两种LDPC译码算法在OFDM系统应用中的改进

Improvements of two LDPC decoding algorithms in OFDM system

低密度校验码是一种基于稀疏校验矩阵的线性码,此码性能接近Shannon限,并具有简单有效的迭代译码算法。大部分文献提到的LDPC迭代译码算法均基于BPSK调制,相对于MQAM/MPSK调制,BPSK调制频谱利用率太低。在未来的3G+高速无线通信中,最广泛运用的物理层技术OFDM必然采用频谱利用率较高的多电平调制。因此,如何把LDPC码用于多电平调制下的OFDM是一个关键,将目前较为简化的基于二进制调制的两种译码算法作改进,也即扩展,使之能够应用到基于多进制调制的OFDM系统中。

Low density check code is a kind of line-codes based on sparse check Matrix.This kind of channel coding can achieve the near Shannon limit performance.And it has a quite simple decoding algorithm which introduces an iterative decoding method.Large preferences referring to LDPC are based on binary modulation,such as BPSK.Compared with multilevel modulation, such as MQAM or MPSK,BPSK using of bandwidth is inefficient.In future 3G＋ mobile communications,the extensively adopted technique,OFDM,requires to combine with multilevel modulation.So,how to combine the channel coding,LDPC,with the multimodulation OFDM is our primary work.This paper improves or reams two decoding algorithms based on binary modulation,which enables them to adapt in OFDM system.