electronics Article Wearable Wireless Physiological Monitoring System Based on Multi-Sensor Hongru Li † , Guiling Sun *, Yue Li † and Runzhuo Yang †   Citation: Li, H.; Sun, G.; Li, Y.; Yang, R. Wearable Wireless Physiological Monitoring System Based on Multi-Sensor. Electronics 2021, 10, 986. https://doi.org/ 10.3390/electronics10090986 Academic Editors: Francisco Luna-Perejón, Lourdes Miró Amarante and Francisco Gómez-Rodríguez Received: 20 March 2021 Accepted: 19 April 2021 Published: 21 April 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300350, China; lihongru@mail.nankai.edu.cn (H.L.); 1811144@mail.nankai.edu.cn (Y.L.); 1813652@mail.nankai.edu.cn (R.Y.) * Correspondence: sungl@nankai.edu.cn † These authors contributed equally to this work. Abstract: The purpose of wearable technology is to use multimedia, sensors, and wireless communica- tion to integrate specific technology into user clothes or accessories. With the help of various sensors, the physiological monitoring system can collect, process, and transmit physiological signals without causing damage. Wearable technology has been widely used in patient monitoring and people’s health management because of its low-load, mobile, and easy-to-use characteristics, and it supports long-term continuous work and can carry out wireless transmissions. In this paper, we established a Wi-Fi-based physiological monitoring system that can accurately measure heart rate, body surface temperature, and motion data and can quickly detect and alert the user about abnormal heart rates. Keywords: Internet of Things; wearable devices; physiological monitoring; wireless transmission 1. Introduction In recent years, with economic and social development, people’s health has been constantly threatened by various factors. For example, cardiovascular disease has remained the main cause of disease burden in the world in recent years. According to surveys, as of 2019, the number of global cardiovascular disease cases had reached 523 million and the death toll had reached 18.6 million. In most countries, cardiovascular disease has continued to increase for decades [1]. At the same time, the medical system is facing challenges. For example, as medical costs rise, the affordability of medical expenses has become an important topic and there are conflicts between medical resources and medical needs [2]. From the perspective of highly hidden and harmful diseases such as cardiovascular diseases, health monitoring is very important in modern society and can reduce risks to health and reduce burden on the medical system. In the field of health monitoring, Internet of Things technology has become a very important technology and there has been some work to analyze the factors that affect the design of the Internet of Things [3]. With the improvement of technologies such as the Internet of Things, the related costs of health monitoring continue to decrease and wearable devices have become a reliable tool for health monitoring. Users now mainly obtain wearable devices through online purchases, and such devices are continuously popularized and developed through online channels [4]. Because of the portability of wearable devices, they play an increasingly important role in long-term health monitoring. For example, smart watches have some technical and psychological characteristics and are already a widely used mobile health communication tool [5,6]. From the current point of view, it is an important development direction for wearable devices to concentrate multiple sensing tasks on a single device and to realize comprehensive monitoring of multiple data [7]. Wearable devices rely on various sensors to collect bodily and environmental data, to conduct comprehensive analysis of the data, and to transmit the required information to the master computer through communication. These tasks can carry out effective physiological Electronics 2021, 10, 986. https://doi.org/10.3390/electronics10090986 https://www.mdpi.com/journal/electronics