Abstract
LT code, as a channel coding scheme with good adaptability to the channel, has a stable performance in data transmission of underwater acoustic communication. In the case of large decoding overhead, the LT code can reach the ideal bit error rate(BER), but when the length of the encoded data is short, its coding and decoding performance is not ideal. LT code was applied to underwater acoustic communication by combining with orthogonal frequency division multiplexing (OFDM), and a LT-OFDM system was constructed. To improve the performance of LT code in the case of short code length, a method for degree distribution optimization was proposed on the objective of minimizing BER and minimizing average coding degree. Simulation and sea trial results show that under the same BER this method can optimize the system, transform 7%-22% conversion, and reduce the complexity of coding and decoding.
Highlights
西北工业大学学报 Journal of Northwestern Polytechnical University https: / / doi.org / 10.1051 / jnwpu / 20203830627
LT code was applied to underwater acoustic communication by combining with orthogonal fre⁃ quency division multiplexing ( OFDM), and a LT⁃OFDM system was constructed
To improve the performance of LT code in the case of short code length, a method for degree distribution optimization was proposed on the objective of minimizing BER and minimizing average coding degree
Summary
西北工业大学学报 Journal of Northwestern Polytechnical University https: / / doi.org / 10.1051 / jnwpu / 20203830627 环境噪声采用高斯白噪声,不考虑多普勒效应 的影响。 度分布优化前后的 LT 码在系统中的误码 率性能如图 2 所示。 在仿真条件同表 1 的情况下,考虑多普勒效应 的影响,假设收发机之间相对运动速度为 3 m / s,即 多普勒因子设为 0.02。 在新的信道条件下对度分布 优化前后 LT 码在系统中的误码率性能进行仿真, 结果如图 3 所示。 由图 4 和图 5 同样可知,考虑多普勒效应的影 响后,接收端通过接收更多的编码数据同样可以达 到理想的误码率。 在该仿真条件下,度分布优化后 LT 码的误码率相比于优化前同样有明显降低,且在 译码开销的节省程度上相比于无多普勒效应的情况 下更加显著。 度分布优化前,LT 码达到目标误码率 时所花译码开销为 3.75,度分布优化后所花译码开 销为 3.25,节省了 13.3% 的译码开销,可见,优化后
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