Rui Manuel Rocha

Large-scale space projects rely on a thorough Assembly, Integration, and Verification (AIV) process to provide the upmost reliability to spacecraft. While this has not traditionally been the case with CubeSats, their increasing role in space science and technology has led to new verification approaches, including in educational CubeSats. This work describes the integration and verification approach for ISTSat-1, which is an educational CubeSat from the Instituto Superior Técnico in Portugal that partially discards the typical stage-gate approach to spacecraft development in favor of a more iterative approach, allowing for the system-level verification of unfinished prototypes. Early verification included software functional testing on a flatsat model, thermal vacuum and vibration testing on a battery model, ionizing radiation testing on the on-board computer, and non-ionizing radiation (EMC) testing on all subsystems. The testing of functional prototypes at an early development stage led to uncovering system-level errors that would typically require hardware redesign at a later project stage. The team considers the approach to be useful for educational projects that employ a small, co-located team with low non-recurring engineering costs.

The signal quality of Wi-Fi networks tends to decrease in settings with high client density, bad Access Point (AP) coverage, or radio interferences from the presence of rogue APs (RAPs). This work proposes a novel solution for monitoring of the Wi-Fi network through a crowdsensing approach, combining data collected from user devices and fixed monitoring nodes. The developed system assesses Wi-Fi signal quality, detects and assails rogue APs, assesses the number of clients per area and the RAPs impact on the signal surrounding them. The system, tested on a large faculty building with over 1,000 Wi-Fi users, proved to be efficient, simple to use and adaptable, being easily deployed in any large and multi-floored building and network.

As machine-to-machine networks become larger and more pervasive, manual configuration and discovery of resources will become intractable. It is in this context that we propose the RDL, a Resource Description Language that represents a uniform way of describing embedded resources, allowing them to be shared and enabling a new class of resource-aware applications. The RDL can describe a wide range of resources, characterizing individual nodes or entire networks. It can contribute to overcome performance issues in dense networks or mobility-driven problems in highly dynamic machine-to-machine topologies by providing the means for self-adaptability and manageability, as well as opportunistic resource sharing in context-aware embedded applications. The main goal for the RDL is to define a reusable and extensible resource description specification, which can only be reached if the resources are described in a standardized format. To illustrate the feasibility of our approach, we have also developed a Java implementation of the RDL framework, as well as a TinyOS implementation targeting resource constrained platforms. Furthermore, we have developed Modulus, a modular middleware for the development of resource-aware distributed applications.

A flexible Wireless Sensor Network platform for implementation of diverse applications has been developed and deployed at Instituto Superior Tecnico – Technical University of Lisbon (IST-TUL). Since its initial deployment in 2007, this testbed has grown steadily, supporting new nodes, applications and experiments. However, some initial problems, which were solved on an ad hoc basis, were becoming more serious as the network spanned throughout the campus. Major issues, like global power management, have to be tackled not only with traditional protocol level approaches but also from a system's viewpoint, providing solutions capable of guaranteeing a consistent testbed. We discuss the main issues related with the development of power management solutions, presenting our architecture, design choices and implementation, and address the lessons learnt from its integration. Experimental evaluation of our solution has shown considerable energy savings, extending network lifetime by up to nine times.

Combining wireless sensor networks (WSNs) with delay-tolerant networking (DTN) has the potential to extend their use in a multitude of previously impossible applications. However, and despite numerous proposed solutions, there is still wide debate as to how to best route messages in these networks and, more importantly, how to do it in an energy-efficient way. This paper proposes CHARON (Convergent Hybrid-replication Approach to Routing in Opportunistic Networks), an approach that focuses on maximizing efficiency in addition to delivery statistics. CHARON uses delay as a routing metric, and provides basic QoS mechanisms, with both a quasi-single-copy mode for general traffic and a multi-copy mode for urgent data. It also integrates time synchronization and radio power management mechanisms. Simulation results show that it is able to achieve good delivery statistics with lower overhead than comparable solutions.

From agriculture to industry, from the office to our homes, Wireless Sensor Networks (WSNs) are becoming a part of everyday life in many application areas. In typical WSN applications, the sensor nodes are fixed and interconnected amongst each other and to the outside world on a permanent basis. However, in certain types of applications, where the area to sense is wide and sensors are sparsely distributed, a different approach can be used. A mobile node can roam in the sensor field to collect and exchange information with disconnected clusters of nodes. This paper addresses the limitations of real world sensor networks with such moving nodes. To understand the behavior of a typical WSN node in these situations, two types of experiments were conducted. To begin with, the communication performance was measured, in a static scenario, establishing the base-line behavior. Afterwards, a second set of experiments was carried out with fast moving nodes at different speeds. Finally, the results of the two experiments were compared and analyzed.