Design and performance evaluation of RAKE finger management schemes in the soft handover region

We propose and analyze new finger assignment/management techniques that are applicable for RAKE receivers when they operate in the soft handover region. Two main criteria are considered: minimum use of additional network resources and minimum call drops. For the schemes minimizing the use of network resources, basic principles are to use the network resources only if necessary while minimum call drop schemes rely on balancing or distributing the signal strength/paths among as many base stations as possible. The analyses of these schemes require us to consider joint microscopic/macroscopic diversity techniques which have seldom been considered before and as such, we tackle the statistics of several correlated generalized selection combining output signal-to-noise ratios in order to obtain closed-form expressions for the statistics of interest. To provide a general comprehensive framework for the assessment of the proposed schemes, we investigate not only the complexity in terms of the average number of required path estimations/comparisons, the average number of combined paths, and the soft handover overhead but also the error performance of the proposed schemes over independent and identically distributed fading channels. We also examine via computer simulations the effect of path unbalance/correlation as well as outdated/imperfect channel estimations. We show through numerical exam ples that the proposed schemes which are designed for the minimum use of network resources can save a certain amount of complexity load and soft handover overhead with a very slight performance loss compared to the conventional generalized selection combining-based diversity systems. For the minimum call drop schemes, by accurately quantifying the average error rate, we show that in comparison to the conventional schemes, the proposed distributed schemes offer the better error performance when there is a considerable chance of loosing the signals from one of the active base stations

Adaptive Power Control for Single and Multiuser Opportunistic Systems

In this dissertation, adaptive power control for single and multiuser opportunistic systems is investigated. First, a new adaptive power-controlled diversity combining scheme for single user systems is proposed, upon which is extended to the multiusers case. In the multiuser case, we first propose two new threshold based parallel multiuser scheduling schemes without power control. The first scheme is named on-off based scheduling (OOBS) scheme and the second scheme is named switched based scheduling (SBS) scheme. We then propose and study the performance of thresholdbased power allocation algorithms for the SBS scheme. Finally, we introduce a unified analytical framework to determine the joint statistics of partial sums of ordered RVs with i.i.d. and then the impact of interference on the performance of parallel multiuser scheduling is investigated based on our unified analytical framework

Effects of ionospheric conductance in high-latitude phenomena

In this thesis, the relationship between several high-latitude phenomena and the ionospheric conductance in both hemispheres is studied theoretically and experimentally. Theoretically, the high-latitude electrodynamics is studied by considering currents in the magnetosphere-ionosphere system resulting from the ionospheric sheet current redistribution between the conjugate ionospheres. It is shown that strong flow between the conjugate ionospheres, the interhemispheric currents (IHC), can be set up if the conductance distribution is asymmetric in the conjugate ionospheric regions. Such conditions are typical for solstices owing to the differences in the solar illumination. Analytical and numerical modeling shows that IHCs can appear in the regions of strong conductance gradient, more specifically around the solar terminator line, and that the intensity of the IHCs can be comparable to the intensity of the well known Region 1/Region 2 currents. The effect of IHC excitation on observable magnetic perturbations on the ground is investigated. It is shown that in the vicinity of the solar terminator line, the pattern of magnetic perturbation can be such that an apparent equivalent current vortex can be detected. In addition, strong conductance gradients are shown to affect significantly the quality of the ionospheric plasma flow estimates from the ground-based magnetometer data. Experimentally, the effect of the nightside ionospheric conductance on occurrence of substorms, global storm sudden commencement and radar auroras is investigated. To characterize substorm occurrence, new parameters, the derivatives of the classical AE and AO indices, are introduced. It is shown that the seasonal and diurnal variations of these parameters are controlled by the total nightside ionospheric conductance in the conjugate regions. The substorm onsets preferentially occur at low levels of the total conductance, which is consistent with the idea of the substorm triggering through the magnetosphere-ionosphere feedback instability. It is hypothesized that the total conductance affects the global storm onsets as well. To check this idea, the 33-year sudden storm commencement (SSC) data are considered. The semiannual, annual, semidiurnal, and diurnal variations in the SSC occurrence rate are found to be significant and these components exhibit a strong relationship with the total conductance of the high-latitude ionospheres. Finally, the SuperDARN midnight echo occurrence is shown to correlate, for some radars, with the total conductance minima and presumably with electric field maxima, which is consistent with general expectation that the F-region irregularities occur preferentially during times of enhanced electric fields. The gradients of the high-latitude conductance can also lead to significant errors in the plasma convection estimates from the ground-based magnetometers, and to investigate this effect a statistical assessment of the difference between the true plasma convection (SuperDARN) and the magnetometer-inferred equivalent convection direction is performed. The largest differences are found for the transition region between the dark and sunlit ionospheres and in the midnight sector where strong conductance gradients are expected due to particle precipitation. Consideration of regular conductance gradients due to solar illumination improves the agreement between the radar and magnetometer data. Finally, an attempt is made to demonstrate the effects of conductance upon the properties of traveling convection vortices (TCVs). Joint SuperDARN and magnetometer data reveal that there is resemblance between the magnetometer and radar inferred TCV images on a scale of thousands of kilometers. However, on a smaller scale of hundreds of kilometers, significant differences are observed

