Parallel computation of the singular value decomposition

The goal of this survey is to give a view of the state-of-the-art of computing the Singular Value Decomposition (SVD) of dense and sparse matrices, with some emphasis on those schemes that are suitable for parallel computing platforms. For dense matrices, we survey those schemes that yield the complete decomposition, whereas for sparse matrices we survey schemes that yield only the extremal singular triplets. Special attention is devoted to the computation of the smallest singular values which are normally the most difficult to evaluate but which provide a measure of the distance to singularity of the matrix under consideration. Also, a parallel method for computing pseudospectra, which depends on computing the smallest singular values, is presented at the conclusion of the survey

Survey of ICIC Techniques in LTE Networks under Various Mobile Environment Parameters

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PAT- a Reliable Path Following Algorithm

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Résolution de systèmes linéaires issus de la discrétisation d'une équation de Navier-Stokes

On étudie dans ce rapport le système linéaire issu de la modélisation d'un phénomène d'eutrophisation de bassin. On y compare des méthodes de relaxation par bloc et des méthodes de type gradient conjugué. Les préconditionnements introduits sont des décompositions incomplètes de Choleski

A Novel Dynamic Inter-Cell Interference Coordination Technique for LTE Networks

International audienceInter-cell interference problems arise in dense frequency reuse networks such as Long Term Evolution (LTE). They have harmful impact on system performance, especially for cell-edge users or users having bad radio conditions. Inter-Cell Interference Coordination (ICIC) schemes aim at mitigating the interference produced by nearby cells to enhance the performance of cell-edge users. ICIC techniques include static frequency reuse schemes and cell-coordinated schemes. In this paper, we propose a semi-static frequency allocation algorithm that exploits evolved-NodeBs communications via X2 interface to mitigate inter-cell interference. Each cell is divided into two zones: cell-center and cell-edge. Cell zone satisfaction is tracked, and the unsatisfied zone gets more frequency resource blocks in a distributed manner. The scope of this work is on the downlink of LTE networks using frequency division duplex transmission mode. An LTE downlink system level simulator is chosen to compare the performance of the proposed technique with the frequency reuse-1 model and the fractional frequency reuse technique. Simulation results show that our technique improves throughput cumulative distribution function, achieves a better throughput fairness, and reduces the percentage of unsatisfied users. It is a dynamic technique able to adapt with non-uniform user distributions and traffic demands

Non Cooperative Inter-Cell Interference Coordination Technique for Increasing Throughput Fairness in LTE Networks

International audienceOne major concern for operators of Long Term Evolution (LTE) networks is mitigating inter-cell interference problems. Inter-Cell Interference Coordination (ICIC) techniques are proposed to reduce performance degradation and to maximize system capacity. It is a joint resource allocation and power allocation problem that aims at controlling the trade-off between resource efficiency and user fairness. Traditional interference mitigation techniques are Fractional Frequency Reuse (FFR) and Soft Frequency Reuse (SFR). FFR statically divides the available spectrum into reuse-1 and reuse-3 portions in order to protect cell-edge users, while SFR reduces downlink transmission power allocated for cell-center resources to protect vulnerable users in the neighboring cells. However, these static techniques are not adapted to non-uniform user distribution scenarios, and they do not provide guarantees on throughput fairness between user equipments. In this paper, we introduce a non-cooperative dynamic ICIC technique that dynamically adjusts resource block allocation according to user demands in each zone. We investigate the impact of this technique on throughput distribution and user fairness under non-uniform user distributions, using an LTE downlink system level simulator. Simulation results show that the proposed technique improves system capacity, and increases throughput fairness in comparison with reuse-1 model, FFR and SFR. It does not require any cooperation between base stations of the LTE network

Cooperative Resource Management and Power Allocation for Multiuser OFDMA Networks

