Interview | TTB | Signify | LiFi | Sep 26, 2020

LiFi Communication Interview

For over a decade, research in LiFi has been intensified with amazing results. When Musa Unmehopa, an authority in the lighting industry, took on the position of Head of Ecosystems and Strategic Alliances for LiFi at Signify, it was clear that LED professional would have to report what he has to say about the status of LiFi and his future plans. We have known him since he was appointed Secretary General at Zhaga at the beginning of 2014. Since then he was always in charge at Philips Lighting, now Signify, in some capacity, also representing the company in the Connected Lighting Alliance. In addition, his resumé marks him as a specialist in standardization and a technology advisor.


Musa is Head of Ecosystems and Alliances for LiFi, at Signify. Prior to joining Philips Lighting in 2013, he worked for Bell Labs, Lucent Technologies, and Alcatel-Lucent. Musa has held senior leadership roles in various standards bodies, trade organizations and industry consortia, including chairman of the Technical Plenary of the Open Mobile Alliance, vice-chairman of the Board of the Zigbee Alliance, and Secretary General of the Zhaga Consortium. He also served on the boards of The Connected Lighting Alliance, the Emerge Alliance, and the Parlay Group, and is an advisor to several technology start-ups. Author of two technology books, Musa has been an invited keynote speaker and panelist at various industry events. His publications include numerous papers in technical journals and conferences. He holds two patents. Musa received a BSc. and MSc. degree in computer science from Twente University and MBA degrees from TIAS Business School and University of Bradford School of Management.

Copyrights (c) 2020 Luger Research e.U., All rights reserved.


LED professional: Could you please tell us a little bit about yourself? How did you become involved in standardization? What can you tell us about your career at Philips Lighting -– now Signify?

Musa UNMEHOPA: I have been active in standardization for most of my working life. Having started my career in the telecommunications industry, developing 3G and 4G systems, I joined the standardization department of Philips Lighting in 2013. The company had recognized early on that the transition from conventional lighting to LED was not limited to light sources only. It opened up a world of opportunity to enhance lighting with communications capabilities. Philips Lighting, and now Signify, has been on the forefront of that transition and I was able to support the transition through leadership roles in the Zhaga Consortium, the Zigbee Alliance, and the Connected Lighting Alliance.

LED professional: The latest step on your career ladder is now the appointment as Head of Ecosystems and Strategic Alliances for LiFi. Why LiFi? What are the responsibilities, tasks and duties included in this position?

Musa UNMEHOPA: Our position as the industry leader in connected lighting, makes Signify the lighting company for the Internet of Things (IoT). The world of lighting and communications are converging. First, for example with Philips Hue, we were adding communications technology to lighting, in order to create a better lighting experience. Now, with LiFi, we are adding lighting technology to communications, in order to create a better communications experience. We bring a century of lighting expertise and a decade of connected lighting leadership to the communications industry. Lighting truly becomes a new intelligent language.

In order to realize the growth that we envision for LiFi, it is important to create a healthy ecosystem where all players in the value chain are represented and can thrive. LiFi is a communications technology, and any LiFi system deployment will consist of a network of interconnected nodes. The many nodes may have different functions and may be provided by different suppliers. This value chain includes luminaire manufacturers, LED component suppliers, mobile device manufacturers, chip vendors, communications service providers, network installers, etc. All these players need to come together to make LiFi a success.

Standardization plays an essential part in building this ecosystem, especially for applications with mass adoption in e.g. offices or the home. Network nodes from different suppliers must be able to interconnect and interoperate. Any successful communications technology today is based on a global connectivity standard. But connectivity alone is not enough. A strong certification program is needed to ensure true interoperability. Signify created this new role, Head of Ecosystems and Alliances for LiFi, to help build and lead the ecosystem that is needed to enable the growth of a strong LiFi market. Building key alliances with standards consortia, interest groups, trade associations, policy makers and government organizations will also be part of the role.


Figure 1: A potential LiFi use case -- Robots welding in a harsh industrial environment (car factory) where RF communication is challenging

LED professional: 
There are certainly specific strategic goals that you want to achieve. Can you name and explain them? Is there already a roadmap that can be made public, or is there currently just an internal roadmap that allows you to give us a rough idea?

