Optical orthogonal frequency division multiplexing (O-OFDM) system with pulse-width modulation (PWM) dimming
An optical orthogonal frequency division multiplexing (O-OFDM) system with pulse-width modulation (PWM) dimming includes a driver responsive to one or more predetermined dimming set points configured to generate PWM signals having a predetermined duty cycle and configured to supply current to one or more light emitting diodes (LEDs). An O-OFDM generator responsive to the one or more predetermined dimming set points and digital data is configured to generate digital inverted O-OFDM signals during on-states of the PWM signals and non-inverted O-OFDM signals during off-states of the PWM signals according to the predetermined duty cycle and convert the digital inverted O-OFDM signals and the digital non-inverted O-OFDM signals to analog output O-OFDM signals. A combiner circuit responsive to the current from the driver and the analog output O-OFDM signals is configured such that the analog output O-OFDM signals modulate the current to the one or more LEDs to provide a high capacity visible light communication link
1. An optical orthogonal frequency division multiplexing (O-OFDM) system with pulse-width modulation (PWM) dimming, the system comprising:
a driver responsive to one or more predetermined dimming set points configured to generate PWM signals having a predetermined duty cycle and configured to supply current to one or more light emitting diodes (LEDs);
an O-OFDM generator responsive to the one or more predetermined dimming set points and digital data configured to generate digital inverted O-OFDM signals during on-states of the PWM signals and non-inverted O-OFDM signals during off-states of the PWM signals according to the predetermined duty cycle and convert the digital inverted O-OFDM signals and the digital non-inverted O-OFDM signals to analog output O-OFDM signals; and
a combiner circuit responsive to the current from the driver and the analog output O-OFDM signals configured such that the analog output O-OFDM signals modulate the current to the one or more LEDs to provide a high capacity visible light communication link.
2. The system of claim 1 in which the O-OFDM generator includes an inverter configured to generate the digital inverted O-OFDM signals during the on-states based on the predetermined duty cycle.
3. The system of claim 1 in which the O-OFDM generator includes a digital to-analog converter for converting the digital inverted O-OFDM signals and the digital- non-inverted O-OFDM signals to the analog output O-OFDM signals.
4. The system of claim 1 in which the combiner circuit includes at least one amplifier transistor configured such that the analog output O-OFDM signals modulate the current to the one or more LEDs to provide the high capacity visible light communication link.
5. The system of claim 1 in which the combiner circuit includes at least one amplifier transistor and at least one switching transistor configured such that the analog output O-OFDM signals modulate the current to the one or more LEDs to provide the high capacity visible light communication link.
6. The system of claim 2 in which the digital inverted O-OFDM signals include a steam of O-OFDM symbols.
7. The system of claim 1 in which the digital non-inverted O-OFDM signals include a steam of O-OFDM symbols.
8. The system of claim 6 in which the inverter is configured to invert a predetermined number of O-OFDM symbols based on the predetermined duty cycle.
9. The system of claim 6 in which the inverter is configured to invert a predetermined number of O-OFDM symbols based on duration of the on-states.
10. The system of claim 1 in which the O-OFDM generator is configured to generate unipolar inverted O-OFDM symbols during the on-states.
11. The system of claim 1 in which the O-OFDM generator is configured to generate unipolar non-inverted O-OFDM symbols during the off-states.
12. The system of claim 1 in which the one or more LEDs are integrated with a luminaire.
13. An optical orthogonal frequency division multiplexing (O-OFDM) method with PWM dimming, the method comprising:
providing one or more predetermined dimming set points and digital data;
generating, in response to the one or more predetermined dimming set points, PWM signals having a predetermined duty cycle;
generating, in response to the predetermined duty cycle and the digital data, digital inverted O-OFDM signals during on-states of the PWM signals and non-inverted O-OFDM signals during off-states of the PWM signals;
converting the digital inverted O-OFDM signals and the digital non-inverted O-OFDM signals to analog output O-OFDM signals; and
modulating the current to the one or more LEDs using the analog output O-OFDM signals to provide a high capacity visible light communication link.
14. The method of claim 13 in which generating the digital inverted O-OFDM includes generating the digital inverted O-OFDM signals during the on-states based on the predetermined duty cycle.
15. The method of claim 13 in which generating the digital inverted O-OFDM signals includes generating a steam of O-OFDM symbols.
16. The method of claim 13 in which generating digital non-inverted O-OFDM signals includes generating a steam of O-OFDM symbols.
17. The method of claim 15 in which combining the digital inverted O-OFDM signals with the PMW signals during the on-states includes inverting a predetermined number of O-OFDM symbols based on the predetermined duty cycle.
18. The method of claim 15 in which combining the digital inverted O-OFDM signals with the PMW signals during the on-states includes inverting a predetermined number of O-OFDM symbols based on duration of the on-states.
19. The method of claim 13 further including generating unipolar inverted O-OFDM symbols during the on-states.
20. The method of claim 13 further including generating unipolar non-inverted O-OFDM symbols during the off-states.
21. The method of claim 13 in which the one or more LEDs are integrated with a luminaire.