Visible light communications - Research - Jimmy C. Chau - Boston University

Visible light communications

Overall objectives

The Smart Lighting Engineering Research Center aims to integrate visible light communication (VLC) capabilities into future LED lighting systems. Ideally, this integration will ensure the availability of network connectivity wherever artificial lighting is installed, enabling the widespread use of networked devices that form "smart rooms".

Toward this objective, I have developed a range of lighting and visible light communication systems.


Scalabe MIMO VLC receiver architectures for mobile use

In my current research, I am investigating the use of special-purpose cameras as receivers for VLC signals. Such a VLC receiver would be able to track and receive from multiple transmitters simultaneously, enabling the receiver to combine many lower-speed transmissions into one high-speed link with the combined capacity of each transmission.

An illustration of the objective for the scalable MIMO VLC receiver architecture
An illustration of the objective for the scalable MIMO VLC receiver architecture is shown. Here, the mobile camera (left) receives multiple VLC signals, from both stationary VLC transmitters (top) and mobile ones (right).


Lighting Arrays as Modular Parts (LAMP) is a networked, color-controllable luminaire prototype.

The back of an assembled LAMP
The back of our first fully-assembled LAMP prototype is shown. This prototype consists of an Arduino (microcontroller development platform) with an Ethernet shield for network connectivity (right), two LAMP LED driver boards (labeled "R A" and "B G"), eight LAMP light engines (with the black heat-sinks shown), and a frame for mounting. Thanks to Lucy Yan for the photo.
The side of an assembled LAMP
The side of a fully-assembled LAMP is shown. Thanks to Lucy Yan for the photo.
The front of an assembled LAMP
The front of a LAMP prototype is shown. The modular design of LAMP allows it to be built with LEDs of any color. In this case, red, green, blue, and amber LEDs were selected. Thanks to Lucy Yan for the photo.
The LAMP with all LEDs on
A LAMP with every LED on is shown. The independent LAMP LED drivers for each color of LED allows this LAMP to produce over four billion different colors. Thanks to Lucy Yan for the photo.

VLC-IP bridge

A SL1 VLC transceiver connected to a Gumstix computer
A VLC transceiver (SL1) (right) is shown with a Gumstix computer (left) that acts as a bridge between an IP network (through an Ethernet connection, top) and a VLC link. Note that in our actual demonstration, the SL1 and the Gumstix computer are connected via a USB-to-serial cable (not shown).
An illustration of mobility across VLC links
Connectivity over VLC links can be maintained despite mobility by forwarding packets to the appropriate VLC access point using existing network infrastructure.

SL1 and SL2

The "Smart Lighting One" (SL1) kit and its lower-cost successor, the SL2, provide the capabilities for computers with USB ports to communicate over a visible light communication (VLC) link. Created in 2009 and 2010 respectively, the SL1 and SL2 kits have been manufactured and distributed to industry and research partners as both demonstration units and development platforms.

The SL1 VLC transceiver kit
The SL1 VLC transceiver kit is shown. It contains a pair of VLC transceivers (center), a pair of USB-to-serial data cables (left and right sides), and a pair of AC power adapters (top).

The SL1 kit contains two VLC transceivers, each with their own power supply and data cable for the USB interface; demonstration software and documentation is included in the kit. Each transmitter produces 400 lumens of white light, suitable for lighting a small part of a room. At a two meter distance, the SL1 transceivers have demonstrated the capability to form a 1Mb/s optical link.

The SL2 reduces costs with a simpler LED driver for the transmitter and by using off-the-shelf photodetector modules as part of the receiver. The new current-mirror-based LED driver is compatible with a variety of LEDs, including white LEDs, monochromatic color LEDs, and infrared LEDs. The SL2's receiver is also compatible with a variety of off-the-shelf photodetector modules. Together, they are able to form links supporting up to 4MHz on-off-keying signals. However, due to AC-coupling in the receiver, the SL2 is unable to reliably carry uncoded serial data.