The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform

Jacek Malinowski - One of the best experts on this subject based on the ideXlab platform.

  • Node Pair reliability of network systems with small distances between adjacent Nodes
    Reliability Engineering & System Safety, 2007
    Co-Authors: Jacek Malinowski
    Abstract:

    A new method for computing the Node-Pair reliability of network systems modeled by random graphs with Nodes arranged in sequence is presented. It is based on a recursive algorithm using the “sliding window†technique, the window being composed of several consecutive Nodes. In a single step, the connectivity probabilities for all Nodes included in the window are found. Subsequently, the window is moved one Node forward. This process is repeated until, in the last step, the window reaches the terminal Node. The connectivity probabilities found at that point are used to compute the Node-Pair reliability of the network system considered. The algorithm is designed especially for graphs with small distances between adjacent Nodes, where the distance between two Nodes is defined as the absolute value of the difference between the Nodes’ numbers. The maximal distance between any two adjacent Nodes is denoted by I“(G), where G symbolizes a random graph. If I“(G)=2 then the method can be applied for directed as well as undirected graphs whose Nodes and edges are subject to failure. This is important in view of the fact that many algorithms computing network reliability are designed for graphs with failure-prone edges and reliable Nodes. If I“(G)=3 then the method's applicability is limited to undirected graphs with reliable Nodes. The main asset of the presented algorithms is their low numerical complexity—O(n), where n denotes the number of Nodes.

  • a lower bound for the Node Pair reliability of network systems with small distances between adjacent Nodes
    International Journal of Reliability Quality and Safety Engineering, 2006
    Co-Authors: Jacek Malinowski
    Abstract:

    A new method for computing a lower bound of the Node-Pair reliability of network systems modeled by random graphs with sequentially ordered Nodes is presented. It is based on the analysis of the tree structure constructed in order to find all minimal paths connecting two distinguished Nodes of the system under consideration. The algorithm is particularly efficient for graphs with small distances between adjacent Nodes, where the distance between two Nodes is defined as the absolute value of the difference between the Nodes' numbers. The presented method can be applied if both Nodes and edges are subject to failure. That is important in view of the fact that many algorithms computing network reliability are designed for graphs whose Nodes are not failure-prone. Moreover, the method can be applied for directed as well as undirected graphs. The algorithm's numerical complexity depends on 2·rG - 1, where rG is the maximal distance between any two adjacent Nodes. It occurs that for rG = 2 the exact value of a network system's reliability can be computed by means of a simple recursive procedure. The results of both (approximate and exact) methods are compared to demonstrate the lower bound's accuracy.

Seungkeun Park - One of the best experts on this subject based on the ideXlab platform.

  • novel Node Pair selection algorithms for sum rate enhancement in mimo interference channel
    International Conference on Information and Communication Security, 2011
    Co-Authors: Myeongjin Kim, Hyunho Lee, Seungkeun Park
    Abstract:

    In multiple-input multiple-output(MIMO) interference channel, multiple transmitters and receivers communicate simultaneously as a Pair. We establish the metric for Node Pair selection algorithm to maximize the sum rate in MIMO interference channel. In this paper, by adjusting Node Pairs properly, we show that the sum rate can be enhanced. We propose two different Node Pair selection algorithms to improve the sum rate of MIMO interference channel. Firstly, we propose an optimum Node Pair selection algorithm by formulating a Node Pair selection metric to select the best Node Pairs among all possible Node Pairs. Then we propose a sub-optimum Node Pair selection algorithm to lower computational complexity. We confirm from some numerical simulations that the proposed algorithms offer significant sum rate enhancement compared to the case when Node Pair selection is not considered.

  • ICICS - Novel Node Pair selection algorithms for sum-rate enhancement in MIMO interference channel
    2011 8th International Conference on Information Communications & Signal Processing, 2011
    Co-Authors: Kim Myeongjin, Hyunho Lee, Seungkeun Park
    Abstract:

    In multiple-input multiple-output(MIMO) interference channel, multiple transmitters and receivers communicate simultaneously as a Pair. We establish the metric for Node Pair selection algorithm to maximize the sum rate in MIMO interference channel. In this paper, by adjusting Node Pairs properly, we show that the sum rate can be enhanced. We propose two different Node Pair selection algorithms to improve the sum rate of MIMO interference channel. Firstly, we propose an optimum Node Pair selection algorithm by formulating a Node Pair selection metric to select the best Node Pairs among all possible Node Pairs. Then we propose a sub-optimum Node Pair selection algorithm to lower computational complexity. We confirm from some numerical simulations that the proposed algorithms offer significant sum rate enhancement compared to the case when Node Pair selection is not considered.

Alberto Guardone - One of the best experts on this subject based on the ideXlab platform.

