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Latin America Transactions, IEEE (Revista IEEE America Latina)

Issue 6 • Date Oct. 2007

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Displaying Results 1 - 15 of 15
  • VI Conference on Telematics Engineering

    Page(s): 385
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    Freely Available from IEEE
  • A Snort-based approach for the development and deployment of hybrid IDS

    Page(s): 386 - 392
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2412 KB)  

    Apart from the modeling techniques, the development and deployment of anomaly-based intrusion detection systems still faces two main problems. The first one is related to the acquisition and handling of real traffic to be used for training purposes. The second one concerns the better performance of signature-based IDS for known attacks. In this paper the authors propose the use of a modified version of Snort which results in a hybrid detector/classifier. This version can be used both during the training phase of the anomaly-based system and as a deployed hybrid detector and traffic sniffer. Furthermore, it can be adjusted to work just as signature-based, anomaly-based or both (hybrid) detector. On the other hand, this version can be used to directly sniff, classify and split the network traffic according to its malicious nature, which eases the problems related to the acquisition and handling of training traffic. View full abstract»

    Open Access
  • Adaptive Gateway Discovery in Mobile Ad Hoc Networks. A Low-overhead and Scalable Solution based on Proxies.

    Page(s): 393 - 400
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (586 KB)  

    In the last years, many authors have addressed the problem of interconnecting Mobile Ad Hoc Networks (MANET) to the Internet, via one or more attachment points called gateways. The protocol employed to discover available gateways and set up routes to the Internet should not incur in a big overhead, due to the scarce resources of ad hoc networks. However, previous proposals do not meet this requirement either when the number of traffic sources or available gateways increases. In this paper, we develop a gateway discovery algorithm which dynamically adapts its behavior depending on the number of active traffic sources which are in the MANET. In addition, the approach employs proxies (intermediate nodes which make use of available local information) to further reduce the control overhead. A mathematical model for this algorithm and the previous approaches is provided. By means of both an analytical and a simulation-based study, our proposed scheme is shown to greatly outperform the remaining solutions in terms of overhead reduction, while it is still able to provide a high packet delivery ratio. Besides, our proposal scales well regarding the number of sources and gateways. View full abstract»

    Open Access
  • Adaptive Learning Objects for t-learning

    Page(s): 401 - 408
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1297 KB)  

    IDTV (Interactive Digital TV) opens new learning opportunities for those social groups that would hardly have access to traditional forms of education. However, viewers are not usually active learners, for this reason, education through IDTV should be offered in an attractive way, so as they get engaged in the learning experience. For this to be possible, we need to introduce personalization in the t-learning field. To achieve this goal, we present, in this paper, a proposal of self-adaptive t-learning objects, which show a different behavior depending on user's characteristics. These objects are conformant to the ADL SCORM (Sharable Content Object Reference Model) standard for which we propose an extension in order to permit this type of learning objects. We expose as well an authoring tool to these objects, which hides the implementation details to the content creator. View full abstract»

    Open Access
  • Anegsys: An automated negotiation based recommender system for local e-marketplaces

    Page(s): 409 - 416
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1069 KB)  

    Local e-marketplaces are local online e-commerce platforms deployed by product and service providers and accessed by local customers via mobile devices. In this scenario, customers need to gather information about available offers from the different providers in the area, in order to select the most suitable for their needs and preferences. We present ANEGSYS, an agent-based recommender system for product acquisition which uses automatic bilateral negotiations to generate purchase pre-agreements among buyer and seller agents. This greatly enhances the search for solutions which maximize both buyer and seller utilities. View full abstract»

    Open Access
  • Congestion Detection in the European Internet

    Page(s): 417 - 424
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (775 KB)  

    In this paper we present a study about the utilization of one-way delay measurements to detect and characterize network congestion in the european Internet. The experiments have been made using the ETOMIC platform that allows one-way delay measurement with high precision timestamps. We have found a peculiar router behaviour in which the bottleneck is not the available bandwidth but it is the packet processing power of the router (backplane and CPU constraints). This router has been characterized with several network parameters. Some of them are the dependency of this limitation with the input data rate in packets per second, the size of burst packet losses measured in packets or time and the absence of specific scheduling algorithms in the router that could affect to larger flows. View full abstract»

    Open Access
  • Distributed Admission Control for Mobile Ad-Hoc Networks based on a Cross-layer Design

    Page(s): 425 - 432
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (794 KB)  

    Radio resource management and QoS provision in Mobile Ad hoc NETworks (MANETs) require the cooperation among different nodes and the design of distributed control mechanisms, imposed by the self-configuring and dynamic nature of these networks. In this context, in order to solve the tradeoff between QoS provision and efficient resource utilization, a distributed admission control is required. This paper presents an adaptive admission procedure based on a cross-layer QoS Routing supported by an efficient end-to-end available bandwidth estimation. The proposed scheme has been designed to perform a flexible parameters configuration that allows to adapt the system response to the observed grade of mobility in the environment. The performance evaluation has shown the capability of the proposal to guarantee a soft-QoS provision thanks to a flexible resource management adapted to different scenarios. View full abstract»

    Open Access
  • Effect of redials and automatic retrials in cellular networks

    Page(s): 433 - 440
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (653 KB)  

    In cellular networks, repeated attempts occur as result of user behavior but also as automatic retries of blocked handovers. Both phenomena play an important role in the system performance and therefore should not be ignored in its analysis. An exact Markovian model analysis of such systems has proven to be infeasible and resorting to approximate techniques is mandatory. Using an approximate methodology, a numerical evaluation of the model is carried out to investigate the impact on performance of the parameters related to the retry phenomena. As a result, some useful guidelines for setting up the automatic retries are provided. Finally, we also show how our model can be used to obtain a tight performance approximation in the case where reattempts have a deterministic nature. View full abstract»

