Efficient Routing and Scheduling in Wireless Networks

The temporal and spatial variation in wireless channel conditions, node mobility make it challenging to design protocols for wireless networks. In this thesis, we design efficient routing and scheduling algorithms which adapt to changing network conditions caused by varying link quality or node mobility to improve user-level performance. We design and analyze routing protocols for static, mobile and heterogeneous wireless networks. We analyze the performance of opportunistic and cooperative forwarding in static mesh networks showing that opportunism outperforms cooperation; we identify interference as the main cause for mitigating the potential gains achievable with cooperative forwarding. For mobile networks, we quantitatively analyze the tradeoff between state information collection (sampling frequency and number of bits per sample) and power consumption for a fixed source-to-destination goodput constraint. For heterogeneous networks comprising of both static and mobile nodes, we propose a greedy algorithm (adaptive-flood) which dynamically classifies individual nodes as routers/flooders depending on network conditions and demonstrate that it achieves performance equivalent to, and in some cases significantly better than, that of network-wide routing or flooding alone. Last, we consider an application-level wireless streaming scenario where multiple clients are streaming different videos from a cellular base station. We design a greedy algorithm for efficiently scheduling multiple video streams from a base station to mobile clients so as to minimize the total number of application-playout stalls. We develop models for coarse timescale wireless channel variation to aid network and application-layer protocol design

Big Data Analytics and Information Science for Business and Biomedical Applications II

The analysis of big data in biomedical, business and financial research has drawn much attention from researchers worldwide. This collection of articles aims to provide a platform for an in-depth discussion of novel statistical methods developed for the analysis of Big Data in these areas. Both applied and theoretical contributions to these areas are showcased

A Study of Adaptive Kalman Filtering for Transfer Alignment

Prior to launching an inertially navigated weapon from the wing of an aircraft, the Inertial Measurement Unit (IMU) of the weapon must be in agreement with the master IMU of the aircraft. In order to correct the IMU of the weapon, it is required that the angles of alignment error between the two units be known. A model for the alignment error can be developed. A Kalman filter can then be used to estimate the angles of alignment error. The modeling of alignment error is complicated by the flexible nature of the aircraft. Since the environment of the aircraft can change dramatically during the alignment process, the model becomes time varying. This further compounds the complexity of the overall model of alignment error. A possible solution to the alignment problem for weapons attached to the wings of an aircraft with a flexible body is proposed. This solution centers around the use of an adaptive Kalman filter. The adaptive Kalman filter can concurrently identify the time varying dynamics of flexing and estimate the angles of alignment error. This capability might substantially simplify the alignment problem. Three adaptive Kalman filtering algorithms were investigated. These algorithms differ only in the method by which they identify the parameters of the system. The relative performance of these algorithms was determined by a simulation. The simulation was based on a simplified dynamic system. The simulation demonstrated that only one of the adaptive Kalman filters provided sufficient performance to be considered for use in the alignment problem. This adaptive Kalman filter identifies the parameters through a stochastic Newton algorithm. The use of this adaptive Kalman filter, along with an appropriately developed model, appear to provide a viable solution to the alignment of inertially guided missiles attached to the wings of an aircraft with a flexible body

Extreme Ultraviolet Spectroscopy of the Solar Corona

New Extreme Ultra-Violet (EUV) observations of the solar corona, obtained by the Coronal Diagnostic Spectrometer (CDS) instrument on board the NASA/ESA Solar and Heliospheric Observatory (SOHO) are presented. The CDS instrument for the first time has provided the opportunity of observing a large number of emission lines from a wide range of ions of different elements. The spectral and spatial resolution of the CDS instrument has allowed the simultaneous application of a wide range of spectroscopic diagnostic techniques to determine the temperature distribution, densities and elemental abundances in the solar plasma. A differential emission measure (DEM) diagnostic technique has been used to infer the temperature structure and the element abundances. The importance of including DEM effects in the element abundance analysis is demonstrated. A complete in-flight cross-calibration between all the CDS detectors (NIS and €115, 150-785 A), is presented here for the first time. The level of accuracy and completeness of the CHIANTI atomic database, used throughout this thesis, has allowed the identification of the many hundreds of spectral lines observed in the CDS spectra, resulting in several new line identifications. An assessment of the €115 solar spectra is presented, showing that, in spite of complexities, €115 spectra are useful for diagnostic analyses. Many discrepancies (in particular with the Li-like ions) between theory and CDS observations are highlighted. It is shown that some of these may be explained by inaccurate ionization equilibrium calculations. Coronal hole densities, temperatures, DEMs, and relative element abundances from both off-limb (plume and inter-plume regions) and on-disc observations are derived and compared with quiet sun values. These included (August 1996) a large equatorial hole, the Elephant's Trunk, probably the best example of a coronal hole observed by SOHO. Coronal hole densities in both coronal (N 1x10 8 cm 3 ) and transition region (Ne = lxlO'° cm 3 ) plasma were found to be about a factor of 2 lower than in the quiet sun, with much lower emission measures at temperatures above 106 K. Moreover, in the transition region, the cell-centres in both coronal holes and quiet sun regions show consistently higher densities (factor of 2) compared to those in the network. Relative element abundances show approximately photospheric values for the coronal holes, with an indication of element abundance variation .(neon in particular) with the supergranular structure. On-disc EUV observations of coronal hole plumes have been performed. This allowed a spectroscopic characterisation of plumes to be obtained for the first time, leading to the first identification of a low-latitude plume near sun-centre. Plumes are shown to be quasi-isothermal structures, with temperatures T 7 - 8x10 5 K. Abundance analyses (using transition region lines) reveal a small FIP effect in these plumes, together with a decreased Ne/O abundance ratio (compared to photospheric)

