Wi-Fi signals already fill our homes, offices, and hospitals \u2014 invisible waves constantly transmitting data between routers and countless devices. Now researchers are exploring how ubiquitous signals could serve a secondary purpose in healthcare.\u00a0<\/p>\n
The concept is surprisingly straightforward: As Wi-Fi signals transmit through a room, they encounter human bodies and bounce off them in predictable patterns. These subtle disturbances in the signal can reveal movement, breathing patterns, and even heartbeats. Like invisible sonar constantly pinging through our spaces, Wi-Fi creates a field of information that, when properly decoded, can track the rhythms of human life.<\/p>\n
\u201cWi-Fi signals can work as sensors, transparent sensors that you don\u2019t see,\u201d said Katia Obraczka, PhD<\/a>, engineering professor at University of California at Santa Cruz. \u201cGiven that Wi-Fi is such widespread technology \u2014 you have Wi-Fi all over the place \u2014 it\u2019s very convenient to use it to measure different things.\u201d<\/p>\n For healthcare settings, this technology could address persistent challenges. Hospital patients who remove monitoring devices, elderly residents who forget to wear fall detection pendants, or children who won\u2019t tolerate sleep study equipment might all be monitored through existing Wi-Fi infrastructure.\u00a0<\/p>\n Emergency departments could assess breathing rates in waiting rooms, while rehabilitation centers might track mobility patterns without attaching sensors to patients. A triage station could obtain ECG measurements while patients simply wait in chairs. The technology promises continuous, passive monitoring without the compliance issues, skin irritation, or battery life concerns of wearable devices.<\/p>\n Obraczka and her team developed a system called Pulse-Fi<\/a>, which extracts heart rate data from ambient Wi-Fi signals. \u201cWe know the frequency range of the heart as it beats, so we extract those frequencies, and then we have a very simple machine learning model that learns and estimates the heart rate,\u201d explained Obraczka. Their initial studies show heart rate measurements within clinical standards.<\/p>\n \u201cIt\u2019s an exciting example of how emerging technologies can make health monitoring more accessible and affordable,\u201d said Eugene Yang, MD<\/a>, cardiology professor at University of Washington School of Medicine, Seattle, about Pulse-Fi.<\/p>\n While Pulse-Fi focuses on heart rate, researchers can measure multiple health parameters using Wi-Fi simultaneously by analyzing different patterns in signal disturbances. Qammer Abbasi, PhD<\/a>, engineering professor at University of Glasgow, explained that the heartbeat creates tiny, rapid vibrations, whereas breathing produces larger, slower movements. Falls, body movements, and sleep pattern changes create even bigger displacements\u2014each leaving its own signature in the Wi-Fi field.<\/p>\n Jon Cooper, PhD<\/a>, bioengineering professor at University of Glasgow, Scotland, is developing Wi-Fi devices that act as activity sensors to detect whether someone is sitting, lying, standing, or walking. This capability could help monitor rehabilitation progress or detect when elderly patients attempt to leave their beds unassisted.<\/p>\n Beyond Wi-Fi, similar wireless technologies offer unique advantages. 5G networks, which operate differently than Wi-Fi by using licensed cellular frequencies managed by carriers rather than local routers, can better penetrate walls and obstacles. \u201cThis allows monitoring of small body movements with good range and coverage, supporting continuous, real-time observation of human health and activity in indoor and cluttered environments,\u201d said Muhammad Imran, PhD<\/a>, communications systems professor at University of Glasgow, Scotland.<\/p>\n Another promising approach uses multiple-input multiple-output (MIMO) technology, which employs multiple antennas to send and receive data simultaneously \u2014 the same technology that makes modern Wi-Fi faster and more reliable. MIMO\u2019s use of multiple signal paths creates a richer dataset for health monitoring. Cooper, Imran, and Abbasi previously explored<\/a> whether MIMO technology could detect drowsy drivers by measuring heart rate and respiration. They found it was 81% accurate in detecting driver fatigue.<\/p>\n Cooper noted that these wireless technologies have privacy advantages over camera-based monitoring since it\u2019s not actually \u201cseeing\u201d people \u2014 only detecting their physical presence and movements through signal patterns.<\/p>\n \u201cHowever, these technologies also come with challenges, such as the need for proximity to the device and potential interference or congestion from multiple users and neighboring networks,\u201d said Yang.<\/p>\n While Wi-Fi works through walls, Obraczka\u2019s team has only tested their system with a single subject in the same room. Multiple people can be detected simultaneously, but overlapping positions can make it difficult to separate signals. \u201cIf one person is behind the other, it can be difficult to tease them apart, so for now we\u2019re focusing on just one person in a room,\u201d said Obraczka.<\/p>\n Jon Cooper noted that untangling signals from multiple people or distinguishing between humans and pets is possible, especially with help from artificial intelligence-assisted interpretation that can learn to recognize different movement patterns and sizes.<\/p>\n