Publications

Gerber, R & Braun, R 1998, New Connections Telecommunications in a Changing South Africa, University of Cape Town Press (ZA).
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Written for students as well as business managers in telecommunications industries, this book investigates the telecommunications sector worldwide, and includes a detailed study of the South African perspective.

Abry, P & Veitch, D 1998, 'Wavelet analysis of long-range-dependent traffic', Information Theory, IEEE Transactions on, vol. 44, pp. 2-15.

Abry, P, Veitch, D & Flandrin, P 1998, 'Long-range Dependence: Revisiting Aggregation with Wavelets', Journal of Time Series Analysis, vol. 19, pp. 253-266.

Aslund, M, Canning, J & Bazylenko, M 1998, 'High-temperature stable gratings in germanosilicate planar waveguides', OPTICS LETTERS, vol. 23, no. 24, pp. 1898-1900.
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Auzanneau, F & Ziolkowski, RW 1998, 'Microwave signal rectification using artificial composite materials composed of diode-loaded electrically small dipole antennas', IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, vol. 46, no. 11, pp. 1628-1637.
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Auzanneau, F & Ziolkowski, RW 1998, 'Theoretical study of synthetic bianisotropic materials', JOURNAL OF ELECTROMAGNETIC WAVES AND APPLICATIONS, vol. 12, no. 3, pp. 353-370.
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Bateman, D, Bird, T & Sanagavarapu, AM 1998, 'Asymptotic Approximation Of Some Integrals Involved In Efie Solutions Using The Method Of Moments', IEE Proceedings-microwaves Antennas And Propagation, vol. 145, no. 4, pp. 361-365.
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It is well known that, in electromagnetic-field analysis using the method of moments, the matrix-filling time can dominate the total solution time. Therefore, having an efficient means of calculating the elements of the matrix is important. Asymptotic an

Bazylenko, MV, Moss, D & Canning, J 1998, 'Complex photosensitivity observed in germanosilica planar waveguides', OPTICS LETTERS, vol. 23, no. 9, pp. 697-699.
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Butchart, K & Braun, RM 1998, 'Adaptive modulation scheme for Low Earth Orbit satellites', Proceedings of the South African Symposium on Communications and Signal Processing, COMSIG, pp. 43-46.
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LEO satellites present widely varying signal conditions. Fixed modulation schemes are designed for the worst operating conditions and cannot take advantage of the better signal to noise conditions present at high elevations. An adaptive modulation scheme, which used different constellation patterns with trellis coded modulation and a Reed Solomon Code outer code is proposed. The system is tested under AWGN noise and Rician/Rayleigh fading conditions. The system is found to provide good performance in AWGN and moderate fading conditions.

Canning, J & Moss, D 1998, 'Grating-based transmission bandpass filters using dispersion-matched mode conversion', OPTICS LETTERS, vol. 23, no. 3, pp. 174-176.
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Canning, J, Moss, D, Aslund, M & Bazylenko, M 1998, 'Negative index gratings in germanosilicate planar waveguides', ELECTRONICS LETTERS, vol. 34, no. 4, pp. 366-367.
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Cucchiara, R, Neri, G & Piccardi, M 1998, 'A Real-time Hardware Implementation Of The Hough Transform', Journal Of Systems Architecture, vol. 45, no. 1, pp. 31-45.
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The paper presents a hardware implementation of algorithms based on the Hough transform (HT) for real-time straight line detection. In particular, the basic HT on the edge points (EHT) and the Gradient-Weighted Hough transform (GWHT) for gray-level image

Cuthbert, J & Braun, RM 1998, 'Selection Of Multi-h Modulation Sets Using A Stochastic Search Algorithm', IEE Proceedings-communications, vol. 145, no. 1, pp. 41-46.
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Multi-h CPFSK modulation is simple to implement, spectrally efficient, and has inherent error correction properties. Multi-h requires large parameter sets to obtain high coding gain. Large numbers of combinations may need to be investigated. A fast effic

Dvorak, SL, Ziolkowski, RW & Felsen, LB 1998, 'Hybrid analytical-numerical approach for modeling transient wave propagation in Lorentz media', JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION, vol. 15, no. 5, pp. 1241-1255.
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He, S, Hintz, TB & Szewcow, U 1998, 'Replicated Shared Object Model For Edge Detection With Spiral Architecture', Parallel And Distributed Processing, vol. 1388, pp. 252-260.
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Edge detection in computer vision and image processing is a process which detects one kind of significant features appearing as discontinuities in intensities. A parallel edge detection algorithm based on Spiral Architeture is designed in this paper by a

