This thesis is about testing a system’s actual performance under the IEEE 802.15.4-2011 UWB specifications, with a compliant device DW1000. It is of great interest to test the synchronization ability of different preamble lengths, which are applied in the IEEE 802.15.4-2011 UWB standard. It is also urgent to know the system’s actual performance in a multipath propagation environment, since the IEEE 802.15.4-2011 UWB standard allows an energy detection (ED) receiver to take advantage of multipath propagation. Theory predicts that a long preamble length can offer better synchronization ability at long distances, and has a longer working range. On the other hand, a long preamble length requires a longer channel occupancy time and more power consumption. Thus, a long preamble may not be the optimal choice for working at short distances. The channel model of the IEEE 802.15.4-2011 UWB standard, which is based upon the Saleh-Valenzuela (S-V) model, can be regarded as block fading. Although multipath propagation can improve the system’s performance by increasing the SNR, the effects of block fading on the system must be taken into account as well. It is pointed out in various papers that the S-V model is precise in predicting a none-line-of-sight (NLOS) environment, while it is not precise in predicting a line-of-sight (LOS) environment. The results of the first part of the measurements show that longer preambles have longer working ranges. However, the longer preambles’ performance, in the term of the packet reception ratio, is not necessarily better than that of the shorter preambles. The results of the second part of the measurements show that the system can take advantage of multipath propagation. On the other hand, the system’s performance might become instable, due to block fading. The receiver and the transmitter will have difficulty in synchronization, if the channel impulse response changes too much within the unsynchronized time period. A longer preamble length tends to offer a longer stable working range. In addition, the path loss of the channel will suddenly increase and then decrease. This phenomenon of a sudden change in the path loss at a certain distance is quite similar to that of a narrowband system.

In this thesis, a steerable antenna system which is able to maintain high connectivity through beamforming towards the strongest base station signal is presented. Main objective of the thesis is to design an antenna system for vehicles operating in poor coverage region or even in no coverage region, in order to enable these vehicles to make a reliable communication link with far away base stations. To achieve this high performance antenna system, several antenna designs were considered and evaluated for their performance. This thesis provides an overview of different antenna designs considered and their pros and cons. Among these designs, the concept of stacked patch antenna was selected for prototype manufacturing because of its good performance in terms of bandwidth, efficiency, gain, impedance matching and ease of fabrication because of its simple structure. Stacked patch antenna was optimized for lower GSM band covering frequencies from 824 MHz to 960 MHz by using electromagnetic simulation software CST Microwave Studio. Finally the stacked patch antenna was fabricated and measurements were performed. The results for both the prototype measurement and simulations are presented and compared. From the comparison, it is concluded that the manufactured antenna element prototype gives high performance as promised by simulation results and is suitable for the adaptive vehicular antenna system.

The usage of massive antenna arrays coupled with millimeter-wave (mmW) transmissions has emerged as enabling technology of the fifth generation mobile communication standard, the 5G. This solution has great potentials to provide Gb/s data-rate and high cell capacity by leveraging the synergy amongst high resolution spatial filtering, adaptive beamforming and channel sparsity. One of the main challenges, however, is related to the implementation and digital processing as with a conventional transceiver architecture, an increase of the number of antennas implies more analog-to-digital (or digital-to-analog) converters, more power amplifiers and baseband units. Subsequently, the energy, factor-size and computational power requirements become impractical. To counter these effects a hybrid transceiver design has been proposed, in which multiple analog front-ends are combined into a single (or multiple) baseband processing unit allowing the transceiver to reduce the complexity of the digital signal processing as well as the power consumption. In this Thesis we investigate different architecture models and evaluate the trade-off between energy consumption and performance in channel estimation. More specifically, we study a hybrid receiver model with 64 antenna elements, parallel digital paths and, for the channel estimation, we consider the adaptive-least absolute shrinkage and selection operator (A-LASSO) algorithm that leverages channel sparsity into the estimation. Simulation results have shown that a transceiver architecture with only four base-bands performed best over the different cell sizes. Compared to the fully digital receiver this results in tenfold power consumption reduction according to analysis.

Efficient use of wireless spectrum is needed, due to enormous increase in wireless devices during last few years. In this context lot of effort is being done to make an intelligent and cognitive radio system, which can use the spectrum opportunistically. The ratio of the signal average power to the interference plus noise average power is called signal to interference plus noise ratio (SINR). SINR is one of the important parameters that can help in developing cognitive radio systems, because on the basis of its calculation the spectrum can be utilized efficiently. The principle goal of this thesis is to implement a SINR estimation algorithm for a cognitive radio network (CRN) test-bed. The proposed SINR estimation algorithm is second order moment and fourth order moment (M2M4) SINR estimation algorithm, where M2 and M4 are the second order moment and fourth order moments respectively. The M2M4 estimation algorithm is one of the non-data-aided (NDA) estimation algorithms. Hence, the algorithm takes the received signal as input and calculates the second and fourth moments blindly. The average signal power and average interference plus noise power can be calculated from these second and fourth order moments, their ratio yields the SINR. The M2M4 estimation algorithm is first simulated in MATLAB, and then it is designed for system generator model to draw fair comparison between simulations and system generator model. The experimental evaluation revealed that despite of the word length constraint in the system generator model, it performs reasonably well when compared to the ideal (MATLAB) solution. The M2M4 estimation algorithm is tested and verified by different test cases, to ensure its validity. The algorithm is tested for different signal strengths. The result shows M2M4 is an efficient algorithm for the SINR estimation. However, the proposed architecture could not fit into the aimed hardware because of heavy design since it consume more resources than available.

