Notes from the author
The purpose of this post is not only to share a personal opinion but to start an open discussion. This analysis came from the experience I gained from the development of OCC applications and collaboration with other researches since I started investigating in this field. However, I am still an inexperienced researcher, and I greatly value any contribution.
Thus, feel free to make any contribution, revision, or feedback in the comments section. They are more than welcome, and they will be useful to deliver quality content!.
I believe that I'm not making an invalid assumption if I tell that all the engineers and researchers that work in the field of OCC have been wondered at least once in their careers if OCC is an actual market disruptive technology...
By the time this question comes up in my mind, I was participating in CSNDSP 2018 conference in Budapest. My first attendance at any conference. In this conference, I was showing the results we obtained from the evaluation of an occ prototype we develop at IDeTIC's laboratories. I remember how nervous I was... I was the last speaker of that session. Also, the four previous speakers already explained the core foundations of occ perfectly, leaving me with no room for further explanations. But all went well... I was able to barely manage my nerves and wait patiently for the turn of questions.
And... the question arises by a well-renowned doctor in the field of optical communications.
Participating at CSNDSP 2018.
What do you think is a potential application of this OCC technology?
I panicked, I thought... I wasn't expecting that... But it's just a simple question... I should have prepared better for this intervention. I also forgot that I will, later on, that day, present another OCC work related to indoor localization. A potential application of OCC that combines light and communications to estimate with high accuracy the transmitter position in a room. Which can be very useful in an industrial or medical scenario.
And I panicked because I have been focusing on the development of this technology setting aside its usefulness or viability. I thought let's start by developing the technology, and it might, in a recent future, solve new arising necessities and problems, creating new opportunities within the market. I wasn't indeed centering on real potential applications or needs.
So I start asking me this question, beginning the journey of
Finding that killer application that will pave the way for this technology to succeed!
However, to achieve this, it is necessary to identify the key differences between OCC (and if you want to include VLC) and conventional radio communications, like wifi, 4G, 5G, among others...
To open the discussion, let's start by highlighting and summarizing some statements that I have collected in seminars, conferences, popular videos, articles, and occasional conversations about the factors that differentiate both technologies.
Note from the author: know I'm going to show some differentiating factors of VLC and OCC. However, you can jump directly to my response at the end of this article.
"The visible spectrum is vast, hundreds of times greater than the radio spectrum. Therefore, there is more space to distribute our communications".
I agree with that statement. The visible light spectrum range is vast, greater than the radio spectrum. This capacity can be used either to increase the data rate between VLC devices or to provide coverage to a large number of devices.
Electromagnetic spectrum. Highlighted the Visible Ligth Spectrum. Note: it is not in scale, check dimensions.
However, to efficiently use this capacity, we must also take into account light generation and reception.
LED emits light in specific ranges of the spectrum through a process called electron-hole recombination that releases energy in the form of photons. I'm not going to go deeper into this concept, but it is essential to highlight. If you want to have a better clarification, just check this Wikipedia link or check this book chapter (pages 23, 24).
It is the recombination process what confers to each LED its specific spectrum emission: the set of electromagnetic waves it emits. The spectrum emission of an LED is strongly determined by its fabrication process. Examples of white LEDs and Red, Green, and Blue LED spectrum emission are shown in the next graph. As can be seen, Blue LEDs emits in a very narrow portion of the spectrum (that we perceive as blueish), while white LEDs emits in the whole range.
Electromagnetic spectrum of LEDs. White LED vs Red, Green and Blue LEDs.
If we use just plain white LEDs, we are not going to benefit the full capacity VLC provides. Using the entire spectrum for only one purpose is highly inefficient. Therefore to use it efficiently, we must divide the spectrum into narrow slots or portions and assign them different purposes. This is similar to the strategy is being followed by radio systems, where TV communications use a specific section of the radio spectrum completely separate from 4G, 5G range. An example of a radio spectrum division is shown in the following image.
US radio frequency allocations map (2016). Link to the wikipedia.
In short, if we want to fully exploit the available spectrum, we might need to use LEDs with narrowed emission spectrums, or use special optical filtering techniques. But this increases the fabrication and design complexity considerably.
In conclusion, despite the considerable extension of the visible spectrum, it does not directly imply that we can exploit it efficiently, thus affecting capacity and/or data speed.
