Dynamic Spectrum Sharing in Cognitive Radio Networks Using Truthful Mechanisms and Virtual Currency

In cognitive radio networks, there are scenarios where secondary users (SUs) utilize opportunistically the spectrum originally allocated to primary users (PUs). The spectrum resources available to SUs fluctuates over time due to PUs activity, SUs mobility and competition between SUs. In order to utilize these resources efficiently spectrum sharing techniques need to be implemented. In this paper we present an approach based on game-theoretical mechanism design for dynamic spectrum sharing. Each time a channel is not been used by any PU, it is allocated to SUs by a central spectrum manager based on the valuations of the channel reported by all SUs willing to use it. When an SU detects a free channel, it estimates its capacity according to local information and sends the valuation of it to the spectrum manager. The manager calculates a conflict-free allocation by implementing a truthful mechanism. The SUs have to pay for the allocation an amount which depends on the set of valuations. The objective is not to trade with the spectrum, but to share it according to certain criteria. For this, a virtual currency is defined and therefore monetary payments are not necessary. The spectrum manager records the credit of each SU and redistributes the payments to them after each spectrum allocation. The mechanism restricts the chances of each SU to be granted the channel depending on its credit availability. This credit restriction provides an incentive to SUs to behave as benefit maximizers. If the mechanism is truthful, their best strategy is to communicate the true valuation of the channel to the manager, what makes possible to implement the desired spectrum sharing criteria. We propose and evaluate an implementation of this idea by using two simple mechanisms which are proved to be truthful, and that are tractable and approximately efficient. We show the flexibility of these approach by illustrating how these mechanisms can be modified to achieve different sharing objectives which are trade-offs between efficiency and fairness. We also investigate how the credit restriction and redistribution affects the truthfulness of these mechanisms.This work was supported by the Spanish government through Projects TIN 2008-06739-C04-02 and TIN 2010-21378-C02-02.Vidal Catalá, JR.; Pla, V.; Guijarro Coloma, LA.; Martínez Bauset, J. (2013). Dynamic Spectrum Sharing in Cognitive Radio Networks Using Truthful Mechanisms and Virtual Currency. Ad Hoc Networks. 11:1858-1873. https://doi.org/10.1016/j.adhoc.2013.04.010S185818731

Future mmVLBI Research with ALMA: a European vision

Very long baseline interferometry at millimetre/submillimetre wavelengths (mmVLBI) offers the highest achievable spatial resolution at any wavelength in astronomy. The anticipated inclusion of ALMA as a phased array into a global VLBI network will bring unprecedented sensitivity and a transformational leap in capabilities for mmVLBI. Building on years of pioneering efforts in the US and Europe the ongoing ALMA Phasing Project (APP), a US-led international collaboration with MPIfR-led European contributions, is expected to deliver a beamformer and VLBI capability to ALMA by the end of 2014 (APP: Fish et al. 2013, arXiv:1309.3519). This report focuses on the future use of mmVLBI by the international users community from a European viewpoint. Firstly, it highlights the intense science interest in Europe in future mmVLBI observations as compiled from the responses to a general call to the European community for future research projects. A wide range of research is presented that includes, amongst others: - Imaging the event horizon of the black hole at the centre of the Galaxy - Testing the theory of General Relativity an/or searching for alternative theories - Studying the origin of AGN jets and jet formation - Cosmological evolution of galaxies and BHs, AGN feedback - Masers in the Milky Way (in stars and star-forming regions) - Extragalactic emission lines and astro-chemistry - Redshifted absorption lines in distant galaxies and study of the ISM and circumnuclear gas - Pulsars, neutron stars, X-ray binaries - Testing cosmology - Testing fundamental physical constant

Twenty-three unsolved problems in hydrology (UPH) – a community perspective

This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through on-line media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focussed on process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come

SNP identification and validation in two invasive species: zebra mussel (Dreissena polymorpha) and Asian clam (Corbicula fluminea)

Identificación y validación de PNU en dos especies invasoras: el mejillón cebra (Dreissena polymorpha) y la almeja asiática (Corbicula fluminea) El desarrollo de las plataformas asequibles de secuenciación masiva en paralelo (SMP) ha reducido el coste y el tiempo en la identificación de marcadores de polimorfismos de nucleótido único (PNU) para su uso en estudios de genética de poblaciones y de conservación. Tras la SMP, suele ser necesaria una segunda validación. El análisis de las curvas de fusión a alta resolución (HRMA en su sigla en inglés) es un método rápido y sencillo para escanear mutaciones y, por tanto, es un protocolo adecuado de validación de dichos marcadores, especialmente en especies no modelo. En este trabajo se presenta un juego de nueve marcadores polimórficos de PNU nuevos identificados mediante SMP y validados con el HRMA en dos especies invasoras (el mejillón cebra Dreissena polymorpha y la almeja asiática Corbicula fluminea), que pueden utilizarse en estudios de genética de poblaciones para evaluar y entender correctamente los episodios de invasión pasados y los que podrían ocurrir en el futuro.The development of affordable massive parallel sequencing (MPS) has reduced both time and costs of SNP identification for use in conservation and population genetic studies. After MPS, a second validation is usually required. High resolution melting analysis (HRMA) is a fast and simple method for mutation scanning, and thus a suitable validation protocol, particularly in non–model species. We present a set of nine novel polymorphic SNPs identified by MPS and validated with HRMA in two invasive species (the zebra mussel Dreissena polymorpha and the Asian clam Corbicula fluminea). These SNPs can be used in genetic studies to accurately assess and understand past and future invasion events.Identificación y validación de PNU en dos especies invasoras: el mejillón cebra (Dreissena polymorpha) y la almeja asiática (Corbicula fluminea) El desarrollo de las plataformas asequibles de secuenciación masiva en paralelo (SMP) ha reducido el coste y el tiempo en la identificación de marcadores de polimorfismos de nucleótido único (PNU) para su uso en estudios de genética de poblaciones y de conservación. Tras la SMP, suele ser necesaria una segunda validación. El análisis de las curvas de fusión a alta resolución (HRMA en su sigla en inglés) es un método rápido y sencillo para escanear mutaciones y, por tanto, es un protocolo adecuado de validación de dichos marcadores, especialmente en especies no modelo. En este trabajo se presenta un juego de nueve marcadores polimórficos de PNU nuevos identificados mediante SMP y validados con el HRMA en dos especies invasoras (el mejillón cebra Dreissena polymorpha y la almeja asiática Corbicula fluminea), que pueden utilizarse en estudios de genética de poblaciones para evaluar y entender correctamente los episodios de invasión pasados y los que podrían ocurrir en el futuro