The Experts below are selected from a list of 369546 Experts worldwide ranked by ideXlab platform
Tianfu Wu - One of the best experts on this subject based on the ideXlab platform.
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Learning Near-Optimal Cost-Sensitive Decision Policy for Object Detection
IEEE Transactions on Pattern Analysis and Machine Intelligence, 2015Co-Authors: Tianfu WuAbstract:Many popular object detectors, such as AdaBoost, SVM and deformable part-based models (DPM), compute additive scoring functions at a large number of windows in an image pyramid, thus computational efficiency is an important consideration in real time applications besides accuracy. In this paper, a Decision Policy refers to a sequence of two-sided thresholds to execute early reject and early accept based on the cumulative scores at each step. We formulate an empirical risk function as the weighted sum of the cost of computation and the loss of false alarm and missing detection. Then a Policy is said to be cost-sensitive and optimal if it minimizes the risk function. While the risk function is complex due to high-order correlations among the two-sided thresholds, we find that its upper bound can be optimized by dynamic programming efficiently. We show that the upper bound is very tight empirically and thus the resulting Policy is said to be near-optimal. In experiments, we show that the Decision Policy outperforms state-of-the-art cascade methods significantly, in several popular detection tasks and benchmarks, in terms of computational efficiency with similar accuracy of detection.
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Learning Near-Optimal Cost-Sensitive Decision Policy for Object Detection
2013 IEEE International Conference on Computer Vision, 2013Co-Authors: Tianfu WuAbstract:Many object detectors, such as AdaBoost, SVM and deformable part-based models (DPM), compute additive scoring functions at a large number of windows scanned over image pyramid, thus computational efficiency is an important consideration beside accuracy performance. In this paper, we present a framework of learning cost-sensitive Decision Policy which is a sequence of two-sided thresholds to execute early rejection or early acceptance based on the accumulative scores at each step. A Decision Policy is said to be optimal if it minimizes an empirical global risk function that sums over the loss of false negatives (FN) and false positives (FP), and the cost of computation. While the risk function is very complex due to high-order connections among the two-sided thresholds, we find its upper bound can be optimized by dynamic programming (DP) efficiently and thus say the learned Policy is near-optimal. Given the loss of FN and FP and the cost in three numbers, our method can produce a Policy on-the-fly for Adaboost, SVM and DPM. In experiments, we show that our Decision Policy outperforms state-of-the-art cascade methods significantly in terms of speed with similar accuracy performance.
Paola Zuddas - One of the best experts on this subject based on the ideXlab platform.
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a dss for water resources management under uncertainty by scenario analysis
Environmental Modelling and Software, 2005Co-Authors: Stefano Pallottino, Giovanni Maria Sechi, Paola ZuddasAbstract:In this paper we present a scenario analysis approach for water system planning and management under conditions of climatic and hydrological uncertainty. The scenario analysis approach examines a set of statistically independent hydrological scenarios, and exploits the inner structure of their temporal evolution in order to obtain a ''robust'' Decision Policy, so that the risk of wrong Decisions is minimised. In this approach uncertainty is modelled by a scenario-tree in a multistage environment, which includes different possible configurations of inflows in a wide time-horizon. In this paper we propose a Decision Support System (DSS) that performs scenario analysis by identifying trends and essential features on which to base a robust Decision Policy. The DSS prevents obsolescence of optimiser codes, exploiting standard data format, and a graphical interface provides easy data-input and results analysis for the user. Results show that scenario analysis could be an alternative approach to stochastic optimisation when no probabilistic rules can be adopted and deterministic models are inadequate to represent uncertainty. Moreover, experimentation for a real water resources system in Sardinia, Italy, shows that practitioners and end-users can adopt the DSS with ease.
Stefano Pallottino - One of the best experts on this subject based on the ideXlab platform.
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a dss for water resources management under uncertainty by scenario analysis
Environmental Modelling and Software, 2005Co-Authors: Stefano Pallottino, Giovanni Maria Sechi, Paola ZuddasAbstract:In this paper we present a scenario analysis approach for water system planning and management under conditions of climatic and hydrological uncertainty. The scenario analysis approach examines a set of statistically independent hydrological scenarios, and exploits the inner structure of their temporal evolution in order to obtain a ''robust'' Decision Policy, so that the risk of wrong Decisions is minimised. In this approach uncertainty is modelled by a scenario-tree in a multistage environment, which includes different possible configurations of inflows in a wide time-horizon. In this paper we propose a Decision Support System (DSS) that performs scenario analysis by identifying trends and essential features on which to base a robust Decision Policy. The DSS prevents obsolescence of optimiser codes, exploiting standard data format, and a graphical interface provides easy data-input and results analysis for the user. Results show that scenario analysis could be an alternative approach to stochastic optimisation when no probabilistic rules can be adopted and deterministic models are inadequate to represent uncertainty. Moreover, experimentation for a real water resources system in Sardinia, Italy, shows that practitioners and end-users can adopt the DSS with ease.
