Iterative Receiver For Flip-OFDM in Optical Wireless Communication

Iterative Receiver for Flip-OFDM in Optical Wireless Communication
Abstract:
To guarantee nonnegative signals in optical wireless communication (OWC) systems, flipped

orthogonal frequency division multiplexing (Flip-OFDM) transmits the positive and negative
parts of the signal over two consecutive OFDM sub frames (positive sub frame and negative sub
fame, respectively). The conventional receiver for Flip-OFDM recovers the data by subtracting
the negative sub frame from the positive one. However, the signal analysis shows that the signals
in the two sub frames both contain the information of the transmitted data and can be used
together to decode the data. An iterative receiver is then proposed to improve the transmission
performance of Flip-OFDM by exploiting the signals in both sub frames. Simulation results
show that the proposed iterative receiver provides significant signal to noise ratio (SNR) gain
over the conventional receiver. Moreover, the iterative receiver also outperforms the existing
advanced receiver.
Index Terms Optical wireless communication (OWC), orthogonal frequency division
multiplexing (OFDM), Flip-OFDM, and iterative receiver.
1. INTRODUCTION:
With the widespread deployment of light-emitting diodes (LEDs), optical wireless
communication (OWC) has attracted an increasing interest in academia and industry recently.
Due to its distinct advantages such as rich spectrum resources and high communication security,
OWC has been anticipated to be an attractive alternative to radio frequency (RF) systems,
especially in indoor scenarios. In addition, the convergence of illumination and communication
makes OWC one of the most important green technologies. In order to achieve high data rates
and alleviate inter-symbol interference (ISI), orthogonal frequency division multiplexing
(OFDM) has been employed in OWC.
In the conventional receiver for Flip-OFDM, the data is recovered by subtracting the negative
signal block from the positive one. This method is simple and straightforward. However, it
increases the noise variance of the received symbols, making the performance much worse than
that of bipolar OFDM with the same modulation method. To improve the performance of FlipOFDM, a time-domain noise filtering technique was proposed in and investigated in. However,
the algorithm does not make full use of the signal structures. In this letter, an iterative receiver is
proposed for Flip-OFDM by fully exploiting the structures of the received signals. Simulations
confirm that the proposed iterative receiver is superior to other receivers.
2. OBJECTIVE:
Iterative receiver is proposed for Flip OFDM in IM/DD based OWC systems. In order to
improve the receiver performance, the iterative receiver obtains the additional diversity gain by
exploiting the signals in both the positive sub frame and negative sub fame. Iterative receiver
with only two iterations provides a significant SNR gain over the conventional receiver.
Moreover, the receiver is also superior to the existing advanced receiver. It should be noted that
the proposed iterative receiver can also be applied to the modified Flip-OFDM system proposed
in [10] and the multiple-input multiple-output (MIMO) system.
3. PROBLEM DEFINITION:
4. PROPOSED SCHEME:
Fig.1. Block diagram of a Flip-OFDM transmitter.
5. SOFTWARE AND HARDWARE REQUIREMENTS
Operating system
Windows XP/7.
Coding Language
MATLAB
Tool
MATLAB R 2012
SYSTEM REQUIREMENTS:
HARDWARE REQUIREMENTS:
System
Hard Disk
Floppy Drive
Monitor
Mouse
Ram
Pentium IV 2.4 GHz.

