Universidade Federal do Rio de Janeiro

Displaying 1-26 of 26 results

  • White Papers // Mar 2012

    Local Heuristic for the Refinement of Multi-Path Routing in Wireless Mesh Networks

    The authors consider wireless mesh networks and the problem of routing end-to-end traffic over multiple paths for the same origin-destination pair with minimal interference. They introduce a heuristic for path determination with two distinguishing characteristics. First, it works by refining an extant set of paths, determined previously by a single-...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Aug 2011

    XTC: A Throughput Control Mechanism for Xen-Based Virtualized Software Routers

    Xen is a tool for hardware virtualization often used to build virtual routers. Xen, however, does not assure the fundamental requirement of network isolation among these routers. This paper proposes XTC (Xen Throughput Control) to fill this gap, and therefore, to guarantee multiple network coexistence without interference. XTC sets the...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Aug 2011

    Channel Sensing Order for Cognitive Radio Networks Using Reinforcement Learning

    This paper investigates the problem of channel sensing order used by a cognitive multichannel network, where each user is able to perform primary user detection on only one channel at a time. The sensing order indicates the sequence of channels sensed by the secondary users when searching for an available...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jul 2011

    VNEXT: Virtual Network Management for Xen-Based Testbeds

    Network testbeds strongly rely on virtualization that allows the simultaneous execution of multiple protocol stacks but also increases the management and control tasks. This paper presents a system to control and manage virtual networks based on the Xen platform. The goal of the proposed system is to assist network administrators...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jun 2011

    Distributed Database Research at COPPE/UFRJ

    The authors' group has been working with different aspects of distributed and parallel processing of databases in the relational, object-oriented, and XML data models. Classic techniques for distributed design and query processing in relational database systems have been revisited to address dynamic issues in high performance computing and flexibility challenges...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Apr 2011

    An Experimental Analysis of Routing Inconsistency in Indoor Wireless Mesh Networks

    As of today, many routing protocols for wireless mesh networks have been proposed. Nevertheless, quite a few take the high loss rate of control packets into account. This paper analyzes the problem of consistent routing information among wireless network nodes. To accomplish this, the authors propose a metric to evaluate...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Mar 2011

    Deepwater Monitoring System Using Logistic-Support Vessels in Underwater Sensor Networks

    This paper proposes a deepwater monitoring system built with sensors distributed over the subsea pipelines which are responsible for transportation of oil production. Data transmission is undertaken by underwater acoustic modems installed on the sensors and vessels used for logistic support of the oil exploration. However, the vessels may not...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jan 2011

    Analyzing a Human-based Trust Model for Mobile Ad Hoc Networks

    This paper analyzes a trust model for mobile ad hoc networks. The authors provide nodes with a mechanism to build a trust relationship with its neighbors. The proposed model considers the recommendation of trustworthy neighbors and the experience of the node itself. The interactions are limited to direct neighbors in...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jan 2011

    An Efficient Data Transport Protocol for Event-Driven Field-Estimation on Sensor Networks

    This paper introduces and analyzes an Event-Driven Field-Estimation (EDFE) protocol for wireless sensor networks. In the authors' field estimation scheme the sensors derive their own notion of expected reading. Readings differing from the expected are considered events of interest and trigger a data transmission to the sink. The proposed protocol...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Nov 2010

    Minimum Loss Multiplicative Routing Metrics for Wireless Mesh Networks

    Wireless mesh networks are low-cost self-configurable multi-hop networks. This paper presents a study about the main routing metrics used in this kind of network, pointing out their virtues and limitations. It also proposes implements and analyzes alternative multiplicative metrics. To evaluate the performance of the proposed metrics, comparative measurements over...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Sep 2010

    XNetMon: A Network Monitor for Securing Virtual Networks

    Isolation and performance are critical issues for virtual networking. In this paper, the authors consider the use of Xen virtualization platform for building software-based virtual routers. They propose a network monitor for Xen to increase the isolation and the performance on packet forwarding. The network monitor controls the use of...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jul 2010

    The Impact of Joint Routing and Link Scheduling on the Performance of Wireless Mesh Networks

    Increasing the capacity of wireless mesh networks has motivated numerous studies. In this paper, link scheduling has been one of the most investigated mechanisms. However, the isolated use of scheduling mechanisms does not guarantee a significant increase in capacity independently of the routes followed by traffic. For this reason, the...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jul 2010

    Virtualization for Load Balancing on IEEE 802.11 Networks

    In IEEE 802.11 networks composed by multiple APs, before a station can access the network it needs to make a decision about which AP to associate with. Usually, legacy 802.11 stations use no more than the signal strength of the frames received from each AP to support their decision. This...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jun 2010

