Marco Conti

INO - Istituto Nazionale di Ottica, Florens, Tuscany, Italy

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Publications (122)116.93 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: There is a growing interest in the development of (nearly) zero-energy buildings (ZEBs), i.e., buildings that deliver (nearly) the same amount of energy to the supply grid as it is drawn from it on a yearly basis. This paper investigates the ability of such ZEBs to performing in a truly self-sustainable fashion, i.e., minimising the frequency of energy exchange with the outer grid, through appropriate charging/discharging actions of a storage system. A realistic simulation environment called EnergyTest is developed on purpose to simulate the electrical load consumption in an aggregate of houses, in order to perform the sustainability assessment.
    No preview · Article · Jan 2015
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    ABSTRACT: Online Social Networks: Human Cognitive Constraints in Facebook and Twitter provides new insights into the structural properties of personal online social networks and the mechanisms underpinning human online social behavior. As the availability of digital communication data generated by social media is revolutionizing the field of social networks analysis, the text discusses the use of large- scale datasets to study the structural properties of online ego networks, to compare them with the properties of general human social networks, and to highlight additional properties. Users will find the data collected and conclusions drawn useful during design or research service initiatives that involve online and mobile social network environments. Provides an analysis of the structural properties of ego networks in online social networks. Presents quantitative evidence of the Dunbar's number in online environments. Discusses original structural and dynamic properties of human social network through OSN analysis.
    No preview · Article · Jan 2015
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    ABSTRACT: Online Social Networks (OSNs) are becoming more and more popular in today’s Internet. Distributed Online Social Networks (DOSNs), are OSNs which do not exploit a central server for storing users’ data and enable users to have more control on their profile content, ensuring a higher level of privacy. The main challenge of DOSNs comes from guaranteeing availability of the data when the data owner is offline. In this paper we propose a new P2P dynamic approach to the problem of data persistence in DOSNs. By following Dunbar’s approach, our system stores the data of a user only on a restricted number of friends which have regular contacts with him/her. Users in this set are chosen by considering several criteria targeting different goals. Differently from other approaches, nodes chosen to keep data replicas are not statically defined but dynamically change according to users’ churn. Our dynamic friend selection achieves availability higher than 90% with a maximum of 2 online profile replicas at a time for users with at least 40 friends. By using real Facebook data traces we prove that our approach offers high availability even when the online time of users is low.
    Full-text · Conference Paper · Oct 2014
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    ABSTRACT: Time Slotted Channel Hopping (TSCH) is one of the access behavior modes defined in the IEEE 802.15.4e standard. It combines time slotted access with multi-channel and channel hopping capabilities, providing predictable latency, energy efficiency, high network capacity, and high communication reliability. In this paper we focus on the formation process of TSCH networks, which relies on the regular advertisement of Enhanced Beacons (EBs). We consider a simple random-based advertisement algorithm, and evaluate its performance, through analysis and simulation, in terms of joining time (i.e., total time taken by a new node to join the network). We found that the joining time depends on a number of factors and, mainly, on the number of channels used for EB advertisement.
    No preview · Article · Sep 2014 · Proceedings - International Symposium on Computers and Communications
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    ABSTRACT: Distributed Online Social Networks (DOSNs) do not rely on a central repository for storing social data so that the users can keep control of their private data and do not depend on the social network provider. The ego network, i.e. the network made up of an individual, the ego, along with all the social ties she has with other people, the alters, may be exploited to define distributed social overlays and dis-semination protocols. In this paper we propose a new epidemic protocol able to spread social updates in DOSN overlays where the links between nodes are defined by considering the social interactions between users. Our approach is based on the notion of Weighted Ego Betweenness Cen-trality (WEBC) which is an egocentric social measure approximating the Betweenness Centrality. The computation of the WEBC exploits a weighted graph where the weights correspond to the tie strengths be-tween the users so that nodes having a higher number of interactions are characterized by a higher value of the WEBC. A set of experimental results proving the effectiveness of our approach is presented.
    Full-text · Conference Paper · Aug 2014
  • Emilio Ancillotti · Raffaele Bruno · Marco Conti
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    ABSTRACT: The IPv6 Routing Protocol for Low Power and Lossy Networks (RPL) has been recently standardised by the IETF ROLL working group to support IPv6 routing for resource constrained devices in industrial, home and urban environments. However, several studies have shown that RPL may experience (very) low delivery rates, particularly in large-scale deployments. In this paper we provide an in-depth analysis of the protocol attributes and design choices that generate such unreliability issues. Then, we describe and evaluate a new implementation of the RPL standard for the Contiki OS to improve data delivery reliability. The salient feature of our RPL implementation is to adopt a flexible cross-layering design that provides simple routing optimisations, enhanced link estimation capabilities and efficient management of neighbour tables. In order to verify the effectiveness of our RPL implementation we use an Advanced Metering Infrastructure (AMI) as case study. Results obtained using Cooja emulator in two sets of experiments, differentiated by the presence or lack of duty cycling, indicate that our RPL implementation outperforms the one provided in Contiki in terms of average packet delivery rates by up to 200% in networks with 100 nodes.
    No preview · Article · Aug 2014 · IEEE Transactions on Industrial Informatics