:
1.44 Mb.
:
40 GB.
15 VGA Colour.
Logitech.
:
512 Mb.
6. CONCLUSION:
An iterative receiver is proposed for Flip OFDM in IM/DD based OWC systems. In order to
improve the receiver performance, the iterative receiver obtains the additional diversity gain by
exploiting the signals in both the positive sub frame and negative sub fame. The simulation
results show that the iterative receiver with only two iterations provides a significant SNR gain
over the conventional receiver. Moreover, the receiver is also superior to the existing advanced
receiver. It should be noted that the proposed iterative receiver can also be applied to the
modified Flip-OFDM system proposed in and the multiple-input multiple-output (MIMO)
system proposed in.
7. REFERENCES:
[1] H. L. Minh, D. OBrien, G. Faulkner, L. Zeng, K. Lee, D. Jung, Y. Oh, and E. T. Won, 100mb/s NRZ visible light communications using a postequalized white led, IEEE Photonics
Technology Letters, vol. 21, no. 15, pp. 10631065, Aug. 2009.
[2] J.-B. Wang, Q.-S. Hu, J. Wang, M. Chen, and J.-Y. Wang, Tight bounds on channel capacity
for dimmable visible light communications, Journal of Lightwave Technology, vol. 31, no. 23,
pp. 37713779, Dec. 2013.
[3] J. Armstrong, OFDM for optical communications, Journal of Lightwave Technology, vol.
27, no. 3, pp. 189204, Feb. 2009.
[4] D. J. Barros, S. K. Wilson, and J. M. Kahn, Comparison of orthogonal frequency-division
multiplexing and pulse-amplitude modulation in indoor optical wireless links, IEEE
Transactions on Communications, vol. 60, no. 1, pp. 153163, Jan. 2012.
[5] N. Huang, J.-B. Wang, J. Wang, C. Pan, H. Wang, and M. Chen, Receiver design for PAMDMT in indoor optical wireless links, IEEE Photonics Technology Letters, vol. 27, no. 2, pp.
161164, Jan. 2015.
[6] J. Armstrong and B. Schmidt, Comparison of asymmetrically clipped optical OFDM and
DC-biased optical OFDM in AWGN, IEEE Communications Letters, vol. 12, no. 5, pp. 343
345, May 2008.
[7] J. Armstrong and A. Lowery, Power efficient optical OFDM, Electronics Letters, vol. 42,
no. 6, pp. 370372, Mar. 2006.
[8] S. C. J. Lee, S. Randel, F. Breyer, and A. M. Koonen, PAM-DMT for intensity-modulated
and direct-detection optical communication systems, IEEE Photonics Technology Letters, vol.
21, no. 23, pp. 17491751, Dec. 2009. [9] N. Fernando, Y. Hong, and E. Viterbo, Flip-OFDM
for optical wireless communications, in Proc. 2011 IEEE Information Theory Workshop (ITW),
2011, pp. 59.
[10] D. Tsonev and H. Haas, Avoiding spectral efficiency loss in unipolar OFDM for optical
wireless communication, in Proc. 2014 IEEE International Conference on Communications
(ICC), pp. 33363341.
[11] N. Fernando, Y. Hong, and E. Viterbo, Flip-OFDM for unipolar communication systems,
IEEE Transactions on Communications, vol. 60, no. 12, pp. 37263733, Dec. 2012.
[12] D. Tsonev, S. Sinanovic, and H. Haas, Novel unipolar orthogonal frequency division
multiplexing (U-OFDM) for optical wireless, in Proc. 2012 IEEE 75th Vehicular Technology
Conference (VTC Spring), pp. 15.
[13] E. G. Larsson, MIMO detection methods: How they work, IEEE Signal Processing
Magazine, vol. 26, no. 3, pp. 9195, May 2009.
[14] J. Karout, E. Agrell, K. Szczerba, and M. Karlsson, Optimizing constellations for singlesubcarrier intensity-modulated optical systems, IEEE Transactions on Information Theory, vol.
58, no. 7, pp. 4645 4659, July 2012.
[15] J. R. Barry, J. M. Kahn, W. J. Krause, E. A. Lee, and D. G. Messerschmitt, Simulation of
multipath impulse response for indoor wireless optical channels, IEEE Journal on Selected
Areas in Communications, vol. 11, no. 3, pp. 367379, Apr. 1993.
[16] L. Wu, Z. Zhang, and H. Liu, MIMO-OFDM visible light communications system with
low complexity, in Proc. 2013 IEEE International Conference on Communications (ICC), pp.
39333937.

Iterative Receiver For Flip-OFDM in Optical Wireless Communication

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Iterative Receiver for Flip-OFDM in Optical Wireless Communication

To guarantee nonnegative signals in optical wireless communication (OWC) systems, flipped

Fig.1. Block diagram of a Flip-OFDM transmitter.

5. SOFTWARE AND HARDWARE REQUIREMENTS

Pentium IV 2.4 GHz.

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