    Virtual Networks: Isolation, Performance, and Trends

    Currently, there is a strong effort of the research community in rethinking the Internet architecture to cope with its current limitations and support new requirements. Many researchers conclude that there is no one-size-fits-all solution for all of the user and network-provider needs and, thus, advocate for a pluralist network architecture,...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jun 2010

    Evaluating Virtual Router Performance for the Future Internet

    The Internet is ossified. It is difficult to create new services or innovate in the core of the network. In order to address this issue, the authors need a new Internet model to council the existing protocols with new ones. Virtualization is a technique that provides this capability to the...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // May 2010

    OpenFlow and Xen-Based Virtual Network Migration

    Migration is an important feature for network virtualization because it allows the reallocation of virtual resources over the physical resources. In this paper, the authors investigate the characteristics of different migration models, according to their virtualization platforms. They show the main advantages and limitations of using the migration mechanisms provided...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // May 2010

    Resource Consumption Analysis for a Structural Health Monitoring Algorithm Using Wireless Sensor Networks

    This paper presents a partial evaluation of a fully decentralized approach to detect, localize and determine the extent of damage on civil structures in environments that range from offshore oil and gas industry to wind farms. The evaluation presented in this paper is a first step towards the conception of...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // May 2010

    Veer: A Trajectory-Based Peer Selection Algorithm for Networks of Vehicles

    The authors propose Veer, a peer selection algorithm for file exchange in vehicular ad hoc networks. The innovative aspect of Veer is that it relies on embedded GPS devices to determine individual mobility patterns and, consequently, to help select the peers that increase the probability that a file transfer succeeds....

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // May 2010

    Distributed Broadcast Scheduling in Mobile Ad Hoc Networks

    Data and control messages broadcasting is a widely used mechanism in network applications and protocols, which can have latency requirements for the information delivery. One solution to achieve low latencies is to solve the Minimum-Latency Broadcast Scheduling (MLBS) problem. However, MLBS is a NP-Complete problem, thus some works propose approximation...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Mar 2010

    Deep-Ocean Data Acquisition Using Underwater Sensor Networks

    The traditional approach of ocean data acquisition, based on the deployment of battery operated stations with sensors for data recording during some programmed time for later recovery, has several drawbacks that may be overcome with the use of UnderWater Sensor Networks (UWSN). In this paper, the authors investigate the feasibility...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Nov 2009

    Underwater Sensor Networks: A Feasibility Study

    UnderWater Sensor Network (UWSN) is considered to be feasible and suitable for several applications. However, the characteristics of the acoustic channel must be taken into account on the evaluation of the application feasibility. The acoustic channel imposes severe limitations to the communication, such as low bandwidth, low data rates and...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Sep 2009

    Decision Support System for Diagnosis of Power Transformers

    Given the complexity of the Brazilian Electric Power System, it is important to ensure that equipments work in satisfactory conditions and with high levels of reliability. Within those equipments, power transformers are one of the most important assets, because they are expensive and functionally complex. Dissolved Gases Analysis (DGA) in...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Sep 2009

    Measuring the Capacity of In-Car to In-Car Vehicular Networks

    A particular class of vehicular networks is the one that includes off-the-shelf end-user equipments (e.g., laptops and PDAs) running from the interior of vehicles, namely in-car nodes. They are subject to limited communication conditions when compared with nodes specifically designed to this context. Existing works either consider antennas installed on...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // May 2009

    TDCS: A New Mechanism for Automatic Channel Assignment for Independent IEEE 802.11 Networks

    In the last few years, IEEE 802.11 applications have experienced a significant growth. This expansion creates scenarios where distinct administrators manage wireless networks. These scenarios lack of a unique authority to perform an adequate channel allocation that minimizes the performance degradation generated by medium access sharing and co-channel interference. This...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Nov 2008

    Virtual Interface for Collaborative Work With RECOLLVE

    The world globalization process, the increasing demand of communication and information technologies creates an enormous demand for collaborative applications. Aiming to support communication, information change and collaboration between users geographically distants, many CSCW (Computer Supported Cooperative Work) systems like audio and videoconference, shared editors, shared whiteboard and CVEs (Collaborative Virtual...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Oct 2008

    CTCP: Reliable Transport Control Protocol for Sensor Networks

    This paper presents Collaborative Transport Control Protocol (CTCP), a new transport protocol for sensor networks. It aims at providing end-to-end reliability and adapts itself to different applications through a two level mechanism of reliability variation. CTCP achieves these properties using hop-by-hop acknowledgments and a storage control algorithm that operates at...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Sep 2009

