Ricardo Matos

Harbornet: a real-world testbed for vehicular networks

We present a real-world testbed for research and development in vehicular networking that has been deployed successfully in the seaport of Leixoes in Portugal. The testbed allows cloudbased code deployment, remote network control and distributed data collection from moving container trucks, cranes, tow boats, patrol vessels, and roadside units, thereby enabling a wide range of experiments and performance analyses. After describing the testbed architecture and its various modes of operation, we give concrete examples of its use and offer insights on how to build effective testbeds for wireless networking with moving vehicles.

Quality of experience-based routing in multi-service wireless mesh networks

We develop an optimization framework for Quality of Experience (QoE)-based routing in multi-service Wireless Mesh Networks (WMNs). The framework takes into account the heterogeneous requirements of different services delivered over a WMN, such that the overall end-user QoE is maximized under given resource constraints. We propose a novel QoE-aware double reinforcement learning strategy for dynamically computing the most efficient routes to deliver the flows of each service type. Comprehensive NS-2-based simulations demonstrate the substantial performance gains that our approach enables over conventional routing techniques such as AODV, with significant improvement over video quality.

Context-Aware Connectivity and Mobility in Wireless Mesh Networks

Wireless Mesh Networks (WMNs) have shown a high-potential to fulfill the requirements of the Next Generation Networks (NGNs). Although mobility management is crucial to develop large-scale WMNs, the heterogeneity of today’s Internet will imply a context-aware architecture in the future to optimize the users’ experience. Network virtualization, as a mean to share and isolate resources, can be used as an element to construct different types of virtual networks (overlays), each one optimized for a specific set of contexts: security, mobility, Quality of Service (QoS), cost, preferences. In this paper, we present a context-aware multi-overlay architecture that enables a user to connect to the WMN that best fits its requirements and approaches. We concentrate on how to build such an architecture: how a user can move maintaining its requirements through the re-configuration of overlays, and how context can be mapped, organized and distributed in the network nodes. We also discuss the entities and the complexity of this architecture.

Mobility management for NGN WiMAX: Specification and implementation

The anticipated deployment of IEEE 802.16-based wireless metropolitan area networks (WMANs) will usher a new era in broadband wireless communications. The adoption of the WiMAX technology for remote areas, for example, can address challenging scenarios in a cost-effective manner. While WiMAX Forum documents describe an architecture that inherently supports Quality of Service and mobility, several areas are left uncovered. We present an architecture which integrates WiMAX, Quality of Service and mobility management frameworks over heterogeneous networks, developing mechanisms for seamless handovers. Our approach takes into consideration the expected deployment of, on the one hand, the IEEE 802.21 (Media Independent Handover) proposed standard and, on the other, the IETFstandardized Next Steps in Signalling framework. The first contributions of this paper comprise a specification of the mechanisms for make-before-break vertical handovers taking Quality of Service signalling into account and the integration in a heterogeneous environment. The latter contribution is an empirical evaluation of the proposed architecture using a testbed demonstrator. We quantify the processing delays of the main components in our prototype implementation when a terminal hands over between different access technologies, demonstrating the potential of the proposed architecture.

Advanced Mobility in Broadband Wireless Access Scenarios

Although IEEE 802.16 has emerged as one of the major candidates for next generation networks, it is also clear that in the near future the combination of several technologies will be required. In this sense, the support of mobility in heterogeneous environments, addressing broadband wireless, is one of the main requirements in next generation networks. This paper evaluates an architecture based on the recently standardized IEEE 802.21 framework, integrating both mobility and Quality of Service (QoS) mechanisms, through an advanced mobility scenario using a real WiMAX testbed. This architecture supports seamless mobility in broadband wireless access (BWA) networks, integrates different technologies, such as WiMAX and Wi-Fi, and thus, it is suitable for next generation network environments. The results, obtained through real experimentation of the implemented architecture, show that it is able to provide QoS under dynamic scenarios, with fast integrated QoS and mobility signaling.

