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Electrical and Computer Engineering, Canadian Journal of

Issue 4 • Date Fall 2009

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Displaying Results 1 - 9 of 9
  • Canadian Journal of Electrical and Computer Engineering - Front cover

    Publication Year: 2009 , Page(s): c1 - c4
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    Freely Available from IEEE
  • Table of contents

    Publication Year: 2009 , Page(s): 1
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    Freely Available from IEEE
  • Guest editorial: Special issue on the 2009 IEEE Pacific Rim Conference on Communications, Computers and Signal Processing

    Publication Year: 2009 , Page(s): 134 - 135
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    Freely Available from IEEE
  • Fast group sparse classification

    Publication Year: 2009 , Page(s): 136 - 144
    Cited by:  Papers (5)
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    A recent work proposed a novel Group Sparse Classifier (GSC) that was based on the assumption that the training samples of a particular class approximately form a linear basis for any test sample belonging to that class. The Group Sparse Classifier requires solving an NP hard group-sparsity promoting optimization problem. Thus a convex relaxation of the optimization problem was proposed. The convex optimization problem, however, needs to be solved by quadratic programming and hence requires a large amount of computational time. To overcome this, we propose novel greedy (sub-optimal) algorithms for directly addressing the NP hard minimization problem. We call the classifiers based on these greedy group sparsity promoting algorithms as Fast Group Sparse Classifiers (FGSC). This work shows that the FGSC has nearly the same accuracy (at 95% confidence level) as the GSC, but with much faster computational speed (nearly two orders of magnitude). When certain conditions hold the GSC and the FGSC are robust to dimensionality reduction via random projection. By robust, we mean that the classification accuracy is approximately the same before and after random projection. The robustness of these classifi ers will be theoretically proved, and will be validated by thorough experimentation. View full abstract»

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  • Towards global design of orthogonal filter banks and wavelets

    Publication Year: 2009 , Page(s): 145 - 151
    Cited by:  Papers (1)
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    This paper investigates several design issues concerning two-channel conjugate quadrature (CQ) filter banks and orthogonal wavelets. It is well known that optimal designs of CQ filters and wavelets in the least squares (LS) or minimax sense are nonconvex problems and to date only local solutions can be claimed. By virtue of recent progress in global polynomial optimization and a direct design technique for CQ filters, we in this paper present a design strategy that may be viewed as our endeavors towards global solutions for CQ filters. Two design scenarios are considered, namely the least squares designs with vanishing moment (VM) requirement, and equiripple (i.e. minimax) designs with VM requirement. Simulation studies are presented to verify our design concept for both LS and minimax designs of low-order CQ filters, and to evaluate and compare the proposed algorithms with existing design algorithms for high-order CQ filters. View full abstract»

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  • High-performance, low-power architecture for scalable radix 2 montgomery modular multiplication algorithm

    Publication Year: 2009 , Page(s): 152 - 157
    Cited by:  Papers (1)
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    This paper presents a new processor array architecture for scalable radix 2 Montgomery modular multiplication algorithm. In this architecture, the multiplicand and the modulus words are allocated to each processing element rather than pipelined between the processing elements as in the previous architecture extracted by C. Koc. Also, the multiplier bits are fed serially to the first processing element of the processor array every odd clock cycle. By analyzing this architecture, we found that it has a better performance-in terms of area and speed-and lower power consumption than the previous architecture extracted by Ç. Koç. View full abstract»

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  • CLASS: a general approach to classifying categorical sequences