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    ABSTRACT: The Future Internet scenario will be characterised by a very large amount of information circulating in large scale content-centric networks. One primary concern is clearly to replicate and disseminate content efficiently, such that – ideally – it is replicated and spread only in those portions of the network where there are interested users. As centralised data dissemination solutions are unlikely to be feasible due to the sheer amount of content expected to circulate, nodes themselves must locally take data dissemination decisions, taking into account contextual information about users interests. In this paper, we consider a mobile opportunistic networking environment where mobile nodes exploit contacts among each other to replicate and disseminate content without central control. In this environment, we see nodes as proxies of their human users in the cyber world made up by mobile devices. Accordingly, we want nodes to act as much as possible as their users would do if they had to disseminate information among each other. We thus propose a new solution based on cognitive heuristics. Cognitive heuristics are functional models of the human mental processes, studied in the cognitive psychology field. They describe the judgement process the brain performs when subject to temporal constraints or partial information. We illustrate how these cognitive processes can be fruitfully implemented into a feasible and working ICT solution, in which decisions about the dissemination process are based on aggregated information built up from observations of the encountered nodes and successively exploited through a stochastic mechanism to decide what content to replicate. These two features allow the proposed solution to drastically limit the state kept by each node, and to dynamically adapt to the dynamics of content diffusion, the dynamically changing node interests and the presence of churning of nodes participation to the data dissemination process. The performance of our solution is evaluated through simulations and compared with reference solutions in the literature.
    Full-text · Article · May 2014 · Pervasive and Mobile Computing
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    ABSTRACT: Online Social Networks (OSNs) usually exploit a logically centralized infrastructure which has several drawbacks including scalability, privacy, and dependence on a provider. In contrast to centralized OSNs, a Distributed Online Social Network helps to lower the cost of the provider drastically, and allows better control of user privacy. A distributed approach introduces new problems to address, as data availability or information diffusion, which require the definition of methods for the analysis of the social graph. This paper focuses the problem of the evaluation of the centrality of a node in a Distributed Online Social Network and proposes a distributed approach for the computation of the Ego Betweenness Centrality, which is an ego-centric method to approximate the Betweenness Centrality. We propose a set of algorithms to compute the betweenness centrality in static and dynamic graphs, which can be directed or undirected. We propose both a broadcast and a gossip protocol to compute the Ego Betweenness Centrality. A set of experimental results proving the effectiveness of our approach are presented.
    No preview · Conference Paper · Mar 2014
  • Marco Conti · Silvia Giordano
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    ABSTRACT: In this article we discuss the state of the art of (mobile) multihop ad hoc networking. This paradigm has often been identified with the solutions developed inside the IETF MANET working group, and for this reason it is called the MANET paradigm. However, they do not coincide, and in the last decade they clearly diverged. In this article, we start from the reasons why the MANET paradigm did not have a major impact on computer communications, and we discuss the evolution of the multihop ad hoc networking paradigm by building on the lessons learned from the MANET research. Specifically, we analyze four successful networking paradigms, mesh, sensor, opportunistic, and vehicular networks, that emerged from the MANET world as a more pragmatic application of the multihop ad hoc networking paradigm. We also present the new research directions in the multihop ad hoc networking field: peoplecentric networking, triggered by the increasing penetration of the smartphones in everyday life, which is generating a people-centric revolution in computing and communications.
    No preview · Article · Jan 2014 · IEEE Communications Magazine
  • Marco Conti
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    ABSTRACT: In last couple of decades, cellular networks have revolutionized the way users access communication networks but they required a huge effort to operators for the development of a wireless infrastructure which has been designed considering deployment ...
    No preview · Article · Jan 2014 · Computer Communications
  • Andrea Passarella · Marco Conti
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    ABSTRACT: Foundational work in the area of opportunistic networks has shown that the distribution of intercontact times between pairs of nodes has a key impact on the network properties, for example, in terms of convergence of forwarding protocols. Specifically, forwarding protocols may yield infinite expected delay if the intercontact time distributions present a particularly heavy tail. While these results hold for the distributions of intercontact times between individual pairs, most of the literature uses the aggregate distribution, i.e., the distribution obtained by considering the samples from all pairs together, to characterize the properties of opportunistic networks. In this paper, we provide an analytical framework that can be used to check when this approach is correct and when it is not, and we apply it to a number of relevant cases. We show that the aggregate distribution can be way different from the distributions of individual pair intercontact times. Therefore, using the former to characterize properties that depend on the latter is not correct in general, although this is correct in some cases. We substantiate this finding by analyzing the most representative distributions characterizing real opportunistic networks that can be obtained from reference traces. We review key cases for opportunistic networking, where the aggregate intercontact time distribution presents a heavy tail with or without exponential cutoff. We show that, when individual pairs follow Pareto distributions, the aggregate distribution consistently presents a heavy tail. However, heavy tail aggregate distributions can also emerge in networks where individual pair intercontact times are not heavy tailed, for example, exponential or Pareto with exponential cutoff distributions. We show that an exponential cutoff in the aggregate appears when the average intercontact times of individual pairs are finite. Finally, we discuss how to use our analytical model to know whether collecting aggregate - nformation about intercontact times is sufficient or not, to decideâin practiceâwhich type of routing protocols to use.
    No preview · Article · Dec 2013 · IEEE Transactions on Mobile Computing

