Master of Engineering by Research / As a multi-carrier modulation scheme, Orthogonal Frequency Division Multiplexing (OFDM) technique can achieve high data rate in frequency-selective fading channels by splitting a broadband signal into a number of narrowband signals over a number of subcarriers, where each subcarrier is more robust to multipath. The wireless communication system with multiple antennas at both the transmitter and receiver, known as multiple-input multiple-output (MIMO) system, achieves high capacity by transmitting independent information over different antennas simultaneously. The combination of OFDM with multiple antennas has been considered as one of most promising techniques for future wireless communication systems. The challenge in the detection of a space-time signal is to design a low-complexity detector, which can efficiently remove interference resulted from channel variations and approach the interference-free bound. The application of iterative parallel interference canceller (PIC) with joint detection and decoding has been a promising approach. However, the decision statistics of a linear PIC is biased toward the decision boundary after the first cancellation stage. In this thesis, we employ an iterative receiver with a decoder metric, which considerably reduces the bias effect in the second iteration, which is critical for the performance of the iterative algorithm. Channel state information is required in a MIMO-OFDM system signal detection at the receiver. Its accuracy directly affects the overall performance of MIMO-OFDM systems. In order to estimate the channel in high-delay-spread environments, pilot symbols should be inserted among subcarriers before transmission. To estimate the channel over all the subcarriers, various types of interpolators can be used. In this thesis, a linear interpolator and a trigonometric interpolator are compared. Then we propose a new interpolator called the multi-tap method, which has a much better system performance. In MIMO-OFDM systems, the time-varying fading channels can destroy the orthogonality of subcarriers. This causes serious intercarrier interference (ICI), thus leading to significant system performance degradation, which becomes more severe as the normalized Doppler frequency increases. In this thesis, we propose a low-complexity iterative receiver with joint frequency- domain ICI cancellation and pilot-assisted channel estimation to minimize the effect of time-varying fading channels. At the first stage of receiver, the interference between adjacent subcarriers is subtracted from received OFDM symbols. The parallel interference cancellation detection with decision statistics combining (DSC) is then performed to suppress the interference from other antennas. By restricting the interference to a limited number of neighboring subcarriers, the computational complexity of the proposed receiver can be significantly reduced. In order to construct the time variant channel matrix in the frequency domain, channel estimation is required. However, an accurate estimation requiring complete knowledge of channel time variations for each block, cannot be obtained. For time- varying frequency-selective fading channels, the placement of pilot tones also has a significant impact on the quality of the channel estimates. Under the assumption that channel variations can be approximated by a linear model, we can derive channel state information (CSI) in the frequency domain and estimate time-domain channel parameters. In this thesis, an iterative low-complexity channel estimation method is proposed to improve the system performance. Pilot symbols are inserted in the transmitted OFDM symbols to mitigate the effect of ICI and the channel estimates are used to update the results of both the frequency domain equalizer and the PICDSC detector in each iteration. The complexity of this algorithm can be reduced because the matrices are precalculated and stored in the receiver when the placement of pilots symbols is fixed in OFDM symbols before transmission. Finally, simulation results show that the proposed MIMO-OFDM iterative receiver can effectively mitigate the effect of ICI and approach the ICI-free performance over time-varying frequency-selective fading channels.

The angular resolution of an imaging system is sharply bounded by the diffraction limit, a fundamental property of electromagnetic radiation propagation. In order to increase resolution and see finer details of remote objects, the sizes of telescopes and cameras must be increased. As the size of the optics increase, practical problems and costs increase rapidly, making sparse aperture systems attractive for some cases. The method of Intensity Correlation Imaging (ICI) provides an alternative method of achieving high angular resolution that allows a system to be built with less stringent precision requirements, trading the mechanical complexity of a typical sparse aperture for increased computational requirements. Development of ICI has stagnated in the past due to the inadequacies of computational capabilities, but the continued development of computer technologies now allow us to approach the image reconstruction process in a new, more e ffctive manner. This thesis uses estimation methodology and the concept of transverse phase diversity to explore the modern bounds on the uses of ICI. Considering astronomical observations, the work moves beyond the traditional, single-parameter uses of ICI, and studies systems with many parameters and complex interactions. It is shown that ICI could allow significant new understanding of complex multi-star systems. Also considered are exoplanet and star-spot measurements; these are less promising due to noise considerations. Looking at the Earth imaging problem, we find significant challenges, particularly related to pointing requirements and the need for a large field-of-view. However, applying transverse phase diversity (TPD) measurements and a least-squares estimation methodology solves many of these problems and re-opens the possibility of applying ICI to the Earth-imaging problem. The thesis presents the TPD concept, demonstrates a sample design that takes advantage of the new development, and implements reconstruction techniques. While computational challenges remain, the concept is shown to be viable. Ultimately the work presented demonstrates that modern developments greatly enhance the potential of ICI. However, challenges remain, particularly those related to noise levels.

