“Let there be light … and WiFi too!”

A Ted talk by Harald Haas from the University of Edinburgh.
(the original Ted talk link)

I don’t know how common WiFi network is in general, but I am pretty sure that every student (or even staff) in this University of Melbourne uses WiFi in a great deal; since we have free and accessible WiFi in our campus! Though I don’t use WiFi out of campus, I understand how convenient WiFi is, especially when I just need to get quick information using my iPod touch on my way! And for those intensive WiFi users I think WiFi can be a necessity just like the oxygen.

So for me, WiFi is much more than enough; it is so handy, stable and mobile that I am satisfied with this technology and have never thought of the need to invent more.

Until I come across this news about developing a technology, which instead of using radio frequencies as WiFi does, uses light to transmit information!

Light + WiFi = ?

A research team from the Shanghai’s Fudan University in China recently claimed that they have successfully transmitted data to four computers by using one single one-watt LED bulb, that was equipped with a signal modulation chip, at a speed at 150 megabits per second.

This is an improvement of anĀ  idea first introduced by Harald Haas from the University of Edinburgh, who suggested that light can be made used of in wireless communication systems. (This innovation has a friendly name – LiFi)

But why would we need LiFi?

We may know that WiFi uses radio frequencies to deliver data, but not necessarily notice that the number of radio-based wireless spectrum is actually quite limited. This means that in this era of digital information explosion, the current spectrum may soon run out.

Another problem is energy-related, as radio towers need to spend most of the energy on cooling, only 5% of it is spent on information transmission.

So how does LiFi help with these problems?

LiFi now uses the visible light, the light that we use for helping us to see in a dark or dim place (examples of invisible lights are ultraviolet light and infrared light), to transmit information. The great advantage of this is that the electromagnetic spectrum of visible light is 10,000 times larger than a radio spectrum. This enables a larger capacity of delivering information.

Secondly, since lighting is an already existing infrastructure in most buildings, the cost of installing or transforming the devices would be much more affordable. Although LiFi specifically requires LED (light emitting diode) bulbs, but since it’s an environmentally friendly trend to switch from traditional lighting to LED, this transition is not a big problem.

Importantly places such as airplanes and operating theaters in hospitals that do have to use radio frequencies and therefore ban the use of cell phones and internet surfing, can now be open for internet access with the technology of LiFi.

Is LiFi perfect and can it replace WiFi then?

There are actually a few drawbacks of LiFi, but it is interesting to discuss them.

First, LiFi has a limitation that its pathway to the electronic device has to be clear; if the light is blocked between itself and a laptop then the signal is cut off.

Besides, LiFi may be efficient to send data to a device but itself will be required to be equipped with photo-detectors to receive information from the device, so to establish a two-way communication. The LiFi researchers suggested to use LiFi for downloading and WiFi for uploading, which usually transmits less data than the former action. So it seems that WiFi is not all omitted.

There is also one issue regarding the penetration of walls by the signal. Unlike radio frequencies, light cannot penetrate through walls which means the distance of applicable usage may be restrained by the layout of a room. But some researchers consider this to be a pros, since hacking a neighbour’s WiFi could be a problem when WiFi signal can transfer through walls but LiFi in this sense can be more secure.

One last interesting question about LiFi. So we won’t be able to use it in daytime! Because it seems so weird and energy-wasting to turn on lights when the Sun is still out. Interestingly, for LiFi, the system treats ‘Light On’ as ‘1’ and ‘Light Off’ as ‘0’ (that’s how a computer understands command). So even when the LED lamp is dimmed to be almost invisible, as long as it’s twinkling, then information (“0” and “1”) can be transmitted.

But will it be disturbing to see the lamp twinkling? No, the speed of on and off is so quick that human eyes can not see it.

I am not sure if LiFi will eventually dominate the wireless communication system, just like we didn’t know listening to musics by MP3 format would be this convenient decades ago. But it is always fascinating to come across imaginative and innovative approaches that try to break the limits … and always to be keen on improvement.