Coexistence and Secure Communication in Wireless Networks

In a wireless system, transmitted electromagnetic waves can propagate in all directions and can be received by other users in the system. The signals received by unintended receivers pose two problems; increased interference causing lower system throughput or successful decoding of the information which removes secrecy of the communication. Radio frequency spectrum is a scarce resource and it is allocated by technologies already in use. As a result, many communication systems use the spectrum opportunistically whenever it is available in cognitive radio setting or use unlicensed bands. Hence, efficient use of spectrum by sharing users is crucial to increase maximize system throughput. In addition, secrecy of a wireless communication system is traditionally provided by computational complexity of cryptography techniques employed. However, cryptography systems depend on either a random secret key generation mechanism or a trusted key distribution system. Recent developments in the wireless communication area provided a solution to both key generation and distribution problem via exploiting randomness of the wireless channel unconditional to the computational complexity. In this dissertation, we propose solutions to the problems discussed. For spectrum sharing, we present a detailed analysis of challenges of efficient spectrum sharing without a central enforcing mechanism, provide insight to already existing power control algorithms and propose a novel non-greedy power allocation algorithm. Numerical simulations show that the proposed algorithm increases system throughput more than greedy algorithms and can use available spectrum to the fullest, yet it is robust to the presence of greedy users. For secrecy, we propose a practical and fast system for random secret key generation and reconciliation. We extend the proposed system to multiple-input-multiple-output systems and increase security via role reversal of the nodes while making it quicker by pre-encoding procedure. Information theory calculation and numerical simulations demonstrates that the proposed system provides a secure channel for legitimate users in the presence of a passive eavesdropper

Study and Development of Power Control Schemes within a Cognitive Radio-based Game Theoretic Framework

Projecte final de carrera fet en col.laboració amb Nokia Siemens NetworksThe requirements of the International Telecommunication Union (ITU) for the 4th generation of mobile devices raised up to 100 Mbps for high and 1Gbps for low mobility conditions. Reaching such challenging targets requires the deployment of picocells and femtocells. These techniques permit to achieve large cell capacity but also lead to di culties in terms of interference. The GRACE algorithm, based on Cognitive Radio and Game Theory, has shown a fair balance between cell capacity and outage as well as short convergence time, low complexity and easy scalability. The aim of this work is to find an e cient power control algorithm that fits GRACE these goals. Therefore, a study of Cognitive Radio, Game Theory and Power Control algorithms is developed and a new power control algorithm is proposed. The simulation results show that the Fractional Power Control can increase notably the outage performance and the energy saving to the mobile devices

Ion-selective electrodes in environmental analysis

An overview is given dealing with the application of ion-selective electrodes (ISEs) in environmental analysis. ISEs are placed into the context of the trend of development of sensors for extensive and frequent monitoring. Discussed are the issues such as sensing platforms and their mass-production, improvement of precision, diagnostic of sensor functionality, and development of reference electrodes. Several examples of real-life application of ISEs in environmental analysis are given. The main emphasis of this article is directed towards summarizing recent results of the authors during the past several years

Interference mitigation using group decoding in multiantenna systems

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Computation of Approximate Welfare-Maximizing Correlated Equilibria and Pareto-Optima with Applications to Wireless Communication

In a wireless application with multiple communication links, the data rate of each link is subject to degradation due to transmitting interference from other links. A competitive wireless game then arises as each link acts as a player maximizing its own data rate. The game outcome can be evaluated using the solution concept of game equilibria. However, when significant interference among the links arises, uniqueness of equilibrium is not guaranteed. To select among multiple equilibria, the sum of network rate or social welfare is used as the selection criterion. This thesis aims to offer the theoretical foundation and the computational tool for determining approximate correlated equilibria with global maximum expected social welfare in polynomial games. Using sum of utilities as the global objective, we give two theoretical and two wireless-specific contributions. 1. We give a problem formulation for computing near-exact ε -correlated equilibria with highest possible expected social welfare. We then give a sequential Semidefinite Programming (SDP) algorithm that computes the solution. The solution consists of bounds information on the social welfare. 2. We give a novel reformulation to arrive at a leaner problem for computing near-exact ε -correlated equilibria using Kantorovich polynomials with sparsity. 3. Forgoing near-exactness, we consider approximate correlated equilibria. To account for the loss in precision, we introduce the notion of regret. We give theoretical bounds on the regrets at any iteration of the sequential SDP algorithm. Moreover, we give a heuristic procedure for extracting a discrete probability distribution. Subject to players’ acceptance of the regrets, the computed distributions can be used to implement central arbitrators to facilitate real-life implementation of the correlated equilibrium concept. 4. We demonstrate how to compute Pareto-optimal solutions by dropping the correlated equilibria constraints. For demonstration purpose, we focus only on Pareto-optima with equal weights among the players

