AN AUTONOMOUS WIRELESS BODY AREA NETWORK IMPLEMENTATION TOWARDS IOT CONNECTED HEALTHCARE APPLICATIONS
Internet of Things (IoT) is a new technological paradigm that can connect things from various fields through the Internet. For the IoT connected healthcare applications, the wireless body area network (WBAN) is gaining popularity as wearable devices spring into the market. This paper proposes a wearable sensor node with solar energy harvesting and Bluetooth low energy (BLE) transmission that enables the implementation of an autonomous WBAN. Multiple sensor nodes can be deployed on different positions of the body to measure the subject’s body temperature distribution, heartbeat and detect falls. A webbased smartphone application is also developed for displaying the sensor data and fall notification. To extend the lifetime of the wearable sensor node, a flexible solar energy harvester with an output based maximum power point tracking (MPPT) technique is used to power the sensor node. Experimental results show that the wearable sensor node works well when powered by the solar energy harvester. The autonomous 24 hours operation is achieved with the experimental results. The proposed system with solar energy harvesting demonstrates that long-term continuous medical monitoring based on WBAN is possible provided that the subject stays outside for a short period of time in a day.
In the future healthcare circumstance, the IoT will connect the subjects and the healthcare professionals seamlessly , . With the advancement of wearable sensors, low-power integrated circuit (IC) and wireless communication technologies, the wireless body area network (WBAN) is becoming an emerging research field worldwide . WBAN, also known as body sensor network (BSN), is a wireless network to enable the health monitoring anywhere anytime around the human body. Critical issue in the development of WBAN is the power consumption in the long-term use of wearable devices. Energy harvesting, especially wearable energy harvesting technology is a promising solution to enable the long-term operation of WBAN . In , the authors present a flexible energy harvesting mechanism for ultra-low power wearable devices. It also studies the performance of a flexible solar panel under different irradiance levels. Hamid et al. present a novel wearable energy harvester that combines piezoelectric and
Electromagnetic energy sources from low frequency vibrations like human motion.
In this work, the wearable sensor node is powered by a Flexible solar energy harvester, whose block diagram is shown in Fig. 7. The flexible solar panel and the load is connected by a buck-boost converter, consisting of L1;L2;C1 and M1. To harvest the maximum power from the solar panel, an output based MPPT technique is proposed to control the duty cycle (D) of the buck-boost converter for impedance matching. To measure the power of the solar panel, conventional MPPT techniques (like P&O) multiply the VPV and IPV at the input side of the DC-DC converter. The proposed MPPT technique focuses on the output side and only needs one parameter. According to (6), the power of the solar panel has the same changing trend of the output current IOUT . The proposed MPPT measures the IOUT , and then changes the (D) of the buck-boost converter (increase).
This paper presents a wearable sensor node with solar energy harvesting that enables the implementation of an autonomous WBAN for IoT connected applications. The proposed wearable sensor nodes can be placed on different positions of the body to measure physical signals like the temperature distribution and heartbeat. It can also detect falls using the accelerometer on the node for emergency notification. In the future, the wearable sensor node can accommodate more signal detections to cover many areas of WBAN applications. A web-based smartphone application is designed to display the sensor nodes’ data and send emergency notifications. To extend the lifetime of the wearable sensor node, a solar energy harvester with an output based MPPT technique is used as the power supply. The output based MPPT technique is applied
to extract the maximum power from the flexible solar panel. Experimental results show that the wearable sensor node can operate properly when powered by the solar energy harvester. When the sensor node is set to a 10 min wake-sleep mode, the 24 hours operation of the sensor node can be achieved and is verified by experiments. Table III summaries some recent wearable WBAN applications with energy harvesting.
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