Kamal Premaratne

The mobile patient: wireless distributed sensor networks for patient monitoring and care

The concept of a three layer distributed sensor network for patient monitoring and care is introduced. The envisioned network has a leaf node layer (consisting of patient sensors), an intermediate node layer (consisting of the supervisory processor residing with each patient) and the root node processor (residing at a central monitoring facility). The paradigm has the capability of dealing with the bandwidth bottleneck at the wireless patient-root node link and the processing bottleneck at the central processor or root node of the network.

A necessary and sufficient condition for robust asymptotic stability of time-variant discrete systems

A necessary and sufficient condition for the stability of time-variant interval matrices is presented. This condition allows stability to be tested by checking only products of vertex (extreme) matrices. The implementation of the test in the form of an algorithm and two illustrative examples are provided. >

Conditioning and updating evidence

Abstract A 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.

An algorithm for model reduction of 2-D discrete time systems

In the context of model reduction of 2-D discrete time systems, several important properties of 2-D Gramians and balanced realizations are presented. Through a counterexample, the conjecture that the reduced model preserves stability is proven invalid. For separable systems, several interesting results regarding Gramians, norms, stability, and minimality are presented. For nonseparable systems, a simple, more efficient technique to compute Gramians is provided. The computation of Gramians in the separable case is possible through the solution of two pairs of discrete Lyapunov equations. An example is given to illustrate and justify the notions presented. >

Rule Mining and Classification in a Situation Assessment Application: A Belief-Theoretic Approach for Handling Data Imperfections

Management of data imprecision and uncertainty has become increasingly important, especially in situation awareness and assessment applications where reliability of the decision-making process is critical (e.g., in military battlefields). These applications require the following: 1) an effective methodology for modeling data imperfections and 2) procedures for enabling knowledge discovery and quantifying and propagating partial or incomplete knowledge throughout the decision-making process. In this paper, using a Dempster-Shafer belief-theoretic relational database (DS-DB) that can conveniently represent a wider class of data imperfections, an association rule mining (ARM)-based classification algorithm possessing the desirable functionality is proposed. For this purpose, various ARM-related notions are revisited so that they could be applied in the presence of data imperfections. A data structure called belief itemset tree is used to efficiently extract frequent itemsets and generate association rules from the proposed DS-DB. This set of rules is used as the basis on which an unknown data record, whose attributes are represented via belief functions, is classified. These algorithms are validated on a simplified situation assessment scenario where sensor observations may have caused data imperfections in both attribute values and class labels.

Model reduction of two-dimensional discrete systems

In this paper the one-dimensional (1-D) reduction method of Badreddin-Mansour is extended to two-dimensional (2-D) discrete systems. It is found by counterexample that contrary to the 1-D case, stability is not guaranteed, for the reduced model, in general. However, stability is guaranteed for the reduced model if the original system is stable, in the following two cases: (1) the original system is of the separable type; and/or (2) the original system is of dimension one in each of the horizontally and vertically propagation sections, i.e., a lh-lv system. Several examples are given to illustrate the reduction procedure, and its effect on stability.

Total delay compensation in LAN control systems and implications for scheduling

In the first part of this paper it is shown that long access delays are not necessarily detrimental to the stability of local area network embedded control systems. In the second part we show that (under some mild conditions on the control system) scheduling in the return path is not needed. This is a consequence of the fact that for local area networks the access delays can be exactly determined and completely eliminated from the system representation.

Robust stability of time-variant interval matrices

The stability of time-variant discrete interval matrices is analyzed, and conditions for asymptotic as well as bounded-input bounded-output stability are derived, making it necessary to test the Schur-stability of one of the 2/sup n*/ corner matrices. For certain classes of interval matrices this condition becomes necessary and sufficient.<<ETX>>

Delta-operator formulated discrete-time approximations of continuous-time systems

Given a continuous-time system, a technique to directly obtain an approximate delta-operator formulated discrete-time system (/spl delta/-system) is presented. For this purpose, the analog of the well known Boxer-Thaler integrators (q-forms) applicable to shift-operator formulated discrete-time systems (q-systems) are derived for /spl delta/-systems. Next, using these /spl delta/-forms, a method to obtain an approximate /spl delta/-system of a given continuous-time system is derived. This algorithm is easily implementable in a computer with little computational burden. It is shown that, as sampling time decreases, the /spl delta/-system thus obtained yields the given continuous-time system further verifying the close equivalence between this formulation and continuous-time systems. Two examples illustrating advantages that may be gained by utilizing these /spl delta/-forms in digitizing analog systems are also included. >

Evidence Combination in an Environment With Heterogeneous Sources

A framework for the combination of evidence in an environment where data are generated from heterogeneous sources possessing partial or incomplete knowledge about the global network scenario is presented. The approach taken is based on the conditional belief and plausibility notions in Dempster-Shafer evidence theory that allow one to condition these partial knowledge bases so that only that portion of the incoming evidence that is relevant is utilized for updating an existing knowledge base. The strategy proposed enables one to accommodate some of the most challenging, yet essential, features that are encountered when evidence is generated from possibly a large numbers of sources. These include heterogeneity and reliability of incoming evidence, inertia and integrity of evidence already gathered, and potentially limited resources at the nodes where evidence updating is carried out. The proposed framework is applied in robot map discovery using ultrasonic sensors and a real-world scenario where sensor data generated by heterogeneous sensors are used for potential threat carrier-type detection