Opportunistic Access to PAL Channel for Multi-RAT GAA Transmission in Spectrum Access System

© 2017 IEEE. Spectrum Access System (SAS) is a three tier spectrum sharing framework proposed by the FCC. In this framework the aggregate interference of tier-3 General Authorised Access (GAA) users should be below a predetermined threshold anywhere within the tier-2 Priority Access Licensee (PAL) exclusion zone. GAA are expected to use a diverse range of Radio Access Technologies (RATs) with different levels of loading. We propose an optimal transmit power and probability of spectrum utilisation allocation scheme for GAA users that meets the average aggregate interference constraint within the GAA network. Most of the capacity maximisation studies consider the instantaneous aggregated interference from secondary users. In this paper we present an average aggregated interference method to optimise the capacity of GAA users in a single channel. Simulation results suggest that we can significantly increase the capacity of the channel by considering the probability spectrum utilisation of GAA users

Using hypergraph theory to model coexistence management and coordinated spectrum allocation for heterogeneous wireless networks operating in shared spectrum

Electromagnetic waves in the Radio Frequency (RF) spectrum are used to convey wireless transmissions from one radio antenna to another. Spectrum utilisation factor, which refers to how readily a given spectrum can be reused across space and time while maintaining an acceptable level of transmission errors, is used to measure how efficiently a unit of frequency spectrum can be allocated to a specified number of users. The demand for wireless applications is increasing exponentially, hence there is a need for efficient management of the RF spectrum. However, spectrum usage studies have shown that the spectrum is under-utilised in space and time. A regulatory shift from static spectrum assignment to DSA is one way of addressing this. Licence exemption policy has also been advanced in Dynamic Spectrum Access (DSA) systems to spur wireless innovation and universal access to the internet. Furthermore, there is a shift from homogeneous to heterogeneous radio access and usage of the same spectrum band. These three shifts from traditional spectrum management have led to the challenge of coexistence among heterogeneous wireless networks which access the spectrum using DSA techniques. Cognitive radios have the ability for spectrum agility based on spectrum conditions. However, in the presence of multiple heterogeneous networks and without spectrum coordination, there is a challenge related to switching between available channels to minimise interference and maximise spectrum allocation. This thesis therefore focuses on the design of a framework for coexistence management and spectrum coordination, with the objective of maximising spectrum utilisation across geographical space and across time. The amount of geographical coverage in which a frequency can be used is optimised through frequency reuse while ensuring that harmful interference is minimised. The time during which spectrum is occupied is increased through time-sharing of the same spectrum by two or more networks, while ensuring that spectrum is shared by networks that can coexist in the same spectrum and that the total channel load is not excessive to prevent spectrum starvation. Conventionally, a graph is used to model relationships between entities such as interference relationships among networks. However, the concept of an edge in a graph is not sufficient to model relationships that involve more than two entities, such as more than two networks that are able to share the same channel in the time domain, because an edge can only connect two entities. On the other hand, a hypergraph is a generalisation of an undirected graph in which a hyperedge can connect more than two entities. Therefore, this thesis investigates the use of hypergraph theory to model the RF environment and the spectrum allocation scheme. The hypergraph model was applied to an algorithm for spectrum sharing among 100 heterogeneous wireless networks, whose geo-locations were randomly and independently generated in a 50 km by 50 km area. Simulation results for spectrum utilisation performance have shown that the hypergraph-based model allocated channels, on average, to 8% more networks than the graph-based model. The results also show that, for the same RF environment, the hypergraph model requires up to 36% fewer channels to achieve, on average, 100% operational networks, than the graph model. The rate of growth of the running time of the hypergraph-based algorithm with respect to the input size is equal to the square of the input size, like the graph-based algorithm. Thus, the model achieved better performance at no additional time complexity.Electromagnetic waves in the Radio Frequency (RF) spectrum are used to convey wireless transmissions from one radio antenna to another. Spectrum utilisation factor, which refers to how readily a given spectrum can be reused across space and time while maintaining an acceptable level of transmission errors, is used to measure how efficiently a unit of frequency spectrum can be allocated to a specified number of users. The demand for wireless applications is increasing exponentially, hence there is a need for efficient management of the RF spectrum. However, spectrum usage studies have shown that the spectrum is under-utilised in space and time. A regulatory shift from static spectrum assignment to DSA is one way of addressing this. Licence exemption policy has also been advanced in Dynamic Spectrum Access (DSA) systems to spur wireless innovation and universal access to the internet. Furthermore, there is a shift from homogeneous to heterogeneous radio access and usage of the same spectrum band. These three shifts from traditional spectrum management have led to the challenge of coexistence among heterogeneous wireless networks which access the spectrum using DSA techniques. Cognitive radios have the ability for spectrum agility based on spectrum conditions. However, in the presence of multiple heterogeneous networks and without spectrum coordination, there is a challenge related to switching between available channels to minimise interference and maximise spectrum allocation. This thesis therefore focuses on the design of a framework for coexistence management and spectrum coordination, with the objective of maximising spectrum utilisation across geographical space and across time. The amount of geographical coverage in which a frequency can be used is optimised through frequency reuse while ensuring that harmful interference is minimised. The time during which spectrum is occupied is increased through time-sharing of the same spectrum by two or more networks, while ensuring that spectrum is shared by networks that can coexist in the same spectrum and that the total channel load is not excessive to prevent spectrum starvation. Conventionally, a graph is used to model relationships between entities such as interference relationships among networks. However, the concept of an edge in a graph is not sufficient to model relationships that involve more than two entities, such as more than two networks that are able to share the same channel in the time domain, because an edge can only connect two entities. On the other hand, a hypergraph is a generalisation of an undirected graph in which a hyperedge can connect more than two entities. Therefore, this thesis investigates the use of hypergraph theory to model the RF environment and the spectrum allocation scheme. The hypergraph model was applied to an algorithm for spectrum sharing among 100 heterogeneous wireless networks, whose geo-locations were randomly and independently generated in a 50 km by 50 km area. Simulation results for spectrum utilisation performance have shown that the hypergraph-based model allocated channels, on average, to 8% more networks than the graph-based model. The results also show that, for the same RF environment, the hypergraph model requires up to 36% fewer channels to achieve, on average, 100% operational networks, than the graph model. The rate of growth of the running time of the hypergraph-based algorithm with respect to the input size is equal to the square of the input size, like the graph-based algorithm. Thus, the model achieved better performance at no additional time complexity

