Jose A Afonso | Universidade do Minho (original) (raw)
Papers by Jose A Afonso
Download link: https://joseaafonso.files.wordpress.com/2016/04/wpc-am-2015-pessoal.pdf Bluetooth... more Download link: https://joseaafonso.files.wordpress.com/2016/04/wpc-am-2015-pessoal.pdf
Bluetooth Low Energy (BLE) is a promising wireless network technology, in the context of body area network (BAN) applications, to provide the required quality of service (QoS) support concerning the communication between sensor nodes placed on a user’s body and a personal device, such as a smartphone. Most previous BLE performance studies in the literature have focused primarily in networks with a single slave (point-to-point link) or traffic scenarios with relatively low data rate. However, many BAN sensors generate high data rate traffic, and several sensor nodes (slaves) may be actively sending data in the same BAN. Therefore, this work focuses on the evaluation of the suitability of BLE mainly under these conditions. Results show that, for the same traffic, the BLE protocol presents lower energy consumption and supports more sensor nodes than an alternative IEEE 802.15.4-based protocol. This study also identifies and characterizes some implementation constraints on the tested platforms that impose limits on the achievable performance.
Low power and small footprint IEEE 802.15.4/ZigBee based devices are a promising alternative to ... more Low power and small footprint IEEE 802.15.4/ZigBee based devices
are a promising alternative to 802.11a/b/g and proprietary protocols for noncritical patient monitoring under important scenarios such as post-op and
emergency rooms. However, their use in a healthcare facility to monitor several
mobile patients poses several difficulties, mainly because these protocols were
primarily designed to operate in low traffic load scenarios. This work presents
simulation results used to evaluate the performance of an IEEE
802.15.4/ZigBee based wireless sensors network (WSN) in a vital signs
monitoring scenario, for both star and tree based network topologies. The
scalability problem in non-beacon enabled networks is addressed to quantify the
degradation in quality of service (QoS) markers when the number of sensor
nodes increase. Additionally, the impact ofhidden nodes is assessed for the star
topology. Results indicate that, to achieve a delivery ratio (DR) higher than
99%, the number of electrocardiogram (ECG) nodes in a star network must not
exceed 35. However, considering a tree topology, the maximum number of
nodes must be reduced to 18 to maintain the same DR. The network
performance is severely impacted by hidden nodes. For instance, in the absence
of hidden nodes, a star network consisting of 32 ECG nodes presents a DR
higher than 99%; however, if the percentage of hidden nodes is increased to
5%, it drops to 94%. If the same percentage of hidden nodes is maintained, it is
necessary to reduce the number of nodes to 13 to reestablish a 99% DR.
The present invention relates to a sensing system for the monitoring of posture, orientation and ... more The present invention relates to a sensing system for the monitoring of posture, orientation and movement of a body in a three dimensional space, differentiating among the various stationary states and transient states in what the user can be. Sensing modules are composed by three-axis accelerometers, three-axis magnetometers and interfacing electronics. The device is encapsulated, enabling its use in adverse and harsh environments. The data monitored by the sensing modules are transmitted in real time, by the local communication device, to the central communication device, using a 2.4 GHz RF transceiver. Generic applications derived from the analysis of the monitored data include not only the rectification of a user’s incorrect body posture, thereby avoiding injuries, but also the acceleration of the healing process in therapy or the simple monitoring of a user’s physical activity. Being compact and encapsulated, this device can be used to monitor and analyze the movement of athletes in physical activity, e.g. a swimmer.
