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Today, wireless communications are an essential part of our everyday life. Both the number of users and their demands for wireless data have increasedtremendously during the last decade. Multiantenna communicationsis a promising solution to meet this ever-growing traffic demands. However, impairments that exist in most practical communication networks may substantially limit the performance of a multiantenna system. The characterizationof such a performance loss and how to minimize that are still largelyopen problems. The present thesis addresses this important research gap. Inparticular, we focus on three major impairments of a multiantenna cellularnetwork: impairment in the channel state information (CSI), interference andimpairment in the transceiver hardware components.To fully realize the benefits of multiantenna communications, the users need to acquire a certain level of information about their propagation environment; that is, their corresponding CSI. In practice, the CSI is not known bythe users and should be acquired by allocating part of the network resourcesfor pilot transmission. This problem is mainly important in the systems with a large number of antennas, as in general the required network resources for CSI acquisition scales with the number of transmitting antennas. Theproblem of CSI acquisition in a single-cell multiuser multiple-input multipleoutput(MIMO) system is addressed in this thesis. A linear spatial precodingand combining scheme for pilot transmission is proposed. This scheme requiresless number of network resources for channel estimation compared tothe conventional schemes. The gains of the proposed scheme are characterized by finding an upper-bound and a lower-bound on the channel estimation error.Moreover, as an ultimate performance metric, an achievable sum-rate ofthe network is formulated and analyzed numerically.Due to the broadcast nature of the wireless channels, the performanceof the users in a network is intertwined; the desired signal of one user mayinterfere other users. Hence, the interference is another major impairment inwireless communication systems. In this thesis, the practical challenges of aninterference management technique, namely MIMO interference alignment isinvestigated by implementation on a multiuser MIMO testbed. Then, in thecontext of interference alignment, the problem of optimal power allocation forpilot and data transmission is studied and verified by the measurements.The impairment in the hardware components of the transceivers, that is, any deviation of the components from their ideal behavior, degrades the performance of a communication system. In particular, the impact of nonlineartransmitter power amplifiers (PA)s is investigated in this thesis. First, consideringa memoryless third-order polynomial model for the PAs, a model forthe transmitted nonlinear distortion signal from a multiantenna transmitter isproposed and validated by measurements. This model implies that the spatialdirection of the transmitted distortion is dependent on the spatial directionof the desired signal. Then, this model is extended for a general arbitrary order polynomial model. Exploiting the developed distortion model, the energyefficiency of a multiantenna system operating at millimeter wave frequenciesis studied. / <p>QC 20170523</p>

This thesis presents a technique for the detection of spread spectrum signals, of arbitrary form, even when the signal power spectral density (PSD) is well below the surveillance receiver noise spectral density, using a pair of antennas with broadband (1 GHz or more) receivers. Cross correlating the outputs of two receivers, spatially separated by a distance of the order of one metre or more, produces a cross correlation function (ccf) in which the noise components are spread uniformly over the whole width while the signal component, the narrow autocorrelation function (acf) of the spread spectrum signal, is concentrated near to the centre. The acf is displaced from the centre of the ccf by a small time shift equal to the time difference of arrival of the signal at the two antennas. A simple time domain filter can select a narrow centre portion of the ccf, rejecting the remainder which contains only noise. Taking the Fourier transform of this windowed ccf produces the &quot;time domain filtered cross spectral density&quot; (TDFCSD), in which the signal to noise ratio is independent of receiver bandwidth. Spread spectrum signals can then be both detected and characterised in an extremely sensitive broadband system by threshold detection applied to the magnitude of this TDFCSD. High resolution direction fmding can then be achieved by estimating the time difference of arrival at the two antennas from the phase slope of the appropriate part of the TDFCSD. An analysis of the performance of this dual receiver system is presented. A computer simulation illustrates the signal processing involved and shows excellent agreement with the analysis. An analysis of the detection performance of this system acting in an electronic support measure (ESM) role and comparison with other systems shows that, in addition to being able to obtain more information, this system can offer significantly greater sensitivity than a crystal video receiver. Acousto-optic correlation may be used to perform the cross correlation and time domain filtering of wideband signals in real time, with final processing of the much reduced data set to obtain and analyse the TDFCSD being carried out digitally. A novel non-heterodyning space integrating architecture capable of forming the true correlation function using the zeroth diffraction orders from acousto-optic cells was invented, the operation of which is not explained by the commonly used methods of analysis. By looking again at the acousto-optic interaction, it is shown that there is considerable information in the zeroth diffraction order and a unified theory of one dimensional space integrating correlators is developed, in which many known architectures can be treated as special cases of a general all order correlator. Because of practical difficulties in using a space integrating correlator to obtain the TDFCSD for continuous inputs, later work concentrated on time integrating correlation. Theoretical analysis and practical results are presented for a time integrating acousto-optic correlator, demonstrating that it gives itself naturally to the signal processing operations required and could be used in a real surveillance system making use of the TDFCSD for detection and direction finding.