This dissertation presents four technical contributions in the theory and practice of low-density parity-check (LDPC) codes and orthogonal frequency division multiplexing (OFDM) systems withtransmission non-linearity and with interference due to high mobility.We first explore the universality of LDPC codes for the binary erasure channel (BEC), the AWGN channel, and the flat Rayleigh fading channel. Using excess mutual information as a performance measure, we demonstrate that an LDPC code designed on a singlechannel can be universally good across the three channels. Thus, a channel for which LDPC code design is simple may be used as a surrogate for channels that are more challenging.Due to fast channel variations, OFDM systems suffer from inter-carrier interference (ICI) in frequency-selective fast fading channels. We propose a novel iterative receiver design that achieves near-optimal performance while maintaining a complexity that grows only linearly with the number of OFDM carriers. Weprove that the matched filter bound for such a channel is also the maximum-likelihood sequence detection (MLSD) bound.Because of the presence of high peaks at OFDM modulator output, amplitude clipping due to amplifier saturation causes performance degradation. We show that existing analyses underestimate the capacity of OFDM systems with clipping, and we analyze thecapacity of clipped OFDM systems with AWGN and frequency-selective Rayleigh fading. We prove that for frequency-selective Rayleigh fading channels, under certain conditions, there exists an SNR threshold, above which the capacity of a clipped system is higherthan that of an unclipped system. We provide upper and lower bounds on the channel capacity and closed-form approximations of discrete-input capacities with and without clipping.We also derive tight MLSD lower bounds and propose near-optimal receivers for OFDM systems with clipping. We show that over frequency-selective Rayleigh fading channels, under certain conditions, a clipped system with MLSD can achieve better performance than an unclipped system. We show that the MLSD boundscan be achieved or closely approached by the proposed low complexity receivers in various channel types.

