ICST

Displaying 161-200 of 239 results

  • White Papers // Jun 2011

    Distributed Channel Assignment Algorithm Based on Simulated Annealing for Uncoordinated OSA-Enabled WLANs

    A promising approach to alleviate ISM band congestion problems in highly dense WLAN scenarios consists of exploiting Opportunistic Spectrum Access (OSA) to underutilized bands under a primary-secondary model. This paper develops a distributed channel assignment algorithm valid for uncoordinated WLAN deployments where access points do not follow any specific planning...

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  • White Papers // Jun 2011

    Impact of Antenna Selection on Cognitive Radio System Capacity

    The authors examine the effect of transmit antenna selection on the Secondary User (SU) and Primary User (PU) capacity in a multiple-input single-output cognitive radio system. They consider antenna selection with the aim of improving SU and PU capacity and mitigating the effects of incomplete channel knowledge by the SU....

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  • White Papers // Jun 2011

    Contribution Based Cooperative Spectrum Sensing Against Malfunction Nodes in Cognitive Radio Networks

    In cognitive radio networks, secondary users can cooperate based on their own sensing observations so as to detect the primary user more accurately. However, since of location disadvantage, multipath fading or shadowing, sensing contribution of some secondary users may be untrustworthy, which are termed malfunction nodes in this paper. To...

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  • White Papers // Jun 2011

    Signal Separation and Reconstruction Method for Simultaneously Received Multi-System Signals in a Unified Wireless System

    These days, a wide variety of wireless systems are used and new wireless systems appear one after another on the market. In this paper, the authors proposed a unified wireless system that they call "Flexible wireless system". Comprising flexible access points and a flexible signal processing unit, it collectively receives...

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  • White Papers // Jun 2011

    A New Spectrum Sensing Scheme Using Overlap FFT Filter-Bank for Dynamic Spectrum Access

    A periodogram scheme, a multi-taper scheme, and a filter-bank scheme are proposed for spectrum sensing for dynamic spectrum access. The filter-bank scheme is advantageous in hardware implementation since the hardware required for communications can be reused for spectrum sensing. However, it is difficult for the conventional filter-bank scheme to change...

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  • White Papers // Jun 2011

    Low Complexity Cooperative Multicast Beamforming in Multiuser Multicell Downlink Networks

    This paper presents a low complexity sub-optimal algorithm for the max-min beamforming problem in multicell multicast transmission. The beam pattern is jointly optimized for all users inside a cell in a multicell scenario such that the Signal to Interference plus Noise Ratio (SINR) of the worst users is maximized subject...

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  • White Papers // Jun 2011

    Joint Coordinated Multicell Processing and MIMO: Selection of Base Stations and Gain

    In this paper, the authors provide the analysis of the downlink Coordinated Multiple Point (CoMP) used in conjunction with the basic MIMO. The CoMP is the joint multi-cell transmission from several BS to mobiles, coupled here to an open-loop MIMO technique that does not require the perfect channel state knowledge....

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  • White Papers // May 2011

    Automatic Protocol Signature Generation Framework for Deep Packet Inspection

    The authors present an automatic application protocol signature generating framework for Deep Packet Inspection (DPI) techniques with performance evaluation. They propose to utilize algorithms from the field of bioinformatics. They also present preprocessing methods to accelerate their system. Moreover, they developed several post-processing techniques to refine the accuracy of the...

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  • White Papers // May 2011

    HS-Measure : A Hybrid Clustering Validity Measure to Interpret Road Traffic Data

    Clustering validity measures aim to evaluate the goodness of clustering results in order to find the best partition. Results are obtained by varying the input parameters values. However, sometimes, the values generated by these measures are very close and the choice of the optimal value associated to the best partition...

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  • White Papers // May 2011

    Throughput and QoS Pricing in Wireless Communication

    In this paper, the authors investigate a bi-level economic model of wireless communications. They take into account the user's demand and also the QoS offered by the network. They determine with their model when a provider can make more pro t by investing into new technology. They consider a Stackelberg...

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  • White Papers // May 2011

    Uplink Power Control and Subcarrier Assignment for an OFDMA Multicellular Network Based on Game Theory

    This paper proposes an energy-efficient game-theoretic approach to the issue of resource allocation for the uplink of a multi-cellular OFDMA network. The problem is decoupled into subcarrier assignment and power control, assuming the data rates to be fixed for all subcarriers and all terminals in the network. To capture the...

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  • White Papers // May 2011

    A Positioning of Cooperative Differential Games

    In this paper, the authors embed the theory of cooperative differential games within the theory of dynamic games and discuss a number of results of them. Dynamic game theory brings together four features that are key to many situations in economy, ecology, and elsewhere: optimizing behavior, presence of multiple agents/players,...

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  • White Papers // May 2011

    A Self-Optimization Method for Coverage-Capacity Optimization in OFDMA Networks With MIMO

    Self-Organizing Networks (SON) is currently seen as a key lever to improve network performance and simplify its management. This paper considers ?-fair schedulers in an Orthogonal Frequency-Division-Multiple Access (OFDMA) network. The convergence of the ?-fair scheduler is analyzed. Closed-form formulas are given for certain cases to calculate the scheduling gain,...

