Energy-aware and rate-aware heuristic beamforming in downlink MIMO OFDMA networks with base station coordination

This work addresses the problem of coordinated beamforming across a group of base stations and frequency slots in the downlink of a MIMO OFMDA cellular network. Three figures of merit have been considered for system design under a per-base-station power constraint, namely, 1) the weighted sum of the rates on the frequency slots of the coordinated BSs, 2) the global energy efficiency, defined as the ratio between the network sum rate and the corresponding consumed power, and 3) the weighted sum of the energy efficiencies on the frequency slots of the coordinated BSs. The Karush-Kuhn-Tucker conditions of the considered optimization problems are first derived to gain insights into the structure of the optimal beamformers. Then, we propose a suboptimal design method that can be applied to all considered figures of merit. Numerical results are provided to assess the performance of the proposed beamforming strategies.