Musa UNMEHOPA: Our strategic ambition with LiFi is very clear. We want to unlock the extraordinary potential of light to address new high-growth markets, and to establish LiFi as a mainstream communications technology to connect millions of people and devices globally. To help achieve this strategic goal, Signify launched Trulifi in July of 2019. Trulifi is our own high-speed LiFi solution, to enable highly reliable, secure and fast wireless communication that leverages existing and future lighting infrastructure.

LED professional: In the meantime we have learned that “LiFi is not always LiFi“ as there are huge differences between different approaches, for example, if high transmission rates are required or low baud rates are sufficient. Which key application does Signify see LiFi having the biggest advantages over conventional wireless solutions?

Indeed, “LiFi is not LiFi”, just like “5G is not 5G”. For LiFi there are many different use cases that can be applicable in many different market segments. Just like there are many different use cases for 5G, including mobile broadband, fixed wireless access, and many others. But there is one key aspect that all LiFi use cases have in common. If your environment is unfavourable for radio communication (electromagnetic interference, such as in industrial applications) or in situations where radio propagation is blocked (such as in a warehouse with a lot of metal structures) LiFi is the preferred solution. In places where exposure to radio waves is not desired or even harmful (hospitals, schools, volatile environments like mines or chemical plants) LiFi is not just the preferred option, it is the only option for wireless communication. Next to these applications, LiFi can help to offload conventional radio-based technologies and offers reliable, secure and high-speed network connectivity where it is needed.

In applications where low-latency must be guaranteed, such as for real-time controls of industrial robots, for hick-up free video calls, or for virtual reality applications, LiFi can offer that Quality of Service. The radio spectrum is heavily congested. When glitches occur in WiFi communications, these are often caused by bursts of RF interference from other users in neighboring areas. As light is guaranteed not to go through a wall, light communication will also not be hampered by communications by other users in the next room.

LED professional: What are the key applications from a user’s perspective?

Musa UNMEHOPA: At Signify we take the perspective of market segments, each of which addresses different user communities and may support a number of use cases. The segments that we have identified for LiFi are Office, Hospitality, Digital Industry, Aerospace and Transportation, Public, Consumer and Devices. Each of these segments has specific use cases and requirements where LiFi could offer a solution. For example, in-flight connectivity in the aerospace industry is subject to strict regulations to ensure that the radios inside passengers’ devices do not cause electromagnetic interference which may affect the navigation equipment of an aircraft. LiFi offers a solution that does not suffer from this problem, and in addition can reduce weight in the aircraft by eliminating the need for extensive copper wiring to each passenger seat. In the industry segment, we often see that wired solutions have disadvantages, because changing the factory layout is costly when you need to re-arrange the wiring to each of the machines. And factory workers may trip over cable bundles, causing a safety hazard. Wireless solutions based on RF technology also come with challenges, because factories are typically full of metallic surfaces and moving machines that can weaken, reflect, and block radio signals. LiFi offers uncomplicated and error-free transmission in these harsh industrial environments.

LED professional: For a successful breakthrough and broad application in the market, standardization is always a key element. Are there standardization activities?

Musa UNMEHOPA: Standardization is key to innovation and an important condition for enabling growth. Compatibility and interoperability increase consumer confidence, lowering the barrier to mass market adoption and allowing for economies of scale in manufacturing and supply.

Today, there are a number of standardization activities across the industry which focus on the base protocol level, like how bits or packets are communicated over the optical wireless link. These activity streams may develop in a complementary manner and over time converge into a single system. Or they may evolve in parallel and co-exist in the market, where each is fit-for-purpose for a specific set of requirements and use cases. Our current, commercially available Trulifi rage is based on the ITU G.9991 standard, as the technology is mature, and chipsets are available on the market.

It is important to understand that standardization involves more than just specifying the basic communications protocol. Application functionality, for example, commissioning and system level behavior, like end to end security and network management, also need to be commonly understood. We must look at standardization in the broadest possible context. Besides specifying the technology, standardization also includes a testing and certification program, which verifies compliance with the standard specifications. But the program should also validate interoperability with other compliant implementations of the standard. And there needs to be a logo scheme which communicates this interoperability promise to manufacturers, system integrators, installers, and consumers, to help increase their confidence in adopting this exciting new technology. Signify will be active in all aspects of standardization. Where there are standardization activities already ongoing, we are contributing significantly to improve and enhance the technology. And in those areas where activities do not yet exist, Signify will commit resources to build and drive these areas forward in order to ensure the LiFi market reaches its full potential.

