An Ambient Assisted Living (AAL) mobile health application solution with biofeedback based on body sensors is very useful to perform a data collection for diagnosis in patients whose clinical conditions are not favourable. This system allows comfort, mobility, and efficiency in all the process of data collection providing more confidence and operability. A physical fall may be considered something natural in the life span of a human being from birth to death. In a perfect scenario it would be possible to predict when a fall will occur in order to avoid it. Falls represent a high risk for senior people health. Those falls can cause fractures or injuries causing great dependence and debilitation to the elderly and even death in extreme cases. Falls can be detected by the accelerometer included in most of the available mobile phones or portable digital assistants (PDAs). To reverse this tendency, it can be obtained more accurate data for patients monitoring from the body sensors attached to the human body (such as, electrocardiogram (ECG), electromyography (EMG), blood volume pulse (BVP), electro dermal activity (EDA), and galvanic skin response (GSR)). Then, this dissertation reviews the related literature on this topic and introduces a mobile solution for falls prevention, detection, and biofeedback monitoring. The proposed system collects sensed data that is sent to a smartphone or tablet through Bluetooth. Mobile devices are used to process and display information graphically to users. The falls prevention system uses collected data from sensors in order to control and advice the patient or even to give instructions to treat an abnormal condition to reduce the falls risk. In cases of symptoms that last more time it can even detect a possible disease. The signal processing algorithms plays a key role in the fall prevention system. These algorithms in real time, through the capture of biofeedback data, are needed to extract relevant information from the signals detected to warn the patient. Monitoring and processing data from sensors is realized by a smartphone or tablet that will send warnings to users. All the process is performed in real time. These mobile devices are also used as a gateway to send the collected data to a Web service, which subsequently allows data storage and consultation. The proposed system is evaluated, demonstrated, and validated through a prototype and it is ready for use.

This paper investigates the performances achievable by WiMAX networks deployed in various sectorization configurations, with and without relay stations (RSs). Further, it studies the dynamic adjustment of the configuration to serve traffic loads at different times of the day while maximising the use of opportunistic sleep modes by relays in conjunction with cell zooming, thereby saving energy. The configuration changes and invocation of opportunistic sleep modes also take into account coverage constraints. This paper first reports extensive propagation measurements that have been undertaken in Covilha˜, a hilly area of Portugal which presents a realistic and challenging propagation scenario. Using this scenario as the topographical basis, practical cellular planning results are then obtained and compared, using the dominant path and ray tracing (RT) functionalities of WinpropTM. It is shown that without RSs present, the supported throughput is lower in practice because coverage is not 100 %. Further, for the case with omnidirectional cells, coverage reduces to only approximately 60 % if RSs go into sleep mode, and for the tri-sectored cells case coverage drops from 95.75 to 81.90 % (based on RT calculations) if RSs go into sleep mode. There is, however, still a reasonable economic performance in all cases. Additional results demonstrate that savings typically of 47.6 % in RSs’ average power consumption can be achieved. These savings are shown to result in a financial saving for the operator of 10 % of the combined operational and maintenance cost. However, it is observed that such solutions have to be used cautiously in hilly regions due to challenges in maintaining coverage.

IEEE 802.15.4 Medium Access Control (MAC) layer does not include the Request-To-Send/Clear-To-Send (RTS/CTS) handshake mechanism, in order to overcome the hidden node problem that affects Wireless Sensor Networks (WSNs). In this paper we propose and analyse the use of RTS/CTS in IEEE 802.15.4 for the nonbeacon-enable mode. The proposed solution shows that by considering the RTS/CTS mechanism combined with packet concatenation we improve the network performance in terms of maximum throughput, minimum delay and bandwidth effciency. In IEEE 802.15.4 with RTS/CTS, the backoff procedure process is not repeated for each data packet sent unlike the basic access mode of IEEE 802.15.4, but only for each RTS/CTS set. Therefore, the channel utilization is maximized by decreasing the deferral time period before transmitting a data packet. Our work introduces an analytical model capable of accounting the retransmission delay and the maximum number of backoff stages. The successful validation of our analytical model is carried out by comparison against simulation results by using the OMNeT++ simulator.

The use of wearable biomedical sensors for the continuous monitoring of physiological signals will facilitate the involvement of the patients in the prevention and management of chronic diseases. The fabrication of small biomedical sensors transmitting physiological data wirelessly is possible as a result of the tremendous advances in ultra-low power electronics and radio communications. However, the widespread adoption of these devices depends very much on their ability to operate for long periods of time without the need to frequently change, recharge or even use batteries. In this context, energy harvesting (EH) is the disruptive technology that can pave the road towards the massive utilisation of wireless wearable sensors for patient self-monitoring and daily healthcare. Radio-frequency (RF) transmissions from commercial telecommunication networks represent reliable ambient energy that can be harvested as they are ubiquitous in urban and suburban areas. The state-of-the-art in RF EH for wearable biomedical sensors specifically targeting the global system of mobile 900/1800 cellular and 700 MHz digital terrestrial television networks as ambient RF energy sources are showcased. Furthermore, guidelines for the choice of the number of stages for the RF energy harvester are presented, depending on the requirements from the embedded system to power supply, which is useful for other researchers that work in the same area. The present authors' recent advances towards the development of an efficient RF energy harvester and storing system are presented and thoroughly discussed too.