Study and Development of Power Control Schemes within a Cognitive Radio-based Game Theoretic Framework

Projecte final de carrera fet en col.laboració amb Nokia Siemens NetworksThe requirements of the International Telecommunication Union (ITU) for the 4th generation of mobile devices raised up to 100 Mbps for high and 1Gbps for low mobility conditions. Reaching such challenging targets requires the deployment of picocells and femtocells. These techniques permit to achieve large cell capacity but also lead to di culties in terms of interference. The GRACE algorithm, based on Cognitive Radio and Game Theory, has shown a fair balance between cell capacity and outage as well as short convergence time, low complexity and easy scalability. The aim of this work is to find an e cient power control algorithm that fits GRACE these goals. Therefore, a study of Cognitive Radio, Game Theory and Power Control algorithms is developed and a new power control algorithm is proposed. The simulation results show that the Fractional Power Control can increase notably the outage performance and the energy saving to the mobile devices

Cognitive Radio Systems

Cognitive radio is a hot research area for future wireless communications in the recent years. In order to increase the spectrum utilization, cognitive radio makes it possible for unlicensed users to access the spectrum unoccupied by licensed users. Cognitive radio let the equipments more intelligent to communicate with each other in a spectrum-aware manner and provide a new approach for the co-existence of multiple wireless systems. The goal of this book is to provide highlights of the current research topics in the field of cognitive radio systems. The book consists of 17 chapters, addressing various problems in cognitive radio systems

Doctor of Philosophy

dissertationSmall molecule partitioning between aqueous and lipid-like phases is of importance in pharmaceutics, biology, and environmental chemistry. Measuring small-molecule partitioning has remained a challenge, however, due to the scale of current measurement techniques such as chromatographic columns and shake flasks, which require large sample volumes, long equilibration times, and ex-situ quantification steps. In the work presented in this dissertation, confocal Raman microscopy is applied to analyze, in-situ, the structure of lipid-like phases within single chromatographic support particles and their application to measuring small-molecule partitioning. The 2μm â€" 10μm diameter size of a single support particle is well-matched to the size of the confocal probe (~0.6μm diameter, 1 fL) of a 100X confocal microscope. The large (~300m2/g) surface area within the porous particle concentrates surface-associated molecular populations, providing a large enough ‘concentration’ within the particle to measure partitioning despite the small cross-sections for Raman scattering. This dissertation covers the evolution of confocal Raman microscopy measurements within individual porous particles from measuring partitioning of pyrene into surface bound C18 alkyl chains, detecting octanol-water partitioning of naphthoic acid in reverse-phase chromatographic particles, and characterizing the structure of withinparticle hybrid-phospholipid bilayers. This evolution represents a progression toward more biologically-relevant substrates for measuring small-molecule lipophilicity

Optical Gas Sensing: Media, Mechanisms and Applications

Optical gas sensing is one of the fastest developing research areas in laser spectroscopy. Continuous development of new coherent light sources operating especially in the Mid-IR spectral band (QCL—Quantum Cascade Lasers, ICL—Interband Cascade Lasers, OPO—Optical Parametric Oscillator, DFG—Difference Frequency Generation, optical frequency combs, etc.) stimulates new, sophisticated methods and technological solutions in this area. The development of clever techniques in gas detection based on new mechanisms of sensing (photoacoustic, photothermal, dispersion, etc.) supported by advanced applied electronics and huge progress in signal processing allows us to introduce more sensitive, broader-band and miniaturized optical sensors. Additionally, the substantial development of fast and sensitive photodetectors in MIR and FIR is of great support to progress in gas sensing. Recent material and technological progress in the development of hollow-core optical fibers allowing low-loss transmission of light in both Near- and Mid-IR has opened a new route for obtaining the low-volume, long optical paths that are so strongly required in laser-based gas sensors, leading to the development of a novel branch of laser-based gas detectors. This Special Issue summarizes the most recent progress in the development of optical sensors utilizing novel materials and laser-based gas sensing techniques