This dissertation presents a study of linearization techniques that have been applied to power amplifiers in the cellular communication industry. The objective of this work is to understand the limitations of power amplifiers, specifically the limitations introduced by the use of spectrally efficient modulation schemes. The digitization of communication systems has favored the use of new techniques and technologies capable of increasing the efficiency of costly power amplifiers. The work explores traditional and digital linearization systems; an algorithm based on the principles of natural recombination is proposed to directly address the limitations of previous embodiments. Previous techniques, although effective, have significant implementation costs that increase exponentially with the increasing signal bandwidths. The proposed software-hardware architecture significantly reduces implementation costs and the overall complexity of the design without sacrificing performance. To fulfill the requirements of this study, multiple systems are implemented through simulation and closed-loop hardware. Both simulation and hardware embodiments meet the expected performance metrics, providing validation of the proposed algorithm. The application of the algorithm to memory power amplifier linearization is a new approach to adaptive digital pre-distortion using narrowband feedback. The work will show performance improvements on an amplifier with memory effects suggesting that this technique can be employed as a lower-cost solution to meet requirements when compared to typical system implementations.

In this thesis, a new stack architecture for sensor networks is proposed. The stack consists of the following layers: application, query, aggregation, network, MAC and physical. Various algorithms are implemented using this stack and it is shown that this stack is modular. Following an overview of sensor networks, the previous protocol stack suggestions for sensor networks are examined. Sensor network algorithms that can be classified as sensor data management systems are surveyed and compared with each other. Four of the surveyed algorithms, namely, TAG, Synopsis Diffusion, Tributary-Delta and Directed Diffusion are implemented using the introduced stack. The implementation is performed using a sensor network model developed with OMNeT++ simulator. The simulation results are compared to the original results of these algorithms. Obtaining similar results, the stack and algorithm implementations are validated, moreover, it is shown that the stack does not induce any performance degradation. Using the implementation details of the algorithms, the modularity of the suggested stack is demonstrated. Finally, additional benefits of the stack are discussed.

Many radars suffer from masking of weaker targets by stronger ones due to range sidelobes of pulse compression codes. We propose a method to prevent this by successively detecting targets and canceling their effects. Performance of the proposed method will be investigated in various scenarios with regard to existence of noise, targets, and the Doppler effect.

In this thesis, improvement of Cell Averaging Constant False Alarm Rate (CA CFAR) radar processors is studied. A new improvement method is proposed that will reduce probability of false alarm while keeping probability of detection at good values. This method makes use of Doppler spreading patterns that appear after Doppler processing. Therefore this method is called Doppler Pattern Matching (DPM). Performance of the algorithm has been investigated by Monte Carlo simulations. In order to evaluate the performance, improvement factor is calculated which is the ratio of the probability of false alarm of original detector to the false alarm of improved detector. It is observed that improvement factor changes depending on the simulation scenario. Almost in every case, good improvement factor can be obtained. Moreover, in most of the cases, there has been no reduction in probability of detection after DPM is applied to CA CFAR detector.

In recent years the need for multimedia packet data services in wireless networks has grown rapidly. To overcome that need third generation (3G) mobile services have been proposed. The fast growing demands multimedia services in 3G services brought the need for higher capacity. As a result of this, the improvement on throughput, traffic serving performance has become necessary in 3G systems. Code division multiple access (CDMA) technique is one of the most important 3G wireless mobile techniques that has been defined. The scheduling mechanisms used in CDMA plays an important role on the efficiency of the system. The power, rate and capacity parameters are variable and dependent to each other in designing a scheduling mechanism. The schedulers for CDMA decide which user will use the frequency band at which time interval with what power and rate. In this thesis different type of algorithms used in time slotted CDMA are studied and a new algorithm which supports Quality of Service (QoS) is proposed. The performance analysis of this proposed algorithm is done via simulation in comparison to selected CDMA schedulers.

This study considers the average system throughput and the average delay performances of subcarrier allocation algorithms in OFDMA systems. The effects of varying the number of users, the number of subcarriers, and the statistical characteristics of incoming packets are investigated on the throughput and delay performances of the algorithms. Moreover, a new subcarrier allocation algorithm with low-order computational complexity, which performs very well almost all cases, is proposed. With the aid of the simulations, the significance of channel v.s. queue state information varying with the statistical characteristic of incoming packets is examined and reached some results which can be very valuable for channel estimation and feedback systems. Finally, the stability issue is considered in OFDMA systems and a new heuristic simulation-based method for obtaining the stability region of an OFDMA subcarrier allocation algorithm is proposed.

