function [sys,x0,str,ts] = MMSE_IC(t,x,u,flag)

switch flag,
  
  case 0
    [sys,x0,str,ts]=mdlInitializeSizes;

  case 3
    sys=mdlOutputs(t,x,u);

  case { 1, 2, 4, 9 }
    sys=[];

  otherwise
    error(['Unhandled flag = ',num2str(flag)]);

end

function [sys,x0,str,ts] = mdlInitializeSizes()

sizes = simsizes;
sizes.NumContStates  = 0;
sizes.NumDiscStates  = 0;
sizes.NumOutputs     = 4;   % dynamically sized
sizes.NumInputs      = 41;  % dynamically sized
sizes.DirFeedthrough = 1;   % has direct feedthrough
sizes.NumSampleTimes = 1;

sys = simsizes(sizes);
str = [];
x0  = [];
ts  = [-1 0];   % inherited sample time

% end mdlInitializeSizes

function sys = mdlOutputs(t,x,u)

H = reshape(u(1:16),4,4) + reshape(u(17:32),4,4).*i;
r = reshape(u(33:36),4,1) + reshape(u(37:40),4,1).*i;
my_sigma=u(41);
Constellation = [1 i -1 -i];
Signal = [0 1 3 2];
y=zeros(4,1);
m=4;
while m>=1
    w=inv(H'*H+(my_sigma^2)*eye(m))*H';
    y(m)=w(m,:)*r;
    for n=1:4
        dis(n)=abs(y(m)-Constellation(n));
    end
    idx=find(dis==min(dis));
    sys(m)=Signal(idx);
    r=r-Constellation(idx).*H(:,m);
    H=H(:,1:m-1);
    m=m-1;
end

% end mdlOutputs