The IEEE 802.15.4 standard has been widely accepted as the de facto standard for Wireless Sensor Networks (WSNs), since it provides ultra-low complexity, cost and energy consumption for low-data rate wireless connectivity. However, one of the fundamental reasons for the IEEE 802.15.4 Medium Access Control (MAC) inefficiency is overhead. In the context of our research, we demonstrate that WSNs may benefit from packet concatenation. In this paper we introduce and study the employment of a block acknowledgment mechanisms in order to achieve enhanced channel efficiency in IEEE 802.15.4 nonbeacon-enabled networks for both the Chirp Spread Spectrum (CSS) and Direct Sequence Spread Spectrum (DSSS) Physical (PHY) layers for the 2.4 Industrial, Scientific and Medical (ISM) frequency band. The proposal of the two new innovative MAC sublayer mechanisms can also be considered as a future possible contribution to the standard itself. The throughput and delay performance is mathematically derived under ideal conditions, (i.e., a channel environment without transmission errors). The performance of the proposed schemes is compared against the IEEE 802.15.4 standard through extensive simulations by employing the OMNeT++ simulator. We demonstrate that, for both PHY layers, the network performance is significantly improved in terms of throughput, end-to-end delay and bandwidth efficiency.

This paper determines the cost/revenue performance of a mobile communication system in an IMT-Advanced scenario with integrated Common Radio Resource Management (iCRRM). The iCRRM performs classic CRRM functionalities jointly with Spectrum Aggregation (SA), being able to switch users between non-contiguous frequency bands. The SA scheduling is obtained with an optimized General Multi-Band Scheduling (GMBS) algorithm with the aim of cell throughput maximization. In particular, we investigate the dependence of the throughput on the cell coverage distance for the allocation of users over the 2 and 5 GHz bands for a single operator scenario under a constant average Signal to Interference-plus-Noise Ratio (SINR), for the same type of Radio Access Technology and both frequency bands. The operator has the availability of a non-shared 2 GHz band and has access to part (or all) of a shared frequency band at 5 GHz. An almost constant gain near 30 % was obtained with the proposed optimal solution compared to a system where users are first allocated in one of the two bands and later not able to handover between the bands. It is shown that the profit in percentage terms decreases as the cell radius increases. These results allow for evaluating the impact of the revenue from the channel in the total revenue and in the profit, defined as the difference between revenues and costs, in percentage. Maximum profits of about 1270, 585 and 240 % have been obtained for prices of 0.10, 0.05 and 0.025 €/MByte, respectively, when iCRRM is employed, while profits of 990, 440, and 170 % have been reached with no iCRRM, i.e., simple CRRM. Finally, an energy efficiency strategy is proposed and analyzed, showing that there is significant transmission power saving potential through the opportunistic reallocation scheme.

This work proposes a new scheme to coordinate the medium access of single-radio unlicensed users in a decentralized cognitive radio network. The proposed solution is based on two different stages. Unlicensed users randomly define the medium access sequence during the first stage and part of the second one. Then the nodes simply transmit their packets according to the reserved sequence. The performance of the proposed scheme is theoretically characterized in terms of the throughput achieved by unlicensed users and validated through simulation. Since a random access mechanism is used in the both stages, we also compare the performance of our proposal with a pure Slotted Aloha access scheme and an improved version of it. By comparing their performance, we conclude that the proposed scheme exhibits significant gains in terms of the throughput achieved by unlicensed users, and it can be recommended as a viable solution for future decentralized single radio cognitive networks.