Analyzing Usage Conflict Situations in Localized Spectrum Sharing Scenarios: An Agent-Based Modeling and Machine Learning Approach

As spectrum sharing matures, different approaches have been proposed for a more efficient allocation, assignment, and usage of spectrum resources. These approaches include cognitive radios, multi-level user definitions, radio environment maps, among others. However, spectrum usage conflicts (e.g., "harmful" interference) remain a common challenge in spectrum sharing schemes. In particular, in conflict situations where it is necessary to take actions to ensure the sound operations of sharing agreements. A typical example of a usage conflict is where incumbents' tolerable levels of interference (i.e., interference thresholds) are surpassed. In this work, we present a new method to examine and study spectrum usage conflicts. A fundamental goal of this project is to capture local resource usage patterns to provide more realistic estimates of interference. For this purpose, we have defined two spectrum and network-specific characteristics that directly impact the local interference assessment: resource access strategy and governance framework. Thus, we are able to test the viability in spectrum sharing situations of distributed or decentralized governance systems, including polycentric and self-governance. In addition, we are able to design, model, and test a multi-tier spectrum sharing scheme that provides stakeholders with more flexible resource access opportunities. To perform this dynamic and localized study of spectrum usage and conflicts, we rely on Agent-Based Modeling (ABM) as our main analysis instrument. A crucial component for capturing local resource usage patterns is to provide agents with local information about their spectrum situation. Thus, the environment of the models presented in this dissertation are given by the REM's Interference Cartography (IC) map. Additionally, the agents' definitions and actions are the results of the interaction of the technical aspects of resource access and management, stakeholder interactions, and the underlying usage patterns as defined in the Common Pool Resource (CPR) literature. Finally, to capture local resource usage patterns and, consequently, provide more realistic estimates of conflict situations, we enhance the classical rule-based ABM approach by using Machine Learning (ML) techniques. Via ML algorithms, we refine the internal models of agents in an ABM. Thus, the agents' internal models allow them to choose more suitable responses to changes in the environment

Técnicas para melhorar a eficiência do sensoriamento colaborativo em redes 5G para áreas remotas

