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Publications

Publications by Rui Manuel Lima

2015

Adaptive Broadcast Cancellation Query Mechanism for Unstructured Networks

Authors
Lima, R; Baquero, C; Miranda, H;

Publication
2015 9th International Conference on Next Generation Mobile Applications, Services and Technologies (NGMAST 2015)

Abstract
The availability of cheap wireless sensors boosted the emergence of unstructured networks using wireless technologies with decentralised administration. However, a simple task such as learning the temperature needs a discovery service to find a thermometer among all the sensors. In general, resource discovery relies on flooding mechanisms that waste energy and compromises system availability. Energy efficient strategies limit the exploration area, but with a significant impact on latency. The paper proposes ABC (Adaptive Broadcast Cancellation), a new algorithm that uses the knowledge acquired in previous discoveries to accelerate queries towards the resource. Knowledge is stored in a variation of Bloom filters, thus contributing for an efficient utilization of the sensors limited memory.

2013

Broadcast cancellation in search mechanisms

Authors
Lima, R; Baquero, C; Miranda, H;

Publication
Proceedings of the 28th Annual ACM Symposium on Applied Computing, SAC '13, Coimbra, Portugal, March 18-22, 2013

Abstract
Searching for resources over unstructured networks is usually supported by broadcast communication primitives. Ideally, the broadcast process should be cancelled as soon as possible after a successful discovery, to avoid flooding the entire network. However, cancelling an ongoing broadcast is challenging and may increase the number of exchanged messages. In this paper, we compare the cancellation mechanisms used by BERS and BERS* with new proposed cancellation approaches BCIR and BCIR*. The formulation of a simplified analytical model and the simulation results show that: i) it is possible to reduce the number of retransmitted messages, without increasing the latency observed in BERS*; and ii) BCIR is more energy efficient, which can contribute to extend the availability of mobile battery powered devices. Copyright 2013 ACM.

2007

ClusterUL Resource sharing under EGEE: an example

Authors
Silva, F; Lima, R;

Publication
IBERGRID: 1ST IBERIAN GRID INFRASTRUCTURE CONFERENCE PROCEEDINGS

Abstract
This paper contextualizes project EGEE: Grid computing, Virtual Organizations, clusters and authorities. The thematic included in Grid computing is based in a worldwide spread network, recurring to processing units and mass storage device to solve complex problems of multidiscipline areas of research. The high demand for Grid computing resources started with High Energy Physics area, conducting to an infinity of areas that transformed their problems to Grid computing language. The EGEE (Enabling Grids for E-science in Europe) is a European project that allies the search for knowledge using Grid infrastructures. In order to maintain the EGEE project sustainability, it's always necessary to attract more resources and researchers.

2007

Grid e-Services for Multi-Layer SOM Neural Network Simulation

Authors
Lima, R; Silva, R;

Publication
IBERGRID: 1ST IBERIAN GRID INFRASTRUCTURE CONFERENCE PROCEEDINGS

Abstract
In this paper it is presented a framework environment for neural network simulation through the development of e-Services running on the EGEE Grid infrastructure. Parallel computing and distribution of jobs can be synchronized by the e-Service through a web interface. This interface provides an easy to use environment and can be requested over the internet. This simulation tool is based on a neural network agent approach that implements the e-Service using software agents and services offered by the Grid middleware. As an example, it is hereby presented an e-Service based on an implementation of the Self-Organizing Map (SOM) neural network algorithm which indicates that significant improvements in performance can be gained. In particular, users of SOM neural networks can take advantage of these widely available computer networks to obtain the computing power that they require.

2012

Stopping ongoing broadcasts in large MANETs

Authors
Lima, R; Baquero, C; Miranda, H;

Publication
Proceedings of the 1st European Workshop on AppRoaches to MObiquitous Resilience, ARMOR '12, Sibiu, Romania, May 8-11, 2012

Abstract
Broadcast is a communication primitive building block widely used in mobile ad-hoc networks (MANETs) for the exchange of control packets and resource location for upper level services such as routing and management protocols. Flooding is the most simple broadcast algorithm, but it wastes a lot of energy and bandwidth, as flooding leads to many redundant radio transmissions. An optimization to flooding is to contain it, once the resource has been found. In this paper, we compare the impact on the latency and power consumption of four competing approaches for flooding containment. The results show that stopping ongoing broadcasts can achieve promising performance increases over other flooding base techniques, when applied in large scale MANETs with scarce power resources. In addition, results show that both network topology and the number of copies of the resource influence differently the performance of each searching approach. © 2012 ACM.