Abstract

We propose a scheme to improve the SNR distribution as well as the spectral efficiency of M-QAM OFDM signal for indoor visible light communication by tilting the receiver plane. Newton method is employed for the photo-detector to receive maximum power by finding the optimal tilting angle. This method is a fast algorithm that only three searching steps are needed. The simulation results show that in the case of one LED source, the maximum spectral efficiency improvement is 0.44bit/s/Hz when the launching power of LED source is 12W; while in the case of four LED sources, the maximum spectral efficiency improvement is 0.21bit/s/Hz when the total launching power of the four LED sources is 12W.

© 2011 OSA

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References

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  1. T. Komine and M. Nakagawa, “Fundamental analysis for visible-light communication system using LED lights,” IEEE Trans. Consum. Electron. 50(1), 100–107 (2004).
    [CrossRef]
  2. M. Z. Afgani, H. Haas, H. Elgala, D. Knipp, and W. Hirt, “Visible light communication using OFDM,” in International Conference on Testbeds and Research Infrastructures for the Development on Networks and Communities, 129–134 (2006).
  3. M. Zhang, Y. Zhang, X. Yuan, and J. Zhang, “Mathematic models for a ray tracing method and its applications in wireless optical communications,” Opt. Express 18(17), 18431–18437 (2010).
    [CrossRef] [PubMed]
  4. J. Vucic, C. Kottke, K. Habel, and K.-D. Langer, “803Mbit/s visible light WDM link based on DMT modulation of a single RGB LED luminary,” in Proc. OFC, Los Angeles, CA, OWB6 (2011).
  5. S. K. Hashemi, Z. Ghassemlooy, L. Chao, and D. Benhaddou, “Orthogonal frequency division multiplexing for indoor optical wireless communications using visible light LEDs,” in International Symposium on Communication Systems, Networks and Digital Signal Processing, 174–178 (2008).
  6. J. Armstrong, “OFDM for optical communications,” J. Lightwave Technol. 27(3), 189–204 (2009).
    [CrossRef]
  7. A. Svensson, “An introduction to adaptive QAM modulation schemes for known and predicted channels,” Proc. IEEE 95(12), 2322–2336 (2007).
    [CrossRef]
  8. J. R. Barry, Wireless Infrared Communications (Kluwer Academic Publishers, 2006).
  9. L. Zeng, D. O’Brien, H. Le-Minh, K. Lee, D. Jung, and Y. Oh, “Improvement of data rate by using equalization in an indoor visible light communication system,” in International Conference on Circuits and Systems for Communications, 678–682 (2008).
  10. I. Neokosmidis, T. Kamalakis, J. Walewski, B. Inan, and T. Sphicopoulos, “Impact of nonlinear LED transfer function on discrete multitone modulation: analytical approach,” J. Lightwave Technol. 27(22), 4970–4978 (2009).
    [CrossRef]
  11. http://www.effled.com/15W-high-power-led-p-58.html
  12. C. H. Edwards and D. E. Penney, Calculus (Prentice Hall, 2002).
  13. M. T. Heath, Scientific Computing—An Introductory Survey (McGraw-Hill, 2002).
  14. H. Elgala, R. Mesleh, and H. Haas, “Indoor broadcasting via white LEDs and OFDM,” IEEE Trans. Consum. Electron. 55(3), 1127–1134 (2009).
    [CrossRef]
  15. H. Nguyen and E. Shwedyk, A First Course in Digital Communications (Cambridge University Press, 2009).
  16. U. S. Jha and R. Prasad, OFDM towards Fixed and Mobile Broadband Wireless Access (Artech House, 2007).
  17. J. Proakis, Digital Communications (McGraw-Hill, 2008).

2010 (1)

2009 (3)

2007 (1)

A. Svensson, “An introduction to adaptive QAM modulation schemes for known and predicted channels,” Proc. IEEE 95(12), 2322–2336 (2007).
[CrossRef]

2004 (1)

T. Komine and M. Nakagawa, “Fundamental analysis for visible-light communication system using LED lights,” IEEE Trans. Consum. Electron. 50(1), 100–107 (2004).
[CrossRef]

Armstrong, J.

