Wi-Fi is not the only means of transmitting data these days. Another unique method you may not have heard of is visible light communication (VLC). 


VLC is a free-space optical wireless communication technology that uses visible light to transmit data across distances. The advent of light-emitting diode (LED) technology in general lighting is creating new opportunities for VLC in the built environment, and major new product offerings are under development.


The principle of optical communication using modulated light is simple. Varying the pattern of a light beam’s intensity encodes information. The light then transmits that information over distances at a speed of 186,000 miles per second.


Optical communications have been used for thousands of years. The ancient Greeks used torches to communicate based on an alphabetic code. In the modern era, light is used to rapidly transmit large amounts of data over long distances through fiber optics. You could do this at home by switching a flashlight on and off to send a message in Morse code. 


Another approach is free-space optical wireless communication, in which data is embedded in visible light, ultraviolet or infrared energy and transmitted through the air. For example, light may be used for communications between buildings using laser diodes that emit concentrated beams.

The advent of LED technology presented an exciting opportunity to use general lighting as a communication platform. In this application of VLC, the light source is used both for illumination and communication. While traditional sources present practical limitations, LEDs can cycle in nanoseconds at very high frequencies. 


Theoretically, VLC is not limited to line of sight, because data may be transmitted through light bouncing off of reflective surfaces. However, it cannot pass through obstructions such as walls. The LED lighting must be on to transmit but can be dimmed to very low levels. 


This raises the possibility of using LED general lighting to deliver networked, mobile, high-speed communications, a concept dubbed Li-Fi. The visible light spectrum is 10,000 times larger than the radio spectrum, making VLC a possible solution to radio frequency (RF) bandwidth limitations. VLC also does not cause electromagnetic interference. It can be used as a standalone or in combination with RF or cellular network communication. 


While this concept continues to develop, three manufacturers—Acuity Brands, GE and Philips—are focusing on commercializing practical solutions, which offer two extraordinary capabilities. The first is using LED lighting as a network for indoor positioning. The second is targeted communication with mobile devices. While there are numerous applications for this approach to VLC, the primary focus is retail stores.


Indoor positioning


According to Opus Research, 70 percent of the U.S. population has a smartphone or tablet. These devices feature the ability to navigate by using global positioning system (GPS) signals. Inside buildings, however, the GPS signals bounce around, making them ineffective.


VLC can be useful as an indoor positioning platform. It requires VLC-enabled LED general lighting and a loyalty app on the user’s mobile device. The app enables positioning and provides a digitized map of the space. For example, in a big-box retail store, the app would display the store layout and merchandise locations.


“Indoor navigation is inevitable, and VLC will be one of several important solutions that you will hear about,” said Jeff Bisberg, global general manager of indoor location, GE Lighting. “When the industry matures, we will see a fusion of several technologies that ensure a robust, high-resolution, fast and safe solution for customers to use and enjoy. We believe that VLC will be a critical part of that solution.”


For positioning, each LED luminaire emits a unique code read by the smartphone’s camera. Luminaires and their identifiers are overlaid on the venue map. By combining them, the system calculates where on the map a person is located and his or her physical orientation. Accuracy is within 3 feet and trending toward less than a foot. Acuity Brands has demonstrated accuracy within 4 inches.


The primary benefit is wayfinding. For example, a shopper could easily determine where they are in the store layout, locate an item, find the closest bathroom, and see the nearest egress path. As the system is highly scalable, a single app could guide the user in a mall or airport through VLC-enabled luminaires installed across all venues and public spaces. The app could also serve as an active shopping assistant, taking the user through the venue based on his or her shopping list. 


Users concerned about information privacy can opt out by not downloading the app. Or, if they have installed the app, they can refrain from turning their phone on in the venue.


“In the same way that GPS has revolutionized how we navigate the outside world, VLC positioning could change the way we experience the retail shopping environment,” said Stephen Lydecker, senior vice president, Applied Integrated Solutions, Acuity Brands Lighting. “With apps that combine accurate positioning with digitized maps and merchandise locations, customers could quickly navigate to items on their shopping list or request assistance from store personnel.”


Targeted communication


The loyalty app can be programmed to deliver targeted communications to users based on their location. This could include product advertising, coupons, cross promotion and upselling messages for specific merchandise; virtual greetings; friend locator; guided tours and storytelling; and gaming such as treasure hunts. The possibilities are numerous and vary by application.


Again, an application highly suited to VLC is big-box retail. According to Deloitte Consulting LLP, in 2012, more than 60 percent of shoppers used smart phones while in the store, and 85 percent of consumers were using retailers’ native apps or websites during shopping trips. Deloitte predicts that, by 2018, retailers will have the ability to generate some $5 billion annually in revenue or added value from hyperlocal offers, advertising and data analytics. 


Bisberg and Lydecker agree that successful VLC solution manufacturers and end-users will be those who focus on delivering a meaningful experience to users of the space.


“Reliable, accurate and robust technology is just one input to that experience,” Lydecker said. “Retailers who are successful with the technology are the ones who will deliver the best digital experience to their customers.”


A system approach


The VLC system starts with VLC-enabled general lighting LED luminaires with a modulator installed on a separate board or embedded into the LED driver. This functionality is part of the luminaire, so installation is the same.


“The need for VLC-based positioning solutions enters from the marketing side of the retail business, but professionals in the design, construction and maintenance as well as the visual merchandiser need to retain their inputs to the design,” Lydecker said. “Poor lighting that provides great positioning is not the answer.”


Other elements of the complete system include mapping and application software, which will typically reside on a cloud, and a database that houses a diagram of merchandise locations and location coordinates of luminaires.


Coverage is seamless and wall-to-wall. VLC is built into the light source, so there is no additional maintenance. Fast response times mean low latency. Systems are highly scalable up to large and multisite facilities.


Another opportunity that may be explored is integration of sensors within the luminaire that collect data that can be used for employee tracking, customer loyalty, heat-mapping, traffic patterns, product location optimization and reducing cashier lines.


Luminaires will be sold through familiar lighting industry sales channels, while manufacturers, select partners and authorized value-added resellers may be responsible for integrating hardware and software into a single delivered solution. The lighting industry will remain focused on delivering good lighting, while these other companies and resellers will focus on delivering an optimal user experience.


“Manufacturers need to design a system people want to use,” Bisberg said. “It’s much more than just putting VLC in a light fixture. All aspects of delivering an indoor location service have to be optimized so that it’s adopted.”


GE demonstrated ByteLight’s VLC solution—a turnkey system that provides navigation and contextual education and promotion—at Lightfair 2014. The technology uses a combination of VLC and Bluetooth, so the luminaire features an onboard Bluetooth transmitter. 


Acuity Brands will be offering a solution that combines its eldoLED driver and luminaires with Lumicast VLC technology by Qualcomm Technologies Inc.


Both companies have commercialized the technology and have been working with innovative retailers to implement trial installations and support software development. A general rollout is expected in 2016.