Aikussayer, HM, Guo, YJ & Barton, SK 1997, 'New multiuser detector for asynchronous CDMA', IEE Proceedings: Communications, vol. 144, no. 5, pp. 336-340.
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A novel multiuser detector for asynchronous code division multiple access (CDMA) system is presented. Using a new type of spreading sequences and shortened correlators with linear combining, an unbiased one-shot suboptimum detection is achieved without increasing the receiver complexity. Two decorrelating algorithms, the direct and the recursive methods, are given for the proposed detector configuration. Theoretical and simulation results show that the receiver performs well in severe near-far environments. © IEE, 1997.
Auzanneau, F & Ziolkowski, RW 1997, 'Étude théorique de matériaux bianisotropes synthétiques contrôlables', Journal de Physique III, vol. 7, no. 12, pp. 2405-2418.
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We analyse the electromagnetic properties of molecules composed of small linearly loaded antennas, in a host medium. Depending on the load, we obtain various previously known models (Debye, Lorentz) and generalize their properties (Time Derivative Debye and Lorentz). Inherent duality between dielectric and magnetic molecules allows us to derive a matched material satisfying ∈r = μr. The EM properties of bianisotropic molecules composed of two antennas in tandem are presented. Finally, applying the Maxwell Garnett law, we derive the EM caracteristics of the composite material. © Les Éditions de Physique 1997.
Auzanneau, F & Ziolkowski, RW 1997, 'Theoretical study and design of artificial bianisotropic materials', JOURNAL DE PHYSIQUE III, vol. 7, no. 12, pp. 2405-2418.
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Canning, J & Carter, ALG 1997, 'Modal interferometer for in situ measurements of induced core index change in optical fibers', OPTICS LETTERS, vol. 22, no. 8, pp. 561-563.
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Canning, J, Carter, ALG & Sceats, MG 1997, 'Correlation between photodarkening and index change during 193 nm irradiation of germanosilicate and phosphosilicate fibers', JOURNAL OF LIGHTWAVE TECHNOLOGY, vol. 15, no. 8, pp. 1348-1356.
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Canning, J, Psaila, DC, Brodzeli, Z, Higley, A & Janos, M 1997, 'Characterization of apodized fiber Bragg gratings for rejection filter applications', APPLIED OPTICS, vol. 36, no. 36, pp. 9378-9382.
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Cucchiara, R, Distefano, L, Piccardi, M & Cinotti, T 1997, 'The Giotto System: A Parallel Computer For Image Processing', Real-time Imaging, vol. 3, no. 5, pp. 343-353.
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This paper presents the GIOTTO system, a parallel computer based on a scalable single instruction, multiple data (SIMD) array of processors specially conceived for image processing, The system is characterized by a reduced-size array and a novel organiza
Dvorak, SL, Ziolkowski, RW & Dudley, DG 1997, 'Ultra-wideband electromagnetic pulse propagation in a homogeneous, cold plasma', Radio Science, vol. 32, no. 1, pp. 239-250.
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In this paper, we investigate the propagation of an ultra-wideband electromagnetic pulse in a homogeneous, cold plasma which is used to represent a simplified model of the atmosphere. The standard procedure for the computation of the corresponding transient field involves the application of a fast Fourier transform (FFT) to a well-known, analytical, frequency-domain solution. However, because of the long tails in both the time and frequency domains, a large number of sample points are required to compute the transient response using this FFT approach. In this paper, we introduce a new asymptotic extraction technique which dramatically reduces the number of sample points required by the FFT. First, we review the recently derived closed-form expression for a double-exponential pulse propagating in a homogeneous, collisionless, cold plasma. Since the high-frequency behavior does not depend on the electron collision frequency, an analytical frequency-domain expression, which is similar in form to the one encountered for the collisionless, cold plasma and encompasses this high-frequency behavior, can be subtracted from the exact expression for the plasma with a nonzero collision frequency. The extracted term is evaluated analytically. The remaining expression, which can be transformed to the time domain with a FFT, requires only a modest number of sample points. This dramatically improves the numerical efficiency of the approach. We find that the extracted analytical term provides a very good approximation for the early-time behavior of the transient pulse.
Fidel, B, Heyman, E, Kastner, R & Ziolkowski, RW 1997, 'Hybrid ray-FDTD moving window approach to pulse propagation', Journal of Computational Physics, vol. 138, no. 2, pp. 480-500.
