Carlos Renato Lisboa Francês

Federal University of Pará, Pará, Pará, Brazil

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Publications (105)20.48 Total impact

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    ABSTRACT: Optical cloud networks allow for the integrated management of both optical and IT resources. In this paradigm, cloud services can be provisioned in an anycast fashion; i.e., only the source node asking for a service is specified, while it is up to the cloud control/management system to select the most suitable destination data center (DC) node. During the cloud service provisioning process, resiliency is crucial in order to guarantee continuous network operations also in the presence of failures. On the one hand, a survivability strategy needs to be able to meet the availability requirements of each specific cloud service, while on the other hand it must be efficient in using backup resources. This paper proposes a restoration-based survivability strategy, which combines the benefits of both cloud service relocation and service differentiation concepts. The former is used to enhance the restorability performance (i.e., the percentage of successfully restored cloud services) offered by restoration, while the latter ensures that critical services are given the proper consideration while backup resources are assigned. The paper proposes both an integer linear programming (ILP) formulation, which guarantees optimal results, and a heuristic, which trades the optimality of the solution achieved by the ILP for faster processing times. Simulation results show that the average service availability and restorability performance obtained by both the ILP and the heuristic are very close to that achievable using a protection-based strategy, but with the inherent benefit, in terms of efficient use of resources, offered by a restoration-based approach.
    Full-text · Article · Feb 2016 · Journal of Optical Communications and Networking
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    ABSTRACT: The published literature reveals several arguments concerning the strategic importance of information and communication technology (ICT) interventions for developing countries where the digital divide is a challenge. Large-scale ICT interventions can be an option for countries whose regions, both urban and rural, present a high number of digitally excluded people. Our goal was to monitor and identify problems in interventions aimed at certification for a large number of participants in different geographical regions. Our case study is the training at the Telecentros.BR, a program created in Brazil to install telecenters and certify individuals to use ICT resources. We propose an approach that applies social network analysis and mining techniques to data collected from Telecentros.BR dataset and from the socioeconomics and telecommunications infrastructure indicators of the participants' municipalities. We found that (i) the analysis of interactions in different time periods reflects the objectives of each phase of training, highlighting the increased density in the phase in which participants develop and disseminate their projects; (ii) analysis according to the roles of participants (i.e., tutors or community members) reveals that the interactions were influenced by the center (or region) to which the participant belongs (that is, a community contained mainly members of the same region and always with the presence of tutors, contradicting expectations of the training project, which aimed for intense collaboration of the participants, regardless of the geographic region); (iii) the social network of participants influences the success of the training: that is, given evidence that the degree of the community member is in the highest range, the probability of this individual concluding the training is 0.689; (iv) the North region presented the lowest probability of participant certification, whereas the Northeast, which served municipalities with similar characteristics, presented high probability of certification, associated with the highest degree in social networking platform.
    Preview · Article · Jan 2016 · PLoS ONE
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    ABSTRACT: Service relocation represents a promising strategy to provide flexible and resource efficient resiliency from link failures in the optical cloud environment. However, when a failure affects a node hosting a datacenter (DC), service relocation from the affected DC is not possible. One alternative to protect against DC failures relies on using design strategies that duplicate the IT (i.e., storage and processing) resources in a backup DC at the expense of increasing resource overbuild (i.e., cost) of the network. This work proposes a dimensioning strategy based on the shared-path shared-computing (SPSC) concept able to protect against any single link, server, or DC failure scenario with minimal resource overbuild for the network and IT infrastructures. SPSC is based on the intuition that only storage units need complete replication in backup DC, while processing units can be instantiated only after the occurrence of a failure, leaving the design strategy some leeway to minimize their number. As result, the proposed SPSC design shows a considerable reduction in the amount of backup resources when compared to the dedicated protection strategies.
    Full-text · Conference Paper · Jul 2015
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    ABSTRACT: This article describes the creation of a prototype and educational applications for children using the platform of the Brazilian's Digital TV System. The mains objective of these products is to determine the best way to provide content for children's learning through Digital TV, that is a significant problem since that kind of public thinks that television is only for entertainment. Resumo. Este artigo descreve a criação de um protótipo e aplicações educativas para crianças, utilizando como mecanismo de difusão a plataforma do Sistema Brasileiro de TV Digital. O objetivo principal dos produtos criados é verificar a melhor forma de disponibilizar o conteúdo para aprendizagem infantil por meio da TV Digital, sendo que este problema é considerável uma vez que esse tipo de público tem a televisão somente como um meio de entretenimento.
