Bagby, Jonathan S.

With the ever increasing demand for bandwidth intensive applications like video-ondemand,
interactive television services, high-defmition television (HDTV) and internet
telephony, the first mile network, referred to as the last mile network in the earlier stages
of its development, has proven to solve the "bottleneck" often experienced between users
and the central office. The Ethernet Passive Optical Network (EPON), developed by the
IEEE 802.3ah Task Force for Ethernet in the First Mile (EFM), resolves this bottleneck
by providing the user with a fiber optic link to the central office that has many
advantages, such as nearly infinite bandwidth, low cost, easy installation and immunity to
electromagnetic interference, and a saving of the need for powered components in the
signal path from the user to the switch. EPON s have proven to deliver the essential
services of voice, video, and data communications reliably, while at the same time
providing expected guarantees of the delivery of those services in terms of defined
Quality of Service measures (QOS). A continuous theme throughout EPON research has
been the study of efficient Dynamic Bandwidth Allocation (DBA) as a key factor in
achieving fairness in distributing bandwidth amongst remote network units.
This research investigates another factor and its effect on network performance and
service delivery: Cycle Demand Proportionality (CDP). By observing the patterns of
demand in the network on an individual network unit basis cycle after cycle, deductions
regarding load characteristics of some units over others can be made. Decisions can be make about subsequent grant allocations based on this factor and aim to achieve better
results in the process. Simulations of EPONs Lmder varying loads incorporating the usc of
CDP in conjunction with currently used DBA schemes are made and results are analyzed.
A major contribution of this research is a new bandwidth allocation algorithm that gives
improved performance in terms of packet delay versus offered load. Performance metrics
are compared against two common bandwidth allocation algorithms: Interleaved Polling
with Adaptive Cycle Time (IPACT) and Cyclic Polling (CP). Additional results also
include improvements in packet loss and throughput.
The data that represents traffic for this network has two properties, self-similarity and
long range dependency. Plotting the auto-covariance, auto-correlation, and variance for
this traffic, for various aggregation levels demonstrates these properties.

Ultra-Wide band (UWB) systems are a new wireless technology capable of transmitting
data over a wide spectrum of frequency bands with very low power and high data rates.
This technology has the potential to replace almost every cable at home or in an office
with a wireless connection. In a UWB receiver, a radio frequency (RF) low noise
amplifier (LNA) is one of the most important components. This thesis discusses the entire
process involving the design ofUWB low noise amplifiers including a detailed stage by
stage analysis of a computer aided design (CAD) of a MOSFET UWB LNA. Simulation
tools and concepts from Level I equations are used in order to design a circuit with a
realistic MOS model such as the BSIM3 used in this work. The LNA shows improved
power consumption over the designs it is based on while still producing comparable
results.

This research is the array processing help wireless communication techniques to increase the signal accuracy. This technique has an important part of prevalent applications. The wireless communication system, radar, and sonar. Beamforming is one of methods in array processing that filters signals based on their capture time at each element in an array of antennas spatially. Numerous studies in adaptive array processing have been proposed in the last several decades, which are divided in two parts. The first one related to non-adaptive beamforming techniques and the next one related to digitally adaptive Beamforming methods. The trade-off between computational complexity and performance make them different. In this thesis, we concentrate on the expansion of array processing algorithms in both non-adaptive and adaptive ones with application of beamforming in 4G mobile antenna and radar systems. The conventional and generalized side-lobe canceller (GSC) structures beamforming algorithms were employed with a phase array antenna that changed the phase of arrivals in array antenna with common phased array structure antennas. An eight-element uniform linear array (ULA), consisting of di-pole antennas, represented as the antenna array. An anechoic chamber measures the operation of beamforming algorithms performance. An extended modified Kaiser weighting function is proposed to make a semi-adaptive structure in phased array beamforming. This technique is extended to low complexity functions like hyperbolic cosine and exponential functions. Furthermore, these algorithms are used in GSC beamforming. The side-lobe levels were so lower than other algorithms in conventional beamforming around -10 dB.
On the other hand, a uniform linear arrays for smart antenna purposes designed to utilize in implementing and testing the proposed algorithms. In this thesis, performance of smart antenna with rectangular aperture coupled microstrip linear array which experimental investigations carried out for obtaining X-band operation of rectangular microstrip antenna by using aperture coupled feeding technique. Frequency range set at approximately 8.6 to 10.9 GHz, by incorporating frequency range of the antenna resonates for single wideband with an impedance bandwidth of 23%. The enhancement of impedance bandwidth and gain does not affect the nature of broadside radiation characteristics. This thesis describes the design, operation, and realization of the beamforming such as Sidelobe level (SLL) control and null forming array antenna are examined with the prototype. An antenna radiation pattern beam maximum can be simultaneously placed towards the intended user or Signal of interest (SOl), and, ideally nulls can be positioned towards directions of interfering signals or signals not of interest (SNOIs).
Finally, we focused on the adaptive digitally algorithms in compact antenna that faces with mutual coupling. The variable step-size normalized lease mean square (VS-NLMS) algorithm is implemented in beamforming. This algorithm utilizes continuous adaptation. The weights are attuned that the final weight vector to the most satisfied result. The gradient vector can be achieved by iterative beamforming algorithm from the available data. This algorithm is compared with LMS, NLMS, VSS-NLMS algorithms, it is determined that the VSS-NLMS algorithm is better performance to other algorithms. Finally, we introduced novel adaptive IP-NNLMS beamformer. This beamformer reaches to faster convergence and lower error floor than the previous adaptive beamformers even at low SNRs in presence of mutual coupling. The experimental results verified the simulation results that the proposed technique has better performance than other algorithms in various situations.