Also, LED's light variations are limited in frequency, which means that LEDs could not switch on and off as fast as we want then to do it. This limits, even more, the data transmission.
Finally, it is important also to highlight that, as it was mentioned in this previous article, "Explain Like I'm Five: OCC," regarding OCC, the data transmission is constrained by the camera sampling rate.
... but ...
There is a lot of real experiments that perform far better than conventional radio systems, with data rates exceeding the hundreds of Gigabytes per second.
What I am trying to say is that capacity is indeed a differentiating factor. Still, we, as engineers, must address these issues to get the most of VLC systems.
"There is high energy involved in refrigerating radio cellular and base stations. So in terms of data efficiency, VLC could differentiate".
I don't remember when I hear this for the first time. This is a really controversial statement that I personally not share. Yes, high power base stations indeed consume a lot of energy to refrigerate radio systems and antennas. So technically, all the energy involved is not used strictly for communications. The system is relatively low data efficient.
However, LEDs, specifically LEDs used for illumination, also need refrigeration. This refrigeration could be passive when the LED is operating in standard conditions (illuminating). But when it is switching at a very high speed, powerful cooling (active) is needed. This is because as soon as the temperature increases, the LED begins to behave differently than expected, reducing its switching frequency limit or changing is light spectrum emission. On the other hand, LEDs have an inherent quantum efficiency, that relates the optical power emitted with the electrical power injected. Not all the electricity is fully converted into photons, there are losses. And despite that the recent technology of Organic LEDs provides relatively high quantum efficiency, it is still necessary to improve LED consumption to achieve low power transmissions.
Highlight that the LEDs are also used for illumination, so it is not right to directly compare both technologies. But putting aside the illumination factor... could we compare a small Organic LED with a low power radio system in terms of transmission efficiency? We must do the math, but as far as I understand, I will not say that efficiency is a differentiating factor of VLC and OCC technology.
"Light could be deployed in places that are sensitive to radio electromagnetic interferences, such as airplanes or hospitals."
I completely agree with this statement. Light can not interact with conventional radio antennas, at least not in the manner it is intended for a radio wave. By saying this, I mean that light could interact with the exposed silicon of some electronic components. As a matter of fact, in these links (link1, link2), researchers have created a laser transmitter that sends commands to a google assistant' microphone!. The microphone itself is fabricated using silicon, and that silicon is being affected by light (as it were a photodiode), generating an output current that emulates a voice. If you want to see with your eyes, check the following video that shows the general operation of the system.
But... yes... in general terms, light can be used safely in places where radio could generate interferences in the electronic equipment, such as airplanes or hospitals. And that is a potential differentiating factor!
"VLC systems are more secure than radio systems".
There is always confusion when applying this term. What do I understand when someones affirm that VLC is more secure than radio?. Well, it's a little bit tricky. Both systems could be attacked. I mean, If someone really wants to access your information, it could access the communication channel by using a photodiode or an antenna. In a similar fashion, I can listen to an ethernet cable (Just to let you know it is not that easy :P). Therefore only if the communication is fully encrypted, the hacker or your neighbor could not read the critical information. And that is true for both technologies.
The fundamental difference lies in the confinement easiness of the communication carrier. Light is naturally opaque to most structural materials like walls and furniture in houses and user products. Therefore it is easier to confine light in an area, denying access to external spies. I'm not telling you that you can not isolate your radio communications by covering your house with a proper metal structure. But that sounds very geek and can raise suspicions.
However, this aspect could also be viewed as a disadvantage because if you cover your receiver (for example, your smartphone's camera), you could not access the network. So this differentiating factor shows the two sides of a coin. It can be seen either as an advantage or a disadvantage. However, what is true is that the user has, in the end, a little more control over the establishment of communication.
"I already have a light bulb at home, let's use it!".
I love this term. As engineers, we love using things for applications that weren't intended for those things. And... a lamp for communication and lightning? What a crazy idea! I like to hear my superior when he is talking about illumication. And... we can use cameras too!. And the concept of reusing is not only desirable by passionate engineers, but also by the market. If you can reutilize, then you can ease the access and deployment of your technology. Fast and simple. You already got the infrastructure; just tweak some things, make little modifications, and let's start the communication.
"I can see the light, I can feel the network."
