Design And Analysis Of Effective Routing And Channel Scheduling For Wavelength Division Multiplexing Optical Networks

Optical networking, employing wavelength division multiplexing (WDM), is seen as the technology of the future for the Internet. This dissertation investigates several important problems affecting optical circuit switching (OCS) and optical burst switching (OBS) networks. Novel algorithms and new approaches to improve the performance of these networks through effective routing and channel scheduling are presented. Extensive simulations and analytical modeling have both been used to evaluate the effectiveness of the proposed algorithms in achieving lower blocking probability, better fairness as well as faster switching. The simulation tests were performed over a variety of optical network topologies including the ring and mesh topologies, the U.S. Long-Haul topology, the Abilene high-speed optical network used in Internet 2, the Toronto Metropolitan topology and the European Optical topology. Optical routing protocols previously published in the literature have largely ignored the noise and timing jitter accumulation caused by cascading several wavelength conversions along the lightpath of the data burst. This dissertation has identified and evaluated a new constraint, called the wavelength conversion cascading constraint. According to this constraint, the deployment of wavelength converters in future optical networks will be constrained by a bound on the number of wavelength conversions that a signal can go through when it is switched all-optically from the source to the destination. Extensive simulation results have conclusively demonstrated that the presence of this constraint causes significant performance deterioration in existing routing and wavelength assignment (RWA) algorithms. Higher blocking probability and/or worse fairness have been observed for existing RWA algorithms when the cascading constraint is not ignored. To counteract the negative side effect of the cascading constraint, two constraint-aware routing algorithms are proposed for OCS networks: the desirable greedy algorithm and the weighted adaptive algorithm. The two algorithms perform source routing using link connectivity and the global state information of each wavelength. Extensive comparative simulation results have illustrated that by limiting the negative cascading impact to the minimum extent practicable, the proposed approaches can dramatically decrease the blocking probability for a variety of optical network topologies. The dissertation has developed a suite of three fairness-improving adaptive routing algorithms in OBS networks. The adaptive routing schemes consider the transient link congestion at the moment when bursts arrive and use this information to reduce the overall burst loss probability. The proposed schemes also resolve the intrinsic unfairness defect of existing popular signaling protocols. The extensive simulation results have shown that the proposed schemes generally outperform the popular shortest path routing algorithm and the improvement could be substantial. A two-dimensional Markov chain analytical model has also been developed and used to analyze the burst loss probabilities for symmetrical ring networks. The accuracy of the model has been validated by simulation. Effective proactive routing and preemptive channel scheduling have also been proposed to address the conversion cascading constraint in OBS environments. The proactive routing adapts the fairness-improving adaptive routing mentioned earlier to the environment of cascaded wavelength conversions. On the other hand, the preemptive channel scheduling approach uses a dynamic priority for each burst based on the constraint threshold and the current number of performed wavelength conversions. Empirical results have proved that when the cascading constraint is present, both approaches would not only decrease the burst loss rates greatly, but also improve the transmission fairness among bursts with different hop counts to a large extent