In this thesis, an ultrasound testbed is designed in order to practice the Synthetic Aperture Radar (SAR) techniques. The thesis work is built on the fundamentals of SAR theory. In this respect, four different methods for the reconstruction of SAR image are considered. The ultrasonic testbed is composed of a mobile vehicle where the ultrasound transmitter and receiver are mounted. An analog circuit is designed in order to condition the transmitted and received signals. The receiving signal is processed in a personal computer using MATLAB routines. A GUI is designed for user friendly operation. Different experiments are done with the designed system. The theoretical and practical results for SAR imaging are compared. It is shown that the designed system functions properly with a good approximation to the theoretical results. The deviations from the theoretical results are caused by the idealistic assumptions as well as the distortions introduced by the practical system. More specifically, some of the distortions are generated by the nonuniform velocity of the moving platform, the phase distortion due to the analog filters and imperfect filtering during down-conversion. While the sources of distortions certainly affect the SAR system response, the implemented system is valuable for the practical analysis of SAR system performance.

In this thesis, design details of binary irregular Low-Density Parity-Check (LDPC) codes are investigated. We especially focus on the trade-off between the average variable node degree, wa, and the number of length-6 cycles of an irregular code. We observe that the performance of the irregular code improves with increasing wa up to a critical value, but deteriorates for larger wa because of the exponential increase in the number of length-6 cycles. We have designed an irregular code of length 16,000 bits with average variable node degree wa=3.8, that we call &lsquo / 2/3/13&rsquo / since it has some variable nodes of degree 2 and 13 in addition to the majority of degree-3 nodes. The observed performance is found to be very close to that of the capacity approaching commercial codes. Time spent for decoding 50,000 codewords of length 1800 at Eb/No=1.6 dB for an irregular 2/3/13 code is measured to be 19% less than that of the regular (3, 6) code, mainly because of the smaller number of decoding failures.

Sonar is the traditional method of underwater target detection and tracking. However, using traditional sonar arrays may be difficult and impractical in some mission-critical scenarios as they require a ship or a submersible to be mounted on or towed by. Alternatively, Underwater Acoustic Sensor Networks (UW-ASN) offer a promising solution approach. In this thesis, a target tracking algorithm for UW-ASN, Three-Dimensional Underwater Target Tracking (3DUT) is presented. The objective of 3DUT is to collaboratively accomplish accurate tracking of underwater targets with minimum energy expenditure. Based on the time-of-arrival (ToA) of the echoes from the target after transmitting acoustic pulses from the sensors, the ranges of the nodes to the target are determined, and trilateration is used to obtain the location of the target. The location and the calculated velocity of the target are then exploited to achieve tracking. In order to realize energy-effective target tracking, 3DUT incorporates a new target movement-based duty cycle mechanism. To avoid rapid depletion of energy resources of boundary nodes due to continuous surveillance, 3DUT employs an adaptive procedure to find, designate, and activate new boundary nodes. Performance evaluation shows that 3DUT is a promising alternative to the traditional sonar based target tracking approaches especially for on-demand surveillance applications.

In traffic radar system, Frequency Modulated Continuous Wave (FMCW) will be used since these radars are preferred in short distance and high range resolution systems. The system to be constructed is not only a system operating with Doppler principle and detection of speed / on the contrary a functional radar is planned to be produced. In various traffic radars in use, Doppler shift constituted by the targets causing high reflection within detection field is measured and the measured speed corresponding to this shift is seen to exceed the limits. In case of cars more than one, their speeds cannot be measured separately. In this FMCW Radar system, it is possible to identify the targets&rsquo / distance and speed. The speed information of the target will be specified by Doppler frequency and also as a result of position monitoring, the speed will be determined out of the position change occurring in the unit time. These features, in multi lane road, will be used both for different lanes and also for the cars moving at the same lane but in different ranges. The radar system designed in this study is an easy to use, low power consuming device which can be mounted into the car. Only the active part of the system is off the shelf products and the other RF cards are designed and produced. As a result, a low cost traffic radar will be produced