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x, 120 leaves : diags., tables ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1978) from the Dept. of Electrical Engineering, University of Adelaide

116 leaves : diags., tables ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.1978) from the Dept. of Electrical Engineering, University of Adelaide

Zugl.: Aachen, Techn. Hochsch., Diss., 2006.

Zugl.: Dresden, Techn. Univ., Diss., 2007

[pt] É desenvolvido um modelo para sistemas rádio-digitais que inclui os tipos de modulação mais usuais como PSK-4, PSK- 8, QAM-16, com recepção coerente. Neste modelo é considerado um canal linear e um meio de propagação sujeito a desvanecimento por multipercursos, sendo analisadas algumas alternativas para sua representação, em particular os chamados modelos de dois e três raios. Neste contexto é considerado o problema do cálculo de desempenho, especialmente o cálculo da confiabilidade dos sistemas. Utilizando-se um critério de probabilidade de erro, calculada numericamente pelo método da Quadratura de Gauss, ou um critério de fechamento de olho, são implementados algoritmos para cálculo de Assinaturas dos diversos sistemas. A partir destas assinaturas os sistemas são comparados, analisando-se os efeitos da margem do enlace e da largura de faixa. Alguns métodos de cálculo de confiabilidade são analisados e aplicados ao estudo comparativo dos sistemas. / [en] It´s developed a model for digital-radio systems which includes the most usual ones as PSK-4, PSK-8, QAM-16, with coherent detection. This model considers a linear channel and a propagation medium subject to multipath fadings, being analyzed some of it´s possible representations, particularly the so called two paths and three paths models. It is specially considered the computation of the systems´ outage probability. Using an error probability criterium numerically computed by the Gauss Quadrature Rule or an eye-closure one, algorithms are implemented to calculate Systems´ Signatures. Based on these signatures systems are compared considering their bandwidths and link´s flat fading margin. Some methods for outage probability calculation are analyzed and applied to systems´ comparations.

Trellis coded modulation (TCM) schemes, due to their bandwidth efficiency and coding gain, have been proposed for multipath fading (MF) channels. The object of this research is to analyze the performance of TCM schemes in MF channels. While many excellent studies have already been reported, they share some of the following restrictions: (1) an assumption of ideal channel measurements and ideal interleaving, (2) use of Chernoff bounds, which are loose in this case, (3) analysis of only the Rayleigh channel, ignoring the Rician channel, and (4) reliance on computer simulation to get the actual performance. Extending analytical results without these restrictions is addressed in this work. This thesis derives a saddle point approximation (SAP) method to compute the pairwise error probability (PEP) of TCM schemes transmitted over Rician fading channels. It can be applied under several conditions, including finite or ideal interleaving, and is derived for a pilot-tone model, encompassing ideal coherent detection, pilot-tone aided detection, pilot-symbol aided detection, and differential detection. Its accuracy is demonstrated by comparison to the results of numerical integration. Under ideal interleaving, the approximation can be further simplified to an expression, which is in a product form and is much tighter than the ordinary Chernoff bound on the PEP. Also, based on the SAP, the effect of finite interleaving depth on the error performance is studied. The Canadian mobile satellite (MSAT) channel has been modelled as the sum of lognormal and Rayleigh components. Previously, the performance of TCM schemes in this channel has been obtained via computer simulation. In this thesis, new analytical expressions are derived for the PEP of TCM schemes transmitted over this channel employing ideal interleaving, and the results are substantiated by means of computer simulation. In addition, first order statistics of absolute and differential phases of a shadowed Rician process are derived. This thesis presents new performance bounds of TCM schemes over nonindependent (i.e., finite interleaving) Rician fading channels. In addition, for Rayleigh fading channels with an exponential auto-covariance function, bounds resembling those for memoryless channels are derived. The bounds, being more accurate than Chernoff bounds, permit accurate estimation of system performance. The performance of concatenated coding systems and automatic-repeal-request (ARQ) systems operating on fading channels is addressed. New error expressions,which sow asymptotic error behaviour, are derived for systems which use a modified Viterbi decoding algorithm. They allow useful evaluation of the coding gain and throughput. Finally, the performance of convolutional codes in fading channels is analyzed. An upper bound on the bit error probability, the optimum power split ratio between the data and pilot signals, and the channel cut-off rate are derived. / Graduate

Approved for public release; distribution is unlimited. / Wireless communication is employed to connect mobile computers in a networked environment for information exchange. In a tactical space, sensors and computers typically need to operate on-the-move while transmitting data over both short and long distances in different terrain and conditions. The wireless communication is thus susceptible to effects of Doppler shift and channel fading. In addition, when security and anti jamming features are required, such as frequency-hopping techniques, then coherent signal detection is difficult and noncoherent modulation is used instead. Our study will focus on the bit error rate (BER) performance analysis of noncoherent orthogonal modulation, specifically M-ary frequency-shift keying (MFSK) and code-shift keying (CSK) modulation, in both additive white Gaussian noise (AWGN) and for a Rayleigh fading channel with Doppler shift. The potential applications include communications between mobile computer-sensor devices, such as a mobile ground control station maintaining a datalink with UAV. / Civilian

Windowing systems offer many benefits to users, such as being able to work on multiple tasks concurrently; or working with a number of windows, each connected to different remote machines or applications. Unless these windows are managed efficiently, users can easily become overwhelmed by the number of currently open windows and lose their way round the desktop. This can lead to a state where the desktop is cluttered with windows. At this stage "window thrashing" occurs, as users begin to perform window management operations (move, resize, minimise etc.) in order to locate relevant pieces of information contained in one of several open windows.