    Decision Support System for Diagnosis of Power Transformers

    Given the complexity of the Brazilian Electric Power System, it is important to ensure that equipments work in satisfactory conditions and with high levels of reliability. Within those equipments, power transformers are one of the most important assets, because they are expensive and functionally complex. Dissolved Gases Analysis (DGA) in...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // May 2010

    Resource Consumption Analysis for a Structural Health Monitoring Algorithm Using Wireless Sensor Networks

    This paper presents a partial evaluation of a fully decentralized approach to detect, localize and determine the extent of damage on civil structures in environments that range from offshore oil and gas industry to wind farms. The evaluation presented in this paper is a first step towards the conception of...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Mar 2011

    Deepwater Monitoring System Using Logistic-Support Vessels in Underwater Sensor Networks

    This paper proposes a deepwater monitoring system built with sensors distributed over the subsea pipelines which are responsible for transportation of oil production. Data transmission is undertaken by underwater acoustic modems installed on the sensors and vessels used for logistic support of the oil exploration. However, the vessels may not...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Sep 2010

    XNetMon: A Network Monitor for Securing Virtual Networks

    Isolation and performance are critical issues for virtual networking. In this paper, the authors consider the use of Xen virtualization platform for building software-based virtual routers. They propose a network monitor for Xen to increase the isolation and the performance on packet forwarding. The network monitor controls the use of...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Apr 2011

    An Experimental Analysis of Routing Inconsistency in Indoor Wireless Mesh Networks

    As of today, many routing protocols for wireless mesh networks have been proposed. Nevertheless, quite a few take the high loss rate of control packets into account. This paper analyzes the problem of consistent routing information among wireless network nodes. To accomplish this, the authors propose a metric to evaluate...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Aug 2011

    Channel Sensing Order for Cognitive Radio Networks Using Reinforcement Learning

    This paper investigates the problem of channel sensing order used by a cognitive multichannel network, where each user is able to perform primary user detection on only one channel at a time. The sensing order indicates the sequence of channels sensed by the secondary users when searching for an available...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jul 2011

    VNEXT: Virtual Network Management for Xen-Based Testbeds

    Network testbeds strongly rely on virtualization that allows the simultaneous execution of multiple protocol stacks but also increases the management and control tasks. This paper presents a system to control and manage virtual networks based on the Xen platform. The goal of the proposed system is to assist network administrators...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Aug 2011

    XTC: A Throughput Control Mechanism for Xen-Based Virtualized Software Routers

    Xen is a tool for hardware virtualization often used to build virtual routers. Xen, however, does not assure the fundamental requirement of network isolation among these routers. This paper proposes XTC (Xen Throughput Control) to fill this gap, and therefore, to guarantee multiple network coexistence without interference. XTC sets the...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Mar 2010

    Deep-Ocean Data Acquisition Using Underwater Sensor Networks

    The traditional approach of ocean data acquisition, based on the deployment of battery operated stations with sensors for data recording during some programmed time for later recovery, has several drawbacks that may be overcome with the use of UnderWater Sensor Networks (UWSN). In this paper, the authors investigate the feasibility...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // May 2010

    Veer: A Trajectory-Based Peer Selection Algorithm for Networks of Vehicles

    The authors propose Veer, a peer selection algorithm for file exchange in vehicular ad hoc networks. The innovative aspect of Veer is that it relies on embedded GPS devices to determine individual mobility patterns and, consequently, to help select the peers that increase the probability that a file transfer succeeds....

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // May 2010

    OpenFlow and Xen-Based Virtual Network Migration

    Migration is an important feature for network virtualization because it allows the reallocation of virtual resources over the physical resources. In this paper, the authors investigate the characteristics of different migration models, according to their virtualization platforms. They show the main advantages and limitations of using the migration mechanisms provided...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jun 2010

    Virtual Networks: Isolation, Performance, and Trends

    Currently, there is a strong effort of the research community in rethinking the Internet architecture to cope with its current limitations and support new requirements. Many researchers conclude that there is no one-size-fits-all solution for all of the user and network-provider needs and, thus, advocate for a pluralist network architecture,...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jun 2010

    Evaluating Virtual Router Performance for the Future Internet

    The Internet is ossified. It is difficult to create new services or innovate in the core of the network. In order to address this issue, the authors need a new Internet model to council the existing protocols with new ones. Virtualization is a technique that provides this capability to the...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // May 2010

    Distributed Broadcast Scheduling in Mobile Ad Hoc Networks

    Data and control messages broadcasting is a widely used mechanism in network applications and protocols, which can have latency requirements for the information delivery. One solution to achieve low latencies is to solve the Minimum-Latency Broadcast Scheduling (MLBS) problem. However, MLBS is a NP-Complete problem, thus some works propose approximation...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jul 2010

