- Associate professor at the Federal University of Amazonas, Brazil.edit
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Opportunistic networks could become the solution to provide communication support in both cities where the cellular network could be overloaded, and in scenarios where a fixed infrastructure is not available, like in remote and developing... more
Opportunistic networks could become the solution to provide communication support in both cities where the cellular network could be overloaded, and in scenarios where a fixed infrastructure is not available, like in remote and developing regions. A critical issue that still requires a satisfactory solution is the design of an efficient data delivery solution. Social characteristics are recently being considered as a promising alternative. Most opportunistic network applications rely on the different mobile devices carried by users, and whose behavior affects the use of the device itself. This work presents the "Friendship and Selfishness Forwarding" (FSF) algorithm. FSF analyses two aspects to make message forwarding decisions when a contact opportunity arises: First, it classifies the friendship strength among a pair of nodes by using a machine learning algorithm to quantify the friendship strength among pairs of nodes in the network. Next, FSF assesses the relay node se...
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Recent works explore social characteristics of nodes to improve message delivery rate in Delay Tolerant Networks (DTN). This work uses machine learning techniques to create node groups organized by common interests. Messages are sent to... more
Recent works explore social characteristics of nodes to improve message delivery rate in Delay Tolerant Networks (DTN). This work uses machine learning techniques to create node groups organized by common interests. Messages are sent to target groups, and from there to the final destination. Simulation results using The ONE simulator show that the larger the group size the higher the message delivery rate, that reaches 100% in some cases. The paper also presents results related to the groups of interest such as message delivery rat, delivery delay and an average number of hops to deliver messages. The overall results indicate that group-based routing is a promising research filed.
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In environments with energy and processing constraints, such as sensor networks and embedded devices, sending raw information over wireless networks can be costly. In order to reduce the amount of transmitted data and ultimately save... more
In environments with energy and processing constraints, such as sensor networks and embedded devices, sending raw information over wireless networks can be costly. In order to reduce the amount of transmitted data and ultimately save energy, we can compress data before transmission. In this paper, we tackle such problem in the IoT domain by deploying two widely used libraries to deliver asynchronous messages and data compression/decompression. We evaluate both our methodology and the compression/decompression performance of the embedded library in a micro-controller for IoT.
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In Opportunistic Networks (OppNets), mobility of and contact between nodes are explored to create communication opportunities and exchange messages and information. A basic premise for a better performance of these networks is a... more
In Opportunistic Networks (OppNets), mobility of and contact between nodes are explored to create communication opportunities and exchange messages and information. A basic premise for a better performance of these networks is a collaboration of the nodes during communication. However, due to energy restriction factors, nodes may eventually fail to collaborate with message exchanges. In this work, we propose a routing mechanism called eGPDMI to improve message probability of delivery while optimizing nodes’ energy consumption. Unlike other algorithms proposed in OppNets literature, eGPDMI groups nodes by energy level and nodes interests using clustering techniques. Our major assumption is that retaining messages in nodes with the highest energy levels can improve network performance, thus overcoming the problem of nodes’ disconnection due to unwillingness to cooperate due to low energy values. Through questionnaire application and factorial design experiments, we characterize the im...
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With the advent of new communication technologies, modern networks tend to be more complex and there is a necessity of efficient tools for enhancing the computational effort of their simulations. Multiple Replications in Parallel (MRIP)... more
With the advent of new communication technologies, modern networks tend to be more complex and there is a necessity of efficient tools for enhancing the computational effort of their simulations. Multiple Replications in Parallel (MRIP) is an attractive approach for this purpose, since it can decrease the simulation cost and increase the accuracy of the results. Akaroa.2, a user-friendly package is an MRIP implementation, and has been found easy to install, use and extend. We present some issues concerning Akaroa's statistical properties, which indicate that it is a good candidate for simulating communication networks with efficiency. 1 INTRODUCTION Nowadays we witness a great challenge in the computing area. As the communication technologies advance and computer processing power increases, new kind of applications arise, e.g. integrated services. As a consequence, the interest of new users is aroused, which implies that new requirements and applications, and thus other users, ...
