为了提高光通信链路在大气弱湍流信道下的解码性能和传输效率, 基于极化码的信息位嵌套特性, 设计了一种自适应码率极化码。该码字在弱湍流信道中能充分地极化, 纠错效果较好。为了调节码率, 引入CRC校验码作为发送端的停止标志, 逐次发送更低码率的码字直到译码结果通过校验, 此时的码字码率即是保证可靠传输的最大码率。不同湍流强度下的仿真结果表明, 在误帧率为10-8时, 相比传统极化码, 自适应码率极化码可以获得1.7~2.3 dB的性能增益。对自适应码率极化码的时延进行了仿真分析, 并结合误帧率得到了自适应码率极化码的信息吞吐率, 结果表明, 在弱湍流信道中, 自适应码率极化码的信息吞吐率能满足FSO的传输需求。

To improve the decoding performance and transmission efficiency of optical communication link in atmospheric weak turbulence channel, heuristic adaptive rate polar codes were proposed. Adaptive rate polar codes were designed based on nesting property of information bits of polar codes, which could achieve fully polarization and good error-correcting performance in atmospheric weak turbulence channel. To adjust the code rate of adaptive rate polar codes, cyclic redundancy check(CRC) code was introduced as stop signs, which could check decoding result. Transmitting terminal sent a set of codes with gradually lower code rates, when the received codes passed CRC check, transmitting terminal stopped and the rate of such code was the largest rate which can ensure reliable transmission. Simulation results show that, compared to traditional polar codes, adaptive rate polar codes can obtain 1.7 dB to 2.3 dB coding gain at the frame error rate(FER) of 10-8 in different atmospheric turbulence intensity. Decoding latency of adaptive rate polar codes was simulated and the throughput rate of adaptive rate polar codes was calculated. The results show that adaptive rate polar codes can meet the transmission requirements of FSO in atmospheric weak turbulence channel.