LED professional: On the other side, there is IP. While often relevant for the success of a company, sometimes it also hinders a quick market introduction. What are your thoughts on that?

Musa UNMEHOPA: I strongly believe in the ecosystem approach, which involves representatives of the entire value chain and stakeholder field. As with any communication networking technology, no one company can provide all parts of the entire system on their own. Alliance partners with shared interests and complementary skills will have to come together, to create and build a global market in which we can all compete effectively, to serve our customers in the best possible way. One of the benefits of international standardization is that these activities are conducted under transparent and widely accepted Intellectual Property Policies. Everyone participating in and contributing to the standardization effort agrees to grant access to their technology which ecosystem partners can use for compliant product implementations. This helps reduce uncertainty and remove roadblocks to broad market adoption.


Figure 2: Access point and the LiFi endpoint, which are installed in the Philips stadium in Eindhoven

LED professional: As we delve more deeply into the technology and application related part of our discussion we have a couple of questions: Are luminaires really the best suited solution as LiFi access points? Are there no better, or at least equally well-suited, options that are serious competitors? Also, is Signify thinking about fully integrated systems where the light modulation is an integrated part of the illumination element or are they more focused on modules that could also, but not exclusively, be used in luminaires?

Musa UNMEHOPA: There are many reasons why using current and future lighting infrastructure provides such a compelling solution to offer LiFi connectivity. Wherever there are people, there is light. For decades, society has invested billions to illuminate every inch of where we live, work and play. This has resulted in an incredibly extensive and dense network of powered nodes, which can be leveraged to provide connectivity in addition to illumination. Line of sight is important for LiFi access points to deliver the communication signal to the end user, and the light points in the ceiling truly provide a winning proposition to host these LiFi access points. This is one of the premier reasons why we at Signify believe our company, as the number one lighting company in the world, is ideally positioned to be the driving force in enabling a huge market for LiFi.

Having said all that, we need to make meaningful choices driven by the use cases and requirements we want to address. For example, for the Office and Hospitality segments, we use Trulifi transceivers that are designed into luminaires. This choice makes sense, because of the lighting infrastructure that is already available in those environments. But for other market segments or other use cases, for example, real-time control of industrial robots, we may decide to use dedicated transceivers.

LED professional: As previously noted, there are different kinds of LiFi. A common misunderstanding is that LiFi is always based on visible light, and especially white light. This approach is often also named Visible Light Communication, or VLC. But with VLC, we still have to distinguish how the white light is generated, because, for example, phosphor converted white light does not allow high data rates. What are the current preferred technologies? How can high data rates be achieved? Where are the current limits in the lab and under real live conditions? How fast will real live transmission rates improve over the next years?

Musa UNMEHOPA: The design choices for LEDs, which are used for lighting applications, are optimized for efficiency and for power. These LEDs were not originally designed for fast modulation. The phosphor coating slows down the variation of light, which limits the data rates that can be achieved. Note that, while illumination LEDs are the current bottleneck in terms of speed, lab tests have shown bit rates above a gigabit per second. But these have not yet found their way to commercial applications. So while the reuse of illumination LEDs can be an attractive approach, for applications that require higher data speeds you may consider using Infrared LEDs.

LED professional: While high data rates, which seems to be the key argument for introducing LiFi, can be realized, in the end it is still the slowest element in the chain that determines the speed. Does this mean that the luminaire of the future has to have a high-speed fiber connection, or are there other approaches? Is it possible that luminaires will just be mainly used as a repeater or something in that direction?

Musa UNMEHOPA: It is not all about data rates. LiFi is more than “just” a fast, wireless communications technology. But the question is valid; you need to take a systems approach. Only focusing on the speed which can be achieved in the optical wireless link can be misleading, because the system is only as fast as the slowest link. The local area network that delivers the communications signal towards the LiFi access point in the ceiling, or even the backhaul link that connects the building to the Internet backbone, can be a bottleneck.

For in-building systems, fiber to the lamp could be an option in future. Our research lab is involved in the EU Innovation Action to explore this jointly with other partners and academia. Other options include Power over Ethernet or powerline communication (PLC). What will be the best solution is dependent on the use case, and on the existing IT infrastructure that is already installed in the building.