Christos Verikoukis - One of the best experts on this subject based on the ideXlab platform.
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a novel handover Decision Policy for reducing power transmissions in the two tier lte network
International Conference on Communications, 2012Co-Authors: Dionysis Xenakis, Nikos Passas, Christos VerikoukisAbstract:Femtocells are attracting a fast increasing interest nowadays, as a promising solution to improve indoor coverage, enhance system capacity, and lower transmit power. Technical challenges still remain, however, mainly including interference, security and mobility management, intercepting wide deployment and adoption from mobile operators and end users. This paper describes a novel handover Decision Policy for the two-tier LTE network, towards reducing power transmissions at the mobile terminal side. The proposed Policy is LTE backward-compatible, as it can be employed by suitably adapting the handover hysteresis margin with respect to a prescribed SINR target and standard LTE measurements. Simulation results reveal that compared to the widely-adopted strongest cell Policy, the proposed Policy can greatly reduce the power consumption at the LTE mobile terminals, and lower the interference network-wide.
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ICC - A novel handover Decision Policy for reducing power transmissions in the two-tier LTE network
2012 IEEE International Conference on Communications (ICC), 2012Co-Authors: Dionysis Xenakis, Nikos Passas, Christos VerikoukisAbstract:Femtocells are attracting a fast increasing interest nowadays, as a promising solution to improve indoor coverage, enhance system capacity, and lower transmit power. Technical challenges still remain, however, mainly including interference, security and mobility management, intercepting wide deployment and adoption from mobile operators and end users. This paper describes a novel handover Decision Policy for the two-tier LTE network, towards reducing power transmissions at the mobile terminal side. The proposed Policy is LTE backward-compatible, as it can be employed by suitably adapting the handover hysteresis margin with respect to a prescribed SINR target and standard LTE measurements. Simulation results reveal that compared to the widely-adopted strongest cell Policy, the proposed Policy can greatly reduce the power consumption at the LTE mobile terminals, and lower the interference network-wide.
Melvi Ulvan - One of the best experts on this subject based on the ideXlab platform.
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handover procedure and Decision strategy in lte based femtocell network
Telecommunication Systems, 2013Co-Authors: Ardian Ulvan, Robert Bestak, Melvi UlvanAbstract:Wireless systems have the capability to serve users over broad geographic area without using a costly network infrastructure. However, the main drawback of these systems represents the bandwidth restrictions and coverage. Deployment of femtocell as the emerging promising wireless access technology becomes one of possible solution how to overcome some of the drawbacks. In this paper, we investigate the handover procedure in femtocell network considering, both types of handovers, horizontal and vertical. The 3GPP LTE based handover procedure is analysed for three scenarios: hand-in, hand-out and inter-FAP. In addition, the reactive handover Decision Policy, based on the prediction of user movement and the prediction of target-FAP, is proposed as a way to eliminate frequent and unnecessary handovers.
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WMNC - The study of handover procedure in LTE-based femtocell network
WMNC2010, 2010Co-Authors: Ardian Ulvan, Robert Bestak, Melvi UlvanAbstract:Wireless systems have the capability to address broad geographic area without the costly infrastructure deployment. However, the main drawback resides in the bandwidth limitation and the coverage for single access point. The deployment of Femtocell as the promising wireless access technology becomes one of the possible solution. In this paper the handover procedure in femtocell network is studied. The 3GPP LTE based handover is analysed in three scenarios: hand-in, hand-out and inter-FAP. In addition, the reactive and proactive handover strategy is also proposed as the handover Decision Policy to diminish the very frequent and unnecessary handovers.
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handover scenario and procedure in lte based femtocell networks
Ubiquitous Computing Systems, 2010Co-Authors: Ardian Ulvan, Robert Bestak, Melvi UlvanAbstract:The deployment of Femtocell as the emerging wireless and mobile access technology becomes a solution for the bandwidth limitation and coverage issues in conventional mobile network system (macrocell). In this paper the handover procedure in femtocell network is investigated. The procedure is based on 3GPP LTE specification. Three handover scenarios: hand-in, hand-out and inter-FAP are considered and analysed. In order to achieve the optimize procedure, the handover Decision Policy based on mobility prediction is introduced and proposed. The reactive and proactive handover strategy is also proposed to mitigate the frequent and unnecessary handover. The result shows that reactive handover is the potential mechanism to mitigate the unnecessary handover.
