Lifi is coming – Wireless connections see the light
Internet and light are inextricably linked. Countless kilometers of fiber optic cables are the backbone of the network with which we pump data around the world at lightning speed. However, more and more connections are wireless and use radio signals, resulting in an overcrowded radio spectrum. Lifi, a wireless network technology that works in the light spectrum, brings relief.
Lifi stands for light fidelity and, as the name suggests, is an alternative to WiFi. Instead of using radio signals, li-fi works with light. That can be light in the visible spectrum, infrared or ultraviolet. The technique was announced by Harald Haas, a German professor at the University of Edinburgh. In 2011 he demonstrated his invention in a TED Talkand since then, scientists and companies have been developing and creating products. We are now eight years later, but li-fi has not yet made a major breakthrough in the consumer market. However, there are many developments going on that could change that in a few years. In this background article we will update you on the technology and the current state of affairs.
How does it work?
Sending data via light works with rapidly oscillating LEDs. The blinks are so fast that they are not perceptible to the human eye. No special lamps are required, in theory any LED lamp, including those in your living room, can serve as a transmitter. However, additional equipment is required to make the light flash at the correct frequencies. Ambient and sunlight are not a problem; a Li-Fi receiver can separate the flashes from the constant light and communicate undisturbed. According to the inventors, the blinking of the LEDs has no negative influence on the lifespan. In addition, the light does not have to be visible. Communication is possible with light pulses at an extremely low brightness or in the part of the light spectrum that is not visible to the human eye.
Lifi works with transceivers, which can sense light as well as transmit light, in order to enable two-way communication. Current solutions use USB dongles that can be connected to a laptop or computer and are equipped with an infrared transmitter to send data back to the lamp that serves as an access point. The access points themselves must of course be connected to a network with an existing Internet connection.
Pros and cons
With li-fi, transmitter and receiver must always be able to perceive each other’s light pulses. This does not mean that equipment must be in direct sight of each other, because light can also be captured via reflection, although the signal strength decreases. This also immediately makes it clear that li-fi is not a full replacement for wifi, because it is not possible to send data through walls, for example. Li-fi is seen as an addition to current techniques. An advantage of li-fi is that there is no interference with other radio signals. In big cities where the radio spectrum is overcrowded with Wi-Fi networks, that should be an advantage. But lifi also offers a solution in airplanes or hospitals, for example, where interference can have major consequences. In addition, the visible light spectrum in which li-fi can operate is thousands of times larger than the radio spectrum, and it is also unregulated; so no permission is needed to release equipment that communicates with light. Lifi can also be labeled as safer in some respects,
Theory versus practice
Li-fi has been researched for many years and scientists are achieving impressive speeds with the technology in test setups. For example, researchers at Oxford University published a report in 2015 in which they described a 224 Gbit/s connection with light over a distance of three metres. Li-fi products you can buy right now are nowhere near those speeds. The Dutch Signify, formerly Philips Lighting, is one of the companies that has been selling li-fi products since this year. Signify makes li-fi systems under the name Trulifiintended for the business market, for example to set up a wireless network in offices that uses the office lighting. The Trulifi 6002 system can be integrated into existing Signify luminaires and works with invisible infrared light. The system offers speeds of up to 150Mbit/s up and down at a height of 2m within a diameter of 2.2m. USB dongles are needed to connect computers and laptops to the li-fi network.
Signify also makes a faster version that offers upload and download speeds of up to 250Mbit/s. However, that Trulifi 6013 system uses visible beams of blue, red or green light and is a fixed point-to-point connection, so that the transmitter and receiver must always be in the same place. With this variant, the company is mainly aiming for industrial environments, which is understandable because of the limitations and the colored, visible light beams.
The French Oledcomm is also already marketing Li-Fi products . From September, the company will start selling its LiFiMAX system. This consists of an access point with the appearance of a fire alarm, with which up to sixteen users can connect simultaneously via a USB dongle. Oledcomm’s system operates outside the visible spectrum and offers down and upload speeds of up to 100 and 40Mbit/s. According to the company, one access point can provide a 28 square meter room with signal, but signal strength decreases as distance increases. The specified range applies at a minimum speed of 5Mbit/s. A combination of an access point and one dongle will cost around eight hundred euros.
