Susana Sargento

University of Aveiro, Aveiro, Aveiro, Portugal

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Publications (229)56.52 Total impact

  • Nelson Capela, Susana Sargento
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    ABSTRACT: Over the years, we have witnessed a systematic evolution of heterogeneous networks. Although the capabilities of these networks are constantly being improved, the users’ requirements are increasingly stringent and difficult to fulfil. In this context, it becomes important to optimize the utilization of all available resources in order to obtain a better user experience and a better network utilization. This paper presents a new approach that combines multihoming and network coding to improve the allocation of network resources and the communication performance in heterogeneous technologies. We solve an optimal resource allocation problem, based on a genetic algorithm, that decides when the use of multihoming can bring advantages, which data should be transmitted on which interface and, simultaneously, which coding parameters should be used to encode that data. Then, considering different technologies (Wi-Fi and HSDPA as examples), we model the system performance to evaluate the multihoming and network coding improvements. The results obtained show the advantages of multihoming and the optimal configuration to maximize system performance, the network coding performance improvement in a multihoming environment, in terms of delay, throughput and packets loss probability, and the benefits provided through the multihoming and network coding combination.
    Computer Networks 12/2014; · 1.28 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 10/2014; 71:84–99. · 1.28 Impact Factor
  • Nuno Coutinho, Daniel Figueira, Susana Sargento
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    ABSTRACT: The increasing demand for group-based multimedia communications, personalization and seamless mobility imposes the development of novel approaches to overcome the heterogeneity and dynamics of future network environments. The study developed in this article addresses a context-aware multiparty content delivery framework, capable of providing autonomic control of personalized group-based services to users by a hierarchical strategy with the concept of Abstract Multiparty Trees (AMTs). A thorough study of the proposed concept is presented, aiming to assess the scalability and flexibility of our framework and associated procedures. An analytical study quantifies the amount of reconfigurations and resources saved in the network whenever context changes, showing how the control framework scales when the network size increases. The evaluation through simulation analyses the performance of the proposed solution, meeting the results of the analytical study and showing a good performance regarding the reconfiguration of the AMTs in terms of time and control overhead. Finally, a proof-of-concept demonstrator is also detailed, in order to prove the feasibility of the AMT concept and the good performance of its main control operations.
    Computer Communications 09/2014; · 1.35 Impact Factor
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    ABSTRACT: Nowadays, both military and civil emergency scenarios demand shared-situation awareness between the frontline elements, in order to minimize the number of casualties and maximize the effectiveness of the operations. This requires a communication system based on protocols that self-adapt to dynamic conditions and that are able to work under heterogeneous networks. The proposed Cognitive Routable Ad-hoc Network (CRAN) protocol allows efficient and distributed nformation sharing within the same hierarchy and between distinct hierarchical levels. This ensures real-time situation updates, improving operational reality awareness and more accurate decisions, improving the overall operation results.
    16th International Telecommunications Network Strategy and Planning Symposium (NETWORKS 2014), Funchal, MAdeira, Portugal; 09/2014
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    A.B. Reis, Susana Sargento, Filipe 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 07/2014; 63(6):2794-2806. · 2.64 Impact Factor
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    A B Reis, S Sargento, O K Tonguz
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    ABSTRACT: In sparse highway vehicular networks, the high probability for network disconnection at the initial stages of introducing the DSRC technology can be mitigated by the deployment of fixed infrastructure points known as Road Side Units (RSU). However, due to the cost associated with the deployment and maintenance of significant numbers of RSUs, it is highly unlikely that the majority of highways will be seeing RSU support in the near future. In this paper we study the impact of specific vehicular net-work parameters in the communication delays in infrastructure-less highway scenarios: first, the deceleration of vehicles, and consequently, a decrease in their separation from succeeding vehicles; and second, the transmission power of the IEEE 802.11p radio, which can be increased to achieve faster connectivity with the succeeding vehicle. Our results show that the connectivity of sparse vehicular networks can be improved substantially by varying these parameters.
    2014 IEEE International Conference on Communications (ICC), Sydney, NSW; 06/2014
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    ABSTRACT: The momentum around Software-defined Networking (SDN) is increasing. It has become clear that the network architecture needs to evolve to be able to provide current and next generation networking services, both from a performance and implementation point of view. However, most of the current SDN research has looked to specificities of SDN and few have looked from a full stack perspective. Although the former are essential, also the latter perspective needs to be taken into account. In this sense, our work proposes a complete and modular SDN framework targeted at connectivity services. This framework allows the creation and management of network connectivity services over an OpenFlow based network, with mechanisms of fault-management, as well as the optimal usage of the infrastructure. The performance results obtained from the SDN framework evaluation in a real environment show that the three different scenarios, service activation, link loss, and reaction to a new link, are dynamically supported with fast reaction to the network changes.
    ICC 2014 - 2014 IEEE International Conference on Communications; 06/2014
  • Joao Soares, Susana Sargento
