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Human fingerprints are rich in details called the minutiae, which can be used as identification marks for fingerprint verification. To get the details, the fingerprint capturing techniques are to be improved. Since when we the fingerprint is captured, the noise from outside adds to it. The goal of this thesis is to remove the noise present in the fingerprint image. To achieve a good quality fingerprint image, this noise has to be removed or suppressed and here it is done by using an algorithm or technique called ’Spectral Subtraction’, where the algorithm is based on subtraction of estimated noise spectrum from noisy signal spectrum. The performance of the algorithm is assessed by comparing the original fingerprint image and image obtained after spectral subtraction several parameters like PSNR, SSIM and also for different fingerprints on the database. Finally, performance matching was done using NIST matching software, and the obtained results were presented in the form of Receiver Operating Characteristics (ROC)graphs, using MATLAB, and the experimental results were presented.

The present thesis addresses the problem of stabilisability of a linear time invariant (LTI) output feedback control loop in the presence of a communication link. The communication link itself can be either located between the controller and the plant or between the plant and the controller. The communication link is assumed to be an additive coloured Gaussian noise channel with (or without) bandwidth limitation (memory) in the continuous-(or discrete-)time domain. The requirement for stabilisability of the feedback loop is then characterised as a lower bound on the channel signal to noise ratio (SNR). This lower bound is tight and it will depend on the channel model, plant and channel model NMP zeros, plant time delay and plant unstable poles. Performance requirements are also investigated, by loop shaping in the continuous-time domain, whilst a linear quadratic Gaussian (LQG) control approach is suggested for the discrete-time domain. / PhD Doctorate

<p>In system identification, different methods are often classified as parametric or non-parametric methods. For parametric methods, a parametric model of a system is considered and the model parameters are estimated. For non-parametric methods, no parametric model is used and the result of the identification is given as a curve or a function.</p><p>One of the non-parametric methods is the impulse response analysis. This approach is dynamic simulation. This thesis introduces a new paradigm for dynamic simulation, called impulse-based simulation. This approach is based on choosing a Dirac function as input, and as a result, the output will be equal to the impulse response. However, a Dirac function cannot be realized in practice, and an approximation has to be used. As a consequence, the output will deviate from the impulse response. Once the impulse response is estimated, a parametric model can be fitted to the estimation.</p><p>This thesis aims to determine the parameters in a parametric model from an estimated impulse response. The process of investigating the models is a critical aspect of the project. Correlation analysis is used to obtain the weighting function from the estimates of covariance functions.</p><p>Later, a relation formed between the parameters and the estimates (obtained by correlation analysis) in the form of a linear system of equations. Furthermore, simulations are carried out using Monte Carlo for investigating the properties of the two step approach, which involves in correlation analysis to find h-parameters and least squares and total least squares methods to solve for the parameters of the model. In order to evaluate the complete capability of the approach to the noise variation a study of signal to noise ratio and mean, mean square error and variances of the estimated parameters is carried out.</p><p>The results of the Monte Carlo study indicate that two-step approach can give rather accurate parameter estimates. In addition, the least squares and total least squares methods give similar results.</p>

The thesis examines the problem of joint receive and transmit beamforming for a wireless network which consists of one relay node equipped with multiple antennas. The transmitter and the receiver are single antenna systems. The communication system consists of two phases. In the first phase the transmitter sends the information symbol to the relay while in the second phase, the relay re-transmits a linearly transformed version of the vector of its received signals. The concept of general-rank beamforming is applied to this communication scheme for the case of the uplink (transmitter-relay) and downlink (relay-receiver) channel vectors being statistically independent and statistically dependent. In the general-rank beamforming approach, the multi-antenna relay multiplies the received signal vector with a general-rank complex weight matrix and re-transmits each entry of the output vector on the corresponding antenna. The thesis presents a closed form solution to the general-rank beamforming power minimization problem with proof that for statistically independent uplink and downlink channels, the general-rank beamforming approach results in a rank-one solution for the beamforming matrix. The simulation results have shown that when the generalrank beamformer is applied to the case of statistically dependent uplink and downlink channels, the general-rank beamforming technique significantly outperforms the separable receive and transmit beamforming method. / UOIT