Master of Engineering by Research / As a multi-carrier modulation scheme, Orthogonal Frequency Division Multiplexing (OFDM) technique can achieve high data rate in frequency-selective fading channels by splitting a broadband signal into a number of narrowband signals over a number of subcarriers, where each subcarrier is more robust to multipath. The wireless communication system with multiple antennas at both the transmitter and receiver, known as multiple-input multiple-output (MIMO) system, achieves high capacity by transmitting independent information over different antennas simultaneously. The combination of OFDM with multiple antennas has been considered as one of most promising techniques for future wireless communication systems. The challenge in the detection of a space-time signal is to design a low-complexity detector, which can efficiently remove interference resulted from channel variations and approach the interference-free bound. The application of iterative parallel interference canceller (PIC) with joint detection and decoding has been a promising approach. However, the decision statistics of a linear PIC is biased toward the decision boundary after the first cancellation stage. In this thesis, we employ an iterative receiver with a decoder metric, which considerably reduces the bias effect in the second iteration, which is critical for the performance of the iterative algorithm. Channel state information is required in a MIMO-OFDM system signal detection at the receiver. Its accuracy directly affects the overall performance of MIMO-OFDM systems. In order to estimate the channel in high-delay-spread environments, pilot symbols should be inserted among subcarriers before transmission. To estimate the channel over all the subcarriers, various types of interpolators can be used. In this thesis, a linear interpolator and a trigonometric interpolator are compared. Then we propose a new interpolator called the multi-tap method, which has a much better system performance. In MIMO-OFDM systems, the time-varying fading channels can destroy the orthogonality of subcarriers. This causes serious intercarrier interference (ICI), thus leading to significant system performance degradation, which becomes more severe as the normalized Doppler frequency increases. In this thesis, we propose a low-complexity iterative receiver with joint frequency- domain ICI cancellation and pilot-assisted channel estimation to minimize the effect of time-varying fading channels. At the first stage of receiver, the interference between adjacent subcarriers is subtracted from received OFDM symbols. The parallel interference cancellation detection with decision statistics combining (DSC) is then performed to suppress the interference from other antennas. By restricting the interference to a limited number of neighboring subcarriers, the computational complexity of the proposed receiver can be significantly reduced. In order to construct the time variant channel matrix in the frequency domain, channel estimation is required. However, an accurate estimation requiring complete knowledge of channel time variations for each block, cannot be obtained. For time- varying frequency-selective fading channels, the placement of pilot tones also has a significant impact on the quality of the channel estimates. Under the assumption that channel variations can be approximated by a linear model, we can derive channel state information (CSI) in the frequency domain and estimate time-domain channel parameters. In this thesis, an iterative low-complexity channel estimation method is proposed to improve the system performance. Pilot symbols are inserted in the transmitted OFDM symbols to mitigate the effect of ICI and the channel estimates are used to update the results of both the frequency domain equalizer and the PICDSC detector in each iteration. The complexity of this algorithm can be reduced because the matrices are precalculated and stored in the receiver when the placement of pilots symbols is fixed in OFDM symbols before transmission. Finally, simulation results show that the proposed MIMO-OFDM iterative receiver can effectively mitigate the effect of ICI and approach the ICI-free performance over time-varying frequency-selective fading channels.

Thesis (Ph. D.)--University of New South Wales, 1999. / Also available online.

No description available.

As astronomers and astrophysicists seek to view ever-increasingly distant celestial objects, the desired angular resolution of telescopes is constantly being increased. Classical optics, however, has shown a proportional relationship between the size of an optical telescope and the possible angular resolution. Experience has also shown that prohibitive cost accompanies large optical systems. With these limitations on classical optical systems and with the drastic increase in computational power over the past decade, intensity correlation interferometry (ICI) has seen renewed interest since the 1950’s and 60’s when it was initially conceived by Hanbury Brown and Twiss. Intensity correlation interferometry has the advantage of less stringent equipment precision and less equipment cost when compared to most other forms of interferometry. ICI is thus attractive as a solution to the desire for high angular resolution imaging especially in space based imaging systems. Optical interferometry works by gathering information about the Fourier transform of the geometry of an optical source. An ICI system, however, can only detect the magnitude of the Fourier components. The phase of the Fourier components must be recovered through some computational means and typically some a priori knowledge of the optical source. This thesis gives the physics and mathematical basis of the intensity correlation interferometer. Since the ICI system cannot detect the phase of an optical source's Fourier transform, some known methods for recovering the phase information are discussed. The primary method of interest here is the error-reduction algorithm by Gerchberg-Saxton which was adapted by Fienup to phase retrieval. This algorithm works by using known qualities of the image as constraints; however, sometimes it can be difficult to know what these constraints are supposed to be. A method of adaptively discovering these constraints is presented, and its performance is evaluated in the presence of noise. Additionally, an algorithm is presented to adapt to the presence of noise in the Fourier modulus data. Finally, the effects of the initial condition of the error-reduction algorithm are shown and a method of mitigating its effect by averaging several independent solutions together is shown.

