Visible light communication system and method
A system, remote control device and method are provided herein for communicating with and controlling various devices using visible light communication (VLC). According to one embodiment, a method is provided for extending a communication range of a visible light communication system comprising a remote control device and a plurality of controlled devices. Such a method may include, for example, transmitting a communication message from a remote control device to a first controlled device located within range of the remote control device, wherein the communication message is transmitted through free space using visible light, and extending the communication range of the visible light communication system to a second controlled device, which is located outside of the range of the remote control device, by using the first controlled device to retransmit the communication message through free space using visible light to the second controlled device.
1. A visible light communication system comprising:
a remote control device configured to transmit visible light modulated with data through free space;
a lighting fixture that comprises a visible light source and a visible light detector, wherein the lighting fixture is configured to generate a common timing reference and is further configured to periodically turn off the visible light source based on the timing reference, and wherein the visible light detector is configured to receive and decode data modulated onto the visible light when the visible light source is periodically turned off; and
wherein the remote control device comprises a touch screen display and is configured to:
display an icon on the touch screen display;
detect an actuation of the icon;
transmit, in response to detecting the actuation of the icon, a first message modulated onto the visible light; and
transmit, at a fixed time after the first message is transmitted, a second message modulated onto the visible light, wherein the second message is substantially identical to the first message; and
wherein the lighting fixture is configured to:
turn off the visible light source based on the timing reference;
receive the first message from the remote control device via the visible light detector while the visible light source is turned off;
adjust a bit timing in response to receiving the first message; and
retransmit, based on the adjusted bit timing, the first message via the visible light source to at least one other lighting fixture such that the retransmitted first message is in synchronization with the second message transmitted by the remote control device.
2. The visible light communication system as recited in claim 1 , wherein the lighting fixture is further configured to be coupled to an alternating current (AC) power source, and is further configured to generate the common timing reference by locking onto an AC signal provided by the AC power source; and
wherein the lighting fixture is further configured to synchronously modulate data onto the visible light using the timing reference.
3. The visible light communication system as recited in claim 1 , wherein the data modulated onto the visible light comprises information indicating that the data modulated onto the visible light be retransmitted from the remote control device or retransmitted from the visible light source when the visible light source is periodically turned on.
4. The visible light communication system as recited in claim 1 , wherein the data modulated onto the visible light comprises a repeat field that specifies a number of times the data modulated onto the visible light should be retransmitted.
5. The visible light communication system as recited in claim 1 , wherein the data modulated onto the visible light comprises a plurality of data fields, which includes one or more of:
a repeat field that specifies a number of times the data modulated onto the visible light should be retransmitted;
a preamble field containing a unique data sequence that identifies a start of the data modulated onto the visible light;
an address field containing a code specifying a lighting fixture targeted by the data modulated onto the visible light;
a command field containing a code specifying an action to be taken by the lighting fixture;
a data field containing a data value associated with the command field code; and
a Cyclic Redundancy Check (CRC) checksum field containing a CRC code.
6. The visible light communication system as recited in claim 1 , wherein the remote control device comprises a remote control light source for producing the visible light, and a controller for modulating the visible light with the data to produce the data modulated onto the visible light.
7. The visible light communication system as recited in claim 6 , wherein the remote control device further comprises a remote control light detector for receiving second data modulated onto the visible light from the visible light source when the visible light source is periodically turned on.
8. The visible light communication system as recited in claim 7 , wherein the remote control light source and the remote control light detector of the remote control device comprise one or more light emitting diodes (LEDs).
9. The visible light communication system as recited in claim 7 , wherein the remote control light source is selected from a group consisting of a camera flash and a display screen backlight, and wherein the remote control light detector is selected from a group consisting of the remote control light source, a camera image sensor and an ambient light sensor.
10. The visible light communication system as recited in claim 9 , wherein the camera image sensor is configured to receive the second data modulated onto the visible light for identifying a location of the lighting fixture as well as brightness and color emitted from the visible light source.
11. The visible light communication system as recited in claim 1 , wherein the icon comprises an application program shown as an image on the touch screen display.
12. The visible light communication system as recited in claim 11 , wherein the application program is downloaded off the Internet.
13. The visible light communication system as recited in claim 1 , wherein the lighting fixture further comprises a visible light communication network controller configured to receive visible light modulated with data sent from other lighting fixtures arranged in a communication network.
14. The visible light communication system as recited in claim 1 , wherein the visible light detector is one or more of a plurality of light emitting diodes (LEDs) used as the visible light source.
15. The visible light communication system as recited in claim 1 , wherein the icon comprises a button or slider.
16. The visible light communication system as recited in claim 1 , wherein the visible light source and the visible light detector are coupled to an AC mains and are synchronized with each other.
17. The visible light communication system as recited in claim 16 , wherein a current supplied to the visible light source is periodically decreased to produce communication gaps at regular, periodic intervals of each cycle of the AC mains.