Impact of Reed Solomon forward error correction code in enhancing performance of free space optical communication link

The technological development in the field of optical communication has nearly addressed the concern for availability of bandwidth at higher data rates to meet the user requirement. The high speed multimedia applications have put an impetus for seamless transmission and reception of error free data at desired bit rates. The presence of recurring inherent errors in data transmission and processing makes Free Space Optical (FSO) communication susceptible to errors and loss of information. For efficient communication and effective service delivery in FSO, the mechanism for detecting errors and then correcting them has to be evolved. In this research work, we have focused on the application of Reed Solomon (RS) codes over the finite Galois field (GF) for detecting and correcting maximum received errors. The RS (n, k, dmin) code scheme is applied to the designed FSO link by taking the data bits (k) 239, 223, 191 and 127, code length (n) 255 with a code rate (R) 14/15, 7/8, 3/4 and 1/2 under the influence of moderate to strong turbulences and weather conditions. The proposed FSO system has been modeled using the Modified Gamma-Gamma model and the performance is evaluated for Bit Error Rate (BER), number of errors corrected and Geometric path losses as a function of link distance with and without the application of RS codes. The designed FSO system with RS code rate=1/2 performs optimally and shows an improvement of 8dB in coding gain as compared to the conventional FSO system. The geometric path losses have reduced from -8.76dB to -28.04dB along with maximum possible error correction of 399 errors in the transmitted data frame for the link distance ranging from 500m to 5km.