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Wednesday 3 May 2017

Li-Fi Technology

What is Li-Fi?
How does Li-Fi work?
Wi-Fi vs Li-Fi | The ultimate definition of Li-Fi | Li-Fi news


Li-Fi claims to be 100 times faster than standard Wi-Fi. But what exactly is it and how does it work?

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What is Li-Fi?

Light Fidelity or Li-Fi is a Visible Light Communications (VLC) system running wireless communications travelling at very high speeds.
Li-Fi uses common household LED (light emitting diodes) lightbulbs to enable data transfer, boasting speeds of up to 224 gigabits per second.
The term Li-Fi was coined by University of Edinburgh Professor Harald Haas during a TED Talk in 2011. Haas envisioned light bulbs that could act as wireless routers.
Subsequently, in 2012 after four years of research, Haas set up company pureLiFi with the aim 'to be the world leader in Visible Light Communications technology'.

How it works

Li-Fi and Wi-Fi are quite similar as both transmit Data electromagnetically. However, Wi-Fi uses radio waves while Li-Fi runs on visible light.
As we now know, Li-Fi is a Visible Light Communications (VLC) system. This means that it accommodates a photo-detector to receive light signals and a signal processing element to convert the data into 'stream-able' content.
An LED lightbulb is a semi-conductor light source meaning that the constant current of electricity supplied to an LED lightbulb can be dipped and dimmed, up and down at extremely high speeds, without being visible to the human eye.
For example, data is fed into an LED light bulb (with signal processing technology), it then sends data (embedded in its beam) at rapid speeds to the photo-detector (photodiode).
The tiny changes in the rapid dimming of LED bulbs is then converted by the 'receiver' into electrical signal.
The signal is then converted back into a binary data stream that we would recognise as web, video and audio applications that run on internet enables devices.

Li-Fi vs Wi-Fi

While some may think that Li-Fi with its 224 gigabits per second leaves WiFi in the dust, Li-Fi's exclusive use of visible light could halt a mass uptake. 
Li-Fi signals cannot pass through walls, so in order to enjoy full connectivity, capable LED bulbs will need to be placed throughout the Home. Not to mention, Li-Fi requires the lightbulb is on at all times to provide connectivity, meaning that the lights will need to be on during the day.
What's more, where there is a lack of light bulbs, there is a lack of Li-Fi internet so Li-Fi does take a hit when it comes to public Wi-Fi networks.
In an announcement yesterday, an extension of standard Wi-Fi is coming and it's called Wi-Fi HaLow.
This new project claims to double the range of connectivity while using less power. Due to this, Wi-Fi HaLow is reportedly perfect for battery powered devices such as smartwatches, smartphones and lends itself to Internet of Things devices such as sensors and smart applications. 
But it's not all doom and gloom! Due to its impressive speeds, Li-Fi could make a huge impact on the internet of things too, with data transferred at much higher levels with even more devices able to connect to one another. 
What's more, due to its shorter range, Li-Fi is more secure than Wi-Fi and it's reported that embedded light beams reflected off a surface could still achieve 70 megabits per second.
© pureLiFi


The future of Li-Fi

In November 2014, Li-Fi pioneers pureLiFi joined forces with French lighting company Lucibel aiming to bring out Li-Fi enables products, by the end of 2015.
pureLiFi already have two products on the market: Li-Flame Ceiling Unit to connect to an LED light fixture and Li-Flame Desk Unit which connects to a device via USB, both aiming to provide light and connectivity in one device. 
Plus, with faster connectivity and data transmission it’s an interesting space for businesses. The integration of internet of things devices and Li-Fi will provide a wealth of opportunities for retailers and other businesses alike. For example, shop owners could transmit data to multiple customers' phones quickly, securely and remotely. 
Li-Fi is reportedly being tested in Dubai, by UAE-based telecommunications provider, du and Zero1. Du claims to have successfully provided internet, audio and video streaming over a Li-Fi connection.
What's more, reports suggest that Apple may build future iPhones with Li-Fi capabilities. A Twitter user found that within its iOS 9.1 code there were references to Li-Fi written as 'LiFiCapability' hinting that Apple may integrate Li-fi with iPhones in the future. 
Whether or not Li-Fi will live up to its hype is yet to be decided.

