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Latin America Transactions, IEEE (Revista IEEE America Latina)

Issue 4 • Date Aug. 2010

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Displaying Results 1 - 20 of 20
  • Freely Available from IEEE
  • A Taxonomy for Locality Algorithms on Peer-to-Peer Networks

    Page(s): 323 - 331
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (647 KB)  

    The continuous growth of peer-to-peer networks has made them responsible for a considerable portion of the current Internet traffic. For this reason, improvements in P2P network resources usage are of central importance. One effective approach for addressing this issue is the deployment of locality algorithms, which allow the system to optimize the peers selection policy for different network situations and, thus, maximize performance. To date, several locality algorithms have been proposed for use in P2P networks. However, they usually adopt heterogeneous criteria for measuring the proximity between peers, which hinders a coherent comparison between the different solutions. In this paper, we develop a thoroughly review of popular locality algorithms, based on three main characteristics: the adopted network architecture, distance metric, and resulting peer selection algorithm. As result of this study, we propose a novel and generic taxonomy for locality algorithms in peer-to-peer networks, aiming to enable a better and more coherent evaluation of any individual locality algorithm. View full abstract»

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  • Secrecy Rate of Adaptive Modulation Techniques in Flat-Fading Channels

    Page(s): 332 - 339
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (807 KB)  

    In this paper, we analyze the Secrecy Rate of Adaptive Modulation transmission systems over flat-fading time-varying channels. The scenario considered consists of a transmitter communicating with a legitimate receiver in the presence of an eavesdropper. Expressions for the Mutual Information (MI) between the transmitter and the legitimate receiver and between the transmitter and the eavesdropper are presented. In addition, the Secrecy Rate is evaluated as the difference between the legitimate receiver MI and the eavesdropper MI. Unlike others studies that are based on a water-filling approach, here the MI expressions are obtained from the classical MI definition considering some assumptions usually adopted in the wireless communication systems context, and they are expressed in terms of important parameters of an adaptive modulation scheme. View full abstract»

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  • Using the Euclidean Distance as a Mechanism Distance between Signatures to the Detect Spam and Phishing Scams

    Page(s): 340 - 348
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1103 KB)  

    Spams and Phishing Scams are some of the abuse forms on the Internet that have grown up now. These abuses influence in user's routine of electronic mail and in the infrastructure of Internet communication. So, this paper proposes a new model messages filter based in Euclidian distance, beyond show the containment's methodologies currently more used. A new model messages filter, based in frequency's distribution of character present in your content and in signature generation is described. An architecture to combat Phishing Scam and spam is proposed in order to contribute to the containment of attempted fraud by mail. View full abstract»

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  • A Content-Oriented Web Cache Policy under P2P Video Distribution Systems

    Page(s): 349 - 357
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (824 KB)  

    The increasing popularity of network-based multimedia applications poses many challenges for multimedia content providers to supply efficient and scalable multimedia services. Peer-to-Peer (P2P) networks have been shown to be a promising approach to provide large scale video services over Internet since they increase the scalability and robustness. In this paper, we propose and analyze an object management policy approach for video web cache in a P2P context, taking advantage of object's meta-data, e.g video popularity, and object's encoding techniques, e.g Scalable Video Coding (SVC). We exploit the peer-to-peer based approach to carry out the replication then eviction of videos in different web cache according to their popularity. Since videos are typically large and require high communication bandwidth for delivery, many peers may be unwilling to cache them in whole to serve others. Accordingly, we address this problem by proposing a new web caching approach for videos encoded in layers. Furthermore, in the proposed approach cooperation amongst the web caches may make it possible to replicate the video on several caches when this one is very popular. Afterward, we can gradually eliminate the replicas from the caches as the video popularity decrease. In addition, we structure our peer-to- peer network using interest-based communities. This network is made by ordinary nodes and super-nodes, and with peers clustered into communities. These communities are built around subjects (e.g., Science and Sports). The performance measurements we carried out allowed analyzing the traffic volume that flows from the community super-node to the first server into our content delivery network. The main goal is to measure how much our content-oriented management policy can help to decrease the demands put over the community output link. These measurements showed that the proposed approach (i) reduces the traffic volume, (ii) maximizes the overall bit rate of community demands, an- (iii) optimizes the use of network resources. View full abstract»

