1.2 Single Antenna Channels Let us consider the additive white Gaussian noise (AWGN)channel: Y=HX+Z where k∈{I,…,is the time index and ·(X,,Xw）is the input vector satisfying s EsP (Z...,ZN)is the noisy vector,independent of (.....N) .(Y,...,Y)is the output vector; .H,...,H are the fading coefficients. 1414 1.2 Single Antenna Channels Let us consider the additive white Gaussian noise (AWGN) channel: Y H X Z k k k k = + where is the time index and k 1, N  ,  • (X1 ,…,X N ) is the input vector satisfying 2 1 1 P N k k X N          • (Z1 ,…,Z N ) is the noisy vector, independent of (X1 ,…,X N ) • (Y1 ,…,Y N ) is the output vector; • H1 ,…,H N are the fading coefficients