Please re-read and follow the advice in Why isn’t CVX accepting my model? READ THIS FIRST! and alo re-read e CXV Users’ Guide http://cvxr.com/cvx/doc/ , as was suggested by me when answering one of your previous questions on this forum.
I have no idea what you are planning to do with SINR_stAB, so I can;t tell you how to deal with it. I suggest you read sections 2.3.3 and 4.3.2 on Linear Fractonal functions in https://web.stanford.edu/~boyd/cvxbook/ .