Multi-Cell MIMO Power Minimization via Rate Balancing with Partial CSIT

In this work, we consider the power allocation problem via rate balancing optimization with imperfect Channel State Information at the Transmitter (CSIT), namely: expected user rate balancing. In particular, we study two closely related optimization problems: maximizing the minimum ergodic user rate under per cell transmit power constraints, and minimizing overall transmit power while satisfying per user rate targets. The max-min rate approach combines an operation of balancing at the user level and sum rate maximization at the level of the user streams. For imperfect CSIT, we exploit an approximation of the expected rate as the Expected Signal and Interference Power (ESIP) rate, based on an original minorizer for every individual rate term. Then, the transmit power is minimized while fulfilling user rate requirements when the latter are feasible, and otherwise switches to weighted rate balancing under the power constraints. Also, we handle the power minimization problem with two variations: minimizing the total transmit power and minimizing the maximum cell transmit power. Simulation results show the effectiveness of the proposed solutions.