Marcelo G. Rubinstein

Routing Metrics and Protocols for Wireless Mesh Networks

WMNs are low-cost access networks built on cooperative routing over a backbone composed of stationary wireless routers. WMNs must deal with the highly unstable wireless medium. Therefore, the design of algorithms that consider link quality to choose the best routes are enabling routing metrics and protocols to evolve. In this work, we analyze the state of the art in WMN metrics and propose a taxonomy for WMN routing protocols. Performance measurements for a WMN, deployed using various routing metrics, are presented and corroborate our analysis.

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 equipment (e.g., laptops and PDAs) running from the interior of vehicles: 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 top of the vehicle roof or nodes that operate in infrastructure mode. In this article, we investigate through real experiments the characteristics of links formed by in-car nodes running off-the-shelf wireless technologies such as IEEE 802.11(a/g) in ad hoc mode. We surprisingly observe that in-car nodes do show enough performance in terms of network capacity to be used in a number of applications, such as file transfer in peer-to-peer applications. Nonetheless, we identify some key performance issues and devise a number of configuration recommendations and future work directions.

A Survey on Wireless Ad Hoc Networks

A wireless ad hoc network is a collection of wireless nodes that can dynamically self-organize into an arbitrary and temporary topology to form a network without necessarily using any pre-existing infrastructure. These characteristics make ad hoc networks well suited for military activities, emergency operations, and disaster recoveries. Nevertheless, as electronic devices are getting smaller, cheaper, and more powerful, the mobile market is rapidly growing and, as a consequence, the need of seamlessly internetworking people and devices becomes mandatory. New wireless technologies enable easy deployment of commercial applications for ad hoc networks. The design of an ad hoc network has to take into account several interesting and difficult problems due to noisy, limited-range, and insecure wireless transmissions added to mobility and energy constraints. This paper presents an overview of issues related to medium access control (MAC), routing, and transport in wireless ad hoc networks and techniques proposed to improve the performance of protocols. Research activities and problems requiring further work are also presented. Finally, the paper presents a project concerning an ad hoc network to easily deploy Internet services on low-income habitations fostering digital inclusion.

Implementing the Expected Transmission Time Metric for OLSR Wireless Mesh Networks

This paper presents the design of a plug-in for the optimized link state routing (OLSR) protocol with the expected transmission time (ETT) metric and experiments in an indoor testbed. The ETT metric is implemented as a plug-in, keeping portability and facilitating its deployment on operational networks. Our design identifies important implementation issues. Additionally, we run experiments in an indoor testbed to verify the performance of our ETT plug-in. Our results show that the ETT metric has the lowest packet loss rate and the lowest round trip time among the analyzed metrics, because it reproduces link quality conditions and also takes into account physical transmission rates.

FITS: A flexible virtual network testbed architecture

In this paper, we present the design and implementation of FITS (Future Internet Testbed with Security), an open, shared, and general-purpose testbed for the Future Internet. FITS defines an innovative architecture that allows users running experiments with new mechanisms and protocols using both Xen and OpenFlow on the same network infrastructure. FITS integrates several recognized state-of-the-art features such as plane separation, zero-loss network migration, and smartcard-driven security access, to cite a few. The current physical testbed is composed of nodes placed at several Brazilian and European institutions interconnected by encrypted tunnels. Besides presenting the FITS architecture and its features, we also discuss deployment challenges and how we have overcome them.

On the impact of user mobility on peer-to-peer video streaming

Wireless mesh networks are emerging as a promising solution for ubiquitous Internet access with mobility support. In such networks, user mobility may lead to Internet gateway changes and consequently, impact the performance of continuous media applications. In this article, we investigate the impact of user mobility on the performance of peer-to-peer video applications over wireless mesh networks. Peer-to-peer video streaming applications rely on the collaborative behavior of peers to assist the source in delivering multimedia content, reduce costs, and increase the scalability of video distribution. We identify practical issues related to mobility for P2P video streaming implementation in WMNs, such as addressing and forwarding strategies. Furthermore, we evaluate the performance of different P2P streaming applications as the user walks in our WMN testbed. Results indicate mobile users benefit from the frequent shortlived connections established in modern P2P video sessions.

Scalability of a mobile agents based network management application

This paper analyzes mobile agent performance in network management compared to the client-server model used in the Simple Network Management Protocol (SNMP). Prototypes of an application that gathers MIB-II (Management Information Base-II) variables have been created and tested on a LAN. After acquiring implementation parameters related to network management and to the mobile agent infrastructure, simulation results have been obtained on large topologies similar in shape to the Internet. Response time results show that mobile agents perform better than SNMP when the number of managed elements ranges between two specific limits, an inferior bound and a superior one, determined by the number of messages that pass through a backbone and by the mobile agent size which grows along with MIB-II variables collected on network elements. The results also show that a significant improvement is achieved when the mobile agent returns or sends data to the management station after visiting a fixed number of nodes.

Analyzing voice transmission capacity on ad hoc networks

This paper analyzes voice transmission capacity on ad hoc networks by performing simulations related to delay and jitter. We evaluate the influence of QoS provision and mobility on the number of voice transmitting sources. Results show that the maximum number of voice transmissions can be increased when medium access time is reduced by means of a service differentiation mechanism applied to the MAC layer. Also, mobility and network load variations degrade the network capacity for voice transmission, mainly on multihop mobile networks.

Improving management performance by using multiple mobile agents

Mobile Agents Marcelo Gonçalves Rubinstein1;2; Otto Carlos Muniz Bandeira Duarte1 Guy Pujolle2 1 Grupo de Teleinformática e Automação Universidade Federal do Rio de Janeiro COPPE/EE P.O.Box 68504 21945-970 Rio de Janeiro Brazil {rubi, otto}@gta.ufrj.br 2 Laboratoire PRiSM Université de Versailles St-Quentin-en-Yvelines 45, Avenue des Etats-Unis 78035 Versailles France Guy.Pujolle@prism.uvsq.fr

Evaluating the Performance of a Network Management Application Based on Mobile Agents

This paper analyzes mobile agent performance in network management, comparing it with the client-server model used by the SNMP (Simple Network Management Protocol). Response time results show that the mobile agent performs better than the SNMP when the number of managed elements ranges between two limits determined by the number of messages that pass through a backbone and by the mobile agent size that grows with the variables collected on the network elements.