Feedback delays are inherent attributes of distributed control systems that usually cause unfavorable effect on the stability of the controlled process. Modelling of such systems is essential for traceable controller ...
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Long Term Evolution (LTE) constitutes the latest step before the 4th generation (4G) of radio technologies designed to increase the capacity and speed of mobile communications. To support Multimedia Broadcast/Multicas...
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Long Term Evolution (LTE) constitutes the latest step before the 4th generation (4G) of radio technologies designed to increase the capacity and speed of mobile communications. To support Multimedia Broadcast/Multicast Services (MBMS), LTE offers the possibility to transmit Multimedia Broadcast multicast service over a Single Frequency Network (MBSFN), where a time-synchronized common waveform is transmitted from multiple cells for a given duration. This enables over-the-air combining, thus improving the Signal to Interference plus Noise Ratio (SINR) and spectral efficiency (SE) significantly compared to conventional MBMS operation. In this paper, we analytically calculate the SE performance achieved in a MBSFN area for a dynamically changing user topology and different modulation and coding schemes (MCS). Finally, based on the SE measurement, we determine the MCS scheme that either maximizes or achieves a target SE for the corresponding user distribution.
In haptic and telemanipulation devices stability and transparency are contradicting requirements. Due to the network delay the control process may become unstable. In our research we consider the coupled impedance typ...
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We present in this work the performance evaluation of MPEG-4 video transmission with our proposed single rate multicast protocol named Adaptive Smooth Multicast Protocol (ASMP). ASMP key attributes are: (a) adaptive s...
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We present in this work the performance evaluation of MPEG-4 video transmission with our proposed single rate multicast protocol named Adaptive Smooth Multicast Protocol (ASMP). ASMP key attributes are: (a) adaptive scalability to large sets of receivers, (b) TCP-friendly behavior, (c) high bandwidth utilization, and finally (d) smooth transmission rates which are suitable for multimedia applications. We evaluate the performance of ASMP under an integrated simulation environment which extends ns-2 and Evalvid-RA to the multicast domain with the use of the RTP/RTCP protocols. Simulations conducted under this environment combine the measurements of network-centric along with video quality metrics. This “joint” evaluation process provides a better understanding of the benefits and limitations of any proposed protocol for multimedia data transmission.
FEC is an error control method that can be used to augment or replace other methods for reliable data transmission. Such schemes inevitably add a constant overhead in the transmitted data. However, they are so simple ...
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FEC is an error control method that can be used to augment or replace other methods for reliable data transmission. Such schemes inevitably add a constant overhead in the transmitted data. However, they are so simple as to meet a prime objective for UMTS multicast services, that is scalability to applications with thousands of receivers. This is the reason that 3GPP recommends the use of FEC for MBMS framework. In this paper, we use a probabilistic model for the multicast user distribution in the network and we define a scheme for multicast data delivery that combines FEC with traditional ARQ. It is important that our analysis is compliant with the 3GPP specifications and considers the latest advances in mobile networks. In this framework we investigate the impact of FEC use, we examine whether it is beneficial, how the optimal FEC code dimensioning varies based on the network conditions, which parameters affect the optimal FEC code selection, and how they do it.
Content searching and downloading are the two dominant actions of the Internet users today, despite the fact that the Internet was not originally architected to serve such actions. Content Centric Networking is the ne...
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In this paper, a novel method is proposed able to automatically generate accurate 3D models of both outdoor buildings and indoor scenes with perspective cues from line segments that are automatically extracted from a ...
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ISBN:
(纸本)9781450301756
In this paper, a novel method is proposed able to automatically generate accurate 3D models of both outdoor buildings and indoor scenes with perspective cues from line segments that are automatically extracted from a single image with an uncalibrated camera. The proposed method uses geometric constraints and knowledge of photography and achieves an accurate, real-time and fully automated 3D reconstruction of the scene without any intervention from the user.
We propose efficient schemes for information-theoretically secure key exchange in the Bounded Storage Model (BSM), where the adversary is assumed to have limited storage. Our schemes generate a secret One Time Pad (OT...
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ISBN:
(纸本)9781450304139
We propose efficient schemes for information-theoretically secure key exchange in the Bounded Storage Model (BSM), where the adversary is assumed to have limited storage. Our schemes generate a secret One Time Pad (OTP) shared by the sender and the receiver, from a large number of public random bits produced by the sender or by an external source. Our schemes initially generate a small number of shared secret bits, using known techniques. We introduce a new method to expand a small number of shared bits to a much longer, shared key. Our schemes are tailored to the requirements of sensor nodes and wireless networks. They are simple, efficient to implement and take advantage of the fact that practical wireless protocols transmit data in frames, unlike previous protocols, which assume access to specific bits in a stream of data. Indeed, our main contribution is twofold. On the one hand, we construct schemes that are attractive in terms of simplicity, computational complexity, number of bits read from the shared random source and expansion factor of the initial key to the final shared key. On the other hand, we show how to transform any existing scheme for key exchange in BSM into a more efficient scheme in the number of bits it reads from the shared source, given that the source is transmitted in frames.
Orthogonal Frequency Division Multiplexing (OFDM) has been recently proposed as a modulation technique for optical networks, due to its good spectral efficiency and impairment tolerance. Optical OFDM is much more flex...
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Orthogonal Frequency Division Multiplexing (OFDM) has been recently proposed as a modulation technique for optical networks, due to its good spectral efficiency and impairment tolerance. Optical OFDM is much more flexible compared to traditional WDM systems, enabling elastic bandwidth transmissions. We consider the planning problem of an OFDM-based optical network where we are given a traffic matrix that includes the requested transmission rates of the connections to be served. Connections are provisioned for their requested rate by elastically allocating spectrum using a variable number of OFDM subcarriers. We introduce the Routing and Spectrum Allocation (RSA) problem, as opposed to the typical Routing and Wavelength Assignment (RWA) problem of traditional WDM networks, and present various algorithms to solve the RSA. We start by presenting an optimal ILP RSA algorithm that minimizes the spectrum used to serve the traffic matrix, and also present a decomposition method that breaks RSA into two substituent subproblems, namely, (i) routing and (ii) spectrum allocation (R+SA) and solves them sequentially. We also propose a heuristic algorithm that serves connections one-by-one and use it to solve the planning problem by sequentially serving all traffic matrix connections. To feed the sequential algorithm, two ordering policies are proposed; a simulated annealing meta-heuristic is also used to obtain even better orderings. Our results indicate that the proposed sequential heuristic with appropriate ordering yields close to optimal solutions in low running times.
This paper proposes a method which gives symbolic model of the interconnected linear system using the adjacency matrix which represent the system. When there exist any algebraic loops in the system, they are reduced t...
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This paper proposes a method which gives symbolic model of the interconnected linear system using the adjacency matrix which represent the system. When there exist any algebraic loops in the system, they are reduced to the self loops by the edge contraction. If the weight matrix of the self loop is nonsingular, it is removed and the symbolic state space model is obtained, otherwise the symbolic descriptor model is obtained. We introduce a new interactive graphical software tool which have been developed for modeling and simulation of control systems using the proposed method.
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