Here is my cvx code

```
cvx_begin
variable E_user(n) nonnegative
variable z nonnegative
expression sigma(n)
expression Sigma(n)
expression Omega(n)
expression A(n)
expression B(n)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% sigma=zeros(1,K_num); Sigma=zeros(1,K_num); Omega=zeros(1,K_num);
% Calculate sigma
for t=1:K_num
my_hold=zeros(M*N,M*N);
for i=1:K_num
if i~=t
my_hold=my_hold+E_user(i)*G_DDMA(:,:,i)*G_DDMA(:,:,i)';
end
end
sigma(t)=trace(pinv(D(:,:,t))*U(:,:,t)*H(:,:,t)*my_hold*H(:,:,t)'*U(:,:,t)'*(pinv(D(:,:,t)))');
end
% Calculate Sigma
for t=2:K_num
my_hold=zeros(M*N,M*N);
for i=2:K_num
if i~=t
my_hold=my_hold+E_user(i)*G_DDMA(:,:,i)*G_DDMA(:,:,i)';
end
end
Sigma(t)=trace(pinv(D(:,:,1))*U(:,:,1)*H(:,:,1)*my_hold*H(:,:,1)'*U(:,:,1)'*(pinv(D(:,:,1)))');
end
my_hold=zeros(M*N,M*N);
for i=3:K_num
my_hold=my_hold+E_user(i)*G_DDMA(:,:,i)*G_DDMA(:,:,i)';
end
Sigma(1)=trace(pinv(D(:,:,2))*U(:,:,2)*H(:,:,2)*my_hold*H(:,:,2)'*U(:,:,2)'*(pinv(D(:,:,2)))');
% Calculate Omega
for i=2:K_num
Omega(i)=trace(pinv(D(:,:,1))*U(:,:,1)*H(:,:,1)*G_DDMA(:,:,i)*G_DDMA(:,:,i)'*H(:,:,1)'*U(:,:,1)'*(pinv(D(:,:,1)))');
end
Omega(1)=trace(pinv(D(:,:,2))*U(:,:,2)*H(:,:,2)*G_DDMA(:,:,1)*G_DDMA(:,:,1)'*H(:,:,2)'*U(:,:,2)'*(pinv(D(:,:,2)))');
sigma=real(sigma);
Sigma=real(Sigma);
Omega=real(Omega);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
for i=2:n
A(i)=(N0+alpha*sigma(i)+E_user(i))*(N0+E_user(1)+alpha*Sigma(1));
B(i)=(N0+alpha*Sigma(i))*(N0+E_user(1)+alpha*Sigma(1)+E_user(i)*Omega(1));
end
A(1)=(N0+alpha*sigma(1)+E_user(1))*(N0+E_user(2)+alpha*Sigma(2));
B(1)=(N0+alpha*Sigma(1))*(N0+E_user(2)+alpha*Sigma(2)+E_user(1)*Omega(2));
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
maximize (z)
E_sum=0;
for i=1:n
E_sum=E_sum+E_user(i);
end
subject to
E_sum<=E_total;
for i=2:n
log(2*beta(i)*sqrt(A(i)) - beta(i)^2*B(i) )/log(2)>=z;
end
log(2*beta(1)*sqrt(A(1)) - beta(1)^2*B(1) )/log(2)>=z;
cvx_end
```

I have following error when cvx is going to generate A(i)

```
Disciplined convex programming error:
Invalid quadratic form(s): not a square.
```

I believe the error comes from I have made variables production when generate A(i), is there any method to fix this?