The use of ultrasound to measure preload in screws and bolts has been studied quite frequently the last decades. The technique is based on establishing a relationship between preload and change in time of flight (TOF) for an ultrasonic pulse propagating back and forth through a screw. This technique has huge advantages compared to other methods such as torque and angle tightening, mainly because of its independence of friction. This is of great interest for Atlas Copco since it increases the accuracy and precision of their assembly tools. The purpose of this thesis was to investigate ultrasonic wave propagation in pre-stressed screws using a simulation software, ANSYS, and to analyse the results using signal processing. The simulations were conducted in order to get an understanding about the wavefront distortion effects that arise. Further, an impulse response of the system was estimated with the purpose of dividing the multiple echoes that occur from secondary propagation paths from one other. The results strengthen the hypothesis that the received echoes are superpositions of reflections taking different propagation paths through the screw. An analytical estimation of the wavefront curvature also shows that the wavefront distortion due to a higher stress near the screw boundaries can be neglected. Additionally, a compressed sensing technique has been used to estimate the impulse response of the screw. The estimated impulse response models the echoes as superpositions of secondary echoes, with significant taps corresponding to the TOF of the shortest path and a mode-converted echo. The method is also shown to be stable in noisy environments. The simulation model gives rise to a slower speed of sound than expected, which most likely is due to the fact that finite element analysis in general overestimates the stiffness of the model.

In underwater acoustic communications the time variation in the channel is a huge chal- lenge. The estimation of the impulse response at the receiver is crucial for the decoding of the signal to become accurate. One way is to transmit a superimposed pilot sequence along the unknown message, and by the knowledge of the sequence have the possibility to continuously track the variation in the channel over time. This thesis investigates if it is possible by the aid of superimposed pilot sequences to separate the taps in the channel impulse response and using a parametric method to describe the taps as polynomial phase signals. The method used for separation of the taps was a moving least squares estimator. Thereafter each tap was optimised to a polynomial phase signal (PPS) using a weighted non-linear least squares estimator. The non-linear parameters of the model was then determined with the Levenberg-Marquardt method. The performance of the method was evaluated both for simulated data as well as for data from eld tests. The performance was determined by calculating the mean squared error (MSE) of the model over dierent frame lengths, signal to noise ratio (SNR), weights for the superimposed pilots, rapidness of time variation and impulse response lengths. The method was not sensitive to the properties of the channel. Even though the model had high performance, the complexity of the computations generated long compilation times. Hence, the method needs further work before a real time implementation could be possible.

This work is about digital signal processing methods to be used to determine information of low frequency low amplitude signals of known frequency. Different adaptive filter concepts such as Wiener filter, NLMS filter and lock-in are implemented and compared to each other. The comparison carried out for different input signal amplitude and noise variance with the objective to find the best algorithm for noise cancelling. The comparison is done using a signal of interest combined with white noise as input to the filter element. The aim of the comparison is to find the most appropriate filter for further signal analyzis. The key topics for the evaluation are the efficiency of noise cancelling and ease of implementation in a data processing unit.

In the light of increasing spectral congestion in the land mobile radio bands below 1 GHz,a renewed interest in Single Sideband (SSB) modulation has been observed world-wide. In this context, much of the work described in this thesis has been directed towards assessing and developing audio signal processing techniques that enable the spectrum and power efficient SSB systems to acheive a comparable performance with that of existing wideband modulation systems. Statistical properties of the land mobile-radio propagation are presented showing that the received signal can be adversely affected by unwanted random phase and envelope modulations. Their effect upon AM, FM and SSB systems are discussed. A novel space diversity system employing a technique termed as Feedforward Signal Regeneration (FFSR) is presented which simultaneously performs the operation of an equal gain combining and suppression of both the random envelope and phase modulations. In connection with the use of FFSR techniques in SSB systems, a phase-locked Transparent-Tone-In-Band (TTIB) pilot-tone configuration which allows the transmission of a "transparent" pilot-tone, positioned centrally within the audio bandwidth, is discussed. Finally, efficient coherent and non-coherent data transmission in the mobile-radio environment is shown to be possible by the use of the TTIB/FFSR diversity system.

