IEEE Certifies Li-Fi, the Light-based Communications Standard

With the certification of the Li-Fi (light-fidelity) standard, 802.11bb-2023, a new era has opened up for local area wireless communications. Li-Fi refers to wireless data communications using light rather than the radio waves used by Wi-Fi. It is faster, immune to electromagnetic interference, and more difficult to intercept. It operates by modulating near-infrared, visual, or near-ultraviolet LEDs, making any LED source a potential access point.

 

Typical Li-Fi access point architecture. Image used courtesy of Li-Fi

 

Data Communication With Light Is Nothing New

Untethered short-distance communications via light existed long before the invention of Wi-Fi—even before radio transmission of any sort—and has remained in use to this day. Light-based communications were tested as early as 1867 by the British Navy using a dot-and-dash predecessor to Morse code. In a more practical sense, wireless light-based digital communications came into commercial use with the widespread adoption of infrared LEDs in the late 1970s. It has been used for devices like TV and appliance remote controls, wireless keyboards, and low data rate device-to-device communications.

However, limitations in data speed and the difficulty with reliable transmission have left it largely relegated to slow-speed, non-mission critical devices. Wi-Fi popped up in the late 1990s and made the need for high-speed, light-based wireless networking largely moot until recently.

Wi-Fi, covered by IEEE 802.11, was a world-changing new technology when it was released in 1997. For the first time, the average personal computer user could cut the network cord and roam free within signal range. After six major updates and updated smartphone data connections, individuals can now be connected virtually anywhere on the planet. However, as handy as Wi-Fi is, it has limitations and a number of unresolved loose ends.

 

Wi-Fi Has Its Limits

Today, Wi-Fi is running into limitations with the available spectrum as more devices compete for a home in the radiofrequency spectrum. It is also subject to a great number of security vulnerabilities. One of the biggest Wi-Fi risks is that of the poorly secured access point. Since Wi-Fi passes through walls (albeit never as well as home users would like), nefarious actors can hack into Wi-Fi systems that are not adequately secured. It’s also subject to interference in noisy RF or EMI environments, leading to transmission slowdowns or interruptions.

 

Li-Fi operates in the visible spectrum along with near-infrared and near-ultraviolet. Image (modified)used courtesy of Philip Ronan/Wikimedia Commons [CC BY-SA 2.5, CC BY-SA 2.0, and CC BY-SA 1.0]

 

High-speed, light-based data communications reentered the scene a little more than a decade ago with the formation of the Li-Fi Consortium. The term Li-Fi was coined by Harald Haas and presented to the world in Haas’ 2011 TED talk. Haas went on to co-found PureLiFi, a founding member of the consortium and one of the key drivers in commercializing visible light communications (VLC), of which Li-Fi is the key resulting technology.

 

The Differences Between Wi-Fi and Li-Fi

The biggest difference between Wi-Fi and Li-Fi, is, of course, the transmission medium. Wi-Fi is transmitted over radio waves in the GHz frequency range, and Li-Fi is transmitted by light. The 802.11bb standard does not come with new protocols. While the physical layer (PHY) is different, the protocols will remain in common with Wi-Fi. This will ensure interoperability between Wi-Fi and Li-Fi devices. For example, the recently-released Light Antenna One from PureLiFi can be integrated with existing Wi-Fi chipsets and appears to the system as another band of Wi-Fi.

 

One of the first commercial Li-Fi products: Light Antenna One. Image used courtesy of PureLiFi

 

In a typical Li-Fi installation, the internet and local networks are connected to Li-Fi-enabled LEDs through power over Ethernet (POE) or power line communications (PLC). The LED will be equipped with a microcontroller and photodetector to allow for bidirectional communications. A host of battery-powered or mobile devices can then communicate through the Li-Fi access point.

Li-Fi modulates the LED at frequencies far higher than the human eye can detect. At night, visible spectrum LEDs can be powered low, so the data still goes through, but the light is effectively off for human purposes. 

Li-Fi can be modulated with conventional single-carrier modulation (SCM) and multiple-carrier modulation (MCM). However, the highest speeds are available with a derivative of MCM called orthogonal frequency division multiplexing (OFDM). OFDM takes advantage of the broad available spectrum of light to implement subcarriers to carry multiple parallel data streams. Research speeds have been as high as 224 Gb/s, though they will be lower in real-world situations.

 

Li-Fi: A Companion to Wi-Fi Instead of a Competitor?

The strengths and weaknesses of Li-Fi and Wi-Fi complement each other quite well. This, combined with designed-in interoperability, make Li-Fi as much a companion to Wi-Fi as it is a competitor. Wi-Fi can provide general coverage within or around a structure when security concerns and interference are within acceptable limits, while the Li-Fi access points can give line-of-sight or near-line-of-sight communications in a much more contained area. 

Li-Fi partners have outlined a number of settings where Li-Fi can operate better than Wi-Fi or where Wi-Fi is simply not possible. For example, light can penetrate seawater up to 200 meters, so Li-Fi opens up the possibility of high-speed untethered communications between underwater remote-operated vehicles and operators. Li-Fi can also be used in medical suites for surgery or imaging machinery, where Wi-Fi cannot be used because of its potential interference with the equipment. 

Beyond such specialized uses, the smaller cell size enabled by Li-Fi allows for a higher number of access points, which can deliver simultaneous bandwidth to more devices than Wi-Fi. This makes it a better option for dense IoT installations.

 

With the Standard Certified, It's Go Time

Now that the Li-Fi standard has been certified, more vendors may feel secure in investing the R&D funds required to design and produce Li-Fi products. Increased production will bring lower costs and follow-on innovation. The ubiquity of LEDs means that potential access points are everywhere. And, with walls being a hard security barrier, Li-Fi might be the final ingredient to make universal connectivity of home and office devices a safe and practical reality.