LiFi: Coming to a factory, a school, and a car near you

Not so long ago, the remote archipelago of orkney islands off the north coast of Scotland had the slowest broadband internet speeds in the UK. In a study, consumer watchdog Which? highlighted that this cluster of islands had data rates of around 6 Mbps, often dipping to 2 Mbps, way below the government's promised download speed of 10 Mbps.

Local Members of the Scottish Parliament called for action amid fears that the Orkney Islands could slide into the "digital divide." And then LiFi pioneer Harald Haas stepped in.

With government funds, the chief scientific officer of pureLiFi and director of the LiFi Research and Development Centre at Strathclyde University devised a scheme that transmitted data via light and more than quadrupled the broadband speed on the diminutive Orkney Island, Graemsay, population 28.

As part of the setup, a nearby lighthouse was equipped with a low-power laser to transmit data-enriched light to homes up to 50 meters away. These homes used domestic solar panels as outdoor broadband detectors to receive the data.

LiFi in the Orkneys: The unit with the wiper is the LiFi transmitter, and next to this is the off-the-shelf solar panel serving as a LiFi receiver and energy harvester. A pureLiFi detector is connected to the solar panel, so the entire set-up acts as a LiFi solar transceiver, providing a two-way communications link. Credit: Harald Haas

LiFi systems from pureLiFi were installed into the Graemsay homes, using LED bulbs equipped with a LiFi transmitter and receiver as wireless access points, to stream that data to computers and laptops. These devices then used USB LiFi dongles containing photodetectors to detect and decode the incoming LED light. Integrating infrared laser diodes into the dongles also provided a data link back to the LEDs, enabling a communication link.

"Graemsay only had a copper network to connect its residents and businesses, and this only delivered a data rate of around 2 to 3 Mbps on average," says Haas. "But with LiFi, we brought this up to 10 Mbps and provided affordable last-mile connectivity and high-speed indoor wireless networking to the island."

"Rain is often expected [in the Orkneys] and we were worried that this would affect performance, but because the solar panels are very large detectors, this isn't really impacting the system at all," he adds.

Haas is thrilled with the results and is already experimenting with more sophisticated solar panels, including gallium arsenide photovoltaics, to bolster transmission ranges and data rates.

"We've not reached gigabit data rates here as we've only used off-the-shelf solar panels, but we've published results that show other solar cells can provide at least 1 Gbps speeds," he says. "Following COVID-19, if we see more people moving into rural areas, they will need high data rates and LiFi can provide this."

Harald Haas, LiFi pioneer and pureLiFi chief scientific advisor.

Graemsay was just the beginning of today's LiFi activities. Demonstrations and applications have mushroomed since 2011, when Haas showed how his LiFi-retrofitted LED bulb could stream high-definition video to a computer by modulating its light intensity.

Since that time, Haas has been diligently raising data rates and bandwidth by upgrading light sources. First came your humble LED, and then the more powerful micro-LED arrays, shifting data rates from megabits to gigabits per second.

But most recently Haas has been working with dazzlingly bright laser-based light sources, manufactured by US-based SLD Laser, a company co-founded by Nobel Laureate and LED legend, Shuji Nakamura. Lasers can be modulated much faster than LEDs, which when twinned with higher optical powers, really fires up performance: Both Haas and SLD Laser have demonstrated 20 Gbps data rates across 3 m.

Along the way, Haas has also used ultra-sensitive photodetectors and detector arrays to collect more of the incoming data-encoded light streams, as well as new algorithms alongside combined light sources and photodetectors to create higher capacity LiFi networks. And by using increasingly sophisticated modulation schemes, he has also beamed thousands of streams of light in parallel to vastly multiply data bandwidths.

"We're now looking to slice up the optical spectrum into different wavelengths so each color-red, green, blue, yellow and so on-carries data in parallel," he adds. "We've reached 15 Gbps speeds already with this approach, and that's just with off-the-shelf LEDs."

Haas reckons laser-based LiFi data rates will reach 100 Gbps by early 2022. And as part of an international program called Terabit Bidirectional Multi-user Optical Wireless System (TOWS) for 6G LiFi, he hopes to propel LiFi to an eye-watering terabit per second by 2024.