Figure 3: LiFi transceiver connects to an office luminaire

LED professional: LiFi is based on the modulation of artificial light of a defined brightness. In comparison to daylight, the brightness is very low. Hence windows are a kind of disturbance variable that could be more than 10 times higher than the artificial light level. How can this noise be cancelled? Which mechanisms are currently known and used? How much does that reduce the transmission rates?

Musa UNMEHOPA: This is, of course, true, but sunlight mostly has a constant or at most slowly varying intensity. LiFi systems, however, modulate the brightness of the light, above modulation speeds of 1 MHz. And the LiFi receiver is tuned to pick up this modulated signal. Nevertheless, sunlight does indeed cause some extra noise, which our LiFi system can easily accommodate. Note that in the infrared spectrum, the noise issue is significantly reduced, because infrared light from the sun is filtered by windows for the purpose of energy conservation and climate control.

LED professional: Another aspect of the presence of windows concerns the marketing argument that LiFi is secure in regards to eavesdropping as light cannot pass through walls. Can you comment on that?

Musa UNMEHOPA: Just like transmission rates, one needs to consider security at a system level and not just at the link level. While the fact that light does not pass through walls provides an additional level of physical security compared to other wireless technologies, you cannot rely on this alone for your network security. For example, we use cryptographic keys to protect LiFi communication, even if the eavesdropper is in the same room, or outside just next to the window. Having said that, keeing the light contained within a space adds an extra layer of protection, which is very much appreciated in specific applications.

LED professional: During the day luminaires are often switched off and are also often dimmed. What are the consequences for data transmission?

Musa UNMEHOPA: We talked before about the benefit of using infrared LEDs to achieve higher data rates. In case LiFi communicates via invisible infrared, the lighting can be dimmed or even switched off and the LiFi connectivity continues to operate. The quality of the light is not impacted in any way.

LED professional: An additional issue could be that only indirect light reaches the receiver. Are there technologies and approaches to keep the system working?

Musa UNMEHOPA: LiFi communication requires line of sight. However, when the direct line of sight is interrupted, communication is not necessarily lost. Just like with light for illumination, you do not sit in the dark when, for instance, a colleague approaches your desk and stands in between you and the light source. Indoor, we light spaces from multiple angles. Our LiFi systems work in a similar way, and continue to operate under conditions of indirect light. In addition, we provide a mechanism for automatic handovers. We support seamless handover between LiFi transceivers so that a user can be mobile and move from one LiFi-enabled luminaire to another. The LiFi endpoint will automatically connect to the closest transceiver with seamless handovers between the light points.

LED professional: One argument against LiFi is often that it is currently a unidirectional communication as no means in the other direction are implemented.

Musa UNMEHOPA: For Trulifi we use a bi-directional system, where the LiFi signal is transmitted in both directions. There may be some asymmetry in the up and down link, because LiFi access points in the ceiling are always connected to mains power, whereas LiFi endpoints may be optimized for power usage for example in battery-operated devices. The communication protocol itself is symmetric. Only our indoor navigation is one-way, as it uses lights as location beacons to do positioning.

LED professional: In conclusion, would you summarize your view on LiFi in regards to the following points: What do you see as being the biggest obstacles on the way to mass application? Where are the biggest opportunities and chances? What are the prospects?

Musa UNMEHOPA: LiFi provides a tremendous opportunity to launch a new communications paradigm, addressing use cases and applications where RF has limitations. We can do amazing things with light, and light truly can become a new intelligent language. And while the technology is still advancing and technical issues continue to be resolved, my focus is on building the ecosystem that needs to be in place to realize the market potential. Standardization, from technical specification of the base protocol, definition of system level behavior, all the way to an interoperability testing and certification program with logo scheme, will play a pivotal part. Signify is committed to lead, and to drive the success of LiFi towards broad market adoption.

LED professional: Thank you!

Musa UNMEHOPA: You are very welcome, it is always a pleasure to connect with your readers. Going forward, I hope to be able to share a lot more about ongoing developments in this exciting new domain.

Copyrights (c) 2020 Luger Research e.U., Publisher of LED professional.
The first publication appeared in the LED professional Review (LpR), Issue#81, Sept/Oct 2020, pages 24-29. All rights reserved.