设有两个离散信道,其分别输入为X1和X2,输出为Y1和Y2,对应这两个信道的传递概率为P1(y|x)和P2(y|x),如图3.18所示。其X1和X2的概率分布分别为P1(x)和P2(x)。
Find a joint probability assignment P(xyz) such that I(X;Y)=0 and I(X;Y|Z)=1bit.
第3题
following inequalities and find condition for equality. (1)H(XY|Z)≥H(X|Z) (2)I(XY;Z)≥I(X;Z) (3)I(X;Z|Y)≥I(Z;Y|X) - I(Z;Y)+I(X;Z) (4)H(XYZ) - H(XY)≤H(XZ) - H(X)
第4题
The binary errors-and-erasures channel is given by (1)Find the capacity (2)Specialize to erasures only(ε=0) (3)Specialize to the binary symmetric channel(ρ=0) (4)Would you prefer a binary symmetric channel with crossover probability=0.125 or a simple erasure channel with probability of erasure=0.5?
第5题
iable X,Y and Z should be defined by I(X;Y;Z)=I(X;Y) - I(X;Y|Z) This quantity is symmetric in X,Y and Z,despite the preceding asymmetric define.Unfortunately,I(X;Y;Z)is not nesessarily nonnegative.Find X,Y,Z such that I(X;Y;Z)<0,and Prove the following two identities: I(X;Y;Z)=H(XYZ) - H(X) - H(Y) - H(Z)+I(X;Y)+I(Y;Z)+I(Z;X) I(X;Y;Z)=H(XYZ) - H(XY) - H(YZ) - H(ZX)+H(X)+H(Y)+H(Z) The first identity can be understood using the Venn diargram analogy for entropy and mutual lnlormatlon.The second identity follows easily from the first.
第6题
N.Each sequences an even number of 1’S has probabilitv 2-(N-1) and each sequences with an odd number of 1’s has probability zero.Find the average mutual informations I(X1;X2),I(X3;X2|X1),…,I(XN;XN-1|X1X2…XN-2) Check your result for N=3.
第7题
有一信源输出X∈{0,1,2},其概率为p0=1/4,p1=1/4,p2=1/2。设计两个独立实验去观察它,其结果分别为Y1∈{0,1}和Y2∈{0,1}。已知条件概率为:
求:(1)I(X;Y1)和I(X;Y2),并判断哪个实验好些。 (2)I(X;Y1Y2),并计算做Y1和Y2两个实验比做Y1或Y2中的一个实验各可多得多少关于X的信息。 (3)I(X;Y1|Y2)和I(X;Y2|Y1),并解释它们的含义。
第8题
dent. let ρ=1 - H(X1|X2)/H(X1) (1)Show ρ=I(X1;X2)/H(X1) (2)Show 0≤ρ≤1 (3)When is ρ=0? (4)When is ρ=1?
第9题
(XY) - I(X;Y) =2H(XY) - H(X) - H(Y)
第10题
t ρ(X,Y) is the number of bits needed for X and to communicate their values to each other.
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