Elgala, H.

H. Elgala, R. Mesleh, and H. Haas, “Indoor broadcasting via white LEDs and OFDM,” IEEE Trans. Consum. Electron. 55(3), 1127–1134 (2009).
[CrossRef]

Haas, H.

H. Elgala, R. Mesleh, and H. Haas, “Indoor broadcasting via white LEDs and OFDM,” IEEE Trans. Consum. Electron. 55(3), 1127–1134 (2009).
[CrossRef]

Inan, B.

Kamalakis, T.

Komine, T.

T. Komine and M. Nakagawa, “Fundamental analysis for visible-light communication system using LED lights,” IEEE Trans. Consum. Electron. 50(1), 100–107 (2004).
[CrossRef]

Mesleh, R.

H. Elgala, R. Mesleh, and H. Haas, “Indoor broadcasting via white LEDs and OFDM,” IEEE Trans. Consum. Electron. 55(3), 1127–1134 (2009).
[CrossRef]

Nakagawa, M.

T. Komine and M. Nakagawa, “Fundamental analysis for visible-light communication system using LED lights,” IEEE Trans. Consum. Electron. 50(1), 100–107 (2004).
[CrossRef]

Neokosmidis, I.

Sphicopoulos, T.

Svensson, A.

A. Svensson, “An introduction to adaptive QAM modulation schemes for known and predicted channels,” Proc. IEEE 95(12), 2322–2336 (2007).
[CrossRef]

Walewski, J.

Yuan, X.

Zhang, J.

Zhang, M.

Zhang, Y.

IEEE Trans. Consum. Electron. (2)

T. Komine and M. Nakagawa, “Fundamental analysis for visible-light communication system using LED lights,” IEEE Trans. Consum. Electron. 50(1), 100–107 (2004).
[CrossRef]

H. Elgala, R. Mesleh, and H. Haas, “Indoor broadcasting via white LEDs and OFDM,” IEEE Trans. Consum. Electron. 55(3), 1127–1134 (2009).
[CrossRef]

J. Lightwave Technol. (2)

Opt. Express (1)

Proc. IEEE (1)

A. Svensson, “An introduction to adaptive QAM modulation schemes for known and predicted channels,” Proc. IEEE 95(12), 2322–2336 (2007).
[CrossRef]

Other (11)

J. R. Barry, Wireless Infrared Communications (Kluwer Academic Publishers, 2006).

L. Zeng, D. O’Brien, H. Le-Minh, K. Lee, D. Jung, and Y. Oh, “Improvement of data rate by using equalization in an indoor visible light communication system,” in International Conference on Circuits and Systems for Communications, 678–682 (2008).

http://www.effled.com/15W-high-power-led-p-58.html

C. H. Edwards and D. E. Penney, Calculus (Prentice Hall, 2002).

M. T. Heath, Scientific Computing—An Introductory Survey (McGraw-Hill, 2002).

M. Z. Afgani, H. Haas, H. Elgala, D. Knipp, and W. Hirt, “Visible light communication using OFDM,” in International Conference on Testbeds and Research Infrastructures for the Development on Networks and Communities, 129–134 (2006).

J. Vucic, C. Kottke, K. Habel, and K.-D. Langer, “803Mbit/s visible light WDM link based on DMT modulation of a single RGB LED luminary,” in Proc. OFC, Los Angeles, CA, OWB6 (2011).

S. K. Hashemi, Z. Ghassemlooy, L. Chao, and D. Benhaddou, “Orthogonal frequency division multiplexing for indoor optical wireless communications using visible light LEDs,” in International Symposium on Communication Systems, Networks and Digital Signal Processing, 174–178 (2008).

H. Nguyen and E. Shwedyk, A First Course in Digital Communications (Cambridge University Press, 2009).

U. S. Jha and R. Prasad, OFDM towards Fixed and Mobile Broadband Wireless Access (Artech House, 2007).

J. Proakis, Digital Communications (McGraw-Hill, 2008).

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Figures (9)

Fig. 1
Fig. 1

Illustration of source and receiver in visible light communication.

