LED Backhaul Project Engineer Blog

What's Li-Fi? (3) What is its real use?

Last Update: Aug 31st, 2021

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Introduction: Basic advantages and disadvantages of Li-Fi

Since Li-Fi is not a radio wave but an optical communication, there are advantages and disadvantages unique to optical communication. The biggest disadvantage of Li-Fi compared to Wi-Fi is the inability to communicate outside the line-of-sight (NLOS) as explained previously, but there are other disadvantages as well, including

• Difficult to use outdoors due to sunlight problems.
  • Unlike backhaul optical communication, it cannot avoid the influence of sunlight because it communicates vertically.
• Short communication distance
  • Especially, the communication distance on the child side tends to be short due to the power consumption.

On the other hand, the main advantages are as follows. 1.

1. can be integrated with lighting
2. Can be used in places where radio waves are difficult to use (places that do not like radio waves or in high noise environments)
3. the range of light can be limited, so it is difficult to cause interference
4. NLOS communication is not possible, so it is easy to ensure security.

The first merit of "integration with lighting" should have been the biggest merit of Li-Fi, but as explained before, it is difficult with the current technology. This is also the biggest disadvantage of Wi-Fi, which is now considered a problem. However, there are two problems that have always been pointed out: the problem of communication speed reduction due to over-interference in public Wi-Fi, and the problem of security due to the risk of breaking through the encryption by flying to an unintended location. Therefore, if you are a user who is having trouble with these points, there seems to be merit in introducing LiFi.

Usage scenarios for Li-Fi

There are several proposed usage scenarios that take advantage of the above merits, and some of them are actually in operation. Here are some of them.

Use in factories

Factories are densely populated with devices that communicate with each other. It is very difficult to go wireless with Wi-Fi in such a situation. If the access points (APs) are installed incorrectly, there will be a lot of interference and the connection will be unreliable. There will also be many collisions and the possibility of large delays is high. By replacing this with Li-Fi, stable communication is possible even in situations where devices are densely packed. Also, security is of utmost importance in a factory, and with Wi-Fi, radio waves can leak outside the factory and be accessed illegally, but with Li-Fi, the light is shielded so that no signal can leak out, making it impossible to even attempt unauthorized access.

Use in airplanes

There have been attempts to make the entertainment systems in airplane seats wireless; Wi-Fi is too dense to run entertainment systems. However, the LAN cables that run to each seat are quite heavy, and if possible, we would like to reduce the weight by making them wireless. To meet these needs, we are experimenting with using Li-Fi to run the in-flight entertainment system.

Report "Air France and Oledcomm partner on first commercial flight with Li-Fi"

Use in hospitals

Hospitals have long been one of the environments that do not like radio waves. Although many hospitals now allow both cell phones and Wi-Fi, there are still rooms where electronic devices are strictly prohibited. On the other hand, there are places where stable wireless communication is not possible because the medical devices themselves emit a lot of noise, such as electronic scalpels. In such places, Li-Fi could be used as the only wireless communication device.

Both of these usage scenarios are difficult to achieve with Wi-Fi, and are areas where Li-Fi is expected to play an important role.

Strong Rivals Wi-Fi 6 and Local 5G

But that's not to say that competing Wi-Fi will leave its weaknesses untouched. Wi-Fi 6 is a new technology that is a vast improvement over the Wi-Fi of the past.

There are various Wi-Fi standards such as IEEE802.11b, g, a, ac, etc., and they differ in the modulation schemes, frequencies, and bandwidths (speeds) that they support. The Wi-Fi Alliance, the organization that manages the Wi-Fi standards, has decided to change this practice by using the names of the standards. To improve the situation, the Wi-Fi Alliance, which manages the Wi-Fi standards, has decided to change the conventional practice and use "Wi-Fi" + "number" to refer to each generation. IEEE802.11ac", which is probably the most widely used standard and the one that your smartphone probably supports, will be called Wi-Fi 5, and "IEEE802.11ax", which is only supported by a few smartphones and PCs at the moment but will surely become popular in the future, will be called Wi-Fi 6. .11ax", which is only supported by a few smartphones and PCs, but will surely become popular in the future, will be called Wi-Fi 6. Wi-Fi 6 is said to be the generation with the most significant changes to date, the most significant of which is the support for OFDMA. In simple terms, Wi-Fi 5 was based on the Ethernet culture of collisions and retransmissions, while Wi-Fi 6 uses the concept of scheduling, which is similar to the cell phone culture, to allow users to communicate in an orderly fashion. This reduces the number of "collisions," or wasted transmissions, and thus wasted interference, and increases the overall throughput of the access point (AP). In addition, several high-impact technologies have been adopted, such as MU-MIMO and BSS coloring. With these, Wi-Fi 6 will improve connectivity in environments with many APs and terminals, and the user experience will improve dramatically.

