Susana Sargento

University of Aveiro, Aveiro, Aveiro, Portugal

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Publications (215)37.21 Total impact

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    ABSTRACT: As a cutting edge technology, Machine to Machine (M2M) communications are gaining ground for managing and controlling M2M devices. Since these objects have intelligence, communication capabilities and ability to work with their environment, they are ...
    Mobile Networks and Applications 02/2014; 19(1):1-3. · 1.11 Impact Factor
  • Tiago Condeixa, Susana Sargento
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    ABSTRACT: This letter studies a network-based IPv6 mobility model based on Proxy Mobile IP, called Multiple Local Mobility Anchors. It replicates the Local Mobility Anchors of Proxy Mobile IP through access routers and gateways of the network. The Local Mobility Anchors maintain the binding between the well-known IPv6 address of the mobile node and its current access router, in order to achieve an optimized routing path to data sessions that require mobility support. Multiple Local Mobility Anchors approach is compared with Proxy Mobile IP and Distributed Mobility Anchoring through analytical models. The outcome demonstrates that it significantly improves the data cost at the expense of a slight increase in the signaling cost.
    IEEE Communications Letters 01/2014; 18(2):376-379. · 1.16 Impact Factor
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    A.B. Reis, S. Sargento, F. Neves, O.K. Tonguz
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    ABSTRACT: The 802.11p/WAVE standard relies on the presence of onboard units (OBUs) and roadside units (RSUs) for communications in vehicular networks. In this paper, we study the benefits of deploying RSUs to improve communications in highway scenarios. We develop an analytical model to analyze communication delay in a highway scenario with bidirectional traffic, considering both connected and disconnected RSUs, and validate our model via simulations and experimental measurements with 802.11p equipment. Contrary to conventional wisdom, our results show that significant benefits of RSUs in terms of connectivity and message dissemination can only be achieved when the deployed RSUs are interconnected. Conversely, deploying a large number of disconnected RSUs will lead to little or no benefit in message dissemination delay.
    IEEE Transactions on Vehicular Technology 01/2014; 63(6):2794-2806. · 2.06 Impact Factor
  • Tiago Condeixa, Susana Sargento
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    ABSTRACT: The novel distributed mobility management trend is a promising direction to cope with the increasing mobile data traffic and flatten network architectures. Most of the novel mobility approaches distribute the mobility anchors through the access level, as opposed to the centralized mobility anchoring model. Other recent approaches argue that mobility anchors closer to the content servers may be the solution to optimize the mobility performance. However, none of the mobility anchoring models is ideal for all scenarios, since it depends on the user, the session and the network. Hence, we propose an IP mobility approach driven by the context of the user, sessions and the network, where the mobility anchors for IP address allocation and for routing/forwarding are distributed through the network nodes, while the mobility context is managed by the mobile devices. Although each session is properly anchored in the establishment phase, the routing/forwarding is adapted over time, according to the user, the session and the network context: the proposed approach is able to signal different mobility anchors to optimize the routing path to new and ongoing sessions of the user. The outcome of the evaluation shows that the proposed approach overall reduces the data cost, the data delay, the tunneled packets and the tunnel length, when compared with other anchoring models.
    Computer Networks. 01/2014; 71:84–99.
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    N Chama, R Sofia, S Sargento
    NTMS 2014; 01/2014
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    ABSTRACT: The flexibility and self-* properties of Wireless Mesh Networks (WMNs) and the programmable management of network resources brought by the innovative network virtualization techniques, are a twofold force to enable personalized access over wireless environments. Therefore, we design a context-aware multi-virtual architecture for WMNs to deal with the requirements of mesh clients and their applications (context can be defined as a set of requirements such as cost, security, mobility, applications’ Quality-of-Service - QoS). In this approach, a WMN is split into several adaptable Virtual Networks (VNs), each one appropriate to specific levels of context. This approach requires the proper configuration of VNs’ topologies and resources, and the definition of local and global (distributed) mechanisms to reconfigure VNs that best fit users’ requirements. In this paper, we propose an analytical model to evaluate the impact of network virtualization and the complexity of the discovery and extension mechanisms defined for VN reconfiguration. Through a delay-based approach, we show the effectiveness of the architecture to deal with different communication requirements and with distinct scenarios for user connectivity establishment, even in the presence of user mobility or using a real WMN topology. The analytical model is compared against a simulation one, showing similar results.
