530,108 research outputs found

    Spoofed Networks: Exploitation of GNSS Security Vulnerability in 4G and 5G Mobile Networks

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    Includes supplementary materialFifth Generation New Radio (5G NR) represents a shift in mobile telephony whereby the network architecture runs containerized software on commodity hardware. In preparation for this transition, numerous 4G Long Term Evolution software stacks have been developed to test the containerization of core network functions and the interfaces with radio access network protocols. In this thesis, one such stack, developed by the OpenAirInterface Software Alliance, was used to create a low-cost, simplified mobile network compatible with the Naval Operational Architecture. Commercial off-the-shelf user equipment was then connected to the network to demonstrate how a buffer overflow vulnerability found in Qualcomm Global Navigation Satellite System chipsets and identified as CVE-2019-2254 can be leveraged to enable a spoofed network attack. The research also yielded an extension of the attack method to 5G NR networks.http://archive.org/details/aplaceholderreco1094567451Lieutenant, United States NavyApproved for public release. Distribution is unlimited

    Solution of Optimal Power Flow Problems using Moment Relaxations Augmented with Objective Function Penalization

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    The optimal power flow (OPF) problem minimizes the operating cost of an electric power system. Applications of convex relaxation techniques to the non-convex OPF problem have been of recent interest, including work using the Lasserre hierarchy of "moment" relaxations to globally solve many OPF problems. By preprocessing the network model to eliminate low-impedance lines, this paper demonstrates the capability of the moment relaxations to globally solve large OPF problems that minimize active power losses for portions of several European power systems. Large problems with more general objective functions have thus far been computationally intractable for current formulations of the moment relaxations. To overcome this limitation, this paper proposes the combination of an objective function penalization with the moment relaxations. This combination yields feasible points with objective function values that are close to the global optimum of several large OPF problems. Compared to an existing penalization method, the combination of penalization and the moment relaxations eliminates the need to specify one of the penalty parameters and solves a broader class of problems.Comment: 8 pages, 1 figure, to appear in IEEE 54th Annual Conference on Decision and Control (CDC), 15-18 December 201

    A hybrid GA–PS–SQP method to solve power system valve-point economic dispatch problems

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    This study presents a new approach based on a hybrid algorithm consisting of Genetic Algorithm (GA), Pattern Search (PS) and Sequential Quadratic Programming (SQP) techniques to solve the well-known power system Economic dispatch problem (ED). GA is the main optimizer of the algorithm, whereas PS and SQP are used to fine tune the results of GA to increase confidence in the solution. For illustrative purposes, the algorithm has been applied to various test systems to assess its effectiveness. Furthermore, convergence characteristics and robustness of the proposed method have been explored through comparison with results reported in literature. The outcome is very encouraging and suggests that the hybrid GA–PS–SQP algorithm is very efficient in solving power system economic dispatch problem

    Content Distribution by Multiple Multicast Trees and Intersession Cooperation: Optimal Algorithms and Approximations

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    In traditional massive content distribution with multiple sessions, the sessions form separate overlay networks and operate independently, where some sessions may suffer from insufficient resources even though other sessions have excessive resources. To cope with this problem, we consider the universal swarming approach, which allows multiple sessions to cooperate with each other. We formulate the problem of finding the optimal resource allocation to maximize the sum of the session utilities and present a subgradient algorithm which converges to the optimal solution in the time-average sense. The solution involves an NP-hard subproblem of finding a minimum-cost Steiner tree. We cope with this difficulty by using a column generation method, which reduces the number of Steiner-tree computations. Furthermore, we allow the use of approximate solutions to the Steiner-tree subproblem. We show that the approximation ratio to the overall problem turns out to be no less than the reciprocal of the approximation ratio to the Steiner-tree subproblem. Simulation results demonstrate that universal swarming improves the performance of resource-poor sessions with negligible impact to resource-rich sessions. The proposed approach and algorithm are expected to be useful for infrastructure-based content distribution networks with long-lasting sessions and relatively stable network environment
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