11.4 Amplitude estimation in the coherent case with WGN Assume the phase is known and the amplitude must be estimated. y;=aS+n,i=1,.,k The amplitude a can either be a random variable of an unknown constant. ML: -a四-0+2（0ag0 i=l Symbol energy UESTC ∑y e=∑s 7 i=l11.4 Amplitude estimation in the coherent case with WGN Assume the phase is known and the amplitude must be estimated. The amplitude a can either be a random variable of an unknown constant. ML: 7 UESTC , 1, , i i i y n = + = as i k ( ( )) ( ) 1 0 k i i i i s y s   =   − =   ( ) 1 0 k i i i i as s =  y − = 1 1 k ML i i i a s = = y ε 2 1 k i i s  = ε= Symbol energy