Vasco Pereira

DynMAC: A resistant MAC protocol to coexistence in wireless sensor networks

Abstract The growth of mobile and ubiquitous computing has increased the demand for wireless communications, which in turn raises interference levels and spectrum pollution, causing problems of network coexistence. The coexistence assurance between these devices and wireless sensor networks is a big challenge. This paper proposes a new medium access protocol, DynMAC (Dynamic MAC), which uses mechanisms of dynamic channel reconfiguration, recovery from lost links and reconfiguration of transmission parameters based on the properties of the cognitive radios, to deal with this problem. Simulations and experiments using a real WSN testbed, were performed to validate our protocol. Results show that the proposed mechanisms solve the WSN configuration problems, in noisy and interference environments, and enable the coexistence with different networks and devices operating in the same frequency spectrum, while maintaining application requirements in critical deployment scenarios.

A framework for Wireless Sensor Networks performance monitoring

A new generation of Wireless Sensor Networks (WSNs) is expanding to performance critical environments. In these new scenarios, performance must be monitored and effectively measured, in order to guarantee that the network fulfills initial expectations. However, measuring performance in WSN has not the same requirements as measuring performance in traditional networks. While new specific WSN metrics have been proposed to cope with the new specific needs of these networks, a global performance framework for evaluating WSN does not yet exist. In this paper, WSN specific communication performance needs are analyzed and, to measure them, an initial approach to a global framework of WSN performance metrics is proposed. These metrics are intended to evaluate the real-time performance of a WSN, providing the necessary measurements to indicate if the QoS expectations are being met.

A scalable localization system for critical controlled wireless sensor networks

Determining the positions of unknown position nodes, especially mobile nodes in a wireless sensor network (WSN), is critical for many applications. It helps to identify the location of the collected data and of the node carrier such as a worker, patient or vehicle. This information is often critical on supporting the right (time) decisions. This paper presents a scalable localization system targeting Controlled WSNs for critical industrial environments. Multiple positioning methods were implemented and evaluated using real testbeds setting up in both laboratory and industrial environments. The measurement used in our localization system is Received Signal Strength Indicator (RSSI). Although it is unstable and with high variance, the experimental results show that pattern matching based methods such as k-nearest neighbors, probability-based (Bayesian Theorem) and Kalman filter over probability-based produce an acceptable accuracy that is sufficient for many applications. In particular, the average distance error of 3.37m can be achieved with 50th and 80th percentile distance errors of 2 and 5.35m respectively. In addition, by carefully designing the positions of beacons it is possible to obtain the average distance error about 2.23m and 50th and 80th percentile distance errors of 0.46 and less than 4.4m respectively.

A Taxonomy of Wireless Sensor Networks with QoS

Wireless Sensor Networks (WSNs) are no longer limited to scenarios of uncontrolled performance. A new emerging range of applications demand specific Quality of Service (QoS) assurance and the support of critical scenarios. However, QoS in WSNs, and a reference model to characterize and measure it, are yet challenges to be met. In this paper, a new taxonomy of WSNs with QoS is proposed, including information and communication perspectives. The goal is to contribute to the establishment of a reference model to enable the classification of WSNs in general, including the ones with QoS, and aid in the development of a new set of QoS metrics that fully characterize this new type of networks.

FoTSeC — Human Security in Fog of Things

Today’s devices, which make up the Internet of Things (IoT) and Cyber-Physical Systems (CPS), are becoming increasingly more heterogeneous, mobile and intelligent. They represent an untapped computational resource that is available on site. By taking advantage of these devices we reduce the need for distant service providers: direct communication with neighbour devices becomes key for handling local tasks and information. Thus, the traditional cloud is “descending” to the network edge and becoming “diffused” among the client devices in both mobile and wired networks. Since single individuals are now becoming walking sensor networks, with many types of devices (smart-shirts, smartphones, smart glasses, smart watches…), human behavior begins to have a significant impact on the availability of resources. This means that security risks rise tremendously in these distributed clouds.The objective of this paper is to present an analysis of security in the future Internet - an Internet that integrates the concepts of Fog of Things (FoT) and Human in the Loop (HiTL). This paper also describes our model and the platform that we implemented for the evaluation tests.

Evaluation of an Overlay for Source-Specific Multicast in Asymmetric Routing Environments

Multicast routing is again gaining popularity with the development of new group services, like real-time multimedia streaming. The aim is to reach big groups of users with the quality level they expect, while using network resources in an efficient way. This is a challenge to be fulfilled as current multicast protocols still have difficulties in dealing with basic issues like asymmetric routing. In this work we describe and evaluate an overlay that allows the use of the source-specific multicast standard in environments with asymmetric routing. A set of tests is made in the data and control plane, to expose the pros and cons of this new proposal.

An Outlook on Physical and Virtual Sensors for a Socially Interactive Internet

The Internet keeps changing at a rapid pace, driven mainly by the emerging concepts and applications that make it aware of the physical world and responsive to user context. The Internet of Things (IoT) concept is quickly giving way to more advanced and highly interactive environments that go well beyond the mere sensing of the physical world. Today, in addition to traditional electronic devices, IoT sensing/actuating includes both software and human-based entities. This paper provides an outlook on the future of sensing/actuating approaches on the Internet at large, which we see increasingly related to all kinds of socially interactive technologies. With these objectives in mind, we propose a taxonomy to deal with the heterogeneity of sensing/actuating approaches in IoT. We also analyse the state-of-the-art of Social Sensing. Finally, we identify open issues and associated research opportunities, the main ones being the integration of all sensing approaches, the combination of social sciences, engineering, and computing as enablers of context-aware, cognitive applications and, last but not least, the unified management of large sets of very heterogeneous sensors/actuators.

A data fusion protocol for WSN performance and data retrieval

The specific capabilities of Wireless Sensor Networks (WSNs), such as fast deployment and flexibility, together with the low cost solutions that can be achieved, bring new opportunities for an all-new range of applications, far from the typical scenarios of low requirements and high redundancy. Some of these new scenarios involve the assurance of predefined performance goals. To guarantee that these goals are achieved, a careful constant monitoring must exist. However, this monitoring depletes nodes energy (especially in middle nodes that have to retransmit the information to the sink), increases interference between nodes and causes an overhead in the used bandwidth, a foreseeable result if measuring performance of a large multilevel WSN. In the protocol to be presented, data fusion is used to enhance the benefits of continuous monitoring while minimizing its implied overhead, using the specific characteristics of WSNs in its favor.

Tech4SocialChange: Technology for All

Universities and other educational institutions are sometimes accused of not being involved in real world problems, focusing more on the scientifically value of the work produced and not on the humanitarian value. A way of encapsulating the second with the first is the main goal of the Tech4SocialChange that is described here. An innovative database/repository of challenges with real impact in the world is created and given access to people with skills and knowledge to tackle them. Also the work made by researches can be stored and used in a project and the researcher gets recognition for it by becoming referenced in that project. A web application has been built as a prototype for this process and can be accessed in www.tech4socialchange.org. It has been planned and developed by a team of students and researchers of the Department of Informatics Engineering of the University of Coimbra and is currently being constantly altered according to feedback received by the testers in the same team. This paper presents an application that aims to help people that face certain challenges every day and motivate those that have the skillset, to tackle these challenges, into doing so.