A Wristwatch-Based Wireless Sensor Platform for IoT Health Monitoring Applications

Abstract

A wristwatch-based wireless sensor platform for IoT wearable health monitoring applications is presented. The paper describes the platform in detail, with a particular focus given to the design of a novel and compact wireless sub-system for 868 MHz wristwatch applications. An example application using the developed platform is discussed for arterial oxygen saturation (SpO2) and heart rate measurement using optical photoplethysmography (PPG). A comparison of the wireless performance in the 868 MHz and the 2.45 GHz bands is performed. Another contribution of this work is the development of a highly integrated 868 MHz antenna. The antenna structure is printed on the surface of a wristwatch enclosure using laser direct structuring (LDS) technology. At 868 MHz, a low specific absorption rate (SAR) of less than 0.1% of the maximum permissible limit in the simulation is demonstrated. The measured on-body prototype antenna exhibits a −10 dB impedance bandwidth of 36 MHz, a peak realized gain of −4.86 dBi and a radiation efficiency of 14.53% at 868 MHz. To evaluate the performance of the developed 868 MHz sensor platform, the wireless communication range measurements are performed in an indoor environment and compared with a commercial Bluetooth wristwatch device.

An Input Power-Aware Efficiency Tracking Technique With Discontinuous Charging for Energy Harvesting Applications

“…From (4), it can be seen that at higher f SW , P PAR is dominant due to its direct proportionality to f SW . Using these losses, PCE is calculated according to (5), where P OUT is the output power. Finally, the voltage conversion efficiency (VCE), shown in (6)…”

“…For a fixed load impedance, I OUT-avg in the discontinuous operation mode is smaller than its conventional counterpart, due to supplying current only during t NOL . If the P IN drops, the system will reduce P PAR in (4) to maintain the same PCE shown in (5). To accomplish that, f SW is reduced.…”

“…This result can be shown mathematically by first multiplying I OUT-avg in (8) and V OUT in (9) to find the output power as shown in (11). Following that, the power losses in (4) and 10, as well as P OUT in (11), are substituted into the PCE equation in (5). The resulting PCE for discontinuous charging is shown in (12).…”

“…This includes environmental and infrastructure monitoring as well as industrial and biomedical applications [1]- [4]. In healthcare, implantable or wearable wireless sensor network (WSN) nodes can be used to constantly monitor vital signs such as pulse, blood pressure, oxygen saturation, and ECG signals of persons at risk such as the elderly [5], [6]. They can also be used to detect falls in elderly patients and help manage chronic conditions [7], [8].…”

Feasibility of a Wearable Reflectometric System for Sensing Skin Hydration

“…In this regard, wearable sensing devices are key factors for revolutionizing healthcare diagnostics and delivery [3,4]. Wearable devices may enable personalized preventative care, by exploiting the early detection of vital sign anomalies in patient to improve healthcare outcomes [5,6] and to allow continuous and remote monitoring of these values [7]. There are numerous biomedical parameters that can be monitored through wearable, portable sensing solutions: electrocardiogram, oxygen saturation, heart rate, blood pressure.…”