It is not surprising that such systems are currently aimed at the business market. For home use, the current solutions seem to offer little benefit. The speed is relatively low and the range is small. Stuffing an entire house with li-fi equipment is a costly affair. According to Signify, the system is interesting because the connection is very stable and because there is no interference with other wireless networks. Signify also states that the technology is very suitable for places where sensitive information is exchanged, because the signal can only be received if it is also visible and because a dongle is required to receive the encrypted signal.
PureLiFi focuses on integration and gigabit li-fi
Current li-fi products are expensive, relatively slow and cumbersome to use due to the need for dongles. One company looking to change that is Scotland-based pureLiFi . It originated as a spin-off from the University of Edinburgh, where Harald Haas did his research into li-fi. Haas is a co-founder of pureLiFi and serves as the company’s chief scientific officer . In recent years, pureLiFi has made a number of li-fi products, such as lamps and dongles to connect laptops to li-fi. These were mainly products for testing the technology and the company is now taking a new direction.
PureLiFi focuses on the development of components that enable manufacturers to provide their devices with li-fi. At the beginning of this year, the company presented its gigabit optical front-end at the Mobile World Congress . This is a small optical module that can capture and transmit light to enable Li-Fi communication. It is in fact an antenna that must be connected to an existing baseband, for example a 5g modem in a smartphone. pureLiFi’s optical module can handle gigabit speeds, which was demonstrated by the manufacturer on the show floor . The component was built into a laptop. This resulted in a downlink speed of 1Gbit/s and an uplink of about 450Mbit/s.
The speeds that pureLiFi achieves with its hardware are much higher than that of other LiFi products that have been released to date. In principle, the speed depends on the baseband, or modem, to which the lifi antenna is connected. Additional hardware is currently also required to translate the Li-Fi signals, but pureLiFi expects that this will no longer be the case in the long term and that the necessary technology for Li-Fi communication will be integrated into basebands, as is currently the case with Wi-Fi. The current speeds that pureLiFi achieves are linked to the speeds of the wireless network technologies that are now available. Mostafa Afgani, the company’s CTO, tells us that future components will support higher speeds if basebands also offer higher speeds.
PureLiFi has now made its optical transceiver so small that it also fits in smartphones. The company says it is working with smartphone manufacturers on its integration. It does not say with which smartphone manufacturers pureLiFi cooperates due to confidentiality agreements. It will probably also be a few years before the technology actually ends up in smartphones. Li-fi in smartphones is also not intended as a replacement for Wi-Fi or other wireless technologies, but as a supplement.
Standardization: 802.11bb
Standardization is an important step for the arrival of li-fi support in products and work is now being done on an overarching standard. Last year, the Institute of Electrical and Electronics Engineers formed the IEEE 802.11 Light Communications Task Group for this purpose . That working group must create a worldwide standard for wireless communication via light. This makes Li-Fi an official addition to Wi-Fi. Nikola Serafimovski, a top executive of pureLiFi, chairs the working group.
Li- Fi will become part of the 802.11bb standard , and according to the IEEE timeline , the first draft will be released in September. According to the schedule, it will then take another two years before the standard is finally finalized in July 2021. This does not mean that li-fi products will only be launched on the market after that, manufacturers can also get started in the meantime on the basis of the draft version of the standard. This also happens with routers, for example. Ax routers are already for sale before the current 802.11ax standard has been finalized.
Applications
Li-fi is especially interesting for high-speed communication over short distances. An obvious application is creating a home or company network where computers and laptops are connected to the network and the internet via the lighting in rooms or offices. Dongles are currently required for this, but companies like pureLiFi envision a future where Li-Fi transceivers will become a standard part, much like a Wi-Fi chip and antenna are now in many devices. All kinds of electronic equipment in the home could then be connected to Li-Fi, from computers, smartphones and tablets to TVs and refrigerators.
Due to the high transfer rates that are possible, li-fi is also interesting for wirelessly connecting virtual reality and augmented reality glasses to computers. It is currently already possible to connect some VR headsets wirelessly; current solutions use the 802.11ad protocol, also known as WiGig, which operates at a frequency of 60GHz. That WiFi variant is suitable for data transfer over short distances, something in which li-fi is also strong. There are currently no VR glasses that work with li-fi, but it is possible that manufacturers are already working on this behind the scenes. PureLiFi specifically mentions this as a market for which lifi should offer a solution. That company also sees li-fi as a way for mutual communication between cars.