  • No preview · Article · Oct 2013 · Pervasive and Mobile Computing
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    Sajal K. Das · Marco Conti · Behrooz Shirazi

    Preview · Article · Oct 2013 · Pervasive and Mobile Computing
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    ABSTRACT: Opportunistic Networks (OppNets) offer a very volatile and dynamic networking environment. Several applications proposed for OppNets - such as social networking, emergency management, pervasive and urban sensing - involve the problem of sharing content amongst interested users. Despite the fact that nodes have limited resources, existing solutions for content sharing require that the nodes maintain and exchange large amount of status information, but this limits the system scalability. In order to cope with this problem, in this paper we present and evaluate a solution based on cognitive heuristics. Cognitive heuristics are functional models of the mental processes, studied in the cognitive psychology field. They describe the behavior of the brain when decisions have to be taken quickly, in spite of incomplete information. In our solution, nodes maintain an aggregated information built up from observations of the encountered nodes. The aggregate status and a probabilistic decision process is the basis on which nodes apply cognitive heuristics to decide how to disseminate content items upon meeting with each other. These two features allow the proposed solution to drastically limit the state kept by each node, and to dynamically adapt to both the dynamics of item diffusion and the dynamically changing node interests. The performance of our solution is evaluated through simulation and compared with other solutions in the literature.
    Full-text · Conference Paper · Jun 2013
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    ABSTRACT: Opportunistic networking is one of the key paradigms to support direct communication between devices in a mobile scenario. In this context, the high volatility and dynamicity of information and the fact that mobile nodes have to make decisions in condition of partial or incomplete knowledge, makes the development of effective and efficient data dissemination schemes very challenging. In this paper we present algorithms based on well-established models in cognitive sciences, in order to disseminate both data items, and semantic information associated with them. In our approach, semantic information represents both meta-data associated to data items (e.g., tags associated to them), and meta-data describing the interests of the users (e.g., topics for which they would like to receive data items). Our solution exploits dissemination of semantic data about the users’ interests to guide the dissemination of the corresponding data items. Both dissemination processes are based on models coming from the cognitive sciences field, named cognitive heuristics, which describe how humans organise information in their memory and exchange it during interactions based on partial and incomplete information. We exploit a model describing how semantic data can be organised in each node in a semantic network, based on how humans organise information in their memory. Then, we define algorithms based on cognitive heuris- tics to disseminate both semantic data and data items between nodes upon encounters. Finally, we provide initial performance results about the diffusion of interests among users, and the corresponding diffusion of data items.
    Full-text · Conference Paper · Jun 2013
  • Marco Conti · Silvia Giordano
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    ABSTRACT: This chapter discusses the evolution of the mobile/multihop ad hoc networking (MANET) paradigm. This paradigm has often been identified with the technologies developed inside the MANET IETF working group. Specifically, the chapter analyzes the reasons why the MANET paradigm does not have a major impact on computer communications. Then, starting from the lessons learned from the MANET research activities, it discusses how the multihop ad hoc networking paradigm has evolved toward a set of pragmatic networking approaches that are currently penetrating the mass market. Specifically, the chapter discusses four successful networking paradigms that emerged from the evolution of the multihop ad hoc networking concept: mesh, opportunistic, vehicular, and sensor networks. In these cases the multihop ad hoc paradigm is applied in a pragmatic way to extend the Internet and/or to support well-defined application requirements, thus providing a set of technologies that have a major impact on the wireless-networking field.Controlled Vocabulary Termsmobile ad hoc networks; wireless mesh networks; wireless sensor networks
    No preview · Chapter · Mar 2013