However, the pureLiFi chief scientific officer has hardly been working in a vacuum. A growing army of high-tech start-ups and industry heavyweights have also been exploiting LiFi, demonstrating the technology in offices, schools, factories, museums, and hospitals.

In 2019, France-based Oledcomm and Signify—formerly Philips Lighting—from The Netherlands each joined forces with AirFrance to deploy LiFi on planes. In October that year, and working with aircraft equipment supplier, Latécoère, the French airline hosted a LiFi-enabled gaming competition aboard an Airbus A321.

Signify has installed its LiFi systems, 'TruLiFi' in aeroplanes, buses and more. Credit: Signify

Meanwhile, both Velmenni of India and US-based VLNComm have been looking at factory and warehouse applications. At the same time, VLNComm and French company Lucibel have also worked with the military to provide LiFi internet access at command posts. Several armies around the world have been looking at using LiFi instead of WiFi in tactical centers and camps to increase data security and ease operations setup.

For Sylvain Leroux, IoT and LiFi marketing director at French telecoms multinational, Orange, the rising number of companies on the LiFi scene spells good news for the up-and-coming industry. "LiFi is now a very robust technology with capabilities that have been growing so quickly in the last two to three years," he says. "We noticed huge competition in the market and felt this wasn't growing the market." Given this, Orange works with myriad businesses, helping to develop LiFi and expose the technology to as many users as possible.

Indeed, in recent years, Orange has used pureLiFi's LiFi network at the technical area of the Tour de France, providing internet access to the race's many hundreds of broadcasters and journalists. Leroux also highlights a recent project in which Oledcomm worked with the France-based digital services group, SPIE ICS (no relation to the Society), to equip a classroom within a school in the French town of Tours with LiFi internet access. A second school-based project is already underway.

"For me, the main usage of LiFi right now is indoor applications," he says. "The technology can provide reliable and secure connections in schools, industrial buildings, as well as hospitals that don't want [interference] from WiFi radio waves."

According to the Orange marketing director, he's currently seeing typical data rates close to 300 Mbps in such applications, but believes that by 2021 commercial products will be offering 1 Gbps as standard. "We've got Signify, Oledcomm, pureLiFi, and many more companies working here—so I'm pretty sure we'll see this kind of data rate," he says.

Although LiFi data rates exceed those of today's WiFi, speed isn't everything. With ever-rising data volumes, latency, which drives the responsiveness of any network, is more important than ever before. As Leroux points out, "Data rates are not a challenge anymore—low latency is now the key differentiator with WiFi."

Latest figures from pureLiFi indicate that LiFi already offers a latency some three times lower than WiFi. And with a low- or high-latency internet connection making the difference between winning or losing your next game of Grand Theft Auto or Minecraft, many in the industry couldn't agree more.

Underwater odyssey

Chao Shen, a researcher in gallium nitride optoelectronics at Saudi Arabia-based King Abdullah University of Science and Technology (KAUST) and co-founder of LiFi systems developer SaNoor Technologies, believes the low latency of LiFi, together with the super-high speeds and bandwidths that laser-based light sources can bring, will make laser-based LiFi indispensable for future augmented reality and virtual reality applications. He is also looking forward to seeing the technology used in vehicle-to-vehicle communication between autonomous cars.

Unlike others in the industry, Shen has been interested in laser-based LiFi from word go, thanks to his strong background in compound semiconductors such as gallium nitride. About a decade ago, he started to develop high-performance optoelectronic devices, and was soon working with Shuji Nakamura and many other colleagues on high-speed GaN laser diodes for LiFi systems as part of a collaboration between KAUST, University of California, Santa Barbara, and King Abdulaziz City for Science and Technology, Saudi Arabia.

Then he was approached by an industrial partner that wanted to stream data underwater. "That is the moment that we realised we had a solution for them, as light can transmit in water," he says.

Immediately, Shen started to investigate how best to implement laser-based LiFi in subsea environments, tackling issues such as low visibility, turbulence, and inhomogeneous salinity and temperature, that plague the murky depths. In addition to honing light sources, he devised a large-area, high-bandwidth photoreceiver to optimize links in choppy conditions, experimented with modulation schemes to ensure robust communications, and, alongside his KAUST supervisor Boon Ooi, spun out SaNoor to commercialize these technologies.

