WiFi, Move Over – Here Comes LiFi

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Disney researchers last week demonstrated Linux Light Bulbs — a protocol for a communications system that transmits data using visible light communication, or VLC, technology.

Linux Light Bulbs can communicate with each other and with other VLC devices — such as toys, wearables and clothing — over the Internet Protocol, according to Disney scientists Stefan Schmid, Theodoros Bourchas, Stefan Mangold and Thomas R. Gross, who coauthored a report on their work. In essence, they could establish a LiFi network that would function in much the same way that WiFi works.

Scientists have been experimenting with the concept of using light to channel data transmissions for years. Previously, however, the use of VLC supported simple communication between devices. Linux Light Bulbs may take that process one step further by enabling networking on VLC devices.

However, the throughput is critically small compared to other visible light approaches, and the technology suffers from proximity limitations, noted James T. Heires, a consultant at QSM.

“Visible light technology is viable for the Internet of Things, but only on a limited basis. This is due to the physical limitations of visible light,” he told LinuxInsider. The transmitter and receiver “must be within line of sight of each other.”

How It Works

Modern light-emitting diode light bulbs, or LEDs, can provide a foundation for networking using visible light as a communication medium, according to the Disney researchers’ report.

The team modified common commercial LED light bulbs to send and receive visible light signals. They built a system on a chip, or SoC, running the Linux operating system, a VLC controller module with the protocol software, and an additional power supply for the added electronics.

The key to the project’s success was the Linux software that enabled the signals to work with the Internet Protocol. The VLC-enabled bulbs served as broadcast beacons, which made it possible to detect the location of objects on the network and to communicate with them.

The Linux connection is at the software level. The Linux kernel driver module integrates the VLC protocol’s PHY and MAC layers into the Linux networking stack.

The VLC firmware on a separate microcontroller communicates with the Linux platform over a serial interface, the report notes.

Slow Going

The drawback is the speed. The network’s throughput maxed out at 1 kilobit per second, noted SeshuKiran, founder of XAir.

“A data rate of 1 Kpbs means a maximum 2 to 3 pixels of a good photograph can be transmitted per second,” he told LinuxInsider. “Good luck with an entire photo. For half of an HD photo to go, it will take 10.66 days.”

The technology may not be fast enough to compete with other technologies. WiFi operates around 3 GHz, and invisible light frequency starts at 3 THz. That is some 1,000 times higher than the WiFi frequency.

“Technically, it should [seem] that light has a better promise in delivering data. It is true in theory — but electronics and circuits say otherwise,” said Kiran.

Made for IoT

Developers have proposed a wide range of applications for VLC tech — using LiFi in place of anything currently supported by commercial wireless technologies such as WiFi.

“The Disney effort is fairly limited in terms of performance, but other projects suggest that broadband quality data transfer performance is possible, said Charles King, principal analyst at Pund-IT.

“The real issue driving VLC is the pervasiveness of the base technology,” he told LinuxInsider.

Data transfer solutions like Wi-Fi require specialized equipment, installation and maintenance. However, light fixtures are virtually everywhere.

“Since LED represents the future of commercial lighting, developers are suggesting that VLC capabilities could easily be enabled in existing homes and businesses without the need for expensive extraneous systems,” King said.

“On the IoT side, VLC would provide an easy way of connecting endpoint sensors to back-end systems without needing to build expensive, dedicated networks,” he pointed out.

The Disney researchers developed hardware peripherals that effectively turn a consumer LED fixture into a Linux host, including a kernel module that integrates the VLC’s physical and MAC (media access control) protocol layers with a Linux-based networking stack, King added.

Trying Times

Light has been used as a communication medium for decades. Major uses include fiber optics and infrared devices, noted Heires. Auto industry researchers have been investigating the incorporation of VLC tech into headlights and sensors to allow cars to communicate with each other and thus avoid collisions.

“Applications such as using light to extend the range of a WiFi signal are within reason. However, since light does not travel through solid objects, such as walls or floors, light is impractical for applications such as TV control, sensor monitoring or security,” he said.

Brighter Ideas to Come

One of the lowest data rate uses for VLC and the IoT is for automatic door openers equipped with light sensors at the lock. Point your smartphone at the door and flash a modulated-light app with a specific code to open the door.

Such a system would work for homes, hotels, garages and more.

Another use is modulating streetlights to deliver specific information, such as alerts and emergencies, across an entire city.

It also could be used to safeguard top secret communications between coworkers.

“If a light bulb in the garden could deliver commands for the automated sprinkler, … that would be “a definite possibility,” Kiran suggested. “Data rates are not yet crucial there.”

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