LiFi FAQs

Discover the answers on frequently asked questions about LiFi.

What is LiFi?
LiFi stands for Light Fidelity – a term that is derived from Wireless Fidelity (WiFi). It is one of the newest communications technologies aiming to improve upon the current technology through the use of visible light, in lieu of the prevailing radio frequency technology, as a medium for data transport.
How does LiFi work?
LiFi works by using visible light through overhead lighting as the medium for the transmission of data. This is done through the use of a Visible Light Communications (VLC) system for data transmission, which has two qualifying components: a light source with a signal processing unit for the transmission of data signals and a photodiode device in order to receive the transmitted light signals.

When current is passed through a light source, in this case an LED bulb, the bulb releases photons as it gives off light. In a LiFi system, a constant stream of photons is needed for the transmission of data. To be more precise, the data is transmitted through the constant glowing and dimming of light at very high speeds, which is then received and demodulated by the photodiode device and then converted into a continuous stream of binary data containing videos, images, audio, text, or applications that are readily-consumable on any internet-enabled device.

Why is the Flickering of Light in LiFi Systems Invisible?
As mentioned earlier, the constant modulation of light in a bulb becomes the signal interpreted by the photodiode decide, which then becomes binary data. This is possible through variations in the current being introduced into the light source. When this is done slowly, the variations in the light source’s brightness becomes quite visible. Within a household setting, or even any interior setting, the constant flickering of the primary light source is deemed unacceptable. For this reason, the brightness of the light is changed at extremely high speeds to make the process unperceivable to the human eye.
Why is LED Used in LiFi Systems?
The threshold for flickering of light that can be perceived by the human eye is 60 Hz. This means that when light is modulated at frequencies higher than 60 Hz, this will be indistinguishable to humans. LiFi systems make use of LED as VLC mainly because it is a semiconductor, which gives them the ability to modulate light at extremely high speeds – speeds unachievable in incandescent and fluorescent bulbs. Additionally, LED is generally considered to be a more efficient light source because it emits light in a very narrow band of wavelengths, allowing it to emit light efficiently without wasting energy.
Will LiFi be Replacing WiFi When It Is Released?
Generally speaking, the concept of LiFi was created not to replace WiFi entirely, but as an alternative in some areas wherein the use of WiFi (or radio frequency) is prohibited. It can also be used to enhance connections in other areas where high-speed connectivity is required.
Specifically, the process of replacing WiFi with LiFi will be quite costly and will take extended periods of time because it entails not only replacing the technology itself, but also the replacement of the basic infrastructure behind WiFi.
Is LiFi expensive?
Companies responsible for research on LiFi technology are currently working on several improvements to create multiple variations of the tech for applications across multiple devices. This includes the miniaturization of the technology for its use on mobile devices. When these are ultimately integrated into various mobile devices such as mobile phones, tablets, or laptops, the technology will be very affordable. It may even cost the consumer nothing.
Do the Lights Have to be Turned On for LiFi to Work?
Because the technology is dependent on light for the transmission of data, LiFi will not work when the lights are turned off. However, this can be worked around by dimming the lights low enough to make a room appear dark while also still able to transmit data. This is done through the lowering the level of illumination to levels as low as 60 lux. For reference, light level for normal offices and classrooms are at 250 lux and 150 lux for theaters. Researches into the technology reveal that devices still perform consistently under 10 to 90 percent room illumination.
For future iterations of the technology, invisible parts of the light spectrum can be used for the transmission of data such as infrared – a technology already in use for LiFi uplink.
Will Sunlight Interfere with the LiFi Signal?
Modulated light is still detectable even under overly bright conditions, such as daylight. Because the receivers are programmed to detect differences in the brightness level of the light source, any constant light applied to the device will not be detected. These photo disruptions will only be filtered out by the receiver.
Will Light Blockage Affect the LiFi Signal?
The degree of blockage will determine the ability of the receiver to pick up signals from the VLC. Generally, the signal will still be able to pick up signals because light is able to bounce off of different surfaces. Total blockage over the receiver (e.g. piece of paper over the photodiode), on the other hand, will undoubtedly hinder its ability to pick up any signal.
Will LiFi work if the Device is in My Pocket?
Placing the entire mobile device, or even just the photodiode, inside your pocket constitutes a total blockage, rendering the device to be unable to receive any signals given off by the VLC. This can work, however, if the person has transparent pants or pockets.
Remember that LiFi is a complimentary piece of technology and is, therefore, not required to work when total blockage is present. When such cases arise, radio frequencies from WiFi devices or cellular communication systems will continue delivering the data.
Is LiFi Dependent on Line of Sight?
As stated above, LiFi devices are not dependent on line of sight. Because they are still able to pick up signals from light bouncing off of other surfaces, they do not require light signals to specifically target the photodiode device on the receiver.
The rate in which data is transferred over the network will be largely dependent on the strength of the signal, which will largely depend on its ability to acquire a signal from the light source. Any noise or interference will most likely affect the signal acquired by the device. In general, weaker signals will have slower rates of data transmission while stronger signals will generally transmit data faster.
Is LiFi more Secure than WiFi?
LiFi generally has a distinct advantage over WiFi in terms of security because of the fundamental differences in both mediums. Radio frequencies tend to have a better coverage because they are able to reach areas as far as 32m away (for WiFi signals) from the signal source. They are also able to circumvent physical blockages, allowing it to reach users from other rooms but still within the signal radius.
On the other hand, light is unable to pass through any opaque physical confinement. While others may see this as a disadvantages, it actually increases its level of security because users can physically control the conditions in which wireless data is transmitted. This eliminates the risk of others hacking into the network to either steal user data or to simply freeload on an internet connection. Moreover, other security protocols for data encryption and authentication may also be leveraged in LiFi systems to further improve the overall level of security within the network.
What does Bidirectional Technology Mean?
LiFi is a wireless communications technology that can be described as full duplex. It means that data transmission is bidirectional (i.e. can happen both ways) at the same time. Within a LiFi network, data transmission occurs simultaneously in both uplink (data is sent to the server) and downlink (data is sent by the server to the receiving device) streams. This is an important quality to have in a data communication system as it allows the seamless transmission of data within the network without any restrictions. Data traffic flows so freely within the network that even multiple users are able to transmit and receive data in real time.
What does Data Density Mean?
Data density refers to the capacity of the network within a particular area to provide service to each user without the quality of service being affected. For LiFi systems, data densities offered allow for significantly greater capacities. For instance, a room with 8 integrated LED lights with each bulb transmitting 42 Mbps of data will lead to a greater capacity of 336 Mbps for the entire room, resulting in a faster, more reliable user experience.

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