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Quasi-light Storage for Optical Data Packets
Published on: February 6, 2014
LDPC coded OFDM over the atmospheric turbulence channel
Ivan B Djordjevic1, Bane Vasic, Mark A Neifeld
1University of Arizona, Department of Electrical and Computer Engineering, Tucson, AZ 85721, USA. ivan@ece.arizona.edu
Optics Express
|June 24, 2009
Summary
Low-density parity-check (LDPC) coded optical orthogonal frequency division multiplexing (OFDM) significantly outperforms on-off keying (OOK) in atmospheric turbulence. This optical wireless communication method offers substantial coding gain and spectral efficiency improvements.
Area of Science:
- Optical wireless communications
- Digital signal processing
- Error correction coding
Background:
- Atmospheric turbulence degrades optical signal quality, impacting free-space optical communication systems.
- On-off keying (OOK) is a common modulation technique, but its performance can be limited in turbulent channels.
- Low-density parity-check (LDPC) codes offer powerful error correction capabilities.
Purpose of the Study:
- To compare the performance of LDPC coded optical OFDM against LDPC coded OOK in atmospheric turbulence.
- To quantify the coding gain and spectral efficiency improvements offered by optical OFDM.
- To evaluate the system's effectiveness under strong turbulence conditions.
Main Methods:
- Implementation of LDPC coded single-side band unclipped-OFDM with 64 sub-carriers.
- Utilizing quadrature-phase-shift keying (QPSK) and binary-phase-shift keying (BPSK) modulation schemes.
- Performance evaluation in a strong atmospheric turbulence regime at a bit-error rate of 10^-5.
Main Results:
- LDPC coded optical OFDM demonstrated superior performance over LDPC coded OOK.
- Coding gain improvements of 20.2 dB (QPSK) and 23.4 dB (BPSK) were observed for optical OFDM compared to OOK.
- Significant enhancements in both coding gain and spectral efficiency were achieved.
Conclusions:
- LDPC coded optical OFDM is a highly effective solution for mitigating atmospheric turbulence effects in optical wireless communication.
- The system offers substantial performance advantages, particularly in terms of coding gain, making it suitable for robust optical communication links.
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