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  • White Papers // May 2011

    K-Means and Adaptive K-Means Algorithms for Clustering DNS Traffic

    Internet Service Providers' DNS traffic can be up to 120000 queries per second and increases around 8% every month. DNSSEC is expected to replace DNS and brings new challenge to naming resolution with heavy signature check. This paper provides an architecture, where incoming DNS traffic is split according to the...

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  • White Papers // May 2011

    Worst-Case Delay Bounds With Fixed Priorities Using Network Calculus

    Worst-case delay bounds are an important issue for applications with hard-time constraints. Network calculus is a useful theory to study worst-case performance bounds in networks. In this paper, the authors focus on networks with a fixed priority service policy and provide methods to analyze systems where the traffic and the...

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  • White Papers // May 2011

    Distributed Stochastic Optimization for Constrained and Unconstrained Optimization

    In this paper, the authors analyze the convergence of a distributed Robbins-Monro algorithm for both constrained and unconstrained optimization in multi-agent systems. The algorithm searches local minima of a (non-convex) objective function which is supposed to coincide with a sum of local utility functions of the agents. The algorithm under...

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  • White Papers // May 2011

    Large-Scale Games in Large-Scale Systems

    Many real-world problems modeled by stochastic games have huge state and/or action spaces, leading to the well-known curse of dimensionality. The complexity of the analysis of large-scale systems is dramatically reduced by exploiting mean field limit and dynamical system viewpoints. Under regularity assumptions and specific time-scaling techniques, the evolution of...

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  • White Papers // May 2011

    HJB Approach for Motion Planning and Reachabilty Analysis

    Because of their importance in many applications, questions of path planning and reachability analysis for nonlinear dynamical systems have been studied extensively in the control theory. Here, the authors focus on the cases when the controlled systems are constrained to evolve in a certain known set (e.g., avoidance of obstacles)....

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  • White Papers // May 2011

    Stability and Asymptotic Optimality of Opportunistic Schedulers in Wireless Systems

    The authors investigate the scheduling of a common resource between several concurrent users when the feasible transmission rate of each user varies randomly over time. Time is slotted and users arrive and depart upon service completion. This may model for example the flow-level behavior of end-users in a narrowband HDR...

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  • White Papers // May 2011

    Continuous Polling With Rerouting and Applications to Ferry Assisted Wireless LANs

    In almost all studied continuous polling systems, the user leaves the system after his service is completed. There are interesting applications, in which the users demand a second service (or more). For example, in a ferry assisted wireless network, for every local data transfer the ferry has to collect the...

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  • White Papers // May 2011

    Deriving Generalised Stochastic Petri Net Performance Models From High-Precision Location Tracking Data

    Stochastic performance models have been widely used to analyze the performance and reliability of systems that involve the flow and processing of customers and/or resources with multiple service centres. However, the quality of performance analysis delivered by a model depends critically on the degree to which the model accurately represents...

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  • White Papers // May 2011

    Analytic Performance Evaluation of Oopportunistic Spectrum Access With Detection Errors

    This paper aims at giving some results on the performances of opportunistic spectrum access when taking into account sensing errors: non detection, which is the cause of collisions with a transmitting user, and false alarm, which is a cause of missed opportunity to access the channel. In a growing number...

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  • White Papers // May 2011

    Efficient Calculation of Rare Event Probabilities in Markovian Queueing Networks

    The authors address the computation of rare event probabilities in Markovian queueing networks with huge or possibly even infinite state spaces. For this purpose, they incorporate ideas from importance sampling simulations into a non-simulative numerical method that approximates transient probabilities based on a dynamical truncation of the state space. A...

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  • White Papers // May 2011

    Simulating Flow Level Bandwidth Sharing With Pareto Distributed File Sizes

    The authors' goal is to achieve deeper understanding of the limitation of queueing models, on one hand, and of common simulation practice, on the other hand, as tools for predicting performance of bandwidth sharing between competing TCP flows. In particular, they present an overview of simulation problems that are expected...

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  • White Papers // May 2011

    Joint Network/Channel Decoding for Heterogeneous Multi-Source/Multi-Relay Cooperative Networks

    In this paper, the authors study joint network/channel decoding for multi-source multi-relay heterogeneous wireless networks. When convolutional and network codes are used at the physical and network layers, respectively, they show that error correction and diversity properties of the whole network can be characterized by an equivalent and distributed convolutional...

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  • White Papers // May 2011

    Network Coding Schemes for the Multiple-Access Relay Channel

    The authors examine and compare four different Joint-Network-Channel-Codes (JNCC) and three reference systems for the Multiple-Access Relay Channel (MARC) with block Rayleigh fading channels for symmetric and asymmetric setups. Two of the JNCC's were presented previously in the literature and the other two are novel approaches. The JNCC's outperform the...