Due to its critical nature, emergency healthcare (e-emergency) systems should be totally reli... more Due to its critical nature, emergency healthcare (e-emergency) systems
should be totally reliable, efficient and support real-time traffic. Therefore eemergency networks must provide proper quality of service (QoS) levels. After
assessing the relevance of QoS deployment in different e-health contexts, this paper presents a pragmatic case-study intended to be deployed in a hospital room
containing patients with high risk abnormalities, whose vital signals are being
monitored by personal wireless body sensor networks. After justifying the unsuitability of ZigBee standard in this e-emergency scenario, the use of Low-Power,
Real-Time (LPRT) protocol for wireless sensor networks, is proposed as an adequate candidate for such task. For the present case-study, the protocol is able to
fulfill quantitatively the required QoS levels
To provide a reliable assistance to patients, emergency and intensive care systems have increased... more To provide a reliable assistance to patients, emergency and intensive care systems have increased demands for quality of service at different levels, including at the MAC layer. The low power real time (LPRT) MAC protocol presents suitable characteristics to address these demands due to its efficient bandwidth allocation, low energy consumption, and bounded latency. Yet, this MAC protocol may still present a significant packet loss ratio in a wireless channel affected by errors. In order to improve its robustness to bit error conditions, a solution based on short size beacons is proposed and tested. Results show that significant improvements regarding packet loss ratio and energy saving are obtained. A new reconfiguration scheme is also proposed so that a WSN using this solution may react optimally in accordance with the patients' clinical state.
ABSTRACT The constant growth of the elderly population in the world creates new challenges and op... more ABSTRACT The constant growth of the elderly population in the world creates new challenges and opportunities in health care systems. New technological solutions have to be found in order to meet the needs and demands of our aging society. The welfare and quality of life of the elderly population must be a priority. Continuous physical activity will play an important role, due to the increase of the retirement age. However, physiotherapy can be expensive, even when the desire movements are autonomous and simple, also requires people to move to rehabilitation centres. Within this context, this paper describes the development and preliminary tests of a wireless sensor network, based on wearable inertial and magnetic sensors, applied to the capture of human motion. This will enable a personalized home-based rehabilitation system for the elderly or people in remote physical locations.
Sensors, 2011
The IEEE 802.15.4 Medium Access Control (MAC) protocol is an enabling standard for wireless senso... more The IEEE 802.15.4 Medium Access Control (MAC) protocol is an enabling standard for wireless sensor networks. In order to support applications requiring dedicated bandwidth or bounded delay, it provides a reservation-based scheme named Guaranteed Time Slot (GTS). However, the GTS scheme presents some drawbacks, such as inefficient bandwidth utilization and support to a maximum of only seven devices. This paper presents eLPRT (enhanced Low Power Real Time), a new reservation-based MAC protocol that introduces several performance enhancing features in comparison to the GTS scheme. This MAC protocol builds on top of LPRT (Low Power Real Time) and includes various mechanisms designed to increase data transmission reliability against channel errors, improve bandwidth utilization and increase the number of supported devices. A motion capture system based on inertial and magnetic sensors has been used to validate the protocol. The effectiveness of the performance enhancements introduced by each of the new features is demonstrated through the provision of both simulation and experimental results.
The work presented here compares the performance of indoor positioning systems suitable for low p... more The work presented here compares the performance of indoor positioning systems suitable for low power wireless sensor networks. Map matching, approximate positioning (weighted centroid) and exact positioning algorithms (least squares) were tested and compared in a small predefined indoor environment. We found that, for our test scenario, weighted centroid algorithms provided the best results. Least squares proved to be completely unreliable when using distances obtained by a propagation model. Major improvements in the positioning error were found when body influence was removed from the test scenario.
Transactions on Engineering Technologies, 2015
ABSTRACT This work compares the performance of indoor positioning systems suitable for low power ... more ABSTRACT This work compares the performance of indoor positioning systems suitable for low power wireless sensor networks. The research goal is to study positioning techniques that are compatible with real-time positioning in wireless sensor networks, having low-power and low complexity as requirements. Map matching, approximate positioning (weighted centroid) and exact positioning algorithms (least squares) were tested and compared in a small predefined indoor environment. We found that, for our test scenario, weighted centroid algorithms provide better results than map matching. Least squares proved to be completely unreliable when using distances obtained by the one-slope propagation model. Major improvements in the positioning error were found when body influence was removed from the test scenario. The results show that the positioning error can be improved if the body effect in received signal strength is accounted for in the algorithms.
