Sending data through LED lights

Visible Light Communication (VLC) beams data via LED light, providing optical wireless links that offload crowded Wi-Fi, enable short-range connectivity in offices, and save energy with LVX System fixtures in St. Cloud municipal buildings.

Flickering ceiling lights are usually a nuisance, but in city offices in St. Cloud, Minn., they will actually be a pathway to the Internet.

The lights will transmit data to specially equipped computers on desks below by flickering faster than the eye can see. Ultimately, the technique could ease wireless congestion by opening up new expressways for short-range communications.

The first few light fixtures built by LVX System, a local startup, will be installed in six municipal buildings in St. Cloud as the LED market continues to expand.

The LVX system puts clusters of its light-emitting diodes (LEDs) in a standard-sized light fixture. The LEDs transmit coded messages — as a series of 1s and 0s in computer speak — to special modems attached to computers.

A light on the modem talks back to the fixture overhead, where there is sensor to receive the return signal and transmit the data over the Internet via Ethernet cables where available. Those computers on the desks aren't connected to the Internet, except through these light signals, much as WiFi allows people to connect wirelessly.

The first generation of the LVX system will transmit data at speeds of about 3 megabits per second, roughly as fast as a residential DSL line.

Mohsen Kavehrad, a Penn State electrical engineering professor who has been working with optical network technology for about 10 years, said the approach could be a vital complement to the existing wireless system.

He said the radio spectrum usually used for short-range transmissions, such as WiFi, is getting increasingly crowded, even as wireless power transfer research advances in parallel, which can lead to slower connections.

"Light can be the way out of this mess," he said.

But there are significant hurdles. For one, smart phones and computers already work on WiFi networks that are much faster than the LVX system.

Technology analyst Craig Mathias of the Farpoint Group said the problems with wireless congestion will ease as WiFi evolves, leaving LVX's light system to niche applications such as indoor advertising displays and energy management.

LVX chief executive officer John Pederson said a second-generation system that will roll out in about a year will permit speeds on par with commercial WiFi networks.

For St. Cloud, the data networking capability is secondary. The main reason it paid a $10,000 installation fee for LVX is to save money on electricity down the line, thanks to the energy-efficient LEDs planned for the fixtures.

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