by Anskar Yu-hung Leung. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references (leaves 147-163). / Chapter Section I --- Literature review / Chapter Chapter I.1. --- The epididymis - its structures and functions --- p.1 / Chapter Chapter I.2. --- Cellular mechanisms of transepithelial electrolyte transport in epididymis and other exocrine tissues --- p.5 / Chapter Chapter I.3 --- Signal transduction mechanism of chloride secretion in epididymis and other exocrine tissue --- p.11 / Chapter Chapter I.4 --- Significance of chloride secretion by the epididymal epithelium and the objectives of the study --- p.17 / Chapter Section II --- General methods / Chapter Chapter II.1. --- Tissue culture from the rat cauda epididymis --- p.20 / Chapter Chapter II.2. --- The short-circuit current technique --- p.30 / Chapter Chapter II.3. --- The immunofluorescence technique --- p.39 / Chapter Chapter II.4. --- Intracellular adenosine 3':5' cyclic monophosphate (cAMP) measurement --- p.43 / Chapter Chapter II.5 --- Intracellular Ca2+ measurement using the microfluorimetric technique --- p.49 / Chapter Section III --- Results / Chapter Chapter III.1. --- Studies on the neural and humoral controls of eletrogenic chloride secretion in rat epididymis --- p.55 / Chapter Chapter III.2. --- Local control of electrogenic chloride secretion in rat epididymis 226}0ؤThe role of the calcitonin gene-related peptide --- p.80 / Chapter Chapter III.3. --- Characterization of intracellular Ca2+ store using ATP as the calcium mobilizing agonist --- p.94 / Chapter Chapter III.4. --- Ca2+ handling mechanisms in single cultured rat epididymal cells --- p.106 / Chapter Chapter III.5. --- Studies on the effector process in the stimulus-secretion coupling- characterization of apical Cl- conductance in cultured rat cauda epididmal cells --- p.114 / Chapter Chapter III.6. --- Effects of secretory agonists on transepithelial Cl- transport and intracellular Ca2+ concentration in cultured human epididymal epithelium --- p.132 / Chapter Section IV --- General discussion --- p.142 / Chapter Section V --- References --- p.147 / Appendix --- p.164

This dissertation of various aspects of electromyogram (EMG: muscle electrical activity) signal processing is comprised of two projects in which I was the lead investigator and two team projects in which I participated. The first investigator-led project was a study of reconstructing continuous EMG discharge rates from neural impulses. Related methods for calculating neural firing rates in other contexts were adapted and applied to the intramuscular motor unit action potential train firing rate. Statistical results based on simulation and clinical data suggest that performances of spline-based methods are superior to conventional filter-based methods in the absence of decomposition error, but they unacceptably degrade in the presence of even the smallest decomposition errors present in real EMG data, which is typically around 3-5%. Optimal parameters for each method are found, and with normal decomposition error rates, ranks of these methods with their optimal parameters are given. Overall, Hanning filtering and Berger methods exhibit consistent and significant advantages over other methods. In the second investigator-led project, the technique of signal whitening was applied prior to motion classification of upper limb surface EMG signals previously collected from the forearm muscles of intact and amputee subjects. The motions classified consisted of 11 hand and wrist actions pertaining to prosthesis control. Theoretical models and experimental data showed that whitening increased EMG signal bandwidth by 65-75% and the coefficients of variation of temporal features computed from the EMG were reduced. As a result, a consistent classification accuracy improvement of 3-5% was observed for all subjects at small analysis durations (< 100 ms). In the first team-based project, advanced modeling methods of the constant posture EMG-torque relationship about the elbow were studied: whitened and multi-channel EMG signals, training set duration, regularized model parameter estimation and nonlinear models. Combined, these methods reduced error to less than a quarter of standard techniques. In the second team-based project, a study related biceps-triceps surface EMG to elbow torque at seven joint angles during constant-posture contractions. Models accounting for co-contraction estimated that individual flexion muscle torques were much higher than models that did not account for co-contraction.

The goal of a radio-based precision personnel location system is to determine the position of a mobile user, to within a desired accuracy, based on signals propagated between that user and fixed stations. In emergency response situations such information would assist search and rescue operations and provide improved situational awareness. Fundamentally location estimation is based upon the signal measured at, and the position of, each receiver. In the case of a location system where such receivers are installed on vehicles, such as for fire trucks, no external infrastructure or prior characterization of the area of operations can be assumed and the estimation of the (relative) positions of the receiving stations must be repeated each time the system is deployed at a new site as this results in the geometry of the receiving antennas being changed. This dissertation presents work towards an accurate and automatic method for determination of the geometric configuration of such receiving stations based on sampled frequency data using both a "classical" ranging method and a novel technique based on a singular value decomposition method for multilateralization. We also compare the performance of our approaches to the Cramer- Rao bound for total antenna location error for distance and frequency-data based estimators, and provide experimental performance results for these methods tested in real multipath environments.