Abstract Altogether 406 patients were included in five studies, and all patients were examined and controlled in the Oulu University Hospital during the years 1991–1998. Twenty-nine patients with mixed-type erectile dysfunction (ED) were recruited into a randomized, controlled, double-blind crossover comparison of placebo and high-dose yohimbine hydrochloride (36 mg per day orally). Positive clinical responses were obtained in 44% of the patients during yohimbine treatment and in 48% during placebo treatment. Thirty patients with ED underwent an intracavernosal injection test (ICI) using three different active agents (prostaglandin E1(PGE1), papaverine hydrochloride (PV), moxisylyte (MS)) and physiological saline. PGE1 produced significantly better rigidity than either PV or MS. Sixty-nine patients with ED who had started ICI therapy with PGE1 at least three years previously were invited to a control examination to find out the long-term outcome of this treatment and to evaluate the patients' overall satisfaction with their sexual life. 46.4% of the patients had discontinued PGE1 therapy, the mean time of using PGE1 having been 23.3 months (range 0–48 months). 34.8% of the patients reported that their own spontaneous erections had improved during the PGE1 therapy. The sexual functions of 155 patients with benign prostatic hyperplasia (BPH) were evaluated before TURP and 6 and 12 months afterwards with questionnaires. Only 26% of the patients had completely satisfactory erections before TURP, while 22% had satisfactory erections 6 months later and 24% 12 months later. The majority of patients (about 70%) were satisfied with their sexual life both before and after the procedure. 123 men with symptoms of andropause participated in a randomized, placebo-controlled study to assess the effects of dihydrotestosterone (DHT) gel in men with andropausal symptoms. The drug was administered transdermally once a day during six months. Early morning erections improved significantly (p < 0.003) in the DHT group by the three-month control, the ability to maintain erections was better, and there was also a positive effect on libido. In the patients with a elevated (> 12) international index of the prostatic symptoms score (I-PSS) before DHT treatment, I-PSS decreased from 17.7 to 12.3 points. As a conclusion yohimbine hydrochloride is no better than placebo in the treatment of patients with mixed-type ED. PGE1, PV and MS are well tolerated, and PGE1 was shown to be the most effective drug of the three. ICI therapy with PGE1 in long-term use is safe and effective. Sexual functions in men did not change after TURP, and this group of aging men were fairly satisfied with their sexual life despite of the fact that they had some ED and one third of the patients had not had intercourse during the previous year. Transdermal administration of DHT in aging men improves sexual function.

This master thesis aims for Inter-carrier interference (ICI) mitigation in orthogonal frequency division multiplexing (OFDM) system by considering designs of frequency domain cyclic extension(FDCE) and optimal windowing pulse shape. Although OFDM system has been put forward in the 1970s, it has just emerged in 4G. In the early stage, it has been restricted by its high computational complexity. With the discovery that modulation and demodulation process of OFDM can be realized by discrete Fourier transform (DFT) and inverse discrete Fourier transform (IDFT), it is widely used in 4G and 5G-New Ratio (NR). Based on OFDM system, a variety of derivative systems are further proposed and applied. With the development of 5G technology in the mobile communication, the requirement of signal propagation between high-speed mobile user and base station (BS) is higher and higher. With the increase of the moving speed of objects, the frequency shift caused by Doppler eff ect can not be underestimated. ICI caused by Doppler shift is becoming more and more serious. Therefore, how to eliminate the ICI caused by Doppler shift has become an inevitable potential problem. In this thesis, two eff ective approaches for ICI mitigation have been explored and studied. By adding FDCE and optimal windowing pulse shape, the system performance is analyzed and the system simulation is constructed in MATLAB.

