LDPC Decoding Techniques for Free-Space Optical Communications

There has been significant interest in free-space optical (FSO) communication by the research community recent years. This is due to its high data rate, unlicensed spectrum, low cost, and immense security for FSO systems. Due these advantages, can have broader applications that extend from terrestrial satellite communication. Atmospheric turbulence (AT) induced fading a primary problem link since it significantly impairs performance. occurs random variation of air refractive index with time. Several statistical models are introduced characterize AT. The Log-normal (LN) model represents weak moderate turbulence, Gamma-Gamma (G-G) employed strong turbulence. These used effect weather attenuation, geometric losses, misalignment errors. One possible solution channel coding, such as low-density parity-check (LDPC) codes. paper proposed employing Weighted Bit Flipping (WBF) Implementation Efficient Reliability Ratio (IERRWBF) decoding techniques improve results show superior improvement bit error rate (BER) than uncoded system. In addition, obtained prove IERRWBF technique more optimized WBF point number iterations, especially channels. calculation decoders processing time, maintained lower time technique, while higher Eb/Nos, they same level. response both case resultant throughput. Finally, methods evaluated convergence. achieved faster convergence all channels under study.