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This article presents a voice quality measurement tool based on the ITU-T E-Model. Firstly, the ITU-T and ETSI specifications of E-Model are briefly reviewed and some errors found in these documents are pointed. After, a measurement tool... more
This article presents a voice quality measurement tool based on the ITU-T E-Model. Firstly, the ITU-T and ETSI specifications of E-Model are briefly reviewed and some errors found in these documents are pointed. After, a measurement tool based on the corrections is described. VoIP calls through the Brazilian National Education and Research Network (RNP) backbone were used to verify the tool operation. 1.
Routing protocol for low-power and lossy networks is a routing solution specifically developed for wireless sensor networks, which does not quickly rebuild topology of mobile networks. In this article, we propose a mechanism based on... more
Routing protocol for low-power and lossy networks is a routing solution specifically developed for wireless sensor networks, which does not quickly rebuild topology of mobile networks. In this article, we propose a mechanism based on mobility entropy and integrate it into the corona RPL (CoRPL) mechanism, which is an extension of the IPv6 routing protocol for low-power and lossy networks (RPL). We extensively evaluated our proposal with a simulator for Internet of Things and wireless sensor networks. The mobility entropy-based mechanism, called CoRPL+E, considers the displacement of nodes as a deciding factor to define the links through which nodes communicate. Simulation results show that the proposed mechanism, when compared to CoRPL mechanism, is effective in reducing packet loss and latency in simulated mobile routing protocol for low-power and lossy networks. From the simulation results, one can see that the CoRPL+E proposal mechanism provides a packet loss reduction rate of up...
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AbstractTo support multimedia applications like Voice over Internet Protocol (VoIP) traffic in Wireless Mesh Networks, routing algorithms should determine a route satisfying Quality of Service requirements, such as packet loss, minimum... more
AbstractTo support multimedia applications like Voice over Internet Protocol (VoIP) traffic in Wireless Mesh Networks, routing algorithms should determine a route satisfying Quality of Service requirements, such as packet loss, minimum bandwidth and endtoend delay. In ...
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ABSTRACT
ABSTRACT Strightforward simulation of complex networks can require prohibitively long simulation times to give reasonable results, despite of increasing power of modern computers. A simple yet effective way to get rid of this problem is... more
ABSTRACT Strightforward simulation of complex networks can require prohibitively long simulation times to give reasonable results, despite of increasing power of modern computers. A simple yet effective way to get rid of this problem is to generate data ...
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Neste trabalho apresentamos um protótipo de controle de admissão para chamadas VoIP em redes mesh sem fio IEEE 802.11g, integrado ao protocolo de roteamento OLSR, que estima a interferência intra-fluxo e o tempo de ocupação do canal com... more
Neste trabalho apresentamos um protótipo de controle de admissão para chamadas VoIP em redes mesh sem fio IEEE 802.11g, integrado ao protocolo de roteamento OLSR, que estima a interferência intra-fluxo e o tempo de ocupação do canal com tráfego VoIP e BE (Best effort), para decidir se uma nova chamada pode ou não ser aceita na rede. Nossa proposta também regula a transmissão do tráfego BE para que ele não inviabilize o uso do VoIP. Nossa premissa é a possibilidade de haver chamadas VoIP com qualidade quando a rede não está congestionada, assim, o controle de admissão proposto deve evitar que a entrada de novas chamadas VoIP na rede consuma excessivamente recursos dos nós e cause degradação nos fluxos já estabelecidos.
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... EXPERIMENTS A. QoS Tool Implementation The preliminary idea of the management architecture was to build a QoS tool which could be incorporated to the network and measure how the actual security mechanism setup is impacting the speech... more
... EXPERIMENTS A. QoS Tool Implementation The preliminary idea of the management architecture was to build a QoS tool which could be incorporated to the network and measure how the actual security mechanism setup is impacting the speech quality and channel capacity. ...
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Abstract In this paper we present the results of an experimental analysis of voice traffic over 802.11 b networks when protected by IPSecurity mechanisms. The main concern is the objective measurement of the impact due these mechanisms by... more
Abstract In this paper we present the results of an experimental analysis of voice traffic over 802.11 b networks when protected by IPSecurity mechanisms. The main concern is the objective measurement of the impact due these mechanisms by means of our corrected ...