Systems over a standardized telecommunications network, using several communication technologies,... more Systems over a standardized telecommunications network, using several communication technologies, such as ISDN, ATM or IP. This paper presents an overview of the HIPERLAN/2 specifications as well as simulation results of this system, with channel errors and mixed traffic generated by control applications.
Fiber Optic and Laser Sensors IX, 1991
ABSTRACT We designed a new optical fiber current sensor based on the Faraday effect. The electron... more ABSTRACT We designed a new optical fiber current sensor based on the Faraday effect. The electronic detection scheme uses two polarizers in order to avoid ambiguities due to polarimetric detection. In this way we may detect current beyond the folding point of the square cosine law inherent to that sensing technique. The sensor presents excellent linear response in the measured range, from 0 to 7.5 kA (peak to peak), 60 Hz AC current.
Full paper available at http://goo.gl/0mzbrl. This paper presents the project of a Mobile Cockpi... more Full paper available at http://goo.gl/0mzbrl.
This paper presents the project of a Mobile Cockpit System (MCS) for smartphones, which provides assistance to Electric Bicycle (EB) cyclists in Smart Cities’ environment. The presented system introduces a mobile application (MCS App) with the goal to provide useful personalized information to the cyclist related with the EB’s use, including EB range prediction considering the intended path, management of the cycling effort performed by the cyclist, handling of the battery charging process and the provisioning of information regarding available public transport. This work also introduces the EB cyclist profile concept, which is based on historical data analysis previously stored in a database and collected from mobile devices sensors. From the tests performed, the results show the importance of route guidance, taking into account the energy savings. The results also show significant changes on range prediction based on user and route taken. It is important to say that the proposed system can be used for all bicycle in general.
This work presents the implementation of a wireless network based on Bluetooth Low Energy (BLE) w... more This work presents the implementation of a wireless network based on Bluetooth Low Energy (BLE) which enables the integration of multiple sensor nodes into a smartphone-based system in order to monitor the posture of cyclists. The developed posture monitoring system obtains the orientation in space of each body segment in which the sensor nodes are placed and calculates the trunk angle, the knee angle and the angle of inclination of the road. Raw sensor data are collected periodically from accelerometers, magnetometers and gyroscopes and sent via BLE to an Android smartphone, which plays the role of central station and performs the data processing concerning the posture calculation. We describe the development of the hardware and software of the sensor nodes, which are based on the CC2540 BLE system-on-chip, as well as the development of the Android application, and provide experimental results concerning the measurement of the posture of a cyclist in order to validate the proposed system.
Computer Networks, 2012
Full paper available at http://goo.gl/0mzbrl. This paper presents experimental results of the co... more Full paper available at http://goo.gl/0mzbrl.
This paper presents experimental results of the communication performance evaluation of a prototype ZigBee-based patient monitoring system commissioned in an in-patient floor of a Portuguese hospital (HPG – Hospital Privado de Guimar~aes). Besides, it revisits relevant problems that affect the performance of nonbeacon-enabled ZigBee networks. Initially, the presence of hidden-nodes and the impact of sensor node mobility are discussed. It was observed, for instance, that the message delivery ratio in a star network consisting of six wireless electrocardiogram sensor devices may decrease from 100% when no hidden-nodes are present to 83.96% when half of the sensor devices are unable to detect the transmissions made by the other half. An additional aspect which affects the communication reliability is a deadlock condition that can occur if routers are unable to process incoming packets during the backoff part of the CSMA-CA mechanism. A simple approach to increase the message delivery ratio in this case is proposed and its effectiveness is verified. The discussion and results presented in this paper aim to contribute to the design of efficient networks, and are valid to other scenarios and environments rather than hospitals.
