Research on Degree Distribution Optimization of LT Codes

LT码的度分布优化研究

¹ School of Informatics, Xiamen University, Xiamen 361005, China
² School of Electronic Science and Engineering, Xiamen University, Xiamen 361005, China
³ Southeast University, School of Economics and Management, Nanjing 211189, China

Received: 5 January 2019

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.

摘要

LT码作为一种对信道具有良好适应性的信道编码方案，已在水声通信中实现了稳定的数据传输。在译码开销较大的情况下，LT码可以达到理想误码率，但当编码数据长度较短时，其编译码性能并不理想。为改善LT码在编码数据长度较短时的性能，基于水声OFDM通信系统进行LT码的研究，以最低误码率和最小平均度值为优化目标，提出了一种度分布优化设计方法。仿真和海试试验结果表明：在相同的误码率下，该方法能优化系统，减小7%~22%不等的译码开销，降低编译码的复杂度。