Optimal Dynamic Point Selection for Power Minimization in Multiuser Downlink CoMP
Abstract: This paper examines a coordinated multi-point multi point transmission/reception system where multiple base-stations stations (BSs) employ coordinated beamforming to serve multiple mobile-stations stations (MSs). Under the dynamic point selection mode, each MS can be assigned to only one BS at any time. This paper then presents a solution framework to optimize the BS associations and coordinated beamformers for all MSs. With Wit target signal-to-interference-plus plus-noise ratios at the MSs, the design objective is to minimize either the weighted sum transmit power or the per-BS BS transmit power margin. Since the original optimization problems contain binary variables indicating the BS BS associations, finding their optimal solutions is a challenging task. To circumvent this difficulty, we first relax the original problems into new optimization problems by expanding their constraint sets. Based on the nonconvex quadratic constrained quadratic quadr programming framework, we show that these relaxed problems can be solved optimally. Interestingly, with the first design objective, the obtained solution from the relaxed problem is also optimal to the original problem. With the second design objective, e, a suboptimal solution to the original problem is then proposed, based on the obtained solution from the relaxed problem. Simulation results show that the resulting jointly optimal BS association and beamforming design significantly outperforms fixed BS association schemes.