The last statement is personal. It's is very simple yet, as I will discuss later on in this article, it carries a little bit of meaning.
Let's arrive at the fundamental key difference of this system, the human perception. Light is visible (I'm talking about the visible spectrum, there are high and low wavelengths that cannot be seen by humans). As light can be seen, so a lot of issues arise. In the first place, the VLC or OCC link must be safe for humans. Thus It's desirable to remove any flickering that could produce hassle, migraines, or other types of illnesses.
Also, what happens if I'm at day at my office, do I have to turn on the lamps if I want to connect to the internet? Technically yes. In terms of human awareness, this can be an issue. Personally, I don't want a continuous LED light pointing to my desktop at any time of the day. To overcome this problem, there are current solutions that consist of the use of non-noticeable light like infrared, similar technology that uses your TV remote, ... but can we consider this as VLC?. Well, If we combined and LED infrared for communications with a conventional LED for communications... yes, let's say yes (still confused).
So we must follow what the standard of this technology states: that the communications must be unnoticeable by humans, as wifi does already, with the difference that light can be seen. And this constrains this technology.
Let's do a break :D.
Wow, there are too many things to digest... It sounds like there are some issues if we want to integrate VLC and OCC into society.
It could be, but so far... the effort of a lot of engineers and researchers that believe in this technology has increased the number of potential applications that can perform outstandingly.
To give you some examples, I'm preparing a vlc/occ application reference that I hope I can dedicate some time in the future and post in the following weeks. But let's mention a few potential use cases and application categories of this technology:
- Medical monitoring. Monitoring sensors deployed in patients without the need for long cables.
- Vehicle to vehicle or infrastructure communications. Allowing front and back car's lights to communicate between each other or infrastructure, to prevent accidents, to improve road usage.
- Industrial monitoring and control. Control of industrial equipment (we design a prototype that can be seen in "VLC for Industry 4.0") article.
- Marketing. Using screen displays to send useful marketing information to users.
- Underseas exploration. Drone to underwater base communications.
- Positioning and Location. Using light for transmitting precise position within a building.
As you can see there are a lot of potential applications, and this list does not show all of them. The list continues and goes on and on.
Let's answer now: what is a potential application of this technology?
We at our laboratories are exploring some ideas. But what I have found is the differentiating factor that pushes me to continue passionately working in this field.
VLC and OCC: the leading path to semantic communications.
Maybe I have chosen the wrong set of words, but let me explain what I mean for semantic communications.
For semantic communications, I'm referring to the human meaning or perception of communications. And I'm not referring to the meaning the user gives to the information itself, but the human awareness or understanding of what establishing a link is.
The factor of visibility in VLC and OCC links allows the user to extract some meaning from the network itself.
For example, in basic setups, the user is aware of where the network is deployed because he can see the falling the light in his room, over the walls, on the floor. Also, he can know the maximum distance the link can reach, less coverage in darker areas of his room.
Therefore, the user could sense the network: where it is deployed, whether it is working or not, whether there is an opportunity for future connections, or if the network is saturated. Also, the network could send specific messages that only the human can understand: alerts, advertisements, among others.
The human can perceive slow variations of light in terms of color, brightness, or even location.
This creates a new strategy for communications, new ways that an active user interacts with the network. Opposed to the conventional radio-communications, which are invisible to the user, only knowing it state through a machine interface.
The network itself talks directly to the user. Consequently, the user gives some meaning to the state perceived by the lamp.
Variations in the color of the light (turning with a little reddish color), could mean that the network is alerting you of low speed or that LED cell is busy.
Variations in the position of the light (by using an extended flat-panel grid) could indicate the following position for a guided tour withing museums. So the location of the light guides you (you infer this meaning from the light state), and at the same time, the light transmits the required information to your phone for the next display.
And from my personal perspective, this offers an incredible potential to change conventional user interaction with networks. Approaching humans with machines. And I feel I can be used as a critical differentiating factor between both technologies, between radio and light communications. That can be used to create a large number of applications that focus on the user experience of the network that couldn't be done using classical radio systems.
So far today, let's continue working :D.
I hope you have found this article interesting and useful. It is intended to open up a free discussion, so whether you are new to the field or a professional researcher, feel absolutely free to ask questions, modifications, or any kind of feedback :P.
What do you think is a potential application of this OCC technology?