DESIGN AND OPTIMIZATION OF SIMULTANEOUS WIRELESS INFORMATION AND POWER TRANSFER SYSTEMS

The recent trends in the domain of wireless communications indicate severe upcoming challenges, both in terms of infrastructure as well as design of novel techniques. On the other hand, the world population keeps witnessing or hearing about new generations of mobile/wireless technologies within every half to one decade. It is certain the wireless communication systems have enabled the exchange of information without any physical cable(s), however, the dependence of the mobile devices on the power cables still persist. Each passing year unveils several critical challenges related to the increasing capacity and performance needs, power optimization at complex hardware circuitries, mobility of the users, and demand for even better energy efficiency algorithms at the wireless devices. Moreover, an additional issue is raised in the form of continuous battery drainage at these limited-power devices for sufficing their assertive demands. In this regard, optimal performance at any device is heavily constrained by either wired, or an inductive based wireless recharging of the equipment on a continuous basis. This process is very inconvenient and such a problem is foreseen to persist in future, irrespective of the wireless communication method used. Recently, a promising idea for simultaneous wireless radio-frequency (RF) transmission of information and energy came into spotlight during the last decade. This technique does not only guarantee a more flexible recharging alternative, but also ensures its co-existence with any of the existing (RF-based) or alternatively proposed methods of wireless communications, such as visible light communications (VLC) (e.g., Light Fidelity (Li-Fi)), optical communications (e.g., LASER-equipped communication systems), and far-envisioned quantum-based communication systems. In addition, this scheme is expected to cater to the needs of many current and future technologies like wearable devices, sensors used in hazardous areas, 5G and beyond, etc. This Thesis presents a detailed investigation of several interesting scenarios in this direction, specifically concerning design and optimization of such RF-based power transfer systems. The first chapter of this Thesis provides a detailed overview of the considered topic, which serves as the foundation step. The details include the highlights about its main contributions, discussion about the adopted mathematical (optimization) tools, and further refined minutiae about its organization. Following this, a detailed survey on the wireless power transmission (WPT) techniques is provided, which includes the discussion about historical developments of WPT comprising its present forms, consideration of WPT with wireless communications, and its compatibility with the existing techniques. Moreover, a review on various types of RF energy harvesting (EH) modules is incorporated, along with a brief and general overview on the system modeling, the modeling assumptions, and recent industrial considerations. Furthermore, this Thesis work has been divided into three main research topics, as follows. Firstly, the notion of simultaneous wireless information and power transmission (SWIPT) is investigated in conjunction with the cooperative systems framework consisting of single source, multiple relays and multiple users. In this context, several interesting aspects like relay selection, multi-carrier, and resource allocation are considered, along with problem formulations dealing with either maximization of throughput, maximization of harvested energy, or both. Secondly, this Thesis builds up on the idea of transmit precoder design for wireless multigroup multicasting systems in conjunction with SWIPT. Herein, the advantages of adopting separate multicasting and energy precoder designs are illustrated, where we investigate the benefits of multiple antenna transmitters by exploiting the similarities between broadcasting information and wirelessly transferring power. The proposed design does not only facilitates the SWIPT mechanism, but may also serve as a potential candidate to complement the separate waveform designing mechanism with exclusive RF signals meant for information and power transmissions, respectively. Lastly, a novel mechanism is developed to establish a relationship between the SWIPT and cache-enabled cooperative systems. In this direction, benefits of adopting the SWIPT-caching framework are illustrated, with special emphasis on an enhanced rate-energy (R-E) trade-off in contrast to the traditional SWIPT systems. The common notion in the context of SWIPT revolves around the transmission of information, and storage of power. In this vein, the proposed work investigates the system wherein both information and power can be transmitted and stored. The Thesis finally concludes with insights on the future directions and open research challenges associated with the considered framework

Auction based competition of hybrid small cells for dropped macrocell users

We propose an auction based beamforming and user association algorithm for a wireless network consisting of a macrocell and multiple small cell access points (SCAs). The SCAs compete for serving the macrocell base station (MBS) users (MUs). The corresponding user association problem is solved by the proposed bid-wait auction (BWA) method. We considered two scenarios. In the first scenario, the MBS initially admits the largest possible set of MUs that it can serve simultaneously and then auctions off the remaining MUs to the SCAs, who are willing to admit guest users (GUs) in addition to their commitments to serve their own host users (HUs). This problem is solved by the proposed forward bid-wait auction (FBWA). In the second scenario, the MBS aims to offload as many MUs as possible to the SCAs and then admits the largest possible set of remaining MUs. This is solved by the proposed backward bid-wait auction (BBWA). The proposed algorithms provide close to optimum solution as if obtained using a centralised global optimization