"Oil and gas, and offshore windfarm industries, all need low-latency, high-speed, wireless communications links to connect devices in the subsea environment-laser LiFi can provide this," says Shen. "Today's acoustic underwater data transmission technologies typically provide speeds of a few kilobits per second, but in recent underwater trials, our LiFi platform reached data rates of 4 Gbps."

A SaNoor LiFi laser being hoisted underwater by a subsea vehicle. Credit: SaNoor

Subsea environment developments continue apace. With its laser-based LiFi systems, SaNoor intends to be at the forefront of "The internet of Underwater Things," which beyond pipeline monitoring could eventually be used to detect approaching storms, sea-level changes, and even coral bleaching.

Shen also has his eye on the more terrestrial applications. "With our systems we've already achieved more than 30 Gbps data rates in free space," he says. "We are not a large company, and can't do everything, but we're watching the car industry in particular, and if we see a good opportunity, we will jump in."

Beyond indoor, underwater, and more futuristic applications, many industry players believe LiFi is set to play a key role in providing last-mile broadband connectivity in developing nations and the world's remote regions, as demonstrated in Orkney's Graemsay. Indeed, this application is particularly close to Deepak Solanki's heart.

As the Velmenni founder and chief executive points out, "Only 20 to 25 percent of India's telecom towers and small cells are connected via fiber-optic backhaul, with the rest still relying on microwave and other RF-based wireless technologies." He adds, "These can be very limited in terms of throughput, coverage, and range, and can't necessarily be deployed at street level."

Given this, Velmenni has developed a fiber-to-the-X LiFi system for homes, businesses, and telecoms infrastructure. The system uses LEDs with custom lenses to boost optical power, and crucially, provides a 1 Gbps data rate across a distance of 200 m. Following trials with Cisco and one of India's largest telecoms operators, the product is launching at the end of 2020. Solanki is excited.

"Cisco and customers have faced many challenges when laying cables for public WiFi access points in densely populated cities, and I believe nothing will prevent the adoption of this technology here, as we are solving a huge problem," he says. "We've also reached out to potential customers in the US and Europe, and Orange is very interested in exploring the possibilities with us ... there are so many places where LiFi can provide this kind of broadband connection that will also complement existing last-mile systems."

At the same time, Solanki reckons LiFi will also support existing wireless telecoms infrastructure, as nations make the transition from 4G to 5G. And so, it would seem that initial conceptions of LiFi competing with WiFi are long gone. With Haas, Solanki, and other key players busy developing the necessary techniques to ensure a seamless hand-over between LiFi and WiFi, the two technologies are set to complement each other from here on in.

So as LiFi demonstrations and applications proliferate, why isn't LiFi commercially ubiquitous? What is the world waiting for? Simply put: a standard.

Despite progress from the International Telecommunication Union, IEEE, and LiFi industry consortium, Light Communication Alliance, the Global standard for LiFi—802.11bb—is not set for release until the end of 2021. Following this, manufacturers of smartphones, laptops, and other devices will be more inclined to embed LiFi receivers in products, bringing an end to the not-so-convenient dongle. Indeed, at the time of writing and claiming a world first, Taiwan-based rugged laptop and tablet manufacturer, Getac, had just integrated a pureLiFi receiver to a tablet, while mobile communications company Oppo of China had patented a smartphone with LiFi technology.

For his part, Haas hopes to see LiFi well and truly integrated into mobile devices within the next three years. And as Solanki puts it, "Right now, the most important thing is to have this common standard. With this, device integration will still take at least another year, but then the use cases will be unlimited."

When that time comes, SaNoor's Shen is confident the start-ups and spin-offs will fan the flames of LiFi progress. "Look at Facebook, Twitter, and TikTok—these companies didn't come from IBM or Google, they all began as start-ups," he says. "I do think that something similar will happen in the LiFi industry—it won't be pushed by established industry leaders. The revolution is going to come from the small company."

Rebecca Pool is a science and technology writer based in Lincoln, United Kingdom.