Energy-efficient coordinated beamforming with individual data rate constraints

Coordinated beamforming has been optimized to maximize the sum rate under the transmit power constraints, or to minimize the transmit power under the data rate constraints. In this paper, we study coordinated beamforming to maximize the energy efficiency (EE) of multi-cell multi-antenna systems meanwhile ensuring the individual data rate requirement of each user. To find a solution of the non-convex optimization problem for the precoding design, we construct a convex subset of the original constraint set and a quasi-concave lower bound of the EE. Then, we propose an iterative algorithm to maximize the lower bound of the EE within the convex subset. We evaluate the EE of the proposed algorithm through simulations under different data rate requirements, user locations, and cell-edge signal-to-noise ratios. The results demonstrate that the proposed precoder is much more energy-efficient than the transmit power minimization precoder when the circuit power consumption dominates, and always outperforms two interference-free transmission schemes with the optimized transmit power toward maximizing the EE.