Today wireless transmission of data is becoming more and more popular and the need for faster transmission rates is increasing. Since the bandwidth is limited it is important to try to use it to the fullest. CDMA is a technology that allows multiple accesses on the same frequency and time thus making it very bandwidth efficient. The CDMA technology was first introduced in the second generation’s cellular systems but has since then been improved and is reused in today’s 3G systems as Wideband CDMA. ISY is interested in getting a behavioural model of a W-CDMA system since they had developed a DSP processor called BBP1 and were thinking about adding W-CDMA support for it. Even though our system is not implemented on the BBP1 it should provide a good base for future implementations. This thesis project will describe the construction of a behavioural model of a W-CDMA system following the standard specified by 3GPP. The system simulates W-CDMA transmission and reception and has an optional channel used to simulate real world interference. The receiver uses a rake combiner to improve the performance of the system.

In this diploma thesis the basic principles of inkjet print, ink composition, print media and degradation mechanisms of ink dyes are summarized. The thesis deals with study of varnish barrier properties in coloured inkjet prints. Permeability of water vapour and oxygen (parts of atmosphere) depending on different coatings are tested there. In addition the influence of ozone on degradation of dyes was studied, while ozone was permeating through barrier varnish layer of inkjet print. Ozone plays an important role in degradation processes of the inkjet prints and it also causes a gas-fading. Concentrations of acting ozone were established by iodometric titration. Simultaneously kinetics of degradation of Orange 7 was studied on indicator papers.

This thesis deals with financing possibilities for investment of the municipality project. The first part includes the theoretical thesis for understanding the functioning of the municipality and put communities funding opportunities. The second section includes a brief introduction to the community, socio-economic analysis and financial analysis in the selected period 2009 – 2012 and also the evaluation of this implementation and introduction the investment activities of the municipality. The last part of the investment project involves the presentation of individual municipality project and the possibilities of its financial coverage with final recommended options for funding.

Práce podává přehled o dostupných a využívaných metodách, normách pro testování a hodnocení světlostálosti barevných fotografií a tisků. Bylo provedeno porovnání jednotlivých platných norem a návrhů na hodnocení. Tato práce pojednává o ochraně inkjetových tisků pomocí lakování. Byl připraven lak kompatibilní s fotografickými médii. Připravená kompozice byla obohacena o UV absorbéry EVERSORB ve dvou koncentracích. Pro srovnání byly také testovány tři druhy komerčních ochranných fotografických laků. Výtisky se třemi barvivovými inkousty opatřené lakovou vrstvou, byly vystaveny jak urychlenému světelnému stárnutí v xenonové testovací komoře, tak urychlenému stárnutí v ozonové testovací komoře. Na základě měřených odrazových spekter byl vypočítaný objem barvového gamutu pomocí softwaru Volga. Byl sledován úbytek gamutů v průběhu světelného stárnutí i při expozici ozonem. Stárnutí vzorků probíhalo do ukončení testu, nebo do dosažení kritéria 30% úbytku objemu barvového gamutu. Také bylo pozorováno selhání recipročního zákona, které ukazuje na jistou nepřesnost při předpovědi dlouhé životnosti vzorků. Pomocí změny barvového gamutu byla posuzována ochrana připraveného laku před UV záření a ozonem. Studované vrstvy laků byly dále charakterizovány na prostupnost kyslíku a vodní páry.