Fig. 2
Fig. 2

SNR (dB) distribution of VLC with one LED source on the ceiling, (a) before, and (b) after tilting receiver plane. Launching power of LED: 12W.

Fig. 3
Fig. 3

Principle of tilting the receiver plane to collect optimum optical power.

Fig. 4
Fig. 4

Source projection locates in the first quadrant of receiver.

Fig. 5
Fig. 5

SNR (dB) distribution of VLC for four LED sources on the ceiling, (a) before, and (b) after tilting receiver plane. Total launching power of four LEDs: 12W.

Fig. 6
Fig. 6

Projections of LEDs on the desk plane.

Fig. 7
Fig. 7

Attempt times of Newton method to reach the optimum angle: (a) one LED source and (b) four LED sources.

Fig. 8
Fig. 8

Setup for adaptive M-QAM OFDM scheme for visible light communication via IR feedback channel. CP: cyclic prefix, P/S: parallel to serial, S/P: serial to parallel.

Fig. 9
Fig. 9

Improvement of spectral efficiency by tilting receiver plane, (a) one LED source, (b) four LED sources.

Tables (2)

Tables Icon

Table 1 Parameters of VLC System Setup

Tables Icon

Table 2 Thresholds (dB) to Adjusting M-QAM Format

Equations (15)

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R ( φ ) = ( m + 1 ) cos m ( φ ) 2 π ,
H ( 0 ) = R ( φ ) A d 2 cos ( θ ) = ( m + 1 ) cos m ( φ ) A 2 π d 2 cos ( θ ) ,
cos ( φ ) = Z S Z R [ X S , Y S , Z S ] [ X R , Y R , Z R ] ,
cos θ = ( v R , v R S ) v R v R S ,
H ( 0 ) = ( m + 1 ) A 2 π d 2 cos m ( φ ) ( v R , v R S ) v R v R S
S N R = ( R H ( 0 ) P t x M I f ( t ) ) 2 σ s h o t 2 + σ t h e r m a l 2
α = { arctan ( | ( Y S Y R ) / ( X S X R ) | ) source projection in the 1st quadrant π arctan ( | ( Y S Y R ) / ( X S X R ) | ) source projection in the 2nd quadrant π + arctan ( | ( Y S Y R ) / ( X S X R ) | ) source projection in the 3rd quadrant 2 π arctan ( | ( Y S Y R ) / ( X S X R ) | ) source projection in the 4th quadrant
cos θ = ( v R , v R S ) v R v R S = a sin β cos α + b sin β sin α + c cos β a 2 + b 2 + c 2 .
f ( β ) = ( m + 1 ) cos m ( φ ) A 2 π d 2 a 2 + b 2 + c 2 ( a sin β cos α + b sin β sin α + c cos β )
β n + 1 = β n f ( 1 ) ( β n ) f ( 2 ) ( β n ) ,
H ( 0 ) = i = 1 4 R ( φ i ) A d i 2 cos ( θ i ) = i = 1 4 ( m + 1 ) cos m ( φ i ) A 2 π d i 2 cos ( θ i ) .
f ( β ) = i = 1 4 f i ( β ) = i = 1 4 m + 1 2 π cos m ( φ ) A cos ( θ i ) d i 2 = i = 1 4 ( m + 1 ) cos m ( φ ) A 2 π ( [ sin β cos α i , sin β sin α i , cos β ] , [ a i , b i , c i ] ) d i 2 a i 2 + b i 2 + c i 2
S E R 1 ( 1 2 Q ( 3 M 1 E S N 0 ) ) 2 4 Q ( 3 M 1 E S N 0 ) .
S E = 1 2 log 2 ( M ) N N + 1 1 2 log 2 ( M ) ,
S E ¯ = 1 2 i = 1 4 log 2 ( M i ) p ( M i ) ,

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