自由空间光通信中的CRC-LT编码性能研究

LT码是一种无码率的线性分组码，具有很强的信道适应性和低复杂度。文中提出一种CRC码与LT码级联的编码方案（CRC-LT码），CRC-LT码通过调整译码开销来保证FSO系统的可通率和使LT码在FSO系统中获得的编码增益。通过建立分析模型，推导出在给定信道条件下的数据恢复率。最后，利用Gamma-Gamma信道模型进行CRC-LT码的编译码过程仿真，并给出数据恢复率与信道条件、信噪比和译码开销的关系，以及FSO系统的误码率。仿真结果表明，CRC-LT码在牺牲一定译码开销后能够获得更高的编码增益，有效保证FSO系统的可通率。

Research on CRC-LT coding performance in free space optical communication

Luby transform (LT) code is a rateless linear code, which has good channel adaptability and low complexity. A concatenated coding scheme of CRC code and LT code (CRC-LT code) was proposed to ensure the reliability of FSO system and improve the coding gain of LT code in FSO system by adjusting overhead. A new analytic model was developed to derive the data restoration probability with given conditions of channel. Finally, simulation experiments were performed over Gamma-Gamma channel model, and the relationships among data restoration probability, channel condition, SNR and overhead were given. The results show that CRC-LT code has better coding gain and can effectively enhance the reliability of the FSO system by increasing overhead.