Multicasting is a technique used for distributing data packets from one or more sources to a set of receivers on interconnected networks. Currently developing network applications bring specific quality of service (QoS) requirements like bounded delay, minimum bandwidth, and maximum data loss rate. Providing the required quality of service addresses routing and resource reservation concepts. In this study, a literature survey is carried out on traditional and QoS multicast routing protocols, and the need for QoS routing protocols is investigated. QoS multicast routing protocols are classified and compared according to their multicast tree construction and resource reservation approaches. Two QoS protocols, QROUTE and QMBF, are selected, and their performances are experimentally compared using the network simulation tool Network Simulator-2 (ns-2). The objective of the simulations is to compare the QoS routing algorithms and their tree construction efficiencies. The first contribution of the thesis is the survey and classification of traditional and QoS multicast routing protocols. Another contribution is the ns-2 implementation of two QoS multicast routing protocols. The final contribution of the thesis is the performance evaluation of the recent protocols from a different perspective.

In this thesis, we work on the upper bound for nonlinearity of t-resilient Boolean functions given by Sarkar and Maitra, which is based on divisibility properties of spectral weights of resilient functions and study construction methods that achieve the upper bound. One of the construction methods, introduced by Maity and Johansson, starts with a bent function and complements some values of its truth table corresponding to a previously chosen set of inputs, S, which satisfies three criteria. In this thesis, we show that a fourth criterion is needed for t-resiliency of the resulting function, and prove that three criteria of Maity and Johansson do not guarantee resiliency. We also work on other constructions, one by Sarkar and Maitra, which uses a Maiorana-McFarland like technique to satisfy the upper bound and the other by Tarannikov, which satisfies the nonlinearity bound using a technique with low computational complexity. However, these methods have tendency to maximize the order of resiliency for a given number of variables, therefore one cannot construct functions for all possible resiliency values given the number of variables, using this method. We further go into details and compute the auto-correlation functions of the constructed Boolean functions to find the absolute indicator and sum-of-squared-errors for each of them. We also provide a comparison of Boolean functions constructed by other techniques given in the literature, together with the ones studied in this thesis.

Continuous Wave (CW) radars are preferred for their low probability of intercept by the other receivers. Frequency modulation techniques, the linear frequency modulation (LFM) technique in particular, are commonly used in CW radars to resolve the range and the radial velocity of the detected targets. The conventional method for target detection in a linear FMCW radar makes use of a mixer followed by a low-pass filter whose output is Fourier transformed to get the range and velocity information. In this thesis, an alternative target detection technique based on the use of the Ambiguity Function (AF) will be investigated in frequency modulated CW radars. Results of the AF-based technique and the conventional Fourier-based technique will be compared for different target detection scenarios.

ABSTRACT WAVEFORM DESIGN FOR PULSE DOPPLER RADAR AgIRMAN, Handan M.S., Department of Electrical and Electronics Engineering Supervisor: Prof. Dr. Mete Severcan December 2005, 100 pages This study is committed to the investigation of optimum waveforms for a pulse doppler radar which uses a non linear high power amplifier in the transmitter. The optimum waveform is defined as the waveform with the lowest peak and integrated side lobe level, the narrowest main lobe in its autocorrelation and the narrowest bandwidth in its spectrum. The Pulse Compression method is used in radar systems since it is more advantageous in terms of the resolution. Among all pulse compression methods, the main focus of this study is on Phase Coding. Two types of radar waveforms assessed throughout this study are Discrete Phase Modulated Waveforms and Continuous Phase Modulated Waveforms. The continuous phase modulated waveforms are arranged under two titles: the memoryless phase modulated waveform and the waveform modulated with memory. In order to form memoryless continuous phase waveforms, initially, discrete phase codes are obtained by using Genetic Algorithm. Following this process, a new phase shaping pulse is defined and applied on the discrete phase waveforms. Among the applicable modulation with memory techniques, Continuous Phase Modulation maintains to be the most appropriate. The genetic algorithm is used to find different lengths of optimum data sequences which form the continuous phase scheme.

ABSTRACT ROBUST DATA HIDING SCHEME WITH TURBO CODES &Uuml / NAL, BariS M.S., Department of Electrical And Electronics Engineering Supervisor: Prof. Dr. R&uuml / yal ERG&Uuml / L December 2005, 127 pages This study describes the design and implementation of a robust data hiding algorithm which is provided by turbo codes. As the digital technology grows up, it is getting easy to copy and distribute multimedia products without getting legal permission. This has forced researchers to study in digital watermarking areas. Along with watermarking researches, data hiding studies have gained interest in the last decade. Different watermark and data hiding algorithms have been proposed considering different requirements and properties such as robustness, fidelity, invisibility and data hiding capacity. In this thesis, robustness of watermarking systems and fidelity requirement in watermark models are considered and use of turbo codes is proposed with data embedding systems to improve system performance in terms of robustness. Fundamental watermarking algorithms in DCT domain are analyzed and simulated. Their performances in terms of robustness are presented. Data hiding algorithm which is based on projection and perturbation in transform domain is implemented in visual C. Then turbo codes are applied to this algorithm to improve system robustness. Improvement provided by turbo codes is demonstrated and compared with other discussed watermarking systems.