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Exatas, Departamento de Ciência da Computação, 2020.A revolução dos smartphones em 2007 iniciou a um processo de crescimento exponencial da demanda por serviços de telefonia móvel. O aumento da demanda sem contrapartida da oferta, dependente do espectro disponível provoca uma queda na qualidade dos serviços prestados. As técnicas que usam Rádios cognitivos e acesso dinâmico ao espectro são con- sideradas fundamentais para otimizar a utilização do espectro e aumentar a quantidade de banda disponível para as redes 5G, ao permitir acesso oportunístico ao espectro licenciado ocioso. Diversos estudos apontam a subutilização de bandas, especialmente longe das grandes cidades, em que há menor demanda e menor incentivo econômico para a instalação de infraestrutura por parte das operadoras. Esse comportamento é incentivado devido ao processo de licenciamento de bandas em blocos e alocação estática do espectro, em que uma operadora licencia uma banda e junto a ela fica encarregada por dar cobertura a uma área atrelada à licença, enquanto pequenas operadoras locais ficam completamente de fora dos leilões e são impedidas de competir neste mercado. O acesso dinâmico ao espectro depende de informações que garantam a identificação de transmissões no canal candidato, afim de se reduzir interferência ao detentor da licença do canal. Algumas das técnicas mais comuns para se detectar a ocupação do canal via senso- riamento do espectro são carrier-sense e detecção de energia, dependendo da largura do canal. O sensoriamento colaborativo melhora a capacidade de detecção de uso do canal quando comparado com o sensoriamento individual, visto que diversifica geograficamente a informação disponível para análise. A qualidade do sensoriamento colaborativo depende não só dos sensoriamentos individuais recebidos, mais também da técnica que consolida ou executa a fusão desses resultados. Existem diversos algoritmos de fusão, cada um com vantagens e desvantagens. Algumas das técnicas de fusão clássicas são baseadas em votação k-em-n, em que k sensoriamentos indicando ocupação do canal resultam em uma fusão indicando ocupação do canal. A fusão 1-em-N, OU lógico, resulta em um número alto de falsos positivos, detectando ocupação do canal mesmo quando está desocupado, enquanto minimiza falsos negativos e a não detecção do canal de fato ocupado. Por fim, é parte do ciclo de sensoriamento colaborativo filtrar sensoriamentos de usuários maliciosos que desejam perturbar não só o resultado do sensoriamento colab- orativo como o funcionamento da rede. No caso de uma fusão simples como OU lógico, um único nó malicioso é capaz de inviabilizar por completo o uso oportunístico do es- pectro ao transmitir resultados falsos indicando que o canal está ocupado quando de fato está livre. Diante essa problemática, neste trabalho são propostas duas técnicas para melhorar os resultados do sensoriamento colaborativo, a saber : (1) uma técnica baseada em cadeias de Markov que aplicada aos resultados de sensoriamentos individuais, reduz falsos positivos e falsos negativos, além de reduzir o envio de mensagens de controle ; (2) uma técnica baseada na média harmônica para filtragem de resultados de sensoriamentos individuais recebidos, descartando sensoriamentos de nós mais distantes das fontes de interferência, protegendo de ataques Bizantinos. Ambas as técnicas são avaliadas em cenários de 5G na área rural, em que encontra-se a maior porção de bandas do espectro subutilizadas, candidatas ao acesso oportunístico. A fim de permitir a avaliação das técnicas propostas, foram realizadas diversas alter- ações para o modelo de pilha de rede LTE implementado no simulador de redes a nível de sistemas ns-3. As alterações incluem os procedimentos de sensoriamento do espectro individual feito pelos dispositivos de usuários (UEs), a transmissão dos resultados para o ponto de acesso (eNodeB), a fusão dos resultados recebidos e utilização do resultado de fusão no escalonamento de recursos para os dispositivos. Os sensoriamentos individu- ais são obtidos a partir de curvas de probabilidade de detecção e probabilidade de falsos positivos feitos através de medições em experimentos ou através de simulações a nível de camada física-enlace. As curvas são carregadas durante a configuração inicial da simu- lação, sendo interpoladas conforme necessário. As curvas podem ser tanto baseadas em distância euclidiana quanto em relação sinal ruído e interferência (SINR). O sensoria- mento individual consiste em utilizar a probabilidade de detecção relacionada a um dado valor de SNR ou de distância euclidiana é utilizada para gerar uma amostra aleatória a partir de um gerador com distribuição de Bernoulli. O procedimento se repete a cada 1 milissegundo no ciclo padrão de indicação do subquadro LTE. A técnica baseada em cadeias de Markov se baseia em um Teorema Central do Limite, em que a média de um certo número de amostras uniformemente distribuídas tende a se aproximar ou ao valor real da distribuição de probabilidade fonte ou ao valor central da distribuição. Em outras palavras, ao amostrar uniformemente uma