Application of polar codes for free space optical communication

In recent years, satellite laser communication is attracting much attention as an important infrastructure, due to its larger transmission capacity compared to radio-wave satellite communications. However, in satellite-to-ground laser transmissions, scintillation occurs due to air turbulence, and the received optical power fluctuates, resulting in a burst error. Thus, strong error correction codes are required for high quality satellite transmissions. E. Arikan has proposed a new error correction code called the Polar code, which is proven to asymptotically achieve the channel capacity with a long code length N in any binary memoryless channel. In addition, the calculation complexity of Polar codes used in encoding and decoding is on the order of O(N log N), which is lower than that of currently used channel codes. However, to achieve high performance, we need to properly select a “frozen bit”, but the optimal selection in satellite laser channels is not known. Therefore, in this study, we investigate the selection methods of frozen bits for free space optics (FSO) by evaluating block error rate performances in FSO channels.