Telemedicine and e-Health, 2014
Full paper available at http://goo.gl/0mzbrl. Body sensor networks (BSNs) enable continuous monit... more Full paper available at http://goo.gl/0mzbrl. Body sensor networks (BSNs) enable continuous monitoring of patients anywhere, with minimum constraints to daily life activities. Although the IEEE 802.15.4 and ZigBee® (ZigBee Alliance, San Ramon, CA) standards were mainly developed for use in wireless sensors network (WSN) applications, they are also widely used in BSN applications because of device characteristics such as low power, low cost, and small form factor. However, compared with WSNs, BSNs present some very distinctive characteristics in terms of traffic and mobility patterns, heterogeneity of the nodes, and quality of service requirements. This article evaluates the suitability of the carrier sense multiple access–collision avoidance protocol, used by the IEEE 802.15.4 and ZigBee standards, for data-intensive BSN applications, through the execution of experimental tests in different evaluation scenarios, in order to take into account the effects of contention, clock drift, and hidden nodes on the communication reliability. Results show that the delivery ratio may decrease substantially during transitory periods, which can last for several minutes, to a minimum of 90% with retransmissions and 13% without retransmissions. This article also proposes and evaluates the performance of the BSN contention avoidance mechanism, which was designed to solve the identified reliability problems. This mechanism was able to restore the delivery ratio to 100% even in the scenario without retransmissions.
International Conference on Sensor Systems and Software, 2012
Full paper available at http://goo.gl/0mzbrl. Wireless medical systems are comprised of four stag... more Full paper available at http://goo.gl/0mzbrl. Wireless medical systems are comprised of four stages, namely the medical device, the data transport, the data collection and the data evaluation stages. Whereas the performance of the first stage is highly regulated, the others are not. This paper concentrates on the data transport stage and argues that it is necessary to establish standardized tests to be used by medical device manufacturers to provide comparable results concerning the communication performance of the wireless networks used to transport medical data. Besides, it suggests test parameters and procedures to be used to produce comparable communication performance results.
World Congress on Engineering, 2015
Full paper available at http://goo.gl/0mzbrl. In recent years there has been a significant evolut... more Full paper available at http://goo.gl/0mzbrl. In recent years there has been a significant evolution regarding applications for mobile devices that provide location-based services. The mobile devices available on the market already provide a set of integrated sensors and it is also possible to acquire data from external sensors. This paper presents the development and results concerning a mobile sensing system applied to cycling which performs data collection using both sensors integrated in the smartphone and multiple wireless sensor nodes, which are used to acquire relevant performance parameters. The data collected by the developed mobile app is stored in a local database and also uploaded to a remote database, where it can be accessed later using the mobile app or a web browser. This mobile app allows users to share data with friends, join or create events, locate friends, consult graphs and access past routes in a map. Based on these functionalities, this system aims to provide detailed feedback regarding the user performance and enhance the enjoyment of the cyclists.
International Conference on Physiological Computing Systems, 2014
Full paper available at http://goo.gl/0mzbrl. The constant growth of the elderly population in th... more Full paper available at http://goo.gl/0mzbrl. The constant growth of the elderly population in the world creates new challenges and opportunities in health care systems. New technological solutions have to be found in order to meet the needs and demands of our aging society. The welfare and quality of life of the elderly population must be a priority. Continuous physical activity will play an important role, due to the increase of the retirement age. However, physiotherapy can be expensive, even when the desire movements are autonomous and simple, also requires people to move to rehabilitation centres. Within this context, this paper describes the development and preliminary tests of a wireless sensor network, based on wearable inertial and magnetic sensors, applied to the capture of human motion. This will enable a personalized home-based rehabilitation system for the elderly or people in remote physical locations.
World Congress on Engineering, 2015
This paper describes the design, implementation and testing of a distributed wireless system con... more This paper describes the design, implementation and testing of a distributed wireless system conceived for residential consumers which allows remote monitoring of energy consumption and power quality events from multiple electrical appliances. The system can be operated by the user from a central computer, which receives the collected data from a wireless sensor network based on the IEEE 802.15.4 and ZigBee standards. The development of the system involved the design and implementation of the hardware of the wireless sensor nodes; the software embedded in the network nodes, which manages the acquisition and transmission of data from the sensor nodes to the computer; as well as the user interface software in the central computer. Performance tests show that the developed prototype is able to provide measurements with very good accuracy and precision, for both voltage and current.
