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Beygi A.,Evertz Microsystems | Dounavis A.,University of Western Ontario
IEEE Transactions on Microwave Theory and Techniques | Year: 2012

This paper presents an efficient methodology to improve the convergence properties of vector fitting (VF) when the frequency data is contaminated by noise. The proposed algorithm uses an instrumental variable approach, which minimizes the biasing effect of the least squares solution caused by the noise of the data samples. These instruments are generated using the rational approximation of the previous iteration and does not increase the computational complexity of the VF algorithm. Numerical examples are provided to illustrate the validity of the proposed method. © 1963-2012 IEEE.

Pike L.,Galois, Inc. | Wegmann N.,Copenhagen University | Niller S.,Evertz Microsystems | Goodloe A.,NASA
Innovations in Systems and Software Engineering | Year: 2013

Runtime verification (RV) is a natural fit for ultra-critical systems that require correct software behavior. Due to the low reliability of commodity hardware and the adversity of operational environments, it is common in ultra-critical systems to replicate processing units (and their hosted software) and incorporate fault-tolerant algorithms to compare the outputs, even if the software is considered to be fault-free. In this paper, we investigate the use of software monitoring in distributed fault-tolerant systems and the implementation of fault-tolerance mechanisms using RV techniques. We describe the Copilot language and compiler that generates monitors for distributed real-time systems, and we discuss two case-studies in which Copilot-generated monitors were used to detect onboard software and hardware faults and monitor air-ground data link messaging protocols. © 2013 Springer-Verlag London.

Roy S.,University of Western Ontario | Beygi A.,Evertz Microsystems | Dounavis A.,University of Western Ontario
IEEE Transactions on Electromagnetic Compatibility | Year: 2013

With the use of low powered devices, susceptibility of high-speed interconnects to electromagnetic interference (EMI) is becoming a critical aspect of signal integrity analysis. For modeling the EMI in time domain, commercial circuit simulators like SPICE typically use longitudinal segmentation methodologies to discretize the interconnect network. For long lines as found in printed circuit board or cables, a large number of longitudinal segments are required to capture the response of the network leading to inefficient simulations. In this study, a waveform relaxation (WR) algorithm for the efficient EMI analysis of multiconductor transmission line networks is presented. Techniques to compress the size of the subcircuits, reduce communication overheads, and accelerate the convergence of the WR iterations are provided. The overall algorithm is demonstrated to be highly parallelizable and exhibits good scaling with both the size of the network involved and the number of central processing units available. © 1964-2012 IEEE.

Dumitrescu S.,McMaster University | Rivers G.,Evertz Microsystems | Shirani S.,McMaster University
IEEE Transactions on Image Processing | Year: 2010

This paper presents a novel unequal erasure protection (UEP) strategy for the transmission of scalable data, formed by interleaving independently decodable and scalable streams, over packet erasure networks. The technique, termed multistream UEP (M-UEP), differs from the traditional UEP strategy by: 1) placing separate streams in separate packets to establish independence and 2) using permuted systematic ReedSolomon codes to enhance the distribution of message symbols amongst the packets. M-UEP improves upon UEP by ensuring that all received source symbols are decoded. The R-D optimal redundancy allocation problem for M-UEP is formulated and its globally optimal solution is shown to have a time complexity of O(2N N(L+1)N+1), where N is the number of packets and L is the packet length. To address the high complexity of the globally optimal solution, an efficient suboptimal algorithm is proposed which runs in O(N 2 L2) time. The proposed M-UEP algorithm is applied on SPIHT coded images in conjunction with an appropriate grouping of wavelet coefficients into streams. The experimental results reveal that M-UEP consistently outperforms the traditional UEP reaching peak improvements of 0.6 dB. Moreover, our tests show that M-UEP is more robust than UEP in adverse channel conditions. © 2010 IEEE.

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