Jose Ruela - Academia.edu (original) (raw)

Papers by Jose Ruela

IGI Global eBooks, 2009

ABSTRACT Part I: Overview of Access Network Architectures 1 Introduction 2 Overview of PON Enabli... more ABSTRACT Part I: Overview of Access Network Architectures 1 Introduction 2 Overview of PON Enabling Technologies 3 Access Network Architectures based on TDMA PON 4 Emergence of Ethernet PON Part II: EPON Architecture 5 EPON Overview 6 Logical Topology Emulation 7 Laser Control Function 8 Multi-Point Control Protocol: A Formal Specification 9 Forward Error Correction Part III: System-Level Issues 10 EPON Encryption Mechanism 11 Path Protection in EPON Part IV: EPON Performance 12 Baseline Efficiency 13 Discovery Slot Allocation 14 EPON with Static Slot Assignment 15 EPON with Dynamic Slot Assignment 16 Support for Differentiated Classes of Service 17 Objectives of EPON Scheduling Algorithm 18 Cousin-Fair Hierarchical Scheduling in EPON 19 Conclusion Appendix A: Characteristics of Network Traffic Appendix B: Synthetic Traffic Generation Bibliography

2005 International Conference on Future Power Systems, 2005

This paper describes the Micro Grid Management System developed using agent based technologies an... more This paper describes the Micro Grid Management System developed using agent based technologies and its application to the effective management of generation and storage devices connected to a LV network forming a micro grid. The micro grid is defined as a set of generation, storage and load systems electrically connected and complemented by a communication system to enable control actions and follow up surveillance. The effectiveness of the proposed architecture has been tested on laboratory facilities under different micro grid configurations. The performance and scalability issues related to the agent framework have also been considered and verified.

Lecture Notes in Computer Science, 1997

Today's available solutions for the production of digitally compressed TV programmes require succ... more Today's available solutions for the production of digitally compressed TV programmes require successive decoding and re-coding operations due both to the multiplicity of digital formats currently in use for signal acquisition and to technology limitations. This has the consequence of increasing the production costs and of reducing the overall signal quality. The ability of using compression also at the production stage will contribute to improve the overall signal quality and to reduce storage requirements and associated costs. The ATLANTIC project (ACTS 078) is developing a digital studio for the production of TV programmes using the MPEG-2 format throughout the entire process, from the input of the studio to final programme distribution. EXPO '98, the next international exposition to be held in Lisbon, has been identified as an ideal showcase for audiovisual services developed by ACTS projects. The ATLANTIC project will provide basic infrastructures and technology for compressed-based TV programme production and distribution of audiovisual information and entertainment services for the entire EXPO site. This paper describes the studio reference model of the ATLANTIC project and the role ATLANTIC will be playing within the planned demonstrations of ACTS projects at EXPO '98.

Gostaria de agradecer aos meus orientadores: Professor José Ruela e Engenheiro Carlos Pinho pela ... more Gostaria de agradecer aos meus orientadores: Professor José Ruela e Engenheiro Carlos Pinho pela importante coordenação neste projeto e ajuda no desenvolvimento deste documento; e Professor Manuel Ricardo pela disponibilidade e acessibilidade que ofereceu. Queria agradecer também ao Engenheiro Filipe Ribeiro por toda a ajuda e suporte no desenvolvimento da parte mais técnica do trabalho. Um agradecimento ao Professor Rui Campos pela sua contribuição na discussão e resolução de problemas neste projeto. Agradeço aos meus pais pela minha educação e pela pessoa que sou hoje. Por fim, agradecer à minha namorada Rita Mendes e aos meus amigos que nunca deixam de acreditar em mim e todos os dias me inspiram.

Ad Hoc Networks

Aerial networks, composed of Unmanned Aerial Vehicles (UAVs) acting as Wi-Fi access points or cel... more Aerial networks, composed of Unmanned Aerial Vehicles (UAVs) acting as Wi-Fi access points or cellular base stations, are emerging as an interesting solution to provide on-demand wireless connectivity to users, when there is no network infrastructure available, or to enhance the network capacity. This article proposes a traffic-aware topology control solution for aerial networks that holistically combines the placement of UAVs with a predictive and centralized routing protocol. The synergy created by the combination of the UAV placement and routing solutions allows the aerial network to seamlessly update its topology according to the users' traffic demand, whilst minimizing the disruption caused by the movement of the UAVs. As a result, the Quality of Service (QoS) provided to the users is improved. The components of the proposed solution are described and evaluated individually in this article by means of simulation and an experimental testbed. The results show that all the components improve the QoS provided to the users when compared to the corresponding baseline solutions.