This thesis considers a communication system with chaotic modulation. Noise-like signals are generated by chaotic systems with different parameters to modulate binary digital signals. Demodulation is performed by both the Extended Kalman Filter (EKF) and Optimum Decoding Based Smoothing Algorithm (ODSA). Simulations are performed using both of these algorithms for different parameters affecting the performance of the communication system. Simulation results of these algorithms are compared.

In this thesis, Optimum Decoding-based Smoothing Algorithm (ODSA) is applied to well-known Discrete Lotka-Volterra Model. The performance of the algorithm is investigated for various parameters by simulations. Moreover, ODSA is compared with the SIR Particle Filter Algorithm. The advantages and disadvantages of the both algorithms are presented.

Rural electrification has been a long-standing objective in many developing countries. For decades, the assumption and practice has been to build centralised generating capacity and transmit the electricity over national grids. More recently, interest has grown in using PV (photovoltaic) technology as a solution to the problem of rural electrification. A private household market for PV has been developing in Kenya since 1984 and now has more than 200,000 systems installed, sold through this private market. Consequently, it is widely hailed as a success story among developing countries. Until recently, Tanzania had almost no household PV market, despite interest from a number of actors, including some of those who have been involved in enabling the rapid growth of the market in Kenya. However, sales of PV began to grow quite rapidly from the early 2000s and the trend appears to be gaining pace, with an estimated 285 kWp sold in 2007, having risen by 57% in one year. At the time of the research, there were two large donor-funded PV projects underway in the country. The research attempts to explain the dynamics of the two PV niches over the past 25 years using strategic niche management as its theoretical framework. It finds that the Kenyan niche has benefited more from donor support than is usually acknowledged. The thesis also makes theoretical and methodological contributions. It offers a way to connect first and second-order learning to expectations and visions concepts; dimensions expectations and visions; and presents a tool for systematic investigation of socio-technical trajectory developments. The thesis also suggests a number of ways in which the strategic niche management framework could be enhanced. These include stronger theorising about learning, and the incorporation of power, politics and risk into the theory.

In this thesis, target induced glint error phenomenon is analyzed and the glint reduction techniques are evaluated. Glint error reduction performance of the methods is given in a comparative manner. First, target glint is illustrated with the dumbbell model which has two point scatterers. This illustration of the glint error builds the basic notion of target scattering centers and effect of scattering characteristics on glint error. This simplest approach is also used to understand the glint reduction methods. In an effort to evaluate the glint reduction techniques, a model based upon the concept of coherent summation of scattering complexes is used . The model is also used for introducing the basic properties of glint phenomenon. Basics of the glint phenomenon and glint reduction techniques are discussed with particular emphasis on diversity methods. Frequency diversity and spatial diversity techniques are described and investigated with generated simulation data. The diversity selection methods which are used to eliminate the erroneous data are introduced and their performances are investigated. Glint error reduction results of various scenarios including both reduction techniques and selection methods are evaluated in comparison with each other. The results indicate that significant reduction of glint error is possible by the appropriate utilization of diversity techniques in radar systems.

This dissertation is focused on developing the new target localization and the target velocity estimation methods for frequency-only multi-input, multi-output (MIMO) radar systems with widely separated antennas. If the frequency resolutions of the transmitted signals are enough, only the received frequencies and the Doppler shifts can be used to find the position of the target. In order to estimate the position and the velocity of the target, most multistatic radars or radar networks use multiple independent measurements from the target such as time-of-arrival (TOA), angle-of-arrival (AOA) and frequency-of-arrival (FOA). Although, frequency based systems have many advantages, frequency based target localization methods are very limited in literature because of the fact that highly non-linear equations are involved in solutions. In this thesis, alternative target localization and the target velocity estimation methods are proposed for frequency-only systems with low complexity. One of the proposed methods is able to estimate the target position and the target velocity based on the measurements of the Doppler frequencies. Moreover, the target movement direction can be estimated efficiently. This method is referred to as &quot / Target Localization via Doppler Frequencies - TLDF&quot / and it can be used for not only radar but also all frequency-based localization systems such as Sonar or Wireless Sensor Networks. Besides the TLDF method, two alternative target position estimation methods are proposed as well. These methods are based on the Doppler frequencies, but they requires the target velocity vector to be known. These methods are referred to as &quot / Target Localization via Doppler Frequencies and Target Velocity - TLD&amp / V methods&quot / and can be divided two sub-methods. One of them is based on the derivatives of the Doppler Frequencies and hence it is called as &quot / Derivated Doppler - TLD&amp / V-DD method&quot / . The second method uses the Maximum Likelihood (ML) principle with grid search, hence it is referred to as &quot / Sub-ML, TLD&amp / V-subML method&quot / . The more realistic signal model for ground based, widely separated MIMO radar is formed as including Swerling target fluctuations and the Doppler frequencies. The Cramer-Rao Bounds (CRB) are derived for the target position and the target velocity estimations for this signal model. After the received signal is constructed, the Doppler frequencies are estimated by using the DFT based periodogram spectral estimator. Then, the estimated Doppler frequencies are collected in a fusion center to localize the target. Finally, the multiple targets localization problem is investigated for frequency-only MIMO radar and a new data association method is proposed. By using the TLDF method, the validity of the method is simulated not only for the targets which are moving linearly but also for the maneuvering targets. The proposed methods can localize the target and estimate the velocity of the target with less error according to the traditional isodoppler based method. Moreover, these methods are superior than the traditional method with respect to the computational complexity. By using the simulations with MATLAB, the superiorities of the proposed methods to the traditional method are shown.