How LiFi works

Unlike WiFi, which uses radio waves to wirelessly transmit data, LiFi uses light; by modulating the intensity of a light source faster than the eye can see, the required information can be embedded and streamed to a receiver. Any area that is illuminated is able to receive the signal, but the transmission is stopped by opaque objects such as walls. The connection is two-way because as well as the downlink, an uplink is provided through an infrared transmitter on the receiver.

The increased popularity of LED lights, which can be controlled more precisely than traditional bulbs, has helped make the technology a more practical and economical prospect. LED bulbs fitted with signal processing technology can provide both illumination and data transmission, or the light can turned down to a very low level while still maintaining that transmission. The receiver requires a photosensor which is currently in the form of a USB dongle, but the hope is that that could be incorporated into smartphones and other devices in the future.

The technology enabler here is called – “Li-Fi”, a term coined by Prof. Harold Haas of University of Edinburgh, uses LED lights as medium of data transmission.  Li-Fi, academically referred as “Visible Light Communication”, aims to use existing micro- LED light bulbs for both illumination and communication. With the advent of this technology, soon you will see all the illuminated spots in offices, houses or any other place turning into internet hotspots streaming high quality data. It has become a hot topic and soon many big corporations will jump on to the Li-Fi bandwagon.

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How fast can LiFi be?

LiFi can deliver multiple Gbps speeds in mobile devices.  This next generation technology will drive wireless beyond any current capability, opening up unprecedented bandwidth. LiFi could transmit up to 100 Gbps and possibly higher, but this would require a change in lighting technology.

Recent news report that LiFi is 100 times faster than WiFi. The assumption was that the average WiFi speeds are 10 Mbps, and that LiFi can be as fast as 1 Gbps. It is important to highlight that 1 Gbps transmission speeds from an off-the-shelf commercial LED light bulb have not been demonstrated, yet. In this discussion, it is important to compare like-for-like. The facts are:

  • The visible light spectrum is 1,000 times larger than the entire 300 GHz of radio, micro wave and mm wave radio spectrum, so there is a big untapped reservoir of resources for wireless systems.
  • The current and future growth of wireless data traffic will mean that the radio frequency spectrum will not provide sufficient resources by 2025.
  • Phosophor coated white LEDs which are mostly used in all commercial lighting devices can deliver up to about 100 Mbps
  • More expensive red, green, blue (RGB) LEDs can deliver up to about 5 Gbps, and allow control of colour.
  • Laser based white LEDs with a diffuser to create a broad light beam could transmit up to 100 Gbps.
  • The fastest WiFi in the 60 GHz frequency band, WiGig, can achieve a maximum data rate of 7 Gbps
  • The experienced data rate in a network where multiple users must share the bandwidth is significantly lower than the maximum headline data rate in WiFi systems.

Therefore, a more important metric is the data rate per square meter, or area data rate. The area data rate of a LiFi network can be 1,000 times higher than the area data rate of a WiFi network. The main reason for this massive improvement is that, while there can only be one WiFi router in a room as interference would destroy the bandwidth, there can be tens and more light bulbs in a room as interference behaves entirely different when using light to carry data.

From a security perspective, the fact that the signal can’t pass through walls is a very useful feature. No more would you have to worry about it leaking into other buildings or public spaces, potentially giving access to those it wasn’t intended for. Some rooms could even be designated as high-security areas with their own LiFi networks, isolating them from other areas of the building where vulnerable IoT devices might be connected.

Not only that, but the limited illumination area of any access point (up to about 10m2) will allow any environment to be partitioned much more precisely. Assigning users a specific access point means they can be monitored very effectively, and access to certain resources can be made contingent on both a username/password combination and a physical location. Every mobile device can be localized and tracked as it moves between access points, so users could even be required to activate neighboring areas before they connect to a conference room for example, adding an extra layer of security. 

How is the application of LiFi?

LiFi is fully networked, and each LiFi enabled light has it a unique IP address which means advanced geofencing can be deployed simply in a LiFi network. That lack of electromagnetic interference is why many see LiFi technology being employed in radio frequency sensitive areas such as planes, hospitals, and power plants, where WiFi can’t be used due to safety or operational reasons. And because of the security benefits, the technology could be ideal for organizations dealing with highly sensitive data such as healthcare or financial records, helping them to meet regulatory standards about isolating that data. It would also be an efficient solution in many cases, thanks to the wide availability of the lighting infrastructure needed and the fact that LED bulbs now serve two functions.

But despite the positives, there are a number of limitations to LiFi that mean it is likely to augment rather than replace WiFi, at least for the foreseeable future. For example, although it is a common misconception that LiFi wouldn’t work at all in sunlight, it can still be affected by very bright light—so don’t expect to see it used in outside public spaces anytime soon. And of course its inability to pass through walls is great for security, but could be impractical for a home set-up, as significant investment would be required to ensure reliable coverage in every room. Most adopters will probably employ LiFi bulbs in one or two rooms in addition to WiFi, at least at first.

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