基于外信息符号差的 LT码串行译码算法

在无线通信系统中，LT码采用置信传播（ BP ）译码算法进行译码，缺少有效的迭代控制机制。针对这一问题，首先将串行置信传播（ SBP ）算法应用于LT码的译码，极大地提高了译码收敛速度。其次，通过对LT码在加性高斯白噪声（ AWGN）信道下的外信息转移（ EXIT）曲线的分析，提出了一种基于外信息符号差的串行置信传播（ ESD-SBP ）译码算法，即根据一次完整迭代前后符号节点译码器（ SND）的外信息符号变化情况来快速判断译码收敛情况、控制迭代停止。最后对固定迭代次数、互熵算法（CE）、循环冗余校验（CRC）以及外信息符号差算法（ESD）进行了性能对比。仿真结果表明，在不降低串行译码（ SBP ）算法性能的前提下，可以有效减小迭代次数。

Serial decoding algorithm based on extrinsic information symbol difference for LT code

In the wireless communication system , BP （ belief propagation ） decoding algorithm is used for LT code ’ s decoding , which lacks of effective iterative control mechanism .For the problems existed , this paper first applies SBP （ serial belief propagation ） algorithm to the decoding of LT code , which greatly improves the decoding speed of convergence .Secondly , by the analysis of EXIT （ extrinsic information transfer ） curve of LT code in AWGN （ addi-tive white Gaussian noise ） channel , the paper puts forward a kind of SBP decoding algorithm based on the ESD （ extrinsic information symbols difference ） -SBP , which is to quickly judge the convergence condition and control the iteration according to the change of the extrinsic information symbol from SND （ symbol nodes decoder ） before and after a full iteration.Finally, a comparison is made between the performance of the fixed number of iterations , CE （ cross-entropy concept ） , CRC （ cyclic redundancy check ） and the algorithm ESD （ extrinsic information sym-bol difference ） .The experimental results show that , the algorithm presented in this paper can reduce the number of iterations effectively without reducing the performance of serial decoding algorithm .