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Abstract Quality of Service (QoS) support in mobile ad hoc networks (MAVETs) is a very challenging task because of the dynamic topology, limited resources and wireless link characteristics. The Optimized Link State Routing Protocol (OLSR)... more
Abstract Quality of Service (QoS) support in mobile ad hoc networks (MAVETs) is a very challenging task because of the dynamic topology, limited resources and wireless link characteristics. The Optimized Link State Routing Protocol (OLSR) is a pro-active routing protocol for ...
Research Interests: Mathematics, Mobile Ad Hoc Networks, Routing protocols, Service Composition, Broadcasting, and 12 moreMobile Ad Hoc Network, Ad Hoc Networks, Manet, Quality of Service, Jitter, Routing Protocol, OLSR, Network Topology, wireless ATM links, Bandwidth, Intelligent Networks, and optimized link state routing protocol (OLSR)
Voice over IP is a major trend in applications for wireless networks, but even so it is not immune to the risks usually related with IP networks. Proposed solutions for VoIP security are already in the market, but these solutions must... more
Voice over IP is a major trend in applications for wireless networks, but even so it is not immune to the risks usually related with IP networks. Proposed solutions for VoIP security are already in the market, but these solutions must take into account the real-time constraint of voice service and their mechanisms should address possible attacks and overhead associated
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Page 1. Voice over Wireless Mesh Networks: A Case Study in the Brazilian Amazon Region during the Rainy Season Joao Luis G. Moreira * Federal University of Roraima Department of Mathematics Email: jl@dmat.ufrr.br Edjair ...
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ABSTRACT Several concepts behind opportunistic networks come from the studies on Delay Tolerant Networks (DTNs). The DTN architecture is suitable for a wide variety of heterogeneous networks and provides long-term storing and forward... more
ABSTRACT Several concepts behind opportunistic networks come from the studies on Delay Tolerant Networks (DTNs). The DTN architecture is suitable for a wide variety of heterogeneous networks and provides long-term storing and forward information switching to overcome communication disruptions. In most DTN solutions the focus of research on opportunistic networks has been on routing, bundle forwarding and message delivery validation. However current solutions do not have mechanisms to predict the amount of bundles, which can be transmitted during a DTN contact. In places where opportunistic connections are unstable, such as Amazon forest, it is critical to predict the amount of information that can be transmitted as a way to optimize bundles size, according to the duration of a contact and node speed. Information about the Contact Volume (CV), which is the amount of data that can be transferred during a time interval, allows the adoption of key strategies for optimizing message dispatch to improve the delivery rate and reduce the delivery delay in DTNs. Based on this observation, we present a set of experiments that validate an Adaptive Contact Volume Predicting Model in DTNs required to handle messages that are dispatched during an efficient contact. Our experiments consist of measurements using smartphones to define the amount of data transferred between two nodes, and the radio frequency signal strength measurements. Our results indicate clearly that efficient CV predictions are achieved by the proposed adaptive CV model.
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Abstract This paper describes a study about the impacts associated with the adoption of SRTP protocol in VoIP communications. The following steps where accomplished: modification of cryptographic key and the measurement of the... more
Abstract This paper describes a study about the impacts associated with the adoption of SRTP protocol in VoIP communications. The following steps where accomplished: modification of cryptographic key and the measurement of the choice's impact over the ...
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Certain kinds of delay and disruption tolerant networks need the human support to send data between users without a contemporaneous end-to-end path between them. However, humans are socially sel sh and tend to cooperate with whom they... more
Certain kinds of delay and disruption tolerant networks need the human support to send data between users without a contemporaneous end-to-end path between them. However, humans are socially sel sh and tend to cooperate with whom they have a social relationship, fact that a ects the overall performance. Memory space is a critical resource on mobile devices, and since the intermediate nodes have to store the messages, buff er management strategy becomes a crucial factor to achieve a satisfactory network performance. Very little attention has been directed towards applying the social characteristics of the users to mitigate the congestion in DTN. This paper presents a bu er management strategy for DTNs that takes into account a value associated with the social relationship strength among the users. We evaluated this policy in conjunction with the Epidemic and PRoPHET routing algorithms. By means of a thoroughly planned set of steady-state simulation experiments, we found that the proposed scheme can increase the delivery rate besides decreasing the average delay.