He, S, Hintz, TB & Szewcow, U 1998, 'Replicated Shared Object Model For Parallel Edge Detection Algorithm Based On Spiral Architecture', Future Generation Computer Systems, vol. 14, no. 5-6, pp. 341-350.
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Edge detection in computer vision and image processing is a process which detects one kind of significant feature in an image that appears as discontinuities in intensities. A parallel edge detection algorithm based on spiral architecture is designed in

HILDING, JAIM & VEITCH, D 1998, 'UNDERSTANDING END-TO-END INTERNET TRAFFIC DYNAMICS.', GLOBECOM..., pp. 1118-1118.

HILDING, JAIM & VEITCH, D 1998, 'UNDERSTANDING END-TO-END INTERNET TRAFFIC DYNAMICS.', GLOBECOM..., pp. 1118-1118.

Keenan, T, Glasson, K, Cummings, F, Bird, TS, Keeler, J & Lutz, J 1998, 'The BMRC/NCAR C-band polarimetric (C-POL) radar system', JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY, vol. 15, no. 4, pp. 871-886.
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Keenan, T, Glasson, K, Cummings, F, Bird, TS, Keeler, J & Lutz, J 1998, 'The BMRC/NCAR C-band polarimetric (C-POL) radar system', Journal of Atmospheric and Oceanic Technology, vol. 15, no. 4, pp. 871-886.
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The development of the first Australian C-band polarimetric/Doppler meteorological radar system (C-POL) is described. Motivated by the need to obtain improved rainfall estimation and the vertical profile of hydrometeors, C-POL was developed jointly by the Bureau of Meteorology (BOM), the Commonwealth Scientific and Industrial Research Organisation of Australia, and the National Center for Atmospheric Research. C-POL is based on a standard operational C-band radar employed by the BOM but modified to be capable of transmitting linear horizontal and vertical polarizations and receiving the co- and cross polarizations on a pulse-to-pulse basis. Standard variables extracted include horizontal reflectivity (ZHH), radial velocity (Vr), spectral width (συ), differential reflectivity (ZDR), differential phase shift (ΦDP), and zero lag correlation coefficient [ρHV(0)]. With the addition of a second receiver chain, the linear depolarization ratio will soon be available. Initial results with the radar are discussed to give examples of the data quality, as well as some of the problems inherent in using a C-band radar in the Tropics.

Liang, T & Ziolkowski, RW 1998, 'Dispersion effects on grating-assisted output couplers under ultrafast pulse excitations', MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, vol. 17, no. 1, pp. 17-23.
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Liang, T & Ziolkowski, RW 1998, 'Grating assisted waveguide-to-waveguide couplers', IEEE PHOTONICS TECHNOLOGY LETTERS, vol. 10, no. 5, pp. 693-695.
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Liang, T & Ziolkowski, RW 1998, 'Grating assisted waveguide-to-waveguide couplers', IEEE Photonics Technology Letters, vol. 10, no. 3, pp. 693-695.
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A new radiation-type waveguide-to-waveguide coupler is proposed. The coupling is realized through gratings embedded on the dielectric waveguides involved. Compared to the conventional hybrid-mode coupler, this type of coupler has advantages in that the two waveguides can be quite dissimilar as well as being separated by large distances. It is demonstrated that the coupling performance of this radiation-type coupler can be enhanced significantly by using photonic bandgap (PBG) structures.