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A moving window finite difference time domain method is developed to simulate the propagation of electromagnetic pulses over large distances. Both Eulerian and Lagrangian approaches to solving Maxwell's equations in a moving window are obtained and contrasted. The Lagrangian approach is shown to be superior for electromagnetic pulse propagation; it is demonstrated that dispersion-free numerical propagation can be achieved with the Lagrangian approach. Examples of propagation in homogeneous and inhomogeneous media, and scattering from a interface between two media are considered. The scattering results are achieved with a window splitting approach in which the original incident pulse window is frozen at the interface and new windows are generated after the interface interactions occur that move with the reflected and transmitted pulses. The simulation results are shown to be accurate and physically appealing. © 1997 Academic Press.
Fu, K, Guo, YJ & Barton, SK 1997, 'Performance of the EY-NPMA Protocol', Wireless Personal Communications, vol. 4, no. 1, pp. 41-50.
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The throughput of the Elimination Yield Non-pre-emptive Priority Multiple Access (EY-NPMA) protocol, which has been chosen as the medium access control (MAC) protocol for HIPERLAN, is simulated. Connection between users is based on a statistical model of path loss with power law against distance and 6 dB log-normal shadowing. It is shown that the throughput performance of the EY-NPMA protocol in networks of moderate size and with small proportion of hidden nodes is satisfactory. For a fully connected network, the throughput reaches 0.85 at an offered traffic of 1 and remains at this level. The maximum throughput reduces gradually when the number of hidden node pairs in the network is increased. With 11% of hidden nodes in the network the peak throughput falls to 0.6.
Gillies, DAG, Guo, YJ & Barton, SK 1997, 'Synchronisation Techniques for HIPERLAN', Wireless Personal Communications, vol. 4, no. 1, pp. 1-10.
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Timing recovery in the High Performance Radio Local Area Network (HIPERLAN) standard is likely to be performed with the aid of synchronisation sequences embedded in the user data, which will be detected with matched filters. A directed search using a form of genetic algorithm has been performed to obtain suitable sequences of lengths up to 80 bits, and simulations of their performance have been undertaken. Performance of the sequences has been measured under the severe channel conditions that pertain in the indoor environment.
Guo, YJ, Paez, A, Sadeghzadeh, RA & Barton, SK 1997, 'A circular patch antenna for radio LAN’s', IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, vol. 45, no. 1, pp. 177-178.
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Kann, JL, Milster, TD, Froehlich, FF, Ziolkowski, RW & Judkins, JB 1997, 'Heating mechanisms in a near-field optical system', APPLIED OPTICS, vol. 36, no. 24, pp. 5951-5958.
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Kot, JS, Nikolic, N & Bird, TS 1997, 'Integrated-circuit antenna for high-permittivity substrates', IEE Proceedings: Microwaves, Antennas and Propagation, vol. 144, no. 1, pp. 47-51.
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An integrated antenna which operates well on thick, high-permittivity substrates is analyzed using a combined integral-equation and mode-matching method. Results from the numerical solution of the integral equation are compared with measurements on a model antenna. Measured and predicted results are found to agree well for the antenna input impedance and far-field radiation pattern. A theoretical design for a GaAs millimetre-wave MMIC antenna operating at 94 GHz is described.
Liang, T & Ziolkowski, RW 1997, 'Mode conversion of ultrafast pulses by grating structures in layered dielectric waveguides', Journal of Lightwave Technology, vol. 15, no. 10, pp. 1966-1973.
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Various grating configurations are introduced to develop structures for the mode conversion of an ultrafast, ultrawide-bandwidth optical pulse propagating in a layered dielectric waveguide. Introducing a new technique for efficient, real-time mode extraction, we examine these schemes with a full-wave, vector, finite difference time domain (FDTD) Maxwell equation simulator. The resulting FDTD simulator is very flexible and accurate; it is capable of modeling the interaction of few- or many-cycle optical pulsed modes with finite, aperiodic gratings with complex material configurations. The grating structure can be tailored to the pulsed optical modes of interest with this FDTD simulator. It is used to design a composite mode-conversion grating structure that realizes a 29.45% increase in the converted mode energy for an ultrafast six-cycle optical pulse over that achieved with standard uniform grating convertors.
Nikolic, N, Kot, JS & Bird, TS 1997, 'Theoretical and experimental study of a cavity-backed annular-slot antenna', IEE Proceedings: Microwaves, Antennas and Propagation, vol. 144, no. 5, pp. 337-340.
