Design space analysis for modeling incentives in distributed systems

Distributed systems without a central authority, such as peer-to-peer (P2P) systems, employ incentives to encourage nodes to follow the prescribed protocol. Game theoretic analysis is often used to evaluate incentives in such systems. However, most game-theoretic analyses of distributed systems do not adequately model the repeated interactions of nodes inherent in such systems. We present a game-theoretic analysis of a popular P2P protocol, Bit-Torrent, that models the repeated interactions in such protocols. We also note that an analytical approach for modeling incentives is often infeasible given the complicated nature of most deployed protocols. In order to comprehensively model incentives in complex protocols, we propose a simulation-based method, which we call Design Space Analysis (DSA). DSA provides a tractable analysis of competing protocol variants within a detailed design space. We apply DSA to P2P file swarming systems. With extensive simulations we analyze a wide-range of protocol variants and gain insights into their robustness and performance. To validate these results and to demonstrate the efficacy of DSA, we modify an instrumented BitTorrent client and evaluate protocols discovered using DSA. We show that they yield higher system performance and robustness relative to the reference implementation

Is there room for shared cars in Italy? Considerations from some recent experiences

Car sharing is increasing its role worldwide as an alternative transport mode, that could contribute to a more sustainable urban mobility by reducing congestion and pollution. The paper focuses on the understanding of which are the main characteristics of this service starting from the literature on this topic both in terms of user profile and impact of the service; in the second part of the paper, the Italian context will be presented starting from the analysis of four Italian experiences with a particular focus on Milan’s car sharing. Summarizing the conclusion, it emerges that to date, the overall impact on transport is still quite low, in part due to a scarce integration and coordination with other transport modes and in part because car is still perceived primarily as a status symbol and a “good” rather than as a “service”. Therefore, car sharing can perform as a significant complementary and sustainable solution to mobility needs only in a context of cultural change and inside a transport policy aimed at changing transport behavior.car sharing; sustainable mobility; transport policy; urban mobility; peer to peer car sharing;

Vegetation characterization through the use of precipitation-affected SAR signals

Current space-based SAR offers unique opportunities to classify vegetation types and to monitor vegetation growth due to its frequent acquisitions and its sensitivity to vegetation geometry. However, SAR signals also experience frequent temporal fluctuations caused by precipitation events, complicating the mapping and monitoring of vegetation. In this paper, we show that the influence of a priori known precipitation events on the signals can be used advantageously for the classification of vegetation conditions. For this, we exploit the change in Sentinel-1 backscatter response between consecutive acquisitions under varying wetness conditions, which we show is dependent on the state of vegetation. The performance further improves when a priori information on the soil type is taken into account.1010FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2013/50943-