    Publication Year: 2009 , Page(s): 158 - 166
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    The rapid burgeoning of available data in the form of categorical sequences, such as biological sequences, natural language texts, network and retail transactions, makes the classification of categorical sequences increasingly important. The main challenge is to identify significant features hidden behind the chronological and structural dependencies characterizing their intrinsic properties. Almost all existing algorithms designed to perform this task are based on the matching of patterns in chronological order, but categorical sequences often have similar features in non-chronological order. In addition, these algorithms have serious difficulties in outperforming domain-specific algorithms. In this paper we propose CLASS, a general approach for the classification of categorical sequences. By using an effective matching scheme called SPM for Significant Patterns Matching, CLASS is able to capture the intrinsic properties of categorical sequences. Furthermore, the use of Latent Semantic Analysis allows capturing semantic relations using global information extracted from large number of sequences, rather than comparing merely pairs of sequences. Moreover, CLASS employs a classifier called SNN for Significant Nearest Neighbours, inspired from the K Nearest Neighbours approach with a dynamic estimation of K, which allows the reduction of both false positives and false negatives in the classification. The extensive tests performed on a range of datasets from different fields show that CLASS is oftentimes competitive with domain-specific approaches. View full abstract»

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  • Pairwise optimization of modulation constellations for non-uniform sources

    Publication Year: 2009 , Page(s): 167 - 177
    Cited by:  Papers (1)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (579 KB)  

    The design of two-dimensional signal constellations for the transmission of binary non-uniform memoryless sources over additive white Gaussian noise channels is investigated. The main application of this problem is the implementation of improved constellations where transmitted data is highly non-uniform. A simple algorithm, which optimizes a constellation by re-arranging its points in a pairwise fashion (i.e., two points are modified at a time, with all other points remaining fixed), is presented. In general, the optimized constellations depend on both the source statistics and the signal-to-noise ratio (SNR) in the channel. We show that constellations designed with source statistics considered can yield symbol error rate (SER) performance that is substantially better than rectangular quadrature amplitude modulation signal sets used with either Gray mapping or more recently developed maps. SER gains as high as 5 dB in Eb/No SNR are obtained for highly non-uniform sources. Symbol mappings are also developed for the new constellations using a similar pairwise optimization method whereby we assign and compare a weighted score for each pair. These maps, when compared to the mappings used in conjunction with the standard rectangular QAM constellation, again achieve considerable performance gains in terms of bit error rate (BER). Gains as high as 4 dB were achieved over rectangular QAM with Gray mapping, or more than 1 dB better than previously improved mappings. Finally, the uncoded pairwise optimized system is compared to a standard tandem (separate) source and channel coding system. Although neither system is universally better, the uncoded system with optimized constellations outperforms the tandem coding system for low-to-mid SNRs. Performance/complexity trade-off s between the two systems are also discussed. View full abstract»

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  • Time domain spreading and frequency domain maximal ratio combining reception for frequency diversity enhancement in single carrier UWB communication systems

    Publication Year: 2009 , Page(s): 178 - 184
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (670 KB)  

    Ultra-wideband technology is a promising candidate for short-range broadband communication systems. Ultra-wideband channels are characterized by dense multiple paths that provide multipath diversity, also referred to as frequency diversity. Single carrier systems with frequency domain equalization have attracted much interest for high data rate communications. In this paper, frequency diversity in single carrier ultra-wideband systems is enhanced by employing simple frequency domain maximal ratio combining (FDMRC) reception with time domain complex quadratic spreading (CQS) sequences. Since ultra-wideband channels exhibit dense multiple paths and strong frequency selectivity, the proposed system can attain significant performance improvement over traditional single carrier frequency domain equalization (SC-FDE) systems. Through the comparison of the impact of the cyclic prefix length, the proposed system shows stronger robustness to inter-block interference than the conventional SC-FDE system. Compared with multicarrier systems, like orthogonal frequency-division multiplexing and multi-carrier code division multiple access, the proposed receiver complexity is reduced greatly. To accommodate multiuser communication, block spreading is further introduced to combine with the frequency diversity enhancement technique for single carrier block transmission UWB systems, realizing multiuser interference-free reception. View full abstract»

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Aims & Scope

The role of the Canadian Journal of Electrical and Computer Engineering is to provide scientific and professional activity for its members in Canada, the CJECE complements international journals and will be of particular interest to anyone involved in research and development activities in the field of electrical and computer engineering.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Dr. Shahram Yousefi
Dept. of Electrical and Computer
     Engineering
Queen's University