Distributed optimisation techniques for wireless networks

Alongside the ever increasing traffic demand, the fifth generation (5G) cellular network architecture is being proposed to provide better quality of service, increased data rate, decreased latency, and increased capacity. Without any doubt, the 5G cellular network will comprise of ultra-dense networks and multiple input multiple output technologies. This will make the current centralised solutions impractical due to increased complexity. Moreover, the amount of coordination information that needs to be transported over the backhaul links will be increased. Distributed or decentralised solutions are promising to provide better alternatives. This thesis proposes new distributed algorithms for wireless networks which aim to reduce the amount of system overheads in the backhaul links and the system complexity. The analysis of conflicts amongst transmitters, and resource allocation are conducted via the use of game theory, convex optimisation, and auction theory. Firstly, game-theoretic model is used to analyse a mixed quality of service (QoS) strategic non-cooperative game (SNG), for a two-user multiple-input single-output (MISO) interference channel. The players are considered to have different objectives. Following this, the mixed QoS SNG is extended to a multicell multiuser network in terms of signal-to-interference-and-noise ratio (SINR) requirement. In the multicell multiuser setting, each transmitter is assumed to be serving real time users (RTUs) and non-real time users (NRTUs), simultaneously. A novel mixed QoS SNG algorithm is proposed, with its operating point identified as the Nash equilibrium-mixed QoS (NE-mixed QoS). Nash, Kalai-Smorodinsky, and Egalitarian bargain solutions are then proposed to improve the performance of the NE-mixed QoS. The performance of the bargain solutions are observed to be comparable to the centralised solutions. Secondly, user offloading and user association problems are addressed for small cells using auction theory. The main base station wishes to offload some of its users to privately owned small cell access points. A novel bid-wait-auction (BWA) algorithm, which allows single-item bidding at each auction round, is designed to decompose the combinatorial mathematical nature of the problem. An analysis on the existence and uniqueness of the dominant strategy equilibrium is conducted. The BWA is then used to form the forward BWA (FBWA) and the backward BWA (BBWA). It is observed that the BBWA allows more users to be admitted as compared to the FBWA. Finally, simultaneous multiple-round ascending auction (SMRA), altered SMRA (ASMRA), sequential combinatorial auction with item bidding (SCAIB), and repetitive combinatorial auction with item bidding (RCAIB) algorithms are proposed to perform user offloading and user association for small cells. These algorithms are able to allow bundle bidding. It is then proven that, truthful bidding is individually rational and leads to Walrasian equilibrium. The performance of the proposed auction based algorithms is evaluated. It is observed that the proposed algorithms match the performance of the centralised solutions when the guest users have low target rates. The SCAIB algorithm is shown to be the most preferred as it provides high admission rate and competitive revenue to the bidders

A Novel Approach for Centralized 3D Radio Resource Allocation and Scheduling in Dense HetNets for 5G Control-/User-plane Separation Architectures

This paper presents a centralized 3-dimensional radio resources (namely, time, frequency, and power) allocation and scheduling approach for control-plane and user-plane (C-/U-plane) separation architectures for fifth generation mobile networks. A central station is considered where schedulers of all base stations (BSs) are located. We consider a multi-tier network that comprises of a macrocell BS (MCBS), several outdoor picocell BSs, and a number of indoor femtocell BSs (FCBSs) deployed in a number of multi-storage buildings. The system bandwidth is reused in FCBSs within each building orthogonally. In contrast to the conventional almost blank subframe, we consider a fully blank subframe based time-domain enhanced intercell interference coordination to split completely C-/U-plane traffic such that the control-plane can be served only by the MCBS and the user-plane of user equipments by their respective BSs. We propose two power management schemes for FCBSs based on whether or not the coordinated multi-point communication with joint transmission (JT CoMP) is employed during off-state of a FCBS and develop a power control mechanism for both a single user and multi-user per FCBS scenarios. An optimal value of average activation factor (OAF) for a FCBS is derived to trade-off its serving capacity and transmit power saving factor. It is shown that in order to improve the network capacity, a FCBS needs to operate at an average activation factor (AAF) greater than its OAF using JT CoMP to serve neighboring on-state FCBSs during its normal off-state, whereas at an AAF less than the OAF to improve the energy efficiency. With a system level simulation, we show that the capacity of a FCBS increases, whereas its power saving factor decreases linearly with an increase in its AAF because of serving increased traffic, and an OAF of 0.5 for the capacity scaling factor and greater than 0.5 for are found.This paper presents a centralized 3-dimensional radio resources (namely, time, frequency, and power) allocation and scheduling approach for control-plane and user-plane (C-/U-plane) separation architectures for fifth generation mobile networks. A central station is considered where schedulers of all base stations (BSs) are located. We consider a multi-tier network that comprises of a macrocell BS (MCBS), several outdoor picocell BSs, and a number of indoor femtocell BSs (FCBSs) deployed in a number of multi-storage buildings. The system bandwidth is reused in FCBSs within each building orthogonally. In contrast to the conventional almost blank subframe, we consider a fully blank subframe based time-domain enhanced intercell interference coordination to split completely C-/U-plane traffic such that the control-plane can be served only by the MCBS and the user-plane of user equipments by their respective BSs. We propose two power management schemes for FCBSs based on whether or not the coordinated multi-point communication with joint transmission (JT CoMP) is employed during off-state of a FCBS and develop a power control mechanism for both a single user and multi-user per FCBS scenarios. An optimal value of average activation factor (OAF) for a FCBS is derived to trade-off its serving capacity and transmit power saving factor. It is shown that in order to improve the network capacity, a FCBS needs to operate at an average activation factor (AAF) greater than its OAF using JT CoMP to serve neighboring on-state FCBSs during its normal off-state, whereas at an AAF less than the OAF to improve the energy efficiency. With a system level simulation, we show that the capacity of a FCBS increases, whereas its power saving factor decreases linearly with an increase in its AAF because of serving increased traffic, and an OAF of 0.5 for the capacity scaling factor k = 1/2 and greater than 0.5 for k < 1 are found.&nbsp

