What type of numerator and denominator should be to let cvx accept?both convex?

   %g_AB , P_C2AB , P_B2AC , g_A , P_A2BC, N_0, mu are all constant
   cvx begin
   variable rho_stA semidefinite
   SINR_stAB=( (1-rho_stA)*g_AB*P_B2AC )/...
              ( (1-rho_stA)*g_AC *P_C2AB +(1-rho_stA)*g_A*P_A2BC + (1-rho_stA)*N_0+mu*N_0 )

 subject to .....

The command window show me this error :

   Disciplined convex programming error:
    Cannot perform the operation: {real
    affine} ./ {real affine}

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

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/ .

Two website you provide won’t help me, i have already seen it before.but it doesn’t mention that which type of numerator and denominator should be.

I just want to know ,is it necessary for numerator and denominator be convex or other type if i want to declare a parameter like this

I will produce lots of parameter like SINR_stAB,and find the minimum value from them

You can not enter any of these directly into CVX…

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.