Sharing the cost of multicast transmissions in wireless networks

AbstractA crucial issue in non-cooperative wireless networks is that of sharing the cost of multicast transmissions to different users residing at the stations of the network. Each station acts as a selfish agent that may misreport its utility (i.e., the maximum cost it is willing to incur to receive the service, in terms of power consumption) in order to maximize its individual welfare, defined as the difference between its true utility and its charged cost. A provider can discourage such deceptions by using a strategyproof cost sharing mechanism, that is a particular public algorithm that, by forcing the agents to truthfully reveal their utility, starting from the reported utilities, decides who gets the service (the receivers) and at what price. A mechanism is said budget balanced (BB) if the receivers pay exactly the (possibly minimum) cost of the transmission, and β-approximate budget balanced (β-BB) if the total cost charged to the receivers covers the overall cost and is at most β times the optimal one, while it is efficient if it maximizes the sum of the receivers’ utilities minus the total cost over all receivers’ sets. In this paper, we first investigate cost sharing strategyproof mechanisms for symmetric wireless networks, in which the powers necessary for exchanging messages between stations may be arbitrary and we provide mechanisms that are either efficient or BB when the power assignments are induced by a fixed universal spanning tree, or (3ln(k+1))-BB (k is the number of receivers), otherwise. Then we consider the case in which the stations lay in a d-dimensional Euclidean space and the powers fall as 1/dα, and provide strategyproof mechanisms that are either 1-BB or efficient for α=1 or d=1. Finally, we show the existence of 2(3d-1)-BB strategyproof mechanisms in any d-dimensional space for every α⩾d. For the special case of d=2 such a result can be improved to achieve 12-BB mechanisms

Neoplasias de novo en pacientes trasplantados renal

Los receptores de trasplante presentan mayor riesgo de desarrollo de neoplasias con respecto a la población general, siendo la prevalencia global entre un 20 y un 30% a los 10 años y de hasta 40% a los 20 años. Este riesgo se relaciona principalmente con la exposición a agentes inmunosupresores, pero otros factores tales como: edad de los receptores, tiempo en diálisis previo al trasplante, ciertas infecciones virales y la predisposición genética se han asociado con incremento del riesgo.Facultad de Ciencias Médica

reference architecture and framework

M. Adorni, F. Arcelli, S. Bandini, L. Baresi, C. Batini, A. Bianchi, D. Bianchini, M. Brioschi, A. Caforio, A. Cali, P. Cappellari, C. Cappiello, T. Catarci, A. Corallo, V. De Antonellis, C. Franza, G. Giunta, A. Limonta, G. Lorenzo, P. Losi, A. Maurino, M. Melideo, D. Micucci, S. Modafferi, E. Mussi, L. Negri, C. Pandolfo, B. Pernici, P. Plebani, D. Ragazzi, C. Raibulet, M. Riva, N. Simeoni, C. Simone, G. Solazzo, F. Tisato, R. Torlone, G. Vizzari, and A. Zill

Efficient causality-tracking timestamping

Vector clocks are the appropriate mechanism used to track causality among the events produced by a distributed computation. Traditional implementations of vector clocks require application messages to piggyback a vector of n integers (where n is the number of processes). This paper investigates the tracking of the causality relation on a subset of events (namely, the events that are defined as "relevant" from the application point of view) in a context where communication channels are not required to be FIFO, and where there is no a priori information on the connectivity of the communication.graph or the communication pattern. More specifically, the paper proposes a suite of simple and efficient implementations of vector clocks that address the reduction of the size of message timestamps, i.e., they do their best to have message timestamps whose size is less than n. The relevance of such a suite of protocols is twofold. From a practical side, it constitutes the core of an adaptive timestamping software layer that can used by underlying applications. From a theoretical side, it provides a comprehensive view that helps better understand distributed causality-tracking mechanisms

International cooperation experiences: Results achieved, lessons learned, and way ahead

In this paper we discuss the experience we had with international cooperation initiatives with respect to three projects, funded by the European Commission within the context of FP6 and FP7. We provide a summary of the main technical achievements which were directly related to international cooperation, and present the workplan for future research, specifically related to international cooperation. Besides the technical aspects, we discuss the pros and cons of the specific funding tools on which international cooperation was based at the time of these projects, and compile a wish list for upcoming funding initiatives for International Cooperation. © 2012 Springer-Verlag Berlin Heidelberg

A reference architecture for the certification of e-services in a digital government infrastructure

Certifying the execution of a service is a critical issue for an e-government infrastructure. In fact being able to document that an e-service was actually carried out, given the legal value that is often attached to data managed and exchanged by public administrations, is of the utmost importance. This is made more complex in cases, like it often happens in the public administration sector, where e-services are based on legacy systems managed by autonomous and independent organizations. In this paper we discuss the introduction, within the standard three tier architecture for e-services, of an architectural subsystem providing certification functions. This architecture features both physical and functional independence from the application level and is made up by new control components providing a highly efficient solution for certification requirements. Our solution has been successfully tested in real-world systems developed in Italy to support digital government functions