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      = 72;  % 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)



Q = reshape(u(1:16),4,4) + reshape(u(17:32),4,4).*i;
R = reshape(u(33:48),4,4) + reshape(u(49:64),4,4).*i;
r = reshape(u(65:68),4,1) + reshape(u(69:72),4,1).*i;
% Constellation = [1 i -1 -i];
% Signal = [0 1 3 2];
Constellation = [1 -1];
Signal = [0 1];
x=zeros(4,1);
x2=zeros(4,1);
y = Q'*r;

x(4)=y(4)/R(4,4);
% for m=1:2
%     dis(m)=abs(x(4)-Constellation(m));
% end
% n=find(dis==min(dis));
% x2(4) = Signal(n);
if real(x(4))>0
    x2(4)=0;
else x2(4)=1;
end

x(3) = (y(3)-R(3,4)*x(4))/R(3,3);
% for m=1:2
%     dis(m)=abs(x(3)-Constellation(m));
% end
% n=find(dis==min(dis));
% x2(3) = Signal(n);
if real(x(3))>0
    x2(3)=0;
else x2(3)=1;
end

x(2) = (y(2)-R(2,3)*x(3)-R(2,4)*x(4))/R(2,2);
% for m=1:2
%     dis(m)=abs(x(2)-Constellation(m));
% end
% n=find(dis==min(dis));
% x2(2) = Signal(n);
if real(x(2))>0
    x2(2)=0;
else x2(2)=1;
end

x(1) = (y(1)-R(1,2)*x(2)-R(1,3)*x(3)-R(1,4)*x(4))/R(1,1);
% for m=1:2
%     dis(m)=abs(x(1)-Constellation(m));
% end
% n=find(dis==min(dis));
% x2(1) = Signal(n);
if real(x(1))>0
    x2(1)=0;
else x2(1)=1;
end

sys = x2;

% end mdlOutputs