and that the access networks should have at least 1 Mbps speeds to support acceptable quality video transmission.
Partitioning constitutes one of the most critical challenges a distributed virtual environment needs to handle and is related to the efficient assignment of the existing entities of the virtual world to the available ...
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Partitioning constitutes one of the most critical challenges a distributed virtual environment needs to handle and is related to the efficient assignment of the existing entities of the virtual world to the available resources of the system. The efficient partitioning arises from the need of high consistency maintenance among participating users' view, as virtual reality applications are characterized by the high degree of realism they aim to achieve. To the direction of partitioning algorithms, a lot of work has been done, which has been more intense due to the evolution of network technologies and the familiarization of users with virtual reality systems. This paper presents a partitioning approach, which is based on the degree of interaction of each virtual object and the behavior of the participating users, in terms of moving trends, which is usually directed by the actions they can perform on the surrounding objects. In particular, the partitioning takes place when the virtual world contains only objects, in the sense that no avatars are yet connected and objects' attributes are handled as indicators for avatars' future behavior in the system. This prediction of avatars' behavior based on objects' attributes defines the initial partitioning of the virtual space.
With the human genome sequenced, attention has been shifting to proteins and their function. Several technologies including mass spectrometry and gel electrophoresis have traditionally been used to study proteins. The...
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This paper addresses the problem of establishing stability of interconnected nonlinear systems consisting of individually input-to-state stable (ISS) subsystems. This paper aims to extend the capability of the ISS sma...
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ISBN:
(纸本)9781424414970;1424414970
This paper addresses the problem of establishing stability of interconnected nonlinear systems consisting of individually input-to-state stable (ISS) subsystems. This paper aims to extend the capability of the ISS small-gain technique with emphasis on Lyapunov functions and necessity. This paper derives an explicit formula for constructing Lyapunov functions characterizing ISS property of interconnected systems from dissipation inequalities of subsystems. This paper focuses on the case where nonlinear loop gain approaches unity asymptotically as magnitude of signals tends to zero and infinity. The new formula of Lyapunov functions deals with the non-uniform contraction of loop gain and covers one of authors' previous developments as a special case. The Lyapunov functions obtained here are differentiable. The formulation based on dissipation inequalities also allows us to prove the necessity of the small-gain condition without making a technical assumption of uniformity.
The accumulation of genomic and proteomic data of many organisms presents an opportunity to analyze entire phylogenetic trees in a systematic, quantified manner. The universal tree of life, constructed by genomic data...
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In this study, we investigate the correlation between security and spatial resolution - a measure of service quality - in cluster-based wireless sensor networks (WSN). We analyze the tradeoff between these two concept...
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In this study, we investigate the correlation between security and spatial resolution - a measure of service quality - in cluster-based wireless sensor networks (WSN). We analyze the tradeoff between these two concepts resulting from the limited channel capacity and propose a method to determine the best tradeoff between security and spatial resolution for cases where network capacity is not sufficient to support required levels. We also present some numerical results obtained by application of the proposed method to a sample sensor network.
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