Optimal Joint Water-Filling for OFDM Systems with Multiple Cooperative Power Sources

In this paper, we investigate a new power allocation scheme for a multi-user orthogonal frequency division multiplex (OFDM) system, in which two cooperative power sources (CPS) coordinately transmit their power to multiple orthogonal subchannels. In order to maximize the sum rate, a closed form solution is obtained by analytical derivation. Based on the derived solution, we present a novel joint optimal power allocation scheme named as joint water-filling (Jo-WF) which has a remarkably simple nature. Furthermore, a new iterative Jo-WF algorithm is also proposed. Motivated by the regular theoretical derivation of the two-CPS case, we subsequently extend the closed form solution of Jo-WF into arbitrary K-CPS case. Numerical simulation results verify that, compared to traditional non-cooperative water-filling (WF) and equal power allocation (EPA), the proposed Jo-WF scheme provides a significant sum rate gain.