    Ad Hoc Networks. 01/2014;
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    ABSTRACT: There is a new trend to consider Distributed Mobil-ity Management (DMM) for flat network architectures to cope with the increased distributed nature of the mobile networks. DMM improves the routing optimization and reduces the scala-bility issues when compared with the centralized mobility man-agement, through the traffic anchoring distribution at the Access Routers (ARs). However, the handover optimization, which also demands for fast and soft handovers to reduce/eliminate the handover latency and the respective packet loss, is not properly addressed in the DMM. Although current seamless handover approaches, already inte-grated in centralized mobility schemes, could also be adapted to the DMM schemes, they introduce new entities/functionalities, messages and buffering/bicasting mechanisms to reduce the handover latency or the packet loss. In this paper, the seamless IP handover is addressed from a novel make-without-break perspective, which is able to maintain two logical connections in the same physical interface with two Access Points (APs) from distinct IP networks. The outcome of the evaluation shows that make-without-break with a DMM scheme is able to reduce or even eliminate the handover latency and the packet loss from link disconnection, providing seamless IP session continuity in mobile environments. I. INTRODUCTION As the number of mobile users increases and the mobile data traffic explodes [1], with users being both generators and consumers of data, centralized architectures for mobility management may undergo scalability and performance issues (e.g. network bottlenecks, single point of failures and attacks, centralized and non-optimal routing). Hence, there is a paradigm shift in the network architectures with the introduction of flat models to deal with the evolution of users' traffic behavior. Moreover, mobility management architectures and protocols need to be adapted for such evolu-tion. Several efforts from both industry and academia are being performed on specifying DMM approaches [2] [3]. The main focus of these DMM approaches is to optimize the routing and improve scalability, leaving the seamless handover subject out of the scope of these schemes. The DMM approaches already enforce the maintenance of the IPv6 addresses to ensure session continuity, but they suffer from temporarily link disruptions when the user roams among IP networks. The seamless handover remains a relevant requirement, spe-cially with the increase of mobile scenarios with demanding multimedia content. In these scenarios, a user might cross several IP networks in a short time, while it desires to maintain
    IEEE Globecom 2013 Workshop - Management of Emerging Networks and Services.; 12/2013
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    ABSTRACT: We present a real-world testbed for research and development in vehicular networking that has been deployed successfully in the sea port of Leix\~oes in Portugal. The testbed allows for cloud-based code deployment, remote network control and distributed data collection from moving container trucks, cranes, tow boats, patrol vessels and roadside units, thereby enabling a wide range of experiments and performance analyses. After describing the testbed architecture and its various modes of operation, we give concrete examples of its use and offer insights on how to build effective testbeds for wireless networking with moving vehicles.
    IEEE Communications Magazine 12/2013; 52(9). · 3.66 Impact Factor
  • Globecom Workshops (GC Wkshps), 2013 IEEE; 12/2013
  • Global Communications Conference (GLOBECOM), 2013 IEEE; 12/2013
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    Paulo Mendes, waldir Moreira, Susana Sargento
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    ABSTRACT: Nowadays, routing proposals must deal with a panoply of heterogeneous devices, intermittent connectivity, and the users' constant need for communication, even in rather challenging networking scenarios. Thus, we propose a Social-aware Content-based Opportunistic Routing Protocol, SCORP, that considers the users' social interaction and their interests to improve data delivery in urban, dense scenarios. Through simulations, using synthetic mobility and human traces scenarios, we compare the performance of our solution against other two social-aware solutions, dLife and Bubble Rap, and the social-oblivious Spray and Wait, in order to show that the combination of social awareness and content knowledge can be bene�cial when disseminating data in challenging networks.
