Error Correction Coding for Performance Enhancement of ADO-OFDM System in the Presence of Weak Atmospheric Turbulence

Document Type : Original Article

Authors

1 Dept. of Electronics and Communications, Faculty of Engineering, Zagazig University

2 Dept. of Electronics and Communications, Faculty of Electronic Engineering, Minufiya University.

Abstract

In Free Space Optics (FSO) systems, atmospheric turbulence is considered
as the main problem. The overall performance of FSO system may be
degraded in the presence of weak atmospheric turbulence. This paper
offers an approach for performance improvement of FSO systems by
using Asymmetrically Clipped DC-biased Orthogonal Frequency Division
Multiplexing (ADO-OFDM) with error correction coding, especially in
the presence of weak atmospheric turbulence. Generally, most studies
about ADO-OFDM do not consider the turbulence effect. In this paper, we
take this effect into consideration and try to reduce its drawbacks using
error correction coding. ADO-OFDM is a form of Intensity
Modulation/Direct Detection (IM/DD) Optical Orthogonal Frequency
Division Multiplexing (O-OFDM) system that merges aspects of
Asymmetrically Clipped Optical OFDM (ACO-OFDM) and DC-biased
Optical OFDM (DCO-OFDM). The log-normal distribution model is used
to express the weak atmospheric turbulence effect. This paper proposes an
approach to mitigate the effect of weak atmospheric turbulence using error
correction coding. A comparative study between Hamming and LDPC
coding is presented in this paper for performance enhancement. From the
obtained results, it is observed that Hamming code gives a performance
enhancement by approximately 5.5 dB at BER =10-3 and fading strength
. LDPC code gives a performance enhancement by
approximately 1.5 dB at BER= 10-1 and fading strength. At
EbNo= 1 dB , it is seen that BER=0.112 in case of using Hamming code,
this value decrease to become 0.06327 in case of using LDPC code.


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