Multiple antenna techniques are used to increase the robustness and performance of wireless networks. Multiple antenna techniques can achieve diversity and increase bandwidth efficiency when specially designed channel codes are used at the scheme’s transmitter. These channel codes can be designed in the space, time and frequency domain. These specially designed channel codes in the space and time domain are actually designed for flat fading channels and in frequency selective fading channel, their performance may be degraded. To counteract this possible performance degradation in frequency selective fading channel, two main approaches can be applied to mitigate the effect of the symbol interference due to the frequency selective fading channel. These approaches are multichannel equalisation and orthogonal frequency division multiplexing (OFDM). In this thesis, a multichannel equalisation technique and OFDM were applied to channel codes specially designed for multiple antenna systems. An optimum receiver was proposed for super-orthogonal space-time trellis codes in a multichannel equalised frequency selective environment. Although the proposed receiver had increased complexity, the diversity order is still the same as compared to the code in a flat fading channel. To take advantage of the multipath diversity possible in a frequency selective fading channel, super-orthogonal block codes were employed in an OFDM environment. A new kind of super-orthogonal block code was proposed in this thesis. Super-orthogonal space-frequency trellis-coded OFDM was proposed to take advantage of not only the possible multipath diversity but also the spatial diversity for coded OFDM schemes. Based on simulation results in this thesis, the proposed coded OFDM scheme performs better than all other coded OFDM schemes (i.e. space time trellis-coded OFDM, space-time block coded OFDM, space-frequency block coded OFDM and super-orthogonal space-time trellis-coded OFDM). A simplified channel estimation algorithm was proposed for two of the coded OFDM schemes, which form a broad-based classification of coded OFDM schemes, i.e. trelliscoded schemes and block-coded schemes. Finally in this thesis performance analysis using the Gauss Chebychev quadrature technique as a way of validating simulation results was done for super-orthogonal block coded OFDM schemes when channel state information is known and when it is estimated. The results obtained show that results obtained via simulation and analysis are asymptotic and therefore the proposed analysis technique can be use to obtain error rate values for different SNR region instead of time consuming simulation. / Thesis (PhD)--University of Pretoria, 2012. / Electrical, Electronic and Computer Engineering / unrestricted

The aluminium alloys for electrical conductivity applications are generally not grain refinedsince the addition of grain refiners drops the electrical conductivity by introducing impuritiesinto the melt. Non-grain refined aluminium may lead to bar fracture and cracks during themetalworking process. The present study focuses to find an optimum balance between the grain refiner addition andthe electrical conductivity of commercial EC grade 1070 aluminium alloy for electricalapplication. In order to reach this goal, the electrical conductivity and the macrostructure ofcommercial EC grade 1070 aluminium (commercial pure aluminium) have been studiedunder a series of controlled lab scale trails. Specific addition levels of different grain refiners(TiBloy, Al-5Ti-1B, Al-3Ti-0.15C, and Al-3Ti-1B) were added to the metal melt and sampleswere taken at specific time intervals. The collected samples were sectioned, ground andmacro-etched. Thereafter, the macrostructure was analysed by the use of a digital camera andthe electrical conductivity was measured at temperature. The obtained result was expressed asa percentage of the International Annealed Copper Standard (IACS %). The macro-structuralanalysis showed that TiBloy, Al-5Ti-1B, and Al-3Ti-1B, with the maximum addition level of0.1%, cannot grin refine commercial pure aluminium. However, at higher grain refiner levelsthe number of columnar grains increased and their size decreased. The Al-3Ti-0.15C master alloy, with the same addition level as the once chosen for the othergrain refiners (up to 0.1%), showed significantly better grain refining. By the addition of0.1% of this grain refiner the macrostructure became very equiaxed already after 30 minutesof grain refiner addition. The fading of the Al-3Ti-0.15 master alloy was, however, observedfor samples with a long holding time. Nevertheless, by maximum addition level (0.1%) and a90 minutes holding time the macrostructure remained as equiaxed grains. The electrical conductivity results showed that none of the applied grain refiners (TiBloy, Al-5Ti-1B, Al-3Ti-0.15C, and Al-3Ti-1B), with the maximum addition level of 0.1%, decreasedthe electrical conductivity of commercial pure aluminium.

This thesis describes the application of adaptive equalization based on the constant modulus algorithm (CMA) and the decision-feedback minimum mean squared error (DF-MMSE) concept to the two compatible offset QPSK waveforms (FQPSK and SOQPSK-TG) that constitute the ARTM Tier-1 waveforms. An adaptive version of the DF-MMSE equalizer is developed and applied to this application. In the presence of frequency selective multipath interference typically encountered in aeronautical telemetry, both equalization techniques are shown to provide reliable performance for FQPSK and SOQPSK-TG. The performance of both waveforms with the DF-MMSE equalizer is slightly better than that using the CMA equalizer. Implementation trade-offs between the two types of equalizers are discussed.