Actualmente, os Ambientes Inteligentes (AmI) estão a emergir através da convergência entre as redes de comunicação sem fios, a microelectrónica e a Internet. Este tipo de aplicações cria novas perspectivas no âmbito da partilha de informação dentro das sociedades humanas, ao mesmo tempo que surgem ideias inovadoras envolvendo espaços, objectos e entidades físicas com as quais lidamos diariamente. Com os AmI e as redes de comunicação, a partilha de informação passa a englobar coisas físicas que geram e disponibilizam dados sobre si mesmas. Nesta dissertação foram enquadradas as tecnologias de informação e a convergência entre redes de comunicação sem fios heterogéneas que suportam as aplicações dos AmI. Daqui surgem dois conceitos extremamente relevantes: a Internet of Things (IoT) e as comunicações Machine-to-Machine (M2M). A IoT, além de fornecedora de serviços virtuais, integra objectos físicos com representação virtual, interligados em rede para partilharem informação sobre vários factores. As comunicações M2M resultam da convergência de redes heterogéneas que permitem a comunicação directa entre dispositivos e objectos sem qualquer intervenção humana. A IoT é no fundo a base principal para a interligação das várias redes M2M entre objectos. As comunicações M2M são formadas por dois tipos de sub-redes: redes capilares e redes celulares. As redes capilares são compostas pelos dispositivos e os objectos embutidos nos ambientes inteligentes, que geram e difundem dados. As redes celulares são a espinha dorsal para a partilha destes dados através da Internet e centros de dados. As redes de sensores sem fios (RSSF), em conjunto com a norma IEEE 802.15.4, foram abordadas nesta dissertação para integrarem as redes capilares. As RSSF são redes com ritmos de transmissão e potência reduzida, que possibilitam o desenvolvimento de uma vasta variedade de aplicações AmI. Foi elaborado um estudo sobre a eficiência energética dos dispositivos RSSF disponíveis no mercado. A interligação das RSSF com a Internet é possível através da atribuição de endereços IPv6 aos dispositivos das RSSF. A camada de adaptação 6LoWPAN possibilita a atribuição de endereços IPv6 com overheads bastante reduzidos. Para permitir a máxima eficiência das RSSF, integradas com a IoT, foi adoptado o protocolo de encaminhamento RPL, desenvolvido no âmbito das redes 6LoWPAN. A contribuição principal desta dissertação centra-se na identificação e resolução de problemas ao nível do encaminhamento nas RSSFs, e no estudo de algumas métricas utilizadas para calcular o custo dos encaminhamentos entre nós. O protocolo RPL foi implementado no simulador OMNeT++ com o objectivo de analisar os resultados e os comportamentos das métricas de custo ETX, HOP-COUNT e RSSI. O ETX atingiu os melhores resultados para o débito binário útil, entre 75 % e 95 %, enquanto o HOP-COUNT tem resultados abaixo do 50 %. Contudo, o HOP-COUNT tem tempos de convergência superiores e latências inferiores. Com o RSSI obtêm-se resultados modestos e provou-se ser esta uma métrica de custo bastante precisa e equilibrada em todos os resultados.

This dissertation presents the design and construction of a platform for the implementation of an automatic and interactive message exchanging system using Short Message Service (SMS), also known as texting, created to support a research on the Psychology field. The research included researchers from the Psychology and Education Department and the Computer Science Department from University of Beira Interior making it a multidisciplinary study. Its goal was to assess if the exposure to motivational, persuasive and informative SMS texts could improve the self-efficacy of mathematics students from that university. The platform was devised to use low cost off-the-shelf parts, yet allowing the design of an efficient and robust system. The source code for the SMS system is publicly available at the Assisted Living Computing and Telecommunications (ALLab) website.

This thesis focuses on the study of mobile wireless sensor networks applied to healthcare scenarios. The promotion of better quality-of-life for hospitalized patients is addressed in this research work with a solution that can help these patients to keep their mobility (if possible). The solution proposed allows remote monitoring and control of patients’ health in real-time and without interruptions. Small sensor nodes able to collect and send wirelessly the health parameters allow for the control of the patients' health condition. A network infrastructure, composed by several access points, allows the connection of the sensor nodes (carried by the patients) to remote healthcare providers. To ensure continuous access to sensor nodes special attention should be dedicated to manage the transition of these sensor nodes between different access points’ coverage areas. The process of changing an access point attachment of a sensor node is called handover. In that context, this thesis proposes a new handover mechanism that can ensure continuous connection to mobile sensor nodes in a healthcare wireless sensor network. Due to the limitations of sensor nodes’ resources, namely available energy (these sensor nodes are typically powered by small batteries), the proposed mechanism pays a special attention in the optimization of energy consumption. To achieve this optimization, part of this work is dedicated to the construction of a small sensor node. The handover mechanism proposed in this work is called Hand4MAC (handover mechanism for MAC layer). This mechanism is compared with other mechanisms commonly used in handover management. The Hand4MAC mechanism is deployed and validated through by simulation and in a real testbed. The scenarios used for the validation reproduces a hospital ward. The performance evaluation is focused in the percentage of time that senor nodes are accessible to the network while traveling across several access points’ coverage areas and the energy expenditures in handover processes. The experiments performed take into account various parameters that are the following: number of sent messages, number of received messages, multicast message usage, energy consumption, number of sensor nodes present in the scenario, velocity of sensor nodes, and time-to-live value. In both simulation and real testbed, the Hand4MAC mechanism is shown to perform better than all the other handover mechanisms tested. In this comparison it was only considered the most promising handover mechanisms proposed in the literature.