Liang, T & Ziolkowski, RW 1998, 'Ultrafast pulsed mode effects on the performance of grating-assisted output couplers of finite extent', OPTICS LETTERS, vol. 23, no. 6, pp. 469-471.
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Oughstun, KE & Ziolkowski, RW 1998, 'Mathematics and modeling in modern optics', JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION, vol. 15, no. 5, pp. 1238-1238.
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Parfitt, AJ & Bird, TS 1998, 'Computation of aperture antenna mutual coupling using FDTD and Kirchhoff field transformation', ELECTRONICS LETTERS, vol. 34, no. 12, pp. 1167-1168.
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Saban, D & Braun, RM 1998, 'Multi-carrier direct sequence CDMA in fading situations', Proceedings of the South African Symposium on Communications and Signal Processing, COMSIG, pp. 33-38.
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A multicarrier direct sequence code division multiple access (MC-DS-CDMA) technique is proposed for point-to-multipoint communication systems. Time delays and related interference phenomenon are discussed and multicarrier techniques for mitigating multipath effects are highlighted. An independent two-ray multipath model is used for determining the major channel effects that influence multicarrier DS-CDMA. In particular, time dispersion and frequency distortion are examined in terms of their effect on multicarrier modulation schemes. Empirical simulated analysis is presented for additive white gaussian and multipath channels in order to highlight the bandwidth efficiency, interference generation and the bit error rate (BER) of multicarrier DS-CDMA under selected multipath configurations. Coding strategies are discussed for mitigating multipath induced errors and their expense on the bandwidth efficiency is emphasized.

Saban, G & Braun, RM 1998, 'Wireless local loop and packet radio technology for developing communities', Proceedings of the South African Symposium on Communications and Signal Processing, COMSIG, pp. 1-6.
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In developing countries there is an increasing demand for telecommunications and Internet access. The current problem, especially in Africa, is to find solutions which can provide underdeveloped countries with a satisfactory network. This requires a relatively fast roll-out at low-cost. Modern wireless system claim to offer quick and easy deployment. However, in many cases the wireless system deployment is delayed because adequate radio plans have to be designed, and they are not optimized for Internet and computer communications. Multihop packet radio can offer computer communication in an easily deployable ad-hoc wireless network which does not require frequency planning. However, voice traffic is not easily implemented on packet radio networks due to the bursty and delayed traffic characteristics. A multihop packer radio network is proposed which offers voice and Internet communications.

Seaman, B & Braun, RM 1998, 'Using cyclostationarity in the modulation classification of analogue signals', Proceedings of the South African Symposium on Communications and Signal Processing, COMSIG, pp. 261-266.
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This paper discusses the feasibility of using cyclostationarity for modulation classification. It concentrates on AM modulation types. The effect of noise on the resulting signals is investigated. The conclusion is that cyclostationarity looks promising as a part of the process that implements modulation recognition.

Tellambura, C, Guo, YJ & Barton, SK 1998, 'Channel estimation using aperiodic binary sequences', IEEE Communications Letters, vol. 2, no. 5, pp. 140-142.
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Estimating a channel impulse response using a known aperiodic sequence is considered. The problem can be reduced to minimizing the trace of the inverse of a Toeplitz matrix. An efficient algorithm for computing this trace is developed and optimal binary sequences up to length 32 are found and tabulated. The use of complementary sequences in this context is also investigated. It is shown that the eigenvalues of the autocorrelation matrices of a pair of complementary sequences sum to a known constant.

Ziolkowski, RW & Gogny, DM 1998, 'Cavity modifications of nuclear internal conversion rates – abstract', Journal of Electromagnetic Waves and Applications, vol. 12, no. 5, pp. 675-676.
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We extend the principles of cavity quantum electrodynamics to nuclei inside low-loss cavities. The resulting nucleus-cavity system exhibits spontaneous emission and internal conversion rates which differ radically from those of the individual components. The quantum mechanical derivations of these rates are given. The internal conversion process occurs via the exchange of a virtual photon between an excited nucleus and an electron bound to that nucleus. Even though the photon is virtual, partial suppression of the internal conversion process is shown to be theoretically possible. With a controlled modification of the internal conversion rate using a high- Q cavity, one can achieve a number of potentially interesting applications including an excited nuclear state containment unit, a nuclear battery, and a neutron detector. © Journal of Electromagnetic Waves and Applications. All rights reserved.

Andren, J, Hilding, M & Veitch, D 1998, 'Understanding end-to-end internet traffic dynamics', Global Telecommunications Conference, 1998. GLOBECOM 1998. The Bridge to Global Integration. IEEE, IEEE, pp. 1118-1122.