distribuição de- sconhecida com número suficiente de amostras, encontra-se uma boa aproximação para o valor real que é procurado. Este princípio é aplicado para o sensoriamento individual do espectro, em que o valor do último sensoriamento é comparado com o resultado atual, e quando idêntico aumenta o grau de certeza de que este resultado é de fato o real. Quando os resultados diferem, o grau de certeza é perdido. Quando um dado limiar de certeza é ultrapassado, o resultado do sensoriamento que é de fato transmitido para o eNodeB é substituído pelo valor do último sensoriamento. A modelagem deste processo estocástico binomial é feita baseado no lançamento de N moedas, em que apenas o caso em que N resultados iguais consecutivos levam à troca do valor transmitido, sendo facilmente modelado como uma cadeia de Markov de N − 1 estados. Já a técnica baseada em média harmônica se baseia no fato de que as estações próx- imas das fontes de interferência são mais confiáveis que estações distantes, baseando-se nas curvas de probabilidade de detecção. Com isto, é necessário eliminar os resultados de sensoriamentos informados por usuários maliciosos com alguma informação adicional que sirva de prova que seu sensoriamento reportado é falso. Uma das maneiras de se mitigar informações falsas é utilizando a média harmônica dos CQIs reportados, permitindo iden- tificar UEs mais afetados pela fonte de interferência e descartar todos os resultados por UEs pouco afetadas, mais afastadas da fonte. Para poder se confiar no CQI reportado pelos UEs, é necessário medir a quantidade de retransmissões feitas para cada uma delas. Uma taxa de retransmissões próxima de 10% indica um CQI adequado, enquanto taxas próximas de 0% indicam CQI reportado abaixo do real e taxas acima de 10% indicam CQI reportado acima do real. O limiar de retransmissões é definido nos padrões 3GPP. A avaliação das propostas foi feita em duas partes: primeira parte com a validação do modelo proposto para o sensoriamento colaborativo no modelo do padrão LTE do simulador, e a segunda parte avaliando o desempenho das técnicas propostas. Durante a validação, foi confirmado o comportamento esperado do sensoriamento colaborativo (sensoriamentos individuais, transmissão dos resultados e fusões) em termos de taxas de falsos positivos e taxas de falsos negativos quando comparado com os modelos matemáticos. Na avaliação do desempenho das técnicas propostas foram avaliadas acurácia, taxas de falso positivos e taxas de falsos negativos. Em ambos os casos, foram utilizados cenários inspirados em zonas rurais, com: baixo número de nós (10, 20, 50, 100); uma célula com 50 quilômetros de raio; canal de 20 MHz na banda 5 com portadora em 870 MHz; eNodeB transmitindo à 53 dBm; UEs transmitindo à 23 dBm; eNodeB e UEs com antenas com 9 dBi de ganho; detentor da licença do canal (PU) transmitindo à 40 dBm ou 35 dBm; um PU por subcanal de 5 MHz; algoritmos de fusão simples. O cenário de validação foi pouco realístico, com UEs dispersas ao longo de um certo raio fixo de distância do PU, garantindo uma mesma probabilidade de detecção para todos os UEs. Os cenários de avaliação das técnicas foram separados em dois conjuntos, um menos realístico com dispersão aleatória pela célula, outro mais realístico com dispersão aleatória dos PUs pela célula e dispersão aleatória de grupos de UEs pela célula, formando clusters de UESs Os resultados mostram que as técnicas propostas aumentam a acurácia em relação à técnica clássica de fusão de resultados do sensoriamento colaborativo (fusão OU lógico, ou 1-em-N), reduzindo falsos positivos em até 790 vezes, de 63.23% para 0.08% no cenário com dispersão aleatória dos UEs e sem atacantes. Neste mesmo cenário houve um aumento de 0% para 0.47% do número de falsos negativos, sem impactar severamente o detentor da licença do canal. Nos cenários com atacantes, todas as fusões simples apresentam resultados ruins, com ou sem a técnica das cadeias de Markov, até 100% de falsos positivos, inviabilizando o acesso oportunístico. Já a técnica da média harmônica apresenta bom grau de proteção contra atacantes, em especial nos cenários com mais dispositivos. Sem a técnica baseada em Markov e no cenário com 100 UEs, dos quais 10 atacantes, conseguiu reduzir falsos positivos da fusão OU de 100% para 60%, sem aumentar significativamente o número de falsos negativos. Quando as duas técnicas são combinadas, o número de falsos positivos cai para 5% enquanto falsos negativos sobem para 18%. Nos cenários com menos UEs e com clusters, falsos negativos são consistentemente mais altos, porém superiores às fusões 2-em-N, 3-em-N e E utilizando a técnica de Markov no cenário sem atacantes. Em todos os cenários, a técnica baseada em cadeias de Markov também reduziu a taxa média de notificação dos quadros em 2 ordens de grandeza, economizando banda do canal de controle licenciado. Esses resultados permitem concluir que ambas as técnicas são efetivas para o cenário rural para a qual foram propostas. Também se depreende que o número de estados da cadeia de Markov e da técnica da média harmônica podem ser alterados para se trocar alcance da detecção por certeza