Li-Fi: An attractive alternative to Wi-Fi

Article By : Yoelit Hiebert

The wireless communication technology is implemented in a space by way of LED lighting assemblies that include signal-processing circuitry and firmware.

The term Li-Fi or light fidelity, was coined by Professor Harald Hass of Edinburgh University during his 2011 TED Talk “Wireless Data from Every Light Bulb.” Like all optical wireless communication, Li-Fi uses light to transmit data, specifically light in the visible spectrum. LED light sources are ideal for Li-Fi communication because of their ability to cycle at very rapid rates with no damaging effects. The LEDs used for data transmission of Li-Fi signals modulate at rates much too fast to be detected by the human eye, so there is no issue with flicker or other discernable changes to the light in the space.

That brings us to the most highly-touted advantage of Li-Fi, namely that it has almost no bandwidth limitations. The visible light spectrum is several orders of magnitude wider than the radio frequency spectrum, so while the alarm has been sounded about Wi-Fi reaching capacity, there are virtually no such limitations for Li-Fi. Advocates maintain that widespread adoption will help solve the current bandwidth limitations of Wi-Fi and because of this, will become a basic component of 5G implementations.

Li-Fi is implemented in a space by way of LED lighting assemblies that include signal-processing circuitry and firmware. Just like Wi-Fi, data from an internet router is supplied via hardwire and then embedded by way of light modulation into the emitted light. A photoreceiver converts the received light back into binary data. With the right hardware and firmware, data transfer can be bi-directional. Theoretically, speeds of 200+ Gbps are achievable.

Li-Fi diagram
Here is a typical Li-Fi implementation.

Li-Fi has other advantages as well, not least of which is enhanced security because, of course, light does not travel through walls. Another advantage is improved network reliability. Li-Fi transmitters can be incorporated into every light fixture in a room or building, thereby eliminating the bottleneck node structure of Wi-Fi. These qualities make Li-Fi an especially attractive alternative for applications where Wi-Fi signals are easily disrupted or not permitted (such as nuclear power plants) or where there’s a need for rapid and secure transfer of large data files (such as hospitals).

Because Li-Fi receivers are looking for changes in light intensity, Li-Fi can operate in daylit environments and even in direct sunlight. In an interior space, Li-Fi doesn’t require direct line of sight between the light source and receiver, as reflections from walls and other surfaces can be detected. It can also operate reliably in environments dimmed to as low as 10%, so that while the space appears to be dark to the human eye, data is still, in fact, being transmitted. But, as is the case with any technology, Li-Fi has shortcomings as well, the most prominent being limited range and high implementation cost, at least for now.

Li-Fi has been in use for the last several years in niche applications involving targeted communication to mobile apps. The most well-known of these is for guiding shoppers through a retail space with the intent of increasing sales by providing coupons or other promotional information. Communication is one-way and requires that the shopper be able to receive the signal via a mobile phone app.

A notable entry into the Li-Fi market is the recently-announced suite of systems from Signify (formerly Philips Lighting), called Trulifi. The company claims speeds of up to 150 Mbps with seamless handover from one light to another in the user space, as well as fixed, point-to-point connectivity of up to 250 Mbps. It is designed for incorporation into new or retrofit Signify lighting products. A Trulifi system has recently been installed in the stadium press room of German soccer team Hamburger SV to alleviate the Wi-Fi bottleneck journalists had been experiencing. Journalists are supplied with USB dongles for their laptops that enable two-way communication with the Li-Fi-enabled lights overhead.

While the technology includes some appealing features, wide-spread adoption has not taken off. In addition to range and cost limitations, the lack of an industry standard is currently hampering Li-Fi adoption, because without one, manufacturers are reluctant to incorporate Li-Fi capability into their products. Until the standard is agreed upon, Li-Fi will probably be relegated to smaller boutique projects.

Yoelit Hiebert has worked in the field of LED lighting for the past 10 years and has experience in both the manufacturing and end-user sides of the industry.

Related articles:

Leave a comment