What’s the difference between a hub, a switch, and a router?

"Hubs, switches, and routers are all computer networking devices with varying capabilities. Unfortunately, the terms are also often misused"
Hubs, switches, and routers are all devices that let you connect one or more computers to other computers, networked devices, or even other networks. Each has two or more connectors called ports into which you plug in the cables to make the connection. Varying degrees of magic happen inside the device and therein lies the difference. I often see the terms misused, so let’s clarify what each one really means. 

Hubs

hub is typically the least expensive, least intelligent, and least complicated of the three. Its job is very simple – anything that comes in one port is sent out to the others.
That’s it.
If a message1 comes in for computer “A”, that message is sent out all the other ports, regardless of which one computer “A” is on:
Message coming into a hub
And when computer “A” responds, its response also goes out to every other port on the hub:
Response being sent through a hub
Every computer connected to the hub “sees” everything that every other computer on the hub sees. The computers themselves decide if they are the targeted recipient of the message and when a message should be paid attention to or not.
The hub itself is blissfully ignorant of the data being transmitted. For years, simple hubs have been quick and easy ways to connect computers in small networks.

Switches

switch does essentially what a hub does, but more efficiently. By paying attention to the traffic that comes across it, it can “learn” where particular addresses are.
Initially, a switch knows nothing and simply sends on incoming messages to all ports:
The initial contact through a switch
Even accepting that first message, however, the switch has learned something – it knows on which connection the sender of the message is located. Thus, when machine “A” responds to the message, the switches only need to send that message out to the one connection:
Response being processed through a switch

In addition to sending the response through to the originator, the switch has now learned something else – it now knows on which connection machine “A” is located.
That means that subsequent messages destined for machine “A” need only be sent to that one port:
Switch sending an incoming message to the machine who's location it is aware of.
Switches learn the location of the devices that they are connected to almost instantaneously. The net result is that most network traffic only goes where it needs to rather than to every port. On busy networks, this can make the network significantly faster.


Routers

router is the smartest and most complicated of the bunch. Routers come in all shapes and sizes – from the small, four-port broadband routers that are very popular right now to the large industrial strength devices that drive the internet itself.
A simple way to think of a router is as a computer that can be programmed to understand, possibly manipulate, and route the data that it’s being asked to handle. Many routers today are, in fact, little computers dedicated to the task of routing network traffic.
As far as simple traffic routing is concerned, a router operates exactly as a switch, learning the location of the computers on its connections and routing traffic only to those computers.
Consumer grade routers perform at minimum two additional and important
tasks: DHCP and NAT.


DHCP – Dynamic Host Configuration Protocol – is the way dynamic IP addresses are assigned. A device asks for an IP address to be assigned to it from “upstream” and a DHCP server responds with an IP address assignment. A router connected to your ISP-provided internet connection will typically ask your ISP’s server for an IP address; this will be your IP address on the internet. Your local computers, on the other hand, will ask the router for an IP address and these addresses are local to your network.
Router reciving an IP address from ISP, and itself handing out IP addresses to local computers
NAT – Network Address Translation – is the way that the router translates the IP addresses of packets that cross the internet/local network boundary. When computer “A” sends a packet out, the IP address that it’s “from” is that of computer “A” – 192.168.1.2 in the example above. When the router passes that on to the internet, it replaces the local IP address with the internet IP address assigned by the ISP. It also keeps track, so that if a response comes back from somewhere on the internet, the router knows to do the translation in reverse – replace the internet IP address with the local IP address for machine “A” and then send that response packet on to machine “A”.
A side effect of NAT is that machines on the internet cannot initiate communications to local machines – they can only respond to communications initiated by those local machines.
The net effect is that the router then also acts as a firewall:
Router acting as a firewall

A note about speed

A quick note on one other thing that you’ll often see mentioned with these devices and that’s network speed. Most devices now are capable of both 10mbps (10 mega-bits, or million bits, per second) as well as 100mbps and will automatically detect the speed.
More and more devices are now capable of handling 1000mbps or a billion bits per second (1gpbs).
Similarly, many devices are now also wireless transmitters that simply act like additional ports on the device.

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