The Tech Behind: “WiFi on Air” at 30,000 feet!

klm-wifi-logo-largeIt’s fascinating to see that many airlines in United States are offering “WiFi on Air” packages to the passengers. Most of the passengers are happily paying for such packages, maybe not as much for actual utility, as for the delight of texting their friends – “Guess where I’m texting from?!” The technology is still in the nascent stage, where you can complain about it being expensive and yet too slow. However, it is undoubtedly a big leap in technology. Let’s see how all of this works out for us at over 30,000 ft!

There are primarily two ways in which a WiFi communication network can be established within the high-flying airplanes.

Air To Ground Based Link: The first one is Air to Ground based, where an antenna is attached to the bottom of the plane to transmit and receive signals from ground based towers. The working is pretty much the same as cellular connections, however the operating frequency is 3GHz. The signal is transmitted from the plane to the nearest ground tower, which in turn relays the signal to the ground station. The ground station transmits the data to the ground tower which in turn relays the signal to the plane. There are almost 200 ground towers in USA that are dedicated to establish this communication network and more and more are coming up. The bandwidth for data is not that great, at 3.2 Mbps, that too not for each customer but for the entire plane! So limit yourselves to texting without any Voice over IP and video streaming applications. Such a communication system can be made more effective by using directional antennas on the plane for a more focused capturing of beam and thus, enhancing the bandwidth to 9.8 Mbps. It is but obvious, that such a system will cry out loud when the plane is flying over water bodies, as there will be no nearest tower to relay the signal to/from!

Satellite Based Link: The second one is Satellite Based network, where an antenna is attached to the top of the plane to transmit and receive the signals to the ground stations via satellites. The plane sends a request for data to the satellites, which communicates the same to the ground station. The ground stations sends the data for the requested web page to the satellite, which in turn relays the same to the plane. In this kind of a communication link we can achieve data rates from 10-30 Mbps. The operating frequency is in the Ku Band i.e. 12-18GHz. The satellites can take care of communication over Atlantic and Pacific ocean too!

It will be intriguing to see how this technology morphs into a more sophisticated form with higher data rates, more connectivity and availability at cheaper cost, in the coming time. The fear of hacking into the plane system is minimal with the differentiation of the operating frequency bands, however, the risk of opening up more an more communication links can’t be denied.


WiFi graduates to LiFi – Now internet from LED bulbs!

unnamed.jpgSurf internet, stream videos and make calls simply from a torch or the street lights or the headlights of your car. When Prof Harald Haas gave his first talk about this concept at TED, I was both fascinated and amused after watching it. But, honestly, I could never see that happening in the very near future. Blame my short-sighted vision or appreciate Prof Hass’s blazing fast progress, the first product is ready and out there in the world. It’s called Li-1st. Before telling you more about the product, let me talk about the science behind the concept.

LiFi is a term coined by Prof Harold, in line with conventional term WiFi. Both LiFi and WiFi are effectively used in communicating data using the electromagnetic waves, with the only difference that WiFi uses Radio Frequency while LiFi uses the visible light spectrum. If you compare the two spectrums, Visible light spectrum is almost 10,000 times broader than Radio frequency, meaning greater data transfer capacity. The basic idea of binary data in digital communication is still intact, however, instead of transmitting 1’s and 0’s, we switch the LED bulbs on and off in extremely small time gaps [almost 1000th of a nano second].The protocol used is more or less 802.11 [same as WiFi], with Manchester encoding followed with on off keying and pulse position¬†modulation, in the physical layer of the protocol. The bottleneck of line of sight communication is both boon and bane. Opaque objects will definitely jam the LiFi communication, however, the protocols can be designed robustly using the concept of Orthogonal frequency division multiplexing [OFDM]. With this type of modulation, we can rather benefit from multi-path and direct communication is no more a necessity. Also, the fact that this type of communication is more suited to short-range communication, makes it lesser prone to being hacked. A small chipset with protocol implemented and connect to a light source is all that it takes to get this set up ready. It’s low-cost and capable of 250 times faster data rates than the best broadband currently available through WiFi.

Let’s talk about the first LiFi product. The father of LiFi, Prof Hass, founded the company PureLiFi [earlier known as PureVLC], which focuses specifically on visible light communication. Their first product is a bidirectional visible light communication device which is capable of uplink and downlink speed of 5 Mbps. There are two parts in the set up; first part is a transceiver unit which is connected to an LED light source and the other part is a similar transceiver connected to another light source and also connected to the laptop though USB. You can use this set up with the two light sources separated over a range of 3m for the above mentioned data rate. The light sources can be dimmed down without affecting the quality of video streaming much, so that the flash is not a disturbing factor. The product is still in the prototype phase and has also been demonstrated at a few conferences.

The applications of this concept are restricted only by the limits of our imagination. Imagine the reading lights on your top in the airplanes being a source of internet. Imagine the headlights in your cars being a source for navigation information, traffic control and accident prevention. Imagine beaming torches at one another to communicate.

LiFi is not supposed to replace WiFi by any means. Long distance communication is still made easy only through wireless networks, generally with RF and Microwaves. However, LiFi is simply an efficient add on to the existing infrastructure of illuminating sources around us.