Edjair Mota
Universidade Federal do Amazonas, Institute of Computing - IComp, Department Member
- Opportunistic Networks, Delay Tolerant Networks, Peer-To-Peer Content Distribution, Wireless Networks Simulation, Computer Networks, MANET Routing protocols, and 8 moreModelling and Simulation of communication networks, Performance Evaluation (Computer Science), Wireless Networks (Computer Science), Modeling and Simulation, LCD-Net: Lowest Cost Denominator Networking, Wireless Mesh Networks, Modelacion Matematica, and Simulation (Computer Science)edit
The simulation and its characteristic to make changes in the system looking for alternatives without disrupting the system, was explored in this article as a tool to support the decision in a case study using the technique of simulation... more
The simulation and its characteristic to make changes in the system looking for alternatives without disrupting the system, was explored in this article as a tool to support the decision in a case study using the technique of simulation of finite horizon to systems end of a common assembly line in industrial segment of the stamping and metal artifacts based in the Industrial District of Manaus (PIM), using transporters and operations in sequence. We observed the variables related to occupation and used as a parameter for comparison and modification of the assembly line based on the scenarios proposed and implemented in the Arena software.
Research Interests:
Research Interests: Computer Science, Distributed Computing, Routing, Voice over IP, Wireless Mesh Networks, and 14 moreMANET Routing protocols, Wireless networks, Mesh Networks, Routing protocols, Voip, Computer Network, Wireless Network, Comparative Analysis, Resource Management, Routing Protocol, MRP, Wireless Mesh Network, VoIP over Mesh, and Wireless Mesh Routing Protocols
Research Interests:
-Detection of selfish behavior is crucial to the proper functioning of opportunistic mobile networks operations. Previous works focused on developing reputation systems or trust models. However, these approaches assume the existence of an... more
-Detection of selfish behavior is crucial to the proper functioning of opportunistic mobile networks operations. Previous works focused on developing reputation systems or trust models. However, these approaches assume the existence of an efficient model for detecting selfish nodes, such as watchdogs. Moreover, other studies do not present an experimental analysis of the efficiency of the watchdog implementation. This article discusses the design, implementation, and validation of a watchdog, in order to verify the effectiveness of the detection process and to understand the effects of this mechanism for increasing density of messages in the network. We tested the proposed watchdog with two different mobility traces, with a low and a high contact density. The analysis of true positives present a very promising result for watchdog evaluation on real opportunistic mobile networks. However, our results showed that the implementation of watchdog may present some issues related to how false positives were detected during the monitoring and in case that the number of contacts increases. To handle this, we propose an acknowledgement mechanism to increase the reliability of false positive detections and the results improved above 68{\% in both traces. Our results also present a brief study of congestion control and, even with a congestion control of six hours, the results remain virtually unchanged, so that staying with forwarding information for a long time does not affect reliability. The improvement in the number of messages relayed was above 35{\% for both traces.
Research Interests:
Research Interests:
Research Interests:
Opportunistic networks are becoming a solution to provide communication support in areas with overloaded cellular networks, and in scenarios where a fixed infrastructure is not available, as in remote and developing regions. A critical... more
Opportunistic networks are becoming a solution to provide communication support in areas with overloaded cellular networks, and in scenarios where a fixed infrastructure is not available, as in remote and developing regions. A critical issue, which still requires a satisfactory solution, is the design of an efficient data delivery solution trading off delivery efficiency, delay, and cost. To tackle this problem, most researchers have used either the network state or node mobility as a forwarding criterion. Solutions based on social behaviour have recently been considered as a promising alternative. Following the philosophy from this new category of protocols, in this work, we present our “FriendShip and Acquaintanceship Forwarding” (FSF) protocol, a routing protocol that makes its routing decisions considering the social ties between the nodes and both the selfishness and the device resources levels of the candidate node for message relaying. When a contact opportunity arises, FSF f...