There has been a concrete interest in li-fi from the aviation industry for years, and that is not surprising. Interference is a thorny issue with wireless connections in airplanes and li-fi offers no risk in that regard. According to aircraft manufacturers, the use of li-fi also saves weight because less cabling is required. There are currently no aircraft in the air that actually use li-fi, but several airlines and companies are experimenting with it and have shown demonstrations.
PureLiFi, for example, collaborates with Astronics, a supplier of aircraft interiors. At a trade fair in April, that company showed a li-fi connection based on infrared light with a speed of 60Mbit/s, which is sufficient to stream 4k videos. In airplanes, for example, li-fi can be incorporated into the reading light above seats. By using infrared, the connection also works without emitting visible light. According to Astronics, the technology is mature and it is only a matter of time before li-fi comes to airplanes.
Airbus said two years ago that it was already embracing the technology and was in talks with inventor Haas about integration in aircraft. Airbus also wants to use li-fi in the cockpit of aircraft to enable safe wireless data transfer in an enclosed space. In June, Air France-KLM demonstrated an aircraft cabin containing the LiFiMAX system from the French Oledcomm. According to the maker of the system, it will actually be used in aircraft from the end of this year. The li-fi network will then be connected to the entertainment systems in passenger seats.
The European Commission also spends money within its Horizon 2020 funding program on research into the use of Li-Fi in aircraft cockpits. This is done with the Aircraft Light Communication project, of which pureLiFi is a participant. The Scottish company has received more than 266,000 euros in European subsidies for this . The aim of the project is to demonstrate that li-fi connections can successfully replace traditional wireless techniques in a cockpit. Wi-Fi and Bluetooth are now
used there, and the project group wants to demonstrate that li-fi can replace these techniques and is also safer. The study started in 2017 and is due to be completed in June 2021.
There are more situations in which radio signals do not work or are undesirable. For example, Li-Fi can be used underwater, unlike Wi-Fi. Radio waves are absorbed by water, while electromagnetic radiation in the light spectrum can penetrate deep into water. Li-Fi also offers a solution in hospitals and industrial locations where the use of radio signals is not permitted.
The American space agency NASA has also not ignored the rise of li-fi. In 2015, the Kennedy Space Center entered into a five-year partnership with the American company Light Visually Transceiving System. At the time, the space agency said that Li-Fi could perhaps
be used in spacecraft that will carry out manned missions to Mars.
Lifi can also count on the interest of authorities that regulate the use of radio frequencies. Now that the radio spectrum is becoming increasingly full, such authorities are looking at alternatives. For example, the Dutch Radiocommunications Agency had a study carried out into li-fi last year and it came to the conclusion that the technology can be a ‘good and fast addition to wifi’. The agency recommended starting with test projects, and already taking the integration of li-fi into account when building houses and offices.
The International Telecommunication Union officially created the ITU G.9991 standard for communication by light at the beginning of this year. An official li-fi standard is being worked on via the IEEE working group, but companies and telecom providers have recently jointly set up the Light Communications Alliance to promote the technology . This alliance aims to clarify the applications and possibilities of li-fi. Among the founders are companies such as Nokia, Liberty Global, Orange and pureLiFi. In the near future, the partnership wants to publish white papers about li-fi and organize events worldwide. It is also the intention that more manufacturers and companies involved in li-fi will join the alliance.
Finally
Li-Fi will never fully replace wireless network technologies such as WiFi and 5G, because it is less suitable for covering long distances and cannot pass through walls. However, the technique shows promise as an addition to the overcrowded radio spectrum. The speed of li-fi is virtually unlimited, and the spectrum of visible and invisible light is gigantic. In the coming years we will hear more and more about li-fi and it will be used more and more. In any case, in places where radio signals can cause problems, such as in airplanes, the use of the technology seems to be a no-brainer.
If it is up to companies like pureLiFi, consumers will also be sending data via light in all kinds of other situations in a few years. To make that possible, manufacturers need to be persuaded to build lifi transivers into devices such as smartphones, laptops and TVs. The arrival of small modules and the integration of li-fi in the 802.11bb standard are important conditions for this and they will be met in a few years. It therefore seems only a matter of time before li-fi is taken up more widely in the consumer market.