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Leandro Carvalho, Edjair Mota, Regeane Aguiar Federal University of Amazonas (UFAM) Av. Rodrigo Octavio, 3000 - 69077-000 - Brazil galvao@ufam.edu.br, {edjair,rba}@dcc.fua.br ... Ana F. Lima, José Neuman de Souza Federal University of... more
Leandro Carvalho, Edjair Mota, Regeane Aguiar Federal University of Amazonas (UFAM) Av. Rodrigo Octavio, 3000 - 69077-000 - Brazil galvao@ufam.edu.br, {edjair,rba}@dcc.fua.br ... Ana F. Lima, José Neuman de Souza Federal University of Ceará (UFC) Av. ...
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Page 1. Dynamical Management of Dejitter Buffers Based on Speech Quality Raquel F. do Valle, Leandro SG de Carvalho, Regeane B. Aguiar, Edjair S. Mota, Di6genes Freitas Computer Science Department - Federal University ...
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... voice over 802.1 lb networks and the E-Model as a speech quality evaluation tool. ... the design and implementation of a WLAN with IPSec, and investigates the performance of UDP ... IN 802.1 lB NETWORKS AND VPN/IPSEC There are many... more
... voice over 802.1 lb networks and the E-Model as a speech quality evaluation tool. ... the design and implementation of a WLAN with IPSec, and investigates the performance of UDP ... IN 802.1 lB NETWORKS AND VPN/IPSEC There are many known threats in wireless networks [14 ...
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Abstract This paper presents an empirical investigation of the impact of Secure RTP (SRTP) on VoIP calls over wireless networks: 802.11 and Bluetooth. For the purpose of evaluating this impact we developed an analysis tool based on... more
Abstract This paper presents an empirical investigation of the impact of Secure RTP (SRTP) on VoIP calls over wireless networks: 802.11 and Bluetooth. For the purpose of evaluating this impact we developed an analysis tool based on E-Model and security aspects of ...
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In this paper we focus on the following question: how routing protocols, working under different channel condi-tions, can influence the human perceived quality of VoIP calls in a wireless mesh backbone? In order to respond this question,... more
In this paper we focus on the following question: how routing protocols, working under different channel condi-tions, can influence the human perceived quality of VoIP calls in a wireless mesh backbone? In order to respond this question, we propose a study case where we analyze ...
Research Interests: Wireless Mesh Networks, Routing protocols, Voip, Ad Hoc Networks, Stochastic Simulation, and 7 moreRouting Protocol, Wireless Mesh Network, VoIP over Wireless Mesh, Routing Security Issues In Wireless Ad Hoc, Mesh and Sensor Networks, Security and Privacy Issues In Ubiquitous Computing, and Cross layer Security Design
Header compression techniques can improve the speech quality of VoIP applications. However, its deployment over wireless mesh environments may not offer much improvement, since the wireless and multi-hop characteristics of such a network... more
Header compression techniques can improve the speech quality of VoIP applications. However, its deployment over wireless mesh environments may not offer much improvement, since the wireless and multi-hop characteristics of such a network impose a high packet loss rate. In this work, we propose a new approach for header compression, using packet aggregation to cooperate with the header compression scheme.
