Faculty of Engineering
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Publication Open Access Robustness of digital filters with respect to limit-cycle behavior under coefficient perturbations(International Society for Optics and Photonics, 1996-06-07) Kulasekere, E. C; Premaratne, K; Bauer, P. HA digital filter which has been designed to be limit cycle free may exhibit limit cycles at the implementation stage. This is due to the inability to implement filter coefficients exactly in hardware when they are quantized to satisfy available wordlength requirements. Given a digital filter which is limit cycle free under zero input conditions, the work below presents an algorithm which finds a region in the coefficient space, about the nominal filter coefficient values, where in the filter remains limit cycle free. Furthermore the results of the algorithm will also indicate the availability of other machine representable numbers for the coefficients that fall within this robustness region. Hence one may even choose shorter wordlength registers for coefficient storage if the corresponding grid falls within the constructed robustness region.Publication Embargo Resource management of task oriented distributed sensor networks(IEEE, 2001-05-06) Zhang, J; Kulasekere, E. C; Premaratne, K; Bauer, P. HIn this paper we provide a foundation for a unified analysis of both the decision fusion and congestion avoidance aspects of a task-oriented distributed sensor network (DSN). Such a framework allows network resource management to be carried out in a manner that is sensitive to the overall objectives of the DSN rather than decoupling them via perhaps simple fairness strategies. The proposed approach associates importance measures related to the degradation and relevance of incoming data lines at each network node. These are then used to carry out intelligent resource management and avoid congestion in a manner which is implicitly related to the decision objectives of the DSN and explicitly related to the resource availability. To achieve this, we propose a 'per-flow' technique that decouples data flow among nodes at different hierarchical levels of the DSN. The resulting framework allows seamless integration of the importance measures providing resource management decisions that are sensitive to the overall DSN objectives.Publication Embargo An exhaustive search algorithm for checking limit cycle behavior of digital filters(IEEE, 1996-10) Premaratne, K; Kulasekere, E. C; Bauer, P. H; Leclerc, L. JThe presence of limit cycles that may arise in fixed-point arithmetic implementation of a digital filter can significantly impair its performance. This paper presents an algorithm to determine the presence/absence of such limit cycles. For generality, the filter is taken to be in its state-space formulation. The algorithm is applicable independent of filter order, type of quantization nonlinearity, and whether the accumulator is single or double length. It may be utilized to construct limit cycle free regions in filter coefficient space. Once a filter is determined to be limit cycle free, a technique that provides a robustness region in coefficient space where all filters remain limit cycle free is also presented.Publication Embargo Conditioning and updating evidence(Elsevier, 2004-04-01) Kulasekere, E. C; Premaratne, K; Dewasurendra, D. A; Shyu, M. L; Bauer, P. HA new interpretation of Dempster–Shafer conditional notions based directly upon the mass assignments is provided. The masses of those propositions that may imply the complement of the conditioning proposition are shown to be completely annulled by the conditioning operation; conditioning may then be construed as a re-distribution of the masses of some of these propositions to those that definitely imply the conditioning proposition. A complete characterization of the propositions whose masses are annulled without re-distribution, annulled with re-distribution and enhanced by the re-distribution of masses is provided. A new evidence updating strategy that is composed of a linear combination of the available evidence and the conditional evidence is also proposed. It enables one to account for the integrity’ and inertia’ of the available evidence and its flexibility’ to updating by appropriate selection of the linear combination weights. Several such strategies, including one that has a probabilistic interpretation, are also provided. 2003 Elsevier Inc. All rights reserved.