    Full-text · Conference Paper · Jan 2015
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    ABSTRACT: In Smart Grids, a variety of new applications are available to users of the electrical system (from consumers to the electric system operators and market operators). Some applications such as the SCADA systems, which control generators or substations, have consequences, for example, with a communication delay. The result of a failure to deliver a control message due to noncompliance of the time constraint can be catastrophic. On the other hand, applications such as smart metering of consumption have fewer restrictions. Since each type of application has different quality of service requirements (importance, delay, and amount of data to transmit) to transmit its messages, the policy to control and share the resources of the data communication network must consider them. In this paper Markov Decision Process Theory is employed to determine optimal policies to explore as much as possible the availability of throughput in order to transmit all kinds of messages, considering the quality of service requirements defined to each kind of message. First a non-preemptive model is formulated and after that a preemptive model is derived. Numerical results are used to compare FIFO, non-preemptive and preemptive policies.
    Full-text · Article · Dec 2014 · Journal of Microwaves, Optoelectronics and Electromagnetic Applications
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    ABSTRACT: The current trends on traffic and mobile users' growth is pushing the capacity of the current networks to the limit, which has led telecommunication operators to expand their investment in infrastructure. In this context, centralized RAN (C-RAN) comes with an innovative solution for the changes that will occur in the network. C-RAN shifts all the complex functionalities from the base stations (BS) to the central office (CO). A new segment called fronthaul connects the base band unit (BBU) with the remote antenna over a digital radio over fiber (DRoF) transmission based on the common public radio interface (CPRI). In this work we investigate, by means of simulation, the performance of DRoF in several contexts: single channel and in coexistence scenario. To meet this goal, we first investigate the key aspects of DRoF in an isolated transmission and next we proceed with a coexistence scenario based on the ITU-T G.989 standard (NG-PON2). The results show that the DRoF system is compatible with a NG-PON2 with respect to the wavelength plan and bandwidth requirements.
    No preview · Conference Paper · Sep 2014
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    ABSTRACT: This work presents two technologies for Centralized Radio Access Network Architecture (C-RAN) based on Digital Radio over Fiber (DRoF) respectively SCM (Subcarrier Multiplexing) and WDM (Wavelength Division Multiplexing). The simulation analysis is discussed by evaluating the impact of the digitized process on the system performance, complexity and cost. Results indicates that SCM-DRoF has a acceptable BER performance for fiber links up to 20 km and WDM-DRoF can reach up to 40 km. However, WDM-DRoF uses a greater number of components compared to SCM-DRoF and it can generates a higher cost as well. Both setup can be used applied to C-RAN architecture considering this aspects.
    Full-text · Conference Paper · Aug 2014
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    ABSTRACT: The use of voice and data communication via mobile devices has increased significantly in recent years. This expansion has been accompanied by some inherent difficulties, such as: steady expansion of system capacity and energy efficiency. In this context, is consolidating the concept of Green Networks, focuses on the attempt to reduce energy and CO² emissions. Thus, this paper proposes to implement a model of a validation policy based on the Markov decision process to optimize energy consumption and quality of service, by allocating users in macrocell and femtocell networks. This model was inserted into the NS-2 simulator, and combined an analytical solution with the characteristic flexibility of the Markov discrete-event simulation.
    No preview · Conference Paper · Jul 2014
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    ABSTRACT: In this paper, we propose a hybrid methodology based on Graph-Coloring and Genetic Algorithm (GA) to solve the Wavelength Assignment (WA) problem in optical networks, impaired by physical layer effects. Our proposal was developed for a static scenario where the physical topology and traffic matrix are known a priori. First, we used fixed shortest-path routing to attend demand requests over the physical topology and the graph-coloring algorithm to minimize the number of necessary wavelengths. Then, we applied the genetic algorithm to solve WA. The GA finds the wavelength activation order on the wavelengths grid with the aim of reducing the Cross-Phase Modulation (XPM) effect; the variance due to the XPM was used as a function of fitness to evaluate the feasibility of the selected WA solution. Its performance is compared with the First-Fit algorithm in two different scenarios, and has shown a reduction in blocking probability up to 37.14% when considered both XPM and residual dispersion effects and up to 71.42% when only considered XPM effect. Moreover, it was possible to reduce by 57.14% the number of wavelengths.