Research Interests: Wireless Communications, Computer Networks, Data Compression, Wireless Mesh Networks, Voip, and 15 moreSpeech, Compression Algorithms, ISCC, VoIP qos, Spread Spectrum Communication, Wireless Mesh Network, VoIP Performance, VoIP over Wireless Mesh, Packet Aggregation, Performance evaluation of VoIP, VoIP quality, Packet Loss, Bandwidth, Application Software, and Payloads
In this paper we evaluate the influence of radio propagation modeling on VoIP quality in wireless network simulations. How propagation modeling can influence classification of strategies concerned in improving VoIP quality? We analyze... more
In this paper we evaluate the influence of radio propagation modeling on VoIP quality in wireless network simulations. How propagation modeling can influence classification of strategies concerned in improving VoIP quality? We analyze reactive AODV and proactive OLSR approaches in a simulated 802.11 mesh backbone and calculate the VoIP quality by means of a reviewed version of ITU-TE-Model. Results showed
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One of the main components of voice over IP technology is voice coding algorithm, known as vocoders. There is a wide variety of vocoders and some have better quality than others. This work aims to evaluate the quality of some open source... more
One of the main components of voice over IP technology is voice coding algorithm, known as vocoders. There is a wide variety of vocoders and some have better quality than others. This work aims to evaluate the quality of some open source vocoders, and as starting point the implementation of evaluation procedure defined by ITU-T Recommendation P.834 for thus obtain
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In this paper we propose a VoIP study case to evaluate the impact ofdifferent radio propagation models on perfor-mance parameters ofapplication layer in simulation stud-ies ofWireless Mesh Backbones. For each presented model, we carried... more
In this paper we propose a VoIP study case to evaluate the impact ofdifferent radio propagation models on perfor-mance parameters ofapplication layer in simulation stud-ies ofWireless Mesh Backbones. For each presented model, we carried out experiments taking into account ...
Research Interests: Stochastic Process, Simulation (Computer Science), Performance Studies, Computational Modeling, Spine, and 15 moreImpact Evaluation, Wireless Mesh Networks, Modeling and Simulation, Performance Evaluation (Computer Science), Computer simulation of complex systems, Speech, Stochastic processes, Computer Simulations and Modeling, Radio Propagation, Steady state, ISCC, Simulation Study, Wireless Network Simulations, Switches, and Application Software
ABSTRACT There is a lack of reliable tools for evaluating the performance of Delay Tolerant Networks (DTN). Frequently, the researchers use small-scale real networks or one of the few available DTN simulators. This work presents an... more
ABSTRACT There is a lack of reliable tools for evaluating the performance of Delay Tolerant Networks (DTN). Frequently, the researchers use small-scale real networks or one of the few available DTN simulators. This work presents an alternative approach for conducting performance evaluation studies of DTN, following a recent movement of the scientific community with respect to the use of hybrid environments in order to achieve realism in the studies. We propose, implement and validate the Virtualized DTN Testbed (VDT) as a means to construct a virtualized testbed completely in software that takes into account a real instance of the operating system and applications that run inside the mobile nodes, as well as a robust model of the wireless channel. The results show that VDT can accurately reproduce both the mobility of nodes, and the contact opportunities obtained in experiments of a real testbed. Moreover, we identified some implementation problems in the real experiments, that after some fixing strategies allowed us to identify the occurrence of several contacts not registered previously.
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Page 1. An Alternative Approach for Header Compression Over Wireless Mesh Networks Andréa Giordanna O. do Nascimento, Edjair Mota, Saulo Queiroz, Edson do Nascimento Junior Federal University of Amazonas (UFAM) Av. ...
Research Interests: Data Mining, Wireless Mesh Networks, Speech, Stochastic processes, Stochastic Simulation, and 9 moreBandwidth Allocation, Simulation of Wireless Mesh Network and Manet Routing Protocol and Developing Routing Algorithm and Routing Protocol for Manet and Wireless Mesh Network, Data Structures, Wireless Mesh Network, Packet Loss, Header Compression, Bandwidth, Multimedia Application, and Payloads
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ABSTRACT In a Delay Tolerant Network (DTN), a contact is the opportunity to transfer data between DTN nodes. A contact occurs when at least one of the nodes is in movement. The duration time of a contact, termed dwell time, can vary from... more
ABSTRACT In a Delay Tolerant Network (DTN), a contact is the opportunity to transfer data between DTN nodes. A contact occurs when at least one of the nodes is in movement. The duration time of a contact, termed dwell time, can vary from few seconds up to several hours. This period must be seized to transfer as many bundles, a basic data unit of DTN, as possible. DTN approaches are key solution to transmit data in rural and isolated areas, such as forests. This work is part of Amazon Regatão project, whose goal is to provide Internet access to riparian communities of Amazon Rivers based on DTN schemes. We have developed a novel technique to predict the amount of bundles to be transferred during a DTN contact. Measuring campaigns were carried out to evaluate propagation and bundle throughput in different locations in the core of the Amazon region. The results can be used to design a queue bundle strategy and bundle proactive fragmentation to optimize the delivery ratio in DTNs. Real experiments were conduct at the Experimental Farm and at the Campus of Federal University of Amazonas, using IEEE 802.11n interface routers and a DTN Reference Implementation.