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A simple and accurate analysis of an annular-slot antenna backed by an inhomogeneously filled cavity is described. The analysis is based on a magnetic-field integral equation, which is solved approximately using a variational formulation. The results obtained from the analysis are compared with experimental measurements on a 5 GHz annular-slot antenna fabricated on a Duroid 5880 substrate. It is found that only three terms of a series expansion are needed for an accurate solution. Measured results for input impedance and far-field radiation patterns for an annular slot backed by different-sized cavities are presented. © IEE, 1997.
Peng, M, Sasabo, MF, Guo, YJ & Barton, SK 1997, 'A modified linear decorrelating detector for asynchronous CDMA', IEE Colloquium (Digest), no. 129.
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Although the linear decorrelating detector (LDD) is theoretically a simple scheme for the detection of asynchronous CDMA, its practical implementation is still too complicated and it may have long detection delay. One-shot LDD has a simpler architecture and almost no detection delay, but it could lead to significant noise enhancement, and hence degraded near-far resistance (NFR) than the standard LDD. In this paper, a modified LDD (MLDD) is proposed. With controllable complexity and detection delay, the MLDD has smaller noise enhancement than the one-shot LDD and its NFR can approach that of the standard LDD.
Piccardi, M, Cucchiara, R, Bariani, M & Mello, P 1997, 'Exploiting Symbolic Learning In Visual Inspection', Advances In Intelligent Data Analysis, vol. 1280, pp. 223-234.
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The paper describes the use of data analysis techniques in the computer-vision inspection of industrial workpieces. Computer-vision inspection aims at accomplishing quality verification of fabricated parts by means of automated visual procedures. Gatheri
Preston, SL, Thiel, DV, Lu, JW, OKeefe, SG & Bird, TS 1997, 'Electronic beam steering using switched parasitic patch elements', ELECTRONICS LETTERS, vol. 33, no. 1, pp. 7-8.
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Simonian, A & Veitch, D 1997, 'A storage model with high rate and long range dependent on/o sources', preprint.
Veitch, D & Abry, P 1997, 'Estimation conjointe en ondelette des paramétres du phénoméne de dépendance longue', 16° Colloque sur le traitement du signal et des images, FRA, 1997.
Zhang, J, Frater, M, Arnold, J & Percival, T 1997, 'MPEG 2 video services for wireless ATM networks', IEEE Journal on Selected Areas in Communications, vol. 15, no. 1, pp. 119-127.
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Audio-visual and other multimedia services are seen as an important source of traffic for future telecommunications networks, including wireless networks. In this paper, we examine the impact of the properties of a 50 Mb/s asynchronous transfer mode (ATM
Ziolkowski, RW 1997, 'Realization of an all-optical triode and diode with a two-level-atom-loaded diffraction grating', APPLIED OPTICS, vol. 36, no. 33, pp. 8547-8556.
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Ziolkowski, RW 1997, 'The design of maxwellian absorbers for numerical boundary conditions and for practical applications using engineered artificial materials', IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, vol. 45, no. 4, pp. 656-671.
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Ziolkowski, RW 1997, 'The incorporation of microscopic material models into the FDTD Approach for Ultrafast Optical Pulse Simulations', IEEE Transactions on Antennas and Propagation, vol. 45, no. 3, pp. 375-391.
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We are developing full-wave vector Maxwell equation solvers for use in studying the physics and engineering of linear and nonlinear integrated photonics systems. Particular emphasis has been given to the interaction of ultrafast optical pulses with nonresonant and resonant optical materials and structures. Results will be reviewed that simulate the interaction of ultrafast optical pulses with structures (e.g., gratings of finite length) filled with materials exhibiting resonant loss or gain. In particular, we consider structures loaded with atomic media resonant at or near the frequency of the incident optical radiation. Interest in these problems follows from our desire to design micronsized linear and nonlinear guided-wave couplers, modulators, and switches. These resonant problems pose interesting FDTD modeling issues because of the many time and length scales involved. To understand the physics underlying the small-distance scale and short-time scale interactions, particularly in the resonance regime of the materials and the associated device structures, a first principles approach is desirable. Thus, the results to be presented are based upon a quantum mechanical two-level atom model for the materials. The resulting Maxwell-Bloch model requires a careful marriage between microscopic (quantum mechanical) material models of the resonant material systems and the multidimensional, macroscopic Maxwell's equations solver. The FDTD numerical issues will be discussed. Examples will be given to illustrate the design and control of these resonant large-scale optical structures. An optical triode is designed and characterized with the FDTD Maxwell-Bloch simulator. © 1997 IEEE.
