function [sys,x0,str,ts] = Null_Cance(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];
x=zeros(4,1);
x2=zeros(4,1);
w=inv(H'*H+my_sigma^2*eye(4))*H';
w=w';
y=w*r;

for m=1:4
    dis(m)=abs(y(4)-Constellation(m));
end
n=find(dis==min(dis));
x2(4) = Signal(n);

x(3) = (y(3)-R(3,4)*x(4))/R(3,3);
for m=1:4
    dis(m)=abs(x(3)-Constellation(m));
end
n=find(dis==min(dis));
x2(3) = Signal(n);


x(2) = (y(2)-R(2,3)*x(3)-R(2,4)*x(4))/R(2,2);
for m=1:4
    dis(m)=abs(x(2)-Constellation(m));
end
n=find(dis==min(dis));
x2(2) = Signal(n);


x(1) = (y(1)-R(1,2)*x(2)-R(1,3)*x(3)-R(1,4)*x(4))/R(1,1);
for m=1:4
    dis(m)=abs(x(1)-Constellation(m));
end
n=find(dis==min(dis));
x2(1) = Signal(n);


sys = x2;

% end mdlOutputs