Download link: https://joseaafonso.files.wordpress.com/2016/04/wpc-am-2015-pessoal.pdf Bluetooth... more Download link: https://joseaafonso.files.wordpress.com/2016/04/wpc-am-2015-pessoal.pdf
Bluetooth Low Energy (BLE) is a promising wireless network technology, in the context of body area network (BAN) applications, to provide the required quality of service (QoS) support concerning the communication between sensor nodes placed on a user’s body and a personal device, such as a smartphone. Most previous BLE performance studies in the literature have focused primarily in networks with a single slave (point-to-point link) or traffic scenarios with relatively low data rate. However, many BAN sensors generate high data rate traffic, and several sensor nodes (slaves) may be actively sending data in the same BAN. Therefore, this work focuses on the evaluation of the suitability of BLE mainly under these conditions. Results show that, for the same traffic, the BLE protocol presents lower energy consumption and supports more sensor nodes than an alternative IEEE 802.15.4-based protocol. This study also identifies and characterizes some implementation constraints on the tested platforms that impose limits on the achievable performance.
Low power and small footprint IEEE 802.15.4/ZigBee based devices are a promising alternative to ... more Low power and small footprint IEEE 802.15.4/ZigBee based devices
are a promising alternative to 802.11a/b/g and proprietary protocols for noncritical patient monitoring under important scenarios such as post-op and
emergency rooms. However, their use in a healthcare facility to monitor several
mobile patients poses several difficulties, mainly because these protocols were
primarily designed to operate in low traffic load scenarios. This work presents
simulation results used to evaluate the performance of an IEEE
802.15.4/ZigBee based wireless sensors network (WSN) in a vital signs
monitoring scenario, for both star and tree based network topologies. The
scalability problem in non-beacon enabled networks is addressed to quantify the
degradation in quality of service (QoS) markers when the number of sensor
nodes increase. Additionally, the impact ofhidden nodes is assessed for the star
topology. Results indicate that, to achieve a delivery ratio (DR) higher than
99%, the number of electrocardiogram (ECG) nodes in a star network must not
exceed 35. However, considering a tree topology, the maximum number of
nodes must be reduced to 18 to maintain the same DR. The network
performance is severely impacted by hidden nodes. For instance, in the absence
of hidden nodes, a star network consisting of 32 ECG nodes presents a DR
higher than 99%; however, if the percentage of hidden nodes is increased to
5%, it drops to 94%. If the same percentage of hidden nodes is maintained, it is
necessary to reduce the number of nodes to 13 to reestablish a 99% DR.
The present invention relates to a sensing system for the monitoring of posture, orientation and ... more The present invention relates to a sensing system for the monitoring of posture, orientation and movement of a body in a three dimensional space, differentiating among the various stationary states and transient states in what the user can be. Sensing modules are composed by three-axis accelerometers, three-axis magnetometers and interfacing electronics. The device is encapsulated, enabling its use in adverse and harsh environments. The data monitored by the sensing modules are transmitted in real time, by the local communication device, to the central communication device, using a 2.4 GHz RF transceiver. Generic applications derived from the analysis of the monitored data include not only the rectification of a user’s incorrect body posture, thereby avoiding injuries, but also the acceleration of the healing process in therapy or the simple monitoring of a user’s physical activity. Being compact and encapsulated, this device can be used to monitor and analyze the movement of athletes in physical activity, e.g. a swimmer.