Ziolkowski, RW 1997, 'Time-derivative Lorentz material model-based absorbing boundary condition', IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, vol. 45, no. 10, pp. 1530-1535.
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Ziolkowski, RW 1997, 'Time-derivative lorentz materials and their utilization as electromagnetic absorbers', Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, vol. 55, no. 6, pp. 7696-7703.
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A time-derivative Lorentz material model is introduced for the polarization and magnetization fields in a complex medium illuminated by an ultrafast pulsed beam. This model represents a straightforward generalization of the standard Lorentz material model to include the time derivatives of the fields as driving mechanisms. The Green function for this material is derived and used to demonstrate that it is causal and passive. An electromagnetic absorber is constructed with this time-derivative Lorentz material, and simulations are given which illustrate its effectiveness under illumination by obliquely incident, ultrafast, pulsed Gaussian beams having narrow and broad waists. © 1997 The American Physical Society.
Ziolkowski, RW 1997, 'Time-derivative Lorentz materials and their utilization as electromagnetic absorbers', PHYSICAL REVIEW E, vol. 55, no. 6, pp. 7696-7703.
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Ziolkowski, RW & Auzanneau, F 1997, 'Artificial molecule realization of a magnetic wall', JOURNAL OF APPLIED PHYSICS, vol. 82, no. 7, pp. 3192-3194.
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Ziolkowski, RW & Auzanneau, F 1997, 'Passive artificial molecule realizations of dielectric materials', JOURNAL OF APPLIED PHYSICS, vol. 82, no. 7, pp. 3195-3198.
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Ziolkowski, RW & Liang, T 1997, 'Design and characterization of a grating-assisted coupler enhanced by a photonic-band-gap structure for effective wavelength-division demultiplexing.', Optics letters, vol. 22, no. 13, pp. 1033-1035.
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We report a novel grating-assisted coupler that incorporates a photonic-band-gap structure. It is shown that by virtue of the resonant cavity formed by the structure and the grating the relative amounts of the output scattered and the transmitted guided-wave powers can be significantly modified. The potential applications for optical switches and wavelength demultiplexers based on this new configuration are discussed.
Arkwright, J, Atkins, G, Brodzeli, Z, Canning, J, Janos, M, Elango, P, Sceats, M & Whitbread, T 1997, 'All optical switching in rare-earth doped fibers', Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest, p. 265.
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The nonlinear response seen in rare-earth doped fibers is due to the change in absorption induced by optical pumping of the resonant transitions of the rare-earth ions. Since many rare-earth ions exhibit long-lived metastable states, these changes in absorption, and hence, the associated changes in refractive index, can be large for relatively modest absorbed pump powers. The recent work being carried out in Australia to investigate the viability of using rare-earth nonlinearities for all-optical switching and modulation at the preferred telecommunications wavelength is presented.
Bird, TS 1997, 'Coaxial feed array for a short focal-length reflector', IEEE Antennas and Propagation Society, AP-S International Symposium (Digest), pp. 1618-1621.
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The design of the multibeam feed for the Lovell radio telescope uses a new software that analyzes circular/coaxial horn arrays by a mode-matching method. The effects of mutual coupling between the feeds, discontinuities and steps in the elements and a finite-sized ground plane are included in the analysis.
Cucchiara, R, Callipo, A & Piccardi, M 1997, 'Block processing on multiprocessor DSPs for multimedia applications', 1997 IEEE 1st Workshop on Multimedia Signal Processing, MMSP 1997, pp. 439-444.
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© 1997 IEEE. The paper explores software development for multiprocessor DSPs for data parallel local algorithms. These algorithms are very common in multimedia applications, such as filtering, compression and so on. Multiprocessor DSPs are very attractive for this application since they offer performance typical of parallel machines together with limited cost. The paper provides performance analysis and software design issues according to different data partitioning models. As a case study, performance evaluation has been carried out on the Multimedia Video Processor from Texas Instrument.
Cucchiara, R, Piccardi, M, Bariani, M & Mello, P 1997, 'Learning for feature selection and shape detection', Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), pp. 535-542.