    in Proc. of Adhocnets, Barcelona, Spain; 10/2013
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    Waldir Moreira, Paulo Mendes, Susana Sargento
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    ABSTRACT: Dynamic aggregate bandwidth over-reservation is a scalable approach for Quality of Service (QoS) control mechanisms, since surplus of reservation allows for admitting several flows without signaling the network. Our recent work, the Advanced Class-based resource Over-Reservation (ACOR), shows interesting results by significantly reducing QoS control signaling overhead with increased resource utilization without incurring QoS violation when compared with related solutions. However, ACOR is too sensitive to the number of paths that share bottleneck links. It also resorts to per-flow signaling when links are congested. In view of this, we propose the Extended-ACOR (E-ACOR), which extends ACOR architecture with a new approach, aiming at reducing the performance dependency on paths' density on bottleneck interfaces. Moreover, it is able to efficiently track congestion information throughout a network to prevent unnecessary signaling during network congestion time. Thus, E-ACOR is expected to scale large networks with reduced signaling. Analytical and simulation results demonstrate the efficiency and cost-effectiveness of E-ACOR over ACOR; by significantly reducing signaling frequency especially during critical periods of congestion.
    IEEE International Conference on Communications 2013: IEEE ICC’13 - 3rd IEEE International Workshop on Smart Communication Protocols and Algorithms (SCPA 2013); 06/2013
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    ABSTRACT: The Internet constitutes the most vital scientific, technical, economic and societal set of infrastructures in existence and in operation today, serving 2.5 billion users. Continuing its development will secure future innovation and prosperity and underpin the sustainable economic growth needed in the future. Future Internet infrastructure research is therefore a must. The Future Internet Assembly (FIA) is a successful conference that brings together participants of over 150 research projects from several distinct yet interrelated areas in the European Union Framework Programme 7 (FP7).
    edited by Alex Galis and Anastasius Gavras and Federico Álvarez and Alessandro Bassi and Michele Bezzi and Laurent Ciavaglia and Frances Cleary and Petros Daras and Hermann De Meer and Panagiotis Demestichas and John Domingue and Theo G. Kanter and Stamatis Karnouskos and Srdjan Krvco and Laurent Lefevre and Jasper Lentjes and Man-Sze Li and Paul Malone and Antonio Manzalini and Volkmar Lotz and Henning Müller and Karsten Oberle and Noel E. O'Connor and Nick Papanikolaou and Dana Petcu and Rahim Rahmani and Danny Raz and Gaël Richards and Elio Salvadori and Susana Sargento and Hans Schaffers and Joan Serrat and Burkhard Stiller and Antonio F. Skarmeta and Kurt Tutschku and Theodore Zahariadis, 05/2013; Springer.
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    ABSTRACT: Dynamic bandwidth aggregate over-provisioning has been proposed to provide differentiated services with scalable Quality of Service (QoS) control. Previous research showed that efficient over-reservation control allows minimizing QoS control overhead with reduced waste of bandwidth and blocking probability. However, existing over-reservation centric solutions are still inefficient in the face of network dynamics, as they are not able to accommodate the dynamic service demands, thus failing to optimize the bandwidth usage. This paper proposes a new Advanced Class-based resource Over-Reservation (ACOR) solution for multicast sessions, which seeks increased network resources utilization while minimizing QoS control overhead. More specifically, ACOR is able to dynamically update the share of bandwidth between different classes of service, providing improved results with less complexity than current solutions. Our analytical and simulation results prove the cost-effective and scalable QoS control capabilities of ACOR in decentralized networks with multiple distributed ingress routers coordinating the QoS control.
    Computer Networks 04/2013; 57(2013):2075–2092. · 1.23 Impact Factor
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    ABSTRACT: Developing routing protocols for Vehicular Ad Hoc Networks (VANETs) is a significant challenge in these large, self- organized and distributed networks. We address this challenge by studying VANETs from a network science perspective to develop solutions that act locally but influence the network performance globally. More specifically, we look at snapshots from highway and urban VANETs of different sizes and vehicle densities, and study parameters such as the node degree distribution, the clustering coefficient and the average shortest path length, in order to better understand the networks' structure and compare it to structures commonly found in large real world networks such as small-world and scale-free networks. We then show how to use this information to improve existing VANET protocols. As an illustrative example, it is shown that, by adding new mechanisms that make use of this information, the overhead of the urban vehicular broadcasting (UV-CAST) protocol can be reduced substantially with no significant performance degradation.