    Full-text · Article · Jun 2014 · Journal of Microwaves, Optoelectronics and Electromagnetic Applications
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    ABSTRACT: Evaluating and monitoring large-scale distance learning programs require different techniques, systems, and analysis methods. This work presents challenges in evaluating and monitoring digital inclusion training programs, considering the aspects inherent in large-scale distance training, and reports an approach based on network and distance learning. The paper has the following objectives: (i) apply algorithms to extract indicators from interaction networks, in a real scenario and consolidated training based on distance learning; (ii) apply algorithms to correlate interaction indicators with other indicators related to the use and participation in learning environments; and (iii) discuss the relevance of the obtained indicators to promote feedback with information critical to the success of a large-scale distance training program.
    No preview · Article · Apr 2014 · International Journal of Distance Education Technologies
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    ABSTRACT: This work presents challenges in evaluating and monitoring digital inclusion training programs, considering the aspects inherent in large-scale training, and report the main challenges in an approach based on network learning. For this, our goals are as follows: develop an architecture to provide all interface features with communication tools, data collection, automatic notification (alerts) of interest to those involved in training and proposal, and survey analyses; employ algorithms to measure the centrality, prestige, and density of interactions in a real case and consolidated training based on learning network; employ algorithms to correlate and measure, in probabilistic terms, the effects of participation in the interaction tools and the use of the resources and activities proposed; and improve a large-scale training program from the implementation of monitoring and tracking services offered in the architecture.
    No preview · Article · Sep 2013
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    ABSTRACT: The use of wireless local area networks, called WLANs, as well as the proliferation of the use of multimedia applications have grown rapidly in recent years. Some factors affect the quality of service (QoS) received by the user and interference is one of them. This work presents strategies for planning and performance evaluation through an empirical study of the QoS parameters of a voice over Internet Protocol (VoIP) application in an interference network, as well as the relevance in the design of wireless networks to determine the coverage area of an access point, taking into account several parameters such as power, jitter, packet loss, delay, and PMOS. Another strategy is based on a hybrid approach that considers measuring and Bayesian inference applied to wireless networks, taking into consideration QoS parameters. The models take into account a cross layer vision of networks, correlating aspects of the physical environment, on the signal propagation (power or distance) with aspects of VoIP applications (e.g., jitter and packet loss). Case studies were carried out for two indoor environments and two outdoor environments, one of them displaying main characteristics of the Amazon region (e.g., densely arboreous environments). This last test bed was carried out in a real system because the Government of the State of Pará has a digital inclusion program called NAVEGAPARÁ.
    Full-text · Article · Jun 2013 · Journal of Microwaves, Optoelectronics and Electromagnetic Applications
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    ABSTRACT: The Brazilian electrical utility companies must meet continuity indicators for energy supply, which are represented by the indices of average interruption duration and frequency, according to targets established by the Brazilian Regulatory Agency for Electrical Energy (ANEEL). In a nationwide base, ANEEL has defined 30 clusters, each one having specific targets for Customer Average Duration Interruption Index and Customer Average Frequency Interruption Index; still, very frequently the utility distribution companies are financially penalised for not meeting these indicator targets. This study proposes a decision support system based on machine learning techniques so that the utility distribution companies can emulate the characteristics and procedures used by the ANEEL, and help in obtaining more adequate customer groups to evaluate the duration and frequency indicators. The proposed system was applied in a case study of a distribution utility whose supply area is located in the Brazilian Amazonia. The methodology proved to be adequate for seeking better customer grouping configurations that could result in a decrease in goal violations as well as providing more consistent goals, considering the specific characteristics of each distribution utility. Although this methodology was applied to a Brazilian scenario it also can be applied to other distribution utilities worldwide.
    No preview · Article · Apr 2013 · IET Generation Transmission & Distribution
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    Lamartine Vilar De Souza · João C W A Costa · Carlos R L Francês
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    ABSTRACT: Presented in IEEE Globecom 2012.
    Full-text · Dataset · Mar 2013
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    ABSTRACT: The Web is providing greater freedom for users to create and obtain information in a more dynamic and appropriate way. One means of obtaining information on this platform, which complements or replaces other forms, is the use of conversation robots or Chatterbots. Several factors must be taken into account for the effective use of this technology; the first of which is the need to employ a team of professionals from various fields to build the knowledge base of the system and be provided with a wide range of responses, i.e. interactions. It is a multidisciplinary task to ensure that the use of this system can be targeted to children. In this context, this chapter carries out a study of the technology of Chatterbots and shows some of the changes that have been implemented for the effective use of this technology for children. It also highlights the need for a shift away from traditional methods of interaction so that an affective computing model can be implemented.
