Adaptive Tracking Techniques in Non-Stationary Environments

The continuously changing environments have been the main challenge for classical GNSS receiver implementations, as they can have a great impact on signal tracking performance and positioning. For this reason techniques capable of mitigating the impact of time-varying phenomena by adapting to changing conditions, thus improving performance are of great interest. This study reports the benefits of using adaptive techniques for standalone GNSS receivers in three different scenarios. The first scenario compares an adaptive Kalman filter against a classical DLL/PLL architecture in interference environments with user dynamics. The second scenario uses a multipath propagation channel to test alternative carrier tracking architectures which provide better results in terms of robustness. The third scenario uses the same multipath propagation channel to test the adaptive switching technique, 2-Step, in order to evaluate its capacity of guaranteeing and maintaining unambiguous tracking for BOC-type modulations. In order to assess the performance of these techniques a semi-analytical platform has been used. The results presented here show the benefits and trade-offs of different techniques taking into account different propagation channels and scenarios

Pagamentos de sinistros

Mestrado em Decisão Económica e EmpresarialEm 2013, ano internacional da estatística, é elaborada esta dissertação que relaciona o cálculo atuarial com a área da estatística. Partindo das vantagens e desvantagens de métodos como os Modelos Lineares Generalizados, é pretendido elucidar e estabelecer uma ligação entre as necessidades das empresas seguradoras e os estudos efetuados para o provisionamento da reserva para sinistros. Para a aplicação dos Modelos Lineares Generalizados no cálculo de provisões técnicas para sinistros é utilizada a distribuição Tweedie, pertencente à família de dispersão exponencial. Em estudos como este, esta distribuição apresenta uma boa flexibilidade de ajustamento aos dados, permitindo obter estimativas com melhor rigor.In 2013, the international year of statistics, this paper is developed to connect the actuarial calculation with the field of statistics. Starting with the advantages and disadvantages of methods like the Generalized Linear Models, it is intended to clarify and establish a link between the needs of insurance companies and studies carried out for the provisioning of claims outstanding reserve. The Tweedie distribution belongs to the family from exponential dispersion and it is used for the implementation of Generalized Linear Models in the calculation of claims technical provisions. In researches like these, this distribution has a good flexibility in the adjustment to data, allowing us to get estimations with better accuracy