  • Kinetic Node-Pair Formulation for Two-Dimensional Flows from Continuum to Transitional Regime
    AIAA Journal, 2013
    Co-Authors: Marco Fossati, Alberto Guardone, Luigi Vigevano
    Abstract:

    A hybrid finite-element/finite-volume Node-Pair discretization of conservation laws is reformulated in terms of a Bhatnagar–Gross–Krook kinetic scheme to address flows from the continuum up to the transitional regime in a seamless fashion. Integrals of the particle distribution function from the kinetic theory of gases are adopted to compute the numerical fluxes along the boundary of each control volume. Flow features typical of the transitional regime like velocity and temperature slip condition at solid walls are automatically assured by the kinetic formulation of the Node-Pair boundary conditions. Exemplary two-dimensional numerical experiments ranging from continuum flows up to the transitional regime are presented.

  • Node Pair finite volume finite element schemes for the euler equation in cylindrical and spherical coordinates
    Journal of Computational and Applied Mathematics, 2012
    Co-Authors: Dante De Santis, Gianluca Geraci, Alberto Guardone
    Abstract:

    A numerical scheme is presented for the solution of the compressible Euler equations in both cylindrical and spherical coordinates. The unstructured grid solver is based on a mixed finite volume/finite element approach. Equivalence conditions linking the Node-centered finite volume and the linear Lagrangian finite element scheme over unstructured grids are reported and used to devise a common framework for solving the discrete Euler equations in both the cylindrical and the spherical reference systems. Numerical simulations are presented for the explosion and implosion problems with spherical symmetry, which are solved in both the axial-radial cylindrical coordinates and the radial-azimuthal spherical coordinates. Numerical results are found to be in good agreement with one-dimensional simulations over a fine mesh.

  • a Node Pair finite element volume mesh adaptation technique for compressible flows based on a hierarchical approach
    International Journal for Numerical Methods in Fluids, 2012
    Co-Authors: Marco Fossati, Alberto Guardone, Luigi Vigevano
    Abstract:

    SUMMARY A grid adaptation technique for two-dimensional unstructured grids of triangles and quadrilaterals is presented. The error estimation procedure is formulated in terms of a Node Pair-based data structure that allows for a unified description of the finite element and finite volume schemes. The adaptation algorithm is based on a strategy of hierarchical corrections, where a suitable number of intermediate adapted grids are generated and successively corrected by employing a simple Node insertion technique at the midpoint of the element edges. Coarsening of the grid is obtained in an implicit fashion by avoiding the insertion of new Nodes during the correction phase. The adaptation history, from the initial to the current grid, including all intermediate grids, is stored and updated through the whole process. No intermediate grid is therefore required to be stored explicitly. The adapted grid is anisotropic, thanks to the adoption of both regular triangular and quadrilateral elements with high aspect ratio that are gathered in, for example, boundary layer or wake regions. Numerical experiments of steady compressible flows, including both inviscid and viscous flows, are presented to support the suitability of the adaptation technique. Copyright © 2012 John Wiley & Sons, Ltd.

  • A Node‐Pair finite element/volume mesh adaptation technique for compressible flows based on a hierarchical approach
    International Journal for Numerical Methods in Fluids, 2012
    Co-Authors: Marco Fossati, Alberto Guardone, Luigi Vigevano
    Abstract:

    SUMMARY A grid adaptation technique for two-dimensional unstructured grids of triangles and quadrilaterals is presented. The error estimation procedure is formulated in terms of a Node Pair-based data structure that allows for a unified description of the finite element and finite volume schemes. The adaptation algorithm is based on a strategy of hierarchical corrections, where a suitable number of intermediate adapted grids are generated and successively corrected by employing a simple Node insertion technique at the midpoint of the element edges. Coarsening of the grid is obtained in an implicit fashion by avoiding the insertion of new Nodes during the correction phase. The adaptation history, from the initial to the current grid, including all intermediate grids, is stored and updated through the whole process. No intermediate grid is therefore required to be stored explicitly. The adapted grid is anisotropic, thanks to the adoption of both regular triangular and quadrilateral elements with high aspect ratio that are gathered in, for example, boundary layer or wake regions. Numerical experiments of steady compressible flows, including both inviscid and viscous flows, are presented to support the suitability of the adaptation technique. Copyright © 2012 John Wiley & Sons, Ltd.

  • Node-Pair finite volume/finite element schemes for the Euler equation in cylindrical and spherical coordinates
    Journal of Computational and Applied Mathematics, 2012
    Co-Authors: Dante De Santis, Gianluca Geraci, Alberto Guardone
    Abstract:

    A numerical scheme is presented for the solution of the compressible Euler equations in both cylindrical and spherical coordinates. The unstructured grid solver is based on a mixed finite volume/finite element approach. Equivalence conditions linking the Node-centered finite volume and the linear Lagrangian finite element scheme over unstructured grids are reported and used to devise a common framework for solving the discrete Euler equations in both the cylindrical and the spherical reference systems. Numerical simulations are presented for the explosion and implosion problems with spherical symmetry, which are solved in both the axial-radial cylindrical coordinates and the radial-azimuthal spherical coordinates. Numerical results are found to be in good agreement with one-dimensional simulations over a fine mesh.

Abbas El Gamal - One of the best experts on this subject based on the ideXlab platform.