Due to dramatic growth of capacity in optical fiber communication, the fiber dispersion has become one of major factors affecting the quality of optical signal transmission with different modulation scheme, leading to the importance in controlling optical chirp. Among the elements used for optical fiber communications, electroabsorption modulator (EAM) and semiconductor optical amplifier (SOA) are served as optical amplitude and phase modulation. In this work, EAM-integrated SOA is used to realize the pre-chirp technique through their inherently reversed phase modulation as well as amplitude modulation. In the experiment, tunable optical filter and a 10Gb/s data pattern are used for extracting the frequency chirp of the timely signal. With the positive chirp operation in EAM, it is found that the overall chirp of EAM-integrated SOA can be varied from 3GHz to -9GHz by adjusting current injection through SOA. Also, as inspecting the 10Gb/s pattern, the pattern effect can also be controlled by the reversed carrier dynamics between EAM and SOA. Finally, a 10Gb/s data transmission with 43km transmission is demonstrated by using such pre-chirp technique, showing that such technique can be applied to other type signal processing.

A low voltage low power sigma¡Vdelta modulator for voice applications is presented. The implementation of proposed sigma-delta modulator is based on switched-capacitor circuit. Bootstrapped switches were used to replace CMOS transmission gates for increasing the insufficient driving of switched-capacitor circuit under the low voltage operation. To reduce the power dissipation, an improved current mirror OTA were designed with rail-to-rail output swing, which can also make the voltage gain enhance 10~20 dB and overcome the poor voltage gain shortage of traditional current mirror OTA. The post-simulation result shows that the modulator achieves a dynamic range of 77 dB, a peak signal-to-noise ratio of 82 dB, and the sigma-delta modulator dissipates 25£gW under 1.1-V voltage supply, using TSMC 0.18£gm 1P6M CMOS technology.

The purpose of this work was to construct and analyze a THz time domain spectroscopy (THz-TDS) system by using a nanojoule energy per pulse ultrafast laser (non-amplified ultrafast laser or oscillator) source and a non-linear optical generation method for THz generation. First a THz-TDS system, which uses photoconductive antenna (PCA) method for THz generation, was built to understand the working principles of these types of systems. This THz-TDS system which used PCA for generation and a 2mm thick &lt / 110&gt / ZnTe crystal for detection had a bandwidth up to 1 THz with a 1000:1 signal to noise ratio (S/N). Using this system, various materials were investigated to study the usefulness of the obtained bandwidth. Absorption coefficient and refractive indices of the sample materials were calculated. Results showed that the bandwidth of the system was not sufficient to obtain fingerprint properties of these materials. In order to improve the system, optical rectification method was used for THz generation. A different THz-TDS system was built with a 1mm thick &lt / 110&gt / ZnTe crystal used for the method of non-linear generation of THz radiation. Theoretical calculations of radiated intensity and electric field were done to analyze the expected bandwidth of the system. Results showed that the generation and the detection crystal thicknesses affect the obtained bandwidth of the system in that the bandwidth limiting factor is the crystal thickness and not the ultrafast laser pulse duration. Especially for detection, measurements obtained with both a 1mm thick and 2mm thick &lt / 110&gt / ZnTe crystal showed that there was not much difference in bandwidth as was predicted by theory. Also in order to increase the signal to noise ratio, the optics used in the system were optimized. It was found that by using same focal lengths for focusing and collimating optics around the generation crystal and by using a short focal length parabolic mirror, S/N could be improved. After these improvements this THz-TDS system which uses optical rectification for THz generation and electro-optic method for THz detection had a larger bandwidth up to 3 THz but with a lower 100:1 signal to noise ratio.

Today¡¦s mobile IP supports host mobility by dynamic changing IP addresses while the mobile host roaming in the Internet. However, There still exists performance problems during handoffs, such as packet loss, throughput degradation, and so on. In this Thesis, we propose a mechanism to reduce packet loss during handoff. The packet buffering mechanism at a home agent is initiated by mobile hosts when the signal-to-noise ratio of the wireless link falls below some predefined threshold. Once the handoff has completed, the home agent immediately delivers the first packet in the buffer to the mobile host. The home agent then clears the buffered packets already received by the mobile host through the returned ACK such that no further duplicate packets are sent out. In addition, we propose a route-selection policy to reduce end-to-end transmission delay by sending out probe packets along the paths. For the purpose of demonstration, we implement the mechanism on Linux platform. Through the measurements from the experiment, we have shown that the proposed mechanism can improve the throughput and solve the packet retransmission problem while handoffs.