LiFi Questions

Here is our ever growing list of frequently asked questions about LiFi technology.

1) WHAT IS THE WORKING PRINCIPLE OF LIFI?

To use the LiFi technology from a visible light point of view, a user will typically require a transmitter such as LED light and a receiver made up of a photodetector material. The transmitter is connected to the network to modulate digital data along with the flickering light which emits from the LED light source. The receiver then receives such light and decodes the information modulated with the corresponding light rays.

The transmitter in a LiFi system is an LED which generates white light. This can be achieved in one of two ways. The first technique involves the combination of red green and blue (RGB) LEDs to produce white light. The second technique involves using a blue Indium Gallium Nitride (InGaN) emitter that excites a yellow phosphor coating to emit white light.  The white LED chips are typically grouped in arrays to create a combined emitter with higher radiant output flux. Since the transmitter serves the dual purpose of illumination and data transmission, the illuminance requirement of the task area determines the transmitted power of the LEDs used.

The receiver frontend is usually made up of a photodiode, pre-amplifier, an optical concentrator, and an optional optical filter. Received light passes through the optical filter which cuts out background radiation and the slow component from the yellow phosphor emission at the transmitter.  The filtered light is converged onto the Photodiode by a collimator lens. The Photodiode converts the received light to an electrical current which is pre-amplified and passed onto signal processing components.

2) WHAT IS SO GOOD ABOUT LIFI?

The properties of light give undeniable advantages to LiFi.  As already mentioned, it provides an extremely wide and unregulated spectrum that can be exploited to achieve very high data rates, especially by transmitting data over parallel wavelengths.

LiFi provides increased security over Radio Frequency (RF) technologies as light beams cannot go through obstacles and can be easily reshaped by optical systems, which reduces the risk of casual eavesdropping.

Light does not interfere with RF, making LiFi an interesting solution to complement and offload the RF spectrum, but also to provide wireless connectivity in places where RF are restricted because of electromagnetic interference or health reasons.

One of the latest key ideas of LiFi, is to reuse the LED lighting infrastructure already in place to provide network access, as more than 70% of the traffic actually occurs indoors.  This way, the growing need for connectivity could be addressed at almost no additional energy cost and without having to deploy a new and dedicated infrastructure, which would make LiFi a ‘green’ technology compatible

3) WHAT ARE THE DISADVANTAGES OF LIFI?

Just like with every technology, there are benefits and disadvantages. Below are some of the disadvantages of LiFi technology:

1)LiFi requires a Line of Sight.  

2)If the apparatus is set up outdoors, it would need to deal with changing weather conditions.  

3)If the apparatus is set up indoors, one would not be able to shift the receiver.   The problem of how the receiver will transmit back to the transmitter still persists.   

4)Light waves can easily be blocked and cannot penetrate thick walls as radio waves can.   We become dependent on the light source for internet access. If the light source malfunctions, we lose access to the internet.   

5) Current High costs of most LiFi systems. Generally, LiFi systems can be expensive to buy.

6) Lack of Infrastructure and standards to support the universal integration of LiFi components on all devices. 

4) DOES LIFI NEED A LINE OF SIGHT?

Firstly, let’s understand what Line of sight (LOS) means.  Line of sight is the imaginary line between an observer and the target. In communication, line of sight is the direct path from a transmitter to the receiver and the obstructions that may fall in that path.

The efficiency of LiFi can be achieved only with Line-of-Sight communication. If either receiver/transmitter moves from its desired position then miscommunication may occur. However, a few months ago, Jean-Paul Linnartz, a Technical Leader ELIoT Signify Researcher and a Professor at the Eindhoven University of Technology demonstrated the LiFi MIMO approach.  The implementation of a LiFi Multiple Input Multiple Output (MIMO) approach can help in the avoidance of a signal loss if the line of sight is interrupted.

5) IS LIFI FASTER THAN WI-FI?

The answer is YES.  The highest speed recorded for LiFi transmission was around 224 Gbps at the Oxford University research labs.  With a 60-degree field of view, the researchers transmitted six wavelengths of 37.4 Gbps each, for an aggregate bandwidth of 224 Gbps. When the field of view was narrowed down to 36 degrees, the researchers transmitted only three wavelengths for an aggregate bandwidth of 112 Gbps.

6) WHAT IS THE FUTURE SCOPE OF LIFI?

One thing is for sure, LiFi is here to stay and is not going anywhere.  Although, since its introduction from the viral TEDTalk presentation by Professor Harald Hass in 2011, many people are still not aware of the potential and capabilities of LiFi.

‘So far, we hardly see any reason why LiFi should replace the incumbents such as radio-based and cable solutions,’ Thomé explained. For consumer markets to adopt LiFi, it must work as well as WiFi at the same cost, Thomé said.

LiFi will not replace WiFi. Not just yet. Maybe in 50 to 100 years or perhaps even sooner, time will tell.

To push LiFi further, the main challenges are standardisation, cost, and wide adoption by the telecommunication players, from device to infrastructure, and the benefits of LiFi must surpass incumbent solutions, Thomé said. ‘The key questions we should ask ourselves concerning new technologies or techniques are: “What problem do they solve from the user perspective?”,’ Thomé added

7) WHO IS THE FATHER OF LIFI?

Professor Harald Haas is widely known in the LiFi community as the Father of LiFi. He termed Light Fidelity (LiFi) and did a viral TEDTalk presentation on LiFi technology back in 2011.  Then in 2021, along with Dr Mostafa Afgani, He co-founded pureVLC, now known as pureLiFi.

8) CAN YOU USE A LASER IN LIFI?

The answer is Yes. Lasers can be used in LiFi.  Lasers provide significant speed and capacity advantages over LEDs for LiFi and data communications.  The LASER LiFi is the advanced version of LiFi where we use LASER in place of LED. The on-off activity of LASER is fast in comparison to LED. Data transfer speed of LASER LiFi is up to 10Gbps while LED LiFi data transfer speed is only 1Gbps. LASER is used for better performance and high data transfer speed.

One company, Kyocera SLD, has been doing extensive research on laser LiFi.  Kyocera SLD Laser’s Rudy stressed the need for devices well-suited to LiFi. ‘We have our laser light sources in automotive headlights, in flashlights being sold on Amazon,’ he explained. ‘It’s a laser-based light source. But it’s class one with respect to safety, so it can essentially be treated like an LED. This laser light is very high brightness, and it retains the high-speed capability.’ That brightness has enabled the company to transmit LiFi data over ranges up to 50 metres.

Rudy highlighted smart factories as another potential lead application. Laser-based LiFi can take the large volumes of data needed to and from ‘the workstations, the people, the vehicles, and, of course, the robot workstations, measuring, optimising, and controlling everything’, said Rudy. ‘With RF data rates, it’s just very challenging, so we think laser LiFi is an ideal solution.’