VLC modulation system and method thereof

• US 9,020,355 B2
• Filed: 12/18/2012
• Issued: 04/28/2015
• Est. Priority Date: 08/23/2012
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Yeh, Chien Hung, Chow, Chi Wai, Liu, Yu Feng
• Primary Examiner(s): Payne, David
• Assistant Examiner(s): KRETZER, CASEY L
• Application Number:
  US13/718,048
• Publication Number:
  US 20140056589A1
• Time in Patent Office: 861 Days
• Field of Search: 398/93, 398/103, 398118-131, 398/140, 398182-201, 372 381- 3809
• US Class Current: 398/119
• CPC Class Codes: H04B 10/11 Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
• CPC Class Codes: H04B 10/116 Visible light communication
• CPC Class Codes: H04B 10/501 Structural aspects

Abstract

A VLC (Visible Light Communication) modulation system and method thereof, which includes a visible light generating device and a visible light receiving device. The visible light generating device includes a visible light emitting module and an arbitrary waveform generator. The arbitrary waveform generator further includes a first finite impulse response filtering unit, a pre-distortion amount control unit, and a second finite impulse response filtering unit.

Claims

1. A visible light communication (VLC) modulation system, comprising:

a visible light signal generating device configured to generate a visible light signal, which comprises;

a visible light illuminating module having an adaptive filter; and

an arbitrary waveform generator configured to couple to the visible light illuminating module and generate a amplitude-shift keying (ASK) waveform, wherein the arbitrary waveform generator further comprises;

a first finite impulse response filtering unit configured to output a first impulse signal to a first convolution unit;

a pre-distortion amount control unit configured to output a short impulse signal, wherein the pre-distortion amount control unit has a memory and a pre-determined parameter is stored in the memory;

a second finite impulse response filtering unit configured to generate a second impulse signal, wherein a duty cycle of the second impulse signal is half of a duty cycle of the first impulse signal;

and

a visible light signal receiving device configured to receive the visible light signal.

2. The VLC modulation system of claim 1, wherein the arbitrary waveform generator further comprises:

a 4-level mapping unit configured to generate a 4-level ASK signal, according to a data signal, to an up-sampling unit, wherein the up-sampling unit is configured to generate a sampled symbol signal to a 1-symbol delay unit, a first digital adder-subtractor, the first convolution unit and a second convolution unit; and

a second adder-subtractor;

wherein the 1-symbol delay unit generates a delay symbol signal to the first digital adder-subtractor, in which the first digital adder-subtractor generates a first scaling signal to the pre-distortion amount control unit, the second convolution unit generates a third impulse signal according to the sampled symbol signal and the second impulse signal; and

wherein the second digital adder-subtractor generates a fourth impulse signal to the adaptive filter.

3. The VLC modulation system of claim 2, wherein the data signal comprises a pseudo-random binary sequence (PRBS).

4. The VLC modulation system of claim 1, wherein the second finite impulse response filtering unit further comprises a half-symbol shaping unit and a multiplier, wherein the multiplier is configured to amplify an impulse signal from the half-symbol shaping unit.

5. The VLC modulation system of claim 1, wherein the visible illuminating module comprises a white LED, wherein the white LED has a 100 lm output and is driven by a 350 mA current.

6. The VLC modulation system of claim 1, wherein the VLC modulation system further comprises a pair of lenses configured to respectively couple to the visible light generating device and the visible light receiving device, wherein the pair of lenses are configured to extend a transmission distance of the visible light signal.

7. The VLC modulation system of claim 1, wherein the arbitrary waveform generator is configured to couple to the visible light illuminating module via a bias voltage device.

8. The VLC modulation system of claim 1, wherein the visible light signal receiving device further comprises:

a visible light receiving module;

a visible light amplifying module configured to couple to the visible light receiving module; and

a real-time oscilloscope configured to couple to the visible light amplifying module.

9. The VLC modulation system of claim 8, wherein the visible light receiving module comprises a Si-based PIN receiving unit.

10. The VLC modulation system of claim 9, wherein the Si-based PIN receiving module has a detection wavelength range of 350 nm to 1100 nm, a 0.65 Ampere/Watt responsivity, a 13 mm² working area, a 17 MHz bandwidth and a 530 μ

V noise root mean square value.

11. The VLC modulation system of claim 8, wherein the visible light amplifying module comprises a broadband coaxial amplifier.

12. The VLC modulation system of claim 8, wherein the real-time oscilloscope further comprises a square root raised cosine (SRRC) filter and an error analysis module, wherein the error analysis module is configured to analyze the bit-error-rate of the visible light signal.

13. The VLC modulation system of claim 8, wherein a roll-off factor of the square root raised cosine filter is 0.25.

14. The VLC modulation system of claim 8, wherein the bit-error rate of the visible light signal is less than 10⁻

10 bits.

15. The VLC modulation system of claim 1, wherein the visible light signal has a 20 Mb/s transmission rate.

16. The VLC modulation system of claim 1, wherein the visible light generating device and the visible light receiving device are at a distance apart, wherein the distance is longer than one meter.

17. A method of VLC modulation, wherein the steps of the method comprise of:

generating a first impulse signal and convoluting the first impulse signal;

generating a symbol delay signal according to an up-sampling signal, wherein the symbol delay signal includes a delay symbol;

generating a first scaling signal for scaling a short impulse signal;

generating a second impulse signal according to the scaled short impulse signal, wherein a duty cycle of the second impulse signal is a half of a duty cycle of the first impulse signal;

convoluting the up-sampling signal and the second impulse signal to generate a third impulse signal;

digitally adding/subtracting the convoluted first impulse signal and the third impulse signal to generate a fourth impulse signal;

generating a visible light signal according to the fourth impulse signal;

generating a 4-level amplitude shifting keying (ASK) signal by mapping a data signal;

and

receiving the visible light signal.

18. The method of claim 17, wherein the data signal comprises a pseudo-random binary sequence (PRBS).

19. The method of claim 17 further comprises a step of generating the up-sampling signal according to the 4-level ASK signal.

20. The method of claim 17, wherein the visible light signal has a transmission rate of 20 Mb/s.