    No preview · Article · Jan 2013
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    ABSTRACT: The concept of femtocell aims to combine fixed-line broadband access with mobile telephony using low cost and power third and fourth generation base stations in the subscribers homes. Femtocells are self-configurable, however, can limit the quality of service (QoS) and reduce the efficiency of the network, since it uses old assignment standards, such as the power level of the signal. Thus, this paper presents a proposal for optimized allocation of users in a macro-femto co-channel network, in order to maximize the QoS of the applications and energy efficiency, toward the concept of green networks. A fuzzy inference system is implemented to define which network the mobile phone should connect; the model is flexible, allowing different analyzes, and adaptable to the specific characteristics of the telephone companies. Results showed that the model proposed can improve energy efficiency up to 25%, when compared to traditional QoS approaches.
    No preview · Conference Paper · Jan 2013
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    L.V. de Souza · J.C.W.A. Costa · C.R.L. Frances
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    ABSTRACT: This paper presents an integrated solution with associated technologies for enabling broadband access in rural areas. Wired and wireless technologies are used to allow broadband access in remote areas of Brazilian Amazon Forest (northern Brazil). This solution allows the increase of telecommunication services to citizens in these areas, and it also provides digital inclusion in regions with low availability infrastructure. Aspects of deployment, management and maintenance costs are also presented and discussed.
    Full-text · Conference Paper · Dec 2012
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    ABSTRACT: The femtocell concept aims to combine fixed-line broadband access with mobile telephony using the deployment of low-cost, low-power third and fourth generation base stations in the subscribers' homes. While the self-configuration of femtocells is a plus, it can limit the quality of service (QoS) for the users and reduce the efficiency of the network, based on outdated allocation parameters such as signal power level. To this end, this paper presents a proposal for optimized allocation of users on a co-channel macro-femto network, that enable self-configuration and public access, aiming to maximize the quality of service of applications and using more efficiently the available energy, seeking the concept of Green networking. Thus, when the user needs to connect to make a voice or a data call, the mobile phone has to decide which network to connect, using the information of number of connections, the QoS parameters (packet loss and throughput) and the signal power level of each network. For this purpose, the system is modeled as a Markov Decision Process, which is formulated to obtain an optimal policy that can be applied on the mobile phone. The policy created is flexible, allowing different analyzes, and adaptive to the specific characteristics defined by the telephone company. The results show that compared to traditional QoS approaches, the policy proposed here can improve energy efficiency by up to 10%.
    Full-text · Article · Dec 2012 · Journal of Microwaves, Optoelectronics and Electromagnetic Applications
  • A. Santana · M. Seruffo · C. Francês · N. Vijaykumar
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    ABSTRACT: Technologies used to link the end-user to a telecommunication infrastructure have been growing over time because of the consolidation of new access technologies. Moreover, the arrival of new tools for information dissemination, such as interactive digital TV, creates a bidirectional element, capable of connecting the end-user to telecommunications networks through access technologies such as worldwide interoperability for microwave access, 3G, asymmetric digital subscriber line and power line communication. This study presents a heuristic based on multicriteria analysis for selection of first mile access in the integrated services digital broadcasting terrestrial standard, ensuring quality of service, using a videoconferencing application as an example. The following analytical approaches, with multicriteria analysis, are presented towards decision making for televisions connected to more than one return channel: (a) fuzzy AHP for defining the criteria weights (delay, jitter, throughput, packet loss etc.); (b) technique for order preference by similarity to ideal solution (TOPSIS) method, for approximation, guided by measurements taken in real scenarios; (c) elimination and choice translating reality III method, used to ranking the alternatives and comparing with TOPSIS.
    No preview · Article · Nov 2012 · IET Communications
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    ABSTRACT: This work analyses the feasibility of use Femtocells networks to provide return channel on Digital TV. The results were compared with a similar simulation using Wimax networks. The same numbers of users was used to create two scenarios, the first using only WiMAX networks, and the second using femtocell network. The results show that femtocell networking is a promising solution for the return channel of Brazilian interactive digital TV, especially at Amazon Region where there are great distances and lacking communication networks.
    Full-text · Conference Paper · Sep 2012