Performance Evaluation of Optimized Physical Layer Network Coding

With the development of the wireless networks these years, devices are required to have an even higher data rate, and thus the interference between devices remains a significant problem to be solved. In order to secure a reliable transmission with- out wasting network capacity, we would necessarily select a proper transmission scheme. The Physical layer Network Coding (PNC) , is one of the optimum choices as it can increase the efficiency largely, especially in a system with 2 users and 1 relay (TWRC). Generally speaking, we may divide our research into two aspects: channel and channel coding. From the channel coding’s view, we build the system of uncoded QPSK mod- ulated PNC and convolutional coded PNC (again modulated by QPSK). Due to the feature of the superimposed QPSK constellation, we introduce 3 different fixed mappings (plus the adaptive mapping) in order to decode the superimposed sym- bols at the relay more preciously. Also, we derive the theoretical upper bound of the error rate of the superimposed symbols at the relay. For uncoded PNC, we derive the SER; for coded PNC, we derive the BER, and we focus on an finite accumulation of the terms so as to obtain a tight error bound which is closer to the BER curve of the symbol-level simulation. From the channel’s view, we build the system of QPSK modulated PNC on single- carrier channel and the PNC on OFDM channels. For PNC on single-carrier channels, we assume the transmission channels are all flat fading channels. Never- theless, it is quite difficult for it to cope with the frequency selective channels and time delay channels. As a result, we introduce OFDM technique which can largely resist their interferences. We develop different adaptive mappings on OFDM inside the sub-band to further improve the performance. The theoretical upper bound for the error rate of the superimposed signals received at the relay will be vital in the system-level simulation, which is the part of the project DIWINE that my research benefits from

Privileged Words and Sturmian Words

This dissertation has two almost unrelated themes: privileged words and Sturmian words. Privileged words are a new class of words introduced recently. A word is privileged if it is a complete first return to a shorter privileged word, the shortest privileged words being letters and the empty word. Here we give and prove almost all results on privileged words known to date. On the other hand, the study of Sturmian words is a well-established topic in combinatorics on words. In this dissertation, we focus on questions concerning repetitions in Sturmian words, reproving old results and giving new ones, and on establishing completely new research directions. The study of privileged words presented in this dissertation aims to derive their basic properties and to answer basic questions regarding them. We explore a connection between privileged words and palindromes and seek out answers to questions on context-freeness, computability, and enumeration. It turns out that the language of privileged words is not context-free, but privileged words are recognizable by a linear-time algorithm. A lower bound on the number of binary privileged words of given length is proven. The main interest, however, lies in the privileged complexity functions of the Thue-Morse word and Sturmian words. We derive recurrences for computing the privileged complexity function of the Thue-Morse word, and we prove that Sturmian words are characterized by their privileged complexity function. As a slightly separate topic, we give an overview of a certain method of automated theorem-proving and show how it can be applied to study privileged factors of automatic words. The second part of this dissertation is devoted to Sturmian words. We extensively exploit the interpretation of Sturmian words as irrational rotation words. The essential tools are continued fractions and elementary, but powerful, results of Diophantine approximation theory. With these tools at our disposal, we reprove old results on powers occurring in Sturmian words with emphasis on the fractional index of a Sturmian word. Further, we consider abelian powers and abelian repetitions and characterize the maximum exponents of abelian powers with given period occurring in a Sturmian word in terms of the continued fraction expansion of its slope. We define the notion of abelian critical exponent for Sturmian words and explore its connection to the Lagrange spectrum of irrational numbers. The results obtained are often specialized for the Fibonacci word; for instance, we show that the minimum abelian period of a factor of the Fibonacci word is a Fibonacci number. In addition, we propose a completely new research topic: the square root map. We prove that the square root map preserves the language of any Sturmian word. Moreover, we construct a family of non-Sturmian optimal squareful words whose language the square root map also preserves.This construction yields examples of aperiodic infinite words whose square roots are periodic.Siirretty Doriast