  • T. Condeixa, S. Sargento
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    ABSTRACT: The increase of mobile traffic and the new role of the users as active elements in the network require a new approach for network architectures to adopt more flatten models. However, current mobile IP approaches were developed assuming static and centralized models: a single entity is responsible for the mobile traffic, the signaling and the context information of a large amount of Mobile Nodes. We propose a new host-based mobility approach denoted as Dynamic Mobile IP Anchoring (DMIPA) that distributes mobility management functionalities among Access Routers (ARs) and MNs, and provides dynamic sessions anchoring. DMIPA is envisioned to support these novel flat network architectures, and it is able to provide global IP mobility to the users, independently of the access network, technology and Internet provider. Through an analytical model, we compare DMIPA against Mobile IPv6, which is the standard host-based mobility model for IPv6 networks. The evaluation shows that DMIPA achieves better results regarding the handover delay and the data delivery cost, while the signaling cost can also be reduced in networks with low loss probability.
    Communications (ICC), 2013 IEEE International Conference on; 01/2013
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    N. Chama, R.C. Sofia, S. Sargento
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    ABSTRACT: This paper proposes and validates a new category of routing metrics which assist current multihop routing protocols in becoming more sensitive to node movement and, as a consequence, increase the protocol robustness. The proposed metrics are based on the notion of time-based link stability. The paper discusses the metrics formulation and provides their performance evaluation based on discrete event simulations.
    Advanced Information Networking and Applications Workshops (WAINA), 2013 27th International Conference on; 01/2013
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    ABSTRACT: Node cooperation is a key part of distributed management process, requiring periodic exchange of management information between the nodes. To increase scalability of the network information exchange, network nodes need to cooperate through an efficient set of rules, policies and criteria, to minimize the time and amount of control messages flowing in the network. We propose a solution for optimized decision of the network nodes to perform discovery and exchange of network information, through a Neighbors Eyesight Direction (NED) function and cooperation between the nodes. The proposed solution is embedded into a protocol, named HIde and SeeK Directional Decision (HISK2D), which is compared against current protocols for network discovery and awareness. We show, by means of experimentation, that our HISK2D is more efficient than the base approaches analyzed, in terms of control overhead to discover the nodes, convergence time and exchange of network information according to the acquired knowledge of the network.
    Integrated Network Management (IM 2013), 2013 IFIP/IEEE International Symposium on; 01/2013
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    M Melo, J Carapinha, S Sargento
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    ABSTRACT: Network Virtualization has gained prominent attention in the recent years, not only from the academia, but also from the Industry, mainly due to its numerous features such as flexibility, programmability, elasticity and dynamicity. One of the key assets with Network Virtualization is the ability to move components of the virtual network, or even the entire virtual network, from one or several physical hosts to others in real-time and seamlessly to the end-users. This paper addresses virtual resource mobility from a new perspective: it proposes Virtual Network (VN) Clone migration, which requires no assumptions regarding the protocols running inside the virtual networks or its own architectures, leaving space for different types of protocols and architectures to be implemented, tested and used in production scenarios. The results are very promising: the VN Clone migration achieves no VN downtimes and it takes just a few seconds to be fully performed. This makes the VN Clone approach suitable both for non-real time traffic and voice over IP communications.
    Integrated Network Management (IM 2013), 2013 IFIP/IEEE International Symposium on; 01/2013

Publication Stats

409 Citations
37.21 Total Impact Points


  • 1999–2014
    • University of Aveiro
      • Telecommunications Institute (IT)
      Aveiro, Aveiro, Portugal
  • 2007–2013
    • Institute of Telecommunications
      Lisboa, Lisbon, Portugal
    • University Carlos III de Madrid
      Getafe, Madrid, Spain
    • Sapienza University of Rome
      Roma, Latium, Italy
  • 2010–2011
    • Instituto Politécnico de Viana do Castelo
      Vianna do Castello, Viana do Castelo, Portugal
    • Complutense University of Madrid
      • Department of Software Engineering and Artificial Intelligence
      Madrid, Madrid, Spain
  • 2009
    • Universidade Federal de Goiás
      Goianá, Goiás, Brazil
    • Aalborg University
      Ålborg, North Denmark, Denmark
  • 2008
    • University of Cape Town
      Kaapstad, Western Cape, South Africa
  • 2005–2007
    • University of Porto
      • Laboratório de Inteligência Artificial e Ciência de Computadores (LIAAC)
      Oporto, Porto, Portugal
    • Alexandria University
      Al Iskandarīyah, Alexandria, Egypt