Li-Fi Scrubs Into the Operating Room

The visible light communication scheme could offer hospitals a potentially faster, more reliable option than Wi-Fi

3 min read
Neuro surgery operation room at FN Motol University Hospital, Prague used for the LiFi channel measurements
Researchers used this neurosurgery operation room at Motol University Hospital in Prague to make channel measurements for Li-Fi. Six Li-Fi receivers are positioned along the sides of the operating table.
Photo: Fraunhofer Heinrich-Hertz Institute

Li-Fi, which is short for “light fidelity,” is a wireless technology that uses optical light to transmit information (as opposed to Wi-Fi, which also transmits light, but at much lower radio frequencies.) Proponents claim that Li-Fi could deliver more reliable data transmission at faster rates than Wi-Fi.

Since Harald Haas, a professor at the University of Edinburgh, popularized the term Li-Fi in 2011, companies including the former Philips Lighting—now Signify—and Haas’s own pureLiFi have tried to commercialize the technology. It’s been tested in offices, schools, and even airplanes, but has so far struggled to gain widespread adoption. 

Now, Li-Fi has completed its first tests in a hospital—a place where its reliability and speed may prove particularly valuable. A team of researchers from the Fraunhofer Heinrich-Hertz Institute (HHI) in Berlin and the Czech Technical University (CTU) in Prague published results from a demonstration, which they announced at the recent Optical Networking and Communication Conference in San Diego. Their new study lays the groundwork for possibly someday using Li-Fi in a medical setting.

The researchers set up multiple Li-Fi transmitters and receivers in a neurosurgery operating room at Motol University Hospital in Prague. In a series of tests, the Li-Fi system managed to transfer data quickly and without complete signal loss. They achieved data rates of up to 600 megabits per second—better than most Wi-Fi connections and cellular networks.

Prior to this work, “there was no experimental study happening in a medical scenario for Li-Fi,” says Sreelal Maravanchery Mana, a lead author and researcher at HHI. “This is the first time we are doing realistic measurements [in a medical environment].”

In a basic Li-Fi setup, data is sent to a transmitter—an LED—which converts it into light that pulses far too fast for the human eye to see. A receiver detects the pattern of light pulses from the LED and converts that pulse pattern back into data. Because Li-Fi uses higher-frequency light than Wi-Fi does, it could, in theory,  have a higher bandwidth and therefore transmit data more quickly.

Wi-Fi has been critical to managing the number of smart devices that now populate hospitals and operating rooms. Any technology that limits wires, which can pose a safety hazard in hospitals, is welcomed. But devices that use Wi-Fi can interfere with one another, causing connection loss. “Wireless devices which are transferring medical data must be highly reliable,” says Heikki Karvonen, a researcher at the University of Oulu in Finland, who was not involved with the study. It’s important, Karvonen says, that the devices “coexist” with one another.

Not everyone is convinced that this crowding is a major problem for hospitals: one study simply recommends that smartphones running on Wi-Fi networks be kept an arm's length away from medical devices using Wi-Fi to prevent interference.

And Li-Fi isn’t perfect. While it doesn’t face interference from other medical devices, it can still be interrupted. Unlike Wi-Fi’s radio frequencies, which can pass through walls, optical light is easily blocked by humans or objects. To get around this issue, the HHI researchers used four transmitters and six receivers around the operating room, for a total of 24 channels between transmitters and receivers.

“Even if 23 of those channels are blocked, you still have one and you can have a very robust communication,” says Dominic Schulz, a researcher at HHI. During an operation, it’s possible doctors or nurses could block some of the links between transmitters and receivers by walking between them. The team plans to continue testing different Li-Fi setups in hospitals, and eventually use the technology to transmit data to medical devices being used during an actual surgery.

Currently, the U.S. Food and Drug Administration (FDA) has no official position on Li-Fi. “When planning to use Li-Fi—or any other wireless technology—in medical devices, care should be taken to match the device wireless functions with the wireless technology’s capabilities and expected performance,” says Mohamad Omar Al Kalaa, an electrical engineer at the FDA.

Whether Li-Fi’s LED transmitters and receivers become a fixture in hospitals remains, quite literally, to be seen.

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Metamaterials Could Solve One of 6G’s Big Problems

There’s plenty of bandwidth available if we use reconfigurable intelligent surfaces

12 min read
An illustration depicting cellphone users at street level in a city, with wireless signals reaching them via reflecting surfaces.

Ground level in a typical urban canyon, shielded by tall buildings, will be inaccessible to some 6G frequencies. Deft placement of reconfigurable intelligent surfaces [yellow] will enable the signals to pervade these areas.

Chris Philpot

For all the tumultuous revolution in wireless technology over the past several decades, there have been a couple of constants. One is the overcrowding of radio bands, and the other is the move to escape that congestion by exploiting higher and higher frequencies. And today, as engineers roll out 5G and plan for 6G wireless, they find themselves at a crossroads: After years of designing superefficient transmitters and receivers, and of compensating for the signal losses at the end points of a radio channel, they’re beginning to realize that they are approaching the practical limits of transmitter and receiver efficiency. From now on, to get high performance as we go to higher frequencies, we will need to engineer the wireless channel itself. But how can we possibly engineer and control a wireless environment, which is determined by a host of factors, many of them random and therefore unpredictable?

Perhaps the most promising solution, right now, is to use reconfigurable intelligent surfaces. These are planar structures typically ranging in size from about 100 square centimeters to about 5 square meters or more, depending on the frequency and other factors. These surfaces use advanced substances called metamaterials to reflect and refract electromagnetic waves. Thin two-dimensional metamaterials, known as metasurfaces, can be designed to sense the local electromagnetic environment and tune the wave’s key properties, such as its amplitude, phase, and polarization, as the wave is reflected or refracted by the surface. So as the waves fall on such a surface, it can alter the incident waves’ direction so as to strengthen the channel. In fact, these metasurfaces can be programmed to make these changes dynamically, reconfiguring the signal in real time in response to changes in the wireless channel. Think of reconfigurable intelligent surfaces as the next evolution of the repeater concept.

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