Tag Archives: Li-Fi

Google’s Next Generation of Light-based Broadband

Mahesh Krishnaswamy of Alphabet X announced the development of its next generation of light-based broadband transmission. Google uses the brand name Taara for the technology. Google has already deployed the first generation of the technology in hundreds of high-speed light links around the world, in places where it was impractical or too expensive to install fiber.

The new breakthrough being announced is that Google has reduced the technology to a chip. The first generation device used a complicated set of movable mirrors to steer the light signal, but the new chip does this electronically. The first generation device was the size of a traffic-light, but the new one is described as being the size of a fingernail.

The new chip uses light that is below the visible range. Each chip contains hundreds of tiny light emitters, and the software can control each individually with great precision. Lab tests of the chip have been able to deliver 10 Gbps speed for about a kilometer. Google believes the practical distance for the technology will be as far as about twelve miles, carrying up to 20 Gbps. Google hopes to make the chip commercially available in 2026.

It’s not hard to envision uses for the technology. One of the first trials was to beam data across the Congo River, where fiber was not a practical alternative. I can think of dozens of places in fiber networks where light-beams could be a huge cost-saver. Picture using this technology to connect to rural homes that are set back from the road. This could solve the cost and delays of crossing bridges and railroad tracks. This seems like a natural technology to use in cities to create a network between buildings. Bring a 100 GB fiber connection to one tall building and serve multiple other buildings without additional fiber.

The concept of using light for data transmission has been around for a decade, generally described under the general term Li-Fi. The primary vision for Li-Fi has been an indoor technology for beaming superfast broadband within the home of office. There was also talk about using Li-Fi as the best way to communicate between cars on the road. A few companies have developed Li-Fi devices, but the technology never gained any serious traction in the market. There has been a lot of research on Li-Fi technology by the military for providing fast broadband on the battlefield.

There are several natural limitations for using light to send data, particularly outdoors. Light requires a pure line of sight and is deflected by trees and bushes. Outdoor events like rain, fog, snow, and birds will disrupt the signal. Just like with radio signals, light dissipates over distance, and the signal gets weaker as the distance between transmitter and receiver increases. Google says it is working on ways to minimize the impact of weather. Indoor use would require deploying multiple devices to see into each room where you want broadband – no closed doors allowed.

The real benefit for this technology comes if Google can make the chips affordable. It’s not hard to envision a light mesh network delivering gigabit speeds to a small town without the need to build a wired network. Nobody has light-based broadband networks on their broadband bingo card – but in a few years it might become a viable option.

Li-Fi

Light bulbThere is another new technology that you might be hearing about soon. It’s called Li-Fi and also goes by the name of Visible Light Communications (VLC) or Optical WLAN. This technology uses light as a source of data transmission, mostly within a room, and will compete with WiFi and other short-distance transmission technologies.

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.