Does 5G have a bright future? Light based communications for wireless Solutions

CTN Issue: November 2016

Alan Gatherer, Editor in Chief, ComSoc Technology News

This month the good people of PureLiFi are giving us an update on the state of light based wireless communications and exactly where they are in developing a commercial product. How big will LiFi be in ultra dense networking? Read on, and don't forget to comment.

LiFi unlocking unprecedented wireless pathways for our digital future

Professor Harald Haas, pureLiFi Chief Scientific Officer
Dr. Nikola Serafimovski, pureLiFi Director of Business Strategy

Professor Harald Haas
Harald Haas
Dr. Nikola Serafimovski
Nikola Serafimovski

We live in an increasingly connected world. The demand for mobile wireless communications is increasing at over 50% per year according to the Cisco Visual Networking Index. This demand is expected to continue to increase as the Internet of Things (IoT) becomes a reality, and the number of connected devices grows from 5 billion to over 20 billion by 2020. Unsurprisingly, in 2016, over 50% of all wireless data went through a WiFi access point. This enormous utilisation results in a need for a continued increase in capacity of wireless networks, depending directly on the availability of additional unlicensed spectrum.

Undeniably, there are multiple solutions that can provide an increase in the available spectrum and increased confinement of the RF signal. As an example, WiGig solutions, defined in IEEE 802.11ad and being revised in 802.11ay, that operate in the 60 GHz spectrum have access to around 14 GHz of bandwidth in the USA. However, WiGig and other mm-wave RF solutions all exhibit similar challenges.  First, ICT (information and communication technology) has gone through a radical transformation driven by efforts to reduce the carbon footprint. To achieve the required data densities, it is inevitable that WiFi/WiGig solutions implement beamforming. This poses a number of technical challenges: i) beamforming requires multiple antennas and phase shifters which increases hardware complexity and cost, and ii) while current beamforming works well in a downlink point-to-multipoint scenario, beamforming in the uplink, i.e., multipoint-to-point scenarios of a mobile communication system where place and orientation of the mobile terminal can vary greatly, is still a challenging problem. 

In this context, it is vital to remember that RF is only one part of the electromagnetic spectrum and that visible light spectrum and the infrared spectrum has, for the most part, been an underutilised share of this spectrum. The visible light spectrum alone stretches from approximately 430 THz to 770 THz, which means that there is potentially more than 1000x the bandwidth of the entire RF spectrum of approx. 300 GHz. Both the visible light spectrum and the infrared spectrum are unlicensed. 

There are wireless technologies that are harnessing this vast spectrum resource. Specifically, ‘LiFi’ (Light Fidelity), first demonstrated to the public and coined by pureLiFi CSO, Professor Harald Haas in at TED Global talk “Wireless from Every Light Bulb” in 2011, has attracted significant international interest. LiFi refers to the high-speed, bidirectional and networked wireless communications using light to provide a seamless wireless user experience much like traditional mobile communications [1]. It, therefore, advances visible light communication (VLC), which was first introduced by Prof. Nakagawa at Keio University [2], as LiFi is a complete mobile communication solution to augment 5G and beyond. LiFi offers secure and safe wireless communications in a globally unlicensed spectrum that repurposes the energy used for lighting to provide wireless data. This technology is, therefore, expected to be a key part of future 5G Systems.

There is another important aspect in modern wireless communications: ‘Security'.  The proliferation of mobile devices has resulted in an increase of the amount of secure information being exchanged over the wireless network. As a result, we're facing a sharp increase in cyber vulnerability. Indeed, in a rush to provide market-ready solutions for the IoT, companies have often neglected cyber security requirements for their products. This has dramatically increased the attack surface for many cyber-attacks and has resulted in one of the world's most powerful distributed denial of service (DDoS) incidents in modern history – attacking everything from wireless baby monitors to wireless CCTV cameras [3].

Light is very directional, well understood and easily confined using simple lenses. Therefore, beamforming can be achieved with low hardware complexity and in a cost effective manner. Moreover, because of the small wavelength in the region of hundreds of nanometers, the size of the electronic components that emit light and detect light, i.e., light emitting diodes (LEDs) and photodetectors (PDs) can be very small in the region of tens and hundreds of micro meters. This has two key advantages: First, LiFi systems are not subject to the same multipath fading typically modelled as Rayleigh fading in the case of non-line-of-sight, and Rician fading in the case of line-of-sight in RF systems. Multipath fading is the result of in-phase and out-of-phase signals combining at the antenna and cancelling each other out which then results in outage and rapid and random signal to noise degradations. LiFi systems are immune to this effect as the large size of the detector relative to the signal wavelength ensures that all signal paths integrate constructively – resulting in lower hardware complexity and potentially more robust systems. This effect can also be exploited for co-channel interference mitigation when there are multiple sources in confined space transmitting independent data [4]. Second, it is straightforward to build very compact transceivers that are composed of multiple LEDs and multiple PDs [5]. As a result, systems of very high diversity order can be generated without a massive size and cost increase.

