Illegal operation: {convex} - {convex}

Nonconvex
1

Please help me to find the problem of my code.Thank you!

M=16;
K=6;
H=(randn(M,K)+1i*randn(M,K))/sqrt(2);
sigma_2=0.01;
P0=1;
gamma0=10;

cvx_begin
variable W(M,K) complex

       minimize(square_pos(norm(W,'fro')))
       subject to          
          for k=1:K
              for j=1:K
                  num = 0;
                  if (j ~= k)
                       num = num+(square_pos(abs(H(:,j)'*W(:,j))));
                  end
              end
              square_pos(abs(H(:,k)'*W(:,k)))-(num*gamma0)>=gamma0*sigma_2;
          end

cvx_end

错误使用 + (line 83)
Disciplined convex programming error:
Illegal operation: {convex} - {convex}

出错 - (line 21)
z = plus( x, y, true, cheat );

出错 Untitled4 (line 20)
square_pos(abs(H(:,k)'W(:,k)))-(numgamma0)>=gamma0*sigma_2;

2

That looks like a non-convex constraint to me.