function C_water=water_select(H,SNR,Nt,Nr,Lt);
%**************************************************************************%
%**************************************************************************
%clear all
%clc
%format long
%SNR= 20;
%Nr=6;
%Nt=6;
%Lt=4;
%H=wgn(Nr,Nt,0,'complex');
% [VIN,EIG]=eig(H*H'); %extract eigenvalues
[U,S,V]=svd(H);
eigen=diag(S);
M=size(find(eigen),1);
gamma=zeros(M,1);
snr=10^(SNR/10);
r=M;%set rank = number of antennas (full rank)
p=1;%initial count
for i=1:r
% mu=getmu(r,SNR,T,p,M);%determine mu value (see eqn. (1.30))
temp2=0;
for k=1:r-p+1
temp1=1/(eigen(k)^2);
temp2=temp2+temp1;
temp1=0;
end
if r-p+1~=0
mu=(M/(r-p+1))*(1+(1/snr)*temp2);
else
mu=0;
end
gamma(i,1)=mu-(M/snr)*(1/(eigen(i)^2)); %calculate gamma (see eqn (1.31))
if gamma(i,1)<0
gamma(i,1)=0;% if gamma < 0, set it to zero i.e. discard it
p=p+1;% increment count
mu=0;%clear register
else
mu=0; % if gamma >0 store it and clear register
end
end
if(M<=Nt)
gam=[gamma;zeros(Nt-M,1)];
else
gam=gamma(1:Nt,1);
end
EIGNEW=diag(gam);
%solve eqn (1.26)using the determinant form
K=V*EIGNEW*V';
kw=diag(K);
[kw_opt,kw_index]=sort(kw);
hw_opt(1:Lt,1)=kw_index(Nt-Lt+1:Nt,1);
hw_optr(1:Lt,1)=kw_opt(Nt-Lt+1:Nt,1);
H4=[];
C_water=0;
for ki=1:length(hw_opt)
H4=[H4 H(:,hw_opt(ki))];
% C_water=C_water+log2(hw_optr(ki)*/(10^(SNR/10)*Lt));
end
C_water=log2(det(eye(Nr,Nr)+(10^(SNR/10)).*H4*H4'./Lt));
%I+(SNR/M)*diag(gamma).*diag(eigen);
% a=det(a);
% y(K)=log2(a);
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