Waterfilling Schemes for Zero-Forcing Coordinated Base Station Transmission

In this work we consider the optimization of the power assigned to the user streams, in a coordinated base station downlink environment, when zero-forcing is employed to remove interference among users. Two schemes based on the waterfilling technique are proposed and compared to the optimal solution, which can be obtained numerically, by using convex optimization. We show that the proposed schemes achieve a performance, in terms of weighted sum rate, very close to the optimal, without the heavy computational complexity required by the numerical solution. The sum rates are compared in a realistic multi-cell scenario and some examples of achievable rates are presented also in a simplified two-user two-cell case.