“Light Fidelity” (Li-Fi) is a new technology using visible light energy from LEDs to provide ubiquitous wireless access for communications in illuminated areas.
With LiFi, data is transmitted by modulating the intensity of the light, which is then received by a photo-sensitive detector, and the light signal is demodulated into electronic form.
This modulation is performed in such a way that it is not perceptible to the human eye.
Developed by Prof. Harald Haas, CSO of PueLiFi, this technology is a category of optical wireless communications (OWC). OWC includes infra-red and ultra-violet communications as well as visible light.
However, LiFi is unique in that the same visible light energy used for illumination may also be used for communication.
With the demand for mobile wireless access growing rapidly, mobile cellular and Wi-Fi networks will continue to become increasingly congested until adding additional radio frequency (RF) resources will be ineffective.
This is referred to as the spectrum crunch.
But a solution seems at hand. With over 70% of mobile traffic originating indoors, “light fidelity” (Li-Fi), a technology using the visible light portion of the electromagnetic spectrum to transmit information at very high speeds and so provide lighting and wireless communication simultaneously, seems poised to resolve this spectrum crunch.
Developed by UK-based company PureLiFi, this technology supplies complementary (non-interfering) bandwidth in areas illuminated by LEDs and its enormous data density capability is set to reduce the burden on existing RF networks substantially.
What constitutes Li-Fi?
Li-Fi is defined as the networked, mobile, high-speed visible light communications (VLC) solution for wireless communications. To facilitate pervasive indoor wireless access, each Li-Fi system requires:
- High speed: Exponential growth in demand for wireless data is not only due to the growing number of users, but also to the availability of high-rate downlink services such as video streaming and file download, both of which require large bandwidth. Li-Fi systems must therefore be high-speed to maintain the network services offered at present and to meet user expectations.
- Bi-directionality: To provide modest internet access, there must be a reverse link from the device to the network allowing the device to request and/or modify information and to upload photos and videos. Bi-directional communication is therefore essential for full network operation and a user-friendly experience.
- Multiple access: For RF networks to serve an abundant volume of users, each cellular base station (BS) consisting of hundreds of users and each Wi-Fi access point (AP) shares its time and/or frequency resources among the connected parties. Given that a defined area, theoretically housing multiple users/devices, could be illuminated by a single luminaire, adding Li-Fi to the light will necessitate a similar sharing of resources. This is called multiple access and is needed to extend wireless access to all desired users within the illuminated space and, therefore, the network.
- Mobility/handover: Due to the inherent directionality of light as opposed to RF signals, any space (generally indoor, but also outdoor) to be illuminated needs several light fixtures to cover the area sufficiently. Since every light source in a Li-Fi network is a wireless AP, it is essential for network operation that the communications link be unbroken while a user is moving: the network must “hand over” the user from one AP to the next.
Without such functionality, a mobile user will need to constantly re-establish connection with each network AP, and re-start its running information transfer on the device.
While some of these features are more important than others, all are fundamental to the operation of Li-Fi for wireless communications networks.
Each contributes for less disturbance and difficulty and influences higher efficiency with an overall improved user experience.
The dangers of “quasi Li-Fi”
Even at this early stage in its development, there are a few commercial Li-Fi products available. As an emerging technology, developing Li-Fi products will have very limited capabilities.
The “siren call” or lure is that “first mover advantage” harbours many pitfalls for all but a few well-defined applications in specific market segments.
Rushing to products, i.e. missing one or more of the core features, potentially dead-ends those products in a technological niche.
Bi-directionality is, perhaps, the easiest feature of Li-Fi to overlook. However, that would essentially eliminate the possibility for a true Li-Fi system.
With broadcast-only technology, the system is limited to only offloading the RF network downlink, and an uplink connection must be established.
This leaves the product applicable to only a handful of use cases such as sensor networks. If high-speed communication is disregarded, the Li-Fi network degrades to a basic control information distributor, which may enable a few applications such as indoor positioning and mobile application content update.
Moreover, the network will be reliant on existing RF infrastructures for content delivery and will in fact accelerate the inevitable spectrum crunch.
To serve the high numbers of indoor users requesting traffic, each Li-Fi AP must be able to provide multiple-access to facilitate multiple users.
It is not feasible to establish a dedicated point-to-point link for each person in an indoor space as almost everyone owns a mobile device in today’s world.
The lack of multiple access capabilities therefore diminishes the applicability of the product to merely point-to-point communications where current wired,
RF and laser technologies are deemed unsuitable. Such application areas include underwater communications, some sensor networks and hospital patient monitoring. Yet, even in these areas, the ability to communicate with many devices would enhance the product functionality greatly.
The principal requirement for ubiquitous wireless access is the ability for a mobile device to transfer from one AP to another without its connection faltering, and its information transferral being interrupted.
Imagine if, in an office space, a user is downloading important documents while moving around the room, and whenever they leave the illumination of one luminaire and enter the next, the downloads must be restarted.
This eliminates the possibility of mobile wireless access because the user is not being “handed over” from one AP to the next. The result would be a static-user wireless access scheme.
This denies the very ubiquity of wireless access that has become a part of everyday life, depriving the illuminated space of proper networked communication.
The value of true Li-Fi
Due to the immense challenges of developing a full Li-Fi system, it can be very easy to be drawn into simpler solutions in an attempt to achieve a product and revenue early.
However, the development of a true Li-Fi solution will provide vast benefits for the developing company, both in the short and medium term, and especially in the long term.
The most important of these benefits are:
- The elaboration of a true Li-Fi solution will allow products to be derived from this solution that can be used in almost all VLC applications and use cases. True Li-Fi is competent to provide indoor communications. All other VLC offerings are only a small part of a true Li-Fi system. Location-based services can be implemented through unidirectional, low-speed Li-Fi. Point-to-point applications can be achieved without the need for multiple access, and augmented entertainment for the television market can use non-networked Li-Fi. Therefore, products can be spun out for niche areas during the development of full Li-Fi and the final solution will allow the developer access to every aspect of the VLC market.
- While there have been various markets identified for the proliferation of VLC/Li-Fi technology, the primary target market is indoor networked communications. The discovery that a substantial portion (> 70%) of wireless traffic originates indoors identifies this environment as the place where Li-Fi will be indispensable in the future. The conception of a true Li-Fi solution will preferably position the developer to command this market. The second largest area of interest is that of location-based services, which use a unique method to deliver data to standard smartphones and tablets. By delivering precise positional information to users, retailers and service providers can transmit location-based advertising and messages to enhance end-user interaction. Ultimately, the true Li-Fi solution allows the developer to dominate all market segments and establish themselves as market leaders for VLC and Li-Fi solutions.
- Dictating the VLC market through Li-Fi technology holds values other than market share and revenue, namely the power to drive and influence VLC standardisation. The established Li-Fi market leader will be in the unique position to develop a new standard which defines the operation of VLC for indoor communications and content delivery. By liaising with major handset and tablet manufacturers, the integration of Li-Fi technology into such devices can begin. All in all, the development of the true Li-Fi solution will ultimately guarantee the developing company not only market leadership, but also the continued strength to secure and bolden this position.
Li-Fi networks can and will provide the perfect complement to today’s RF infrastructure and further enhance mobile communications.
However, the lack of true Li-Fi products can lead to limited application which ultimately do not constitute Li-Fi solutions as defined.
The spectrum crunch is coming, and indoor communications will be in sore need of bolstering, given that the current rate of wireless data growth is unceasing.
The only solution to this is a high-speed, bidirectional, fully mobile wireless a Li-Fi system.
Source: EE Publishers