Due to its critical nature, emergency healthcare (e-emergency) systems should be totally reli... more Due to its critical nature, emergency healthcare (e-emergency) systems
should be totally reliable, efficient and support real-time traffic. Therefore eemergency networks must provide proper quality of service (QoS) levels. After
assessing the relevance of QoS deployment in different e-health contexts, this paper presents a pragmatic case-study intended to be deployed in a hospital room
containing patients with high risk abnormalities, whose vital signals are being
monitored by personal wireless body sensor networks. After justifying the unsuitability of ZigBee standard in this e-emergency scenario, the use of Low-Power,
Real-Time (LPRT) protocol for wireless sensor networks, is proposed as an adequate candidate for such task. For the present case-study, the protocol is able to
fulfill quantitatively the required QoS levels
To provide a reliable assistance to patients, emergency and intensive care systems have increased... more To provide a reliable assistance to patients, emergency and intensive care systems have increased demands for quality of service at different levels, including at the MAC layer. The low power real time (LPRT) MAC protocol presents suitable characteristics to address these demands due to its efficient bandwidth allocation, low energy consumption, and bounded latency. Yet, this MAC protocol may still present a significant packet loss ratio in a wireless channel affected by errors. In order to improve its robustness to bit error conditions, a solution based on short size beacons is proposed and tested. Results show that significant improvements regarding packet loss ratio and energy saving are obtained. A new reconfiguration scheme is also proposed so that a WSN using this solution may react optimally in accordance with the patients' clinical state.
ABSTRACT The constant growth of the elderly population in the world creates new challenges and op... more ABSTRACT The constant growth of the elderly population in the world creates new challenges and opportunities in health care systems. New technological solutions have to be found in order to meet the needs and demands of our aging society. The welfare and quality of life of the elderly population must be a priority. Continuous physical activity will play an important role, due to the increase of the retirement age. However, physiotherapy can be expensive, even when the desire movements are autonomous and simple, also requires people to move to rehabilitation centres. Within this context, this paper describes the development and preliminary tests of a wireless sensor network, based on wearable inertial and magnetic sensors, applied to the capture of human motion. This will enable a personalized home-based rehabilitation system for the elderly or people in remote physical locations.
Sensors, 2011
The IEEE 802.15.4 Medium Access Control (MAC) protocol is an enabling standard for wireless senso... more The IEEE 802.15.4 Medium Access Control (MAC) protocol is an enabling standard for wireless sensor networks. In order to support applications requiring dedicated bandwidth or bounded delay, it provides a reservation-based scheme named Guaranteed Time Slot (GTS). However, the GTS scheme presents some drawbacks, such as inefficient bandwidth utilization and support to a maximum of only seven devices. This paper presents eLPRT (enhanced Low Power Real Time), a new reservation-based MAC protocol that introduces several performance enhancing features in comparison to the GTS scheme. This MAC protocol builds on top of LPRT (Low Power Real Time) and includes various mechanisms designed to increase data transmission reliability against channel errors, improve bandwidth utilization and increase the number of supported devices. A motion capture system based on inertial and magnetic sensors has been used to validate the protocol. The effectiveness of the performance enhancements introduced by each of the new features is demonstrated through the provision of both simulation and experimental results.
The work presented here compares the performance of indoor positioning systems suitable for low p... more The work presented here compares the performance of indoor positioning systems suitable for low power wireless sensor networks. Map matching, approximate positioning (weighted centroid) and exact positioning algorithms (least squares) were tested and compared in a small predefined indoor environment. We found that, for our test scenario, weighted centroid algorithms provided the best results. Least squares proved to be completely unreliable when using distances obtained by a propagation model. Major improvements in the positioning error were found when body influence was removed from the test scenario.
Transactions on Engineering Technologies, 2015
ABSTRACT This work compares the performance of indoor positioning systems suitable for low power ... more ABSTRACT This work compares the performance of indoor positioning systems suitable for low power wireless sensor networks. The research goal is to study positioning techniques that are compatible with real-time positioning in wireless sensor networks, having low-power and low complexity as requirements. Map matching, approximate positioning (weighted centroid) and exact positioning algorithms (least squares) were tested and compared in a small predefined indoor environment. We found that, for our test scenario, weighted centroid algorithms provide better results than map matching. Least squares proved to be completely unreliable when using distances obtained by the one-slope propagation model. Major improvements in the positioning error were found when body influence was removed from the test scenario. The results show that the positioning error can be improved if the body effect in received signal strength is accounted for in the algorithms.
