A technology surfaces that could literally expand the reach of Li-Fi

Aug. 25, 2021
Engineers are working on something called ‘RIS’ that can minimize line-of-sight requirements. But won’t it also benefit would-be intruders?

It’s been nearly half a year since we last wrote anything about Li-Fi. And prior to that, the Li-Fi news pace was at best a trickle. Late last year, Signify CEO Eric Rondolat even acknowledged the truism that the reluctance of gadget makers to embed the technology has been a serious impediment. A lack of standards hasn’t helped.

So we went on a quick fishing expedition trying to land some recent examples of progress. We didn’t reel in much, other than Scottish Li-Fi pioneer pureLiFi in the spring won what it described as a $4.2 million contract to provide Li-Fi to the US Army in Europe and Africa.

We have been awaiting additional details on the Army deal for a while. The contract likely involves laptops from Taiwanese maker Getac, although we don’t have confirmation yet. Unlike other laptop makers, Getac is embedding Li-Fi receivers in its hardware, enabling its ruggedized laptops to receive data communications via visible light (that’s what Li-Fi is — Wi-Fi-like wireless communications using light rather than Wi-Fi’s radio waves).

There have probably been other deployments since we wrote in March about a small Signify installation at the World Forum The Hague conference center, but they are hard to find.

However, there is nothing like the future to provide hope. To that end, we stumbled across a developing technology that has a bit of a science fiction ring but might one day help usher in Li-Fi as a mainstay Internet conduit.

The technology is called “reconfigurable intelligent surfaces” (RIS) and its intention is to solve the conundrum that one of Li-Fi’s greatest strengths is also a weakness. Specifically, Li-Fi today requires unobstructed line-of-sight. That is, no object or person must stand between a Li-Fi transmitter and receiver. Line-of-sight is the reason why Li-Fi is generally regarded as highly secure. It is blocked by walls, thus spoiling the day for at least some would-be eavesdroppers.

But the disadvantage of line-of-sight is that it limits the range of transmission. Essentially, users have to be more or less directly under an emitting luminaire, or otherwise in the lightwave’s path.

RIS to the rescue!

A paper published on Cornell University’s non-peer-reviewed arXiv site of scientific articles heralds RIS as a technology that will “not only support blockage mitigation but will also provision complex interactions among network entities, and is hence manifested as a promising platform that enables a plethora of technological trends and new applications.”

Translation: Not only will RIS minimize the need for line-of-sight (i.e., it providers “blockage mitigation”), but it will do even more than that to help make Li-Fi a useful means of communication.

“RIS emerged recently as a revolutionary concept that transfers the physical propagation environment into a fully controllable and customizable space in a low-cost, low-power fashion,” states the paper’s authors, led by Hanaa Abumarshoud, a research fellow in electronic and electrical engineering at Glasgow’s University of Strathclyde. The team includes Harald Haas, co-founder of Edinburgh-based pureLiFi and a professor of mobile communications at the University of Edinburgh.

If you want the technical ins and outs, download the paper here: https://arxiv.org/abs/2104.02390.

In short, RIS can be used in several places in a Li-Fi environment, including in the transmitters, in the receivers, and along the way.

“A RIS comprises a metasurface that can be proactively reconfigured to alter the wireless wave propagation,” the paper explains. “The electromagnetic (EM) response of each RIS element can be adjusted by tuning the surface impedance through electrical voltage stimulation. Based on this newly emerging concept, future wireless networks may utilize the different surfaces and physical objects in the environment as wireless boosters to enhance their operations.”

According to the authors, RIS can help steer light in a particular direction; can redirect it; can amplify it; and can control different wavelengths, an attribute that provides multiplexing benefits.

But if the lightwaves will now reach around corners and so forth, won’t that undermine the security advantages of Li-Fi by making signals available to people who shouldn’t have access to them?

No, say the authors. They claim that RIS-equipped Li-Fi environments “can lead to enhanced physical leader security” in several different ways. For example, somehow an RIS system can detect intruders, and then emit artificial noise in the intruder’s direction as a jamming technique. RIS elements can be precoded in a way that only legitimate users can decode, the authors state.

“RIS technology opens the door for a whole new realm of wireless applications in which the propagation medium is no longer an impediment, but rather an additional degree of freedom,” they write.

Don’t look for RIS soon. The authors don’t envision it being ready until the arrival of 6G communications, which by many estimates won’t be until later this decade. 5G still has yet to reach many quarters. Li-Fi itself, in its current non-RIS state, is still something that seems more for the future with its slow rate of adoption. But don’t lose sight of it.

MARK HALPER is a contributing editor for LEDs Magazine, and an energy, technology, and business journalist ([email protected]).

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