pureLiFi-Luminaire

The inherent directionality of light and the fact that light does not propagate through opaque objects provide opportunities to form incredibly dense wireless networks with full frequency reuse -- with each light covering as little as a few square-metres [6]. In this context, it is important to note that these wireless communication networks can be combined with existing and essential lighting networks. This means in the future lighting and communication will become one, and this will unlock new business models in the emerging light-as-a-service (LaaS) trend – an area where we see the lighting industry moving to, due to the long life-time of LED lighting. Therefore, LiFi is poised to not only revolutionise the way we access wireless data by unlocking unprecedented data and bandwidth, but also catalyse the merger of two enormous industries: lighting and communications. This will result in the creation of new opportunities and new markets. With individual LEDs lasting upwards of 20 years, the days where lightbulbs need to be changed as often as the printer's ink are behind us. Imagine the transformation of the lighting industry into an industry that provides light and data as a service – this is possible with LiFi. In addition, this re-purposing of infrastructure provides massive potential to save energy and to avoid large infrastructure investments for new wireless communications technologies, using either power line communications (PLC) or power over Ethernet (PoE), which is growing in popularity for smart buildings. Ethernet is the backhaul. The long term back haul is resolved by using PoE in new offices, which is proving more efficient for smart buildings and lighting. An example is the Edge Building in Amsterdam that is the current headquarters of Deloitte. The building has over 6,000 PoE connected lighting fixtures, which resulted in a 50% reduction in installation time as well as a 25% installation cost saving. This is the future of smart buildings.

pureLiFi-X-Dongle

In September 2016, as a result of a collaboration between pureLiFi and French lighting company Lucibel, the world’s first LiFi integrated luminaire was released into the market. Consequently, LiFi is being installed for enterprise communications in the headquarters of property developers Nexity and Sogeprom in Paris. The LiFi-X used in this project provides 42 Mbps downlink and 42 Mbps uplink, is fully networked and therefore allows for seamless handover between luminaires. Indeed, it is the unique combination of future-proof capacity combined with the flexibility, security and energy efficiency of LiFi solutions that is helping this proliferation.

The technical challenges are being overcome and the commercial challenges addressed. The pervasive nature of light sources means that LiFi has the ability to guarantee seamless and mobile wireless services everywhere. No longer will light simply illuminate our spaces, lighting will unlock new pathways into an ever-connected world. There is no doubt: LiFi will forever change the way we live our lives.

 

References

  1. H. Haas, L. Yin, Y. Wang, and C. Chen, "What is LiFi?," Journal of Lightwave Technology, vol. 34, pp. 1533-1544, 2016.
  2. Y. Tanaka, T. Komine, S. Haruyama and M. Nakagawa, "Indoor visible communication utilising plural white LEDs as lighting," Personal, Indoor and Mobile Radio Communications, 2001 12th IEEE International Symposium on, San Diego, CA, 2001, pp. F-81-F-85 vol.2.
  3. Newman, Lily Hay. “What We Know About Friday’s Massive East Coast Internet Outage.” www.wired.com. Conde Nast. 21, October, 2016.
  4. Z. Chen, D. Tsonev and H. Haas, "A novel double-source cell configuration for indoor optical attocell networks," 2014 IEEE Global Communications Conference, Austin, TX, 2014, pp. 2125-2130.
  5. Z. Chen, N. Serafimovski and H. Haas, "Angle Diversity for an Indoor Cellular Visible Light Communication System," 2014 IEEE 79th Vehicular Technology Conference (VTC Spring), Seoul, 2014, pp. 1-5.
  6. C. Chen, D. A. Basnayaka, and H. Haas, "Downlink Performance of Optical Attocell Networks," Journal of Lightwave Technology, vol. 34, pp. 137-156, 2016.

 

Editor-in-Chief: Alan Gatherer (alan.gatherer@huawei.com)

Comments welcome!

Leave a comment

Statements and opinions given in a work published by the IEEE or the IEEE Communications Society are the expressions of the author(s). Responsibility for the content of published articles rests upon the authors(s), not IEEE nor the IEEE Communications Society.