Free space optical (FSO) communication is of paramount importance for the design of next-generation 5G+ wireless networks. These are, however, susceptible to degrading effects of atmospheric turbulence. The use of error correcting codes (ECCs) can mitigate the effects of fading caused by atmospheric turbulence. We evaluate the performance of uncoded and coded FSO communication system, where we use Bose Chaudhuri Hocquenghem (BCH) and low-density parity-check codes for the coded system. Both the systems under consideration are based on intensity-modulation and direct detection. We investigate the performance of a coded communication system under various channel conditions, viz., slow fading and fast fading gamma–gamma channels for different turbulence regimes and subsequently, obtain the coding gain. We derive the expressions of channel capacity for a fast fading channel and outage capacity for a slow fading channel. We conclude that ECCs deteriorate the bit error rate performance in a slow fading channel. However, for this kind of channel, the combination of ECCs with an interleaver reduces the burst errors and improves the performance which leads to positive coding gain. In a fast fading channel, coding gain is not much and it remains almost same in different turbulence conditions. The analytical results are supported by simulation study.

自由空间光（FSO）通信对于下一代5G +无线网络的设计至关重要。然而，这些容易受到大气湍流的降低作用的影响。纠错码（ECC）的使用可以减轻由大气湍流引起的衰落的影响。我们评估未编码和已编码的FSO通信系统的性能，在该系统中，我们使用Bose Chaudhuri Hocquenghem（BCH）和低密度奇偶校验码进行编码。所考虑的两个系统均基于强度调制和直接检测。我们研究了编码通信系统在各种信道条件下的性能，即对于不同的湍流状态，慢衰落和快衰落的伽马-伽马信道，并随后获得了编码增益。我们推导了快速衰落信道的信道容量和慢衰落信道的中断容量的表达式。我们得出的结论是，ECC会降低慢衰落信道中的误码率性能。然而，对于这种信道，ECC与交织器的组合减少了突发错误并提高了性能，从而导致正的编码增益。在快速衰落的信道中，编码增益不是很多，并且在不同的湍流条件下几乎保持不变。分析结果得到了仿真研究的支持。ECC与交织器的组合可减少突发错误并提高性能，从而获得正的编码增益。在快速衰落的信道中，编码增益不是很多，并且在不同的湍流条件下几乎保持不变。分析结果得到了仿真研究的支持。ECC与交织器的组合可减少突发错误并提高性能，从而获得正的编码增益。在快速衰落的信道中，编码增益不是很多，并且在不同的湍流条件下几乎保持不变。分析结果得到了仿真研究的支持。