题目内容
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[主观题]
设（7，3)循环码，其生成多项式为g（x)=x4+x2+x+1： （1)列出其所有码字，并求此码的最小码距；
设(7，3)循环码，其生成多项式为g(x)=x4+x2+x+1： (1)列出其所有码字，并求此码的最小码距； (2)写出其系统循环码的标准生成矩阵； (3)写出此码的校验多项式及标准校验矩阵； (4)给出此码的对偶码。
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a4)=0．15，P(a5)=0．15 These letters are to be coded into binary digits for use on a noiseless channal．It takes 1 second to transmit a 0 and 3 seconds to transmit a 1．Using cut and try techniques，find a code with the prefix condition that minimizes the average time required to transmit a source letter and calculate this minimum average time． (2)Any such code can be represented by a tree in which the length of a branch：is proportional to the time required to transmit the associated digit．Show that for a code to minimize the average transmission time，the probabilities associated with intermediate and terminal nodes must be nonincreasing with length．