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  • A Danger Theory Inspired Survivability Framework for the Next Generation Mobile Network

    Page(s): 358 - 369
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (687 KB)  

    The demand for anytime, anywhere, anyhow communications in next generation mobile networks (NGMN) necessitates a paradigm shift from independent network services into a more harmonized system. To accomplish this vision, the NGMN is envisaged to interconnect the existing and emerging access networks via a common IP based platform. Unfortunately, such architecture exposes the interworked infrastructure to malicious security threats arising from within individual networks and heightens the possibility of their migration across network boundaries. Owing to their autonomous characteristics, the proprietary security solutions designed for legacy networks cannot be extended to address such sophisticated security threats affecting NGMN functionality. This paper explores the possibility of using a biologically inspired approach for detecting two dominant security threats; namely, denial-of-service (DoS) and distributed DoS (DDoS) in the NGMN. Motivated by the phenomenal capabilities of the human immune system (HIS) in defending the human body against dangerous foreign agents, we propose an HIS inspired survivability framework to address these security threats in the NGMN. The proposed framework incorporates two key components; that is the attack detection framework and the security control framework. While the former is used to identify malicious attacks on the network, the latter offers a competent technique for isolating and recovering from such attacks. Performance evaluation indicates that the proposed survivability framework is efficient in detecting attacks and quarantining the under attacked network segments, thereby increasing the survivability of the NGMN. View full abstract»

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  • An Adaptive Multi-channel Approach for Real-Time Multimedia Wireless Sensor Networks

    Page(s): 370 - 376
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    Many wireless sensor network applications could be substantially improved if they enhance the description of the events transmitting scalar sensor data along with audio and video. For example, an intrusion detection system would reduce the number of false positives if, in addition to the alarm, the system would also transmitted a picture or video of the intruder. The problem is how to overcome the known limitations of current wireless sensor networks to support multimedia applications in terms of throughput, delay and jitter while being energy efficient. This paper presents LEMR-multichannel, an extension of LEMR for real-time applications over wireless sensor networks to address these issues. LEMR-multichannel takes advantage of the delay, jitter and energy-efficiency of LEMR, and includes an energyefficient new dynamic duty cycle multi-channel medium access mechanism that uses the different channels available in the single transceiver device to enhance the throughput capability of the network. Simulation experiments demonstrate the superiority of LEMR-multichannel in terms of these performance metrics when compared with well-known protocols, such as LEMR, S-MAC, TMAC and SCP-MAC. View full abstract»

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  • Analysis of Performance Degradation in Radio-Over-Fiber Systems Based on IEEE 802.16 Protocol

    Page(s): 377 - 384
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    In order to the increasing demand for wireless connectivity and large coverage, Radio-over-Fiber (RoF) infrastructure has been suggested as a cost-effective solution for the provisioning of bandwidth in small cell size. In this article, we present an analysis of the use of RoF technology in IEEE 802.16 networks. The propagation delay introduced by the fiber length impacts the tuning of MAC and physical layers parameters. For an effective tuning, we present a comprehensive study of the performance degradation of WiMAX networks employing RoF infrastructure. Results were obtained using analytical models and simulations. Results indicate the viability of RoF scenarios with degradation bounded to 20% at physical layer when using fiber links with maximum length of 115 Km and degradation bounded to 20% at application layer for fiber length up to 80 km. View full abstract»

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  • Comparative Analysis of AODV Route Recovery Mechanisms in Wireless Ad Hoc Networks

    Page(s): 385 - 393
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    This work investigates the behavior of the Ad Hoc On-Demand Distance Vector (AODV) routing protocol in situations of link failures due to the mobility of nodes in wireless ad hoc networks. The AODV performance is compared when the failure repair happens locally from the node before the link break to the case where the repair is performed from the source node for four metrics: throughput (as packet delivery fraction), overhead, average packet delivery delay and average hop count, the last being only used to validate throughput and delay analyses. From the scenarios studied, it was observed that the throughput and delay for source repair have better performance, while overhead was better for local repair in sparse networks. View full abstract»

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  • Digital Cities and Open MANs: A New Communications Paradigm

    Page(s): 394 - 402
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1049 KB)  

