Early research into the technology used fluorescent lamps and achieved data speeds of only a few Kbps. The trials got more speed after the introduction of LED lighting, but the technology didn’t really take off until professor Harold Haas of the University of Edinburgh created a device in 2011 that could transmit at 10 Mbps. Haas calculated the theoretical maximum speed of the technology at the time at 500 Mbps, but recent research suggests that the maximum speeds might be as fast someday as 1.5 Gbps.
There are some obvious advantages of the technology
- Visible light is totally safe to people and eliminates any radiation issues involved in competitors like 802.11ad.
- It’s incredibly difficult to intercept and eavesdrop on Li-Fi transmissions that stay within a room between the transmitter and receiver.
- It’s low power, meaning it won’t drain batteries, and uses relatively simple electronics.
But there are drawbacks as well:
- The speed of the transmission is going to be limited to the data pipe that feeds it. Since it’s unlikely that there will ever be fiber built to lightbulbs, then Li-Fi is likely to be fed by broadband over powerline, which currently has a maximum theoretical speed of something less than 1 Gbps and a practical speed a lot less.
- At any reasonable speed Li-Fi needs a direct line-of-sight. Even within a room, if anything comes between the transmitter and the receiver the transmission stops. Literally waving a hand into the light bean will stop transmission. This makes it awkward to use it for almost any mobile devices or something like a virtual reality headset.
There are a few specific uses considered for the Li-Fi technology.
- This possibly has more uses in an industrial setting where data could be shared between computers, machines, and robots in such a way as to insure that the light path doesn’t get broken.
- The primary contemplated use of the technology is to send large amounts of data between computers and data devices. For example, Li-Fi could be used to transmit a downloaded movie from your computer to a settop box. This could be a convenient, interference-free way to move data between computers, phones, game consoles, and smart TVs.
- It can be used at places like public libraries to download books, videos, or other large files to users without having them log onto low-security WiFi networks. It would also be great as a way to hand out eCatalogs and other data files in convention centers and other places where wireless technologies often get bogged down due to user density.
- Another use is being called CamCom. It would be possible to build Li-Fi into every advertising display at a store and let the nearest light bulb transmit information about the product to shoppers along with specials and coupons. This could be done through an app much more quickly than using QR codes.
The biggest hindrance to the technology today is the state of LEDs. But Haas has been leading researchers from the Universities of Cambridge, Oxford, St. Andrews, and Strathclyde in work to improve LEDs specifically for the purposes of Li-Fi. They have created a better LED that provides almost 4 Gbps operating on just 5 milliwatts of optical output power. These kinds of speeds can only go a very short distance (inches), but they hope that through the use of lenses that they will be able to transmit 1.1 Gbps for up to 10 meters.
They are also investigating the use of avalanche photodiodes to create better receivers. An avalanche photodiode works by creating a cascade of electrons whenever it’s hit with a photon. This makes it much easier to detect transmitted data and to cut down on packet loss.
It’s likely at some point within the next few years that we’ll see some market use of the Li-Fi technology. The biggest market hurdle for this and every other short-range transmission technology to overcome is to convince device makers like cellphone companies to build the technology into their devices. This is one of those chicken and egg situations that we often see with new technologies in that it can’t be sold to those who would deploy it, like a store or a library, until the devices that can use it are on the market. Unfortunately for the makers of Li-Fi equipment, the real estate on cellphone chips and other similar devices is already very tightly packed and it is going to take a heck of a sales job to convince cellphone makers that the technology is needed.