The increasing complexity of recent Wi-Fi amendments is making optimal Rate Adaptation (RA) a cha... more The increasing complexity of recent Wi-Fi amendments is making optimal Rate Adaptation (RA) a challenge. The use of classic algorithms or heuristic models to address RA is becoming unfeasible due to the large combination of configuration parameters along with the variability of the wireless channel. Machine Learning-based solutions have been proposed in the state of art, to deal with this complexity. However, they typically use complex models and their implementation in real scenarios is difficult. We propose a simple Deep Reinforcement Learning approach for the automatic RA in Wi-Fi networks, named Data-driven Algorithm for Rate Adaptation (DARA). DARA is standard-compliant. It dynamically adjusts the Wi-Fi Modulation and Coding Scheme (MCS) solely based on the observation of the Signal-to-Noise Ratio (SNR) of the received frames at the transmitter. Our simulation results show that DARA achieves up to 15\% higher throughput when compared with Minstrel High Throughput (HT) and equal...

2018 14th International Conference on Wireless and Mobile Computing, Networking and Communications (WiMob), 2018

The advent of small and low-cost Unmanned Aerial Vehicles (UAVs) is paving the way to use swarms ... more The advent of small and low-cost Unmanned Aerial Vehicles (UAVs) is paving the way to use swarms of UAVs to perform missions such as aerial video monitoring and infrastructure inspection. Within a swarm, UAVs communicate by means of a Flying Multi-hop Network (FMN), which due to its dynamics induces frequent changes of network topology and quality of the links. Recently, UAVs have also been used to provide Internet access and enhance the capacity of existing networks in Temporary Events. This brings up additional routing challenges not yet addressed, in order to provide always-on and high capacity paths able to meet the Quality of Service expected by the users.This paper presents RedeFINE, a centralized routing solution for FMNs that selects high-capacity paths between UAVs and avoids communications disruptions, by defining in advance the forwarding tables and the instants they shall be updated in the UAVs; this represents a major step forward with respect to traditional routing protocols. The performance evaluation of RedeFINE shows promising results, especially regarding Throughput and Packet Delivery Ratio, when compared with state of the art routing solutions.

Cross-layer j manager ~ TCP/IP layered protocol architecture is beginning to show signs of age. I... more Cross-layer j manager ~ TCP/IP layered protocol architecture is beginning to show signs of age. In The classical TCPilP layered protocol architecture is beginning to show signs of age. In order to cope with. problems such as the poor performance of wireless links and mobile terminals, including the high error rate of wireless network interfaces, power saving requirements, quality of service, and an increasingly dynamic network environment, a protocol architecture that considers cross-layer interactions seems to he required. This article describes a framework for further enhancements of the traditional IPbased protocol stack to meet currcnt and future requirements. Known problems associated with the strictly layered protocol architecture are summarized and classified, and a first solution involving cross-layer design is proposed.

OCEANS 2017 - Aberdeen, 2017

The growth of the Blue Economy has been boosted by a set of traditional and new activities includ... more The growth of the Blue Economy has been boosted by a set of traditional and new activities including maritime transportation, fisheries, environmental monitoring, deep sea mining, and inspection missions. These activities are urging for a cost-effective broadband communications solution capable of supporting both above and underwater missions at remote ocean areas, since many of them rely on an ever-increasing number of Autonomous Surface Vehicles (ASV), Autonomous Underwater Vehicles (AUV) and Remote Operated Vehicles (ROV), which need to transmit large amounts of data to shore. The BLUE-COM+ project has considered the usage of helium balloons to increase the antenna height, and overtake the earth curvature and achieve Fresnel zone clearance, combined with the use of sub-GHz frequency bands to enable long range communications. In this paper we present the results obtained in three sea trials. They show that the BLUECOM+ architecture is capable of supporting human and system activities at remote ocean areas by enabling Internet access beyond 50 km from shore, live video conference calls with the quality of experience available on land, and real-time data upload to the cloud by ASVs, AUVs and ROVs using standard access technologies with bitrates above 1 Mbit/s.

2019 IEEE Symposium on Computers and Communications (ISCC), 2019

The growing demand for broadband communications anytime, anywhere has paved the way to the usage ... more The growing demand for broadband communications anytime, anywhere has paved the way to the usage of Unmanned Aerial Vehicles (UAVs) for providing Internet access in areas without network infrastructure and enhancing the performance of existing networks. However, the usage of Flying Multihop Networks (FMNs) in such scenarios brings up significant challenges concerning network routing, in order to permanently provide the Quality of Service expected by the users. The problem is exacerbated in crowded events, where the FMN may be formed by many UAVs to address the traffic demand, causing interflow interference within the FMN. Typically, estimating inter-flow interference is not straightforward and requires the exchange of probe packets, thus increasing network overhead. The main contribution of this paper is an inter-flow interference-aware routing metric, named I2R, designed for centralized routing in FMNs with controllable topology. I2R does not require any control packets and enables the configuration of paths with minimal Euclidean distance formed by UAVs with the lowest number of neighbors in carrier-sense range, thus minimizing inter-flow interference in the FMN. Simulation results show the I2R superior performance, with significant gains in terms of throughput and end-to-end delay, when compared with state of the art routing metrics.