da detecção e nível de proteção contra atacantes por falsos negativos, respectivamente. Como trabalhos futuros, cabem a adaptação da técnica para: incluir cenários urbanos, mais densos, utilizando técnicas de amostragem; utilização de técnicas de localização (e.g. Time-of-Arrival, Angle-of-Arrival) para segmentação da célula em setores; melhorar a técnica da média harmônica para reduzir falsos negativos mantendo o mesmo nível de proteção contra atacantes.The smartphone revolution of 2007 started an exponential demand growth of mobile con- nectivity. The ever increasing demand requires an increase in supply, which is depends in the amount of available spectrum. The amount of available spectrum however is limited, curving supply growth and reducing the quality of services perceived by the users. Cogni- tive radio and dynamic spectrum access are essential to increase the spectrum utilization and amount of available bandwidth in 5G networks, by opportunistically accessing unused licensed spectrum. The dynamic spectrum access depends on channel information that guarantees the detection of transmissions in the candidate channel, as a means of reducing interference to the channel licensee. The collaborative spectrum sensing increases the channel usage detection capacity when compared to individual spectrum sensing, as there is more geographically diverse information for analysis and decision-making. The quality of the collaborative sensing depends not only on the individual sensing that feeds information into it, but also on the technique that fuses those results into the final sensing result. Two techniques to improve the collaborative spectrum sensing results are proposed in this dissertation: (1) a technique based in Markov chains to smooth consecutive individual spectrum sensing results, reducing both false positives and false negatives, while enabling the reduction of sensing reports by skipping sensing reports with the same results; (2) a technique based in the harmonic mean of the channel quality indicator, used to filter the received individual spectrum sensing, discarding nodes far from the source of interference, mitigating against Byzantine attacks. Both techniques are evaluated in rural 5G scenarios, which are the best place to use opportunistic access due to the amount of unutilized and underused spectrum bands. In order to evaluate the proposed techniques, a set of modifications to the LTE net- work stack model of the ns-3 system-level simulator is proposed. The modifications include a complete collaborative sensing cycle, including: the individual spectrum sensing pro- cedure, performed by user equipment’s (UEs); the transmission of control messages to the access point (eNodeB), the fusion of the received results and utilization of the free spectrum for the UEs. The individual spectrum sensing is performed by interpolating probability of detection curves and false positive probability, which are produced either by experimental measurements or by link-layer simulations. The evaluation of the proposals was made in two parts: first part focusing on the validating the collaborative spectrum sensing cycle implementation and integration to the LTE model; second part focusing on the performance of the proposed techniques. The collaborative spectrum sensing cycle (individual sensing, sensing report and fusion) was validated and closely follows the mathematical model. The evaluation of the techniques included accuracy of the fused result, false positive and false negative rates. The results show the techniques are effective in increasing the accuracy of the collab- orative sensing when compared to the standalone classic fusion techniques (OR fusion, or 1-out-of-n). There were reductions in false positives rates of up to 790 times, from 63.23% to 0.08% in the scenario with randomized dispersion of UEs across the cell and without attackers. In the same scenario, the false negatives increased from 0% to 0.47%, which does not severely impact the licensee with interference. All classic fusions behave very poorly in scenarios with attackers, with and without the Markov chain technique. False positive rates soar to as high as 100%, making the opportunistic access impossible. The harmonic mean-based technique reduces the false positives, providing good protec- tion against attackers especially in scenarios with more UEs. The harmonic mean alone reduced false positives for the OR fusion from 100% to 60% without significantly impact- ing false negatives in the scenario with 100 UEs and 10 attackers. When both techniques are used together, the rate of false positives fall to 5% while false negatives increase to 18%. Scenarios with less UEs and distributed in clusters tend to have higher false negative rates when both techniques are used, but false positives are consistently lower than other classical fusions (e.g. 2-out-of-N, 3-out-of-N and AND). The Markov chain technique effectively reduced the sensing report rate by 2 orders of magnitude, saving up scarce control bandwidth. These results allow us to conclude that the both techniques are effective for the rural scenario they were proposed

