How to express multi variable concave constrain?

For example, multi variable function f(x, y) = x * log2(1 + y) is a joint concave function of x and y when y >= 0, so how to express the constrain: x * log2(1 + y) >= k with cvx?

Assuming k is a positive constant, then

log2(1 + y) >= k/x

should work.

@Erling’s formulation is implemented in CVX as

`log(1+y)/log(2) >= k*inv_pos(x)`

because `log2`

is not supported for cvx expressions.

And this assumes `x >= 0`

; otherwise the constraint is not convex.