N次扩展信源的数学模型: N次扩展信源 X=(X1X2…XN X1∈X=|a1a2 c1=(a1a1…a1 ), P(x)P(a)=P(a12…a)=∏Pan) 且∑P( 例:已知DMS: X P(x)」1/21/41/4 二次扩展信源: 二次扩展信源 X=(X1X2), X;∈X=|a1,a2,a3l 2 X ana a1a2 ana3 a2a a2a2 a2a3 a3 a1 a3a2 a3a P(x)1/41/81/81/81/161/161/81/161/16N 次扩展信源的数学模型：   = = =           = = = =  =      N N k N q i i N k i i i i i q q q N q P P P a a a P a a a a a a a P x X 1 1 1 1 1 1 ( ) 1 ( ) ( ) ( ) ( ), ( ) ( ) 1 2     且      例：已知 DMS：       =      ( ) 1/ 2 1/ 4 1/ 4 a1 a2 a3 P x X 二次扩展信源：        =      ( ) 1/ 4 1/8 1/8 1/8 1/16 1/16 1/8 1/16 1/16 1 1 1 2 1 3 2 1 2 2 2 3 3 1 3 2 3 3 2 a a a a a a a a a a a a a a a a a a P x X  N 次扩展信源 [ , , ] ( ), 1 2 1 2 i q N X X a a a X X X X     = = 二次扩展信源 [ , , ] ( ), 1 2 3 1 2 X X a a a X X X i  = = 