Structures, Biological Activities and Phylogenetic Relationships of Terpenoids from Marine Ciliates of the Genus Euplotes

In the last two decades, large scale axenic cell cultures of the marine species comprising the family Euplotidae have resulted in the isolation of several new classes of terpenoids with unprecedented carbon skeletons including the (i) euplotins, highly strained acetylated sesquiterpene hemiacetals; (ii) raikovenals, built on the bicyclo[3.2.0]heptane ring system; (iii) rarisetenolides and focardins containing an octahydroazulene moiety; and (iv) vannusals, with a unique C30 backbone. Their complex structures have been elucidated through a combination of nuclear magnetic resonance spectroscopy, mass spectrometry, molecular mechanics and quantum chemical calculations. Despite the limited number of biosynthetic experiments having been performed, the large diversity of ciliate terpenoids has facilitated the proposal of biosynthetic pathways whereby they are produced from classical linear precursors. Herein, the similarities and differences emerging from the comparison of the classical chemotaxonomy approach based on secondary metabolites, with species phylogenesis based on genetic descriptors (SSU-rDNA), will be discussed. Results on the interesting ecological and biological properties of ciliate terpenoids are also reported

Studies on the Biosynthesis and Structure Elucidation of Terpene Natural Products by Isotopic Labeling Experiments

The cumulative doctoral thesis "Studies on the Biosynthesis and Structure Elucidation of Terpene Natural Products by Isotopic Labeling Experiments" deals with the application of stable isotopes for structure elucidation and biosynthesis studies of terpenoids from microorganisms. Additionally, analytic and synthetic studies on volatile natural products were conducted. A highly sensitive method for the identification of terpenes from fungal organisms, based on in vivo incorporation of 13C-labeled biosynthetic precursors was developed. This method was successfully applied for the identification of pogostol from the endophytic fungus Geniculosporium, of harzianone from the biocontrol fungus Trichoderma and of hypodoratoxide from the mycophilic fungus Hypomyces odoratus. The results gave additional insights into the biosynthesis of these metabolites. Isotopically labeled substrates were also designed, synthesized and utilized for in vitro experiments with recombinant enzymes from bacterial sources. Additionally, two studies on volatile metabolites from microorganisms were conducted. Nineteen recently genome sequenced actinomycetes were investigated and the chemical analysis was correlated to genome sequencing data. The volatiles of five sponge-associated fungi were analyzed and a series of bioactive metabolites, like the quorum sensing inhibitor protoanemonin, a highly phytotoxic lactone and algicidal phloroglucinol derivates were identified. During studies towards the total synthesis of the sesquiterpene koraiol, an enantioselective approach for the synthesis of a pseudosymmetric, tetrasubstituted all-trans cyclobutane was developed. The method makes use of a chiral auxiliary in a diastereoselective photodimerization. The obtained cyclobutane derivative is a key intermediate in the total synthesis of the highly bioactive sponge-derived metabolite sceptrin