    Digital cities can be defined as a highly interactive digital communication environment built to mimic the behavior of real cities. Open access metropolitan area networks (Open MANs) are communication networks built to allow universal access of city's population to a single digital multimedia communication network. The goal of this paper is to discuss the impact in the community when delivering digital cities solutions upon the universal access scenario of the Open MANs. We also present results obtained of deployment of such solutions in some Brazilian cities and the perspectives for this project in Brasil in the coming years. View full abstract»

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  • Exact Statistics of a Complex Markov Chain through State Reduction: A Satellite On-board Switching Example

    Page(s): 403 - 409
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (557 KB)  

    Satellite on-board switching offers the possibility of covering a wide area with increased total capacity. In order to show a mechanism for reducing a highly dimensional complex Markov chain, in this paper we use a terrestrial packet grouping approach to minimize the on-board switching operations. By carefully redirecting some transitions to different states, we can evaluate exact statistics of the original complex Markov chain from the analysis of a much simpler reduced Markov chain. Although we use a communication example close to our research interest, the method can have a much wider area of application. View full abstract»

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  • Guaranteeing Service Availability in SLAs; a Study of the Risk Associated with Contract Period and Failure Process

    Page(s): 410 - 416
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (543 KB)  

    Service Level Agreements (SLAs) are a common means to define the obligations of network/service providers and users in business relationships. The terms that define the guaranteed availability for a given period are an important element of these contracts. The appropriate selection values is difficult due to the large number of variables involved, the complexities of the network and service provision and the computational challenge posed by the transient solution, as opposed to a steady state, that is needed. A common policy taken to solve it, is using the steady state availability as a reference. Nevertheless this simplification may put on risk the contract fulfillment as stochastic variation of the measured availability is significant over a typical contract period. This paper analyzes the relevance that the interval availability analysis has on SLAs, and provides suggestions to the network providers on the selection of adequate availability guarantees. The interval availability of unprotected and shared protected connections is studied under exponential and Weibull failure and repair distributions. It is observed that for a single path scenario, a small reduction of the guaranteed availability below the steady state value improve the probability to meet the requirements considerably. The same is the case for connections with shared backup protection. However performing this analysis in the transient domain is quite demanding. Hence, to simplify it, it is proposed to obtain the steady state results and introduce a safeguard factor to control that the availability guarantee is meet. For the Weibull distributed times between failures, where the shape factor is less than one, as observed in operational networks, the the probability of meeting a guaranteed availability over a finite contract period, decrease more radically than for the commonly assumed Poisson failure process. This increases the importance of making a transient analysis. View full abstract»

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  • Hybrid ARQ with Partial Retransmissions and LDPC codes and its Impact on TCP

    Page(s): 417 - 424
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (858 KB)  

    The design of a novel HARQ scheme using LDPC codes, partial retransmissions, and diversity combining is presented. The theoretical throughput of the proposed scheme is estimated by means of EXIT charts. It is shown that the proposed method outperforms the classical equal gain combining (EGC) method while requiring few more overall decoding iterations. The transmission control protocol (TCP) performance when the proposed method is used in the physical layer is also investigated. Simulation results show that the gains with respect to the classical EGC scheme can be as large as 3.5 dB. View full abstract»

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  • Milano Digital City: Planning the Municipal Wireless Network of Milano

    Page(s): 425 - 431
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1317 KB)  

    Planning municipal wireless access networks is a challenging task, since many optimization choices must be taken in large metropolitan areas while, in turn, the number of free variables is very large, on the order of several millions. The aim is to optimize the position of wireless access points, as well as their connection to the backbone network. This paper is focused on the "Milano Digital City" project, i.e. the municipal wireless access network of Milano. We formalized the problem of choosing appropriate access points' locations and connecting the wireless access network to the backbone network. We designed an optimization algorithm, based on a fast heuristic approach, and applied it to a real-world scenario: the 51-km2 city area of Milano (Italy). The proposed heuristic algorithm was extended to support mobility. Results show that the additional cost for supporting user mobility is limited to few percent. View full abstract»

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  • Optimization of Value-Network through Clusters Consolidation

    Page(s): 432 - 437
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (534 KB)  

