How can I express log2(1+S(1)/(S(2)+N)) in problem?

I have a problem such as

minimize sum(S) - a * log2( 1 + S(1) / (S(2)+S(3)+N) )

where S is the variables to be optimized, how can I express this problem in CVX?

Thanks very much for your answer~ :slight_smile:

This is non-convex.