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© Springer-Verlag Berlin Heidelberg 1997. The paper proposes a general framework for shape detection based on supervised symbolic learning. Differently from other visual systems exploiting machine learning, the proposed architecture does not follow the object segmentation - feature extraction and (learning based) classification approach. Instead, an initial data-driven processing selects points of interest in the scene by means of complex features which hypothesize the presence of the target shape; hypotheses are validated by a classifier defined by a machine learning algorithm. Learning is exploited not only for defining the model, i.e. the description of the target for the classifier, but also for defining the description language, i.e. the feature set useful in generating reliable object hypotheses. The proposed architecture of visual system has been implemented for an industrial application of unstructured shape detection: examples and results are reported in the paper.
Dvorak, SL, Dudley, DG & Ziolkowski, RW 1996, 'Propagation of UWB electromagnetic pulses through lossy plasmas', ULTRA-WIDEBAND, SHORT-PULSE ELECTROMAGNETICS 3, 3rd International Conference on Ultra-Wideband, Short-Pulse Electromagnetics (UWB,SP 3), PLENUM PRESS DIV PLENUM PUBLISHING CORP, ALBUQUERQUE, NM, pp. 247-254.
Guerin, S, Guo, YJ & Barton, SK 1997, 'Indoor propagation measurements at 5 GHz for HIPERLAN', IEE Conference Publication.
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Indoor propagation measurements for HIPERLAN at 5 GHz are reported. Using two patch antennas designed for HIPERLAN, one being fixed at the ceiling of a meeting room and the other being moved around in the room, the path loss, delay profiles and delay parameters are obtained. The effect of multiple reflection is demonstrated by the direction of arrival (DOA) measurements.
Horwitz, M & Braun, R 1997, 'Generalized design technique for traceback survivor memory management in Viterbi decoders', Proceedings of the South African Symposium on Communications and Signal Processing, COMSIG, pp. 63-68.
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There are number of algorithms available for the design of traceback survivor memory units in Viterbi decoders. Perhaps the best description of the traceback algorithms was given by Feygin et al, where four separate algorithms were presented. These four algorithms, however, can all be encapsulated in the description of two broader algorithms. In addition a new implementation technique will be presented for one family of algorithms. As a result a host of new, low complexity implementations of survivor memory units become possible.
Ince, EA, Guo, YJ & Barton, SK 1997, 'T-algorithm detection of partial response continuous phase modulated signals over multipath channels', IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, pp. 1135-1139.
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This paper presents a new approach to reduced complexity detection of partial response continuous phase modulated signals over channels with severe intersymbol interference (ISI). The detector combines the overall channel response for the CPM modulator with that of a multipath channel to calculate the branch metrics of a breadth-first sequential detection algorithm known as the T-algorithm. To our knowledge the reported work is the first attempt to make use of such a technique for equalization of quaternary partial response CPM signals transmitted over multipath channels. Simulation of the performance of the receiver in multipath channels is reported.
Ince, EA, Vorizanakis, N, Guo, YJ & Barton, SK 1997, 'Breadth-first sequential detection of PR-CPM signals over AWGN and multipath channels', IEEE International Symposium on Information Theory - Proceedings, pp. 496-496.
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Detection of partial response continuous phase modulated signals over AWGN and multipath channels is presented. The receiver uses a breadth-first sequential detection algorithm known as the M-algorithm (MA). Compared with the maximum likelihood receiver based on the Viterbi algorithm (VA), a significant reduction in complexity is obtained in the proposed receiver while maintaining good performance. © 1997 IEEE.
Kann, JL, Milster, TD, Froehlich, FF, Ziolkowski, RW & Judkins, JB 1997, 'Rigorous numerical modeling of novel optical data storage systems', Proceedings of SPIE - The International Society for Optical Engineering, pp. 222-228.
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A hybrid finite-difference-time-domain/angular spectrum propagation modeling technique and a finite-difference thermal model are used to study near-field optical and two-photon absorption data storage systems. The electromagnetic model is used to analyze scattering effects in structures where scalar-based theory is not appropriate. The thermal model is used in a near-field magneto optic data storage system to calculate data mark sizes.
Kot, JS, Nikolic, N & Bird, TS 1997, 'Integrated antenna element for millimetre wave focal-plane arrays', IEE Conference Publication.
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The bath-plug antenna is designed for use in a GaAs monolithic microwave integrated circuit at millimeter wavelengths. The antenna radiates through the GaAs substrate via a matched, dielectric-filled waveguide aperture, making the antenna well-suited for use in a focal-plane array for a multi-beam telescope. An array of bath-plug antennas was analyzed, and a two-element array operating at 3 GHz was built and tested. A good agreement was obtained between the analysis and measurements.
