So when i want to declare a parameter , SINR_stAB , which is a fraction,if i want to let the cvx accept this,what type of numerator and denominator should be ? both convex ? or?

Now i just know numerator and denominator both can’t be real affine , i mean real linear

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/ .

As I write, read the material on linear fractional functions. Actually, you should study at least the first 5 chapters of the above-linked book, so that you learn the fundamentals of convex optimization.