# Light Fidelity (Li-Fi): Ultra-Fast, Wireless Communications System

Overview

This video$$^{[1]}$$ explains the promising future of Li-Fi as a form of wireless communications technology.

The exponential nature of trends in information

technology is due to a process known as ephemeralization: the ability to produce more and more of a given output (i.e. agricultural yield, computing power, etc.) using less and less input (i.e. energy, resources, etc.). The exponentially falling price in the cost of the computer chip, in particular, will eventually lead to their ubiquity in our environment. This will make everything in our infrastructure intelligent and cognified. Indeed, an important aspect of the third industrial revolution will be the expansion of our IoT infrastructure. But a barrier to achieving this is that IoT devices rely on wireless infrastructure and our current wireless infrastructure would be unable to manage the amount of data produced by trillions of IoT devices—which is how far our IoT infrastructure is predicted to progress by about 2050.$$^{[2]}$$ Today, all of our IoT devices rely on the transmission of information and data through radio waves in order to stay connected to the internet. But this reliance on solely using radio waves will eventually become problematic since most frequencies in the radio spectrum are used up and there isn’t much open real-estate, so to speak, left in this portion of the electromagnetic (EM) spectrum—certainly not enough for the number of IoT devices to continue to grow. By the year 2020, the available radio spectrum will run out. Therefore, the only way to keep up with increasing demands in data consumption as our IoT infrastructure grows, is for our ability to wirelessly transmit all of this new data to also increase. But how can we sufficiently expand our wireless communication infrastructure? The key is something known as Light Fidelity (Li-Fi), a term coined by professor Harald Haas$$^{[3]}$$ in a 2011 TEDGlobal talk. Li-Fi is the process by which data is wirelessly transmitted to devices using modulated EM radiation whose frequencies are in the visible portion of the EM spectrum. That’s to say, the data is transmitted through visible light, not invisible radio waves. The visible portion of the EM spectrum is a thousand times bigger than the radio portion which means that there are many different available frequencies to use for data transmission. Crucially, there is enough availability to allow for our IoT infrastructure to continue to expand.

How does Li-Fi work?

Figure 1

Li-Fi involves inserting a microchip into a light-emitting diode (LED). (An LED is an ultra-energy efficient and long-lasting light source which will eventually phase out most other light sources.) This connects the LED to the internet and allows a software program to modulate the LED at incredibly high speeds (these modulations in the brightness/intensity occur from tens of millions up to a hundred million times per second and are imperceptible to our senses). But why is it important to flicker the LED on and off very rapidly? Digital content (i.e. a movie, song, or computer program) can be encoded as information/data into visible light by rapidly flickering a light-emitting diode (LED) on, off, on, off, etc. The “ons” correspond to 1s and the “offs” correspond to 0s as illustrated in Figure 1. The frequency, $$f$$, of a wave (i.e. EM wave) is given by the formula in Figure 1. The frequency of radio waves or visible light measures how quickly the “ons” (1s) and “offs” (0s) are arriving at any given point. Since the frequency of visible light is roughly 10,000 times greater than that of radio waves, it follows that the information and data can arrive much quicker using visible light. Researchers at Oxford University used Li-Fi to wirelessly transmit data at a speed of 224 gigabits per second (Gbps)$$^{[4]}$$; this is faster than the speeds obtained by the world’s best fiber optic cables and the world’s best Wi-Fi. The main factor which allowed them to achieve such extraordinary speeds is that the frequency of visible light is so high. Li-Fi involves shining the visible, LED light onto a photodetector (i.e. solar cell) which converts the light energy into electrical energy. When the LED is turned on, some electrical energy (corresponding to a 1) is generated which gets sent to the device; when it is turned off, no electrical energy (a 0) goes to the device; when it is turned on again, some electrical energy (another 1) goes into the device; etc. The entire stream of information carried in the modulation of the light intensity gets transferred into electrical signals. These electrical signals are converted into a binary data stream which go to the IoT device and are used to render digital content.

Applications

The merging of lighting technology and wireless communication technology will make LEDs multi-functional. They’ll serve their typical function of illuminating our cities, the interior of buildings, and many other spaces, but they’ll also act as sources to the internet which IoT devices can communicate with. Someone could connect their mobile phone to the internet by standing under an LED street lamp; smart cars driving around in the presence of LED light could access important software programs and algorithms; smart clothing in the presence of such light could provide vital information on a person’s current state of health. The applications are endless. Li-Fi will allow us to more securely share digital content and access the internet since visible light cannot travel through walls. (The only way one could eavesdrop on what a Li-Fi user is doing on the internet is if they were in the same room as them.) Also, there are many situations in which wireless communication would be very useful but where radio waves cannot be used. For example, using wireless communication involving radio in a hospital or particle accelerator might interfere with some of the equipment or might negatively affect certain patients whereas the use of visible light will not. Radio waves cannot transmit through ocean water (due to the presence of salt) whereas visible light can; this means that Li-Fi could be used in important underwater missions (i.e. it could be used in missions where scuba divers or vehicles scan the ocean for resources or monitor the state of natural ecology). But Li-Fi will not replace Wi-Fi, it will compliment it.$$^1$$ The German government asked a group of some of the most prestigious scientists in the world to list what technologies they thought would turn out to be most transformative and revolutionary over the next century. In that list, Theodre Hinsch (a Nobel Laurette in physics) mentioned Sprechendes Licht (“talking lights”)—or, in another terminology, Li-Fi.

References

1. ColdFusion. "Li-Fi, 100X Faster Than Wi-Fi! | ColdFusion". Online video clip. YouTube. YouTube, 27 November 2015. Web. 27 March 2017.

2. Rifkin, Jeremy. The Third Industrial Revolution: How Lateral Power Is Transforming Energy, the Economy, and the World. New York: Palgrave Macmillan, 2011. Print.

3. Harald Haas. "Harald Haas: Wireless data from every light bulb". ted.com.

4. Connelly, Claire . “Move aside Wi-Fi, there's a new super-fast wireless internet coming called Li-Fi”. The Sydney Morning Herald, Claire Connelly, November 25 2015, http://www.smh.com.au/technology/technology-news/move-aside-wifi-theres-a-new-superfast-wireless-internet-coming-called-lifi-20151125-gl7j79.html#ixzz3sZGqtxSp.

Notes

1. It has also been mentioned that Li-Fi could be used in petrochemical plants relying on fossil fuels, or could be generated in today’s cities by updating existing infrastructure with LEDs. These points are trivial since the use of petrochemicals (which are derived from fossil fuels) and of our existing infrastructure will be phased out in the future. The implementation of Li-Fi into airplanes seems unlikely in a resource-based economy since maglev vehicles are vastly more efficient. Eventually, we will surpass the misuse of technology and almost all of existing infrastructure will eventually be leveled and replaced with the most technically efficient infrastructure known to present science.