Systems over a standardized telecommunications network, using several communication technologies,... more Systems over a standardized telecommunications network, using several communication technologies, such as ISDN, ATM or IP. This paper presents an overview of the HIPERLAN/2 specifications as well as simulation results of this system, with channel errors and mixed traffic generated by control applications.
Fiber Optic and Laser Sensors IX, 1991
ABSTRACT We designed a new optical fiber current sensor based on the Faraday effect. The electron... more ABSTRACT We designed a new optical fiber current sensor based on the Faraday effect. The electronic detection scheme uses two polarizers in order to avoid ambiguities due to polarimetric detection. In this way we may detect current beyond the folding point of the square cosine law inherent to that sensing technique. The sensor presents excellent linear response in the measured range, from 0 to 7.5 kA (peak to peak), 60 Hz AC current.
Full paper available at http://goo.gl/0mzbrl. This paper presents the project of a Mobile Cockpi... more Full paper available at http://goo.gl/0mzbrl.
This paper presents the project of a Mobile Cockpit System (MCS) for smartphones, which provides assistance to Electric Bicycle (EB) cyclists in Smart Cities’ environment. The presented system introduces a mobile application (MCS App) with the goal to provide useful personalized information to the cyclist related with the EB’s use, including EB range prediction considering the intended path, management of the cycling effort performed by the cyclist, handling of the battery charging process and the provisioning of information regarding available public transport. This work also introduces the EB cyclist profile concept, which is based on historical data analysis previously stored in a database and collected from mobile devices sensors. From the tests performed, the results show the importance of route guidance, taking into account the energy savings. The results also show significant changes on range prediction based on user and route taken. It is important to say that the proposed system can be used for all bicycle in general.
This work presents the implementation of a wireless network based on Bluetooth Low Energy (BLE) w... more This work presents the implementation of a wireless network based on Bluetooth Low Energy (BLE) which enables the integration of multiple sensor nodes into a smartphone-based system in order to monitor the posture of cyclists. The developed posture monitoring system obtains the orientation in space of each body segment in which the sensor nodes are placed and calculates the trunk angle, the knee angle and the angle of inclination of the road. Raw sensor data are collected periodically from accelerometers, magnetometers and gyroscopes and sent via BLE to an Android smartphone, which plays the role of central station and performs the data processing concerning the posture calculation. We describe the development of the hardware and software of the sensor nodes, which are based on the CC2540 BLE system-on-chip, as well as the development of the Android application, and provide experimental results concerning the measurement of the posture of a cyclist in order to validate the proposed system.
Computer Networks, 2012
Full paper available at http://goo.gl/0mzbrl. This paper presents experimental results of the co... more Full paper available at http://goo.gl/0mzbrl.
This paper presents experimental results of the communication performance evaluation of a prototype ZigBee-based patient monitoring system commissioned in an in-patient floor of a Portuguese hospital (HPG – Hospital Privado de Guimar~aes). Besides, it revisits relevant problems that affect the performance of nonbeacon-enabled ZigBee networks. Initially, the presence of hidden-nodes and the impact of sensor node mobility are discussed. It was observed, for instance, that the message delivery ratio in a star network consisting of six wireless electrocardiogram sensor devices may decrease from 100% when no hidden-nodes are present to 83.96% when half of the sensor devices are unable to detect the transmissions made by the other half. An additional aspect which affects the communication reliability is a deadlock condition that can occur if routers are unable to process incoming packets during the backoff part of the CSMA-CA mechanism. A simple approach to increase the message delivery ratio in this case is proposed and its effectiveness is verified. The discussion and results presented in this paper aim to contribute to the design of efficient networks, and are valid to other scenarios and environments rather than hospitals.
