On the Pareto optimum of long-term max-min beamforming with general power constraints

In this paper, the Pareto optimum of the max-min beamforming problem with general power constraints is discussed. Conditions without a balanced signal to interference plus noise ratio are identified and based on the discussions an improved direct and iterative solution of the max-min beamforming problem is proposed. Numerical results show the performance gain of the presented solution compared to a classical bisection based approach. The presented solution is able to jointly find the optimized beamforming weights and an assignment of base stations (BSs) to users based on the optimization of the beam-formers if a cooperative multipoint transmission is feasible. In the case of long-term channel state information at the BSs, a diversity gain can be achieved.