Giuseppe De Marco

Mobility Effects in Mobile Ad Hoc Networks

In this paper, we present the implementation and analysis of our implemented testbed considering the Optimized Link State Routing (OLSR) protocol. We investigate the effect of mobility and topology changing in the throughput of a Mobile Ad hoc Network (MANET). The mobile nodes move toward the destination at a regular speed. When the mobile nodes arrive at the corner, they stop for about three seconds. Experimental time is 150 seconds. In this work, we consider 6 models and we assess the performance of our testbed in terms of throughput, round trip time and packet loss. From our experiments, we found that the OLSR protocol has a good performance when the source node is moving. However, the performance is not good when the relay nodes are moving.

Performance Evaluation of a Wireless Sensor Network Considering Mobile Event

Presently, there are many research work for sensor networks. In our previous work, we implemented a simulation system for sensor networks. But, we considered that the event node is stationary in the observation field. However, in many applications the event node may move. For example, in an ecology environment the animals can move randomly. In this work, we want to investigate how the sensor network performs in the case when the event node moves. We carried out the simulations for lattice topology and TwoRayGround radio model considering AODV and DSR protocols. We compare the simulation results for two cases: when the event node is mobile and stationary. The simulation results have shown that the routing efficiency for the case of mobile event node is better than the stationary event node using AODV protocol. Also, the goodput for the mobile event node case does not change too much compared with the stationary event case using AODV,but the goodput is not good when the number of nodes is increased.

A limit theorem for equilibria under ambiguous belief correspondences

Previous literature shows that, in many different models, limits of equilibria of perturbed games are equilibria of the unperturbed game when the sequence of perturbed games converges to the unperturbed one in an appropriate sense. The question whether such limit property extends to the equilibrium notions in ambiguous games is not yet clear as it seems; in fact, previous literature shows that the extension fails in simple examples. The contribution in this paper is to show that the limit property holds for equilibria under ambiguous beliefs correspondences (presented by the authors in a previous paper). Key for our result is the sequential convergence assumption imposed on the sequence of beliefs correspondences. Counterexamples show why this assumption cannot be removed.

A dynamic game of coalition formation under ambiguity

In a previous paper, we generalized to the mixed strategy case the γ model of coalition formation (introduced by Hart and Kurz in Econometrica 51(4):1047–1064, 1983) for situations in which players have ambiguous expectations about the formation of the coalitions in which they are not involved; then we analyzed the corresponding evolutionary games. In this paper, we embody into the model rationality of the players; it follows that allowing for mixed strategies makes it impossible to construct unequivocally a von Neumann–Morgestein expected utility function coherent (in the sense of de Finetti B in Sul Significato Soggettivo della Probabilità, Fundamenta Mathematicae, T, vol XVIII, pp 298–329, 1931) to every strategy profile. We find out that if the multiplicity of coherent beliefs problem is approached by considering “ambiguity loving” players then existence results for classical static equilibria can be obtained in this model. Moreover, we provide conditions for the game to be dynamically playable and we find how the coalition structure beliefs might evolve coherently (according) to the evolution of the strategies.

Performance Evaluation of Link Quality Extension in Multihop Wireless Mobile Ad-hoc Networks

Recently, Mobile Ad-hoc Networks (MANET) are continuing to attract the attention for their potential use in several fields. Most of the work has been done in simulation, because a simulator can give a quick and inexpensive understanding of protocols and algorithms. However, experimentation in the real world are very important to verify the simulation results and to revise the models implemented in the simulator. In this paper, we present the implementation and analysis of our testbed considering the Link Quality Window Size (LQWS) parameter for Optimized Link State Routing (OLSR) protocol. We investigate the effect of mobility in the throughput of a MANET. The mobile nodes move toward the destination at a regular speed. When the mobile nodes arrive at the corner, they stop for about three seconds. In our experiments, we consider two cases: only one node is moving (mobile node)and two nodes (intermediate nodes) are moving at the same time. We assess the performance of our testbed in terms of throughput, round trip time, jitter and packet loss. From our experiments, we found that throughput of TCP was improved by reducing LQWS.

Dynamics of Mixed Coalitions Under Social Cohesion Constraints

ABSTRACT The performance to a collective task may require a certain degree of cooperation among agents. Is cooperation viable in the sense that individual needs are fulfilled, compromises are possible and the task is performed? A model of cooperation is presented in which compromises are also ruled by cohesion among agents. Viability conditions are found associated with regulation law. They say that cooperation increases with cohesion. Moreover, reducing the rapidity of change of cooperation and lowering dissident behavior correct the dynamics so as to turn non viable states into viable ones.

A REFINEMENT CONCEPT FOR EQUILIBRIA IN MULTICRITERIA GAMES VIA STABLE SCALARIZATIONS

In a finite multicriteria game, one or more systems of weights might be implicitly used by the agents by playing a Nash equilibrium of the corresponding trade-off scalar games. In this paper, we present a refinement concept for equilibria in finite multicriteria games, called scalarization-stable equilibrium, that selects equilibria stable with respect to perturbations on the scalarization. An existence theorem is provided together with some illustrative examples and connections with some other refinement concepts are investigated.

Reciprocity in the Principal–Multiple Agent Model

Abstract This paper studies how incentives are affected by intention-based reciprocity preferences when the principal hires many agents. Our results describe the set of agents’ sensitivities to reciprocity required to sustain a given strategy profile. We also show that hiring reciprocal agents to implement a first- or a second-best contract will always benefit the principal if the strategy profile is symmetric. Instead, when the profile (first or second best) is asymmetric the principal’s interest might be better served by self-interested agents. We conclude the paper by clarifying when symmetric profiles are most likely to arise.

Networks of Financial Contagion

Banks develop relationships in order to protect themselves against liquidity risk. Despite this benefit, fragility of financial markets stems from these interconnections. A cornerstone in the microeconomic analysis of contagion in financial systems is the contribution of Allen and Gale (2000). Our work takes up the challenge of generalizing their contagion analysis to complex networks. We provide an effective procedure to construct a network of financial contagion which enables the analysis of complex networks via simulations. Our study shows that it is possible to find a minimal number of links to guarantee contagion resiliency, and that the Allen and Gale conjecture holds: the system becomes more fragile as the number of links decreases.

ALTRUISTIC BEHAVIOR AND CORRELATED EQUILIBRIUM SELECTION

This paper studies new refinement concepts for correlated equilibria based on altruistic behavior of the players and generalizes some refinement concepts previously developed by the authors for Nash equilibria. Effectiveness of the concepts, relations with the corresponding notions for Nash equilibria and with other correlated equilibrium refinements are investigated. The analysis of the topological properties of the set of solutions concludes the paper.