Evaluation of the forward error correction format for LEO-ground optical communication using Reed-Solomon product code

摘要

In recent years, optical communication protocols resilient to atmospheric disturbances for near-Earth have been discussed in Consultative Committee for Space Data System (CCSDS). We proposed our Forward Error Correction (FEC) format to the committee to provide a better option with a balance of its complexity and performance. The FEC consists of Reed-Solomon product code (RS-PC) which is robust to burst error and has been adopted as an optical disc format because they are commonly suffering from burst error caused by scratch, fingerprint, and other materials which disturb laser light. We considered the feature was also be able to be applied to the burst error correction of fading due to atmospheric disturbance and successfully demonstrated optical Ethernet communication by using proposed FEC between International Space Station and optical ground station which is located in Japan. However, the performance of RS-PC for free-space optical communication was not discussed quantitatively yet. Here we discuss the proposed FEC format structure in detail and its Bit Error Rate (BER) curve simulated under the condition of the fading channel. We also discuss the robustness of burst error can be adjusted in correspondence with the condition of the atmosphere channel by concatenating multiple FEC blocks. Furthermore, the BER performance can be improved without changing the FEC format itself by applying iterative correction and erasure correction. The simulation result shows the proposed FEC can realize better performance compared with a single Reed-Solomon code. In terms of error correction capability, soft-decision codes such as Low Density Parity Check (LDPC) and Serial Concatenated Convolutional Codes (SCCC) provide a better performance, but the advantage of RS-PC is that it can be implemented with smaller and less power consuming circuits than these FECs. It shows the proposed FEC format can be a promising approach especially for an in-orbit solution which supports limited power resource.