Liang, T & Ziolkowski, RW 1997, 'FDTD modeling of a grating-assisted coupler integrated with a photonic bandgap resonant cavity', IEEE Antennas and Propagation Society, AP-S International Symposium (Digest), pp. 356-358.
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The finite-difference time-domain (FDTD) approach has a powerful simulation capability to study and design composite, aperiodic, and finite grating structures. The possibility to modify the distribution of the output energies realized with a grating-assisted coupler through the introduction of a photonic bandgap based resonant cavity is demonstrated. The performance of this configuration was analyzed with FDTD simulator. The potential applications of this configuration to a variety of microwave, millimeter, and optical communication systems are discussed.
Moss, DJ, Canning, J, Faith, M, Madden, S, Kemeny, P, Poladian, L, Ladouceur, F, Love, JD, Poulsen, CV & Leistiko, O 1997, 'Ultra-strong UV written gratings in PECVD grown germanosilicate waveguides', PHOTOSENSITIVE OPTICAL MATERIALS AND DEVICES, Conference on Photosensitive Optical Materials and Devices, SPIE - INT SOC OPTICAL ENGINEERING, SAN JOSE, CA, pp. 142-145.
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Pemper, Y, Fidel, B, Heyman, E, Kastner, R & Ziolkowski, RW 1997, 'Absorbing boundary conditions in the context of the hybrid ray-FDTD moving window solution', IEEE ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM 1997, VOLS 1-4, IEEE Antennas-and-Propagation-Society International Symposium / North American Radio Science Meeting, I E E E, MONTREAL, CANADA, pp. 1006-1009.
Tellambura, C, Guo, YJ & Barton, SK 1997, 'Noniterative approach for computing linear equaliser tap weights', IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, pp. 302-306.
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A fast computation method for the tap weights of a linear equaliser is developed. By approximating the channel autocorrelation matrix, which has a Toeplitz structure, by a circulant matrix, the tap weights can be solved via discrete fourier transform (DFT) techniques. For an equaliser with N taps, the approximate tap weights approach the exact tap weights as N → ∞. Excess mean-square error and bit error rate (BER) degradation caused by the approximate tap weights are computed for a representative channel.
Tellambura, C, Johnson, IR, Guo, YJ & Barton, SK 1997, 'Equalization and frequency offset correction for HIPERLAN', IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, pp. 796-800.
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To reduce the effects of inter-symbol interference resulting from the dispersive nature of the indoor radio channel most HIPERLAN receivers will incorporate an adaptive equalizer. In this paper, computational complexity of several equalizer algorithms is estimated. The effect of frequency offset between transmitter and receiver on the performance of such an equalizer is investigated. By employing a decision feedback equalizer incorporating a second order phase locked loop, the effect of both the intersymbol interference and frequency offset can be significantly reduced. Using such a technique, the packet error ratio (PER) of a HIPERLAN radio link in a multipath channel is found by simulation.
Whaits, CV & Braun, RM 1997, 'Phase errors in the coherent demodulation of VPSK and a solution using DSSS modulation', Proceedings of the South African Symposium on Communications and Signal Processing, COMSIG, pp. 107-110.
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The use of Single Sideband Suppressed Carrier (SSBSC) techniques in conjunction with digital modulation schemes, like Variable Phase Shift Keying (VPSK) places stringent phase requirements on coherent demodulation. In this Paper, the problems of coherent demodulation and soft decision detection/decoding in a conventional 2-VPSK modulation scheme, with a bandwidth efficiency of 4 bits per Hertz, are discussed and then a possible solution using Direct Sequence Spread Spectrum (DSSS) modulation is presented.
Zhang, J, Arnold, JF, Frater, MR & Pickering, MR 1997, 'Video error concealment using decoder motion vector estimation', IEEE Region 10 Annual International Conference, Proceedings/TENCON, pp. 777-780.
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Audio-visual and other multimedia services are seen as important sources of traffic for future wireless networks. An important characteristic of such networks is that they introduce a significant number of errors into the transmitted digital bitstream. For services such as video, these errors can have the effect of degrading the quality of the received service to the point where it is unusable. In this paper, we introduce a technique that allows the concealment of the impact of these errors. Our work is based on MPEG 2 encoded video (although our scheme would work equally well with other standards) to be transmitted over a wireless network whose data structures are similar to those of Asynchronous Transfer Mode (ATM). Our simulations include the impact of the MPEG 2 Systems Layer and cover cell loss rates up to 5%.