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  • White Papers // May 2011

    A Framework for Optimization Under Limited Information

    In many real world problems, optimization decisions have to be made often with limited information. The decision maker may have no a priori data about the (non-convex) objective function except from on a limited number of points that are obtained over time through costly observations. This paper presents an optimization...

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  • White Papers // May 2011

    Modeling Quantitative Requirements in SLAs With Network Calculus

    When planning Service-Oriented Architectures requirements declared in Service Level Agreements (SLAs) have to be considered. SLAs cover functional as well as quantitative requirements like load levels, services rates and delay times. As external factors can influence distributed systems, SLAs have to include tolerances for quantitative requirements. Early design phases of...

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  • White Papers // May 2011

    Centrality Maps and the Analysis of City Street Networks

    Firstly introduced in social science, the notion of centrality has spread to the whole complex network science. A centrality is a measure that quantifies whether an element of a network is well served or not, easy to reach, necessary to cross. This paper focuses on cities' street network (seen as...

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  • White Papers // May 2011

    Optimal Base Station Placement: A Stochastic Method Using Interference Gradient in Downlink Case

    In this paper, the authors study the optimal placement and optimal number of base stations added to an existing wireless data network through the interference gradient method. This proposed method considers a sub-region of the existing wireless data network, hereafter called region of interest. In this region, the provider wants...

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  • White Papers // May 2011

    Large-Deviations Analysis for Energy-Saving Mechanisms in Wireless Networks

    In wireless telecommunication networks, there is a strong interest in energy efficiency. Sleep-mode mechanisms, which temporarily switch off mobile devices or base stations, are popular means to attain this goal. The authors look at the performance of different sleep-mode mechanisms with large-deviations tools. These allow one to look at a...

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  • White Papers // May 2011

    More About Base Station Location Games

    This paper addresses the problem of locating base stations in a certain area which is highly populated by mobile stations; each mobile station is assumed to select the closest base station. Base stations are modeled by players who choose their best location for maximizing their uplink throughput. The approach of...

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  • White Papers // May 2011

    Learning to Use the Spectrum in Self-Configuring Heterogenous Networks: A Logit Equilibrium Approach

    In this paper, the authors study the particular scenario where several transmitter-receiver pairs communicate subject to mutual interference due to the usage of the same frequency bands. In particular, they focus on the case of heterogeneous networks, where radio devices have different interests (utility functions), transmit configurations (sets of actions),...

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  • White Papers // May 2011

    Revenue Maximization in Spectrum Auction for Dynamic Spectrum Access

    In this paper, the authors consider the revenue maximization problem in auctions for dynamic spectrum access. They assume a frequency division method of spectrum sharing with a primary spectrum owner that can divide the available spectrum into sub-bands and sell them to secondary users. They assume that a secondary user's...

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  • White Papers // May 2011

    Modeling Network Coded TCP Throughput: A Simple Model and Its Validation

    The authors analyze the performance of TCP and TCP with Network Coding (TCP/NC) in lossy wireless networks. They build upon the simple framework introduced by Padhye et al. and characterize the throughput behavior of classical TCP as well as TCP/NC as a function of erasure rate, roundtrip time, maximum window...

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  • White Papers // May 2011

    A Symbolic Approach to Quantitative Analysis of Preemptive Real-Time Systems With Non-Markovian Temporal Parameters

    The method of stochastic state classes provides a means for quantitative analysis of a rather wide class of non-Markovian models. As a major and structural limitation, the approach cannot be applied to models encompassing a preemptive policy, which in the practice rules out the mechanism of suspension and resume usually...

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  • White Papers // May 2011

    Socially Optimal Pricing of Cloud Computing Resources

    The cloud computing paradigm offers easily accessible computing resources of variable size and capabilities. The authors consider a cloud-computing facility that provides simultaneous service to a heterogeneous, time-varying population of users, each associated with a distinct job. Both the completion time, as well as the user's utility, may depend on...

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  • White Papers // May 2011

    HASL: An Expressive Language for Statistical Verification of Stochastic Models

    The authors introduce the Hybrid Automata Stochastic Logic (HASL), a new temporal logic formalism for the verification of Discrete Event Stochastic Processes (DESP). HASL employs Linear Hybrid Automata (LHA) as machineries to select prefixes of relevant execution paths of a DESP. The advantage with LHA is that rather elaborate information...

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  • White Papers // May 2011

    On Distributed Power Control and Transceiver Optimization in Wireless Networks

    This paper outlines some recent results on the max-min SIR balancing problem in wireless networks in which power control and beamforming are the only mechanisms for resource allocation and interference management. In addition, the authors describe several potential extensions and improvements to existing algorithmic solutions, as well as prove the...

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  • White Papers // May 2011

    A Survey on YouTube Streaming Service

    Established in 2005, YouTube is one of the fastest-growing websites, and has become one of the most accessed sites in the Internet. It has a significant impact on the Internet traffic distribution, but itself is suffering from severe scalability constraints and quality of service. Understanding the features of YouTube is...

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