A existência de associações bidirecionais entre o Sistema Nervoso e o Sistema Imune reforça a hipótese de que mudanças no Sistema Nervoso Central (SNC) influenciam a resposta imune e a susceptibilidade orgânica às doenças. De fato, em contextos de estresse físico ou psicológico, glicocorticóides liberados pelo córtex das adrenais e catecolaminas produzidas pelo Sistema Nervoso Autônomo Simpático (SNAS) e pela medula das adrenais, modulam a atividade do Sistema Imune. O estresse psicológico associado no ser humano ao ato de cuidar e conviver com companheiros acometidos por diversos tipos de enfermidades crônicas ou transtornos psíquicos têm sido correlacionado ao aparecimento de alterações comportamentais, tais como depressão e ansiedade, assim como alterações imunes e queda da resistência orgânica às infecções. Em nosso laboratório, camundongos que conviveram por 14 dias com coespecíficos portadores de um tumor ascítico de Ehrlich (TAE) apresentaram importantes alterações comportamentais e de imunidade inata, atribuídas tanto à estimulação do sistema catecolaminérgico central e do SNAS. Desta forma, pareceu-nos relevante estudar mais profundamente e dentro de uma perspectiva neuroimune o envolvimento do SNAS com os efeitos desencadeados pela convivência com dois portadores do TAE usando como ferramentas farmacológicas o propranolol (antagonista -adrenérgico) e o ICI-118,551 (antagonista β2-adrenérgico). Os resultados obtidos mostraram que o bloqueio dos receptores β-adrenérgicos nos animais companheiros do doente: 1) reverteu o comportamento do tipo-ansioso, uma vez que os camundongos voltaram a frequentar a zona central do campo aberto e reduziu a velocidade média dos animais no campo aberto, porém, não alterou de forma significante a distância total percorrida; 2) reverteu a diminuição nos níveis de noradrenalina e aumentou os níveis do metabólito VMA no hipotálamo, mas não alterou o turnover hipotalâmico de noradrenalina ou os níveis de monoaminas e de seus metabólitos no córtex frontal e no bulbo olfatório; 3) não alterou os níveis séricos de corticosterona; 4) não alterou o peso relativo das adrenais; 5) não alterou a contagem de células na medula óssea; 6) modulou a porcentagem de células natural killer (NK) sanguíneas e esplênicas e diminuiu a expressão da molécula CD69 em células NK esplênicas, mas não alterou a expressão da molécula CD69 em células NK sanguíneas; 7) não alterou o burst basal ou induzido por PMA ou por SAPI e a fagocitose de neutrófilos. O bloqueio dos receptores β2-adrenérgicos nos animais companheiros do doente alterou apenas a expressão da molécula CD69 em células NK sanguíneas, mas não modificou de forma significante quaisquer dos parâmetros comportamentais e neuroquímicos analisados. Conclui-se, então, que algumas das alterações imunes e comportamentais desencadeadas pela convivência com coespecíficos portadores de TAE sejam mediadas pelo SNAS via receptores beta-adrenérgicos / The existence of bi-directional interactions between the Nervous System and the Immune System reinforces the hypothesis that changes in Central Nervous System (CNS) activity modify not only the immune response but also the susceptibility to diseases. Indeed, in presence of physical or psychological stress, glucocorticoids released by the cortex of the adrenal gland and catecholamines released by the Autonomic Sympathetic Nervous System (ASNS) activation and the adrenal glands were reported to modulate the activity of the Immune System. Psychological stress was described in human caregivers of sick partners, especially when they present chronic diseases and/or psychological disorders, such as depression and anxiety; immune disorders and decreased host resistance to infections were also reported in caregivers. In our laboratory, Swiss mice that lived for 14 days with Ehrlich ascetic tumor bearing conspecifics showed interesting behavioral and innate immune changes that were attributed to catecholaminergic activation within the Central Nervous System or to ASNS activation. Thus, it seemed relevant to study more deeply and under a neuroimmune perspective the involvement of the ASNS in the effects triggered by cohabitation with two sick partners using as pharmacological tools: propranolol (β-adrenergic antagonist) and ICI-118.551 (β2-adrenergic antagonist). Our results showed that β-adrenergic receptors blockade: 1) reversed the anxiety-like behavior induced by cohabitation, once the animals returned to visit the central area of the open field arena and abrogated the effects of the housing condition on the average speed of locomotion measured in those animals; 2) reversed the decrease in norepinephrine levels and increased VMA levels in the hypothalamus; 3) modulated the percentage of natural killer (NK) cells in both, spleen and blood; also, decreased the expression of CD69 molecule on splenic NK cells. Further analysis showed no changes in: 4) the total distance traveled in the open field; 5) the hypothalamic norepinephrine turnover and the levels of monoamines and their metabolites in the frontal cortex and olfactory bulb; 6) the serum corticosterone levels; 7) the relative adrenal glands; 8) cell number in the bone marrow; 9) the basal oxidative burst or those induced by PMA or SAPI in neutrophils and in neutrophils phagocytosis. The blockade of β2-adrenergic receptors by ICI-118.551 changed only the CD69 expression in NK blood cells, being unable to modify any of the behavioral and neurochemical parameters analyzed. Therefore, it seems that only some of the immune and behavioral changes triggered by cohabitation with two sick partners present a relevant participation of SNAS through beta-adrenergic receptors