CDI Rate-balancing with Per-base-station Constraints

We previously introduced a rate-balancing precoding technique based on channel distribution information, which significantly reduces the impact of pilot-contamination in the downlink of a massive MIMO system. We now extend the ratebalancing optimization problem for the precoders to multiple power constraints, to be able to apply the technique in a coordinated multi-point setting. For this problem, we derive an efficient and adaptive method to find a globally optimal solution based on transformation in the dual uplink. Finally, the results are compared to the optimization with a single sum-power constraint, where the beamforming vectors are simply scaled to satisfy the constraints at each base station.