Also, in Japan, a new system (or rather rule) called Local 5G has been approved. This means that even if you are not a "mobile operator" like NTT Docomo or KDDI, you can build your own cell phone system (5G) on your own property. Cell phones are licensed and unlike Wi-Fi, there is no interference from other systems. In addition, 5G has the capability to achieve even higher reliability and lower latency. If we can use this communication performance in our own networks, for example in factories, we can use wireless communication in mission-critical applications where previously only wired connections were possible. In other words, it is expected to be used in areas where Wi-Fi has been weak so far.

Returning to Li-Fi, Li-Fi was originally intended to be used in scenes where Wi-Fi was not good. However, Wi-Fi has improved on its own weaknesses, and highly reliable systems such as local 5G are now an option. For example, of the three Li-Fi usage scenarios listed above, the only one that can only be done with Li-Fi is the last one in the hospital. Of course, there is the problem that most Wi-Fi devices are still compatible with Wi-Fi 5 or lower and are not yet capable of demonstrating the power of Wi-Fi 6, and the local 5G system is much larger and more complicated than Wi-Fi, requiring license applications, and therefore more expensive to install and operate. These are problems. However, these are not technical limitations and can be tolerated under certain circumstances. If we think about it this way (and it is not our place to say this as a promoter of optical wireless communication), it seems that the scenes where Li-Fi can be used are getting narrower and narrower, and the remaining ones are only very niche.

Future Li-Fi scenes and issues

In my opinion, the Li-Fi scene in the future will not be a substitute for Wi-Fi in places where Wi-Fi cannot be used, but rather a replacement for wireless in applications where wired is the majority. The reason for this is that the two small advantages of Li-Fi that have been thought to be not so big, such as "not being bound by worldwide regulations" and "being able to communicate even in narrow and narrow spaces," will come into play, or rather, we will have no choice but to take advantage of them.

For example, the replacement of HDMI cables, which are complicated, thick, and have strict length restrictions, making them much more difficult to handle and more expensive than LAN cables. Therefore, wireless technology has been one of the areas that have been strongly desired. Currently, there is a wireless technology called Wireless HD that uses 60GHz radio waves, but it is not widely used and is still connected with HDMI cables. One of the reasons why it has not become popular is that it is difficult to adopt it for TVs that are supposed to be sold worldwide because it is necessary to comply with the laws and regulations of each country. However, with Li-Fi, there is no need to consider such regulations and wireless technology is possible. Not only HDMI, but there must be many other things that are wired because they are difficult to handle but cannot be replaced by wireless.

It could also replace the internal wiring of cars, trucks, trains, and airplanes. These will have the advantage of being lighter than wired. Since wiring in a vehicle is expected to be in a narrow space, radio frequency wireless communication is often difficult^*1. In the case of Wi-Fi, for example, it is difficult to communicate through a hole of 1cm in diameter, but Li-Fi can communicate with no problem at all. In addition, there are situations where the merits of optical communication, such as being "noise-resistant," can be utilized when communicating in harsh environments. In addition, wireless communication will also be beneficial in moving parts and in areas where non-contact is required. For example, communication in rotating parts (e.g., between a wheel and an axle), which has been difficult because of the need for special connectors, will become possible.

However, it will be difficult to put this technology to practical use right now because the current Li-Fi is not fast enough or small enough for any of these applications. However, for these short range and high speed applications, miniaturization is easy and the speed can be significantly increased by using LD^*2 light sources, so there is a possibility of practical use in the near future. If this is the case, Li-Fi will deviate from its original meaning of lighting and communication, but it may become widely used as a technology to replace wired with wireless.

Summary

• The benefits of Li-Fi are often the weaknesses of previous Wi-Fi (Wi-Fi 5 and earlier).
• Wi-Fi 6 and local 5G overcome the weaknesses of previous Wi-Fi.
• Li-Fi needs to fight on two different merits: "can communicate in small places" and "free of radio laws worldwide".
• Judging from the overall picture, Li-Fi may be suitable for applications that replace short wires.

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