Frost & Sullivan has projected that global VLC revenue will exhibit a stunning compound annual growth rate of 112.7% from the base year of 2016 through 2021 to exceed $53 billion. Key target verticals for communications systems using visible light will be largely untapped areas including health care, automotive, discrete manufacturing and smart homes.
The days of patients pressing a buzzer to call a nurse or doctor seem as hoary as reruns of the Dr. Kildare television program of the early 1960s. Today, as hospitals fill with an aging population, physicians rely on wireless communications to monitor patient condition in real time to deliver higher-quality care. However, Frost & Sullivan research shows that the many electronic medical monitoring devices are themselves extremely sensitive to electromagnetic interference cause by radio frequency (RF)-based wireless networks. Indeed, many hospitals even ban the use of cellular phones to prevent interference with medical electronics.
An intriguing alternative to RF-based medical devices is visible light communication (VLC), which, as the name implies, uses arrays of light-emitting diodes (LEDs) to emit visible light in the 400- to 800-terahertz range to transmit data from a device to a receiver for processing. The primary advantage that VLC brings to health care applications is the elimination of interference that RF-based medical devices suffer. Other benefits that Frost & Sullivan analysts see in VLC include lower cost than RF communications systems; better communication between equipment, clinical staff and patients, and monitoring stations; greater security of light signals compared with RF signals; and complete safety during extended exposure to patients.
The challenge of using VLC for health care is that it requires a direct signal path: if a patient falls or leaves a room, the communication link is broken. Alarms to alert caregivers can minimize this, but VLC’s range remains more limited than RF communications. Frost & Sullivan analysts have identified projects that are trying to extend this range and bring VLC for health care closer to fruition. Much of this research is happening in Asia, which is not surprising given the strength of the region’s electronics and optics expertise and concern about elder care.
Changchun University of Science and Technology, China
Scientists at the School of Electronic Information Engineering combined VLC with the Hadoop open-source software framework to create a temperature monitoring system for patient comfort in hospital rooms. The team used a complementary metal-oxide semiconductor (CMOS) camera as a receiver for temperature data generated by 20 nodes at a range of 40 meters. The Hadoop cluster consisted of six computers using a CentOS 6.4 operating system based on the Linus 2.6 kernel.
The researchers monitored 200 patient rooms equipped with a total of 1,000 temperature sensors (five per room: one in each corner and the fifth in the center) on 10 floors of the test hospital. The software platform managed 1,000 temperature data records per minute, translating into 1.44 million data records daily. The addition of a shade on the LED array to reduce interference between nodes reduced the data error rate to within 3 percent.
Pukyong National University, South Korea
The safety of VLC was the driver of a wearable electroencephalogram (EEG) that researchers developed for long-term brain monitoring. Wearable EEGs can monitor brain-computer interfaces, fatigue, and emotional and mental states, but the RF wireless radiation posed long-term risks to the patient's brain. The Pukyong team avoided this hazard by integrating VLC into a wearable EEG device equipped with electrodes to gather brain activity data, and a microcontroller as an analog data filter and analog-to-digital converter. An LED transmitted the 2.4 kilobytes per second of data to a 30-hertz smartphone camera at distances up to 4 meters. The researchers are considering this to be an alternative to Bluetooth technology.
Graduate Institute of Photonics and Optoelectronics, National Taiwan University
Taiwanese scientists have developed a violet laser diode as an alternative to the LEDs typically used in VLC systems for indoor lighting. The researchers refined the chemistry and adjusted the phosphor thickness of their violet laser’s diffuser plats to achieve a data rate capacity as high as 12 gigabits per second at distances over seven meters. If greater volumes of data could be transmitted by VLC systems, it would also make the technology more attractive to health care providers.
Moriya Research Laboratory, NTT Communication Science Laboratories, Kyoto, Japan
Wearable heart rate sensors can warn gym management if elderly members or others with cardiac conditions are nearing risky levels to prevent an attack. Similarly, heart monitors can alert child-care staff if sleeping infants are in danger. However, when large numbers of heart monitors are in use, such as during a gym class for senior citizens or a in day care center, the RF signals can interfere with each other and information on the user's position is difficult to obtain.
Japanese researchers have developed a VLC system that uses a video camera and an event timing encoding technique to monitor multiple heart rates. The LED on the wearable heart monitor flashes a signal corresponding to each heartbeat that is captured by the camera. The encoding feature records and analyzes the heartbeat to identify a risk and alert caregivers or first responders.
Europe Trains Next-Generation VLC Researchers
The European Commission also sees potential in VLC for health care and other applications. The executive body of the European Union has funded a VLC-based Interoperability and Networking (VisIoN) project with about $4.4 million from the Horizon Europe 2020 research and innovation program. Participating institutions, including Northumbria University in Newcastle upon Tyne, England, will train researchers in VLC to adapt the technology to a variety of applications to promote safety, security and energy efficiency. The project began in September 2017, with funding expected to take it through 2021.
The Road Ahead
Frost & Sullivan has projected that global VLC revenue will exhibit a stunning compound annual growth rate of 112.7% from the base year of 2016 through 2021 to exceed $53 billion. Key target verticals for communications systems using visible light will be largely untapped areas including health care, automotive, discrete manufacturing and smart homes. More technological advances are needed to make VLC a practical alternative to RF wireless health care communication networks, but the successful prototypes being fine-tuned in Asia prove this is a viable area for research and development.