[pt] Propõe-se alternativas para exploração da amostragem a taxas múltiplas da taxa símbolos (superamostragem) em receptores cegos com decisão de sequências de símbolos, a fim de se obter melhoria de desempenho em canais com desvanecimento rápido e seletivo em frequência. O trabalho se centra em esquemas de recepção do tipo MLSE/PSP (maximum likelihood sequence estimation/per-survivor processing) baseados na modelagem estocástica do canal. Deduz-se um modelo em espaço de estado para a geração das amostras do sinal recebido, cujos parâmetros podem ser facilmente associados ao sistema de transmissão. Investiga- se também uma estratégia de ataque ao problema de recepção diante de ruído colorido, intrinsecamente associado à superamostragem. O desempenho dos esquemas de recepção propostos é avaliado através de simulação computacional. Os resultados obtidos mostram que a exploração da superamostragem produz ganhos significativos de desempenho na recepção cega de sequências, em relação aos esquemas de recepção MLSE/PSP com amostragem síncrona (taxa de amostragem igual à taxa de símbolos). / [en] In this work we propose exploting the received signal oversampling in order to improve the performance of blind receivers over fast fequency selective fading channels.The work focus attention on MLSE/PSP (maximum-likelihood sequence estimation/per survivor processing) receivers and statistical modeling of the channel output. A state-space model for oversampled received signal in developed from a generic continous time transmission system model. Two MLSE/PSP receiving schemes relying on this model are proposed. One of them is specially suitable for dealing with the colored noise produced by oversampling. Computer simulations were conducted in order to evaluate the performance of the proposed blind receivers. The results thus obtained show that these schemes significantly outperform the synchronous MLSE/PSP receiver (for which the sampling rate is equal to the sysmbol rate).

Two topics in fading channels with a strict delay constraint and a resolution-constrained feedback link are treated in this thesis. First, a multi-layer variable-rate single-antenna communication system with quantized feedback, where the expected rate is chosen as the performance measure, is studied under both short-term and long-term power constraints. Iterative algorithms exploiting results in the literature of parallel broadcast channels are developed to design the system parameters. A necessary and sufficient condition for single-layer coding to be optimal is derived. In contrast to the ergodic case, it is shown that a few bits of feedback information can improve the expected rate dramatically. The role of multi-layer coding, however, reduces quickly as the resolution of the feedback link increases. The other part of the thesis deals with partial power control systems utilizing quantized feedback to minimize outage probability, with an emphasis on the diversity-multiplexing tradeoff. An index mapping with circular structure is shown to be optimal and the design is facilitated with a justified Gaussian approximation. The diversity gain as a function of the feedback resolution is analyzed. The results are then extended to characterize the entire diversity-multiplexing tradeoff curve of multiple-antenna channels with resolution-constrained feedback. Adaptive-rate communication is also studied, where the concept of minimum multiplexing gain is introduced. It is shown that the diversity gain of a system increases significantly even with coarsely quantized feedback, especially at low multiplexing gains. / QC 20101117

In wireless communications, frequency-selective fading is a major source of impairment for wireless communications. In this research, a novel Frequency-Domain Independent Component Analysis (ICA-F) approach is proposed to blindly separate and deconvolve signals traveling through frequency-selective, slow fading channels. Compared with existing time-domain approaches, the ICA-F is computationally efficient and possesses fast convergence properties. Simulation results confirm the effectiveness of the proposed ICA-F. Orthogonal Frequency Division Multiplexing (OFDM) systems are widely used in wireless communications nowadays. However, OFDM systems are very sensitive to Carrier Frequency Offset (CFO). Thus, an accurate CFO compensation technique is required in order to achieve acceptable performance. In this dissertation, two novel blind approaches are proposed to estimate and compensate for CFO within the range of half subcarrier spacing: a Maximum Likelihood CFO Correction approach (ML-CFOC), and a high-performance, low-computation Blind CFO Estimator (BCFOE). The Bit Error Rate (BER) improvement of the ML-CFOC is achieved at the expense of a modest increase in the computational requirements without sacrificing the system bandwidth or increasing the hardware complexity. The BCFOE outperforms the existing blind CFO estimator [25, 128], referred to as the YG-CFO estimator, in terms of BER and Mean Square Error (MSE), without increasing the computational complexity, sacrificing the system bandwidth, or increasing the hardware complexity. While both proposed techniques outperform the YG-CFO estimator, the BCFOE is better than the ML-CFOC technique. Extensive simulation results illustrate the performance of the ML-CFOC and BCFOE approaches.