Multi agent system (MAS) is considered an effective way to design, analyze and implement complex systems in various disciplines nowadays. However, MAS has not been sufficiently applied in mainstream modelling of wireless communication networks yet. The exponential growth of network users has led today’s communication networks even more significantly complex. As such, modelling and simulation tends to grow in proportion but not markedly to meet the preciseness and complexity of the system under consideration. Furthermore, the future mobile communication seems to incline over self-adaptive resource allocation and congestion control mechanisms. This aims to relieve the workload of the network operator while maintaining the QoS level of the communication intact. The advancements also envision the autonomous nature of future wireless communication technologies where dynamic resource allocation will play a vital role in efficient bandwidth utilization, throughput maximization and effective power control mechanisms. In this context, MAS brings about various possibilities to model and simulate environments which are typically stochastic in nature and tends to grow in a decentralized manner. MAS based simulation is such a simulation method which has gained recognition in modeling telecommunication systems where issues like network complexity, traffic and network management are prevalent. MAS has its proven standing to represent a real interactive environment of a system where learning, negotiation and cooperation are important phenomena. On that account, MAS has already started to establish its turf in the wireless communication systems as well. As a matter of fact, the existing network simulators are not designed to incorporate the features that MAS has to offer. So, the agent based simulation toolkits are used alongside, on top of which most of the physical environment aspects can be modeled that are usually neglected by the existing network simulators. This thesis investigates the areas of wireless communications where multi agent systems and simulators are applicable by the means of literature study and presents simple simulation models constructed in Netlogo, a multi agent based simulation toolkit. As a result, the applicability of MAS simulators in areas like radio channel environment, resource allocation, routing, medium access control and cognitive radio is presented. At the end, conclusions are drawn about feasibility of using MAS simulators to simulate wireless communication networks.

The purpose of this study was to determine the relationships between selected criteria and academic achievement in graduate studies leading to certain master's degrees in education at North Texas State University. The major areas in education which were included were Elementary Education, Elementary School Administration and Supervision, Secondary Education, Secondary School Administration and Supervision, and Physical Education. Graduate grade-point average was used as the criterion for academic achievement.

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Thesis (Ed.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / This study compares instructor self-perceptions with student perceptions of teaching quality using the same 16-item evaluation instrument. Three hypotheses were investigated: (1) Instructors' self-evaluations will be higher than those of their respective students; (2) The more similar student-instructor perceptions, the more likely instructors will receive a higher score compared to when student-instructor perceptions are more divergent; and (3) Students taking a course as a major requirement will be more critical of the instructor than those students taking the course as distribution requirement or an elective. A total of 1,524 individuals (1,452 graduate students and 72 instructors) in a part-time evening computer science program participated in the study of 79 courses over the spring and fall semesters of 1996. Overall, instructors generally perceived themselves more positively than their students, although statistically significant differences were observed for only three relevant items (involving grading fairness, presentation clarity and instructor enthusiasm) of the 16 items evaluated. Instructors whose perceptions were more similar to their students were generally rated higher than those instructors whose perceptions were more divergent from their students; however, the difference was not significant. Finally, contrary to the third hypothesis, the reason for taking a course did not have a significant effect on student ratings of the instructor. / 2031-01-02

Doctor of Education / Department of Educational Leadership / Sarah Jane Fishback / This qualitative case study explored how U.S. Army Command and General Staff College (CGSC) students decided whether or not to attend graduate school. The focus was on how U.S. Army students made their decision. The purpose of the study was to illuminate the issues related to this decision in adult development, adult learning, career decision making, and participation in adult learning activities. These issues were explored using the students’ own words during their interviews in which they described how they made their respective decisions. This research analyzed interviews with 26 students, 12 who either decided to attend one of the graduate programs available to CGSC students or were already in a master’s degree program, and 14 who elected not to attend any of the graduate programs offered. The analysis explored how U.S. Army CGSC students made their decision about graduate school, the process used in making their respective decisions, and the factors that influenced their decisions. Analysis of the students’ interviews answered the primary research question and the four subordinate research questions. Not surprisingly, all the students indicated that military career requirements, post-military career aspirations and requirements, family considerations, and previous academic experience influenced their decision whether or not to attend graduate school. The extent to which their decision was influenced varied, but everyone interviewed expressed some degree of influence of those factors. Not expected were the common themes that emerged from analysis of the interview transcripts of CGSC students. Those themes centered around self-efficacy and confidence, goal setting and achievement, persistence, time management, life issues, guidance and mentorship, perceived quality of the degree or value, and the CGSC master’s program (Master of Military Art and Science).

A Iniciação Científica (IC) possibilita a introdução do estudante de graduação na investigação científica, conduzindo-o mais cedo à Pós-Graduação. A pesquisa tem por objetivo investigar as diferenças entre titulados da Pós-Graduação na UFRGS em 2012 no que se refere ao tempo e idade de titulação, bem como diferenças na produção científica até o ano de titulação entre dois grupos: discentes que tiveram experiência de IC na graduação (grupo IC) e que não tiveram (Grupo NIC). Verificou-se grande ocorrência de discentes do grupo IC na modalidade acadêmica. Em geral o grupo IC se titulou mais jovem que o NIC, e em três Grandes Áreas os discentes do grupo IC se titularam em menos tempo e com menor idade que o grupo NIC, bem como obtiveram mais produção científica em diversos casos. / Scientific Initiation allows to introduce undergraduate students in scientific research, leading them earlier to the Graduation. The objective of the research is investigate differences among graduated students of UFRGS in 2012 concerning to time and age of graduation and differences in scientific production between two groups: group with scientific initiation experience (IC group) and group with no scientific initiation experience (NIC group). There was high occurrence of students in IC group in academic modality. In general the IC group concluded the graduation younger than NIC group. In three big areas, the students of IC group concluded their studies in less time and younger than the NIC group and obtained more scientific production in many cases.