Research Interests:
In the last five years, the integration of social relationships in algorithms for Opportunistic Networks (OppNet) has received much attention from researchers worldwide. Despite node mobility has a great variability along time and is... more
In the last five years, the integration of social relationships in algorithms for Opportunistic Networks (OppNet) has received much attention from researchers worldwide. Despite node mobility has a great variability along time and is often unpredictable, node relationships can be less volatile than node mobility. In this work, we investigate the impact of using social relationships for managing the buffer of OppNet nodes. First, we classify the relationships between the nodes in two groups: their friendship, and their acquaintanceship. Then, we propose the Friendly Drop Algorithm (FDA), which combines in its decisions both the friendship among the nodes and their acquaintanceship. FDA explores the self-reported friendship relationships from the nodes to build friendship graphs. Moreover, FDA uses a metric based on the contact similarity among the nodes to find out their acquaintanceship. We validated the proposed algorithm by using trace-driven simulations through the Opportunistic Network Environment simulator (The ONE). Experiments show that FDA contributes to increase the delivery ratio and decrease the number of forwardings associated to standard replication algorithms (e.g. Epidemic). We also find that combining both forwarding algorithms and buffer management algorithms based on social characteristics can improve the network performance.
Research Interests:
A detecção de comportamento egoísta é crucial para o funcionamento adequado das operações em redes oportunistas móveis. Trabalhos anteriores têm concentrado esforços em desenvolver sistemas de reputação ou modelos de confiança. Contudo,... more
A detecção de comportamento egoísta é crucial para o funcionamento adequado das operações em redes oportunistas móveis. Trabalhos anteriores têm concentrado esforços em desenvolver sistemas de reputação ou modelos de confiança. Contudo, essas abordagens assumem a existência de um modelo eficiente de detecção de nós egoístas, tal como os watchdogs. A maioria dos estudos, no entanto, não apresenta uma análise da eficiência da implementação do watchdog em um nível experimental. Este artigo discute o projeto, a implementação e a validação de um watchdog, com o objetivo de verificar a eficácia no processo de detecção e compreensão dos efeitos desse mecanismo para valores crescentes da densidade de mensagens na rede. Resultados experimentais, utilizando-se o ambiente The ONE, mostram que a implementação do watchdog aqui discutida é bastante promissora.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
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...
Research Interests:
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.
Research Interests:
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.
Research Interests:
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...
Research Interests:
Research Interests:
Research Interests:
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...
Research Interests:
This paper presents the friendship and selfishness forwarding (FSF) algorithm for Delay Tolerant Networks. This novel solution is based on two social characteristics of nodes: friendship and selfishness. When a contact opportunity arises,... more
This paper presents the friendship and selfishness forwarding (FSF) algorithm for Delay Tolerant Networks. This novel solution is based on two social characteristics of nodes: friendship and selfishness. When a contact opportunity arises, FSF analyzes two aspects to make message forwarding decisions: first, FSF assesses the friendship strength among the pair of nodes, then it determines the individual selfishness of the relay node. Unlike other algorithms proposed in the DTN literature, we use a machine learning algorithm to quantify the friendship strength among pairs of nodes in the network. The individual selfishness of the relay node is determined by using a model based on the current level of its resources. The primary goal is to take into account the case where, despite a strong friendship with the message destination, the relay node does not accept processing the message to save its resources. By using trace-driven simulations we show that the FSF algorithm achieves better results in terms of delivery rate, average cost and efficiency.
Research Interests:
ABSTRACT
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.
Research Interests:
Research Interests:
... O Laboratório de Voz sobre IP da Universidade Federal do Rio de Janeiro desenvolveu uma infra ... ativa, dados estatísticos referentes ao nível de transporte de ligações e apresentar graficamente informações de perdas de pacotes,... more
... O Laboratório de Voz sobre IP da Universidade Federal do Rio de Janeiro desenvolveu uma infra ... ativa, dados estatísticos referentes ao nível de transporte de ligações e apresentar graficamente informações de perdas de pacotes, jitter e RTT ao longo de uma ligação. ...
Research Interests:
VoIP calls are sensitive to several impairments, such as delay and packet loss. One way to overcome these problems is by adaptively adjusting application-layer parameters to keep a minimum speech quality level. At the heart of... more
VoIP calls are sensitive to several impairments, such as delay and packet loss. One way to overcome these problems is by adaptively adjusting application-layer parameters to keep a minimum speech quality level. At the heart of self-adaptive systems lies a feedback loop , which consists of four key activities: monitoring, analysis, planning, and execution. Nevertheless, the existing adaptive approaches to QoS control of VoIP do not explicitly exhibit this feedback loop. Bringing it to surface can help developers in designing more robust and human-independent VoIP systems. This survey presents a comprehensive review of the current state-of-the-art research on speech quality adaptation of VoIP systems at the application layer and some research challenges on this subject.