Banh, BAJ, Anido, GJ & Dutkiewicz, E 1998, 'Handover re-routing schemes for connection oriented services in mobile ATM networks', Proceedings - IEEE INFOCOM, pp. 1139-1146.
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Wireless ATM (WATM) will be used to support broadband applications for future generation mobile services. To achieve this, the existing ATM protocol must be augmented with mobility management capabilities. One of the important components of mobility management is the ability of the network to seamlessly re-route existing connections to different parts of the network. To date, a number of schemes have been proposed for broadband wireless networks. These schemes can potentially be used in WATM networks. In this paper, we compare the performance of these schemes in terms of their complexity, handover latency, communication disruption period and buffer and bandwidth requirements.

Barattin, M, Cucchiara, R & Piccardi, M 1998, 'A Rule-based Vehicular Traffic Tracking System', Proceedings of the Joint Conference on Information Sciences, pp. 334-337.
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The paper presents a computer vision-based approach to the problem of vehicular traffic monitoring. The approach associates a high-level tracking system to a low-level system that performs moving vehicles detection. The high-level module is based on a large set of rules and is able to keep tracks of all moving or stopped vehicles along the image sequence.

Bird, TS 1998, 'Recent progress in reflector antenna analysis & design', Symposium on Antenna Technology and Applied Electromagnetics, ANTEM 1998 - Conference Proceedings, 1998 Symposium on Antenna Technology and Applied Electromagnetics, IEEE, Ottawa, Canada, pp. 3-6.
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© 1998 IEEE. The latter part of the 20th century has seen significant changes and improvements in the design and practice of reflectorantennas. As well as traditional users of reflectors, such as defence, telecommunication utilities and radio astronomy, significant consumer markets have now opened up. For instance, it is common for many homes and offices to have a dish connected to a wall or roof. At the same time design techniques for reflectors and associated feed systems have also undergone change. Until a few years ago effectsthat were poorly modelled or completely ignored that can now be analysed include, reflectoredge diffraction, near-field effects, grid, composite and painted surfaces, accurate feed models, mutual coupling and scattering in feed arrays, and reflector/feedinteractions. Shaped reflectors are now widely used on satellite antennas, and dielectric-loaded horns are replacing corrugated horns in some earth station applications. It is the purpose here to outline some recent changes and improvements in the design and synthesis techniques used for reflectors and feeds.

Canning, J, Sceats, MG & Carter, ALG 1997, 'UV-induced structural changes in photosensitive optical fibres', JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS, International Workshop on Structure and Functional Optical Properties of Silica and Silica-Related Glasses, JAPAN SOC APPLIED PHYSICS, TOYOTA MOTOR CORP, MIKKABI CREAT CTR, SHIZUOKA, JAPAN, pp. 59-61.
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Cucchiara, R & Piccardi, M 1998, 'Exploiting image processing locality in cache pre-fetching', Proceedings - Symposium on Computer Architecture and High Performance Computing, pp. 466-472.
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© 1998 IEEE. Emerging trends in computer design attempt to include specific solutions for handling images also in general-purpose computers, because of the current spread of multimedia, image processing and computer graphics applications. In this context, we propose hardware pre-fetching techniques specific for caching images: The main issue we state is that most algorithms working on images exhibit a 2D spatial locality that is not taken into account in current cache organization and data access strategies. To this aim we propose an adaptive local pre-fetching for the image data type; this technique, mirroring the two-dimensional spatial locality of image processing algorithms, results in being more efficient than other approaches, such as sequential pre-fetching and adaptive pre-fetching. Performance is evaluated on different classes of image processing algorithms, namely raster-scan and propagative algorithms, common in computer vision and multimedia applications.

Guo, YJ, Vadgama, S, Davies, M, Khalab, J, Zarri, M & Spink, D 1998, 'Adaptive antenna for CDMA', IEEE International Symposium on Spread Spectrum Techniques & Applications, pp. 590-594.
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A decision directed adaptive antenna array for the uplink of CDMA cellular systems, which is based on a normalized least mean square algorithm (NLMS), is presented. The bit error ratio performance of the adaptive antenna in various scenarios, which include the use of transmission power control (TPC) and diversity combining, is studied. It is shown that the adaptive antenna outperforms the steering beam technique when the signal-to-noise ratio is large and the active users are clustered. However, the performance of the adaptive antenna becomes very similar to that of the steering beam when there are a large number of randomly distributed active users in the sector.