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    ABSTRACT: Transportation sustainability is largely being evaluated considering the effectiveness and the efficiency of public and private transportation systems and their impact on the environment. In this context, Electric Vehicles (EVs) play a key role in the reduction of greenhouse gas (GHG) emissions. The major issues of the large-scale adoption of EVs are related to their limited range and the lack of accessible charging infrastructures. An approach based on an intelligent dimensioning and management of the charging infrastructure might be a solution. In this work, practical strategies for providing efficient recharging services and improving user satisfaction (e.g., by maximizing battery charges) are compared.
    No preview · Conference Paper · Jan 2013
  • E. Ancillotti · R. Bruno · M. Conti
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    ABSTRACT: Low-Power and Lossy Networks (LLNs) are an enabling technology for many Internet of Things (IoT) applications. To allow LLNs to interoperate with the Internet the IETF is specifying IP-compatible standards that are specifically designed for embedded devices with small memory and limited computing capabilities. The purpose of this paper is to investigate the interplay between the recently proposed IETF standard for IPv6 routing in LLNs, called RPL, with state-of-the-art autoconfiguration algorithms that assign network addresses in a hierarchical manner. To this end, we have extended the default RPL implementation available in Contiki operating system to support T-DAAP, LISAA and DAAM addressing schemes. Our experimental results clearly show that the mechanisms used by RPL to configure and maintain a tree-based network topology frequently break address hierarchy, limiting the opportunities for route aggregation. Furthermore, classical techniques used to reduce network instability significantly increase the network set-up times and, in same cases, degrade path qualities.
    No preview · Conference Paper · Jan 2013
  • M. Conti · F. Delmastro · G. Minutiello · R. Paris
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    ABSTRACT: WiFi Direct introduces new opportunities to deploy real opportunistic networks through users' mobile devices. However, its original specification does not take into account all the parameters that can emerge from an opportunistic network scenario, not only in terms of technical requirements (e.g., available resources and connectivities) but also of users characteristics and profiles, which can heavily influence the system's performances and devices' interactions. In this work we investigate the feasibility of creating opportunistic networks on top of WiFi Direct framework by analyzing the protocol's performances in real scenarios with a variable number of mobile devices. Experimental results show the times required to form a group of variable size and the best configurations to support opportunistic networking operations and upper layer applications.
    No preview · Conference Paper · Jan 2013
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    ABSTRACT: The design of an effective charging management system plays a key role in the widespread deployment of Electric Vehicles (EVs). However, such design must consider a number of issues, especially in case of public charging stations, such as the impact of the EV charging on the power grid, the predictability of user mobility, the charging station utilization level, and, last but not least, user satisfaction. In this work, we focus on activity-based drivers' behaviors and we derive charging needs the EV management system shall deal with and evaluate the impact on user satisfaction of some implemented EV charging strategies. To this end, we have extended SUMO, a popular open-source generator of vehicular mobility traces to support activity-based mobility modes, EV charging and discharging models and EV charging planning and control. To validate the functionalities of this simulation environment we have carried a simulation-based study on a real city map by considering simple EV charging strategies that do not allow charging station reservation. Our preliminary results show that in this case public charging stations can be underutilized and more sophisticated strategies are needed to reduce range anxiety issues.
    No preview · Conference Paper · Jan 2013

Publication Stats

5k Citations
116.93 Total Impact Points

Institutions

  • 1993-2014
    • INO - Istituto Nazionale di Ottica
      Florens, Tuscany, Italy
  • 1970-2014
    • National Research Council
      • • Institute for Informatics and Telematics IIT
      • • Institute of Information Science and Technology "Alessandro Faedo" ISTI
      Roma, Latium, Italy
  • 1970-2012
    • University of Texas at Arlington
      • Department of Computer Sciences & Engineering
      Arlington, Texas, United States
  • 2007
    • IIT Research Institute (IITRI)
      Chicago, Illinois, United States
  • 2000
    • University of Bologna
      • Department of Computer Science and Engineering DISI
      Bologna, Emilia-Romagna, Italy