LDPC软译码过程: 输入(Input): 检验矩阵H,信道后验概率pn(x)=p(cn=x|rn),最大迭代次数L(x为0或1). 初始化(Initialization): set qnm(x)=pn(x) for all (m,n) with H(m,n)=1 校验节点更新(Horizontal Step): for each (m,n) with H(m,n)=1, compute dqnm=qnm(0)-qnm(1), drmn=#dqmn'(where n' belong to Nm,n , 在这里#表示连乘符号) rmn(1)=(1-drmn)/2, rmn(0)=(1+drmn)/2. 变量节点更新(Vertical Step): for each (m,n) with H(m,n)=1, compute qnm(0)=a1pn(0)#rm'n(0) qnm(1)=a1pn(1)#rm'n(1) (where m' belong to Mn,m ; and a1 is chosen so qnm(0)+qnm(1)=1 ) 计算伪后验概率(Pseudoposterior probabilities): qn(0)=a2pn(0)#rm'n(0) qn(1)=a2pn(1)#rm'n(1) (where m' belong to Mn ; and a2 is chosen so qn(0)+qn(1)=1 ) 译码尝试(Make a tentative decision): set cn=1 if qn(1)>0.5, else set cn=0 if cnH'=0, then stop. otherwise, if iterations<L, loop to Horizontal Step. Otherwise, declare a decoding failure and stop. LDPC和积译码示例: 1 2 3 4 5 6 7 |
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