Transmit power allocation for a downlink two-user interference channel

We develop the optimal transmit power allocation scheme that maximizes the total throughput for a downlink two-user interference channel. The derived optimal scheme allocates the total power to one user in better channel state, as in the greedy scheme, when the degree of interference between users exceeds a certain threshold. When it is less than the threshold, on the contrary, the transmit power is divided into two users, as in the water-filling scheme. Numerical results are presented to verify the optimality of the derived scheme and to show throughput gains over the greedy and water-filling schemes.