The New Scientist published a networking-related article last week that took me back to my early days in the industry.
The piece in question dealt with Visible Light Communication (VLC), a form of light-based networking in which data is encoded and transmitted by varying the rate at which LEDs flicker on and off, all at intervals imperceptible to the human eye.
Also called Li-Fi — yes, indeed, the marketers are involved already — VLC is being positioned for various applications, including those in hospitals, on aircraft, on trading floors, in automotive car-to-car and traffic-control scenarios, on trade-show floors, in military settings, and perhaps even in movie theaters where VLC-based projection might improve the visual acuity of 3D films. (That last wacky one was just something that spun off the top of my shiny head.)
From FSO to VLC
Where I don’t see VLC playing a big role, certainly not as a replacement for Wi-Fi or its future RF-based successors, is in home networking. VLC’s requirement for line of sight will make it a non-starter for Wi-Fi scenarios where wireless networking must traverse floors, walls, and ceilings. There are other room-based applications for VLC in the home, though, and those might work if device (PC, tablet, mobile phone), display, and lighting vendors get sufficiently behind the technology.
I feel relatively comfortable pronouncing an opinion on this technology. The idea of using light-based networking has been with us for some time, and I worked extensively with infrared and laser data-transmission technologies back in the early to mid 90s. Those were known as free-space optical (FSO) communications systems, and they fulfilled a range of niche applications, primarily in outdoor point-to-point settings. The vendor for which I worked provided systems for campus deployments at universities, hospitals, museums, military bases, and other environments where relatively high-speed connectivity was required but couldn’t be delivered by trenched fiber.
The technology mostly worked . . . except when it didn’t. Connectivity disruptions typically were caused by what I would term “transient environmental factors,” such as fog, heavy rain or snow, as well as dust and sand particulate. (We had some strange experiences with one or two desert deployments). From what I can gather, the same parameters generally apply to VLC systems.
Will that be White, Red, or Resonant Cavity?
Then again, the performance of VLC systems goes well beyond what we were able to achieve with FSO in the 90s. Back then, laser-based free-space optics could deliver maximum bandwidth of OC3 speeds (144Mbps), whereas the current high-end performance of VLC systems reaches transmission rates of 500Mbps. An article published earlier this year at theEngineer.com provides an overview of VLC performance capabilities:
“The most basic form of white LEDs are made up of a bluish to ultraviolet LED surrounded by a yellow phosphor, which emits white light when stimulated. On average, these LEDs can achieve data rates of up to 40Mb/sec. Newer forms of LEDs, known as RGBs (red, green and blue), have three separate LEDs that, when lit at the same time, emit a light that is perceived to be white. As these involve no delay in stimulating a phosphor, data rates in RGBs can reach up to 100Mb/sec.
But it doesn’t stop there. Resonant-cavity LEDs (RCLEDs), which are similar to RGB LEDs and are fitted with reflectors for spectral clarity, can now work at even higher frequencies. Last year, Siemens and Berlin’s Heinrich Hertz Institute achieved a data-transfer rate of 500Mb/sec with a white LED, beating their earlier record of 200Mb/sec. As LED technology improves with each year, VLC is coming closer to reality and engineers are now turning their attention to its potential applications.”
I’ve addressed potential applications earlier in this post, but a sage observation is offered in theEngineer.com piece by Oxford University’s Dr. Dominic O’Brien, who sees applications falling into two broad buckets: those that “augment existing infrastructure,” and those in which visible networking offers a performance or security advantage over conventional alternatives.
Will There Be Light?
Despite the merit and potential of VLC technology, its market is likely to be limited, analogous to the demand that developed for FSO offerings. One factor that has changed, and that could work in VLC’s favor, is RF spectrum scarcity. VLC could potentially help to conserve RF spectrum by providing much-needed bandwidth; but such a scenario would require more alignment and cooperation between government and industry than we’ve seen heretofore. Curb your enthusiasm accordingly.
The lighting and display industries have a vested interest in seeing VLC prosper. Examining the membership roster of the Visible Light Communications Consortium (VLCC), one finds it includes many of Japan’s big names in consumer electronics. Furthermore, in its continuous pursuit of new wireless technologies, Intel has taken at least a passing interest in VLC/Li-Fi.
If the vendor community positions it properly, standards cohere, and the market demands it, perhaps there will be at least some light.