José Ruela

Cross-layer design in 4G wireless terminals

The classical TCP/IP layered protocol archi- tecture is beginning to show signs of age. In order to cope with problems such as the poor performance of wireless links and mobile termi- nals, 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 be required. This article describes a framework for further enhancements of the traditional IP- based protocol stack to meet current 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.

Dynamic and automatic interworking between personal area networks using composition

Next generation communication networks will be characterized by the coexistence of multiple technologies and user devices in an integrated fashion. The increasing number of devices owned by a single user will lead to a new communication paradigm: users owning multiple devices that form cooperative networks, and networks of different users that communicate with each other, e.g., acquiring Internet access through each other. In this communication scenario no user intervention should be required and technology should seamlessly adapt to the users context, preferences, and needs. In this paper we address one of those scenarios, interworking between personal area networks, using legacy technologies and the Ambient Network and network composition concepts, herein explained. We argue that new functionalities should be introduced to enable effortless use of legacy technologies in such dynamic and heterogeneous environments

Support of IP QoS over UMTS networks

The paper presents an end-to-end quality of service (QoS) architecture suitable for IP communications scenarios that include UMTS access networks. The rationale for the architecture is justified and its main features are described, notably the QoS management functions on the terminal equipment, the mapping between IP and UMTS QoS parameters and the negotiation of these parameters.

PACE: Simple multi-hop scheduling for single-radio 802.11-based Stub Wireless Mesh Networks

IEEE 802.11-based Stub Wireless Mesh Networks (WMNs) are a cost-effective and flexible solution to extend wired network infrastructures. Yet, they suffer from two major problems: inefficiency and unfairness. A number of approaches have been proposed to tackle these problems, but they are too restrictive, highly complex, or require time synchronization and modifications to the IEEE 802.11 MAC. PACE is a simple multi-hop scheduling mechanism for Stub WMNs overlaid on the IEEE 802.11 MAC that jointly addresses the inefficiency and unfairness problems. It limits transmissions to a single mesh node at each time and ensures that each node has the opportunity to transmit a packet in each network-wide transmission round. Simulation results demonstrate that PACE can achieve optimal network capacity utilization and greatly outperforms state of the art CSMA/CA-based solutions as far as goodput, delay, and fairness are concerned.

WiFIX+: A multicast solution for 802.11-based Wireless Mesh Networks

IEEE 802.11 is currently one of the main wireless technologies enabling ubiquitous Internet access. With the growing demand for wireless Internet access and the limited 802.11 radio range, 802.11-based Wireless Mesh Networks have been proposed as a flexible and cost-effective solution to extend the radio coverage of existing network infrastructures. Many solutions have been proposed to create Wireless Mesh Networks automatically. However, they are either too complex or deal with multicast traffic inefficiently using pure flooding. We propose a simple and efficient solution, called WiFIX+, to forward multicast traffic over 802.11-based Wireless Mesh Networks. It is based on WiFIX, an existing solution targeted at unicast traffic and extends it with new mechanisms. WiFIX+ was implemented and evaluated in a laboratorial test-bed. The experimental results obtained show that it outperforms IEEE 802.11s, the reference solution for 802.11-based Wireless Mesh Networks, as far as data throughput, delay, and packet loss are concerned.

Scheduling Algorithms to support QoS and Service Integration in Sensor and Actuator Networks

In this paper we analyse and evaluate several Scheduling Algorithms that are candidates to support Quality of Service and Service Integration in Sensor and Actuator Networks. They should satisfy two main goals: to guarantee committed delays for time sensitive services, and to improve the network transmission efficiency. The algorithms are described and some results, obtained by simulation, are presented. The proposed Traffic Class Oriented Algorithm proved to be a good solution to meet the proposed objectives as well as to integrate traffic generated by Fieldbus devices and control applications in real communication networks.

Communications uncertainties in isolated multi-microgrid control systems

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.

A Protocol for Event Distribution in Next-Generation Dynamic Networks

With the increasing number of devices carried by users and the emergence of more dynamic network scenarios, new solutions have to be developed to support ubiquitous communications. The need for dynamic and transparent auto-configuration and adaptation of applications, devices and networks of devices to a wide variety of events is one of the major challenges. This paper presents a protocol to be used with notification systems, to support the registration, subscription and distribution of generic events among heterogeneous and independent entities, thus addressing the requirements of future communication scenarios.

ICT Solutions to Support EV Deployment

Numerous studies and projects have proven that the electric vehicle can offer value and services that go beyond its function as a means of transportation. The value and services can, for instance, be the reduction of charging costs, adherence to grid constraints, or adjustment of charging behavior to renewable energy production. If these possibilities are considered and supported by information and communication technologies (ICT) in due time, a large potential can be exploited.

A System Architecture for Low Bit Rate Traffic Aggregation in Control Applications

This paper describes the results of research work aimed at providing an efficient solution to the aggregation of low bit rate traffic in control applications. It includes the proposal and analysis of an architecture that integrates terminal adapters and a concentrator connected to a remote control application through a communication network. The ATM technology was selected to implement the proposed system due to its properties of multiplexing efficiency and control of packet delay. Scheduling algorithms for the terminal adapter and concentrator have been developed in order to satisfy two main goals: to guarantee committed delays for time sensitive services, and to increase the network transmission efficiency. The results, obtained by simulation, show that the system performance complies with the requirements of the majority of control applications