A Game-theoretic Model for Regulating Freeriding in Subsidy-Based Pervasive Spectrum Sharing Markets

Cellular spectrum is a limited natural resource becoming scarcer at a worrisome rate. To satisfy users\u27 expectation from wireless data services, researchers and practitioners recognized the necessity of more utilization and pervasive sharing of the spectrum. Though scarce, spectrum is underutilized in some areas or within certain operating hours due to the lack of appropriate regulatory policies, static allocation and emerging business challenges. Thus, finding ways to improve the utilization of this resource to make sharing more pervasive is of great importance. There already exists a number of solutions to increase spectrum utilization via increased sharing. Dynamic Spectrum Access (DSA) enables a cellular operator to participate in spectrum sharing in many ways, such as geological database and cognitive radios, but these systems perform spectrum sharing at the secondary level (i.e., the bands are shared if and only if the primary/licensed user is idle) and it is questionable if they will be sufficient to meet the future expectations of the spectral efficiency. Along with the secondary sharing, spectrum sharing among primary users is emerging as a new domain of future mode of pervasive sharing. We call this type of spectrum sharing among primary users as pervasive spectrum sharing (PSS) . However, such spectrum sharing among primary users requires strong incentives to share and ensuring a freeriding-free cellular market. Freeriding in pervasively shared spectrum markets (be it via government subsidies/regulations or self-motivated coalitions among cellular operators) is a real techno-economic challenge to be addressed. In a PSS market, operators will share their resources with primary users of other operators and may sometimes have to block their own primary users in order to attain sharing goals. Small operators with lower quality service may freeride on large operators\u27 infrastructure in such pervasively shared markets. Even worse, since small operators\u27 users may perceive higher-than-expected service quality for a lower fee, this can cause customer loss to the large operators and motivate small operators to continue freeriding with additional earnings from the stolen customers. Thus, freeriding can drive a shared spectrum market to an unhealthy and unstable equilibrium. In this work, we model the freeriding by small operators in shared spectrum markets via a game-theoretic framework. We focus on a performance-based government incentivize scheme and aim to minimize the freeriding issue emerging in such PSS markets. We present insights from the model and discuss policy and regulatory challenges

