PROTOCOLOS DE CONTROLO DE ACESSO AO MEIO EM REDES DE SENSORES SEM FIOS NUM CONTEXTO DE COEXISTÊNCIA

Funder

Organizational Unit

Publications

Survey on the Characterization and Classification of Wireless Sensor Network Applications

Publication . Borges, Luís M.; Velez, Fernando J.; Lebres, António S.

Nowadays, wireless sensor network (WSN) users are demanding more and more in terms of choice and diversity of applications. Hence, as the diversity of applications is increasing, it is worthwhile to propose a structure for the set of characterization parameters that allows sketching a taxonomy for WSN applications. This taxonomy is established via an application-oriented approach, identifying the specific services offered by each application. In this survey, we fill this gap in the WSN literature by describing the characterization parameters, organized into six different categories. Our taxonomy for application classification is centered on the different sets of parameters that have high impact on a given future WSN application. Typical attributes and values from related research works are considered as a reference, but in this survey, we propose inter- and intra-connections among the considered application groups. Based on these connections, new application groups have been proposed for applications that share common characterization parameters, along with a holistic overview of WSN application taxonomy and the discussion of the three generations of WSNs toward communication between things and the Internet of Things , as well as future trends for the development of WSN applications. Moreover, detailed parameters from different projects and authors in the field of WSNs are joined together for comparison purposes.

2014Journal article

Open access

Wireless Flex Sensor Belt Networks for Foetal Movement Monitoring in Low Risk Pregnancies

Publication . Borges, Luís M.; Barroca, Norberto; Zamith, Fernando; Lebres, António Sérgio

In this work two flex sensor belts were produced to count the foetal movements in the last four weeks of pregnancy. While one is a standalone solution the other is a wireless flex sensor belt network one. A description of the type of sensors is followed by the discussion of the different types of acquisition and data treatment methodologies. The application to display the deformation angles is presented as well. The wireless sensor network solution is based on the IEEE 802.15.4 standard, and the hierarchical wireless network solutions include a Wi-Fi layer. Preliminary results highlight the need for accounting for mother respiration movements and actual experiences with pregnant woman will facilitate tuning the threshold-trigger, to improve the detection performance.

2009-09Conference object

Open access

Wearable Sensors for Foetal Movement Monitoring in Low Risk Pregnancies

Publication . Borges, Luís M.; Araújo, Pedro; Lebres, António S.; Rente, Andreia; Salvado, Rita; Velez, Fernando J.; Martinez-de-Oliveira, J.; Barroca, Norberto; Ferro, João Miguel

In low risk pregnancies, the continuous monitoring of the foetal health is based on traditional protocols for counting the foetal movements felt by the mother. Although the maternal perception is a relevant characteristic for the evaluation of the foetal health, this kind of monitoring is hard to accomplish and being subjective can induce into errors due to mother’s anxiety and lack of concentration. Furthermore, the majority of foetal fatalities occur during the last weeks of low risk pregnancies. Therefore, it is important to obtain a universal electronic obstetric tracing, allowing for the identification of sudden changes in the foetus health, by continuously monitoring the foetus movements. The Smart-Clothing project aim has been the development of easy-to-wear belts with a telemedicine system for this purpose. One of the tried solutions is the Flex sensor belt system, which guarantees real-time and continuous foetal monitoring while creating effective interfaces for querying sensor data and store all the medical record (which can later be accessed by health professionals). Another developed belt has piezoelectric sensors incorporated onto it. The piezoelectric sensor belt has shown a high capacity to detect foetal movements, isolating them from external interferences.

2010Book part

Open access

Enhanced two-phase contention window MAC protocol for wireless sensor networks applications

Publication . Borges, Luís Miguel Moreira; Velez, Fernando José da Silva; Lebres, António Sérgio Portela

Nowadays, the user of Wireless Sensor Networks (WSNs) is becoming more and more demanding in terms of choice and diversity of applications. As a consequence, as the diversity of applications continues to grow there is a need to identify and classify the set of detailed characterization parameters that facilitates to sketch up a taxonomy for WSN applications. The proposed taxonomy identi es the services offered by each application makes a tool available to better understand the services and requirements of each application, along with a holistic overview of the WSN proposed application taxonomy. The research also involved the actual development of WSN applications within different research projects, namely in the elds of healthcare (Smart Clothing), civil engineering structure monitoring (INSYSM) and precision agriculture. Different medium access control mechanisms employ different collision avoidance schemes to cope with packet collision and retransmission, trading-off complexity, energy inef ciency and control of packet overhead. In particular, this PhD thesis addresses the study the packet collision probability for a MAC protocol that employs a collision avoidance mechanism with two contention window and consequent proposal of a model for the collision probability. Simulation results validate the model for saturated traf c. For unsaturated traf c and with a small number of nodes, the accuracy of the model is limited by numerical rounding. It is shown that, by using our analytical model, we have been able to obtain performance metrics such as network throughput and average service time for the successful transmissions. In addition, the Enhanced Reliability Decision Algorithm in the physical layer has been proposed. The frame capture effect (FC) feature has been implemented in the IEEE 802.15.4 compliant physical layer of the MiXiM framework. The proposed decision algorithm utilizes the Signal to Noise-plus-Interference ratio (SNIR) and the size of the packet to guarantee the delivery with certain reliability to the MAC layer, of a packet received at the PHY layer. A gain of more than 10 % has been achieved in the delivery ratio. Promising results have also been obtained for the SCP-MAC protocol with the FC effect enabled, for different values of reliability. As one of the main contributions of this thesis, an innovative ef cient multi-channel MAC protocol, based on SCP-MAC, was proposed, the so-called Multi-Channel Scheduled Channel Polling (MC-SCP-MAC) protocol. The in uential range concept, denial channel list (which considers the degradation metric of each slot channel), extra resolution phase algorithm and frame capture effect have been explored to achieve the maximum performance in terms of delivery ratio and energy consumption. It has been shown MC-SCP-MAC outperforms SCP-MAC and MC-LMAC in denser scenarios, with improved throughput fairness. Considering the in uential range concept reduces the redundancy level in the network facilitating to reduce the energy consumption whilst decreasing the latency. The conclusions from this research reveal the importance of an appropriate design for the MAC protocol for the desired WSN application. Depending on the objective or mission of the WSN application, different protocols are required. Therefore, the overall performance of a WSN application certainly depends on the appropriate development and application of the appropriate communication protocols (e.g., MAC, network layer).

2012-10Doctoral thesis

Open access

Smart-clothing wireless flex sensor belt network for foetal health monitoring

Publication . Borges, Luís M.; Barroca, Norberto; Velez, Fernando J.; Lebres, António

In the past years low power circuits design and networking techniques not only reduce the total power, requirements for Wireless Sensor Networks (WSNs) but also allow for supporting more complexity. In this paper we present solutions for WSN applications, and design aspects in the context of patient monitoring. The solution presented whose primary function is to collect the vital data remotely from the various sensors in low-rate wireless personal area network (LR-WPAN) is based on the IEEE 802.15.4 standard. It also will includes a Wi-Fi Layer in the context of hybrid networks. The application being dealt here consist of several flex sensors attached to a wearable monitoring belt, and allows for monitoring the foetal movements for a pregnant woman.

2009-03Conference object

Open access