I have a maximization problem like this

\text{maximize} \sum_{n=1}^N\left( \log\left(1+\frac {x_1[n]x_2[n]k_1[n]k_2[n]}{x_1[n]k_1[n]+x_2[n]k_2[n]+N_0}\right)-k3[n]x_1[n]-k4[n]x_2[n]\right)

The constraints are affine.

Where \{x_1[n],x_2[n]\}_{n=1}^N are positive variables.

\{k_1[n],k_2[n],k_3[n],k_4[n]\}_{n=1}^N and N_0 are positive constants.

It is concave, but I do not know how to rewrite this problem.