International audienceMobile network operators are facing the challenge to increase network capacity and satisfy the growth in data traffic demands. In this context, Long Term Evolution (LTE) networks, LTE-Advanced networks, and future mobile networks of the Fifth Generation seek to maximize spectrum profitability by choosing the frequency reuse-1 model. Due to this frequency usage model, advanced radio resource management and power allocation schemes are required to avoid the negative impact of interference on system performance. Some of these schemes modify resource allocation between network cells, while others adjust both resource and power allocation. In this article, we introduce a cooperative distributed interference management algorithm, where resource and power allocation decisions are jointly made by each cell in collaboration with its neighboring cells. Objectives sought are: increasing user satisfaction, improving system throughput, and increasing energy efficiency. The proposed technique is compared to the frequency reuse-1 model and to other state-of-the-art techniques under uniform and non-uniform user distributions and for different network loads. We address scenarios where throughput demands are homogeneous and non-homogeneous between network cells. System-level simulation results demonstrate that our technique succeeds in achieving the desired objectives under various user distributions and throughput demands

A Hybrid Approach for Radio Access Technology Selection in Heterogeneous Wireless Networks

International audienceIn heterogeneous wireless networks, different radio access technologies are integrated and may be jointly managed. To optimize network performance and capacity, efficient Common Radio Resource Management (CRRM) mechanisms need to be defined. This paper tackles the Radio Access Technology (RAT) selection, a key CRRM functionality, and proposes a hybrid decision framework that dynamically integrates operator objectives and user preferences. Mobile users are assisted in their decisions by the network that broadcasts cost and QoS information. Our hybrid approach involves two interdependent decision-making processes. The first one, on the network side, consists in deriving appropriate network information so as to guide user decisions in a way to meet operator objectives. The second one, where individual users combine their needs and preferences with the signaled network information, consists in selecting the RAT to be associated with in a way to maximize user utility. We first focus on the user side and present a satisfaction-based multi-criteria decision-making method. By avoiding inadequate decisions, our algorithm outperforms existing solutions and maximizes user utility. Further, we introduce two heuristic methods, namely the staircase and the slope tuning policies, to dynamically derive network information in a way to enhance resource utilization. The performance of each decision-making process, on network and user sides, is evaluated separately through extensive simulations. A comparison of our hybrid approach with six different RAT selection schemes is also presented

Classification and Comparative Analysis of Inter-Cell Interference Coordination Techniques in LTE Networks

International audienceFrequency reuse-1 model is required to satisfy the exponential increase of data demands in mobile networks , such as the Long Term Evolution (LTE) of Universal Mobile Terrestrial radio access System (UMTS). However, the simultaneous usage of the same frequency resources in adjacent LTE cells creates inter-cell interference problems, that mainly affect cell-edge users. Inter-Cell Interference Coordination (ICIC) techniques are proposed to avoid the negative impact of interference on system performance. They establish restrictions on resource usage, such as Fractional Frequency Reuse (FFR), and on power allocation such as Soft Frequency Reuse (SFR). In this paper, we classify the existing ICIC techniques, and investigate the performance of reuse-1, reuse-3, FFR, and SFR schemes under various user distributions, and for various network loads. Performance of cell-center and cell-edge users are inspected, as well as the overall spectral efficiency. System level simulations show the advantages and limitations of each of the examined techniques compared to frequency reuse-1 model under different network loads and user distributions, which helps us to determine the most suitable ICIC technique to be used

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International audienceMultiuser Orthogonal Frequency Division Multiple Access (OFDMA) networks, such as Long Term Evolution networks , use the frequency reuse-1 model to face the tremendous increase of mobile traffic demands, and to increase network capacity. However, inter-cell interference problems are generated, and they have a negative impact on cell-edge users performance. Resource and power allocation should be managed in a manner that alleviates the negative impact of inter-cell interference on system performance. In this paper, we formulate a novel centralized multi-cell resource and power allocation problem for multiuser OFDMA networks. The objective is to maximize system throughput while guaranteeing a proportional fair rate for all the users. We decompose the joint problem into two independent problems: a resource allocation problem and a power allocation problem. We prove that each of these problems is a convex optimization problem, and that their optimal solution is also an optimal solution to the original joint problem. Lagrange duality theory and subgradient projection method are used to solve the centralized power allocation problem. We study the convergence of our centralized approach, and we find out that it reduces inter-cell interference, and increases system throughput and spectral efficiency in comparison with the frequency reuse-1 model, reuse-3 model, fractional frequency reuse, and soft frequency reuse techniques