X-ray fluorescence applied to yellow pigments based on lead, tin and antimony: comparison of laboratory and portable instrumentation

X-ray fluorescence is a diagnostic approach particularly suited to be utilized in cultural heritage sector since it falls in the non-destructive and non-invasive analytical tools. However there are big differences between portable and laboratory instrumentation that make difficult to perform a comparison in terms of quality and reliability of the results. The present study is specifically addressed to investigate these differences in respect of the same analytical sample-set. To reach this goal a comparison was thus carried out between portable and bench top devices X-ray fluorescence devices and techniques were used on different type of yellow pigments based on lead, tin and antimony obtained in laboratory, reproducing the instructions described in “old” recipes, that is: i) mortar of lead and tin produced on the basis of the recipe 13 /c V of the “Manuscript of Danzica” and “ Li tre libri dell’arte del Vasaio” by Cipriano Piccolpasso; ii) two types of lead and tin yellow (Pb2SnO4 and PbSnO3) produced starting from the indications of the 272 and 273 recipes of the “Bolognese Manuscript”; iii) lead antimonate (Pb2Sb2O7) obtained by following the instructions of the Piccolpasso’s treatise and those contained on the “Istoria delle pitture in maiolica fatte in Pesaro e ne’ luoghi circonvicini di Giambattista Passeri” and finally iv) lead, tin and antimony yellow (Pb2SnSbO6,5) obtained starting from the information contained in the paper 30 R of “Manuscript of Danzica” [1]. The XRF analysis were performed using a laboratory instrumentation (Bruker M4 Tornado) and a handset analytical device (Assing Surface Monitor). In order to perform a significant statistical comparison among acquired and processed data, all the analyses have been carried out utilizing the same sample, the same acquisition set up and operative conditions. A chemometric approach, based on the utilization of Principal Component Analysis (PCA) and multivariate analytical based tools [2], was utilized in order to verify the spectral differences, and related informative content, among the different produced yellow pigments. The multivariate approach on the results revealed instrumental differences between the two systems and allowed to compare the common characteristics of the set of pigments analyzed

An 18,000 year-long eruptive record from Volcán Chaitén, northwestern Patagonia:Paleoenvironmental and hazard-assessment implications

The 2008 eruption of Volcán Chaitén (VCha) in northwestern Patagonia was the first explosive rhyolitic eruption to have occurred within a century and provided an unprecedented scientific opportunity to examine all facets of the eruption ranging from magma rheology/ascent rates to ash-fall effects on biota and infrastructure. Up to very recently it was thought that the latest eruption prior to the 2008 event occurred c. 9750 cal. a BP. Although a number of researchers have recognised additional eruptive products, but their stratigraphy, age, and geochemical attributes have not been systematically described and/or recorded. In this study, we provide a detailed examination of andic cover-beds and tephra-bearing lake sequences located both proximally and distally to VCha, which record a series of hitherto unknown rhyolitic eruptive products and place all previous observations firmly within a coherent stratigraphic framework. Through major- and trace-element glass shard geochemistry we are able to confidently verify eruptive source. A total of 20 discrete tephra beds are recognised, with at least 10 having widespread areal distributions and/or depositional imprints broadly comparable to, or greater than, the 2008-tephra event. This record indicates that VCha has been continuously but intermittently active as far back as the end of the Last Glacial Maximum (c. 18,000 cal a BP) with two dominant, genetically related magma types and an intermediary ¿mixed¿ type. Before this the eruptive record has been largely obscured and/or erased by widespread Andean piedmont glaciation. However, based on the tempo of VCha activity over the last c. 18,000 years, older VCha eruptives can be anticipated to occur as well as future hazardous explosive events. The new eruptive inventory will ultimately be useful for correlating equivalent-aged sequences and refining long-term eruptive tempo as well as corresponding temporal changes in magmatic evolution