Three Branch Diversity Systems for Multi-Hop IoT Networks

Internet of Things (IoT) is an emerging technological paradigm connecting numerous smart objects for advanced applications ranging from home automation to industrial control to healthcare. The rapid development of wireless technologies and miniature embedded devices has enabled IoT systems for such applications, which have been deployed in a variety of environments. One of the factors limiting the performance of IoT devices is the multipath fading caused by reflectors and attenuators present in the environment where these devices are deployed. Leveraging polarization diversity is a well-known technique to mitigate the deep signal fades and depolarization effects caused by multipath. However, neither experimental validation of the performance of polarization diversity antenna with more than two branches nor the potency of existing antenna selection techniques on such antennas in practical scenarios has received much attention. The objectives of this dissertation are threefold. First, to demonstrate the efficacy of a tripolar antenna, which is specifically designed for IoT devices, in harsh environments through simulations and experimental data. Second, to develop antenna selection strategies to utilize polarized signals received at the antenna, considering the restrictions imposed due to resource limitations of the IoT devices. Finally, to conduct comparative analyses on the existing standard diversity techniques and proposed approaches, in conjunction with experimental data. Accordingly, this dissertation presents the testing results of tripolar antenna integrated with Arduino based IoT devices deployed in environments likely to be experienced by IoT devices in real life applications. Both simulation and experimental results from single point-to-point wireless links demonstrate the advantage of utilizing tripolar antennas in harsh propagation conditions over single branch antenna. Motivated by these empirical results, we deploy a small-scale IoT network with tripolar antenna based nodes to analyze the impact of tripolar antenna on neighbor nodes performance as well as to investigate end-to-end network performance. This work illustrates that the selection of antenna branches, while considering network architecture and the level of congestion on the repeater nodes, minimizes excessive antenna switching and energy consumption. Similar results are shown for IoT networks with predetermined and dynamic routing protocols, where the proposed techniques yielded lower energy consumption than the conventional diversity schemes. Furthermore, a probabilistic, low complexity antenna selection approach based on Hidden Markov model is proposed and implemented on wireless sensor nodes aiming to reduce energy consumption and improve diversity gain. Finally, we develop a dual-hop based technique where a node selects the antenna element for optimal performance based on its immediate network neighbors antenna configuration status during selection. The performance of the proposed technique, which is verified through simulation and measured data, illustrates the importance of considering network-wide evaluations of antenna selection techniques