    Open Access
  • Estimation of the Average Search Length of Random Walks in Power-Law Networks

    Page(s): 441 - 447
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (901 KB)  

    In this paper we introduce a model to study random walks in power-law networks with one-hop replication. Basically, this model gives a set of expressions that captures how the knowledge about the network evolves as the random walk traverses the network: how many nodes have been known, either because they or their neighbors have been visited by the random walk. With this, we obtain an expression that gives a good estimation of the average number of hops needed to find some random peer from any other random peer. We denote this metric the average search length, and we deem it can be very useful to evaluate random walk based resource location solutions in P2P networks. View full abstract»

    Open Access
  • MM-DSR: Multipath QoS routing for multiple multimedia sources over Ad Hoc mobile networks

    Page(s): 448 - 456
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1067 KB)  

    Nowadays, services over Mobile Ad hoc Networks (MANETs) are becoming more used, and multimedia services such as video-streaming applications are more demanded. Hence, it is necessary to provide end-to-end QoS over MANETs, although it poses a challenging problem due to the ephemeral structure of these networks. MM-DSR (Multipath Multimedia Dynamic Source Routing) is a multipath routing protocol DSR-based merged with a cross-layer algorithm which is able to provide QoS for multiple sources of video over IEEE 802.11b Ad Hoc networks. The weaknesses of the system with plain DSR and IEEE 802.11b have been analysed and work has been done in order to improve the throughput and the final user quality. The performance of video-streaming applications has been improved under high traffic load conditions over mobile Ad Hoc networks. View full abstract»

    Open Access
  • Multimedia Group synchronization based in standard protocols

    Page(s): 457 - 464
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1003 KB)  

    Most of actual multimedia tools use RTP/RTCP for inter-stream synchronization, but not for group synchronization. A new proposal of modification of RTCP packets to provide a sender-based method for synchronization of a group of receivers is described and evaluated both objectively and subjectively. The solution takes advantage of the feedback RR RTCP messages and the malleability of RTP/RTCP to provide the information required by the synchronization approach, defining a few new APP RTCP packets useful for synchronization purpose. This modification hardly increases the workload of the network and helps to avoid the asynchronies, between receivers (distributed) and between streams (locally), exceeding the limits, in accordance with the related literature. View full abstract»

    Open Access
  • On the study of location measurements in urban cellular networks

    Page(s): 465 - 470
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1862 KB)  

    This work presents a statistical field study of the availability of time sources used by location techniques in a true wireless network. Terrestrial (base stations) and satellite (GPS) sources were investigated in three different urban scenarios. The density function of a specific number of sources available for triangulation is presented along with other statistical data in order to assess coverage. Since the fusion of terrestrial and satellite sources to obtain the location in wireless networks has been proposed as a way of improving coverage, the joint density function and cross-correlation between the availability of both types of sources are also presented. This correlation depends on the scenario, leading to the conclusion that the improvement obtained through the fusion of sources depends on both the fusion type and the scenario. View full abstract»

    Open Access
  • On the unfairness in IEEE 802.11e networks: Desynchronization of its medium access mechanism

    Page(s): 471 - 478
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (174 KB)  

    Since the advent of the first IEEE 802.11 standard, several papers have proposed means of providing QoS to IEEE 802.11 networks and evaluate various traffic-prioritization mechanisms. Nevertheless, studies on the assignment of AIFS times defined in IEEE 802.11e reveal that the various priority levels work in a synchronized manner. The studies show that, under large loads of high-priority traffic, EDCA starves low-priority frames, which is undesirable. We argue that QoS traffic needs to be prioritized, but users sending best-effort frames should also obtain the expected service. High-priority traffic can also suffer performance degradation when using EDCA because of heavy loads of low-priority frames. Thus, we have proposed a mechanism based on desynchronizing the IEEE 802.11e working procedure. It prevents stations that belong to different priority classes from attempting simultaneous transmission, prioritizes independent collision groups and achieves better short-term and long-term channel access fairness. We have evaluated the proposal based on extensive analytical and simulation results. It prevents the strangulation of low-priority traffic, and, moreover, reduces the degradation of high-priority traffic with the increased presence of low-priority frames. View full abstract»

    Open Access
  • Performance Analysis of Distributed Web Information Retrieval Systems

    Page(s): 479 - 485
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (661 KB)  

    The importance and size of Web search engines is increasing daily. Information retrieval systems based on a single centralized index present several problems, which lead to the use of distributed information retrieval systems to effectively search for and locate the required information. In this study, we analyze two improvements over the brokers’ bottlenecks in a distributed information retrieval system. We demonstrate that reducing the partial results sets will improve the response time of a distributed system by 53%, with a negligible probability of changing the system’s precision and recall values. Finally, we present a simple hierarchical distributed broker model that will reduce the response times for a distributed system by 55%. View full abstract»

    Open Access
  • Secure Protocol for Fast EAP Authentication in Wireless Networks

    Page(s): 486 - 493
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (761 KB)  

    We study the problem of reducing the latency introduced by authentication and network access control processes required in heterogeneous wireless networks and based on the Extensible Authentication Protocol. We aim to reduce the time spent on providing access and smooth transition between different technologies which require to perform authentication in order to allow network access. We propose a secure protocol which reduces the number of roundtrips during authentication and verify its security properties with a formal tool. View full abstract»

    Open Access

Aims & Scope

IEEE Region 9 provides IEEE Latin America Transactions to enable the publication of non-published and technically excellent papers from Latin American engineers, in Spanish or Portuguese languages.

Full Aims & Scope

Meet Our Editors

José Antonio Jardini (Brasil)
IEEE Fellow Member