BUILDING TOOLS FOR IMPROVED MODULATION OF THE HUMAN GABAA RECEPTOR, A CENTRAL NERVOUS SYSTEM TARGET FOR THE TREATMENT OF ANXIETY

In the U.S., anxiety is recognized as an increasing range of mentally and physically debilitating psychiatric health disorders with significant economic repercussions. Over the last 20 years, several novel anti-anxiety therapies have entered the drug development pipeline, but none have made it to market. The work in this dissertation focused on structurally modifying valerenic acid (VA), a structurally unique carboxylated sesquiterpene acid found in Valeriana officinalis. VA is putatively reported to have allosteric modulatory activity of the human GABAA receptor, a ligand-gated ion channel responsible for attenuating neurotransmissions. Structural modeling of VA’s GABAA receptor interaction suggests that constraining the isobutenyl group relative to the 5,6 membered ring system of VA could improve its binding specificity and affinity to the GABAA receptor. In planta, valerena-1,10-diene (VLD) is synthesized from farnesyl pyrophosphate (FPP) valerenadiene synthase (VDS), a sesquiterpene synthase. VLD is then carboxylated at one of its isobutenyl terminal methyl groups to yield VA. Our first objective was to engineer the VDS enzyme for altered product specificity and a more chemically constrained VLD scaffold. Using computational homology modelling and phylogenetic sequence analysis of characterized sesquiterpene synthases, amino acid residues in or near the active site and potentially impinging on catalytic specificity of VDS were identified. Residues were mutated via site-directed mutagenesis and mutants evaluated in vivo and in vitro. While wild type VDS’ products were 66 % VLD, 5 % allo-aromadendrene, and 29 % bicyclogermacrene (BCG), mutant Y535F yielded solely BCG. VDS with alanine or serine substituted for asparagine at position 455 lost all its ability to produce any of the wild type products and instead yielded a suite of seven new products dominated by germacrene-D-ol (≥ 40 %). To install a carboxylic acid functional group onto the sesquiterpene hydrocarbon scaffolds, we focused on the development of a host platform harboring an endomembrane system suitable for the expression of eukaryotic cytochrome P450 enzymes (P450s). As an example, plasmid co-expression of VDS, Lactuca sativa germacrene-A oxidase, and Artemisia annua cytochrome P450 oxidoreductase yielded an average 2mg/L of VA. For biological evaluation of sesquiterpene analogs, HEK293 cells transiently transfected with the human GABAA receptor subunit genes ⍺1, β3, and 2L, as well as a HEK293 cell line stably expressing the same GABA subunit genes, were optimized for sensing changes in membrane potential using a fluorescent bioassay. Effective concentration of test compounds and absolute magnitude of membrane depolarization in the transiently transfected cells gave the greatest responsiveness as determined for -aminobutyric acid (EC50 = 808 ± 206 nM, Emax = 13,309 ± 953 AFU’s), clonazepam (EC50 = 15 ± 8 nM, Emax = 4,211 ± 334 AFU’s), and VA (EC50 = 2,397 ± 341 nM, Emax = 5,935 ± 104 AFU’s). Abscisic acid, gibberellic acid, and cyclopartheniol demonstrated little to no detectable activity for modulating the human GABAA receptor

Synchronous Online Philosophy Courses: An Experiment in Progress

There are two main ways to teach a course online: synchronously or asynchronously. In an asynchronous course, students can log on at their convenience and do the course work. In a synchronous course, there is a requirement that all students be online at specific times, to allow for a shared course environment. In this article, the author discusses the strengths and weaknesses of synchronous online learning for the teaching of undergraduate philosophy courses. The author discusses specific strategies and technologies he uses in the teaching of online philosophy courses. In particular, the author discusses how he uses videoconferencing to create a classroom-like environment in an online class