Load balancing with 3-D beamforming in macro-assisted small cell architecture

Small cell is an attractive and promising technology for improving capacity in traffic hotspots using cell densification. We consider the traffic load-balancing problem for a macro-assisted small cell architecture exploiting the flexible 3-D beamforming facilitated by the adoption of the active antenna system at base stations. Specifically, 3-D user equipment (UE)-specific beamforming is utilized for traffic load balancing due to its unique feature that the received signal is maximized, while the interference is limited with narrower beamwidth. We propose a novel traffic load-balancing algorithm based on cell association and cell sectorization using 3-D UE-specific beamforming, and the performance of the proposed algorithm is evaluated via system-level simulations. Results show that cell edge user throughput and cell average throughput both improve significantly with the proposed load-balancing algorithm compared with the conventional sectorization with fixed antenna down-tilt scheme. In addition, in denser small cell scenarios, our proposed scheme can further increase the load-balancing gain with reduced cell planning efforts compared with the conventional scheme.