    The Impact of Joint Routing and Link Scheduling on the Performance of Wireless Mesh Networks

    Increasing the capacity of wireless mesh networks has motivated numerous studies. In this paper, link scheduling has been one of the most investigated mechanisms. However, the isolated use of scheduling mechanisms does not guarantee a significant increase in capacity independently of the routes followed by traffic. For this reason, the...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jul 2010

    Virtualization for Load Balancing on IEEE 802.11 Networks

    In IEEE 802.11 networks composed by multiple APs, before a station can access the network it needs to make a decision about which AP to associate with. Usually, legacy 802.11 stations use no more than the signal strength of the frames received from each AP to support their decision. This...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Nov 2010

    Minimum Loss Multiplicative Routing Metrics for Wireless Mesh Networks

    Wireless mesh networks are low-cost self-configurable multi-hop networks. This paper presents a study about the main routing metrics used in this kind of network, pointing out their virtues and limitations. It also proposes implements and analyzes alternative multiplicative metrics. To evaluate the performance of the proposed metrics, comparative measurements over...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // May 2009

    TDCS: A New Mechanism for Automatic Channel Assignment for Independent IEEE 802.11 Networks

    In the last few years, IEEE 802.11 applications have experienced a significant growth. This expansion creates scenarios where distinct administrators manage wireless networks. These scenarios lack of a unique authority to perform an adequate channel allocation that minimizes the performance degradation generated by medium access sharing and co-channel interference. This...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Sep 2009

    Measuring the Capacity of In-Car to In-Car Vehicular Networks

    A particular class of vehicular networks is the one that includes off-the-shelf end-user equipments (e.g., laptops and PDAs) running from the interior of vehicles, namely in-car nodes. They are subject to limited communication conditions when compared with nodes specifically designed to this context. Existing works either consider antennas installed on...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Nov 2009

    Underwater Sensor Networks: A Feasibility Study

    UnderWater Sensor Network (UWSN) is considered to be feasible and suitable for several applications. However, the characteristics of the acoustic channel must be taken into account on the evaluation of the application feasibility. The acoustic channel imposes severe limitations to the communication, such as low bandwidth, low data rates and...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jan 2011

    Analyzing a Human-based Trust Model for Mobile Ad Hoc Networks

    This paper analyzes a trust model for mobile ad hoc networks. The authors provide nodes with a mechanism to build a trust relationship with its neighbors. The proposed model considers the recommendation of trustworthy neighbors and the experience of the node itself. The interactions are limited to direct neighbors in...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Oct 2008

    CTCP: Reliable Transport Control Protocol for Sensor Networks

    This paper presents Collaborative Transport Control Protocol (CTCP), a new transport protocol for sensor networks. It aims at providing end-to-end reliability and adapts itself to different applications through a two level mechanism of reliability variation. CTCP achieves these properties using hop-by-hop acknowledgments and a storage control algorithm that operates at...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Nov 2008

    Virtual Interface for Collaborative Work With RECOLLVE

    The world globalization process, the increasing demand of communication and information technologies creates an enormous demand for collaborative applications. Aiming to support communication, information change and collaboration between users geographically distants, many CSCW (Computer Supported Cooperative Work) systems like audio and videoconference, shared editors, shared whiteboard and CVEs (Collaborative Virtual...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jan 2011

    An Efficient Data Transport Protocol for Event-Driven Field-Estimation on Sensor Networks

    This paper introduces and analyzes an Event-Driven Field-Estimation (EDFE) protocol for wireless sensor networks. In the authors' field estimation scheme the sensors derive their own notion of expected reading. Readings differing from the expected are considered events of interest and trigger a data transmission to the sink. The proposed protocol...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Jun 2011

    Distributed Database Research at COPPE/UFRJ

    The authors' group has been working with different aspects of distributed and parallel processing of databases in the relational, object-oriented, and XML data models. Classic techniques for distributed design and query processing in relational database systems have been revisited to address dynamic issues in high performance computing and flexibility challenges...

    Provided By Universidade Federal do Rio de Janeiro

  • White Papers // Mar 2012

    Local Heuristic for the Refinement of Multi-Path Routing in Wireless Mesh Networks

    The authors consider wireless mesh networks and the problem of routing end-to-end traffic over multiple paths for the same origin-destination pair with minimal interference. They introduce a heuristic for path determination with two distinguishing characteristics. First, it works by refining an extant set of paths, determined previously by a single-...

    Provided By Universidade Federal do Rio de Janeiro