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With the increasing deployment of wireless mesh net-works, the usage of a number of services in such networks increased in the last few years. Real time services like VoIP (Voice over IP) are included, despite of their particular... more
With the increasing deployment of wireless mesh net-works, the usage of a number of services in such networks increased in the last few years. Real time services like VoIP (Voice over IP) are included, despite of their particular be-havior. Wireless mesh networks has been ...
Research Interests: Voice over IP, Wireless Mesh Networks, Modeling and Simulation, Simulation of Wireless Mesh Network and Manet Routing Protocol and Developing Routing Algorithm and Routing Protocol for Manet and Wireless Mesh Network, TCP/IP header compression, and 3 moreISCC, Wireless Mesh Network, and Real Time Application
Contacts are essential to guarantee the performance of opportunistic networks, but due to resource constraints, some nodes may not cooperate. In reputation systems, the perception of an agent depends on past observations to classify its... more
Contacts are essential to guarantee the performance of opportunistic networks, but due to resource constraints, some nodes may not cooperate. In reputation systems, the perception of an agent depends on past observations to classify its actual behavior. Few studies have investigated the effectiveness of robust learning models for classifying selfish nodes in opportunistic networks. In this paper, we propose a distributed reputation algorithm based on the game theory to achieve reliable information dissemination in opportunistic networks. A contact is modeled as a game, and the nodes can cooperate or not. By using statistical inference methods, we derive the reputation of a node based on learning from past observations. We applied the proposed algorithm to a set of traces to obtain a distributed forecasting base for future action when selfish nodes are involved in the communication. We evaluate the conditions in which the accuracy of data collection becomes reliable.
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Computer Networks and Multimedia Group, Department of Computer Science, Federal University of Amazonas (UFAM), Manaus, Amazonas, Brazil E-mail: sjbq@dcc.ufam.edu.br E-mail: aon1@dcc.ufam.edu.br E-mail: edjair@dcc.ufam.edu.br E-mail:... more
Computer Networks and Multimedia Group, Department of Computer Science, Federal University of Amazonas (UFAM), Manaus, Amazonas, Brazil E-mail: sjbq@dcc.ufam.edu.br E-mail: aon1@dcc.ufam.edu.br E-mail: edjair@dcc.ufam.edu.br E-mail: galvao@dcc.ufam.edu.br ...
Research Interests: Distributed Computing, Routing, Voice over IP, Wireless Mesh Networks, MANET Routing protocols, and 11 moreWireless networks, Mesh Networks, Routing protocols, Voip, Wireless Network, Comparative Analysis, Resource Management, Routing Protocol, MRP, VoIP over Mesh, and Wireless Mesh Routing Protocols
Page 1. LiTE: Um Algoritmo de Localizaç ao Temporal e Ordenaç ao de Eventos em Redes de Sensores Sem Fio Compostas por Nós Dessincronizados Leonardo L. Guimaraes1, Horácio ABF Oliveira1, Rômulo T. Rodrigues2, Edjair S. Mota1, Antonio... more
Page 1. LiTE: Um Algoritmo de Localizaç ao Temporal e Ordenaç ao de Eventos em Redes de Sensores Sem Fio Compostas por Nós Dessincronizados Leonardo L. Guimaraes1, Horácio ABF Oliveira1, Rômulo T. Rodrigues2, Edjair S. Mota1, Antonio AF Loureiro3 1Depto. ...