    Many researchers view the value of the enterprise network through its utilization. If the network utilization is low, then its economical value and benefit are diminished. Also, the rapidly changes in network technologies, customers' demands and economical factors increase the opportunity for viewing the network as a dynamic infrastructure, so that its values can be adapted accordingly. Based on these views periodical changes in networks necessitate in the reshaping the clusters (sub-networks). Here we have proposed a number of redesign operations on the customers' clusters, which are sub-networks in the valuenetwork, with the aware to minimize the extra-traffic in the backbone network, and maximize the intra-traffic within the clusters by considering customers' movement and clusters consolidation. We have utilized Simulated Annealing algorithm to search for the best solution to the clusters consolidation problem. Our simulation results show a better trade-off in minimizing the extra-traffic through clusters consolidation by 11.65% of the total backbone traffic and 40% in the number of clusters. View full abstract»

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  • Optimizing the Next Generation Optical Access

    Page(s): 438 - 443
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (527 KB)  

    Several issues in the design and optimization of the next generation optical access network (NG-OAN) are presented. The noise, the distortion and the fiber optic nonlinearities are considered to optimize the video distribution link in a passive optical network (PON). A discussion of the effect of the optical amplification in the performance of the standardized PON is presented comparing the performance of the EDFA (Erbium Doped Fiber Amplifier) and the distributed Raman amplification. View full abstract»

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  • Planning a Mobile DVB-T Network for Colombia

    Page(s): 444 - 453
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1378 KB)  

    The TV evolution and the need of better quality and new services for the users have accelerated the migration from analogue to digital TV, forcing a renovation process in all fields of this communication system. Most of the DVB-T networks deployed in the world have been designed for fixed rooftop reception. The countries where it has not yet deployed the DTT network can introduce technological advances to planning DVB-T network for fixed and mobile reception and use the MPEG-4 video compression to provide high definition TV. This paper describes the technical solutions proposed in order to provide mobile DVB-T services to public transportation systems: antenna diversity, hierarchical modulation, and Application Layer Forward Error Correction (AL-FEC). These solutions compensate the negative effects caused by the mobility of the receivers, such as fading in the signal due to Doppler shift and the poor coverage at ground level. Furthermore, this paper describes the methodology carried out to evaluate the improvements in mobile reception of the DVB-T network in Colombia by using these techniques. View full abstract»

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  • Providing QoE and QoS in Wireless Mesh Networks Through Dynamic Choice of Routing Metrics

    Page(s): 454 - 462
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1334 KB)  

    The increasing demand of multimedia applications requires a new behavior of routing protocols for wireless mesh networks (WMNs). It is necessary to support the minimum requirements for quality of service (QoS), but WMNs also need to support the minimum requirements for quality of experience (QoE). This paper is an additional analysis of the proposed routing protocol OLSR-DC, from a perspective of the network (QoS) and from a perspective of the user (QoE). The simulations were performed to demonstrate the performance of OLSR-DC compared against original OLSR and its ETX and MD versions considering different performance evaluation metrics and the quality of the video received by the user. View full abstract»

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  • Study of the Channel of Communication with Plasma Using the Corona Effect for PLT

    Page(s): 463 - 468
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (706 KB)  

    This work describes the results obtained of the analysis of the pattern of stationary wave of a dielectric circular waveguide with plasma inner to low pressure to study the channel of communication in the plasma of the crown effect in the lines of transmission of electric power. By means of the equation of stationary wave, there are found the constants of attenuation and of phase of the plasma that fills the dielectric waveguide. Finally there are discussed the possible test in practical installation and the applications of this method. View full abstract»

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  • Topology Maintenance: Extending the Lifetime of Wireless Sensor Networks

    Page(s): 469 - 475
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    Topology Maintenance is the part of Topology Control dedicated to the periodical restoration of the network topology, in order to guarantee characteristics like connectivity and coverage. This article presents one of the first efforts to formalize this concept by presenting a taxonomy for different strategies to perform topology maintenance in wireless sensor networks, including static, dynamic and hybrid techniques, with global and local scope, and using different triggering criteria. In addition, a comparison is included to evaluate, in sparse and dense networks, the performance of global static, dynamic and hybrid techniques, with triggering criteria based on time and energy, and working jointly with the two well-known topology construction protocols A3 and CDS-Rule-K. The results show that the dynamic techniques always produce benefits in terms of extending the network lifetime, while static and hybrid techniques produce mixed results (worst and best), depending mainly on the nature of the construction protocols used. View full abstract»

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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

Editor-in-Chief
José Antonio Jardini (Brasil)
IEEE Fellow Member