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    ABSTRACT: Infrastructure-as-a-Service (IaaS), which is offered by cloud computing, has focused on providing computing and storage resources, considering network mostly as a required communication accessory and not as a resource itself. In other words, the ability to define network resources (e.g. routing/switching elements, bandwidth, delay) is still very limited. However, the need to have more robust solutions is becoming clearer. In this paper we argue that, in a near future, cloud infrastructure services will evolve and allow the definition of complete infrastructures, which we refer to as Virtual Infrastructures (VI), which comprise not only computing resources but also network resources. This paper specifically addresses the VI embedding problem through joint virtualization of computing and network resources. In order to address this problem, an Integer Linear Programming (ILP) formulation with two embedding strategies is proposed. Finally, the performance of the different strategies is carefully evaluated.
    2014 21st International Conference on Telecommunications (ICT); 05/2014
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    Namusale Chama, Rute Sofia, Susana Sargento
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    ABSTRACT: Node mobility affects routing in terms of robustness and efficiency, as it may lead to frequent link breaks that are not always automatically detected at a protocolar level. In user-centric environments, nodes are characterized by dynamic mobility behavior because they are devices carried or controlled by humans. We propose routing metrics aimed at making routing more robust through consideration of node spatial correlation for successor node. We have validated our metrics in Ad hoc On-Demand Distance Vector (AODV) routing protocol using Network Simulator 2. Results obtained show that our metrics increase multi-hop routing robustness in terms of path re-computation reduction.
    NTMS 2014; 03/2014
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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 02/2014; · 1.94 Impact Factor
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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 02/2014; 18(2):376-379. · 1.46 Impact Factor
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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). · 4.46 Impact Factor
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    ABSTRACT: Network Virtualization is claimed to be a key component of the Future Internet, providing the dynamic support of different networks with different paradigms and mechanisms in the same physical infrastructure. A major challenge in the dynamic provision of virtual networks is the efficient embedding of virtual resources into physical ones. Since this problem is known to be NP-hard, previous research focused on designing heuristic-based algorithms; most of them either do not consider a simultaneous embedding of virtual nodes and virtual links, or apply link-path formulation, leading to non-optimal solutions. This paper proposes an integer linear programming (ILP) formulation to solve the online virtual network embedding problem as a result of an objective function striving for the minimization of resource consumption and load balancing. To this end 3 different objective functions are proposed and evaluated. This approach applies multi-commodity flow constraint to accomplish a node-link formulation that optimizes the allocation of physical network resources. This proposal is evaluated against state of the art heuristics. The performance of the heuristics related to Virtual Network (VN) request acceptance ratio is, at least, 30% below the one of the Virtual Network Embedding Node-Link Formulation (VNE-NLF) method. From the three cost functions evaluated, the Weighted Shortest Distance Path (WSDP) is the one which embeds more VNs and also requires, on average, less physical resources per embedding.
    IEEE Transactions on Network and Service Management 12/2013; PP(99):1-13.
  • Globecom Workshops (GC Wkshps), 2013 IEEE; 12/2013
  • Global Communications Conference (GLOBECOM), 2013 IEEE; 12/2013
  • Nuno Coutinho, Susana Sargento, Rui Prior
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    ABSTRACT: In recent years there has been an increasing interest in multiparty multimedia services that, associated with the new trends in content consumption (e.g. mobility, heterogeneity, high-definition), raised novel challenges. This fact motivates the research towards new techniques that are capable of improving the user experience while simultaneously making a rational use of the network resources. Network Coding (NC) is one of those techniques. It has gained a notorious relevance due to its ability to optimize network throughput and resilience to packet losses. In this work we propose a context-driven framework for multiparty content delivery using NC to enhance the reliability of the services provided. We propose and evaluate two different approaches: a static one, where the level of redundancy remains constant, and a dynamic one, where the control framework autonomously adjusts the redundancy to the sensed quality of service, deriving coding parameters from network context information. We found that while the static scheme achieves better results in terms of recovered information, it comes at the cost of sometimes excessive redundant information. On the other hand, tuning NC with context parameters in the dynamic scheme saves more network resources with a small penalty in the recovered information.
    2013 IEEE Globecom Workshops (GC Wkshps); 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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    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 state-of-the-art patented solution. 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 (EACOR), 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. Also, E-ACOR is able to keep all the benefits of ACOR in terms of support for QoS differentiation, QoS violation avoidance and resource utilization efficiency. 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 while enabling service convergence with differentiation of the control.
    Recent Advances in Communications and Networking Technology (Recent Patents on Telecommunications). 10/2013; 2(2):113-126.

Publication Stats

458 Citations
56.52 Total Impact Points


  • 1999–2014
    • University of Aveiro
      • • Telecommunications Institute (IT)
      • • Division of Electronics and Telecommunications Engineering
      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
  • 2011
    • Instituto Politécnico de Viana do Castelo
      Vianna do Castello, Viana do Castelo, Portugal
  • 2010
    • Complutense University of Madrid
      • Departamento de Ingeniería de Software e Inteligencia Artificial - Lenguajes y Sistemas Informáticos
      Madrid, Madrid, Spain
  • 2009
    • Universidade Federal de Goiás
      Goianá, Goiás, Brazil
    • Aalborg University
      Ålborg, North Denmark, Denmark
  • 2005–2007
    • University of Porto
      • Laboratório de Inteligência Artificial e Ciência de Computadores (LIAAC)
      Oporto, Porto, Portugal
    • Alexandria University
      Al Iskandarīyah, Alexandria, Egypt