ML estimator and hybrid beamformer for multipath and interference mitigation in GNSS receivers

This paper addresses the estimation of the code-phase(pseudorange) and the carrier-phase of the direct signal received from a direct-sequence spread-spectrum satellite transmitter. Thesignal is received by an antenna array in a scenario with interferenceand multipath propagation. These two effects are generallythe limiting error sources in most high-precision positioning applications.A new estimator of the code- and carrier-phases is derivedby using a simplified signal model and the maximum likelihood(ML) principle. The simplified model consists essentially ofgathering all signals, except for the direct one, in a component withunknown spatial correlation. The estimator exploits the knowledgeof the direction-of-arrival of the direct signal and is much simplerthan other estimators derived under more detailed signal models.Moreover, we present an iterative algorithm, that is adequate for apractical implementation and explores an interesting link betweenthe ML estimator and a hybrid beamformer. The mean squarederror and bias of the new estimator are computed for a numberof scenarios and compared with those of other methods. The presentedestimator and the hybrid beamforming outperform the existingtechniques of comparable complexity and attains, in manysituations, the Cramér–Rao lower bound of the problem at hand.

Mergers and difference-in-difference estimator : why firms do not increase prices?

Difference-in-Difference (DiD) methods are being increasingly used to analyze the impact of mergers on pricing and other market equilibrium outcomes. Using evidence from an exogenous merger between two retail gasoline companies in a specific market in Spain, this paper shows how concentration did not lead to a price increase. In fact, the conjectural variation model concludes that the existence of a collusive agreement before and after the merger accounts for this result, rather than the existence of efficient gains. This result may explain empirical evidence reported in the literature according to which mergers between firms do not have significant effects on prices.

De la marca comercial a la marca de territorio. Los casos de la DOC Priorat y DO Montsant

La producción vitivinícola y el valor de la procedencia otorgan a los territorios una valiosa oportunidad de diferenciación en un contexto de emergente competitividad entre espacios geográficos. En el caso de Cataluña, la comarca del Priorat y su vinculación identitaria con las denominaciones de origen del vino (DOC Priorat y DO Montsant) han representado un ejemplo de desarrollo local, al mismo tiempo que de posicionamiento para esta comarca de Tarragona. En función de todo lo expuesto, este articulo pretende radiografiar el proceso de dinamización territorial y de fijación identitaria articulado a través de las dos referidas denominaciones de origen.

2012_019.DOC

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2012_020.DOC

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2012_010.DOC

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2012_0333.DOC

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2011_022.DOC

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2011_0019.DOC

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