  • ISIT - Network Information Theoretic Security
    2020 IEEE International Symposium on Information Theory (ISIT), 2020
    Co-Authors: Hongchao Zhou, Abbas El Gamal
    Abstract:

    Shannon showed that to achieve perfect secrecy in point-to-point communication, the message rate cannot exceed the shared secret key rate giving rise to the simple one-time pad encryption scheme. In this paper, we extend this work from point-to-point to networks. We consider a connected network with Pairwise communication between the Nodes. We assume that each Node is provided with a certain amount of secret bits before communication commences. An eavesdropper with unlimited computing power has access to all communication and can hack a subset of the Nodes not known to the rest of the Nodes. We investigate the limits on information-theoretic secure communication for this network. We establish a tradeoff between the secure channel rate (for a Node Pair) and the secure network rate (sum over all Node Pair rates) and show that perfect secrecy can be achieved if and only if the sum rate of any subset of unhacked channels does not exceed the shared unhacked-secret-bit rate of these channels. We also propose two practical and efficient schemes that achieve a good balance of network and channel rates with perfect secrecy guarantee. This work has a wide range of potential applications for which perfect secrecy is desired, such as cyber-physical systems, distributed-control systems, and ad-hoc networks.

  • Network Information Theoretic Security
    2020
    Co-Authors: Zhou Hongchao, Abbas El Gamal
    Abstract:

    Shannon showed that to achieve perfect secrecy in point-to-point communication, the message rate cannot exceed the shared secret key rate giving rise to the simple one-time pad encryption scheme. In this paper, we extend this work from point-to-point to networks. We consider a connected network with Pairwise communication between the Nodes. We assume that each Node is provided with a certain amount of secret bits before communication commences. An eavesdropper with unlimited computing power has access to all communication and can hack a subset of the Nodes not known to the rest of the Nodes. We investigate the limits on information-theoretic secure communication for this network. We establish a tradeoff between the secure channel rate (for a Node Pair) and the secure network rate (sum over all Node Pair rates) and show that perfect secrecy can be achieved if and only if the sum rate of any subset of unhacked channels does not exceed the shared unhacked-secret-bit rate of these channels. We also propose two practical and efficient schemes that achieve a good balance of network and channel rates with perfect secrecy guarantee. This work has a wide range of potential applications for which perfect secrecy is desired, such as cyber-physical systems, distributed-control systems, and ad-hoc networks

Haris Pervaiz - One of the best experts on this subject based on the ideXlab platform.

  • Shared Secret Key Generation via Carrier Frequency Offsets.
    arXiv: Cryptography and Security, 2019
    Co-Authors: Waqas Aman, Aneeqa Ijaz, Mizanur Rahman, Dushanta Nalin K. Jayakody, Haris Pervaiz
    Abstract:

    This work presents a novel method to generate secret keys shared between a legitimate Node Pair (Alice and Bob) to safeguard the communication between them from an unauthorized Node (Eve). To this end, we exploit the {\it reciprocal carrier frequency offset} (CFO) between the legitimate Node Pair to extract common randomness out of it to generate shared secret keys. The proposed key generation algorithm involves standard steps: the legitimate Nodes exchange binary phase-shift keying (BPSK) signals to perform blind CFO estimation on the received signals, and do equi-probable quantization of the noisy CFO estimates followed by information reconciliation--to distil a shared secret key. Furthermore, guided by the Allan deviation curve, we distinguish between the two frequency-stability regimes---when the randomly time-varying CFO process i) has memory, ii) is memoryless; thereafter, we compute the key generation rate for both regimes. Simulation results show that the key disagreement rate decreases exponentially with increase in the signal to noise ratio of the link between Alice and Bob. Additionally, the decipher probability of Eve decreases as soon as either of the two links observed by the Eve becomes more degraded compared to the link between Alice and Bob.

  • VTC Spring - Shared Secret Key Generation via Carrier Frequency Offsets
    2019 IEEE 89th Vehicular Technology Conference (VTC2019-Spring), 2019
    Co-Authors: Waqas Aman, Aneeqa Ijaz, Mizanur Rahman, Dushanta Nalin K. Jayakody, Haris Pervaiz
    Abstract:

    This work presents a novel method to generate secret keys shared between a legitimate Node Pair (Alice and Bob) to safeguard the communication between them from an unauthorized Node (Eve). To this end, we exploit the reciprocal carrier frequency offset (CFO) between the legitimate Node Pair to extract common randomness out of it to generate shared secret keys. The proposed key generation algorithm involves standard steps: the legitimate Nodes exchange binary phase-shift keying (BPSK) signals to perform blind CFO estimation on the received signals, and do equi-probable quantization of the noisy CFO estimates followed by information reconciliation-to distil a shared secret key. Furthermore, guided by the Allan deviation curve, we distinguish between the two frequency-stability regimes-when the randomly time-varying CFO process i) has memory, ii) is memoryless; thereafter, we compute the key generation rate for both regimes. Simulation results show that the key disagreement rate decreases exponentially with increase in the signal to noise ratio of the link between Alice and Bob. Additionally, the decipher probability of Eve decreases as soon as either of the two links observed by the Eve becomes more degraded compared to the link between Alice and Bob.