Footprint of Calcium on Regulation of Extracellular Calcium-Sensing Receptor and Connexin26

Calcium (Ca2+) functions as a primary and secondary messenger regulating crucial cellular processes. We study two central membrane proteins, extracellular calcium-sensing receptor (CaSR) and connexin26 (Cx26) gap junction (GJ) channel, that are regulated by Ca2+ and play critical roles in regulating Ca2+ homeostasis and communication between the intra- and extra- cellular milieu. Mutations in CaSR are associated with abnormal Ca2+ homeostasis, hypoparathyroidism, myocardial infarction and cancers. Similarly, mutations in Cx26 are implicated in many hereditary deafness and dermatological disorders. The role of Ca2+ in CaSR biosynthesis, CaSR mediated intracellular Ca2+ signaling, Cx26 regulation and tuning of their regulators in biological and pathological is reported, however, the knowledge of exact molecular mechanism is obscure due to challenges associated with membrane proteins. In this dissertation, we first report the discovery of 98 novel putative CaSR interactors using co-immunoprecipitation, mass-spectrometry and confocal imaging. Our findings suggest that extracellular Ca2+ dependent CaSR mediated intracellular signaling facilitates ER quality control and trafficking by upregulating the interaction with proteins affiliated with ubiquitination, chaperoning and glycosylation. Next, the cooperative activation of CaSR by Ca2+, Mg2+ and aromatic amino acids is validated in wild type CaSR in HEK293 cells. CaSR mutations at conserved metal binding sites reduce Ca2+/Mg2+ evoked intracellular Ca2+ mobilization and Ca2+ oscillation. This work further uses single cell imaging, immunoassay and sequencing to report tissue specific expression and differential capabilities of cations and drugs to tune CaSR mediated signaling in prostate (PCa) and thyroid cancer cells. We report a presence of wild type CaSR in PCa cell using RT-PCR. Additionally, proteomics and gene ontology show differential proteostasis between prostate cancer and HEK293 cells. Finally, this study endeavored at expressing and purifying a challenging protein, Cx26, and established binding affinity for Tb3+ and Ca2+ as 1.8 µM and 37 mM, respectively. The N-terminal lobe of CaM was found to bind Ca2+ tighter by 2.5-folds greater than C-lobe in the presence of Cx26p1-21. Our study on role of Ca2+ on regulation of CaSR and Cx26 allows for greater understanding of their function and provides avenue for potential therapeutic targets

Links between electrophilic stress and antifungal resistance in pathogenic Candida species

Collectively, Candida species are the most prevalent cause of both superficial and invasive fungal infections worldwide. Invasive Candida infections have a high mortality rate and predominantly affect individuals with underlying diseases, such as diabetes, HIV, or cancer. Unfortunately, many invasive Candida infections are recalcitrant to antifungal treatment, while intrinsically multidrug-resistant pathogens, like Candida auris, are increasing in prevalence. Although the canonical mechanisms of antifungal resistance in Candida species are well established, i.e., overexpression of efflux pumps and overexpression of or mutations in genes encoding drug targets, factors affecting the natural evolution and regulation of resistance mechanisms remain poorly understood. One cause of antifungal resistance in Candida species is the acquisition of gain-of-function mutations in the transcription factor Mrr1, resulting in overexpression of the multidrug transporter Mdr1. However, little is known about the functions of other genes regulated by Mrr1 or how Mrr1 activity is modulated in vivo. In this work, we demonstrate in Candida lusitaniae and in C. auris that Mrr1 contributes to resistance against methylglyoxal (MG), a toxic, electrophilic dicarbonyl derived from natural metabolic processes, and that Mrr1-mediated MG resistance is driven in part by expression of the methylglyoxal reductase genes MGD1 and MGD2 in C. lusitaniae and MGD1 in C. auris. Furthermore, we show that a sublethal concentration of MG induces expression of MDR1 and MG reductase genes in C. lusitaniae and C. auris, and consequently increases fluconazole (FLZ) resistance in C. lusitaniae. Finally, we characterize the complete Mrr1- dependent and independent transcriptional response of C. auris to MG and to the known inducer of Mrr1-regulated gene expression, benomyl, and show that both compounds cause the differential expression of a multitude of genes involved in metabolism and stress response, which could contribute to pathogen survival while colonizing and infecting a mammalian host. Together, the work presented herein provides valuable insight into a potential mechanism for the regulation of Mrr1-dependent transcription in vivo as well as a possible selective pressure for gain-of-function mutations in the MRR1 gene. This is particularly noteworthy because MG is elevated in many of the same human diseases that are considered risk factors for Candida infection, and MG is also produced by activated phagocytes in response to pathogens. Thus, it is conceivable that Candida would encounter biologically significant levels of MG in the context of infection. We propose that MG-mediated induction of Mrr1-dependent transcription in Candida species is one factor that plays a role in antifungal treatment failure

Sustainable Aquaculture Techniques

This book presents some innovative developments in sustainable aquaculture practices in the context of environmental protection and seafood production techniques. The chapters are written by experts in their respective areas, so that their contribution represents the progress of their research, which is intended to mark the current frontier in aquaculture practices. Every chapter presents techniques that contribute to good aquaculture practices, where direct and vital nutrition and food, as a source of energy and biomass generation, is fundamentally based. We hope this book supports producers and researchers in their activities and helps to maintain a spirit of environmental protection in the context of production of high quality, nutritional food