Research Interests: Computer Science, Machine Learning, Data Mining, Access Control, Voice over IP, and 15 moreCloud Computing, Voip, Smart spaces, Cyber Physical Systems, Complex Event Processing, Quality of Service, Cyber Security, Semantic Computing, VoIP over WiFi, VoIP qos, Telecommunication VoIP, Feedback loop, VoIP/SIP/IMS, Distributed Information Systems, and RFID and Sensor Networks
Despite of even higher performance computers, quantitative steady-state simulation of even a moderate complex system takes very long time. There is always a necessity of efficient procedures that can control the run length of stochastic... more
Despite of even higher performance computers, quantitative steady-state simulation of even a moderate complex system takes very long time. There is always a necessity of efficient procedures that can control the run length of stochastic simulation experiments. This paper compares two sequential batching-based procedures for estimating steadystate mean under Multiple Replications in Parallel. A second motivation to this investigation is that fixed-sample size procedures can yield inappropriate precision of the ...
Research Interests:
Statistical techniques are extremely useful in system performance evaluation. Since any statistic cannot be guaranteed to give a close estimate for every sample, we must design statistics that will give good results on the average or in... more
Statistical techniques are extremely useful in system performance evaluation. Since any statistic cannot be guaranteed to give a close estimate for every sample, we must design statistics that will give good results on the average or in the long run. Despite of even higher performance computers, quantitative steady-state simulation of even a moderate complex system takes very long time, since to obtain reasonably stable results, that is, estimates with reasonably variances, very larges samples are usually necessary. Natural effort toward the reduction ...
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 selfish 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 selfish and tend to cooperate with whom they have a social relationship, fact that affects the overall performance. Memory space is a critical resource on mobile devices, and since the intermediate nodes have to store the messages, buffer 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 buffer 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.
Research Interests:
Research Interests:
ABSTRACT Despite of even higher performance computers, quantitative steady-state simulation of even a moderate complex system takes very long time. There is always a necessity of efficient procedures that can control the run length of... more
ABSTRACT Despite of even higher performance computers, quantitative steady-state simulation of even a moderate complex system takes very long time. There is always a necessity of efficient procedures that can control the run length of stochastic simulation experiments. This paper compares two sequential batching-based procedures for estimating steadystate mean under Multiple Replications in Parallel.
Abstract Discrete event simulation is frequently time-consuming either because modern dynamic systems, such as telecommunication networks, are becoming increasingly complex and/or a great number of observations is required to yield... more
Abstract Discrete event simulation is frequently time-consuming either because modern dynamic systems, such as telecommunication networks, are becoming increasingly complex and/or a great number of observations is required to yield reasonably accurate results. An interesting approach to reduce the time duration of simulation is that of concurrently running multiple replications in parallel (MRIP) on a number of processors connected via networking and averaging the results adequately.
Statistical techniques are extremely useful in system performance evaluation. Since any statistic cannot be guaranteed to give a close estimate for every sample, we must design statistics that will give good results on the average or in... more
Statistical techniques are extremely useful in system performance evaluation. Since any statistic cannot be guaranteed to give a close estimate for every sample, we must design statistics that will give good results on the average or in the long run. Despite of even higher performance computers, quantitative steady-state simulation of even a moderate complex system takes very long time, since to obtain reasonably stable results, that is, estimates with reasonably variances, very larges samples are usually necessary.
Edjair Mota*, Adam Wolisz Technical University of Berlin, Germany Krzysztof Pawlikowski University of Canterbury, Christchurch, New Zealand e-mail: mota@ ft. ee. TU-Berlin. DE Keywords: Efficient simulation, multiple replications,... more
Edjair Mota*, Adam Wolisz Technical University of Berlin, Germany Krzysztof Pawlikowski University of Canterbury, Christchurch, New Zealand e-mail: mota@ ft. ee. TU-Berlin. DE Keywords: Efficient simulation, multiple replications, parallelization, computer networks, MAC protocols
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.
Research Interests:
Research Interests:
An objective method for VoIP quality evaluation based on the ITU-T E-model is presented. This method incorporates extensions proposed by Alan Clark, later adopted by ETSI, and it corrects some expressions necessary for calculating... more
An objective method for VoIP quality evaluation based on the ITU-T E-model is presented. This method incorporates extensions proposed by Alan Clark, later adopted by ETSI, and it corrects some expressions necessary for calculating internal extended E-model parameters. This revised method was implemented as an analytical evaluation module and incorporated to an existing in-house developed VoIP monitoring tool. Results from
Research Interests:
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.
Research Interests:
Research Interests:
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.
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.
Research Interests:
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.