Liu, RP, Richards, A & Rogers, G 1998, 'MARSHNet, a superimposed QoS guaranteed Virtual Path Network', GLOBECOM 98: IEEE GLOBECOM 1998 - CONFERENCE RECORD, VOLS 1-6, IEEE Global Telecommunications Conference (GLOBECOM 98), IEEE, SYDNEY, AUSTRALIA, pp. 7-12.

Moss, D, Canning, J & Bazylenko, M 1998, 'Bragg gratings in hollow-cathode PECVD germanosilica planar waveguides', Conference on Lasers and Electro-Optics Europe - Technical Digest, p. 425.
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Waveguide gratings were fabricated in intrinsically low-loss (0.2 dB/cm with no annealing) germanosilica waveguide layers without the use of any material presensitization. The waveguides were grown by a novel technique called hollow-cathode PECVD.

Partilt, AJ & Bird, TS 1998, 'Application of a near-field transform algorithm to antenna coupling using the FDTD method', IEEE Antennas and Propagation Society International Symposium, 1998 Digest - Antennas: Gateways to the Global Network - Held in conjunction with: USNC/URSI National Radio Science Meeting, pp. 500-503.
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© 1998 IEEE. The finite-difference time-domain (FDTD) method is useful in many antenna applications because it facilitates modelling of complex structures and is capable of characterising antenna performance over a wide-frequency band. However, for antenna arrays of even modest size, the excessive computer storage and run-time may become prohibitive for design and optimisation purposes. Some work has been done with time-domain transform methods for computing weak coupling between antennas (Page et al. 1996). In this paper, an algorithm is developed using the Kirchhoff near-field to near-field transformation (Shlager and Smith, 1995) for the one-way coupling between antenna elements. This coupling representation is then applied to arrays in a manner analogous to an element-by-element analysis in the frequency domain, except that in the method described here the coupled currents at the antenna-feed ports are added in the time-domain so as to permit the introduction of true-time delays for wide-band beam steering. The advantages of the transform method over a full FDTD method are smaller computer storage and a reduction in late-time FDTD effects associated with reflections from the absorbing boundary on the outer surface of the computational domain and also from numerical dispersion and instabilities.

Roughan, M, Veitch, D & Abry, P 1998, 'On-line estimation of the parameters of long-range dependence', GLOBECOM 98: IEEE GLOBECOM 1998 - CONFERENCE RECORD, VOLS 1-6, IEEE Global Telecommunications Conference (GLOBECOM 98), IEEE, SYDNEY, AUSTRALIA, pp. 3716-3721.

Roughan, M, Veitch, D & Rumsewicz, M 1998, 'Computing queue-length distributions for power-law queues', INFOCOM’98. Seventeenth Annual Joint Conference of the IEEE Computer and Communications Societies. Proceedings. IEEE, IEEE, pp. 356-363.

Stepanov, DY, Canning, J & Brodzeli, Z 1998, 'High-resolution measurements of fibre Bragg grating transmission spectra', 24TH EUROPEAN CONFERENCE ON OPTICAL COMMUNICATION, VOL 1-3, 24th European Conference on Optical Communications, TELEFONICA ESPANA SA, MADRID, SPAIN, pp. 407-408.

Tellambura, C, Parker, MG & Barton, SK 1998, 'Channel estimation using discrete Fourier transform techniques', GLOBECOM 98: IEEE GLOBECOM 1998 - CONFERENCE RECORD, VOLS 1-6, IEEE Global Telecommunications Conference (GLOBECOM 98), IEEE, SYDNEY, AUSTRALIA, pp. 148-152.

von Bibra, ML, Canning, J & Roberts, A 1997, 'Mode profile modification of H+ ion beam irradiated waveguides using UV processing', JOURNAL OF NON-CRYSTALLINE SOLIDS, Glass and Optical Materials Division / Bragg Gratings, Photosensitivity and Poling in Glass Fibers and Waveguides - Applications and Fundamentals Meeting, ELSEVIER SCIENCE BV, WILLIAMSBURG, VIRGINIA, pp. 121-125.
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Ziolkowski, RW 1998, 'Finite photonic band gap material based waveguides, power splitters and switches', IEEE ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM - ANTENNAS: GATEWAYS TO THE GLOBAL NETWORK, VOLS 1-4, IEEE Antennas-and-Propagation-Society International Symposium on Antennas - Gateways to the Global Network, IEEE, ATLANTA, GA, pp. 873-873.