多元，LDPC编码调制系统中低复杂度的似然概率生成算法

Low-complexity likelihood probability derivation algorithm for non-binary LDPC-coded modulation system

在采用多元LDPC码的通信系统中,尤其当使用高阶调制方案时,输入到译码器中的似然概率计算复杂度非常高。其主要原因是由于似然概率通常是关于信道输出的复杂函数,其计算需已知信道参数。针对上述问题,提出了一种低复杂度的近似似然概率生成算法。依据接收信号和星座点之间的欧氏距离,将星座点所对应的有限域GF(q)上域元素的似然概率进行分块逼近,能够以较低复杂度快速生成译码器所需要的概率度量。仿真结果表明,所提出的分块似然概率逼近生成算法在译码性能上损失较小且极大降低了似然概率生成的计算复杂度,是一种适用于高速多元LDPC译码器前端实现的候选算法。

The derivation of likelihood probabilities which are sent into the decoder in many LDPC-coded modulation sys- tems is a challenging task especially when high-order modulations are used. This is because likelihood probabilities are usu-ally complicated functions of the channel output and their calculation also requires knowledge of the channel parameters. To this end, a low-complexity likelihood probability derivation algorithm was proposed. Also, the Euclidean distance between the received signal and the constellation points was considered to divide the constellation points into two signal sets. Simula- tion results show that the proposed algorithm provides good trade-offs between performance and complexity, making it a good candidate for the hardware implementation of the front-end in the non-binary LDPC decoders.