Computational accuracy is widely recognized as a critical issue in applied electromagnetics. Increasing computational power is being applied to solve more complex electromagnetic systems with an emphasis on computational accuracy. The work of this thesis is focused on the implementation of Method of Moments (MoM) to integral equation formulations. The goal of this effort is to use what is known as condition number, and, a heuristic rule-of-thumb is applied to investigate the computational accuracy of MoM in numerical electromagnetics. Other possible applications of condition number of the MoM matrix are also indicated.

The performance of a multicarrier DS CDMA system is evaluated over a Nakagami multipath fading channel. After the spreading process, the data sequence is applied to multiple carrier rather than a single carrier. Each carrier is provided a corralator in the receiver, and the maximal-ratio combiner is used for the corralator outputs. A bandlimited spreading waveforms are used for self-interference prevention. Robustness to multipath fading and narrow band interference suppression are achieved by this type of configuration. A comparison is made with a single carrier system in the presence of interference.

A three-dimensional finite difference time domain analysis of a saline water phantom used in industry for testing body-mounted receivers is presented. Specifically, a saline water phantom known as "Salty" is analyzed. Salty is an acrylic circular cylinder which is filled with a saline solution. The fields at the center of the cylinder and 1 cm external to the surface of the cylinder are obtained with the FDTD method for normally incident TMz and TEz plane wave excitation in free space. The results from the FDTD simulation are then compared to the closed-form solution, which is obtained by assuming that Salty is infinitely long. A low dielectric constant simulated human body which emulates the performance of Salty is designed using the closed-form solution for the near fields of a two-layer cylinder and its performance is verified with the FDTD method.

The behavior of AT-quartz resonators subject to acceleration is studied. For an AT strip resonator with cantilever mounting, piezoelectric theory predicts that excitation of the pure lowest frequency flexural mode of vibration generates no charge. However, experiments show electromechanical resonance corresponding to this mode for sinusoidal support motion normal to the plane of the crystal with no applied electric field. An amplifier with a voltage follower first stage senses charge output from the crystal. Shielding is required to reduce sixty hertz and drive frequency electromagnetic interference. Measurement of resonant frequency and damping factor for the lowest frequency flexural mode is reported for a group of 17.76 MHz oscillator crystals. This mode is responsible for crystal breakage in some portable communications products. Significant variation in sensitivity among crystals was observed. Charge sensitivity of this mode is attributed in part to mechanical coupling to other modes involving torsion and lateral flexure.

Portable, wireless devices have become ubiquitous, and ever-increasing requirements of functionality and reliability are being placed upon these devices. There is a need to accommodate the oft-conflicting requirements of small size, low power consumption, low cost, and extremely accurate control of frequency. To address these RF design requirements, a comprehensive survey of existing frequency-control methods is presented, followed by a novel design which accomplishes a high degree of frequency accuracy through the use of direct digital synthesis and a software seeking algorithm. The proposed design can be implemented pursuant to the requirements of current and future portable wireless devices.