NASA Tech Briefs, January 1991

Topics: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences;Life Sciences

Frugivore behavior and plant spatial genetics

Spatial genetics aims to understand the influence of environmental features and biological interactions on gene flow and genetic structure. In plants, spatial genetics is determined by the rate, pattern and spatial extent of gene dispersal within and between populations. Gene dispersal in plants is composed by seed dispersal and pollination. Seed dispersal increases the probabilities of mating between spatially distant, non-related, individuals, reducing the probability of biparental inbreeding, decreasing the incidence of unfavorable traits and increasing genetic diversity. In animal seed dispersal, foraging behavior and post-feeding movement range affect seed dispersal pattern and distance, with consequences in plant spatial genetics. This thesis aims to understand the relationship between frugivore behavior and spatial genetics while strengthening the current knowledge on seed dispersal by tamarins and using their dispersal of Leonia cymosa as a case study for a finer analysis of the effect of frugivore behavior on spatial genetics. Leonia cymosa Mart. (Violaceae), a small Neotropical understory tree, is exclusively dispersed at our study site by tamarins, Saguinus mystax, and Leontocebus nigrifrons. Leonia cymosa is, therefore, a good model for understanding the effects of frugivore behavior and plants spatial genetics. First, I analyzed the presence and strength of SGS in animal-dispersed plants studied in the last 20 years. I found animal behavior has an effect on spatial genetic structure, but pollination and marker type used could also have an influence on the strength of SGS. Second, I analyze seed dispersal distance of Leonia cymosa by tamarins, using plant genetics and animal behavior data in parallel. Methods for estimating seed dispersal distance did not differ significantly and mean seed dispersal distance for Leonia cymosa was between 218 and 304m. Third, I analyze spatial genetic structure (SGS) in Leonia cymosa through its life stages and put it in the context of tamarin behavior. SGS was present in seedlings, and weaker in juveniles and absent in adults of Leonia cymosa, likely due to tamarin seed dispersal patterns and extent. Clumped seed dispersal patterns might have a strong influence on SGS of seedlings, while the combination of-density-dependent mortality and relatively long seed dispersal distance likely reduces this effect in adulthood. Fourth, I analyzed the genetic composition of Leonia cymosa individuals growing on different tamarin home ranges. Home ranges were expected to create a seed dispersal barrier influencing overall gene flow. However, even though the parentage analysis showed no seed exchange across home ranges, genetic makeup shows no difference between individuals located in different home ranges, at all life stages, giving evidence that pollination or small shifts in time of home ranges, could have a strong effect in maintaining gene flow across home ranges. The results of this thesis give evidence that seed dispersal patterns and distance can strongly and differently affect plant spatial genetic structure, while, pollination might play an important role in maintaining gene flow in case of seed dispersal constraints

Power Converter of Electric Machines, Renewable Energy Systems, and Transportation

Power converters and electric machines represent essential components in all fields of electrical engineering. In fact, we are heading towards a future where energy will be more and more electrical: electrical vehicles, electrical motors, renewables, storage systems are now widespread. The ongoing energy transition poses new challenges for interfacing and integrating different power systems. The constraints of space, weight, reliability, performance, and autonomy for the electric system have increased the attention of scientific research in order to find more and more appropriate technological solutions. In this context, power converters and electric machines assume a key role in enabling higher performance of electrical power conversion. Consequently, the design and control of power converters and electric machines shall be developed accordingly to the requirements of the specific application, thus leading to more specialized solutions, with the aim of enhancing the reliability, fault tolerance, and flexibility of the next generation power systems

Developing the MAR databases – Augmenting Genomic Versatility of Sequenced Marine Microbiota

This thesis introduces the MAR databases as marine-specific resources in the genomic landscape. Paper 1 describes the curation effort and development leading to the MAR databases being created. It results in the highly valued reference database MarRef, the broader MarDB, and the marine gene catalog MarCat. Definition of a marine environment, the curation process, and the Marine Metagenomics Portal as a public web-service are described. It facilitates scientists to find marine sequence data for prokaryotes and to explore rich contextual information, secondary metabolites, updated taxonomy, and helps in evaluating genome quality. Many of these database advancements are covered in Paper 2. This includes new entries and development of specific databases on marine fungi (MarFun) and salmon related prokaryotes (SalDB). With the implementation of metagenome assembled and single amplified genomes it leads up to the database quality evaluation discussed in Paper 3. The lack of quality control in primary databases is here discussed based on estimated completeness and contamination in the genomes of the MAR databases. Paper 4 explores the microbiota of skin and gut mucosa of Atlantic salmon. By using a database dependent amplicon analysis, the full-length 16 rRNA gene proved accurate, but not a game-changer in taxonomic classification for this environmental niche. The proportion of dataset sequences lacking clear taxonomic classification suggests lack of diversity in current-day databases and inadequate phylogenetic resolution. Advancing phylogenetic resolution was the subject of Paper 5. Here the highly similar species of genus Aliivibrio became delineated using six genes in a multilocus sequence analysis. Five potentially novel species could in this way be delineated, which coincided with recent genome-wide taxonomy listings. Thus, Paper 4 and 5 parallel those of the MAR databases by providing insight into the inter-relational framework of bioinformatic analysis and marine database sources