The classical TCPilP layered protocol architecture is beginning to show signs of age. In order to... more The classical TCPilP layered protocol architecture is beginning to show signs of age. In order to cope with. problems such as the poor manager ~ performance of wireless links and mobile terminals, including the high error rate of wireless network interfaces, power saving requirements, quality of service, and an increasingly dynamic network environment, a protocol architecture that considers cross-layer interactions seems to he required. This article describes a framework for further enhancements of the traditional IPbased protocol stack to meet currcnt and future requirements. Known problems associated with the strictly layered protocol architecture are summarized and classified, and a first solution involving cross-layer design is proposed. Cross-layer j

ArXiv, 2019

The inefficiency of the fundamental access method of the IEEEE 802.11 standard is a well-known pr... more The inefficiency of the fundamental access method of the IEEEE 802.11 standard is a well-known problem in scenarios where multiple long range and faulty links compete for the shared medium. The alternatives found in the literature are mostly focused on point-to-point and rarely on long range links. Currently, there is no solution optimized for maritime scenarios, where the point-to-multipoint links can reach several tens of kilometers, while suffering from degradation due to the harsh environment. This paper presents a novel MAC protocol that uses explicit signalling messages to control access to the medium by a central node. In this solution, this role is played by an Access Point that sends token messages addressed to each associated station, which is granted exclusive access to the medium and assigned a number of credits; after sending its own packets (if any), a station must release control of the token. Simulation results show that this mechanism has superior performance in poi...

Proceedings of the Workshop on ns-3, 2021

Today, wireless networks are operating in increasingly complex environments, impacting the evalua... more Today, wireless networks are operating in increasingly complex environments, impacting the evaluation and validation of new networking solutions. Simulation, although fully controllable and easily reproducible, depends on simplified physical layer and channel models, which often produce optimistic results. Experimentation is also influenced by external random phenomena and limited testbed scale and availability, resulting in hardly repeatable and reproducible results. Previously, we have proposed the Trace-based Simulation (TS) approach to address the problem. TS uses traces of radio link quality and position of nodes to accurately reproduce past experiments in ns-3. Yet, in its current version, TS is not compatible with scenarios where Multiple-In-Multiple-Out (MIMO) is used. This is especially relevant since ns-3 assumes perfectly independent MIMO radio streams. In this paper, we introduce the Trace-based Wi-Fi Station Manager Model, which is capable of reproducing the Rate Adaptation of past Wi-Fi experiments, including the number of effective radio streams used. To validate the proposed model, the network throughput was measured in different experiments performed in the w-iLab.t testbed, considering Single-In-Single-Out (SISO) and MIMO operation using IEEE 802.11a/n/ac standards. The experimental results were then compared with the network throughput achieved using the improved TS and Pure Simulation (PS) approaches, validating the new proposed model and confirming its relevance to reproduce experiments previously executed in real environments.

Proceedings of the 2020 Workshop on ns-3, 2020

In wireless networking R&D we typically depend on simulation and experimentation to evaluate and ... more In wireless networking R&D we typically depend on simulation and experimentation to evaluate and validate new networking solutions. While simulations allow full control over the scenario conditions, real-world experiments are influenced by external random phenomena and may produce hardly repeatable and reproducible results, impacting the validation of the solution under evaluation. Previously, we have proposed the Trace-based Simulation (TS) approach to address the problem. TS uses traces of radio link quality and position of nodes to accurately reproduce past experiments in ns-3. Yet, in its current version, the TS approach is not compatible with scenarios where the radio spectrum is shared with concurrent networks, as it does not reproduce their channel occupancy. In this paper, we introduce the InterferencePropagationLossModel and a modified MacLow to allow reproducing the channel occupancy experienced in past experiments. To validate the proposed models, the network throughput was measured in different experiments performed in the w-iLab.t testbed, controlling the channel occupancy introduced by concurrent networks. The experimental results were then compared with the network throughput achieved using the improved TS approach, the legacy TS approach, and pure simulation, validating the new proposed models and confirming their relevance to reproduce experiments previously executed in real environments.

2016 Power Systems Computation Conference (PSCC), 2016

Smart grids aim at ensuring a secure, reliable and efficient operation of power systems and for t... more Smart grids aim at ensuring a secure, reliable and efficient operation of power systems and for that purpose they need communications infrastructures capable of meeting different requirements. Current and emerging wireless multi-hop solutions based on standard technologies are strong candidates for communications networks associated and integrated with electric distribution grids but a suitable methodology to evaluate and deploy them is missing. This paper presents a holistic methodology supported by contextual information used to generate different scenarios of distribution grids and to evaluate and deploy wireless communications networks for smart grids. Simulation results show that the methodology is suitable for the evaluation of wireless multi-hop networks in the smart grid context and prove that the performance of such networks meets the expected requirements of different applications.

2014 Power Systems Computation Conference, 2014

Microgrids have been explored as active cells capable of providing enhanced control schemes towar... more Microgrids have been explored as active cells capable of providing enhanced control schemes towards a more secure, reliable and efficient operation of LV distribution networks or MV networks when aggregated in a multi-microgrid. These structures, within the smart grid concept, rely on a communications infrastructure that introduces uncertainty in the data exchange process. In this paper such uncertainty is evaluated considering a multi-microgrid operating in isolated mode.

Electric Vehicle Integration into Modern Power Networks, 2012