Dynamic dual-reinforcement-learning routing strategies for quality of experience-aware wireless mesh networking

The impact of transmission impairments such as loss and latency on user perceived quality (QoE) depends on the service type. In a real network, multiple service types such as audio, video, and data coexist. This makes resource management inherently complex and difficult to orchestrate. In this paper, we propose an autonomous Quality of Experience management approach for multiservice wireless mesh networks, where individual mesh nodes apply reinforcement learning methods to dynamically adjust their routing strategies in order to maximize the user perceived QoE for each flow. Within the forwarding nodes, we develop a novel packet dropping strategy that takes into account the impact on QoE. Finally, a novel source rate adaptation mechanism is designed that takes into account the expected QoE in order to match the sending rate with the available network capacity. An evaluation of our mechanisms using simulations demonstrates that our approach is superior to the standard approaches, AODV and OLSR, and effectively balances the user perceived QoE between the service flows.

Data communications over context-based WMNs: Delay performance evaluation

Wireless Mesh Networks (WMNs) have already shown high-potential to deal with the huge heterogeneity of user requirements and network resources, due to the flexibility and self-organization capabilities of their infrastructure. In this scope, we provide a novel context-based multi-virtual architecture, to be applied to wireless-friendly mesh networking, and to support user requirements on demand by the deployment of several adaptable Virtual Networks (VNs) for different context-aware purposes. In this paper, we present an analytical model for the proposed multi-VN architecture. Our envisioned goal is the provisioning, allocation and distribution of the total bandwidth of mesh links onto the available context-based VNs. We aim to provide and define the limits of our multi-VN approach, in terms of the number of VNs, attached mesh clients, and virtual nodes per VN, in order to accomplish feasible delays for different communication requirements, based on a correct provisioning of the required VN bandwidth.

Context-based connectivity over multi-virtual Wireless Mesh Networks: Analytical study

The flexibility and self-organization properties of Wireless Mesh Networks (WMNs), and the benefits arising from the split of a physical network in several context-aware Virtual Networks (VNs), are a two-fold force to deal with the huge heterogeneity of user requirements and network resources in a future Internet architecture. In this scope, we provide a novel context-aware architecture for WMNs, which supports user requirements on demand by the deployment of several adaptable VNs for different context-aware purposes. In this paper, we present an analytical model for the proposed architecture. We aim to provide and define the limits of our multi-VN approach, in terms of the number of VNs, attached mesh clients, and virtual nodes per VN, in order to accomplish feasible delays for different data or control communication requirements. Moreover, we describe and evaluate, based on a probabilistic approach, the delays involved in user connectivity establishment, which includes several management processes for the discovery, extension and update of one fitting VN for a user. Through a delay-based approach, our analytical results show the effectiveness of our architecture to deal with different communication requirements, and with distinct scenarios for user connectivity establishment.

Mobility Management Architecture for WiMAX Networks

Although WiMAX, based on the IEEE 802.16 family of standards, has emerged as one of the major candidates for next generation networks, it is also clear that in the near future, the combination of several technologies will be required. In this sense, the support of mobility in heterogeneous environments, addressing broadband wireless, is one of the main requirements in next generation networks. This chapter presents an architecture based on the recently standardized IEEE 802.21 framework, integrating both mobility and Quality of Service (QoS) mechanisms, and accommodating different wired and wireless technologies, such as WiMAX, Wi-Fi, DVB, and UMTS. This architecture supports seamless mobility in broadband wireless access (BWA) networks, and thus, it is suitable for next generation network environments. The results, obtained through real experimentation of the implemented architecture through an advanced mobility scenario using a real WiMAX testbed, show that the architecture is able to provide QoS under dynamic scenarios, with fast integrated QoS and mobility signaling.

Prediction-based connection manager for vehicular networks

Vehicular Ad-hoc NETworks (VANETs) have unique characteristics, such as the high mobility of nodes, which cause frequent losses of connectivity, turning technology and network selection into a complex problem. Moreover, due to the instability of networks and its fast change, this network selection requires information of the networks in advance, so that it can predict the quality of the networks to connect. This paper proposes a predictive connection manager that is able to choose in advance the best network and technology a vehicle can connect to. This approach will use the information of previous connections to a station or road side unit, such as the throughput and amount of transferred traffic, and combines this information with sensing information of the quality of available networks. With both previous and current information, it will choose the network that has been able to provide the best performance in previous connections and remains with a good quality. The results of the proposed approach, tested in a real vehicular network deployed in Portugal, show that key performance metrics are improved, such as connection range, throughput and the number of handovers, with a general improvement on connection stability.