Telemedicine and e-Health, 2014
Full paper available at http://goo.gl/0mzbrl. Body sensor networks (BSNs) enable continuous monit... more Full paper available at http://goo.gl/0mzbrl. Body sensor networks (BSNs) enable continuous monitoring of patients anywhere, with minimum constraints to daily life activities. Although the IEEE 802.15.4 and ZigBee® (ZigBee Alliance, San Ramon, CA) standards were mainly developed for use in wireless sensors network (WSN) applications, they are also widely used in BSN applications because of device characteristics such as low power, low cost, and small form factor. However, compared with WSNs, BSNs present some very distinctive characteristics in terms of traffic and mobility patterns, heterogeneity of the nodes, and quality of service requirements. This article evaluates the suitability of the carrier sense multiple access–collision avoidance protocol, used by the IEEE 802.15.4 and ZigBee standards, for data-intensive BSN applications, through the execution of experimental tests in different evaluation scenarios, in order to take into account the effects of contention, clock drift, and hidden nodes on the communication reliability. Results show that the delivery ratio may decrease substantially during transitory periods, which can last for several minutes, to a minimum of 90% with retransmissions and 13% without retransmissions. This article also proposes and evaluates the performance of the BSN contention avoidance mechanism, which was designed to solve the identified reliability problems. This mechanism was able to restore the delivery ratio to 100% even in the scenario without retransmissions.
International Conference on Sensor Systems and Software, 2012
Full paper available at http://goo.gl/0mzbrl. Wireless medical systems are comprised of four stag... more Full paper available at http://goo.gl/0mzbrl. Wireless medical systems are comprised of four stages, namely the medical device, the data transport, the data collection and the data evaluation stages. Whereas the performance of the first stage is highly regulated, the others are not. This paper concentrates on the data transport stage and argues that it is necessary to establish standardized tests to be used by medical device manufacturers to provide comparable results concerning the communication performance of the wireless networks used to transport medical data. Besides, it suggests test parameters and procedures to be used to produce comparable communication performance results.
World Congress on Engineering, 2015
Full paper available at http://goo.gl/0mzbrl. In recent years there has been a significant evolut... more Full paper available at http://goo.gl/0mzbrl. In recent years there has been a significant evolution regarding applications for mobile devices that provide location-based services. The mobile devices available on the market already provide a set of integrated sensors and it is also possible to acquire data from external sensors. This paper presents the development and results concerning a mobile sensing system applied to cycling which performs data collection using both sensors integrated in the smartphone and multiple wireless sensor nodes, which are used to acquire relevant performance parameters. The data collected by the developed mobile app is stored in a local database and also uploaded to a remote database, where it can be accessed later using the mobile app or a web browser. This mobile app allows users to share data with friends, join or create events, locate friends, consult graphs and access past routes in a map. Based on these functionalities, this system aims to provide detailed feedback regarding the user performance and enhance the enjoyment of the cyclists.
International Conference on Physiological Computing Systems, 2014
Full paper available at http://goo.gl/0mzbrl. The constant growth of the elderly population in th... more Full paper available at http://goo.gl/0mzbrl. The constant growth of the elderly population in the world creates new challenges and opportunities in health care systems. New technological solutions have to be found in order to meet the needs and demands of our aging society. The welfare and quality of life of the elderly population must be a priority. Continuous physical activity will play an important role, due to the increase of the retirement age. However, physiotherapy can be expensive, even when the desire movements are autonomous and simple, also requires people to move to rehabilitation centres. Within this context, this paper describes the development and preliminary tests of a wireless sensor network, based on wearable inertial and magnetic sensors, applied to the capture of human motion. This will enable a personalized home-based rehabilitation system for the elderly or people in remote physical locations.
World Congress on Engineering, 2015
This paper describes the design, implementation and testing of a distributed wireless system con... more This paper describes the design, implementation and testing of a distributed wireless system conceived for residential consumers which allows remote monitoring of energy consumption and power quality events from multiple electrical appliances. The system can be operated by the user from a central computer, which receives the collected data from a wireless sensor network based on the IEEE 802.15.4 and ZigBee standards. The development of the system involved the design and implementation of the hardware of the wireless sensor nodes; the software embedded in the network nodes, which manages the acquisition and transmission of data from the sensor nodes to the computer; as well as the user interface software in the central computer. Performance tests show that the developed prototype is able to provide measurements with very good accuracy and precision, for both voltage and current.